HomeMy WebLinkAboutCity Approved Southport LWB Widening Phase 3 TIR C17004398.pdf
ENGINEERING REPORT
Technical Information Report
Lake Washington Boulevard Improvements
Phase III for Southport Development
Renton, WA
July 16, 2018
PREPARED BY:
COUGHLIN PORTER LUNDEEN
801 Second Avenue, Suite 900
Seattle, WA 98104
P 206.343.0460
CONTACT / Tim Brockway, PE, LEED AP BD+C
SURFACE WATER UTILITY
rstraka 07/30/2018
DEVELOPMENT ENGINEERING
rnair 07/31/2018
C17004398
TABLE OF CONTENTS
I. PROJECT OVERVIEW .................................................................................................................................... 1
General Description .......................................................................................................................................... 1
Existing Conditions ........................................................................................................................................... 1
Proposed Drainage System .............................................................................................................................. 1
II. CONDITIONS AND REQUIREMENTS ............................................................................................................ 3
Special Requirements:...................................................................................................................................... 3
Project Specific Requirements:......................................................................................................................... 4
III. OFF-SITE ANALYSIS ..................................................................................................................................... 5
Task 1 – Study Area Definition and Maps ........................................................................................................ 5
Task 2 - Resource Review ................................................................................................................................ 5
Task 3 - Field Inspection ................................................................................................................................... 5
Task 4 - Drainage System Description and Problem Descriptions ................................................................... 5
Upstream Analysis ........................................................................................................................................ 6
Downstream Analysis .................................................................................................................................... 6
Task 5 – Mitigation of Existing or Potential Problems....................................................................................... 6
IV. FLOW CONTROL AND WATER QUALITY FACILITY ANALYSIS AND DESIGN ....................................... 8
Existing Site Hydrology (Part A) ....................................................................................................................... 8
Developed Site Hydrology (Part B) ................................................................................................................... 8
Performance Standards and Onsite BMP’s (Parts C and D) ....................................................................... 9,10
Water Quality System (Part E) ........................................................................................................................ 10
Flow Control - N/A .............................................................................................................................................
V. CONVEYANCE SYSTEM ANALYSIS AND DESIGN .................................................................................. 12
Standard Requirements (based on KCSWDM and SAO): .............................................................................. 12
On-site Conveyance ....................................................................................................................................... 12
Existing Conditions: ..................................................................................................................................... 12
Developed Storm system description: ......................................................................................................... 12
VI. SPECIAL REPORTS AND STUDIES ........................................................................................................... 13
VII. OTHER PERMITS ....................................................................................................................................... 15
VIII. CSWPPP ANALYSIS AND DESIGN .......................................................................................................... 16
Standard Requirements .................................................................................................................................. 15
IX. BOND QUANTITY, FACILITY SUMMARIES, AND DECLARATION OF COVENANT ............................... 16
X. OPERATION AND MAINTENANCE MANUAL ............................................................................................ 18
Standard Maintenance.................................................................................................................................... 18
Appendix A – Figures and Calculations......................................................................................................... 28
Figures ........................................................................................................................................................ 28
Engineering Calculations ............................................................................................................................ 29
Appendix B - Reports 30
JARPA and Hydraulics & Hydraulics Analysis Memo & Geotech Report
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I. PROJECT OVERVIEW
GENERAL DESCRIPTION
The following Technical Information Report (TIR) provides the technical information and design analysis
required for developing the Drainage and Temporary Erosion and Sedimentation Control Plan (TESC) for the
Southport Lake Washington Boulevard Improvements Project. The stormwater design for the project was
based on the requirements set forth in the 2017 Renton Surface Water Design Manual (RSWDM) (See Figure
1 – Technical Information Report Worksheet).
The Lake Washington Boulevard Improvements –Phase III for Southport Development, is located within the
City of Renton, situated at the southern tip of Lake Washington between Houser Way N and NE Park Avenue
(See Figure 2 – Site Location). The site is in the NW ¼ of the NW ¼ of Section 8, Township 23 North, Range
5 East, Willamette Meridian. The project will occupy a portion of the Northbound lane of Lake Washington
Boulevard, including the culvert crossing for John’s Creek.
Overall, the project will widen Lake Washington Boulevard which will include new paving, channelization,
retaining walls, signage, and the installation of large pipe elbows to direct the existing culverts from the south
into the new creek section being constructed with this project. The widening along John’s Creek will be
accomplished using culvert extensions and a new retaining wall made from Hilfiker baskets. The existing site
consists of 0.03 acres of impervious area and 0.15 acres of pervious area. The proposed conditions will
consist of approximately 0.18 acres of entirely impervious area. Runoff from the site will be discharged directly
to John’s Creek after being treated in Filterra boxes. Soils for the area were mapped using the King County
Soil Survey maps (See Figure 3 – Soil Survey Map), and a Geotechnical exploration has been performed to
address slope and wall stability.
EXISTING CONDITIONS
The existing site consists of an asphalt paved roadway over crossing culverts carrying the flows for John’s
Creek. See Table 1 for site surface cover information. The roadway is currently two lanes, one running in
each direction. Refer to Section IV for more information.
PROPOSED DRAINAGE SYSTEM
The proposed site consists of additional roadway paving, retaining walls, culvert extensions, Filterra boxes, a
relocated confluence channel for John’s Creek and some landscaping. See Table 2 for site surface cover
information. According to Table 1.1.2.A of the 2017 Renton Surface Water Design Manual (RSWDM), this
project meets the criteria for a Full Drainage Review, including water quality requirements. Per the 2017
RSWDM, since 100% of the runoff will come from commercial land or roadways (Lake Washington Boulevard)
Enhanced Basic Water Quality measures apply.
The proposed drainage improvements are confined within the limits of disturbance for the road widening and
revision to the John’s Creek channel, along the south and east side of Lake Washington Boulevard. The
project site lies within the City’s Existing Peak Flow Control basin. This project is therefore not required to
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provide flow control for the additional impervious area, provided the existing downstream system has sufficient
capacity to safely convey the added flows.
Storm runoff will be conveyed by gutter flow to the two new Contech Filterra systems (See Figure 4 – Post
Treatment Area). After being treated, all runoff from the capture area and unaffected existing street areas that
currently drain to John’s Creek, will be conveyed through storm pipes and discharged into the revised creek
section which is part of this project. Flows will then be conveyed through the existing culverts underneath the
road and continue along John’s Creek.
All conveyance on site will be designed according to Chapter 4 of the 2017 Renton Surface Water Design
Manual (RSWDM).
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II. CONDITIONS AND REQUIREMENTS
This section will address the requirements set forth by the Core and Special Requirements listed in Chapter 1
of the City of Renton’s Amendments to the King County Surface Water Design Manual.
City of Renton Amendments to the King County Surface Water Management Design Manual Core
Requirements:
1. Discharge at the Natural Location (1.2.1): All runoff from the site will be conveyed to the natural
discharge location (Lake Washington via Johns Creek).
2. Off-site Analysis (1.2.2): Refer to Sections III and IV. A Level 1 downstream analysis has been
performed by the Environmental consultant, as this project will discharge to Johns Creek. A detailed
drainage description was provided in the JARPA report , included in Appendix B.
3. Flow Control (1.2.3.1): Refer to Section IV. The project is located in a Peak Flow Control Area. Flow
control has not been provided for the proposed improvements, due to the miniscule increase in flow
during the 100-year event (0.04 cfs).
4. Conveyance System (1.2.4): Refer to Section V. Closed pipe systems, modified culvert and custom
elbows for extension connections have been provided for stormwater conveyance.
5. Erosion and Sedimentation Control (1.2.5): Refer to Section VIII and the demolition/TESC provided
as part of this submittal. The project will construct a series of sediment controls to address the
specific conditions at the site.
6. Maintenance and Operations (1.2.6): Refer to Section X. The proposed storm drainage system will
be owned, operated and maintained by the City of Renton.
7. Financial Guarantees and Liability (1.2.7): The owner and contractor will obtain all necessary
permits and bonds prior to the beginning of construction.
8. Water Quality (1.2.8): Refer to Section IV. Water quality treatment for runoff from target pollution
generating surfaces will be provided by Contech Filterra systems. See Section IV for more
information.
9. Onsite BMP (1.2.9): Refer to Section IV. Onsite BMP’s have been assessed to the maximum extent
possible. See Section IV for more information.
SPECIAL REQUIREMENTS:
Special Requirement #1. Other Adopted Area-Specific Requirements Section 1.3.1
• Critical Drainage Areas (CDAs): Not Applicable
• Master Drainage Plans (MDPs): There are no known master drainage plans covering this project site.
• Basin Plans (BPs): The project is located within the East Lake Washington – Renton drainage basin.
• Lake Management Plans (LMPs): Not Applicable
• Shared Facility Drainage Plans (SFDPs): Not Applicable
Special Requirement #2. Flood Hazard Area Delineation, Section 1.3.2: See Figure 9 for 100-yr flood zone.
The site is not within a flood hazard area therefore no 100-yr flood plains have been delineated on the plans.
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Proposed LWB improvements will not increase the flood storage within the 100-yr flood zone through the
additional creek area and elongated culverts.
Special Requirement #3. Flood Protection Facilities, Section 1.3.3: Not Applicable
Special Requirement #4. Source Controls, Section 1.3.4: See attached Activity Worksheet and Required
BMP’s.
Special Requirement #5. Oil Control, Section 6.1.5. Traffic counts in this section of roadway do not trigger
this requirement due to WSDOT Average Daily Traffic tabulations. No oil control is required. However, water
quality Filterra systems will be “proprietary facilities” as categorized under the High-Use menu (Section 6.1.5)
and will contain floatables and remove targeted pollutants.
Special Requirement #6. Aquifer Protection Area. Section 1.3.6: See attached Aquifer Protection Map under
Appendix A. The site is not located in an Aquifer Protection Zone. Not applicable.
PROJECT SPECIFIC REQUIREMENTS:
There are no applicable project specific instructions
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III. OFF-SITE ANALYSIS
TASK 1 – STUDY AREA DEFINITION AND MAPS
The Renton drainage basin map was used to verify that the site was fully in the Lake Washington East
drainage basin (See Figure 5 – Drainage Basin Map).
TASK 2 - RESOURCE REVIEW
a) Adopted Basin Plans Lake Washington East drainage basin
b) Floodplain/floodway (FEMA) Maps Site is not located in the floodplain (See Figure 9)
c) Off-site Analysis Reports Included in the JARPA Report and
Hydraulics/Hydrologic Memo (See Appendix B)
d) Sensitive Areas Folio No Sensitive Areas. See Figure 5B and 10
e) Drainage Complaints and Studies No Drainage Complaints. See Figure 5B
f) Road Drainage Problems See JARPA
g) King County Soils Survey: See Figure 3 – USDA Soil Map
h) Wetland Inventory Maps: No Wetlands. See Figure 5B
i) Migrating Rivers Study Stream Assessment and Final Mitigation Plan
j) DOE’s Section 303d List of Polluted Waters See JARPA
k) KC Designated Water Quality Problems See JARPA
l) City of Renton critical maps: See Figure 5 and 10. No Critical Areas.
TASK 3 - FIELD INSPECTION
Multiple site visits have been made to gather information including an analysis of the discharge from the site.
Geoengineers and Coughlin Porter Lundeen conducted multiple site visits to the site in preparing the
published JARPA report, included in Appendix B. A JARPA and Hydrology & Hydraulics Analysis Memo has
been provided in the Appendix to evaluate the conveyance capacity of four existing culverts under Lake
Washington Boulevard North (LWB). Please refer to Task 4, Downstream Analysis below for more information.
TASK 4 - DRAINAGE SYSTEM DESCRIPTION AND PROBLEM
DESCRIPTIONS
Runoff from the site will be conveyed through new and existing storm system elements that discharge to
John’s Creek. The road widening is designed to direct flows from LWB’s curb system to the Filterra catch
basin systems, located on the east side of the road, which collect and treat the runoff before discharging into
the channel. See Appendix A, Figure 11 – Offsite Analysis Map and Appendix B – Hydrology and Hydraulics
Memo. For over ¼ mile upstream a network of storm pipe and storm structures, culverts, and channels as well
as private structures have been highlighted in blue. This provides a general sense of the area tributary to the
four-storm pipe system that outfall into the channel being modified. Two pipes that come from the southwest
direction and two pipes that come from the southeast direction. These pipes discharge into what is considered
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to be the upper limit of John’s Creek. The site discharges through an extension of existing culverts underneath
the railroad and discharges into John’s Creek. The stream then gets routed through culverts underneath
Houser Way N which in turn discharge into an open creek. The distance from the point of discharge to Lake
Washington is approximately one quarter mile downstream, with the creek entering a culvert/piped storm
system through the County’s Gene Coulon Park parking lot. For a more detail description of the drainage
system and problem description see JARPA prepared by Geo Engineer Inc.
Upstream Analysis
Upstream of the channel that the 4 existing culverts discharge into is a network of multiple series of storm
pipe, storm structures, culverts, and channels as well as private structures that carry flows from off-site areas
to the channel of John’s Creek in the project site. These have been highlighted in blue, See Appendix Figure
11 – Offsite Analysis Map. In addition to the storm structure map provided by the City of Renton, a JARPA and
Hydrology & Hydraulics Analysis Memo has been provided in the Appendix B to address and analyze
upstream conditions. Two of the storm pipes (48” and 72” diameter) come from the southwest direction and
stem off of their own individual networks at the intersection of Garden Avenue North and Park Avenue North.
The 72” pipe connects upstream to a network of pipes that pick up runoff from the Lowes shopping center
parking lot and other commercial retailers further south of Garden Avenue. The other 48” pipe is connected to
a network upstream surrounding residential and commercial infrastructure.
The other two existing storm pipes (24” and 36”) that discharge into the channel from the north/northeast
direction also branch into a network of storm pipes. The 24” storm pipe connects into a network of storm pipe
that picks up runoff from industrial retailers off of Houser Way North. The 36” storm pipe leads upstream to a
series of storm pipes from the eastern direction along Southport Drive N and Interstate 405.
Within the new roadway work, the 12” diameter storm pipe storm proposed with the improvements will connect
to the northern Filterra which will discharge directly into the channel. The second Filterra to the south, will treat
the water that is not captured in the first unit, and then be conveyed in a pipe to discharge into the constructed
channel.
Downstream Analysis
As delineated in red on Figure 11 - Offsite Analysis Map, the downstream analysis begins immediately after
the four existing 48” concrete culverts discharged on the opposite side of Lake Washington Boulevard. The
project site discharges through a minor extension of existing culverts underneath LWB and the railroad that
discharge into the middle portion of John’s Creek. The stream then gets routed under the new bridge on the
Southport site, then along Coulon Park Access Road into the lower section of John’s Creek that flows through
Gene Coulon Park. The distance from the point of discharge to Lake Washington is approximately one quarter
mile downstream. Additional information on the existing creek and culvert system is included in the JARPA
and Hydraulics/Hydrology Memo in Appendix B. The distance from the point of discharge to Lake Washington
is approximately one quarter mile downstream, County’s Gene Coulon Park parking lot. No known drainage
problems have been reported with this conveyance system.
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TASK 5 – MITIGATION OF EXISTING OR POTENTIAL PROBLEMS
The proposed project will increase the impervious surface to 0.18 acres, an increase of only 7,800
square feet, and will not provide flow control facilities, per the City’s requirements for work in this area.
Since this added area is a miniscule portion of the large upstream drainage basin that drains to this
project site through the existing culverts, the proposed mitigation’s design should work to assure no
increased velocities are experienced in the downstream system. Runoff from the site will be conveyed
through new and existing storm system elements that discharge to John’s Creek. The road widening is
designed to direct flows from LWB to the Filterra catch basin systems, located on the east side of the road,
which collect and treat the runoff before discharging into the channel. Stormwater improvements include
proposed treatment of 8,000 SF of pollution-generating impervious surfaces associated with the roadway,
which exceeds the 7,800 SF of new impervious surfaces being added. In order to provide treatment for the
project, we propose to treat an equivalent area of Lake Washington Boulevard that is not currently being
treated, along with the bulk of the area being added, for a total treatment area that exceeds the added area of
impervious surface. With these mitigation measures, the project should not create downstream problems
nor exacerbate existing ones.
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IV. FLOW CONTROL AND WATER QUALITY FACILITY ANALYSIS
AND DESIGN
EXISTING SITE HYDROLOGY (PART A)
Due to the nature of this site being a public improvement, the total disturbed area will be considered the site
area for purposes of tabulation. The disturbed area of 0.53 acres and consists of primarily undisturbed
landscaped area and existing gravel area beyond the edge of pavement. A portion of the site generally slopes
toward the John’s Creek channel, the other portion flows south away from John’s Creek channel confluence
discharge. The site area conditions are illustrated in Figure 6 and summarized in Table 1 below.
TABLE 1 - EXISTING SITE CONDITIONS AREA BREAKDOWN
DESCRIPTION AREA (SQUARE FEET) AREA (ACRES)
TOTAL PERVIOUS 17,300 0.40
TOTAL IMPERVIOUS 5,900 0.13
TOTAL DISTURBED
AREA
23,200 0.53
DEVELOPED SITE HYDROLOGY (PART B)
The developed site hydrology will increase the amount of impervious area by 7,800 square feet (approximately
0.18 acres). The site area conditions are illustrated in Figure 7 and summarized in Table 2 below. The
widening of the roadway, retaining wall and culverts modifications and additional proposed improvements will
result in a similar site hydrology as it exists currently, before flowing into the culvert and discharging into
John’s Creek (See Figure 11). Flow from the area being widened will be captured and treated before being
discharged into John’s Creek. Sheet flow runoff from upstream of the northern Filterra #2, will be treated in
that unit, and any additional runoff will be treated with the southern Filterra #1.
Since most of the new PGIS added with this project will be downhill of the proposed capture area, additional
existing PGIS area treated by the Filterra units that is not disturbed or added by this project will be captured
and treated to compensate for the new PGIS area not being treated.
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TABLE 2 - DEVELOPED SITE CONDITIONS AREA BREAKDOWN
DESCRIPTION AREA (SQUARE FEET) AREA (ACRES)
TOTAL PERVIOUS 9,500 0.22
NEW IMPERVIOUS (NEW PGIS)
REPLACED IMPERVIOUS (REPLACED PGIS)
TOTAL IMPERVIOUS
7,800
5,800
13,600
0.18
0.13
0.31
TOTAL DISTURBED AREA 23,100 0.53
PERFORMANCE STANDARDS (PARTS C)
According to Section 1.2.3.1 (See Figure 8 - Flow Control Application Map) of the 2017 Renton Surface Water
Design Manual (RSWDM), this project is located within the Peak Flow Control area. Although this project lies
within a flow control basin, the project improvements are allowed to discharge directly to John’s Creek without
detention. Given that the project development satisfies all of the Direct Discharge Exemption criteria
(discussed below), the City has indicated that flow control will not be required.
Direct Discharge Exemption Criteria:
A) The project site discharges to Johns Creek downstream of I-405.
B) The conveyance system between the project site and the major receiving water (John Creek) will
extend to the ordinary high-water mark and will be comprised of manmade conveyance elements
(pipes) and will be within a public or private drainage easement.
C) The conveyance system will have adequate capacity to convey the 25-year peak flow (per Core
Requirement #4, Conveyance System) for the entire contributing drainage area.
D) The conveyance system will be adequately stabilized to prevent erosion
E) The direct discharge proposal will not divert flows from or increase flows to an existing wetland or
stream sufficient to cause a significant adverse impact (0.04 cfs increase at 100-year event).
A portion of the disturbed area is not collected in the treatment facilities due to topography. The bypass
areas are mitigated by using area trades, meaning a different area with the same surface characteristics
are included in the drainage basin for the treatment facilities.
To mitigate the impacts of storm and surface water runoff generated by new impervious surface onsite BMP’s
were proposed. Per Section 1.2.9.4.1. (A) of the 2017 Renton Surface Water Design Manual (RSWDM) for
implementation of BMPs within Road Right-of-Way, an evaluation of the BMPs within the Right of way was
done. These Filterras serve impervious area only within the Lake Washington Boulevard right-of-way as
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Boulevard right-of-way as shown per figure 4: Proposed Treatment Area. The city will assume maintenance of
the Filterras as they comply with the drainage facility financial guarantee and liability requirements.
ON-SITE BEST MANAGEMENT PRACTICES (ON-SITE BMPS) PART D
Onsite BMP’s have been assessed for this project to mitigate the impacts of storm and surface water runoff
generated by new impervious surfaces, existing impervious surfaces, and replaced impervious surface
targeted for mitigation. Due to direct discharge to John’s Creek that leads to Lake Washington, the LID
performance standard does not need to be met and bioretention, permeable pavement, and full dispersion are
not required to be considered. However, all other BMP’s have been assessed to the maximum extent possible
per section 1.2.9 of the 2017 Renton Surface Water Design Manual (RSWDM). See assessment below.
On-site BMPs Assessment
SECTION
REFERENCE BMP DESCRIPTION ACTION
Section
C.2.2
Full Infiltration
Full Infiltration is infeasible because the
majority of the site has slopes greater than
15% (45%-55%).
Section
C.2.3 Limited Infiltration
Limited Infiltration is infeasible because the
majority of the site has slopes greater than
15% (45%-55%).
Section
C.2.4
Basic Dispersion
Basic Dispersion is infeasible because the
majority of the site has slopes greater than
15%, there is not sufficient length to install a
dispersion trench, and there are no locations
where a “vegetated flowpath segment” of at
least 25-feet can be created.
Section
C.2.13
Soil Amendment
Soil Amendment is feasible and has been
proposed for the site (See landscape plans).
WATER QUALITY SYSTEM (PART E)
Section 1.2.8.1(A) of the 2017 Renton Surface Water Design Manual (RSWDM) outlines the specific land uses
within Basic WQ Treatment areas which are subject to providing Enhanced Basic WA treatment. Due to the
nature of the project, the Lake Washington Boulevard Improvements – Phase III of Southport Development
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falls into the category of Enhanced Basic WQ Treatment. Therefore, Enhanced Basic water quality treatment
for all new and replaced pollution generating impervious surfaces (PGIS) will be provided by the two Contech
Filterra systems. The Filterra system has a Conditional Use Level Designation from the Washington
Department of Ecology for enhanced basic treatment and was deemed suitable for this application.
FILTERRA SYSTEM: The project will add roughly 7,800 of new PGIS, see Figure 7 for Proposed Conditions.
Unfortunately, this area is downhill from the eventual discharge to John’s Creek. In order to provide treatment
for the project, we propose to treat an area greater than the added impervious area of Lake Washington
Boulevard that is not currently being treated. Figure 4 shows the proposed area to be treated to compensate
for the new PGIS. Table 1 summarizes the required and provided treatment areas.
TABLE 1. WATER QUALITY TREATMENT AREA SUMMARY
NEW PGIS
(REQ. TREATMENT AREA)
PROPOSED TREATMENT AREA
(SEE FIG 4)
% DIFFERENCE
7,800 SF 8,000 SF 3%
According to the attached Figure 7B Filterra Sizing table provided by Contech Engineering Solutions LLC, the
area can be either be treated by one large Filterra unit or two smaller units. We have decided that providing
two Filterra units (one 4x6 and one 4x4) is the best solution because it allows for redundancy in the design.
Contech has confirmed specific Filterra sizing based on the basin size and site characteristics (See Filterra
Sizing under Engineering Calculations). The two Filterra curb inlet units will be installed on the south side of
Lake Washington Boulevard and will discharge to the modified area of John’s Creek being constructed with
this project. See Figure 4 for the proposed water quality design and treatment area swap. Per the water quality
implementation requirements, of Section 1.2.8.2. (C) of the 2017 RSWDM, a treatment area swap was
implemented for this project. The runoff from target pollution-generating surfaces may be released untreated if
an existing nontargeted pollution-generating surface of equivalent size and pollutant characteristics lying within
the same watershed or stream reach tributary area is treated on the project site. Due to existing topography,
the area highlighted in yellow will not be treated and will follow existing drainage patters downstream. For this
reason, an area larger than the untreated area (less than 5,000 SF) will be treated to compensate for the PGIS
left untreated (highlighted in blue).
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V. CONVEYANCE SYSTEM ANALYSIS AND DESIGN
This section discusses the criteria that will be used to analyze and design the proposed storm conveyance
system.
STANDARD REQUIREMENTS (BASED ON 2017 RSWDM AND SAO):
1. Facilities must convey the 100-year flow without overtopping the crown of the roadway,
flooding buildings, and if sheet flow occurs it must pass through a drainage easement. All
stormwater conveyance will be designed such that the 100-year flow is conveyed without overtopping
the crown of the roadway (or drive aisle) or flooding any building. The JARPA documents and
Hydrology and Hydraulics Analysis Memo found in Appendix B will confirm the ability of the existing
culverts to convey the 100-year flow with adequate clearance. The water surface elevation profile
depicts that the 100-year WS elevation is well under the crown of the roadway.
2. New pipe systems and culverts must convey the 25-year flow with at least 0.5 feet of
freeboard. (1.2.4.1). The 2 new pipe systems discharging from the 2 Filterras will be designed to
convey the 25-year flow. See Conveyance Calculations under Appendix A for both the East Basin
(0.04 acres) and West Basin (0.14 acres). These new 12” pipes will meet the conveyance requirement
per Section 1.2.4.1. of the 2017 RSWDM.
The new culvert extensions that will accommodate the roadway widening will improve the
overall conveyance with improved inlet geometry. The slope, size, and material of the pipe will remain
the same. The only minor modification made in addition to the extension is an improvement to the
inlet geometry at the culvert entrance. The JARPA and Hydrology and Hydraulics Analysis Memo will
confirm the ability of the culvert to convey the 100-year flow with adequate clearance.
The conveyance requirement of Johns Creek’s downstream of the site is addressed with the
JARPA report and Hydrologic and Hydraulic Analysis Memo prepared by Geo Engineers, Inc.
Although, the memo was prepared with a concrete vault in mind, the basin size, discharges and
general hydraulics for the analysis still maintain the same. As demonstrated in the JARPA report and
Memo, the 100- year peak discharge of 22 cfs will not impose or create any severe flooding problems
or severe erosion problems.
3. Bridges must convey the 100-year flow and provide a minimum of two feet, varying up to six
feet, of clearance based on 25% of the mean channel width. (1.2.4-2)(4.3.5-6). The existing
gabion wall and culverts under the road are being extended as part of the design of the LWB road
widening improvement. A JARPA application is being filed to support the design of the proposed
reconstruction of John’s Creek. The proposed system will improve the overall conveyance with
improved inlet geometry at the culvert entrance. The JARPA application and Hydrology and
Hydraulics Analysis Memo will confirm the ability of the culvert to convey the 100-year flow with
adequate clearance.
4. Drainage ditches must convey the 25-year flow with 0.5 feet of freeboard and the 100-year flow
without overtopping. (1.2.4-2). This project has provided a hydraulic analysis of the proposed
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improvements as a part of the JARPA permit process. Please refer to that document for that
information.
5. Floodplain Crossings must not increase the base flood elevation by more than 0.01 feet
[41(83.C)] and shall not reduce the flood storage volume [37(82.A)]. Piers shall not be
constructed in the FEMA floodway. [41(83.F.1)]. No work is being proposed within the base flood
elevation or within the FEMA floodway other than the work and impacts being addressed in the
JARPA documents.
6. Stream Crossings shall require a bridge for class 1 streams that does not disturb or banks.
For type 2 and type 3 steams, open bottom culverts or other method may be used that will not
harm the stream or inhibit fish passage. [60(95.B)]. As previously mentioned, this proposal
involves the widening of Lake Washington Boulevard improvement as part of the final phase of
mitigation for the Southport Development. The widening will include new paving, channelization, and
retaining walls along with local modifications to the existing storm water conveyance. A JARPA
application will be filed to address stream and fish passage concerns.
7. Discharge at natural location is required and must produce no significant impacts to the
downstream property (1.2.1-1). The project will discharge to the existing storm system and to the
redesigned channel, permitted with the JARPA and analyzed in the Hydrologic and Hydraulic Analysis
Memo.
ON-SITE CONVEYANCE
Existing Conditions:
Four culverts currently discharge stormwater runoff into this depression from the north, east and south, and
four existing culverts cross LWB to the west draining the depression. The JARPA report and Hydrologic and
Hydraulic Analysis Memo (found in Appendix B) closely describe the hydrology and hydraulics analysis used
to evaluate the conveyance capacity of the four culverts.
Developed Storm system description:
Lake Washington Boulevard’s existing culvert system is being retrofitted for the widening of the road. The
project will add roughly 7,800 SF of new PGIS. Storm runoff will be conveyed by gutter flow to the two new
Contech Filterra systems (See Figure 4 – Post Treatment Area). After being treated, all runoff from the
capture area and unaffected existing street areas that currently drain to John’s Creek, will be conveyed
through storm pipes and discharged into the revised creek section which ultimately gets routed through the
extended culverts to be discharged to John’s Creek across Lake Washington Boulevard.
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VI. SPECIAL REPORTS AND STUDIES
Geotechnical Engineering Report, Southport Lake Washington Boulevard Improvements – Phase II & III.
Prepared by Geo Engineers, Inc (dated April 22, 2016)
Revised Report Addendum to “Geotechnical Engineering Services Report, Southport Development, Lake
Washington Boulevard Improvements, (dated May 8, 2018)
Joint Aquatic Resources Permit Application (JARPA)
Prepared by Geo Engineers, Inc.
Hydrologic and Hydraulics Analysis Memorandum
Memo by Geo Engineers, Inc. (to address the LWB Phase III road improvements)
Stream Assessment and Final Mitigation Plan: LWB North Road Improvements
Prepared by Geo Engineers, Inc. (Submitted separately by Geo Engineers Inc.)
15
VII. OTHER PERMITS
This project will require a Civil Construction permit and land use permit from The City of Renton.
Additionally, the project will require the completion of the Joint Aquatic Resource Permit Application (JARPA)
process to properly mitigate the project effects on John’s Creek. A copy of this document will be provided to
the City. The JARPA can be found in Appendix B.
16
VIII. CSWPPP ANALYSIS AND DESIGN
This section lists the requirements that will be used when designing the TESC plan for this site. A copy of the
Draft CSWPPP has been included at this time.
STANDARD REQUIREMENTS
Erosion/Sedimentation Plan shall include the following:
1. Facilities required include: Catch basin filter socks. (1.2.5-1). The project will provide sediment
protection at existing and proposed catch basins.
2. Timing - For the period between November 1 through March 1 disturbed areas greater than
5,000 square feet left undisturbed for more than 12 hours must be covered with mulch,
sodding, or plastic covering. A construction phasing plan shall be provided to ensure that
erosion control measures are installed prior to clearing and grading. (1.2.5-1). The TESC plan
will include provisions for disturbed areas to be covered in accordance with City of Renton
requirements and that all TESC measures are in place before any construction activity occurs.
3. Planning - Plan shall limit tributary drainage to an area to be cleared and graded. Delineate
dimension, stake and flag clearing limits (1.2.5-1). The clearing limits will be indicated on the
TESC plan.
4. Revegetation - Revegetate areas to be cleared as soon as practicable after grading. (1.2.5-1).
Notes addressing this item will be included on the TESC plan.
5. Baker Tank sizing – Sizing calculations for proposed baker tank is per Section D.2.1.5.1 of the 2017
RSWDM. The design inflow used is the 2-year peak discharge per MGS Flood using 15 min time
steps.
17
IX. BOND QUANTITY, FACILITY SUMMARIES, AND DECLARATION
OF COVENANT
A Bond Quantity Worksheet is included with this report.
A Water Quality Facility Summary Sheet outlining the proposed water quality system will be included with this
report.
Any required Declarations of Covenant will be included prior to issuance of the permit.
18
X. OPERATION AND MAINTENANCE MANUAL
STANDARD MAINTENANCE
All facilities are to be maintained by the city of Renton after a 2-year maintenance warranty. Sections of the
2017 Renton Surface Water Design Manual (RSWDM) under this section outline the Maintenance
Requirements for stormwater facilities and on-site BMPs have been included in this section on the following
pages for use by the City in the maintenance of the designed facilities.
19
MAINTENANCE STANDARDS FOR
PRIVATELY MAINTAINED DRAINAGE
FACILITIES AT SOUTHPORT OFFICE
NO. 5 - CATCH BASINS
Maintenance
Component
Defect Conditions When Maintenance is
Needed
Results Expected
When Maintenance is
performed
General Trash &
Debris
(Includes
Sediment)
Trash or debris of more than 1/2 cubic
foot which is located immediately in front
of the catch basin opening or is blocking
capacity of the basin by more than 10%
No Trash or debris
located immediately in
front of catch basin
opening.
Trash or debris (in the basin) that
exceeds 1/3 the depth from the bottom of
basin to invert the lowest pipe into or out
of the basin.
No trash or debris in the
catch basin.
Trash or debris in any inlet or outlet pipe
blocking more than 1/3 of its height.
Inlet and outlet pipes
free of trash or debris.
Dead animals or vegetation that could
generate odors that could cause
complaints or dangerous gases (e.g.,
methane).
No dead animals or
vegetation present
within the catch basin.
Deposits of garbage exceeding 1 cubic
foot in volume
No condition present
which would attract or
support the breeding of
insects or rodents.
Structure
Damage to
Frame and/or
Top Slab
Corner of frame extends more than 3/4
inch past curb face into the street (If
applicable).
Frame is even with curb.
Top slab has holes larger than 2 square
inches or cracks wider than 1/4 inch
(intent is to make sure all material is
running into basin).
Top slab is free of holes
and cracks.
Frame not sitting flush on top slab, i.e.,
separation of more than 3/4 inch of the
frame from the top slab.
Frame is sitting flush on
top slab.
20
Maintenance
Components
Defect Condition When Maintenance is
Needed
Results Expected
When Maintenance is
Performed.
Cracks in
Basin Walls/
Bottom
Cracks wider than 1/2 inch and longer
than 3 feet, any evidence of soil
particles entering catch basin through
cracks, or maintenance person judges
that structure is unsound.
Basin replaced or
repaired to design
standards.
Cracks wider than 1/2 inch and longer
than 1 foot at the joint of any inlet/ outlet
pipe or any evidence of soil particles
entering catch basin through cracks.
No cracks more than
1/4 inch wide at the
joint of inlet/outlet pipe.
Sediment/
Misalignment
Basin has settled more than 1 inch or
has rotated more than 2 inches out of
alignment.
Basin replaced or
repaired to design
standards.
Fire Hazard Presence of chemicals such as natural
gas, oil and gasoline.
No flammable
chemicals present.
Vegetation Vegetation growing across and blocking
more than 10% of the basin opening.
No vegetation blocking
opening to basin.
Vegetation growing in inlet/outlet pipe
joints that is more than six inches tall
and less than six inches apart.
No vegetation or root
growth present.
Pollution Nonflammable chemicals of more than
1/2 cubic foot per three feet of basin
length.
No pollution present
other than surface film.
Catch Basin
Cover
Cover Not in
Place
Cover is missing or only partially in
place. Any open catch basin requires
maintenance.
Catch basin cover is
closed
Locking
Mechanism
Not Working
Mechanism cannot be opened by on
maintenance person with proper tools.
Bolts into frame have less than 1/2 inch
of thread.
Mechanism opens with
proper tools.
Cover Difficult
to Remove
One maintenance person cannot
remove lid after applying 80 lbs. of lift;
intent is keep cover from sealing off
access to maintenance.
Cover can be removed
by one maintenance
person.
Ladder Ladder Rungs
Unsafe
Ladder is unsafe due to missing rungs,
misalignment, rust, cracks, or sharp
edges.
Ladder meets design
standards and allows
maintenance person
safe access.
Metal Grates
(If Applicable)
Grate with opening wider than 7/8 inch. Grate opening meets
design standards.
21
Trash and
Debris
Trash and debris that is blocking more
than 20% of grate surface.
Grate free of trash and
debris.
Damaged or
Missing.
Grate missing or broken member(s) of
the grate.
Grate is in place and
meets design
standards.
22
NO. 9 - FENCING
Maintenance
Components
Defect Conditions When Maintenance is
Needed
Results Expected
When Maintenance is
Performed
General Missing or
Broken Parts
Any defect in the fence that permits
easy entry to a facility.
Parts in place to provide
adequate security.
Erosion Erosion more than 4 inches high and
12-18 inches wide permitting an
opening under a fence.
No opening under the
fence that exceeds 4
inches in height.
Wire Fences Damaged
Parts
Post out of plumb more than 6 inches. Post plumb to within 1-
1/2 inches.
Top rails bent more than 6 inches.
Top rail free of bends
greater than 1 inch.
Any part of fence (including post, top
rails) more than 1 foot out of design
alignment.
Fence is aligned and
meets design
standards.
Missing or loose tension wire.
Tension wire in place
and holding fabric.
Extension arm missing, broken, or
bent out of shape more than 1 1/2
inches.
Extension arm in place
with no bends larger
than 3/4 inch.
Deteriorated
Paint or
Protective
Coating
Part or parts that have a rusting or
scaling condition that has affected
structural adequacy.
Structurally adequate
posts or parts with a
uniform protective
coating.
23
NO. 6 - CONVEYANCE SYSTEMS (PIPES & DITCHES)
Maintenance
Component
Defect Conditions When Maintenance is
Needed
Results Expected
When Maintenance is
Performed
Pipes Sediment &
Debris
Accumulated sediment that exceeds
20% of the diameter of the pipe.
Pipe cleaned of all
sediment and debris.
Vegetation Vegetation that reduces free
movement of water through pipes.
All vegetation removed
so water flows freely
through pipes.
Damaged Protective coating is damaged; rust is
causing more than 50% deterioration
to any part of pipe.
Pipe repaired or
replaced.
Any dent that decreases the cross
section area of pipe by more than
20%.
Pipe repaired or
replaced.
Open Ditches Trash & Debris Trash and debris exceeds 1 cubic foot
per 1,000 square feet of ditch and
slopes.
Trash and debris
cleared from ditches.
Sediment Accumulated sediment that exceeds
20 % of the design depth.
Ditch cleaned/ flushed
of all sediment and
debris so that it matches
design.
Vegetation Vegetation that reduces free
movement of water through ditches.
Water flows freely
through ditches.
Erosion
Damage to
Slopes
See “Rain gardens” Standard No. 1 See “Rain gardens”
Standard No. 1
Rock Lining
Out of Place or
Missing (If
Applicable).
Maintenance person can see native
soil beneath the rock lining.
Replace rocks to design
standards.
Catch Basins See “Catch Basins: Standard No. 4 See “Catch Basins”
Standard No. 4
Debris
Barriers (e.g.,
Trash Rack)
See “Debris Barriers” Standard No.5 See “Debris Barriers”
Standard No. 5
24
NO. 11 - GROUNDS (LANDSCAPING)
Maintenance
Component
Defect Conditions When Maintenance is
Needed
Results Expected
When Maintenance is
Performed
General Weeds
(Nonpoisonous
)
Weeds growing in more than 20% of
the landscaped area (trees and shrubs
only).
Weeds present in less
than 5% of the
landscaped area.
Safety Hazard Any presence of poison ivy or other
poisonous vegetation.
No poisonous vegetation
present in landscaped
area.
Trash or Litter Paper, cans, bottles, totaling more
than 1 cubic foot within a landscaped
area (trees and shrubs only) of 1,000
square feet.
Area clear of litter.
Trees and
Shrubs
Damaged Limbs or parts of trees or shrubs that
are split or broken which affect more
than 25% of the total foliage of the tree
or shrub.
Trees and shrubs with
less than 5% of total
foliage with split or
broken limbs.
Trees or shrubs that have been blown
down or knocked over.
Tree or shrub in place
free of injury.
Trees or shrubs which are not
adequately supported or are leaning
over, causing exposure of the roots.
Tree or shrub in place
and adequately
supported; remove any
dead or diseased trees.
25
NO. 12 - ACCESS ROADS/ EASEMENTS
Maintenance
Component
Defect Condition When Maintenance is
Needed
Results Expected
When Maintenance is
Performed
General Trash and
Debris
Trash and debris exceeds 1 cubic foot
per 1,000 square feet i.e., trash and
debris would fill up one standards size
garbage can.
Roadway free of debris
which could damage
tires.
Blocked
Roadway
Debris which could damage vehicle
tires (glass or metal).
Roadway free of debris
which could damage
tires.
Any obstruction which reduces
clearance above road surface to less
than 14 feet.
Roadway overhead clear
to 14 feet high.
Any obstruction restricting the access to
a 10 to 12 foot width for a distance of
more than 12 feet or any point
restricting access to less than a 10 foot
width.
Obstruction removed to
allow at least a 12 foot
access.
Road Surface Settlement,
Potholes, Mush
Spots, Ruts
When any surface defect exceeds 6
inches in depth and 6 square feet in
area. In general, any surface defect
which hinders or prevents maintenance
access.
Road surface uniformly
smooth with no evidence
of settlement, potholes,
mush spots, or ruts.
Vegetation in
Road Surface
Weeds growing in the road surface that
are more than 6 inches tall and less
than 6 inches tall and less than 6
inches apart within a 400-square foot
area.
Road surface free of
weeds taller than 2
inches.
26
NO. 12- WATER QUALITY FACILITIES
A.) Cartridge Filter Vault
27
Maintenance
Component
Defect or
Problem
Condition When Maintenance is
Needed
Recommended
Maintenance to
Correct Problem
Facility –
General
Requirements
Life cycle Once per year, except mulch and trash
removal twice per year.
Facility is re-inspected
and any needed
maintenance performed
Contaminants
and pollution
Any evidence of contaminants or
pollution such as oil, gasoline, concrete
slurries, or paint
Materials removed and
disposed of according to
applicable regulations.
Source control BMPs
implemented if
appropriate. No
contaminants present
other than a surface oil
film.
Inlet Excessive
sediment or
trash
accumulation
Accumulated sediments or trash impair
free flow of water into system
inlet should be free of
obstructions allowing free
distributed flow of water
into system
Mulch Cover Trash and
floatable debris
accumulation
Excessive trash and/or debris
accumulation
Minimal trash or other
debris on mulch cover.
Mulch cover raked level.
Proprietary
Filter Media/
Vegetation
Substrate
“Ponding” of
water on mulch
cover after
mulch cover
has been
maintained
Excessive fine sediment passes the
mulch cover and clogs the filter
media/vegetative substrate
Stormwater should drain
freely and evenly through
mulch cover. Replace
substrate and vegetation
when needed
Plants not
growing or in
poor condition
Soil/mulch too wet, evidence of spill,
incorrect plant selection, pest
infestation, and/or vandalism to plants
Plants should be healthy
and pest free
Damaged
Pipes
Any part of the pipes that are crushed,
damaged due to corrosion and/ or
settlement.
Pipe repaired and/ or
replaced.
Access Cover
Damaged/ Not
Working
Cover cannot be opened, one person
cannot open the cover, corrosion/
deformation of cover.
Cover repaired to proper
working specifications or
replaced.
Vault Structure
Includes
Cracks in Wall,
Bottom,
Damage to
Frame and/ or
Top Slab
Cracks wider than 1/2-inch and any
evidence of soil particles entering the
structure through the cracks, or
maintenance/ inspection personnel
determines that the vault is not
structurally sound.
Vault replaced or
repaired to design
specifications.
28
Structure Structure has
visible cracks
Cracks wider than ½ inch Evidence of
soil particles entering the structure
through the cracks
Structure is sealed and
structurally sound
Appendix A – Figures and Calculations
Figures
1. Technical Information Report Worksheet
2. Site Location
3. USGS Soil Map
4. Proposed Treatment Area Swap
5. Drainage Basin Map - City of Renton (Sensitive Areas, Drainage Complaints)
5B. King County iMap
6. Existing Conditions
7. Proposed Conditions
7B. Filterra Sizing – Based on the Western Washington Hydrology Model (WWHM)
8. Flow Control Basin Map
9. FEMA Flood Insurance Rate Map (FIRM)
10. Aquifer Protection Map
11. Offsite Analysis Map
Engineering Calculations
CONVEYANCE CALCULATIONS
FILTERRA SIZING (BY CONTECH)
Appendix B – Reports
1. Joint Aquatic Resources Permit Application (JARPA)
2. Hydrologic and Hydraulics Analysis – Memo by GeoEngineers (dated March 20, 2017)
3. Geotechnical Engineering Report, Southport Lake Washington Boulevard Improvements – Phase II &
III. Prepared by Geo Engineers, Inc.
4. Revised Report Addendum to “Geotechnical Engineering Services Report, Southport Development,
Lake Washington Boulevard Improvements, (dated May 8, 2018)
SECO Development
(425) 282-5833
1083 Lake Washington Blvd, Suite 50
Renton, WA 98056
Tim Brockway, P.E.
Coughlin Porter Lundeen
206-343-0460
LWB Improvemments - Final Phasefor Southport Development
23N
5E
8
LWB between Park Dr and
Coulon Park Entrance Road
05/15/18
x
05/15/18
x
x
x
x JARPA
x
x
x
Flow Control not required. Providing matching peak rates for 2/10/100 Yr Single Event storm.Enhanced Basic WQ required.
Green River Valley
Lake Washington East Drainage Basin
Monitoring, if required, will be per terms ofJARPA/NPDES permits
TBD/Unknown if req'd
x
x
See Section IV- Downstream Analysis
No work within/above OHWM until HPA/USCOE approval
See Section IV- Downstream Analysis
LWB Roadway Widening Site
per JARPA Report
1(John's Creek)
3 of 1.2.8.1(A)
N/A
TBD
TBD
TBD
Loose non-silty/silty sand
Medium stiff silt & clay
Medium stiff silt
0-40%
LWB widening. Culvert and retaining wallmodifications
Drive and bridge (culvert) elevations designedto pass 100-year peak safely
Contech WQ Filterras
Contech WQ filterras at each side of the culvert.
x Hilfiker Structural slope stability assembly.
x
x
x
x
x
x
x
x
x
x
x
x
x Contech Filterras
x
x
x
lLWB Improvements Phase III
SECO
05-15-2018ALC
TBB
Project Site
Figure 2 - Site LocationNTS
801 SECOND AVENUE, SUITE 900 SEATTLE WA 98104
6
Custom Soil Resource Report
Soil Map
52611305261160526119052612205261250526128052613105261130526116052611905261220526125052612805261310560080 560110 560140 560170 560200 560230 560260 560290 560320 560350 560380
560080 560110 560140 560170 560200 560230 560260 560290 560320 560350 560380
47° 30' 8'' N 122° 12' 8'' W47° 30' 8'' N122° 11' 53'' W47° 30' 2'' N
122° 12' 8'' W47° 30' 2'' N
122° 11' 53'' WN
Map projection: Web Mercator Corner coordinates: WGS84 Edge tics: UTM Zone 10N WGS84
0 50 100 200 300
Feet
0 20 40 80 120
Meters
Map Scale: 1:1,400 if printed on A landscape (11" x 8.5") sheet.
Soil Map may not be valid at this scale.
Figure 3: USDA Soil Map
MAP LEGEND MAP INFORMATION
Area of Interest (AOI)
Area of Interest (AOI)
Soils
Soil Map Unit Polygons
Soil Map Unit Lines
Soil Map Unit Points
Special Point Features
Blowout
Borrow Pit
Clay Spot
Closed Depression
Gravel Pit
Gravelly Spot
Landfill
Lava Flow
Marsh or swamp
Mine or Quarry
Miscellaneous Water
Perennial Water
Rock Outcrop
Saline Spot
Sandy Spot
Severely Eroded Spot
Sinkhole
Slide or Slip
Sodic Spot
Spoil Area
Stony Spot
Very Stony Spot
Wet Spot
Other
Special Line Features
Water Features
Streams and Canals
Transportation
Rails
Interstate Highways
US Routes
Major Roads
Local Roads
Background
Aerial Photography
The soil surveys that comprise your AOI were mapped at
1:24,000.
Warning: Soil Map may not be valid at this scale.
Enlargement of maps beyond the scale of mapping can cause
misunderstanding of the detail of mapping and accuracy of soil
line placement. The maps do not show the small areas of
contrasting soils that could have been shown at a more detailed
scale.
Please rely on the bar scale on each map sheet for map
measurements.
Source of Map: Natural Resources Conservation Service
Web Soil Survey URL:
Coordinate System: Web Mercator (EPSG:3857)
Maps from the Web Soil Survey are based on the Web Mercator
projection, which preserves direction and shape but distorts
distance and area. A projection that preserves area, such as the
Albers equal-area conic projection, should be used if more
accurate calculations of distance or area are required.
This product is generated from the USDA-NRCS certified data as
of the version date(s) listed below.
Soil Survey Area: King County Area, Washington
Survey Area Data: Version 13, Sep 7, 2017
Soil map units are labeled (as space allows) for map scales
1:50,000 or larger.
Date(s) aerial images were photographed: Aug 31, 2013—Oct 6,
2013
The orthophoto or other base map on which the soil lines were
compiled and digitized probably differs from the background
imagery displayed on these maps. As a result, some minor
shifting of map unit boundaries may be evident.
Custom Soil Resource Report
7
Map Unit Legend
Map Unit Symbol Map Unit Name Acres in AOI Percent of AOI
Ur Urban land 7.6 100.0%
Totals for Area of Interest 7.6 100.0%
Custom Soil Resource Report
8
801 SECOND AVENUE, SUITE 900 SEATTLE, WA 98104 / P 206.343.0460 / cplinc.com2014Lake Washington Blvd. Improvements - Phase III forSouthport DevelopmentC140194-12SECO Development6/22/2018ALCTBBScale 1" = 40'LEGENDNew Impervious (0.18 ac) = 7800SFTotal water quality catchment area = 8000SFFigure 4: Proposed Treatment Area SwapPARK AVENUE N10+0011+0012+0013+0014+0015+0010+5011+5012+5013+0013+5014+0014+5015+0015+50Total Catchment = 8,000 SF (0.18 AC)25.9 sf
4x6 Filterra #14x4 Filterra #2Untreated Area Inside Site(0.10 AC) (Area Swap)West Basin Treated Area inside Site (0.07 AC)West Basin = 0.14 ACInside site (green) = 0.07 ACOutside site (blue) = 0.07 ACEast basin(outside site) = 0.04 ACBasin BoundaryWest Basin Inside Site 0.07 AC(Green)0.10 ACUntreated area(Yellow)0.07 AC0.07 AC0.04 AC0.10 ACWest Basin Treated Area Outside Site (0.07 AC)East Basin Treated Area Outside Site (0.04 AC) (Area Swap)
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202nd
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Victoria
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UnnamedUnnamedU
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Kent
Tukwila
Newcastle
Seattle
Bellevue
King County
Mercer Island
King County
King County
SeaTac
King County
King County
King County
King County
Kent
Renton City Limits
Potential Annexation Area
Basins
Black River
Duamish
Lake Washington East
Lake Washington West
Lower Cedar River
May Creek
Soos Creek
´
Surface Water UtilityComprehensive PlanPrinted 10/16/2009
Basin Locations 0 10.5
Miles
Project Location -
Lake Washington East
Figure 5 - Drainage Basin Map
Point of Discharge
to Lake Washington
9,0281505
City of Renton Print map Template
This map is a user generated static output from an Internet mapping site and is for
reference only. Data layers that appear on this map may or may not be accurate,
current, or otherwise reliable.
WGS_1984_Web_Mercator_Auxiliary_Sphere
Notes
None
5/10/2018
Legend
1023 512
THIS MAP IS NOT TO BE USED FOR NAVIGATION
Feet1023
Information Technology - GIS
0
RentonMapSupport@Rentonwa.gov
City and County Boundary
Parcels
Erosion hazard - high
Floodway
Special Flood Hazard Areas (100
year flood)
Landslide
VERY HIGH
HIGH
MODERATE
UNCLASSIFED
Environment Designations
Natural
Shoreline High Intensity
Shoreline Isolated High Intensity
Shoreline Residential
Urban Conservancy
Jurisdictions
Streams (Classified)
Type S
Type F
Type Np
Type Ns
Wetlands
Lake Washington Boulevard
Project Site
Figure 5B- City of Renton
Sensitive Areas Map
PARK AVENUE N10+0011+0012+0013+0014+0015+0010+5011+5012+5013+0013+5014+0014+5015+0015+50801 SECOND AVENUE, SUITE 900 SEATTLE, WA 98104 / P 206.343.0460 / cplinc.com2014Lake Washington Blvd. Improvements - Final Phase forSouthport DevelopmentC140194-12SECO Development6/22/2018ALCTBBScale 1" = 40'Existing Pervious (0.40 ac)Existing Impervious (0.13 ac)LEGENDFigure 6: Existing ConditionsLimits ofDisturbance= 0.53 Ac
801 SECOND AVENUE, SUITE 900 SEATTLE, WA 98104 / P 206.343.0460 / cplinc.com2014Lake Washington Blvd. Improvements - Final Phase forSouthport DevelopmentC140194-12SECO Development6/22/2018ALCTBBScale 1" = 40'Existing Pervious (0.22 ac)LEGENDReplaced Impervious (0.13 ac)Figure 7: Proposed ConditionsPARK AVENUE N10+0011+0012+0013+0014+0015+0010+5011+5012+5013+0013+5014+0014+5015+0015+50Limits ofDisturbance= 0.53 AcNew Impervious (0.18 ac)7,800 SF
Configuration No. of Cartridges
LowDrop Flow
Capacity (cfs)
18" Flow
Capacity (cfs)
27" Flow
Capacity (cfs)
LowDrop Flow
Capacity (cfs)
18" Flow
Capacity (cfs)
27" Flow Capacity
(cfs)
48" MH/CB 3 0.033 0.050 0.075 0.056 0.084 0.126
60"MH/CB 4 0.045 0.067 0.100 0.074 0.112 0.167
72" MH 7 0.078 0.117 0.175 0.130 0.195 0.293
96" MH/ 8x6 Vault 11 0.122 0.184 0.276 0.205 0.307 0.460
96" MH/ 8x11 Vault 14 0.156 0.234 0.351 0.260 0.391 0.586
8x11 Vault 26 0.290 0.434 0.651 0.484 0.726 1.088
8x14 Vault 34 0.379 0.568 0.852 0.632 0.949 1.423
8x16 Vault 39 0.434 0.651 0.977 0.725 1.088 1.632
8x18 Vault 44 0.490 0.735 1.102 0.818 1.228 1.841
8x20 Vault 51 0.568 0.852 1.278 0.948 1.423 2.134
8x22 Vault 56 0.624 0.935 1.403 1.041 1.563 2.344
8x24 Vault 61 0.679 1.019 1.528 1.134 1.702 2.553
TSS/Phosphorous Oil/Grease Metals
70.92 in/hr 35.46 in/hr 24.82 in/hr
VANCOUVER Size Acres Treated Acres Treated Acres Treated
4x4 0.349 0.187 0.136
4x6 & 6x4 0.528 0.279 0.202
4x8 & 8x4 0.705 0.372 0.269
6x6 0.794 0.419 0.303
precip factor = 1.11 6x8 & 8x6 1.063 0.561 0.404
6x10 & 10x6 1.332 0.702 0.507
6x12 & 12x6 1.615 0.844 0.609
TACOMA Size Acres Treated Acres Treated Acres Treated
4x4 0.421 0.219 0.159
4x6 & 6x4 0.633 0.325 0.234
4x8 & 8x4 0.845 0.433 0.31
6x6 0.952 0.487 0.349
precip factor = 1 6x8 & 8x6 1.272 0.651 0.465
6x10 & 10x6 1.594 0.814 0.582
1901‐2059 (yr) 6x12 & 12x6 1.925 0.981 0.701
EVERETT Size Acres Treated Acres Treated Acres Treated
4x4 0.391 0.206 0.151
4x6 & 6x4 0.589 0.309 0.223
4x8 & 8x4 0.795 0.413 0.297
6x6 0.886 0.463 0.335
6x8 & 8x6 1.185 0.619 0.447
6x10 & 10x6 1.485 0.774 0.558
6x12 & 12x6 1.805 0.933 0.671
SEATTLE Size Acres Treated Acres Treated Acres Treated
4x4 0.384 0.203 0.148
4x6 & 6x4 0.578 0.303 0.219
4x8 & 8x4 0.771 0.403 0.29
6x6 0.871 0.454 0.327
6x8 & 8x6 1.165 0.607 0.437
6x10 & 10x6 1.461 0.76 0.547
6x12 & 12x6 1.787 0.914 0.657
Notes:
1. All treatment areas are based on 100% impervious contributing drainage area.
2. Filterra size assumes offline configuration and 21" of media
3. For sizing in other areas, contact your Contech Engineered Solutions Stormwater Design Engineer.
4. General Guidelines Only. Each site is unique and requires sizing per the DOE GULD Approval.
Seatac rain gauge
StormFilter Max Water Quality Flow Capacities
Vancouver NNE
rain gauge
38 in CENTRAL
rain gauge
Hydraulic Conductivity:
Everett rain gage
Basic (1gpm/sqft) Phosphorus (1.67gpm/sqft)
Filterra Sizing Based on the Western Washington Hydrology Model (WWHM)
Metals removal was usedto estimate EnhancedBasic Treatment
Seatac rain gauge is theclosest to the project site
Either (2) 4x4 or (1) 4x8provides requiredtreatment capacity
Figure 7B: Filterra SizingNote: See Filterra Calculations for
detailed Calculations/ Sizing from
Contech
LakeDesire
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LakeWashington
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,§-405
,§-405
µ0 1 2Miles
Flow Control Application Map
Reference 11-A
Date: 01/09/2014
Flow Control Standards
Peak Rate Flow Control Standard (Existing Site Conditions)
Flow Control Duration Standard (Existing Site Conditions)
Flow Control Duration Standard (Forested Conditions)
Flood Problem Flow
Unincorporated King County Flow Control Standards
Renton City Limits
Potential Annexation Area
PROJECT SITE
Figure 8 - Flow Control Application Map
Lake Washington Boulevard Project SiteFigure 9 - FEMA Flood Insurance Rate Map(FIRM)
Figure 10 - Aquifer Protection
Map
Lake Washington Boulevard
Project Site
Upstream Stormwater
Pipe routing
Downstream routing
Figure 11 - Offsite Analysis Map
Lake Washington
Boulevard
Project Site
Note: This map to be
used in conjunction
with JARPA and
Hydrology/Hydraulic
s Analysis Memo in
Appendix B
Engineering Calculations
CONVEYANCE CALCULATIONS
FILTERRA SIZING (BY CONTECH)
Lake Washington Blvd. Improvements - Phase III forSouthport DevelopmentC140624-01 SECO
05/13/18ALC
TBb
Conveyance Calculations - West Basin
From 2017 RSWDM:
aR = 2.61
bR = 0.63
Tc = 6.3
n = 0.012
C Factor = 0.90
P = 3.9 in
From Applicable Equations:
iR = aR x (Tc)(-br)
I = P x iR
CC = ∑(CxA)/Atotal
Q100 = CC x I x A
Qcapacity = (1.49 x A x R2/3 x S1/2)/n
Given: See Figure 4 and plan for areas and pipe dimensions and slopes
Tributary Area (Ac) = 0.14
Pipe Diameter (in) = 12
Pipe Area (SF) = 0.7854
Slope = 14.4 % (from Fillterra) and 12.5% (outfall)
100 Year Flow: Calculated using Manning's equation
iR = aR x (Tc)(-br) = (2.61) x (6.3)(-0.63) = 0.82
I = P x iR = (2) x (0.82) = 3.19 in/hr
Q100 = C x I x A = (0.9) x (3.19) x (0.14) = 0.40 cfs
Pipe Capacity:
Qcapacity = [(1.49 x A x R2/3 x S1/2)/n =1.49 x (0.7854) x (0.252/3) x (0.011/2)]/ 0.012 = 3.87 cfs
Flow Ratio:
Q100/Qcapacity = (0.40) / (3.87) = 0.10
The flow ratio is less than one indicating that the system is adequately designed
Qcapacity = [(1.49 x A x R2/3 x S1/2)/n =1.49 x (0.7854) x (0.252/3) x (0.01251/2)]/ 0.012 = 4.33 cfs
2014801 SECOND AVENUE, SUITE 900 SEATTLE, WA 98104 / P 206.343.0460 / cplinc.com
Lake Washington Blvd. Improvements - Phase III forSouthport DevelopmentC140624-01 Seco
05/13/18ALC
TBB
Conveyance Calculations - East Basin
From 2017 RSWDM:
aR = 2.61
bR = 0.63
Tc = 6.3
n = 0.012
C Factor = 0.90
P = 3.9 in
From Applicable Equations:
iR = aR x (Tc)(-br)
I = P x iR
CC = ∑(CxA)/Atotal
Q100 = CC x I x A
Qcapacity = (1.49 x A x R2/3 x S1/2)/n
Given: See Figure 4 and plan for areas and pipe dimensions and slopes
Tributary Area (Ac) = 0.04
Pipe Diameter (in) = 12
Pipe Area (SF) = 0.7854
Slope = 10.0 % (from Filterra) and 12.5% (outfall)
100 Year Flow: Calculated using Manning's equation
iR = aR x (Tc)(-br) = (2.61) x (6.3)(-0.63) = 0.82
I = P x iR = (2) x (0.82) = 3.19 in/hr
Q100 = C x I x A = (0.9) x (3.19) x (0.04) = 0.11 cfs
Pipe Capacity:
Qcapacity = [(1.49 x A x R2/3 x S1/2)/n =1.49 x (0.7854) x (0.252/3) x (0.011/2)]/ 0.012 = 3.87 cfs
Flow Ratio:
Q100/Qcapacity = (0.11) / (3.87) = 0.028
The flow ratio is less than one indicating that the system is adequately designed
Qcapacity = [(1.49 x A x R2/3 x S1/2)/n =1.49 x (0.7854) x (0.252/3) x (0.01251/2)]/ 0.012 = 4.33 cfs
2014801 SECOND AVENUE, SUITE 900 SEATTLE, WA 98104 / P 206.343.0460 / cplinc.com
WWHM2012
PROJECT REPORT
default[13]5/14/2018 3:54:01 PM Page 2
General Model Information
Project Name:default[13]
Site Name:
Site Address:
City:
Report Date:5/14/2018
Gage:Seatac
Data Start:1948/10/01
Data End:2009/09/30
Timestep:15 Minute
Precip Scale:1.00
Version Date:2016/02/25
Version:4.2.12
POC Thresholds
Low Flow Threshold for POC1:50 Percent of the 2 Year
High Flow Threshold for POC1:50 Year
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Landuse Basin Data
Predeveloped Land Use
default[13]5/14/2018 3:54:01 PM Page 4
Mitigated Land Use
Basin 1
Bypass:No
GroundWater:No
Pervious Land Use acre
Pervious Total 0
Impervious Land Use acre
ROADS MOD 0.14
Impervious Total 0.14
Basin Total 0.14
Element Flows To:
Surface Interflow Groundwater
Sand Filter 1 Sand Filter 1
default[13]5/14/2018 3:54:01 PM Page 5
Routing Elements
Predeveloped Routing
default[13]5/14/2018 3:54:01 PM Page 6
Mitigated Routing
Sand Filter 1
Bottom Length:4.00 ft.
Bottom Width:6.00 ft.
Depth:0.75 ft.
Side slope 1:0 To 1
Side slope 2:0 To 1
Side slope 3:0 To 1
Side slope 4:0 To 1
Filtration On
Hydraulic conductivity:24.82
Depth of filter medium:1.8
Total Volume Infiltrated (ac-ft.):20.694
Total Volume Through Riser (ac-ft.):0.885
Total Volume Through Facility (ac-ft.):21.579
Percent Infiltrated:95.9
Total Precip Applied to Facility:0
Total Evap From Facility:0
Discharge Structure
Riser Height:0.7 ft.
Riser Diameter:100 in.
Element Flows To:
Outlet 1 Outlet 2
Sand Filter Hydraulic Table
Stage(feet)Area(ac.)Volume(ac-ft.)Discharge(cfs)Infilt(cfs)
0.0000 0.000 0.000 0.000 0.000
0.0083 0.000 0.000 0.000 0.013
0.0167 0.000 0.000 0.000 0.013
0.0250 0.000 0.000 0.000 0.014
0.0333 0.000 0.000 0.000 0.014
0.0417 0.000 0.000 0.000 0.014
0.0500 0.000 0.000 0.000 0.014
0.0583 0.000 0.000 0.000 0.014
0.0667 0.000 0.000 0.000 0.014
0.0750 0.000 0.000 0.000 0.014
0.0833 0.000 0.000 0.000 0.014
0.0917 0.000 0.000 0.000 0.014
0.1000 0.000 0.000 0.000 0.014
0.1083 0.000 0.000 0.000 0.014
0.1167 0.000 0.000 0.000 0.014
0.1250 0.000 0.000 0.000 0.014
0.1333 0.000 0.000 0.000 0.014
0.1417 0.000 0.000 0.000 0.014
0.1500 0.000 0.000 0.000 0.014
0.1583 0.000 0.000 0.000 0.015
0.1667 0.000 0.000 0.000 0.015
0.1750 0.000 0.000 0.000 0.015
0.1833 0.000 0.000 0.000 0.015
0.1917 0.000 0.000 0.000 0.015
0.2000 0.000 0.000 0.000 0.015
0.2083 0.000 0.000 0.000 0.015
0.2167 0.000 0.000 0.000 0.015
0.2250 0.000 0.000 0.000 0.015
default[13]5/14/2018 3:54:01 PM Page 7
0.2333 0.000 0.000 0.000 0.015
0.2417 0.000 0.000 0.000 0.015
0.2500 0.000 0.000 0.000 0.015
0.2583 0.000 0.000 0.000 0.015
0.2667 0.000 0.000 0.000 0.015
0.2750 0.000 0.000 0.000 0.015
0.2833 0.000 0.000 0.000 0.016
0.2917 0.000 0.000 0.000 0.016
0.3000 0.000 0.000 0.000 0.016
0.3083 0.000 0.000 0.000 0.016
0.3167 0.000 0.000 0.000 0.016
0.3250 0.000 0.000 0.000 0.016
0.3333 0.000 0.000 0.000 0.016
0.3417 0.000 0.000 0.000 0.016
0.3500 0.000 0.000 0.000 0.016
0.3583 0.000 0.000 0.000 0.016
0.3667 0.000 0.000 0.000 0.016
0.3750 0.000 0.000 0.000 0.016
0.3833 0.000 0.000 0.000 0.016
0.3917 0.000 0.000 0.000 0.016
0.4000 0.000 0.000 0.000 0.016
0.4083 0.000 0.000 0.000 0.016
0.4167 0.000 0.000 0.000 0.017
0.4250 0.000 0.000 0.000 0.017
0.4333 0.000 0.000 0.000 0.017
0.4417 0.000 0.000 0.000 0.017
0.4500 0.000 0.000 0.000 0.017
0.4583 0.000 0.000 0.000 0.017
0.4667 0.000 0.000 0.000 0.017
0.4750 0.000 0.000 0.000 0.017
0.4833 0.000 0.000 0.000 0.017
0.4917 0.000 0.000 0.000 0.017
0.5000 0.000 0.000 0.000 0.017
0.5083 0.000 0.000 0.000 0.017
0.5167 0.000 0.000 0.000 0.017
0.5250 0.000 0.000 0.000 0.017
0.5333 0.000 0.000 0.000 0.017
0.5417 0.000 0.000 0.000 0.017
0.5500 0.000 0.000 0.000 0.018
0.5583 0.000 0.000 0.000 0.018
0.5667 0.000 0.000 0.000 0.018
0.5750 0.000 0.000 0.000 0.018
0.5833 0.000 0.000 0.000 0.018
0.5917 0.000 0.000 0.000 0.018
0.6000 0.000 0.000 0.000 0.018
0.6083 0.000 0.000 0.000 0.018
0.6167 0.000 0.000 0.000 0.018
0.6250 0.000 0.000 0.000 0.018
0.6333 0.000 0.000 0.000 0.018
0.6417 0.000 0.000 0.000 0.018
0.6500 0.000 0.000 0.000 0.018
0.6583 0.000 0.000 0.000 0.018
0.6667 0.000 0.000 0.000 0.018
0.6750 0.000 0.000 0.000 0.019
0.6833 0.000 0.000 0.000 0.019
0.6917 0.000 0.000 0.000 0.019
0.7000 0.000 0.000 0.000 0.019
0.7083 0.000 0.000 0.067 0.019
default[13]5/14/2018 3:54:01 PM Page 8
0.7167 0.000 0.000 0.190 0.019
0.7250 0.000 0.000 0.349 0.019
0.7333 0.000 0.000 0.538 0.019
0.7417 0.000 0.000 0.752 0.019
0.7500 0.000 0.000 0.989 0.019
0.7583 0.000 0.000 1.246 0.019
default[13]5/14/2018 3:54:01 PM Page 9
Analysis Results
POC 1
POC #1 was not reported because POC must exist in both scenarios and both scenarios
must have been run.
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Model Default Modifications
Total of 0 changes have been made.
PERLND Changes
No PERLND changes have been made.
IMPLND Changes
No IMPLND changes have been made.
default[13]5/14/2018 3:54:01 PM Page 11
Appendix
Predeveloped Schematic
default[13]5/14/2018 3:54:02 PM Page 12
Mitigated Schematic
default[13]5/14/2018 3:54:02 PM Page 13
Predeveloped UCI File
default[13]5/14/2018 3:54:02 PM Page 14
Mitigated UCI File
RUN
GLOBAL
WWHM4 model simulation
START 1948 10 01 END 2009 09 30
RUN INTERP OUTPUT LEVEL 3 0
RESUME 0 RUN 1 UNIT SYSTEM 1
END GLOBAL
FILES
<File> <Un#> <-----------File Name------------------------------>***
<-ID-> ***
WDM 26 default[13].wdm
MESSU 25 Mitdefault[13].MES
27 Mitdefault[13].L61
28 Mitdefault[13].L62
30 POCdefault[13]1.dat
END FILES
OPN SEQUENCE
INGRP INDELT 00:15
IMPLND 2
RCHRES 1
COPY 1
COPY 501
DISPLY 1
END INGRP
END OPN SEQUENCE
DISPLY
DISPLY-INFO1
# - #<----------Title----------->***TRAN PIVL DIG1 FIL1 PYR DIG2 FIL2 YRND
1 Sand Filter 1 MAX 1 2 30 9
END DISPLY-INFO1
END DISPLY
COPY
TIMESERIES
# - # NPT NMN ***
1 1 1
501 1 1
END TIMESERIES
END COPY
GENER
OPCODE
# # OPCD ***
END OPCODE
PARM
# # K ***
END PARM
END GENER
PERLND
GEN-INFO
<PLS ><-------Name------->NBLKS Unit-systems Printer ***
# - # User t-series Engl Metr ***
in out ***
END GEN-INFO
*** Section PWATER***
ACTIVITY
<PLS > ************* Active Sections *****************************
# - # ATMP SNOW PWAT SED PST PWG PQAL MSTL PEST NITR PHOS TRAC ***
END ACTIVITY
PRINT-INFO
<PLS > ***************** Print-flags ***************************** PIVL PYR
# - # ATMP SNOW PWAT SED PST PWG PQAL MSTL PEST NITR PHOS TRAC *********
END PRINT-INFO
PWAT-PARM1
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<PLS > PWATER variable monthly parameter value flags ***
# - # CSNO RTOP UZFG VCS VUZ VNN VIFW VIRC VLE INFC HWT ***
END PWAT-PARM1
PWAT-PARM2
<PLS > PWATER input info: Part 2 ***
# - # ***FOREST LZSN INFILT LSUR SLSUR KVARY AGWRC
END PWAT-PARM2
PWAT-PARM3
<PLS > PWATER input info: Part 3 ***
# - # ***PETMAX PETMIN INFEXP INFILD DEEPFR BASETP AGWETP
END PWAT-PARM3
PWAT-PARM4
<PLS > PWATER input info: Part 4 ***
# - # CEPSC UZSN NSUR INTFW IRC LZETP ***
END PWAT-PARM4
PWAT-STATE1
<PLS > *** Initial conditions at start of simulation
ran from 1990 to end of 1992 (pat 1-11-95) RUN 21 ***
# - # *** CEPS SURS UZS IFWS LZS AGWS GWVS
END PWAT-STATE1
END PERLND
IMPLND
GEN-INFO
<PLS ><-------Name-------> Unit-systems Printer ***
# - # User t-series Engl Metr ***
in out ***
2 ROADS/MOD 1 1 1 27 0
END GEN-INFO
*** Section IWATER***
ACTIVITY
<PLS > ************* Active Sections *****************************
# - # ATMP SNOW IWAT SLD IWG IQAL ***
2 0 0 1 0 0 0
END ACTIVITY
PRINT-INFO
<ILS > ******** Print-flags ******** PIVL PYR
# - # ATMP SNOW IWAT SLD IWG IQAL *********
2 0 0 4 0 0 0 1 9
END PRINT-INFO
IWAT-PARM1
<PLS > IWATER variable monthly parameter value flags ***
# - # CSNO RTOP VRS VNN RTLI ***
2 0 0 0 0 0
END IWAT-PARM1
IWAT-PARM2
<PLS > IWATER input info: Part 2 ***
# - # *** LSUR SLSUR NSUR RETSC
2 400 0.05 0.1 0.08
END IWAT-PARM2
IWAT-PARM3
<PLS > IWATER input info: Part 3 ***
# - # ***PETMAX PETMIN
2 0 0
END IWAT-PARM3
IWAT-STATE1
<PLS > *** Initial conditions at start of simulation
# - # *** RETS SURS
2 0 0
END IWAT-STATE1
default[13]5/14/2018 3:54:02 PM Page 16
END IMPLND
SCHEMATIC
<-Source-> <--Area--> <-Target-> MBLK ***
<Name> # <-factor-> <Name> # Tbl# ***
Basin 1***
IMPLND 2 0.14 RCHRES 1 5
******Routing******
IMPLND 2 0.14 COPY 1 15
RCHRES 1 1 COPY 501 16
END SCHEMATIC
NETWORK
<-Volume-> <-Grp> <-Member-><--Mult-->Tran <-Target vols> <-Grp> <-Member-> ***
<Name> # <Name> # #<-factor->strg <Name> # # <Name> # # ***
COPY 501 OUTPUT MEAN 1 1 48.4 DISPLY 1 INPUT TIMSER 1
<-Volume-> <-Grp> <-Member-><--Mult-->Tran <-Target vols> <-Grp> <-Member-> ***
<Name> # <Name> # #<-factor->strg <Name> # # <Name> # # ***
END NETWORK
RCHRES
GEN-INFO
RCHRES Name Nexits Unit Systems Printer ***
# - #<------------------><---> User T-series Engl Metr LKFG ***
in out ***
1 Sand Filter 1 2 1 1 1 28 0 1
END GEN-INFO
*** Section RCHRES***
ACTIVITY
<PLS > ************* Active Sections *****************************
# - # HYFG ADFG CNFG HTFG SDFG GQFG OXFG NUFG PKFG PHFG ***
1 1 0 0 0 0 0 0 0 0 0
END ACTIVITY
PRINT-INFO
<PLS > ***************** Print-flags ******************* PIVL PYR
# - # HYDR ADCA CONS HEAT SED GQL OXRX NUTR PLNK PHCB PIVL PYR *********
1 4 0 0 0 0 0 0 0 0 0 1 9
END PRINT-INFO
HYDR-PARM1
RCHRES Flags for each HYDR Section ***
# - # VC A1 A2 A3 ODFVFG for each *** ODGTFG for each FUNCT for each
FG FG FG FG possible exit *** possible exit possible exit
* * * * * * * * * * * * * * ***
1 0 1 0 0 4 5 0 0 0 0 0 0 0 0 2 2 2 2 2
END HYDR-PARM1
HYDR-PARM2
# - # FTABNO LEN DELTH STCOR KS DB50 ***
<------><--------><--------><--------><--------><--------><--------> ***
1 1 0.01 0.0 0.0 0.5 0.0
END HYDR-PARM2
HYDR-INIT
RCHRES Initial conditions for each HYDR section ***
# - # *** VOL Initial value of COLIND Initial value of OUTDGT
*** ac-ft for each possible exit for each possible exit
<------><--------> <---><---><---><---><---> *** <---><---><---><---><--->
1 0 4.0 5.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0
END HYDR-INIT
END RCHRES
SPEC-ACTIONS
END SPEC-ACTIONS
default[13]5/14/2018 3:54:02 PM Page 17
FTABLES
FTABLE 1
91 5
Depth Area Volume Outflow1 Outflow2 Velocity Travel Time***
(ft) (acres) (acre-ft) (cfs) (cfs) (ft/sec) (Minutes)***
0.000000 0.000551 0.000000 0.000000 0.000000
0.008333 0.000551 0.000005 0.000000 0.013853
0.016667 0.000551 0.000009 0.000000 0.013917
0.025000 0.000551 0.000014 0.000000 0.013980
0.033333 0.000551 0.000018 0.000000 0.014044
0.041667 0.000551 0.000023 0.000000 0.014108
0.050000 0.000551 0.000028 0.000000 0.014172
0.058333 0.000551 0.000032 0.000000 0.014236
0.066667 0.000551 0.000037 0.000000 0.014300
0.075000 0.000551 0.000041 0.000000 0.014363
0.083333 0.000551 0.000046 0.000000 0.014427
0.091667 0.000551 0.000051 0.000000 0.014491
0.100000 0.000551 0.000055 0.000000 0.014555
0.108333 0.000551 0.000060 0.000000 0.014619
0.116667 0.000551 0.000064 0.000000 0.014683
0.125000 0.000551 0.000069 0.000000 0.014746
0.133333 0.000551 0.000073 0.000000 0.014810
0.141667 0.000551 0.000078 0.000000 0.014874
0.150000 0.000551 0.000083 0.000000 0.014938
0.158333 0.000551 0.000087 0.000000 0.015002
0.166667 0.000551 0.000092 0.000000 0.015066
0.175000 0.000551 0.000096 0.000000 0.015129
0.183333 0.000551 0.000101 0.000000 0.015193
0.191667 0.000551 0.000106 0.000000 0.015257
0.200000 0.000551 0.000110 0.000000 0.015321
0.208333 0.000551 0.000115 0.000000 0.015385
0.216667 0.000551 0.000119 0.000000 0.015449
0.225000 0.000551 0.000124 0.000000 0.015513
0.233333 0.000551 0.000129 0.000000 0.015576
0.241667 0.000551 0.000133 0.000000 0.015640
0.250000 0.000551 0.000138 0.000000 0.015704
0.258333 0.000551 0.000142 0.000000 0.015768
0.266667 0.000551 0.000147 0.000000 0.015832
0.275000 0.000551 0.000152 0.000000 0.015896
0.283333 0.000551 0.000156 0.000000 0.015959
0.291667 0.000551 0.000161 0.000000 0.016023
0.300000 0.000551 0.000165 0.000000 0.016087
0.308333 0.000551 0.000170 0.000000 0.016151
0.316667 0.000551 0.000174 0.000000 0.016215
0.325000 0.000551 0.000179 0.000000 0.016279
0.333333 0.000551 0.000184 0.000000 0.016342
0.341667 0.000551 0.000188 0.000000 0.016406
0.350000 0.000551 0.000193 0.000000 0.016470
0.358333 0.000551 0.000197 0.000000 0.016534
0.366667 0.000551 0.000202 0.000000 0.016598
0.375000 0.000551 0.000207 0.000000 0.016662
0.383333 0.000551 0.000211 0.000000 0.016725
0.391667 0.000551 0.000216 0.000000 0.016789
0.400000 0.000551 0.000220 0.000000 0.016853
0.408333 0.000551 0.000225 0.000000 0.016917
0.416667 0.000551 0.000230 0.000000 0.016981
0.425000 0.000551 0.000234 0.000000 0.017045
0.433333 0.000551 0.000239 0.000000 0.017108
0.441667 0.000551 0.000243 0.000000 0.017172
0.450000 0.000551 0.000248 0.000000 0.017236
0.458333 0.000551 0.000253 0.000000 0.017300
0.466667 0.000551 0.000257 0.000000 0.017364
0.475000 0.000551 0.000262 0.000000 0.017428
0.483333 0.000551 0.000266 0.000000 0.017491
0.491667 0.000551 0.000271 0.000000 0.017555
0.500000 0.000551 0.000275 0.000000 0.017619
0.508333 0.000551 0.000280 0.000000 0.017683
0.516667 0.000551 0.000285 0.000000 0.017747
0.525000 0.000551 0.000289 0.000000 0.017811
0.533333 0.000551 0.000294 0.000000 0.017874
default[13]5/14/2018 3:54:02 PM Page 18
0.541667 0.000551 0.000298 0.000000 0.017938
0.550000 0.000551 0.000303 0.000000 0.018002
0.558333 0.000551 0.000308 0.000000 0.018066
0.566667 0.000551 0.000312 0.000000 0.018130
0.575000 0.000551 0.000317 0.000000 0.018194
0.583333 0.000551 0.000321 0.000000 0.018258
0.591667 0.000551 0.000326 0.000000 0.018321
0.600000 0.000551 0.000331 0.000000 0.018385
0.608333 0.000551 0.000335 0.000000 0.018449
0.616667 0.000551 0.000340 0.000000 0.018513
0.625000 0.000551 0.000344 0.000000 0.018577
0.633333 0.000551 0.000349 0.000000 0.018641
0.641667 0.000551 0.000354 0.000000 0.018704
0.650000 0.000551 0.000358 0.000000 0.018768
0.658333 0.000551 0.000363 0.000000 0.018832
0.666667 0.000551 0.000367 0.000000 0.018896
0.675000 0.000551 0.000372 0.000000 0.018960
0.683333 0.000551 0.000376 0.000000 0.019024
0.691667 0.000551 0.000381 0.000000 0.019087
0.700000 0.000551 0.000386 0.000000 0.019151
0.708333 0.000551 0.000390 0.067333 0.019215
0.716667 0.000551 0.000395 0.190433 0.019279
0.725000 0.000551 0.000399 0.349825 0.019343
0.733333 0.000551 0.000404 0.538557 0.019407
0.741667 0.000551 0.000409 0.752610 0.019470
0.750000 0.000551 0.000413 0.989273 0.019534
END FTABLE 1
END FTABLES
EXT SOURCES
<-Volume-> <Member> SsysSgap<--Mult-->Tran <-Target vols> <-Grp> <-Member-> ***
<Name> # <Name> # tem strg<-factor->strg <Name> # # <Name> # # ***
WDM 2 PREC ENGL 1 PERLND 1 999 EXTNL PREC
WDM 2 PREC ENGL 1 IMPLND 1 999 EXTNL PREC
WDM 1 EVAP ENGL 0.76 PERLND 1 999 EXTNL PETINP
WDM 1 EVAP ENGL 0.76 IMPLND 1 999 EXTNL PETINP
END EXT SOURCES
EXT TARGETS
<-Volume-> <-Grp> <-Member-><--Mult-->Tran <-Volume-> <Member> Tsys Tgap Amd ***
<Name> # <Name> # #<-factor->strg <Name> # <Name> tem strg strg***
RCHRES 1 HYDR RO 1 1 1 WDM 1000 FLOW ENGL REPL
RCHRES 1 HYDR O 1 1 1 WDM 1001 FLOW ENGL REPL
RCHRES 1 HYDR O 2 1 1 WDM 1002 FLOW ENGL REPL
RCHRES 1 HYDR STAGE 1 1 1 WDM 1003 STAG ENGL REPL
COPY 1 OUTPUT MEAN 1 1 48.4 WDM 701 FLOW ENGL REPL
COPY 501 OUTPUT MEAN 1 1 48.4 WDM 801 FLOW ENGL REPL
END EXT TARGETS
MASS-LINK
<Volume> <-Grp> <-Member-><--Mult--> <Target> <-Grp> <-Member->***
<Name> <Name> # #<-factor-> <Name> <Name> # #***
MASS-LINK 5
IMPLND IWATER SURO 0.083333 RCHRES INFLOW IVOL
END MASS-LINK 5
MASS-LINK 15
IMPLND IWATER SURO 0.083333 COPY INPUT MEAN
END MASS-LINK 15
MASS-LINK 16
RCHRES ROFLOW COPY INPUT MEAN
END MASS-LINK 16
END MASS-LINK
END RUN
default[13]5/14/2018 3:54:02 PM Page 19
Predeveloped HSPF Message File
default[13]5/14/2018 3:54:02 PM Page 20
Mitigated HSPF Message File
default[13]5/14/2018 3:54:02 PM Page 21
Disclaimer
Legal Notice
This program and accompanying documentation is provided 'as-is' without warranty of any kind. The
entire risk regarding the performance and results of this program is assumed by the user. Clear Creek
Solutions, Inc. disclaims all warranties, either expressed or implied, including but not limited to
implied warranties of program and accompanying documentation. In no event shall Clear Creek
Solutions, Inc. be liable for any damages whatsoever (including without limitation to damages for
loss of business profits, loss of business information, business interruption, and the like) arising
out of the use of, or inability to use this program even if Clear Creek Solutions, Inc. has been
advised of the possibility of such damages.
Clear Creek Solutions, Inc.
6200 Capitol Blvd. Ste F
Olympia, WA. 98501
Toll Free 1(866)943-0304
Local (360)943-0304
www.clearcreeksolutions.com
WWHM2012
PROJECT REPORT
default[13]5/14/2018 3:49:21 PM Page 2
General Model Information
Project Name:default[13]
Site Name:
Site Address:
City:
Report Date:5/14/2018
Gage:Seatac
Data Start:1948/10/01
Data End:2009/09/30
Timestep:15 Minute
Precip Scale:1.00
Version Date:2016/02/25
Version:4.2.12
POC Thresholds
Low Flow Threshold for POC1:50 Percent of the 2 Year
High Flow Threshold for POC1:50 Year
default[13]5/14/2018 3:49:21 PM Page 3
Landuse Basin Data
Predeveloped Land Use
default[13]5/14/2018 3:49:21 PM Page 4
Mitigated Land Use
Basin 1
Bypass:No
GroundWater:No
Pervious Land Use acre
Pervious Total 0
Impervious Land Use acre
ROADS MOD 0.04
Impervious Total 0.04
Basin Total 0.04
Element Flows To:
Surface Interflow Groundwater
Sand Filter 1 Sand Filter 1
default[13]5/14/2018 3:49:21 PM Page 5
Routing Elements
Predeveloped Routing
default[13]5/14/2018 3:49:21 PM Page 6
Mitigated Routing
Sand Filter 1
Bottom Length:4.00 ft.
Bottom Width:4.00 ft.
Depth:0.75 ft.
Side slope 1:0 To 1
Side slope 2:0 To 1
Side slope 3:0 To 1
Side slope 4:0 To 1
Filtration On
Hydraulic conductivity:24.82
Depth of filter medium:1.8
Total Volume Infiltrated (ac-ft.):5.472
Total Volume Through Riser (ac-ft.):0.015
Total Volume Through Facility (ac-ft.):5.487
Percent Infiltrated:99.73
Total Precip Applied to Facility:0
Total Evap From Facility:0
Discharge Structure
Riser Height:0.7 ft.
Riser Diameter:100 in.
Element Flows To:
Outlet 1 Outlet 2
Sand Filter Hydraulic Table
Stage(feet)Area(ac.)Volume(ac-ft.)Discharge(cfs)Infilt(cfs)
0.0000 0.000 0.000 0.000 0.000
0.0083 0.000 0.000 0.000 0.009
0.0167 0.000 0.000 0.000 0.009
0.0250 0.000 0.000 0.000 0.009
0.0333 0.000 0.000 0.000 0.009
0.0417 0.000 0.000 0.000 0.009
0.0500 0.000 0.000 0.000 0.009
0.0583 0.000 0.000 0.000 0.009
0.0667 0.000 0.000 0.000 0.009
0.0750 0.000 0.000 0.000 0.009
0.0833 0.000 0.000 0.000 0.009
0.0917 0.000 0.000 0.000 0.009
0.1000 0.000 0.000 0.000 0.009
0.1083 0.000 0.000 0.000 0.009
0.1167 0.000 0.000 0.000 0.009
0.1250 0.000 0.000 0.000 0.009
0.1333 0.000 0.000 0.000 0.009
0.1417 0.000 0.000 0.000 0.009
0.1500 0.000 0.000 0.000 0.010
0.1583 0.000 0.000 0.000 0.010
0.1667 0.000 0.000 0.000 0.010
0.1750 0.000 0.000 0.000 0.010
0.1833 0.000 0.000 0.000 0.010
0.1917 0.000 0.000 0.000 0.010
0.2000 0.000 0.000 0.000 0.010
0.2083 0.000 0.000 0.000 0.010
0.2167 0.000 0.000 0.000 0.010
0.2250 0.000 0.000 0.000 0.010
default[13]5/14/2018 3:49:21 PM Page 7
0.2333 0.000 0.000 0.000 0.010
0.2417 0.000 0.000 0.000 0.010
0.2500 0.000 0.000 0.000 0.010
0.2583 0.000 0.000 0.000 0.010
0.2667 0.000 0.000 0.000 0.010
0.2750 0.000 0.000 0.000 0.010
0.2833 0.000 0.000 0.000 0.010
0.2917 0.000 0.000 0.000 0.010
0.3000 0.000 0.000 0.000 0.010
0.3083 0.000 0.000 0.000 0.010
0.3167 0.000 0.000 0.000 0.010
0.3250 0.000 0.000 0.000 0.010
0.3333 0.000 0.000 0.000 0.010
0.3417 0.000 0.000 0.000 0.010
0.3500 0.000 0.000 0.000 0.011
0.3583 0.000 0.000 0.000 0.011
0.3667 0.000 0.000 0.000 0.011
0.3750 0.000 0.000 0.000 0.011
0.3833 0.000 0.000 0.000 0.011
0.3917 0.000 0.000 0.000 0.011
0.4000 0.000 0.000 0.000 0.011
0.4083 0.000 0.000 0.000 0.011
0.4167 0.000 0.000 0.000 0.011
0.4250 0.000 0.000 0.000 0.011
0.4333 0.000 0.000 0.000 0.011
0.4417 0.000 0.000 0.000 0.011
0.4500 0.000 0.000 0.000 0.011
0.4583 0.000 0.000 0.000 0.011
0.4667 0.000 0.000 0.000 0.011
0.4750 0.000 0.000 0.000 0.011
0.4833 0.000 0.000 0.000 0.011
0.4917 0.000 0.000 0.000 0.011
0.5000 0.000 0.000 0.000 0.011
0.5083 0.000 0.000 0.000 0.011
0.5167 0.000 0.000 0.000 0.011
0.5250 0.000 0.000 0.000 0.011
0.5333 0.000 0.000 0.000 0.011
0.5417 0.000 0.000 0.000 0.012
0.5500 0.000 0.000 0.000 0.012
0.5583 0.000 0.000 0.000 0.012
0.5667 0.000 0.000 0.000 0.012
0.5750 0.000 0.000 0.000 0.012
0.5833 0.000 0.000 0.000 0.012
0.5917 0.000 0.000 0.000 0.012
0.6000 0.000 0.000 0.000 0.012
0.6083 0.000 0.000 0.000 0.012
0.6167 0.000 0.000 0.000 0.012
0.6250 0.000 0.000 0.000 0.012
0.6333 0.000 0.000 0.000 0.012
0.6417 0.000 0.000 0.000 0.012
0.6500 0.000 0.000 0.000 0.012
0.6583 0.000 0.000 0.000 0.012
0.6667 0.000 0.000 0.000 0.012
0.6750 0.000 0.000 0.000 0.012
0.6833 0.000 0.000 0.000 0.012
0.6917 0.000 0.000 0.000 0.012
0.7000 0.000 0.000 0.000 0.012
0.7083 0.000 0.000 0.067 0.012
default[13]5/14/2018 3:49:21 PM Page 8
0.7167 0.000 0.000 0.190 0.012
0.7250 0.000 0.000 0.349 0.012
0.7333 0.000 0.000 0.538 0.012
0.7417 0.000 0.000 0.752 0.013
0.7500 0.000 0.000 0.989 0.013
0.7583 0.000 0.000 1.246 0.013
default[13]5/14/2018 3:49:21 PM Page 9
Analysis Results
POC 1
POC #1 was not reported because POC must exist in both scenarios and both scenarios
must have been run.
default[13]5/14/2018 3:49:21 PM Page 10
Model Default Modifications
Total of 0 changes have been made.
PERLND Changes
No PERLND changes have been made.
IMPLND Changes
No IMPLND changes have been made.
default[13]5/14/2018 3:49:21 PM Page 11
Appendix
Predeveloped Schematic
default[13]5/14/2018 3:49:21 PM Page 12
Mitigated Schematic
default[13]5/14/2018 3:49:21 PM Page 13
Predeveloped UCI File
default[13]5/14/2018 3:49:21 PM Page 14
Mitigated UCI File
RUN
GLOBAL
WWHM4 model simulation
START 1948 10 01 END 2009 09 30
RUN INTERP OUTPUT LEVEL 3 0
RESUME 0 RUN 1 UNIT SYSTEM 1
END GLOBAL
FILES
<File> <Un#> <-----------File Name------------------------------>***
<-ID-> ***
WDM 26 default[13].wdm
MESSU 25 Mitdefault[13].MES
27 Mitdefault[13].L61
28 Mitdefault[13].L62
30 POCdefault[13]1.dat
END FILES
OPN SEQUENCE
INGRP INDELT 00:15
IMPLND 2
RCHRES 1
COPY 1
COPY 501
DISPLY 1
END INGRP
END OPN SEQUENCE
DISPLY
DISPLY-INFO1
# - #<----------Title----------->***TRAN PIVL DIG1 FIL1 PYR DIG2 FIL2 YRND
1 Sand Filter 1 MAX 1 2 30 9
END DISPLY-INFO1
END DISPLY
COPY
TIMESERIES
# - # NPT NMN ***
1 1 1
501 1 1
END TIMESERIES
END COPY
GENER
OPCODE
# # OPCD ***
END OPCODE
PARM
# # K ***
END PARM
END GENER
PERLND
GEN-INFO
<PLS ><-------Name------->NBLKS Unit-systems Printer ***
# - # User t-series Engl Metr ***
in out ***
END GEN-INFO
*** Section PWATER***
ACTIVITY
<PLS > ************* Active Sections *****************************
# - # ATMP SNOW PWAT SED PST PWG PQAL MSTL PEST NITR PHOS TRAC ***
END ACTIVITY
PRINT-INFO
<PLS > ***************** Print-flags ***************************** PIVL PYR
# - # ATMP SNOW PWAT SED PST PWG PQAL MSTL PEST NITR PHOS TRAC *********
END PRINT-INFO
PWAT-PARM1
default[13]5/14/2018 3:49:21 PM Page 15
<PLS > PWATER variable monthly parameter value flags ***
# - # CSNO RTOP UZFG VCS VUZ VNN VIFW VIRC VLE INFC HWT ***
END PWAT-PARM1
PWAT-PARM2
<PLS > PWATER input info: Part 2 ***
# - # ***FOREST LZSN INFILT LSUR SLSUR KVARY AGWRC
END PWAT-PARM2
PWAT-PARM3
<PLS > PWATER input info: Part 3 ***
# - # ***PETMAX PETMIN INFEXP INFILD DEEPFR BASETP AGWETP
END PWAT-PARM3
PWAT-PARM4
<PLS > PWATER input info: Part 4 ***
# - # CEPSC UZSN NSUR INTFW IRC LZETP ***
END PWAT-PARM4
PWAT-STATE1
<PLS > *** Initial conditions at start of simulation
ran from 1990 to end of 1992 (pat 1-11-95) RUN 21 ***
# - # *** CEPS SURS UZS IFWS LZS AGWS GWVS
END PWAT-STATE1
END PERLND
IMPLND
GEN-INFO
<PLS ><-------Name-------> Unit-systems Printer ***
# - # User t-series Engl Metr ***
in out ***
2 ROADS/MOD 1 1 1 27 0
END GEN-INFO
*** Section IWATER***
ACTIVITY
<PLS > ************* Active Sections *****************************
# - # ATMP SNOW IWAT SLD IWG IQAL ***
2 0 0 1 0 0 0
END ACTIVITY
PRINT-INFO
<ILS > ******** Print-flags ******** PIVL PYR
# - # ATMP SNOW IWAT SLD IWG IQAL *********
2 0 0 4 0 0 0 1 9
END PRINT-INFO
IWAT-PARM1
<PLS > IWATER variable monthly parameter value flags ***
# - # CSNO RTOP VRS VNN RTLI ***
2 0 0 0 0 0
END IWAT-PARM1
IWAT-PARM2
<PLS > IWATER input info: Part 2 ***
# - # *** LSUR SLSUR NSUR RETSC
2 400 0.05 0.1 0.08
END IWAT-PARM2
IWAT-PARM3
<PLS > IWATER input info: Part 3 ***
# - # ***PETMAX PETMIN
2 0 0
END IWAT-PARM3
IWAT-STATE1
<PLS > *** Initial conditions at start of simulation
# - # *** RETS SURS
2 0 0
END IWAT-STATE1
default[13]5/14/2018 3:49:21 PM Page 16
END IMPLND
SCHEMATIC
<-Source-> <--Area--> <-Target-> MBLK ***
<Name> # <-factor-> <Name> # Tbl# ***
Basin 1***
IMPLND 2 0.04 RCHRES 1 5
******Routing******
IMPLND 2 0.04 COPY 1 15
RCHRES 1 1 COPY 501 16
END SCHEMATIC
NETWORK
<-Volume-> <-Grp> <-Member-><--Mult-->Tran <-Target vols> <-Grp> <-Member-> ***
<Name> # <Name> # #<-factor->strg <Name> # # <Name> # # ***
COPY 501 OUTPUT MEAN 1 1 48.4 DISPLY 1 INPUT TIMSER 1
<-Volume-> <-Grp> <-Member-><--Mult-->Tran <-Target vols> <-Grp> <-Member-> ***
<Name> # <Name> # #<-factor->strg <Name> # # <Name> # # ***
END NETWORK
RCHRES
GEN-INFO
RCHRES Name Nexits Unit Systems Printer ***
# - #<------------------><---> User T-series Engl Metr LKFG ***
in out ***
1 Sand Filter 1 2 1 1 1 28 0 1
END GEN-INFO
*** Section RCHRES***
ACTIVITY
<PLS > ************* Active Sections *****************************
# - # HYFG ADFG CNFG HTFG SDFG GQFG OXFG NUFG PKFG PHFG ***
1 1 0 0 0 0 0 0 0 0 0
END ACTIVITY
PRINT-INFO
<PLS > ***************** Print-flags ******************* PIVL PYR
# - # HYDR ADCA CONS HEAT SED GQL OXRX NUTR PLNK PHCB PIVL PYR *********
1 4 0 0 0 0 0 0 0 0 0 1 9
END PRINT-INFO
HYDR-PARM1
RCHRES Flags for each HYDR Section ***
# - # VC A1 A2 A3 ODFVFG for each *** ODGTFG for each FUNCT for each
FG FG FG FG possible exit *** possible exit possible exit
* * * * * * * * * * * * * * ***
1 0 1 0 0 4 5 0 0 0 0 0 0 0 0 2 2 2 2 2
END HYDR-PARM1
HYDR-PARM2
# - # FTABNO LEN DELTH STCOR KS DB50 ***
<------><--------><--------><--------><--------><--------><--------> ***
1 1 0.01 0.0 0.0 0.5 0.0
END HYDR-PARM2
HYDR-INIT
RCHRES Initial conditions for each HYDR section ***
# - # *** VOL Initial value of COLIND Initial value of OUTDGT
*** ac-ft for each possible exit for each possible exit
<------><--------> <---><---><---><---><---> *** <---><---><---><---><--->
1 0 4.0 5.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0
END HYDR-INIT
END RCHRES
SPEC-ACTIONS
END SPEC-ACTIONS
default[13]5/14/2018 3:49:21 PM Page 17
FTABLES
FTABLE 1
91 5
Depth Area Volume Outflow1 Outflow2 Velocity Travel Time***
(ft) (acres) (acre-ft) (cfs) (cfs) (ft/sec) (Minutes)***
0.000000 0.000367 0.000000 0.000000 0.000000
0.008333 0.000367 0.000003 0.000000 0.009235
0.016667 0.000367 0.000006 0.000000 0.009278
0.025000 0.000367 0.000009 0.000000 0.009320
0.033333 0.000367 0.000012 0.000000 0.009363
0.041667 0.000367 0.000015 0.000000 0.009405
0.050000 0.000367 0.000018 0.000000 0.009448
0.058333 0.000367 0.000021 0.000000 0.009491
0.066667 0.000367 0.000024 0.000000 0.009533
0.075000 0.000367 0.000028 0.000000 0.009576
0.083333 0.000367 0.000031 0.000000 0.009618
0.091667 0.000367 0.000034 0.000000 0.009661
0.100000 0.000367 0.000037 0.000000 0.009703
0.108333 0.000367 0.000040 0.000000 0.009746
0.116667 0.000367 0.000043 0.000000 0.009788
0.125000 0.000367 0.000046 0.000000 0.009831
0.133333 0.000367 0.000049 0.000000 0.009874
0.141667 0.000367 0.000052 0.000000 0.009916
0.150000 0.000367 0.000055 0.000000 0.009959
0.158333 0.000367 0.000058 0.000000 0.010001
0.166667 0.000367 0.000061 0.000000 0.010044
0.175000 0.000367 0.000064 0.000000 0.010086
0.183333 0.000367 0.000067 0.000000 0.010129
0.191667 0.000367 0.000070 0.000000 0.010171
0.200000 0.000367 0.000073 0.000000 0.010214
0.208333 0.000367 0.000077 0.000000 0.010257
0.216667 0.000367 0.000080 0.000000 0.010299
0.225000 0.000367 0.000083 0.000000 0.010342
0.233333 0.000367 0.000086 0.000000 0.010384
0.241667 0.000367 0.000089 0.000000 0.010427
0.250000 0.000367 0.000092 0.000000 0.010469
0.258333 0.000367 0.000095 0.000000 0.010512
0.266667 0.000367 0.000098 0.000000 0.010554
0.275000 0.000367 0.000101 0.000000 0.010597
0.283333 0.000367 0.000104 0.000000 0.010640
0.291667 0.000367 0.000107 0.000000 0.010682
0.300000 0.000367 0.000110 0.000000 0.010725
0.308333 0.000367 0.000113 0.000000 0.010767
0.316667 0.000367 0.000116 0.000000 0.010810
0.325000 0.000367 0.000119 0.000000 0.010852
0.333333 0.000367 0.000122 0.000000 0.010895
0.341667 0.000367 0.000125 0.000000 0.010937
0.350000 0.000367 0.000129 0.000000 0.010980
0.358333 0.000367 0.000132 0.000000 0.011023
0.366667 0.000367 0.000135 0.000000 0.011065
0.375000 0.000367 0.000138 0.000000 0.011108
0.383333 0.000367 0.000141 0.000000 0.011150
0.391667 0.000367 0.000144 0.000000 0.011193
0.400000 0.000367 0.000147 0.000000 0.011235
0.408333 0.000367 0.000150 0.000000 0.011278
0.416667 0.000367 0.000153 0.000000 0.011321
0.425000 0.000367 0.000156 0.000000 0.011363
0.433333 0.000367 0.000159 0.000000 0.011406
0.441667 0.000367 0.000162 0.000000 0.011448
0.450000 0.000367 0.000165 0.000000 0.011491
0.458333 0.000367 0.000168 0.000000 0.011533
0.466667 0.000367 0.000171 0.000000 0.011576
0.475000 0.000367 0.000174 0.000000 0.011618
0.483333 0.000367 0.000178 0.000000 0.011661
0.491667 0.000367 0.000181 0.000000 0.011704
0.500000 0.000367 0.000184 0.000000 0.011746
0.508333 0.000367 0.000187 0.000000 0.011789
0.516667 0.000367 0.000190 0.000000 0.011831
0.525000 0.000367 0.000193 0.000000 0.011874
0.533333 0.000367 0.000196 0.000000 0.011916
default[13]5/14/2018 3:49:21 PM Page 18
0.541667 0.000367 0.000199 0.000000 0.011959
0.550000 0.000367 0.000202 0.000000 0.012001
0.558333 0.000367 0.000205 0.000000 0.012044
0.566667 0.000367 0.000208 0.000000 0.012087
0.575000 0.000367 0.000211 0.000000 0.012129
0.583333 0.000367 0.000214 0.000000 0.012172
0.591667 0.000367 0.000217 0.000000 0.012214
0.600000 0.000367 0.000220 0.000000 0.012257
0.608333 0.000367 0.000223 0.000000 0.012299
0.616667 0.000367 0.000227 0.000000 0.012342
0.625000 0.000367 0.000230 0.000000 0.012384
0.633333 0.000367 0.000233 0.000000 0.012427
0.641667 0.000367 0.000236 0.000000 0.012470
0.650000 0.000367 0.000239 0.000000 0.012512
0.658333 0.000367 0.000242 0.000000 0.012555
0.666667 0.000367 0.000245 0.000000 0.012597
0.675000 0.000367 0.000248 0.000000 0.012640
0.683333 0.000367 0.000251 0.000000 0.012682
0.691667 0.000367 0.000254 0.000000 0.012725
0.700000 0.000367 0.000257 0.000000 0.012767
0.708333 0.000367 0.000260 0.067333 0.012810
0.716667 0.000367 0.000263 0.190433 0.012853
0.725000 0.000367 0.000266 0.349825 0.012895
0.733333 0.000367 0.000269 0.538557 0.012938
0.741667 0.000367 0.000272 0.752610 0.012980
0.750000 0.000367 0.000275 0.989273 0.013023
END FTABLE 1
END FTABLES
EXT SOURCES
<-Volume-> <Member> SsysSgap<--Mult-->Tran <-Target vols> <-Grp> <-Member-> ***
<Name> # <Name> # tem strg<-factor->strg <Name> # # <Name> # # ***
WDM 2 PREC ENGL 1 PERLND 1 999 EXTNL PREC
WDM 2 PREC ENGL 1 IMPLND 1 999 EXTNL PREC
WDM 1 EVAP ENGL 0.76 PERLND 1 999 EXTNL PETINP
WDM 1 EVAP ENGL 0.76 IMPLND 1 999 EXTNL PETINP
END EXT SOURCES
EXT TARGETS
<-Volume-> <-Grp> <-Member-><--Mult-->Tran <-Volume-> <Member> Tsys Tgap Amd ***
<Name> # <Name> # #<-factor->strg <Name> # <Name> tem strg strg***
RCHRES 1 HYDR RO 1 1 1 WDM 1000 FLOW ENGL REPL
RCHRES 1 HYDR O 1 1 1 WDM 1001 FLOW ENGL REPL
RCHRES 1 HYDR O 2 1 1 WDM 1002 FLOW ENGL REPL
RCHRES 1 HYDR STAGE 1 1 1 WDM 1003 STAG ENGL REPL
COPY 1 OUTPUT MEAN 1 1 48.4 WDM 701 FLOW ENGL REPL
COPY 501 OUTPUT MEAN 1 1 48.4 WDM 801 FLOW ENGL REPL
END EXT TARGETS
MASS-LINK
<Volume> <-Grp> <-Member-><--Mult--> <Target> <-Grp> <-Member->***
<Name> <Name> # #<-factor-> <Name> <Name> # #***
MASS-LINK 5
IMPLND IWATER SURO 0.083333 RCHRES INFLOW IVOL
END MASS-LINK 5
MASS-LINK 15
IMPLND IWATER SURO 0.083333 COPY INPUT MEAN
END MASS-LINK 15
MASS-LINK 16
RCHRES ROFLOW COPY INPUT MEAN
END MASS-LINK 16
END MASS-LINK
END RUN
default[13]5/14/2018 3:49:21 PM Page 19
Predeveloped HSPF Message File
default[13]5/14/2018 3:49:21 PM Page 20
Mitigated HSPF Message File
default[13]5/14/2018 3:49:21 PM Page 21
Disclaimer
Legal Notice
This program and accompanying documentation is provided 'as-is' without warranty of any kind. The
entire risk regarding the performance and results of this program is assumed by the user. Clear Creek
Solutions, Inc. disclaims all warranties, either expressed or implied, including but not limited to
implied warranties of program and accompanying documentation. In no event shall Clear Creek
Solutions, Inc. be liable for any damages whatsoever (including without limitation to damages for
loss of business profits, loss of business information, business interruption, and the like) arising
out of the use of, or inability to use this program even if Clear Creek Solutions, Inc. has been
advised of the possibility of such damages.
Clear Creek Solutions, Inc.
6200 Capitol Blvd. Ste F
Olympia, WA. 98501
Toll Free 1(866)943-0304
Local (360)943-0304
www.clearcreeksolutions.com
Earth Science + Technology
Geotechnical Engineering Services
Revised Report
Southport Development
Lake Washington Boulevard Improvement
Renton, Washington
for
Southport, LLC
April 22, 2016
Geotechnical Engineering Services
Revised Report
Southport Development
Lake Washington Boulevard Improvement
Renton, Washington
for
Southport, LLC
April 22, 2016
1101 South Fawcett Avenue, Suite 200
Tacoma, Washington 98402
253.383.4940
April 22, 2016 | Page i File No. 21854-001-01
Table of Contents
1.0 INTRODUCTION AND PROJECT UNDERSTANDING ........................................................................................ 1
2.0 SCOPE OF SERVICES ...................................................................................................................................... 1
3.0 SITE CONDITIONS ............................................................................................................................................ 2
3.1. Geologic Setting .......................................................................................................................................... 2
3.2. Surface Conditions...................................................................................................................................... 3
3.3. Subsurface Conditions ............................................................................................................................... 3
4.0 CONCLUSIONS AND RECOMMENDATIONS ................................................................................................... 4
4.1. General ........................................................................................................................................................ 4
4.2. Earthwork and Site Preparation ................................................................................................................. 5
4.2.1. Temporary Excavations, Construction Shoring, and Dewatering .................................................. 5
4.3. Permanent Slopes ...................................................................................................................................... 7
4.3.1. Fill Materials .................................................................................................................................... 7
4.4. Earthquake Engineering ............................................................................................................................. 9
4.4.1. Seismic Design Parameters ............................................................................................................ 9
4.4.2. Liquefaction ..................................................................................................................................... 9
4.5. Pile Foundations ...................................................................................................................................... 10
4.5.1. Lateral Resistance ........................................................................................................................ 10
4.5.2. Axial Resistance ............................................................................................................................ 10
4.5.3. Pile Installation Requirements .................................................................................................... 11
4.6. Culverts and Culvert Foundations ........................................................................................................... 12
4.7. Lateral Earth Pressures ........................................................................................................................... 12
4.8. Tunnel Design Parameters ...................................................................................................................... 13
4.9. Creek Bank Stability................................................................................................................................. 13
5.0 LIMITATIONS ................................................................................................................................................ 14
LIST OF FIGURES
Figure 1. Vicinity Map
Figure 2. Site Plan
APPENDICES
Appendix A. Subsurface Explorations and Laboratory Testing
Figure A-1 – Key to Exploration Logs
Figures A-2 through A-4 – Logs of Borings
Figure A-5 – Sieve Analysis Results
Figure A-6 – Atterberg Limits Test Results
Appendix B. Report Limitations and Guidelines for Use
April 22, 2016 | Page 1 File No. 21854-001-01
1.0 INTRODUCTION AND PROJECT UNDERSTANDING
This report presents the results of our geotechnical engineering study for the Southport Development Lake
Washington Boulevard Improvement project located in Renton, Washington. The Southport Development
Project, is a 17.5-acre mixed-use community waterfront site located in Renton, Washington adjacent to
Gene Coulon Memorial Beach Park and Lake Washington. A vicinity map is provided as Vicinity Map,
Figure 1. Our understanding of the project is based on information provided by Coughlin, Porter, Lundeen
(CPL), the project civil engineer, and Shearer Design, the project structural engineer.
The purpose of this project is to improve traffic flow entering and exiting the Southport development site.
The project is divided into two phases. The first phase includes improvements where the Southport
entrance road crosses the BNSF Railway Company (BNSF) railroad tracks, west of Lake Washington
Boulevard. The first phase is complete or nearly complete. The second phase is anticipated to include
widening the Southport entrance road from two lanes to four lanes where it crosses Johns Creek and
widening a portion of Lake Washington Boulevard from Garden Avenue North to Houser Way North. A site
plan is provided as Site Plan, Figure 2. In order to widen the Southport access road, an existing set of three
60-inch pipe culverts installed across Johns Creek will be removed and replaced with a new crossing. The
crossing will consist of either a bridge spanning the creek or a four sided box culvert. About 5 feet of fill will
be placed on either side of the crossing to establish a new road grade that ties into the widened roadway
and crossing structure.
This construction of the bridge would be phased with half (one or two lanes) of the bridge constructed at a
time so that traffic and access can be maintained during construction. The construction of the box culvert
would occur in one phase over a few days with traffic temporarily routed around the crossing.
Lake Washington Boulevard will also be widened to the south of the existing alignment from Garden Avenue
North to Houser Way North. This road widening will extend the road over an existing ditch that conveys
Johns Creek to the north. Currently, this ditch captures water from four 36- to 60-inch culverts entering
from the east and the west and redirects the water to four, 48-inch-diameter culverts exiting to the north
under Lake Washington Boulevard. A 10-foot-tall gabion rock wall is located on the north side of the ditch
between the ditch and the shoulder of the road. Initial plans showed this ditch being replaced with a precast
reinforced concrete stormwater vault. The current design concept consists of constructing an open bridge
or “roof” structure to span the ditch (widening structure).
This report provides a discussion of the geology and observed subsurface conditions in both areas. Detailed
design recommendations are only provided for the Southport entrance crossing. The design for the Lake
Washington Boulevard structure has not been advanced to the point that final detailed geotechnical
recommendations can be provided. These recommendations will be provided in a report addendum when
appropriate.
2.0 SCOPE OF SERVICES
The purpose of our geotechnical engineering services is to explore subsurface conditions as a basis for
developing geotechnical design recommendations for the proposed Southport entrance crossing and the
proposed widening structure for Lake Washington Boulevard, which was originally envisioned as a
April 22, 2016 | Page 2 File No. 21854-001-01
stormwater vault. Our services are being performed in accordance with our agreement dated
June 15, 2015. The geotechnical tasks addressed in this report included the following items:
1. Developing an understanding of geologic conditions at the site by reviewing information you provide,
readily available published geologic data and our in-house files.
2. Notifying the one-call utility locate service to check for underground utilities in accordance with
Washington State requirements.
3. Exploring subsurface conditions at the proposed crossing location and the proposed road widening
structure by drilling three hollow-stem auger exploratory borings, one at each side of the proposed creek
and one adjacent to the widening structure. The borings were located as close as practical to the
proposed structures considering equipment access and utilities. The borings at the proposed crossing
were planned to extend 60 feet below ground surface (bgs). Adverse drilling conditions limited the
depth of one exploration to 55 feet. We used an “air-knife” Vacuum Truck to more safely excavate the
first 5 to 10 feet around underground utilities. The explorations were backfilled by the drillers in
accordance with Washington State Department of Ecology (Ecology) regulations.
4. Conducting laboratory testing of selected samples obtained during site exploration. Our testing program
included moisture content determinations, gradation analyses, Atterberg Limits, and an organic
content determination.
5. Providing foundation, abutment wall, and slope stability seismic design criteria in accordance with
current editions of the Washington State Department of Transportation (WSDOT) Bridge Design
Manual, Geotechnical Design Manual and American Association of State Highway and Transportation
Officials (AASHTO) Standard Specifications for Highways, including our opinion of the potential for soil
liquefaction.
6. Providing recommendations for design of either small diameter drilled shaft, driven pile or spread
footing foundations with ground improvement for support of the proposed crossing. Our report contains
recommendations for driven piles and spread footing foundations.
7. Providing recommended lateral earth pressures for design of the abutment or other subsurface walls.
We will include design pressures for static and seismic design conditions.
8. Evaluating the stability of the creek bank slopes based on the results of our subsurface exploration and
proposed alignment. We consider stability under static and design seismic conditions.
9. Providing recommendations for design and construction of the Lake Washington Boulevard Widening
Structure. These recommendations will be provided in an addendum to follow this report.
10. Providing a discussion of potential dewatering that could be required during construction.
3.0 SITE CONDITIONS
3.1. Geologic Setting
Geologic conditions at the site were evaluated in part by reviewing the “Preliminary Geologic Map of Seattle
and Vicinity” (Waldron, H.H., et al., 1962). Three geologic units, Artificial Fill (m), Alluvium (Qa) and Peat (Qp),
are all mapped at or near the site. The upland area to the east is mapped as glacially consolidated soils,
Vashon Till (Qt) and Older Clay Till and Gravel (Qc).
April 22, 2016 | Page 3 File No. 21854-001-01
The artificial fill is mapped to the northwest of the site, towards the main Southport Development. Artificial
fill is only described as being “highly variable”. The peat is mapped at the site and to the north of the site
where Coulon Park is currently located. Peat is described as containing inorganic clay and silt in addition to
organic material. Alluvium is mapped to the south of the site and “may contain interbedded peat and muck.”
The Vashon till is described as a “graded mixture of clay to gravel sizes” that “may contain local lenses of
sand and gravel.” The older clay till and gravel is described as having “much vertical and lateral variation.”
3.2. Surface Conditions
The site is located south of Lake Washington and south of Gene Coulon Memorial Beach Park. The project
includes widening Lake Washington Boulevard, widening Coulon Beach Park Drive (completed as part of
the first phase), and widening the entrance to the Southport Development, which is located west of Coulon
Beach Park Drive. Our geotechnical services are focused on two specific locations within the site, the
Southport entrance bridge west of Coulon Beach Park Drive and the Lake Washington Boulevard widening
structure located on the east side of Lake Washington Boulevard. These areas are shown in Figure 2.
Lake Washington Boulevard is oriented in a general northeast-southwest direction through the project area.
A ditch is located on the southeast side of the road. Currently, this ditch captures water from four, 36- to
60-inch culverts entering from the east and the west and redirects the water to four, 48-inch-diameter
culverts exiting to the north under Lake Washington Boulevard. The water in these culverts are ultimately
conveyed to Johns Creek to the north. An approximate 10-foot-tall gabion rock wall is located between the
ditch and the shoulder of the road. A fill embankment constructed to support NE Park Drive is located
southeast of the ditch and rises to about Elevation 50 feet adjacent to the proposed widening structure.
The Southport entrance bridge will be constructed to replace three, 60-inch culverts that are currently used
to cross Johns Creek. Based on topographic data provided by CPL, the existing creek banks are inclined at
about 2H:1V (Horizontal to Vertical) to 2.5H:1V. The bottom of the creek is at about Elevation 18 feet and
the top of the creek banks are at about Elevation 25 to 28 feet. The proposed bridge structure is expected
to span about 60 feet. Finish road grade will be at about Elevation 31 feet, which will require placing some
fill at the abutments.
3.3. Subsurface Conditions
We explored the subsurface conditions near the proposed Lake Washington Boulevard widening structure
(exploration B-1) and near the proposed Southport entrance bridge (explorations B-2 and B-3). The
exploration locations, especially for exploration B-1, were constrained by site topography and the presence
of underground utilities. The approximate exploration locations are shown on the Site Plan, Figure 2.
The subsurface conditions observed in our explorations was generally consistent across both areas. We
observed brown fine to coarse sand with silt and gravel and brown silty fine to coarse sand with gravel and
cobbles in the upper portions of our explorations. We characterized this soil as fill. The upper 4.5 to 5.5 feet
of explorations B-1 and B-2 were excavated using an Air Knife (vacuum system) in order to more safely
check the exploration location for underground utilities. This method also allowed for direct observation of
larger soil particles, cobbles for example. The fill was observed from the ground surface to about
Elevation 25 in exploration B-1 (Lake Washington Boulevard area) and to about Elevation 16 feet to
Elevation 18 feet in explorations B-2 and B-3 (Southport entrance area). This quantity of fill is consistent
with our understanding of the history of the site.
April 22, 2016 | Page 4 File No. 21854-001-01
Below the fill and down to about Elevation 4 to -17 we encountered interbedded layers of brown organic
silt with organic matter and peat, silty sand, and sand. We characterized these soils as alluvium. The
composition of these soils are consistent with the alluvium described in the geologic mapping. The location
and layering of the sand and silt layers were generally consistent between B-2 and B-3 (Southport entrance
area), which were drilled relatively close to each other, but did not match with the layering in B-1 (Lake
Washington Boulevard area), which was further away. We expect the soil layering within the alluvium to be
variable across the site, but generally contain similar materials.
Below the alluvium we observed dense to very dense silty sand, sand and gravel with silt. We characterized
these soils as glacial deposits based on the density and gravel content. Glacial till is mapped in the area
on the hillside to the east of the site. In our opinion the material observed in our explorations is more
consistent with glacial outwash which contains less fines, more sand and gravel, and is often found below
glacial till.
The glacial deposits were observed to be deeper in the borings further to the west (B-2 and B-3). This is
consistent with the glacial deposits being part of the same geologic unit as the hillside to the east. Based
on this, we also expect the glacial deposits layer in the Lake Washington Boulevard widening area to be
somewhat deeper to the west of exploration B-1.
Groundwater was observed during drilling at about Elevation 15 feet. These groundwater observations were
taken at the time of drilling from within the drill augers. This method is not as accurate as a measurement
taken from an installed well or piezometer. We expect that groundwater will fluctuate in response to
precipitation and water levels within Johns Creek, the ditch adjacent to Lake Washington Boulevard, and in
Lake Washington.
All three of our explorations encountered heaving and/or caving soil within the glacial deposits. Heave and
caving soil in an exploration, especially within a dense gravel unit, can be an indication of groundwater
under pressure. While the water pressure observed in the explorations does not appear to be artesian (i.e.,
it did not have enough pressure to reach the ground surface), it may be sub-artesian (i.e., it has a higher
pressure head than groundwater in the overlaying alluvium). In our experience, higher groundwater heads
are not uncommon in porous glacial deposits near the edge of a valley. In these cases, the water table is
in a transition zone between the high elevation groundwater levels in the upland areas and the lower
elevation groundwater levels in the valley. In these transition zones some of the pressure from the higher
elevations can still present at the bottom of the slope.
4.0 CONCLUSIONS AND RECOMMENDATIONS
4.1. General
The site is underlain by about 20 to 40 feet of alluvium. This alluvium contains highly compressible soils
such as organic silt and some peat. Adding load to this soil by either filling or supporting structures on
shallow foundations will induce settlement. The granular layers within the alluvium are also potentially
liquefiable under the design seismic event.
In our opinion shallow foundations or precast culverts are appropriate for the proposed crossing structure
provided that the structure is designed to accommodate the predicted total and differential settlement. The
April 22, 2016 | Page 5 File No. 21854-001-01
subgrade must be prepared as recommended to reduce the potential for additional total and differential
settlements resulting from soft or uneven bearing surfaces.
Heavy structures that cannot tolerate significant total and differential settlements should be supported on
deep foundations bearing in the underlying glacial deposits. Caving and heaving soils were observed within
the glacial deposits. This caving and heaving soil could make the installation of drilled shafts difficult and
costly. We recommend that driven pipe piles, rather than drilled shafts, be used for deep foundation
support.
Shallow foundations supported on improved ground (i.e., stone columns or rammed aggregate piers) could
provide the bearing resistance and seismic performance required for the proposed structures. However,
vibrations and ground disturbance associated with installation of stone columns or similar ground
improvement methods could damage existing structures or newly constructed structures if the construction
is phased. Ground improvement methods that cause less disturbance such as jet grouting or compaction
grouting are typically more expensive than driven pipe piles.
4.2. Earthwork and Site Preparation
4.2.1. Temporary Excavations, Construction Shoring, and Dewatering
4.2.1.1. General
The proposed improvements will likely require some excavation adjacent to existing site structures. In the
Lake Washington Boulevard area this could include supporting the existing roadway and utilities to allow
for overexcavation of fill areas, structure excavations, or utility excavations.
We anticipate that construction of an entrance bridge will need to be completed in two parts in order to
maintain traffic access during construction. The first part will construct the bridge and approach structure
to the south of the existing culverts. The second part will remove the existing culverts and road so that the
north half of the bridge can be constructed. During the first part of construction the existing roadway may
need to be supported by construction shoring to allow for the bridge foundation excavation. After the bridge
abutment and approach embankment are constructed on the south half of the bridge construction shoring
may be required to protect the newly constructed roadway during excavation for the north side of the bridge
abutment.
Depending on the elevation of the bridge abutment and the level of Lake Washington at the time of
construction, cofferdams may also be required to prevent water from Johns Creek from flowing into the
abutment excavation.
We anticipate the construction of a four-sided box culvert will require completely closing the entrance road
during construction. We anticipate that prior to closing the road, shoring and/or cofferdams will be installed
on the upstream and downstream ends of the proposed crossing and the creek bypass will be established.
After the road is closed, the existing culverts will be removed and the new culvert subgrade will be excavated
to remove near surface organic soils. Subgrade elevation will be reestablished with quarry spalls or similar
fill and the new culvert segments will be placed and backfilled.
Shoring or cofferdams and dewatering systems are interdependent and their design must be coordinated.
For example, more extensive shoring systems that can cut off some groundwater flow into the excavation
April 22, 2016 | Page 6 File No. 21854-001-01
will reduce the amount of dewatering that is required. Similarly, dewatering systems that lower surrounding
groundwater levels can be used to reduce pressures on the shoring system.
We recommend that the contractor performing the work be made responsible for designing and installing
construction shoring and for controlling and collecting groundwater encountered. The contract documents
must specify that the contractor is responsible for selecting excavation and dewatering methods,
monitoring the excavations for safety, and providing shoring, as required, to protect personnel and
structures. Excavation shoring, cofferdams, and dewatering systems must be designed by a qualified
engineer in accordance with WSDOT Standard Specification 2-09.3(3) D “Shoring and Cofferdams.” We
recommend that we be retained to review the proposed shoring and dewatering plan before construction.
All excavations deeper than 4 feet must be shored or laid back at a stable slope if workers are required to
enter the excavation. Shoring and temporary slope inclinations must conform to the provisions of Title 296
Washington Administrative Code (WAC), Part N, “Excavation, Trenching and Shoring.” Regardless of the soil
type encountered in the excavation, shoring, trench boxes or sloped sidewalls will be required under
Washington Industrial Safety and Health Act (WISHA) if the excavation is deeper than 4 feet.
4.2.1.2. Excavation Shoring
The soil pressures against a shoring wall are dependent on the type of wall, the soil retained, the method
of construction, and the extent of dewatering. For preliminary purposes, we suggest that loads against a
shoring system be estimated using the soil properties in Table 1. These values are based on our
explorations and our experience. These values are for preliminary planning purposes. Soil and water
pressures used in final design should be determined by a qualified engineer and be based on the specific
shoring system that will be constructed. The shoring designer must also confirm that the soil conditions
observed during construction are consistent with the soil conditions assumed during design.
TABLE 1. PRELIMINARY SOIL PARAMETERS FOR SHORING
Soil Type1
Friction Angle
(degrees)
Cohesion
(psf)
Total Moist Unit Weight
(pcf)
Fill (Existing) 29 – 33 0 120
Granular Alluvium (SP, SP-SM, and SM) 29 – 33 0 115
Cohesive Alluvium (OL, OH, and ML) 0 500 – 1,000 105
Glacial Deposits 34 – 42 0 135
Notes:
1 See boring logs for description of soil types and approximate locations.
psf – pounds per square foot.
pcf – pounds per cubic foot.
Based on our current understanding of the proposed construction, we do not anticipate that shoring will be
required to extend into the dense glacial deposits. If shoring is required to this depth, pre-drilling or
spudding may be required to loosen the dense glacial deposits for shoring installation. If pre-drilling or
spudding is used, the intended location, depth, and method must all be specifically stated in the shoring
submittal. Pre-drilling or spudding shall not be permitted within 10 feet of installed or partially installed
permanent foundations or other subsurface structures except as approved by the geotechnical engineer.
April 22, 2016 | Page 7 File No. 21854-001-01
In a two-phase construction approach, shoring could be required to retain the fill placed as part of a new
entrance bridge construction. In our opinion it may be more efficient to use a “self-supporting” fill for this
half of the approach embankment so that shoring between the north and south halves will not be required
or will be less extensive. Self-supporting fill can consist of a geotextile reinforced soil mass, similar to a
wrapped face geosynthetic wall or controlled density fill (CDF). If this method is used, the shoring submittal
must provide details on the fill and reinforcing materials used and provide details on how the permanent
wall drainage measures and other proposed improvements will be incorporated.
4.2.1.3. Dewatering
Constructing the entrance bridge abutments may require installing a cofferdam and removing water from
within the cofferdam. In our opinion most of the water flow into the cofferdam will come from seepage that
enters through the base of the excavation or through gaps in the cofferdam. Dewatering inside the
excavation will create an imbalance in the hydrostatic pressures inside to outside of the excavation and
can result in “quick” or boiling sand conditions in the excavation base. This condition must be considered
in the design. Methods to counteract this include: (1) extending the sheets further below the base of the
excavation to reduce the groundwater gradient; or (2) installing dewatering wells in the interior of the
excavation to relieve excess water pressure.
In our opinion, dewatering of a cofferdam to about Elevation 16 feet (approximate elevation required for
construction of cast-in-place bridge footings) can be achieved with sump pumps or dewatering wells
installed within the cofferdam. Using sump pumps will likely require temporarily grading the subgrade inside
of the cofferdam to drain to a sump. Sump pumps would likely need to be installed after some excavation
has occurred, requiring some excavation to occur “in the wet.”
Installing a precast culvert will require deeper excavations and greater dewatering. Dewatering of a
cofferdam to about Elevation 8 feet (approximate elevation required for overexcavation of organic soils)
may require more robust dewatering systems in order to control groundwater seepage and heave of the
excavation subgrade. This could include installing well points below the excavation depth.
4.3. Permanent Slopes
In general, we recommend that permanent cut and fill slopes be constructed at a maximum inclination of
2H:1V. Where 2H:1V permanent slopes are not feasible, armored or reinforced slopes or retaining
structures should be considered. Slopes should be re-vegetated or armored as soon as practical to reduce
the potential for surface erosion and sloughing. Temporary protection should be used until permanent
protection is established. In order to achieve uniform compaction, we recommend that fill slopes be
overbuilt and subsequently cut back to expose well-compacted fill. Fill placement on slopes steeper than
5H:1V must be benched into the slope face. The configuration of the bench will depend on the equipment
being used and the slope geometry.
4.3.1. Fill Materials
4.3.1.1. On-site Soil
Based on our subsurface explorations, it is our opinion that the inorganic granular native soil and fill present
on site may be considered for use as non-structural fill for backfilling excavations outside of structure or
pavement areas. However, a significant portion of the near-surface soils observed on the site have relatively
high fines contents and are moisture sensitive, which could make them difficult or impossible to compact
when wet or if earthwork is performed during wet weather.
April 22, 2016 | Page 8 File No. 21854-001-01
In our opinion, on-site soils with greater than about 5 to 10 percent fines are not suitable for re-use as fill
during periods of wet weather, but may be considered as a structural fill during prolonged periods of dry
weather. Even during periods of prolonged dry weather, on-site soil may require drying out to reduce the
moisture content to near optimum. Site space constraints may make handling and moisture conditioning
(either drying or wetting) of the on-site soil difficult.
4.3.1.2. Structural Fill
Imported structural fill must be free of debris, organic material and rock fragments larger than 6 inches.
The workability of material used as structural fill will depend on the gradation and moisture content of the
soil. As the amount of fines increases, soil becomes increasingly sensitive to small changes in moisture
content and adequate compaction may become difficult or impossible to achieve. Weather and the time of
year should be considered when determining the type of material brought to the project as a structural fill.
For earthwork conducted during prolonged periods of dry weather, we recommend that imported structural
fill material have gradation characteristics similar to “Select Borrow” as described in Section 9-03.14(2) of
the WSDOT Standard Specifications.
If construction is performed during wet weather, we recommend imported structural fill consist of sand and
gravel or crushed rock with a maximum particle size of 6 inches and less than 5 percent fines by weight
based on the minus ¾-inch fraction. Organic matter, debris or other deleterious material should not be
present. In our opinion, material with gradation characteristics similar to WSDOT Specification 9-03.9
(Aggregates for Ballast and Crushed Surfacing), 9-03.10 (Aggregate for Gravel Base) or 9-03.14(1) (Gravel
Borrow) is suitable for use as select granular fill, provided that the fines content is less than 5 percent
(based on the minus ¾-inch fraction) and the maximum particle size is 6 inches.
4.3.1.3. Structural Fill Placement and Compaction
We recommend that all proposed fills in the roadway or behind abutments be placed as structural fill.
Structural fill should be compacted at a moisture content near optimum. The optimum moisture content
varies with the soil gradation and must be evaluated during construction. Silty soil and other fine-grained
soil can be difficult or impossible to compact during wet conditions.
Fill and backfill material must be placed in uniform, horizontal lifts and uniformly densified with vibratory
compaction equipment. The maximum lift thickness will vary depending on the material and compaction
equipment used, but generally should not exceed 12 inches in loose thickness. Structural fill placed to raise
site grades and aggregate base materials under approach slabs and pavements must be placed on a
subgrade that is compacted to a firm and unyielding condition. All structural fill placed beneath pavements
or other structural areas must be compacted to at least 95 percent of the maximum dry density (MDD)
determined by ASTM International (ASTM) D 1557.
4.3.1.4. Fill Placement Below the Water Table
Where fill placement is required on wet subgrades below the water table, for culvert subgrades for example,
we recommend that fill consist of angular rock with few fines. In our opinion, material conforming to WSDOT
Standard Specification 9-03.9(2) “Permeable Ballast” is suitable for this purpose. The rock must be placed
in lifts and tamped with an excavator bucket. A geotextile may be required between the rock and any
overlaying fill to prevent pipe bedding material from being lost into the voids in the rock.
Alternatively, where soft subgrade soils are present the subgrade may be amended by pushing or tamping
quarry spalls into the soft subgrade to provide a firm surface. Quarry spalls must conform to WSDOT
April 22, 2016 | Page 9 File No. 21854-001-01
Standard Specification 9-13.6 “Quarry Spalls” and be placed in lifts about one spall diameter thick. This
method often raises the subgrade elevation as soft material is displaced. Accordingly, some additional
overexcavation prior to placing quarry spalls may be required to maintain subgrade elevation.
Where quarry spalls are used for fill, we recommend that a capping or leveling lift of permeable ballast be
used directly below footings or precast structures. The permeable ballast is easier to grade flat and
therefore provides a more uniform bearing surface.
The subgrade preparation described above is intended to amend soft silts or loose sands to create a more
uniform bearing surface for subsurface structures. It may not be adequate to repair subgrades softened or
loosened by heaving or boiling. If heaving or boiling conditions occur, excess water pressures must be
controlled before the subgrade is overexcavated or amended.
4.4. Earthquake Engineering
4.4.1. Seismic Design Parameters
Bridge design parameters for seismic design category, site class, acceleration coefficient and spectral
acceleration coefficients are presented in Table 2. These parameters were developed in accordance with
the procedures described in the Seventh Edition of the AASHTO Load Resistance Factor Design (LRFD)
Bridge Design Specifications 2014. The specification recommends a 7 percent probability of exceedance
in 75 years design event (nominal 1,000-year return period earthquake) for development of a design
spectrum for bridges. These values are appropriate for both structure locations.
TABLE 2. AASHTO SEISMIC DESIGN PARAMETERS
AASHTO Seismic Parameter Recommended Value
Site Class D
Effective Peak Ground Acceleration Coefficient
As = FpgaPGA = 1.056 x 0.444 0.469g
Design Spectral Acceleration Coefficient at 0.2 second period
SDS = FaSs = 1.106 x 0.986 1.090g
Design Spectral Acceleration Coefficient at 1.0 second period
SD1 = FvS1 = 1.744 x 0.328 0.572g
Average (modal) earthquake magnitude contributing to seismic hazard 7.0
4.4.2. Liquefaction
Liquefaction refers to a condition where vibration or shaking of the ground, usually from earthquake forces,
results in development of excess pore pressures in saturated soils and subsequent loss of strength in the
deposit of the affected soil. In general, soils that are susceptible to liquefaction include loose to medium
dense “clean” to silty sands that are below the water table. We identified layers of potentially liquefiable
soils by using empirical correlations between anticipated peak ground accelerations (PGA), earthquake
magnitude and soil relative density.
Based on our exploration and analysis the alluvium layer is potentially liquefiable during the design seismic
event. We estimate liquefaction during the design event could result in loss of soil strength and settlement
April 22, 2016 | Page 10 File No. 21854-001-01
at ground surface on the order of 2 to 16 inches. Because of the unpredictable nature of earthquakes and
variability of on-site soil conditions, differential settlement under earthquake conditions could be similar to
the total settlement.
The seismic hazard distribution at this site is such that a coupled analysis is not required; seismic inertial
forces do not need to be considered in combination with liquefied (reduced) soil strengths.
4.5. Pile Foundations
4.5.1. Lateral Resistance
Lateral displacement of the piles can be calculated using the LPILE computer program. We recommend
that the LPILE parameters in Table 3, below, be used to calculate lateral displacements of the piles. In our
opinion the lateral resistance reduction factors provided in Table 10.7.2.4-1 – Pile P-Multipliers, Pm, for
Multiple Row Shading of the AASHTO LRFD Bridge Design Specifications, Seventh Edition, 2014, are
appropriate for the proposed piles.
TABLE 3. LPILE PARAMETERS
Material
Elevation
Range Soil Model
Effective
Unit Weight
(pcf)
Friction
Angle
(degrees)
Cohesion
(psf)
K
(pci) E50
Fill 20 to 14 feet Sand (Reese) 63 33 -- 60 --
Alluvium (Organic
Silt)
14 to 6 feet Soft Clay
(Matlock)
38 -- 750 100 0.015
Alluvium (Sand) 6 to -9 feet Sand (Reese) 58 33 -- 60 --
Alluvium (Organic
Silt)
-9 to -16 feet Soft Clay
(Matlock)
38 -- 750 100 0.015
Glacial (Medium
Dense)
-16 to -23 feet Sand (Reese) 68 37 -- 150 --
Glacial (Very
Dense)
-23 feet and
below
Sand (Reese) 68 41 -- 150 --
The alluvium layers (organic silt and sand) are potentially liquefiable. To model soil resistance of liquefied
soil layers we recommend that the “Liquefied Sand (Rollins)” soil model be used in LPILE. We consider this
model to be a conservative estimate of the liquefied resistance.
4.5.2. Axial Resistance
We developed pile capacities for individual 8- and 12-inch-diameter steel pipe piles. Design pile resistances
are provided in Table 4 below. No axial reduction is required for piles spaced more than three diameters
apart center-to-center.
April 22, 2016 | Page 11 File No. 21854-001-01
TABLE 4. PRELIMINARY AXIAL FOUNDATION RESISTANCES
Foundation
Type
Minimum Tip
Elevation
Service Limit
Downward
(Uplift)
Strength Limit
Downward
(Uplift)
Extreme Limit
(Ultimate)
Downward
(Uplift)
Extreme Limit
Including
Liquefaction and
Downdrag Downward
(Uplift)
Driven Pipe Pile;
8-inch -16 feet 60 kips
(20 kips)
50 kips
(20 kips)
120 kips
(40 kips)
50 kips
(10 kips)
Driven Pipe Pile;
12-inch -16 feet 125 kips
(25 kips)
100 kips
(25 kips)
225 kips
(60 kips)
120 Kips
(15 kips)
The service limit state is based on total settlements of 1 inch. Most of the settlement should occur rapidly
as the load is applied. Most post-construction differential settlement between piles is expected to be the
result of elastic shortening of the pile and the difference in length between the top of the pile and the top
of the bearing layer.
The strength limit states are based on static resistance factors; specifically, 0.45 for downward loads and
0.35 for uplift. Lower reduction factors, and therefore relatively higher strength limit states, can be achieved
if dynamic measurements of the pile driving are used to confirm the as-installed resistance during pile
installation.
The extreme limit states are divided into two groups, an ultimate resistance and a net resistance that
includes the effects of liquefaction and downdrag. The uplift value for both includes a 0.8 resistance factor.
Downdrag is estimated to be 30 kips for the 8-inch pile and 50 kips for the 12-inch pile.
The estimated pile resistances provided are based on the installation methods described below. If different
methods are proposed, we should be contacted for revised estimates of axial resistances.
4.5.3. Pile Installation Requirements
We expect that the most efficient way to install steel pipe piles will be to use a vibratory hammer to set the
piles to the minimum tip elevation and then use an impact hammer to drive the piles into the bearing layer.
Impact driving the pile can increase the resistance of the pile. The impact force can compact and densify
the soil at the tip of the pile. Additionally, in smaller diameter piles, the force from impact driving can wedge
soil into the pile tip, plugging the pile, and increasing the tip bearing area. We expect piles smaller than
18 inches in diameter will plug if driven more than about 5 or 10 feet with an impact hammer into granular
material. The vibratory hammer will reduce the potential for the pile tip to plug above the minimum tip
elevation, allowing for decreased resistance through the fill and alluvium layers.
Driving the pile also provides a record of the pile resistance during installation. This information greatly
decreases the risk that a pile is unknowingly installed in a localized soft area with inadequate resistance,
and, therefore, allows for higher resistance factors (lower factors of safety) to be used when establishing
field driving and pile acceptance criteria.
April 22, 2016 | Page 12 File No. 21854-001-01
The axial pile resistances provided are based on estimates of ultimate pile resistances. A contingency
should be included when estimating pile lengths to ensure pile tips are adequately embedded into the
glacial soils and have sufficient axial resistance.
We recommend that we be retained to evaluate the pile and impact hammer combination proposed by the
contractor. We will perform a pile driving analysis to establish pile driving criteria for the pile and hammer
combination selected and will check that the proposed hammer will not damage the pile during installation.
In addition, we recommend that a member of our firm monitor the pile installation to observe installation
procedures, keep continuous installation records and evaluate the adequacy of individual pile installations.
Picking and lifting long piles may be difficult at the entrance bridge structure due to the proximity to
overhead power lines. Splices may be required for installation depending on design pile lengths. The pile
installation plan proposed by the contractor must address height restrictions and their proposed method
and location of the pile splices.
4.6. Culverts and Culvert Foundations
Current concept plans indicate that the proposed culvert will be founded at about Elevation 16 feet. Our
nearest explorations (B-2 and B-3) indicate that there is a highly organic silt layer right at or just below the
proposed foundation elevation. Some overexcavation and replacement of this organic layer will be required
to provide a firm working and bearing surface. We recommend at least 2 feet of overexcavation in order to
provide a firm bearing surface. Fill should be placed and compacted as described in “Section 4.3.1.4. Fill
Placement Below the Water Table.”
If only the minimum recommended amount of overexcavation (2 feet) occurs, long-term settlement of the
culvert could be on the order of 3 to 5 inches. Differential settlements across the length of the culvert could
be on the order of 1.5 to 2.5 inches and sharp differential settlements (i.e., differential settlement between
precast units) on the order of 0.5 to 1.0 inches. This settlement is primarily due to the weight of the
overlaying backfill and weight of the fill used to raise site grades at the approaches.
If this upper organic layer is overexcavated and replaced to Elevation 8 feet, we estimate that long-term
settlement of the culvert could be on the order of 0.5 to 2.0 inches. Differential settlements across the
length of the culvert could be on the order of 0.5 to 1.0 inch. Sharp differential settlements are expected
to be negligible provided the structural fill is appropriately compacted and leveled prior to placement of the
culvert.
The culvert may be evaluated using a Strength Limit bearing resistance of 5,500 pounds per square foot
(psf) and an Extreme Event Limit bearing resistance of 13,000 psf. The resistance presented for the
Strength Limit State has been factored with a resistance factor of 0.45. The Extreme Event Limit State has
not been factored. A resistance factor of 0.9 should be applied to this value for seismic loading cases.
These bearing pressures are based on a punching or shear failure of the soil subgrade and do not take into
consideration excessive the settlement as described above.
4.7. Lateral Earth Pressures
We recommend that abutments, wing walls, and culverts be backfilled with imported structural fill (WSDOT
Standard Specification 9-03.12(2) Gravel Backfill for Walls, or similar) that is placed and compacted as
April 22, 2016 | Page 13 File No. 21854-001-01
described in the “4.3.1.3. Structural Fill Placement and Compaction” section of this report. The following
table provides design parameters for subsurface structures.
TABLE 5. LATERAL SOIL PRESSURE PARAMETERS FOR PERMANENT SUBSURFACE STRUCTURES
Soil Parameter Structural Fill Submerged Structural Fill
Soil Unit Weight Total Weight = 130 pcf Total Weight = 135 pcf
Buoyant Weight = 73 pcf
Friction Angle 36 degrees 36 degrees
Cohesion 0 psf 0 psf
Active Earth Pressure Ka = 0.26
Equivalent Fluid Pressure: Ka*Unit
Weight = 33.8 pcf
Ka = 0.26
Total Equivalent Fluid Pressure: (Ka*Buoyant
Unit Weight)+hydrostatic = 81.2 pcf
At-rest Earth Pressure Ko = 0.41
Equivalent Fluid Pressure: Ka*Unit
Weight = 53.6 pcf
Ko = 0.41
Total Equivalent Fluid Pressure: (Ka*Buoyant
Unit Weight)+hydrostatic = 92.3 pcf
The subsurface structures will need to include drainage measures (drainpipes or weep holes) to prevent
buildup of excessive hydrostatic pressures or be designed for full hydrostatic pressures and submerged
structural fill values. Even with drainage measures included, we recommend that the abutment and wing
walls be designed to withstand at least 1 foot of hydrostatic differential (i.e., a groundwater level behind
the abutment 1 foot higher than the water level in the creek). This will allow for some time lag in the
drainage if the creek or lake level drops suddenly or if the wall drainage becomes temporarily clogged.
If subsurface structures are to be designed for seismic forces, we recommend that the seismic loading be
approximated using a uniform lateral pressure equal to 9.6*H psf, where H is the height (in feet) of the
structure. This seismic lateral pressure is in addition to the static soil load and any anticipated hydrostatic
pressures. This assumes that the wall is free to yield somewhat during a seismic event.
4.8. Tunnel Design Parameters
We understand that the crossing, depending on what type of structure is selected, could be designed and
analyzed in part using methods in FHWA-NHI-09-010 Technical Manual for Design and Construction of
Road Tunnels – Civil Elements. Specifically, the simplified methods described in Sections 13.5.1.1 and
13.5.1.3, which account for racking or twisting of the structure during a seismic event. In our opinion an
average soil shear modulus (Gm) of 17.7 ksi and a peak particle velocity (Vs) of 32 in/sec are appropriate
parameters for use with these simplified methods. The average soil shear modulus is based on the soil
surrounding the structure consisting of compacted structural fill as recommended above. The peak particle
velocity is based on the AASHTO design earthquake as described above and correlations provided in NCHRP
Report 611.
4.9. Creek Bank Stability
The current plans indicate that the creek banks will be inclined at about a 3H:1V slope near the crossing.
The top of the bank is at about Elevation 31 feet and the creek bed is at about Elevation 18 feet and is
about 20 feet wide. Based on our analysis, the creek bank geometries proposed have a global factor of
safety of about 2.0 in the static condition and about 1.1 for a seismic case. It is our opinion based on our
April 22, 2016 | Page 14 File No. 21854-001-01
analysis and the proposed channel geometry that global deformation (lateral spread) of the creek banks
will not result in additional lateral load on the crossing structure during the design seismic event.
5.0 LIMITATIONS
We have prepared this report for the exclusive use of Southport, LLC and their authorized agents for
Southport Development Lake Washington Boulevard Improvement project located in Renton, Washington.
Within the limitations of scope, schedule and budget, our services have been executed in accordance with
generally accepted practices in the field of geotechnical engineering in this area at the time this report was
prepared. No warranty or other conditions, express or implied, should be understood.
Please refer to Appendix B titled “Report Limitations and Guidelines for Use” for additional information
pertaining to use of this report.
µ
SITE
Vicinity Map
Figure 1
Southport DevelopmentLake Washington Blvd ImprovementsRenton, Washington
2,000 2,0000
Feet
Data Source: Mapbox Open Street Map, 2015
Notes:1. The locations of all features shown are approximate.2. This drawing is for information purposes. It is intended to assist in showing features discussed in an attached document. GeoEngineers, Inc. cannot guarantee the accuracy and content of electronic files. The master file is stored by GeoEngineers, Inc. and will serve as the official record of this communication.
Projection: NAD 1983 UTM Zone 10N
\\tac\projects\21\21854001\GIS\MXDs\2185400101_F01_VicinityMap.mxd Date Exported: 07/27/15 by cgonzales
!A
!A
!A
South Port Entran
c
e Proposed Entrance Crossing
BNSF RRJohn's
CreekLake Washington Blvd NCulverts
Proposed WideningStructure NE Park DrCoulon Beach Park DrHouser Way
N
B-3
B-2
B-1
Site Plan
Southport DevelopmentLake Washington Blvd ImprovementsRenton, Washington
Figure 2
µ50 0 50
Feet
Legend
!A Boring Number and Approximate Location
Approximate Stream Location
Notes:1. The locations of all features shown are approximate.2. This drawing is for information purposes. It is intended to assist in showing features discussed in an attacheddocument. GeoEngineers, Inc. cannot guarantee the accuracy and content of electronic files. The master fileis stored by GeoEngineers, Inc. and will serve as the official record of this communication.
Projection: NAD 1983 StatePlane Washington North FIPS 4601 Feet
P:\21\21854001\GIS\MXDs\2185400101_F02_SitePlan103.mxd Date Exported: 03/21/16 by cchelf
Data Source: Aerial from ESRI
APPENDIX A Subsurface Explorations and Laboratory Testing
April 22, 2016 | Page A-1 File No. 21854-001-01
APPENDIX A
SUBSURFACE EXPLORATIONS AND LABORATORY TESTING
Subsurface Explorations
Soil conditions at the site were explored on July 20 and 21, 2015 by advancing three borings. Explorations
were advanced to between 41 and 61 feet below ground surface (bgs), using a track-mounted hollow-stem
auger and mud rotary drill rig. The approximate location of each exploration is shown on the Site Plan,
Figure 2.
The explorations were located in the field by pacing from existing site features such as roadways or
structures. The elevations presented on the boring logs are based on contours presented on a topographic
map provided by CPL. The locations and elevations of the explorations should be considered approximate.
The explorations were continuously monitored by an engineer or geologist from our firm who examined and
classified the soil encountered, obtained representative soil samples, and maintained a detailed log of the
explorations. Soil encountered in the borings was classified in general accordance with ASTM International
(ASTM) D 2488 and the classification chart listed in Key to Exploration Logs, Figure A-1. Logs of the borings
are presented in Logs of Borings, Figures A-2 through A-4. The logs are based on interpretation of the field
and laboratory data, and indicate the depth at which we interpret subsurface materials or their
characteristics to change, although these changes might actually be gradual.
Samples of soil from the borings were obtained at approximate 5-foot-depth intervals using a 2-inch,
outside-diameter, standard split-spoon sampler (Standard Penetration Test [SPT]) in general accordance
with ASTM D 1586. The samplers were driven into the soil using a 140-pound automatic hammer, free-
falling 30 inches. The number of blows required to drive the samplers each of three, 6-inch increments of
penetration were recorded in the field, along with visual-manual descriptions of soil based on ASTM D 2488.
The sum of the blow counts for the final 12 inches of penetration, unless otherwise noted, is reported on
the boring logs.
Laboratory Testing
Soil samples obtained from the borings were returned to our laboratory for further examination and testing.
Our laboratory testing program consisted of: two particle size analyses (ASTM D 6913), three Atterberg
Limits (ASTM D 4318), and seven fines content determinations (ASTM D 1140). Sieve results are presented
in Sieve Analysis Results, Figure A-5, Atterberg Limits results are presented in Atterberg Limits Test Results,
Figure A-6, and fines content determinations are presented on the exploration logs at the respective sample
depths.
1
2%F
3%F
4%F
5AL
6
7
18
18
18
18
18
18
12
Brown silty fine to coarse sand with gravel andoccasional cobbles (medium dense, moist)(fill)
Gray silty fine to medium sand with occasionalgravel (loose, moist) (alluvium)
Gray fine to medium sand with silt (mediumdense, wet) (alluvium)
Gray silty fine to medium sand withinterbedded lenses of gray fine to coarse
sand with silt (medium dense, wet)(alluvium)
Brown to gray organic silt with organic matter(very soft, wet) (alluvium)
Gray silty fine to coarse sand with gravel (verydense, wet) (glacial deposits)
SM
SM
SP-SM
SM
OH
SM
17(24)
2(3)
22(30)
8(11)
6(8)
67(93)
50/6"
Air knife to 4.5 feet bgs
Groundwater observed at approximately14 feet during drilling
Drilling mud added
AL (LL=99; PI=23)
Increased drilling resistance at 27 feet
18
24
27
98
23
36
7
13
11
TotalDepth (ft)
HammerData
SystemDatum
Start End
Checked By
Logged By
LJSDrilled
Notes:
BEL
Surface Elevation (ft)Vertical Datum
Driller
Groundwater Depth toWater (ft)Date Measured Elevation (ft)
Easting (X)Northing (Y)
Diedrich D-50 Track Rig
Holocene Drilling, Inc.DrillingMethod Hollow-Stem Auger41
Autohammer (83% Efficient)140 (lbs) / 30 (in) Drop
DrillingEquipment
7/20/20157/20/2015
See Remarks
30
NAVD88
Note: See Figure A-1 for explanation of symbols.
FIELD DATA
Depth (feet)0
5
10
15
20
25
30
35 IntervalElevation (feet)2520151050-5Sample NameTestingRecovered (in)Graphic LogCollected SampleMATERIAL
DESCRIPTION
GroupClassificationWater LevelBlows/foot(N60)Log of Boring B-1
Southport Development, Lake Washington Blvd Improve
Renton, Washington
21854-001-01
Project:
Project Location:
Project Number:Figure A-2
Sheet 1 of 2Tacoma: Date:4/13/16 Path:P:\21\21854001\GINT\21854001.GPJ DBTemplate/LibTemplate:GEOENGINEERS8.GDT/GEI8_GEOTECH_STANDARDREMARKS
MoistureContent, %% Fines
8
9
11
12
50/5"
50/6"
Note: See Figure A-1 for explanation of symbols.
FIELD DATA
Depth (feet)35
40 IntervalElevation (feet)-10Sample NameTestingRecovered (in)Graphic LogCollected SampleMATERIALDESCRIPTION
GroupClassificationWater LevelBlows/foot(N60)Log of Boring B-1 (continued)
Southport Development, Lake Washington Blvd Improve
Renton, Washington
21854-001-01
Project:
Project Location:
Project Number:Figure A-2
Sheet 2 of 2Tacoma: Date:4/13/16 Path:P:\21\21854001\GINT\21854001.GPJ DBTemplate/LibTemplate:GEOENGINEERS8.GDT/GEI8_GEOTECH_STANDARDREMARKS
MoistureContent, %% Fines
1
2
3OC
4%F
5%F
6
6
12
18
6
18
18
Brown silty fine to coarse sand with gravel(dense, moist) (fill)
Brown silty fine to coarse sand with gravel
(medium dense, moist) (alluvium)
Brown organic silt with organic matter (wood,leaves) and with interbedded gray silty sand
lenses (medium stiff, wet) (alluvium)
Gray fine to coarse sand with silt (mediumdense, wet) (alluvium)
Gray silty fine to medium sand with occasionalorganic matter (small wood pieces)(medium dense, wet) (alluvium)
Brown organic silt with sand (medium stiff, wet)(alluvium)
SM
SM
OL
SP-SM
SM
OL
37(51)
11(15)
4(6)
12(17)
13(18)
11(15)
Air knife to 5.5 feet bgs
Drilling mud added
OC=18%
Groundwater observed at approximately17 feet during drilling
118
23
25
11
7
TotalDepth (ft)
HammerData
SystemDatum
Start End
Checked By
Logged By
LJSDrilled
Notes:
BEL
Surface Elevation (ft)Vertical Datum
Driller
Groundwater Depth toWater (ft)Date Measured Elevation (ft)
Easting (X)Northing (Y)
Diedrich D-50 Track Rig
Holocene Drilling, Inc.DrillingMethod Hollow-Stem Auger61
Autohammer (83% Efficient)140 (lbs) / 30 (in) Drop
DrillingEquipment
7/20/20157/20/2015
See Remarks
29
NAVD88
Note: See Figure A-1 for explanation of symbols.
FIELD DATA
Depth (feet)0
5
10
15
20
25
30
35 IntervalElevation (feet)2520151050-5Sample NameTestingRecovered (in)Graphic LogCollected SampleMATERIAL
DESCRIPTION
GroupClassificationWater LevelBlows/foot(N60)Log of Boring B-2
Southport Development, Lake Washington Blvd Improve
Renton, Washington
21854-001-01
Project:
Project Location:
Project Number:Figure A-3
Sheet 1 of 2Tacoma: Date:4/13/16 Path:P:\21\21854001\GINT\21854001.GPJ DBTemplate/LibTemplate:GEOENGINEERS8.GDT/GEI8_GEOTECH_STANDARDREMARKS
MoistureContent, %% Fines
7AL; MC
8MC
9SA
10
11
12
18
6
18
6
18
18
Gray sandy silt with occasional organic matterand gravel (stiff, wet) (alluvium)
Gray silty fine to medium sand with fine gravel(medium dense, wet) (glacial deposits)
Grades to dense
Grades to very dense
Gray fine to coarse sand with silt (mediumdense, wet) (glacial deposits)
ML
SM
SP-SM
5(7)
11(15)
21(28)
24(33)
62(85)
28(38)
AL (LL=45; PI=6)
7 feet of heave at 60 feet bgs,unable to sample due to heave
54
105
38
15 32
Note: See Figure A-1 for explanation of symbols.
FIELD DATA
Depth (feet)35
40
45
50
55
60 IntervalElevation (feet)-10-15-20-25-30Sample NameTestingRecovered (in)Graphic LogCollected SampleMATERIALDESCRIPTION
GroupClassificationWater LevelBlows/foot(N60)Log of Boring B-2 (continued)
Southport Development, Lake Washington Blvd Improve
Renton, Washington
21854-001-01
Project:
Project Location:
Project Number:Figure A-3
Sheet 2 of 2Tacoma: Date:4/13/16 Path:P:\21\21854001\GINT\21854001.GPJ DBTemplate/LibTemplate:GEOENGINEERS8.GDT/GEI8_GEOTECH_STANDARDREMARKS
MoistureContent, %% Fines
1
2%F
3MC
4%F
5
6SA
6
12
18
12
12
12
Sod
Brown fine to coarse sand with silt and gravel(loose, moist) (fill)
Gray fine to coarse sand with trace silt (loose,wet) (alluvium)
Brown organic silt with sand and organicmatter (medium stiff, wet) (alluvium)
Gray fine to coarse sand with gravel and tracesilt (loose, wet) (alluvium)
SOD
SP-SM
SP
OL
SP
3(4)
9(12)
4(6)
13(18)
19(26)
10(14)
Switched to mud rotary at 20 feet
Drill chatter at 27 feet
21
105
18
23
4
2
5
TotalDepth (ft)
HammerData
SystemDatum
Start End
Checked By
Logged By
LJSDrilled
Notes:
EAW
Surface Elevation (ft)Vertical Datum
Driller
Groundwater Depth toWater (ft)Date Measured Elevation (ft)
Easting (X)Northing (Y)
Diedrich D-50 Track Rig
Holocene Drilling, Inc.DrillingMethod
Hollow-Stem Auger/Mud
Rotary55
Autohammer (83% Efficient)140 (lbs) / 30 (in) Drop
DrillingEquipment
7/21/20157/21/2015
See Remarks
26
NAVD88
Note: See Figure A-1 for explanation of symbols.
FIELD DATA
Depth (feet)0
5
10
15
20
25
30
35 IntervalElevation (feet)2520151050-5Sample NameTestingRecovered (in)Graphic LogCollected SampleMATERIAL
DESCRIPTION
GroupClassificationWater LevelBlows/foot(N60)Log of Boring B-3
Southport Development, Lake Washington Blvd Improve
Renton, Washington
21854-001-01
Project:
Project Location:
Project Number:Figure A-4
Sheet 1 of 2Tacoma: Date:4/13/16 Path:P:\21\21854001\GINT\21854001.GPJ DBTemplate/LibTemplate:GEOENGINEERS8.GDT/GEI8_GEOTECH_STANDARDREMARKS
MoistureContent, %% Fines
7
8AL
9
10
12
18
12
Gray silty fine to medium sand with trace
organic matter (loose, wet) (alluvium)
Gray organic silt with occasional sand and
trace organic matter (medium stiff, wet)(alluvium)
Gray fine gravel with sand and silt (mediumdense, wet) (glacial deposits)
Grades to dense
SM
OH
GP-GM
9(12)
4(6)
14(19)
38(53)
AL (LL=71; PI=15)
5 feet of heave in hole at 45 feet bgs,attempted flushing holeNo recovery with sampler
Increased drilling resistance
7 feet of heave in hole at 55 feet bgs,
unable to flush hole
No recovery with sampler
58
Note: See Figure A-1 for explanation of symbols.
FIELD DATA
Depth (feet)35
40
45
50
55 IntervalElevation (feet)-10-15-20-25Sample NameTestingRecovered (in)Graphic LogCollected SampleMATERIALDESCRIPTION
GroupClassificationWater LevelBlows/foot(N60)Log of Boring B-3 (continued)
Southport Development, Lake Washington Blvd Improve
Renton, Washington
21854-001-01
Project:
Project Location:
Project Number:Figure A-4
Sheet 2 of 2Tacoma: Date:4/13/16 Path:P:\21\21854001\GINT\21854001.GPJ DBTemplate/LibTemplate:GEOENGINEERS8.GDT/GEI8_GEOTECH_STANDARDREMARKS
MoistureContent, %% Fines
Note:This report may not be reproduced,except in full,without written approval of GeoEngineers,Inc.Test results are applicable only to the specific sample on which they wereperformed,and should not be interpretedas representativeof any other samples obtainedat othertimes,depths or locations,orgeneratedby separateoperations orprocesses.
Thegrain size analysis resultswereobtained ingeneral accordancewith ASTMD 6913.
.Figure A-5Sieve Analysis ResultsSouthport Development Lake Washington Blvd ImprovementsRenton, Washington21854-001-01 Date Exported: 07/23/15
EXPLORATION NUMBER DEPTH(ft)USCS SOIL CLASSIFICATION
B-2B-3 40
30.5
Silty sand with gravel (SM)Poorly graded sand with gravel (SP)
SYMBOL
SAND SILT OR CLAYCOBBLESGRAVEL
COARSE MEDIUM FINECOARSEFINEBOULDERS
3/8”3”#20 #200#40 #60 #1001.5”#10#43/4”
0
10
20
30
40
50
60
70
80
90
100
0.0010.010.11101001000PERCENT PASSING BY WEIGHT GRAIN SIZE IN MILLIMETERS
U.S. STANDARD SIEVE SIZE
Note: This report may not be reproduced, except in full, without written approval of GeoEngineers, Inc. Test results are applicable only to the specific sample on which they were performed, and should not be interpreted as representative of any other
samples obtained at other times, depths or locations, or generated by separate operations or processes.
The liquid limit and plasticity index were obtained in general accordance with ASTM D 4318.
Figure A-6
Atterberg Limits Test Results
Southport Development
Lake Washington Blvd Improvements
Renton, Washington
21854-001-01 Date Exported: 07/27/15Symbol Boring
Number
Depth
(feet)
Moisture
Content
(%)
Liquid
Limit
(%)
Plasticity
Index
(%)USCS Soil Description
B-1
B-2
B-3
25
35
40
98
54
58
99
46
71
23
6
15
Organic silt (OH)
Organic silt (OL)
Organic silt with sand (OH)
0
10
20
30
40
50
60
0 10 20 30 40 50 60 70 80 90 100PLASTICITY INDEX LIQUID LIMIT
PLASTICITY CHART
CL-ML ML or OL
CL or OL
OH or MH
CH or OH
APPENDIX B Report Limitations and Guidelines for Use
April 22, 2016 | Page B-1 File No. 21854-001-01
APPENDIX B
REPORT LIMITATIONS AND GUIDELINES FOR USE1
This appendix provides information to help you manage your risks with respect to the use of this report.
Read These Provisions Closely
It is important to recognize that the geoscience practices (geotechnical engineering, geology and
environmental science) rely on professional judgment and opinion to a greater extent than other
engineering and natural science disciplines, where more precise and/or readily observable data may exist.
To help clients better understand how this difference pertains to our services, GeoEngineers includes the
following explanatory “limitations” provisions in its reports. Please confer with GeoEngineers if you need to
know more how these “Report Limitations and Guidelines for Use” apply to your project or site.
Geotechnical Services are Performed for Specific Purposes, Persons and Projects
This report has been prepared for Southport, LLC and for the Project(s) specifically identified in the report.
The information contained herein is not applicable to other sites or projects.
GeoEngineers structures its services to meet the specific needs of its clients. No party other than the party
to whom this report is addressed may rely on the product of our services unless we agree to such reliance
in advance and in writing. Within the limitations of the agreed scope of services for the Project, and its
schedule and budget, our services have been executed in accordance with our Agreement with Southport,
LLC dated June 15, 2015 and generally accepted geotechnical practices in this area at the time this report
was prepared. We do not authorize, and will not be responsible for, the use of this report for any purposes
or projects other than those identified in the report.
A Geotechnical Engineering or Geologic Report is based on a Unique Set of Project-Specific
Factors
This report has been prepared for Southport Development Lake Washington Boulevard Improvement
located in Renton, Washington. GeoEngineers considered a number of unique, project-specific factors when
establishing the scope of services for this project and report. Unless GeoEngineers specifically indicates
otherwise, it is important not to rely on this report if it was:
■ not prepared for you,
■ not prepared for your project,
■ not prepared for the specific site explored, or
■ completed before important project changes were made.
1 Developed based on material provided by ASFE, Professional Firms Practicing in the Geosciences; www.asfe.org.
April 22, 2016 | Page B-2 File No. 21854-001-01
For example, changes that can affect the applicability of this report include those that affect:
■ the function of the proposed structure;
■ elevation, configuration, location, orientation or weight of the proposed structure;
■ composition of the design team; or
■ project ownership.
If changes occur after the date of this report, GeoEngineers cannot be responsible for any consequences
of such changes in relation to this report unless we have been given the opportunity to review our
interpretations and recommendations. Based on that review, we can provide written modifications or
confirmation, as appropriate.
Environmental Concerns are Not Covered
Unless environmental services were specifically included in our scope of services, this report does not
provide any environmental findings, conclusions, or recommendations, including but not limited to, the
likelihood of encountering underground storage tanks or regulated contaminants.
Subsurface Conditions Can Change
This geotechnical or geologic report is based on conditions that existed at the time the study was performed.
The findings and conclusions of this report may be affected by the passage of time, by man-made events
such as construction on or adjacent to the site, new information or technology that becomes available
subsequent to the report date, or by natural events such as floods, earthquakes, slope instability or
groundwater fluctuations. If more than a few months have passed since issuance of our report or work
product, or if any of the described events may have occurred, please contact GeoEngineers before applying
this report for its intended purpose so that we may evaluate whether changed conditions affect the
continued reliability or applicability of our conclusions and recommendations.
Geotechnical and Geologic Findings are Professional Opinions
Our interpretations of subsurface conditions are based on field observations from widely spaced sampling
locations at the site. Site exploration identifies the specific subsurface conditions only at those points where
subsurface tests are conducted or samples are taken. GeoEngineers reviewed field and laboratory data
and then applied its professional judgment to render an informed opinion about subsurface conditions at
other locations. Actual subsurface conditions may differ, sometimes significantly, from the opinions
presented in this report. Our report, conclusions and interpretations are not a warranty of the actual
subsurface conditions.
Geotechnical Engineering Report Recommendations are Not Final
We have developed the following recommendations based on data gathered from subsurface
investigation(s). These investigations sample just a small percentage of a site to create a snapshot of the
subsurface conditions elsewhere on the site. Such sampling on its own cannot provide a complete and
accurate view of subsurface conditions for the entire site. Therefore, the recommendations included in this
report are preliminary and should not be considered final. GeoEngineers’ recommendations can be
finalized only by observing actual subsurface conditions revealed during construction. GeoEngineers
April 22, 2016 | Page B-3 File No. 21854-001-01
cannot assume responsibility or liability for the recommendations in this report if we do not perform
construction observation.
We recommend that you allow sufficient monitoring, testing and consultation during construction by
GeoEngineers to confirm that the conditions encountered are consistent with those indicated by the
explorations, to provide recommendations for design changes if the conditions revealed during the work
differ from those anticipated, and to evaluate whether earthwork activities are completed in accordance
with our recommendations. Retaining GeoEngineers for construction observation for this project is the most
effective means of managing the risks associated with unanticipated conditions. If another party performs
field observation and confirms our expectations, the other party must take full responsibility for both the
observations and recommendations. Please note, however, that another party would lack our project-
specific knowledge and resources.
A Geotechnical Engineering or Geologic Report Could Be Subject to Misinterpretation
Misinterpretation of this report by members of the design team or by contractors can result in costly
problems. GeoEngineers can help reduce the risks of misinterpretation by conferring with appropriate
members of the design team after submitting the report, reviewing pertinent elements of the design team’s
plans and specifications, participating in pre-bid and preconstruction conferences, and providing
construction observation.
Do Not Redraw the Exploration Logs
Geotechnical engineers and geologists prepare final boring and testing logs based upon their interpretation
of field logs and laboratory data. The logs included in a geotechnical engineering or geologic report should
never be redrawn for inclusion in architectural or other design drawings. Photographic or electronic
reproduction is acceptable, but separating logs from the report can create a risk of misinterpretation.
Give Contractors a Complete Report and Guidance
To help reduce the risk of problems associated with unanticipated subsurface conditions, GeoEngineers
recommends giving contractors the complete geotechnical engineering or geologic report, including these
“Report Limitations and Guidelines for Use.” When providing the report, you should preface it with a clearly
written letter of transmittal that:
■ advises contractors that the report was not prepared for purposes of bid development and that its
accuracy is limited; and
■ encourages contractors to confer with GeoEngineers and/or to conduct additional study to obtain the
specific types of information they need or prefer.
Contractors are Responsible for Site Safety on Their Own Construction Projects
Our geotechnical recommendations are not intended to direct the contractor’s procedures, methods,
schedule or management of the work site. The contractor is solely responsible for job site safety and for
managing construction operations to minimize risks to on-site personnel and adjacent properties.
April 22, 2016 | Page B-4 File No. 21854-001-01
Biological Pollutants
GeoEngineers’ Scope of Work specifically excludes the investigation, detection, prevention or assessment
of the presence of Biological Pollutants. Accordingly, this report does not include any interpretations,
recommendations, findings or conclusions regarding the detecting, assessing, preventing or abating of
Biological Pollutants, and no conclusions or inferences should be drawn regarding Biological Pollutants as
they may relate to this project. The term “Biological Pollutants” includes, but is not limited to, molds, fungi,
spores, bacteria and viruses, and/or any of their byproducts.
A Client that desires these specialized services is advised to obtain them from a consultant who offers
services in this specialized field.
1101 South Fawcett Avenue, Suite 200
Tacoma, Washington 98402
253.383.4940
May 8, 2018
Southport, LLC
1083 Lake Washington Boulevard, Suite 50
Renton, Washington 98056
Attention: Scott Rosenstock
Subject: Report Addendum-Revised
Southport Development Lake Washington Boulevard Improvement
Renton, Washington
File No. 21854-001-04
INTRODUCTION AND PROJECT UNDERSTANDING
This revised report addendum supplements our geotechnical design report “Geotechnical Engineering
Services Revised Report, Southport Development, Lake Washington Boulevard Improvement, Renton,
Washington” dated April 22, 2016.
Lake Washington Boulevard will be widened to the south of the existing alignment from Garden Avenue
North to Houser Way North. This road widening will extend the road over an existing ditch that conveys
Johns Creek to the north. The revised road widening design will require excavation into the Park Avenue
embankment to achieve the required dimensions for the Johns Creek Confluence. Portions of the Park
Avenue embankment will be modified to create a reinforced slope for the final condition. This addendum
addresses the proposed embankment modification including additional geotechnical analysis and design
recommendations for the proposed reinforced slope. Our April 2016 report includes subsurface data near
the site of the Lake Washington Boulevard North Road Improvements.
We understand the proposed embankment modification will consist of a Hilfiker spiral nail system to
support a portion of the Park Avenue embankment. We were provided with preliminary shop drawings
(dated May 3, 2018) and internal stability calculations (dated May 7, 2018) from Hilfiker Retaining Walls
for the proposed spiral nail system. We understand the proposed road widening will consist of a welded
wire face wall (Hilfiker system, or similar) to support Lake Washington Boulevard.
Our services are provided in accordance with the terms and conditions from our initial contract dated
June 15, 2015 and as described in a change order initiated on March 16, 2018.
Southport, LLC | May 8, 2018 Page 2
File No. 21854-001-04
CONCLUSIONS AND RECOMMENDATIONS
General
This addendum provides recommendations specific to the proposed road widening of Lake Washington
Boulevard and the reinforced slope at the Park Avenue embankment. Recommendations provided in our
April 2016 report for earthwork and site preparation, permanent slopes, earthquake engineering, culverts
and culvert foundations, and creek bank stability are still applicable. GeoEngineers’ recommendations for
fill materials placed within the creek channel for habitat and hydraulic concerns are being addressed
separately.
Global Stability
We evaluated the static global stability of one cross section of the spiral nail system using the computer
program SLOPE/W (GeoStudio International, Ltd., 2012). For our global stability analysis, we modeled a
cross section based on the two-tiered Hilfiker spiral nail system as proposed in the preliminary shop
drawings and internal stability calculations provided by Hilfiker. Our model and analysis results are
presented as Figure 3. We modeled wall heights equal to 6 feet for both upper and lower tier, with a
5-foot horizontal bench between tiers. Spiral nail geometry for the upper tier is 20-foot nail lengths at an
inclination of 16 degrees below horizontal. Spiral nail geometry for the lower tier is 12-foot nail lengths at
an inclination of 15 degrees below horizontal. Both walls have a lateral nail spacing of 6 feet. Based on
the values used in the Hilfiker internal resistance calculations, we assumed a nominal pullout resistance
of the spiral nails equal to 942 pounds per linear foot (plf).
The Washington State Department of Transportation (WSDOT) Geotechnical Design Manual (GDM)
recommends a minimum safety factor of 1.3 for all embankments and reinforced slopes under static
conditions. Our analysis indicates a factor of safety equal to 1.3 for global stability under static conditions
for the proposed slope. Internal strength design of the proposed system shall be the responsibility of
others.
Design Recommendations
We recommend that reinforced slopes be designed using the methods described in WSDOT GDM Chapter
15 “Abutments, Retaining Walls, and Reinforced Slopes” or other appropriate design methods.
We anticipate the proposed slopes and walls can be supported on undisturbed firm granular alluvium
soils. Soil observed during subsurface explorations included loose sands and soft organic silts within the
alluvial deposits. Overexcavation of loose, soft or highly organic soils could be required to achieve suitable
foundation support. For planning purposes, we recommend up to 2 feet of overexcavation below the base
of fill wall sections. Overexcavated areas should extend laterally beyond the wall edges a distance equal
to the depth of overexcavation. The overexcavated areas should be backfilled with compacted structural
fill consisting of angular rock with few fines. In our opinion, material conforming to WSDOT Standard
Specification 9-03.9(2) “Permeable Ballast” is suitable for this purpose, as described in Section 4.3.1.4
of our April 2016 report. GeoEngineers should observe subgrade conditions to evaluate if overexcavation
is required during construction.
We recommend elements bearing on underlying alluvial deposits are evaluated using a Strength Limit
bearing resistance 5,000 pounds per square foot (psf) and an Extreme Event Limit bearing resistance of
11,500 psf. These bearing resistances are applicable for a minimum footing width of 10 feet. The
Southport, LLC | May 8, 2018 Page 3
File No. 21854-001-04
resistance presented for the Strength Limit State has been factored with a resistance factor of 0.45. The
Extreme Event Limit State has not been factored. A resistance factor of 0.9 should be applied to this
value for seismic loading cases. These bearing resistances are based on a punching or shear failure of
the soil subgrade and do not take into consideration excessive settlement.
The revised design will consist of excavation into the existing Park Avenue embankment and construction
of a reinforced slope to match existing grades. Since this results in a net removal of load we do not
anticipate significant total settlements due to this work. We anticipate differential settlements on the
order of 1 inch in 50 feet could occur due to inherent variations in the alluvial soils underneath the
proposed slope.
Drainage
Permanent drainage systems should intercept surface water runoff at the top of the proposed slope to
prevent it from flowing in an uncontrolled manner across the slope face. Water levels in the adjacent
Johns Creek Confluence are expected to fluctuate. We recommend that permanent drainage systems be
provided to prevent hydrostatic pressures developing behind the reinforced slope sections. In our opinion,
positive drainage can be provided by installing drain board behind the shotcrete wall facing.
LIMITATIONS
We have prepared this addendum for the exclusive use of Southport, LLC and their authorized agents for
Southport Development Lake Washington Boulevard Improvement project located in Renton, Washington.
The data and addendum should be provided to prospective contractors for their bidding or estimating
purposes, but our addendum, conclusions and interpretations should not be construed as a warranty of
the subsurface conditions.
Within the limitations of scope, schedule and budget, our services have been executed in accordance
with generally accepted practices in the field of geotechnical engineering in this area at the time this
addendum was prepared. No warranty or other conditions, express or implied, should be understood.
Notes:
1. The locations of all features shown are approximate.
2. This drawing is for information purposes. It is intended to assist in showing features discussed in an attached document. GeoEngineers, Inc. cannot guarantee the accuracy and content of electronic files. The master file is stored by GeoEngineers, Inc. and will
serve as the official record of this communication.Figure 3
Global Slope Stability-Static Conditions
Lake Washington Boulevard Improvement
Renton, Washington
21854-001-04 Date Exported: 05/08/2018
Existing Fill
Alluvium (Sand)
Glacial
Existing Fill
1.30
Alignment (ft.)
0 10 20 30 40 50 60 70 80 90 100 110 120 130 140Elevation (ft)-20
-10
0
10
20
30
40
50
60
70
Alignment with moment slab
Name Unit Weight (pcf)
Cohesion'(psf)Phi' (°)
Existing Fill 135 0 34
Alluvium (Sand)120 0 32
Glacial 135 0 36
Existing grade
Surcharge - 250 psf
Surcharge - 250 psf
Hilfiker Spiral Nail
---------------------------------------------Upper Tier: L = 20 feet, α = 16°Lower Tier: L = 12 feet, α = 15°
Appendix B – Reports
1. Joint Aquatic Resources Permit Application (JARPA)
2. Hydrologic and Hydraulics Analysis – Memo by GeoEngineers (dated March 20, 2017)
3. Geotechnical Engineering Report, Southport Lake Washington Boulevard Improvements – Phase II &
III. Prepared by Geo Engineers, Inc.
4. Revised Report Addendum to “Geotechnical Engineering Services Report, Southport Development,
Lake Washington Boulevard Improvements, (dated May 8, 2018)
JARPA Revision 2015.1 Page 1 of 13
WASHINGTON STATE
Joint Aquatic Resources Permit
Application (JARPA) Form1,2 [help]
USE BLACK OR BLUE INK TO ENTER ANSWERS IN THE WHITE SPACES BELOW.
Part 1–Project Identification
1. Project Name (A name for your project that you create. Examples: Smith’s Dock or Seabrook Lane Development) [help]
Lake Washington Boulevard North Road Improvements
Part 2–Applicant
The person and/or organization responsible for the project. [help]
2a. Name (Last, First, Middle)
Rosenstock, Scott
2b. Organization (If applicable)
Office at Southport LLC
2c. Mailing Address (Street or PO Box)
1083 Lake Washington Boulevard North, Suite 50
2d. City, State, Zip
Renton, Washington 98056
2e. Phone (1) 2f. Phone (2) 2g. Fax 2h. E-mail
(425) 282-5833 (206) 383-3484 (425) 282-5838 srosenstock@secodev.com
1Additional forms may be required for the following permits:
• If your project may qualify for Department of the Army authorization through a Regional General Permit (RGP), contact the U.S. Army Corps of
Engineers for application information (206) 764-3495.
• If your project might affect species listed under the Endangered Species Act, you will need to fill out a Specific Project Information Form (SPIF) or
prepare a Biological Evaluation. Forms can be found at
http://www.nws.usace.army.mil/Missions/CivilWorks/Regulatory/PermitGuidebook/EndangeredSpecies.aspx.
• Not all cities and counties accept the JARPA for their local Shoreline permits. If you need a Shoreline permit, contact the appropriate city or county
government to make sure they accept the JARPA.
2To access an online JARPA form with [help] screens, go to
http://www.epermitting.wa.gov/site/alias__resourcecenter/jarpa_jarpa_form/9984/jarpa_form.aspx.
For other help, contact the Governor’s Office for Regulatory Innovation and Assistance at (800) 917-0043 or help@oria.wa.gov.
AGENCY USE ONLY
Date received:
Agency reference #:
Tax Parcel #(s):
JARPA Revision 2015.1 Page 2 of 13
Part 3–Authorized Agent or Contact
Person authorized to represent the applicant about the project. (Note: Authorized agent(s) must sign 11b of this
application.) [help]
3a. Name (Last, First, Middle)
Conlin, David
3b. Organization (If applicable)
GeoEngineers, Inc.
3c. Mailing Address (Street or PO Box)
1101 South Fawcett Avenue, Suite 200
3d. City, State, Zip
Tacoma, Washington 98402
3e. Phone (1) 3f. Phone (2) 3g. Fax 3h. E-mail
(253) 383-4940 dconlin@geoengineers.com
Part 4–Property Owner(s)
Contact information for people or organizations owning the property(ies) where the project will occur. Consider both
upland and aquatic ownership because the upland owners may not own the adjacent aquatic land. [help]
Same as applicant. (Skip to Part 5.)
Repair or maintenance activities on existing rights-of-way or easements. (Skip to Part 5.)
There are multiple upland property owners. Complete the section below and fill out JARPA Attachment A for
each additional property owner.
Your project is on Department of Natural Resources (DNR)-managed aquatic lands. If you don’t know,
contact the DNR at (360) 902-1100 to determine aquatic land ownership. If yes, complete JARPA Attachment E
to apply for the Aquatic Use Authorization.
4a. Name (Last, First, Middle)
4b. Organization (If applicable)
4c. Mailing Address (Street or PO Box)
4d. City, State, Zip
4e. Phone (1) 4f. Phone (2) 4g. Fax 4h. E-mail
JARPA Revision 2015.1 Page 3 of 13
Part 5–Project Location(s)
Identifying information about the property or properties where the project will occur. [help]
There are multiple project locations (e.g. linear projects). Complete the section below and use JARPA
Attachment B for each additional project location.
5a. Indicate the type of ownership of the property. (Check all that apply.) [help]
Private
Federal
Publicly owned (state, county, city, special districts like schools, ports, etc.) – Road Right of Way
Tribal
Department of Natural Resources (DNR) – managed aquatic lands (Complete JARPA Attachment E)
5b. Street Address (Cannot be a PO Box. If there is no address, provide other location information in 5p.) [help]
LAKE WASHINGTON BLVD N
5c. City, State, Zip (If the project is not in a city or town, provide the name of the nearest city or town.) [help]
Renton, Washington 98056
5d. County [help]
King
5e. Provide the section, township, and range for the project location. [help]
¼ Section Section Township Range
NW 8 23 North 05 East
5f. Provide the latitude and longitude of the project location. [help]
• Example: 47.03922 N lat. / -122.89142 W long. (Use decimal degrees - NAD 83)
47.501878° N lat. / -122.200382° W long
5g. List the tax parcel number(s) for the project location. [help]
• The local county assessor’s office can provide this information.
N/A – Public Right of Way
5h. Contact information for all adjoining property owners. (If you need more space, use JARPA Attachment C.) [help]
Name Mailing Address Tax Parcel # (if known)
BNSF PO Box 961089 0823059027
Fort Worth, TX 76161
5i. List all wetlands on or adjacent to the project location. [help]
N/A – there are no wetlands on or adjacent to the project location.
JARPA Revision 2015.1 Page 4 of 13
5j. List all waterbodies (other than wetlands) on or adjacent to the project location. [help]
Johns Creek
5k. Is any part of the project area within a 100-year floodplain? [help]
Yes No Don’t know
5l. Briefly describe the vegetation and habitat conditions on the property. [help]
The project is located along the east side of Lake Washington Blvd within undeveloped public right-of-way. The
area has recently been cleared of vegetation, primarily Himalayan blackberry (Rubus armeniacus), and very little
vegetation currently remains. Puget Sound Energy (PSE) operates a series of utility poles through this area,
which have recently been relocated up to 25 feet east of the former alignment to accommodate the road
widening. An open-water depression associated with Johns Creek is present at the site; four culverts discharge
stormwater runoff into this depression from the north, east and south; four additional parallel culverts cross Lake
Washington Blvd to the west draining the depression.
5m. Describe how the property is currently used. [help]
The project site consists of undeveloped cleared right-of-way as well as stormwater/surface water conveyance
features.
5n. Describe how the adjacent properties are currently used. [help]
The landscape surrounding the project area is heavily developed and surrounded by roadways in all directions.
BNSF railroad tracks and a public road (Lake Washington Boulevard) border the site to the west, an
undeveloped slope and NE Park Dr border the site to the east, an intersection with Houser Way N bounds the
site the north, and an intersection with NE Park Dr bounds the site to the south.
5o. Describe the structures (above and below ground) on the property, including their purpose(s) and current
condition. [help]
The depression is lined with riprap on the north, east, and south banks, and bounded by a gabion wall on the
west side. Four concrete culverts discharge stormwater runoff into the depression from the north, east, and
south. Four concrete culverts drain the depression to the west across Lake Washington Boulevard N. A PSE
overhead electric utility system supported on wooden poles runs parallel to the road on its east side.
5p. Provide driving directions from the closest highway to the project location, and attach a map. [help]
From Interstate 405, take Exit 5 for Washington 900 E and turn west onto NE Park Dr. Take the next right onto
Lake Washington Boulevard N, and then the site will be on the right side of the road before the intersection with
Coulon Beach Park Dr.
Part 6–Project Description
6a. Briefly summarize the overall project. You can provide more detail in 6b. [help]
The proposed project includes widening of Lake Washington Blvd to support additional traffic capacity needed
as a result of the Southport Mixed-Use Development. Road improvements will be accomplished by adding
roadway surface to the east side of the road. The currently existing surface water depression will be relocated
laterally to the east, existing tributary culverts will be redirected into the new channel, and the existing discharge
culverts will be extended under the widened roadway to continue to provide similar drainage conditions as the
current baseline.
6b. Describe the purpose of the project and why you want or need to perform it. [help]
The project is intended to improve increased traffic flow entering and exiting the Southport Mixed-Use
Development, as well as existing traffic volumes associated with the public park, an existing PSE substation,
and existing developments and neighborhoods further to the north. Relocating the open-water depressional
feature to the east side of the widened roadway is the most feasible option for accommodating road widening,
as approved in the SEPA determination for the development, while simultaneously maintaining existing fish
JARPA Revision 2015.1 Page 5 of 13
passage conditions, as requested by regulatory agencies and tribes.
6c. Indicate the project category. (Check all that apply) [help]
Commercial Residential Institutional Transportation Recreational
Maintenance Environmental Enhancement
6d. Indicate the major elements of your project. (Check all that apply) [help]
Aquaculture
Bank Stabilization
Boat House
Boat Launch
Boat Lift
Bridge
Bulkhead
Buoy
Channel Modification
Culvert
Dam / Weir
Dike / Levee / Jetty
Ditch
Dock / Pier
Dredging
Fence
Ferry Terminal
Fishway
Float
Floating Home
Geotechnical Survey
Land Clearing
Marina / Moorage
Mining
Outfall Structure
Piling/Dolphin
Raft
Retaining Wall
(upland)
Road
Scientific
Measurement Device
Stairs
Stormwater facility
Swimming Pool
Utility Line
Other:
6e. Describe how you plan to construct each project element checked in 6d. Include specific construction
methods and equipment to be used. [help]
• Identify where each element will occur in relation to the nearest waterbody.
• Indicate which activities are within the 100-year floodplain.
Preliminary design drawings are attached. Project construction activities, which are listed in the approximate
anticipated construction sequence, include:
■ Traffic Control. Traffic Control Devices will be installed prior to beginning construction activities. Signage,
barriers and flagging stations, if applicable, will be placed within the road right-of-way and outside of critical
areas.
■ Temporary Erosion and Sedimentation Control (TESC) BMP Installation. General TESC BMPs will be
installed in accordance with an approved TESC and Construction Stormwater Pollution Prevention Plan.
■ Vegetation Clearing. Most vegetation has already been cleared as part of a separate interdependent action
and the area will not be replanted until the roadway widening is complete. Some minimal additional
vegetation clearing may be required to complete the work, such as removing remaining low-growing weeds,
primarily invasive blackberry, at the stream bank where the replacement channel will be constructed.
■ Channel Relocation. The existing open-water channel will be relocated laterally to the east side of the
widened roadway. The channel geometry has been designed to mimic existing conditions and flow modeling
has been completed to ensure capacity to pass the 100-year flood. Channel substrate will be sized
according to flow modeling and adjacent reference reaches to ensure appropriate fish habitat and scour
protection are provided.
■ Culvert Modifications. The two tributary culverts from the south will be redirected into the new open water
channel. The two tributary culverts from the north will be cut short and intercepted by the new channel. The
four culverts under Lake Washington Boulevard, which convey Johns Creek toward Lake Washington, will
be extended under the widened roadway to the relocated channel.
■ Retaining Walls. Retaining walls will be constructed at the road edge on the west side of the relocated
JARPA Revision 2015.1 Page 6 of 13
channel to retain road fill as well as east of the relocated channel where the existing slope will be cut. The
slope retaining wall will be set back from the channel OHWM at the toe and terraced upwards to the east to
provide riparian planting area.
■ Earthwork. The project will require earthwork both within and outside of the OHWM. The entire area of the
existing open-water channel will be dewatered and filled behind the new road retaining wall. The existing
slope will be cut back, sloped, and retained with walls where necessary to accommodate the relocated
channel geometry and extents.
■ Work Area Exclusion and Dewatering. The existing open-water feature is not typically utilized by fish;
however, a biologist will be on site to monitor the dewatering as a precautionary measure and will have all
tools available to capture and transport fish if encountered. The work area will be dewatered and a
temporary diversion will be implemented during construction. It is anticipated that the temporary diversion
will require a system of coffer dams, pumps and hoses to convey flow around the work area. Once
construction has been completed, flow will be redirected back into the extended discharge culverts and the
diversion will be removed. Dewatering activities will follow local, state, and federal permit requirements.
■ Road Construction. Once channel relocation, culvert extensions, and road fill is complete, a base course
will be placed and then the road surfacing, striping, curbs and guard rails.
■ Mitigation and Restoration Activities. All temporary construction impacts will be restored following
completion of construction activities. A planting plan for disturbed areas adjacent to the roadway is included
in Appendix B, Sheets 5-6.
6f. What are the anticipated start and end dates for project construction? (Month/Year) [help]
• If the project will be constructed in phases or stages, use JARPA Attachment D to list the start and end dates of each phase or
stage.
Start date: June 2018 End date: September 2018 See JARPA Attachment D
6g. Fair market value of the project, including materials, labor, machine rentals, etc. [help]
$1.5-1.7 million
6h. Will any portion of the project receive federal funding? [help]
• If yes, list each agency providing funds.
Yes No Don’t know
Part 7–Wetlands: Impacts and Mitigation
Check here if there are wetlands or wetland buffers on or adjacent to the project area.
(If there are none, skip to Part 8.) [help]
7a. Describe how the project has been designed to avoid and minimize adverse impacts to wetlands. [help]
Not applicable
7b. Will the project impact wetlands? [help]
Yes No Don’t know
7c. Will the project impact wetland buffers? [help]
Yes No Don’t know
JARPA Revision 2015.1 Page 7 of 13
7d. Has a wetland delineation report been prepared? [help]
• If Yes, submit the report, including data sheets, with the JARPA package.
Yes No
7e. Have the wetlands been rated using the Western Washington or Eastern Washington Wetland Rating
System? [help]
• If Yes, submit the wetland rating forms and figures with the JARPA package.
Yes No Don’t know
7f. Have you prepared a mitigation plan to compensate for any adverse impacts to wetlands? [help]
• If Yes, submit the plan with the JARPA package and answer 7g.
• If No, or Not applicable, explain below why a mitigation plan should not be required.
Yes No Not applicable
7g. Summarize what the mitigation plan is meant to accomplish, and describe how a watershed approach was
used to design the plan. [help]
7h. Use the table below to list the type and rating of each wetland impacted, the extent and duration of the
impact, and the type and amount of mitigation proposed. Or if you are submitting a mitigation plan with a
similar table, you can state (below) where we can find this information in the plan. [help]
Activity (fill,
drain, excavate,
flood, etc.)
Wetland
Name1
Wetland
type and
rating
category2
Impact
area (sq.
ft. or
Acres)
Duration
of impact3
Proposed
mitigation
type4
Wetland
mitigation area
(sq. ft. or
acres)
1 If no official name for the wetland exists, create a unique name (such as “Wetland 1”). The name should be consistent with other project documents, such
as a wetland delineation report. 2 Ecology wetland category based on current Western Washington or Eastern Washington Wetland Rating System. Provide the wetland
rating forms with the JARPA package.
3 Indicate the days, months or years the wetland will be measurably impacted by the activity. Enter “permanent” if applicable.
4 Creation (C), Re-establishment/Rehabilitation (R), Enhancement (E), Preservation (P), Mitigation Bank/In-lieu fee (B)
Page number(s) for similar information in the mitigation plan, if available:
7i. For all filling activities identified in 7h, describe the source and nature of the fill material, the amount in cubic
yards that will be used, and how and where it will be placed into the wetland. [help]
7j. For all excavating activities identified in 7h, describe the excavation method, type and amount of material in
cubic yards you will remove, and where the material will be disposed. [help]
JARPA Revision 2015.1 Page 8 of 13
Part 8–Waterbodies (other than wetlands): Impacts and Mitigation
In Part 8, “waterbodies” refers to non-wetland waterbodies. (See Part 7 for information related to wetlands.) [help]
Check here if there are waterbodies on or adjacent to the project area. (If there are none, skip to Part 9.)
8a. Describe how the project is designed to avoid and minimize adverse impacts to the aquatic environment.
[help]
Not applicable
The primary minimization efforts for this project focusses on protecting water quality leaving the site. While fish
habitat is not mapped east of Lake Washington Blvd, water quality impacts could affect downstream sections of
Johns Creek, where fish are more likely to be present, and there is no barrier precluding fish use of the site at
some flow levels.
The project has been designed to provide compensatory fish habitat for all impacts to the open-water channel.
The open-water channel will be relocated laterally to the east, and the total amount of proposed open-water
habitat exceeds the current baseline. Furthermore, riparian vegetation enhancement will provide a substantial
improvement in habitat conditions.
Clearing, grading, and other construction activities will result in removal of invasive vegetation and could cause
suspended sediment to enter the waterway. Potential short-term impacts to water quality resulting from
construction will be controlled through typical BMPs for sedimentation and erosion control. Exposed soils will be
covered during construction and restored as soon as reasonably possible to prevent sediment-laden water
leaving the work area. Disturbed areas will be re-planted with native species once construction activities have
been completed.
Potential long-term impacts to water quality will be minimized by restoring disturbed areas with native vegetation
and by providing stormwater treatment improvements to runoff from the roadway.
8b. Will your project impact a waterbody or the area around a waterbody? [help]
Yes No
8c. Have you prepared a mitigation plan to compensate for the project’s adverse impacts to non-wetland
waterbodies? [help]
• If Yes, submit the plan with the JARPA package and answer 8d.
• If No, or Not applicable, explain below why a mitigation plan should not be required.
Yes No Not applicable
8d. Summarize what the mitigation plan is meant to accomplish. Describe how a watershed approach was used
to design the plan.
• If you already completed 7g you do not need to restate your answer here. [help]
The proposed roadway fill will displace approximately 483 square feet (SF) of open-water aquatic habitat within
the depression (which does not constitute fish habitat), and 3,235 SF of existing degraded vegetated area within
the regulatory buffer. The mitigation plan focuses on three components: (1) replacing the open water channel
with a larger channel that is relocated laterally to the east to accommodate the road widening; (2) restoring and
enhancing vegetation conditions at the site, and (3) stormwater treatment improvements to road runoff. The
replacement channel configuration is illustrated on JARPA Drawing Sheets 3 and 4; the replacement channel
creates 1,067 SF of open-water aquatic habitat. Mitigation planting areas and species selections are provided
on JARPA Drawing Sheets 5 and 6; the total planting area is 14,573 SF, exceeding the impact area by a ratio of
approximately 4.5:1. Stormwater improvements include proposed treatment of 7,500 SF of pollution-generating
impervious surfaces associated with the roadway, which exceeds the 6,800 SF of new impervious surface that
JARPA Revision 2015.1 Page 9 of 13
will be created by this project. Two Filterra 4x4 curb inlets, approved for ‘Enhanced Basic’ water quality
treatment in the City of Renton Stormwater Design Manual (SWDM), will be installed adjacent to the road.
Although the project impact area is not documented as fish and wildlife habitat, the project has the potential to
impact downstream habitats resulting from changes to water quality. The mitigation plan has been designed to
ensure fish habitat is not lost, water quality impacts do not occur in downstream habitats, and riparian conditions
are improved over the long-term, which will be documented in a post-construction vegetation monitoring plan .
8e. Summarize impact(s) to each waterbody in the table below. [help]
Activity
(clear,
dredge, fill,
pile drive,
etc.)
Waterbody
name1
Impact
location2
Duration of impact3
Amount of
material (cubic
yards) to be
placed in or
removed from
waterbody
Area (sq. ft.
or linear ft.)
of waterbody
directly
affected
Fill Johns
Creek
Within
(waterward
of OHWM)
Permanent 170 CY of
imported fill
483 SF
(entire
depression
within OHW)
Fill Johns
Creek
Adjacent
(landward of
OHWM)
Permanent 50 CY of
imported soil
N/A
Excavate Johns
Creek
Adjacent
(landward of
OHWM)
Permanent 1,200 CY of
existing soil and
riprap will be
excavated to
create the new
channel and
side slopes
New open
channel
created
adjacent to
existing
channel will
amount to
1,067 SF
1 If no official name for the waterbody exists, create a unique name (such as “Stream 1”) The name should be consistent with other documents provided.
2 Indicate whether the impact will occur in or adjacent to the waterbody. If adjacent, provide the distance between the impact and the waterbody and
indicate whether the impact will occur within the 100-year flood plain.
3 Indicate the days, months or years the waterbody will be measurably impacted by the work. Enter “permanent” if applicable.
8f. For all activities identified in 8e, describe the source and nature of the fill material, amount (in cubic yards)
you will use, and how and where it will be placed into the waterbody. [help]
Fill material will completely displace the existing open-water channel of Johns Creek at the site, which will be
mitigated by creating a new channel on the east side of the widened roadway. The existing drainage culverts
under Lake Washington Boulevard will be extended east to a new roadway retaining wall, and imported fill will
be placed behind the wall. Once the road fill has been placed, a base course (gravel) will be added, and then a
pavement overlay (hot-mix asphalt), curbs (concrete), etc.
8g. For all excavating or dredging activities identified in 8e, describe the method for excavating or dredging,
type and amount of material you will remove, and where the material will be disposed. [help]
Excavation for the relocated channel, side slopes, and retaining walls will be completed using typical machinery,
such as an excavator or backhoe. Excavation spoils will be stockpiled onsite for potential re-use as road fill.
Excess spoils will be transported offsite for disposal at an appropriate facility.
JARPA Revision 2015.1 Page 10 of 13
Part 9–Additional Information
Any additional information you can provide helps the reviewer(s) understand your project. Complete as much of
this section as you can. It is ok if you cannot answer a question.
9a. If you have already worked with any government agencies on this project, list them below. [help]
Agency Name Contact Name Phone Most Recent
Date of Contact
Wash. Dept. of Fish &
Wildlife
Larry Fisher (425) 313-5683 November 28, 2017
( )
9b. Are any of the wetlands or waterbodies identified in Part 7 or Part 8 of this JARPA on the Washington
Department of Ecology’s 303(d) List? [help]
• If Yes, list the parameter(s) below.
• If you don’t know, use Washington Department of Ecology’s Water Quality Assessment tools at:
http://www.ecy.wa.gov/programs/wq/303d/.
Yes No
9c. What U.S. Geological Survey Hydrological Unit Code (HUC) is the project in? [help]
• Go to http://cfpub.epa.gov/surf/locate/index.cfm to help identify the HUC.
17110012
9d. What Water Resource Inventory Area Number (WRIA #) is the project in? [help]
• Go to http://www.ecy.wa.gov/services/gis/maps/wria/wria.htm to find the WRIA #.
8 – Cedar Sammamish
9e. Will the in-water construction work comply with the State of Washington water quality standards for
turbidity? [help]
• Go to http://www.ecy.wa.gov/programs/wq/swqs/criteria.html for the standards.
Yes No Not applicable
9f. If the project is within the jurisdiction of the Shoreline Management Act, what is the local shoreline
environment designation? [help]
• If you don’t know, contact the local planning department.
• For more information, go to: http://www.ecy.wa.gov/programs/sea/sma/laws_rules/173-26/211_designations.html.
Rural Urban Natural Aquatic Conservancy Other ____________
N/A – The project is not within the shoreline management jurisdiction
9g. What is the Washington Department of Natural Resources Water Type? [help]
• Go to http://www.dnr.wa.gov/forest-practices-water-typing for the Forest Practices Water Typing System.
Shoreline Fish Non-Fish Perennial Non-Fish Seasonal
9h. Will this project be designed to meet the Washington Department of Ecology’s most current stormwater
manual? [help]
• If No, provide the name of the manual your project is designed to meet.
JARPA Revision 2015.1 Page 11 of 13
Yes No
Name of manual:
9i. Does the project site have known contaminated sediment? [help]
• If Yes, please describe below.
Yes No
9j. If you know what the property was used for in the past, describe below. [help]
The site appears to have been in its current state since the 1990s (based on interpretation of aerial imagery
available from Google Earth).
9k. Has a cultural resource (archaeological) survey been performed on the project area? [help]
• If Yes, attach it to your JARPA package.
Yes No
9l. Name each species listed under the federal Endangered Species Act that occurs in the vicinity of the project
area or might be affected by the proposed work. [help]
There are no endangered or threatened species at the project site according to WDFW PHS interactive map
viewer.
Lake Washington, which is northwest of the project site and outside of the project Action Area, contains the
following ESA-listed fish species: Puget Sound Chinook salmon (Oncorhynchus tshawytscha), Puget Sound
steelhead (Oncorhynchus mykis), and bull trout (Salvelinus malma). The channel downstream of the work area
contains some fish habitat. Please refer to the BE developed for the project for a detailed ESA analysis.
9m. Name each species or habitat on the Washington Department of Fish and Wildlife’s Priority Habitats and
Species List that might be affected by the proposed work. [help]
Osprey (Pandion haliaetus) – WDFW PHS mapper indicates a nest approximately 600 feet to the southeast. No
other priority habitats or species are mapped on or adjacent to the project site. Personal communication with
Larry Fisher, WDFW Area Habitat Biologist, indicates that coho and sockeye salmon potentially occur in Johns
Creek, downstream of the work area, during some times of year.
Part 10–SEPA Compliance and Permits
Use the resources and checklist below to identify the permits you are applying for.
• Online Project Questionnaire at http://apps.oria.wa.gov/opas/.
• Governor’s Office for Regulatory Innovation and Assistance at (800) 917-0043 or help@oria.wa.gov.
• For a list of addresses to send your JARPA to, click on agency addresses for completed JARPA.
10a. Compliance with the State Environmental Policy Act (SEPA). (Check all that apply.) [help]
• For more information about SEPA, go to www.ecy.wa.gov/programs/sea/sepa/e-review.html.
A copy of the SEPA determination or letter of exemption is included with this application.
A SEPA determination is pending with _______________ (lead agency). The expected decision date is
____________.
I am applying for a Fish Habitat Enhancement Exemption. (Check the box below in 10b.) [help]
This project is exempt (choose type of exemption below).
Categorical Exemption. Under what section of the SEPA administrative code (WAC) is it exempt?
Other:
JARPA Revision 2015.1 Page 12 of 13
SEPA is pre-empted by federal law.
10b. Indicate the permits you are applying for. (Check all that apply.) [help]
LOCAL GOVERNMENT
Local Government Shoreline permits:
Substantial Development Conditional Use Variance
Shoreline Exemption Type (explain):
Other City/County permits:
Floodplain Development Permit Critical Areas Ordinance
STATE GOVERNMENT
Washington Department of Fish and Wildlife:
Hydraulic Project Approval (HPA) Fish Habitat Enhancement Exemption – Attach Exemption Form
Washington Department of Natural Resources:
Aquatic Use Authorization
Complete JARPA Attachment E and submit a check for $25 payable to the Washington Department of Natural Resources.
Do not send cash.
Washington Department of Ecology:
Section 401 Water Quality Certification
FEDERAL GOVERNMENT
United States Department of the Army permits (U.S. Army Corps of Engineers):
Section 404 (discharges into waters of the U.S.) Section 10 (work in navigable waters)
United States Coast Guard permits:
Private Aids to Navigation (for non-bridge projects)
Vicinity Map
0
SCALE IN FEET
1,000 2,000
Data Source:
Mapbox Open Street Map, 2016.
Projection:
NAD83 Washington State Planes,
North Zone, US Foot.
1
Datum: WA State Plane North
Horizontal=NAD83
Vertical=NAVD 88
Adjacent Property Owners:
1.Existing Right-of-Way (Public)
2.BNSF
Applicant: Office at Southport LLC
1083 Lake Washington
Boulevard North, Suite 50
Renton, WA 98056
Open-water depression associated with Johns
Creek on east side of Lake Washington
Boulevard North and within public right-of-way
Proposed Project:
Lake Washington Boulevard
North Road Improvements
Sheet: of 7 Date: 01/09/2018
Lat/Long: 47.501878°N, -122.200382°W
Reference Number:In: Johns Creek
Near/At: Renton
County: King
State: WA
P:\21\21854001\CAD\04\JARPA\2185400104_JARPA_S01_Vicinity Map.dwg TAB:S1 Date Exported: 01/09/18 - 16:37 by syiSW 1/4 of SEC. 5 & NW 1/4 of
SEC. 8, T23N, R05E, W.M.
Location:
Sect/Town/Range:
Sheet Title
1 Vicinity Map
2 Existing Conditions and Parcels
3 Proposed Roadway Plan
4 Channel Layout
5 Channel Elevation and Section
6 Planting Plan
7 Planting Schedule
E(P)(P)(P)(P)(P)(P)(P)(P)(P)(P)(P)
(P)
(P)
(P)
(P)
(P)RAILROAD TRACKSSSSSSSSSSSSSSS8'CWTGASGASGASGASGASTTWWEEEEEEEETTTGASRAILROAD TRACKSRR RR
R
SSSSSSSSSS(P)(P)(P)(P)(P)(P)(P)(P)(T)(T)WWWWWWWWWWWW2520 3030252525202530303030303035253025 30302525305550454035555045403530504540353045403530403530353020
20
25
BURLINGTON NORTHERNRAILROAD R/WNE PARK DRIVEBURLINGTON NORTHERNRAILROAD R/WJOHNS CREEKLAKE WASHINGTON BLVD N2
Datum: WA State Plane North
Horizontal=NAD83
Vertical=NAVD 88
Adjacent Property Owners:
1.Existing Right-of-Way (Public)
2.BNSF
Applicant: Office at Southport LLC
1083 Lake Washington
Boulevard North, Suite 50
Renton, WA 98056
Open-water depression associated with Johns
Creek on east side of Lake Washington
Boulevard North and within public right-of-way
Proposed Project:
Lake Washington Boulevard
North Road Improvements
Sheet: of 7 Date: 01/09/2018
Lat/Long: 47.501878°N, -122.200382°W
Reference Number:In: Johns Creek
Near/At: Renton
County: King
State: WA
P:\21\21854001\CAD\04\JARPA\2185400104_JARPA_S02_Existing Conditions and Parcels.dwg TAB:S2 Date Exported: 01/09/18 - 16:39 by syiSW 1/4 of SEC. 5 & NW 1/4 of
SEC. 8, T23N, R05E, W.M.
Location:
Sect/Town/Range:
Existing Conditions and Parcels
30 600
SCALE IN FEET
Data Source:
Background from Bush, Roed & Hitchings, Inc. dated 03/08/16.
Existing Ordinary High Water
Existing Right-Of-Way
Existing Right-Of-Way
John's Creek
Existing Culverts
Existing Culverts
Existing Culverts
Existing Culverts
Existing Roadway
E(P)(P)(P)(P)(P)(P)(P)(P)(P)(P)(P)
(P)
(P)
(P)
(P)
(P)RAILROAD TRACKSSSSSSSSSSSSSSS8'CWTGASGASGASGASGASTTWWEEEEEEEETTTGASRAILROAD TRACKSRR RR
R
SSSSSSSSSS(P)(P)(P)(P)(P)(P)(P)(P)(T)(T)WWWWWWWWWWWW2520 3030252525202530303030303035253025 30302525305550454035555045403530504540353045403530403530353020
20
25
BURLINGTON NORTHERNRAILROAD R/WNE PARK DRIVEBURLINGTON NORTHERNRAILROAD R/WJOHNS CREEK11+0012+0013+0014+0015+0010+5011+5012+5013+0013+5014+0014+5015+0029LAKE WASHINGTON BLVD N3
Datum: WA State Plane North
Horizontal=NAD83
Vertical=NAVD 88
Adjacent Property Owners:
1.Existing Right-of-Way (Public)
2.BNSF
Applicant: Office at Southport LLC
1083 Lake Washington
Boulevard North, Suite 50
Renton, WA 98056
Open-water depression associated with Johns
Creek on east side of Lake Washington
Boulevard North and within public right-of-way
Proposed Project:
Lake Washington Boulevard
North Road Improvements
Sheet: of 7 Date: 01/09/2018
Lat/Long: 47.501878°N, -122.200382°W
Reference Number:In: Johns Creek
Near/At: Renton
County: King
State: WA
P:\21\21854001\CAD\04\JARPA\2185400104_JARPA_S03_Proposed Roadway Plan.dwg TAB:S3 Date Exported: 01/09/18 - 16:47 by syiSW 1/4 of SEC. 5 & NW 1/4 of
SEC. 8, T23N, R05E, W.M.
Location:
Sect/Town/Range:
Proposed Roadway Plan
30 600
SCALE IN FEET
Data Source:
Background from Bush, Roed & Hitchings, Inc. dated 03/08/16.
Proposed background from Coughlin Porter Lundeen, dated 03/09/17.
Proposed Retaining Wall
(MSE Wall or Similar)
Proposed Roadway Expansion
Proposed Retaining Wall
(MSE Wall or Similar)
Proposed LWB Retaining Wall Proposed OHW
LAKE WASHINGTONBOULEVARD NORTHFLOW 25 30 30LWB RETAININGWALL 35OHW HILLSIDERETAININGWALL 20 25
HILLSIDE RETAININGWALL, TYP.FLOWA-CULVERT EXTENSIONS, TYP.EXISTING CULVERTSEXISTING CULVERTSSTORMFILTERSTORMFILTERChannel Layout200SCALE IN FEET104
Datum: WA State Plane North
Horizontal=NAD83
Vertical=NAVD 88
Adjacent Property Owners:
1.Existing Right-of-Way (Public)
2.BNSF
Applicant: Office at Southport LLC
1083 Lake Washington
Boulevard North, Suite 50
Renton, WA 98056
Open-water depression associated with Johns
Creek on east side of Lake Washington
Boulevard North and within public right-of-way
Proposed Project:
Lake Washington Boulevard
North Road Improvements
Sheet: of 7 Date: 01/09/2018
Lat/Long: 47.501878°N, -122.200382°W
Reference Number:In: Johns Creek
Near/At: Renton
County: King
State: WA
P:\21\21854001\CAD\04\JARPA\2185400104_JARPA_S04_S05_S07_Channel Layout_Planting Schedule.dwg TAB:S4 Date Exported: 01/09/18 - 16:48 by syiSW 1/4 of SEC. 5 & NW 1/4 of
SEC. 8, T23N, R05E, W.M.
Location:
Sect/Town/Range:
Data Source:
Background from Shearer Design, L.L.C., dated 01/02/18.
Scale: 1" = 20'ELEVATIONREFERENCE ELEV.= 10.00100 YR WSEL =21.0725 YR WSEL =20.94TRAFFICBARRIER135'-0" RETAINING WALL LENGTHLWB RETAINING WALLREFERENCE ELEV. =10.0011'-0"LANE11'-0"LANE7'-0" MIN.BIKE LANEEXISTINGGROUND25 YR WSEL=20.94LWB RETAININGWALLScale: 1" = 10'SECTIONA-CULVERTEXTENSIONCULVERTCOUPLEREXISTING GABIONBASKETS, TOREMAINOHW SEL=20.54CHANNEL BED TO MATCH INVERTELEVATION OF LOWEST OUTLET CULVERTHILLSIDERETAINING WALLRIPARIANPLANTINGS(TYP.)Channel Elevation and Section
5
Datum: WA State Plane North
Horizontal=NAD83
Vertical=NAVD 88
Adjacent Property Owners:
1.Existing Right-of-Way (Public)
2.BNSF
Applicant: Office at Southport LLC
1083 Lake Washington
Boulevard North, Suite 50
Renton, WA 98056
Open-water depression associated with Johns
Creek on east side of Lake Washington
Boulevard North and within public right-of-way
Proposed Project:
Lake Washington Boulevard
North Road Improvements
Sheet: of 7 Date: 01/11/2018
Lat/Long: 47.501878°N, -122.200382°W
Reference Number:In: Johns Creek
Near/At: Renton
County: King
State: WA
P:\21\21854001\CAD\04\JARPA\2185400104_JARPA_S04_S05_S07_Channel Layout_Planting Schedule.dwg TAB:S5 Date Exported: 01/11/18 - 15:25 by syiSW 1/4 of SEC. 5 & NW 1/4 of
SEC. 8, T23N, R05E, W.M.
Location:
Sect/Town/Range:
Data Source:
Background from Shearer Design, L.L.C., dated 01/02/18.
E(P)(P)(P)(P)(P)(P)(P)(P)(P)(P)(P)
(P)
(P)
(P)
(P)
(P)RAILROAD TRACKSSSSSSSSSSSSSSS8'CWTGASGASGASGASGASTTWWEEEEEEEETTTGASRAILROAD TRACKSRR RR
R
SSSSSSSSSS(P)(P)(P)(P)(P)(P)(P)(P)(T)(T)WWWWWWWWWWWW2520 3030252525202530303030303035253025 30302525305550454035555045403530504540353045403530403530353020
20
25
BURLINGTON NORTHERNRAILROAD R/WNE PARK DRIVEBURLINGTON NORTHERNRAILROAD R/WJOHNS CREEK11+0012+0013+0014+0015+0010+5011+5012+5013+0013+5014+0014+5015+0029LAKE WASHINGTON BLVD N6
Datum: WA State Plane North
Horizontal=NAD83
Vertical=NAVD 88
Adjacent Property Owners:
1.Existing Right-of-Way (Public)
2.BNSF
Applicant: Office at Southport LLC
1083 Lake Washington
Boulevard North, Suite 50
Renton, WA 98056
Open-water depression associated with Johns
Creek on east side of Lake Washington
Boulevard North and within public right-of-way
Proposed Project:
Lake Washington Boulevard
North Road Improvements
Sheet: of 7 Date: 01/09/2018
Lat/Long: 47.501878°N, -122.200382°W
Reference Number:In: Johns Creek
Near/At: Renton
County: King
State: WA
P:\21\21854001\CAD\04\JARPA\2185400104_JARPA_S06_Planting Plan.dwg TAB:S6 Date Exported: 01/09/18 - 16:49 by syiSW 1/4 of SEC. 5 & NW 1/4 of
SEC. 8, T23N, R05E, W.M.
Location:
Sect/Town/Range:
Planting Plan
30 600
SCALE IN FEET
Data Source:
Background from Bush, Roed & Hitchings, Inc. dated 03/08/16.
Proposed background from Coughlin Porter Lundeen, dated 03/09/17.
Tree & Shrub Community
(10,750 sq. ft.)
Groundcover Plantings
(3,823 sq. ft.)
Planting Schedule
7
Datum: WA State Plane North
Horizontal=NAD83
Vertical=NAVD 88
Adjacent Property Owners:
1.Existing Right-of-Way (Public)
2.BNSF
Applicant: Office at Southport LLC
1083 Lake Washington
Boulevard North, Suite 50
Renton, WA 98056
Open-water depression associated with Johns
Creek on east side of Lake Washington
Boulevard North and within public right-of-way
Proposed Project:
Lake Washington Boulevard
North Road Improvements
Sheet: of 7 Date: 01/10/2018
Lat/Long: 47.501878°N, -122.200382°W
Reference Number:In: Johns Creek
Near/At: Renton
County: King
State: WA
P:\21\21854001\CAD\04\JARPA\2185400104_JARPA_S04_S05_S07_Channel Layout_Planting Schedule.dwg TAB:S7 Date Exported: 01/10/18 - 13:39 by syiSW 1/4 of SEC. 5 & NW 1/4 of
SEC. 8, T23N, R05E, W.M.
Location:
Sect/Town/Range:
1. Shrub community based on planting plan developed by Puget Sound Energy.
2. Groundcover community plantings on 3-foot centers.
1 2
Disclaimer: Any electronic form, facsimile or hard copy of the original document (email, text, table, and/or figure), if provided, and any attachments are only a copy of the
original document. The original document is stored by GeoEngineers, Inc. and will serve as the official document of record.
Memorandum
1101 South Fawcett Avenue, Suite 200, Tacoma, Washington 98402, Telephone: 253.383.4940 www.geoengineers.com
To: Scott Rosenstock, Southport LLC
From: Ryan S. Carnie, PE, David B. Conlin, PWS, and Joe Callaghan, PWS
Date: March 20, 2017
File: 21854-001-04
Subject: Hydrologic and Hydraulic Analysis
Lake Washington Boulevard North Road Improvements
Renton, Washington
INTRODUCTION / PROPOSED CONDITIONS
GeoEngineers, Inc. (GeoEngineers) prepared this memorandum to describe the hydrologic and hydraulic
analysis used to evaluate the conveyance capacity of four existing culverts under Lake Washington Boulevard
North (LWB) as part of the Southport LLC Lake Washington Boulevard North Road Improvements project. The
proposed project includes widening of LWB to support additional traffic capacity as a result of the Southport
Mixed-Use Development. Road improvements will be accomplished by adding roadway surface to the east side
of LWB within undeveloped public right-of-way as indicated on the vicinity map (Figure 1). An open-water
depression associated with Johns Creek is present at the site. Four culverts currently discharge stormwater
runoff into this depression from the north, east and south, and four existing culverts cross LWB to the west
draining the depression. The existing surface water depression will be replaced with a new concrete vault and
the new road surface widened over top of the vault.
HYDROLOGY
Geoengineers evaluated the Johns Creek drainage basin using the online USGS StreamStats tool and
developed a basin area boundary. The approximate basin area is 231 acres. We utilized the basin area to
calculate the 2-year, 25-year, and 100-year peak discharges for the Johns Creek Crossing using the Western
Washington Hydrology Model, version 4.2.12, developed by Clear Creek Solutions, Inc. as described in the King
County Surface Water Design Manual (KCSWDM) 1. We described the basin in the hydrologic model as type C,
forest, with moderate slopes. The resulting 2-year, 25-year, and 100-year peak discharges are 6.9 cfs, 17.5 cfs,
and 22.0 cfs, respectively.
HYDRAULICS
GeoEngineers performed a hydraulic analysis of the conceptual-level proposed conditions of Johns Creek,
including the modified LWB crossing using Version 5.0.3 of the HEC-RAS hydraulic computer model2. We
previously developed a hydraulic model to support the construction of the box culvert at Southport entrance
and published methods and results in a letter dated June 14, 20163. For the current proposed project, we
modified the 2016 hydraulic model geometry by adding the proposed vault upstream of the LWB crossing. The
proposed vault dimensions were obtained from drawings supplied by Coughlin Porter Lundeen, dated
1King County, Washington. 2009. Stormwater Design Manual
2 U.S. Army Corps of Engineers. 2016. Hydrologic Engineering Center-River Analysis System (HEC-RAS). Available at
http://www.hec.usace.army.mil/software/hec-ras/.
3 GeoEngineers Inc. 2016. Hydraulic Design – Culvert and Johns Creek Enhancement. Submitted to Southport LLC on June 14,
2016. GeoEngineers File No. 21854-001-04.
Memorandum to Scott Rosenstock
March 20, 2017
Page 2
March 7, 2017. We applied to this modified model the peak discharge values described in the preceding
section.
GeoEngineers used the results of the hydraulic model to evaluate the proposed culvert conveyance and
demonstrate compliance with conveyance criteria. Table 1 includes a summary of conveyance criteria as
defined in the Washington Department of Transportation (WSDOT) Hydraulic Manual Section 3-3.1 (WSDOT
2006). The results of the hydraulic analysis and a summary of criteria compliance are indicated in Table 2.
Based on the results of the hydraulic model, the existing culverts and proposed storm water vault provide
sufficient conveyance capacity to meet WSDOT criteria.
TABLE 1: RSWDM AND WSDOT CONVEYANCE CRITERIA
Agency/Document
Recurrence
Interval Design Criteria
WSDOT Section
3.3.1 25-Year 25-year discharge will not exceed the allowable headwater = 1.25 times
culvert height
WSDOT Section
3.3.1 100-Year Culverts shall convey the 100-year discharge without overtopping the
roadway
TABLE 2: HYDRAULIC RESULTS
Recurrence Interval Discharge (cfs) Depth in Culvert (feet)
Freeboard in
Culverts (feet)
WSEL at Culvert
Inlets (feet)
25-Year 17.5 1.5 2.5 20.9
100-Year 22.0 1.6 2.4 21.0
SUMMARY
GeoEngineers performed hydrologic and hydraulic modeling to support the Lake Washington Boulevard Road
North Road Improvements project proposed by Southport, LLC. Our modeling was completed within the
constraints of the scope limitations, schedule, budget and key assumptions established at the beginning of the
project. We evaluated the design to demonstrate conveyance criteria compliance. Based on our hydrologic and
hydraulic analyses, it is our opinion that the proposed vault design meets the criteria identified.
Attachment:
Figure 1. Vicinity Map
Figure 2. Water Surface Elevation Profiles
Figure 3. Cross Sections
µ
SITE
Vicinity Map
Figure 1
Lake Washington Boulevard NorthRoad ImprovementsRenton, Washington
2,000 2,0000
Feet
Data Source: Mapbox Open Street Map, 2015
Notes:1. The locations of all features shown are approximate.2. This drawing is for information purposes. It is intended to assist in showing features discussed in an attached document. GeoEngineers, Inc. cannot guarantee the accuracy and content of electronic files. The master file is stored by GeoEngineers, Inc. and will serve as the official record of this communication.
Projection: NAD 1983 UTM Zone 10N
P:\21\21854001\GIS\MXDs\2185400104_F01_VicinityMap.mxd Date Exported: 03/10/17 by cchelf
Figure 2Water Surface Elevation ProfileLake Washington Boulevard North Road ImprovementsRenton, Washington21854-001-00 Date Exported: 03/10/17Lake Washington Blvd.(4 Culverts)Burlington Northern Railroad(3 Culverts)Southport Development Entrance Road(Box Culvert)Storm Water Vault
Figure 3Storm Water Vault SectionLake Washington Boulevard North Road ImprovementsRenton, Washington21854-001-00 Date Exported: 03/10/17Storm Water Vault
15
VIII. CSWPPP ANALYSIS AND DESIGN
This section lists the requirements that will be used when designing the TESC plan for this site. A copy of the
Draft CSWPPP has been included at this time.
STANDARD REQUIREMENTS
Erosion/Sedimentation Plan shall include the following:
1. Facilities required include: Catch basin filter socks. (1.2.5-1). The project will provide sediment
protection at existing and proposed catch basins.
2. Timing - For the period between November 1 through March 1 disturbed areas greater than
5,000 square feet left undisturbed for more than 12 hours must be covered with mulch,
sodding, or plastic covering. A construction phasing plan shall be provided to ensure that
erosion control measures are installed prior to clearing and grading. (1.2.5-1). The TESC plan
will include provisions for disturbed areas to be covered in accordance with City of Renton
requirements and that all TESC measures are in place before any construction activity occurs.
3. Planning - Plan shall limit tributary drainage to an area to be cleared and graded. Delineate
dimension, stake and flag clearing limits (1.2.5-1). The clearing limits will be indicated on the
TESC plan.
4. Revegetation - Revegetate areas to be cleared as soon as practicable after grading. (1.2.5-1).
Notes addressing this item will be included on the TESC plan.
5. Baker Tank sizing – Sizing calculations for proposed baker tank is per Section D.2.1.5.1 of the 2017
RSWDM. The design inflow used is the 2-year peak discharge per MGS Flood using 15 min time
steps.
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Stormwater Pollution Prevention Plan
For
Lake Washington Blvd. Improvements:
Phase III for Southport Development
Prepared For
Northwest Regional Office
3190 - 160th Avenue SE
Bellevue, WA 98008-5452
425-649-7000
Owner Developer Operator/Contractor
SECO Development, Inc. SECO Development, Inc. TBD
1083 Lake Washington
Boulevard North, #50
1083 Lake Washington
Boulevard North, #50
TBD
Renton, Washington 98056 Renton, Washington 98056 TBD
Project Site Location
Renton, Washington
Certified Erosion and Sediment Control Lead
TBD
SWPPP Prepared By
Coughlin Porter Lundeen
801 Second Ave Suite# 900
Seattle, WA 98104
(206) 343-0460
Chase Blood, Civil Engineer
SWPPP Preparation Date
5/14/2018
Approximate Project Construction Dates
07-01-2018 to 09-01-2018
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Contents
1.0 Introduction ...............................................................................................................................1
2.0 Site Description ........................................................................................................................3
2.1 Existing Conditions ...........................................................................................................3
2.2 Proposed Construction Activities ......................................................................................3
3.0 Construction Stormwater BMPs ...............................................................................................5
3.1 The 12 BMP Elements .......................................................................................................5
3.1.1 Element #1 – Mark Clearing Limits ...................................................................5
3.1.2 Element #2 – Establish Construction Access .....................................................5
3.1.3 Element #3 – Control Flow Rates .......................................................................6
3.1.4 Element #4 – Install Sediment Controls .............................................................6
3.1.5 Element #5 – Stabilize Soils ...............................................................................7
3.1.6 Element #6 – Protect Slopes ...............................................................................8
3.1.7 Element #7 – Protect Drain Inlets .......................................................................8
3.1.8 Element #8 – Stabilize Channels and Outlets .....................................................9
3.1.9 Element #9 – Control Pollutants .........................................................................9
3.1.10 Element #10 – Control Dewatering .................................................................11
3.1.11 Element #11 – Maintain BMPs .......................................................................11
3.1.12 Element #12 – Manage the Project ..................................................................11
5.0 Pollution Prevention Team ......................................................................................................17
5.1 Roles and Responsibilities ...............................................................................................17
5.2 Team Members ................................................................................................................17
6.0 Site Inspections and Monitoring .............................................................................................19
6.1 Site Inspection .................................................................................................................19
6.1.1 Site Inspection Frequency ................................................................................19
6.1.2 Site Inspection Documentation .........................................................................19
6.2 Stormwater Quality Monitoring ......................................................................................20
6.2.2 pH Sampling .....................................................................................................20
7.0 Reporting and Recordkeeping ................................................................................................23
7.1 Recordkeeping .................................................................................................................23
7.1.1 Site Log Book ...................................................................................................23
7.1.2 Records Retention.............................................................................................23
7.1.3 Access to Plans and Records ............................................................................23
7.1.4 Updating the SWPPP ........................................................................................23
7.2 Reporting .........................................................................................................................24
7.2.1 Discharge Monitoring Reports .........................................................................24
7.2.2 Notification of Noncompliance ........................................................................24
7.2.3 Permit Application and Changes ......................................................................24
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Appendix A – Site Plans .........................................................................................................25
Appendix B – Construction BMPs .........................................................................................26
Appendix C – Alternative BMPs ............................................................................................27
Appendix D – General Permit ................................................................................................29
Appendix E – Site Inspection Forms (and Site Log) ..............................................................30
Appendix F – Engineering Calculations .................................................................................39
Appendix A Site plans
Appendix B Construction BMPs
Appendix C Alternative Construction BMP list
Appendix D General Permit
Appendix E Site Log and Inspection Forms
Appendix F Engineering Calculations
Stormwater Pollution Prevention Plan
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1.0 Introduction
This Stormwater Pollution Prevention Plan (SWPPP) has been prepared as part of the NPDES
stormwater permit requirements for the Lake Washington Blvd Improvements – Phase III for
Southport Development construction project in Renton, Washington. The site is situated at the
southern tip of Lake Washington to the west of the Gene Coulon Memorial Beach Park. The site
is in the NW ¼ of the NW ¼ of Section 8, Township 23 North, Range 5 East, Willamette
Meridian. The site will occupy parcels 0823059216, with an area of 245,086-SF, respectively.
The existing site consists of 0.11 acres of impervious area and 0.42 acres of pervious area.
Overall, the proposed project will include roadway paving, retaining walls, culvert extensions,
Filterra boxes, a relocated confluence channel for the Creek and some landscaping.
The proposed conditions will consist of approximately 0.29 acres of impervious area and 0.24
acres of pervious area.
Construction activities will include demolition, excavation, grading, relocation of onsite
services/utilities, construction of a high-rise office complex with associated parking and
landscaping. The purpose of this SWPPP is to describe the proposed construction activities and
all temporary and permanent erosion and sediment control (TESC) measures, pollution
prevention measures, inspection/monitoring activities, and recordkeeping that will be
implemented during the proposed construction project. The objectives of the SWPPP are to:
1. Implement Best Management Practices (BMPs) to prevent erosion and
sedimentation, and to identify, reduce, eliminate or prevent stormwater
contamination and water pollution from construction activity.
2. Prevent violations of surface water quality, ground water quality, or
sediment management standards.
3. Prevent, during the construction phase, adverse water quality impacts
including impacts on beneficial uses of the receiving water by controlling
peak flow rates and volumes of stormwater runoff at the Permittee’s
outfalls and downstream of the outfalls.
This SWPPP was prepared using the Ecology SWPPP Template downloaded from the Ecology
website. This SWPPP was prepared based on the requirements set forth in the Construction
Stormwater General Permit and Stormwater Management Manual for Western Washington
(SWMMWW 2005). The report is divided into seven main sections with several appendices that
include stormwater related reference materials. The topics presented in the each of the main
sections are:
Stormwater Pollution Prevention Plan
2
Section 1 – INTRODUCTION. This section provides a summary
description of the project, and the organization of the SWPPP document.
Section 2 – SITE DESCRIPTION. This section provides a detailed
description of the existing site conditions, proposed construction activities,
and calculated stormwater flow rates for existing conditions and post–
construction conditions.
Section 3 – CONSTRUCTION BMPs. This section provides a detailed
description of the BMPs to be implemented based on the 12 required
elements of the SWPPP.
Section 4 – CONSTRUCTION PHASING AND BMP
IMPLEMENTATION. This section provides a description of the timing
of the BMP implementation in relation to the project schedule.
Section 5 – POLLUTION PREVENTION TEAM. This section identifies
the appropriate contact names (emergency and non-emergency),
monitoring personnel, and the onsite temporary erosion and sedimentation
control inspector
Section 6 – INSPECTION AND MONITORING. This section provides a
description of the inspection and monitoring requirements such as the
parameters of concern to be monitored, sample locations, sample
frequencies, and sampling methods for all stormwater discharge locations
from the site.
Section 7 – RECORDKEEPING. This section describes the requirements
for documentation of the BMP implementation, site inspections,
monitoring results, and changes to the implementation of certain BMPs
due to site factors experienced during construction.
Supporting documentation and standard forms are provided in the following Appendices:
Appendix A – Site plans
Appendix B – Construction BMPs
Appendix C – Alternative Construction BMP list
Appendix D – General Permit
Appendix E – Site Log and Inspection Forms
Appendix F – Engineering Calculations
Stormwater Pollution Prevention Plan
3
2.0 Site Description
2.1 Existing Conditions
The existing site consists of asphalt and gravel parking lots as well as open grassy areas. The site
was previously home to the Shuffleton Steam Plant, which was built in the 1930’s and
demolished in 2001. Portions of the steam plant infrastructure are still in place, including a large
underground concrete vault, to be demolished with the construction of the office project.
The site is situated at the southern tip of Lake Washington to the west of the Gene Coulon
Memorial Beach Park. The site is in the NW ¼ of the NW ¼ of Section 8, Township 23 North,
Range 5 East, Willamette Meridian. The site will occupy parcel 0823059216, with an area of
245,086-SF. The site is 5.63 acres in size and includes a landscaped area with associated
parking. The topography of the site and surrounding properties gently slopes to the northwest.
Per the geotechnical report, soil depth and thickness varies greatly throughout the site. Generally,
the site is silty sand and clay over silt. Groundwater lies approximately three to nine feet below
existing grade, varying on the elevation of the adjacent Lake Washington.
Runoff from the site generally infiltrates or sheet flows into the existing catch basins which
divert runoff to the existing storm network, ultimately discharging directly to Lake Washington.
There are no critical areas on the site such as high erosion risk areas, wetlands, streams, or steep
slopes (potential landslide area).
2.2 Proposed Construction Activities
Overall, the project will include a additional roadway paving, Hilfiker retaining walls, a slope
reinforced hill, culvert extensions, Filterra boxes, catch basins, light poles, a relocated
confluence channel for the Creek and some landscaping.
Construction activities will include site preparation, TESC installation, demolition of the existing
vault on site, excavation for the building foundations, poured concrete foundations, concrete
construction, site-wide grading, and asphalt paving. The schedule and phasing of BMPs during
construction is provided in Section 4.0.
Stormwater runoff volumes were calculated using the computer software KCRTS. The
temporary sedimentation will be provided by Baker tanks that will be used during construction
was designed using the 2-year storm event. These are peak flows based on the developed
conditions throughout construction.
The Baker tank was sized using BMP 251 and are intended for stormwater treatment of total
suspended solids and stormwater detention.
Stormwater Pollution Prevention Plan
5
3.0 Construction Stormwater BMPs
3.1 The 12 BMP Elements
3.1.1 Element #1 – Mark Clearing Limits
To protect adjacent properties and to reduce the area of soil exposed to construction, the limits of
construction will be clearly marked before land-disturbing activities begin. Trees that are to be
preserved, as well as all sensitive areas and their buffers, shall be clearly delineated, both in the
field and on the plans. In general, natural vegetation and native topsoil shall be retained in an
undisturbed state to the maximum extent possible. The BMPs relevant to marking the clearing
limits that will be applied for this project include:
· High Visibility Plastic or Metal Fence (BMP C103)
Alternate BMPs for marking clearing limits are included in Appendix C as a quick reference tool
for the onsite inspector in the event the BMP(s) listed above are deemed ineffective or
inappropriate during construction to satisfy the requirements set forth in the General NPDES
Permit (Appendix D). To avoid potential erosion and sediment control issues that may cause a
violation(s) of the NPDES Construction Stormwater permit (as provided in Appendix D), the
Certified Erosion and Sediment Control Lead will promptly initiate the implementation of one or
more of the alternative BMPs listed in Appendix C after the first sign that existing BMPs are
ineffective or failing.
3.1.2 Element #2 – Establish Construction Access
Construction access or activities occurring on unpaved areas shall be minimized, yet where
necessary, access points shall be stabilized to minimize the tracking of sediment onto public
roads, and wheel washing, street sweeping, and street cleaning shall be employed to prevent
sediment from entering state waters. All wash wastewater shall be controlled on site. The
specific BMPs related to establishing construction access that will be used on this project
include:
· Stabilized Construction Entrance (BMP C105)
· Wheel Wash (BMP C106)
· Construction Road/Parking Area Stabilization (BMP C107)
Alternate construction access BMPs are included in Appendix C as a quick reference tool for the
onsite inspector in the event the BMP(s) listed above are deemed ineffective or inappropriate
during construction to satisfy the requirements set forth in the General NPDES Permit (Appendix
D). To avoid potential erosion and sediment control issues that may cause a violation(s) of the
NPDES Construction Stormwater permit (as provided in Appendix D), the Certified Erosion and
Sediment Control Lead will promptly initiate the implementation of one or more of the
Stormwater Pollution Prevention Plan
6
alternative BMPs listed in Appendix C after the first sign that existing BMPs are ineffective or
failing.
3.1.3 Element #3 – Control Flow Rates
In order to protect the properties and waterways downstream of the project site, stormwater
discharges from the site will be controlled. The specific BMPs for flow control that shall be used
on this project include:
No BMPs to be implemented
Alternate flow control BMPs are included in Appendix C as a quick reference tool for the onsite
inspector in the event the BMP(s) listed above are deemed ineffective or inappropriate during
construction to satisfy the requirements set forth in the General NPDES Permit (Appendix D).
To avoid potential erosion and sediment control issues that may cause a violation(s) of the
NPDES Construction Stormwater permit (as provided in Appendix D), the Certified Erosion and
Sediment Control Lead will promptly initiate the implementation of one or more of the
alternative BMPs listed in Appendix C after the first sign that existing BMPs are ineffective or
failing.
The project site is located west of the Cascade Mountain Crest. As such, the project must
comply with Minimum Requirement 7 (Ecology 2005).
In general, discharge rates of stormwater from the site will be controlled where increases in
impervious area or soil compaction during construction could lead to downstream erosion, or
where necessary to meet local agency stormwater discharge requirements (e.g. discharge to
combined sewer systems).
3.1.4 Element #4 – Install Sediment Controls
All stormwater runoff from disturbed areas shall pass through an appropriate sediment removal
BMP before leaving the construction site or prior to being discharged to an infiltration facility.
The specific BMPs to be used for controlling sediment on this project include:
· Detention Pond Or Vault
· Storm Drain Inlet Protection (BMP C220)
Alternate sediment control BMPs are included in Appendix C as a quick reference tool for the
onsite inspector in the event the BMP(s) listed above are deemed ineffective or inappropriate
during construction to satisfy the requirements set forth in the General NPDES Permit (Appendix
D). To avoid potential erosion and sediment control issues that may cause a violation(s) of the
NPDES Construction Stormwater permit (as provided in Appendix D), the Certified Erosion and
Sediment Control Lead will promptly initiate the implementation of one or more of the
Stormwater Pollution Prevention Plan
7
alternative BMPs listed in Appendix C after the first sign that existing BMPs are ineffective or
failing.
In addition, sediment will be removed from paved areas in and adjacent to construction work
areas manually or using mechanical sweepers, as needed, to minimize tracking of sediments on
vehicle tires away from the site and to minimize washoff of sediments from adjacent streets in
runoff.
Whenever possible, sediment laden water shall be discharged into onsite, relatively level,
vegetated areas (BMP C240 paragraph 5, page 4-102).
In some cases, sediment discharge in concentrated runoff can be controlled using permanent
stormwater BMPs (e.g., infiltration swales, ponds, trenches). Sediment loads can limit the
effectiveness of some permanent stormwater BMPs, such as those used for infiltration or
biofiltration; however, those BMPs designed to remove solids by settling (wet ponds or detention
ponds) can be used during the construction phase. When permanent stormwater BMPs will be
used to control sediment discharge during construction, the structure will be protected from
excessive sedimentation with adequate erosion and sediment control BMPs. Any accumulated
sediment shall be removed after construction is complete and the permanent stormwater BMP
will be restabilized with vegetation per applicable design requirements once the remainder of the
The following BMPs will be implemented as end-of-pipe sediment controls as required to meet
permitted turbidity limits in the site discharge(s). Prior to the implementation of these
technologies, sediment sources and erosion control and soil stabilization BMP efforts will be
maximized to reduce the need for end-of-pipe sedimentation controls.
Temporary Sediment Pond (BMP C241)
Construction Stormwater Filtration (BMP C251)
Construction Stormwater Chemical Treatment (BMP C 250)
(implemented only with prior written approval from Ecology).
3.1.5 Element #5 – Stabilize Soils
Exposed and unworked soils shall be stabilized with the application of effective BMPs to prevent
erosion throughout the life of the project. The specific BMPs for soil stabilization that shall be
used on this project include:
· Temporary and Permanent Seeding (BMP C120)
Alternate soil stabilization BMPs are included in Appendix C as a quick reference tool for the
onsite inspector in the event the BMP(s) listed above are deemed ineffective or inappropriate
Stormwater Pollution Prevention Plan
8
during construction to satisfy the requirements set forth in the General NPDES Permit (Appendix
D). To avoid potential erosion and sediment control issues that may cause a violation(s) of the
NPDES Construction Stormwater permit (as provided in Appendix D), the Certified Erosion and
Sediment Control Lead will promptly initiate the implementation of one or more of the
alternative BMPs listed in Appendix C after the first sign that existing BMPs are ineffective or
failing.
The project site is located west of the Cascade Mountain Crest. As such, no soils shall remain
exposed and unworked for more than 7 days during the dry season (May 1 to September 30) and
2 days during the wet season (October 1 to April 30). Regardless of the time of year, all soils
shall be stabilized at the end of the shift before a holiday or weekend if needed based on weather
forecasts.
In general, cut and fill slopes will be stabilized as soon as possible and soil stockpiles will be
temporarily covered with plastic sheeting. All stockpiled soils shall be stabilized from erosion,
protected with sediment trapping measures, and where possible, be located away from storm
drain inlets, waterways, and drainage channels.
3.1.6 Element #6 – Protect Slopes
All cut and fill slopes will be designed, constructed, and protected in a manner than minimizes
erosion. The following specific BMPs will be used to protect slopes for this project:
· Temporary and Permanent Seeding (BMP C120)
Alternate slope protection BMPs are included in Appendix C as a quick reference tool for the
onsite inspector in the event the BMP(s) listed above are deemed ineffective or inappropriate
during construction to satisfy the requirements set forth in the General NPDES Permit (Appendix
D). To avoid potential erosion and sediment control issues that may cause a violation(s) of the
NPDES Construction Stormwater permit (as provided in Appendix D), the Certified Erosion and
Sediment Control Lead will promptly initiate the implementation of one or more of the
alternative BMPs listed in Appendix C after the first sign that existing BMPs are ineffective or
failing.
3.1.7 Element #7 – Protect Drain Inlets
All storm drain inlets and culverts made operable during construction shall be protected to
prevent unfiltered or untreated water from entering the drainage conveyance system. However,
the first priority is to keep all access roads clean of sediment and keep street wash water separate
from entering storm drains until treatment can be provided. Storm Drain Inlet Protection (BMP
C220) will be implemented for all drainage inlets and culverts that could potentially be impacted
by sediment-laden runoff on and near the project site. The following inlet protection measures
will be applied on this project:
Stormwater Pollution Prevention Plan
9
Drop Inlet Protection
· Catch Basin Filters
If the BMP options listed above are deemed ineffective or inappropriate during construction to
satisfy the requirements set forth in the General NPDES Permit (Appendix D), or if no BMPs are
listed above but deemed necessary during construction, the Certified Erosion and Sediment
Control Lead shall implement one or more of the alternative BMP inlet protection options listed
in Appendix C.
3.1.8 Element #8 – Stabilize Channels and Outlets
Where site runoff is to be conveyed in channels, or discharged to a stream or some other natural
drainage point, efforts will be taken to prevent downstream erosion. The specific BMPs for
channel and outlet stabilization that shall be used on this project include:
No BMPs to be implemented
Alternate channel and outlet stabilization BMPs are included in Appendix C as a quick reference
tool for the onsite inspector in the event the BMP(s) listed above are deemed ineffective or
inappropriate during construction to satisfy the requirements set forth in the General NPDES
Permit (Appendix D). To avoid potential erosion and sediment control issues that may cause a
violation(s) of the NPDES Construction Stormwater permit (as provided in Appendix D), the
Certified Erosion and Sediment Control Lead will promptly initiate the implementation of one or
more of the alternative BMPs listed in Appendix C after the first sign that existing BMPs are
ineffective or failing.
The project site is located west of the Cascade Mountain Crest. As such, all temporary on-site
conveyance channels shall be designed, constructed, and stabilized to prevent erosion from the
expected peak 10 minute velocity of flow from a Type 1A, 10-year, 24-hour recurrence interval
storm for the developed condition. Alternatively, the 10-year, 1-hour peak flow rate indicated by
an approved continuous runoff simulation model, increased by a factor of 1.6, shall be used.
Stabilization, including armoring material, adequate to prevent erosion of outlets, adjacent
streambanks, slopes, and downstream reaches shall be provided at the outlets of all conveyance
systems.
3.1.9 Element #9 – Control Pollutants
All pollutants, including waste materials and demolition debris, that occur onsite shall be
handled and disposed of in a manner that does not cause contamination of stormwater. Good
housekeeping and preventative measures will be taken to ensure that the site will be kept clean,
well organized, and free of debris. If required, BMPs to be implemented to control specific
sources of pollutants are discussed below.
Stormwater Pollution Prevention Plan
10
Vehicles, construction equipment, and/or petroleum product storage/dispensing:
All vehicles, equipment, and petroleum product storage/dispensing areas
will be inspected regularly to detect any leaks or spills, and to identify
maintenance needs to prevent leaks or spills.
On-site fueling tanks and petroleum product storage containers shall
include secondary containment.
Spill prevention measures, such as drip pans, will be used when
conducting maintenance and repair of vehicles or equipment.
In order to perform emergency repairs on site, temporary plastic will be
placed beneath and, if raining, over the vehicle.
Contaminated surfaces shall be cleaned immediately following any
discharge or spill incident.
Demolition:
Dust released from demolished sidewalks, buildings, or structures will be
controlled using Dust Control measures (BMP C140).
Storm drain inlets vulnerable to stormwater discharge carrying dust, soil,
or debris will be protected using Storm Drain Inlet Protection (BMP C220
as described above for Element 7).
Process water and slurry resulting from sawcutting and surfacing
operations will be prevented from entering the waters of the State by
implementing Sawcutting and Surfacing Pollution Prevention measures
(BMP C152).
Concrete and grout:
Process water and slurry resulting from concrete work will be prevented
from entering the waters of the State by implementing Concrete Handling
measures (BMP C151).
Sanitary wastewater:
Portable sanitation facilities will be firmly secured, regularly maintained,
and emptied when necessary.
Stormwater Pollution Prevention Plan
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Wheel wash or tire bath wastewater shall be discharged to a separate on-
site treatment system or to the sanitary sewer as part of Wheel Wash
implementation (BMP C106).
Solid Waste:
Solid waste will be stored in secure, clearly marked containers.
The facility does not require a Spill Prevention, Control, and Countermeasure (SPCC) Plan under
the Federal regulations of the Clean Water Act (CWA).
3.1.10 Element #10 – Control Dewatering
Extensive dewatering is occuring with this project. Dewatering is pumped to settlement tanks to
control sediment if needed, otherwise dewatering wells discharging clean groundwater is
discharged through underground conveyance systems to an existing discharge location to Lake
Washington.
3.1.11 Element #11 – Maintain BMPs
All temporary and permanent erosion and sediment control BMPs shall be maintained and
repaired as needed to assure continued performance of their intended function. Maintenance and
repair shall be conducted in accordance with each particular BMPs specifications (attached).
Visual monitoring of the BMPs will be conducted at least once every calendar week and within
24 hours of any stormwater or non-stormwater discharge from the site. If the site becomes
inactive, and is temporarily stabilized, the inspection frequency will be reduced to once every
month.
All temporary erosion and sediment control BMPs shall be removed within 30 days after the
final site stabilization is achieved or after the temporary BMPs are no longer needed. Trapped
sediment shall be removed or stabilized on site. Disturbed soil resulting from removal of BMPs
or vegetation shall be permanently stabilized.
3.1.12 Element #12 – Manage the Project
Erosion and sediment control BMPs for this project have been designed based on the following
principles:
Design the project to fit the existing topography, soils, and drainage
patterns.
Emphasize erosion control rather than sediment control.
Minimize the extent and duration of the area exposed.
Keep runoff velocities low.
Stormwater Pollution Prevention Plan
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Retain sediment on site.
Thoroughly monitor site and maintain all ESC measures.
Schedule major earthwork during the dry season.
In addition, project management will incorporate the key components listed below:
As this project site is located west of the Cascade Mountain Crest, the project will be managed
according to the following key project components:
Phasing of Construction
The construction project is being phased to the extent practicable in order
to prevent soil erosion, and, to the maximum extent possible, the transport
of sediment from the site during construction.
Revegetation of exposed areas and maintenance of that vegetation shall be
an integral part of the clearing activities during each phase of construction,
per the Scheduling BMP (C 162).
Seasonal Work Limitations
From October 1 through April 30, clearing, grading, and other soil
disturbing activities shall only be permitted if shown to the satisfaction of
the local permitting authority that silt-laden runoff will be prevented from
leaving the site through a combination of the following:
Site conditions including existing vegetative coverage, slope, soil
type, and proximity to receiving waters; and
Limitations on activities and the extent of disturbed areas; and
Proposed erosion and sediment control measures.
Based on the information provided and/or local weather conditions, the
local permitting authority may expand or restrict the seasonal limitation on
site disturbance.
The following activities are exempt from the seasonal clearing and grading
limitations:
Routine maintenance and necessary repair of erosion and sediment
control BMPs;
Stormwater Pollution Prevention Plan
13
Routine maintenance of public facilities or existing utility
structures that do not expose the soil or result in the removal of the
vegetative cover to soil; and
Activities where there is 100 percent infiltration of surface water
runoff within the site in approved and installed erosion and
sediment control facilities.
Coordination with Utilities and Other Jurisdictions
Care has been taken to coordinate with utilities, other construction
projects, and the local jurisdiction in preparing this SWPPP and
scheduling the construction work.
Inspection and Monitoring
All BMPs shall be inspected, maintained, and repaired as needed to assure
continued performance of their intended function. Site inspections shall
be conducted by a person who is knowledgeable in the principles and
practices of erosion and sediment control. This person has the necessary
skills to:
Assess the site conditions and construction activities that could
impact the quality of stormwater, and
Assess the effectiveness of erosion and sediment control measures
used to control the quality of stormwater discharges.
A Certified Erosion and Sediment Control Lead shall be on-site or on-call
at all times.
Whenever inspection and/or monitoring reveals that the BMPs identified
in this SWPPP are inadequate, due to the actual discharge of or potential
to discharge a significant amount of any pollutant, appropriate BMPs or
design changes shall be implemented as soon as possible.
Maintaining an Updated Construction SWPPP
This SWPPP shall be retained on-site or within reasonable access to the
site.
The SWPPP shall be modified whenever there is a change in the design,
construction, operation, or maintenance at the construction site that has, or
could have, a significant effect on the discharge of pollutants to waters of
the state.
Stormwater Pollution Prevention Plan
14
The SWPPP shall be modified if, during inspections or investigations
conducted by the owner/operator, or the applicable local or state
regulatory authority, it is determined that the SWPPP is ineffective in
eliminating or significantly minimizing pollutants in stormwater
discharges from the site. The SWPPP shall be modified as necessary to
include additional or modified BMPs designed to correct problems
identified. Revisions to the SWPPP shall be completed within seven (7)
days following the inspection.
Alternate dewatering control BMPs are included in Appendix C as a quick reference tool
for the onsite inspector in the event the BMP(s) listed above are deemed ineffective or
inappropriate during construction to satisfy the requirements set forth in the General
NPDES Permit (Appendix D). To avoid potential erosion and sediment control issues
that may cause a violation(s) of the NPDES Construction Stormwater permit (as provided
in Appendix D), the Certified Erosion and Sediment Control Lead will promptly initiate
the implementation of one or more of the alternative BMPs listed in Appendix C after the
first sign that existing BMPs are ineffective or failing.
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4.0 Construction Phasing and BMP
Implementation
The BMP implementation schedule will be driven by the construction schedule. The following
provides a sequential list of the proposed construction schedule milestones and the corresponding
BMP implementation schedule. The list contains key milestones such as wet season
construction.
The BMP implementation schedule listed below is keyed to proposed phases of the construction
project, and reflects differences in BMP installations and inspections that relate to wet season
construction. The project site is located west of the Cascade Mountain Crest. As such, the dry
season is considered to be from May 1 to September 30 and the wet season is considered to be
from October 1 to April 30.
Estimate of Construction start date: TBD
Estimate of Construction finish date: TBD
Mobilize equipment on site: TBD
Mobilize and store all ESC and soil stabilization products
(store materials on hand BMP C150): TBD
Install ESC measures: TBD
Install stabilized construction entrance: TBD
Begin clearing and grubbing: TBD
Demolish existing one-story building structure: TBD
Excavation for building foundations TBD
Soil stabilization on excavated sideslopes (in idle, no
work areas as shown on ESC plans) TBD
Temporary erosion control measures (hydroseeding) TBD
Site inspections reduced to monthly: TBD
Begin concrete pour and implement BMP C151: TBD
Excavate and install new utilities and services (Phase 1): TBD
Begin building construction: TBD
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Complete Phase 1 utility construction TBD
Begin implementing soil stabilization and sediment
control BMPs throughout the site in preparation for wet
season: TBD
Wet Season starts: 10 / 01 / 2015
Site inspections and monitoring conducted weekly and
for applicable rain events as detailed in Section 6 of this
SWPPP: TBD
Implement Element #12 BMPs and manage site to
minimize soil disturbance during the wet season TBD
No site work such as grading or excavation planned:
Dry Season starts: 05 / 01 / 2016
Site grading begins: TBD
Excavate and install new utilities and services (Phase 2): TBD
Site grading ends: TBD
Building construction complete: TBD
Final landscaping and planting begins: TBD
Permanent erosion control measures (hydroseeding): TBD
8
8
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5.0 Pollution Prevention Team
5.1 Roles and Responsibilities
The pollution prevention team consists of personnel responsible for implementation of the
SWPPP, including the following:
Certified Erosion and Sediment Control Lead (CESCL) – primary
contractor contact, responsible for site inspections (BMPs, visual
monitoring, sampling, etc.); to be called upon in case of failure of any
ESC measures.
Resident Engineer – For projects with engineered structures only
(sediment ponds/traps, sand filters, etc.): site representative for the owner
that is the project's supervising engineer responsible for inspections and
issuing instructions and drawings to the contractor's site supervisor or
representative
Emergency Ecology Contact – individual to be contacted at Ecology in
case of emergency.
Emergency Owner Contact – individual that is the site owner or
representative of the site owner to be contacted in the case of an
emergency.
Non-Emergency Ecology Contact – individual that is the site owner or
representative of the site owner than can be contacted if required.
Monitoring Personnel – personnel responsible for conducting water
quality monitoring; for most sites this person is also the Certified Erosion
and Sediment Control Lead.
5.2 Team Members
Names and contact information for those identified as members of the pollution prevention team
are provided in the following table.
Title Name(s) Phone Number
Certified Erosion and Sediment Control Lead (CESCL) TBD TBD
Resident Engineer TBD TBD
Emergency Ecology Contact TBD TBD
Emergency Owner Contact TBD TBD
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Non-Emergency Ecology Contact TBD TBD
Monitoring Personnel TBD TBD
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6.0 Site Inspections and Monitoring
Monitoring includes visual inspection, monitoring for water quality parameters of concern, and
documentation of the inspection and monitoring findings in a site log book. A site log book will
be maintained for all on-site construction activities and will include:
A record of the implementation of the SWPPP and other permit
requirements;
Site inspections; and,
Stormwater quality monitoring.
For convenience, the inspection form and water quality monitoring forms included in this
SWPPP include the required information for the site log book. This SWPPP may function as the
site log book if desired, or the forms may be separated and included in a separate site log book.
However, if separated, the site log book but must be maintained on-site or within reasonable
access to the site and be made available upon request to Ecology or the local jurisdiction.
6.1 Site Inspection
All BMPs will be inspected, maintained, and repaired as needed to assure continued performance
of their intended function. The inspector will be a Certified Erosion and Sediment Control Lead
(CESCL) per BMP C160. The name and contact information for the CESCL is provided in
Section 5 of this SWPPP.
Site inspection will occur in all areas disturbed by construction activities and at all stormwater
discharge points. Stormwater will be examined for the presence of suspended sediment,
turbidity, discoloration, and oily sheen. The site inspector will evaluate and document the
effectiveness of the installed BMPs and determine if it is necessary to repair or replace any of the
BMPs to improve the quality of stormwater discharges. All maintenance and repairs will be
documented in the site log book or forms provided in this document. All new BMPs or design
changes will be documented in the SWPPP as soon as possible.
6.1.1 Site Inspection Frequency
Site inspections will be conducted at least once a week and within 24 hours following any
discharge from the site. For sites with temporary stabilization measures, the site inspection
frequency can be reduced to once every month.
6.1.2 Site Inspection Documentation
The site inspector will record each site inspection using the site log inspection forms provided in
Appendix E. The site inspection log forms may be separated from this SWPPP document, but
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will be maintained on-site or within reasonable access to the site and be made available upon
request to Ecology or the local jurisdiction.
6.2 Stormwater Quality Monitoring
Monitoring requirements for the proposed project will include either turbidity or water
transparency sampling to monitor site discharges for water quality compliance with the 2005
Construction Stormwater General Permit (Appendix D). Sampling will be conducted at all
discharge points at least once per calendar week.
Turbidity or transparency monitoring will follow the analytical methodologies described in
Section S4 of the 2005 Construction Stormwater General Permit (Appendix D). The key
benchmark turbidity value is 25 nephelometric turbidity units (NTU) for the downstream
receiving water body. If the 25 NTU benchmark is exceeded in any sample collected from CB5,
the following steps will be conducted:
1. Ensure all BMPs specified in this SWPPP are installed and functioning as
intended.
2. Assess whether additional BMPs should be implemented, and document
modified BMPs in the SWPPP as necessary.
3. Sample discharge daily until the discharge is 25 NTU or lower.
If the turbidity exceeds 250 NTU at any time, the following steps will be conducted:
1. Notify Ecology by phone within 24 hours of analysis (see Section 5.0 of
this SWPPP for contact information).
2. Continue sampling daily until the discharge is 25 NTU or lower Initiate
additional treatment BMPs such as off-site treatment, infiltration, filtration
and chemical treatment within 24 hours, and implement those additional
treatment BMPs as soon as possible, but within a minimum of 7 days.
3. Describe inspection results and remedial actions taken in the site log book
and in monthly discharge monitoring reports as described in Section 7.0 of
this SWPPP.
6.2.2 pH Sampling
Stormwater runoff will be monitored for pH starting on the first day of any activity that includes
more than 40 yards of poured or recycled concrete, or after the application of “Engineered Soils”
such as, Portland cement treated base, cement kiln dust, or fly ash. This does not include
fertilizers. For concrete work, pH monitoring will start the first day concrete is poured and
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continue until 3 weeks after the last pour. For engineered soils, the pH monitoring period begins
when engineered soils are first exposed to precipitation and continue until the area is fully
stabilized.
Stormwater samples will be collected weekly from all points of discharge from the site and
measured for pH using a calibrated pH meter, pH test kit, or wide range pH indicator paper. If
the measured pH is 8.5 or greater, the following steps will be conducted:
1. Prevent the high pH water from entering storm drains or surface water.
2. Adjust or neutralize the high pH water if necessary using appropriate
technology such as CO2 sparging (liquid or dry ice).
3. Contact Ecology if chemical treatment other than CO2 sparging is planned.
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7.0 Reporting and Recordkeeping
7.1 Recordkeeping
7.1.1 Site Log Book
A site log book will be maintained for all on-site construction activities and will include:
A record of the implementation of the SWPPP and other permit
requirements;
Site inspections; and,
Stormwater quality monitoring.
For convenience, the inspection form and water quality monitoring forms included in this
SWPPP include the required information for the site log book.
7.1.2 Records Retention
Records of all monitoring information (site log book, inspection reports/checklists, etc.), this
Stormwater Pollution Prevention Plan, and any other documentation of compliance with permit
requirements will be retained during the life of the construction project and for a minimum of
three years following the termination of permit coverage in accordance with permit condition
S5.C.
7.1.3 Access to Plans and Records
The SWPPP, General Permit, Notice of Authorization letter, and Site Log Book will be retained
on site or within reasonable access to the site and will be made immediately available upon
request to Ecology or the local jurisdiction. A copy of this SWPPP will be provided to Ecology
within 14 days of receipt of a written request for the SWPPP from Ecology. Any other
information requested by Ecology will be submitted within a reasonable time. A copy of the
SWPPP or access to the SWPPP will be provided to the public when requested in writing in
accordance with permit condition S5.G.
7.1.4 Updating the SWPPP
In accordance with Conditions S3, S4.B, and S9.B.3 of the General Permit, this SWPPP will be
modified if the SWPPP is ineffective in eliminating or significantly minimizing pollutants in
stormwater discharges from the site or there has been a change in design, construction, operation,
or maintenance at the site that has a significant effect on the discharge, or potential for discharge,
of pollutants to the waters of the State. The SWPPP will be modified within seven days of
determination based on inspection(s) that additional or modified BMPs are necessary to correct
problems identified, and an updated timeline for BMP implementation will be prepared.
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7.2 Reporting
7.2.1 Discharge Monitoring Reports
If cumulative soil disturbance is 5 acres or larger: Discharge Monitoring Reports (DMRs) will be
submitted to Ecology monthly. Of there was no discharge during a given monitoring period, the
Permittee shall submit the form as required, with the words “No discharge” entered in the place
of monitoring results. The DMR due date is 15 days following the end of each month.
7.2.2 Notification of Noncompliance
If any of the terms and conditions of the permit are not met, and it causes a threat to human
health or the environment, the following steps will be taken in accordance with permit section
S5.F:
1. Ecology will be immediately notified of the failure to comply.
2. Immediate action will be taken to control the noncompliance issue and to
correct the problem. If applicable, sampling and analysis of any
noncompliance will be repeated immediately and the results submitted to
Ecology within five (5) days of becoming aware of the violation.
3. A detailed written report describing the noncompliance will be submitted
to Ecology within five (5) days, unless requested earlier by Ecology.
7.2.3 Permit Application and Changes
In accordance with permit condition S2.A, a complete application form will be submitted to
Ecology and the appropriate local jurisdiction (if applicable) to be covered by the General
Permit.
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Appendix A – Site Plans
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Appendix B – Construction BMPs
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Appendix C – Alternative BMPs
The following includes a list of possible alternative BMPs for each of the 12 elements not
described in the main SWPPP text. This list can be referenced in the event a BMP for a specific
element is not functioning as designed and an alternative BMP needs to be implemented.
Element #1 - Mark Clearing Limits
Element #2 - Establish Construction Access
Element #3 - Control Flow Rates
Element #4 - Install Sediment Controls
Straw Bale Barrier (BMP C230)
Straw Wattles (BMP C235)
Storm Drain Inlet Protection (BMP C220)
Advanced BMPs:
Element #5 - Stabilize Soils
Preserving Natural Vegetation (BMP C101)
Element #6 - Protect Slopes
Element #8 - Stabilize Channels and Outlets
Channel Lining (BMP C202)
Straw Wattles (BMP C235)
Interceptor Dike and Swale (BMP C200)
Element #10 - Control Dewatering
Check Dams (BMP C207)
Outlet Protection (BMP C209)
Additional Advanced BMPs to Control Dewatering:
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Appendix D – General Permit
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Appendix E – Site Inspection Forms (and Site Log)
The results of each inspection shall be summarized in an inspection report or checklist
that is entered into or attached to the site log book. It is suggested that the inspection
report or checklist be included in this appendix to keep monitoring and inspection
information in one document, but this is optional. However, it is mandatory that this
SWPPP and the site inspection forms be kept onsite at all times during construction, and
that inspections be performed and documented as outlined below.
At a minimum, each inspection report or checklist shall include:
a. Inspection date/times
b. Weather information: general conditions during inspection,
approximate amount of precipitation since the last inspection,
and approximate amount of precipitation within the last 24 hours.
c. A summary or list of all BMPs that have been implemented,
including observations of all erosion/sediment control structures or
practices.
d. The following shall be noted:
i. locations of BMPs inspected,
ii. locations of BMPs that need maintenance,
iii. the reason maintenance is needed,
iv. locations of BMPs that failed to operate as designed or
intended, and
v. locations where additional or different BMPs are needed, and
the reason(s) why
e. A description of stormwater discharged from the site. The presence
of suspended sediment, turbid water, discoloration, and/or oil
sheen shall be noted, as applicable.
f. A description of any water quality monitoring performed during
inspection, and the results of that monitoring.
g. General comments and notes, including a brief description of any
BMP r repairs, maintenance or installations made as a result of the
inspection.
h. A statement that, in the judgment of the person conducting the site
inspection, the site is either in compliance or out of compliance
with the terms and conditions of the SWPPP and the NPDES
permit. If the site inspection indicates that the site is out of
compliance, the inspection report shall include a summary of the
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remedial actions required to bring the site back into compliance, as
well as a schedule of implementation.
i. Name, title, and signature of person conducting the site inspection;
and the following statement: “I certify under penalty of law that
this report is true, accurate, and complete, to the best of my
knowledge and belief”.
When the site inspection indicates that the site is not in compliance with any terms and
conditions of the NPDES permit, the Permittee shall take immediate action(s) to: stop,
contain, and clean up the unauthorized discharges, or otherwise stop the noncompliance;
correct the problem(s); implement appropriate Best Management Practices (BMPs),
and/or conduct maintenance of existing BMPs; and achieve compliance with all
applicable standards and permit conditions. In addition, if the noncompliance causes a
threat to human health or the environment, the Permittee shall comply with the
Noncompliance Notification requirements in Special Condition S5.F of the permit.
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Site Inspection Form
General Information
Project Name:
Inspector Name: Title:
CESCL # :
Date: Time:
Inspection Type: □ After a rain event
□ Weekly
□ Turbidity/transparency benchmark exceedance
□ Other
Weather
Precipitation Since last inspection In last 24 hours
Description of General Site Conditions:
Inspection of BMPs
Element 1: Mark Clearing Limits
BMP:
Location Inspected Functioning Problem/Corrective Action Y N Y N NIP
BMP:
Location Inspected Functioning Problem/Corrective Action Y N Y N NIP
Element 2: Establish Construction Access
BMP:
Location Inspected Functioning Problem/Corrective Action Y N Y N NIP
BMP:
Location Inspected Functioning Problem/Corrective Action Y N Y N NIP
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Element 3: Control Flow Rates
BMP:
Location Inspected Functioning Problem/Corrective Action Y N Y N NIP
BMP:
Location Inspected Functioning Problem/Corrective Action Y N Y N NIP
Element 4: Install Sediment Controls
BMP:
Location Inspected Functioning Problem/Corrective Action Y N Y N NIP
BMP:
Location Inspected Functioning Problem/Corrective Action Y N Y N NIP
BMP:
Location Inspected Functioning Problem/Corrective Action Y N Y N NIP
BMP:
Location Inspected Functioning Problem/Corrective Action Y N Y N NIP
BMP:
Location Inspected Functioning Problem/Corrective Action Y N Y N NIP
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Element 5: Stabilize Soils
BMP:
Location Inspected Functioning Problem/Corrective Action Y N Y N NIP
BMP:
Location Inspected Functioning Problem/Corrective Action Y N Y N NIP
BMP:
Location Inspected Functioning Problem/Corrective Action Y N Y N NIP
BMP:
Location Inspected Functioning Problem/Corrective Action Y N Y N NIP
Element 6: Protect Slopes
BMP:
Location Inspected Functioning Problem/Corrective Action Y N Y N NIP
BMP:
Location Inspected Functioning Problem/Corrective Action Y N Y N NIP
BMP:
Location Inspected Functioning Problem/Corrective Action Y N Y N NIP
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Element 7: Protect Drain Inlets
BMP:
Location Inspected Functioning Problem/Corrective Action Y N Y N NIP
BMP:
Location Inspected Functioning Problem/Corrective Action Y N Y N NIP
BMP:
Location Inspected Functioning Problem/Corrective Action Y N Y N NIP
Element 8: Stabilize Channels and Outlets
BMP:
Location Inspected Functioning Problem/Corrective Action Y N Y N NIP
BMP:
Location Inspected Functioning Problem/Corrective Action Y N Y N NIP
BMP:
Location Inspected Functioning Problem/Corrective Action Y N Y N NIP
BMP:
Location Inspected Functioning Problem/Corrective Action Y N Y N NIP
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Element 9: Control Pollutants
BMP:
Location Inspected Functioning Problem/Corrective Action Y N Y N NIP
BMP:
Location Inspected Functioning Problem/Corrective Action Y N Y N NIP
Element 10: Control Dewatering
BMP:
Location Inspected Functioning Problem/Corrective Action Y N Y N NIP
BMP:
Location Inspected Functioning Problem/Corrective Action Y N Y N NIP
BMP:
Location Inspected Functioning Problem/Corrective Action Y N Y N NIP
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Stormwater Discharges From the Site
Observed? Problem/Corrective Action Y N
Location
Turbidity
Discoloration
Sheen
Location
Turbidity
Discoloration
Sheen
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Water Quality Monitoring
Was any water quality monitoring conducted? □ Yes □ No
If water quality monitoring was conducted, record results here:
If water quality monitoring indicated turbidity 250 NTU or greater; or transparency 6
cm or less, was Ecology notified by phone within 24 hrs?
□ Yes □ No
If Ecology was notified, indicate the date, time, contact name and phone number
below:
Date:
Time:
Contact Name:
Phone #:
General Comments and Notes
Include BMP repairs, maintenance, or installations made as a result of the inspection.
Were Photos Taken? □ Yes □ No
If photos taken, describe photos below:
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Appendix F – Engineering Calculations
COUGHLINPORTERLUNDEEN
A CONSULTING STRUCTURAL AND CIVIL ENGINEERING CORPORATION
Total Site:Area (ac)
Pervious Area 0.240
Impervious Area 0.290
Total Area 0.530
MGS-FLOOD:
Data Type Reduced
Time Step 15-min
MGS - Flood 2-Yr developed flow 0.320 cfs
Temporary Sediment Pond Sizing: Storage Volume per DOE II-4-104 BMP 241 (pg. 162)
Vr=S.A. x 3.5'Vr = Minimum Required Storage Volume
S.A. = Minimum allowable top surface area of pond
S.A. = (Qx2)/Vsed
Q = design peak flow rate
Vsed = 0.00096 Settling Velocity (0.00096 ft/sec)
Q=.320 cfs INPUT (note that this is the 2-yr design peak flow rate in cfs)
S.A. = 667 sf
Vr=2333 cf cf Volume Required
17455 gal
1 sediment storage tank is required.
Project: Lake Washington Blvd Improvements - Phase III for Southport DevelopmentDesigned by: ALC
Project No.: Client: Checked by: TBB Sheet 1 of 1
* the volume is based a minimum pond depth of 3.5' - this depth does not
include the minimum sediment storage volume or freeboard
Assume 18,100 gallons per sediment storage tank, then
Date: 05/14/2016
801 Second Avenue ∙ Suite 900 ∙ Seattle, WA 98104 ∙ P: (206) 343-0460
BAKER TANK CALCULATIONS:
Proposed Runoff Conditions for TESC - Entire Site
BMP C101:Preserving Natural Vegetation
Purpose
The purpose of preserving natural vegetation is to reduce erosion wherever practicable.
Limiting site disturbance is the single most effective method for reducing erosion.For
example,conifers can hold up to about 50 percent of all rain that falls during a storm.Up
to 20-30 percent of this rain may never reach the ground but is taken up by the tree or
evaporates.Another benefit is that the rain held in the tree can be released slowly to the
ground after the storm.
Conditions of Use
Natural vegetation should be preserved on steep slopes,near perennial and intermittent
watercourses or swales,and on building sites in wooded areas.
l As required by local governments.
l Phase construction to preserve natural vegetation on the project site for as long as
possible during the construction period.
Design and Installation Specifications
Natural vegetation can be preserved in natural clumps or as individual trees,shrubs and
vines.
The preservation of individual plants is more difficult because heavy equipment is gen-
erally used to remove unwanted vegetation.The points to remember when attempting to
save individual plants are:
l Is the plant worth saving?Consider the location,species,size,age,vigor,and the
work involved.Local governments may also have ordinances to save natural veget-
ation and trees.
l Fence or clearly mark areas around trees that are to be saved.It is preferable to
keep ground disturbance away from the trees at least as far out as the dripline.
Plants need protection from three kinds of injuries:
l Construction Equipment -This injury can be above or below the ground level.
Damage results from scarring,cutting of roots,and compaction of the soil.Placing
a fenced buffer zone around plants to be saved prior to construction can prevent
construction equipment injuries.
l Grade Changes -Changing the natural ground level will alter grades,which affects
the plant's ability to obtain the necessary air,water,and minerals.Minor fills usu-
ally do not cause problems although sensitivity between species does vary and
should be checked.Trees can typically tolerate fill of 6 inches or less.For shrubs
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and other plants,the fill should be less.
When there are major changes in grade,it may become necessary to supply air to
the roots of plants.This can be done by placing a layer of gravel and a tile system
over the roots before the fill is made.A tile system protects a tree from a raised
grade.The tile system should be laid out on the original grade leading from a dry
well around the tree trunk.The system should then be covered with small stones to
allow air to circulate over the root area.
Lowering the natural ground level can seriously damage trees and shrubs.The
highest percentage of the plant roots are in the upper 12 inches of the soil and cuts
of only 2-3 inches can cause serious injury.To protect the roots it may be neces-
sary to terrace the immediate area around the plants to be saved.If roots are
exposed,construction of retaining walls may be needed to keep the soil in place.
Plants can also be preserved by leaving them on an undisturbed,gently sloping
mound.To increase the chances for survival,it is best to limit grade changes and
other soil disturbances to areas outside the dripline of the plant.
l Excavations -Protect trees and other plants when excavating for drainfields,
power,water,and sewer lines.Where possible,the trenches should be routed
around trees and large shrubs.When this is not possible,it is best to tunnel under
them.This can be done with hand tools or with power augers.If it is not possible to
route the trench around plants to be saved,then the following should be observed:
o Cut as few roots as possible.When you have to cut,cut clean.Paint cut root
ends with a wood dressing like asphalt base paint if roots will be exposed for
more than 24-hours.
o Backfill the trench as soon as possible.
o Tunnel beneath root systems as close to the center of the main trunk to pre-
serve most of the important feeder roots.
Some problems that can be encountered with a few specific trees are:
l Maple,Dogwood,Red alder,Western hemlock,Western red cedar,and Douglas fir
do not readily adjust to changes in environment and special care should be taken
to protect these trees.
l The windthrow hazard of Pacific silver fir and madrona is high,while that of
Western hemlock is moderate.The danger of windthrow increases where dense
stands have been thinned.Other species (unless they are on shallow,wet soils
less than 20 inches deep)have a low windthrow hazard.
l Cottonwoods,maples,and willows have water-seeking roots.These can cause
trouble in sewer lines and infiltration fields.On the other hand,they thrive in high
moisture conditions that other trees would not.
l Thinning operations in pure or mixed stands of Grand fir,Pacific silver fir,Noble fir,
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Sitka spruce,Western red cedar,Western hemlock,Pacific dogwood,and Red
alder can cause serious disease problems.Disease can become established
through damaged limbs,trunks,roots,and freshly cut stumps.Diseased and
weakened trees are also susceptible to insect attack.
Maintenance Standards
Inspect flagged and/or fenced areas regularly to make sure flagging or fencing has not
been removed or damaged.If the flagging or fencing has been damaged or visibility
reduced,it shall be repaired or replaced immediately and visibility restored.
l If tree roots have been exposed or injured,“prune”cleanly with an appropriate prun-
ing saw or loppers directly above the damaged roots and recover with native soils.
Treatment of sap flowing trees (fir,hemlock,pine,soft maples)is not advised as
sap forms a natural healing barrier.
BMP C102:Buffer Zones
Purpose
Creation of an undisturbed area or strip of natural vegetation or an established suitable
planting that will provide a living filter to reduce soil erosion and runoff velocities.
Conditions of Use
Natural buffer zones are used along streams,wetlands and other bodies of water that
need protection from erosion and sedimentation.Vegetative buffer zones can be used to
protect natural swales and can be incorporated into the natural landscaping of an area.
Critical-areas buffer zones should not be used as sediment treatment areas.These
areas shall remain completely undisturbed.The local permitting authority may expand
the buffer widths temporarily to allow the use of the expanded area for removal of sed-
iment.
Design and Installation Specifications
l Preserving natural vegetation or plantings in clumps,blocks,or strips is generally
the easiest and most successful method.
l Leave all unstable steep slopes in natural vegetation.
l Mark clearing limits and keep all equipment and construction debris out of the nat-
ural areas and buffer zones.Steel construction fencing is the most effective method
in protecting sensitive areas and buffers.Alternatively,wire-backed silt fence on
steel posts is marginally effective.Flagging alone is typically not effective.
l Keep all excavations outside the dripline of trees and shrubs.
l Do not push debris or extra soil into the buffer zone area because it will cause
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damage from burying and smothering.
l Vegetative buffer zones for streams,lakes or other waterways shall be established
by the local permitting authority or other state or federal permits or approvals.
Maintenance Standards
Inspect the area frequently to make sure flagging remains in place and the area remains
undisturbed.Replace all damaged flagging immediately.
BMP C103:High Visibility Fence
Purpose
Fencing is intended to:
1.Restrict clearing to approved limits.
2.Prevent disturbance of sensitive areas,their buffers,and other areas required to be
left undisturbed.
3.Limit construction traffic to designated construction entrances,exits,or internal
roads.
4.Protect areas where marking with survey tape may not provide adequate pro-
tection.
Conditions of Use
To establish clearing limits plastic,fabric,or metal fence may be used:
l At the boundary of sensitive areas,their buffers,and other areas required to be left
uncleared.
l As necessary to control vehicle access to and on the site.
Design and Installation Specifications
High visibility plastic fence shall be composed of a high-density polyethylene material
and shall be at least four feet in height.Posts for the fencing shall be steel or wood and
placed every 6 feet on center (maximum)or as needed to ensure rigidity.The fencing
shall be fastened to the post every six inches with a polyethylene tie.On long continuous
lengths of fencing,a tension wire or rope shall be used as a top stringer to prevent sag-
ging between posts.The fence color shall be high visibility orange.The fence tensile
strength shall be 360 lbs./ft.using the ASTM D4595 testing method.
If appropriate install fabric silt fence in accordance with BMP C233:Silt Fence (p.367)to
act as high visibility fence.Silt fence shall be at least 3 feet high and must be highly vis-
ible to meet the requirements of this BMP.
2014 Stormwater Management Manual for Western Washington
Volume II -Chapter 4 -Page 269
Metal fences shall be designed and installed according to the manufacturer's spe-
cifications.
Metal fences shall be at least 3 feet high and must be highly visible.
Fences shall not be wired or stapled to trees.
Maintenance Standards
If the fence has been damaged or visibility reduced,it shall be repaired or replaced
immediately and visibility restored.
BMP C105:Stabilized Construction Entrance /Exit
Purpose
Stabilized Construction entrances are established to reduce the amount of sediment
transported onto paved roads by vehicles or equipment.This is done by constructing a
stabilized pad of quarry spalls at entrances and exits for construction sites.
Conditions of Use
Construction entrances shall be stabilized wherever traffic will be entering or leaving a
construction site if paved roads or other paved areas are within 1,000 feet of the site.
For residential construction provide stabilized construction entrances for each residence,
rather than only at the main subdivision entrance.Stabilized surfaces shall be of suf-
ficient length/width to provide vehicle access/parking,based on lot size/configuration.
On large commercial,highway,and road projects,the designer should include enough
extra materials in the contract to allow for additional stabilized entrances not shown in
the initial Construction SWPPP.It is difficult to determine exactly where access to these
projects will take place;additional materials will enable the contractor to install them
where needed.
Design and Installation Specifications
See Figure II-4.1.1 Stabilized Construction Entrance (p.273)for details.Note:the 100’
minimum length of the entrance shall be reduced to the maximum practicable size when
the size or configuration of the site does not allow the full length (100’).
Construct stabilized construction entrances with a 12-inch thick pad of 4-inch to 8-inch
quarry spalls,a 4-inch course of asphalt treated base (ATB),or use existing pavement.
Do not use crushed concrete,cement,or calcium chloride for construction entrance sta-
bilization because these products raise pH levels in stormwater and concrete discharge
to surface waters of the State is prohibited.
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Volume II -Chapter 4 -Page 270
A separation geotextile shall be placed under the spalls to prevent fine sediment from
pumping up into the rock pad.The geotextile shall meet the following standards:
Grab Tensile Strength (ASTM D4751)200 psi min.
Grab Tensile Elongation (ASTM D4632)30%max.
Mullen Burst Strength (ASTM D3786-80a)400 psi min.
AOS (ASTM D4751)20-45 (U.S.standard sieve size)
l Consider early installation of the first lift of asphalt in areas that will paved;this can
be used as a stabilized entrance.Also consider the installation of excess concrete
as a stabilized entrance.During large concrete pours,excess concrete is often
available for this purpose.
l Fencing (see BMP C103:High Visibility Fence (p.269))shall be installed as neces-
sary to restrict traffic to the construction entrance.
l Whenever possible,the entrance shall be constructed on a firm,compacted sub-
grade.This can substantially increase the effectiveness of the pad and reduce the
need for maintenance.
l Construction entrances should avoid crossing existing sidewalks and back of walk
drains if at all possible.If a construction entrance must cross a sidewalk or back of
walk drain,the full length of the sidewalk and back of walk drain must be covered
and protected from sediment leaving the site.
Maintenance Standards
Quarry spalls shall be added if the pad is no longer in accordance with the spe-
cifications.
l If the entrance is not preventing sediment from being tracked onto pavement,then
alternative measures to keep the streets free of sediment shall be used.This may
include replacement/cleaning of the existing quarry spalls,street sweeping,an
increase in the dimensions of the entrance,or the installation of a wheel wash.
l Any sediment that is tracked onto pavement shall be removed by shoveling or
street sweeping.The sediment collected by sweeping shall be removed or sta-
bilized on site.The pavement shall not be cleaned by washing down the street,
except when high efficiency sweeping is ineffective and there is a threat to public
safety.If it is necessary to wash the streets,the construction of a small sump to con-
tain the wash water shall be considered.The sediment would then be washed into
the sump where it can be controlled.
l Perform street sweeping by hand or with a high efficiency sweeper.Do not use a
non-high efficiency mechanical sweeper because this creates dust and throws
soils into storm systems or conveyance ditches.
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Volume II -Chapter 4 -Page 271
l Any quarry spalls that are loosened from the pad,which end up on the roadway
shall be removed immediately.
l If vehicles are entering or exiting the site at points other than the construction
entrance(s),fencing (see BMP C103)shall be installed to control traffic.
l Upon project completion and site stabilization,all construction accesses intended
as permanent access for maintenance shall be permanently stabilized.
2014 Stormwater Management Manual for Western Washington
Volume II -Chapter 4 -Page 272
Figure II-4.1.1 Stabilized Construction Entrance
DEP A RTMENT OF
ECOLOG Y
State of Washington
Please see http://www.ecy.wa.gov/copyright.html for copyright notice including permissions,
limitation of liability, and disclaimer.
Figure II-4.1.1
Stabilized Construction Entrance
Revised June 2015
NOT TO SCALE
Existing
R
o
a
d
Notes:
1.Driveway shall meet
the requirements of the
permitting agency.
2.It is recommended that
the entrance be
crowned so that runoff
drains off the pad.
Install driveway
culvert if there is a
roadside ditch present 4" - 8" quarry
spalls
Geotextile
12" minimum thickness
15' min.
100' min.
Provide full width
of ingress/egress
area
2014 Stormwater Management Manual for Western Washington
Volume II -Chapter 4 -Page 273
Approved as Equivalent
Ecology has approved products as able to meet the requirements of BMP C105:Stab-
ilized Construction Entrance /Exit.The products did not pass through the Technology
Assessment Protocol –Ecology (TAPE)process.Local jurisdictions may choose not to
accept this product approved as equivalent,or may require additional testing prior to con-
sideration for local use.The products are available for review on Ecology’s website at
http://www.ecy.wa.gov/programs/wq/stormwater/newtech/equivalent.html
BMP C106:Wheel Wash
Purpose
Wheel washes reduce the amount of sediment transported onto paved roads by motor
vehicles.
Conditions of Use
When a stabilized construction entrance (see BMP C105:Stabilized Construction
Entrance /Exit (p.270))is not preventing sediment from being tracked onto pavement.
l Wheel washing is generally an effective BMP when installed with careful attention
to topography.For example,a wheel wash can be detrimental if installed at the top
of a slope abutting a right-of-way where the water from the dripping truck can run
unimpeded into the street.
l Pressure washing combined with an adequately sized and surfaced pad with dir-
ect drainage to a large 10-foot x 10-foot sump can be very effective.
l Discharge wheel wash or tire bath wastewater to a separate on-site treatment sys-
tem that prevents discharge to surface water,such as closed-loop recirculation or
upland land application,or to the sanitary sewer with local sewer district approval.
l Wheel wash or tire bath wastewater should not include wastewater from concrete
washout areas.
Design and Installation Specifications
Suggested details are shown in Figure II-4.1.2 Wheel Wash (p.276).The Local Per-
mitting Authority may allow other designs.A minimum of 6 inches of asphalt treated base
(ATB)over crushed base material or 8 inches over a good subgrade is recommended to
pave the wheel wash.
Use a low clearance truck to test the wheel wash before paving.Either a belly dump or
lowboy will work well to test clearance.
Keep the water level from 12 to 14 inches deep to avoid damage to truck hubs and filling
the truck tongues with water.
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Volume II -Chapter 4 -Page 274
Midpoint spray nozzles are only needed in extremely muddy conditions.
Wheel wash systems should be designed with a small grade change,6-to 12-inches for
a 10-foot-wide pond,to allow sediment to flow to the low side of pond to help prevent re-
suspension of sediment.A drainpipe with a 2-to 3-foot riser should be installed on the
low side of the pond to allow for easy cleaning and refilling.Polymers may be used to
promote coagulation and flocculation in a closed-loop system.Polyacrylamide (PAM)
added to the wheel wash water at a rate of 0.25 -0.5 pounds per 1,000 gallons of water
increases effectiveness and reduces cleanup time.If PAM is already being used for dust
or erosion control and is being applied by a water truck,the same truck can be used to
change the wash water.
Maintenance Standards
The wheel wash should start out the day with fresh water.
The wash water should be changed a minimum of once per day.On large earthwork
jobs where more than 10-20 trucks per hour are expected,the wash water will need to
be changed more often.
2014 Stormwater Management Manual for Western Washington
Volume II -Chapter 4 -Page 275
Figure II-4.1.2 Wheel Wash
DEP A RTMENT OF
ECOLOG Y
State of Washington
Please see http://www.ecy.wa.gov/copyright.html for copyright notice including permissions,
limitation of liability, and disclaimer.
Figure II-4.1.2
Wheel Wash
Revised June 2015
NOT TO SCALE
Notes:
1.Build 8' x 8' sump to accomodate
cleaning by trackhoe.
6" sewer pipe with
butterfly valves
8' x 8' sump with 5' of catch
3" trash pump with
floats on suction hose
2" schedule 40
1 12 " schedule 40 for sprayers
midpoint spray nozzles, if needed
15' ATB apron to protect
ground from splashing water
6" sleeve under road
6" ATB construction entrance
Asphalt curb on the low road
side to direct water back to pond
Ball valves
2% slope 5:1 slope
1:1 slope
5:1 slope 2% slope
A
A
Plan View
15'15'20'15'50'
Curb
6" sleeve
Elevation View
Locate invert of top pipe 1'
above bottom of wheel wash
8' x 8' sump
5'
Drain pipe
12'
3'
18'
Water level
1:1 slope
Section A-A
2014 Stormwater Management Manual for Western Washington
Volume II -Chapter 4 -Page 276
BMP C107:Construction Road/Parking Area Stabilization
Purpose
Stabilizing subdivision roads,parking areas,and other on-site vehicle transportation
routes immediately after grading reduces erosion caused by construction traffic or runoff.
Conditions of Use
Roads or parking areas shall be stabilized wherever they are constructed,whether per-
manent or temporary,for use by construction traffic.
l High Visibility Fencing (see BMP C103:High Visibility Fence (p.269))shall be
installed,if necessary,to limit the access of vehicles to only those roads and park-
ing areas that are stabilized.
Design and Installation Specifications
l On areas that will receive asphalt as part of the project,install the first lift as soon
as possible.
l A 6-inch depth of 2-to 4-inch crushed rock,gravel base,or crushed surfacing base
course shall be applied immediately after grading or utility installation.A 4-inch
course of asphalt treated base (ATB)may also be used,or the road/parking area
may be paved.It may also be possible to use cement or calcium chloride for soil
stabilization.If cement or cement kiln dust is used for roadbase stabilization,pH
monitoring and BMPs (BMP C252:High pH Neutralization Using CO2 (p.409)and
BMP C253:pH Control for High pH Water (p.412))are necessary to evaluate and
minimize the effects on stormwater.If the area will not be used for permanent
roads,parking areas,or structures,a 6-inch depth of hog fuel may also be used,
but this is likely to require more maintenance.Whenever possible,construction
roads and parking areas shall be placed on a firm,compacted subgrade.
l Temporary road gradients shall not exceed 15 percent.Roadways shall be care-
fully graded to drain.Drainage ditches shall be provided on each side of the road-
way in the case of a crowned section,or on one side in the case of a super-
elevated section.Drainage ditches shall be directed to a sediment control BMP.
l Rather than relying on ditches,it may also be possible to grade the road so that run-
off sheet-flows into a heavily vegetated area with a well-developed topsoil.Land-
scaped areas are not adequate.If this area has at least 50 feet of vegetation that
water can flow through,then it is generally preferable to use the vegetation to treat
runoff,rather than a sediment pond or trap.The 50 feet shall not include wetlands
or their buffers.If runoff is allowed to sheetflow through adjacent vegetated areas,it
is vital to design the roadways and parking areas so that no concentrated runoff is
created.
2014 Stormwater Management Manual for Western Washington
Volume II -Chapter 4 -Page 277
l Storm drain inlets shall be protected to prevent sediment-laden water entering the
storm drain system (see BMP C220:Storm Drain Inlet Protection (p.357)).
Maintenance Standards
Inspect stabilized areas regularly,especially after large storm events.
Crushed rock,gravel base,etc.,shall be added as required to maintain a stable driving
surface and to stabilize any areas that have eroded.
Following construction,these areas shall be restored to pre-construction condition or bet-
ter to prevent future erosion.
Perform street cleaning at the end of each day or more often if necessary.
BMP C120:Temporary and Permanent Seeding
Purpose
Seeding reduces erosion by stabilizing exposed soils.A well-established vegetative
cover is one of the most effective methods of reducing erosion.
Conditions of Use
Use seeding throughout the project on disturbed areas that have reached final grade or
that will remain unworked for more than 30 days.
The optimum seeding windows for western Washington are April 1 through June 30 and
September 1 through October 1.
Between July 1 and August 30 seeding requires irrigation until 75 percent grass cover is
established.
Between October 1 and March 30 seeding requires a cover of mulch with straw or an
erosion control blanket until 75 percent grass cover is established.
Review all disturbed areas in late August to early September and complete all seeding
by the end of September.Otherwise,vegetation will not establish itself enough to
provide more than average protection.
l Mulch is required at all times for seeding because it protects seeds from heat,mois-
ture loss,and transport due to runoff.Mulch can be applied on top of the seed or
simultaneously by hydroseeding.See BMP C121:Mulching (p.284)for spe-
cifications.
l Seed and mulch,all disturbed areas not otherwise vegetated at final site sta-
bilization.Final stabilization means the completion of all soil disturbing activities at
the site and the establishment of a permanent vegetative cover,or equivalent per-
2014 Stormwater Management Manual for Western Washington
Volume II -Chapter 4 -Page 278
manent stabilization measures (such as pavement,riprap,gabions,or geotextiles)
which will prevent erosion.
Design and Installation Specifications
Seed retention/detention ponds as required.
Install channels intended for vegetation before starting major earthwork and hydroseed
with a Bonded Fiber Matrix.For vegetated channels that will have high flows,install
erosion control blankets over hydroseed.Before allowing water to flow in vegetated
channels,establish 75 percent vegetation cover.If vegetated channels cannot be estab-
lished by seed before water flow;install sod in the channel bottom—over hydromulch
and erosion control blankets.
l Confirm the installation of all required surface water control measures to prevent
seed from washing away.
l Hydroseed applications shall include a minimum of 1,500 pounds per acre of
mulch with 3 percent tackifier.See BMP C121:Mulching (p.284)for specifications.
l Areas that will have seeding only and not landscaping may need compost or meal-
based mulch included in the hydroseed in order to establish vegetation.Re-install
native topsoil on the disturbed soil surface before application.
l When installing seed via hydroseeding operations,only about 1/3 of the seed actu-
ally ends up in contact with the soil surface.This reduces the ability to establish a
good stand of grass quickly.To overcome this,consider increasing seed quantities
by up to 50 percent.
l Enhance vegetation establishment by dividing the hydromulch operation into two
phases:
1.Phase 1-Install all seed and fertilizer with 25-30 percent mulch and tackifier
onto soil in the first lift.
2.Phase 2-Install the rest of the mulch and tackifier over the first lift.
Or,enhance vegetation by:
1.Installing the mulch,seed,fertilizer,and tackifier in one lift.
2.Spread or blow straw over the top of the hydromulch at a rate of 800-1000
pounds per acre.
3.Hold straw in place with a standard tackifier.
Both of these approaches will increase cost moderately but will greatly improve
and enhance vegetative establishment.The increased cost may be offset by the
reduced need for:
2014 Stormwater Management Manual for Western Washington
Volume II -Chapter 4 -Page 279
l Irrigation.
l Reapplication of mulch.
l Repair of failed slope surfaces.
This technique works with standard hydromulch (1,500 pounds per acre minimum)
and BFM/MBFMs (3,000 pounds per acre minimum).
l Seed may be installed by hand if:
l Temporary and covered by straw,mulch,or topsoil.
l Permanent in small areas (usually less than 1 acre)and covered with mulch,
topsoil,or erosion blankets.
l The seed mixes listed in the tables below include recommended mixes for
both temporary and permanent seeding.
l Apply these mixes,with the exception of the wetland mix,at a rate of 120
pounds per acre.This rate can be reduced if soil amendments or slow-
release fertilizers are used.
l Consult the local suppliers or the local conservation district for their recom-
mendations because the appropriate mix depends on a variety of factors,
including location,exposure,soil type,slope,and expected foot traffic.Altern-
ative seed mixes approved by the local authority may be used.
l Other mixes may be appropriate,depending on the soil type and hydrology of
the area.
l Table II-4.1.2 Temporary Erosion Control Seed Mix (p.280)lists the standard mix
for areas requiring a temporary vegetative cover.
%Weight %Purity %Germination
Chewings or annual blue grass
Festuca rubra var.commutata or Poa anna
40 98 90
Perennial rye
Lolium perenne
50 98 90
Redtop or colonial bentgrass
Agrostis alba or Agrostis tenuis
5 92 85
White dutch clover
Trifolium repens
5 98 90
Table II-4.1.2 Temporary Erosion Control Seed Mix
l Table II-4.1.3 Landscaping Seed Mix (p.281)lists a recommended mix for land-
scaping seed.
2014 Stormwater Management Manual for Western Washington
Volume II -Chapter 4 -Page 280
%Weight %Purity %Germination
Perennial rye blend
Lolium perenne
70 98 90
Chewings and red fescue blend
Festuca rubra var.commutata or Festuca rubra
30 98 90
Table II-4.1.3 Landscaping Seed Mix
l Table II-4.1.4 Low-Growing Turf Seed Mix (p.281)lists a turf seed mix for dry situ-
ations where there is no need for watering.This mix requires very little main-
tenance.
%Weight %Purity %Germination
Dwarf tall fescue (several varieties)
Festuca arundinacea var.
45 98 90
Dwarf perennial rye (Barclay)
Lolium perenne var.barclay
30 98 90
Red fescue
Festuca rubra
20 98 90
Colonial bentgrass
Agrostis tenuis
5 98 90
Table II-4.1.4 Low-Growing Turf Seed Mix
l Table II-4.1.5 Bioswale Seed Mix*(p.281)lists a mix for bioswales and other inter-
mittently wet areas.
%Weight %Purity %Germination
Tall or meadow fescue
Festuca arundinacea or Festuca ela-
tior
75-80 98 90
Seaside/Creeping bentgrass
Agrostis palustris
10-15 92 85
Redtop bentgrass
Agrostis alba or Agrostis gigantea
5-10 90 80
*Modified Briargreen,Inc.Hydroseeding Guide Wetlands Seed Mix
Table II-4.1.5 Bioswale Seed Mix*
l Table II-4.1.6 Wet Area Seed Mix*(p.282)lists a low-growing,relatively non-invas-
ive seed mix appropriate for very wet areas that are not regulated wetlands.Apply
2014 Stormwater Management Manual for Western Washington
Volume II -Chapter 4 -Page 281
this mixture at a rate of 60 pounds per acre.Consult Hydraulic Permit Authority
(HPA)for seed mixes if applicable.
%Weight %Purity %Germination
Tall or meadow fescue
Festuca arundinacea or Festuca ela-
tior
60-70 98 90
Seaside/Creeping bentgrass
Agrostis palustris
10-15 98 85
Meadow foxtail
Alepocurus pratensis
10-15 90 80
Alsike clover
Trifolium hybridum
1-6 98 90
Redtop bentgrass
Agrostis alba
1-6 92 85
*Modified Briargreen,Inc.Hydroseeding Guide Wetlands Seed Mix
Table II-4.1.6 Wet Area Seed Mix*
l Table II-4.1.7 Meadow Seed Mix (p.282)lists a recommended meadow seed mix
for infrequently maintained areas or non-maintained areas where colonization by
native plants is desirable.Likely applications include rural road and utility right-of-
way.Seeding should take place in September or very early October in order to
obtain adequate establishment prior to the winter months.Consider the appro-
priateness of clover,a fairly invasive species,in the mix.Amending the soil can
reduce the need for clover.
%Weight %Purity %Germination
Redtop or Oregon bentgrass
Agrostis alba or Agrostis oregonensis
20 92 85
Red fescue
Festuca rubra
70 98 90
White dutch clover
Trifolium repens
10 98 90
Table II-4.1.7 Meadow Seed Mix
l Roughening and Rototilling:
l The seedbed should be firm and rough.Roughen all soil no matter what the
slope.Track walk slopes before seeding if engineering purposes require
2014 Stormwater Management Manual for Western Washington
Volume II -Chapter 4 -Page 282
compaction.Backblading or smoothing of slopes greater than 4H:1V is not
allowed if they are to be seeded.
l Restoration-based landscape practices require deeper incorporation than
that provided by a simple single-pass rototilling treatment.Wherever prac-
tical,initially rip the subgrade to improve long-term permeability,infiltration,
and water inflow qualities.At a minimum,permanent areas shall use soil
amendments to achieve organic matter and permeability performance
defined in engineered soil/landscape systems.For systems that are deeper
than 8 inches complete the rototilling process in multiple lifts,or prepare the
engineered soil system per specifications and place to achieve the specified
depth.
l Fertilizers:
l Conducting soil tests to determine the exact type and quantity of fertilizer is
recommended.This will prevent the over-application of fertilizer.
l Organic matter is the most appropriate form of fertilizer because it provides
nutrients (including nitrogen,phosphorus,and potassium)in the least water-
soluble form.
l In general,use 10-4-6 N-P-K (nitrogen-phosphorus-potassium)fertilizer at a
rate of 90 pounds per acre.Always use slow-release fertilizers because they
are more efficient and have fewer environmental impacts.Do not add fer-
tilizer to the hydromulch machine,or agitate,more than 20 minutes before
use.Too much agitation destroys the slow-release coating.
l There are numerous products available that take the place of chemical fer-
tilizers.These include several with seaweed extracts that are beneficial to
soil microbes and organisms.If 100 percent cottonseed meal is used as the
mulch in hydroseed,chemical fertilizer may not be necessary.Cottonseed
meal provides a good source of long-term,slow-release,available nitrogen.
l Bonded Fiber Matrix and Mechanically Bonded Fiber Matrix:
l On steep slopes use Bonded Fiber Matrix (BFM)or Mechanically Bonded
Fiber Matrix (MBFM)products.Apply BFM/MBFM products at a minimum rate
of 3,000 pounds per acre of mulch with approximately 10 percent tackifier.
Achieve a minimum of 95 percent soil coverage during application.Numer-
ous products are available commercially.Installed products per man-
ufacturer’s instructions.Most products require 24-36 hours to cure before
rainfall and cannot be installed on wet or saturated soils.Generally,products
come in 40-50 pound bags and include all necessary ingredients except for
seed and fertilizer.
2014 Stormwater Management Manual for Western Washington
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l BFMs and MBFMs provide good alternatives to blankets in most areas requir-
ing vegetation establishment.Advantages over blankets include:
l BFM and MBFMs do not require surface preparation.
l Helicopters can assist in installing BFM and MBFMs in remote areas.
l On slopes steeper than 2.5H:1V,blanket installers may require ropes
and harnesses for safety.
l Installing BFM and MBFMs can save at least $1,000 per acre com-
pared to blankets.
Maintenance Standards
Reseed any seeded areas that fail to establish at least 80 percent cover (100 percent
cover for areas that receive sheet or concentrated flows).If reseeding is ineffective,use
an alternate method such as sodding,mulching,or nets/blankets.If winter weather pre-
vents adequate grass growth,this time limit may be relaxed at the discretion of the local
authority when sensitive areas would otherwise be protected.
l Reseed and protect by mulch any areas that experience erosion after achieving
adequate cover.Reseed and protect by mulch any eroded area.
l Supply seeded areas with adequate moisture,but do not water to the extent that it
causes runoff.
Approved as Equivalent
Ecology has approved products as able to meet the requirements of BMP C120:Tem-
porary and Permanent Seeding.The products did not pass through the Technology
Assessment Protocol –Ecology (TAPE)process.Local jurisdictions may choose not to
accept this product approved as equivalent,or may require additional testing prior to con-
sideration for local use.The products are available for review on Ecology’s website at
http://www.ecy.wa.gov/programs/wq/stormwater/newtech/equivalent.html.
BMP C121:Mulching
Purpose
Mulching soils provides immediate temporary protection from erosion.Mulch also
enhances plant establishment by conserving moisture,holding fertilizer,seed,and top-
soil in place,and moderating soil temperatures.There is an enormous variety of
mulches that can be used.This section discusses only the most common types of mulch.
Conditions of Use
As a temporary cover measure,mulch should be used:
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BMP C123:Plastic Covering
Purpose
Plastic covering provides immediate,short-term erosion protection to slopes and dis-
turbed areas.
Conditions of Use
Plastic covering may be used on disturbed areas that require cover measures for less
than 30 days,except as stated below.
l Plastic is particularly useful for protecting cut and fill slopes and stockpiles.Note:
The relatively rapid breakdown of most polyethylene sheeting makes it unsuitable
for long-term (greater than six months)applications.
l Due to rapid runoff caused by plastic covering,do not use this method upslope of
areas that might be adversely impacted by concentrated runoff.Such areas include
steep and/or unstable slopes.
l Plastic sheeting may result in increased runoff volumes and velocities,requiring
additional on-site measures to counteract the increases.Creating a trough with
wattles or other material can convey clean water away from these areas.
l To prevent undercutting,trench and backfill rolled plastic covering products.
l While plastic is inexpensive to purchase,the added cost of installation,main-
tenance,removal,and disposal make this an expensive material,up to $1.50-2.00
per square yard.
l Whenever plastic is used to protect slopes install water collection measures at the
base of the slope.These measures include plastic-covered berms,channels,and
pipes used to covey clean rainwater away from bare soil and disturbed areas.Do
not mix clean runoff from a plastic covered slope with dirty runoff from a project.
l Other uses for plastic include:
1.Temporary ditch liner.
2.Pond liner in temporary sediment pond.
3.Liner for bermed temporary fuel storage area if plastic is not reactive to the
type of fuel being stored.
4.Emergency slope protection during heavy rains.
5.Temporary drainpipe (“elephant trunk”)used to direct water.
2014 Stormwater Management Manual for Western Washington
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Design and Installation Specifications
l Plastic slope cover must be installed as follows:
1.Run plastic up and down slope,not across slope.
2.Plastic may be installed perpendicular to a slope if the slope length is less
than 10 feet.
3.Minimum of 8-inch overlap at seams.
4.On long or wide slopes,or slopes subject to wind,tape all seams.
5.Place plastic into a small (12-inch wide by 6-inch deep)slot trench at the top
of the slope and backfill with soil to keep water from flowing underneath.
6.Place sand filled burlap or geotextile bags every 3 to 6 feet along seams and
tie them together with twine to hold them in place.
7.Inspect plastic for rips,tears,and open seams regularly and repair imme-
diately.This prevents high velocity runoff from contacting bare soil which
causes extreme erosion.
8.Sandbags may be lowered into place tied to ropes.However,all sandbags
must be staked in place.
l Plastic sheeting shall have a minimum thickness of 0.06 millimeters.
l If erosion at the toe of a slope is likely,a gravel berm,riprap,or other suitable pro-
tection shall be installed at the toe of the slope in order to reduce the velocity of run-
off.
Maintenance Standards
l Torn sheets must be replaced and open seams repaired.
l Completely remove and replace the plastic if it begins to deteriorate due to ultra-
violet radiation.
l Completely remove plastic when no longer needed.
l Dispose of old tires used to weight down plastic sheeting appropriately.
Approved as Equivalent
Ecology has approved products as able to meet the requirements of BMP C123:Plastic
Covering.The products did not pass through the Technology Assessment Protocol –
Ecology (TAPE)process.Local jurisdictions may choose not to accept this product
approved as equivalent,or may require additional testing prior to consideration for local
use.The products are available for review on Ecology’s website at
http://www.ecy.wa.gov/programs/wq/stormwater/newtech/equivalent.html
2014 Stormwater Management Manual for Western Washington
Volume II -Chapter 4 -Page 295
BMP C140:Dust Control
Purpose
Dust control prevents wind transport of dust from disturbed soil surfaces onto roadways,
drainage ways,and surface waters.
Conditions of Use
l In areas (including roadways)subject to surface and air movement of dust where
on-site and off-site impacts to roadways,drainage ways,or surface waters are
likely.
Design and Installation Specifications
l Vegetate or mulch areas that will not receive vehicle traffic.In areas where plant-
ing,mulching,or paving is impractical,apply gravel or landscaping rock.
l Limit dust generation by clearing only those areas where immediate activity will
take place,leaving the remaining area(s)in the original condition.Maintain the ori-
ginal ground cover as long as practical.
l Construct natural or artificial windbreaks or windscreens.These may be designed
as enclosures for small dust sources.
l Sprinkle the site with water until surface is wet.Repeat as needed.To prevent
carryout of mud onto street,refer to BMP C105:Stabilized Construction Entrance /
Exit (p.270).
l Irrigation water can be used for dust control.Irrigation systems should be installed
as a first step on sites where dust control is a concern.
l Spray exposed soil areas with a dust palliative,following the manufacturer’s
instructions and cautions regarding handling and application.Used oil is pro-
hibited from use as a dust suppressant.Local governments may approve other
dust palliatives such as calcium chloride or PAM.
l PAM (BMP C126:Polyacrylamide (PAM)for Soil Erosion Protection (p.300))
added to water at a rate of 0.5 lbs.per 1,000 gallons of water per acre and applied
from a water truck is more effective than water alone.This is due to increased infilt-
ration of water into the soil and reduced evaporation.In addition,small soil
particles are bonded together and are not as easily transported by wind.Adding
PAM may actually reduce the quantity of water needed for dust control.Use of
PAM could be a cost-effective dust control method.
Techniques that can be used for unpaved roads and lots include:
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l Lower speed limits.High vehicle speed increases the amount of dust stirred up
from unpaved roads and lots.
l Upgrade the road surface strength by improving particle size,shape,and mineral
types that make up the surface and base materials.
l Add surface gravel to reduce the source of dust emission.Limit the amount of fine
particles (those smaller than .075 mm)to 10 to 20 percent.
l Use geotextile fabrics to increase the strength of new roads or roads undergoing
reconstruction.
l Encourage the use of alternate,paved routes,if available.
l Restrict use of paved roadways by tracked vehicles and heavy trucks to prevent
damage to road surface and base.
l Apply chemical dust suppressants using the admix method,blending the product
with the top few inches of surface material.Suppressants may also be applied as
surface treatments.
l Pave unpaved permanent roads and other trafficked areas.
l Use vacuum street sweepers.
l Remove mud and other dirt promptly so it does not dry and then turn into dust.
l Limit dust-causing work on windy days.
l Contact your local Air Pollution Control Authority for guidance and training on other
dust control measures.Compliance with the local Air Pollution Control Authority
constitutes compliance with this BMP.
Maintenance Standards
Respray area as necessary to keep dust to a minimum.
BMP C150:Materials on Hand
Purpose
Keep quantities of erosion prevention and sediment control materials on the project site
at all times to be used for regular maintenance and emergency situations such as unex-
pected heavy summer rains.Having these materials on-site reduces the time needed to
implement BMPs when inspections indicate that existing BMPs are not meeting the Con-
struction SWPPP requirements.In addition,contractors can save money by buying some
materials in bulk and storing them at their office or yard.
2014 Stormwater Management Manual for Western Washington
Volume II -Chapter 4 -Page 311
Conditions of Use
l Construction projects of any size or type can benefit from having materials on
hand.A small commercial development project could have a roll of plastic and
some gravel available for immediate protection of bare soil and temporary berm
construction.A large earthwork project,such as highway construction,might have
several tons of straw,several rolls of plastic,flexible pipe,sandbags,geotextile fab-
ric and steel “T”posts.
l Materials are stockpiled and readily available before any site clearing,grubbing,or
earthwork begins.A large contractor or developer could keep a stockpile of mater-
ials that are available for use on several projects.
l If storage space at the project site is at a premium,the contractor could maintain
the materials at their office or yard.The office or yard must be less than an hour
from the project site.
Design and Installation Specifications
Depending on project type,size,complexity,and length,materials and quantities will
vary.A good minimum list of items that will cover numerous situations includes:
Material
Clear Plastic,6 mil
Drainpipe,6 or 8 inch diameter
Sandbags,filled
Straw Bales for mulching,
Quarry Spalls
Washed Gravel
Geotextile Fabric
Catch Basin Inserts
Steel "T" Posts
Silt fence material
Straw Wattles
Maintenance Standards
l All materials with the exception of the quarry spalls,steel “T”posts,and gravel
should be kept covered and out of both sun and rain.
l Re-stock materials used as needed.
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Volume II -Chapter 4 -Page 312
BMP C151:Concrete Handling
Purpose
Concrete work can generate process water and slurry that contain fine particles and high
pH,both of which can violate water quality standards in the receiving water.Concrete
spillage or concrete discharge to surface waters of the State is prohibited.Use this BMP
to minimize and eliminate concrete,concrete process water,and concrete slurry from
entering waters of the state.
Conditions of Use
Any time concrete is used,utilize these management practices.Concrete construction
projects include,but are not limited to,the following:
l Curbs
l Sidewalks
l Roads
l Bridges
l Foundations
l Floors
l Runways
Design and Installation Specifications
l Assure that washout of concrete trucks,chutes,pumps,and internals is performed
at an approved off-site location or in designated concrete washout areas.Do not
wash out concrete trucks onto the ground,or into storm drains,open ditches,
streets,or streams.Refer to BMP C154:Concrete Washout Area (p.317)for inform-
ation on concrete washout areas.
l Return unused concrete remaining in the truck and pump to the originating batch
plant for recycling.Do not dump excess concrete on site,except in designated con-
crete washout areas.
l Wash off hand tools including,but not limited to,screeds,shovels,rakes,floats,
and trowels into formed areas only.
l Wash equipment difficult to move,such as concrete pavers in areas that do not dir-
ectly drain to natural or constructed stormwater conveyances.
l Do not allow washdown from areas,such as concrete aggregate driveways,to
drain directly to natural or constructed stormwater conveyances.
l Contain washwater and leftover product in a lined container when no formed areas
2014 Stormwater Management Manual for Western Washington
Volume II -Chapter 4 -Page 313
are available.Dispose of contained concrete in a manner that does not violate
ground water or surface water quality standards.
l Always use forms or solid barriers for concrete pours,such as pilings,within 15-
feet of surface waters.
l Refer to BMP C252:High pH Neutralization Using CO2 (p.409)and BMP C253:
pH Control for High pH Water (p.412)for pH adjustment requirements.
l Refer to the Construction Stormwater General Permit for pH monitoring require-
ments if the project involves one of the following activities:
l Significant concrete work (greater than 1,000 cubic yards poured concrete or
recycled concrete used over the life of a project).
l The use of engineered soils amended with (but not limited to)Portland
cement-treated base,cement kiln dust or fly ash.
l Discharging stormwater to segments of water bodies on the 303(d)list (Cat-
egory 5)for high pH.
Maintenance Standards
Check containers for holes in the liner daily during concrete pours and repair the same
day.
BMP C152:Sawcutting and Surfacing Pollution Prevention
Purpose
Sawcutting and surfacing operations generate slurry and process water that contains
fine particles and high pH (concrete cutting),both of which can violate the water quality
standards in the receiving water.Concrete spillage or concrete discharge to surface
waters of the State is prohibited.Use this BMP to minimize and eliminate process water
and slurry created through sawcutting or surfacing from entering waters of the State.
Conditions of Use
Utilize these management practices anytime sawcutting or surfacing operations take
place.Sawcutting and surfacing operations include,but are not limited to,the following:
l Sawing
l Coring
l Grinding
l Roughening
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Volume II -Chapter 4 -Page 314
l Hydro-demolition
l Bridge and road surfacing
Design and Installation Specifications
l Vacuum slurry and cuttings during cutting and surfacing operations.
l Slurry and cuttings shall not remain on permanent concrete or asphalt pavement
overnight.
l Slurry and cuttings shall not drain to any natural or constructed drainage con-
veyance including stormwater systems.This may require temporarily blocking
catch basins.
l Dispose of collected slurry and cuttings in a manner that does not violate ground
water or surface water quality standards.
l Do not allow process water generated during hydro-demolition,surface rough-
ening or similar operations to drain to any natural or constructed drainage con-
veyance including stormwater systems.Dispose process water in a manner that
does not violate ground water or surface water quality standards.
l Handle and dispose cleaning waste material and demolition debris in a manner
that does not cause contamination of water.Dispose of sweeping material from a
pick-up sweeper at an appropriate disposal site.
Maintenance Standards
Continually monitor operations to determine whether slurry,cuttings,or process water
could enter waters of the state.If inspections show that a violation of water quality stand-
ards could occur,stop operations and immediately implement preventive measures such
as berms,barriers,secondary containment,and vacuum trucks.
BMP C153:Material Delivery,Storage and Containment
Purpose
Prevent,reduce,or eliminate the discharge of pollutants to the stormwater system or
watercourses from material delivery and storage.Minimize the storage of hazardous
materials on-site,store materials in a designated area,and install secondary con-
tainment.
Conditions of Use
These procedures are suitable for use at all construction sites with delivery and
storage of the following materials:
2014 Stormwater Management Manual for Western Washington
Volume II -Chapter 4 -Page 315
1.If the discharge velocity at the outlet is less than 5 fps (pipe slope less than 1
percent),use 2-inch to 8-inch riprap.Minimum thickness is 1-foot.
2.For 5 to 10 fps discharge velocity at the outlet (pipe slope less than 3 per-
cent),use 24-inch to 48-inch riprap.Minimum thickness is 2 feet.
3.For outlets at the base of steep slope pipes (pipe slope greater than 10 per-
cent),an engineered energy dissipater shall be used.
l Filter fabric or erosion control blankets should always be used under riprap to pre-
vent scour and channel erosion.
l New pipe outfalls can provide an opportunity for low-cost fish habitat improve-
ments.For example,an alcove of low-velocity water can be created by con-
structing the pipe outfall and associated energy dissipater back from the stream
edge and digging a channel,over-widened to the upstream side,from the outfall.
Overwintering juvenile and migrating adult salmonids may use the alcove as shel-
ter during high flows.Bank stabilization,bioengineering,and habitat features may
be required for disturbed areas.This work may require a HPA.See Volume V
(p.765)for more information on outfall system design.
Maintenance Standards
l Inspect and repair as needed.
l Add rock as needed to maintain the intended function.
l Clean energy dissipater if sediment builds up.
BMP C220:Storm Drain Inlet Protection
Purpose
Storm drain inlet protection prevents coarse sediment from entering drainage systems
prior to permanent stabilization of the disturbed area.
Conditions of Use
Use storm drain inlet protection at inlets that are operational before permanent sta-
bilization of the disturbed drainage area.Provide protection for all storm drain inlets
downslope and within 500 feet of a disturbed or construction area,unless conveying run-
off entering catch basins to a sediment pond or trap.
Also consider inlet protection for lawn and yard drains on new home construction.These
small and numerous drains coupled with lack of gutters in new home construction can
add significant amounts of sediment into the roof drain system.If possible delay
installing lawn and yard drains until just before landscaping or cap these drains to pre-
2014 Stormwater Management Manual for Western Washington
Volume II -Chapter 4 -Page 357
vent sediment from entering the system until completion of landscaping.Provide 18-
inches of sod around each finished lawn and yard drain.
Table II-4.2.2 Storm Drain Inlet Protection (p.358)lists several options for inlet protection.
All of the methods for storm drain inlet protection tend to plug and require a high fre-
quency of maintenance.Limit drainage areas to one acre or less.Possibly provide emer-
gency overflows with additional end-of-pipe treatment where stormwater ponding would
cause a hazard.
Type of Inlet
Protection
Emergency
Overflow
Applicable for
Paved/Earthen
Surfaces
Conditions of Use
Drop Inlet Protection
Excavated drop
inlet protection
Yes,tem-
porary flood-
ing will occur
Earthen
Applicable for heavy flows.Easy
to maintain.Large area Require-
ment:30'x30'/acre
Block and
gravel drop inlet
protection
Yes Paved or Earthen Applicable for heavy concentrated
flows.Will not pond.
Gravel and wire
drop inlet pro-
tection
No
Applicable for heavy concentrated
flows.Will pond.Can withstand
traffic.
Catch basin fil-
ters Yes Paved or Earthen Frequent Maintenance required.
Curb Inlet Protection
Curb inlet pro-
tection with
wooden weir
Small capacity
overflow Paved Used for sturdy,more compact
installation.
Block and
gravel curb inlet
protection
Yes Paved Sturdy,but limited filtration.
Culvert Inlet Protection
Culvert inlet Sed-
iment trap 18 month expected life.
Table II-4.2.2 Storm Drain Inlet Protection
Design and Installation Specifications
Excavated Drop Inlet Protection -An excavated impoundment around the storm drain.
Sediment settles out of the stormwater prior to entering the storm drain.
2014 Stormwater Management Manual for Western Washington
Volume II -Chapter 4 -Page 358
l Provide a depth of 1-2 ft as measured from the crest of the inlet structure.
l Slope sides of excavation no steeper than 2H:1V.
l Minimum volume of excavation 35 cubic yards.
l Shape basin to fit site with longest dimension oriented toward the longest inflow
area.
l Install provisions for draining to prevent standing water problems.
l Clear the area of all debris.
l Grade the approach to the inlet uniformly.
l Drill weep holes into the side of the inlet.
l Protect weep holes with screen wire and washed aggregate.
l Seal weep holes when removing structure and stabilizing area.
l Build a temporary dike,if necessary,to the down slope side of the structure to pre-
vent bypass flow.
Block and Gravel Filter -A barrier formed around the storm drain inlet with standard con-
crete blocks and gravel.See Figure II-4.2.8 Block and Gravel Filter (p.360).
l Provide a height of 1 to 2 feet above inlet.
l Recess the first row 2-inches into the ground for stability.
l Support subsequent courses by placing a 2x4 through the block opening.
l Do not use mortar.
l Lay some blocks in the bottom row on their side for dewatering the pool.
l Place hardware cloth or comparable wire mesh with ½-inch openings over all
block openings.
l Place gravel just below the top of blocks on slopes of 2H:1V or flatter.
l An alternative design is a gravel donut.
l Provide an inlet slope of 3H:1V.
l Provide an outlet slope of 2H:1V.
l Provide a1-foot wide level stone area between the structure and the inlet.
l Use inlet slope stones 3 inches in diameter or larger.
l Use gravel ½-to ¾-inch at a minimum thickness of 1-foot for the outlet slope.
2014 Stormwater Management Manual for Western Washington
Volume II -Chapter 4 -Page 359
Figure II-4.2.8 Block and Gravel Filter
DEP A RTMENT OF
ECOLOG Y
State of Washington
Please see http://www.ecy.wa.gov/copyright.html for copyright notice including permissions,
limitation of liability, and disclaimer.
Figure II-4.2.8
Block and Gravel Filter
Revised August 2015
NOT TO SCALE
Plan View
A
A
Section A-A
Drain grate
Concrete block
Gravel backfill
Less than
5% slop
e
Gravel backfill
Concrete block
Water
Overflow
water
Drop inlet
Ponding height
Wire screen or
filter fabric
Notes:
1.Drop inlet sediment barriers are to be used for small, nearly level drainage areas. (less
than 5%)
2.Excavate a basin of sufficient size adjacent to the drop inlet.
3.The top of the structure (ponding height) must be well below the ground elevation
downslope to prevent runoff from bypassing the inlet. A temporary dike may be
necessary on the downslope side of the structure.
2014 Stormwater Management Manual for Western Washington
Volume II -Chapter 4 -Page 360
Gravel and Wire Mesh Filter -A gravel barrier placed over the top of the inlet.This struc-
ture does not provide an overflow.
l Use a hardware cloth or comparable wire mesh with ½-inch openings.
l Use coarse aggregate.
l Provide a height 1-foot or more,18-inches wider than inlet on all sides.
l Place wire mesh over the drop inlet so that the wire extends a minimum of 1-foot
beyond each side of the inlet structure.
l Overlap the strips if more than one strip of mesh is necessary.
l Place coarse aggregate over the wire mesh.
l Provide at least a 12-inch depth of gravel over the entire inlet opening and extend
at least 18-inches on all sides.
Catchbasin Filters –Use inserts designed by manufacturers for construction sites.The
limited sediment storage capacity increases the amount of inspection and maintenance
required,which may be daily for heavy sediment loads.To reduce maintenance require-
ments combine a catchbasin filter with another type of inlet protection.This type of inlet
protection provides flow bypass without overflow and therefore may be a better method
for inlets located along active rights-of-way.
l Provides 5 cubic feet of storage.
l Requires dewatering provisions.
l Provides a high-flow bypass that will not clog under normal use at a construction
site.
l Insert the catchbasin filter in the catchbasin just below the grating.
Curb Inlet Protection with Wooden Weir –Barrier formed around a curb inlet with a
wooden frame and gravel.
l Use wire mesh with ½-inch openings.
l Use extra strength filter cloth.
l Construct a frame.
l Attach the wire and filter fabric to the frame.
l Pile coarse washed aggregate against wire/fabric.
l Place weight on frame anchors.
Block and Gravel Curb Inlet Protection –Barrier formed around a curb inlet with concrete
blocks and gravel.See Figure II-4.2.9 Block and Gravel Curb Inlet Protection (p.363).
2014 Stormwater Management Manual for Western Washington
Volume II -Chapter 4 -Page 361
l Use wire mesh with ½-inch openings.
l Place two concrete blocks on their sides abutting the curb at either side of the inlet
opening.These are spacer blocks.
l Place a 2x4 stud through the outer holes of each spacer block to align the front
blocks.
l Place blocks on their sides across the front of the inlet and abutting the spacer
blocks.
l Place wire mesh over the outside vertical face.
l Pile coarse aggregate against the wire to the top of the barrier.
Curb and Gutter Sediment Barrier –Sandbag or rock berm (riprap and aggregate)3 feet
high and 3 feet wide in a horseshoe shape.See Figure II-4.2.10 Curb and Gutter Barrier
(p.364).
l Construct a horseshoe shaped berm,faced with coarse aggregate if using riprap,3
feet high and 3 feet wide,at least 2 feet from the inlet.
l Construct a horseshoe shaped sedimentation trap on the outside of the berm sized
to sediment trap standards for protecting a culvert inlet.
Maintenance Standards
l Inspect catch basin filters frequently,especially after storm events.Clean and
replace clogged inserts.For systems with clogged stone filters:pull away the
stones from the inlet and clean or replace.An alternative approach would be to use
the clogged stone as fill and put fresh stone around the inlet.
l Do not wash sediment into storm drains while cleaning.Spread all excavated
material evenly over the surrounding land area or stockpile and stabilize as appro-
priate.
Approved as Equivalent
Ecology has approved products as able to meet the requirements of BMP C220:Storm
Drain Inlet Protection.The products did not pass through the Technology Assessment
Protocol –Ecology (TAPE)process.Local jurisdictions may choose not to accept this
product approved as equivalent,or may require additional testing prior to consideration
for local use.The products are available for review on Ecology’s website at
http://www.ecy.wa.gov/programs/wq/stormwater/newtech/equivalent.html
2014 Stormwater Management Manual for Western Washington
Volume II -Chapter 4 -Page 362
Figure II-4.2.9 Block and Gravel Curb Inlet Protection
DEP A RTMENT OF
ECOLOG Y
State of Washington
Please see http://www.ecy.wa.gov/copyright.html for copyright notice including permissions,
limitation of liability, and disclaimer.
Figure II-4.2.9
Block and Gravel Curb Inlet Protection
Revised August 2015
NOT TO SCALE
Plan View
A
A
Section A-A
Notes:
1.Use block and gravel type sediment barrier when curb inlet is located in gently sloping street
segment, where water can pond and allow sediment to separate from runoff.
2.Barrier shall allow for overflow from severe storm event.
3.Inspect barriers and remove sediment after each storm event. Sediment and gravel must be
removed from the traveled way immediately.
Back of sidewalk
Catch basin
Back of curb Curb inlet Concrete block
2x4 Wood stud
Concrete block34 inch (20 mm)
Drain gravel
Wire screen or
filter fabric
34 inch (20 mm)
Drain gravel
Wire screen or
filter fabric
Ponding height
Overflow
2x4 Wood stud
(100x50 Timber stud)
Concrete block
Curb inlet
Catch basin
2014 Stormwater Management Manual for Western Washington
Volume II -Chapter 4 -Page 363
Figure II-4.2.10 Curb and Gutter Barrier
DEP A RTMENT OF
ECOLOG Y
State of Washington
Please see http://www.ecy.wa.gov/copyright.html for copyright notice including permissions,
limitation of liability, and disclaimer.
Figure II-4.2.10
Curb and Gutter Barrier
Revised September 2015
NOT TO SCALE
Plan View
Back of sidewalk
Runoff
Runoff Spillway
Burlap sacks to
overlap onto curb
Gravel filled sandbags
stacked tightly
Curb inlet
Catch basin
Back of curb
Notes:
1.Place curb type sediment barriers on gently sloping street segments, where water can
pond and allow sediment to separate from runoff.
2.Sandbags of either burlap or woven 'geotextile' fabric, are filled with gravel, layered
and packed tightly.
3.Leave a one sandbag gap in the top row to provide a spillway for overflow.
4.Inspect barriers and remove sediment after each storm event. Sediment and gravel
must be removed from the traveled way immediately.
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BMP C232:Gravel Filter Berm
Purpose
A gravel filter berm is constructed on rights-of-way or traffic areas within a construction
site to retain sediment by using a filter berm of gravel or crushed rock.
Conditions of Use
Where a temporary measure is needed to retain sediment from rights-of-way or in traffic
areas on construction sites.
Design and Installation Specifications
l Berm material shall be ¾to 3 inches in size,washed well-grade gravel or crushed
rock with less than 5 percent fines.
l Spacing of berms:
o Every 300 feet on slopes less than 5 percent
o Every 200 feet on slopes between 5 percent and 10 percent
o Every 100 feet on slopes greater than 10 percent
l Berm dimensions:
o 1 foot high with 3H:1V side slopes
o 8 linear feet per 1 cfs runoff based on the 10-year,24-hour design storm
Maintenance Standards
l Regular inspection is required.Sediment shall be removed and filter material
replaced as needed.
BMP C233:Silt Fence
Purpose
Use of a silt fence reduces the transport of coarse sediment from a construction site by
providing a temporary physical barrier to sediment and reducing the runoff velocities of
overland flow.See Figure II-4.2.12 Silt Fence (p.369)for details on silt fence con-
struction.
Conditions of Use
Silt fence may be used downslope of all disturbed areas.
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l Silt fence shall prevent soil carried by runoff water from going beneath,through,or
over the top of the silt fence,but shall allow the water to pass through the fence.
l Silt fence is not intended to treat concentrated flows,nor is it intended to treat sub-
stantial amounts of overland flow.Convey any concentrated flows through the
drainage system to a sediment pond.
l Do not construct silt fences in streams or use in V-shaped ditches.Silt fences do
not provide an adequate method of silt control for anything deeper than sheet or
overland flow.
2014 Stormwater Management Manual for Western Washington
Volume II -Chapter 4 -Page 368
Figure II-4.2.12 Silt Fence
DEP A RTMENT OF
ECOLOG Y
State of Washington
Please see http://www.ecy.wa.gov/copyright.html for copyright notice including permissions,
limitation of liability, and disclaimer.
Figure II-4.2.12
Silt Fence
Revised October 2014
NOT TO SCALE
Joints in filter fabric shall be spliced
at posts. Use staples, wire rings or
equivalent to attach fabric to posts
6' max
Post spacing may be increased
to 8' if wire backing is used
2"x2" by 14 Ga. wire or equivalent,
if standard strength fabric used
Minimum
4"x4" trench
2"x2" wood posts, steel
fence posts, or equivalent
12" min
2' min
2"x2" by 14 Ga. wire or equivalent,
if standard strength fabric used
Filter fabric
Minimum
4"x4" trench
2"x2" wood posts, steel
fence posts, or equivalent
Backfill trench with
native soil or 34" -
1.5" washed gravel
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Volume II -Chapter 4 -Page 369
Design and Installation Specifications
l Use in combination with sediment basins or other BMPs.
l Maximum slope steepness (normal (perpendicular)to fence line)1H:1V.
l Maximum sheet or overland flow path length to the fence of 100 feet.
l Do not allow flows greater than 0.5 cfs.
l The geotextile used shall meet the following standards.All geotextile properties lis-
ted below are minimum average roll values (i.e.,the test result for any sampled roll
in a lot shall meet or exceed the values shown in Table II-4.2.3 Geotextile Stand-
ards (p.370)):
Polymeric Mesh AOS
(ASTM D4751)
0.60 mm maximum for slit film woven (#30 sieve).
0.30 mm maximum for all other geotextile types (#50 sieve).
0.15 mm minimum for all fabric types (#100 sieve).
Water Permittivity
(ASTM D4491)
0.02 sec-1 minimum
Grab Tensile Strength
(ASTM D4632)
180 lbs.Minimum for extra strength fabric.
100 lbs minimum for standard strength fabric.
Grab Tensile Strength
(ASTM D4632)
30%maximum
Ultraviolet Resistance
(ASTM D4355)
70%minimum
Table II-4.2.3 Geotextile Standards
l Support standard strength fabrics with wire mesh,chicken wire,2-inch x 2-inch
wire,safety fence,or jute mesh to increase the strength of the fabric.Silt fence
materials are available that have synthetic mesh backing attached.
l Filter fabric material shall contain ultraviolet ray inhibitors and stabilizers to provide
a minimum of six months of expected usable construction life at a temperature
range of 0°F.to 120°F.
l One-hundred percent biodegradable silt fence is available that is strong,long last-
ing,and can be left in place after the project is completed,if permitted by local reg-
ulations.
l Refer to Figure II-4.2.12 Silt Fence (p.369)for standard silt fence details.Include
the following standard Notes for silt fence on construction plans and specifications:
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Volume II -Chapter 4 -Page 370
1.The contractor shall install and maintain temporary silt fences at the locations
shown in the Plans.
2.Construct silt fences in areas of clearing,grading,or drainage prior to starting
those activities.
3.The silt fence shall have a 2-feet min.and a 2½-feet max.height above the
original ground surface.
4.The filter fabric shall be sewn together at the point of manufacture to form fil-
ter fabric lengths as required.Locate all sewn seams at support posts.Altern-
atively,two sections of silt fence can be overlapped,provided the Contractor
can demonstrate,to the satisfaction of the Engineer,that the overlap is long
enough and that the adjacent fence sections are close enough together to
prevent silt laden water from escaping through the fence at the overlap.
5.Attach the filter fabric on the up-slope side of the posts and secure with
staples,wire,or in accordance with the manufacturer's recommendations.
Attach the filter fabric to the posts in a manner that reduces the potential for
tearing.
6.Support the filter fabric with wire or plastic mesh,dependent on the properties
of the geotextile selected for use.If wire or plastic mesh is used,fasten the
mesh securely to the up-slope side of the posts with the filter fabric up-slope
of the mesh.
7.Mesh support,if used,shall consist of steel wire with a maximum mesh spa-
cing of 2-inches,or a prefabricated polymeric mesh.The strength of the wire
or polymeric mesh shall be equivalent to or greater than 180 lbs.grab tensile
strength.The polymeric mesh must be as resistant to the same level of ultra-
violet radiation as the filter fabric it supports.
8.Bury the bottom of the filter fabric 4-inches min.below the ground surface.
Backfill and tamp soil in place over the buried portion of the filter fabric,so
that no flow can pass beneath the fence and scouring cannot occur.When
wire or polymeric back-up support mesh is used,the wire or polymeric mesh
shall extend into the ground 3-inches min.
9.Drive or place the fence posts into the ground 18-inches min.A 12–inch min.
depth is allowed if topsoil or other soft subgrade soil is not present and 18-
inches cannot be reached.Increase fence post min.depths by 6 inches if the
fence is located on slopes of 3H:1V or steeper and the slope is perpendicular
to the fence.If required post depths cannot be obtained,the posts shall be
adequately secured by bracing or guying to prevent overturning of the fence
due to sediment loading.
10.Use wood,steel or equivalent posts.The spacing of the support posts shall
2014 Stormwater Management Manual for Western Washington
Volume II -Chapter 4 -Page 371
be a maximum of 6-feet.Posts shall consist of either:
l Wood with dimensions of 2-inches by 2-inches wide min.and a 3-feet
min.length.Wood posts shall be free of defects such as knots,splits,or
gouges.
l No.6 steel rebar or larger.
l ASTM A 120 steel pipe with a minimum diameter of 1-inch.
l U,T,L,or C shape steel posts with a minimum weight of 1.35 lbs./ft.
l Other steel posts having equivalent strength and bending resistance to
the post sizes listed above.
11.Locate silt fences on contour as much as possible,except at the ends of the
fence,where the fence shall be turned uphill such that the silt fence captures
the runoff water and prevents water from flowing around the end of the fence.
12.If the fence must cross contours,with the exception of the ends of the fence,
place gravel check dams perpendicular to the back of the fence to minimize
concentrated flow and erosion.The slope of the fence line where contours
must be crossed shall not be steeper than 3H:1V.
l Gravel check dams shall be approximately 1-foot deep at the back of
the fence.Gravel check dams shall be continued perpendicular to the
fence at the same elevation until the top of the check dam intercepts the
ground surface behind the fence.
l Gravel check dams shall consist of crushed surfacing base course,
gravel backfill for walls,or shoulder ballast.Gravel check dams shall be
located every 10 feet along the fence where the fence must cross con-
tours.
l Refer to Figure II-4.2.13 Silt Fence Installation by Slicing Method (p.374)for slicing
method details.Silt fence installation using the slicing method specifications:
1.The base of both end posts must be at least 2-to 4-inches above the top of
the filter fabric on the middle posts for ditch checks to drain properly.Use a
hand level or string level,if necessary,to mark base points before install-
ation.
2.Install posts 3-to 4-feet apart in critical retention areas and 6-to 7-feet apart
in standard applications.
3.Install posts 24-inches deep on the downstream side of the silt fence,and as
close as possible to the filter fabric,enabling posts to support the filter fabric
from upstream water pressure.
4.Install posts with the nipples facing away from the filter fabric.
2014 Stormwater Management Manual for Western Washington
Volume II -Chapter 4 -Page 372
5.Attach the filter fabric to each post with three ties,all spaced within the top 8-
inches of the filter fabric.Attach each tie diagonally 45 degrees through the fil-
ter fabric,with each puncture at least 1-inch vertically apart.Each tie should
be positioned to hang on a post nipple when tightening to prevent sagging.
6.Wrap approximately 6-inches of fabric around the end posts and secure with
3 ties.
7.No more than 24-inches of a 36-inch filter fabric is allowed above ground
level.
Compact the soil immediately next to the filter fabric with the front wheel of
the tractor,skid steer,or roller exerting at least 60 pounds per square inch.
Compact the upstream side first and then each side twice for a total of four
trips.Check and correct the silt fence installation for any deviation before
compaction.Use a flat-bladed shovel to tuck fabric deeper into the ground if
necessary.
2014 Stormwater Management Manual for Western Washington
Volume II -Chapter 4 -Page 373
Figure II-4.2.13 Silt Fence Installation by Slicing Method
DEP A RTMENT OF
ECOLOG Y
State of Washington
Please see http://www.ecy.wa.gov/copyright.html for copyright notice including permissions,
limitation of liability, and disclaimer.
Figure II-4.2.13
Silt Fence Installation by Slicing Method
Revised November 2015
NOT TO SCALE
Completed Installation
Silt Fence
Post
installed
after
compaction
Vibratory plow is not acceptable because of horizontal compaction
Slicing blade
(18 mm width)
Horizontal chisel point
(76 mm width)
Fabric
above
ground
200 -
300mm
Roll of silt fenceOperation
No more than 24" of a 36"
fabric is allowed above groundSteel support post100% compaction 100% compaction
FLOW
Drive over each side of
silt fence 2 to 4 times
with device exerting 60
p.s.i. or greater
Attach fabric to
upstream side of post
Ponding height max. 24"
POST SPACING:
7' max. on open runs
4' max. on pooling areas
POST DEPTH:
As much below ground
as fabric above ground
Top of Fabric
Belt
top 8"
Diagonal attachment
doubles strength
Attachment Details:
x Gather fabric at posts, if needed.
x Utilize three ties per post, all within top 8"
of fabric.
x Position each tie diagonally, puncturing
holes vertically a minimum of 1" apart.
x Hang each tie on a post nipple and tighten
securely. Use cable ties (50 lbs) or soft
wire.
2014 Stormwater Management Manual for Western Washington
Volume II -Chapter 4 -Page 374
Maintenance Standards
l Repair any damage immediately.
l Intercept and convey all evident concentrated flows uphill of the silt fence to a sed-
iment pond.
l Check the uphill side of the fence for signs of the fence clogging and acting as a
barrier to flow and then causing channelization of flows parallel to the fence.If this
occurs,replace the fence or remove the trapped sediment.
l Remove sediment deposits when the deposit reaches approximately one-third the
height of the silt fence,or install a second silt fence.
l Replace filter fabric that has deteriorated due to ultraviolet breakdown.
BMP C234:Vegetated Strip
Purpose
Vegetated strips reduce the transport of coarse sediment from a construction site by
providing a temporary physical barrier to sediment and reducing the runoff velocities of
overland flow.
Conditions of Use
l Vegetated strips may be used downslope of all disturbed areas.
l Vegetated strips are not intended to treat concentrated flows,nor are they intended
to treat substantial amounts of overland flow.Any concentrated flows must be con-
veyed through the drainage system to a sediment pond.The only circumstance in
which overland flow can be treated solely by a strip,rather than by a sediment
pond,is when the following criteria are met (see Table II-4.2.4 Contributing Drain-
age Area for Vegetated Strips (p.375)):
Average Contributing
Area Slope
Average Contributing Area
Percent Slope
Max Contributing area
Flowpath Length
1.5H :1V or flatter 67%or flatter 100 feet
2H :1V or flatter 50%or flatter 115 feet
4H :1V or flatter 25%or flatter 150 feet
6H :1V or flatter 16.7%or flatter 200 feet
10H :1V or flatter 10%or flatter 250 feet
Table II-4.2.4 Contributing Drainage Area for Vegetated Strips
2014 Stormwater Management Manual for Western Washington
Volume II -Chapter 4 -Page 375
Design and Installation Specifications
l The vegetated strip shall consist of a minimum of a 25-foot flowpath length con-
tinuous strip of dense vegetation with topsoil.Grass-covered,landscaped areas
are generally not adequate because the volume of sediment overwhelms the
grass.Ideally,vegetated strips shall consist of undisturbed native growth with a
well-developed soil that allows for infiltration of runoff.
l The slope within the strip shall not exceed 4H:1V.
l The uphill boundary of the vegetated strip shall be delineated with clearing limits.
Maintenance Standards
l Any areas damaged by erosion or construction activity shall be seeded imme-
diately and protected by mulch.
l If more than 5 feet of the original vegetated strip width has had vegetation removed
or is being eroded,sod must be installed.
l If there are indications that concentrated flows are traveling across the buffer,sur-
face water controls must be installed to reduce the flows entering the buffer,or addi-
tional perimeter protection must be installed.
BMP C235:Wattles
Purpose
Wattles are temporary erosion and sediment control barriers consisting of straw,com-
post,or other material that is wrapped in biodegradable tubular plastic or similar encas-
ing material.They reduce the velocity and can spread the flow of rill and sheet runoff,
and can capture and retain sediment.Wattles are typically 8 to 10 inches in diameter
and 25 to 30 feet in length.Wattles are placed in shallow trenches and staked along the
contour of disturbed or newly constructed slopes.See Figure II-4.2.14 Wattles (p.378)for
typical construction details.WSDOT Standard Plan I-30.30-00 also provides information
on Wattles (http://www.wsdot.wa.gov/Design/Standards/Plans.htm#SectionI)
Conditions of Use
l Use wattles:
l In disturbed areas that require immediate erosion protection.
l On exposed soils during the period of short construction delays,or over
winter months.
l On slopes requiring stabilization until permanent vegetation can be estab-
lished.
2014 Stormwater Management Manual for Western Washington
Volume II -Chapter 4 -Page 376
l The material used dictates the effectiveness period of the wattle.Generally,
Wattles are typically effective for one to two seasons.
l Prevent rilling beneath wattles by properly entrenching and abutting wattles
together to prevent water from passing between them.
Design Criteria
l Install wattles perpendicular to the flow direction and parallel to the slope contour.
l Narrow trenches should be dug across the slope on contour to a depth of 3-to 5-
inches on clay soils and soils with gradual slopes.On loose soils,steep slopes,
and areas with high rainfall,the trenches should be dug to a depth of 5-to 7-
inches,or 1/2 to 2/3 of the thickness of the wattle.
l Start building trenches and installing wattles from the base of the slope and work
up.Spread excavated material evenly along the uphill slope and compacted using
hand tamping or other methods.
l Construct trenches at intervals of 10-to 25-feet depending on the steepness of the
slope,soil type,and rainfall.The steeper the slope the closer together the
trenches.
l Install the wattles snugly into the trenches and abut tightly end to end.Do not over-
lap the ends.
l Install stakes at each end of the wattle,and at 4-foot centers along entire length of
wattle.
l If required,install pilot holes for the stakes using a straight bar to drive holes
through the wattle and into the soil.
l Wooden stakes should be approximately 3/4 x 3/4 x 24 inches min.Willow cuttings
or 3/8-inch rebar can also be used for stakes.
l Stakes should be driven through the middle of the wattle,leaving 2 to 3 inches of
the stake protruding above the wattle.
Maintenance Standards
l Wattles may require maintenance to ensure they are in contact with soil and thor-
oughly entrenched,especially after significant rainfall on steep sandy soils.
2014 Stormwater Management Manual for Western Washington
Volume II -Chapter 4 -Page 377
Figure II-4.2.14 Wattles
DEP A RTMENT OF
ECOLOG Y
State of Washington
Please see http://www.ecy.wa.gov/copyright.html for copyright notice including permissions,
limitation of liability, and disclaimer.
Figure II-4.2.14
Wattles
Revised November 2015
NOT TO SCALE
3' - 4'
(1.2m)
Adjacent rolls
shall tightly abut
Straw rolls must be
placed along slope
contours
Spacing depends
on soil type and
slope steepness
10' - 25' (3-8m)
Sediment, organic matter,
and native seeds are
captured behind the rolls.
Live Stake
1" x 1" Stake
(25 x 25mm)
3" - 5" (75-125mm)
8" - 10" Dia.
(200-250mm)
NOTE:
1.Straw roll installation requires the placement and secure staking
of the roll in a trench, 3" - 5" (75-125mm) deep, dug on contour.
Runoff must not be allowed to run under or around roll.
2014 Stormwater Management Manual for Western Washington
Volume II -Chapter 4 -Page 378
l Inspect the slope after significant storms and repair any areas where wattles are
not tightly abutted or water has scoured beneath the wattles.
Approved as Equivalent
Ecology has approved products as able to meet the requirements of BMP C235:Wattles.
The products did not pass through the Technology Assessment Protocol –Ecology
(TAPE)process.Local jurisdictions may choose not to accept this product approved as
equivalent,or may require additional testing prior to consideration for local use.The
products are available for review on Ecology’s website at http://www.ecy.wa.gov-
/programs/wq/stormwater/newtech/equivalent.html
BMP C236:Vegetative Filtration
Purpose
Vegetative Filtration may be used in conjunction with BMP C241:Temporary Sediment
Pond (p.388),BMP C206:Level Spreader (p.348)and a pumping system with surface
intake to improve turbidity levels of stormwater discharges by filtering through existing
vegetation where undisturbed forest floor duff layer or established lawn with thatch layer
are present.Vegetative Filtration can also be used to infiltrate dewatering waste from
foundations,vaults,and trenches as long as runoff does not occur.
Conditions of Use
l For every five acre of disturbed soil use one acre of grass field,farm pasture,or
wooded area.Reduce or increase this area depending on project size,ground
water table height,and other site conditions.
l Wetlands shall not be used for filtration.
l Do not use this BMP in areas with a high ground water table,or in areas that will
have a high seasonal ground water table during the use of this BMP.
l This BMP may be less effective on soils that prevent the infiltration of the water,
such as hard till.
l Using other effective source control measures throughout a construction site will
prevent the generation of additional highly turbid water and may reduce the time
period or area need for this BMP.
l Stop distributing water into the vegetated area if standing water or erosion results.
Design Criteria
l Find land adjacent to the project that has a vegetated field,preferably a farm field,
or wooded area.
l If the project site does not contain enough vegetated field area consider obtaining
2014 Stormwater Management Manual for Western Washington
Volume II -Chapter 4 -Page 379
COUGHLINPORTERLUNDEEN
A CONSULTING STRUCTURAL AND CIVIL ENGINEERING CORPORATION
Total Site:Area (ac)
Pervious Area 0.240
Impervious Area 0.290
Total Area 0.530
MGS-FLOOD:
Data Type Reduced
Time Step 15-min
MGS - Flood 2-Yr developed flow 0.320 cfs
Temporary Sediment Pond Sizing: Storage Volume per DOE II-4-104 BMP 241 (pg. 162)
Vr=S.A. x 3.5'Vr = Minimum Required Storage Volume
S.A. = Minimum allowable top surface area of pond
S.A. = (Qx2)/Vsed
Q = design peak flow rate
Vsed = 0.00096 Settling Velocity (0.00096 ft/sec)
Q=.320 cfs INPUT (note that this is the 2-yr design peak flow rate in cfs)
S.A. = 667 sf
Vr=2333 cf cf Volume Required
17455 gal
1 sediment storage tank is required.
Project: Lake Washington Blvd Improvements - Phase III for Southport DevelopmentDesigned by: ALC
Project No.: Client: Checked by: TBB Sheet 1 of 1
* the volume is based a minimum pond depth of 3.5' - this depth does not
include the minimum sediment storage volume or freeboard
Assume 18,100 gallons per sediment storage tank, then
Date: 05/14/2016
801 Second Avenue ∙ Suite 900 ∙ Seattle, WA 98104 ∙ P: (206) 343-0460
BAKER TANK CALCULATIONS:
Proposed Runoff Conditions for TESC - Entire Site
16
IX. BOND QUANTITY, FACILITY SUMMARIES, AND DECLARATION
OF COVENANT
A Bond Quantity Worksheet is included with this report.
A Water Quality Facility Summary Sheet outlining the proposed water quality system will be included with this
report.
Any required Declarations of Covenant will be included prior to issuance of the permit.