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Technical Information
Report (TIR) – 60%
Design
King County South Wastewater Treatment Plant
Loop Pilot Compost Facility
DRAFT
Renton, Washington
March 10, 2021
EXHIBIT 10
RECEIVED
Clark Close 04/19/2021
PLANNING DIVISION
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Technical Information Report (TIR) – 60% Design
King County South Wastewater Treatment Plant Loop Pilot Compost Facility
March 10, 2021 | i
Contents
1 Project Overview ................................................................................................................................. 1
2 Conditions and Requirements Summary ............................................................................................ 9
2.1 Core Requirements ................................................................................................................... 9
2.1.1 Core Requirement #1: Discharge at the Natural Location ........................................... 9
2.1.2 Core Requirement #2: Offsite Analysis ...................................................................... 10
2.1.3 Core Requirement #3: Flow Control Facilities ........................................................... 10
2.1.4 Core Requirement #4: Conveyance Systems ............................................................ 10
2.1.5 Core Requirement #5: Construction Stormwater Pollution Prevention ...................... 11
2.1.6 Core Requirement #6: Maintenance and Operations ................................................ 11
2.1.7 Core Requirement #7: Financial Guarantees and Liabilities...................................... 11
2.1.8 Core Requirement # 8: Water Quality Facilities ......................................................... 11
2.1.9 Core Requirement #9: On-site BMPs ......................................................................... 11
2.2 Special Requirements ............................................................................................................. 11
2.2.1 Special Requirement #1: Other Adopted Area-Specific Requirements ..................... 11
2.2.2 Special Requirement #2: Flood Hazard Area Delineation ......................................... 11
2.2.3 Special Requirement #3: Flood Protection Facilities ................................................. 12
2.2.4 Special Requirement #4: Source Controls ................................................................. 12
2.2.5 Special Requirement #5: Oil Control .......................................................................... 12
3 Offsite Analysis .................................................................................................................................. 12
3.1 Task 1: Study Area Definition and Maps ................................................................................. 12
3.2 Task 2: Resource Review ....................................................................................................... 13
3.3 Task 3: Field Inspection .......................................................................................................... 14
3.4 Task 4: Drainage System Description and Problem Descriptions .......................................... 14
3.5 Task 5: Mitigation of Existing or Potential Problems ............................................................... 16
4 Flow Control, Low Impact Development (LID) and Water Quality Facility Analysis and
Design ............................................................................................................................................... 16
4.1 Part A - Existing Site Hydrology .............................................................................................. 16
4.2 Part B - Developed Site Hydrology ......................................................................................... 18
4.3 Part C - Performance Standards ............................................................................................. 20
4.4 Part D - Flow Control System .................................................................................................. 20
4.5 Part E - Water Quality System ................................................................................................ 22
5 Conveyance System Analysis and Design ........................................................................................ 22
6 Special Reports and Studies ............................................................................................................. 23
7 Other Permits .................................................................................................................................... 23
8 CSWPP Analysis and Design............................................................................................................ 23
8.1 Part A – ESC Plan Analysis and Design ................................................................................. 23
8.2 Part B – SWPPS Plan Design ................................................................................................. 25
9 Bond Quantities, Facility Summaries, and Declaration of Covenant ................................................ 25
10 Operations and Maintenance Manual ............................................................................................... 27
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Tables
Table 1. Offsite analysis drainage system table ......................................................................................... 16
Table 2. Existing land cover ........................................................................................................................ 17
Table 3. Proposed land cover ..................................................................................................................... 18
Table 4. Conveyance pipe maintenance ..................................................................................................... 27
Table 5. Grounds maintenance ................................................................................................................... 28
Table 6. Catch basin and manhole maintenance ....................................................................................... 29
Figures
Figure 1. TIR worksheet ................................................................................................................................ 2
Figure 2. Site location ................................................................................................................................... 7
Figure 3. Drainage basins, subbasins, and site characteristics .................................................................... 8
Figure 4. Soils ............................................................................................................................................... 9
Figure 5. Offsite study area ......................................................................................................................... 13
Figure 6. Sensitive areas ............................................................................................................................ 14
Figure 7. Downstream conveyance ............................................................................................................ 15
Figure 8. Existing hydrology ........................................................................................................................ 18
Figure 9. Proposed hydrology ..................................................................................................................... 20
Figure 10. WWHM peak flow rate results ................................................................................................... 21
Figure 11. WWHM LID duration results ...................................................................................................... 21
Figure 12. Conveyance calculations ........................................................................................................... 22
Appendices
Appendix A. Erosion Sediment Control Plan .............................................................................................A-1
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1 Project Overview
An overview of project stormwater elements is given in the Technical Information Report
(TIR) worksheet (Figure 1). The project is located in Renton, Washington at the King
County South Wastewater Treatment Plant (South Plant) (Figure 2).
The purpose of the project is to construct a small-scale, temporary pilot demonstration
(not for a permanent facility) to pilot an alternative process at King County’s South Plant
which will further process Class B Loop® biosolids into a Class A Loop compost. Once
operational, information from the composting pilot will be used to demonstrate proof of
concept and develop a business case for composting, develop reliable sources of
feedstocks and bulking agents, conduct product and process optimization, develop
markets and distribution channels, build community support and collect data to inform the
capital project process for a larger, permanent facility (located off-site).
The site is divided into two basins which are within the same threshold discharge area
(TDA) with a total site area of 0.7376 acres. Both basins currently sheet flow to an
adjacent access road where runoff is collected at catch basins (Figure 3) and conveyed
in the wastewater treatment plant’s stormwater system to an outfall in the Black River. In
Drainage Basin 1, a Finished Product Storage area will be constructed, a non-pollution
generating impervious surface constructed from crushed gravel, and will continue to
sheet flow to the access road with runoff collected by the stormwater system. Drainage
Basin 2 will house the composting facility. As a composting facility, all stormwater that
contacts any active composting areas is considered leachate. Per source control best
management practice (BMP) A-24 from the King County Stormwater Pollution Prevention
Manual, all leachate from composting operations should drain to a sanitary sewer.
Therefore, all runoff from the impervious surfaces in Drainage Basin 2 will have all runoff
collected in new catch basins which will discharge into the sanitary sewer system. The
sanitary sewer system will convey collected runoff to South Plant.
Soils at the project site per the NRCS Websoil Survey consist of sandy loams (Figure 4).
The 2001 report by CivilTech states that existing documents indicate that the site was
covered with fill material as part of the Enlargement II project in the 1980’s. At that time
the elevation of the site was raised from 116 to 126 feet and was relatively flat. A 2019
survey reports a site elevation of 126 feet, so there has not been significant settling.
Previous geotechnical field explorations determined the subsurface condition at the site
by performing four Cone Penetration Tests (CPT). The CPT test results were correlated
with borings previously completed in the vicinity of the site by Shannon & Wilson, Inc.
and referenced in a 1992 report entitled Final Design Geotechnical Report, Metro Renton
Wastewater Treatment Plant Enlargement III, Renton, Washington and a 1993 report
entitled Geotechnical Report, Metro Renton Wastewater Treatment Plant Enlargement II,
Solid Stream Improvements (Contract III C). Based on these reports, the soils at the site
The capturing of Drainage Basin 2 by the sanitary sewer system provides all flow
control and water quality treatment necessary. Stormwater runoff from the project
site will decrease after the completion of the project and therefore meets the flow
control and low impact development standards. No other stormwater related
facilities are constructed as part of this project.
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consist of a layer of fill soils mantling native soils. The fill soils consist of soft to stiff,
sandy, clayey silt and extend to a depth of approximately 17 feet. The groundwater table
is expected to be on the order of 22 to 23 feet below the ground surface. The risk of
liquefaction is minimal.
Figure 1. TIR worksheet
King County (Ashley Mihle, PM)
1200 Monster Rd SW
Renton, WA
Jeff Hansen
HDR
360.570.4410
SWWTP Loop Pilot Compost Facility
1200 Monster Rd SW
Renton, WA
T23N
R04E
24
X
X
X
Jan 12, 2020
Feb 2020
206.477.2743
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Duwamish – Green River: Black River
X
X
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Sandy loam 1% to 9% Low
None known
None known
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X
X
X
X
X
X
X
X
X
X
X
X Discharge to sanitary
system leading to
WWTP.
Discharge to sanitary system
leading to WWTP.
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Figure 2. Site location
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Figure 3. Drainage basins, subbasins, and site characteristics
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Figure 4. Soils
2 Conditions and Requirements Summary
This section contains a summary of the applicability of the core and special requirements
as outlined in the City of Renton 2017 Surface Water Design Manual (SWDM).
2.1 Core Requirements
2.1.1 Core Requirement #1: Discharge at the Natural Location
Currently, runoff from the site sheet flows to an adjacent access road where runoff is
collected in catch basins and conveyed in the stormwater system through the treatment
plant site, where stormwater then is discharged to an outfall to the Black River (on the
east side of the South Plant site) which ultimately flows to the Puget Sound. After
construction, runoff from all areas of the site except for the Finished Product Storage
area will enter catch basins (that are separate from the stormwater system) and enter the
sanitary sewer system which is conveyed to the South Plant’s treatment system which
discharges to Puget Sound through a 12-mile long, 8-foot diameter transfer line. The
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Finished Product Storage area will continue to sheet flow to the access road with runoff
collected by the existing stormwater catch basins.
As discussed in Section 3.2, there are steep slopes in the vicinity of the project site.
However, in all cases, stormwater will be collected into tightline systems at or
immediately adjacent to the project site and will not discharge to any steep slopes.
2.1.2 Core Requirement #2: Offsite Analysis
Per the SWDM all projects must submit an offsite analysis report that assesses potential
offsite drainage and water quality impacts associated with development of the project
site, and that proposes appropriate mitigation of those impacts. All runoff from the project
area, except for the Finished Product Storage area, will be collected via catch basins and
enter the sanitary sewer system for treatment at the wastewater treatment plant while the
Finished Product Storage area will continue to discharge to existing stormwater catch
basins. This causes a net decrease in the flows entering the stormwater system. A Level
1 Offsite Analysis was completed for the project and discussed in Section 3.
2.1.3 Core Requirement #3: Flow Control Facilities
Per the SWDM, all proposed projects, including redevelopment projects, must provide
onsite flow control facilities to mitigate the impacts of storm and surface water runoff
generated by new impervious surface, new pervious surface, and replaced impervious
surface targeted for flow mitigation.
Per the City’s flow control application map, the project site is within an area where a peak
rate flow control standard is used against existing site conditions.
With all runoff from the project area, except for the Finished Product Storage area, being
collected via catch basins and entering the sanitary sewer system for treatment at the
wastewater treatment plant while the Finished Product Storage area will continue to
discharge to existing stormwater catch basins, a net decrease in the flows entering the
stormwater system is seen without the use of flow control infrastructure. Therefore, the
project meets the peak flow rate control standard of having the proposed peak discharge
rates for the 2-, 10-, and 100-year return periods staying below the existing peak
discharge rates.
2.1.4 Core Requirement #4: Conveyance Systems
All pipe conveyance systems were designed to convey the 25-year peak flow rate per the
SWDM. Peak flow rates were calculated using the rational method per Section 3.2.1 of
the SWDM. Additional discussion of conveyance systems is provided in Section 5.
Modeling of the runoff from the site tributary to the existing conveyance system (Section
4.4) shows that peak runoff to the existing storm system will decrease because most of
the site will change to being conveyed into the sanitary sewer system. Because of this a
capacity analysis was not completed for the existing storm system. Capacity sizing was
completed for the new piping to connect to the sanitary sewer system and is discussed in
Section 5.
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2.1.5 Core Requirement #5: Construction Stormwater Pollution
Prevention
Construction stormwater pollution is being provided as part of the project which meets
the requirements of the SWDM. Further discussion is provided in Section 8.
2.1.6 Core Requirement #6: Maintenance and Operations
Ongoing maintenance and operation of the facilities after the completion of construction
will be completed by King County. Additional information on O&M is provided in Section
10.
2.1.7 Core Requirement #7: Financial Guarantees and Liabilities
Discussions regarding Core Requirement # 7, including information regarding the Site
Improvement Bond Quantities Worksheet and Flow Control and Water Quality Facility
Summary Sheet and Sketch are found in Section 9.
2.1.8 Core Requirement # 8: Water Quality Facilities
Water quality treatment will be provided for all pollution-generating impervious surfaces
which will drain to the sanitary sewer system and conveyed to South Plant for treatment.
2.1.9 Core Requirement #9: On-site BMPs
The project can be considered a commercial composting facility where any stormwater
contacting any active composting areas is considered leachate. Per BMP A-24
(commercial composting) of the King County Stormwater Pollution Prevention Manual, all
leachate should drain to the sanitary sewer. Because of this all runoff from the project
area, except for the Finished Product Storage area, is being collected via catch basins
and discharged to the sanitary sewer system for treatment at the wastewater treatment
plant while the Finished Product Storage area will continue to discharge to existing
stormwater catch basins. By having most of the area drain to the sanitary sewer, a net
decrease in the flows entering the stormwater system is seen without the use of flow
control infrastructure. The net decrease in discharge to the stormwater system surpasses
the low impact development (LID) performance standard.
2.2 Special Requirements
2.2.1 Special Requirement #1: Other Adopted Area-Specific
Requirements
As the project resides in the City of Renton, the project was designed to conform to the
requirements of the 2017 Renton Surface Water Design Manual.
2.2.2 Special Requirement #2: Flood Hazard Area Delineation
The City of Renton GIS maps show that the project site is outside of the 100-year flood
plain.
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2.2.3 Special Requirement #3: Flood Protection Facilities
There are no flood protection facilities located on or directly adjacent to the site.
2.2.4 Special Requirement #4: Source Controls
A commercial building or commercial site development permit are not needed as part of
his project. Therefore this special requirement does not apply for this project.
2.2.5 Special Requirement #5: Oil Control
The project does not develop or redevelop or considered a high-use site based upon the
number of anticipated average daily trips (ADTs). Therefore this special requirement
does not apply for this project.
3 Offsite Analysis
This section summarizes the Level 1 offsite analysis completed for the project.
3.1 Task 1: Study Area Definition and Maps
The offsite study area is shown on Figure 5. The offsite drainage area tributary to the
project site is limited to the area between the site and the access road immediately to the
west of the Finished Product Storage area (approximately 60 feet away). Therefore,
offsite drainage tributary to the site is limited.
The project site currently drains to a stormwater conveyance system which drains to a
stormwater pump station approximately 1,100 feet downstream. The pump station then
pumps through approximately 2,000 feet of force main. After flowing approximately 1,700
feet through a series of wet ponds and wetlands, stormwater is discharged to the Black
River (Springbrook Creek) at an outfall approximately 4,800 feet downstream from the
site. From the outfall, runoff from the site flows approximately 4,100 feet down the Black
River until it reaches the Duwamish River—passing through the Black River Pump
Station in-between.
After the project is completed, the Finished Product Storage area will continue to follow
the above flow path shown on Figure 5; however, the rest of the site will discharge to the
sanitary sewer system and flow into the South Plant treatment system.
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Figure 5. Offsite study area
3.2 Task 2: Resource Review
Figure 6 provides an overview of sensitive areas near the project site and offsite study
area. Slopes hazard and seismic hazards exist within the immediate project site while
wetlands and flood hazards exists in the offsite study area.
As part of the resource review, the City of Renton Basin Locations map was also
reviewed which shows that the site is within the Black River basin and the Duwamish
watershed.
A review of the Washington State Department of Ecology’s published Clean Water Act
Section 303d list of polluted waters shows that the Black River (which the stormwater
system discharges to) is a 303d listed water body for dissolved oxygen, bioassessment,
and bacteria.
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Figure 6. Sensitive areas
3.3 Task 3: Field Inspection
Due to the COVID, a field inspection was not completed. However, no drainage issues
were reported by South Plant staff.
3.4 Task 4: Drainage System Description and Problem
Descriptions
The downstream drainage path for stormwater collected by the stormwater conveyance
system within a quarter mile of the site is shown on Figure 7. From the project site,
stormwater is collected by several catch basins and conveyed south through a 12-inch
pipe (Item #1). This is then intercepted by a 30-inch pipe and conveyed to a stormwater
pump station (Item #2). The pump station then discharges to a 12-inch force main (Item
#3) and then discharges to a series of wet ponds and a wetland.
There are no known drain problems, inadequate capacity, or erosion problems within a
quarter mile downstream from the project site. Any unidentified issues will not be made
worse by the project due to the project reducing the stormwater runoff from the project
site.
A summary of the downstream conveyance features and distance from the site discharge
are given in Table 2.
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Figure 7. Downstream conveyance
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Table 1. Offsite analysis drainage system table
Symbol
Drainage
component
Drainage
component
description Slope %
Distance
from site
discharge
Existing
problems
Potential
problems Observations
Item #1 Existing 100
ft of 12-inch
pipe
Collects
runoff from
access road
CBs and
conveys to
30-inch
pipe.
Unknown 0 to 100 ft None None None
Item #2 Existing
1,000 ft of
30-inch pipe
Conveys
stormwater
to Pump
Station
Unknown 100 to
1,100 ft
None None None
Item #3 Pump
station and
existing
2,000 ft of
12-inch
force main
Conveys
stormwater
to wet
ponds
N/A 1,100 to
3,100 ft
None None None
3.5 Task 5: Mitigation of Existing or Potential Problems
No existing problems are known within a quarter mile of the site discharge. Once the
project is completed, due to all areas of the site except for the Finished Product Storage
area draining to the sanitary sewer system, the runoff to the storm system will decrease
which will mitigate any additional runoff generated by the impervious surfaces added by
the project. Therefore, no potential problems are expected by the creation of this project.
4 Flow Control, Low Impact Development
(LID) and Water Quality Facility Analysis
and Design
4.1 Part A - Existing Site Hydrology
The site is divided into two basins which are within the same TDA with a total site area of
0.7376 acres. Both basins currently sheet flow to an adjacent access road where runoff
is collected at catch basins (Figure 3) and conveyed in the wastewater treatment plant’s
stormwater system to an outfall in the Black River (see Figure 5and Figure 7). The
existing hydrology and land cover are shown on Figure 8 with land cover areas
summarized in Table 2.
The soils at the site consist of a layer of fill soils mantling native soils. The fill soils
consist of soft to stiff, sandy, clayey silt and extend to a depth of approximately 17 feet.
Soils were assumed to have characteristics of till for modeling.
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Table 2. Existing land cover
Land cover Area (acres)
Drainage Basin 1
Impervious 0.0334
Pervious 0.0563
Total area 0.0897
Drainage Basin 2
Impervious 0.4727
Pervious 0.1752
Total area 0.6479
Total Project Site
Impervious 0.5061
Pervious 0.2315
Total area 0.7376
Offsite run-on to Drainage Basin 1
Impervious 0.0628
Pervious 0.0677
Total area 0.1305
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Figure 8. Existing hydrology
4.2 Part B - Developed Site Hydrology
In Drainage Basin 1, a Finished Product Storage area will be constructed, a non-pollution
generating impervious surface constructed from crushed gravel, and will continue to
sheet flow to the access road with runoff collected by the stormwater system. Drainage
Basin 2 will house the composting facility and will have all runoff collected in new catch
basins which will discharge into the sanitary sewer system. The sanitary sewer system
will convey collected runoff to South Plant. The capturing of Drainage Basin 2 by the
sanitary sewer system provides any flow control and water quality treatment necessary.
No other stormwater related facilities are constructed as part of this project.
The proposed hydrology and land cover are shown on Figure 8 with land cover areas
summarized in Table 3. No change is soils will occur as part of the project. Soils were
assumed to have characteristics of till for modeling.
Table 3. Proposed land cover
Land cover Area (acres)
Drainage Basin 1
Impervious 0.0897
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Table 3. Proposed land cover
Land cover Area (acres)
Pervious 0.0000
Total area 0.0897
Drainage Basin 2
Impervious 0.5492
Pervious 0..0987
Total area 0.6479
Total Project Site
Impervious 0.6389
Pervious 0.0987
Total area 0.7376
Offsite run-on to Drainage Basin 1
Impervious 0.0628
Pervious 0.0677
Total area 0.1305
The proposed site will create 5,731 square feet of new impervious surface while
converting 390 square feet of impervious surface to pervious surface for a net increase
of 5,341 square feet of impervious surface.
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Figure 9. Proposed hydrology
4.3 Part C - Performance Standards
Flow Control Standard
Per the City’s flow control application map, the project site is within an area where a peak
rate flow control standard is used against existing site conditions. Therefore, peak flow
rate from the proposed site for the 2-year, 10-year, and 100-year events must be at or
below the peak flow rate for those events for the existing site conditions. Given the
downstream conditions described in Section 3, no additional flow control or mitigation is
needed for this project.
LID Performance Standard
To meet Minimum Requirement #9, the project will meet the LID performance standard
which is defined as having stormwater discharges shall match developed discharge
durations to pre-developed durations for the range of pre-developed discharge rates from
8% of the 2-year peak flow to 50% of the 2-year peak flow—assuming historical
(forested) site conditions as the predeveloped condition.
4.4 Part D - Flow Control System
Per the City’s flow control application map, the project site is within an area where a peak
rate flow control standard is used against existing site conditions.
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A Western Washington Hydrology Model (WWHM) model was used to determine the
peak flow rates generated given the existing site and the proposed site. As only the
Finished Product Storage area will continue to drain to the stormwater system once the
project is completed, this is the only area included in the proposed condition in the
WWHM model and is all impervious area. In the existing model, the entire site is included
using the current land cover.
The peak flow rate results from the WWHM model are summarized in Figure 10 which
shows that the peak flow rate control standard is met by keeping the peak discharge
rates for the 2-, 10-, and 100-year return periods below the existing peak discharge
rates.
Figure 10. WWHM peak flow rate results
The WWHM model was used to determine of the LID duration standard was met to fulfill
Core Requirement #9. The LID duration results from the WWHM model are summarized
in Figure 11 which shows that the LID duration standard is met.
Figure 11. WWHM LID duration results
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4.5 Part E - Water Quality System
All pollution generation impervious surfaces will drain to catch basins that are connected
to the sanitary sewer system which conveys to South Plant for treatment.
5 Conveyance System Analysis and Design
Conveyance piping was sized to convey the 25-year, 24-hour design storm calculated
using the rational method as outlined in Section 3.2.1 of the SWDM. The manning’s
equation was used to verify that the capacity of a full flowing pipe exceeds the flow
generated by the 25-year, 24-hour design storm.
The calculations are shown in Figure 12. The rational method calculated a peak 25-year
flow rate of 1.41 cubic feet per second (cfs). A 12-inch pipe placed at a slope of 0.0056
feet per foot has a capacity of 2.48 cfs which exceeds the calculated 1.44 cfs peak flow
rate. 12-inch pipes will be used to connect the proposed catch basins to the sanitary
sewer system.
Figure 12. Conveyance calculations
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6 Special Reports and Studies
No additional special reports or studies were created as part of this project.
7 Other Permits
The following permits are being acquired for the completion of this project:
• City of Renton
o Type II Temporary Use Permit
o Civil Construction Permit / Grading Permit
o Critical Areas Permit
• Puget Sound Clean Air Agency
o Notice of Construction
• King County WTD
o SEPA Environmental Checking / Threshold Determination
8 CSWPP Analysis and Design
The project will follow construction stormwater pollution prevention (CSWPP) standards
as outlined in Appendix D of the SWDM.
A CSWPP Plan with its associated erosion sediment control (ESC) plan and stormwater
pollution prevention and spill control (SWPPS) plan are included in Appendix A.
8.1 Part A – ESC Plan Analysis and Design
Site specific details for temporary erosion and sediment control (ESC) that will be used
during construction are included in Appendix A. In addition to the site specific plans, the
following general Best Management Practices (BMPs) for ESC will be used in
accordance with Appendix D of the SWDM.
• Marking clearing limits - Prior to any site clearing or grading, areas to remain
undisturbed during project construction shall be delineated and physically marked on
the project site.
• Cover measures - Temporary and permanent cover measures shall be provided
when necessary to protect disturbed areas. The intent of these measures is to
prevent erosion by having as much area as possible covered during any period of
precipitation.
• Perimeter protection - Perimeter protection to filter sediment from sheet flow shall be
provided downstream of all disturbed areas prior to upslope grading.
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• Traffic area stabilization - Unsurfaced entrances, roads, and parking areas used by
construction traffic shall be stabilized to minimize erosion and tracking of sediment
offsite.
• Sediment retention - Surface water collected from all disturbed areas of the site shall
be routed through a sediment pond or trap prior to release from the site, except those
areas at the perimeter of the site small enough to be treated solely with perimeter
protection. Sediment retention facilities shall be installed prior to grading any
contributing area.
• Surface water collection - Surface water collection measures (e.g., ditches, berms,
etc.) shall be installed to intercept all surface water from disturbed areas, convey it to
a sediment pond or trap, and discharge it downstream of any disturbed areas. Areas
at the perimeter of the site, which are small enough to be treated solely with
perimeter protection, do not require surface water collection. Surface water collection
measures shall be installed concurrently with or immediately following rough grading
and shall be designed, constructed, and stabilized as needed to minimize erosion.
• Dewatering control – Interception of the water table is not expected to occur as part
of this project; therefore, dewatering activities are not planned to occur. However, if
dewatering were to take place, the water resulting from construction site de-watering
activities must be treated prior to discharge or disposed of as specified.
• Dust control - Preventative measures to minimize wind transport of soil shall be
implemented when a traffic hazard may be created or when sediment transported by
wind is likely to be deposited in water resources.
• Flow control - Surface water from disturbed areas must be routed through the
project's onsite flow control facility or other provisions must be made to prevent
increases in the existing site conditions 2-year and 10-year runoff peaks discharging
from the project site during construction.
• Control pollutants - Stormwater pollution prevention (SWPPS) measures are
required to prevent, reduce, or eliminate the discharge of pollutants to onsite or
adjacent stormwater systems or watercourses from construction-related activities
such as materials delivery and storage, onsite equipment fueling and maintenance,
demolition of existing buildings and disposition of demolition materials and other
waste, and concrete handling, washout and disposal.
• Protecting existing and proposed flow control BMPs - Sedimentation and soil
compaction reduce the infiltration capacity of native and engineered soils. Protection
measures shall be applied/installed and maintained so as to prevent adverse impacts
to existing flow control BMPs and areas of proposed flow control BMPs for the
project. Adverse impacts can prompt the requirement to restore or replace affected
BMPs.
• Maintain protective BMPs - Protection measures shall be maintained to assure
continued performance of their intended function, to prevent adverse impacts to
existing flow control BMPs and areas of proposed flow control BMPs, and protect
other disturbed areas of the project.
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• Manage the project - Coordination and timing of site development activities relative
to ESC concerns, and timely inspection, maintenance and update of protective
measures are necessary to effectively manage the project and assure the success of
protective ESC and SWPPS design and implementation.
8.2 Part B – SWPPS Plan Design
The general Best Management Practices (BMPs) outlined in the King County Stormwater
Pollution Prevention Manual for the following activities to prevent the contribution of
pollutants to surface and stormwater during construction will be followed.
• A-27: Clearing, Grading, and Preparation of Land for Small Construction Projects
• A-28: Demolition of Buildings
• A-29: Building Repair, Remodeling, and Construction
The general BMPs outlined in the King County Stormwater Pollution Prevention Manual
for the following activities to prevent the contribution of pollutants to surface and
stormwater after construction will be followed.
• A-1: Required Best Management Practices for all Properties with Commercial
Activities
• A-24: Commercial composting
Additionally, some of ESC BMPs described in Section 8.1 will also be utilized for
SWPPS.
9 Bond Quantities, Facility Summaries, and
Declaration of Covenant
A preliminary Site Improvement Bond Quantities Worksheet is included. While the project
resides on a parcel for a public entity (King County Department of Natural Resources &
Parks Wastewater Treatment Division), cost items associated with the project have been
entered into the Site Improvement Bond Quantities Worksheet as a “Private
Improvement” as these will be maintained by King County and not the City of Renton.
The site does not install a flow control or water quality treatment facility (and instead
discharges a portion of the site to the sanitary sewer). Therefore a Flow Control and
Water Quality Facility Summary Sheet and Sketch is not included.
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10 Operations and Maintenance Manual
Stormwater features of this project include catch basins and conveyance pipes. The
following tables outline operation and maintenance (O&M) requirements for the various
stormwater features that are a part of the project.
Table 4. Conveyance pipe maintenance
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Table 5. Grounds maintenance
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Table 6. Catch basin and manhole maintenance
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Appendix A. Erosion Sediment Control Plan
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DocuSign Envelope ID: 6CE3899A-1D0A-43F4-A678-6B93041EB30C
WKLWKLWKLWKLWKLWKLWKLWKLX X X X
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12345DESIGNED/DRAWN:PROJECT ENGINEER:PROJECT ACCEPTANCE:DESIGN APPROVAL:CONTRACT NO:DRAWING NO:SCALE:PROJECT FILE NO:DEPARTMENT OF NATURAL RESOURCES & PARKSWASTEWATER TREATMENT DIVISIONDATE:SHT NO / TOTALREVNO:BORDER FILE EDITION: KCWTD-2015R0-Dsize-TB-Border12345EFGHBCDACHECKED:REFERENCE1"0C:\pwworking\west01\d1361620\1136470-SP220-C-10001.dwg | Layout: C-10001PLOTTED: Feb 28, 2020-08:08:51am By JALFONSOXREFS: KCWTD-Dsize-TB-Border.dwg; 10175211_DE.dwg; X-MECH.dwg; 10175211_BA.dwg; X-EXISTING-UTILITIES.dwg; 10175211_EG-Display.dwg; 10175211_UT.dwgIMAGES: HDR_Logo_K.jpg;NOREVISION DESCRIPTIONBYAPVDDATEEFGHBCDAKING COUNTY SOUTH WASTEWATER TREATMENT PLANTLOOP PILOT COMPOST FACILITY#C1136470 CALL 24 HOURS BEFORE YOU DIG: 811INFORMATION ONLYPRELIMINARY ISSUE DRAWINGEROSION CONTROL PLANAS NOTED#0CONSTRUCTION NOTES:SILT CONTROL FENCE PER DETAIL C-40001-3.TEMPORARY CONSTRUCTION ENTRANCE PERDETAIL C-40001-1.CATCH BASIN PROTECTION PER DETAIL C-40001-2.LIMITS OF CONSTRUCTIONPROTECT EXISTING STAIRWELL.23NOTES:1.THIS DRAWING WAS PREPARED TO OBTAIN PERMITS ANDREPRESENTS A TESC AND TEMPORARY DRAINAGE SYSTEM THATCOULD BE PROVIDED BY THE CONTRACTOR DURING THE INITIALPHASE OF WORK.2.THE CONTRACTOR IS RESPONSIBLE FOR DEVELOPING ANDIMPLEMENTING A CONTRACTOR-PREPARED CONSTRUCTIONSTORMWATER POLLUTION PREVENTION PLAN (CSWPPP) WHICHINCLUDES AN EROSION AND SEDIMENT CONTROL PLAN (CESCP) INACCORDANCE WITH SPECIFICATION SECTION 31 25 00. THE PLAN ISTO BE COMPLETE AND IMPLEMENTED PRIOR TO ANY GROUNDDISTURBING ACTIVITY.3.WHEN POSSIBLE, CONTRACTOR TO PROVIDE TEMPORARY SUMPSWITHIN THE WORK AREA FOR STORAGE OR FROM WHICH PUMPINGCAN OPTIMIZE CONTROL OF RUNOFF FROM SEDIMENT GENERATINGAREAS.4.CONSTRUCTION RUNOFF SHALL BE CONTROLLED AND CONVEYEDAND NOT BE ALLOWED TO ENTER BEYOND THE CONSTRUCTIONLIMITS AT ANY TIME, UNLESS AUTHORIZED IN WRITING BY THEPROJECT REPRESENTATIVE.5.CESCP SHALL PROVIDE FOR INSTALLATION AND MAINTENANCE OFCATCH BASIN INSERTS IN ALL EXISTING AND NEW CATCH BASINSAND MH THAT CAPTURE CONSTRUCTION RUNOFF.6.SPOILS & STAGING AREA TO BE GRADED TO NATURAL GROUND ANDVEGETATION ESTABLISHED PRIOR TO ACCEPTANCE.7.EXISTING CONTOUR INFORMATION SHOWN IS AT ONE (1) FOOTINTERVALS.8.ON-SITE DUST CONTROL SHALL BE IN ACCORDANCE WITH SECTIOND.3.8 OF KING COUNTY'S SURFACE WATER DESIGN MANUAL.9.CONTRACTOR WILL CLEAN-UP SPOILS THAT MIGRATE ONTO THEROADS A MINIMUM OF ONCE DAILY.10.ANY DIRT, MUD, ROCK, DEBRIS, ETC. THAT IS SPILLED TRACKED, OROTHERWISE DEPOSITED ON ANY EXISTING PAVED STREETS SHALLBE CLEANED UP IMMEDIATELY.541SCALE:EROSION CONTROL PLAN1" = 20'PLANC-10001102040601" = 20'C:\pwworking\west01\d1361620\1136470-SP220-C-10001.dwg, C-10001, 2/28/2020 8:08:46 AM, JALFONSO60% DESIGNEROSION SEDIMENTCONTROL PLANDocuSign Envelope ID: 6CE3899A-1D0A-43F4-A678-6B93041EB30C
EXISTING ROADR=25' MIN.INSTALL DRIVE WAY CULVERTIF THERE IS A ROADSIDEDITCH PRESENT, AS PER KINGCOUNTY ROAD STANDARDS4"-8" QUARRY SPALLS12" MIN.THICKNESS15' MIN'GEOTEXTILE ASDIRECTED BYPROJECTREPRESENTATIVEMIN. 100' OR ASDIRECTED BY PROJECT REPRESENTATIVE AS PER KING COUNTY ROAD STANDARDS,DRIVEWAYS SHALL BE PAVED TO THEEDGE OF R-O-W PRIOR TO INSTALLATIONOF THE CONSTRUCTION ENTRANCE TOAVOID DAMAGING OF THE ROADWAY.IT IS RECOMMENDED THAT THEENTRANCE BE CROWNED SO THATRUNOFF DRAINS OFF THE PAD.PROVIDE FULL WIDTH OFINGRESS/EGRESS AREA.2'12" MIN2"x2" BY 14 GA. WIRE OREQUIVALENT, IF STANDARDSTRENGTH FABRIC USEDFILTER FABRICBACKFILL TRENCH WITHNATIVE SOIL OR 3/4" - 1.5"WASHED GRAVEL10'-25'SPACING VARIES DEPENDINGON SOIL TYPE AND SLOPESTEEPNESSMIN 4"x4" TRENCH2"x2" WOOD POSTS, STEELFENCE POSTS, OR EQUIVALENTCOMPOST SOCKSOVERFLOW (TO BYPASSPEAK STORM VOLUMES)TO PREVENT SEDIMENT FROM ENTERING STORMDRAINAGE SYSTEMS PRIOR TO PERMANENTSTABILIZATION OF THE DISTURBED AREA.REASON:PRE-MANUFACTUREDCATCH BASIN ORINLET INSERTINSERTS SHOULD BE INSPECTED DAILY AND AFTERSIGNIFICANT RAINFALL. CLEAN OR REPLACE INSERTSWHEN HALF OF THE TRAP IS FILLED WITH SEDIMENT.NOTE: SEDIMENTATIONTRAPS SHALL BECLEANED AT REGULARINTERVALS AND SHALLREMAIN IN PLACE UNTILCONSTRUCTION ISCOMPLETE.12345DESIGNED/DRAWN:PROJECT ENGINEER:PROJECT ACCEPTANCE:DESIGN APPROVAL:CONTRACT NO:DRAWING NO:SCALE:PROJECT FILE NO:DEPARTMENT OF NATURAL RESOURCES & PARKSWASTEWATER TREATMENT DIVISIONDATE:SHT NO / TOTALREVNO:BORDER FILE EDITION: KCWTD-2015R0-Dsize-TB-Border12345EFGHBCDACHECKED:REFERENCE1"0C:\pwworking\west01\d1361620\1136470-SP220-C-40001.dwg | Layout: C-40001PLOTTED: Feb 28, 2020-09:27:23am By JALFONSOXREFS: KCWTD-Dsize-TB-Border.dwgIMAGES: HDR_Logo_K.jpg;NOREVISION DESCRIPTIONBYAPVDDATEEFGHBCDAKING COUNTY SOUTH WASTEWATER TREATMENT PLANTLOOP PILOT COMPOST FACILITY#C1136470 CALL 24 HOURS BEFORE YOU DIG: 811INFORMATION ONLYPRELIMINARY ISSUE DRAWINGCIVIL DETAILSAS NOTED#0SCALE:TYPICAL COMPOST SOCK/SILT FENCENTSDETAILC-400013SCALE: STORM DRAIN INLET INSERTNTSDETAILC-400012SCALE: STABILIZED CONSTRUCTION ENTRANCENTSDETAILC-400011C:\pwworking\west01\d1361620\1136470-SP220-C-40001.dwg, C-40001, 2/28/2020 9:27:22 AM, JALFONSO60% DESIGNEROSION SEDIMENTCONTROL PLANDocuSign Envelope ID: 6CE3899A-1D0A-43F4-A678-6B93041EB30C