HomeMy WebLinkAboutF_RS_TIR_170828.pdfIN COMPIANCE WITH CITY OF RENTON STANDARDS
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LUA-16000782
C-17001068
PR-16000382 R-3947
Firestone Complete Auto Care Technical Information Report Renton, Washington
PACLAND Project #10439013 Page 1
Section Page
EXECUTIVE SUMMARY ........................................................................................................................................... 2
SECTION 1 - PROJECT OVERVIEW ........................................................................................................................... 4
SITE LOCATION .............................................................................................................................................................. 9
DRAINAGE BASINS, SUBBASINS, AND SITE CHARACTERISTICS ................................................................................................ 10
SOILS ......................................................................................................................................................................... 11
SECTION 2 - CONDITIONS AND REQUIREMENTS SUMMARY ................................................................................ 14
SECTION 3 - OFF-SITE ANALYSIS ........................................................................................................................... 18
SECTION 4 - FLOW CONTROL AND WATER QUALITY FACILITY ANALYSIS AND DESIGN ......................................... 22
HYDROLOGIC ANALYSIS ................................................................................................................................................. 22
EXISTING SITE HYDROLOGY ............................................................................................................................................ 22
DEVELOPED SITE HYDROLOGY ........................................................................................................................................ 23
FLOW CONTROL ANALYSIS ............................................................................................................................................. 23
WATER QUALITY SYSTEM .............................................................................................................................................. 24
PRE-TREATMENT ......................................................................................................................................................... 25
SUMMARY .................................................................................................................................................................. 25
SECTION 5 - CONVEYANCE SYSTEM ANALYSIS AND DESIGN ................................................................................. 26
CONVEYANCE .............................................................................................................................................................. 26
100-YEAR FLOOD/OVERFLOW CONDITION ....................................................................................................................... 26
SECTION 6 - SPECIAL REPORTS AND STUDIES ....................................................................................................... 27
SECTION 7 - OTHER PERMITS ............................................................................................................................... 28
SECTION 8 - CSWPPP ANALYSIS AND DESIGN ....................................................................................................... 29
SECTION 9 - BOND QUANTITIES, FACILITY SUMMARIES, AND DECLARATION OF COVENANT ............................... 31
SECTION 10 - OPERATIONS AND MAINTENANCE MANUAL .................................................................................. 32
APPENDICES: A – EXHIBITS
B – PLANS
C – DESIGN CALCULATIONS
D – WATER QUALITY DEPARTMENT OF ECOLOGY CERTIFICATION
E – GEOTECHNICAL REPORTS
F – BOND QUANTITIES WORKSHEET
G – DECLARATION OF COVENANT FOR MAINTENANCE OF STORMWATER FACILITIES
Table of Contents
Firestone Complete Auto Care Technical Information Report Renton, Washington
PACLAND Project #10439013 Page 2
Site Location:
The project property is located at 17808 108th Ave SE in Renton, Washington. The site is
bordered by 108th Ave SE/WA 515 to the west, Jiffy Lube to the north, a vacant commercial
building to the south, and 109th Ave SE to the east. There is also a residential property to the NE
as well. The site is currently developed as the Skipper’s Seafood and Chowder House, which has
a building footprint of 2,552 square feet, with associated parking and landscaping. The entire lot
is approximately 0.88 acres in size. This project proposes to demolish the existing restaurant and
parking lot, then redevelop the site to become a Firestone Complete Auto Care.
The project site lies within the Lower Green River Subwatershed, which is part of the
Green/Duwamish Watershed. It is in the City of Renton Black River drainage basin.
The project site is located in the City of Renton Commercial Mixed-Use Overlay District
(Community Planning area). The property is zoned CA (Commercial Arterial).
Design Criteria:
The City of Renton has adopted the 2017 Renton Surface Water Design Manual (RSWDM),
however, this project is vested to the King County Surface Water Management Design Manual
(KCSWDM), 2009 Edition, along with the City of Renton Amendments to the King County
Surface Water Design Manual, dated February 2010, for the design of stormwater facilities. The
existing site is developed and primarily impervious with the exception of landscape islands and
an undeveloped piece of land between the parking lot and 109th Ave SE. The proposed
development will lead to a slight increase in the amount of overall impervious area. Per the
requirements of KCSWDM, both flow control and water quality mitigation will be required as a
result of the proposed development.
Table 1
Jurisdictional Requirements
Peak Runoff Control:
Flow Control Duration Standard
Matching Forested Site Conditions
Matching durations from 50% of 2-
year flow up to full 50-year events,
and peak flow rates for the 2-year
and 10-year runoff events
Water Quality:
Enhanced Basic WQ Treatment
Preceding detention
60% of the developed 2-year peak
flow rate
Downstream of detention The full 2-year release rate from
detention facility
Executive Summary
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PACLAND Project #10439013 Page 3
Proposed Drainage System:
This project proposes to utilize a detention vault for storage and modular wetland system for
water quality treatment. The proposed grading will generally direct water from the northeast
corner of the site toward the west side of the site. There is currently a storm pipe that runs west
from 109th Ave SE toward the building. The existing pipe will be relocated to the north edge of
the site, and will continue to receive and detain off-site runoff from the east.
Stormwater will collect into catch basins along the valley on the east and north side of the
building and be conveyed via pipe to the northwest corner of the site to the stormwater
treatment structure. After treatment, stormwater will be directed to a detention vault, which in
conjunction with a flow control structure, will provide flow control as required by the
jurisdictional requirements identified in Table 1. After detention, stormwater will be released
existing stormwater system in 108th Ave. SE.
A stormwater adjustment shall be obtained for the use of the modular wetland system and the
use of the proposed detention facility in accordance with Section 1.4.5 of the City of Renton
Amendments to the 2009 KCSWDM.
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PACLAND Project #10439013 Page 4
Figure 1 - TIR Worksheet (KCSWDM 2009)
Section 1 - Project Overview
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PACLAND Project #10439013 Page 5
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PACLAND Project #10439013 Page 6
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PACLAND Project #10439013 Page 9
Site Location
Figure 2 - Site Location
Location: 17808 108th Ave SE, Renton, WA 98055
Section/Township/Range: NE Quarter of Section 32, Township 23, Range 05
Parcel/Tax Lot(s): 3223059104
Size: 0.88 acres
City, County, State: Renton, King County, Washington
Governing Agency: City of Renton
Design Criteria: 2009 King County Surface Water Design Manual (KCSWDM), and the City of
Renton Amendments to the KCSWDM (February 2010)
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PACLAND Project #10439013 Page 10
Drainage Basins, Subbasins, and Site Characteristics
Drainage Basin
The project site is located in the Lower Green River Subwatershed, which is part of the
Green/Duwamish Watershed. It is in the City of Renton Black River drainage basin.
Existing Sub-basins
The existing site consists of a single basin with an area of 0.88 acres. The southeast portion of
the site of the highest in elevation at 410’, and the area gradually slopes west toward the
building, which has a finished floor elevation of approximately 402’. The northeast side of the
site starts at an elevation of 408’ and slopes downward toward the west side of the site where it
has an elevation of 400’. Runoff is collected at a catch basin on the west side of the property,
where it is then conveyed into the municipal stormwater system. Refer to Section 3 for existing
discharge points to and from the site.
Proposed Sub-basins
The proposed storm drainage system will be comprised of one sub-basin. The sub-basin is
about 0.88 acres in size. Stormwater that lands north of the ridge follows the grading toward
the valley just north of the proposed building footprint and drains north to the detention
system. Water that lands in the south of the ridge drains into the valley and into a catch basin
which leads to the same stormwater pipe water that lands north of the ridge. Stormwater that
falls south of the retaining wall follows the grading below the proposed footprint and out
toward 108th Ave SE. See Appendix B for plans showing the distance from the farthest
upstream end to the nearest proposed flow control facility.
Table 2 – Site Areas
Surface Existing Area (AC) Proposed Area (AC)
Roof 0.06 0.19
Landscaping
(Pervious)
0.36 0.27
Pavement
(PGIS)
0.44 0.38
Sidewalk
(NPGIS)
0.02 0.04
Total 0.88 0.88
Site Characteristics
The property is located at 17808 108th Ave SE in Renton, Washington. The site is bordered by
108th Ave SE/WA 515 to the west, Jiffy Lube to the north, a residential area to the northeast, a
vacant commercial building to the south, and 109th Ave SE to the east. The site is currently
developed as the Skipper’s Seafood and Chowder House, which has a building footprint of 2,552
square feet, with associated parking and landscaping. The entire lot is approximately 0.88 acres
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PACLAND Project #10439013 Page 11
in size. This project proposes to demolish the existing restaurant and parking lot, then redevelop
the site to become a Firestone Complete Auto Care.
The proposed project will include the construction of an approximately 8,261 SF Firestone
Complete Auto Care building. The overall paved area will be approximately 0.38 AC, and the
overall change in impervious surfaces (roof and pavement) is approximately 0.07 AC. Water
quality treatment will be provided for an area equivalent to the pollution generating impervious
surface on site.
Soils
Websoil Survey
Figure 3a - Site Soils (USDA Web Soil Survey Map)
The site is mapped as Alderwood gravelly sandy loam 0 to 8 percent slopes (AgB) and
Alderwood gravelly sandy loam 8 to 15 percent slopes (AgC) according to the USDA Natural
Resource Conservation Service, Web Soil Survey for King County Area, Washington.
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PACLAND Project #10439013 Page 12
Figure 3b - Downstream Site Soils (USDA Web Soil Survey Map)
The downstream area is mapped as Alderwood gravelly sandy loam 0 to 8 percent slopes (AgB),
Alderwood gravelly sandy loam 8 to 15 percent slopes (AgC), and Arents 6 to 15 percent slopes
according to the USDA Natural Resource Conservation Service, Web Soil Survey for King County
Area, Washington.
Geotechnical Report
The following information was gathered from a report created by Zipper Geo Associates, LLC. on
August 29, 2016. 4 feet deep under the surface, ZGA’s infiltration test recorded that the soil
observed was glacial till with medium dense, light brown with some oxidation, sandy loam with
gravel. Underneath this soil was unweathered glacial till consisting of dense, tan, sandy loam
with gravel. The bottom of the infiltration test was at 8 feet. The report showed dense, tan,
unweathered glacial till at this depth.
No groundwater was observed during the infiltration test. There were also no signs that the
seasonal groundwater may be higher than when observed.
ZGA performed a single small-scale Pilot Infiltration Test per standard of the Storm Water
Manual. The results of the test were that the infiltration test was approximately 0.21
inches/hour. Correction factors were applied to the measured infiltration rate to produce a
design infiltration rate per the guidelines of KCSWDM Section 5.4.1.
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PACLAND Project #10439013 Page 13
Idesign = Imeasured x Ftesting x Fgeometry x Fplugging
Imeasured = 0.21 inches/hour
Ftesting = 0.30 for small-scale testing
Fgeometry = 1.0 (no groundwater or impermeable surface encountered)
Fplugging = 0.8 for fine sands and loamy sands
Idesign = 0.21 x 0.30 x 1.0 x 0.8 = 0.05 inches/hour
The geotechnical report, along with a previous report performed by Professional Service
Industries, Inc., (PSI) are presented in Appendix E.
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PACLAND Project #10439013 Page 14
As required by the 2009 King County Surface Water Design Manual (KCSWDM) and City of
Renton Amendment, this project is subject to a full drainage review. Therefore, the storm
drainage design for this project is required to comply with all eight (8) Core Requirements, and
six (6) Special Requirements. The requirements have been met as follows:
Core Requirement #1: Discharge at Natural Location
All surface and storm water runoff from a project must be discharged at the natural location so
as not to be diverted onto or away from downstream properties. The manner in which runoff is
discharged from the project site must not create a significant adverse impact to downhill
properties or drainage systems.
Response: Onsite runoff will be collected, conveyed, and when necessary, treated. All onsite runoff
is subsequently conveyed to the City of Renton stormwater system. The city system discharges
northwest of the site into Panther Creek. No downstream impacts are anticipated as a result of the
proposed improvements as the impervious area will remain approximately the same.
Core Requirement #2: Off-site Analysis
All proposed projects must submit an offsite analysis report that assesses potential offsite
drainage and water quality impacts associated with development of the project site and propose
appropriate mitigation of those impacts. The initial permit submittal shall include, at minimum, a
Level 1 downstream analysis.
Response: See Section 3 of this report for a complete off-site analysis. A Level 1 downstream
analysis will be submitted upon civil plan submittal.
Core Requirement #3: Flow Control
All proposed projects, including redevelopment projects, must provide onsite flow control
facilities or flow control BMPs or both to mitigate the impacts of storm and surface runoff
generated by new impervious surface, new pervious surface, and replaced impervious surface
targeted for flow mitigation.
Response:
Per KCSWDM and the City of Renton amendments, flow control will be provided for Flow Control
Duration Standard Matching Forested Site Conditions. A stormwater detention system and flow
control structure will be put in place to match pre-development conditions for 50% of the 2-year
up to the full 50-year design storm event and also the 2-year and 10-year peak flows. The
detention system shall have an open bottom, thus utilizing the available infiltration capacity of on-
site soils to contribute to flow control. A detailed summary and analysis of the existing and
proposed conditions is provided in Section 4 of this report.
Section 2 - Conditions and Requirements
Summary
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PACLAND Project #10439013 Page 15
Core Requirement #4: Conveyance System
All engineered conveyance system elements for proposed projects must be analyzed, designed,
and constructed to provide a minimum level of protection against overtopping, flooding,
erosion, and structural failure.
Response: Portions of the existing conveyance system will be reused as part of this project with
additional conveyance added to accommodate the new building configuration and site layout. The
proposed conveyance system has been designed to convey the 100-year peak flow.
Core Requirement #5: Erosion and Sediment Control
All proposed projects that will clear, grade, or otherwise disturb the site must provide erosion
and sediment controls to prevent, to the maximum extent practicable, the transport of sediment
from the project site to downstream drainage facilities, water resources, and adjacent properties.
Both temporary and permanent ESC measures shall be implemented.
Response: Erosion and sediment control requirements will be an integral part of the project
construction documents. These measures will include methods to reduce erosion of onsite site soils
and to prevent sediments from inadvertently leaving the project site. Additionally, the ESC
measures will prevent sediment-laden discharge from entering the wetland or existing stormwater
water quality or flow control facilities.
Core Requirement #6: Maintenance and Operations
Maintenance and operation of all drainage facilities is the responsibility of the property owner,
except those facilities for which the City of Renton assumes maintenance and operation, and
must be maintained and operated in accordance with King County or other maintenance
standards as approved by the City of Renton.
Response: An Operations and Maintenance Manual is included in this report- see Section 10.
Core Requirement #7: Financial Guarantees and Liability
In accordance with RMC 4-6-030J, RDSD shall require all persons constructing any surface water
facilities (including flow control/water quality facilities, conveyance systems, erosion control, and
road drainage), to post with the City of Renton a bond, assignment of funds or certified check.
The applicant must also maintain liability insurance.
Response: See Section 9- Bond Quantities, Facility Summaries, and Declaration of Covenant. The
Site Improvement Bond Quantity Worksheet and Declarations of Covenants will be submitted
upon approval of the Building Permit plans.
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PACLAND Project #10439013 Page 16
Core Requirement #8: Water Quality
All proposed projects, including redevelopment projects, must provide water quality (WQ)
facilities to treat the runoff from those new and replaced pollution-generating impervious
surfaces and new pollution-generating pervious surfaces targeted for treatment.
Response: Enhanced Basic Treatment is required, as more than 50% of the runoff that drains to
the proposed treatment facility is from commercial land use. Additionally, an oil/water separator,
which will discharge to the sanitary sewer system, will be provided for discharges from the
building. A detailed summary and analysis of the water quality basin and design is provided in
Section 4 of this report.
Special Requirement #1: Other Adopted Area-Specific Requirements
The City of Renton may apply requirements for controlling drainage on an area-specific basis.
Potential other adopted area-specific requirements may include: Master Drainage Plans, Basin
Plans, Stormwater Compliance Plans, etc.
Response: The project site is within Washington State Water Resource Inventory Area 9:
Green/Duwamish and Central Puget Sound Watershed Salmon Habitat Recovery. However, the
proposed project will have no effect on any salmon habitats. The project site does not lie within
any City of Renton Master Drainage or Basin Plans.
Special Requirement #2: Flood Hazard Area Delineation
If a proposed project contains or is adjacent to a flood hazard area as determined by the Renton
Department of Storm Drainage, the project must determine those components that are
applicable and delineate them on the project’s site improvement plans and recorded maps.
Response: The project site does not lie within or adjacent to a City of Renton Flood Hazard Area
(determined by FEMA FIRM Panel 53033C0979F dated May 16, 1995) and therefore does not need
to apply the provisions of this requirement.
Special Requirement #3: Flood Protection Facilities
Proper analysis, design, and construction are necessary to protect against the potentially
catastrophic consequences if flood protection facilities such as levees and revetments should
fail.
Response: The proposed project will not rely on an existing flood protection facility, or modify or
construct a new flood protection facility.
Special Requirement #4: Source Control
If a proposed project requires a commercial building or commercial site development permit
then the water quality source controls applicable to the proposed project shall be applied in
accordance with the King County Stormwater Pollution Prevention Manual and Renton Municipal
Code IV.
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PACLAND Project #10439013 Page 17
Response: Water quality source controls will be applied in accordance with the KCSWDM and
Renton Municipal Code IV. A pollution prevention plan has been included in section 8 of this
report.
Special Requirement #5: Oil Control
Projects proposing to develop or redevelop a high-use site must provide oil control in addition
to other water quality controls required.
Response: High use sites area defined as a commercial or industrial site that (1) has an expected
average daily traffic count equal to or greater than 100 vehicles/1,000 SF of gross building area:
(2) is subject to petroleum storage in excess of 1,500 gallons per year; (3) is subject to use, storage,
or maintenance of a fleet of 25 or more diesel vehicles. The proposed development does not exceed
any of these thresholds, and is therefore not required to provide oil control.
Special Requirement #6: Aquifer Protection Area
If a proposed project is located within the Aquifer Protection Area as identified in the RMC 4-3-
050, this special requirement requires the project to determine those components that are
applicable and delineate them on the project’s site improvement plans.
Response: The project is not located within an Aquifer Protection Area, and therefore this
requirement does not apply.
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PACLAND Project #10439013 Page 18
Upstream Analysis
The municipal storm drainage system in 109th Ave. SE currently discharges stormwater via a 12”
pipe sloped at approximately 0.3% to a small swale in the northeast corner of the site.
Stormwater is then routed via pipe to a catch basin located centrally in the parking lot, enters
into a 36” CMP detention pipe, goes through a flow control manhole, and eventually enters into
the municipal stormwater system in 108th Ave. SE.
Upon development of the site, upstream drainage from 109th Ave. SE will be routed directly to a
catch basin rather than entering the drainage swale. A new 18” storm drain pipe will convey this
stormwater to the 36” pipe, which shall be relocated to the north side of the site. Per the
requirements of KCSWDM Section 1.2.3.F for bypass of runoff from non-target surfaces, the
upstream flows must bypass the on-site detention system. The new conveyance infrastructure
shall convey the upstream flows for the 25-year design storm event.
Based on available GIS information and aerial imagery, the upstream tributary area is
approximately 13.9 acres in size, approximately 48% of which is comprised of impervious area.
As detailed in the upstream analysis portion of Appendix C, the proposed conveyance pipes
have capacities in excess of the peak flow for the 25-year design storm event, and thus are
adequate to convey the design storm.
Downstream Analysis
After the runoff passes through the existing stormwater detention/treatment facilities, runoff
enters the municipal stormwater system at 108th Ave SE. After crossing over 108th Ave SE, the
system travels northwest about 2500 feet until discharge into Panther Creek. As discussed
earlier in the report, the storm runoff leaves the site at the northwest corner and enters into the
Renton Municipal storm system. The system runs underneath the Fred Meyer strip mall and
across SE Carr Rd until feeding into Panther Creek. A map of the downstream analysis can be
seen in Figure 4.
Section 3 - Off-Site Analysis
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PACLAND Project #10439013 Page 19
Figure 4 - Downstream Area (Renton COR Maps)
DISCHARGE
POINT
PROJECT
SITE
POINT OF
ENTRY TO CITY
OF RENTON
STORM SYSTEM
PANTHER
CREEK
UPSTREAM
TRIBUTARY
AREA
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PACLAND Project #10439013 Page 20
Resource Review
The following resources were reviewed in preparing an offsite analysis:
• FEMA flood maps
• Sensitive areas maps (King County DDES)
• King County Soils Survey (USDA)
• Wetlands Inventory (RDSD)
• Section 303d list of polluted waters (WSDOE)
• City of Renton Erosion and Landslide Maps
Field Inspection
The downstream system ¼ mile from the site is entirely within subsurface piping, therefore it is
not feasible for the design engineer to physically perform a field inspection. A resource review
was performed in order to fulfill the following field inspection requirements:
1. There were not any issues found during the resource review.
2. There are no anticipated constrictions or lack of capacity in the existing drainage system.
3. Problem Type 1 - There are no anticipated failures of the conveyance system downstream
from the project site.
Problem Type 2 - After reviewing the City of Renton Erosion Hazard Map, neither the
project site nor downstream area are within an erosion hazard area.
Problem Type 3 - After reviewing the City of Renton Flood Hazard Map along with the
FEMA flood map, there not any concerns regarding the potential of a severe building or
roadway flooding problem.
4. There is no anticipated or existing overtopping, scouring bank sloughing, or
sedimentation problems because the site is not within a flood or erosion hazard area.
5. After reviewing the Wetlands Inventory, there is no anticipated destruction of aquatic
habitat or organisms because there are no major streams or lakes downstream of the
project site.
6. The land uses of the project site, downstream area, and other businesses within the
vicinity are primarily commercial. Impervious surfaces within the area include paving for
108th Ave SE, the proposed Firestone building, and the associated parking lot. See
Section 1 for soil details. The topography of this project site and downstream is fairly
flat.
7. There are no major streams or wetlands downstream of this project within ¼ mile. The
project site and downstream area are not within a landslide hazard area or erosion
hazard area. The storm drainage pipes downstream of the project site are 12” and 24”.
8. The tributary basin delineated in Task 1 are confirmed.
9. After the resource review, there are no concerning existing drainage problems.
10. N/A
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PACLAND Project #10439013 Page 21
Drainage System Description and Problem Descriptions
See Figure 4 above for the location of the project site with respect to the discharge points. The
downstream drainage system is comprised of 24” and 12” storm drain pipe running at
approximately 0.5% slope. The land cover just downstream of the site is primarily impervious.
There are no existing or anticipated problems because the site and downstream area are not in
an erosion or flooding hazard area, steep slope hazard area, wetland area.
Mitigation of Existing or Potential Problems
There is no necessary mitigation because there are no anticipated drainage issues downstream
of the site.
Conclusion:
The proposed stormwater management system for this project has been designed in accordance
with regulatory criteria described above and is consistent with sound engineering practice. The
site has been analyzed to determine the requirements for detention and water quality treatment,
and no significant adverse impacts to the stormwater management system are expected as a
result of the proposed development.
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PACLAND Project #10439013 Page 22
The City of Renton Amendment to the KCSWDM applies flow control standards based on
geographic areas as determined by the Flow Control Application Map. The project site lies
within a Conservation Flow Control Area. This requires a level 2 downstream analysis. This area
requires peak runoff control within the Flow Control Duration Standard Matching Forested Site
Conditions area such that it matches the flow duration of predeveloped rates for the existing
site conditions over the range of flows extending from 50% of 2-year up to the full 50-year flow.
This matches the flow duration of predeveloped rates for the existing site conditions over the
range of flows extending from 50% of 2-year up to the full 50-year flow and the 2-year and 10-
year peak flows.
Hydrologic Analysis
The existing and proposed site conditions were evaluated using both the King County Runoff
Time Series (KCRTS) The detailed KCRTS output has been included in Appendix C.
The historic 1-hour duration in the Sea-Tac rainfall region (location scale factor ST-1.0) was used
to model runoff in KCRTS.
Existing Site Hydrology
The existing site consists primarily of a single sub-basin. The site generally flows from east to
west, ranging from an elevation of 410 in the southeast corner to 400 at the western edge,
where a catch basin collects runoff and conveys it to the existing City of Renton municipal storm
drainage system in 108th Ave. SE. The municipal stormwater system routes to a discharge point
of Panther Creek across SE Carr Rd. Adjacent properties to the north and south do not drain
toward the project, and therefore do not contribute any runoff to the drainage basin. A drainage
swale in the northeast corner of the site accepts runoff from 109th Ave. SE prior to being
collected in a 36” detention pipe, then released to the existing storm drainage system in 108th
Ave. SE. The pre-developed (existing) conditions and historic peak runoff rates for the project
site area are shown in Tables 4 and 5 below. An exhibit showing the existing conditions is
provided in Appendix A. Existing peak runoff rates were determined using the King County
Runoff Time Series modeling software and the calculations can be found in Appendix C.
Table 4
Pre-Developed (Existing) Conditions
Area Condition
0.44 AC Pavement/Sidewalk
0.38 AC Landscape
0.06 AC Roof
*For KCRTS analysis, a fully forested condition
was assumed per City of Renton requirements.
Section 4 - Flow Control and Water Quality Facility Analysis
and Design
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PACLAND Project #10439013 Page 23
Table 5
Historic Peak Runoff Rate
Event Rate (cfs)
2-year 0.028
10-year 0.044
100-year 0.097
Developed Site Hydrology
The developed site will preserve the general configuration of the site, with runoff generally
flowing from east to west, being collected in catch basins located throughout the site prior to
being conveyed to a treatment structure and a detention facility, then released into the existing
system in 108th Ave. SE. Therefore, existing drainage pattern and discharge locations will be
maintained. The existing detention pipe will be relocated to the northern portion of the site, and
will continue to receive and detain runoff from 109th Ave. SE. The post-developed conditions
and un-detained peak runoff rates for the entire basin area are shown in Tables 6 and 7 below.
An exhibit showing the developed conditions is provided in Appendix A. The proposed grading
and drainage plan is included in Appendix B. Developed peak runoff rates were determined
using the King County Runoff Time Series modeling software and the calculations can be found
in Appendix C.
Table 6
Post-Developed Conditions
Area Condition
0.38 AC Pavement (PGIS)
0.04 AC Sidewalk
0.27 AC Landscape
0.19 AC Roof
Table 7
Developed Peak Runoff Rate
Event Rate (cfs)
2-year 0.295
10-year 0.409
100-year 0.863
Flow Control Analysis
The proposed project includes installation of a subsurface open-bottom modular detention
vault system in order to meet the requirements associated with the Flow Control Duration
Standard. Details for this system can be found in Appendix B. A small amount of infiltration,
based on the geotechnical information provided in Appendix E, was taken into consideration in
the design calculations. The total storage provided by the vault system is 9,975 cubic feet, which
is in excess of the required volume of 9,750 cf. Discharges from the detention system are shown
in Table 8.
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PACLAND Project #10439013 Page 24
Table 8
Mitigated Peak Runoff Rate
Event Rate (cfs)
2-year 0.013
10-year 0.033
100-year 0.096
A flow control structure (per City of Renton standard plan 237.00) will be installed downstream
of detention to regulate discharge rates. The structure shall incorporate a flow control tee
consisting of two orifices and a riser pipe. The lower orifice, located at the bottom of the tee,
shall be 0.6 inches in diameter. The upper orifice, located 1.8 feet above the outlet invert, shall
be 1.2 inches in diameter. The riser pipe shall have a diameter of 12 inches.
Per KCSWDM Section 5.2.1.3, the project is subject to the Large Lot High Impervious BMP
Requirements since the lot is greater than 22,000 square feet and results in greater than 45%
impervious area. This section requires evaluation of multiple BMPs to provide flow control. Since
full dispersion is not feasible, the project is proposing to utilize limited infiltration using the
open-bottom detention system. Limited infiltration, per Appendix C Section C.2.1, involves the
use of infiltration devices in soils that are not as permeable as the medium sands or coarse
sands/cobbles targeted for full infiltration. Although limited infiltration facilities are only
required to be applied to 20% of the target impervious surface, the open-bottom detention
system manages runoff from all site impervious areas, thus satisfying the requirement.
Water Quality System
In order to provide enhanced basic treatment as required by KCSWDM and the City of Renton
amendments, a modular wetland will be installed upstream of detention. The modular wetland is
intended to collect and treat runoff generated by the pollutant-generating impervious areas on
the site, mimicking the treatment effects of a wetland by utilizing a combination of pre-
treatment using separation and pre-treatment cartridges and treatment utilizing biofiltration. A
detail drawing of this system is provided in Appendix B. The modular wetland systems have
been granted General Use Level Designation (GULD) by the Washington State Department of
Ecology (DOE) for Basic, Enhanced, and Phosphorous treatment. The approval documentation
has been included in Appendix D. Since the project utilizes limited infiltration for flow control,
the water quality structure has been located upstream of detention to maximize removal of
pollutants prior to infiltration, thereby maximizing the effectiveness of the infiltration and
minimizing maintenance requirements.
Table 9
Water Quality Flow Rates and Facility Sizing
Basin Design Event Rate (cfs) MWS-L-4-8-V Treatment
Flow Rate (cfs)
A 60% of 2-year (Upstream of
Detention)
0.114
(0.190x0.60) 0.115
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PACLAND Project #10439013 Page 25
Pre-Treatment
In addition to the pre-treatment element provided in the Modular Wetland System, the inlet
chambers of the detention/infiltration system will provide pre-treatment volumes equal to the
“first flush” volume, which is equal to 0.75 times the runoff from the mean annual storm, per
KCSWDM Section 6.5.1. The pre-treatment volume, calculated per the methodology in KCSWDM
Section 6.4.1.1, is as follows:
A = 16,788 SF
Vr = 0.90 x 16788 SF x 0.039 FT= 589.26 CF
Vb = 0.75 x Vr = 441.94 CF
The volume provided in the two full depth units (considered to be the volume below the outlet)
where stormwater from pollutant-generating surfaces enters the system totals 840 CF (7’x15’x4’x
2), which exceeds the first flush volume calculated above.
Summary
Flow Control
Event Historic Flow
Rate (cfs)
Developed
Flow Rate (cfs)
Mitigated Flow
Rate/Discharge (cfs)
100-year 0.097 0.863 0.096
10-year 0.044 0.409 0.033
2-year 0.028 0.295 0.013
Flow control provided by the open-bottom detention system meets the requirements for the
Flow Control Duration Standard (City of Renton Amendments, Section 1.2.3.1), and also meets
the requirements for Individual Lot Flow Control BMPs (KCSWDM Section 5.2.1.3) via the use of
limited infiltration.
Water Quality
Water Quality Flow Rates and Facility Sizing
Basin Design Event 2-Year Flow
Rate (cfs)
Design WQ
Flow Rate
(cfs)
MWS-L-4-8-V
Treatment
Flow Rate (cfs)
A
60% of 2-year
(Upstream of
Detention)
0.190 0.114 0.115
Water quality provided by the modular wetland units meets the requirements for the Enhanced
Basic Water Quality standard (KCSWDM Section 6.1.2) for treatment upstream of detention.
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PACLAND Project #10439013 Page 26
Conveyance
Per the 2009 King County Surface Water Design Manual, Section 4.2.1.2, the on-site stormwater
conveyance can be calculated based on gravity flow analysis of the piping network. Peak run-off
associated with and up to a 25-year storm event has been determined to be adequate. Uniform
flow analysis utilizing Manning’s equation, shown below, was employed with a Manning’s
Roughness Coefficient (n) of 0.012.
Manning’s equation - Q=n49.1 xAxR2/3xS1/2
With: Q = Flow (CFS)
n = Manning’s Roughness Coefficient (0.012)
A = Flow Area (SF)
R = Hydraulic Radius = Area /Wetted Perimeter (LF)
S = Slope of the pipe (ft/ft)
Based on the basin areas and pipe sizes, the proposed conveyance system is adequate for the
25-year storm event. All new conveyance pipes have been designed to convey the 25-year storm
event. Additionally, the overflow from a 100-year storm event will not create or aggravate a
severe flooding problem or severe erosion problem. See Appendix C for conveyance design
calculations.
100-Year Flood/Overflow Condition
Review of the current FEMA FIRM maps (Panel 0979 F) indicates that the project site lies within
the Zone X, which is determined to be outside of the 100-year flood plain. If the existing storm
system were to experience a major storm event, the stormwater detention area would overflow
in to the front access and drain out toward 108th Ave SE.
The stormwater system for this project has been designed to address the storm events in
accordance with design criteria described previously. In the event of a larger storm, it is unlikely
that the system would fail. Based on a review of the site and immediate surroundings, the
overflow of the stormwater conveyance system would allow surface water to sheet flow to the
public storm system in 108th Ave SE.
Section 5 - Conveyance System Analysis and Design
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PACLAND Project #10439013 Page 27
The following Special Reports and Studies were used or have been completed for this project:
• Field Infiltration Testing- by Zipper Geo Associates
• Geotechnical Engineering Report - by Professional Service Industries, Inc.
• FEMA FIRM Panels 0979F dated May 16, 1995
Section 6 - Special Reports and Studies
Firestone Complete Auto Care Technical Information Report Renton, Washington
PACLAND Project #10439013 Page 28
The following governmental approvals or permits will likely be required for this project:
• City of Renton SEPA Determination
• City of Renton Site Plan Review
• City of Renton Building Permit
• City of Renton Construction Permit
• City of Renton Demolition Permit These permits will require approval by the City of Renton Planning Division or the Department of Ecology.
Section 7 - Other Permits
Firestone Complete Auto Care Technical Information Report Renton, Washington
PACLAND Project #10439013 Page 29
All erosion and sediment control measures shall be governed by the requirements of the City of
Renton and the Washington State Department of Ecology. A temporary erosion and
sedimentation control plan will be prepared to assist the contractor in complying with these
requirements. The Erosion and Sediment Control (ESC) plan will be included with the
construction plans.
1. Erosion Risk Assessment
The degree of erosion risk on the proposed project site is minimal. Slope across the site is
minimal. Runoff will not travel at high velocities across the site and, therefore, will not cause
noticeable erosion impacts.
2. Construction Sequence and Procedure
The proposed development will include an erosion/sedimentation control plan designed to
prevent sediment-laden run-off from leaving the site during construction. The erosion potential
of the site is influenced by four major factors: soil characteristics, vegetative cover, topography,
and climate. Erosion/sedimentation control is achieved by a combination of structural
measures, cover measures, and construction practices that are tailored to fit the specific site.
Prior to the start of any grading activity upon the site, all erosion control measures, including
stabilized construction entrances, shall be installed in accordance with the construction
documents.
The best construction practice will be employed to properly clear and grade the site and to
schedule construction activities. The planned construction sequence for the construction of the
site is as follows:
1. Attend a pre-construction meeting with the City of Renton.
2. Install temporary erosion control features.
3. Demolish existing structure(s).
4. Clear and grub site.
5. Grade site.
6. Construct buildings.
7. Pave site and install landscaping.
8. Remove temporary erosion control features once site is fully stabilized.
Section 8 - CSWPPP Analysis and Design
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PACLAND Project #10439013 Page 30
3. Trapping Sediment
Structural control measures will be used to reduce erosion and retain sediment on the
construction site. The control measures will be selected to fit specific site and seasonal
conditions.
The following structural items will be used to control erosion and sedimentation processes:
• Stabilized construction entrances
• Filter fabric fences
• Catch Basin Inlet Sediment Protection
• Proper Cover measures
Weekly inspection of the erosion control measures will be required during construction. Any
sediment buildup shall be removed and disposed of off-site.
A stabilized construction entrance will be installed at the site entrance to avoid vehicle tracking
off mud off-site. The entrances are a minimum requirement and may be supplemented if
tracking of mud onto public streets becomes excessive. In the event that mud is tracked off site,
it shall be swept up and disposed of off site on a daily basis. Depending on the amount of
tracked mud, a vehicle road sweeper may be required.
Because vegetative cover is the most important form of erosion control, construction practices
must adhere to stringent cover requirements. More specifically, the contractor will not be allowed
to leave soils open for more than 14 days and, in some cases, immediate seeding will be required.
4. Wet Season TESC Operating Plan
Work between October 1st and April 30th must adhere to the Wet Season Special Provisions
noted in the 2009 KCSWDM.
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PACLAND Project #10439013 Page 31
See Appendix B for details of the proposed flow control and water quality facilities. See
Appendix F for a copy of the Bond Quantities Worksheet including the summary of costs for
flow control and water quality facilities. See Appendix G for the Declaration of Covenant and
Facility Summary.
Section 9 - Bond Quantities, Facility Summaries, and Declaration of
Covenant
Firestone Complete Auto Care Technical Information Report Renton, Washington
PACLAND Project #10439013 Page 32
A manual detailing the operations and maintenance for all privately-maintained flow control and
water quality facilities has been prepared and can be found in Appendix G.
Section 10 - Operations and Maintenance Manual
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Appendix A – Exhibits
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Appendix B – Plans
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Appendix C – Design Calculations
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Historic Time Series
Historic Peak Flow Rates
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Developed Time Series
Developed Peak Flow Rates
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Retention/Detention Facility Design
Retention/Detention Facility Information
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Historic vs. Developed Duration Analysis
Discharge Flow Rates
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Developed Time Series - WQ
Water Quality Flow Rates
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Stage Storage
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Stage Storage Graph
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Conveyance Design Calculations
Manning’s equation: Q=n49.1 xAxR2/3xS1/2
With: Q = Flow (CFS)
n = Manning’s Roughness Coefficient (0.012)
A = Flow Area (SF)
R = Hydraulic Radius = Area /Wetted Perimeter (LF)
S = Slope of the pipe (ft/ft)
12” Pipe @ 0.5% slope:
Q=n49.1 xAxR2/3xS1/2 = 2.94 CFS
n = 0.012
A = 0.771 (SF)
R = 0.286 @ 95% full
S = 0.005
Pipe capacity exceeds peak flows generated by development.
Firestone Complete Auto Care Technical Information Report Renton, Washington
PACLAND Project #10507003
Conveyance Design Calculations (Upstream Analysis)
18” Pipe @ 4.0% slope:
Q=n49.1 xAxR2/3xS1/2 = 24.33 CFS
n = 0.012
A = 1.72 (SF)
R = 0.43 @ 95% full
S = 0.040
36” Pipe @ 0.5% slope:
Q=n49.1 xAxR2/3xS1/2 = 55.21 CFS
n = 0.012
A = 6.90 (SF)
R = 0.87 @ 95% full
S = 0.005
Upstream tributary design flow based on Rational Method:
Q = CIA
Q = Peak Flow (cfs), using 25-year design storm
C = Coefficient of Runoff
I = Peak Rainfall Intensity (in/hr)
A = Drainage Area (acres)
I = m/Tcn
Using WSDOT rainfall coefficients for the 25-year rainfall event
m = 6.89
Tc = 5 (min)
n = 0.539
I = 6.89 / (50.539) = 2.89
A = 13.9 acres
C = ((CIMP x AIMP) + (CPER x APER)) / A = ((0.90 x 6.7) + (0.25 x 7.2)) / 13.9 = 0.56
Q = (0.56) x (2.89) x (13.9) = 22.50 cfs
Pipe capacities exceed peak design flow. Therefore, the pipes are adequate to convey the flow.
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Appendix D – Operations and Maintenance Manual
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Appendix E – Water Quality Department of Ecology
Certification
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Appendix F – Geotechnical Reports
(Presented Without Appendices)
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Appendix G – Bond Quantities Worksheet
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Appendix H – Declaration of Covenant for
Maintenance of Stormwater Facilities
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Maintain Stormwater Facilities
The owner or operator of the project shall be responsible for maintaining the stormwater
facilities in accordance with local requirements. Proper maintenance is important for adequate
functioning of the stormwater facilities. The following maintenance program is recommended
for this project:
King County Surface Water Design Manual
DenisLawMayorCommunity&EconomicDevelopmentC.E.“Chip”Vincent,AdministratorAugust7,2017Mr.BillFortunato,PEPacLand1505WestlakeAveN.,Suite305Seattle,WA98109RE:Firestone(C17001068)—MWS-LinearModularWetlandStormwaterTreatmentSystemandModifiedAccessRequirementsforInfiltrationVaultsusingtheStormCaptureDetention/InfiltrationSystemforPrivateUse-Adjustment2017-03DearMr.Fortunato:TheCityofRentonhascompletedreviewoftheadjustmentrequestfortheFirestone(C17001068)inaccordancewithCityadopted2009KingCountySurfaceWaterDesignManualandassociatedCityAmendmentstowhichtheprojectisvestedtoinaccordanceRMC4-1-045.Astheapplicant’sengineer,youarerequestinganadjustmentfromthe2009KingCountySurfaceWaterDesignManualtoSection5.4.4InfiltrationFacilitiesandSection6.1.2,EnhancedBasicWaterQualityMenu,requirements.Morespecifically,youarerequestinganadjustmenttotheaccessrequirementsforinfiltrationvaultsasoutlinedintheManualwiththeuseoftheproposedStormCaptureInfiltrationSystemandanadjustmentfortheimplementationoftheMWS-LinearModularWetlandStormwaterTreatmentSystemlocatedonaprivatecommercialproperty;bothfacilitieswillbeownedandmaintainedbythepropertyowner(s).Findings:1.Theprojectsiteislocatedat17808108thAveSE.Theprojectisacommerciallanduse,whichpertheCity’sAmendmentstothe2009KingCountySurfaceWaterDesignManualSection1.2.8.1,isrequiredtoprovideFlowControlandEnhancedBasicWaterQualityTreatment.1055SouthGradyWay,Renton,WA98057•rentonwa.gov
Mr.BillFortunadoPage2of6August7,20172.ThesurfacewaterfromtheproposeddevelopmentwillbecollectedthenroutedthroughtheMWS-LinearModularWetlandStormwaterTreatmentSystempriortoenteringtheproposedStormCaptureSystem.3.TheStormCaptureSystemandtheMWS-LinearModularWetlandStormwaterTreatmentSystem,andotheron-sitedrainagefacilitiesandconveyancesystemswillbeprivatelyownedandmaintained.4.TheMWS-LinearModularWetlandStormwaterTreatmentSystemisnotanapprovedfacilityinthe2009KingCountySurfaceWaterDesignManual,thereforeanadjustmentisrequiredtoallowtheuseoftheMWS-LinearmodularWetlandStormwaterTreatmentSystemonprivateorpubliclyownedandmaintainedstormsystems.5.TheWashingtonStateDepartmentofEcologyhasapprovedtheMWS-LinearModularWetlandStormwaterTreatmentSystemforGeneralUseLevelDesignationforBasic,Phosphorous,andEnhancedtreatment.6.TheStormCaptureSystemmodifiesthefollowingaccessrequirementsasoutlinedinSection5.3.3.1oftheManual.#7—Internalstructuralwallsoflargevaultsshallbeprovidedwithopeningssufficientformaintenanceaccessbetweencells.#8-Theminimuminternalheightshallbe7-feetfromthehighestpointofthevaultfloor(notsump),andtheminimumwidthshallbe4-feet.TheproposedStormCapturesystemhasaninternalheightof3-ft.IntheStormCapturesystem,maintenanceisonlyrequiredinspecificlocations,suchasinletandoutletunits.Becauseofthis,physicalaccessisnotrequiredforotherunits.Therefore,accessbetweenunitsisnotproposed.Surfacewaterwilltransfertoadjacentcellsthrougha6-inchtall,4-footwidecut-outintheinternalwallsoftheStormCaptureunits.Thecut-outsarepositionedapproximately10-inchesabovethebottomoftheunitsinordertocapturesedimentpriortotransferringtoadjacentunits.Basedontheinformationprovidedintheenclosedadjustmentrequest,theModifiedAccessRequirementsforInfiltrationVaultsusingtheStormCaptureDetention/InfiltrationSystemandtheMWS-LinearModularWetlandStormwaterTreatmentSystemisapprovedfortheproposedFirestonewiththefollowingconditions:1055SouthGradyWay,Renton,WA98057.rentonwa.9OV
Mr.BillFortunadoPage3of6August7,2017Conditions:1.Thepropertyowner(s)isresponsibleforthemaintenanceandoperationoftheStormCaptureSystemandtheMWS-LinearModularWetlandStormwaterTreatmentSystem.2.Thepropertyowner(s)shallenterintoaservicecontractwithanapprovedcontractororLinearModularWetlandrepresentativeforthelongterminspectionandmaintenanceoftheMWS-LinearModularWetlandStormwaterTreatmentSystem.3.Thepropertyowner(s)shallenterintoaservicecontractwithanapprovedcontractororStormCapturerepresentativeforthelongterminspectionandmaintenanceoftheStormCaptureSystem.4.TheMWS-LinearModularWetlandinstalledupstreamofdetentionshallbedesignedwithawaterqualitydesignflowrateofthe60%ofthedevelopedtwo-yearpeakflowrate,asdeterminedusingtheKCRTSmodelwith15-minutetimestepscalibratedtositeconditions.5.TheMWS-LinearModularWetlandStormwaterTreatmentSystemunitsshallbedesigned,assembled,installed,operatedandmaintainedinaccordancewiththeModularWetlandSystems,Inc.applicablemanualsanddocumentsandtheEcologyDecision.6.EachsiteplanmustundergoModularWetlandSystems,Inc.reviewandapprovalbeforesiteinstallation.ThisensuresthatsitegradingandslopeareappropriateforuseofaMWS-LinearModularWetlandStormwaterTreatmentSystemunit.7.MWS-LinearModularWetlandStormwaterSystemmediashallconformtothespecificationssubmittedto,andapprovedby,Ecology.8.TheStormCaptureSystemshallincludethefollowingdesignelementsasdepictedontheenclosedpreliminaryGradingandDrainagePlan(ExhibitA).a.AllinletandoutletunitsoftheStormCaptureSystemshallbe7-feetindepthandclosedbottomunitswithmanwayandladderaccess.b.AdditionalunitsneartheprimaryinletoftheStormCaptureSystemshallbe7-feetindepthandclosedbottomunitswithmanwayandladderaccess.TheseunitsareidentifiedonExhibitA.c.Inspectionports,24-inches,shallbeprovidedatthemiddleandendrowsoftheStormCaptureSystem.1055SouthGradyWay,Renton,WA98057.rentonwa.gov
Mr.BillFortunadoPage4of6August7,20179.AdditionalPre-Treatmentisrequired,inaccordancewiththe2009KCSWDMandtheCityAmendmentstotheManual,priortotheMWS-LinearModularWetlandStormwaterTreatmentSystemtofurtherminimizethesedimentthatentersthefacilityandreducethepotentialmaintenancerequirementsoftheStormCaptureSystem.10.Facilityinspection,maintenance,andreportingarerequiredbytheCityofRentonSurfaceWaterUtilityforthePropertyOwnermaintainedStormCaptureSystemandtheMWS-LinearModularWetlandStormwaterTreatmentSysteminperpetuity.Thefacilityinspection,maintenanceandreportingisrequiredpertheEcologyNationalPollutantDischargeEliminationSystemPhaseIIMunicipalStormwaterPermit(SectionS5.C.4.c.iii).Facilityownersareresponsibleforensuringthatstormwaterfacilitiesareproperlymaintainedandfunctioningasdesignedandpermitted.11.TheMWS-LinearModularWetlandStormwaterTreatmentSystemshallbeinspectedandmaintainedinaccordancewithmanufacturerrecommendationsand,inaddition,beinspectedandmaintainedasdetailedbelow:a.Forthefirstyearafterconstruction,theMWS-LinearModularWetlandStormwaterTreatmentSystemshallbeinspectedeverysixmonthstoassureproperperformance.Inspectionreportswillbeusedtodeterminefuturesite-specificmaintenanceschedulesandrequirements.b.Followingthefirstyearofoperation,thefacilityowner(s)shallannuallyhavetheMWS-LinearModularWetlandStormwaterTreatmentSysteminspectedandmaintainedpertheproceduresinthemostrecentversionoftheMWS-LinearModularWetlandStormwaterTreatmentSystemOperationandMaintenanceManuals.AllwrittenrecordsoftheinspectionandmaintenanceshallbesubmittedtotheCityofRentonSurfaceWaterUtility,totheattentionofSurfaceWaterUtilityPrivateStormwaterFacilityInspectionProgram.IfmorefrequentinspectionandmaintenanceoftheMWS-LinearModularWetlandStormwaterTreatmentSystemisrequiredbythemanufacturerorisneededtoensureperformanceofthefacility,thentheadditionalinspectionandmaintenancereportscompletedwithintheyearshallbeprovidedwiththeannualreport.c.Uponcompletionofthetwo-yearinspectionperiodafterconstructionoftheMWS-LinearModularWetlandStormwaterTreatmentSystem,theCitywillreviewtheinspectionreportandfacilitymaintenancelogtoreevaluatefutureinspectionsfrequencyofthesystem.Theinformationwill1055SouthGradyWay,Renton,WA98057•rentonwa.gov
Mr.BillFortunadoPage5of6August7,2017beusedtodetermineiftheminimuminspectionfrequencyofonceayearcanbeallowed.d.Maintenanceactivities,toassureproperperformanceoftheMWS-LinearModularWetlandStormwaterTreatmentSystem,shallbeasneeded,orasdeterminedintheannualinspection,tocomplywiththerequirementsinthe2009KingCountySurfaceWaterDesignManualformaintenanceofdrainagefacilities.Inaddition,maintenanceproceduresshouldfollowthosegiveninthemostrecentversionoftheMWS-LinearModularWetlandStormwaterTreatmentSystemOperationandMaintenanceManuals.12.TheStormCaptureSystemshallbeinspectedandmaintainedinaccordancewithmanufacturerrecommendationsand,inaddition,beinspectedandmaintainedasdetailedbelow:a.Forthefirstyearafterconstruction,theStormCaptureSystemshallbeinspectedquarterlytoassureproperperformance.Inspectionreportswillbeusedtodeterminefuturesite-specificmaintenanceschedulesandrequirements.b.Followingthefirstyearofoperation,thefacilityowner(s)shallannuallyhavetheStormCaptureSysteminspectedandmaintainedpertheproceduresinthemostrecentversionoftheStormCaptureSystemOperationandMaintenanceManuals.AllwrittenrecordsoftheinspectionandmaintenanceshallbesubmittedtotheCityofRentonSurfaceWaterUtility,totheattentionofSurfaceWaterUtilityPrivateStormwaterFacilityInspectionProgram.IfmorefrequentinspectionandmaintenanceoftheStormCaptureSystemisrequiredbythemanufacturerorisneededtoensureperformanceofthefacility,thentheadditionalinspectionandmaintenancereportscompletedwithintheyearshallbeprovidedwiththeannualreport.C.Uponcompletionofthetwo-yearinspectionperiodafterconstructionoftheStormCaptureSystem,theCitywillreviewtheinspectionreportandfacilitymaintenancelogtore-evaluatefutureinspectionsfrequencyofthesystem.Theinformationwillbeusedtodetermineiftheminimuminspectionfrequencyofonceayearcanbeallowed.d.Maintenanceactivities,toassureproperperformanceoftheStormCaptureSystem,shallbeasneeded,orasdeterminedintheannualinspection,tocomplywiththerequirementsinthe2009KingCountySurfaceWaterDesignManualformaintenanceofdrainagefacilities.In1055SouthGradyWay,Renton,WA98057‘rentonwa.gov
Mr.BillFortunadoPage6of6August7,2017addition,maintenanceproceduresshouldfollowthosegiveninthemostrecentversionoftheStormCaptureSystemOperationandMaintenanceManuals.13.TheapplicantwillneedtosubmitaDrainageFacilityCovenanttoallowtheCityaccesstothefacilityforinspectionoftheprivateStormCaptureSystemandtheMWS-LinearModularWetlandStormwaterTreatmentSystemandotherstormwaterfacilitiesonthesitethatwillbeprivatelymaintained.TheDrainageFacilityCovenantmustbeapprovedforrecordingpriortotheCity’sUtilitypermitbeingissuedfortheconstructionofthefacilities.Thisadjustmentapprovalletteristobeincludedwiththerecordedcovenant.TheDrainageFacilityCovenantcanbefoundinReferenceJoftheCityofRentonAmendmentstothe2009KingCountySurfaceWaterDesignManual.AsiteplanshowingthelocationoftheStormCaptureSystemandtheMWS-LinearModularWetlandStormwaterTreatmentSystemandotherstormwaterfacilitiesmustbeincludedasExhibitAwiththedeclarationofcovenant.ThesiteplanmustmeetallKingCountyrecordingdocumentrequirements(i.e.textsize,clarity,etc.).14.Theapprovalofthisadjustmentdoesnotrelievetheapplicantfromothercity,state,orfederalrequirements.Ifyouhaveanyquestionsaboutthisadjustment,pleasecontactBrianneBannwarth,DevelopmentEngineeringManager,at(425)430-7299orRonStraka,SurfaceWaterUtilityEngineeringManager,at(425)430-7248.Sincrely,7-BrianneBannwarth,P.E.RonStraka,P.E.DevelopmentEngineeringManagerSurfaceWaterUtilityEngineeringManagercc:LysHornsby,P.E.,UtilitySystemsDirectorGaryFink,CivilEngineerIllAnnFowler,CivilEngineerIIMatthewHerrera,SeniorPlannerH:\FileSys\SWP-SurfaceWaterProjects\SWP-27-SurfaceWaterProjects(CIP)\27-3129RentonStormwaterManual\ADJUSTMENTS\2017\2017-3Firestone-PrivateModularWetland.docx1055SouthGradyWay,Renton,WA98057‘rentonwa.gov
IN COMPLIANCE WITH CITY OF RENTON STANDARDSRENTON FIRESTONE17808 108TH AVE SERENTON FIRESTONE1505 Westlake Ave. N.Suite 305Seattle, WA 98109T (206) 522-9510F (206) 522-8344WWW.PACLAND.COMTED-40-3947
C-17001068LUA: 16-000782PR16000382PRELIMINARYNOT FOR CONSTRUCTIONKnow what'sbelow.before you dig.CallRGRADING AND DRAINAGE PLANKnow what'sbelow.before you dig.CallRR-394708EXHIBIT - A