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ATS Office Expansion
432 Shattuck Avenue South
Renton, WA 98057
Technical Information Report
May 4, 20 I 5
The information contained in this report was
prepared by and under the direct supervision of
the undersigned:
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Prepared by: Prepared for:
Laurie J.Pfarr,P.E. WeaverArchitects
LPD Engineering,PLLC Contact Paul Grundhoffer
91 I Western Avenue,Suite 420 I 4 I I 4"'Avenue,Suite 8 I 0
Seattle,WA 98104 Seattle,WA 98101
(206)725-I 2 I I (206)262-9622
Owner:
Team Properties,LLC
Conract Brian Allen - ''r U�- rt�S����
432 Shattuck Avenue South }`C C E(vE d
Renton,WA 98057 ���� 2 5 2015
(425)25 I-9680
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ATS OFFICE EXPANSION -
TECHNICAL INFORMATION REPORT
TABLE OF CONTENTS
SectionI —Project Overview...................................................................................................................................... I
Sect�on 2—Conditions and Requiremenu Summary...........................................................................................3
Section3—Offsite Analysis..........................................................................................................................................6
Section 4—Flow Control and Water Quality Facility Analysis and Design...................................................9
Section 5—Conveyance Systems Analysis and Design......................................................................................I 3
Section 6—Special Reports and Studies.................................................................................................................I 3
Section7—Other Permiu..........................................................................................................................................14
Seaion8—CSWPPP Analysis and Design.............................................................................................................14
Section 9—Bond Quantities, Facility Summaries,and Declaration of Covenant......................................14
Section 10—Operations and Maintenance Manual.............................................................................................14
FIGURES
Figure I:TIR Worksheet
Figure 2:Vicinity Map
Figure 3: Existing Impervious Coverage
Figure 4: 6cisting Conditions
Figure 5: Soils Map
Figure 6: Proposed Conditions
Figure 7: Downstream Drainage Map
APPENDICES
Appendix A—Design Drawings
� Appendix B—Design Calculations and Supporting Information
Appendix C—Stormwater Pollution Prevention and Spill Plan (SWPPS) &Preliminary Construction
Stormwater Pollution Prevention Plan (SWPPP} Narrative
Appendix D—Operation and Maintenance Guidelines
Appendix E—Geotechnical Report
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ATS OFFICE EXPANSION I
432 SHATTUCKAVE S
TECHNICAL INFORMATION REPORT
MAY 4,20 I 5
SECTION I —PROJEGT OVERVIEW
This Technical Information Report(TIR)is for a new office building expansion,adjacent to the existing
ATS Automation building. Refer to Figure 1 - TTR Worksheet for basic site information. The project is
located at 432 Shattuck Avenue S within the City of Renton. The site is in Section 18, Township 23
North,Range 5 East,Willamette Meridian.Refer to Figure 2-Vicinity Map.
The City of Renton has adopted the 2009 King County Surface Water Design Manual (KCSWDM)
with the City's Amendments, dated February 2010. Based upon the City of Renton amendments to the
2009 KCSWDM, the project is subject to drainage review as it is subject to a City of Renton
development permit because it includes greater than 2,000 square feet (SF) of new plus replaced
impervious surface and 7,000 SF of land disturbing activity. Based upon Figure 1.1.2.A in the Renton
Amendments, the Flow Chart for Determining Type of Drainage Review Required, the project is
subject to a "Full Drainage Review" because the project results in greater than 2,000 SF of new plus
replaced impervious surface, and it is not a large project or single family residential project. Per the
"Full Drainage Review"requirements in Table 1.1.2.A,the TIR addresses Core Requirements#1-8 and
Special Requirements#1-6 of the City of Renton Amendments to the 2009 KCSWDM.
The proposed project is a new office/storage building on the north side of the existing ATS building,
along with proposed parking,walkways,and drainage infrastructure.
Existing Site
The project disturbance area will mostly take place on one parcel (78413001'75). The parcel is about
0.95 acres. Previously, the site consisted of three individual parcels, but a City of Renton Lot
Combination Application has been approved in April 2015 to combine the parcels. The project
disturbance area will mostly be on the north side of this parcel, consisting of an existing gravel parking
lot and a small commercial building that will be demolished. On the southern end of this parcel is the
existing ATS building. The total disturbance area is approximately 16,909 SF (0.388 acres). The
disturbance area also includes a portion of the right-of-way along Shattuck Avenue S and the alley to
the northeast of the ATS site. The project area is bounded by Shattuck Ave S to the west,a public alley
to the east,a single-family residence to the north,and the existing ATS building to the south.
The existing topography on site is relatively flat,with slopes of 0-2%throughout the project disturbance
limits. Based on site survey, there does not appear to be any stormwater infrastructure within the
proposed project area. There is an existing public storm drain main line on the west side of Shattuck ',
Avenue,to which the proposed drainage infrastructure will connect. '
The project is considered a redevelopment project based upon the following definition from the Renton
Amendments to the KCSWDM: "Redevelopmentproject means a project thatproposes to add, '
replace, or modify impervious surfaces(for purposes other than a residential subdivision or ,
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maintenance)on a site that is already substantially developed in a manner consistent with its current
zoning or with a legal non-conforming use, or has an existing impervious surface coverage of 35%or
more."An aerial image was scaled and used in AutoCAD to delineate the eacisting impervious coverage
for the parcel.All building,roof,concrete and asphalt surfaces are considered impervious.
The existing gravel parking area was not counted as impervious based upon the KCSWDM's definition
of"new impervious"surface,which states that proposed surfaces over existing gravel aze new
impervious surfaces(See Section 4 for further explanation).Refer to Figure 3—Existing Impervious
Coverage.The existing impervious coverage is approximately 61%,which exceeds 35%and therefore
the project is considered a Redevelopment.
See Figure 4—Existing Conditions for a layout of the existing impervious areas within the disturbance
area. i
According to the USDA Natural Resources Conservation Service, the site soils are mapped as Urban
Land. Refer to Figure 5 - Soils Map. The SCS Soil Type is recognized as Renton(RE),classified under '
the Hydrologic Soil Group D and will be defined as Till in the stormwater calculations (Table 3.2.2.B,
2009 KCSWDM}. A Geotechnical Engineering Report has been prepared by PanGeo, Inc. dated
December 23, 2014; a copy has of been provided in Appendix E. Based upon the exploration pits, the
underlying soils were generally described as silty clays. Groundwater was encountered at a depth of
about 8 feet below grade.
The site is located within the Cedar Valley Sole Source Aquifer area. According to City of Renton GIS,
there aze no other environmentally sensitive areas within or in close proximity to the site.
Proposed Site Improvements
Proposed improvements include a new off'ice building, constructed off the north side of the existing
ATS Automation building. The existing one-story commercial building north of the existing ATS
building will be demolished. A paved parking lot will be established along the north and east sides of
the building expansion, including a heavy duty asphalt driving lane to accommodate truck traffic. The
west patio and onsite portion of the walkway will be surfaced with permeable pavers. Access
improvements will be made to ensure ADA compliance.
Utility improvements include a new fire hydrant assembly, connecting to the existing water line in
Shattuck Avenue. There is an existing 6-inch side sewer connection coming onto the site near the
northwest corner of the existing ATS building. A new side sewer connection is proposed for the
building expansion.
Refer to Figure 6-Proposed Conditions for a layout of the proposed improvements.
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Proposed Stormwater Management Improvements
As noted above, the proposed project meets the criteria subject to a "Full Drainage Review."
Stormwater management improvements include catch basins and pipes for conveyance,along with roof
downspouts for the proposed building addition.
The project proposes the use of Flow Control BMPs to mitigate runofF from the impervious area
associated with the project. This will consist of pervious pavers to the southwest and southeast of the
office building addition.
To address water quality treatment requirements, there will be a two-facility treatment train, consisting
of a wetvault followed by a StorniFilter structure installed in the parking lot to the north.
The site discharge point is near the northwest comer of the disturbance area, with the proposed
conveyance system connecting to the existing storm line on the west side of Shattuck Avenue.
Refer to Section 4 of this report for more information regarding the stormwater design.
SECTION 2—CONDITIONSAND REQUIREMENTS SUMMARY
This section addresses the Core Requirements (Section 1.2) and Special Requirements (Section 1.3)
requirements set forth by the City of Renton Amendments to the 2009 KCSWDM.
Core Requirements
Core Requirement 1-Discharge at Natural Location(1.2.1): The proposed stormwater system will
connect to the existing storm line in Shattuck Avenue S.Drainage will then follow the existing
downstream drainage path.
Core Requirement 2-Off-site Analysis(1.2.2): An offsite analysis for the project has been completed
and is included within Section 3 of this Report.
Core Requirement 3—Flow Control(1.2.3):
According to the Renton Amendments to the KCSWDM Flow Control Application Map(Reference
11-A),the project site is located in a Peak Rate Flow Control Standard Area.According to the Renton !
Amendments to the KCSWDM Section 1.2.3.1.A,Peak Rate Flow Control Standard Areas,flow '
control mitigation to existing site conditions is required for the project's target surfaces.Below is a
description of the target surfaces for this project:
1. New impervious surface that is not fully dispersed per the criteria in Section 1.2.3.2 (p. 1-41).
For individual lots within residential subdivision projects, the eztent of new impervious surface ',
shall be assumed as specified in Chapter 3.Note, any new impervious surface such as a bridge ',
that spans the ordinary high water of a stream,pond, or lake may be excluded as a target I
surface if the runofffrom such span is conveyed to the ordinary high water area in accordance �,
with Criteria(b), (c), (d), and(e)of the "Direct Discharge Exemption"(p 1-33). New ,
impervious surfaces will be considered a target surface. '
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2. New pervious surface that is not fully dispersed. For individual lots within residential
subdivision projects, the ectent of new pervious surface shal!be assumed to be the entire lot
area, except the assumed impervious portion and any portion in which native conditions are '
preserved by covenant, tract, or easement.In addition, the new pervious surface on individual '
lots shall be assumed to be 100'�grass. The project does not create any"new"pervious
surface.
Thus based upon the above requirements,only new imnervious surfaces will be considered as"Target I
Impervious Surface." However, as described in Section 4 of this report, a flow control facility is not �
required due to Exception 1 in Section 1.2.3.1 of the Renton Amendments to the KCSWDM, which
asserts that a flow control facility is not required if the difference in the 100-year peak runoff rate �,
between the existing site condition and the developed condition is less than 0.1 cubic feet per second I
(cfs). ',
Flow control BMPs must be implemented per section 1.2.3.3 of the Renton Amendments to the I�
KCSWDM. Flow control BMPs will include pervious pavers. Refer to Section 4 — Flow Control and
Water Quality Facility Analysis and Design in this report for more detailed information.
Core Requirement 4-Conveyance System(1.2.4):Refer to Section 5 of this Report for the
conveyance design and analysis.
Core Requirement 5-Erosion and Sedimentation Control(1.2.5): A full temporary erosion and
sedimentation control(TESC)plan will be included with the permit submittal. This plan will be
considered the minimum for anticipated site conditions.The Contractor will be responsible for
implementing all TESC measures and upgrading as necessary.The TESC facilities will be in place prior
to any clearing,grubbing or construction. See sheet C1.0 in Appendix A and the preliminary
construction stormwater pollution prevention(SWPPP)narrative in Appendix C.
Core Requirement 6-Maintenance and Operations(1.2.6): The property owner will maintain and
operate the water quality treatment facilities.Conveyance facilities and drainage structures within the
right-of-way and/or drainage easements will be operated and maintained by the City of Renton.An
Operation and Maintenance Manual,per Section 2.3.1 of the Renton Amendments to the KCSWDM,
will be provided to the property owner and City prior to permit issuance. Operation and Maintenance
Guidelines are attached in Appendix D of this report.
Core Requirement 7—Financial Guarantees and Liability(1.2.7): Financial guarantees and liability
for the proposed project will be completed by the owner prior to pennit issuance.
Core Requirement 8—Water Quality(1.2.8): The redevelopment project contains more than 5,000
SF of new plus replaced pollution-generating impervious surface(PGIS)that is not fully dispersed.
Because the site is classified as commercial land use,water quality facilities must be selected from the
Enhanced Basic WQ Treatment Menu.A two-facility treatment train,consisting of a wetvault followed
by a StormFilter structure was chosen.Refer to Section 4 of this report for water quality facility design
and analysis.
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Special Requirements
Special Requirement 1—Other Adopted Area-Specific Requirements(1.3.1):
• Master Drainage Plans (MDPs) — Project is not within an area covered by an approved
Master Drainage Plan.
• Basin Plans (BPs) — The project site is in the Black River drainage basin. There is no
specific basin plan for the Black River basin.
• Salmon Conservation Plans (SCPs) —Project is not within an area governed by a Salmon
Conservation Plan.
• Stormwater Compliance Plans (SWCPs)—The project is not within an area governed by a
SWCP.
• Flood Hazard Reduction Plan (FHRPs)—The project site is not within a designated flood
hazard azea.
• Shared Facility Drainage Plan (SFDPs) —The proposed project is not within an area with
SFDP.
Special Requirement 2 — Flood Hazard Area Delineation (1.3.2): The project site is not within or
adjacent to a designated flood hazard area.
Special Requirement 3—Flood Protection Facilities(1.3.3): The project does not rely on an existing
flood protection facility, nor will a new flood protection facility be constructed; therefore this
requirement is not applicable.
Special Requirement 4 — Source Control (13.4): The project requires a commercial
building/commercial site development permit; therefore source controls are applicable in accordance
with the King County Stormwater Pollution Prevention Manual and Renton Municipal Code N.Water
quality facilities will include a two-facility treatment train from the Enhanced Basic Water Quality
Menu of the KCSWDM.
Special Requirement 5—Oil Control (13.�: The project will not have high-use site characteristics;
therefore oil controls are not applicable.
Special Requirement 6—Aquifer ProtecNon Area (13.6): Per Reference 11-B, the project is within
the "Cedar Valley Sole Source Aquifer Project Review Area." However, the project is not within an
Aquifer Protection Area(APA)zone.
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SECTION 3 —OFFSITE ANALYSIS �
The following is the Level 1 downstream analysis for the proposed project. Refer to Figure 7 -
Downstream Drainage Map. II
Task I —Study Area Definition and Maps I,
The study area consists of one parcels(7841300175)and the total disturbance azea is about 0388 acres. �I
The downstream analysis for the project site is based upon the following resources: i
• Site Survey,completed by Duncanson Company,Inc. '
• King County iMap
• City of Renton Online GIS Map Application
Task 2— Resource Review
Basin Summary
Based upon King County iMap, the site is located within the Black River drainage basin, which is
within the Duwamish-Green River Watershed. �
Floodway Map
� Per FEMA Flood Insurance Rate Map Number 53033C0977F,the site is not located within floodway or
flood plain.
Serrsitive Areas
The sensitive areas within one-mile upstream and downstream of the subject property were examined
using the City of Renton Amendments to the 2009 KCSWDM and King County iMap application. T'he
following are the sensitive area designations for the project site and within one mile downstream of the
site:
• SAO Erosion Hazard—The ro'ect is not within a desi ated erosion hazard area.
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• SAO Seismic Hazard—The project site is not within a designated seismic hazard area. .
• SAO Landslide Hazard—The project is not within a designated landslide hazard area.
• SAO Coal Mine-There are no known coal mines on the site or within one mile of the site.
• SAO Stream—There are no streams within the project site or within the downstream
drainage course.
• SAO Wetland—There are no wetlands located within the project site or within the
downstream drainage course.
• Groundwater Contamination-The project site and upstream study area are within an area
designated as a"low"groundwater contamination zone.
• Sole Source Aquifer—According to Reference 11-B and iMap,the project site area,
upstream area,and downstream area are within the Cedar Valley Sole Source Aquifer.
• Channel Migration Hazard-There are no known channel migration hazards on the site or
within one mile of the site.
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Critical Areas
The critical areas within one mile upstream and downstream of the subject property were examined
using the King County GIS iMap application. Based on the GIS mapping,the following are the critical
area designations for the project site and within one mile downstream of the site:
• Critical area ordinance(CAO)Basin Condition—The project area,upstream area,and
downstream area is designated as"low."The"low"basin condition designation is due to the
high development intensity within the project and downstream area.The majority of the
project site and downstream area has reduced forest cover and large amounts of impervious
surfaces.
• Critical area ordinance(CAO)Shoreline Condition—The project site,upstream area,and
downstream azea are not within a CAO Shoreline Condition.
Topographic Map
The topographic information for the site is shown on the Grading and Drainage Plan. (Refer to
Appendix A).
Drainage Complaints
According to King County's iMap program,there have been no drainage complaints within the last 10
years within the project site,upstream area,or downstream area.
King County Soils Survey
According to the USDA Natural Resources Conservation Service, the site soils are mapped as Urban
Land (Ur). Refer to Figure 5 - Soils Map. A Geotechnical Engineering Report has been prepared by
PanGeo,Inc. dated December 23,2014.T'he geotechnical report is attached in Appendix E. �
Migrating River Studies 'I
According to King County iMap,the project site is not located within a channel migration hazard area. '�
303d List of Polluted Waters �'�
There are no waters that aze within the project site area or within one-mile downstream of the project
site that are on the current Washington State Depariment of Ecology's Clean Water Act 303d list.
Water Quality Problems
According to King County's iMap program,neither the project site,nor the downstream area is within a
designated King County water quality problem area.
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Task 3—Field Inspection
Onsite Conditions
Currently there is a commercial building located in the project area north of the existing ATS building.
To the north of the commercial building is a gravel drive. To the west of the commercial building is a
small paved parking area. The existing ATS building and the small commercial building are separated
by a driveway.
Topography of the site is generally flat, sloping down in the northerly direction at an approximate slope
of 1%. There does not appear to be any onsite stormwater infrastructure within the project disturbance
area.
Upstream Areas
Due to the flat topography of the project area, offsite runoff from the surrounding properties is assumed
to be limited to none.
Task 4—Drainage System Description and Problem Descriptions
As described earlier, due to the relatively flat topography, stormwater is assumed to sheet flow west off
the site, and then flows southward along the existing curb. At the manhole at the intersection of
Shattuck Avenue S and S 4"' Place, the drainage course can split in two directions (west and south),
both joining further downstream. Refer to Figure 7 — Downstream Drainage Map. Below is a
description of the"west"downstream drainage course:
1. Surface runoff will flow along the curb and enter an inlet structure and 12-inch storm drain line
near the intersection of Shattuck Avenue S and S 4�'Place.
2. The 12-inch system flows west, becoming an 18-inch system after a manhole in the center of
the aforementioned intersection.
3. The 18-inch storm drain system conveys flow westbound along S 4�'Place for about 570 feet to
a manhole neaz the intersection of S 4�'Place and Rainier Avenue S.
4. From this manhole, the system turns south and conveys flow along Rainier Avenue S to
another manhole approximately 270 feet to the south.
5. The stormwater system tums west and enters a stormwater pump station. The force-main piped
system continues west for about 880 feet through an existing parking lot to a manhole at the
northwest corner of the lot,passing the '/-mile point downstream from the site.
6. At this point, the system becomes a 60-inch gravity system that flows to a manhole within
Hazdie Avenue SW.
7. The storm system becomes 60-inch and continues west through another parking lot. The
system reduces to 48-inch and turns south at a sUucture approximately 825 feet away from the
manhole in Hardie Avenue SW.
8. After the piped system flows south for about 340 feet,reaching a manhole in SW 7�`Street,the
piped system becomes 54inch and riuns to the west.
9. The 54-inch system discharges into a vault near the intersection of SW 7�' Street and Lind
Avenue SW. The outlet from the vault is a 60-inch piped system that continues west along SW
7'�Street.
10. The 60-inch system continues to the west for approximately another 2,700 feet to a manhole at
the northwest corner of the intersection of SW 7�'Street and Naches Avenue SW.
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11. The 60-inch storm line heads north for approximately 640 feet and outfalls into the Black River
at a point about 1.25 miles from the site.
12. The Black River eventually discharges to the Duwamish River.
The following is the "south" downstream drainage course, starting from the manhole indicated in #2
above.
13. From the manhole at the intersection of Shattuck Avenue & 4�'' Place, a 48-inch conveyance
system continues soutb along Shattuck Avenue S for about 1,150 feet.
14. This 48-inch storm line enters a vault within the intersection of Shattuck Ave S and SW 7�'
Street.
15. T'he outlet is a 60-inch storm line heading in the westbound direction for about 2,500 feet,
where it enters a vault (see item 8 above) at the intersection of Lind Avenue SW and SW 7`�
Street. Along this stretch of 60-inch storm drain main, the system passes the '/o-mile point
downstream from the site.
16. From this point, the downstream course is the same as #8-11 from the "wesY' downstream
course noted above.
SECTION 4 — FLOW CONTROL AND WATER QUALITY FACILITY ANALYSIS
AND DESIGN
Existing Site Hydrology
Based on the site survey, there is no existing stormwater infrastructure within the project disturbance
area. It is assumed that runoff from the west side of the site sheet flows and leaves khe site at the
driveway cut near the small parking area to the west of the existing commercial building. Runoff from
the east side of the site appears to flow toward a catch basin in the existing ATS parking lot, southeast
of the project area. Based on site topography and GIS information, the eastbound drainage is assumed
to join the same downstream course as the westbound runoff. Refer to the Offsite Analysis section for
information.
Developed Site Hydrology
The proposed drainage design includes catch basins and conveyance pipes throughout the parking lot to
collect and convey stormwater. The stormwater is routed toward the northwest comer of the site, where
the runoff from the pollution-generating impervious surfaces (PGIS) will be routed to the proposed
wetvault and StormFilter system for water quality treatment. The roof surfaces will be routed north to a
catch basin downstream of the water quality treatment systems. From this catch basin, a proposed 12-
inch storm drain line will connect to the existing storm main in Shattuck Avenue S.
Refer to sheet C2.0 in Appendix A,which shows the storm drainage plan for the site.
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Flow Control System
The proposed project improvements will include the construction of a new office building expansion
and accompanying parking lot, along with walkways. Refer to Figure 6—Proposed Conditions, which
shows the proposed site conditions and a summary of the surface areas.
The project is within a Peak Rate Flow Control Standard area, and thus the true existing conditions aze
allowed to be evaluated as the predeveloped condition. Per section 1.2.3.1 of the Renton Amendments
to the KCSWDM, Execptionl was evaluated to determine if flow control facilities are necessary.
Exception 1 states: "The facility requirement in Peak Flow Control Standard Areas is waived for any
threshold discharge area in which the target surfaces subject to this requirement will generate no more
than a 0.1-cfs increase in the exishing site conditions 100 year peak flox�. " So the gravel will not be
considered an existing impervious surface in the calculations.
According to the Renton Amendments to the KCSWDM, the defmition for new impervious surface is
"the addition of a hard or compacted surface like roofs,pavement,gravel, or dirt; or the addition of a
more compacted surface, like paving over pre-e.risting dirt or gravel." Thus, the existing gravel
parking on the north side of the site that will be replaced by paving will be considered a new impervious
surface.Therefore,the existing gravel is not counted an existing impervious surface.
Table 1 shows a breakdown of the proposed effective impervious surfaces and how the target
impervious surface was determined. The pervious pavers will be modeled as 50% impervious, 50%
grass per Tab1e1.2.3.0 of the KCSWDM. All other impervious surfaces will be considered 100%
effective impervious. Areas involving utility trenching were not counted as new/replaced or existing
impervious surfaces.
Table 1—Proposed Effective Impervious Areas
Square Feet Acres
New Plus Replaced Building 4,140 0.095
(Considered to be 100%e(fecti►e impervious)
New Plus Replaced Standard Concrete
(Considered to be 100%effective impervious) 1,716 0.039
New Plus Replaced Asphalt
(Considered to be 100%ef fective impervious) 7,181 0.165 i
New Plus Replaced Pervious Pavers
(1,158 SF iotal,considered to be SO'�6 e(fective impervious) 579 0.013
Toral New Plus Replaced Impervious 13,616 0.3 I 3
Existing Impervious to be Removed(Replaced Impervious)
(Considered os replaced impervious and deduded from the total ubove to give the new -7,917 -0.I 82
impervious surface.See Figure 4 for exisbng impervious area)
Total New Impervious Surface
(Target Impervious Surface) 5,699 0.13 I
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As outlined previously, only new impervious surfaces will be considered as the target impervious
surface requiring flow control mitigation and BMPs. However, Exception 1 of the Peak Rate Flow
Control Standard area was evaluated, which allows for the comparison of 100-year peak flow rates
between the developed condition and the true existing site conditions.
Using the King County Runoff Time Series(KCRTS),the peak flow rates for the developed condition
and the predeveloped existing site conditions was determined. The KCRTS output is included in
Appendix B. In the predeveloped time series, the 0.182 acres of existing impervious(See Figure 4)was
modeled as impervious, while the remaining area was modeled as till grass. The developed time series
includes proposed site conditions,which consists of a total new plus replaced impervious of 0.313 acres
(See Table 1) and the remaining area modeled as till grass. The following table summarizes the 100-
year peak flow rates.
Table 2-100-year Peak Flow Rates
100-year Existing Site Conditions Peak Flow Rate 0.I 30 cfs
I 00-year Developed Site Conditions Peak Flow Rate 0.I 64 cfs
Difference in 100-yr Peak Flow Rate 0.034 cfs
The difference between the peak flow rates in the existing site conditions and developed site conditions
runoff in the 100-year event is below the 0.1 cfs threshold; therefore a flow control facility is not
required.However,flow control BMPs are still required.
Flow Control BMPs
According to Section 5.2.1 of the KCSWDM,since the site area is greater than 22,000 square feet with
more than 45%impervious coverage,the project is characterized as"Large Lot High Impervious."
Therefore flow control BMPs must be evaluated per section 5.2.1.3 of the KCSWDM.Full dispersion
of roof runoff will not be feasible due to the lack of unpaved open space on the site.The project must
implement another option from the listed BMI's in section 5.2.1.3.The project will result in impervious
surface coverage of more than 65%; therefore,flow control BMPs must be applied to an impervious
area equal to 10%of the site/lot or 20%of the target impervious surface,whichever is less.In this case,
the lesser value is 20%of the target impervious surface(5,699 SF),which means a minimum of 1,140
SF of impervious area must be mitigated with a flow control BMP.
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Below is Figure 5.2.1.A from the KCSWDM,outlining the path described above for Flow Control
BMPs.
FIGURE 5.21.A FIAW CIIART FOR DETERMING INDIVIDUAL LOT BMP REQl11REMEN7'S
k Ihe projeG on�slfdbt Yes Is il leatible and
smalNr Man 22.000 aqwn NN7 appUcable lo
YnpiemeM full Y� No Mrther BMPs
nppy aw w moro ot che�a�owing w k�fperwa,s area dupsrs�oo wr v�e reyi.rea. Mooe:
210%of s/toAd br alteAd sizes�11.000 sf and 2 20%ol rool ana as per /vry poposed
tJtMot fa tJtw4o1 slzes belwCen 11.000 end 22.000 sf(Fa SEttian C.2,17 cornettbn d rool
prqeda�ocatea�n uNAw aqrr�er ieararys araea n�eae dov�sPoas�o '
inpervbus area amounls dabk): No local dralnage I
t. LNMad In1lMrat{on(Sedim C.2.9) Is It(easide syalem must be I
2. Basic Dlspersion(SeWm C.2A) vla pkfaated
3. RNn Gardan(Secuon C.2.5) e���� pipe eonrwctlo�
4. P�rmeabN Pavomant(SeeUan C.2.8) Nu ����� Y� per Seclion
s. Rr�«►i,�wscrp�secuon c.2.� run�nraemion c.z i i
No 8. N�pNrisd Roo1(Seclio�G2.8) °��rO°�
7. Roducad Imparviovs Swrlu Cndil(Sedion C.2.9) np1OK��
8. Natfva Growlh R�tentlon Credlt(Sedion C2.10) Sec�on C.2.27
s on s �quan
a la�par wOth Imp�rvbus suAaq Y a Is q(eas�le aia
ol�6 or Nss7 aPP�bb to Implertienl --_ ._---
fuN disponbn on aM Y�
���i — No hrther BMPs
srwlaca as per reqWred. Nob:
On�or mor� np s nwnt Sedion C.2.19 �^f�P��OE°d
comectlon d root
� wr�►,at porta�w wpor Imit,.rvious:uraee na aaaressed � downspouls Io waa�
with hAI dspenbn a wilh W�infilV�ion ol rool nndf: drahape ayslam
1. FufllMiltratlon(Sedion C22 or SecUon 6A) Is R feasable and appNceble lo ! musl be vfa
2. Limfted In11Mr�tlon(Sedfan C.2.� No y�p�rR fWl I�fikntfon M p�rlorabd pipa
3. Basic Dlap�rsbn(SeeGon C.2.1) (fb roo(runoM as pet conn�ctbn per
4. Raln Oardan(Sectlm C.T.� Sedion C.22 a Seclbn 5.�9 Seqion C2.11. �
5. P�tmpbM Pawment(Sedbn C.2.� Yea
8. Ralmwter Huwstlnp(Sedim C.2.� Y°�
7. VopNated Roo1(SecUon C.2.8) It C�ae arry rertuMing fa►yM i
e. rteaucad rnparvlous s.rwa.c►.dn(sea+a,c.�.� Nnp�vlous swfs�.oa �
9, Nativs Growlh RsUMbn C�vdlt�SeCtlon C.2.1 eddressed witll fuI dispefslon of
whh h�ll titiltrs0on of rooi ruaM7
The project musl Ee a t!ldlot 22.000 squan Is M feaslde and
or larpar wih Imp�rvious wrbes �pp��ple lo impiert�erit
coraap�o!more tlian 15%7 Idl dkparsbn on a1
Wyet�pa►�dot�
� suAice as per
wAlh YnpeMoua sea gteeler 45 b or Seclbn C2.i T
tlwn 8516 one a more d!he 1oHowkig musl be applled W an
area g�ealcr Man a equal b 20%d the aite a 40%of Yea
tsryef Impervlous s�etscs v+fictiever b less OR lor projeds
eater Man 8576 'ous one a mae d rie ldlowing mul be No Nrlher BNPs 'I
W an YnpeMa�s area greakr Ihan a equel W 109L of a'le required. Nole �
20%ot fs�Det h+Mwvlous sw/ae�.wtichever is kaa: �:
1. futl M IMnNon( .�) ���;
2. Lknllod Mfilpatlon(Sectlon C2.3) �s�o �
3. Bssk Dbparslon�Sec6on C.2.1) bcal drainege :
4. Raln Garden SeUion C.2.5 $ys���be i
5. Parmwbb Pavert�nt Sedion C2. ��{o�d
8. Ralnwatar Han�sllnp(Seclbn c.z.� pips eonneetlo�
7. V�yNaled Roo((Sedion C.2.8) ��{p� .
6. R�duced Imparvian Service CredN(Seclion C.2.9) C.2.11
9. Nativa GrowM R�Eantbn CredM Sedbn C.2.t
The chosen Flow Control BMP for this project is permeable pavers. See sheet C3.1 for a detail of the
permeable pavers. The permeable paver surface will be used on the patios southwest and southeast of
the proposed building addition(excluding the ramp and stairs). The total area of the permeable pavers is
1,158 SF,thus satisfying the flow control BMP requirements.
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Water Quality Treatment
As described earlier, the redevelopment project contains more than 5,000 SF of new plus replaced
pollution-generating impervious surface (PGIS) that is not fully dispersed. The project will have
commercial land use, thus requiring the utilization of the Enhanced Basic Water Quality Menu per
section 6.1.2 of the KCSWDM.
A two-facility treatment train is proposed in the pazking lot area north of the proposed office building.
The treatment train will include a wetvault followed by a StormFilter structure with leaf compost(CSF)
media. The wetvault was sized per section 6.4.1.1 of the 2009 KCSWDM.A minimum wetpool volume
of 843 cubic feet was calculated based upon the tributary impervious areas. The wetpool calculation
spreadsheet is included in Appendix B. The wetvault will have dimensions of 24'x6'x8',allowing for 6
feet of permanent wetpool storage, 1 foot of freeboard, and 1 foot of sediment storage. 1'he actual
wetpool volume will be 864 cubic feet.
The StormFilter structure was designed with input from Contech Stormwater Solutions. Per section
6.5.5.1 of the KCSWDM, the CSF StormFilter for enhance basic treatment must be "sized using both
the flow-based and mass-based methods, and the designer shall select the result yielding the larger
number of cartridges." The water quality flow for StormFilters with CSF media far enhanced basic
treatment is 60% of the developed 2-year flow. Based on Contech's analysis, the flow-based method
yielded more cartridges. Therefore, the StormFilter structure will have 4 cartridges within a 60-inch
manhole. Refer to Contech's StormFilter cost estimate attached in Appendix B.Also refer to the details
of both the wetvault and StormFilter on sheet C2.1 in Appendix A.
SEGTION 5 —CONVEYANCE SYSTEMSANALYSISAND DESIGN
The proposed conveyance system was designed in accordance with the 2009 KCSWDM.The proposed
conveyance systems are sized to convey at minimum the 25-year runoff event without overtopping. The
proposed 12-inch storm drain line connecting to the existing 18-inch line was analyzed for conveyance.
This pipe was assumed to be conveying flow from the entire project area, which is a tributary
impervious area of 13,645 SF (0.313 acres). See the Conveyance Analysis Worksheet and associated
KCRTS Output in Appendix B.
The full-flow capacity of the pipe was determined using Manning's Equation. The proposed 12-inch
pipe (n=0.011) is at a slope of 1.7%, which yields a full-flow capacity of 5.50 cubic feet per second
(cfs). KCRTS was used with 15-minute time step to find the 25-year and 100-year peak flow, which
were found to be 0.30 cfs and 0.41 cfs,respectively. Thus, the proposed conveyance system will have
adequate capacity to accommodate the 25-year and 100-year storm event.
SECTION 6—SPECIAL REPORTSAND STUDIES
A geotechnical report,dated December 23,2014,has been conducted by PanGeo,Inc. and is attached in
Appendix E of this report.
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SECTION 7—OTHER PERMITS
There will be no other permits required for this project.
SECTION H—CSWPPPANALYSISAND DESIGN
The construction storm water pollution prevention plan (CSWPPP) consists of the TESC plan in the
drawing set with the accompanying preliminary construction SWPPP narrative per the 2012
Washington State Department of Ecology (DOE) Stormwater Management Manual for Western
Washington, and a Stormwater Pollution Prevention and Spill (SWPPS) plan per the Renton
Amendments to the KCSWDM. The TESC plan is in Appendir a, �vhile the S�T��'PPP narrative and
SWPPS plan are provided in Appendix C of this report.
Sizing calculations were performed for a sediment settling facility and the calculations are included i�
Appendix B. The proposed wetvault will be utilized as a sediment settling facility in the TESC phas�
��'� I�l�' ��� f�E�E� il.tt�l.i',Il�' li.�t� ill��r� ;��j�,i-lll.!!I�"'. .
SECTION 9 — BOND QUANTIT�FS. Fnr�� ��v S��n�r.�r�R��s ANn ���i_ARn�!�:,r�
OF COVENANT
Financial Quarantees and liability for the proposed project w�ill be completed by o���ner prior to per�nit �'
issuance.
SECTION I O—OPERATIONSAND MAINTENANCE MANUAL
Recommended operations and maintenance guidelines for the stormwater drainage facilities located
within the project are provided in Appendix D of this report. An Operations and Maintenance Manual,
per section 2.3.1 of the Renton Amendments to the KCSWDM, will be provided with the pecmit
submittal.
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FIGURES
Figure I: TIR Worksheet
Figure 2: Vicinity Map
Figure 3: F�cisting Impervious Coverage
Figure 4: Existing Conditions
Figure 5: Soils Map
Figure 6: Proposed Conditions
Figure 7: Downstream Drainage Map
�Figur�: i_ TIR Worksheet .
KING COUNTY, WASHINGTON, SURFACE WATER DESIGN MANUAL
TECHNICAL INFORMATION REPORT (TIR) WORKSHEET
Part 1 PROJECT OWNER AND Part 2 PROJECT LOCATION AND
PROJECT ENGINEER DESCRIPTION
Project Owner Team F'rope���e5a LL�_ Project Name R T S I+,��-oM�+1on
Phone �N 2.5� L51 -9�$O DDES Permit#
Address y5 b SI�a-t�4-uc.k �VG s. Location Township �-3 N
Re.�n�'c��ln�f� 9 8057 Range S E
Project Engineer �o��� Ser V�Z� � PE Section ��
Company �PD tn ine:e,��n �Q�.LG Site Address `t 3Z-Shq��c.k- �ve 5
Phone Z06 7 2-5 - 12 l 1 �`�^��, W� `�go5�
Part 3 TYPE OF PERMIT APPLICATION Part 4 OTHER REVIEWS AND PERMITS
❑ Landuse Services ❑ DFW HPA ❑ Shoreline
Subdivison / Short Subd. / UPD Management
❑ COE 404
� Buildin rvices ❑ DOE Dam Safety � Structural
M/F/ ommerical / SFR RockeryNaulU
❑ Clearing and Grading ❑ FEMA Floodplain � ESA Section 7
❑ Right-of-Way Use ❑ COE Wetlands
❑ Other � ❑ Other
Part 5 PLAN AND REPORT INFORMATION I
Technical Information Report Site Improvement Plan (Engr. Plans)
� -_
Type of Drainage Review �ul / Targeted / Type (circle one): LFulll / Modified /
(circle): Large Site Small Site
Date(include revision Date(include revision
dates): dates):
Date of Final: Date of Final:
Part 6 AD
JUSTMENT APPROVALS II
Type(circle one): Standard / Complex / Preapplication / Experimental/ Blanket I
Description: (include conditions in TIR Section 2) I
Date of A rovaL
2009 Surface Water Design Manual 1/9/2009
l
I{ING COUNTY, WASHINGTON, SURFACE WATER DESIGN MANUAL
� TECHNICAL INFORMATION REPORT (TIR) WORKSHEET
Part 7 MONITORING REQUIREMENTS
Monitoring Required: Yes / �lo> Describe:
Start Date:
Completion Date: ,
Part 8 SITE COMMUNITY AND DRAINAGE BASIN I!
Community Plan : /�:�%i �
Special District Overlays: aJ �A
Drainage Basirr. g � ���.►L (ti_�vP-�'
Stormwater Requirements: Pe�k �o.te_ Flou� ��n�� ��;�nr�,u��.
Part 9 ONSITE AND ADJACENT SENSITIVE AREAS
❑ RiverlStream ❑ Steep Slope
❑ Lake ❑ Erosion Hazard '
❑ Wetlands ❑ Landslide Hazard
❑ Closed Depression ❑ Coal Mine Hazard
❑ Floodplain ❑ Seismic Hazard
❑ Other ❑ Habitat Protection
❑
Part 10 SOILS
Soil Type Slopes Erosion Potential
l)r b�..n �3 �l�r j u h�o t�.)✓1
❑ High Groundwater Table(within 5 feet) � Sole Source Aquifer
❑ Other ❑ Seeps/Springs
❑ Additional Sheets Attached '
2009 Surface Water Design Mamial 1/9/2009
2
KING COUNTY, WASHINGTON, SURFACE WATER DESIGN MANUAL
TECHNICAL INFORMATION REPORT (TIR) WORKSHEET
Part 11 DRAINAGE DESIGN LIMITATIONS
REFERENCE LIMITATION/SITE CONSTRAINT
❑ Core 2—Offsite Analvsis
❑ Sensitive/Critical Areas
❑ SEPA
❑ Other
❑
❑ Additional Sheets Attached
Part 12 TIR SUMMARY SHEET rovide one TIR Summa Sheet r Threshold Dischar e Area
Threshold Discharge Area:
name or descri tion Aj� WP�� }'' �� ��'^�+�-�u- �'•�P-
Core Requirements (all 8 apply)
Dischar e at Natural Location Number of Natural Dischar e Locations:
Offsite Analysis Level: 1 j/ 2 / 3 dated: �!z.q! �5
Flow Control Level: 1 / 2 / 3 or Exemption Number �
incl.facilit summa sheet Small Site BMPs (' P :�,� `c�. :�: , n'-
Conveyance System Spill containment located at:
Erosion and Sediment Control ESC Site Supervisor:
Contact Phone: 7�� C C.onlr-a,:,��>
After Hours Phone:
Maintenance and Operation Responsibility: � riva� / Public
If Private, Maintenance Lo Re uired: Yes
Financial Guarantees and Provided: Yes / No �BD
Liabilit
Water Quality Type: Basic / Sens. Lake / n anced / Bog
(include facility summary sheet) or Exemption No.
Landsca e Mana ement Plan: Yes /
S ecial Re uirements as a licable
Area Specific Drainage Type: CDA/SDO/MDP/BP/LMP/Shared Fac. one�
Re uirements Name: -
Floodplain/Floodway Delineation
Type: Major / Minor / Exemption / (�lon>
100-year Base Flood Elevation (or range):
Datum:
Flood Protection Facilities Describe: N��
Source Control Describe landuse: �or„�,nec-c,�a�,
(comm.rndustrial landuse) Describe any structural controls: ����
2009 Surface Water Design Manual 1/9/2009
3
KING COUNTl', WASHINGTON, SURFACE WATER DESIGN MANUAL
� TECHNICAL INFORMATION REPORT (TIR) WORKSHEET
Oil Control High-use Site: Yes / o
Treatment BMP:
Maintenance Agreement: Yes /�
with whom?
Other Draina e Structures
Describe:
none.
Part 13 EROSION AND SEDIMENT CONTROL REQUIREMENTS
MINIMUM ESC REQUIREMENTS MINIMUM ESC REQUIREMENTS
DURING CONSTRUCTION AFTER CONSTRUCTION
� Clearing Limits � Stabilize Exposed Surfaces
� Cover Measures � Remove and Restore Temporary ESC Facilities
� Perimeter Protection � Clean and Remove All Silt and Debris, Ensure
� Traffic Area Stabilization Operation of Permanent Facilities
� Sediment Retention ❑ Flag Limits of SAO and open space
rv� preservation areas
�Y Surface Water Collection ❑ Other
� Dewatering Control
� Dust Control
� Flow Control
Part 14 STORMWATER FACILITY DESCRIPTIONS Note: Include Facilit Summa and Sketch
Flow Control T e/Descri tion Water Qualit T e/Descri tion
❑ Detention ❑ Biofiltration
❑ Infiltration ❑ Wetpool
❑ Regional Facility � Media Filtration 5}�r�,`.��u.r� w�GSFn,�d�
❑ Shared Facility ❑ Oil Control
� Flow Control �e�m��, ❑ Spill Control
BMPs ��p�-
❑ Flow Control BMPs
❑ Other
� Other
w e-�vo_u�.�'
2009 Surface Water Design Manual t/9/2009
4
KING COUNTY, WASHINGTON, SURFACE WATER DESIGN MANUAL
TECHNICAL INFORMATION REPORT (TIR) WORKSHEET
Part 15 EASEMENTS/TRACTS Part 16 STRUCTURAL ANALYSIS
❑ Drainage Easement ❑ Cast in Place Vault
❑ Covenant ❑ Retaining Wall
❑ Native Growth Protection Covenant ❑ Rockery>4' High
❑ Tract ❑ Structural on Steep Slope
❑ Other ❑ Other
Part 17 SIGNATURE OF PROFESSIONAL ENGINEER
I, or a civil engineer under my supervision, have visited the site. Actual site conditions as observed were
incorporated into this worksheet a the attached Technical Information Report. To the best of my
knowlcrdg it�ormation p ed here is accurate. _
� � , y �
Si ned/Date ,
2009 Surface Water Design Manual I!9/2009
5
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- ATS AUTOMATION
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�2015 LPD Engineering PLLC 911 WestemAve., DESCRIPTION �AAY 4, 2015 FIGURE ,
, Suite 420, I
, 5ea��,WA98104 DOWNSTREAM
p.206J25.1211
f.206.9735344 I
engineering pllc www.IpdenglnE�tl�.cW11 D RAI NAG E MA P '
. �
engineering p c �'
%
APPENDIX A I!,
Design Documents '
. 1
engineering p c
APPENDIX B
Design Calculations and Supporting Information
�
;
Flow Control Exemption �
input.exc
KCRTS Program. . .File Directory:
C:\KC`SWDM\KC_DATA\
[C] CREATE a new Time Series
ST
0.00 0.00 0.000000 Till Forest
0.00 0.00 0.000000 Till Pasture
0.21 0.00 0.000000 r;l l �rass Existing Site Conditions
0.00 0.00 0.000000 Outwash Forest
0.00 0.00 0.000000 outwash Pasture
0.00 0.00 0.000000 outwash Grass
0.00 0.00 0.000000 wetland
0.18 0.00 0.000000 zmpervious
PREDEV.TSF
T
1.00000
T
[C] CREATE a new Time Series
ST
0.00 0.00 0.000000 Till Forest
0.00 0.00 0.000000 Till Pasture
0.08 0.00 0.000000 Till Grass
0.00 0.00 0.000000 outwash Forest Developed Site Conditions
0.00 0.00 0.000000 outwash Pasture
0.00 0.00 0.000000 Outwash Grass
0.00 0.00 0.000000 wetland
0.31 0.00 0.000000 zmpervious
DEV.TSF
T
1.00000
T
[T] Enter the ,4nalysis TOOLS Module
[P] Compute PEAKS and Flow Frequencies
predev.tsf
PREDEV.pkS
[P] Compute PEAKS and Flow Frequencies
dev.tsf
DEV.pkS
[R] RETURN to Previous Menu
[X] eXit KCRTS Program
Page 1
(Flow Control Exemption: I
Existing Site Conditians
PREDEV.pkS
Flow Frequency Analysis
Time Series File:predev.tsf
Project �ocation:sea-Tac
---Annual Peak Flow Rates--- -----Flow Frequency Analysis-------
Flow Rate Rank Time of Peak - - Peaks - - Rank Return Prob
(CFS) CFS Period
0.063 5 2/09/O1 2:00 0.130 1 100.00 0.990
0.048 8 1/05/02 16:00 0.076 2 25.00 0.960
0.076 2 2/27/03 7:00 0.072 3 10.00 0.900
0.049 7 8/26/04 2:00 0.066 4 5.00 0.800
0.060 6 10/28/04 16:00 0.063 5 3.00 0.667
0.066 4 1/18/06 16:00 0.060 6 2.00 0. 500
0.072 3 10/26/06 0:00 0.049 7 1.30 0.231
0.130 1 1/09/08 6:00 0.048 8 1.10 0.091
computed Peaks 0.112 50.00 0.980
Page 1
Flow Control Exemption: .
Developed Site Conditions
DEV.pkS
Flow Frequency Analysis
Time Series File:dev.tsf
Project Location:Sea-Tac
---Annual Peak Flow Rates--- -----Flow Frequency Analysis-------
Flow rtate Rank Time of Peak - - Peaks - - Rank Return Prob
(CFS) CFS Period
0.083 6 2/09/O1 2:00 . 1 . 0.990
0.070 8 1/05/02 16:00 0.116 2 25.00 0.960
0.100 3 12/08/02 18:00 0.100 3 10.00 0.900
0.079 7 8/26/04 2:00 0.095 4 5.00 0.800
0.095 4 10/28/04 16:00 0.088 5 3.00 0.667
0.088 5 1/18/06 16:00 0.083 6 2.00 0. 500
0.116 2 10/26/06 0:00 0.079 7 1.30 0.231
0.164 1 1/09/08 6:00 0.070 8 1.10 0.091
computed Peaks 0.148 50.00 0.980
Page 1
ATS Office Expansion-432 Shattuck Ave 5 5/4/2015
Conveyance Analysis Spreadsheet
Pipe Run Size Mannings N Plan Qfull Tributary Basins Tributary Impervious Grass 4trib Qtrib 'Yo Full %Full
Slope Area (25yr-15min) (100yr-15min) (25yr) (300yr)
(inches / J ( sJ (acres) (acres) (acresJ (c s c s
12"Outlet to Storm Drain in
12 0.011 0.017 5.50 Entire Site 0.388 0.313 0.075 0.30 0.41 5% 7%
Shattuck Ave
Conveyance - outlet from site .
�Ev.pks
Flow Frequency Analysis
Time Series File:dev.tsf
Project Location:5ea-Tac
---Annual Peak Flow Rates--- -----Flow Frequency Analysis-------
Flow Rate Rank Time of Peak - - Peaks - - Rank rteturn Prob
(CFS) �
0.149 6 8/27/O1 18:00 0.407 1 100.00 0.990
0.104 8 9/17/02 17:45 0.298 2 25.00 0.960
0.298 2 12/08/02 17:15 1 . 0.900
0.120 7 8/23/04 14:30 0.172 4 5.00 0.800
0.163 5 10/28/04 16:00 0.163 5 3.00 0.667
0.172 4 10/27/OS 10:45 0.149 6 2.00 0. 500
0.205 3 10/25/06 22:45 0.120 7 1.30 0.231
0.407 1 1/09/08 6:30 0.104 8 1.10 0.091
Computed Peaks 0.371 50.00 0.980
Page 1
Sediment Sizin Calculations I
9
Per Section D.3.5.1 of the 2009 King County Surface Water Design Manual
Project Name: ATS Office Expansion
432 Shattuck Ave S
Required Sediment Trap SurFace Area(SA):
SA=2*QNsed
Where: Q = 2-year developed flow rate from KCRTS
with 15-minute time steps
Vsed = Settling Velocity(0.00096 ft/sec)
Calculation: multiplier= 2
Q = 0.15 cfs
Vsed = 0.00096 fps
Re uired SA= 312.5 square feet
Equivalent Sediment Trap Volume:
To determine the minimum sediment trap volume, an equivalent sediment
trap was sized based upon the required surface area.
Length of Top Surface Area = 18 feet
Width of Top Surface Area = 18 feet
Surface Area Provided = 324 square feet
Side Slope = 3 (H:1 V)
Total Depth of Sediment Trap = 3.5 feet
Bottom Length of Sediment Trap = -3 feet
Bottom Width of Sediment Trap= -3 feet
Total pond Volume= 582.75 cubic feet
4358.97 gallons
Sediment Volume provided with detention vault:
Vault Interior Dimensions: 24'x6'x8'
Total Volume provided: 1,152 CF (8,617 gallons)
TESC Sizing •
DEV.pks
Flow Frequency Analysis
Time series File:dev.tsf
Project Location:5ea-Tac
---Annual Peak Flow Rates--- -----Flow Frequency Analysis-------
Flow rtate Rank Time of Peak - - Peaks - - rtank Return Prob
(CFS) (CFS) Period
0.150 6 8/27/O1 18:00 0.408 1 100.00 0.990
0.105 8 9/17/02 17:45 0.299 2 25.00 0.960
0.299 2 12/08/02 17:15 0.205 3 10.00 0.900
0.121 7 8/23/04 14:30 0.172 4 5.00 0.800
0.163 5 10/28/04 16:00 0.163 5 3.00 0.667
0.172 4 10/27/05 10:45 0.150 6 2.00 0.500
0.205 3 10/25/06 22:45 0.121 7 1.30 0.231
0.408 1 1/09/08 6:30 0.105 8 1.10 0.091
computed Peaks 0.371 50.00 0.980
Page 1
. �
engineering p c
APPENDIX C
Stormwater Pollution Prevention and Spill Plan (SWPPS) &
Preliminary Construction Stormwater Pollution Prevention Plan
(SWPPP) Narrative
ATS Office Expansion
/ Stormwater Palluaan Prevendon and Spill Plan
Mar 4, 2015
eng�neenng p c
ATS OFFICE EXPANSION
STORMWATER POLLUTION PREVENTION AND SPILL PLAN
MAY 4,20 I 5
The following report is in accordance with the City of Renton Amendments to the 2009
King County Surface Water Design Manual Section 2.3.1.4 for the Stormwater Pollution
Prevention and Spill (SWPPS) Plan.
The following is a summary of the items to be addressed on the TESC Plan of the
contract documents and an indication of their applicability to this project.
PAarA:ACTIVITY SPECIFIC INFORMATION REQUIRED
Storage and Handlin o�quids:
No petroleum products, fuel, solvents, detergents,paint, pesticides, and concrete
admixtures are expected to be stored on site. There may be small quantities of paint or
form oil stored on site during construction. They are expected to be stored in a protected
axea such as inside a construction trailer, or inside a fenced enclosure in the contractor's
work area. Exact quantities and storage locations are not known at this time.
Stora�e and Stockpilin�of Construction Materials and Wastes:
Construction materials and waste may be stockpiled temporarily but shall be hauled off
regularly. Refer to Note 2 below for additional information.
Fuelin�:
No stationary fuel tank will be allowed on site during construction. Fueling will be
allowed on site during daylight hours only by a mobile fuel truck, and only in paved
areas. Refer to notes 3, 4, and 5 below for additional information.
Maintenance, Repairs, and Storage of Vehicles and Equipment:
Equipment that requires significant repair will be removed from the site to repair. Minor
repairs or maintenance may be allowed on site only in an approved area. Refer to note 6
below for additional information.
Concrete Saw Cuttin ,g Slurry, and Washwater Disposal:
The project anticipates limited concrete saw cutting. All concrete saw cutting slurry shall
be controlled such that it does not contaminate onsite stormwater. Concrete truck
washout will not be allowed on site. Refer to note 7 below.
Handlin�of�H Elevated Water:
Because construction stormwater runoff will be routed to a sediment settling tank,
monitoring for elevated pH can be conducted as necessary by sampling from the tank.
Page I
ATS Office Expansion
� ' Stormwater Pollutian Prevention and Spill Plan
. May 4, 2015
engineering pl c
Application of Chemicals includin�Pesticides and Fertilizers:
No chemicals are expected to be used in this project.
PA�rr B:SWPPS SiTE Puo►N
Refer to Sheet C1.1 of the drawings. Also, per Section 2.3.1.4.B of the Renton
i Amendments to the KCSWDM:
1. Liquids including petroleum products, fuel, solvents, detergents, pesticides, and
I� concrete admixtures are not anticipated to be stored on site. If products such as
fuel are required, these items will be brought in small quantities, used, and
removed from the site. Items such as paint or form oils, if needed, will be
�'I delivered to the site in small quantities and stored inside a construction trailer
prior to use. A note is included on the plan as follows: "No hazardous liquid
products including but not limited to petroleum products, fuel, solvents,
detergents,paint, pesticides, concrete admixtures and form oils shall be stored on-
site without prior approval. If requested, the Contractor shall provide for spill
containment in accordance with City of Renton requirements. Contractor shall
provide a list of the types and sizes of liquids that will be storedThandled on site.
Contractor will also show the proposed location for storage on a project site plan
and will provide a proposed method of secondary containment. The Owner's
Representative and the County shall review and approve the plan prior to
storage."
2. The proposed improvements will require demolition of a small existing building.
Any demolished material will be removed immediately upon demolition. 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. A note is
included in the SWPPS notes as follows: "Construction waste shall be promptly
removed from the site and shall not be stockpiled."
3. No stationary tanks will be used for this project. A note is included in the SWPPS
notes as follows: `Tio stationary fuel tank shall be allowed."
4. If required, a mobile fuel truck will be brought to the site to fuel the excavation
equipment. A note is included in the SWPPS notes as follows: "Fueling of
construction equipment shall be by a mobile fuel truck and shall be allowed only
in paved areas. Contractor shall provide a plan for fueling area spill containment
to the Owner's Representative and City of Renton with a proposed method of
secondary containment. The Owner's Representative and City of Renton shall
review and approve the plan prior to fueling. All spills, containment, and clean up
shall be the contractor's responsibility and at their own expense."
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Mar 4, 2015 -
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5. Equipment will only be fueled during daylight hours. A note is included in the
SWPPS notes as follows: "Fueling of construction equipment shall only be
allowed during daylight hours."
6. Equipment that requires significant repair will be removed from the site to repair.
Minor repairs or maintenance may be allowed on site only in an approved area. A
note is included in the SWPPS notes as follows: "The Contractor shall remove
from the site all equipment that requires significant repair. Minor repairs or
maintenance may be allowed on site in an approved area. The Contractor shall
submit a plan for the proposed locarion of vehicle maintenance and repair and
shall indicate the proposed method of containment for possible leaking vehicle
fluids. The contractor shall also provide a plan to the Owner's Representative and
City of Renton for the collection, storage, and disposal of the vehicle fluids. The
Owner's Representative and City of Renton shall review and approve plan prior to ,
any on-site maintenance."
7. Truck washout will not be allowed on site. A note is included in the SWPPS notes
as follows: "Truck washout shall not be allowed on site. The Contractor shall
provide truck washout off-site at an approved and legal location."
8. No chemicals are anticipated to be required for this project.
9. Selected Contractor shall provide location for spill response materials, and
identify disposal methods for contaminated water and soil. A note is included in
the SWPPS notes as follows: "Contractor shall provide to the Owner's
Representative and City of Renton the location of spill response materials.
Contractor will also identify disposal methods for contaminated water and soil
after a spill."
PART C:POLLUTION PREVENTION REPORT
The project will be bid thus no excavation contractor is currently under contract. The
possible sources of pollution are limited and are addressed above. In addition to the
above information provided on the contract documents, the following notes are included
to specifically address pollution prevention:
• "The Contractor shall provide a report to the Owner's Representative and City of
Renton identifying the personnel responsible for pollution prevention, including
contact information, and clearly listing the responsibilities of these personnel."
• "The Contractor shall also provide a description of the procedures to be used in
monitoring the pollution prevention BMPs and responding to a BMP that needs
attention, including record keeping."
PArrr D:SPILL PREVENTION AND CLEANUP REPORT
Due to the public bid process, an earthwork subcontractor is not yet under contract for
this project. The personnel responsible for spill prevention and cleanup will be identified
at the pre-construction meeting for the project. Spill prevention is addressed with notes
on the contract documents as stated above. The sources of potential spills are limited and
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May 4, 2015
eng�neering pllc
have been addressed on the plan with notes. In addition to the above information
provided on the contract documents,the following notes have been added in the SWPPS
notes to specifically address spill prevention:
• "The Contractor shall provide a report to the Owner's Representative and City of
Renton identifying the personnel responsible for spill prevention, including
contact information, and clearly listing the responsibilities of these personnel."
• "The Contractor shall provide a description of the procedures to be used in
monitoring the spill prevention BMPs and responding to a spill incident, including
record keeping."
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Preliminary �onstrucdon SWPPP NarraOve
May 4, 2015
engineering p c
ATS OFFICE EXPANSION
PRELIMINARY CONSTRUCTION SWPPP NARRATIVE
MAY 4,20 I 5
The following Preliminary Construction Storm Water Pollution Prevention Plan (SWPPP)
Narrative for the ATS Automation project at 432 Shattuck Avenue S in Renton supplements the
Temporary Erosion and Sediment Control drawings. This narrative and the drawings address the
requirements of Section 3.3 of Volume II of the 2012 Washington State Department of Ecology
(DOE) Stormwater Management Manual for Western Washington.
I . CONSTRUCTION STORMWATER POLLUTION PREVENTION ELEMENTS
1) Mark Clearing Limits: Clearing limits will be defined by erosion control components,
and/or construction fencing, as shown on the TESC and Site Demolition plan. The actual
limits of clearing will most likely be smaller than the limit of work area, but this
identifies the maximum extent of the clearing limits. Areas impacted and not anticipated
to be covered with fmal measures shall be stabilized using approved ESC methods.
2) Establish Construction Access: A temporary construction access(BMP C 105)will be
installed prior to construction. The quarry spall stabilized construction entrance will
extend off Shariuck Avenue S in the north portion of the project area. The Contractor
shall provide wheel wash if necessary.
3) Control Flow Rates: Stormwater flow control during construction is anticipated to be
mitigated by routing runoff to the proposed wetvault,which is to be utilized as a
temporary sediment storage facility. Refer to the Sediment Sizing calculations and the
King County Runoff Time Series(KCRTS)output included within Appendix B of the
project's Stormwater Technical Information Report.
4) Install Sediment Controls: DOE approved BMPs for sediment controls are shown on
the TESC plan. Sediment will be controlled using triangular silt dike(BMP C208), storm
drain inlet protection(BMP C220),tree protection fencing, and the proposed sediment
settling facility.
5) Stabilize Soils: It is possible that some of the earthwork and grading may occur in wet
weather conditions. The site must be stabilized and no soils will be allowed to remain
unstabilized for more than two days between October 151 and Apri130�'. From May 1
through September 30, install cover measures to protect disturbed areas that will remain
unworked for seven days or more. By October 8, seed all areas that will remain unworked
from October 1 through Apri130.Mulch all seeded areas.
Exposed slopes will be protected by DOE-approved coverage methods. BMPs including,
but not limited to: C101,Preserving Natural Vegetation; C121,Mulching; C123,Plastic
Covering; C 130, Surface Roughening; C 140,Dust Control; and T5.13 Post Construction
Soil Amendment will be used to stabilize on-site soils during construction.
6) Protect Slopes: DOE-approved BMPs for slope protection will be utilized during
construction.Concentrated discharges shall not be allowed to flow over the top of steep
slopes. BMPs including,but not limited to C 101,Preserving Natural Vegetation; C 121,
Mulching; C 123, Plastic Covering; C 130, Surface Roughening; C 140, Dust Control;
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1 Preliminary Construction SWPPP Narraove
� May 4, 2015
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C200, Interceptor Dike and Swale; C207, Check Dams; and C233, Silt Fence are to be
utilized to protect slopes during construction.
7) Protect Drain Inlets: Drainage structures in areas where no work occurs will remain and
will be protected; discharge points to the public storm drain main line will also be
protected. To prevent discharge of turbid water downstream, all existing catch basins
located within the disturbance area and outside of the disturbance area within
approacimately 300 feet downstream of the site will be protected with storm drain inlet
protection(BMP C220). Proposed inlets will also be protected with catch basin inserts,
and where feasible,their outlets will be temporarily plugged until the site is stabilized.
The Contractor shall remove inlet protection at the end of the project without releasing
captured sediment into the storm system.
8) Stabilize Channels and Outlets: T'his project is not expected to involve any channels or
outlets. If necessary,DOE-approved BMPs for channel stabilization will be utilized
during construction, including,but not limited to: C200, Interceptor Dike and Swale; and
C207, Check Dams.
9) Control Pollutants: Temporary protection of the disturbed soils provides the first level
of protection for pollution control, and perimeter measures downstream will mitigate the
remaining pollutants. The temporary protection of disturbed soils may be mitigated with
a temporary sump and pump facility to provide the second level of interception of
pollutants. This collection system filters sediments prior to the pump system. The pump
system will then route stormwater via force mains into the proposed wetvault to be
utilized as a sediment facility.The sediment settling tank must provide at least 4,400
gallons of storage,and will be located north of the proposed wazehouse addition. The
wetvault does have adequate capacity to provide the needed storage. Construction debris
will be removed from the site.Contractor will be responsible for managing their
construction equipment per DOE-approved BMPs. T'he stabilized construction entrance is
assumed to be sufficient for the construction period. If something more substantial is
required,the Contractor is to coordinate with the Owner's Representative and the City of
Renton inspector. If a truck wheel wash is required, truck wheel wash water and concrete
truck washout water shall be collected and discharged to the public sanitary sewer(SS)
system. To apply for SS release,contact the local sewer purveyor for authorization.
For information regarding spill control,refer to the Stormwater Pollution Prevention and
Spill Plan(SWPPS)plan/namative, attached.
10) Control De-Watering: The majority of the earthwork on the project will be constructed
during the dry season,therefore it is not anticipated that groundwater will be encountered
in the excavations for this project. In the event that perched groundwater is encountered
during any wet season construction,the Contractor shall route it to the sediment settling
facility by pumping it out of the excavation.
11) Maintain BMPs: DOE-approved standard BMP maintenance will be required in
accordance with the standard King County Temporary Erosion and Sedimentation
Control Plan and Notes.
12} Manage the Project: All phases of construction will be managed by the Contractor. The
site must be stabilized and no soils will be allowed to remain exposed and unworked for
more than two days between October 1 S`and Apri130`�and for more than seven days
between May 1 S`and September 30"`. The Contractor will provide maintenance and
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Preliminary Lonsvudion SWPPP Narradre
May 4, 2015
engineermg p c
monitoring of TESC BMPs. Work of all contractors will be coordinated to minimize the
duration of disturbance on the site.The best management practices shown on the TESC
plan are minimum requirements. Failure to maintain SWPPP measures in accordance
with adopted standards may result in the work being performed at the County's direction
and the costs assessed as a lien against the property where such facilities are located.
13) Protect Low Impact Development BMPs: The Contractor must control erosion and
avoid introducing sediment from surrounding land uses onto the permeable pavement on
the patios southwest and southeast of the building addition. Pavements experiencing
sediment issues or no longer passing an initial infiltration tests must be cleaned using
procedures from the local stormwater manual or the manufacturer's procedures.
2. PROJECT DESCRIPTION
Proposed improvements include a n���� ���areh�us�.��f�t i�� buil�iin�„ cunstru�t«i ut�f the north �i�i,
of the existing ATS Automation building. The existing commercial building directly north of t]
existing ATS building will be demolished. A paved parking lot will be established along the n� '
and east sides of the building expansion, including a heavy duty asphalt driving lane to
accommodate truck traffic. Access im�r�vements ���il] be made t� enstire A1�A c�mpliance. T'
area of the site parcel(#78413001"
The project proposes 13,616 squar�
located within a Peak Rate Flow Control Standard Area as designated by the City oY Renton.
There will be no flow contml facilities for the projcct: permcable pavers «�ill bc installed as a
flow control Best Management Practice (BM P i.
Enhanced Basic Water Quality Treatment is reyuir��i au�i ���ill i�� a��ir��;��i �� �ili :� i»��-t�a�iiit�
treatment train,consisting of a wetvault followed by a StormFilter structure with leaf compost
(CSF)media. See the project's technical information report for more on the stormwater
improvements.
3. EXISTING SITE CONDITIONS
The eacisting project area consists of a small commercial building, with limited paved parking and a
gravel parking area. The existing building is separated from the main ATS building by a drive lane
and pazking. Stormwater runoff generally sheet flows off the site and enters the existing storm
system within Shattuck Avenue.The site is located within the Black River Drainage Basin.
The existing topography within the project area is relatively flat, with slopes of around 0-2%
throughout the project disturbance limits.
4. ADJACENTAREAS
The project area is bounded by Shattuck Ave S to the west, a public alley to the east, a single-
family residence to the north, and the existing ATS building to the south.
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ATS Office Expansion �',
1 Preliminary Construction SWPPP Narrauve ��
. Mar 4, 2015 '
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5. CRITICAL AREAS
The site is located within the Cedar Valley Sole Source Aquifer. Based on City of Renton GIS
and mapping, there do not appear to be any other environmentally sensitive areas within or in
close proximiry to the site.
6. Soi�s
According to the USDA Natural Resources Conservation Service,the site soils are mapped as
Urban Land. The SCS Soil Type is recognized as Renton(RE),classified under the Hydrologic
Soil Group D and is defined as Till in the project's stormwater calculations(Table 3.2.2.B, 2009
KCSWDM). A Geotechnical Engineering Report has been prepared by PanGeo, Inc. dated
December 23, 2014; a copy has of been provided in Appendix E of the technical information
report.Based upon the exploration pits,the underlying soils were generally described as silty
clays. Groundwater was encountered at a depth of about 8 feet.
7. POTENTIAL EROSION PROBLEM AREAS
Per the proposed contract documents,the contractor is to provide protection for soils to limit the
exposure to erosion.The limitation of disturbance, adequate cover practices,and runoff control
are the most effective methods for reduction of turbidity in stormwater runoff. Any runoff that
does occur will be directed to a temporary sump and then pumped to the sediment settling
facility. Areas that have not been permanently stabilized will be addressed using DOE-approved
BMPs,per the construction documents.
8. CONSTRUCTION PHASING
At this time it is not expected that the project will be formally phased.The contractor is
responsible for coordinating work of all subcontractors to keep the duration of site disturbance
limited to the maximum extent possible.
9. CONSTRUCTION SGHEDULE
Construction of project is expected to begin in July 2015 and be completed by March 2016.
I O. FINANCIAL/�WNERSHIP RESPONSIBILITIES
The property is privately owned. Financial guarantees and liability for the proposed project will
be completed by owner prior to permit issuance.
I I . ENGINEERING CALCULATIONS
A copy of any calculations performed during design of the project and relevant storm drainage
modeling discussions is included in the project's Stormwater Technical Information Report.
I 2. CERTIFIED EROSION CONTROL SPECIALIST
The contractor will name their Certified Erosion Control Specialist and provide contact
information at the pre-construction meeting.
Page 4 �!,
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engineering p c
APPENDIX D
Operation and Maintenance Guidelines
, APPENDIX A MAINTENANCE REQUIREMENTS FOR FLOW CONTROL,CONVEYANCE,AND WQ FACILITIES
• NO. 5-CATCH BASINS AND MANHOLES
Maintenance Defect or Problem Condition When Maintenance is Needed Results Expected When
Component Maintenance is Performed
Structure Sediment Sediment exceeds 60°�of the depth from the Sump of catch basin contains no
bottom of the catch basin to the invert of the sediment.
lowest pipe into or out of the catch basin or is
within 6 inches of the invert of the lowest pipe
into or out of the catch basin.
Trash and debris Trash or debris of more than Yz cubic foot which No Trash or debris blocking or
is located immediatety in front of the catch basin poten6ally blocking entrance to
opening or is blocking capacity of the catch basin catch basin.
by more than 10°�.
Trash or debris in the catch basin that exceeds No trash or debris in the catch basin.
'/3 the depth irom the bottom of basin to invert the
lowest pipe into or out of the basin.
Dead animals or vegetation that could generate No dead animals or vegetation
odors that could cause complaints or dangerous present within catch basin.
gases(e.g.,methane).
Deposits of garbage exceeding 1 cubic foot in No condition present which would
volume. attract or support the breeding of
insects or rodents.
Damage to irame Comer of frame extends more than'/.inch past Frame is even with curb.
and/or top slab curb face into the street(If applicable).
Top slab has holes larger than 2 square inches or Top slab is free of holes and cracks.
cracks wider than Y.inch.
Frame not sitting flush on top slab,i.e., Frame is sitting flush on top slab.
separation of more than'/,inch of the frame from
the top slab.
Cracks in walls or Cracks wider than'/:inch and longer than 3 feet, Catch basin is sealed and
bottom any evidence of soil particles entering catch structurally sound.
basin through cracks,or maintenance person
judges that catch basin is unsound.
Cracks wider than'/z inch and longer than 1 foot No cracks more than'/4 inch wide at
at the joint of any inleUoutlet pipe or any evidence the joint of inleUoutlet pipe.
of soil partides entering catch basin through
cracks.
SettlemenU Catch basin has settled more than 1 inch or has Basin replaced or repaired to design
misalignment rotated more than 2 inches out of alignment. standards.
Damaged pipe joints Cracks wider than Yrinch at the joint of the No cxacks more than'h-inch wide at
inleUoutlet pipes or any evidence of soil entering the joint of inleUouUet pipes.
the catch basin at the joint of the inleUouUet
pipes.
Contaminants and Any evidence of contaminants or pollution such Materials removed and disposed of
pollution as oil,gasoline,concrete slurries or paint. according to applicable regulations_
Source control BMPs implemented if
appropriate. No contaminants
present other than a surface oil film.
InIeVOutlet Pipe Sediment Sediment filling 20%or more of the pipe. InleUoutlet pipes clear of sediment.
accumulation
Trash and debris Trash and debris accumulated in inleUoutlet No trash or debris in pipes.
pipes(includes floatables and non-floatables).
Damaged Cracks wider than'/rinch at the joint of the No cracks more than'/.-inch wide at
inleUoutlet pipes or any evidence of soil entering the joint of the inleUoutlet pipe.
at the joints of the inleVoutlet pipes.
2009 Surface W'ater Design Manual—Appendix A 1/9/2009
A-9
APPENDIX A MAINTENANCE REQUIREMENTS FLOV��CONTROL,CONVEYANCG,AND VVQ FACILITIES -
NO. 5-CATCH BASINS AND MANHOLES �
Maintenance Defect or Problem Condition When Maintenance is Needed Results Expected When
Component Maintenance is Performed
Metal Grates Unsafe grate opening Grate with opening wider than'/e inch. Grate opening meets design
(Catch Basins) standards.
Trash and debris Trash and debris that is blocking more than 20°� Grate free of trash and debris.
of grate surface. footnote to guidelines for disposal
Damaged or missing Grate missing or broken member(s)of the grate. Grate is in place and meets design
My open structure requires urgent standards.
maintenance.
Manhole CoverlLid Cover/lid not in place Cover/lid is missing or only partially in place. CoverAid protects opening to
My open structure requires urgent structure.
maintenance.
Locking mechanism Mechanism cannot be opened by one Mechanism opens with proper tools.
Not Working maintenance person with proper tools.Bolts
cannot be seated. Self-I�king coverAid dces not
work.
Cover/lid difficuk to One maintenance person cannot remove Cover/lid can be removed and
Remove cover/lid after applying 80 Ibs.of lift. reinstalled by one maintenance
person.
1/9/2009 2009 Surface Water Design Manual—Appendix A
A-10
• APPENDi\ A MAIT�TENANCF. RGQUIREMt;NTS FOR FLOti'V COI�"IROL,CONVEI'ANCE,AND VGQ PACILIT[ES
• NO. 6-CONVEYANCE PIPES AND DITCHES
Maintenance Defect or Problem Conditions When Maintenance is Needed Results Expected When
Component Maintenance is Performed
Pipes Sediment&debris Accumutated sediment or debris that exceeds Water flows freely through pipes.
accumulation 20%of the diameter of the pipe.
Vegetationlroots VegetationJroots that reduce free movement of Water flows freely through pipes. I
water through pipes.
Contaminants and Any evidence of contaminants or pollution such Materials removed and disposed of I
pollution as oil,gasoline,concrete slurries or paint. according to applicable regulations_ �I
Source control BMPs implemented'rf �
appropriate. No contaminants '
present other than a surface oil film.
Damage to protective Protective coating is damaged;rust or corrosion Pipe repaired or replaced.
coating or corrosion is weakening the structural integrity of any part of
pipe.
Damaged Any dent that decreases the cross section area of Pipe repaired or replaced.
pipe by more than 20%or is deteRnined to have
weakened structural integrity of the pipe.
Ditches Trash and debris Trash and debris exceeds 1 cubic foot per 1,000 Trash and debris cleared from
square feet of ditch and slopes. ditches.
Sediment Accumulated sediment that exceeds 20%of the Ditch cleaned/flushed of all sediment
accumulation design depth. and debris so that it matches design.
Noxious weeds Any noxious or nuisance vegetation which may Noxious and nuisance vegetation
constitute a hazard to County personnel or the removed according to applicable
public. regulations. No danger of noxious
vegetation where County personnel
or the public might normally be.
ContaminaMs and Any evidence of contaminants or pollution such Materials removed and disposed of
pollu6on as oil,gasoline,concxete slurries or paint. according to applicable regulations.
Source control BMPs implemented if '
appropnate. No contaminants
present other than a surface oil film.
Vegetation Vegetation that reduces free movement of water Water flows freely through ditches.
through ditches.
Erosion damage to Any erosion observed on a ditch slope. Slopes are not eroding.
slopes
Rock lining out of One layer or less of rock exists above native soil Replace rocks to design standards.
place or missing(If area 5 square feet or more,any exposed native
Applicable) soil.
2009 SurFace W'ater Design Manual—Appendix A 1/9/2009
A-t 1
APPENDIX A MAINTENANCE REQUIREMENTS FOR FLOW CONTROL,CONVEYANCE,AND WQ FACILITIES
N0. 17-WETVAULT
Malntenance Defect or Problem Conditlon When Malntenance is Needed Results Expected When
Component Maintenance is Pertormed
Site Trash and debris Trash and debris accumulated on facility site. Trash and debris removed from
faGlity site.
Treatment Area Trash and debris Any trash and debris accumulated in vault No trash or debris in vauit.
(includes floatables and non-floatables).
Sediment Sediment accumulation in vault bottom exceeds No sediment in vault.
accumulation the depth of the sediment zone plus 6 inches.
Contaminants and Arry evidence of contamfnants or pollutlon such Maierials removed and disposed of
polution as oil,gasoline,concrete slurzies or paint. according to applicable regulations.
Source control BMPs implemented if
appropriate. No contaminants
presenl other tha�a surface oil film.
Vault Structure Damage to wall, Cracks wider than%:-inch,any evidence of soil Vault is sealed and structurally
frame,bottom,and/or enlering the structure through cracks,vault does sound.
top slab not retain water or qualified inspectlon personnel
determines that the vault is not structurally
sound.
Baffles damaged Baffles conoding,cracking,warping andlor Repalr or replace baffles or walls to
showing signs of failure or baffle cannot be specl8cations,
removed.
Venlilation Ventilation area blocked or plugged. No reduction of ventilaUon area
exfsts.
InIeUOutlet Pipe Sediment Sediment filling 2096 or more of the pipe. InleUoullet pipes dear of sediment.
accumulation
Trash and debris Trash and debris accumulated in fnleUoutlel No trash or debris in pipes.
pipes{includes floatables and non-floatables).
Damaged Cracks wider than�-inch ai the Joint of the No cracks more than Y.-inch wide at
InleUoutlet pipes or any evidence of soil entering the joint of the inleUoutlet pipe.
at the joints of the inleUoutiet pipes.
Gravity Drain Inoperable valve Valve will not open and close. Valve opens and closes normally.
Valve won't seal Valve does not seal cor�►letely. Valve completely seals closed.
Access Manhole Access coveNlid Access coverllid cannoi be easfly opened by one Access coverAid can be opened by
damaged or difficult to person. CorcosioNdeformation of covedlid. one person.
open
Locking mechanism Mechanism cannot be opened by one Mechanism opens with proper tools.
not working malntenance person with proper tools. 8olts
cannot be seated. Self-locking coveNlid does not
work.
CoverRid difficult to One maintenance person cannot remove Co�erAid can be removerJ and
remove coverllid after applying 80 Ibs of lift. reinstalled by one maintenance
person.
Access doorsJpiate Large access doors not flat andlor access Doors close flat and covers access
has gaps,doesn't openirtg not completely covered. opening completely.
cover completefy
Lifling Rfngs missing, Lifting rings not capable of lifting wefght of door Lifting rings sufficient to lift or
rusted or plate. remove door or plate.
Ladder rungs unsafe Missing rungs,misalignment,rust,or cracks. Ladder meets design standards.
Allows maintenance person safe
access.
2009 Surface Water Design Manual—Appendix A 1/9/2009
A-23
, APPENDIX A MAINTENANCE REQUIREMENTS FLOW CONTROL,CONVEYANCE,AND WQ FACILITIES
• NO. 21 -STORMFILTER(CARTRIDGE TYPE)
Maintenance Defect or Problem Conditlon When Malntenance is Needed Results Expected When
Component Maintenance is Performed
Site Trash and debris Any trash or debris which impairs the function of Trash and debris removed from
the facility. facility.
Contaminants and Any evidence of contaminants or pollutlon such Materials removed and disposed of
pollution as oils,gasoline,concrete slurries or paint. according to applicable regulations.
Source control BMPs implemented if
. appropriate. No contaminants
� present other than a surface oil film.
Life cycle System has not been inspected for three years. Facility is re-inspected and any
needed maintenance pertormed.
Vault Treatment Sediment on vauli Greater than 2 inches of sediment. Vault Is free of sertlment.
Area floor . I
Sediment on lop of Greater than i4 inch of sediment. Vault is free of sediment. �
cartridges ,
Multiple scum lines Thick or multiple scum lines above top of Cause of plugging corrected,
above lop of cartridges. Probably due to plugged canisters or canlsters replaced if necessary.
cartridges underdrain manifold,
Vault Structure Damage to wall, Cracks wider than'/rinch and any evidence of Vault replaced or repaired to design
Frame,Bottom,arxi/or soll particles entering the structure through the specifications.
Top Slab cracks,or quali8ed inspection personnel
determines the vault is not structurally sound.
Baffles damaged Baffles corroding,cracking warping,andlor Repalr or repiace baffles to
showing signs of failure as determined by specification. '�
maintenancefinspection person.
Filter Media Standing water in 9 inches or greater of siatic water in the vault for No standing water In vault 24 hours I
vault more than 24 hours following a rain event and/or after a rafn event. '
overftow occurs frequently. Probably due to
plugged filter media,underdrain or outlet pipe. I
Short clrculUng Flows do not properly enter fifter car#ridges. Flows go through filter media. I
Underdrains and SedimenUdebris UndeMrains or clean-outs partially piugged or Underdrains and clean-outs free of I,
Clean-Outs filled with sediment and/or debris. sediment and debds. '
InIeUOutlet Pfpe Sediment Sediment filling 20%or more of the pipe. InleUoutlet pipes clear of sediment.
accumulation
Trash and debris Trash and debris accumulated in inleUoutlet No trash or debris in pipes.
pipes(includes floatables and non-floatables).
Damaged Cracks wider than%rinch at the joint of lhe No cracks more than'/.-fnch wide at
inleUoullet pipes or arry evidence of soil ente�ing the joint of the InleUoutlet pipe.
at the joinfs of the inlet/outlet pipes.
Access Manhofe Cover/lid not in place Coverllid is missing or only partially in place. Manhole access covered.
Any open manhole requires immedlate
maintenance.
Locking mechanism Mechanism cannot be opened by one Mechanism opens with proper tools.
not worlcing maintenance person with proper tools.Bolts
cannot be seated. Self-locking coverllld does not
work.
Cover/lid difficult to One maintenance person cannot remove CoverAid can be removed and
remove cover/lid after applying 80 Ibs of lift. reinstalled by one maintenance
person.
Ladder rungs unsafe Missing rungs,misalignment,rust,or cracks. Ladder meets design standards.
Allows maintenance person safe
access.
Large access Damaged or difficult Large access doors or plates cannot be Replace or repair access door so it
doorslplate to open openedJremoved using normal equipment. can opened as designed.
1/9/2009 2009 Surface WaterDesign Manual—Appendix A
A-30
APPENDIX A MAWTENANCE REQUIREMENTS FOR FLOW CONTROL,COl`'VEYANCE,AND WQ FACILITIES •
NO. 21 -STORMFILTER (CARTRIDGE TYPE)
Maintenance Defect or Problem Condition When Malntenance Is Needed Results Expected When
Component Malntenance Is Performed
Gaps,doesn't oover Large access doors not flat and/or access Doors Gose flat and cover access
completely opening not completely covered. opening completely.
Lifting Rings missing, Lifling rings not capable of Iffting wefght of door Liiting rings sufficient to lifl or
rusted or piaie. remove door or plate.
2009 Surface Water Design Manual—Appendix A 1/9/2009
A-31
. 1
engineering p c
APPENDIX E
Geotechnical Report
�
i