HomeMy WebLinkAboutRS_TIR_210608_V3
SNOHOMISH COUNTY
125 E Main Street, Suite 104
Monroe, Washington 98272
tel: 360. 794.7811 | fax: 360.805.9732
ISLAND COUNTY
840 SE 8th Avenue, Suite 102
Oak Harbor, Washington 98277
tel: 360. 675.5973 | fax: 360.675.7255
www.HarmsenLLC.com
SKAGIT COUNTY
603 South First Street
Mount Vernon, Washington 98273
tel: 360. 336.9199 | fax: 360.982.2637
TECHNICAL INFORMATION REPORT
FOR THE
4TH DIMENSION MIXED USE BUILDING
RENTON, WASHINGTON
JUNE 3, 2021
6/3/21
RECEIVED
06/09/2021 striplett
BUILDING DIVISION
B20003319_v3
tir reviewed under civil
construction permit
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I. PROJECT OVERVIEW
PROJECT DESCRIPTION
This technical information report and has been prepared for the 4th Dimension Mixed Use
Building project located at the City of Renton. The developer is proposing to construct a 12,370
sf mixed use building on the 0.55 acre site. After dedication of right‐of‐way the site contains
0.44 acres. The site currently contains a single family home. The property is surrounded by
multi family housing to the north and west, across Bremerton Avenue NE and by commercial
uses to the east and south, across NE 4th Street.
PREDEVELOPED CONDITIONS
The site located at the northeast corner of the intersection of NE 4th Street and Bremerton
Avenue NE. The property currently contains a 1,053 sf single family residence, 665 sf walkways
and concrete on the southern end of the site. The remainder of the southern portion of the site
is lawn, 0.16 ac, and the northern 0.24 ac is trees and brush. There is a 24” storm pipe that
crosses through the center of the site. It is proposed as part of this project to remove that pipe
and provide for an open flow path under the building.
A review of King County iMAP and City of Renton mapping show the site is does not contain any
critical areas or lay within a hazard area, see mapping in Appendix C.
DEVELOPED CONDITIONS
4th Dimension Mixed Use project has proposed to construct a 12,370 sf mixed use building, and
underground parking access drive on the site. The building will include 3 stories of residential
units with a portion of the first floor being commercial and parking. An additional level of
parking lays below that. A stormwater detention vault will be constructed below the lowest
parking level and discharge to the storm system that existing on the site.
SITE AREA: 0.44 acres
PROJECT SITE AREA: 0.44 acres
SIZE OF IMPROVEMENTS
Roof Area: 0.28 ac
Walks: 0.02
Asphalt: 0.07 ac
Landscaping: 0.07 ac
DISPOSITION OF RUNOFF BEFORE/AFTER DEVELOPMENT
Runoff currently leaves the site in the 24” storm system that flows through the site. After
development detained and treated runoff will flow to the 24” storm system that flows through
the site.
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DIFFICULT SITE PARAMETERS
The project geoptechnical engineer observed 2.5‐9 feet of fill soils on the site and groundwater
at a depths of 5‐7 feet in two test pits.
NATURAL DRAINAGE SYSTEM
The topography of the site shows that most of the rainfall that falls on the site flows to a catch
basin located centrally along the western edge of the site.
ADJACENT PROPERTY DRAINAGE
The site and surrounding properties are developed and do not contribute significant surface
runoff to the site. There is an existing 24” storm main that crosses through the site. It will be
relocated as part of the site work. A discussion of the upstream basin is included in Section III of
this report.
BYPASS FLOWS
There is no portion of the proposed improvements that can not be collected and conveyed to
the detention facility.
DRAINAGE BASIN ANALYSIS
The entire site drains to the north and is within one drainage basin. The 0.76 acres basin used
for calculations consists of the street frontages and the 0.44 acre property.
SOIL DESCRIPTION
GEO Group Northwest explored the soil and groundwater conditions at the subject parcel by
excavating five test pits by mini‐excavator at the site. The test pits were excavated to depths of
up to 9‐feet 8‐inches below ground surface. Soils observed at the test pits generally consist of
variable density silty soils and fills which include brick, wood, organic material, concrete and
asphalt debris overlying apparent dense and competent till and gravelly SAND and sandy
GRAVEL. The depth of fills ranged from 2.5‐feet at the test pit TP‐5 to around 9‐feet at the test
pit TP‐3. Groundwater seepage was not encountered at the test pits TP‐1 through TP‐3.
Significant groundwater seepage was encountered at a depth of 7‐feet bgs at the test pit TP‐4
and 5‐feet bgs at the test pit TP‐5. Based on the fill soils revealed in the geotechnical report, Till
soil parameters have been used in WWHM2012. See GEO Group Northwest report in Section IV,
Special Reports and Studies on page 18, for additional information.
The observed underlying soils appear to match the USDA SCS soil description for Alderwood
gravelly sandy loam (AgC) at the uplands and Everett very gravelly sandy loam (EvB) at the
depression as shown the SCS Soil Map, see Appendix A.
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II. PRELIMINARY CONDITIONS SUMMARY
CONDITIONS OF APPROVAL
Per the Hearing Examiners Decision Condition of Approval #11, “requires that permeable
pavement be used on the sidewalks, where feasible, consistent with the 2017 RSWDM.” See
Section IV, Part B of this report for the feasibility analysis for permeable pavement.
There are no other project specific conditions of approval for the project other than those from
the 2017 RSWDM as adopted by the City of Renton. The site is subject to Full Drainage Review,
including all 9 Core Requirements and all 6 Special Requirements.
SURFACE WATER MANAGEMENT DESIGN MANUAL CORE REQUIREMENTS:
1. Discharge at Natural Location: Runoff currently leaves the site in the 24” storm system that
flows through the site. After development, that pipe will be removed and a new extension
made to the storm system in Bremerton using 30” pipe. An open channel will be extended
under the building. Site runoff, after it is detained and treated, will flow to a new 30” pipe
to replace the existing 24” storm system.
2. Off‐site Analysis: This is covered in Section III of this report.
3. Flow Control: The site will use a detention vault to meet the Flow Control Duration –
Forested Condition Area requirement. See Section IV of this report.
4. Conveyance System: A backwater analysis has been prepared for the project see Section V.
5. Erosion and Sedimentation Control: The project will construct a series of sedimentation
controls to address the specific site conditions. See Section IX of this report.
6. Maintenance and Operations: The proposed onsite storm system will be owned, operated
and maintained by the owner. A Maintenance and Operation Manual has been included in
Section X.
7. Financial Guarantees and Liability: The owner and contractor will obtain all necessary
permits prior to beginning of construction. The owner will be responsible for any bonds.
8. Water Quality: The site is located within a Basic Water Quality Treatment Area. Though
being a commercial project it is required to meet the Enhanced Basic Water Quality
standard. The BioPod Treatment System has been chosen to meet the runoff treatment
requirements for the site runoff. See Section IV of this report for the design of the
treatment systems.
9. Onsite BMPs: In addition to the required detention facility, the RSWDM also requires the
implementation of Flow Control BMPs to a portion of the impervious surfaces on the site.
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The intent of this requirement is to lessen the impact of the runoff from the proposed
impervious surfaces.
SPECIAL REQUIRMENTS
1. Other Adopted Area‐Specific Requirements:
a. Critical Drainage Areas: The site is not within a CDA.
b. Master Drainage Plans: The site is not within a MDP.
c. Basin Plan: The site is not within a BP.
d. Salmon Conservation Plan: The site is not within a SCP.
e. Stormwater Compliance Plan: The site is not within a SWCP.
f. Lake Management Plan: The site is not within a LMP.
g. Flood Hazard Reduction Plan Update: The site is not within a FHRP.
h. Shared Facility Drainage Plan: The site is not within a SFDP.
2. Flood Hazard Area Delineation: This site not within the 100‐year flood plain per the City of
Renton Flood Hazard Area Map in Appendix C. The site has been determined to have an
infrastructure induced floodplain to elevation 394.87. The 24” culvert exiting the site is not
adequate to pass runoff through the site with out a backwater effect, both inlet controlled
and a backwater from the downstream storm system. This was originally determined in a
report by Coughlin‐Porter‐Lundeen (CPL) and the City has mandataed that compensatory
storage be provided for any reduction in storage volume. See page 7 for additional
information.
3. Flood Protection Facilities: The site does not rely on an existing flood protection facility or
modify or construct a new flood protection facility.
4. Source Control: The project is considered a commercial project and therefore is required to
have source control measures, see Section IV of this report for more information.
5. Oil Control: The site does not meet the criteria for a high‐use site, see Section IV of this
report for more information.
6. Aquifer Protection: The site is not within a critical aquifer recharge area and is shown in the
low groundwater contamination suseptability area, see maps in Appendic C.
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III: OFFSITE ANALYSIS
Task 1: Study Area Definition and Maps
See Figures 3, 3a, 3b and 4 in Appendix A for sub basins and downstream analysis map.
Task 2: Resource Review
a. Adopted Drainage Plans – The site is within the Lower Cedar River Drainage Basin per
the City of Renton Drainage Basin Map in Appendix C. There is no specific adopted
drainage plan for this area.
b. FEMA maps – the site is not within Flood Hazard Zone per the City of Renton Flood
Hazard Area Map in Appendix C.
c. Sensitive Areas Folio – the site is not within a shoreline, erosion hazard, coal mine
hazard, channel migration hazard or seismic hazard area. see King County SAO and
CAO Basin Condition Maps in Appendix C.
d. DNRP Drainage Complaints and studies – see Appendix B.
e. Wetland Inventory Maps – none per the City of Renton online mapping, see Appendix
C.
f. Community Plan – None
g. Review of the 303d Listings – see Appendix B and Task 4, below.
Task 3: Field Investigation
See Downstream Table and Downstream Map in Appendix B for a detailed breakdown of the
actual pipe components. Runoff leaves the site in the 30 storm piping that conveys flow
through the site. This piped storm system continues to the west across Bremerton Avenue,
through the apartment complex and into the shopping center. At a distance of about 850 feet
from the site the storm system bends to the south, across NE 4th Street, then back to the west,
outfalling at the headwater for the west fork of Maplewood Creek. The creek meanders in a
southerly direction through wooded tracts of several residential developments. At a distance of
3,160 feet from the site a culvert conveys the stream under Bremerton Place NE. The stream
continues to a distance of about 5,760 feet from the site where it joins the east fork of
Maplewood Creek. At this point a deep gulley has formed where the creek drops down to the
valley floor. At about 8,000 feet from the site the creek enters the Maplewood Golf Course. The
channel continues through both open and wooded stretches of the golf course, bending to the
west, then back to the south where it crosses under Highway 169 and into the Cedar River
about 9,860 feet from the site. Cedar creek flows westerly an additional 3.3 miles to Lake
Washington.
Task 4: Drainage System Description and Problem Descriptions
There are no known drainage problems along the downstream drainage route. Beyond the
initial 1000 feet an opened unnamed stream.
A review of the drainage complaint data revealed the closest two drainage complaints, both
over 30 years old and located about 2,650 feet from the site. One was related to water on the
adjacent roadway and is unrelated to the stream system. The second was regarding diversion of
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the stream onto filled land. There are no other known drainage issues along the downstream
flowpath within the area of study.
The City’s Lower Cedar River Habitat Study list several restoration projects within Reach 3 of
the river see Herrera figure in Appendix B. These projects are to be implemented by the City
using grant and other public funding.
Review of the 303d Listings
The Washington State Department of Ecology Water Quality Atlas Map has been reviewed for
any 303d listings associated with the downstream drainage system. A portion of the
Maplewood Creek, at a distance of about 7,000 feet from the site, is listed as Category 5 for
Bioassesment. Further downstream the Cedar River is listed as Category 5 for pH, temperature
and dissolved oxygen levels. See figures in Appendix B.
Task 5: Mitigation of Existing or Potential Problems
Downstream Flooding Issues
None known beyond the local infrastructure related flooding.
Conclusions
With the proposed installation of the new drainage channel and upsized outlet pipe, combined
with additional compensatory storage the local flood problem caused by the undersized storm
outlet will be improved and the proposed site improvements should not result in any increased
flooding issues, but should improve the local area.
UPSTREAM BASIN
The 24" culvert that crosses the property collects a significant upstream drainage basin. The
culvert needs to be rerouted to clear the proposed building construction. Based on City of
Renton GIS for storm systems and Lidar contours, a basin boundary has been estimated that
encompasses 140 acres of mostly developed property, see Figure in Appendix B.
Complicating a calculation of upstream runoff rates are the approximately 11 existing detention
systems that have been constructed in the basin over the years and designed over several
drainage manual iterations. In working with City Staff, Rohini Nair, Engineer for the City of
Renton provided the following guidance:
“The City of Renton will allow a modified Level 2 Offsite Analysis to be conducted to
meet the City's requirements, which include the following:
a. Perform a hydrologic analysis comparing the existing condition and developed
condition at the 25‐year and 100‐year peak flow per Core requirement #4. The
intent of the comparison is to show that the developed conditions will not adversely
impact the existing and future conveyance system.
i. This analysis will compare the existing and developed condition under the
following tailwater conditions:
1. The downstream pipe at the point of compliance is empty
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2. The downstream pipe at the point of compliance is full
3. The downstream pipe at the point of compliance is 1/2 full
4. The downstream pipe at the point of compliance is near full with 1" of
freeboard from top of pipe
*Note: The POC of the site is the catch basin with the Facility ID No. 131550 per
COR maps
ii. To determine the upstream land‐use designation the City of Renton will allow the
following options:
1. All upstream land‐use shall be existing unless shown to have a detention
facility. If there is a detention facility the associated land‐use can be designated
as pasture.
2. All upstream land‐use shall be existing unless shown to have a detention
facility with an available recorded TIR.
*Note: The upstream flows shall be modeled assuming that there are no
upstream conveyance systems beyond the property line.”
Based on this guidance the upstream basin has been analyzed using the following land uses:
Impervious roads, parking, and roofs 22.01 ac
Pasture (sites with existing detention) 75.67 ac
Lawn and landscaping 19.25 ac
Native vegetation areas 25.67 ac
The upstream basin has the following current 25 year and 100 year flow frequency runoff rates,
see Appendix D:
Storm Event Rate
25 Year 26.50 cfs
100 Year 35.52 cfs
The project site itself has the following existing and mitigated 25 year and 100 year flow
frequency runoff rates:
Storm Event Existing Mitigated
25 Year 0.14 cfs 0.08 cfs
100 Year 0.17 cfs 0.10 cfs
Note: The tailwater conditions in the original requirements no longer apply as a larger study of
the downstream has been performed to obtain tailwater conditions per the floodplain
calculations below.
FLOODPLAIN CALCULATIONS
The site has been determined to have an infrastructure induced floodplain. The 24” culvert is
not adequate to pass runoff through the site with out a backwater effect, both inlet controlled
and a backwater from the downstream storm system. This was originally determined in a report
by Coughlin‐Porter‐Lundeen (CPL) and the City has mandataed that compensatory storage be
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provided for any reduction in storage volume. Therefore, to account for the development, it is
proposed to have the flow system run under the building with the building constructed on
columns, leaving space for water storage.
CPL has assumed that the downstream system had no backwater onto the site. Harmsen has
determined that there is a backwater. Since the elevation of the backwater has a direct impact
through storage on how much water flows through the culvert and the amount of flow through
the culvert determines the elevation of the backwater, an iterative calculation needed to be
made that matched those two elevations. The intial step is to determine the flood plain stage
storage. This was calculated by creating a surface model in Autocad Civil 3D using the following
three topographic sources. First the topographic survey for the project has been used, modified
to include the proposed compensatory storage under the building. The second source of
information is the proposed flood plain compensatory storage plan by Coughlin‐Porter‐Lundeen
for the Renton Highlands project. The proposed grading contours shown on this plan have been
used to create a ground surface model. It was found that this would create a more accurate
map than using available lidar as the area is heavily vegetated. Lastly, available lidar
topographic information, obtained from the Lidar Consortium, has been used to fill between
the two primary flood plain sources.
Using Autocad Civil 3D, the flood plain storage volume was calculated in one foot increments to
prepare a stage – storage – discharge table for input into WWHM2012. The table is as follows:
Elevation (ft) Area (ac) Volume (ac‐ft) Discharge (cfs)
388 0.00 0.00 varies
389 0.15 0.14
390 0.16 0.28
391 0.17 0.45
392 0.24 0.61
393 0.70 1.16
394 1.02 2.00
395 1.50 3.47
396 1.88 5.10
397 2.05 7.12
398 2.16 9.04
399 2.20 11.39
400 2.30 13.59
To get outflow rates for a variety of storage depths, the upstream runoff was routed through
the ‘pond’ with a spread of different orifice sizes to force the flow to reach various depths and
thus give various outflows. Then these flows would be used in the downstream backwater
calculations to determine backwater elevations. Once the two models match, that would be the
storage elevation.
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The discharge values for 13 different orifice sizes (10”, 12”, 14”, 15”, 16”, 17”, 18”, 19”, 20”,
21”, 22”, 24” and 26”) were calculated using the orifice equation for elevations between 388
and 400. Each of these stage – storage – discharge tables were input into WWHM2012 to
calculate the 100 year discharge from the flood plain. The cooresponding 100 year ponding
elevation could then be interpolated from the stage – storage – discharge table for each orifice
size creating a data point. These data points are as follows:
Orifice Size 100yr Discharge (cfs) 100yr Elevation (feet)
10” 8.52 397.73
12” 11.53 396.79
14” 14.62 395.56
15” 16.20 395.00
16” 17.38 394.23
17” 18.75 393.73
18” 20.20 393.27
19” 22.55 392.84
20” 23.33 392.64
21” 24.70 392.25
22” 25.90 391.89
24” 28.41 391.32
26” 29.86 390.67
These data points were then graphed:
DOWNSTREAM BACKWATER CALCULATIONS
Backwater calculations have been prepared for the removal of the culvert through the site. The
downstream system is based on the CPL report and the flows therein with the addition of the
upstream flow calculated above. The Hydraflow Storm Sewer Extension for Autodesk Civil 3D
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was used perform the backwater calculations. A 30” smooth‐walled pipe was proposed to
replace the 24” cmp. An open channel will be used under the building with a special inlet in the
west wall of the facility per plan detail. Below is a graph showing the elevation and flow rate
where the backwater and upstream floodplain calcalutions match up. This is at 16.7 cfs and
elevation 394.82, see Hydraflow output in Appendix D.
This then indicates that the artificial floodplain is expected to have a 100 year elevation of
394.81 and compensatory calculations and building clearances are calculated from that
elevation.
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IV: RETENTION/DETENTION ANALYSIS AND DESIGN
PART A: EXISTING SITE HYDROLOGY
The site located at the northeast corner of the intersection of NE 4th Street and Bremerton
Avenue NE. The property currently contains a 1,053 sf single family residence, 665 sf walkways
and concrete on the southern end of the site. The remainder of the southern portion of the site
is lawn, 0.16 ac, and the northern 0.24 ac is trees and brush, see Figure 3A: Existing Drainage
Basin Map in Appendix A. There is a 24” storm pipe that crosses through the center of the site.
This pipe will be removed, replaced with an open channel under the building, and a 30”
connection to the storm system in Bremerton.
Existing Basin
The basin for the existing condition contains 0.76 acres including 0.32 ac of existing and future
right or way. There is currently 0.15 acres of the right‐of‐way that is paved and is included in
the basin. The remainder of the basin, the portion being redeveloped has been modeled as
forest. Based on the geotechnical report the site is underlain with till soils so the appropriate
parameters have been used in WWHM2012.
The existing basin has the following land uses and areas:
Land Use Area(ac)
Impervious 0.15
Forest 0.61
The existing basin has the following flow frequency runoff rates:
2 Year 0.08
10 Year 0.12
50 Year 0.16
100 Year 0.17
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PART B: DEVELOPED SITE HYDROLOGY
Developed Basin
The 0.76 acre basin includes the frontage street, access drive, walkways and landscaping and
the proposed building, see Figure 3B: Developed Drainage Basin Map in Appendix A.
The runoff from the road, walkways, landscaping and access will be collected and treated, then
will be routed to the proposed detention vault to be located under the building. The building
roof will flow directly to the vault. The impervious areas have been calculated for the access,
parking areas, walkways and building using AutoCAD by constructing a polyline around the
specific area.
The developed basin has the following land uses and areas:
Land Use Area(ac)
Impervious (roof) 0.28
Impervious (paving) 0.38
Landscaping 0.10
The developed basin has the following flow frequency runoff rates:
2 Year 0.28
10 Year 0.41
50 Year 0.54
100 Year 0.60
ONSITE BMP’S
In addition to the required detention facility, the RSWDM also requires the implementation of
Onsite BMPs to a portion of the impervious surfaces on the site. The intent of this requirement
is to lessen the impact of the runoff from the proposed impervious surfaces. The site area is
0.44 ac or 19,166 sf which is more than 22,000 sf so the Large Lot BMP Requirement applies.
The BMP must be applied to a minimum of 20% of the site area in this case an area of atleast
3,850 sf. Per Section 1.2.9.2.2 Large Lot BMP Requirements, there are 12 possible ways to meet
this requirement. They are addressed below:
Full Dispersion
Full Dispersion is not a feasible Onsite BMP for this project. Per Section C.2.1.1.1.3 in the
RSWDM:
“A native vegetated flowpath segment of at least 100 feet in length (25 feet for sheet
flow from a nonnative pervious surface) must be available along the flowpath”.
There is no native vegetation on the site, nor is there a vegetated flowpath longer than 5 feet
from the proposed improvements to a property line. Therefore Full Dispersion is not a feasible
for this site.
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Full infiltration
GEO Group Northwest explored the soil and groundwater conditions at the subject parcel and
documented their findings in their report titled Geotechnical Report With Infiltration
Evaluation, dated May 18, 2018. From pages 2 and 3 of their report:
“The soils observed at the uplands, overlying much of the site consist of silty soils which
are relatively impermeable. The soils observed at the depression (lowland) portion of
the site include where located below silty fills may have relatively high permeability,
however, the groundwater level at this area is also relatively high, thereby reducing the
effectiveness for an infiltration system. Groundwater seepage ranged in depth at test
pits TP‐4 and TP‐5 from 5 to 7‐feet below ground surface. This level may vary dependent
upon the time of year, precipitation amounts and changed land use in the area. Due to
the presence of silty soils overlying much of the site and the relatively high groundwater
conditions we do not recommend attempting to infiltrate stormwater at the subject
site.”
Per Section C.2.2.2.1.a in the RSWDM:
“Existing soils must be coarse sands or cobbles or medium sands and cannot be
comprised of fill materials where the infiltration device will be located.”
The site soils are silty sands and fill, therefore full infiltration is not feasible on the site.
Limited infiltration
Limited Infiltration is similar to Full Infiltration except that per Section C.2.2.2.1.a in the
RSWDM:
“The minimum design requirements for limited infiltration are the same as those for full
infiltration, except infiltration depressions are excluded and existing soils in the location
of the infiltration device may be fine sands, loamy sands, sandy loams, or loams as
opposed to only medium sands or better.”
And:
“Silt and clay loams, and cemented till (hardpan) are not suitable for limited infiltration
systems.”
The GEO Group Northwest report titled Geotechnical Report With Infiltration Evaluation, dated
May 18, 2018. From pages 2 and 3 of their report:
“Soils observed at the test pits generally consist of variable density silty soils and fills which
include brick, wood, organic material, concrete and asphalt debris overlying apparent dense
and competent till and gravelly SAND and sandy GRAVEL.
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“Due to the presence of silty soils overlying much of the site and the relatively high
groundwater conditions we do not recommend attempting to infiltrate stormwater at
the subject site.”
The site soils are silty sands and fill with more pervious soils below, however groundwater
encroaches into the pervious soils, therefore limited infiltration is not feasible on the site.
Rain Garden
Rain Gardens are not a feasible Onsite BMP for this project. Per Section C.2.6.21 in the RSWDM:
“21. Where appropriate field testing indicates soils have a measured (a.k.a., initial)
native soil saturated hydraulic conductivity less than 0.3 inches per hour.”
Bioretention
Bioretention facilities are not a feasible Onsite BMP for this project. Per Section C.2.6.21 in the
RSWDM:
“21. Where appropriate field testing indicates soils have a measured (a.k.a., initial)
native soil saturated hydraulic conductivity less than 0.3 inches per hour.”
Permeable Pavement
Permeable paving is not a feasible Onsite BMP for this project. Per Section C.2.7.24 in the
RSWDM:
“24. Where appropriate field testing indicates soils have a measured (a.k.a., initial)
native soil saturated hydraulic conductivity less than 0.3 inches per hour.”
Initial unfactored infiltration rates were calculated by GEO Group Northwest. Page 4 of their
report states:
“From Darcy’s Law for permeability and using the D10 grain size correlation we calculate
that the initial infiltration rate for the soils at the TP‐4 2’ and TP‐5 2’‐8”sampled depths
is 0.14 to 1.3 inches/hour. These rates are relatively low, highly variable and subject to
correction due to the potential for groundwater mounding and possible groundwater
movement. “
“If stormwater infiltration is to occur for the subject development then we recommend
that the designer apply appropriate correction factors to account for site variability, the
test methodology and siltation/maintenance.”
The Washington State Department of Ecology Stormwater Management Manual, DOE Manual,
was reviewed to determine the appropriate correction factors to determine a design infiltration
rate. From Section 3.3.6 of the DOE Manual, Table 3.3.1, the following factors have been
applied:
Correction Factor for Site Variability, CFv = 0.40
Correction Factor for Testing Procedure, CFt = 0.40
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Correction Factor for Influent Control, CFm = 0.90
Therefore CFT = CFv x CFt x CFm = 0.144. After applying the correction factor the resulting
design infiltration rates would be 0.02 to 0.18 inches per hour. This is significantly less than the
minimum rate of 0.3 inches per hour so the use of permeable pavement is not feasible.
Basic Dispersion
With a possible maximum vegetated flow length of 5 feet the use of Basic Dispersion is not
feasible for this site. The minimum required vegetated flow path for each dispersion device is
addesssed below:
USE OF SPLASH BLOCKS FOR BASIC DISPERSION
Per Section C.2.4.2.2 in the RSWDM:
“2. A “vegetated flowpath segment” of at least 50 feet in length must be available along
the flowpath that runoff would follow upon discharge from the splash block.”
USE OF ROCK PADS FOR BASIC DISPERSION
Per Section C.2.4.3.2 in the RSWDM:
“2. A “vegetated flowpath segment” of at least 50 feet in length as illustrated in Figure
C.2.4.C must be available along the flowpath that runoff would follow upon discharge
from the rock pad.”
C.2.4.4 USE OF GRAVEL FILLED TRENCHES FOR BASIC DISPERSION
Per Section C.2.4.4.2 in the RSWDM:
“2. A “vegetated flowpath segment” of at least 25 feet in length must be available along
the flowpath that runoff would follow upon discharge from a dispersion trench. This
length must be increased to 50 feet if the discharge is toward a steep slope hazard area
or a landslide hazard steeper than 15%. All or a portion of the vegetated flowpath
segment may be within the buffer for the steep slope hazard area or landslide hazard.”
USE OF SHEET FLOW FOR BASIC DISPERSION
Per Section C.2.4.5.3 in the RSWDM:
“3. A “vegetated flowpath segment” of at least 10 feet in length must be available along
the flowpath that runoff would follow upon discharge from the strip of crushed rock.”
Reduced Impervious Surface Credit
The CA zone has no limit on impervious coverage, however the proposed site layout does not
have contain 3,850 sf of pervious area. Therefore this BMP is infeasible.
Native Growth Retention Credit
There is no native growth areas on the site.
Tree Retention Credit
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There are no significant trees on the site.
Soil Amendment
This BMP will be used in the planter beds and other landscaped areas on site and disturbed
areas adjacent to the site.
Perforated Stubout Connection
The building roof runoff will be directed through the building to the detention vault. There is
also no area where a perforated stubout could be installed where stormwater would not
impact the building foundation.
PART C: PERFORMANCE STANDARDS
1. The drainage design for the site was prepared using the requirements of the 2009 City
of Renton Surface Water Design Manual, (RSWDM Manual). WWHM2012, by the
Department of Ecology, has been used to calculate basin runoff and for
retention/detention facility sizing.
2. The Flow Control Duration Standard – Forested Conditions, has been applied for sizing
of the detention facilities.
3. The site is subject to Flow Control BMPs per Section 5.2.1.3 Large Lot High Impervious
BMP Requirements.
4. The conveyance system is subject to the design standards applicable to “Conveyance
Requirements for New Systems”.
5. The Enhanced Basic Water Quality Treatment standard has been used for design of the
treatment facilities.
6. The site has been evaluated in respect to the Enhanced Basic Treatment requirement,
see Part E of this Section.
7. The site has been evaluated in respect to Special Requirement #4 – Source Controls and
Special Requirement #5 – Oil Controls, see Part E of this Section.
PART D: FLOW CONTROL SYSTEM
Flow Control Design
The site is located within the Flow Control Duration Standard – Forested Condition Area. Storm
water detention will be accomplished through the use of a rectangular detention vault located
along the north side of the building. WWHM2012 has been used to size the detention pond.
The required vault contains a ‘live’ storage volume of 8,540 cf, see Appendix D.
The proposed detention vault has the following dimensions:
Vault Length 70 feet
Vault Width 20 feet
Bottom of ‘Live’ Elevation 100.00 feet (assumed)
Top of ‘Live’ Elevation 106.10 feet
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Release from the vault will be controlled by a three orifice flow control riser with the following
dimensions:
Riser Diameter 12
Outlet Elevation 100.00 feet
1st Orifice Elevation 98.00 feet
1st Orifice Diameter 0.89”
2nd Orifice Elevation 103.90 feet
2nd Orifice Diameter 0.88”
3rd Orifice Elevation 105.50 feet
3rd Orifice Diameter 1.30”
Top of Riser Elevation 106.10 feet
The existing and mitigated flow frequency runoff rates are:
Storm Event Existing Mitigated
2 Year 0.08 cfs 0.04 cfs
10 Year 0.12 cfs 0.06 cfs
50 Year 0.16 cfs 0.09 cfs
100 Year 0.17 cfs 0.11 cfs
An emergency overflow will be installed along the west edge of the vault to allow for a safe
discharge of rogue storm events.
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PART E: WATER QUALITY SYSTEM
Water Quality Facility
The site is located within the Basic Water Quality Treatment Area. As runoff to the facility is
from roadway and the development is considered a commercial land use, it is necessary to
meet the Enhanced Basic Water Quality Treatment standards. The BioPod Treatment System by
Oldcastle has been chosen to meet the runoff treatment requirements for the site runoff. The
BioPod system has received a General Use Level Designation (GULD) approval from the
Washington State Department of Ecology for Basic (TSS), Phosphorus, and Enhanced (dissolved
metals) treatment.
BioPod Operation
BioPod systems utilize an advanced biofiltration design for filtration, sorption and biological
uptake to remove Total Suspended Solids (TSS), dissolved metals, nutrients, gross solids, trash
and debris as well as petroleum hydrocarbons from storm water runoff. BioPod systems use
StormMix media, an engineered high‐flow rate media (153 in/hr) to remove stormwater
pollutants. Stormwater runoff flows through the media and into an underdrain system at the
bottom of the container, where the treated water is discharged. The High‐Flow Bypass BioPod
system used for this project includes an internal high‐flow bypass that eliminates the need for a
separate bypass structure.
Sizing of the treatment facilities has been performed using WWHM2012 to determine the
Water Quality flowrate for each of the basins, see output in Appendix D. The treatment
standard dictates that atleast 91% of the runoff must be filtered by the facility. The GULD
approval from DOE for the BioPod specifies a flowrate of 1.6 gallons per minute per square foot
of media surface area. The water quality flowrate is converted from cubic feet per second to a
gallons per minute flowrate. Then the required BioPod model can be selected that has a
treatment capacity that meets or exceeds the basin water quality flowrate.
Treatment Treatment
Flowrate (CFS) Flowrate (GPM)
0.046 20.6 GPM
The facility identification, vault dimensions, model nuber, treatment capacity and basin water
quality flow rate is listed below.
Facility Vault BioPod Treatment Basin
Dimensions Model Capacity Flowrate
BioPod 4’x6’ BPU‐46IB 25.6 GPM 20.6 GPM
ROOF AREA
The building roof will not be constructed using leachable metals per covenant, therefore it does
not require treatment.
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Special Requirement #4 – Source Controls
Structural Source Controls
Structural source controls will include covered garbage and recycle areas. Additionally, vehicle
washing will not be permitted on the site.
Non‐Structural Source Controls
See Section VIII of this report for the Construction Stormwater Pollution Prevention Plan. This
includes Erosion and Sedimentation Control Plan design where the minimum requirements of
Core Requirement #5: Temporary Erosion and Sedimentation Control are discussed. The section
also includes discussion of the Construction Stormwater Pollution Prevention where the BMPs
contained in Volume II of the current DOE Manual will be used to control pollution from
sources other than sedimentation.
Special Requirement #5 – Oil Controls
The site does not qualify as a high use site as it is does not meet the three criteria of a high use
site per Section 1.3.5 of the RSWDM. The site is does not contain an open parking lot as the
parking is under the structure and will discharge any runoff to the sewer. Petroleum storage or
transfer will not occur on the site. The site is not subject to use, storage or maintenance of 25
or more 10 ton diesel vehicles.
Special Requirement #6 – Aquifer Protection Area
The site is not located within a Zone 1 or Zone 2 Aquifer Protection Area per the City of Renton
Aquifer Protection Area Map. No additional aquifer proterction BMPs are required for this site.
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V. CONVEYANCE SYSTEM ANALYSIS AND DESIGN
The primary conveyance of runoff is piped downspout collectors for the building. The
uncovered parking and underground parking is limited to the access drive along the north side
of the building. Conveyance calculations are provided at the end of Appendix D. The rational
method was used to determine runoff for the individual sub‐basins based on the 100 year
storm event. An Excel spreadsheet was then used to perform the backwater analysis for the
individual pipe runs.
The upstream storm system re‐routing conveyance calculations are included in Section III of this
report.
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VI. SPECIAL REPORTS AND STUDIES
The geotechnical report prepared by GEO Group Northwest for the project follows.
No other special reports or studies have been prepared at this time.
13705 Bel-Red Road, Bellevue, Washington 98005
Phone 425/649-8757 · Fax 425/649-8758
December 28, 2020 G-4661
Hari Ghadia
4th Creek Meadows LLC
12505 Bel-Red Rd, Suite 212
Bellevue, WA 98005-2510
Send via: ghadia_hari@hotmail.com
Subject: ADDENDUM LETTER – RESPONSE TO CITY COMMENTS
PROPOSED 4TH CREEK MEADOWS DEVELOPMENT
4502 NE 4TH ST
RENTON, WASHINGTON
Ref: See end of letter
Dear Hari Ghadia:
We have been provided with preliminary plans with “redlined” City comments and asked to
provide responses by Mr. Martin Reimers of Concept Architecture. The pdf document provided
is 599 pages and a link was emailed on October, 26, 2020. On November 17, 2020 we were
provided with a link to another set of plans, documents and review comments having a total of
455 pages. We have reviewed both pdf documents.
The following letter has been prepared in order to document our review of the plans and provide
recommendations with regard to the “redlined” City comments. This letter shall serve as an
addendum to the referenced geotechnical report. We have been asked to specifically address
comments directed to the geotechnical engineer on plan sheets: C5.2 and C4.0.
Site and Project Description
At the time of our site investigation the subject site consisted of a developed parcel containing
one building which is located at the south side of the lot. The existing building is a 1-story
building with daylight basement which daylights toward the north. The property has an
approximate area of 0.55 acres. There is an ecology block retaining wall which is located at the
west side of the lot or at the adjacent west right-of-way which has an estimated height of around
12-feet and retains Bremerton Ave NE. The site topography includes a relative depression at the
north-central portion of the lot with moderate to steep relatively minor slopes at the north and
December 28, 2020 G-4661
4502 NE 4th St, Renton, WA – Addendum Letter Page 2
GEO Group Northwest, Inc.
south sides of the lot. In addition, we understand that there is underground stormwater piping
which transits the central portion of the lot with water flowing from east to west.
Based upon review of the referenced plans we understand that the proposed development is to
consist of removing the existing building and associated development and the construction of a
new 4-story commercial mixed-use building having one level of underground parking. A
detention tank is proposed at the north side of the building. The building is to have a finish floor
elevation of 410.33, presumably at the main floor level. The plans also indicate street/sidewalk
improvements at the frontage within the adjacent right-of-ways for NE 4th St and Bremerton Ave
NE.
We understand that the project proposes to remove a section of the existing underground
stormwater piping which crosses the site and allow stormwater to flow and backwater below the
building within a compensatory storage area since the downstream pipe is undersized for the
design flood event. Concrete columns will be used the support the north half of the building
within the compensatory storage area. The current infrastructure induced floodplain is at an
elevation of 394.87-feet. The plans indicate that the 100-year flood elevation for the project is at
394.81-feet and the calculated 100-year backwater is 399.5-feet. Based upon the plans the
lowest parking garage level located directly above the compensatory storage is at an elevation of
400.17-feet. An eight-foot wide and one-foot deep concrete lined channel will be constructed at
the flow line between the pipe discharge at the east and the pipe inlet at the west. The concrete
channel is to be 6-inch thickness of Class 3000 concrete constructed on top of a 2-inch thickness
of crushed surface top course, presumably placed on top of the existing grades. The concrete
channel will be reinforced with #4 bars at 16-inches on-center, both directions. Two-feet wide
ballast rock surfacing areas are proposed at both the sides of the flow channel. Based upon the
Technical Information Report the anticipated flow rate during flooding is 16.7 cfs. We note that
the concrete channel has a cross-sectional area of 18 square-feet.
The project plans indicate that the new footings are to be a minimum of 18-inches below
adjacent finish grades, this includes footings within the compensatory storage area.
The referenced project site plans do not note the existence or proposed removal of the existing
ecology block retaining wall at the Bremerton Ave NE right-of-way where street improvements
are proposed. The wall is shown on the survey. At the time of geotechnical report preparation
the wall was proposed to be removed.
City of Renton Geotechnically Related Comments
Below we list the City of Renton plan review comments which we have addressed, where
appropriate, in the Conclusions and Recommendations section of this letter.
December 28, 2020 G-4661
4502 NE 4th St, Renton, WA – Addendum Letter Page 3
GEO Group Northwest, Inc.
1. At several locations on the referenced plans, our reviewed geotechnical report (pdf
document) as well as the Oct. 6, 2020 letter from the City of Renton there is a
requirement that GEO Group Northwest review the plans and produce a plan review
letter approving of the plans, per the IBC requirement. We have performed a plan review
for this letter. However, we have provided additional recommendations herein, which we
recommend are implemented in the final plan set, prior to issuance of our plan review
letter.
2. The following comment by the City of Renton was placed on the referenced geotechnical
report and also on sheet C4.0 of the “redlined” plans by Harmsen (6-22-20):
The geotechnical and structural design of the 4th Dimension Building and the portion of
the building providing compensatory storage must be prepared in a way that will prevent
damage to the subject building and surrounding properties from seepage of water into the
subbase material and potential settlement and erosion that might result. Possible means
of accomplishing this include providing a watertight concrete base slab and/or a
waterproof liner below the open channel and compensatory storage area to prevent
infiltration of water into the subbase material. The project’s geotechnical and structural
engineers must provide the City with a correspondence bearing a professional
engineering stamp stating that in their opinion the project as designed will not result in
property damage caused by settlement or erosion of the subbase material.
3. The “redlined” (City Comments) plans by Harmsen Engineers C5.2 (6-22-20) has the
following City comment related to the road widening at project site frontage (NE 4th St
and Bremerton Ave NE:
Add Pavement Section: Provide pavement design per RMC 4-6-060.F.5 for arterials and
collectors. Include pavement design in geotechnical report.
Conclusions and Recommendations
General
The subject site is mapped as being overlain with glacially consolidated soils. However,
thicknesses of loose and unsuitable fills were encountered at some of the test pit locations.
Please see the referenced geotechnical report for the locations and depths of encountered
overlying apparent loose soils and fills. We note that these unsuitable soil conditions were found
to a depth of 9-feet below ground surface at the test pit TP-3. We recommend that the loose and
unsuitable fills are removed from all foundation subgrade areas and areas where the structural
December 28, 2020 G-4661
4502 NE 4th St, Renton, WA – Addendum Letter Page 4
GEO Group Northwest, Inc.
support is required for slabs, including at the compensatory storage concrete channel. Where the
excavations extend below the proposed bottom of footing or slabs these excavations are termed
over-excavated. In our geotechnical report over-excavated areas at footing and slab subgrade
locations are recommended to be filled with lean mix concrete or compacted structural fills
placed and compacted in accordance with the geotechnical report. Due to the proposed drainage
conditions, the creation of compensatory storage below the building, we revise our
recommendation for fill placement below footings and slab-on-grade floors within the building
footprint to consist of either clean crushed ballast rock (no fines, poorly graded), controlled
density fills (CDF) or lean-mix concrete. Over-excavation areas should be completely de-
watered prior to the placement of these fill materials. We also recommend that GEO Group
Northwest is retained to observe the condition of prepared foundation subgrade areas prior to the
placement of fills and then also monitor the placement of fills to verify compliance with our
recommendations.
Footings at Compensatory Storage Area
We have reviewed the referenced project plans. General specifications on the structural plans
indicate that the footings shall be founded at 18-inches below adjacent/finish grade. The footing
schedules indicate that the footing “depth” dimension (no relation to depth below grade) will
range from 18 to 24-inches. Accordingly, the current plans would allow for a portion of the
footings to presumably project above the adjacent grade elevation at some locations. In addition,
it appears that portions of the footings proposed at gridline F will be located at the compensatory
storage channel location.
The creation of a compensatory storage area for drainage below the building does present risks to
the building from erosion and footing subgrade damage. For these reasons we recommend risk
mitigation include the following and that these items are illustrated on the plans:
1. The over-excavated slab and footing areas as noted above are recommended to be filled
with clean crushed ballast rock (no fines, poorly graded), controlled density fills (CDF)
or lean-mix concrete. It is recommended that over-excavated trench areas which are to
be filled with lean-mix concrete or CDF have dimensions which are equal to or wider
than the proposed footings or slab areas which they support. If clean crushed rock is used
for backfill at over-excavated footing subgrades then the bottom of the over-excavated
trench should be widened as necessary to insure that an approved fill prism extends
downward from the outside/bottom edge of the footings at a 1H:1V imaginary plane.
2. It is recommended that the bottom of all footings within or adjacent to the compensatory
storage area have a depth of at least 24-inches below the finish adjacent grade in order to
mitigate erosion risks. In addition, we recommend that at all areas within the
December 28, 2020 G-4661
4502 NE 4th St, Renton, WA – Addendum Letter Page 5
GEO Group Northwest, Inc.
compensatory storage area except for the concrete channel the finish grade should be
overlain with a minimum 8-inch thickness of clean crushed ballast rock (2-inch clean). If
vehicular traffic (for maintenance) is ever anticipated at the grades within the
compensatory storage area than it is recommended that the ballast rock is placed on top
of a layer of filter fabric.
3. Where the plans indicate that new building footings intersect the compensatory storage
concrete channel we recommend that the footing is deepened as necessary to maintain 1-
foot clearance from the bottom of the concrete channel to the top of the footing. Fills
placed below the channel are recommended to be primarily clean crushed ballast rock
although the designer may use filter fabric separation to place a top-course (crushed rock
minus) as currently specified.
Response to City Comment #2
It is the opinion of GEO Group Northwest that provided the project foundations are bearing on
the underlying competent site soils or fills, as specified herein, which are placed on top of the
competent and approved subgrade soils then the risk of soil related settlements at the building is
minimized and mitigated per our geotechnical report. The risk of erosion at foundation elements
can be mitigated at the compensatory storage area by properly implementing the
recommendations presented herein. Additional mitigation regarding these risks can be
implemented by constructing a waterproof slab or installing a waterproof liner as suggested by
the reviewer. If a waterproof liner is designed to be installed we recommend that it is properly
protected from damage due to ballast rock fill placement.
Pavement Recommendations and Design – Site Frontage
The following recommendations and the pavement design attached as Appendix A – Pavement
Design have been prepared to address the City of Renton comment #3 noted above.
We understand that the project proposes to construct some new pavement at the adjacent NE 4th
Street and Bremerton Ave NE right-of-ways where the street widening fronting the subject site is
proposed. We recommend that new asphalt pavements are constructed on firm, unyielding
medium dense to dense site soils or compacted structural fills meeting the following compaction
(relative density) standards per ASTM-D-1557 (modified Proctor):
1. 90% or higher relative density for all depths of greater than 12-inches from the pavement
surface;
2. 95% or higher relative density for all depths of less than 12-inches from the pavement
surface.
December 28, 2020 G-4661
4502 NE 4th St, Renton, WA – Addendum Letter Page 6
GEO Group Northwest, Inc.
We recommend that GEO Group Northwest is retained to observe the condition of excavated
pavement subgrade areas and the placement of compacted structural fills at such areas.
Based upon the traffic counts noted in the referenced Gibson Traffic Consultants study (July
2019) GEO Group Northwest has performed calculations in support of pavement section design
for the street widening areas. Our calculations and supporting documentation are attached as
Appendix A – Pavement Design. Accordingly, we recommend the following minimum
pavement sections:
Site Frontage at South (NE 4th St) Site Frontage at West (Bremerton)
Asphalt (in) 5 4
Crushed Surfacing (in) 8 6
Existing Ecology Block Retaining Wall
We note that the existing 12-foot tall ecology block retaining wall at or adjacent to the west
property line is not labeled on the current site plan or grading plans. At the time of our
geotechnical report preparation the plans indicated the wall would be removed and presumably
the area would be filled as necessary to match the proposed finish grades at the building and at
the right-of-way. The referenced current plan set suggests that the Bremerton Ave NE roadway
widening will occur at the location of the existing retaining wall. So, if the wall is left in place
the roadway will bear on top of the existing wall. We do not recommend constructing a roadway
on top of the existing retaining wall. We did not find details or specifications in the referenced
plans clarifying the removal process for the existing block wall. We recommend that the
designer clarify the plans to indicate the existing wall removal, temporary excavation
requirements and structural fill placement requirements at the existing wall location.
We recommend that GEO Group Northwest be retained to perform a final review of the project
plans prior to permit issuance in order to verify that our recommendations have been properly
incorporated into the project construction drawings. We also recommend that we are retained to
provide geotechnical construction monitoring services for the project in order to verify that our
recommendations are properly impacted and to insure that appropriate revisions can be made if
site conditions are found to vary from our subsurface investigation.
We appreciate the opportunity to provide geotechnical consulting regarding the proposed
development. Please contact us if there are any questions or concerns.
December 28, 2020 G-4661
4502 NE 4th St, Renton, WA – Addendum Letter Page 7
GEO Group Northwest, Inc.
Sincerely,
GEO GROUP NORTHWEST, INC.
Adam Gaston
Project Engineer
William Chang, P.E.
Principal
Attachment: Appendix A – Pavement Design
December 28, 2020 G-4661
4502 NE 4th St, Renton, WA – Addendum Letter Page 8
GEO Group Northwest, Inc.
REFERENCES
Plans:“4th Dimension Mixed Use”, Concept Architecture, 6-1-2020, Sheets: A0.1, A0.2, A0.2.1,
A0.2.2, A0.2.3, A0.2.4, A1.0, A2.1, A2.2, A2.3, A2.4, A2.5, A2.6, A2.7, A2.8, A2.9,
A2.10, A2.11, A3.1, A3.2, A3.3, A3.3B, A3.3C, A3.5, A3.6, A3.7, A4.1, A4.2, A4.3,
A4.4, A5.1, A5.2, A5.3, A6.1, A7.1, A7.2, A8.1, A8.2, A8.3, A9.1, A9.2, A9.3, A9.4,
A9.5, A9.6.
“4th Dimension Mixed Use, Renton, WA”, Harmsen Engineers Surveyors, 3-20-20,
Sheets C1.0, C2.0, C3.0, C3.1, C4.0, C4.1, C4.2, C4.3, C4.4, C4.5, C5.0, C5.1, C5.2,
C6.0.
“4th Dimension Mixed Use”, Coffman Engineers, 3-27-20, Sheets S1.1, S1.2, S1.3, S2.1,
S2.2, S2.3, S2.3a, S2.4, S2.5, S2.6, S5.1, S5.2, S5.3, S5.4, S5.5, S5.6, S5.7, S5.8, S5.11,
S5.12, S5.13, S5.14, S5.15, SA1.
“4th Dimension Mixed Use”, Origin Design Group, 3-4-20, Sheets L-1, L-2, L-3, L-4, L-
5.
“4th Dimension Mixed Use”, Berona Engineers, 6-04-20, Sheets: M0.0, M0.1, M2.1,
M2.2, M2.3, M2.4, M2.5, M2.6, M3.0, P0.0, P0.1, P2.0, P2.1, P2.2, P2.3, P2.4, P2.5,
P2.6, P3.0, P4.0.
“4th Dimension Mixed Use”, Cross Engineers, 8-9-2018, Sheets E0.0, E1.0, E2.0, E2.1,
E2.2, E2.3, E2.4, E2.5, E3.0, E4.0, E4.1, E5.0, E5.1, E6.0,
“Geotechnical Report with Infiltration Evaluation, 4502 NE 4th St, Renton, Washington”, GEO
Group Northwest, May 14, 2014.
“Building Permit Structural Plan Review – First Submittal, 4502 NE 4th Street (B20003319)”,
City of Renton, Oct. 6, 2020.
“4th Dimension Building Traffic Impact Analysis”, Gibson Traffic Consultants, GTC #18-102,
July 2019.
“Technical Memorandum, 4th Dimension Renton, Stream and Wetland Reconnaissance”,
Raedeke Associates, Project No: 2019-052-001, June 25, 2019.
December 28, 2020 G-4661
4502 NE 4th St, Renton, WA – Addendum Letter Page 9
GEO Group Northwest, Inc.
“Technical Information Report for the 4th Dimension Mixed Use Building, Renton,
Washington”, Harmsen, March 13, 2020.
APPENDIX A
PAVEMENT DESIGN
G-4661
Pavement Design Calculations G-4661
Project: 4th Creek Meadows Page 1 of 4
Address: 4502 NE 4th St, Renton, WA
Traffic Counts (Daily):
NE 4th St @ E side of Int.Eastbound:13909
Westbound: 14822
Bremerton Ave NE @ N side of int.Northbound:727
Southbound:681.0
Per Gibson Traffic Consultants anticipated daily trips from completed project:277
*Assume average daily traffic in one direction adjacent to site in 2020 (2.5% growth rate) with project added trips:
NE 4th St westbound:15665
One Lane (1/2):7833 Site Frontage at South
Bremerton Ave NE northbound:1042 Site Frontage at West
7833 x 0.045 x 0.4=140.994 ESAL/Day 1042 x 0.045 x 0.4=18.756 ESAL/Day
7833 x 0.005 x 1.0=5.21 ESAL/Day 1042 x 0.005 x 1.0=5.21 ESAL/Day
146 ESAL/Day 24 ESAL/Day
53364 ESAL/Year 8748 ESAL/Year
Growth (%): 2.5
Design Life (yr): 20
Growth Factor: 25.544658
1363177 ESAL/design life 223454 ESAL/design life
12/22/20
Site Frontage at South Site Frontage at West
GEO GROUP NORTHWEST, INC.
Intro/Assumptions/References:
Require pavement thickness design for road widening fronting the subject site at the north side (northern-most westbound)
lane/shoulder of NE 4th St and at the east side (northbound) lane/shoulder at Bremerton Ave NE. Per plan new flexible
pavement width at NE 4th St is 5-feet. At Bremerton Ave NE the new pavement width is 11-feet.
Assume pavement design lifetime of 20 years and a 2.5% annual growth rate in traffic counts.
"4th Dimension Building Traffic Analysis", Gibson Traffic Consultants, July 2019 cites traffic count data from IDAX July 18,
2018 which is used as basis for the design.
Soils are assumed based upon "Geotechnical Report with Infiltration Evaluation, Proposed Development, 4502 NE 4th St,
Heavy Traffic Count Review:
From Gibson cited data. Percentage "heavy" units is 1% of total traffic at NE 4th St and 2% of total traffic at Bremerton Ave NE.
FHWA Classification System:
Assume 95% of vehicles are cars and other negligable traffic loads. 5% of vehicles are heavy with 4.5% single units and 0.5%
Pavement Design Calculations G-4661
Project: 4th Creek Meadows Page 2 of 4
Address: 4502 NE 4th St, Renton, WA 12/22/20
1. W18 [Accumulated ESALs]1,363,177
Zr -1.28 ZR
Std Dev 0.45 S
ΔPSI 2.20 DPSI
2. Subgrade M[r]9600 psi
Surface mix Base mix P.A.B. subbase
a[i]0.44 0.34 0.14 0.11
D[i], inches 5.00 0.00 8.00 0.00 inches
m[i]1.00 1.00 1.00
3. Reliability, %90 R
4. Initial and terminal serviceability Po Pt
ΔPSI 4.20 2.00
Provided SN 3.32
Required SN (Solver will fill in)3.19 Adequate
log10(W18) =6.13 left side
6.13 right side
target cell 0.00
Site Frontage At South
Pavement Design Calculations G-4661
Project: 4th Creek Meadows Page 3 of 4
Address: 4502 NE 4th St, Renton, WA 12/22/20
1. W18 [Accumulated ESALs]223,454
Zr -1.28 ZR
Std Dev 0.45 S
ΔPSI 2.20 DPSI
2. Subgrade M[r]9600 psi
Surface mix Base mix P.A.B. subbase
a[i]0.44 0.34 0.14 0.11
D[i], inches 4.00 0.00 6.00 0.00 inches
m[i]1.00 1.00 1.00
3. Reliability, %90 R
4. Initial and terminal serviceability Po Pt
ΔPSI 4.20 2.00
Provided SN 2.60
Required SN (Solver will fill in)2.42 Adequate
log10(W18) =5.35 left side
5.35 right side
target cell 0.00
Site Frontage At West
Pavement Design Calculations G-4661
Project: 4th Creek Meadows Page 4 of 4
Address: 4502 NE 4th St, Renton, WA
AC - Asphaltic Concrete (Class B) (in):
Crushed Surfacing (in):
12/22/20
Site Frontage at South (NE 4th)
5
8
Site Frontage at West (Bremerton)
4
6
Summary:
For the proposed street widening, pavement design per AASHTO 1993 Empirical Method indicates that for the anticipated
design lifetime minimum flexible pavement thicknesses are as follows:
Checked By:
William Chang, P.E.
Principal
GEO GROUP NORTHWEST, INC.
Prepared By:
Adam Gaston
13705 Bel-Red Rd – Bellevue, WA 98005
Phone: 425/649-8757 – Fax: 425/649-8758
GEO Geotechnical Engineers, Geologists, & Environmental Scientists Group Northwest, Inc.
May 14, 2018 G-4661
Hari Ghadia
12505 Bel-Red Rd, Suite 212
Bellevue, WA 98005-2510
Send via: ghadia_hari@hotmail.com
Subject: GEOTECHNICAL REPORT WITH INFILTRATION EVALUATION
PROPOSED DEVELOPMENT
4502 NE 4TH ST
RENTON, WASHINGTON
Dear Hari Ghadia:
In accordance with our March 8, 2018 contract with you we have investigated the soil and
groundwater conditions at the subject property and prepared the following geotechnical report
for the proposed commercial/residential development.
SITE AND PROJECT DESCRIPTION
The subject site consists of a developed parcel containing one building which is located at the
south side of the lot as shown on the attached Plate 2 – Topographic Map. The existing
building is a 1-story building with daylight basement which daylights toward the north. The
property has an approximate area of 0.55 acres. There is an ecology block retaining wall which
is located at the west side of the lot or at the adjacent west right-of-way which has an estimated
height of around 12-feet and retains Bremerton Ave NE. The site topography includes a relative
depression at the north-central portion of the lot with moderate to steep relatively minor slopes at
the north and south sides of the lot.
Based upon plans provided by Kaul Design Associates the subject site is proposed to be
developed with a mixed-use building containing parking as shown on the attached Plate 2 – Site
Plan. We understand that the development will consist of the following:
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GEO Group Northwest, Inc.
1. The building and garage lowest level is roughly at the existing grade at the depression near
the center of the lot.
2. At the "6600 sf commercial" portion of the building there will be main floor level (above the
garage) which roughly matches the adjacent existing grades at the south side of the lot and then
will have 3-stories of apartments above this level.
3. At the "structured garage" section we understand that the top of the garage roughly matches
existing grade at the adjacent Bremerton Ave NE (also main floor level for the "6600 sf
commercial" building). A ramp goes down to the lower garage level at the east side of the
garage building. A detention or infiltration system may be constructed below the lowest level in
the garage although depth/elevation information for this structure has not been provided.
GEOLOGIC CONDITIONS
The USGS geologic map1 for the site vicinity indicates that the soils at the subject lot consist of
Quaternary-age Ground Moraine deposits. These soils consist of ablation till overlying
lodgement till. Till soils are generally described as a mixture of silt, sand and gravel which was
both deposited and overridden by glacial ice at least 14,000 years ago.
SUBSURFACE CONDITIONS
On April 18, 2018 GEO Group Northwest explored the soil and groundwater conditions at the
subject parcel by excavating five test pits by mini-excavator at the Test Pit locations noted on the
attached Plate 2 – Site Plan. The test pits were excavated to depths of up to 9-feet 8-inches
below ground surface (bgs).
Soils observed at the test pits generally consist of variable density silty soils and fills which
include brick, wood, organic material, concrete and asphalt debris overlying apparent dense and
competent till and gravelly SAND and sandy GRAVEL. The depth of fills ranged from 2.5-feet
at the test pit TP-5 to around 9-feet at the test pit TP-3.
The observed underlying soils appear to match the USDA SCS soil description for Alderwood
gravelly sandy loam (AgC) at the uplands and Everett very gravelly sandy loam (EvB) at the
depression as shown on the attached Plate 4 – SCS Soil Map.
1 “Geologic Map of the Renton Quadrangle, King County, Washington”, USGS, D.R. Mullineaux, 1965.
May 14, 2018 G-4661
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GEO Group Northwest, Inc.
Groundwater seepage was not encountered at the test pits TP-1 through TP-3. Significant
groundwater seepage was encountered at a depth of 7-feet bgs at the test pit TP-4 and 5-feet bgs
at the test pit TP-5.
The results of our subsurface investigation are shown on the attached Appendix A - Test Pit
Logs and USCS Soil Legend.
GRADATIONAL ANALYSES
We performed gradational analyses for soil samples collected at a depth of 2-feet at the test pit
TP-4 and a depth of 2-feet 8-inches at the test pit TP-5. These analyses confirmed the soil
descriptions at these levels as being gravelly silty SAND. The results of these analyses are
attached as Plates 5 and 6 – Gradational Analysis. Extrapolation of the gradation curves
indicates that the D10 value for the sampled soils at TP-4 and TP-5 to be 0.01 mm and 0.03 mm,
respectively.
INFILTRATION EVALUATION
The USDA NRCS maps the site soils as Alderwood gravelly sandy loam AgC) and Everett very
gravelly sandy loam (EvB) which appear to match the observed conditions at our test pits. The
USDA NRCS online data indicates that for the AgC soil unit the capacity of the most limiting
layer to transmit water (Ksat): very low to moderately low. Per NRCS for the EvB soil unit the
capacity of the most limiting layer to transmit water (Ksat): is high.
The soils observed at the uplands, overlying much of the site consist of silty soils which are
relatively impermeable. The soils observed at the depression (lowland) portion of the site
include where located below silty fills may have relatively high permeability, however, the
groundwater level at this area is also relatively high, thereby reducing the effectiveness for an
infiltration system. Groundwater seepage ranged in depth at test pits TP-4 and TP-5 from 5 to 7-
feet below ground surface. This level may vary dependent upon the time of year, precipitation
amounts and changed land use in the area. Due to the presence of silty soils overlying much of
the site and the relatively high groundwater conditions we do not recommend attempting to
infiltrate stormwater at the subject site. If site stormwater must be infiltrated then we
recommend that infiltration rate testing be performed at the infiltration location and it may also
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GEO Group Northwest, Inc.
be necessary to install a monitoring well to determine the groundwater level conditions
throughout the year.
INFILTRATION RATE
From Darcy’s Law for permeability and using the D10 grain size correlation we calculate that the
initial infiltration rate for the soils at the TP-4 2’ and TP-5 2’-8”sampled depths is 0.14 to 1.3
inches/hour. These rates are relatively low, highly variable and subject to correction due to the
potential for groundwater mounding and possible groundwater movement. As noted above we
recommend performing infiltration rate testing at the infiltration rate location and depth if it is
determined that infiltration must occur at the site.
If stormwater infiltration is to occur for the subject development then we recommend that the
designer apply appropriate correction factors to account for site variability, the test methodology
and siltation/maintenance. Catchbasins with sump pits should be installed between the
stormwater collection system and the infiltration system(s) and periodic maintenance should be
required to clean-out the catchbasin sump pit(s). The infiltration system may eventually clog due
to siltation and require replacement construction. This reason may also make it difficult to
maintain an infiltration system below the proposed structure as currently proposed.
SEISMIC DESIGN CRITERIA
Based upon our subsurface investigation the project site has Site Class D soil (Stiff Soil) per the
IBC based upon the observed subsurface soil conditions and provided that the buildings are
constructed to bear on the competent soils as described herein.
CONCLUSIONS AND RECOMMENDATIONS
General
Based upon the results of our study, it is our professional opinion that the site is geotechnically
suitable for the proposed development. The primary geotechnical concern with regard to the
design for the proposed building is the presence of loose and unacceptable fill soils which
present risks of damage due to soil settlement, if not properly over-excavated and filled with
compacted structural fill. It is our opinion that these risks can be mitigated by implementing a
building pad improvement program. Building foundations should not be constructed to bear
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Geotechnical Report – 4502 NE 4th St, Renton, Washington Page 5
GEO Group Northwest, Inc.
directly on top of the loose fill soils or fill debris. An alternative to the building pad
improvement program would be to construct the building on top of a pile foundation system. In
the final recommendations section of this report we provide recommendations for an augercast
pile foundation which may be used as an alternative to the recommended building pad
improvement. It may also be an option for a portion of the building to be supported on a spread
footing foundation, such as at the south side of the property, with the remainder of the building
supported on a pile foundation, provided that competent soils are encountered at the foundation
subgrades at the proposed spread footing areas.
Site Preparation and General Earthwork
The building pad areas should be stripped and cleared of surface vegetation and organic soils
(forest duff).
Silt fences should be installed around areas disturbed by construction activity to prevent
sediment-laden surface runoff from being discharged off-site. Exposed soils that are subject to
erosion should be compacted and covered with plastic sheeting.
Temporary Excavation Slopes
Under no circumstances should temporary excavation slopes be greater than the limits specified
in local, state and national government safety regulations. Temporary cuts greater than four feet
in height should be sloped at an inclination no steeper than 1H:1V (Horizontal:Vertical) in the
overlying loose site soils. If seepage is encountered at the excavation slopes should have
inclinations of no steeper than 2H:1V for the temporary construction time period. If excavations
with the aforementioned slope inclinations encroach upon the adjacent properties or remove
support for the existing ecology block wall at the west side of the site than shoring may be
required.
Structural Fill
All fill material used to achieve design site elevations below the building areas and below non-
structurally supported slabs, parking lots, sidewalks, driveways, and patios, should meet the
requirements for structural fill. During wet weather conditions, material to be used as structural
fill should have the following specifications:
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Geotechnical Report – 4502 NE 4th St, Renton, Washington Page 6
GEO Group Northwest, Inc.
1. Be free draining, granular material containing no more than five (5) percent fines (silt and
clay-size particles passing the No. 200 mesh sieve);
2. Be free of organic material and other deleterious substances, such as construction debris
and garbage;
3. Have a maximum size of three (3) inches in diameter.
All fill material should be placed at or near the optimum moisture content. The optimum
moisture content is the water content in soil that enables the soil to be compacted to the highest
dry density for a given compaction effort.
Based upon our subsurface investigation the overlying apparent fill site soils consist of sandy
SILT and silty SAND with some organic soils and debris. These soils are relatively silty and
may be difficult to compact to meet the minimum structural fill compaction requirements. If
work occurs during a period of wet weather it is likely that the native site soils may become too
wet to achieve the compaction criteria. We recommend that the contractor take measures to
protect the site soils from wet weather impacts such as using plastic sheeting to cover stockpiles.
Additionally all unsuitable debris such as concrete, wood, organic soil, plastic sheeting and other
deleterious materials must be removed from the site soils if they are to be used as structural fill.
An imported granular fill material may provide more uniformity and be easier to compact to the
required structural fill specification, especially if work occurs during periods of wet weather.
Structural fill should be placed in thin horizontal lifts not exceeding ten inches in loose thickness.
Structural fill under building areas (including foundation and slab areas), should be compacted to
at least 95 percent of the maximum dry density, as determined by ASTM Test Designation D-
1557-91 (Modified Proctor).
Structural fill under driveways, parking lots and sidewalks should be compacted to at least 90
percent maximum dry density, as determined by ASTM Test Designation D-1557-91 (Modified
Proctor). Fill placed within 12-inches of finish grade should meet the 95% requirement.
We recommend that GEO Group Northwest, Inc., be retained to evaluate the suitability of
structural fill material and to monitor the compaction work during construction for quality
assurance of the earthwork.
May 14, 2018 G-4661
Geotechnical Report – 4502 NE 4th St, Renton, Washington Page 7
GEO Group Northwest, Inc.
Building Pad Improvement
The observed overlying loose soils and fills observed at the test pits present risks of soil
settlement related damage to proposed building if the building is constructed to bear on top of
these soils. Consequently we recommend that the building pad areas on which foundations and
any building slabs are to be constructed be over-excavated to remove loose fills, organic soils
and deleterious debris to a depth where the underlying medium dense to dense soils are
encountered and then replaced with compacted structural fill as required, dependent upon the
proposed building/floor elevations. These fills and unacceptable loose soils were observed at
depths as deep as 9-feet below the existing ground surface at the test pit TP-3. Following
removal of the unsuitable loose soils and debris fills the base of the excavation should be
compacted by vibratory equipment to a firm and unyielding condition, approved by GEO Group
Northwest and then backfilled with compacted structural fill placed in accordance with the
Structural Fill section of this report. The over-excavation and fill placement at the building pad
area is expected to require a significant amount of earthwork and may also present difficulties if
loose and unsuitable fills are encountered at the base of the existing block wall at the west side of
the site since this would necessitate shoring for the adjacent right-of-way. New building
foundations and slabs may be constructed to bear on the compacted structural fill which is in turn
placed on top of the competent medium dense to dense underlying soils.
Spread Footing Foundations
The proposed buildings can be supported on conventional spread footings bearing on top of an
improved building pad constructed per our recommendations noted above and which has been
approved by GEO Group Northwest, Inc., at the time of construction.
Individual spread footings may be used for supporting columns and strip footings for bearing
walls. Our recommended minimum design criteria for foundations bearing on improved building
pad or on compacted structural fill placed on top of the improved building pad are as follows:
- Allowable bearing pressure, including all dead and live loads
Medium dense to dense native soils (competent soils) = 2,000 psf
Compacted structural fill on top of competent soil (improved building pad) = 2,000 psf
- Minimum depth to bottom of perimeter footing below adjacent final exterior grade = 18
inches
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GEO Group Northwest, Inc.
- Minimum depth to bottom of interior footings below top of floor slab = 18 inches
- Minimum width of wall footings = 16 inches
- Minimum lateral dimension of column footings = 24 inches
- Estimated post-construction settlement = 1/4 inch
- Estimated post-construction differential settlement; across building width = 1/4 inch
A one-third increase in the above allowable bearing pressures can be used when considering
short-term transitory wind or seismic loads.
Lateral loads can also be resisted by friction between the foundation and the supporting
compacted fill subgrade or by passive earth pressure acting on the buried portions of the
foundations. For the latter, the foundations must be poured "neat" against the existing
undisturbed soil or be backfilled with a compacted fill meeting the requirements for structural
fill. Our recommended parameters are as follows:
- Passive Pressure (Lateral Resistance)
• 350 pcf equivalent fluid weight for compacted structural fill
• 350 pcf equivalent fluid weight for native dense soil.
- Coefficient of Friction (Friction Factor)
• 0.35 for compacted structural fill
• 0.35 for native dense soil
We recommend that footing drains be placed around all perimeter footings. More specific
details of perimeter foundation drains are provided below in the section titled: Subsurface
Drainage.
Conventional Retaining Walls and Basement Walls
Based upon the preliminary plans we understand that conventional concrete retaining walls are
proposed for the below-grade portions of the building and this may be at the lower level at the
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GEO Group Northwest, Inc.
south side of the site. These walls should be constructed on top of footings which bear on the
building pad improvement discussed above or on top of augercast concrete piles.
Permanent retaining walls restrained horizontally on top (such as basement walls) are considered
unyielding and should be designed for a lateral soil pressure under the at-rest condition; while
conventional reinforced concrete walls free to rotate on top should be designed for an active
lateral soil pressure.
Active Earth Pressure
Conventional reinforced concrete walls that are designed to yield an amount equal to
0.002 times the wall height, should be designed to resist the lateral earth pressure
imposed by an equivalent fluid with a unit weight of 35 pcf for level backfill;
At-Rest Earth Pressure
Walls supported horizontally by floor slabs are considered unyielding and should be
designed for lateral soil pressure under the at-rest condition. The design lateral soil
pressure should have an equivalent fluid pressure of 40 pcf for level backfill;
Seismic Surcharge
For the anticipated 100 year seismic event a horizontal surcharge load of 8H psf should
be applied;
Passive Earth Pressure
350 pcf equivalent fluid weight for compacted structural fill and native undisturbed soil;
Base Coefficient of Friction
0.35 for compacted structural fill and native undisturbed soil;
To prevent the buildup of hydrostatic pressure behind permanent concrete basement or
conventional retaining walls, we recommend that a vertical drain mat, such as Miradrain 6000 or
equivalent, be used to facilitate drainage behind such walls. The drain mat core should be placed
against the wall(s) with the filter fabric side facing the backfill. The drain mat should extend
from near the finished surface grade down to the footing drain system. Additionally all backfill
placed between the excavation slopes or temporary shoring and the new basement/retaining walls
should consist of free-draining fills having less than 5% passing the No. 200 sieve. Also, a
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GEO Group Northwest, Inc.
waterproofing layer should be placed between the drainage mat layer and the concrete wall, for
moisture protection at all basement wall locations.
The top 12 inches of backfill behind retaining or basement walls should consist of compacted
and relatively impermeable soil. This cap material can be separated from the underlying more
granular drainage material by a geotextile fabric, if desired. Alternatively, the surface can be
sealed with asphalt or concrete paving. Where possible the ground surface should be sloped to
drain away from the wall.
GEO Group Northwest, Inc., recommends that backfill material which will support structures or
improvements (such as patios, sidewalks, driveways, etc.) behind permanent concrete retaining
walls and basement walls be placed and compacted consistent with the structural fill
specifications in the Structural Fill section of this report.
Slab-on-Grade Concrete Floors
Slab-on-grade concrete floors may be constructed directly on top of the native medium dense to
dense site soils or on top of compacted structural fills placed on top of the medium dense to
dense site soils (building pad improvement). If structural fills are to be placed at these areas then
they should be compacted in accordance with the specifications in the section titled: Structural
Fill.
To avoid moisture build-up on the subgrade, slab-on-grade concrete floors should be placed on a
capillary break, which is in turn placed on the prepared subgrade. The capillary break should
consist of a minimum of a six (6) inch thick layer of free-draining crushed rock or gravel
containing no more than five (5) percent finer than the No. 4 sieve. A vapor barrier, such as a
10-mil plastic membrane, is recommended to be placed over the capillary break beneath the slab
to reduce water vapor transmission through the slab. Two to four inches of sand may be placed
over the barrier membrane for protection during construction.
Subsurface Drainage
We recommend that subsurface drains, footing drains, be installed around the perimeter of the
foundation footings. The drains should consist of a four (4) inch minimum diameter perforated
rigid drain pipe laid at or near the bottom of the footing with a gradient sufficient to generate
flow. The drain line should be bedded on, surrounded by, and covered with a free-draining rock,
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GEO Group Northwest, Inc.
pea gravel, or other free-draining granular material. The drain rock and drain line should be
completely surrounded by a geotextile filter fabric, Mirafi 140N or equivalent. Once the drains
are installed, the excavation should be backfilled with a compacted fill material. The footing
drains should be tightlined to discharge to the stormwater collection system.
Under no circumstances should roof downspout drain lines be connected to the footing drainage
system. All roof downspouts must be separately tightlined to discharge into the stormwater
collection system. We recommend that sufficient cleanouts be installed at strategic locations to
allow for periodic maintenance of the footing drains and downspout tightline systems.
Augercast Concrete Pile Foundations
An alternative to implementing the building pad improvement noted above the new building may
be supported on augercast concrete piles that are embedded at least 10-feet into the underlying
dense native soils which are anticipated at a depth of around 10-feet below the ground surface.
Implementing this option may allow for less excavation at the site and may reduce the risk that
temporary shoring will be necessary. Concrete grade beams should be used to connect the pile
foundations and distribute the building loads. A structural concrete slab may be designed and
constructed to support the slab loads and transfer these loads to the piling. Based upon the depth
to competent soils at the test pits we estimate pile lengths may be on the order of 20-feet with 10-
foot embedment into the competent dense soil. The piles should be designed with a minimum
diameter of 14 inches. For concrete piles 14 to 18 inches in diameter embedded 10 feet into the
underlying dense soils, the following allowable bearing capacities may be used:
AUGERCAST CONCRETE PILE CAPACITIES
Pile Diameter
(Inches)
Pile Embedment
(Feet)
Allowable Bearing
(Tons)
Allowable Uplift
(Tons)
14 10 13 6.5
16 10 16 8
18 10 19 9.5
Note: Pile embedment length is based on the embedment depth below the top of the dense, native soil.
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GEO Group Northwest, Inc.
No reduction in pile capacity is required if the pile spacing is at least three times the pile
diameter. A one-third increase in the above allowable pile capacities can be used when
considering short-term transitory wind or seismic loads.
Lateral forces can also be resisted by the passive earth pressures acting on the grade beams and
friction with the subgrade. To fully mobilize the passive pressure resistance, the grade beams
must be poured “neat” against compacted fill. Our recommended allowable passive soil pressure
for lateral resistance is 350 pcf (pounds per cubic foot) equivalent fluid weight. A coefficient of
friction of 0.35 may be used between the subgrade and the grade beams. We estimate that the
maximum total post-construction settlement should be one-half (1/2) inch or less, and the
differential settlement across building width should be one-quarter (1/4) inch or less.
The performance of piles depends on how and to what bearing stratum the piles are installed. It
is critical that judgement and experience be used as a basis for determining the embedment
length and acceptability of a pile. Therefore, we recommend that GEO Group Northwest, Inc.,
be retained to monitor the pile installation operation, collect and interpret installation data, and
verify suitable bearing stratum. We also suggest that the contractor’s equipment and installation
procedure be reviewed by GEO Group Northwest, Inc., prior to pile installation to help mitigate
problems which may delay work progress.
ADDITIONAL SERVICES
GEO Group Northwest, Inc., can provide additional exploration and testing services for the
project such as infiltration rate testing if it is determined to be necessary. We recommend that
GEO Group Northwest Inc. be retained to perform a general plan review of the final design and
specifications for the proposed development to verify that the earthwork and foundation
recommendations have been properly interpreted and implemented in the design and in the
construction documents. We also recommend that GEO Group Northwest Inc. be retained to
provide monitoring and testing services for geotechnically-related work during construction.
This is to observe compliance with the design concepts, specifications or recommendations and
to allow design changes in the event subsurface conditions differ from those anticipated prior to
the start of construction. We anticipate the following construction monitoring inspections may
be necessary:
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GEO Group Northwest, Inc.
1. Site clearing and grubbing;
2. Grading of temporary excavation slopes;
3. Preparation of building foundation subgrades;
4. Over-excavation and structural fill placement at building pad improvement areas, removal of
unsuitable fill soils;
5. Permanent subsurface drainage installation;
6. Installation of augercast piling, if implemented;
LIMITATIONS
This report has been prepared for the specific application to this site for the exclusive use of 4th
Creek Meadows LLC and their authorized representatives. Any use of this report by other
parties is solely at that party’s own risk. We recommend that this report be included in its
entirety in the project contract documents for reference during construction.
Our findings and recommendations stated herein are based on field observations, our experience
and judgement. The recommendations are our professional opinion derived in a manner
consistent with the level of care and skill ordinarily exercised by other members of the
profession currently practicing under similar conditions in this area and within the budget
constraint. No warranty is expressed or implied. In the event that soil conditions not anticipated
in this report are encountered during site development, GEO Group Northwest, Inc., should be
notified and the above recommendations should be re-evaluated.
If you have any questions, or if we may be of further service, please do not hesitate to contact us.
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GEO Group Northwest, Inc.
Sincerely,
GEO GROUP NORTHWEST, INC.
Adam Gaston
Project Engineer
William Chang, P.E.
Principal
Attachments: Plate 1 – Vicinity Map
Plate 2 – Site Plan
Plate 3 – Topographic Map
Plate 4 – SCS Soil Map
Plates 5 – 6 – Gradational Analyses
Appendix A – USCS Soil Legend and Test Pit Logs
cc: Mr. Martin Reimer – Kaul Design Associates
APPENDIX A
TEST PIT LOGS AND USCS SOIL LEGEND
G-4661
CLEAN
GRAVELS
GW
(little or no
fines)GP
DIRTY
GRAVELS
GM
(with some
fines)GC
CLEAN
SANDS
SW
(little or no
fines)SP < 5% Fine Grained:
GW, GP, SW, SP
DIRTY
SANDS
SM > 12% Fine Grained:
GM, GC, SM, SC
(with some
fines)SC
5 to 12% Fine
Grained: use dual
symbols
Liquid Limit
< 50%ML
Liquid Limit
> 50%MH
Liquid Limit
< 30%CL
Liquid Limit
> 50%CH
Liquid Limit
< 50%OL
Liquid Limit
> 50%OH
Pt
Sieve Size
(mm)Sieve Size
(mm)
SILT / CLAY #200 0.075
SAND 0 - 4 0 -15 Very Loose < 2 < 0.25 Very soft
FINE #40 0.425 #200 0.075 4 - 10 15 - 35 26 - 30 Loose 2 - 4 0.25 - 0.50 Soft
MEDIUM #10 2 #40 0.425 10 - 30 35 - 65 28 - 35 Medium Dense 4 - 8 0.50 - 1.00 Medium Stiff
COARSE #4 4.75 #10 2 30 - 50 65 - 85 35 - 42 Dense 8 - 15 1.00 - 2.00 Stiff
GRAVEL > 50 85 - 100 38 - 46 Very Dense 15 - 30 2.00 - 4.00 Very Stiff
FINE 19 #4 4.75 > 30 > 4.00 Hard
COARSE 76 19
COBBLES
BOULDERS
ROCK
FRAGMENTS
ROCK PLATE A1
CONTENT OF
FINES
EXCEEDS
12%
Cu = (D60 / D10) greater than 6
Cc = (D302 ) / (D10 * D60) between 1 and 3
Cu = (D60 / D10) greater than 4
Cc = (D302 ) / (D10 * D60) between 1 and 3
SILTY & CLAYEY SOILS
Blow
Counts
N
Unconfined
Strength
qu, tsf
Description
Bellevue, WA 98005
NOT MEETING ABOVE REQUIREMENTS
Fax (425) 649-8758Phone (425) 649-8757
Blow
Counts
N
Relative
Density
%
Friction
Angle
N, degree
Description
> 76 mm
>0.76 cubic meter in volume
13240 NE 20th Street, Suite 10
DETERMINE
PERCENTAGES OF
GRAVEL AND SAND
FROM GRAIN SIZE
DISTRIBUTION
CURVE
COARSE GRAINED
SOILS ARE
CLASSIFIED AS
FOLLOWS:SANDS
(More Than Half
Coarse Grains
Smaller Than No.
4 Sieve)
SILTS
(Below A-Line on
Plasticity Chart,
Negligible
Organic)
CLAYS
(Above A-Line on
Placticity Chart,
Negligible
Organic)
HIGHLY ORGANIC SOILS
NOT MEETING ABOVE REQUIREMENTS
UNIFIED SOIL CLASSIFICATION SYSTEM (USCS)
LEGEND OF SOIL CLASSIFICATION AND PENETRATION TEST
CONTENT
OF FINES
EXCEEDS
12%
ATTERBERG LIMITS BELOW
"A" LINE.
or P.I. LESS THAN 4
ATTERBERG LIMITS ABOVE
"A" LINE.
or P.I. MORE THAN 7
CLAYEY GRAVELS, GRAVEL-SAND-CLAY
MIXTURES
TYPICAL DESCRIPTION LABORATORY CLASSIFICATION CRITERIA
ATTERBERG LIMITS BELOW
"A" LINE
with P.I. LESS THAN 4
ATTERBERG LIMITS ABOVE
"A" LINE
with P.I. MORE THAN 7
U.S. STANDARD SIEVE
SOIL PARTICLE SIZE
FRACTION Passing Retained
GENERAL GUIDANCE OF SOIL ENGINEERING PROPERTIES FROM STANDARD PENETRATION TEST (SPT)
SANDY SOILS
INORGANIC CLAYS OF HIGH PLASTICITY, FAT
CLAYS
ORGANIC SILTS AND ORGANIC SILTY CLAYS OF
LOW PLASTICITY
ORGANIC CLAYS OF HIGH PLASTICITY
PEAT AND OTHER HIGHLY ORGANIC SOILS
CLAYEY SANDS, SAND-CLAY MIXTURES
INORGANIC SILTS, ROCK FLOUR, SANDY SILTS
OF SLIGHT PLASTICITY
INORGANIC SILTS, MICACEOUS OR
DIATOMACEOUS, FINE SANDY OR SILTY SOIL
INORGANIC CLAYS OF LOW PLASTICITY,
GRAVELLY, SANDY, OR SILTY CLAYS, CLEAN
CLAYS
WELL GRADED SANDS, GRAVELLY SANDS,
LIITLE OR NO FINES
POORLY GRADED SANDS, GRAVELLY SANDS,
LITTLE OR NO FINES
SILTY SANDS, SAND-SILT MIXTURES
WELL GRADED GRAVELS, GRAVEL-SAND
MIXTURE, LITTLE OR NO FINES
POORLY GRADED GRAVELS, AND GRAVEL-
SAND MIXTURES LITTLE OR NO FINES
SILTY GRAVELS, GRAVEL-SAND-SILT MIXTURES
> 203 mm
FINE-GRAINED
SOILS
More Than Half
by Weight
Smaller Than No.
200 Sieve
MAJOR DIVISION GROUP
SYMBOL
76 mm to 203 mm
ORGANIC SILTS
& CLAYS
(Below A-Line on
Placticity Chart)
More Than Half
by Weight Larger
Than No. 200
Sieve
COARSE-
GRAINED SOILS
GRAVELS
(More Than Half
Coarse Grains
Larger Than No. 4
Sieve)
0
10
20
30
40
50
60
0 10 20 30 40 50 60 70 80 90 100 110PLASTICITY INDEX (%)LIQUID LIMIT (%)
CL-ML
CL or OL
MH or OH
OL or ML
A-LinePLASTICITY CHART
FOR SOIL PASSING
NO. 40 SIEVE
7
4
CH or OH
Geotechnical Engineers, Geologists, &
Environmental Scientists
GEO Group Northwest, Inc.
TEST PIT NO. TP-1
LOGGED BY AG TEST PIT DATE:04/18/2018
DEPTH SAMPLE Water OTHER TESTS/
ft.USCS SOIL DESCRIPTION No.%COMMENTS
5
10
15
TEST PIT NO. TP-2
LOGGED BY AG TEST PIT DATE:04/18/2018
DEPTH SAMPLE Water OTHER TESTS/
ft.USCS SOIL DESCRIPTION No.%COMMENTS
5
10
15
TEST PIT LOGS
PROPOSED DEVELOPMENT
4502 NE 4TH ST
RENTON, WA
DATE 4/19/18 PLATE A2JOB NO. G-4661
Total depth of test pit = 7 feet bgs No groundwater seepage
Competent dense soils below 4-feet bgs SCS Classification: AgC
Geotechnical Engineers, Geologists, &
Environmental Scientists
GEO Group Northwest, Inc.
S-1
Total depth of test pit = 6.5 bgs No groundwater seepage Mottled soils from 5 to 6-feet bgs Competent dense soils below 5-feet bgs
SCS Classification: AgC
Dark brown to tan silty SAND with gravel and gravelly silty SAND,
moist, variable density - dense to loose, also containing trace debris, bone, ceramics and spoon (FILL)
SM
Brown to tan gravelly silty SAND to gravelly sandy SILT, moist,
Brown silty SAND with brick debris, moist, loose (FILL)
SM/
ML
SM
Gray and mottled gravelly sandy SILT and gravelly silty SAND,
cemented, moist, dense (TILL)
S-2
Tan gravelly silty SAND to gravelly sandy SILT, moist, dense,
cemented below 5.5-ft bgs (TILL)
SM/
ML
S-1
10.5
10.8
S-3
S-2
23.8
14.1
11.5 SM/
ML
TEST PIT NO. TP-3
LOGGED BY AG TEST PIT DATE:04/18/2018
DEPTH SAMPLE Water OTHER TESTS/
ft.USCS SOIL DESCRIPTION No.%COMMENTS
5
10
15
TEST PIT NO. TP-4
LOGGED BY AG TEST PIT DATE:04/18/2018
DEPTH SAMPLE Water OTHER TESTS/
ft.USCS SOIL DESCRIPTION No.%COMMENTS
5
10
15
TEST PIT LOGS
PROPOSED DEVELOPMENT
4502 NE 4TH ST
RENTON, WA
DATE 4/19/18 PLATE A3JOB NO. G-4661
Total depth of test pit = 9-ft - 8-inches bgs (max excavator depth) No groundwater seepage Competent dense soils below 9-ft bgs
SCS Classification: EgB (below fill)
Geotechnical Engineers, Geologists, &
Environmental Scientists
GEO Group Northwest, Inc.
S-1
Total depth of test pit = 8-ft - 3-inches bgs Significant groundwater seepage at 7-ft bgs - prevented further exploration due to caving gravels
Competent dense soils below 8-ft bgs SCS Classification: EgB (below fill)
Brown and gray gravelly sandy SILT, SILT and silty SAND with
plastic sheeting, organic material and debris, moist, variable dense to loose (FILL), fill includes concrete and asphalt debris observed at a depth of 8-feet bgs
SM/ML
Gray gravelly sandy SILT, moist, dense (FILL)
Brown gravelly fine silty SAND and drain rock zones, moist, loose (FILL)
ML
SM
Gravelly SAND and sandy GRAVEL with some cobbles, wet,
apparent dense soil at 8-ft bgs
S-2
Brown fine to medium SAND with some silt, moist, dense
S-1
9.7
23.1
S-3
S-2
10.9
21.0
12.6 SP/
GP
S-4 13.5 SP-SM
Brown gravelly SAND with some silt and occasional cobbles, moist, loose (APPARENT FILL) SP-
SM
TEST PIT NO. TP-5
LOGGED BY AG TEST PIT DATE:04/18/2018
DEPTH SAMPLE Water OTHER TESTS/
ft.USCS SOIL DESCRIPTION No.%COMMENTS
5
10
15
TEST PIT NO.
LOGGED BY TEST PIT DATE:
DEPTH SAMPLE Water OTHER TESTS/
ft.USCS SOIL DESCRIPTION No.%COMMENTS
5
10
15
TEST PIT LOGS
PROPOSED DEVELOPMENT
4502 NE 4TH ST
RENTON, WA
DATE 4/24/18 PLATE A4JOB NO. G-4661
Total depth of test pit = 7-ft bgs
Groundwater seepage at 5-ft bgs Competent dense soils below 3.5-ft bgs SCS Classification: EgB (below fill)
Geotechnical Engineers, Geologists, &
Environmental Scientists
GEO Group Northwest, Inc.
S-1 Tan cobbly and gravelly silty SAND, moist, medium dense (FILL)
SM
S-2 Dark brown gravelly silty SAND, moist, medium dense
18.5
S-3
16.6
19.9
SM
Gray gravelly sandy SILT, moist, dense (FILL)
SM
Dark brown silty SAND grading to gravelly SAND / sandy GRAVEL with some cobbles, moist to wet, dense
SM/SP-GP
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VII. OTHER PERMITS
No other special storm drainage permits are required for the proposed work.
Clearing and Grading and Utility permits will be required for the infrastructure installation.
Sewer and water infrastructure permits will be required for the utility connections.
NPDES Permit will not be required from the Department of Ecology, as the site is less than 1
acre in size.
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VIII. CSWPPP ANALYSIS AND DESIGN
PART A: ESC PLAN DESIGN AND ANALYSIS
The minimum requirements of Core Requirement #5: Temporary Erosion and Sedimentation
Control are as follows:
CLEARING LIMITS
D.3.1.1, Plastic Clearing Limits Fencing. The clearing limits and trees to be saved will be marked
in the field with orange clearing limits fencing prior to any construction activities.
COVER MEASURES
Temporary cover will be provided for all areas to remain unworked for more than 7 days during
the dry season and more than 2 days during the wet season. Any areas to remain unworked for
more than 30 days will be seeded. Specific cover measures are listed below:
D.3.2.1, Slope Roughening. This will be used on slopes greater than 3:1 and greater than 5 feet
in height. It will reduce flow velocities until vegetation becomes established. This is commonly
accomplished by tracking equipment un and down the slope to leave horizontal depressions in
the soil.
D.3.2.2, Mulching. During construction, mulch can be placed to prevent raindrops from
impacting exposed soils causing erosion. Straw is the most common method of mulching. This
BMP is one of the options that can be employed to meet the temporary cover requirements:
D.3.2.4, Plastic Covering:
This involves covering a bare area with clear plastic that provides immediate protection,
especially of uncompacted soils such as stockpiles. This BMP will be used on this site for areas
requiring immediate protection and for stockpiles. This BMP is employed to meet the
temporary cover requirements:
D.3.2.6, Temporary & Permanent Seeding. Temporary seeding of topsoil stockpiles and other
stripped areas will be necessary during construction depending on weather conditions and the
use of other temporary cover BMP’s. All exposed surfaces will be final seeded or landscaped
when construction is completed. This BMP will be employed to meet the temporary cover
requirements as well as supplying permanent cover upon completion of the project.
PERIMETER PROTECTION
D.3.3.1, Silt Fence. Filter fabric fencing will be installed, where necessary, downslope of all
disturbed areas to filter runoff before it leaves the site.
Filter fabric inserts will also be placed in the catch basins along the fronting streets as additional
sediment collection.
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TRAFFIC AREA STABILIZATION
D.3.4.1, Stabilized Construction Entrance. The existing gravel site access drive will be used for
the construction entrance. This will help to prevent vehicle tires from transporting sediment
off‐site.
D3.4.2, Construction Road Stabilization. Construction road stabilization will be used on this site.
This involves covering the road with crushed rock, gravel base or crushed surfacing base course
to protect exposed erosion sensitive soil from rainfall. Much of the parking area is gravel and
already stabilized.
Dust Control will be used on this site during construction activities when dry weather causes
loose soil to be transported by the wind. The soil will be moistened with water to hold down
the dust. This BMP will be performed routinely during dry weather construction.
SEDIMENT RETENTION
D.3.5.2, Sediment Pond. With the site being less than one acre of disturbed area it should not
be necessary to construct a sediment pond. In addition much of the area will be stabilized with
temporary gravel paving and the building slab itself once construction commences. If necessary
the detention vault can be configured as a sedimentation pond.
D.3.5.3, Storm Drain Inlet Protection. Silt sacks will be installed in the existing catch basins on
and near the site and in the new catch basins as they are installed. This will trap coarse
sediment; preventing it from being conveyed downstream.
SURFACE WATER CONTROL
The site currently contains a storm drainage system that collects site runoff. Clean construction
runoff will be directed to this system.
DE‐WATERING CONTROL
Generally, de‐watering is not expected to be needed on the site. If pumping is necessary, the
discharge will be directed to a portable sediment tanks, such as a Baker tank prior to discharge
from the site.
DUST CONTROL
The proposed timing, during the dry months, will increase the chance of wind born material to
leave the site. The application of water to bare and dry soil will occur as conditions dictate.
FLOW CONTROL
With installation of the detention facility early in construction and by directing site runoff to the
vault, the increases in runoff due to the changing site cover characteristics will be mitigated.
WET SEASON CONSTRUCTION
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The site work for this project is expected to occur during the Summer of 2018. However if
delays occur the completion date may extend into the wet season (October 1 through April 30).
No soil shall remain exposed for more than 2 consecutive working days. In addition any exposed
soils shall be stabilized at the end of the workday prior to a weekend, holiday or predicted rain
event. During wet season construction, additional erosion control measures may be required.
These include but are not limited to additional filter fabric fencing, rock and straw bale check
dams, mulching and plastic sheeting.
CRITICAL AREA RESTRICTIONS
There are no critical areas on or adjacent to the site.
POLLUTION PREVENTION & SPILL PREVENTION AND CLEANUP REPORT
For additional information see the Pollution Prevention & Spill Prevention and Cleanup Report.
CERTIFIED EROSION CONTROL SPECIALIST
The project will result in less than 1 acre of disturbance. As such a Certified Professional in
Erosion and Sediment Control or a Certified Erosion and Sediment Control Lead is not required.
TURBIDITY REQUIREMENTS
The ESC supervisor or the County may determine at any time during construction that the
approved ESC measures are not sufficient and that additional action is required based on one of
the following criteria:
1. IF a turbidity test of surface and storm water discharges leaving the project site is
greater than the benchmark value of 25 NTU (nephelometric turbidity units) set by the
Washington State Department of Ecology, but less than 250 NTU, the ESC Supervisor
shall do all of the following:
a) Review the ESC plan for compliance and make appropriate revisions within 7
days of the discharge that exceeded the benchmark of 25 NTU, AND
b) Fully implement and maintain appropriate ESC measures as soon as possible
but no later than 10 days after the discharge that exceeded the benchmark, AND
c) Document ESC implementation and maintenance in the site log book.
2. IF a turbidity test of surface or storm water entering onsite wetlands, streams, or
lakes indicates a turbidity level greater than 5 NTU above background when the
background turbidity is 50 NTU or less, or 10% above background when the background
turbidity is greater than 50 NTU, then corrective actions and/or additional measures
beyond those specified in Section 1.2.5.1 shall be implemented as deemed necessary by
the County inspector or onsite ESC supervisor.
3. IF discharge turbidity is 250 NTU or greater, the ESC Supervisor shall do all of the
following:
a) Notify the County by telephone, AND
b) Review the ESC plan for compliance and make appropriate revisions within 7
days of the discharge that exceeded the benchmark of 25 NTU, AND
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c) Fully implement and maintain appropriate ESC measures as soon as possible
but no later than 10 days after the discharge that exceeded the benchmark, AND
d) Document ESC implementation and maintenance in the site log book. AND
e) Continue to sample discharges until turbidity is 25 NTU or lower, or the
turbidity is no more than 10% over background turbidity.
4. IF the County determines that the condition of the construction site poses a hazard to
adjacent property or may adversely impact drainage facilities or water resources, THEN
additional measures beyond those specified in Section 1.2.5.1 may be required by the
County.
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PART B: SWPPS PLAN DESIGN
Those BMPs contained in Volume II of the current DOE Manual will be used to control pollution
from sources other than sedimentation. Volume II of the DOE Manual shall also be reviewed
during construction if any other BMPs become relevant.
STORAGE AND HANDLING OF LIQUIDS
Cover, containment, and protection from vandalism shall be provided for all chemicals, liquid
products, petroleum products, solvents, detergents, paint, pesticides, concrete admixtures and
non‐inert wastes present on the site (see Chapter 173‐304 WAC for the definition of inert
waste). Secondary containment systems shall be sized to adequately provide for containment
of all liquids on site.
STORAGE AND STOCKPILING OF CONSTRUCTION MATERIALS AND WASTES
All pollutants, including waste materials and demolition debris, that occur on site during
construction shall be handled and disposed of in a manner that does not cause contamination
of stormwater. Woody debris may be chopped and spread on site.
FUELING
Cover, containment, and protection from vandalism shall be provided for all chemicals, liquid
products, petroleum products, and non‐inert wastes present on the site (see Chapter 173‐304
WAC for the definition of inert waste).
MAINTENANCE, REPAIRS AND STORAGE OF VEHICLES AND EQUIPMENT
Maintenance and repair of heavy equipment and vehicles involving oil changes, hydraulic
system drain down, solvent and de‐greasing cleaning operations, fuel tank drain down and
removal, and other activities which may result in discharge or spillage of pollutants to the
ground or into stormwater runoff must be conducted using spill prevention measures, such as
drip pans. Contaminated surfaces shall be cleaned immediately following any discharge or spill
incident. Emergency repairs may be performed on‐site using temporary plastic placed beneath
and, if raining, over the vehicle.
CONCRETE SAW CUTTING, SLURRY AND WASHWATER DISPOSAL
Concrete saw water, wheel wash or tire bath wastewater shall be discharged to a separate on‐
site treatment system or to the sanitary sewer.
HANDLING OF Ph ELEVATED WATER
BMP’s shall be used to prevent or treat contamination of stormwater runoff by pH modifying
sources. These sources include bulk cement, cement kiln dust, fly ash, new concrete washing
and curing waters, waste streams generated from concrete grinding and sawing, exposed
aggregate processes, and concrete pumping and mixer washout waters. Stormwater runoff
shall not cause a violation of the water quality standard for pH in the receiving water.
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APPLICATION OF CHEMICALS INCLUDING PECTICIDES AND FERTILIZERS
Application of agricultural chemicals including fertilizers and pesticides shall be conducted in a
manner and at application rates that will not result in loss of chemical to stormwater runoff.
Manufacturers’ recommendations for application rates and procedures shall be followed.
303d LISTINGS REVIEW
The Washington State Department of Ecology Water Quality Atlas Map has been reviewed for
any 303d listings associated with the downstream drainage system. A portion of the
Maplewood Creek, at a distance of about 7,000 feet from the site, is listed as Category 5 for
Bioassesment. Further downstream the Cedar River is listed as Category 5 for pH, temperature
and dissolved oxygen levels. See figures in Appendix B.
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IX. BOND QUANTITIES WORKSHEET, RETENTION/ DETENTION FACILITY
SUMMARY SHEET
King County’s Bond Quantity worksheet for the site and storm drainage improvements follow.
The Flow Control and Water Quality Facility Summary Sheets follow.
The Draft Declaration of Covenant for Privately Maintained Drainage Facilities & Onsite BMPS
follow.
Planning Division |1055 South Grady Way – 6th Floor | Renton, WA 98057 (425) 430‐7200Date Prepared: Name:PE Registration No:Firm Name:Firm Address:Phone No.Email Address:Project Name:Project Owner:SITE IMPROVEMENT BOND QUANTITY WORKSHEETPROJECT INFORMATIONEngineer Stamp Required (all cost estimates must have original wet stamp and signature)Project Location and Description Project Owner Information4thDimensionMixedUse4th Creek Meadows LLCDatePrepared by:FOR APPROVALProject Phase 1stephenm@harmsenllc.comStephen Mason35197Harmsen LLC125 East Main Street, Monroe, WA 98272360‐794‐7811Project Name: Project Owner:CED Plan # (LUA): Phone:CED Permit # (U):Address: Site Address:Street Intersection: Addt'l Project Owner:Parcel #(s): Phone:Address: Clearing and grading greater than or equal to 5,000 board feet of timber? Yes/No:NOWater Service Provided by:If Yes, Provide Forest Practice Permit #:Sewer Service Provided by: CITY OF RENTONCITY OF RENTON1 Select the current project status/phase from the following options: For Approval ‐ Preliminary Data Enclosed, pending approval from the City; For Construction ‐ Estimated Data Enclosed, Plans have been approved for contruction by the City; Project Closeout ‐ Final Costs and Quantities Enclosed for Project Close‐out SubmittalPhoneClearing and Grading Utility ProvidersN/A4th Dimension Mixed UseBellevue, WA 98005102305‐90684th Creek Meadows LLC##‐###### Phone4502 NE 4th Street12505 NE Bellevue‐Redmond Rd, #512Additional Project OwnerNE 4th Street & Bremerton Ave NE########AddressAbbreviated Legal Description:S 290.4 FT OF W 1/2 OF SW 1/4 OF SE 1/4 OF SW 1/4 LESS E 203 FT LESS CO RDCity, State, ZipPage 1 of 1Ref 8‐H Bond Quantity WorksheetSECTION I PROJECT INFORMATIONUnit Prices Updated: 06/14/2016Version: 04/26/2017Printed 6/3/2021
CED Permit #:########Existing Future Public PrivateRight‐of‐Way Improvements Improvements(D) (E)Description No. Unit Price Unit Quant. Cost Quant. Cost Quant. Cost Quant. CostGENERAL ITEMSBackfill & Compaction‐ embankment GI‐1 6.00$ CYBackfill & Compaction‐ trench GI‐2 9.00$ CYClear/Remove Brush, by hand (SY) GI‐3 1.00$ SYBollards ‐ fixed GI‐4 240.74$ EachBollards ‐ removable GI‐5 452.34$ EachClearing/Grubbing/Tree Removal GI‐6 10,000.00$ Acre 0.454,500.00Excavation ‐ bulk GI‐7 2.00$ CY 9001,800.00Excavation ‐ Trench GI‐8 5.00$ CYFencing, cedar, 6' high GI‐9 20.00$ LFFencing, chain link, 4' GI‐10 38.31$ LFFencing, chain link, vinyl coated, 6' high GI‐11 20.00$ LFFencing, chain link, gate, vinyl coated, 20' GI‐12 1,400.00$ EachFill & compact ‐ common barrow GI‐13 25.00$ CY 60015,000.00340085,000.00Fill & compact ‐ gravel base GI‐14 27.00$ CYFill & compact‐screened topsoilGI‐1539 00$CYSITE IMPROVEMENT BOND QUANTITY WORKSHEETFOR STREET AND SITE IMPROVEMENTSQuantity Remaining (Bond Reduction) (B) (C)Fill & compact screened topsoilGI 1539.00$ CYGabion, 12" deep, stone filled mesh GI‐16 65.00$ SYGabion, 18" deep, stone filled mesh GI‐17 90.00$ SYGabion, 36" deep, stone filled mesh GI‐18 150.00$ SYGrading, fine, by hand GI‐19 2.50$ SYGrading, fine, with grader GI‐20 2.00$ SYMonuments, 3' Long GI‐21 250.00$ EachSensitive Areas Sign GI‐22 7.00$ EachSodding, 1" deep, sloped ground GI‐23 8.00$ SYSurveying, line & grade GI‐24 850.00$ DaySurveying, lot location/lines GI‐25 1,800.00$ AcreTopsoil Type A (imported) GI‐26 28.50$ CY 501,425.00Traffic control crew ( 2 flaggers ) GI‐27 120.00$ HR 809,600.00Trail, 4" chipped wood GI‐28 8.00$ SYTrail, 4" crushed cinder GI‐29 9.00$ SYTrail, 4" top course GI‐30 12.00$ SYConduit, 2" GI‐31 5.00$ LFWall, retaining, concrete GI‐32 55.00$ SFWall, rockery GI‐33 15.00$ SFSUBTOTAL THIS PAGE:15,000.00 102,325.00(B)(C)(D)(E)Page 1 of 3Ref 8‐H Bond Quantity WorksheetSECTION II.b TRANSPORTATIONUnit Prices Updated: 06/14/2016Version: 04/26/2017Printed 6/3/2021
CED Permit #:########Existing Future Public PrivateRight‐of‐Way Improvements Improvements(D) (E)Description No. Unit Price Unit Quant. Cost Quant. Cost Quant. Cost Quant. CostSITE IMPROVEMENT BOND QUANTITY WORKSHEETFOR STREET AND SITE IMPROVEMENTSQuantity Remaining (Bond Reduction) (B) (C)ROAD IMPROVEMENT/PAVEMENT/SURFACINGAC Grinding, 4' wide machine < 1000sy RI‐1 30.00$ SYAC Grinding, 4' wide machine 1000‐2000sy RI‐2 16.00$ SYAC Grinding, 4' wide machine > 2000sy RI‐3 10.00$ SYAC Removal/Disposal RI‐4 35.00$ SYBarricade, Type III ( Permanent ) RI‐5 56.00$ LFGuard Rail RI‐6 30.00$ LFCurb & Gutter, rolled RI‐7 17.00$ LFCurb & Gutter, vertical RI‐8 12.50$ LF 4105,125.00Curb and Gutter, demolition and disposal RI‐9 18.00$ LF 1703,060.00Curb, extruded asphalt RI‐10 5.50$ LFCurb, extruded concrete RI‐11 7.00$ LFSawcut, asphalt, 3" depth RI‐12 1.85$ LF 400740.00Sawcut, concrete, per 1" depth RI‐13 3.00$ LFSealant, asphalt RI‐14 2.00$ LF 400800.00Shoulder gravel 4"thickRI‐1515 00$SYShoulder, gravel, 4 thickRI 1515.00$ SYSidewalk, 4" thick RI‐16 38.00$ SY 803,040.001606,080.00Sidewalk, 4" thick, demolition and disposal RI‐17 32.00$ SY 973,104.00Sidewalk, 5" thick RI‐18 41.00$ SYSidewalk, 5" thick, demolition and disposal RI‐19 40.00$ SYSign, Handicap RI‐20 85.00$ EachStriping, per stall RI‐21 7.00$ EachStriping, thermoplastic, ( for crosswalk ) RI‐22 3.00$ SFStriping, 4" reflectorized line RI‐23 0.50$ LFAdditional 2.5" Crushed Surfacing RI‐24 3.60$ SYHMA 1/2" Overlay 1.5" RI‐25 14.00$ SYHMA 1/2" Overlay 2" RI‐26 18.00$ SYHMA Road, 2", 4" rock, First 2500 SY RI‐27 28.00$ SYHMA Road, 2", 4" rock, Qty. over 2500SY RI‐28 21.00$ SYHMA Road, 4", 6" rock, First 2500 SY RI‐29 45.00$ SYHMA Road, 4", 6" rock, Qty. over 2500 SY RI‐30 37.00$ SYHMA Road, 4", 4.5" ATB RI‐31 38.00$ SYGravel Road, 4" rock, First 2500 SY RI‐32 15.00$ SYGravel Road, 4" rock, Qty. over 2500 SY RI‐33 10.00$ SYThickened Edge RI‐34 8.60$ LFSUBTOTAL THIS PAGE:15,869.00 6,080.00(B)(C)(D)(E)Page 2 of 3Ref 8‐H Bond Quantity WorksheetSECTION II.b TRANSPORTATIONUnit Prices Updated: 06/14/2016Version: 04/26/2017Printed 6/3/2021
CED Permit #:########Existing Future Public PrivateRight‐of‐Way Improvements Improvements(D) (E)Description No. Unit Price Unit Quant. Cost Quant. Cost Quant. Cost Quant. CostSITE IMPROVEMENT BOND QUANTITY WORKSHEETFOR STREET AND SITE IMPROVEMENTSQuantity Remaining (Bond Reduction) (B) (C)PARKING LOT SURFACING No.2" AC, 2" top course rock & 4" borrow PL‐1 21.00$ SY2" AC, 1.5" top course & 2.5" base course PL‐2 28.00$ SY4" select borrow PL‐3 5.00$ SY1.5" top course rock & 2.5" base course PL‐4 14.00$ SYSUBTOTAL PARKING LOT SURFACING:(B)(C)(D)(E)LANDSCAPING & VEGETATION No.Street Trees LA‐1 500.00$ EA 84,000.00Median Landscaping LA‐2Right‐of‐Way Landscaping LA‐3 6,000.00$ LS 16,000.00Wetland Landscaping LA‐4SUBTOTAL LANDSCAPING & VEGETATION:10,000.00(B)(C)(D)(E)TRAFFIC & LIGHTING No.Signs TR‐1 1,000.00$ EA 11,000.00Street Light System ( # of Poles) TR‐2 10,000.00$ EA 220,000.00330,000.00Traffic Signal TR‐3Traffic Signal Modification TR‐4SUBTOTAL TRAFFIC & LIGHTING:21,000.00 30,000.00(B)(C)(D)(E)WRITE‐IN‐ITEMS3" AC, 6" top course 33.00$ SY 40013,200.00401,320.001755,775.00Site Landscaping 9,000.00$ LS 19,000.00Traffic Striping 6,000.00$ LS 16,000.00SUBTOTAL WRITE‐IN ITEMS:19,200.00 1,320.00 14,775.00STREET AND SITE IMPROVEMENTS SUBTOTAL: 56,069.00 62,400.00 117,100.00SALES TAX @ 10% 5,606.90 6,240.00 11,710.00STREET AND SITE IMPROVEMENTS TOTAL: 61,675.90 68,640.00 128,810.00(B)(C)(D)(E)Page 3 of 3Ref 8‐H Bond Quantity WorksheetSECTION II.b TRANSPORTATIONUnit Prices Updated: 06/14/2016Version: 04/26/2017Printed 6/3/2021
CED Permit #:########Existing Future Public PrivateRight‐of‐Way Improvements Improvements(D) (E)Description No. Unit Price Unit Quant. Cost Quant. Cost Quant. Cost Quant. CostDRAINAGE(CPE=Corrugated Polyethylene Pipe, N12 or Equivalent) For Culvert prices, Average of 4'cover was assumed. Assume perforated PVC is same price as solid pipe.)Access Road, R/D D‐1 26.00$ SY* (CBs include frame and lid)Beehive D‐2 90.00$ EachThrough‐curb Inlet Framework D‐3 400.00$ EachCB Type I D‐4 1,500.00$ Each 57,500.00CB Type IL D‐5 1,750.00$ EachCB Type II, 48" diameter D‐6 2,300.00$ Each 12,300.00 for additional depth over 4' D‐7 480.00$ FT 2960.00CB Type II, 54" diameter D‐8 2,500.00$ Each for additional depth over 4' D‐9 495.00$ FTCB Type II, 60" diameter D‐10 2,800.00$ Each for additional depth over 4' D‐11 600.00$ FTCB Type II, 72" diameter D‐12 6,000.00$ Each for additional depth over 4' D‐13 850.00$ FTCB Type II, 96" diameter D‐14 14,000.00$ Each for additional depth over 4' D‐15 925.00$ FTTrash Rack 12"D‐16350 00$EachSITE IMPROVEMENT BOND QUANTITY WORKSHEETFOR DRAINAGE AND STORMWATER FACILITIESQuantity Remaining (Bond Reduction)(B) (C)Trash Rack, 12D‐16350.00$ EachTrash Rack, 15" D‐17 410.00$ EachTrash Rack, 18" D‐18 480.00$ EachTrash Rack, 21" D‐19 550.00$ EachCleanout, PVC, 4" D‐20 150.00$ EachCleanout, PVC, 6" D‐21 170.00$ EachCleanout, PVC, 8" D‐22 200.00$ Each 1200.00Culvert, PVC, 4" D‐23 10.00$ LFCulvert, PVC, 6" D‐24 13.00$ LFCulvert, PVC, 8" D‐25 15.00$ LF 2333,495.00Culvert, PVC, 12" D‐26 23.00$ LF 2565,888.0030690.0031713.00Culvert, PVC, 15" D‐27 35.00$ LFCulvert, PVC, 18" D‐28 41.00$ LFCulvert, PVC, 24" D‐29 56.00$ LFCulvert, PVC, 30" D‐30 78.00$ LFCulvert, PVC, 36" D‐31 130.00$ LFCulvert, CMP, 8" D‐32 19.00$ LFCulvert, CMP, 12" D‐33 29.00$ LF 17493.00SUBTOTAL THIS PAGE:13,388.00 690.00 8,161.00(B) (C) (D) (E)Page 1 of 5Ref 8‐H Bond Quantity WorksheetSECTION II.c DRAINAGEUnit Prices Updated: 06/14/2016Version: 04/26/2017Printed 6/3/2021
CED Permit #:########Existing Future Public PrivateRight‐of‐Way Improvements Improvements(D) (E)Description No. Unit Price Unit Quant. Cost Quant. Cost Quant. Cost Quant. CostSITE IMPROVEMENT BOND QUANTITY WORKSHEETFOR DRAINAGE AND STORMWATER FACILITIESQuantity Remaining (Bond Reduction)(B) (C)DRAINAGE (Continued)Culvert, CMP, 15" D‐34 35.00$ LFCulvert, CMP, 18" D‐35 41.00$ LFCulvert, CMP, 24" D‐36 56.00$ LFCulvert, CMP, 30" D‐37 78.00$ LFCulvert, CMP, 36" D‐38 130.00$ LFCulvert, CMP, 48" D‐39 190.00$ LFCulvert, CMP, 60" D‐40 270.00$ LFCulvert, CMP, 72" D‐41 350.00$ LFCulvert, Concrete, 8" D‐42 42.00$ LFCulvert, Concrete, 12" D‐43 48.00$ LFCulvert, Concrete, 15" D‐44 78.00$ LFCulvert, Concrete, 18" D‐45 48.00$ LFCulvert, Concrete, 24" D‐46 78.00$ LFCulvert, Concrete, 30" D‐47 125.00$ LFCulvert, Concrete, 36" D‐48 150.00$ LFCulvert, Concrete, 42" D‐49 175.00$ LFCulvert Concrete 48"D‐50205 00$LFCulvert, Concrete, 48D‐50205.00$ LFCulvert, CPE Triple Wall, 6" D‐51 14.00$ LFCulvert, CPE Triple Wall, 8" D‐52 16.00$ LFCulvert, CPE Triple Wall, 12" D‐53 24.00$ LFCulvert, CPE Triple Wall, 15" D‐54 35.00$ LFCulvert, CPE Triple Wall, 18" D‐55 41.00$ LFCulvert, CPE Triple Wall, 24" D‐56 56.00$ LFCulvert, CPE Triple Wall, 30" D‐57 78.00$ LFCulvert, CPE Triple Wall, 36" D‐58 130.00$ LFCulvert, LCPE, 6" D‐59 60.00$ LFCulvert, LCPE, 8" D‐60 72.00$ LFCulvert, LCPE, 12" D‐61 84.00$ LFCulvert, LCPE, 15" D‐62 96.00$ LFCulvert, LCPE, 18" D‐63 108.00$ LFCulvert, LCPE, 24" D‐64 120.00$ LFCulvert, LCPE, 30" D‐65 132.00$ LFCulvert, LCPE, 36" D‐66 144.00$ LFCulvert, LCPE, 48" D‐67 156.00$ LFCulvert, LCPE, 54" D‐68 168.00$ LFSUBTOTAL THIS PAGE:(B) (C) (D) (E)Page 2 of 5Ref 8‐H Bond Quantity WorksheetSECTION II.c DRAINAGEUnit Prices Updated: 06/14/2016Version: 04/26/2017Printed 6/3/2021
CED Permit #:########Existing Future Public PrivateRight‐of‐Way Improvements Improvements(D) (E)Description No. Unit Price Unit Quant. Cost Quant. Cost Quant. Cost Quant. CostSITE IMPROVEMENT BOND QUANTITY WORKSHEETFOR DRAINAGE AND STORMWATER FACILITIESQuantity Remaining (Bond Reduction)(B) (C)DRAINAGE (Continued)Culvert, LCPE, 60" D‐69 180.00$ LFCulvert, LCPE, 72" D‐70 192.00$ LFCulvert, HDPE, 6" D‐71 42.00$ LFCulvert, HDPE, 8" D‐72 42.00$ LFCulvert, HDPE, 12" D‐73 74.00$ LFCulvert, HDPE, 15" D‐74 106.00$ LFCulvert, HDPE, 18" D‐75 138.00$ LFCulvert, HDPE, 24" D‐76 221.00$ LFCulvert, HDPE, 30" D‐77 276.00$ LFCulvert, HDPE, 36" D‐78 331.00$ LFCulvert, HDPE, 48" D‐79 386.00$ LFCulvert, HDPE, 54" D‐80 441.00$ LFCulvert, HDPE, 60" D‐81 496.00$ LFCulvert, HDPE, 72" D‐82 551.00$ LFPipe, Polypropylene, 6" D‐83 84.00$ LFPipe, Polypropylene, 8" D‐84 89.00$ LFPipe Polypropylene 12"D8595 00$LFPipe, Polypropylene, 12D‐8595.00$ LFPipe, Polypropylene, 15" D‐86 100.00$ LFPipe, Polypropylene, 18" D‐87 106.00$ LFPipe, Polypropylene, 24" D‐88 111.00$ LFPipe, Polypropylene, 30" D‐89 119.00$ LF 435,117.00Pipe, Polypropylene, 36" D‐90 154.00$ LFPipe, Polypropylene, 48" D‐91 226.00$ LFPipe, Polypropylene, 54" D‐92 332.00$ LFPipe, Polypropylene, 60" D‐93 439.00$ LFPipe, Polypropylene, 72" D‐94 545.00$ LFCulvert, DI, 6" D‐95 61.00$ LFCulvert, DI, 8" D‐96 84.00$ LF 413,444.00Culvert, DI, 12" D‐97 106.00$ LFCulvert, DI, 15" D‐98 129.00$ LFCulvert, DI, 18" D‐99 152.00$ LFCulvert, DI, 24" D‐100 175.00$ LFCulvert, DI, 30" D‐101 198.00$ LFCulvert, DI, 36" D‐102 220.00$ LFCulvert, DI, 48" D‐103 243.00$ LFCulvert, DI, 54" D‐104 266.00$ LFCulvert, DI, 60" D‐105 289.00$ LFCulvert, DI, 72" D‐106 311.00$ LFSUBTOTAL THIS PAGE:8,561.00(B) (C) (D) (E)Page 3 of 5Ref 8‐H Bond Quantity WorksheetSECTION II.c DRAINAGEUnit Prices Updated: 06/14/2016Version: 04/26/2017Printed 6/3/2021
CED Permit #:########Existing Future Public PrivateRight‐of‐Way Improvements Improvements(D) (E)Description No. Unit Price Unit Quant. Cost Quant. Cost Quant. Cost Quant. CostSITE IMPROVEMENT BOND QUANTITY WORKSHEETFOR DRAINAGE AND STORMWATER FACILITIESQuantity Remaining (Bond Reduction)(B) (C)Specialty Drainage ItemsDitching SD‐1 9.50$ CY 2001,900.0030285.0080760.00Flow Dispersal Trench (1,436 base+) SD‐3 28.00$ LF French Drain (3' depth) SD‐4 26.00$ LFGeotextile, laid in trench, polypropylene SD‐5 3.00$ SYMid‐tank Access Riser, 48" dia, 6' deep SD‐6 2,000.00$ EachPond Overflow Spillway SD‐7 16.00$ SYRestrictor/Oil Separator, 12" SD‐8 1,150.00$ Each 11,150.00Restrictor/Oil Separator, 15" SD‐9 1,350.00$ EachRestrictor/Oil Separator, 18" SD‐10 1,700.00$ EachRiprap, placed SD‐11 42.00$ CY 10420.00Tank End Reducer (36" diameter) SD‐12 1,200.00$ EachInfiltration pond testing SD‐13 125.00$ HRPermeable Pavement SD‐14Permeable Concrete Sidewalk SD‐15Culvert, Box __ ft x __ ft SD‐16SUBTOTAL SPECIALTY DRAINAGE ITEMS:1,900.00 285.00 2,330.00(B) (C) (D) (E)STORMWATER FACILITIES (Include Flow Control and Water Quality Facility Summary Sheet and Sketch)Detention Pond SF‐1 Each Detention Tank SF‐2 Each Detention Vault SF‐3 98,000.00$ Each 198,000.00Infiltration Pond SF‐4 Each Infiltration Tank SF‐5 Each Infiltration Vault SF‐6 Each Infiltration Trenches SF‐7 Each Basic Biofiltration Swale SF‐8 Each Wet Biofiltration Swale SF‐9 Each Wetpond SF‐10 Each Wetvault SF‐11 Each Sand Filter SF‐12 Each Sand Filter Vault SF‐13 Each Linear Sand Filter SF‐14 Each Proprietary Facility SF‐15 10,000.00$ Each 110,000.00Bioretention Facility SF‐16 Each SUBTOTAL STORMWATER FACILITIES:108,000.00(B) (C) (D) (E)Page 4 of 5Ref 8‐H Bond Quantity WorksheetSECTION II.c DRAINAGEUnit Prices Updated: 06/14/2016Version: 04/26/2017Printed 6/3/2021
CED Permit #:########Existing Future Public PrivateRight‐of‐Way Improvements Improvements(D) (E)Description No. Unit Price Unit Quant. Cost Quant. Cost Quant. Cost Quant. CostSITE IMPROVEMENT BOND QUANTITY WORKSHEETFOR DRAINAGE AND STORMWATER FACILITIESQuantity Remaining (Bond Reduction)(B) (C)WRITE‐IN‐ITEMS (INCLUDE ON‐SITE BMPs)6" Thick Concrete Drainage Channel WI‐1 55.00$ SY 603,300.00Inlet Structure WI‐2 8,000.00$ LS 18,000.00WI‐3WI‐4WI‐5WI‐6WI‐7WI‐8WI‐9WI‐10WI‐11WI‐12WI‐13WI‐14WI‐15SUBTOTAL WRITE‐IN ITEMS:11,300.00DRAINAGE AND STORMWATER FACILITIES SUBTOTAL: 23,849.00 975.00 129,791.00SALES TAX @ 10% 2,384.90 97.50 12,979.10DRAINAGE AND STORMWATER FACILITIES TOTAL: 26,233.90 1,072.50 142,770.10(B) (C) (D) (E)Page 5 of 5Ref 8‐H Bond Quantity WorksheetSECTION II.c DRAINAGEUnit Prices Updated: 06/14/2016Version: 04/26/2017Printed 6/3/2021
CED Permit #:########Existing Future Public PrivateRight‐of‐Way Improvements Improvements(D) (E)Description No. Unit Price Unit Quant. Cost Quant. Cost Quant. Cost Quant. CostConnection to Existing Watermain W‐1 2,000.00$ Each 510,000.00Ductile Iron Watermain, CL 52, 4 Inch Diameter W‐2 50.00$ LF 1105,500.00Ductile Iron Watermain, CL 52, 6 Inch Diameter W‐3 56.00$ LF 854,760.00Ductile Iron Watermain, CL 52, 8 Inch Diameter W‐4 60.00$ LFDuctile Iron Watermain, CL 52, 10 Inch Diameter W‐5 70.00$ LFDuctile Iron Watermain, CL 52, 12 Inch Diameter W‐6 80.00$ LFGate Valve, 4 inch Diameter W‐7 500.00$ Each 1500.00Gate Valve, 6 inch Diameter W‐8 700.00$ Each 21,400.00Gate Valve, 8 Inch Diameter W‐9 800.00$ EachGate Valve, 10 Inch Diameter W‐10 1,000.00$ EachGate Valve, 12 Inch Diameter W‐11 1,200.00$ Each 33,600.00Fire Hydrant Assembly W‐12 4,000.00$ Each 14,000.00Permanent Blow‐Off Assembly W‐13 1,800.00$ EachAir‐Vac Assembly, 2‐Inch Diameter W‐14 2,000.00$ EachAir‐Vac Assembly, 1‐Inch Diameter W‐15 1,500.00$ EachCompound Meter Assembly 3‐inch Diameter W‐16 8,000.00$ Each 18,000.00SITE IMPROVEMENT BOND QUANTITY WORKSHEETFOR WATERQuantity Remaining (Bond Reduction) (B) (C)Compound Meter Assembly 4‐inch Diameter W‐17 9,000.00$ EachCompound Meter Assembly 6‐inch Diameter W‐18 10,000.00$ EachPressure Reducing Valve Station 8‐inch to 10‐inch W‐19 20,000.00$ EachWATER SUBTOTAL:37,760.00SALES TAX @ 10% 3,776.00WATER TOTAL: 41,536.00(B) (C) (D) (E)Page 1 of 1Ref 8‐H Bond Quantity WorksheetSECTION II.d WATERUnit Prices Updated: 06/14/2016Version: 04/26/2017Printed 6/3/2021
CED Permit #:########Existing Future Public PrivateRight‐of‐Way Improvements Improvements(D) (E)Description No. Unit Price Unit Quant. Cost Quant. Cost Quant. Cost Quant. CostClean Outs SS‐1 1,000.00$ Each 22,000.00Grease Interceptor, 500 gallon SS‐2 8,000.00$ EachGrease Interceptor, 1000 gallon SS‐3 10,000.00$ EachGrease Interceptor, 1500 gallon SS‐4 15,000.00$ EachSide Sewer Pipe, PVC. 4 Inch Diameter SS‐5 80.00$ LFSide Sewer Pipe, PVC. 6 Inch Diameter SS‐6 95.00$ LF 605,700.00Sewer Pipe, PVC, 8 inch Diameter SS‐7 105.00$ LFSewer Pipe, PVC, 12 Inch Diameter SS‐8 120.00$ LFSewer Pipe, DI, 8 inch Diameter SS‐9 115.00$ LFSewer Pipe, DI, 12 Inch Diameter SS‐10 130.00$ LFManhole, 48 Inch Diameter SS‐11 6,000.00$ EachManhole, 54 Inch Diameter SS‐13 6,500.00$ EachManhole, 60 Inch Diameter SS‐15 7,500.00$ EachManhole, 72 Inch Diameter SS‐17 8,500.00$ EachManhole, 96 Inch Diameter SS‐19 14,000.00$ EachPipe, C‐900, 12 Inch Diameter SS‐21 180.00$ LFOtidDSS 241 500 00$LSSITE IMPROVEMENT BOND QUANTITY WORKSHEETFOR SANITARY SEWERQuantity Remaining (Bond Reduction)(B) (C)Outside DropSS‐241,500.00$ LSInside Drop SS‐25 1,000.00$ LSSewer Pipe, PVC, ____ Inch Diameter SS‐26Lift Station (Entire System) SS‐27 LSSANITARY SEWER SUBTOTAL:7,700.00SALES TAX @ 10% 770.00SANITARY SEWER TOTAL: 8,470.00(B) (C) (D) (E)Page 1 of 1Ref 8‐H Bond Quantity WorksheetSECTION II.e SANITARY SEWERUnit Prices Updated: 06/14/2016Version: 04/26/2017Printed 6/3/2021
Planning Division |1055 South Grady Way – 6th Floor | Renton, WA 98057 (425) 430‐7200Date:Name:Project Name: PE Registration No:CED Plan # (LUA):Firm Name:CED Permit # (U):Firm Address:Site Address:Phone No.Parcel #(s):Email Address:Project Phase: Site Restoration/Erosion Sediment Control Subtotal (a)Existing Right‐of‐Way Improvements Subtotal (b) (b)111,681.90$ 360‐794‐7811stephenm@harmsenllc.com4th Dimension Mixed Use##‐######4502 NE 4th Street102305‐9068FOR APPROVAL########125 East Main Street, Monroe, WA 98272SITE IMPROVEMENT BOND QUANTITY WORKSHEET BOND CALCULATIONSDateStephen Mason35197Harmsen LLCPrepared by:Project InformationCONSTRUCTION BOND AMOUNT */**(prior to permit issuance)MAINTENANCE BOND */**(after final acceptance of construction)5,596.25$ 111,681.90$ Future Public Improvements Subtotal(c)68,640.00$ Stormwater & Drainage Facilities (Public & Private) Subtotal(d) (d)170,076.50$ (e)(f)Site RestorationCivil Construction PermitMaintenance Bond70,079.68$ Bond Reduction2Construction Permit Bond Amount 3Minimum Bond Amount is $10,000.001 Estimate Only ‐ May involve multiple and variable components, which will be established on an individual basis by Development Engineering.2 The City of Renton allows one request only for bond reduction prior to the maintenance period. Reduction of not more than 70% of the original bond amount, provided that the remaining 30% willcover all remaining items to be constructed. 3 Required Bond Amounts are subject to review and modification by Development Engineering.* Note: The word BOND as used in this document means any financial guarantee acceptable to the City of Renton.** Note: All prices include labor, equipment, materials, overhead and profit. 343,195.60$ P (a) x 100%R((b x 150%) + (d x 100%))S(e) x 150% + (f) x 100%Bond Reduction: Existing Right‐of‐Way Improvements (Quantity Remaining)2Bond Reduction: Stormwater & Drainage Facilities (Quantity Remaining)2T(P +R ‐ S)EST1((b) + (c) + (d)) x 20%‐$ 337,599.35$ 5,596.25$ ‐$ 170,076.50$ ‐$ Page 1 of 1Ref 8‐H Bond Quantity WorksheetSECTION III. BOND WORKSHEETUnit Prices Updated: 06/14/2016Version: 04/26/2017Printed 6/3/2021
2016 KING COUNTY SURFACE WATER DESIGN MANUAL, REFERENCE D
4/24/2016
Page 1
STORMWATER FACILITY SUMMARY SHEET DPER Permit No.___________________
(provide one Stormwater Facility Summary Sheet per Natural Discharge Location)Date ___________________
OVERVIEW:NPDES Permit No.___________________
Project Name
Parcel No.____________________________
Project Location Retired Parcel No.____________________________
Downstream Drainage Basins:Project includes Landscape Management Plan?yes
Major Basin Name ______________________________________________(include copy with TIR as Appendix)no
Immediate Basin Name ______________________________________________
GENERAL FACILITY INFORMATION: Leachable Metals
Infiltration Impervious Surface Limit
Type # of Type # of Type # of facilities Flow Control BMPs
Ponds ______ Ponds ______ Ponds ______ Basic Clearing Limit
Vaults ______ Tanks ______ Vaults ______ Conservation Drainage Facility
Tanks ______ Trenches _____ Tanks ______ Flood Problem Landscape Management Plan
If no flow control facility, check one:
Project qualifies for KCSWDM Exemption (KCSWDM 1.2.3):
Basic Exemption (Applies to Commercial parcels only)Area % of Total
Redevelopment projects
Cost Exemption for Parcel Redevelopment projects
Direct Discharge Exemption
Other _____________________ Total impervious surface served by
Project qualifies for 0.1 cfs Exception per KCSWDM 1.2.3 flow control facility(ies) (sq ft)
Impervious surface served by flow
KCSWDM Adjustment No. ___________________control facility(ies) designed
1990 or later (sq ft)
approved KCSWDM Adjustment No. __________________ Impervious surface served by
Shared Facility Name/Location: _________________________ pervious surface absorption (sq ft)
No flow control required (other, provide justification): Impervious surface served by approved
____________________________________________________ water quality facility(ies) (sq ft)
Flow Control
Performance Std
Declarations of Covenant Recording No.
Water QualityDetention
TREATMENT SUMMARY FOR TOTAL IMPERVIOUS SURFACES
-----
Total Impervious Acreage (ac)
No flow control required per approved
Flow control provided in regional/shared facility per approved
PROVIDE FACILITY DETAILS AND FACILITY SKETCH FOR EACH FACILITY ON REVERSE. USE ADDITIONAL SHEETS AS NEEDED FOR ADDITIONAL FACILITIES
Impervious Surface Exemption for Transportation Total Acreage (ac)
4th Dimension Mixed use
4502 NE 4th Street
Maplewood
1 x
x
1
0.44
0.37
0.37
84%
0.37 100%
100%
0 0%
0 0%
2016 KING COUNTY SURFACE WATER DESIGN MANUAL, REFERENCE D
4/24/2016
Page 2
STORMWATER FACILITY SUMMARY SHEET DPER Permit No.___________________
(provide one Stormwater Facility Summary Sheet per Natural Discharge Location)
Project Name Downstream Drainage Basins:
Major Basin Name _______________________________
Project Location Immediate Basin Name ___________________________
FLOW CONTROL FACILITY:Basin:
Facility Name/Number _______________________________________ New Facility Project Impervious
Facility Location ____________________________________________ Existing Facility Acres Served ________
UIC? □ yes □ no UIC Site ID:% of Total Project Impervious
cu.ft.Volume Factor Acres Served ________
_____________ ac.ft.____________of Safety ______No. of Lots Served ________
Control Structure location: _______________________________________________
Type of Control Structure:No. of Orifices/Restrictions __________
Riser in vault Size of Orifice/Restriction (in.) No.1 ______ cu.ft.
Riser in Type II CB (numbered starting with lowest No.2 ______ ac.ft.
Weir in Type II CB orifice): No.3 ______
(inches in decimal format)No.4 ______
WATER QUALITY FACILITIES Design Information
Indicate no. of water quality facilities/BMPs for each type:Water Quality design flow (cfs)
_______Flow dispersion Water Quality treated volume (sandfilter) (cu.ft.)
_______Filter strip Water Quality storage volume (wetpool) (cu.ft.)
_______Biofiltration swale regular, wet or Landscape management plan Farm management plan
continuous inflow
_______Wetvault combined w/detention ______High flow bypass structure (e.g., flow-splitter catch basin)
_______Wetpond basic large combined w/detention ______Oil/water separator baffle coalescing plate
_______Pre-settling pond ______Storm filter
_______Stormwater wetland ______Pre-settling structure (Manufacturer:______________________)
_______Sand filter basic large Sand bed depth ______Catch basin inserts (Manufacturer:________________________)
regular linear vault (inches)______________Source controls _________________________________________
● Is facility lined? yes no If so, what marker is used above liner?_____________________________________________________
Facility Summary Sheet Sketch: All detention, infiltration and water quality facilities must include a detailed sketch (11"x17" reduced size plan sheets preferred).
Dam Safety Regulations (WA State Dept of
Ecology):
Reservoir Volume
above natural grade
Depth of Reservoir
above natural grade (ft)
Live Storage
Volume
Live Storage
Depth (ft)
4th Dimension Mixed Use
4502 NE 4th Street
Maplewood
Detention Vault x
North edge of property
8,540
x
6.1'0%
0.44
100%
1
x
Southeast corner of vault
3
0.89"
0.88"
1.30"
1
0.046
- BioPod
Page 1 of ___
Return Address:
City Clerk’s Office
City of Renton
1055 S Grady Way
Renton, WA 98057
DECLARATION OF COVENANT
FOR INSPECTION AND MAINTENANCE OF DRAINAGE FACILITIES AND
ON-SITE BMPS
Grantor:
Grantee: City of Renton, a Washington municipal corporation
Legal Description:
Assessor's Tax Parcel ID#:
IN CONSIDERATION of the approved City of Renton (check one of the following)
Residential Building Permit Commercial Building Permit
Clearing and Grading Permit Civil Construction or Utility Permit
for Permit(s)_____________________ (Construction/Building/Utility Permit #) relating to the real property
("Property") described above, the Grantor(s), the owner(s) in fee of that Property, hereby
covenants (covenant) with the City of Renton (“City of Renton” or “City”), a municipal corporation
of the state of Washington, that he/she (they) will observe, consent to, and abide by the conditions
and obligations set forth and described in Paragraphs 1 through 9 below with regard to the
Property, and hereby grants (grant) an easement as described in Paragraphs 2 and 3. Grantor(s)
hereby grants (grant), covenants (covenant), and agrees (agree) as follows:
1.The Grantor(s) or his/her (their) successors in interest and assigns ("Owners ") shall at their own
cost, operate, maintain, and keep in good repair, the Property's drainage facilities constructed
as required in the approved construction plans and specifications __________________ (Project
Plan #) on file with the City of Renton and submitted to the City of Renton for the review and
approval of permit(s) _____________________________ (Construction/Building/Utility Permit #). The
Property's drainage facilities are shown and/or listed on Exhibit A – Site Plan. The Property’s
drainage facilities shall be maintained in compliance with the operation and maintenance
schedule included and attached herein as Exhibit B – Operations and Maintenance. Drainage
facilities include pipes, channels, flow control facilities, water quality facilities, on-site best
management practices (BMPs) and other engineered structures designed to manage and/or
Page 2 of ___
treat stormwater on the Property. On-site BMPs include dispersion and infiltration devices,
bioretention, permeable pavements, rainwater harvesting systems, tree retention credit,
reduced impervious surface footprint, vegetated roofs and other measures designed to mimic
pre-developed hydrology and minimize stormwater runoff on the Property.
2.City of Renton shall have the right to ingress and egress over those portions of the Property
necessary to perform inspections of the stormwater facilities and BMPs and conduct
maintenance activities specified in this Declaration of Covenant and in accordance with the
Renton Municipal Code. City of Renton shall provide at least thirty (30) days’ written notice to
the Owners that entry on the Property is planned for the inspection of drainage facilities. After
the thirty (30) days, the Owners shall allow the City of Renton to enter for the sole purpose of
inspecting drainage facilities. In lieu of inspection by the City, the Owners may elect to engage
a licensed civil engineer registered in the state of Washington who has expertise in drainage to
inspect the drainage facilities and provide a written report describing their condition. If the
engineer option is chosen, the Owners shall provide written notice to the City of Renton within
fifteen (15) days of receiving the City’s notice of inspection. Within thirty (30) days of giving this
notice, the Owners, or engineer on behalf of the Owners, shall provide the engineer’s report to
the City of Renton. If the report is not provided in a timely manner as specified above, the City
of Renton may inspect the drainage facilities without further notice.
3.If City of Renton determines from its inspection, or from an engineer’s report provided in
accordance with Paragraph 2, that maintenance, repair, restoration, and/or mitigation work is
required to be done to any of the drainage facilities, City of Renton shall notify the Owners of
the specific maintenance, repair, restoration, and/or mitigation work (“Work”) required
pursuant to the Renton Municipal Code. The City shall also set a reasonable deadline for the
Owners to complete the Work, or to provide an engineer’s report that verifies completion of
the Work. After the deadline has passed, the Owners shall allow the City access to re-inspect
the drainage facilities unless an engineer’s report has been provided verifying completion of
the Work. If the Work is not completed within the time frame set by the City, the City may
initiate an enforcement action and/or perform the Work and hereby is given access to the
Property for such purposes. Written notice will be sent to the Owners stating the City’s
intention to perform such Work. This Work will not commence until at least seven (7) days after
such notice is mailed. If, within the sole discretion of the City, there exists an imminent or
present danger, the seven (7) day notice period will be waived and Work will begin
immediately.
4.The Owners shall assume all responsibility for the cost of any Work, or any measures taken by
the City to address conditions as described in Paragraph 3. Such responsibility shall include
reimbursement to the City within thirty (30) days of the receipt of the invoice for any such Work
performed. Overdue payments will require payment of interest at the maximum legal rate
allowed by RCW 19.52.020 (currently twelve percent (12%)). If the City initiates legal action to
enforce this agreement, the prevailing party in such action is entitled to recover reasonable
litigation costs and attorney’s fees.
5.The Owners are required to obtain written approval from City of Renton prior to filling, piping,
cutting, or removing vegetation (except in routine landscape maintenance) in open vegetated
stormwater facilities (such as swales, channels, ditches, ponds, etc.), or performing any
alterations or modifications to the drainage facilities referenced in this Declaration of Covenant.
Page 3 of ___
6.Any notice or consent required to be given or otherwise provided for by the provisions of this
Agreement shall be effective upon personal delivery, or three (3) days after mailing by Certified
Mail, return receipt requested.
7.With regard to the matters addressed herein, this agreement constitutes the entire agreement
between the parties, and supersedes all prior discussions, negotiations, and all agreements
whatsoever whether oral or written.
8.This Declaration of Covenant is intended to protect the value and desirability and promote
efficient and effective management of surface water drainage of the real property described
above, and shall inure to the benefit of all the citizens of the City of Renton and its successors
and assigns. This Declaration of Covenant shall run with the land and be binding upon
Grantor(s), and Grantor's(s') successors in interest, and assigns.
9.This Declaration of Covenant may be terminated by execution of a written agreement by the
Owners and the City that is recorded by King County in its real property records.
IN WITNESS WHEREOF, this Declaration of Covenant for the Inspection and Maintenance of
Drainage Facilities is executed this _____ day of ____________________, 20_____.
GRANTOR, owner of the Property GRANTOR, owner of the Property
STATE OF WASHINGTON )
COUNTY OF KING )ss.
On this day personally appeared before me:
, to me known to be the individual(s)
described in and who executed the within and foregoing instrument and acknowledged that they
signed the same as their free and voluntary act and deed, for the uses and purposes therein stated.
Given under my hand and official seal this _____ day of ___________________, 20_____.
Printed name
Notary Public in and for the State of
Washington, residing at
My appointment expires
EXHIBIT A
SITE PLAN
EXHIBIT B
OPERATIONS & MAINTENANCE
APPENDIX A MAINTENANCE REQUIREMENTS FOR STORMWATER FACILITIES AND ON-SITE BMPS
12/12/2016 2017 City of Renton Surface Water Design Manual A-6
NO. 3 – DETENTION TANKS AND VAULTS
MAINTENANCE
COMPONENT
DEFECT OR
PROBLEM
CONDITIONS WHEN
MAINTENANCE IS NEEDED
RESULTS EXPECTED WHEN
MAINTENANCE IS PERFORMED
Site Trash and debris Any trash and debris which exceed 1 cubic foot per 1,000 square feet (this is about equal to the amount of trash it would take to fill up one standard size office garbage can). In general, there should be no visual evidence of dumping.
Trash and debris cleared from site.
Noxious weeds Any noxious or nuisance vegetation which may constitute a hazard to City personnel or the public.
Noxious and nuisance vegetation removed according to applicable regulations. No danger of noxious vegetation where City personnel or the public might normally be.
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.
Excessive growth of grass/groundcover Grass or groundcover exceeds 18 inches in height. Grass or groundcover mowed to a height no greater than 6 inches.
Tank or Vault Storage Area Trash and debris Any trash and debris accumulated in vault or tank (includes floatables and non-floatables).
No trash or debris in vault.
Sediment accumulation Accumulated sediment depth exceeds 10% of the diameter of the storage area for ½ length of storage vault or any point depth exceeds 15% of diameter. Example:
72-inch storage tank would require cleaning when sediment reaches depth of 7 inches for more than ½ length of tank.
All sediment removed from storage area.
Tank Structure Plugged air vent Any blockage of the vent. Tank or vault freely vents.
Tank bent out of shape Any part of tank/pipe is bent out of shape more than 10% of its design shape. Tank repaired or replaced to design.
Gaps between sections, damaged
joints or cracks or tears in wall
A gap wider than ½-inch at the joint of any tank sections or any evidence of soil
particles entering the tank at a joint or through a wall.
No water or soil entering tank through joints or walls.
Vault Structure Damage to wall, frame, bottom, and/or top slab
Cracks wider than ½-inch, any evidence of soil entering the structure through cracks or qualified inspection personnel determines that the vault is not structurally sound.
Vault is sealed and structurally sound.
Inlet/Outlet Pipes Sediment accumulation Sediment filling 20% or more of the pipe. Inlet/outlet pipes clear of sediment.
Trash and debris Trash and debris accumulated in inlet/outlet pipes (includes floatables and non-floatables).
No trash or debris in pipes.
Damaged inlet/outlet pipes Cracks wider than ½-inch at the joint of the inlet/outlet pipes or any evidence of soil entering at the joints of the inlet/outlet pipes.
No cracks more than ¼-inch wide at the joint of the inlet/outlet pipe.
Access Manhole Cover/lid not in place Cover/lid is missing or only partially in place. Any open manhole requires immediate maintenance.
Manhole access covered.
APPENDIX A MAINTENANCE REQUIREMENTS FOR STORMWATER FACILITIES AND ON-SITE BMPS
2017 City of Renton Surface Water Design Manual 12/12/2016 A-7
NO. 3 – DETENTION TANKS AND VAULTS
MAINTENANCE
COMPONENT
DEFECT OR
PROBLEM
CONDITIONS WHEN
MAINTENANCE IS NEEDED
RESULTS EXPECTED WHEN
MAINTENANCE IS PERFORMED
Access Manhole (cont.) Locking mechanism not working Mechanism cannot be opened by one maintenance person with proper tools. Bolts cannot be seated. Self-locking cover/lid does not work.
Mechanism opens with proper tools.
Cover/lid difficult to remove One maintenance person cannot remove cover/lid after applying 80 lbs of lift. Cover/lid can be removed and 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
doors/plate
Damaged or difficult
to open
Large access doors or plates cannot be
opened/removed using normal equipment.
Replace or repair access door so it can
opened as designed.
Gaps, doesn't cover completely Large access doors not flat and/or access opening not completely covered. Doors close flat; covers access opening completely.
Lifting rings missing, rusted Lifting rings not capable of lifting weight of door or plate. Lifting rings sufficient to lift or remove door or plate.
APPENDIX A MAINTENANCE REQUIREMENTS FOR STORMWATER FACILITIES AND ON-SITE BMPS
12/12/2016 2017 City of Renton Surface Water Design Manual A-8
NO. 4 – CONTROL STRUCTURE/FLOW RESTRICTOR
MAINTENANCE
COMPONENT
DEFECT OR
PROBLEM
CONDITION WHEN MAINTENANCE
IS NEEDED
RESULTS EXPECTED WHEN
MAINTENANCE IS PERFORMED
Structure Trash and debris Trash or debris of more than ½ cubic foot which is located immediately in front of the structure opening or is blocking capacity of the structure by more than 10%.
No Trash or debris blocking or potentially blocking entrance to structure.
Trash or debris in the structure 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 structure.
Deposits of garbage exceeding 1 cubic foot in volume. No condition present which would attract or support the breeding of insects or rodents.
Sediment accumulation Sediment exceeds 60% of the depth from the bottom of the structure to the invert of the lowest pipe into or out of the structure or the bottom of the FROP-T section or is
within 6 inches of the invert of the lowest pipe into or out of the structure or the bottom of the FROP-T section.
Sump of structure contains no sediment.
Damage to frame and/or top slab Corner of frame extends more than ¾ 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 ¼ inch. Top slab is free of holes and cracks.
Frame not sitting flush on top slab, i.e., separation of more than ¾ inch of the frame from the top slab.
Frame is sitting flush on top slab.
Cracks in walls or bottom Cracks wider than ½ inch and longer than 3 feet, any evidence of soil particles entering structure through cracks, or maintenance person judges that structure is unsound.
Structure is sealed and structurally sound.
Cracks wider than ½ inch and longer than 1 foot at the joint of any inlet/outlet pipe or
any evidence of soil particles entering structure through cracks.
No cracks more than 1/4 inch wide at the joint of inlet/outlet pipe.
Settlement/ misalignment Structure has settled more than 1 inch or has rotated more than 2 inches out of alignment.
Basin replaced or repaired to design standards.
Damaged pipe joints Cracks wider than ½-inch at the joint of the inlet/outlet pipes or any evidence of soil entering the structure at the joint of the inlet/outlet pipes.
No cracks more than ¼-inch wide at the joint of inlet/outlet pipes.
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.
Ladder rungs missing or unsafe Ladder is unsafe due to missing rungs, misalignment, rust, cracks, or sharp edges. Ladder meets design standards and allows maintenance person safe access.
FROP-T Section Damaged FROP-T T section is not securely attached to
structure wall and outlet pipe structure should support at least 1,000 lbs of up or down pressure.
T section securely attached to wall and
outlet pipe.
Structure is not in upright position (allow up to 10% from plumb). Structure in correct position.
APPENDIX A MAINTENANCE REQUIREMENTS FOR STORMWATER FACILITIES AND ON-SITE BMPS
2017 City of Renton Surface Water Design Manual 12/12/2016 A-9
NO. 4 – CONTROL STRUCTURE/FLOW RESTRICTOR
MAINTENANCE
COMPONENT
DEFECT OR
PROBLEM
CONDITION WHEN MAINTENANCE
IS NEEDED
RESULTS EXPECTED WHEN
MAINTENANCE IS PERFORMED
FROP-T Section (cont.) Damaged FROP-T (cont.) Connections to outlet pipe are not watertight or show signs of deteriorated grout.
Connections to outlet pipe are water tight; structure repaired or replaced and works as designed.
Any holes—other than designed holes—in
the structure.
Structure has no holes other than designed
holes.
Cleanout Gate Damaged or missing cleanout gate Cleanout gate is missing. Replace cleanout gate.
Cleanout gate is not watertight. Gate is watertight and works as designed.
Gate cannot be moved up and down by one maintenance person. Gate moves up and down easily and is watertight.
Chain/rod leading to gate is missing or damaged. Chain is in place and works as designed.
Orifice Plate Damaged or missing
orifice plate
Control device is not working properly due
to missing, out of place, or bent orifice plate.
Plate is in place and works as designed.
Obstructions to orifice plate Any trash, debris, sediment, or vegetation blocking the plate. Plate is free of all obstructions and works as designed.
Overflow Pipe Obstructions to
overflow pipe
Any trash or debris blocking (or having the
potential of blocking) the overflow pipe.
Pipe is free of all obstructions and works
as designed.
Deformed or damaged lip of overflow pipe
Lip of overflow pipe is bent or deformed. Overflow pipe does not allow overflow at an elevation lower than design
Inlet/Outlet Pipe Sediment accumulation Sediment filling 20% or more of the pipe. Inlet/outlet pipes clear of sediment.
Trash and debris Trash and debris accumulated in
inlet/outlet pipes (includes floatables and non-floatables).
No trash or debris in pipes.
Damaged inlet/outlet
pipe
Cracks wider than ½-inch at the joint of the
inlet/outlet pipes or any evidence of soil entering at the joints of the inlet/outlet pipes.
No cracks more than ¼-inch wide at the
joint of the inlet/outlet pipe.
Metal Grates (If applicable) Unsafe grate opening Grate with opening wider than 7/8 inch. Grate opening meets design standards.
Trash and debris Trash and debris that is blocking more
than 20% of grate surface.
Grate free of trash and debris. footnote to
guidelines for disposal
Damaged or missing grate Grate missing or broken member(s) of the grate. Grate is in place and meets design standards.
Manhole Cover/Lid Cover/lid not in place Cover/lid is missing or only partially in place. Any open structure requires urgent maintenance.
Cover/lid protects opening to structure.
Locking mechanism
not working
Mechanism cannot be opened by one
maintenance person with proper tools. Bolts cannot be seated. Self-locking cover/lid does not work.
Mechanism opens with proper tools.
Cover/lid difficult to remove One maintenance person cannot remove cover/lid after applying 80 lbs. of lift. Cover/lid can be removed and reinstalled by one maintenance person.
APPENDIX A MAINTENANCE REQUIREMENTS FOR STORMWATER FACILITIES AND ON-SITE BMPS
12/12/2016 2017 City of Renton Surface Water Design Manual A-10
NO. 5 – CATCH BASINS AND MANHOLES
MAINTENANCE
COMPONENT
DEFECT OR
PROBLEM
CONDITION WHEN MAINTENANCE
IS NEEDED
RESULTS EXPECTED WHEN
MAINTENANCE IS PERFORMED
Structure Sediment accumulation Sediment exceeds 60% of the depth from the bottom of the catch basin to the invert of the 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.
Sump of catch basin contains no sediment.
Trash and debris Trash or debris of more than ½ cubic foot which is located immediately in front of the catch basin opening or is blocking capacity of the catch basin by more than 10%.
No Trash or debris blocking or potentially blocking entrance to catch basin.
Trash or debris in the catch 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.
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 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.
Damage to frame and/or top slab Corner of frame extends more than ¾ 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 ¼ inch. Top slab is free of holes and cracks.
Frame not sitting flush on top slab, i.e., separation of more than ¾ inch of the frame from the top slab.
Frame is sitting flush on top slab.
Cracks in walls or bottom Cracks wider than ½ inch and longer than 3 feet, any evidence of soil particles entering catch basin through cracks, or maintenance person judges that catch
basin is unsound.
Catch basin is sealed and is structurally sound.
Cracks wider than ½ 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.
Settlement/ misalignment Catch basin has settled more than 1 inch or has rotated more than 2 inches out of alignment.
Basin replaced or repaired to design standards.
Damaged pipe joints Cracks wider than ½-inch at the joint of the inlet/outlet pipes or any evidence of soil entering the catch basin at the joint of the inlet/outlet pipes.
No cracks more than ¼-inch wide at the joint of inlet/outlet pipes.
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/Outlet Pipe Sediment accumulation Sediment filling 20% or more of the pipe. Inlet/outlet pipes clear of sediment.
Trash and debris Trash and debris accumulated in
inlet/outlet pipes (includes floatables and non-floatables).
No trash or debris in pipes.
APPENDIX A MAINTENANCE REQUIREMENTS FOR STORMWATER FACILITIES AND ON-SITE BMPS
2017 City of Renton Surface Water Design Manual 12/12/2016 A-11
NO. 5 – CATCH BASINS AND MANHOLES
MAINTENANCE
COMPONENT
DEFECT OR
PROBLEM
CONDITION WHEN MAINTENANCE
IS NEEDED
RESULTS EXPECTED WHEN
MAINTENANCE IS PERFORMED
Inlet/Outlet Pipe (cont.) Damaged inlet/outlet pipe Cracks wider than ½-inch at the joint of the inlet/outlet pipes or any evidence of soil entering at the joints of the inlet/outlet pipes.
No cracks more than ¼-inch wide at the joint of the inlet/outlet pipe.
Metal Grates (Catch Basins) Unsafe grate opening Grate with opening wider than 7/8 inch. Grate opening meets design standards.
Trash and debris Trash and debris that is blocking more than 20% of grate surface. Grate free of trash and debris. footnote to guidelines for disposal
Damaged or missing grate Grate missing or broken member(s) of the grate. Any open structure requires urgent maintenance.
Grate is in place and meets design standards.
Manhole Cover/Lid Cover/lid not in place Cover/lid is missing or only partially in place. Any open structure requires urgent maintenance.
Cover/lid protects opening to structure.
Locking mechanism not working Mechanism cannot be opened by one maintenance person with proper tools. Bolts cannot be seated. Self-locking cover/lid does not work.
Mechanism opens with proper tools.
Cover/lid difficult to remove One maintenance person cannot remove cover/lid after applying 80 lbs. of lift. Cover/lid can be removed and reinstalled by one maintenance person.
APPENDIX A MAINTENANCE REQUIREMENTS FOR STORMWATER FACILITIES AND ON-SITE BMPS
12/12/2016 2017 City of Renton Surface Water Design Manual A-12
NO. 6 – CONVEYANCE PIPES AND DITCHES
MAINTENANCE
COMPONENT
DEFECT OR
PROBLEM
CONDITIONS WHEN
MAINTENANCE IS NEEDED
RESULTS EXPECTED WHEN
MAINTENANCE IS PERFORMED
Pipes Sediment & debris accumulation Accumulated sediment or debris that exceeds 20% of the diameter of the pipe. Water flows freely through pipes.
Vegetation/root growth in pipe Vegetation/roots that reduce free movement of water through pipes. Water flows freely through pipes.
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.
Damage to protective coating or corrosion Protective coating is damaged; rust or corrosion is weakening the structural integrity of any part of pipe.
Pipe repaired or replaced.
Damaged pipes Any dent that decreases the cross section area of pipe by more than 20% or is determined to have weakened structural integrity of the pipe.
Pipe repaired or replaced.
Ditches Trash and debris Trash and debris exceeds 1 cubic foot per 1,000 square feet of ditch and slopes. Trash and debris cleared from ditches.
Sediment accumulation Accumulated sediment that exceeds 20% of the design depth. Ditch cleaned/flushed of all sediment and debris so that it matches design.
Noxious weeds Any noxious or nuisance vegetation which may constitute a hazard to City personnel or the public.
Noxious and nuisance vegetation removed according to applicable regulations. No danger of noxious vegetation where City personnel or the public might normally be.
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.
Excessive vegetation growth Vegetation that reduces free movement of water through ditches. Water flows freely through ditches.
Erosion damage to
slopes
Any erosion observed on a ditch slope. Slopes are not eroding.
Rock lining out of place or missing (If applicable)
One layer or less of rock exists above native soil area 5 square feet or more, any exposed native soil.
Replace rocks to design standards.
APPENDIX A MAINTENANCE REQUIREMENTS FOR STORMWATER FACILITIES AND ON-SITE BMPS
12/12/2016 2017 City of Renton Surface Water Design Manual A-14
NO. 8 – ENERGY DISSIPATERS
MAINTENANCE
COMPONENT
DEFECT OR
PROBLEM
CONDITIONS WHEN
MAINTENANCE IS NEEDED
RESULTS EXPECTED WHEN
MAINTENANCE IS PERFORMED.
Site Trash and debris Trash and/or debris accumulation. Dissipater clear of trash and/or debris.
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.
Rock Pad Missing or moved
rock
Only one layer of rock exists above native
soil in area five square feet or larger or any exposure of native soil.
Rock pad prevents erosion.
Dispersion Trench Pipe plugged with sediment Accumulated sediment that exceeds 20% of the design depth. Pipe cleaned/flushed so that it matches design.
Not discharging water
properly
Visual evidence of water discharging at
concentrated points along trench (normal condition is a “sheet flow” of water along trench).
Water discharges from feature by sheet
flow.
Perforations plugged Over 1/4 of perforations in pipe are plugged with debris or sediment. Perforations freely discharge flow.
Water flows out top of “distributor” catch basin.
Water flows out of distributor catch basin during any storm less than the design storm.
No flow discharges from distributor catch basin.
Receiving area over-saturated Water in receiving area is causing or has potential of causing landslide problems. No danger of landslides.
Gabions Damaged mesh Mesh of gabion broken, twisted or deformed so structure is weakened or rock may fall out.
Mesh is intact, no rock missing.
Corroded mesh Gabion mesh shows corrosion through more than ¼ of its gage. All gabion mesh capable of containing rock and retaining designed form.
Collapsed or deformed baskets Gabion basket shape deformed due to any cause. All gabion baskets intact, structure stands as designed.
Missing rock Any rock missing that could cause gabion to loose structural integrity. No rock missing.
Manhole/Chamber Worn or damaged post, baffles or side of chamber
Structure dissipating flow deteriorates to ½ or original size or any concentrated worn spot exceeding one square foot which would make structure unsound.
Structure is in no danger of failing.
Damage to wall, frame, bottom, and/or top slab
Cracks wider than ½-inch or any evidence of soil entering the structure through cracks, or maintenance inspection personnel determines that the structure is not structurally sound.
Manhole/chamber is sealed and structurally sound.
Damaged pipe joints Cracks wider than ½-inch at the joint of the inlet/outlet pipes or any evidence of soil entering the structure at the joint of the inlet/outlet pipes.
No soil or water enters and no water discharges at the joint of inlet/outlet pipes.
APPENDIX A MAINTENANCE REQUIREMENTS FOR STORMWATER FACILITIES AND ON-SITE BMPS
2017 City of Renton Surface Water Design Manual 12/12/2016 A-17
NO. 11 – GROUNDS (LANDSCAPING)
MAINTENANCE
COMPONENT
DEFECT OR
PROBLEM
CONDITIONS WHEN
MAINTENANCE IS NEEDED
RESULTS EXPECTED WHEN
MAINTENANCE IS PERFORMED
Site Trash and debris Any trash and debris which exceed 1 cubic foot per 1,000 square feet (this is about equal to the amount of trash it would take to fill up one standard size office garbage can). In general, there should be no visual evidence of dumping.
Trash and debris cleared from site.
Noxious weeds Any noxious or nuisance vegetation which may constitute a hazard to City personnel or the public.
Noxious and nuisance vegetation removed according to applicable regulations. No danger of noxious vegetation where City personnel or the public might normally be.
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.
Excessive growth of grass/groundcover Grass or groundcover exceeds 18 inches in height. Grass or groundcover mowed to a height no greater than 6 inches.
Trees and Shrubs Hazard tree identified Any tree or limb of a tree identified as having a potential to fall and cause property damage or threaten human life. A hazard tree identified by a qualified arborist must be removed as soon as possible.
No hazard trees in facility.
Damaged tree or
shrub identified
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.
No blown down vegetation or knocked over
vegetation. Trees or shrubs 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; dead or diseased trees removed.
October 2019
GENERAL USE LEVEL DESIGNATION FOR BASIC (TSS), DISSOLVED
METALS (ENHANCED), AND PHOSPHORUS TREATMENT
For
Oldcastle Infrastructure, Inc.’s
The BioPod™ Biofilter
(Formerly the TreePod Biofilter)
Ecology’s Decision:
Based on Oldcastle Infrastructure, Inc. application submissions for the The BioPod™
Biofilter (BioPod), Ecology hereby issues the following use level designation:
1. General Use Level Designation (GULD) for Basic, Enhanced, and Phosphorus
Treatment:
Sized at a hydraulic loading rate of 1.6 gallons per minute (gpm) per square foot (sq
ft) of media surface area.
Constructed with a minimum media thickness of 18-inches (1.5-feet).
2. Ecology approves the BioPod at the hydraulic loading rate listed above, to achieve the
maximum water quality design flow rate. The water quality design flow rates are
calculated using the following procedures:
Western Washington: For treatment installed upstream of detention or retention,
the water quality design flow rate is the peak 15-minute flow rate as calculated using
the latest version of the Western Washington Hydrology Model or other Ecology-
approved continuous runoff model.
Eastern Washington: For treatment installed upstream of detention or retention,
the water quality design flow rate is the peak 15-minute flow rate as calculated using
one of the three methods described in Chapter 2.2.5 of the Stormwater Management
Manual for Eastern Washington (SWMMEW) or local manual.
Entire State: For treatment installed downstream of detention, the water quality
design flow rate is the full 2-year release rate of the detention facility.
3. The GULD has no expiration date, but may be amended or revoked by Ecology.
Ecology’s Conditions of Use:
The BioPod shall comply with these conditions:
1) Applicants shall design, assemble, install, operate, and maintain the BioPod
installations in accordance with Oldcastle Infrastructure, Inc.’s applicable manuals and
the Ecology Decision.
2) The minimum size filter surface-area for use in Washington is determined by using the
design water quality flow rate (as determined in Ecology Decision, Item 3, above) and
the Infiltration Rate (as identified in Ecology Decision, Item 1, above). Calculate the
required area by dividing the water quality design flow rate (cu-ft/sec) by the
Infiltration Rate (converted to ft/sec) to obtain required surface area (sq ft) of the
BioPod unit
3) BioPod media shall conform to the specifications submitted to and approved by Ecology
4) Maintenance: The required inspection/maintenance interval for stormwater treatment
devices is often dependent on the efficiency of the device and the degree of pollutant
loading from a particular drainage basin. Therefore, Ecology does not endorse or
recommend a “one size fits all” maintenance cycle for a particular model/size of
manufactured filter treatment device.
The BioPod is designed for a target maintenance interval of 1 year. Maintenance
includes replacing the mulch, assessing plant health, removal of trash, and raking
the top few inches of engineered media.
A BioPod system tested at the Lake Union Ship Canal Test Facility in Seattle, WA
required maintenance after 1.5 months, or 6.3% of a water year. Monitoring
personnel observed similar maintenance issues with other systems evaluated at the
Test Facility. The runoff from the Test Facility may be unusual and maintenance
requirements of systems installed at the Test Facility may not be indicative of
maintenance requirements for all sites.
Test results provided to Ecology from a BioPod System evaluated in a lab following
New Jersey Department of Environmental Protection Laboratory Protocol for
Filtration MTDs have indicated the BioPod System is capable of longer maintenance
intervals.
Owners/operators must inspect BioPod systems for a minimum of twelve months
from the start of post-construction operation to determine site-specific
inspection/maintenance schedules and requirements. Owners/operators must
conduct inspections monthly during the wet season, and every other month during
the dry season. (According to the SWMMWW, the wet season in western
Washington is October 1 to April 30. According to the SWMMEW, the wet season
in eastern Washington is October 1 to June 30.) After the first year of operation,
owners/operators must conduct inspections based on the findings during the first
year of inspections.
Conduct inspections by qualified personnel, follow manufacturer’s guidelines, and
use methods capable of determining either a decrease in treated effluent flow rate
and/or a decrease in pollutant removal ability.
5) Install the BioPod in such a manner that you bypass flows exceeding the maximum
operating rate and you will not resuspend captured sediment.
6) Discharges from the BioPod shall not cause or contribute to water quality standards
violations in receiving waters.
Approved Alternate Configurations
BioPod Internal Bypass
1) The BioPod Internal Bypass configuration may be combined with a Curb Inlet, Grated
Inlet, and Piped-In Inlet. Water quality flows and peak flows are directed from the
curb, overhead grate, or piped inlet to a contoured inlet rack. The inlet rack disperses
water quality flows over the top surface of the biofiltration chamber. Excess flows are
diverted over an curved bypass weir to the outlet area without passing through the
treatment area. Both water quality flows and bypass flows are combined in the outlet
area prior to being discharged out of the system.
2) To select a BioPod Internal Bypass unit, the designer must determine the size of the
standard unit using the sizing guidance described above. Systems that have an internal
bypass, may use the off-line water quality design flow rate.
3) The internal bypass configuration has a maximum flow rate of 900 gallons per minute.
Sites where the anticipated flow rate at the treatment device is larger than 900 gpm must use an
external bypass, or size the treatment device for the on-line water quality design flow rate.
Applicant: Oldcastle Infrastructure, Inc.
Applicant’s Address: 7100 Longe St, Suite 100
Stockton, CA 95206
Application Documents:
Technical Evaluation Report TreePod™ BioFilter System Performance Certification Project,
Prepared for Oldcastle, Inc., Prepared by Herrera Environmental Consultants, Inc. February 2018
Technical Memorandum: Response to Board of External Reviewers’ Comments on the Technical
Evaluation Report for the TreePod™ Biofilter System Performance Certification Project,
Oldcastle, Inc. and Herrera Environmental Consultants, Inc., February 2018
Technical Memorandum: Response to Board of External Reviewers’ Comments on the Technical
Evaluation Report for the TreePod™ Biofilter System Performance Certification Project,
Oldcastle, Inc. and Herrera Environmental Consultants, Inc., January 2018
Application for Pilot Use Level Designation, TreePod™ Biofilter – Stormwater Treatment
System, Oldcastle Stormwater Solutions, May 2016
Emerging Stormwater Treatment Technologies Application for Certification: The TreePod™
Biofilter, Oldcastle Stormwater Solutions, April 2016
Applicant’s Use Level Request:
General Use Level Designation as a Basic, Enhanced, and Phosphorus Treatment device
in accordance with Ecology’s Stormwater Management Manual for Western Washington
Applicant’s Performance Claims:
Based on results from laboratory and field-testing, the applicant claims the BioPod™ Biofilter
operating at a hydraulic loading rate of 153 inches per hour is able to remove:
80% of Total Suspended Solids (TSS) for influent concentrations greater than 100 mg/L
and achieve a 20 mg/L effluent for influent concentrations less than 100 mg/L.
60% dissolved zinc for influent concentrations 0.02 to 0.3 mg/L.
30% dissolved copper for influent concentrations 0.005 to 0.02 mg/L.
50% or greater total phosphorus for influent concentrations 0.1 to 0.5 mg/L.
Ecology’s Recommendations:
Ecology finds that:
Oldcastle Infrastructure, Inc. has shown Ecology, through laboratory and field testing,
that the BioPod™ Biofilter is capable of attaining Ecology’s Basic, Total Phosphorus,
and Enhanced treatment goals.
Findings of Fact:
Field Testing
1. Herrera Environmental Consultants, Inc. conducted monitoring of the BioPod™ Biofilter at
the Lake Union Ship Canal Test Facility in Seattle Washington between November 2016 and
April 2018. Herrera collected flow-weight composite samples during 14 separate storm
events and peak flow grab samples during 3 separate storm events. The system was sized at
an infiltration rate of 153 inches per hour or a hydraulic loading rate of 1.6 gpm/ft2.
2. The D50 of the influent PSD ranged from 3 to 292 microns, with an average D50 of 28
microns.
3. Influent TSS concentrations ranged from 17 mg/L to 666 mg/L, with a mean concentration of
98 mg/L. For all samples (influent concentrations above and below 100 mg/L) the bootstrap
estimate of the lower 95 percent confidence limit (LCL 95) of the mean TSS reduction was
84% and the bootstrap estimate of the upper 95 percent confidence limit (UCL95) of the
mean TSS effluent concentration was 8.2 mg/L.
4. Dissolved copper influent concentrations from the 17 events ranged from 9.0 µg/L to 21.1
µg/L. The 21.1 µg/L data point was reduced to 20.0 µg/L, the upper limit to the TAPE
allowed influent concentration range, prior to calculating the pollutant removal. A bootstrap
estimate of the LCL95 of the mean dissolved copper reduction was 35%.
5. Dissolved zinc influent concentrations from the 17 events ranged from 26.1 µg/L to 43.3
µg/L. A bootstrap estimate of the LCL95 of the mean dissolved zinc reduction was 71%.
6. Total phosphorus influent concentrations from the 17 events ranged from 0.064 mg/L to 1.56
mg/L. All influent data greater than 0.5 mg/L were reduced to 0.5 mg/L, the upper limit to the TAPE
allowed influent concentration range, prior to calculating the pollutant removal. A bootstrap
estimate of the LCL95 of the mean total phosphorus reduction was 64%.
7. The system experienced rapid sediment loading and needed to be maintained after 1.5
months. Monitoring personnel observed similar sediment loading issues with other systems
evaluated at the Test Facility. The runoff from the Test Facility may not be indicative of
maintenance requirements for all sites.
Laboratory Testing
1. Good Harbour Laboratories (GHL) conducted laboratory testing at their site in Mississauga,
Ontario in October 2017 following the New Jersey Department of Environmental Protection
Laboratory Protocol for Filtration MTDs. The testing evaluated a 4-foot by 6-foot standard
biofiltration chamber and inlet contour rack with bypass weir. The test sediment used during
the testing was custom blended by GHL using various commercially available silica sands,
which had an average d50 of 69 µm. Based on the lab test results:
a. GHL evaluated removal efficiency over 15 events at a Maximum Treatment Flow Rate
(MTFR) of 37.6 gpm, which corresponds to a MTFR to effective filtration treatment area
ratio of 1.80 gpm/ft2. The system, operating at 100% of the MTFR with an average
influent concentration of 201.3 mg/L, had an average removal efficiency of 99 percent.
b. GHL evaluated sediment mass loading capacity over an additional 16 events using an
influent SSC concentration of 400 mg/L. The first 11 runs were evaluated at 100% of the
MTFR. The BioPod began to bypass, so the remaining 5 runs were evaluated at 90% of
the MTFR. The total mass of the sediment captured was 245.0 lbs and the cumulative
mass removal efficiency was 96.3%.
2. Herrera Environmental Consultants Inc. conducted laboratory testing in September 2014 at
the Seattle University Engineering Laboratory. The testing evaluated the flushing
characteristics, hydraulic conductivity, and pollutant removal ability of twelve different
media blends. Based on this testing, Oldcastle Infrastructure, Inc. selected one media blend,
Mix 8, for inclusion in their TAPE evaluation of the BioPod™ Biofilter.
a. Herrera evaluated Mix 8 in an 8-inch diameter by 36-inch tall polyvinyl chloride (PVC)
column. The column contained 18-inches of Mix 8 on top of 6-inches of pea gravel. The
BioPod will normally include a 3-inch mulch layer on top of the media layer; however,
this was not included in the laboratory testing.
b. Mix 8 has a hydraulic conductivity of 218 inches per hour; however, evaluation of the
pollutant removal ability of the media was based on an infiltration rate of 115 inches per
hour. The media was tested at 75%, 100%, and 125% of the infiltration rate. Based on the
lab test results:
The system was evaluated using natural stormwater. The dissolved copper and
dissolved zinc concentrations in the natural stormwater were lower than the TAPE
influent standards; therefore, the stormwater was spiked with 66.4 mL of 100 mg/L
Cu solution and 113.6 mL of 1,000 mg/L Zn solution.
The BioPod removed an average of 81% of TSS, with a mean influent concentration
of 48.4 mg/L and a mean effluent concentration of 9.8 mg/L.
The BioPod removed an average of 94% of dissolved copper, with a mean influent
concentration of 10.6 µg/L and a mean effluent concentration of 0.6 µg/L.
The BioPod removed an average of 97% of dissolved zinc, with a mean influent
concentration of 117 µg/L and a mean effluent concentration of 4 µg/L.
The BioPod removed an average of 97% of total phosphorus, with a mean influent
concentration of 2.52 mg/L and a mean effluent concentration of 0.066 mg/L. When
total phosphorus influent concentrations were capped at the TAPE upper limit of 0.5
mg/L, calculations showed an average removal of 87%.
Other BioPod Related Issues to be Addressed By the Company:
1. Conduct hydraulic testing to obtain information about maintenance requirements on a site
with runoff that is more typical of the Pacific Northwest.
Technology Description: Download at
https://oldcastleprecast.com/stormwater/bioretention-
biofiltration-applications/bioretention-biofiltration-
solutions/
Contact Information:
Applicant: Chris Demarest
Oldcastle Infrastructure, Inc.
(925) 667-7100
Chris.demarest@oldcastle.com
Applicant website: https://oldcastleprecast.com/stormwater/
Ecology web link: https://ecology.wa.gov/Regulations-Permits/Guidance-technical-
assistance/Stormwater-permittee-guidance-resources/Emerging-stormwater-treatment-
technologies
Ecology: Douglas C. Howie, P.E.
Department of Ecology
Water Quality Program
(360) 407-6444
douglas.howie@ecy.wa.gov
Revision History
Date Revision
March 2018 GULD granted for Basic Treatment
March 2018 Provisional GULD granted for Enhanced and Phosphorus Treatment
June 2016 PULD Granted
April 2018 GULD for Basic and Provisional GULD for Enhanced and
Phosphorus granted, changed name to BioPod from TreePod
July 2018 GULD for Enhanced and Phosphorus granted
September 2018 Changed Address for Oldcastle
December 2018 Added minimum media thickness requirement
May 2019 Changed language on who must Install and maintain the device from
Oldcastle to Applicants
August 2019 Added text on sizing using infiltration rate and water quality design
flow rate
October 2019 Added text describing ability to use off-line design water quality flow
rate for sizing due to internal bypass
Inspection and Maintenance Guide
BIOPODTM SYSTEM
WITH STORMMIX™ MEDIA
BioPod™ Biofilter with StormMix™ Biofiltration Media
Description
The BioPod™ Biofilter System (BioPod) is a stormwater biofiltration treatment system used to remove pollutants
from stormwater runoff. Impervious surfaces and other urban and suburban landscapes generate a variety of contaminants that can enter stormwater and pollute downstream receiving waters unless treatment is provided. The BioPod system uses proprietary StormMix™ biofiltration media to capture and retain pollutants including
total suspended solids (TSS), metals, nutrients, gross solids, trash and debris as well as petroleum hydrocarbons.
Function
The BioPod system uses engineered, high-flow rate filter media to remove stormwater pollutants, allowing for a smaller footprint than conventional bioretention systems. Contained within a compact precast concrete vault, the
BioPod system consists of a biofiltration chamber and an optional integrated high-flow bypass with a contoured
inlet rack to minimize scour. The biofiltration chamber is filled with horizontal layers of aggregate (which may or
may not include an underdrain), biofiltration media and mulch. Stormwater passes vertically down through the mulch and biofiltration media for treatment. The mulch provides pretreatment by retaining most of the solids or sediment. The biofiltration media provides further treatment by retaining finer sediment and dissolved pollutants.
The aggregate allows the media bed to drain evenly for discharge through an underdrain pipe or by infiltration.
Configuration
The BioPod system can be configured with either an internal or external bypass. The internal bypass allows both
water quality and bypass flows to enter the treatment vault. The water quality flows are directed to the biofiltration
chamber while the excess flows are diverted over the bypass weir without entering the biofiltration chamber. Both
the treatment and bypass flows are combined in the outlet area prior to discharge from the structure. BioPod units without an internal bypass are designed such that only treatment flows enter the treatment structure. When the system has exceeded its treatment capacity, ponding will force bypass flows to continue down the gutter to
the nearest standard catch basin or other external bypass structure.
The BioPod system can be configured as a tree box filter with tree and grated inlet, as a planter box filter with shrubs, grasses and an open top, or as an underground filter with access risers, doors and a subsurface inlet pipe. The optional internal bypass may be incorporated with any of these configurations. In addition, an open
bottom configuration may be used to promote infiltration and groundwater recharge. The configuration and size
of the BioPod system is designed to meet the requirements of a specific project.
Inspection & Maintenance Overview
State and local regulations require all stormwater management systems to be inspected on a regular basis and
maintained as necessary to ensure performance and protect downstream receiving waters. Without maintenance,
excessive pollutant buildup can limit system performance by reducing the operating capacity of the system and
increasing the potential for scouring of pollutants during periods of high flow.
Some configurations of the BioPod may require periodic irrigation to establish and maintain vegetation. Vegetation
will typically become established about two years after planting. Irrigation requirements are ultimately dependent
on climate, rainfall and the type of vegetation selected.
2
INSPECTION AND MAINTENANCE GUIDE
3
Maintenance Frequency
Periodic inspection is essential for consistent system performance and is easily completed. Inspection is typically conducted a minimum of twice per year, but since pollutant transport and deposition varies from site to
site, a site-specific maintenance frequency should be established during the first two or three years of operation.
Inspection Equipment
The following equipment is helpful when conducting BioPod inspections:
• Recording device (pen and paper form, voice recorder, iPad, etc.)
• Suitable clothing (appropriate footwear, gloves, hardhat, safety glasses, etc.)• Traffic control equipment (cones, barricades, signage, flagging, etc.)• Manhole hook or pry bar
• Flashlight
• Tape measure
Inspection Procedures
BioPod inspections are visual and are conducted without entering the unit. To complete an inspection, safety
measures including traffic control should be deployed before the access covers or tree grates are removed. Once the covers have been removed, the following items should be checked and recorded (see form provided on page 6) to determine whether maintenance is required:
• If the BioPod unit is equipped with an internal bypass, inspect the contoured inlet rack and outlet chamber
and note whether there are any broken or missing parts. In the unlikely event that internal parts are broken or missing, contact Oldcastle Stormwater at (800) 579-8819 to determine appropriate corrective action.
• Note whether the curb inlet, inlet pipe, or – if the unit is equipped with an internal bypass – the inlet rack is blocked or obstructed.
• If the unit is equipped with an internal bypass, observe, quantify and record the accumulation of trash
and debris in the inlet rack. The significance of accumulated trash and debris is a matter of judgment. Often, much of the trash and debris may be removed manually at the time of inspection if a separate maintenance visit is not yet warranted.
• If it has not rained within the past 24 hours, note whether standing water is observed in the biofiltration chamber.
• Finally, observe, quantify and record presence of invasive vegetation and the amount of trash and debris and sediment load in the biofiltration chamber. Erosion of the mulch and biofiltration media bed should also be recorded. Sediment load may be rated light, medium or heavy depending on the conditions.
Loading characteristics may be determined as follows:
o Light sediment load – sediment is difficult to distinguish among the mulch fibers at the top of the
mulch layer; the mulch appears almost new.
o Medium sediment load – sediment accumulation is apparent and may be concentrated in some areas; probing the mulch layer reveals lighter sediment loads under the top 1” of mulch.
o Heavy sediment load – sediment is readily apparent across the entire top of the mulch layer; individual mulch fibers are difficult to distinguish; probing the mulch layer reveals heavy sediment load under the
top 1” of mulch.
Often, much of the invasive vegetation and trash and debris may be removed manually at the time of inspection if a separate maintenance visit is not yet warranted.
4
Maintenance Indicators
Maintenance should be scheduled if any of the following conditions are identified during inspection:
•The concrete structure is damaged or the tree grate or access cover is damaged or missing.•The curb inlet or inlet rack is obstructed.•Standing water is observed in the biofiltration chamber more than 24 hours after a rainfall event (use
discretion if the BioPod is located downstream of a storage system that attenuates flow).
•Trash and debris in the inlet rack cannot be easily removed at the time of inspection.
•Trash and debris, invasive vegetation or sediment load in the biofiltration chamber is heavy or excessiveerosion has occurred.
Maintenance Equipment
The following equipment is helpful when conducting BioPod maintenance:
•Suitable clothing (appropriate footwear, gloves, hardhat, safety glasses, etc.)•Traffic control equipment (cones, barricades, signage, flagging, etc.)
•Manhole hook or pry bar
•Flashlight
•Tape measure•Rake, hoe, shovel and broom•Bucket
•Pruners
•Vacuum truck (optional)
Maintenance Procedures
Maintenance should be conducted during dry weather when no flows are entering the system. All maintenance
may be conducted without entering the BioPod structure. Once safety measures such as traffic control are
deployed, the access covers may be removed and the following activities may be conducted to complete maintenance:
•Remove all trash and debris from the curb inlet and inlet rack manually or by using a vacuum truck as
required.
•Remove all trash and debris and invasive vegetation from the biofiltration chamber manually or by using avacuum truck as required.•If the sediment load is medium or light but erosion of the biofiltration media bed is evident, redistribute
the mulch with a rake or replace missing mulch as appropriate. If erosion persists, rocks may be placed in
the eroded area to help dissipate energy and prevent recurring erosion.
•If the sediment load is heavy, remove the mulch layer using a hoe, rake, shovel and bucket, or by using avacuum truck as required. If the sediment load is particularly heavy, inspect the surface of the biofiltrationmedia once the mulch has been removed. If the media appears clogged with sediment, remove and
replace one or two inches of biofiltration media prior to replacing the mulch layer.
•Prune vegetation as appropriate and replace damaged or dead plants as required.
•Replace the tree grate and/or access covers and sweep the area around the BioPod to leave the site clean.•All material removed from the BioPod during maintenance must be disposed of in accordance with localenvironmental regulations. In most cases, the material may be handled in the same manner as disposal
of material removed from sumped catch basins or manholes.
Natural, shredded hardwood mulch should be used in the BioPod. Timely replacement of the mulch layer
according to the maintenance indicators described above should protect the biofiltration media below the
mulch layer from clogging due to sediment accumulation. However, whenever the mulch is replaced, the BioPod should be visited 24 hours after the next major storm event to ensure that there is no standing water in the biofiltration chamber. Standing water indicates that the biofiltration media below the mulch layer is
clogged and must be replaced. Please contact Oldcastle Infrastructure at (800) 579-8819 to purchase the
proprietary StormMix™ biofiltration media.
5
BioPod Tree Module BioPod Media Module
BioPod Planter Module BioPod Media Vault
6
Curb Inlet or Inlet Rack Blocked Notes:
Yes No
BioPod Inspection &
Maintenance Log
BioPod Model__________________________ Inspection Date________________________
Location______________________________________________________________________________
Condition of Internal Components Notes:
Good Damaged Missing
Standing Water in Biofiltration Chamber Notes:
Yes No
Trash and Debris in Inlet Rack Notes:
Yes No
Trash and Debris in Biofiltration Chamber Notes:
Yes No
Maintenance Requirements
Yes - Schedule Maintenance No - Schedule Re-Inspection
Invasive Vegetation in Biofiltration Chamber Notes:
Yes No
Sediment in Biofiltration Chamber Notes:
Light Medium Heavy
Erosion in Biofiltration Chamber Notes:
Yes No
BIOPODTM SYSTEM
WITH STORMMIX™ MEDIA
BUILDINGSTRUCTURES
OUR MARKETS
TRANSPORTATION
WATER
ENERGYCOMMUNICATIONS
December 2018 v.1
www.oldcastleinfrastructure.com
800-579-8819
MAINTENANCE INSTRUCTIONS FOR A RAIN GARDEN
Your property contains an on-site BMP (best management practice) called a “rain garden,” which was
installed to mitigate the stormwater quantity and quality impacts of some or all of the impervious or
nonnative pervious surfaces on your property.
Rain gardens include vegetated closed depressions (ponds) that retain and filter stormwater from an
area of impervious surface or nonnative pervious surface on your property. The soil in the rain garden
has been enhanced to encourage and support vigorous plant growth that serves to filter the water and sustain infiltration capacity. Depending on soil conditions, the rain garden area may have water in it
throughout the wet season and may overflow during major storm events. This on-site BMP shall be maintained per Appendix A of the City of Renton’s Surface Water Design Manual.
MAINTENANCE RESTRICTIONS
The size, placement, and design of the rain garden as depicted by the site plan and design details must be maintained and may not be changed without written approval from the City of Renton or through a
future development permit from City of Renton. Plant materials may be changed to suit tastes, but
chemical fertilizers and pesticides must not be used.
INSPECTION FREQUENCY AND MAINTENANCE GUIDELINES
• Rain gardens must be inspected annually for physical defects and sediment accumulation.
• Rain gardens have inflow and overflow inlets and outlets. These need to be maintained to
ensure that water is moving into and out of the rain garden. Check inlets/outlets for debris/sediment blockage, bare spots (exposed soil), or other signs of erosion damage (soil
movement). Remove debris and obstructions as necessary.
• After major storm events, the system should be checked to see that the overflow system is
working properly and sedimentation is not occurring at the inlet. If erosion damage or bare
spots are evident, they should be stabilized with soil, plant material, mulch, or landscape rock. Sediment deposits should be carefully removed and the sediment source eliminated.
• Plants must be adapted to wet winter conditions and dry summer conditions. Vegetation is to be watered and pruned as needed.
• Frequent watering is required to keep the plants healthy:
o Year 1: weekly,
o Year 2: bimonthly,
o Year 3: bimonthly,
o Year 4 & beyond: as needed for established plantings and dry periods.
• Chemical fertilizers and pesticides must not be used.
• Soil must be replaced in areas where sediment accumulation is preventing adequate infiltration
of water through the soil.
• Compacted soil should be decompacted.
• Trash and debris must be removed often from the rain garden depression.
• Mulch must be applied to bare soil at a minimum of 2 inches to maintain healthy growth.
• Compost may be added if soil nutrients are no longer adequate to support plant growth.
• Vegetation should be maintained as follows:
1) Replace all dead vegetation as soon as possible;
2) Remove fallen leaves and debris as needed;
3) Remove all noxious vegetation when discovered;
4) Manually weed without herbicides or pesticides;
5) To protect infiltration performance, do not compact soils in the bioretention cell with heavy
maintenance equipment and/or excessive foot traffic;
6) During drought conditions, use mulch to prevent excess solar damage and water loss.
RECORDING REQUIREMENT
These rain garden on-site BMP maintenance and operation instructions must be recorded as an attachment to the required declaration of covenant and grant of easement per Requirement 3 of Section C.1.3.4 of the City of Renton Surface Water Design Manual. The intent of these instructions is
to explain to future property owners, the purpose of the BMP and how it must be maintained and operated. These instructions are intended to be a minimum; the City of Renton may require additional
instructions based on site-specific conditions. See the City of Renton’s Surface Water Design Manual
website for additional information and updates.
TECHNICAL INFORMATION REPORT JUNE 3, 2021
4TH DIMENSION MIXED USE PAGE 30
P:\Work\Projects\2018\18-196 Concept Arch\CE\DOCS\CDs\18-196 TIR.doc SRM/dwh
X. MAINTENANCE AND OPERATIONS MANUAL
Following are the applicable Maintenance and Operations Guidelines taken from the RSWDM.
APPENDIX A MAINTENANCE REQUIREMENTS FOR STORMWATER FACILITIES AND ON-SITE BMPS
12/12/2016 2017 City of Renton Surface Water Design Manual A-6
NO. 3 – DETENTION TANKS AND VAULTS
MAINTENANCE
COMPONENT
DEFECT OR
PROBLEM
CONDITIONS WHEN
MAINTENANCE IS NEEDED
RESULTS EXPECTED WHEN
MAINTENANCE IS PERFORMED
Site Trash and debris Any trash and debris which exceed 1 cubic foot per 1,000 square feet (this is about equal to the amount of trash it would take to fill up one standard size office garbage can). In general, there should be no visual evidence of dumping.
Trash and debris cleared from site.
Noxious weeds Any noxious or nuisance vegetation which may constitute a hazard to City personnel or the public.
Noxious and nuisance vegetation removed according to applicable regulations. No danger of noxious vegetation where City personnel or the public might normally be.
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.
Excessive growth of grass/groundcover Grass or groundcover exceeds 18 inches in height. Grass or groundcover mowed to a height no greater than 6 inches.
Tank or Vault Storage Area Trash and debris Any trash and debris accumulated in vault or tank (includes floatables and non-floatables).
No trash or debris in vault.
Sediment accumulation Accumulated sediment depth exceeds 10% of the diameter of the storage area for ½ length of storage vault or any point depth exceeds 15% of diameter. Example:
72-inch storage tank would require cleaning when sediment reaches depth of 7 inches for more than ½ length of tank.
All sediment removed from storage area.
Tank Structure Plugged air vent Any blockage of the vent. Tank or vault freely vents.
Tank bent out of shape Any part of tank/pipe is bent out of shape more than 10% of its design shape. Tank repaired or replaced to design.
Gaps between sections, damaged
joints or cracks or tears in wall
A gap wider than ½-inch at the joint of any tank sections or any evidence of soil
particles entering the tank at a joint or through a wall.
No water or soil entering tank through joints or walls.
Vault Structure Damage to wall, frame, bottom, and/or top slab
Cracks wider than ½-inch, any evidence of soil entering the structure through cracks or qualified inspection personnel determines that the vault is not structurally sound.
Vault is sealed and structurally sound.
Inlet/Outlet Pipes Sediment accumulation Sediment filling 20% or more of the pipe. Inlet/outlet pipes clear of sediment.
Trash and debris Trash and debris accumulated in inlet/outlet pipes (includes floatables and non-floatables).
No trash or debris in pipes.
Damaged inlet/outlet pipes Cracks wider than ½-inch at the joint of the inlet/outlet pipes or any evidence of soil entering at the joints of the inlet/outlet pipes.
No cracks more than ¼-inch wide at the joint of the inlet/outlet pipe.
Access Manhole Cover/lid not in place Cover/lid is missing or only partially in place. Any open manhole requires immediate maintenance.
Manhole access covered.
APPENDIX A MAINTENANCE REQUIREMENTS FOR STORMWATER FACILITIES AND ON-SITE BMPS
2017 City of Renton Surface Water Design Manual 12/12/2016 A-7
NO. 3 – DETENTION TANKS AND VAULTS
MAINTENANCE
COMPONENT
DEFECT OR
PROBLEM
CONDITIONS WHEN
MAINTENANCE IS NEEDED
RESULTS EXPECTED WHEN
MAINTENANCE IS PERFORMED
Access Manhole (cont.) Locking mechanism not working Mechanism cannot be opened by one maintenance person with proper tools. Bolts cannot be seated. Self-locking cover/lid does not work.
Mechanism opens with proper tools.
Cover/lid difficult to remove One maintenance person cannot remove cover/lid after applying 80 lbs of lift. Cover/lid can be removed and 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
doors/plate
Damaged or difficult
to open
Large access doors or plates cannot be
opened/removed using normal equipment.
Replace or repair access door so it can
opened as designed.
Gaps, doesn't cover completely Large access doors not flat and/or access opening not completely covered. Doors close flat; covers access opening completely.
Lifting rings missing, rusted Lifting rings not capable of lifting weight of door or plate. Lifting rings sufficient to lift or remove door or plate.
APPENDIX A MAINTENANCE REQUIREMENTS FOR STORMWATER FACILITIES AND ON-SITE BMPS
12/12/2016 2017 City of Renton Surface Water Design Manual A-8
NO. 4 – CONTROL STRUCTURE/FLOW RESTRICTOR
MAINTENANCE
COMPONENT
DEFECT OR
PROBLEM
CONDITION WHEN MAINTENANCE
IS NEEDED
RESULTS EXPECTED WHEN
MAINTENANCE IS PERFORMED
Structure Trash and debris Trash or debris of more than ½ cubic foot which is located immediately in front of the structure opening or is blocking capacity of the structure by more than 10%.
No Trash or debris blocking or potentially blocking entrance to structure.
Trash or debris in the structure 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 structure.
Deposits of garbage exceeding 1 cubic foot in volume. No condition present which would attract or support the breeding of insects or rodents.
Sediment accumulation Sediment exceeds 60% of the depth from the bottom of the structure to the invert of the lowest pipe into or out of the structure or the bottom of the FROP-T section or is
within 6 inches of the invert of the lowest pipe into or out of the structure or the bottom of the FROP-T section.
Sump of structure contains no sediment.
Damage to frame and/or top slab Corner of frame extends more than ¾ 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 ¼ inch. Top slab is free of holes and cracks.
Frame not sitting flush on top slab, i.e., separation of more than ¾ inch of the frame from the top slab.
Frame is sitting flush on top slab.
Cracks in walls or bottom Cracks wider than ½ inch and longer than 3 feet, any evidence of soil particles entering structure through cracks, or maintenance person judges that structure is unsound.
Structure is sealed and structurally sound.
Cracks wider than ½ inch and longer than 1 foot at the joint of any inlet/outlet pipe or
any evidence of soil particles entering structure through cracks.
No cracks more than 1/4 inch wide at the joint of inlet/outlet pipe.
Settlement/ misalignment Structure has settled more than 1 inch or has rotated more than 2 inches out of alignment.
Basin replaced or repaired to design standards.
Damaged pipe joints Cracks wider than ½-inch at the joint of the inlet/outlet pipes or any evidence of soil entering the structure at the joint of the inlet/outlet pipes.
No cracks more than ¼-inch wide at the joint of inlet/outlet pipes.
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.
Ladder rungs missing or unsafe Ladder is unsafe due to missing rungs, misalignment, rust, cracks, or sharp edges. Ladder meets design standards and allows maintenance person safe access.
FROP-T Section Damaged FROP-T T section is not securely attached to
structure wall and outlet pipe structure should support at least 1,000 lbs of up or down pressure.
T section securely attached to wall and
outlet pipe.
Structure is not in upright position (allow up to 10% from plumb). Structure in correct position.
APPENDIX A MAINTENANCE REQUIREMENTS FOR STORMWATER FACILITIES AND ON-SITE BMPS
2017 City of Renton Surface Water Design Manual 12/12/2016 A-9
NO. 4 – CONTROL STRUCTURE/FLOW RESTRICTOR
MAINTENANCE
COMPONENT
DEFECT OR
PROBLEM
CONDITION WHEN MAINTENANCE
IS NEEDED
RESULTS EXPECTED WHEN
MAINTENANCE IS PERFORMED
FROP-T Section (cont.) Damaged FROP-T (cont.) Connections to outlet pipe are not watertight or show signs of deteriorated grout.
Connections to outlet pipe are water tight; structure repaired or replaced and works as designed.
Any holes—other than designed holes—in
the structure.
Structure has no holes other than designed
holes.
Cleanout Gate Damaged or missing cleanout gate Cleanout gate is missing. Replace cleanout gate.
Cleanout gate is not watertight. Gate is watertight and works as designed.
Gate cannot be moved up and down by one maintenance person. Gate moves up and down easily and is watertight.
Chain/rod leading to gate is missing or damaged. Chain is in place and works as designed.
Orifice Plate Damaged or missing
orifice plate
Control device is not working properly due
to missing, out of place, or bent orifice plate.
Plate is in place and works as designed.
Obstructions to orifice plate Any trash, debris, sediment, or vegetation blocking the plate. Plate is free of all obstructions and works as designed.
Overflow Pipe Obstructions to
overflow pipe
Any trash or debris blocking (or having the
potential of blocking) the overflow pipe.
Pipe is free of all obstructions and works
as designed.
Deformed or damaged lip of overflow pipe
Lip of overflow pipe is bent or deformed. Overflow pipe does not allow overflow at an elevation lower than design
Inlet/Outlet Pipe Sediment accumulation Sediment filling 20% or more of the pipe. Inlet/outlet pipes clear of sediment.
Trash and debris Trash and debris accumulated in
inlet/outlet pipes (includes floatables and non-floatables).
No trash or debris in pipes.
Damaged inlet/outlet
pipe
Cracks wider than ½-inch at the joint of the
inlet/outlet pipes or any evidence of soil entering at the joints of the inlet/outlet pipes.
No cracks more than ¼-inch wide at the
joint of the inlet/outlet pipe.
Metal Grates (If applicable) Unsafe grate opening Grate with opening wider than 7/8 inch. Grate opening meets design standards.
Trash and debris Trash and debris that is blocking more
than 20% of grate surface.
Grate free of trash and debris. footnote to
guidelines for disposal
Damaged or missing grate Grate missing or broken member(s) of the grate. Grate is in place and meets design standards.
Manhole Cover/Lid Cover/lid not in place Cover/lid is missing or only partially in place. Any open structure requires urgent maintenance.
Cover/lid protects opening to structure.
Locking mechanism
not working
Mechanism cannot be opened by one
maintenance person with proper tools. Bolts cannot be seated. Self-locking cover/lid does not work.
Mechanism opens with proper tools.
Cover/lid difficult to remove One maintenance person cannot remove cover/lid after applying 80 lbs. of lift. Cover/lid can be removed and reinstalled by one maintenance person.
APPENDIX A MAINTENANCE REQUIREMENTS FOR STORMWATER FACILITIES AND ON-SITE BMPS
12/12/2016 2017 City of Renton Surface Water Design Manual A-10
NO. 5 – CATCH BASINS AND MANHOLES
MAINTENANCE
COMPONENT
DEFECT OR
PROBLEM
CONDITION WHEN MAINTENANCE
IS NEEDED
RESULTS EXPECTED WHEN
MAINTENANCE IS PERFORMED
Structure Sediment accumulation Sediment exceeds 60% of the depth from the bottom of the catch basin to the invert of the 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.
Sump of catch basin contains no sediment.
Trash and debris Trash or debris of more than ½ cubic foot which is located immediately in front of the catch basin opening or is blocking capacity of the catch basin by more than 10%.
No Trash or debris blocking or potentially blocking entrance to catch basin.
Trash or debris in the catch 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.
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 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.
Damage to frame and/or top slab Corner of frame extends more than ¾ 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 ¼ inch. Top slab is free of holes and cracks.
Frame not sitting flush on top slab, i.e., separation of more than ¾ inch of the frame from the top slab.
Frame is sitting flush on top slab.
Cracks in walls or bottom Cracks wider than ½ inch and longer than 3 feet, any evidence of soil particles entering catch basin through cracks, or maintenance person judges that catch
basin is unsound.
Catch basin is sealed and is structurally sound.
Cracks wider than ½ 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.
Settlement/ misalignment Catch basin has settled more than 1 inch or has rotated more than 2 inches out of alignment.
Basin replaced or repaired to design standards.
Damaged pipe joints Cracks wider than ½-inch at the joint of the inlet/outlet pipes or any evidence of soil entering the catch basin at the joint of the inlet/outlet pipes.
No cracks more than ¼-inch wide at the joint of inlet/outlet pipes.
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/Outlet Pipe Sediment accumulation Sediment filling 20% or more of the pipe. Inlet/outlet pipes clear of sediment.
Trash and debris Trash and debris accumulated in
inlet/outlet pipes (includes floatables and non-floatables).
No trash or debris in pipes.
APPENDIX A MAINTENANCE REQUIREMENTS FOR STORMWATER FACILITIES AND ON-SITE BMPS
2017 City of Renton Surface Water Design Manual 12/12/2016 A-11
NO. 5 – CATCH BASINS AND MANHOLES
MAINTENANCE
COMPONENT
DEFECT OR
PROBLEM
CONDITION WHEN MAINTENANCE
IS NEEDED
RESULTS EXPECTED WHEN
MAINTENANCE IS PERFORMED
Inlet/Outlet Pipe (cont.) Damaged inlet/outlet pipe Cracks wider than ½-inch at the joint of the inlet/outlet pipes or any evidence of soil entering at the joints of the inlet/outlet pipes.
No cracks more than ¼-inch wide at the joint of the inlet/outlet pipe.
Metal Grates (Catch Basins) Unsafe grate opening Grate with opening wider than 7/8 inch. Grate opening meets design standards.
Trash and debris Trash and debris that is blocking more than 20% of grate surface. Grate free of trash and debris. footnote to guidelines for disposal
Damaged or missing grate Grate missing or broken member(s) of the grate. Any open structure requires urgent maintenance.
Grate is in place and meets design standards.
Manhole Cover/Lid Cover/lid not in place Cover/lid is missing or only partially in place. Any open structure requires urgent maintenance.
Cover/lid protects opening to structure.
Locking mechanism not working Mechanism cannot be opened by one maintenance person with proper tools. Bolts cannot be seated. Self-locking cover/lid does not work.
Mechanism opens with proper tools.
Cover/lid difficult to remove One maintenance person cannot remove cover/lid after applying 80 lbs. of lift. Cover/lid can be removed and reinstalled by one maintenance person.
APPENDIX A MAINTENANCE REQUIREMENTS FOR STORMWATER FACILITIES AND ON-SITE BMPS
12/12/2016 2017 City of Renton Surface Water Design Manual A-12
NO. 6 – CONVEYANCE PIPES AND DITCHES
MAINTENANCE
COMPONENT
DEFECT OR
PROBLEM
CONDITIONS WHEN
MAINTENANCE IS NEEDED
RESULTS EXPECTED WHEN
MAINTENANCE IS PERFORMED
Pipes Sediment & debris accumulation Accumulated sediment or debris that exceeds 20% of the diameter of the pipe. Water flows freely through pipes.
Vegetation/root growth in pipe Vegetation/roots that reduce free movement of water through pipes. Water flows freely through pipes.
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.
Damage to protective coating or corrosion Protective coating is damaged; rust or corrosion is weakening the structural integrity of any part of pipe.
Pipe repaired or replaced.
Damaged pipes Any dent that decreases the cross section area of pipe by more than 20% or is determined to have weakened structural integrity of the pipe.
Pipe repaired or replaced.
Ditches Trash and debris Trash and debris exceeds 1 cubic foot per 1,000 square feet of ditch and slopes. Trash and debris cleared from ditches.
Sediment accumulation Accumulated sediment that exceeds 20% of the design depth. Ditch cleaned/flushed of all sediment and debris so that it matches design.
Noxious weeds Any noxious or nuisance vegetation which may constitute a hazard to City personnel or the public.
Noxious and nuisance vegetation removed according to applicable regulations. No danger of noxious vegetation where City personnel or the public might normally be.
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.
Excessive vegetation growth Vegetation that reduces free movement of water through ditches. Water flows freely through ditches.
Erosion damage to
slopes
Any erosion observed on a ditch slope. Slopes are not eroding.
Rock lining out of place or missing (If applicable)
One layer or less of rock exists above native soil area 5 square feet or more, any exposed native soil.
Replace rocks to design standards.
APPENDIX A MAINTENANCE REQUIREMENTS FOR STORMWATER FACILITIES AND ON-SITE BMPS
12/12/2016 2017 City of Renton Surface Water Design Manual A-14
NO. 8 – ENERGY DISSIPATERS
MAINTENANCE
COMPONENT
DEFECT OR
PROBLEM
CONDITIONS WHEN
MAINTENANCE IS NEEDED
RESULTS EXPECTED WHEN
MAINTENANCE IS PERFORMED.
Site Trash and debris Trash and/or debris accumulation. Dissipater clear of trash and/or debris.
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.
Rock Pad Missing or moved
rock
Only one layer of rock exists above native
soil in area five square feet or larger or any exposure of native soil.
Rock pad prevents erosion.
Dispersion Trench Pipe plugged with sediment Accumulated sediment that exceeds 20% of the design depth. Pipe cleaned/flushed so that it matches design.
Not discharging water
properly
Visual evidence of water discharging at
concentrated points along trench (normal condition is a “sheet flow” of water along trench).
Water discharges from feature by sheet
flow.
Perforations plugged Over 1/4 of perforations in pipe are plugged with debris or sediment. Perforations freely discharge flow.
Water flows out top of “distributor” catch basin.
Water flows out of distributor catch basin during any storm less than the design storm.
No flow discharges from distributor catch basin.
Receiving area over-saturated Water in receiving area is causing or has potential of causing landslide problems. No danger of landslides.
Gabions Damaged mesh Mesh of gabion broken, twisted or deformed so structure is weakened or rock may fall out.
Mesh is intact, no rock missing.
Corroded mesh Gabion mesh shows corrosion through more than ¼ of its gage. All gabion mesh capable of containing rock and retaining designed form.
Collapsed or deformed baskets Gabion basket shape deformed due to any cause. All gabion baskets intact, structure stands as designed.
Missing rock Any rock missing that could cause gabion to loose structural integrity. No rock missing.
Manhole/Chamber Worn or damaged post, baffles or side of chamber
Structure dissipating flow deteriorates to ½ or original size or any concentrated worn spot exceeding one square foot which would make structure unsound.
Structure is in no danger of failing.
Damage to wall, frame, bottom, and/or top slab
Cracks wider than ½-inch or any evidence of soil entering the structure through cracks, or maintenance inspection personnel determines that the structure is not structurally sound.
Manhole/chamber is sealed and structurally sound.
Damaged pipe joints Cracks wider than ½-inch at the joint of the inlet/outlet pipes or any evidence of soil entering the structure at the joint of the inlet/outlet pipes.
No soil or water enters and no water discharges at the joint of inlet/outlet pipes.
APPENDIX A MAINTENANCE REQUIREMENTS FOR STORMWATER FACILITIES AND ON-SITE BMPS
2017 City of Renton Surface Water Design Manual 12/12/2016 A-17
NO. 11 – GROUNDS (LANDSCAPING)
MAINTENANCE
COMPONENT
DEFECT OR
PROBLEM
CONDITIONS WHEN
MAINTENANCE IS NEEDED
RESULTS EXPECTED WHEN
MAINTENANCE IS PERFORMED
Site Trash and debris Any trash and debris which exceed 1 cubic foot per 1,000 square feet (this is about equal to the amount of trash it would take to fill up one standard size office garbage can). In general, there should be no visual evidence of dumping.
Trash and debris cleared from site.
Noxious weeds Any noxious or nuisance vegetation which may constitute a hazard to City personnel or the public.
Noxious and nuisance vegetation removed according to applicable regulations. No danger of noxious vegetation where City personnel or the public might normally be.
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.
Excessive growth of grass/groundcover Grass or groundcover exceeds 18 inches in height. Grass or groundcover mowed to a height no greater than 6 inches.
Trees and Shrubs Hazard tree identified Any tree or limb of a tree identified as having a potential to fall and cause property damage or threaten human life. A hazard tree identified by a qualified arborist must be removed as soon as possible.
No hazard trees in facility.
Damaged tree or
shrub identified
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.
No blown down vegetation or knocked over
vegetation. Trees or shrubs 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; dead or diseased trees removed.
October 2019
GENERAL USE LEVEL DESIGNATION FOR BASIC (TSS), DISSOLVED
METALS (ENHANCED), AND PHOSPHORUS TREATMENT
For
Oldcastle Infrastructure, Inc.’s
The BioPod™ Biofilter
(Formerly the TreePod Biofilter)
Ecology’s Decision:
Based on Oldcastle Infrastructure, Inc. application submissions for the The BioPod™
Biofilter (BioPod), Ecology hereby issues the following use level designation:
1. General Use Level Designation (GULD) for Basic, Enhanced, and Phosphorus
Treatment:
Sized at a hydraulic loading rate of 1.6 gallons per minute (gpm) per square foot (sq
ft) of media surface area.
Constructed with a minimum media thickness of 18-inches (1.5-feet).
2. Ecology approves the BioPod at the hydraulic loading rate listed above, to achieve the
maximum water quality design flow rate. The water quality design flow rates are
calculated using the following procedures:
Western Washington: For treatment installed upstream of detention or retention,
the water quality design flow rate is the peak 15-minute flow rate as calculated using
the latest version of the Western Washington Hydrology Model or other Ecology-
approved continuous runoff model.
Eastern Washington: For treatment installed upstream of detention or retention,
the water quality design flow rate is the peak 15-minute flow rate as calculated using
one of the three methods described in Chapter 2.2.5 of the Stormwater Management
Manual for Eastern Washington (SWMMEW) or local manual.
Entire State: For treatment installed downstream of detention, the water quality
design flow rate is the full 2-year release rate of the detention facility.
3. The GULD has no expiration date, but may be amended or revoked by Ecology.
Ecology’s Conditions of Use:
The BioPod shall comply with these conditions:
1) Applicants shall design, assemble, install, operate, and maintain the BioPod
installations in accordance with Oldcastle Infrastructure, Inc.’s applicable manuals and
the Ecology Decision.
2) The minimum size filter surface-area for use in Washington is determined by using the
design water quality flow rate (as determined in Ecology Decision, Item 3, above) and
the Infiltration Rate (as identified in Ecology Decision, Item 1, above). Calculate the
required area by dividing the water quality design flow rate (cu-ft/sec) by the
Infiltration Rate (converted to ft/sec) to obtain required surface area (sq ft) of the
BioPod unit
3) BioPod media shall conform to the specifications submitted to and approved by Ecology
4) Maintenance: The required inspection/maintenance interval for stormwater treatment
devices is often dependent on the efficiency of the device and the degree of pollutant
loading from a particular drainage basin. Therefore, Ecology does not endorse or
recommend a “one size fits all” maintenance cycle for a particular model/size of
manufactured filter treatment device.
The BioPod is designed for a target maintenance interval of 1 year. Maintenance
includes replacing the mulch, assessing plant health, removal of trash, and raking
the top few inches of engineered media.
A BioPod system tested at the Lake Union Ship Canal Test Facility in Seattle, WA
required maintenance after 1.5 months, or 6.3% of a water year. Monitoring
personnel observed similar maintenance issues with other systems evaluated at the
Test Facility. The runoff from the Test Facility may be unusual and maintenance
requirements of systems installed at the Test Facility may not be indicative of
maintenance requirements for all sites.
Test results provided to Ecology from a BioPod System evaluated in a lab following
New Jersey Department of Environmental Protection Laboratory Protocol for
Filtration MTDs have indicated the BioPod System is capable of longer maintenance
intervals.
Owners/operators must inspect BioPod systems for a minimum of twelve months
from the start of post-construction operation to determine site-specific
inspection/maintenance schedules and requirements. Owners/operators must
conduct inspections monthly during the wet season, and every other month during
the dry season. (According to the SWMMWW, the wet season in western
Washington is October 1 to April 30. According to the SWMMEW, the wet season
in eastern Washington is October 1 to June 30.) After the first year of operation,
owners/operators must conduct inspections based on the findings during the first
year of inspections.
Conduct inspections by qualified personnel, follow manufacturer’s guidelines, and
use methods capable of determining either a decrease in treated effluent flow rate
and/or a decrease in pollutant removal ability.
5) Install the BioPod in such a manner that you bypass flows exceeding the maximum
operating rate and you will not resuspend captured sediment.
6) Discharges from the BioPod shall not cause or contribute to water quality standards
violations in receiving waters.
Approved Alternate Configurations
BioPod Internal Bypass
1) The BioPod Internal Bypass configuration may be combined with a Curb Inlet, Grated
Inlet, and Piped-In Inlet. Water quality flows and peak flows are directed from the
curb, overhead grate, or piped inlet to a contoured inlet rack. The inlet rack disperses
water quality flows over the top surface of the biofiltration chamber. Excess flows are
diverted over an curved bypass weir to the outlet area without passing through the
treatment area. Both water quality flows and bypass flows are combined in the outlet
area prior to being discharged out of the system.
2) To select a BioPod Internal Bypass unit, the designer must determine the size of the
standard unit using the sizing guidance described above. Systems that have an internal
bypass, may use the off-line water quality design flow rate.
3) The internal bypass configuration has a maximum flow rate of 900 gallons per minute.
Sites where the anticipated flow rate at the treatment device is larger than 900 gpm must use an
external bypass, or size the treatment device for the on-line water quality design flow rate.
Applicant: Oldcastle Infrastructure, Inc.
Applicant’s Address: 7100 Longe St, Suite 100
Stockton, CA 95206
Application Documents:
Technical Evaluation Report TreePod™ BioFilter System Performance Certification Project,
Prepared for Oldcastle, Inc., Prepared by Herrera Environmental Consultants, Inc. February 2018
Technical Memorandum: Response to Board of External Reviewers’ Comments on the Technical
Evaluation Report for the TreePod™ Biofilter System Performance Certification Project,
Oldcastle, Inc. and Herrera Environmental Consultants, Inc., February 2018
Technical Memorandum: Response to Board of External Reviewers’ Comments on the Technical
Evaluation Report for the TreePod™ Biofilter System Performance Certification Project,
Oldcastle, Inc. and Herrera Environmental Consultants, Inc., January 2018
Application for Pilot Use Level Designation, TreePod™ Biofilter – Stormwater Treatment
System, Oldcastle Stormwater Solutions, May 2016
Emerging Stormwater Treatment Technologies Application for Certification: The TreePod™
Biofilter, Oldcastle Stormwater Solutions, April 2016
Applicant’s Use Level Request:
General Use Level Designation as a Basic, Enhanced, and Phosphorus Treatment device
in accordance with Ecology’s Stormwater Management Manual for Western Washington
Applicant’s Performance Claims:
Based on results from laboratory and field-testing, the applicant claims the BioPod™ Biofilter
operating at a hydraulic loading rate of 153 inches per hour is able to remove:
80% of Total Suspended Solids (TSS) for influent concentrations greater than 100 mg/L
and achieve a 20 mg/L effluent for influent concentrations less than 100 mg/L.
60% dissolved zinc for influent concentrations 0.02 to 0.3 mg/L.
30% dissolved copper for influent concentrations 0.005 to 0.02 mg/L.
50% or greater total phosphorus for influent concentrations 0.1 to 0.5 mg/L.
Ecology’s Recommendations:
Ecology finds that:
Oldcastle Infrastructure, Inc. has shown Ecology, through laboratory and field testing,
that the BioPod™ Biofilter is capable of attaining Ecology’s Basic, Total Phosphorus,
and Enhanced treatment goals.
Findings of Fact:
Field Testing
1. Herrera Environmental Consultants, Inc. conducted monitoring of the BioPod™ Biofilter at
the Lake Union Ship Canal Test Facility in Seattle Washington between November 2016 and
April 2018. Herrera collected flow-weight composite samples during 14 separate storm
events and peak flow grab samples during 3 separate storm events. The system was sized at
an infiltration rate of 153 inches per hour or a hydraulic loading rate of 1.6 gpm/ft2.
2. The D50 of the influent PSD ranged from 3 to 292 microns, with an average D50 of 28
microns.
3. Influent TSS concentrations ranged from 17 mg/L to 666 mg/L, with a mean concentration of
98 mg/L. For all samples (influent concentrations above and below 100 mg/L) the bootstrap
estimate of the lower 95 percent confidence limit (LCL 95) of the mean TSS reduction was
84% and the bootstrap estimate of the upper 95 percent confidence limit (UCL95) of the
mean TSS effluent concentration was 8.2 mg/L.
4. Dissolved copper influent concentrations from the 17 events ranged from 9.0 µg/L to 21.1
µg/L. The 21.1 µg/L data point was reduced to 20.0 µg/L, the upper limit to the TAPE
allowed influent concentration range, prior to calculating the pollutant removal. A bootstrap
estimate of the LCL95 of the mean dissolved copper reduction was 35%.
5. Dissolved zinc influent concentrations from the 17 events ranged from 26.1 µg/L to 43.3
µg/L. A bootstrap estimate of the LCL95 of the mean dissolved zinc reduction was 71%.
6. Total phosphorus influent concentrations from the 17 events ranged from 0.064 mg/L to 1.56
mg/L. All influent data greater than 0.5 mg/L were reduced to 0.5 mg/L, the upper limit to the TAPE
allowed influent concentration range, prior to calculating the pollutant removal. A bootstrap
estimate of the LCL95 of the mean total phosphorus reduction was 64%.
7. The system experienced rapid sediment loading and needed to be maintained after 1.5
months. Monitoring personnel observed similar sediment loading issues with other systems
evaluated at the Test Facility. The runoff from the Test Facility may not be indicative of
maintenance requirements for all sites.
Laboratory Testing
1. Good Harbour Laboratories (GHL) conducted laboratory testing at their site in Mississauga,
Ontario in October 2017 following the New Jersey Department of Environmental Protection
Laboratory Protocol for Filtration MTDs. The testing evaluated a 4-foot by 6-foot standard
biofiltration chamber and inlet contour rack with bypass weir. The test sediment used during
the testing was custom blended by GHL using various commercially available silica sands,
which had an average d50 of 69 µm. Based on the lab test results:
a. GHL evaluated removal efficiency over 15 events at a Maximum Treatment Flow Rate
(MTFR) of 37.6 gpm, which corresponds to a MTFR to effective filtration treatment area
ratio of 1.80 gpm/ft2. The system, operating at 100% of the MTFR with an average
influent concentration of 201.3 mg/L, had an average removal efficiency of 99 percent.
b. GHL evaluated sediment mass loading capacity over an additional 16 events using an
influent SSC concentration of 400 mg/L. The first 11 runs were evaluated at 100% of the
MTFR. The BioPod began to bypass, so the remaining 5 runs were evaluated at 90% of
the MTFR. The total mass of the sediment captured was 245.0 lbs and the cumulative
mass removal efficiency was 96.3%.
2. Herrera Environmental Consultants Inc. conducted laboratory testing in September 2014 at
the Seattle University Engineering Laboratory. The testing evaluated the flushing
characteristics, hydraulic conductivity, and pollutant removal ability of twelve different
media blends. Based on this testing, Oldcastle Infrastructure, Inc. selected one media blend,
Mix 8, for inclusion in their TAPE evaluation of the BioPod™ Biofilter.
a. Herrera evaluated Mix 8 in an 8-inch diameter by 36-inch tall polyvinyl chloride (PVC)
column. The column contained 18-inches of Mix 8 on top of 6-inches of pea gravel. The
BioPod will normally include a 3-inch mulch layer on top of the media layer; however,
this was not included in the laboratory testing.
b. Mix 8 has a hydraulic conductivity of 218 inches per hour; however, evaluation of the
pollutant removal ability of the media was based on an infiltration rate of 115 inches per
hour. The media was tested at 75%, 100%, and 125% of the infiltration rate. Based on the
lab test results:
The system was evaluated using natural stormwater. The dissolved copper and
dissolved zinc concentrations in the natural stormwater were lower than the TAPE
influent standards; therefore, the stormwater was spiked with 66.4 mL of 100 mg/L
Cu solution and 113.6 mL of 1,000 mg/L Zn solution.
The BioPod removed an average of 81% of TSS, with a mean influent concentration
of 48.4 mg/L and a mean effluent concentration of 9.8 mg/L.
The BioPod removed an average of 94% of dissolved copper, with a mean influent
concentration of 10.6 µg/L and a mean effluent concentration of 0.6 µg/L.
The BioPod removed an average of 97% of dissolved zinc, with a mean influent
concentration of 117 µg/L and a mean effluent concentration of 4 µg/L.
The BioPod removed an average of 97% of total phosphorus, with a mean influent
concentration of 2.52 mg/L and a mean effluent concentration of 0.066 mg/L. When
total phosphorus influent concentrations were capped at the TAPE upper limit of 0.5
mg/L, calculations showed an average removal of 87%.
Other BioPod Related Issues to be Addressed By the Company:
1. Conduct hydraulic testing to obtain information about maintenance requirements on a site
with runoff that is more typical of the Pacific Northwest.
Technology Description: Download at
https://oldcastleprecast.com/stormwater/bioretention-
biofiltration-applications/bioretention-biofiltration-
solutions/
Contact Information:
Applicant: Chris Demarest
Oldcastle Infrastructure, Inc.
(925) 667-7100
Chris.demarest@oldcastle.com
Applicant website: https://oldcastleprecast.com/stormwater/
Ecology web link: https://ecology.wa.gov/Regulations-Permits/Guidance-technical-
assistance/Stormwater-permittee-guidance-resources/Emerging-stormwater-treatment-
technologies
Ecology: Douglas C. Howie, P.E.
Department of Ecology
Water Quality Program
(360) 407-6444
douglas.howie@ecy.wa.gov
Revision History
Date Revision
March 2018 GULD granted for Basic Treatment
March 2018 Provisional GULD granted for Enhanced and Phosphorus Treatment
June 2016 PULD Granted
April 2018 GULD for Basic and Provisional GULD for Enhanced and
Phosphorus granted, changed name to BioPod from TreePod
July 2018 GULD for Enhanced and Phosphorus granted
September 2018 Changed Address for Oldcastle
December 2018 Added minimum media thickness requirement
May 2019 Changed language on who must Install and maintain the device from
Oldcastle to Applicants
August 2019 Added text on sizing using infiltration rate and water quality design
flow rate
October 2019 Added text describing ability to use off-line design water quality flow
rate for sizing due to internal bypass
Inspection and Maintenance Guide
BIOPODTM SYSTEM
WITH STORMMIX™ MEDIA
BioPod™ Biofilter with StormMix™ Biofiltration Media
Description
The BioPod™ Biofilter System (BioPod) is a stormwater biofiltration treatment system used to remove pollutants
from stormwater runoff. Impervious surfaces and other urban and suburban landscapes generate a variety of contaminants that can enter stormwater and pollute downstream receiving waters unless treatment is provided. The BioPod system uses proprietary StormMix™ biofiltration media to capture and retain pollutants including
total suspended solids (TSS), metals, nutrients, gross solids, trash and debris as well as petroleum hydrocarbons.
Function
The BioPod system uses engineered, high-flow rate filter media to remove stormwater pollutants, allowing for a smaller footprint than conventional bioretention systems. Contained within a compact precast concrete vault, the
BioPod system consists of a biofiltration chamber and an optional integrated high-flow bypass with a contoured
inlet rack to minimize scour. The biofiltration chamber is filled with horizontal layers of aggregate (which may or
may not include an underdrain), biofiltration media and mulch. Stormwater passes vertically down through the mulch and biofiltration media for treatment. The mulch provides pretreatment by retaining most of the solids or sediment. The biofiltration media provides further treatment by retaining finer sediment and dissolved pollutants.
The aggregate allows the media bed to drain evenly for discharge through an underdrain pipe or by infiltration.
Configuration
The BioPod system can be configured with either an internal or external bypass. The internal bypass allows both
water quality and bypass flows to enter the treatment vault. The water quality flows are directed to the biofiltration
chamber while the excess flows are diverted over the bypass weir without entering the biofiltration chamber. Both
the treatment and bypass flows are combined in the outlet area prior to discharge from the structure. BioPod units without an internal bypass are designed such that only treatment flows enter the treatment structure. When the system has exceeded its treatment capacity, ponding will force bypass flows to continue down the gutter to
the nearest standard catch basin or other external bypass structure.
The BioPod system can be configured as a tree box filter with tree and grated inlet, as a planter box filter with shrubs, grasses and an open top, or as an underground filter with access risers, doors and a subsurface inlet pipe. The optional internal bypass may be incorporated with any of these configurations. In addition, an open
bottom configuration may be used to promote infiltration and groundwater recharge. The configuration and size
of the BioPod system is designed to meet the requirements of a specific project.
Inspection & Maintenance Overview
State and local regulations require all stormwater management systems to be inspected on a regular basis and
maintained as necessary to ensure performance and protect downstream receiving waters. Without maintenance,
excessive pollutant buildup can limit system performance by reducing the operating capacity of the system and
increasing the potential for scouring of pollutants during periods of high flow.
Some configurations of the BioPod may require periodic irrigation to establish and maintain vegetation. Vegetation
will typically become established about two years after planting. Irrigation requirements are ultimately dependent
on climate, rainfall and the type of vegetation selected.
2
INSPECTION AND MAINTENANCE GUIDE
3
Maintenance Frequency
Periodic inspection is essential for consistent system performance and is easily completed. Inspection is typically conducted a minimum of twice per year, but since pollutant transport and deposition varies from site to
site, a site-specific maintenance frequency should be established during the first two or three years of operation.
Inspection Equipment
The following equipment is helpful when conducting BioPod inspections:
• Recording device (pen and paper form, voice recorder, iPad, etc.)
• Suitable clothing (appropriate footwear, gloves, hardhat, safety glasses, etc.)• Traffic control equipment (cones, barricades, signage, flagging, etc.)• Manhole hook or pry bar
• Flashlight
• Tape measure
Inspection Procedures
BioPod inspections are visual and are conducted without entering the unit. To complete an inspection, safety
measures including traffic control should be deployed before the access covers or tree grates are removed. Once the covers have been removed, the following items should be checked and recorded (see form provided on page 6) to determine whether maintenance is required:
• If the BioPod unit is equipped with an internal bypass, inspect the contoured inlet rack and outlet chamber
and note whether there are any broken or missing parts. In the unlikely event that internal parts are broken or missing, contact Oldcastle Stormwater at (800) 579-8819 to determine appropriate corrective action.
• Note whether the curb inlet, inlet pipe, or – if the unit is equipped with an internal bypass – the inlet rack is blocked or obstructed.
• If the unit is equipped with an internal bypass, observe, quantify and record the accumulation of trash
and debris in the inlet rack. The significance of accumulated trash and debris is a matter of judgment. Often, much of the trash and debris may be removed manually at the time of inspection if a separate maintenance visit is not yet warranted.
• If it has not rained within the past 24 hours, note whether standing water is observed in the biofiltration chamber.
• Finally, observe, quantify and record presence of invasive vegetation and the amount of trash and debris and sediment load in the biofiltration chamber. Erosion of the mulch and biofiltration media bed should also be recorded. Sediment load may be rated light, medium or heavy depending on the conditions.
Loading characteristics may be determined as follows:
o Light sediment load – sediment is difficult to distinguish among the mulch fibers at the top of the
mulch layer; the mulch appears almost new.
o Medium sediment load – sediment accumulation is apparent and may be concentrated in some areas; probing the mulch layer reveals lighter sediment loads under the top 1” of mulch.
o Heavy sediment load – sediment is readily apparent across the entire top of the mulch layer; individual mulch fibers are difficult to distinguish; probing the mulch layer reveals heavy sediment load under the
top 1” of mulch.
Often, much of the invasive vegetation and trash and debris may be removed manually at the time of inspection if a separate maintenance visit is not yet warranted.
4
Maintenance Indicators
Maintenance should be scheduled if any of the following conditions are identified during inspection:
•The concrete structure is damaged or the tree grate or access cover is damaged or missing.•The curb inlet or inlet rack is obstructed.•Standing water is observed in the biofiltration chamber more than 24 hours after a rainfall event (use
discretion if the BioPod is located downstream of a storage system that attenuates flow).
•Trash and debris in the inlet rack cannot be easily removed at the time of inspection.
•Trash and debris, invasive vegetation or sediment load in the biofiltration chamber is heavy or excessiveerosion has occurred.
Maintenance Equipment
The following equipment is helpful when conducting BioPod maintenance:
•Suitable clothing (appropriate footwear, gloves, hardhat, safety glasses, etc.)•Traffic control equipment (cones, barricades, signage, flagging, etc.)
•Manhole hook or pry bar
•Flashlight
•Tape measure•Rake, hoe, shovel and broom•Bucket
•Pruners
•Vacuum truck (optional)
Maintenance Procedures
Maintenance should be conducted during dry weather when no flows are entering the system. All maintenance
may be conducted without entering the BioPod structure. Once safety measures such as traffic control are
deployed, the access covers may be removed and the following activities may be conducted to complete maintenance:
•Remove all trash and debris from the curb inlet and inlet rack manually or by using a vacuum truck as
required.
•Remove all trash and debris and invasive vegetation from the biofiltration chamber manually or by using avacuum truck as required.•If the sediment load is medium or light but erosion of the biofiltration media bed is evident, redistribute
the mulch with a rake or replace missing mulch as appropriate. If erosion persists, rocks may be placed in
the eroded area to help dissipate energy and prevent recurring erosion.
•If the sediment load is heavy, remove the mulch layer using a hoe, rake, shovel and bucket, or by using avacuum truck as required. If the sediment load is particularly heavy, inspect the surface of the biofiltrationmedia once the mulch has been removed. If the media appears clogged with sediment, remove and
replace one or two inches of biofiltration media prior to replacing the mulch layer.
•Prune vegetation as appropriate and replace damaged or dead plants as required.
•Replace the tree grate and/or access covers and sweep the area around the BioPod to leave the site clean.•All material removed from the BioPod during maintenance must be disposed of in accordance with localenvironmental regulations. In most cases, the material may be handled in the same manner as disposal
of material removed from sumped catch basins or manholes.
Natural, shredded hardwood mulch should be used in the BioPod. Timely replacement of the mulch layer
according to the maintenance indicators described above should protect the biofiltration media below the
mulch layer from clogging due to sediment accumulation. However, whenever the mulch is replaced, the BioPod should be visited 24 hours after the next major storm event to ensure that there is no standing water in the biofiltration chamber. Standing water indicates that the biofiltration media below the mulch layer is
clogged and must be replaced. Please contact Oldcastle Infrastructure at (800) 579-8819 to purchase the
proprietary StormMix™ biofiltration media.
5
BioPod Tree Module BioPod Media Module
BioPod Planter Module BioPod Media Vault
6
Curb Inlet or Inlet Rack Blocked Notes:
Yes No
BioPod Inspection &
Maintenance Log
BioPod Model__________________________ Inspection Date________________________
Location______________________________________________________________________________
Condition of Internal Components Notes:
Good Damaged Missing
Standing Water in Biofiltration Chamber Notes:
Yes No
Trash and Debris in Inlet Rack Notes:
Yes No
Trash and Debris in Biofiltration Chamber Notes:
Yes No
Maintenance Requirements
Yes - Schedule Maintenance No - Schedule Re-Inspection
Invasive Vegetation in Biofiltration Chamber Notes:
Yes No
Sediment in Biofiltration Chamber Notes:
Light Medium Heavy
Erosion in Biofiltration Chamber Notes:
Yes No
BIOPODTM SYSTEM
WITH STORMMIX™ MEDIA
BUILDINGSTRUCTURES
OUR MARKETS
TRANSPORTATION
WATER
ENERGYCOMMUNICATIONS
December 2018 v.1
www.oldcastleinfrastructure.com
800-579-8819
APPENDIX A
FIGURES & MAPS
CITY OF RENTON SURFACE WATER DESIGN MANUAL
2017 City of Renton Surface Water Design Manual 12/12/2016 8-A-1
REFERENCE 8-A
TECHNICAL INFORMATION REPORT (TIR)
WORKSHEET
Part 1 PROJECT OWNER AND
PROJECT ENGINEER Part 2 PROJECT LOCATION AND
DESCRIPTION
Project Owner _____________________________
Phone ___________________________________
Address __________________________________
_________________________________________
Project Engineer ___________________________
Company _________________________________
Phone ___________________________________
Project Name __________________________
CED Permit # ________________________
Location Township ________________
Range __________________
Section _________________
Site Address __________________________
_____________________________________
Part 3 TYPE OF PERMIT APPLICATION Part 4 OTHER REVIEWS AND PERMITS
Land Use (e.g., Subdivision / Short Subd.)
Building (e.g., M/F / Commercial / SFR)
Grading
Right-of-Way Use
Other _______________________
DFW HPA
COE 404
DOE Dam Safety
FEMA Floodplain
COE Wetlands
Other ________
Shoreline Management
Structural Rockery/Vault/_____
ESA Section 7
Part 5 PLAN AND REPORT INFORMATION
Technical Information Report Site Improvement Plan (Engr. Plans)
Type of Drainage Review
(check one):
Date (include revision
dates):
Date of Final:
Full
Targeted
Simplified
Large Project
Directed
____________________________________
__________________
Plan Type (check
one):
Date (include revision
dates):
Date of Final:
Full
Modified
Simplified
____________________________________
__________________
4th Creek Meadows LLC
12505 NE Bellevue-Redmond Rd, Suite 212
Bellevue, WA 98005
David Harmsen
Harmsen LLC
360-794-7811
4th Dimension Mixed Use
23
5
10
4502 NE 4th Street
x
x
x
x
REFERENCE 8: PLAN REVIEW FORMS AND WORKSHEET
TECHNICAL INFORMATION REPORT (TIR) WORKSHEET
12/12/2016 2017 City of Renton Surface Water Design Manual 8-A-2
Part 6 SWDM ADJUSTMENT APPROVALS
Type (circle one): Standard / Blanket
Description: (include conditions in TIR Section 2)
____________________________________________________________________________________
____________________________________________________________________________________
____________________________________________________________________________________
Approved Adjustment No. ______________________ Date of Approval: _______________________
Part 7 MONITORING REQUIREMENTS
Monitoring Required: Yes / No
Start Date: _______________________
Completion Date: _______________________
Describe: _________________________________
_________________________________________
_________________________________________
Re: SWDM Adjustment No. ________________
Part 8 SITE COMMUNITY AND DRAINAGE BASIN
Community Plan: ____________________________________________________________________
Special District Overlays: ______________________________________________________________
Drainage Basin: _____________________________________________________________________
Stormwater Requirements: _____________________________________________________________
Part 9 ONSITE AND ADJACENT SENSITIVE AREAS
River/Stream ________________________
Lake ______________________________
Wetlands ____________________________
Closed Depression ____________________
Floodplain ___________________________
Other _______________________________
_______________________________
Steep Slope __________________________
Erosion Hazard _______________________
Landslide Hazard ______________________
Coal Mine Hazard ______________________
Seismic Hazard _______________________
Habitat Protection ______________________
_____________________________________
N/A
Fall 2020
Summer 2021
Maplewood
Flow Control Duration - Forested Condition, Enhanced Basic Treatment
None
None
Construction turbidity monitoring.
x Local infrastructure induced floodplain
REFERENCE 8-A: TECHNICAL INFORMATION REPORT (TIR) WORKSHEET
TECHNICAL INFORMATION REPORT (TIR) WORKSHEET
2017 City of Renton Surface Water Design Manual 12/12/2016 Ref 8-A-3
Part 10 SOILS
Soil Type
______________________
______________________
______________________
______________________
Slopes
________________________
________________________
________________________
________________________
Erosion Potential
_________________________
_________________________
_________________________
_________________________
High Groundwater Table (within 5 feet)
Other ________________________________
Sole Source Aquifer
Seeps/Springs
Additional Sheets Attached
Part 11 DRAINAGE DESIGN LIMITATIONS
REFERENCE
Core 2 – Offsite Analysis_________________
Sensitive/Critical Areas__________________
SEPA________________________________
LID Infeasibility________________________
Other________________________________
_____________________________________
LIMITATION / SITE CONSTRAINT
_______________________________________
_______________________________________
_______________________________________
_______________________________________
_______________________________________
_______________________________________
Additional Sheets Attached
Part 12 TIR SUMMARY SHEET (provide one TIR Summary Sheet
per Threshold Discharge Area)
Threshold Discharge Area:
(name or description)
Core Requirements (all 8 apply):
Discharge at Natural Location Number of Natural Discharge Locations:
Offsite Analysis Level: 1 / 2 / 3 dated:__________________
Flow Control (include facility
summary sheet)
Standard: _______________________________
or Exemption Number: ____________
On-site BMPs: _______________________________
Conveyance System Spill containment located at: _____________________________
Erosion and Sediment Control /
Construction Stormwater Pollution
Prevention
CSWPP/CESCL/ESC Site Supervisor: _____________________
Contact Phone: _________________________
After Hours Phone: _________________________
Alderwood 2-8%Slight
Everett 8-15%Slight
x Till Soils
1
6/12/20
Flow Duration-Forested Conditions
Rain Gardens
Vault
TBD
REFERENCE 8: PLAN REVIEW FORMS AND WORKSHEET
TECHNICAL INFORMATION REPORT (TIR) WORKSHEET
12/12/2016 2017 City of Renton Surface Water Design Manual 8-A-4
Part 12 TIR SUMMARY SHEET (provide one TIR Summary Sheet
per Threshold Discharge Area)
Maintenance and Operation Responsibility (circle one): Private / Public
If Private, Maintenance Log Required: Yes / No
Financial Guarantees and Liability Provided: Yes / No
Water Quality (include facility
summary sheet)
Type (circle one): Basic / Sens. Lake / Enhanced Basic / Bog
or Exemption No. _______________________
Special Requirements (as applicable):
Area Specific Drainage
Requirements
Type: SDO / MDP / BP / Shared Fac. / None
Name: ________________________
Floodplain/Floodway Delineation Type (circle one): Major / Minor / Exemption / None
100-year Base Flood Elevation (or range): _______________
Datum:
Flood Protection Facilities Describe:
Source Control
(commercial / industrial land use)
Describe land use:
Describe any structural controls:
Oil Control High-Use Site: Yes / No
Treatment BMP: _________________________________
Maintenance Agreement: Yes / No
with whom? _____________________________________
Other Drainage Structures
Describe:
Mixed Use Residential
Detention Vault
REFERENCE 8-A: TECHNICAL INFORMATION REPORT (TIR) WORKSHEET
TECHNICAL INFORMATION REPORT (TIR) WORKSHEET
2017 City of Renton Surface Water Design Manual 12/12/2016 Ref 8-A-5
Part 13 EROSION AND SEDIMENT CONTROL REQUIREMENTS
MINIMUM ESC REQUIREMENTS
DURING CONSTRUCTION
Clearing Limits
Cover Measures
Perimeter Protection
Traffic Area Stabilization
Sediment Retention
Surface Water Collection
Dewatering Control
Dust Control
Flow Control
Control Pollutants
Protect Existing and Proposed BMPs/Facilities
Maintain Protective BMPs / Manage Project
MINIMUM ESC REQUIREMENTS
AFTER CONSTRUCTION
Stabilize exposed surfaces
Remove and restore Temporary ESC Facilities
Clean and remove all silt and debris, ensure operation of Permanent BMPs/Facilities, restore
operation of BMPs/Facilities as necessary
Flag limits of sensitive areas and open space
preservation areas
Other _______________________
Part 14 STORMWATER FACILITY DESCRIPTIONS (Note: Include Facility Summary and Sketch)
Flow Control Type/Description Water Quality Type/Description
Detention
Infiltration
Regional Facility
Shared Facility
On-site BMPs
Other
________________
________________
________________
________________
________________
________________
Vegetated Flowpath
Wetpool
Filtration
Oil Control
Spill Control
On-site BMPs
Other
________________
________________
________________
________________
________________
________________
________________
Part 15 EASEMENTS/TRACTS Part 16 STRUCTURAL ANALYSIS
Drainage Easement
Covenant
Native Growth Protection Covenant
Tract
Other ____________________________
Cast in Place Vault
Retaining Wall
Rockery > 4′ High
Structural on Steep Slope
Other _______________________________
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x Vault
x Rain Gardens
x BioPod
x
x
REFERENCE 8: PLAN REVIEW FORMS AND WORKSHEET
TECHNICAL INFORMATION REPORT (TIR) WORKSHEET
12/12/2016 2017 City of Renton Surface Water Design Manual 8-A-6
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 and the attached Technical Information Report. To the best of my
knowledge the information provided here is accurate.
____________________________________________________________________________________ Signed/Date
FIGURE 2: VICINITY MAP
FIGURE 3A: EXISTING DRAINAGE BASIN MAP
FIGURE 3B: DEVELOPED DRAINAGE BASIN MAP
FIGURE 4: SOILS MAP
APPENDIX B
DOWNSTREAM MAPS
DOWNSTREAM ANALYSIS MAP
DRAINAGE COMPLAINT MAP
DEPARTMENT OF ECOLOGY 303d LISTING
DEPARTMENT OF ECOLOGY 303d LISTING CONT.
UPSTREAM BASIN MAP
APPENDIX C
SITE CRITICAL AREAS & HAZARD MAPS
DRAINAGE BASIN MAP
FLOOD HAZARD AREA MAP
WETLAND LOCATION MAP
SHORELINE MAP
LANDSLIDE HAZARD MAP
EROSION HAZARD MAP
SEISMIC HAZARD MAP
COAL MINE HAZARD MAP
AQUIFER PROTECTION AREA MAP
APPENDIX D
WWHM2012 BASIN & DETENTION
FACILITY SIZING
CONVEYANCE CALCULATIONS
UPSTREAM BASIN CALCULATIONS
WWHM2012
PROJECT REPORT
___________________________________________________________________
Project Name: 4th Dimension
Report Date: 2/13/2020
Gage : Seatac
Data Start : 1948/10/01
Data End : 2009/09/30
Precip Scale: 1.00
Version Date: 2017/04/14
Version : 4.2.13 ___________________________________________________________________
Low Flow Threshold for POC 1 : 50 Percent of the 2 Year
High Flow Threshold for POC 1: 50 year
___________________________________________________________________
PREDEVELOPED LAND USE
Name : Basin 1
Bypass: No
GroundWater: No
Pervious Land Use acre
C, Forest, Mod .61
Pervious Total 0.61
Impervious Land Use acre
ROADS MOD 0.15
Impervious Total 0.15
Basin Total 0.76
Element Flows To:
Surface Interflow Groundwater ___________________________________________________________________
MITIGATED LAND USE
Name : Basin 1
Bypass: No
GroundWater: No
Pervious Land Use acre
C, Lawn, Flat .1
Pervious Total 0.1
Impervious Land Use acre
ROADS MOD 0.38
ROOF TOPS FLAT 0.28
Impervious Total 0.66
Basin Total 0.76
Element Flows To:
Surface Interflow Groundwater Vault 1 Vault 1 ___________________________________________________________________
Name : Vault 1
Width : 20 ft.
Length : 70 ft.
Depth: 7 ft.
Discharge Structure
Riser Height: 6.1 ft.
Riser Diameter: 12 in.
Orifice 1 Diameter: 0.89 in. Elevation: 0 ft.
Orifice 2 Diameter: 0.88 in. Elevation: 3.9 ft.
Orifice 3 Diameter: 1.3 in. Elevation: 5.5 ft.
Element Flows To:
Outlet 1 Outlet 2
___________________________________________________________________
Vault Hydraulic Table
Stage(feet) Area(ac.) Volume(ac-ft.) Discharge(cfs) Infilt(cfs) 0.0000 0.032 0.000 0.000 0.000 0.0778 0.032 0.002 0.006 0.000 0.1556 0.032 0.005 0.008 0.000 0.2333 0.032 0.007 0.010 0.000 0.3111 0.032 0.010 0.012 0.000 0.3889 0.032 0.012 0.013 0.000 0.4667 0.032 0.015 0.014 0.000 0.5444 0.032 0.017 0.015 0.000 0.6222 0.032 0.020 0.017 0.000 0.7000 0.032 0.022 0.018 0.000 0.7778 0.032 0.025 0.019 0.000 0.8556 0.032 0.027 0.019 0.000 0.9333 0.032 0.030 0.020 0.000 1.0111 0.032 0.032 0.021 0.000 1.0889 0.032 0.035 0.022 0.000 1.1667 0.032 0.037 0.023 0.000 1.2444 0.032 0.040 0.024 0.000 1.3222 0.032 0.042 0.024 0.000 1.4000 0.032 0.045 0.025 0.000 1.4778 0.032 0.047 0.026 0.000 1.5556 0.032 0.050 0.026 0.000
1.6333 0.032 0.052 0.027 0.000 1.7111 0.032 0.055 0.028 0.000 1.7889 0.032 0.057 0.028 0.000
1.8667 0.032 0.060 0.029 0.000 1.9444 0.032 0.062 0.030 0.000 2.0222 0.032 0.065 0.030 0.000
2.1000 0.032 0.067 0.031 0.000 2.1778 0.032 0.070 0.031 0.000 2.2556 0.032 0.072 0.032 0.000
2.3333 0.032 0.075 0.032 0.000 2.4111 0.032 0.077 0.033 0.000 2.4889 0.032 0.080 0.033 0.000 2.5667 0.032 0.082 0.034 0.000 2.6444 0.032 0.085 0.035 0.000 2.7222 0.032 0.087 0.035 0.000
2.8000 0.032 0.090 0.036 0.000 2.8778 0.032 0.092 0.036 0.000 2.9556 0.032 0.095 0.037 0.000 3.0333 0.032 0.097 0.037 0.000 3.1111 0.032 0.100 0.037 0.000 3.1889 0.032 0.102 0.038 0.000 3.2667 0.032 0.105 0.038 0.000 3.3444 0.032 0.107 0.039 0.000
3.4222 0.032 0.110 0.039 0.000 3.5000 0.032 0.112 0.040 0.000 3.5778 0.032 0.115 0.040 0.000 3.6556 0.032 0.117 0.041 0.000 3.7333 0.032 0.120 0.041 0.000 3.8111 0.032 0.122 0.042 0.000 3.8889 0.032 0.125 0.042 0.000 3.9667 0.032 0.127 0.048 0.000 4.0444 0.032 0.130 0.051 0.000 4.1222 0.032 0.132 0.053 0.000 4.2000 0.032 0.135 0.055 0.000 4.2778 0.032 0.137 0.057 0.000 4.3556 0.032 0.140 0.059 0.000 4.4333 0.032 0.142 0.060 0.000 4.5111 0.032 0.145 0.062 0.000 4.5889 0.032 0.147 0.063 0.000 4.6667 0.032 0.150 0.064 0.000 4.7444 0.032 0.152 0.066 0.000 4.8222 0.032 0.155 0.067 0.000
4.9000 0.032 0.157 0.068 0.000 4.9778 0.032 0.160 0.069 0.000 5.0556 0.032 0.162 0.070 0.000 5.1333 0.032 0.165 0.072 0.000 5.2111 0.032 0.167 0.073 0.000 5.2889 0.032 0.170 0.074 0.000
5.3667 0.032 0.172 0.075 0.000 5.4444 0.032 0.175 0.076 0.000 5.5222 0.032 0.177 0.084 0.000
5.6000 0.032 0.180 0.092 0.000 5.6778 0.032 0.182 0.098 0.000 5.7556 0.032 0.185 0.103 0.000
5.8333 0.032 0.187 0.107 0.000 5.9111 0.032 0.190 0.111 0.000 5.9889 0.032 0.192 0.115 0.000
6.0667 0.032 0.195 0.118 0.000 6.1444 0.032 0.197 0.220 0.000 6.2222 0.032 0.200 0.573 0.000
6.3000 0.032 0.202 1.035 0.000 6.3778 0.032 0.205 1.513 0.000 6.4556 0.032 0.207 1.920 0.000 6.5333 0.032 0.210 2.195 0.000 6.6111 0.032 0.212 2.389 0.000 6.6889 0.032 0.215 2.557 0.000 6.7667 0.032 0.217 2.714 0.000 6.8444 0.032 0.220 2.863 0.000 6.9222 0.032 0.222 3.003 0.000 7.0000 0.032 0.225 3.138 0.000 7.0778 0.032 0.227 3.266 0.000 7.1556 0.000 0.000 3.390 0.000 ___________________________________________________________________
___________________________________________________________________
ANALYSIS RESULTS
Stream Protection Duration
___________________________________________________________________
Predeveloped Landuse Totals for POC #1
Total Pervious Area:0.61
Total Impervious Area:0.15
___________________________________________________________________
Mitigated Landuse Totals for POC #1
Total Pervious Area:0.1
Total Impervious Area:0.66
___________________________________________________________________
Flow Frequency Return Periods for Predeveloped. POC #1
Return Period Flow(cfs)
2 year 0.076519
5 year 0.099559
10 year 0.115906
25 year 0.13785
50 year 0.155162
100 year 0.173326
Flow Frequency Return Periods for Mitigated. POC #1
Return Period Flow(cfs)
2 year 0.035982
5 year 0.050655
10 year 0.062414
25 year 0.079847
50 year 0.094879
100 year 0.111821 ___________________________________________________________________
Stream Protection Duration
Annual Peaks for Predeveloped and Mitigated. POC #1
Year Predeveloped Mitigated
1949 0.105 0.032 1950 0.091 0.034 1951 0.073 0.066 1952 0.052 0.028 1953 0.052 0.031 1954 0.063 0.031 1955 0.064 0.039 1956 0.067 0.035 1957 0.078 0.035 1958 0.060 0.032 1959 0.060 0.033 1960 0.085 0.061 1961 0.067 0.033 1962 0.048 0.026 1963 0.068 0.033 1964 0.067 0.031 1965 0.077 0.034 1966 0.057 0.027 1967 0.103 0.037 1968 0.102 0.030 1969 0.064 0.032
1970 0.072 0.031 1971 0.080 0.034 1972 0.087 0.041 1973 0.049 0.029 1974 0.080 0.029 1975 0.083 0.038 1976 0.070 0.032 1977 0.056 0.027 1978 0.082 0.034 1979 0.098 0.026 1980 0.137 0.042 1981 0.068 0.030 1982 0.106 0.064 1983 0.076 0.035 1984 0.056 0.028 1985 0.063 0.033 1986 0.079 0.054 1987 0.086 0.060 1988 0.058 0.029
1989 0.090 0.025 1990 0.171 0.058 1991 0.128 0.064 1992 0.063 0.029 1993 0.063 0.031 1994 0.054 0.023
1995 0.062 0.035 1996 0.115 0.064 1997 0.081 0.069
1998 0.069 0.031 1999 0.133 0.041 2000 0.072 0.034
2001 0.077 0.028 2002 0.084 0.058 2003 0.103 0.027
2004 0.132 0.144 2005 0.068 0.036 2006 0.066 0.034
2007 0.147 0.094 2008 0.144 0.110 2009 0.095 0.041 ___________________________________________________________________
Stream Protection Duration
Ranked Annual Peaks for Predeveloped and Mitigated. POC #1
Rank Predeveloped Mitigated 1 0.1712 0.1435 2 0.1472 0.1103 3 0.1438 0.0945 4 0.1373 0.0685 5 0.1333 0.0662 6 0.1317 0.0644 7 0.1280 0.0639 8 0.1149 0.0636 9 0.1060 0.0609 10 0.1052 0.0600 11 0.1030 0.0581 12 0.1030 0.0577 13 0.1024 0.0538 14 0.0984 0.0417 15 0.0948 0.0414 16 0.0913 0.0412
17 0.0900 0.0406 18 0.0872 0.0386 19 0.0863 0.0375 20 0.0845 0.0368 21 0.0841 0.0359 22 0.0828 0.0351 23 0.0817 0.0349 24 0.0807 0.0349 25 0.0803 0.0347 26 0.0798 0.0345 27 0.0794 0.0344 28 0.0785 0.0341 29 0.0773 0.0339 30 0.0767 0.0339 31 0.0759 0.0335 32 0.0729 0.0334 33 0.0716 0.0331 34 0.0716 0.0329 35 0.0700 0.0326
36 0.0695 0.0321 37 0.0680 0.0320 38 0.0678 0.0319 39 0.0678 0.0316 40 0.0671 0.0314 41 0.0668 0.0311
42 0.0667 0.0311 43 0.0660 0.0311 44 0.0639 0.0309
45 0.0638 0.0306 46 0.0633 0.0300 47 0.0630 0.0295
48 0.0629 0.0293 49 0.0627 0.0291 50 0.0624 0.0289
51 0.0602 0.0287 52 0.0595 0.0282 53 0.0575 0.0278
54 0.0568 0.0277 55 0.0564 0.0272 56 0.0564 0.0270 57 0.0543 0.0266 58 0.0523 0.0264 59 0.0520 0.0257 60 0.0488 0.0248 61 0.0482 0.0234 ___________________________________________________________________
Stream Protection Duration
POC #1
The Facility PASSED
The Facility PASSED.
Flow(cfs) Predev Mit Percentage Pass/Fail 0.0383 2184 2098 96 Pass 0.0394 1959 1672 85 Pass 0.0406 1761 1299 73 Pass 0.0418 1585 977 61 Pass 0.0430 1435 851 59 Pass 0.0442 1314 830 63 Pass 0.0453 1194 816 68 Pass
0.0465 1101 799 72 Pass 0.0477 1005 780 77 Pass 0.0489 925 765 82 Pass 0.0501 853 723 84 Pass 0.0512 770 691 89 Pass 0.0524 712 648 91 Pass 0.0536 652 600 92 Pass 0.0548 599 557 92 Pass 0.0560 552 518 93 Pass 0.0572 491 465 94 Pass 0.0583 438 418 95 Pass 0.0595 393 371 94 Pass 0.0607 354 321 90 Pass 0.0619 318 280 88 Pass 0.0631 293 240 81 Pass 0.0642 278 203 73 Pass 0.0654 258 182 70 Pass 0.0666 240 160 66 Pass 0.0678 224 147 65 Pass
0.0690 211 134 63 Pass 0.0701 190 124 65 Pass 0.0713 180 115 63 Pass 0.0725 170 102 60 Pass 0.0737 155 93 60 Pass 0.0749 143 83 58 Pass
0.0760 131 73 55 Pass 0.0772 120 70 58 Pass 0.0784 115 67 58 Pass
0.0796 107 65 60 Pass 0.0808 97 63 64 Pass 0.0820 88 62 70 Pass
0.0831 82 60 73 Pass 0.0843 80 58 72 Pass 0.0855 74 55 74 Pass
0.0867 69 54 78 Pass 0.0879 62 53 85 Pass 0.0890 56 50 89 Pass
0.0902 51 48 94 Pass 0.0914 46 46 100 Pass 0.0926 43 44 102 Pass 0.0938 39 42 107 Pass 0.0949 37 38 102 Pass 0.0961 37 37 100 Pass 0.0973 36 34 94 Pass 0.0985 33 34 103 Pass 0.0997 32 32 100 Pass 0.1008 30 31 103 Pass 0.1020 27 28 103 Pass 0.1032 24 26 108 Pass 0.1044 24 25 104 Pass 0.1056 21 23 109 Pass 0.1067 20 20 100 Pass 0.1079 20 19 95 Pass 0.1091 19 16 84 Pass 0.1103 18 13 72 Pass 0.1115 18 11 61 Pass 0.1127 17 9 52 Pass 0.1138 17 9 52 Pass 0.1150 15 7 46 Pass 0.1162 15 6 40 Pass 0.1174 15 5 33 Pass
0.1186 14 5 35 Pass 0.1197 14 4 28 Pass 0.1209 14 4 28 Pass 0.1221 14 3 21 Pass 0.1233 13 3 23 Pass 0.1245 12 3 25 Pass 0.1256 11 3 27 Pass 0.1268 10 3 30 Pass 0.1280 9 3 33 Pass 0.1292 8 3 37 Pass 0.1304 8 3 37 Pass 0.1315 8 3 37 Pass 0.1327 7 2 28 Pass 0.1339 6 2 33 Pass 0.1351 6 1 16 Pass 0.1363 6 1 16 Pass 0.1374 5 1 20 Pass 0.1386 5 1 20 Pass 0.1398 5 1 20 Pass
0.1410 5 1 20 Pass 0.1422 4 1 25 Pass 0.1434 4 1 25 Pass 0.1445 3 0 0 Pass 0.1457 3 0 0 Pass 0.1469 3 0 0 Pass
0.1481 2 0 0 Pass 0.1493 2 0 0 Pass 0.1504 2 0 0 Pass
0.1516 2 0 0 Pass 0.1528 2 0 0 Pass 0.1540 2 0 0 Pass
0.1552 2 0 0 Pass _____________________________________________________
TREATMENT FACILITY SIZING
Name : Treatment Basin
Bypass: No
GroundWater: No
Pervious Land Use acre
C, Lawn, Flat .10
Pervious Total 0.10
Impervious Land Use acre
ROADS MOD 0.38
ROOF TOPS FLAT 0.09
Impervious Total 0.47
Basin Total 0.57
Element Flows To:
Surface Interflow Groundwater
___________________________________________________________________
Water Quality BMP Flow and Volume for POC #2
On-line facility volume: 0.0609 acre-feet
On-line facility target flow: 0.0819 cfs.
Adjusted for 15 min: 0.0819 cfs.
Off-line facility target flow: 0.046 cfs.
Adjusted for 15 min: 0.046 cfs. ___________________________________________________________________
BACKWATER CALCULATIONS
UPSTREAM BASIN ANALYSIS
& CALCULATIONS
WWHM2012
PROJECT REPORT
___________________________________________________________________
Project Name: RENTON UPSTREAM
Site Name:
Site Address:
City :
Report Date: 5/21/2019
Gage : Seatac
Data Start : 1948/10/01
Data End : 2009/09/30
Precip Scale: 1.00
Version Date: 2017/04/14
Version : 4.2.13 ___________________________________________________________________
PREDEVELOPED LAND USE
Name : Basin 1
Bypass: No
GroundWater: No
Pervious Land Use acre
C, Forest, Flat 140.6
Pervious Total 140.6
Impervious Land Use acre
Impervious Total 0
Basin Total 140.6
Element Flows To:
Surface Interflow Groundwater
___________________________________________________________________
MITIGATED LAND USE
Name : Basin 1
Bypass: No
GroundWater: No
Pervious Land Use acre
C, Forest, Flat 25.67
C, Pasture, Flat 73.67
C, Lawn, Flat 19.25
Pervious Total 118.59
Impervious Land Use acre
ROADS MOD 10.65
PARKING FLAT 11.36
Impervious Total 22.01
Basin Total 140.6
Element Flows To:
Surface Interflow Groundwater SSD Table 1 SSD Table 1 ___________________________________________________________________
Name : SSD Table 1
Depth: 400 ft.
Element Flows To:
Outlet 1 Outlet 2 ___________________________________________________________________
SSD Table Hydraulic Table
Stage Area Volume Discharge
(feet) (ac.) (ac-ft.) (cfs.) NotUsed NotUsed NotUsed NotUsed 388.0 0.000 0.000 0.000 0.000 0.000 0.000 0.000 389.0 0.150 0.140 3.906 0.000 0.000 0.000 0.000 390.0 0.160 0.280 5.524 0.000 0.000 0.000 0.000 391.0 0.170 0.450 6.765 0.000 0.000 0.000 0.000 392.0 0.240 0.610 7.811 0.000 0.000 0.000 0.000 393.0 0.700 1.160 8.734 0.000 0.000 0.000 0.000 394.0 1.020 2.000 9.567 0.000 0.000 0.000 0.000 395.0 1.500 3.470 10.33 0.000 0.000 0.000 0.000 396.0 1.880 5.100 11.05 0.000 0.000 0.000 0.000 397.0 2.050 7.120 11.72 0.000 0.000 0.000 0.000 398.0 2.160 9.040 12.35 0.000 0.000 0.000 0.000
399.0 2.200 11.39 12.95 0.000 0.000 0.000 0.000 400.0 2.300 13.59 13.53 0.000 0.000 0.000 0.000 ___________________________________________________________________ ___________________________________________________________________
ANALYSIS RESULTS
Stream Protection Duration
___________________________________________________________________
Predeveloped Landuse Totals for POC #1
Total Pervious Area:140.6
Total Impervious Area:0
___________________________________________________________________
Mitigated Landuse Totals for POC #1
Total Pervious Area:118.59
Total Impervious Area:22.01
___________________________________________________________________
Flow Frequency Return Periods for Predeveloped. POC #1
Return Period Flow(cfs)
2 year 4.133758
5 year 6.492226
10 year 7.828811
25 year 9.244806
50 year 10.121029
100 year 10.866296
Flow Frequency Return Periods for Mitigated. POC #1
Return Period Flow(cfs)
2 year 7.14541
5 year 8.495664
10 year 9.300155
25 year 10.242169
50 year 10.900842
100 year 11.529425 ___________________________________________________________________