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Technical Information Report
PREPARED FOR:
Studio19 Architects
207 ½ 1st Avenue South, Suite 300
Seattle, WA 98104-3462
PROJECT:
Watershed Affordable Housing
Apartments
625 Williams Avenue South
Renton, WA
2200335.10
PREPARED BY:
Jesse Newman, EIT
Project Engineer
REVIEWED BY:
Douglas G. Tapp, PE
Principal
DATE:
November 2020
Revised May and October 2021
Revised February 2022
DEVELOPMENT ENGINEERING
JChavez 05/17/2022
SURFACE WATER UTILITY
JFarah 05/17/2022
Technical Information Report
PREPARED FOR:
Studio19 Architects
207 ½ 1st Avenue South, Suite 300
Seattle, WA 98104-3462
PROJECT:
Watershed Affordable Housing
Apartments
625 Williams Avenue South
Renton, WA
2200335.10
PREPARED BY:
Jesse Newman, EIT
Project Engineer
REVIEWED BY:
Douglas G. Tapp, PE
Principal
DATE:
November 2020
Revised May and October 2021
Revised February 2022
I hereby state that this Technical
Information Report for the Watershed
Affordable Housing Apartments project
has been prepared by me or under my
supervision and meets the standard of
care and expertise that is usual and
customary in this community for
professional engineers. I understand that
City of Renton does not and will not
assume liability for the sufficiency,
suitability, or performance of drainage
facilities prepared by me.
02/28/2022
Technical Information Report Watershed Affordable Housing Apartments
2200335.10
Table of Contents
1.0 Project Overview ......................................................................................................................... 1-1
Purpose and Scope.......................................................................................................... 1-1
Existing Conditions........................................................................................................... 1-1
Post-Development Conditions ......................................................................................... 1-1
Section 1.0 Figures
Figure 1-1 ................................... TIR Worksheet
Figure 1-2 ................................... Vicinity Map
Figure 1-3A ................................ Predeveloped Site Area Map
Figure 1-3B ................................ Proposed Area Map
Figure 1-4 ................................... Soils Map
2.0 Conditions and Requirements Summary ................................................................................. 2-1
Core Requirements .......................................................................................................... 2-1
2.1.1 CR 1 – Discharge at the Natural Location .......................................................... 2-1
2.1.2 CR 2 – Offsite Analysis ....................................................................................... 2-1
2.1.3 CR 3 – Flow Control ............................................................................................ 2-1
2.1.4 CR 4 – Conveyance System ............................................................................... 2-1
2.1.5 CR 5 – Erosion and Sediment Control ................................................................ 2-1
2.1.6 CR 6 – Maintenance and Operations ................................................................. 2-2
2.1.7 CR 7 – Financial Guarantees and Liability ......................................................... 2-2
2.1.8 CR 8 – Water Quality .......................................................................................... 2-2
2.1.9 CR 9 – Onsite BMPs ........................................................................................... 2-2
Special Requirements ...................................................................................................... 2-2
2.2.1 SR 1 – Other Adopted Area-Specific Requirements........................................... 2-2
2.2.2 SR 2 – Flood Hazard Area Delineation ............................................................... 2-2
2.2.3 SR 3 – Flood Protection Facilities ....................................................................... 2-2
2.2.4 SR 4 – Source Controls ...................................................................................... 2-2
2.2.5 SR 5 – Oil Control ............................................................................................... 2-2
2.2.6 SR 6 – Aquifer Protection ................................................................................... 2-3
Section 2.0 Figures
Figure 2-1 ................................... FEMA Floodplains Map
3.0 Offsite Analysis ........................................................................................................................... 3-1
Purpose and Scope.......................................................................................................... 3-1
Existing Conditions........................................................................................................... 3-1
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Offsite Analysis ................................................................................................................ 3-1
3.3.1 Downstream Analysis ......................................................................................... 3-1
3.3.2 Upstream Analysis .............................................................................................. 3-7
Conclusion ....................................................................................................................... 3-7
Section 3.0 Figures
Figure 3-1 .................................. Vicinity Map
Figure 3-2 ................................... Existing Conditions Map
Figures 3-3A through 3-3F ......... Offsite Analysis Maps
Figure 3-4 ................................... Offsite Analysis Drainage Table
Figure 3-5 ................................... Offsite Drainage Photos
Figure 3-6 ................................... FEMA Flood Insurance Rate Map
Figure 3-7 ................................... Critical Area Map
Figure 3-8 ................................... Soil Survey
Figure 3-9 ................................... WA DOE Clean Water Act Section 303(d) Map
Figure 3-10 ................................. Wetland Inventory Map
4.0 Flow Control and Water Quality Facility Analysis and Design............................................... 4-1
Flow Control ..................................................................................................................... 4-1
4.1.1 Existing Site Hydrology (Part A) .......................................................................... 4-1
4.1.2 Developed Site Hydrology (Part B) ..................................................................... 4-1
4.1.3 Performance Standards (Part C) ........................................................................ 4-2
4.1.4 Flow Control System (Part D) ............................................................................. 4-4
Water Quality System (Part E) ......................................................................................... 4-5
Section 4.0 Figures
Figure 4-1 ................................... MGSFlood Report
Figure 4-2 ................................... Proposed Area Map
Figure 4-3 ................................... Water Quality Area Map
Figure 4-4 ................................... BioPod Sizing Chart
5.0 Conveyance System Analysis and Design ............................................................................... 5-1
Section 5.0 Figures
Figure 5-1 ................................... MGS Flood 100-Year Flow Calculation
Figure 5-2 ................................... Manning’s Full Flow Calculation
6.0 Special Reports and Studies ..................................................................................................... 6-1
Section 6.0 Figures
Figure 6-1 ................................... Geotechnical Report
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7.0 Other Permits .............................................................................................................................. 7-1
8.0 CSWPPP Analysis and Design .................................................................................................. 8-1
ESC Plan Analysis and Design (Part A) .......................................................................... 8-1
8.1.1 ESC Maintenance ............................................................................................... 8-1
8.1.2 ESC Supervisor................................................................................................... 8-2
8.1.3 Documentation .................................................................................................... 8-2
8.1.4 Review Timing ..................................................................................................... 8-2
Stormwater Pollution Prevention and Spill (SWPPS) Plan Design (Part B) .................... 8-2
8.2.1 Pollution and Spill Prevention Source Controls and BMPs ................................ 8-2
8.2.2 Responsible Personnel and Contact Information ............................................... 8-4
8.2.3 Pollution and Spill Prevention Worksheets ......................................................... 8-4
8.2.4 Disposal Methods................................................................................................ 8-4
Section 8.0 Figures
Figure 8-1 ................................... Sediment Trap Sizing Calculation
9.0 Bond Quantities, Facility Summaries, and Declaration of Covenant .................................... 9-1
Section 9.0 Figures
Figure 9-1 ................................... Declaration of Covenant (Draft)
Figure 9-2 ................................... Stormwater Facility Summary Sheet
Figure 9-3 ................................... Bond Quantity Worksheet (Draft)
10.0 Operations and Maintenance Plan .......................................................................................... 10-1
Facility Descriptions ....................................................................................................... 10-1
Maintenance Tasks ........................................................................................................ 10-2
Maintenance Requirements ........................................................................................... 10-2
Section 10.0 Figures
Figure 10-1 ................................. Stormwater Facility Checklist
Figure 10-2 ................................. Operations and Maintenance (O&M) Manual
11.0 Conclusion ................................................................................................................................. 11-1
Technical Information Report Watershed Affordable Housing Apartments
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Section 1
Project Overview
Technical Information Report Watershed Affordable Housing Apartments 1-1
2200335.10
1.0 Project Overview
Purpose and Scope
This report accompanies the civil engineering plans and documents for the Watershed Affordable
Housing Apartments located at 625 Williams Avenue South, Renton, Washington. The site is
divided into four parcels, Title Parcel A – 172305-9069 (southeast), Title Parcel B – 172305-9136
(northeast), Title Parcel C – 182305-9115 t(west), and Title Parcel D – 182305-9282 (southwest).
The project site is approximately 1.34 acres in size; with the right-of-way dedication, the project
site measures 1.28 acres. Refer to Figure 1-1 for the TIR Worksheet and Figure 1-2 for a Vicinity
Map.
The project proposes to construct two buildings (one with 50 residential units and one with
28 residential units) over at-grade parking. In addition, the project proposes to construct exterior
parking. The buildings will be served with new water, sewer, fire, and storm utilities to support the
buildings. Frontage improvements include new sidewalk along South Grady Way and Williams
Avenue South. Street trees will be planted in an amenity strip along South Grady Way and in tree
pits along Williams Avenue South. In addition, a walking path/emergency access drive will
connect South Grady Way to Burnett Linear Park, running west of the building.
The site is located within the city of Renton, which has adopted the 2017 King County Surface
Water Design Manual, herein referenced as the City of Renton Surface Water Design Manual
(RSWDM). Per the RSWDM, Flow Control Best Management Practices (BMPs), Peak Rate Flow
Control, and Enhanced Basic Water Quality Menus will apply to the proposed project.
Existing Conditions
The existing site is developed with one existing condominium, a gravel driveway, and an existing
billboard. The site is vegetated with lawn and sparse trees. Access to the site is from the gravel
driveway at the southwest portion of the project site along South Grady Way and from the parking
area at the northeast corner along Williams Avenue South.
The topography of the site is relatively flat and slightly undulating, with less than 1-foot fall from
one end to the other. Based on a geotechnical report dated June 10, 2020, in general, site soils
beneath the topsoil consist of very loose to medium dense alluvial, and floodplain deposits
consisting of non-plastic silt (ML), silty fine sand (SM), and sand (SP, SP-SM) were encountered
extending to the maximum exploration depth of 46.5 feet. Per the King County Soil Survey Map
(Figure 1-4), site soils consist primarily of Urban Land (Ur) soils. Per the Geotechnical Report, the
groundwater table was observed at an average depth of 6 to 9 feet below existing grades on one
visit, and between 9 and 10 feet on another visit. Refer to the attached Geotechnical Report titled,
“Updated Geotechnical Engineering Study,” by Earth Solutions NW, Figure 6-1.
The site drains to a catch basin found at the southwest corner of the site near South Grady Way.
The existing drainage patterns are analyzed and discussed in the Level One Downstream
Analysis in Section 3.0. Refer to the attached Predeveloped Site Area Map, Figure 1-3A.
Post-Development Conditions
The project proposes to construct an apartment building over at-grade parking, new exterior
parking, and an emergency access drive/pedestrian walk on the west portion of the property. In
addition, the project proposes to construct new curb and sidewalk along South Grady Way and
Williams Avenue South. Drainage along Williams Avenue South and South Grady Way will be
improved by sloping the gutters more steeply.
Technical Information Report Watershed Affordable Housing Apartments 1-2
2200335.10
Stormwater from the new parking area and a portion of the emergency access road will be
conveyed to a BioPod system. After the BioPod treats the runoff for water quality, flows will be
conveyed to a detention pipe system. The detention pipe will also accept flows from the new
building roof and areas that could not be treated for water quality.
A portion of the parking lot is situated in such a way that runoff cannot be collected and conveyed
to the water quality system; however, runoff can be conveyed to the detention pipe.
Following detention, stormwater will discharge via pipe to the existing public downstream
conveyance system along South Grady Way.
Technical Information Report Watershed Affordable Housing Apartments
2200335.10
Section 1.0 Figures
Figure 1-1 ......... TIR Worksheet
Figure 1-2 ......... Vicinity Map
Figure 1-3A ...... Predeveloped Site Area Map
Figure 1-3B ...... Proposed Area Map
Figure 1-4 ......... Soils Map
Jesse Newman
AHBL
206-267-2425
Watershed Affordable
Housing Apartments
617 Williams Ave S.
Renton, Washington.
23N
5E
Section 18 and 17
Black River
Fill Flat Minimal
Vertical Limitations,
only 4.9-feetfrom rim to invert of discharge location.
TDA 1
1
Peak Rate Flow Control
June 8, 2020
NA
BIOPOD
PIPE TANK
1200 6th AvenueSuite 1620Seattle, WA 98101206.267.2425 TEL206.267.2429 FAXWATERSHED AFFORDABLE HOUSING APARTMENTSVICINITY MAPEX1-2GRAPHIC SCALE050010001" = 500 FEET250NPROJECT SITE
1200 6th Avenue
Suite 1620
Seattle, WA 98101
206.267.2425 TEL
206.267.2429 FAX DRAWN BY:DATE:JOB NO.:
12"CON.14DL8"CON.14DL
18"CON.
25DL
14"CON.18DL
48"DEC.40DL
48"DEC.40DL
60"DEC.
50DL
36"DEC.45DL
32"DEC.
40DL
60"DEC.50DL
72"DEC.55DL
8"DEC.20DL
WATERSHED AFFORDABLE HOUSING APARTMENTS
PREDEVELOPED SITE AREA MAP
JN 11/2020 20201106
EX
1-3A
GRAPHIC SCALE
0 40 80
1" = 40 FEET
20
N
LEGEND
Description Quantity Unit
EXISTING IMPERVIOUS AREA 0.30 ac
TOTAL PROJECT SITE AREA WITH DEDICATION 1.28 ac
TOTAL PROJECT SITE AREA 1.34 ac
PROJECT
SITE
DISCHARGE
LOCATION
EXISTING ROW
LINE
1200 6th Avenue
Suite 1620
Seattle, WA 98101
206.267.2425 TEL
206.267.2429 FAX DRAWN BY:DATE:JOB NO.:
EG: 30.14
UP
UP
32
3232 323
2
3133
3332UP
UP
Grady Way Apartments
Developed Conditions Map
JN 10/11/2021 2200335
EX-1-3B
GRAPHIC SCALE
0 40 80
1" = 40 FEET
20
N
LEGEND
Description Quantity Unit
BYPASS IMPERVIOUS 0.01 ac
BYPASS TOTAL AREA 0.03 ac
GRASS PAVE 0.02 ac
NEW + REPLACED IMPERVIOUS 1.08 ac
TOTAL PROJECT SITE AREA WITH DEDICATION 1.28 ac
VEGETATED ROOF 0.05 ac
LIMITS OF
DEVELOPMENT
3-FOOT FLOW
CONTROL
TANK
WATER QUALITY TREATMENT
WITH BIO POD
WATER QUALITY TREATMENT
WITH BIOPOD
LONGEST
PATH TO FC
FACILITY
APPROX 100'
DISHARGE
LOCATION
Bypass Grass
Bypass Landscape
0.03 ac (Bypass Total Area)
-0.01 ac (Bypass Impervious)
0.02 ac
Flow Control Grass (exclusding BMPs)=
1.28 ac (Total Project Site Area With Dedication)
- 0.03 ac (Bypass Total Area)
- 0.02 ac (Grass Pave)
- 0.05 ac (Vegetated Roof Area)
-1.08 ac (New + Replaced Impervious)
0.10 ac
Total grass including BMPs
0.10 ac (Flow Control Grass)
+ 0.02 ac (Grass Pave)
+0.025 ac (1/2 Vegetated Roof Area)
0.145ac
New + Replaced Impervious Total
1.08 ac (New + Replaced Impervious)
+0.025 (1/2 Vegetated Roof Area)
1.105 ac
Soil Map—King County Area, Washington
Natural Resources
Conservation Service
Web Soil Survey
National Cooperative Soil Survey
6/15/2020
Page 1 of 3525810052581105258120525813052581405258150525816052581705258180525819052582005258210525822052581005258110525812052581305258140525815052581605258170525818052581905258200525821052582205258230559690559700559710559720559730559740559750559760559770559780
559690 559700 559710 559720 559730 559740 559750 559760 559770 559780
47° 28' 29'' N 122° 12' 28'' W47° 28' 29'' N122° 12' 23'' W47° 28' 24'' N
122° 12' 28'' W47° 28' 24'' N
122° 12' 23'' WN
Map projection: Web Mercator Corner coordinates: WGS84 Edge tics: UTM Zone 10N WGS84
0 30 60 120 180
Feet
0 5 10 20 30
Meters
Map Scale: 1:666 if printed on A portrait (8.5" x 11") sheet.
Soil Map may not be valid at this scale.
MAP LEGEND MAP INFORMATION
Area of Interest (AOI)
Area of Interest (AOI)
Soils
Soil Map Unit Polygons
Soil Map Unit Lines
Soil Map Unit Points
Special Point Features
Blowout
Borrow Pit
Clay Spot
Closed Depression
Gravel Pit
Gravelly Spot
Landfill
Lava Flow
Marsh or swamp
Mine or Quarry
Miscellaneous Water
Perennial Water
Rock Outcrop
Saline Spot
Sandy Spot
Severely Eroded Spot
Sinkhole
Slide or Slip
Sodic Spot
Spoil Area
Stony Spot
Very Stony Spot
Wet Spot
Other
Special Line Features
Water Features
Streams and Canals
Transportation
Rails
Interstate Highways
US Routes
Major Roads
Local Roads
Background
Aerial Photography
The soil surveys that comprise your AOI were mapped at
1:24,000.
Warning: Soil Map may not be valid at this scale.
Enlargement of maps beyond the scale of mapping can cause
misunderstanding of the detail of mapping and accuracy of soil
line placement. The maps do not show the small areas of
contrasting soils that could have been shown at a more detailed
scale.
Please rely on the bar scale on each map sheet for map
measurements.
Source of Map: Natural Resources Conservation Service
Web Soil Survey URL:
Coordinate System: Web Mercator (EPSG:3857)
Maps from the Web Soil Survey are based on the Web Mercator
projection, which preserves direction and shape but distorts
distance and area. A projection that preserves area, such as the
Albers equal-area conic projection, should be used if more
accurate calculations of distance or area are required.
This product is generated from the USDA-NRCS certified data as
of the version date(s) listed below.
Soil Survey Area: King County Area, Washington
Survey Area Data: Version 15, Sep 16, 2019
Soil map units are labeled (as space allows) for map scales
1:50,000 or larger.
Date(s) aerial images were photographed: Jul 1, 2019—Jul 25,
2019
The orthophoto or other base map on which the soil lines were
compiled and digitized probably differs from the background
imagery displayed on these maps. As a result, some minor
shifting of map unit boundaries may be evident.
Soil Map—King County Area, Washington
Natural Resources
Conservation Service
Web Soil Survey
National Cooperative Soil Survey
6/15/2020
Page 2 of 3
Map Unit Legend
Map Unit Symbol Map Unit Name Acres in AOI Percent of AOI
Ur Urban land 1.4 100.0%
Totals for Area of Interest 1.4 100.0%
Soil Map—King County Area, Washington
Natural Resources
Conservation Service
Web Soil Survey
National Cooperative Soil Survey
6/15/2020
Page 3 of 3
Technical Information Report Watershed Affordable Housing Apartments
2200335.10
Section 2
Conditions and Requirements Summary
Technical Information Report Watershed Affordable Housing Apartments 2-1
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2.0 Conditions and Requirements Summary
Core Requirements
2.1.1 CR 1 – Discharge at the Natural Location
The project site naturally drains to a catch basin at the southwest corner of the site via
conveyance and sheet flow. The proposed project will pipe developed flows to the same drainage
facility. This meets the requirement for discharging at the natural location.
2.1.2 CR 2 – Offsite Analysis
AHBL staff performed a Level One Downstream Analysis for the project. The analysis included:
• Defining and mapping the study area.
• Reviewing available information on the study area.
• Field inspecting the study area.
• Describing the existing drainage system, including its existing and predicted drainage and
water quality problems.
Refer to Section 3.0 for the full offsite analysis.
2.1.3 CR 3 – Flow Control
This project is in a Peak Rate Flow Control Standard area, which requires matching existing site
conditions for the 2-, 10-, and 100-year peak rate runoff. Because there were no observed
drainage problems within 1 mile downstream, there are no further flow control requirements. Flow
control and flow control BMPs are further discussed in Section 4.0, Flow Control and Water
Quality Facility Analysis and Design.
2.1.4 CR 4 – Conveyance System
The project has designed all new conveyance systems to convey the 25-year storm event and to
not overtop in the 100-year storm event. If overtopping occurs, the drainage will be routed to the
natural discharge location without creating a severe flooding or severe erosion problem. The
design and calculations for the new conveyance system are included in Section 5.0.
The project will not change the flow characteristics of the existing conveyance systems because
flow control will be provided prior to discharging to the existing public system. For flow control
analysis, refer to Section 4.0, Flow Control and Water Quality Facility Analysis and Design.
Spill control is required because the project constructs a new onsite conveyance system that
collects runoff from non-rooftop pollution generating impervious surface (PGIS). Spill control will
be provided by use of a tee section in a manhole.
2.1.5 CR 5 – Erosion and Sediment Control
An erosion and sediment control plan will be developed for this site in accordance with the
RSWDM and to conform to the requirements of the Construction Stormwater National Pollutant
Discharge Elimination System (NPDES) permit issued by the Department of Ecology (Ecology).
The preliminary erosion and sediment control plan is described further in Section 8.0 and in the
project plans.
Technical Information Report Watershed Affordable Housing Apartments 2-2
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2.1.6 CR 6 – Maintenance and Operations
The onsite drainage facilities will be privately maintained by the owner. An Operations and
Maintenance Manual will be provided in Section 10.0 at a later submittal.
2.1.7 CR 7 – Financial Guarantees and Liability
This project will provide a Drainage Facilities Restoration and Site Stabilization Financial
Guarantee. Bond Quantity Worksheets are provided in Section 9.0.
2.1.8 CR 8 – Water Quality
The project site is subject to the Enhanced Basic Water Quality Treatment Menu per the
RSWDM. Design of these water quality facilities is discussed further in Section 4.0.
2.1.9 CR 9 – Onsite BMPs
The project is subject to meet onsite BMPs, as dictated by the 2017 RSWDM. See Section 4.1.3
for Onsite Flow Control BMP requirements.
Special Requirements
2.2.1 SR 1 – Other Adopted Area-Specific Requirements
To our knowledge, no other adopted area-specific requirements apply to the project site.
2.2.2 SR 2 – Flood Hazard Area Delineation
Floodplain/Floodway (FEMA) Maps: The project site is located in Zone X per Flood Insurance
Rate Map No. 53033C0977G, Panel 977, which is determined to be outside the 500-year
(0.02 percent reoccurrence) floodplain. Refer to Figure 2-1 of this section for the FEMA
Floodplains Map.
2.2.3 SR 3 – Flood Protection Facilities
The project does not contain, will not construct, and is not adjacent to any existing flood
protection facilities.
2.2.4 SR 4 – Source Controls
The proposed project consists of a parking lot and apartments. The King County Stormwater
Pollution Prevention Manual (KCSPPM) will be referenced for source control measures, in
addition to erosion and sediment control measures, during construction. For construction source
controls, see Section 8.0 CSWPPP Analysis and Design. Post-construction source controls will
be supplied at a later submittal in Section 10.0, Operations and Maintenance Plan.
2.2.5 SR 5 – Oil Control
The project does not fit the definition of a high-use site; therefore, it is not subject to oil control
requirements.
Technical Information Report Watershed Affordable Housing Apartments 2-3
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2.2.6 SR 6 – Aquifer Protection
The site is located in Zone 1 modified and Zone 2 of the City’s aquifer protection area (APA).
There are no open conveyance systems or open-bottomed water quality systems to provide a
liner for.
Technical Information Report Watershed Affordable Housing Apartments
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Section 2.0 Figures
Figure 2-1 ......... FEMA Floodplains Map
1200 6th Avenue
Suite 1620
Seattle, WA 98101
206.267.2425 TEL
206.267.2429 FAX
COMMUNITY NUMBER PANEL SUFFIX
CONTAINS:
(SEE MAP INDEX FOR FIRM PANEL LAYOUT)
Federal Emergency Management Agency
FLOOD INSURANCE RATE MAPFIRM
Notice to User: The Map Number shown belowshould be used when placing map orders; theCommunity Number shown above should beused on insurance applications for the subject community.
MAP REVISED
MAP NUMBER53033C0977G
KING COUNTY,WASHINGTONAND INCORPORATED AREAS
KING COUNTY 530071 0977 GRENTON, CITY OF 530088 0977 G
NFIP
NATIONAL FLOOD INSURANCE PROGRAMPANEL 0977G
PANEL 977 OF 1700
PRELIMINARY
9/15/2017
D :,,SSBE
A
C
O
N
WAYSWHITWORTHMOSESAVENUE¥k405
ST
SSMITHERSAVENUE S WYGRANTMORRIS4TH
LANE SSSTREET
AVENUE530088 CEDAR4TH
AVENUES
ZONE AH MILLS
HIGHRENTONS AVENUEAVENUEWHITWORTHSMORRISAVEAVENUEMILLS
PedestrianBridge
S GRADYSG R A DYAVENUE S9THAVENUEWAY S5TH
S
S 10TH STR
R
O
A
D RAILRO ADLOGA
WILLIAMSTALB
O
T
ZONEX
AVENUECITY OF RENTON BURNETTSSTREET
AVENUE7TH
SSMITHERSAVENUESTREETSS3RDSTREETSS R
AILROAD
AVENUEAVENUEWHITWORTHSS
41
ROAD3RD
STREET SS
19 AVENUEMAINW
AY
SY0624 X6TH SLANEBENSONWELLSSÑ
WATERSHED AFFORDABLE HOUSING APARTMENTS
FEMA FLOODMAPS
EXHIBIT
2-1
OTHER AREAS
ZONE X
ZONE D
mile; and areas protected by levees from 1% annual chance flood.
Areas determined to be outside the 0.2% annual chance floodplain.Areas in which flood hazards are undetermined, but possible.
250 10000FEET
150 3000METERS
MAP SCALE 1" = 500'500
150
COMMUNITY NUMBER PANEL SUFFIX
CONTAINS:
(SEE MAP INDEX FOR FIRM PANEL LAYOUT)
Federal Emergency Management Agency
FLOOD INSURANCE RATE MAPFIRM
Notice to User: The Map Number shown belowshould be used when placing map orders; theCommunity Number shown above should beused on insurance applications for the subject community.
MAP REVISED
MAP NUMBER53033C0977G
KING COUNTY,WASHINGTONAND INCORPORATED AREAS
KING COUNTY 530071 0977 GRENTON, CITY OF 530088 0977 G
NFIP
NATIONAL FLOOD INSURANCE PROGRAMPANEL 0977G
PANEL 977 OF 1700
PRELIMINARY
9/15/2017
PROJECT SITE
Technical Information Report Watershed Affordable Housing Apartments
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Section 3
Offsite Analysis
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3.0 Offsite Analysis
Purpose and Scope
The project encompasses four tax parcels at and surrounding 625 Williams Avenue South in
Renton, Washington. site is divided into four parcels, Title Parcel A – 172305-9069 (southeast),
Title Parcel B – 172305-9136 (northeast), Title Parcel C – 172305-9136 (west), and Title Parcel D
– 182305-9282 (southwest). The project is bordered by Williams Avenue South to the east, South
Grady Way to the south, and parcel properties to the north and west. The combined parcel size is
1.34 acres and the project site is a zero-lot development.
The project proposes to construct two buildings, one with 50 residential units and one with
28 residential units, over at-grade parking. In addition, the project proposes to construct exterior
parking onsite. The buildings will be served with new water, sewer, fire, and storm utilities to
support the buildings.
This report has been prepared to review the upstream and downstream conditions, research any
downstream challenges, review any potential downstream impacts, provide a field inspection
report, and provide recommendations for mitigation.
Existing Conditions
The existing site is developed with one existing condominium, a gravel driveway, and lawn. In
addition, there are six trees located on the site. Access to the site is from the gravel driveway at
the southwest portion of the project site along South Grady Way and from the parking area at the
northeast corner along Williams Avenue South.
The site is relatively flat and slightly undulating, with less than 1-foot fall from one end to the
other. The site drains to a catch basin found at the southwest corner of the site near South Grady
Way. Refer to Figure 3-2 for the Existing Conditions Map for topographical and aerial depiction of
project site.
Soils for the downstream analysis area, including the project site, are typically of the Urban Land
or Woodinville Silt Loam variety, per the King County Soil Survey Map (Figure 3-8). Refer to the
attached Geotechnical Report (Figure 6-1) for further soil information.
Offsite Analysis
3.3.1 Downstream Analysis
Task 1 – Study Area Definition Maps
The project is in the Black River Subbasin and has one Threshold Discharge Area. Stormwater
drains to the existing City of Renton storm pipe that borders the east and south edge of the
project site. Stormwater in this existing system flows south on Williams Avenue South in a series
of pipe and catch basins, and then drains west along South Grady Way to a catch basin located
at the south edge of the project site.
The study area includes the downstream drainage path from the project site for 1 mile
downstream. Field inspection was extended 0.25 mile downstream from the project site. The
upstream was analyzed for identifying potential impacts to the site and drainage systems.
Refer to Figures 3-3A through 3-3F, 3-4, and 3-5 for maps, the offsite analysis table, and photos.
Technical Information Report Watershed Affordable Housing Apartments 3-2
2200335.10
Task 2 – Resource Review
The following resources were reviewed to discover any existing or potential problems in the study
area:
• Adopted Basin Plans: The project site is located within the Black River Subbasin, which is
part of the Green River North Basin, as identified by the CSI Project: Green River North
Sub Regional Planning Area, dated May 2003.
• Floodplain/Floodway (FEMA) Maps: The project site is in Zone X per Flood Insurance Rate
Map No. 53033C0977G, Panel 977, which is determined to be outside the 500-year
(0.02 percent reoccurrence) floodplain. Refer to Figure 3-6.
• Other Offsite Analysis Reports: No other known offsite analysis reports have been
identified for the areas immediately upstream or downstream of this project site.
• Sensitive Areas Folio: Refer to Figure 3-7 for the Critical Area Map, per City of Renton GIS.
The project in within a seismic hazard area; otherwise, the City of Renton GIS does not
show any other sensitive areas near the project site or within 1-mile downstream of the
project. In addition, there are riparian wetlands surrounding the Black River (see Wetland
Inventory Map, Figure 3-10.
• Drainage Complaints: There was a drainage complaint listed on the City of Renton GIS at
645 Shattuck Avenue near the associated drainage system. The complaint was that the
sidewalk was flooding, per discussion with a City of Renton Public Works Maintenance
employee. The drainage complaint has been closed since April 18, 2018. Based on the
aerial imagery, it appears that the sidewalk in this area has been replaced.
• USDA Soils Survey: Soils for the downstream analysis area, including the project site, are
typically of the Urban Land (58.4%) or Woodinville Silt Loam variety (40.8%), per the King
County Soil Survey Map (Figure 3-8).
• Wetlands Inventory: There is a non-delineated wetland surrounding the Black River. Refer
to the Wetlands Inventory Map, Figure 3-10.
• Section 303d List of Polluted Waters: No polluted waters are located within 1 mile
downstream of the project site per Ecology’s Clean Water Act Section 303d list of polluted
waters and published maps. There was a 303d listed waterbody approximately 1.4 miles
downstream from the project site. Refer to Figure 3-9 for a copy of the area map.
Task 3 – Field Inspect the Study Area (Level 1)
A Level 1 (qualitative) downstream field inspection was completed on June 8, 2020. Weather was
sunny, with temperatures around 70° F. The site was dry.
The Level 1 inspection included the following tasks:
1. Investigate any problems reported or observed during the resource review – No problems
were found downstream of the project area.
2. Locate all existing/potential constrictions or lack of capacity in the existing drainage system –
At one location, based on City of Renton GIS, the drainage system went from 42-inch
diameter pipe to 36-inch diameter pipe. No drainage complaints have been reported in this
area.
Technical Information Report Watershed Affordable Housing Apartments 3-3
2200335.10
3. Identify all existing/potential downstream drainage problems as defined in Section 1.2.2.1 –
All existing and potential drainage problems are listed in the drainage table, Figure 3-4.
4. Identify existing/potential overtopping, scouring, bank sloughing, or sedimentation – None of
these problems were identified during field inspection.
5. Identify significant destruction of aquatic habitat or organisms – No areas of destruction were
identified, including siltation, bank erosion, or incision in a stream.
6. Collect qualitative data on features such as land use, impervious surfaces, topography, and
soil types – Data reviewed during resource review were confirmed during the field inspection.
7. Collect information on pipe sizes, channel characteristics, drainage structures, and relevant
critical areas – This information is identified in Task 4; however, some of the catch basins
were located in a busy roadway and we were not able to collect information.
8. Verify tributary basins delineated in Task 1 – Tributary basins were confirmed from Task 1.
9. Contact neighboring property owners or residents in the area about past or existing drainage
problems, and describe these in the report – We spoke with a City employee, Gary Fink, who
stated that there were no known drainage issues in the area.
10. Note the date and weather conditions at the time of inspection – Noted above.
Task 4 – Describe the Drainage System, and Its Existing and Predicted Drainage and Water
Quality Problems
The field inspection including walking the downstream flow path from the south site discharge
location to just beyond the 1 mile downstream. The Offsite Analysis Maps, Offsite Analysis
Drainage Table, and Offsite Drainage Photos from the field inspection are provided in
Figures 3-3A through 3-3F (Offsite Analysis Maps), Figure 3-4 (Offsite Analysis Drainage Table),
and Figure 3-5 (Offsite Drainage Photos), respectively. A written description of the downstream
drainage system is given below.
The downstream inspection began at the catch basin located near the southwest corner of the
site adjacent to South Grady Way. Runoff from the project site is directed to this catch basin via
surface flow. The inlet appeared to be surrounded with a slightly bare area, with little or no
vegetation; this does have potential to introduce sediment into the drainage system. In addition,
sediment was observed in the catch basin. The sediment did not appear to hinder the flow
characteristics of the drainage system; there was a small amount of sediment at the invert of the
pipe. Refer to Element 1 in the Downstream Analysis Map (Figure 3-3B), Offsite Analysis
Drainage Table (Figure 3-4), and Offsite Drainage Photos (Figure 3-5).
Drainage Problem Review at Element 1:
1. Description of the problem – Little or no vegetation found directly surrounding inlet and
sediment in standing water.
2. Magnitude of damage caused by the drainage problem – No damage was observed. There
were some signs of sediment in the catch basin. There were no signs of erosion around the
catch basin, and no signs of flooding or significant destruction of aquatic habitat to
organisms.
3. General frequency and duration of drainage problem – There are no known issues with this
area.
Technical Information Report Watershed Affordable Housing Apartments 3-4
2200335.10
4. Return frequency of storm or flow of the water when the problem occurs (option for Level 1)
– Frequency and duration of the drainage problems have not been reported.
5. Water surface elevation when problem occurs – No water has been observed to be backed
up.
6. Names and concerns of involved parties (optional) – No involved parties have identified a
concern.
7. Current mitigation of drainage problem – None identified.
8. Possible cause of the drainage problem – Lack of vegetation surrounding the catch basin.
9. Will project aggravate problem – No. The improved condition will use peak flow control
standards, assuming existing conditions. It is expected that the detained flows may
experience a net decrease in peak flows and durations. In addition, the landscaping in this
area will all be new.
Based on reviews of the nine areas above, the identified potential existing drainage problem may
not meet the definition of any of the four defined problem types in Section 1.2.2.1.1 of the
RSWDM.
The inlet discharges to the southwest in a 24-inch concrete pipe to another catch basin located at
the southwest corner of the property line. This structure has a single vine of a blackberry bush
growing inside of it, and there appeared to be a small amount of soil at the bottom of the catch
basin. Refer to Element 2 in the Downstream Analysis Map (Figure 3-3B), Offsite Analysis
Drainage Table (Figure 3-4), and Offsite Drainage Photos (Figure 3-5).
Drainage Problem Review at Element 2
1. Description of the problem – The catch basin has a single blackberry vine growing within it.
If left unchecked, more blackberry vines could sprout up, creating a potential drainage
problem.
2. Magnitude of damage caused by the drainage problem – No damage was observed. There
were some signs of sediment in the catch basin. There were no signs of flooding or
significant destruction of aquatic habitat to organisms.
3. General frequency and duration of drainage problem – There are no known issues with this
area.
4. Return frequency of storm or flow of the water when the problem occurs (option for Level 1)
– Frequency and duration of the drainage problems have not been reported.
5. Water surface elevation when problem occurs – No water has been observed to be backed
up.
6. Names and concerns of involved parties (optional) – No involved parties have identified a
concern.
7. Current mitigation of drainage problem – None identified.
8. Possible cause of the drainage problem – Vegetation inside the catch basin.
Technical Information Report Watershed Affordable Housing Apartments 3-5
2200335.10
9. Will project aggravate problem – No. The improved condition will use peak flow control
standards, assuming existing conditions. It is expected that the detained flows may
experience a net decrease in peak flows and durations. This catch basin will be cleared
during construction.
Based on reviews of the nine areas above, the identified potential existing drainage problem may
not meet the definition of any of the four defined problem types in Section 1.2.2.1.1 of the
RSWDM.
Drainage flows west in a 24-inch concrete pipe to a catch basin located on South 7th Street, found
east of Burnett Avenue South. The structure appeared to be in good condition. An orange liquid
was observed entering the catch basin from the inlet pipe; this orange material is most likely iron
oxidized bacteria. As seen in the following Elements, this liquid was observed throughout the
drainage system. Refer to Element 3 in the Downstream Analysis Map (Figure 3-3B), Offsite
Analysis Drainage Table (Figure 3-4), and Offsite Drainage Photos (Figure 3-5).
Drainage continues west in a 24-inch concrete pipe, to the next catch basin, approximately
25 feet downstream. This catch basin appeared to be in good condition. Refer to Element 4 in the
Downstream Analysis Map (Figure 3-3B), Offsite Analysis Drainage Table (Figure 3-4), and
Offsite Drainage Photos (Figure 3-5).
Drainage then travels beneath South 7th Street through a 24-inch ductile iron pipe to a solid-
rimmed catch basin in Burnett Linear Park. This catch basin appeared to be in good condition.
Refer to Element 5 in the Downstream Analysis Map (Figure 3-3B), Offsite Analysis Drainage
Table (Figure 3-4), and Offsite Drainage Photos (Figure 3-5).
Afterward, drainage travels west along South 7th Street through a series of catch basins and
36-inch polyethylene pipes. Elements 6 through 8 were not observed due to safety concerns with
accessing the catch basins in the roadway. The City of Renton GIS was consulted to determine
the characteristics of the existing system. Refer to Elements 6 through 8 in the Downstream
Analysis Map (Figure 3-3B) and the Offsite Analysis Drainage Table (Figure 3-4).
Element 8 drains through a 36-inch pipe to a catch basin located at an alley found between
Smithers Avenue South and Morris Avenue South. This structure appeared to be in good
condition. Refer Element 9 in the Downstream Analysis Map (Figure 3-3B), Offsite Analysis
Drainage Table (Figure 3-4), and Offsite Drainage Photos (Figure 3-5).
Similar to Elements 6 through 8, Elements 10 through 14 were not observed due to safety
concerns with accessing the catch basins in the roadway. According to City of Renton GIS,
drainage continues west through a series of 36-inch polypropylene pipes until Element 11. At
Element 11, the outlet size changes to a 42-inch polypropylene pipe. At Element 12, the outlet
pipe size changes back to a 36-inch polypropylene pipe. This introduces a potential constriction
of flows at this location.
Drainage Problem Review at Element 12
1. Description of the problem – The pipe size changes from 42-inch to 36-inch.
2. Magnitude of damage caused by the drainage problem – No damage was observed around
the catch basins. No drainage complaints have been filed in the area.
3. General frequency and duration of drainage problem – There are no known issues with this
area.
Technical Information Report Watershed Affordable Housing Apartments 3-6
2200335.10
4. Return frequency of storm or flow of the water when the problem occurs (option for Level 1)
– Frequency and duration of the drainage problems have not been reported.
5. Water surface elevation when problem occurs – No water has been observed to be backed
up.
6. Names and concerns of involved parties (optional) – No involved parties have identified a
concern.
7. Current mitigation of drainage problem – None identified.
8. Possible cause of the drainage problem – Pipe size changing from larger to smaller
diameter.
9. Will project aggravate problem – No. The improved condition will use peak flow control
standards, assuming existing conditions. It is expected that the detained flows may
experience a net decrease in peak flows and durations.
10. Based on reviews of the nine areas above, the identified potential existing drainage
problem may not meet the definition of any of the four defined problem types in Section
1.2.2.1.1 of the RSWDM.
Following Element 12, drainage continues west along South 7th Street in a 36-inch polypropylene
pipe to a catch basin located east of Whitworth Lane South. The catch basin structure appeared
to be in good condition.
Drainage continues west on South 7th Street to the 0.25-mile point downstream from the project
site to a catch basin at Whitworth Lane South. This structure appeared to be in working order.
According to City of Renton GIS, drainage continues west along South 7th Street through a series
of catch basins and increasing pipe diameters ranging from 36-inch to 60-inch at the outfall to the
Black River drainage basin. Refer to Element 17 in the Downstream Analysis Map (Figure 3-3B),
Offsite Analysis Drainage Table (Figure 3-4), and Offsite Drainage Photos (Figure 3-5).
The field investigation ended at this point.
Task 5 – Mitigation of Existing or Potential Problems
The downstream path is entirely comprised of a manmade system composed of pipes and catch
basins. The piped conveyance system appears to have adequate capacity. Pipe sizes appear to
generally increase as flow continues downstream. Where present, flows appeared to be shallow
and slow. No signs of flooding or overtopping of structures were observed.
Based on the review of the areas discussed in Task 4, the identified potential existing drainage
problems may not meet the definition of any of the four defined problem types in Section 1.2.2.1.1
of the RSWDM. As such, mitigation of potential or existing problems will be provided through
Flow Control and Water Quality Management.
Flow control BMPs will not be proposed. The project will use a detention tank to match peak flows
of the 2-, 10-, and 100-year events. In addition, the project will use a bipod system to treat water
quality. The project is not expected to aggravate any downstream drainage issues.
Technical Information Report Watershed Affordable Housing Apartments 3-7
2200335.10
3.3.2 Upstream Analysis
The project site is in a large flat area with little to no drainage entering the project site from
adjacent properties. It was determined that upstream drainage will not adversely impact the site
drainage.
Conclusion
This analysis is based on data and records either supplied to or obtained by AHBL, Inc. These
documents are referenced within the text of the analysis. The analysis has been prepared using
procedures and practices within the standard accepted practices of the industry. We conclude
that this analysis represents the field conditions as observed and researched by AHBL.
Technical Information Report Watershed Affordable Housing Apartments
2200335.10
Section 3.0 Figures
Figure 3-1 .................................. Vicinity Map
Figure 3-2 ................................... Existing Conditions Map
Figures 3-3A through 3-3F ......... Offsite Analysis Maps
Figure 3-4 ................................... Offsite Analysis Drainage Table
Figure 3-5 ................................... Offsite Drainage Photos
Figure 3-6 ................................... FEMA Flood Insurance Rate Map
Figure 3-7 ................................... Critical Area Map
Figure 3-8 ................................... Soil Survey
Figure 3-9 ................................... WA DOE Clean Water Act Section 303(d) Map
Figure 3-10 ................................. Wetland Inventory Map
1200 6th AvenueSuite 1620Seattle, WA 98101206.267.2425 TEL206.267.2429 FAXWATERSHED AFFORDABLE HOUSING APARTMENTSVICINITY MAPEX3-1GRAPHIC SCALE050010001" = 500 FEET250NPROJECT SITE
1,128 94
Existing Conditions Map
This map is a user generated static output from an Internet mapping site and
is for reference only. Data layers that appear on this map may or may not be
accurate, current, or otherwise reliable.
None
6/9/2020
Legend
64032
THIS MAP IS NOT TO BE USED FOR NAVIGATION
Feet
Notes
64
WGS_1984_Web_Mercator_Auxiliary_Sphere
Information Technology - GIS
RentonMapSupport@Rentonwa.gov
City and County Labels
City and County Boundary
Addresses
Parcels
Streets
Points of Interest
Parks
Waterbodies
2019.sid
Red: Band_1
Green: Band_2
Blue: Band_3
Map
PROJECT SITE
STORMWATER
DISCHARGE
LOCATION
EX 3-2
9,0281505
Downstream Analysis Map
This map is a user generated static output from an Internet mapping site and
is for reference only. Data layers that appear on this map may or may not be
accurate, current, or otherwise reliable.
THIS MAP IS NOT TO BE USED FOR NAVIGATIONWGS_1984_Web_Mercator_Auxiliary_Sphere
Notes
None
06/05/2020
Legend
1023 0 512 1023Feet
Information Technology - GIS
RentonMapSupport@Rentonwa.gov
Pump Stations
Discharge Points
Stormwater Mains
Culverts
Open Drain
Facility Outlines
Private Pump Stations
Private Discharge Points
Private Pipes
Private Culverts
Private Open Drain
Private Facility Outlines
Stormwater Ponds
Streets
Parks
Waterbodies
2019.sid
Red: Band_1
Green: Band_2
Blue: Band_3
Map
FLOW PATH PROJECT SITE
TDA 1
DISCHARGE TO
BLACK RIVER,
APPRX. 1.4 MILES
DOWNSTREAM.
1- MILE
DOWNSTREAM
1/4 MILE
DOWNSTREAM
EX 3-3A
2,257376
Downstream Analysis Map
This map is a user generated static output from an Internet mapping site and
is for reference only. Data layers that appear on this map may or may not be
accurate, current, or otherwise reliable.
THIS MAP IS NOT TO BE USED FOR NAVIGATIONWGS_1984_Web_Mercator_Auxiliary_Sphere
Notes
None
06/05/2020
Legend
256 0 128 256 Feet
Information Technology - GIS
RentonMapSupport@Rentonwa.gov
Parcels
Network Structures
Access Riser
Inlet
Manhole
Utility Vault
Clean Out
Unknown
Control Structures
Pump Stations
Discharge Points
Water Quality
Detention Facilities
Pond
Tank
Vault
Bioswale
Wetland
Other
Stormwater Mains
Culverts
Open Drain
Virtual Drainlines
Facility Outlines
Private Network Structures
Access Riser
Inlet
Manhole
Clean Out
Utility Vault
Unknown
Private Control Structures
Private Pump Stations
Private Discharge Points
Private Water Quality
Private Detention Facilities
Tank
Wetland
Filter Strip
Infiltration Trench
Vault
Pond
Bioswale
Stormtech Chamber
Other
Private Pipes
Private Culverts
Private Open Drain
Private Facility Outlines
Flow Control BMPs
Fences
Stormwater Ponds
Streets
Points of Interest
Parks
Waterbodies
2019.sid
1/4 MILE
DOWNSTREAM
1
2
FLOW
PATH
3
4
5
6
7
8
9
10
11-13
1415
16
FLOW PATH
CONTINUED
3-3C
LEGEND
Description
1/4 MILE FLOW PATH
a
DRAINAGE ELEMENT
SEE PHOTOS
PROJECT
SITE
DISCHARGE
LOCATION
EX 3-3B
2,257376
Downstream Analysis Map
This map is a user generated static output from an Internet mapping site and
is for reference only. Data layers that appear on this map may or may not be
accurate, current, or otherwise reliable.
THIS MAP IS NOT TO BE USED FOR NAVIGATIONWGS_1984_Web_Mercator_Auxiliary_Sphere
Notes
None
06/05/2020
Legend
256 0 128 256 Feet
Information Technology - GIS
RentonMapSupport@Rentonwa.gov
Parcels
Network Structures
Access Riser
Inlet
Manhole
Utility Vault
Clean Out
Unknown
Control Structures
Pump Stations
Discharge Points
Water Quality
Detention Facilities
Pond
Tank
Vault
Bioswale
Wetland
Other
Stormwater Mains
Culverts
Open Drain
Virtual Drainlines
Facility Outlines
Private Network Structures
Access Riser
Inlet
Manhole
Clean Out
Utility Vault
Unknown
Private Control Structures
Private Pump Stations
Private Discharge Points
Private Water Quality
Private Detention Facilities
Tank
Wetland
Filter Strip
Infiltration Trench
Vault
Pond
Bioswale
Stormtech Chamber
Other
Private Pipes
Private Culverts
Private Open Drain
Private Facility Outlines
Flow Control BMPs
Fences
Stormwater Ponds
Streets
Points of Interest
Parks
Waterbodies
2019.sid
0.61 MILES
FLOW PATH
CONTINUED
3-3D
FLOW PATH
EX 3-3C
2,257376
Downstream Analysis Map
This map is a user generated static output from an Internet mapping site and
is for reference only. Data layers that appear on this map may or may not be
accurate, current, or otherwise reliable.
THIS MAP IS NOT TO BE USED FOR NAVIGATIONWGS_1984_Web_Mercator_Auxiliary_Sphere
Notes
None
06/05/2020
Legend
256 0 128 256 Feet
Information Technology - GIS
RentonMapSupport@Rentonwa.gov
Parcels
Network Structures
Access Riser
Inlet
Manhole
Utility Vault
Clean Out
Unknown
Control Structures
Pump Stations
Discharge Points
Water Quality
Detention Facilities
Pond
Tank
Vault
Bioswale
Wetland
Other
Stormwater Mains
Culverts
Open Drain
Virtual Drainlines
Facility Outlines
Private Network Structures
Access Riser
Inlet
Manhole
Clean Out
Utility Vault
Unknown
Private Control Structures
Private Pump Stations
Private Discharge Points
Private Water Quality
Private Detention Facilities
Tank
Wetland
Filter Strip
Infiltration Trench
Vault
Pond
Bioswale
Stormtech Chamber
Other
Private Pipes
Private Culverts
Private Open Drain
Private Facility Outlines
Flow Control BMPs
Fences
Stormwater Ponds
Streets
Points of Interest
Parks
Waterbodies
2019.sid
FLOW PATH
FLOW PATH
CONTINUED
3-3E
0.95 MILES
DOWNSTREAM
EX 3-3D
2,257376
Downstream Analysis Map
This map is a user generated static output from an Internet mapping site and
is for reference only. Data layers that appear on this map may or may not be
accurate, current, or otherwise reliable.
THIS MAP IS NOT TO BE USED FOR NAVIGATIONWGS_1984_Web_Mercator_Auxiliary_Sphere
Notes
None
06/05/2020
Legend
256 0 128 256 Feet
Information Technology - GIS
RentonMapSupport@Rentonwa.gov
Parcels
Network Structures
Access Riser
Inlet
Manhole
Utility Vault
Clean Out
Unknown
Control Structures
Pump Stations
Discharge Points
Water Quality
Detention Facilities
Pond
Tank
Vault
Bioswale
Wetland
Other
Stormwater Mains
Culverts
Open Drain
Virtual Drainlines
Facility Outlines
Private Network Structures
Access Riser
Inlet
Manhole
Clean Out
Utility Vault
Unknown
Private Control Structures
Private Pump Stations
Private Discharge Points
Private Water Quality
Private Detention Facilities
Tank
Wetland
Filter Strip
Infiltration Trench
Vault
Pond
Bioswale
Stormtech Chamber
Other
Private Pipes
Private Culverts
Private Open Drain
Private Facility Outlines
Flow Control BMPs
Fences
Stormwater Ponds
Streets
Points of Interest
Parks
Waterbodies
2019.sid
1 MILE
DOWNSTREAM
FLOW PATH
CONTINUED
3-3F
FLOW PATH
EX 3-3E
2,257376
Downstream Analysis Map
This map is a user generated static output from an Internet mapping site and
is for reference only. Data layers that appear on this map may or may not be
accurate, current, or otherwise reliable.
THIS MAP IS NOT TO BE USED FOR NAVIGATIONWGS_1984_Web_Mercator_Auxiliary_Sphere
Notes
None
06/05/2020
Legend
256 0 128 256 Feet
Information Technology - GIS
RentonMapSupport@Rentonwa.gov
Parcels
Network Structures
Access Riser
Inlet
Manhole
Utility Vault
Clean Out
Unknown
Control Structures
Pump Stations
Discharge Points
Water Quality
Detention Facilities
Pond
Tank
Vault
Bioswale
Wetland
Other
Stormwater Mains
Culverts
Open Drain
Virtual Drainlines
Facility Outlines
Private Network Structures
Access Riser
Inlet
Manhole
Clean Out
Utility Vault
Unknown
Private Control Structures
Private Pump Stations
Private Discharge Points
Private Water Quality
Private Detention Facilities
Tank
Wetland
Filter Strip
Infiltration Trench
Vault
Pond
Bioswale
Stormtech Chamber
Other
Private Pipes
Private Culverts
Private Open Drain
Private Facility Outlines
Flow Control BMPs
Fences
Stormwater Ponds
Streets
Points of Interest
Parks
Waterbodies
2019.sid
DISCHARGE TO
BLACK RIVER
17
LEGEND
Description
a
DRAINAGE ELEMENT
DRAINAGE ELEMENT OBSERVED, SEE PHOTOS
FLOW PATH
EX 3-3F
DATE:6/8/2020BY:Jesse Newman#DESCRIPTIONINOUTEXISTINGPOTENTIALPHOTOSOBSERVATIONS OF FIELD INSPECTOR1 Catch Basin Inlet 24" CONC. 24" CONC. 0-2% 0'Inlet appeared to be surrounded by a bare area, where little grass was growing, water appeared to have sediment in it.Element 1 PhotosStanding water in catch basin has some sediment visible, inlet surrounded by vegetation2 Catch Basin Inlet 24" CONC. 24" CONC. 0-2% 51'Catch basin has vegetation growing inside Element 2 Photos Black berry bush growing from inside the CB.3 Catch Basin Inlet 24" CONC. 24" CONC. 0-2% 344'Element 3 PhotosSome orage liquid observed. Potentially from iron oxidizing bacteria.4 Catch Basin Solid LID 24" CONC. 24" DIP 0-2% 389'Element 4 PhotosSome orage liquid observed. Potentially from iron oxidizing bacteria.5 Catch Basin Solid LID 24" DIP 36" PP 0-2% 435'Element 5 PhotosSome orage liquid observed. Potentially from iron oxidizing bacteria.6 Catch Basin Solid LID 36" PP 36" PP 0-2% 523'Not observed due to safety concerns accessing CB in roadway. (sizes from City of Renton GIS.7 Catch Basin Inlet 36" PP 36" PP 0-2% 598'Not observed due to safety concerns accessing CB in roadway. (sizes from City of Renton GIS.8 Catch Basin Solid LID 36" PP 36" PP 0-2% 654'Not observed due to safety concerns accessing CB in roadway. (sizes from City of Renton GIS.9 Catch Basin Inlet 36" PP 36" PP 0-2% 797'Element 9 Photos10 Catch Basin Inlet 36" PP 36" PP 0-2% 923'Not observed due to safety concerns accessing CB in roadway. (sizes from City of Renton GIS.11 Catch Basin Solid LID 36" PP 42" DIP 0-2% 940'Not observed due to safety concerns accessing CB in roadway. (sizes from City of Renton GIS.12 Catch Basin Solid LID 42" DIP 36" PP 0-2% 951'Constriction of storm Pipe from 42" to 36"Not observed due to safety concerns accessing CB in roadway. (sizes from City of Renton GIS.13 Catch Basin Solid LID 36" PP 36" CONC. 0-2% 965'Not observed due to safety concerns accessing CB in roadway. (sizes from City of Renton GIS.14 Catch Basin Solid LID 36" CONC. 36" PP 0-2% 1073'Not observed due to safety concerns accessing CB in roadway. (sizes from City of Renton GIS.15 Catch Basin Solid Inlet 36" PP 36" PP 0-2% 1254'Element 15 Photos16 Catch Basin Solid Inlet 36" PP 36" PP 0-2% 1363'Element 16 Photos Some orage liquid observed. Potentially from iron oxidizing bacteria.17 Outfall to Black River 60-72" Corrugated Metal, oval 2-4% 1.4 milesElement 17 PhotosDRAINAGE ELEMENT (SEE MAP)PROBLEMSDISTANCE FROM SITE DISCHARGEAPPROXIMATE SLOPE OUTEX 3-4Watershed Affordable Housing ApartmentsOffsite Drainage Table
EXHIBIT 3-5 OFFSITE DRAINAGE PHOTOSELEMENT 1 PHOTOS
ELEMENT 2 PHOTOS
ELEMENT 3 PHOTOS
ELEMENT 4 PHOTO
ELEMENT 5 PHOTOS
ELEMENT 9 PHOTOS
ELEMENT 16 PHOTOS
ELEMENT 17 PHOTOS
1200 6th Avenue
Suite 1620
Seattle, WA 98101
206.267.2425 TEL
206.267.2429 FAX
COMMUNITY NUMBER PANEL SUFFIX
CONTAINS:
(SEE MAP INDEX FOR FIRM PANEL LAYOUT)
Federal Emergency Management Agency
FLOOD INSURANCE RATE MAPFIRM
Notice to User: The Map Number shown belowshould be used when placing map orders; theCommunity Number shown above should beused on insurance applications for the subject community.
MAP REVISED
MAP NUMBER53033C0977G
KING COUNTY,WASHINGTONAND INCORPORATED AREAS
KING COUNTY 530071 0977 GRENTON, CITY OF 530088 0977 G
NFIP
NATIONAL FLOOD INSURANCE PROGRAMPANEL 0977G
PANEL 977 OF 1700
PRELIMINARY
9/15/2017
D :,,SSBE
A
C
O
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WAYSWHITWORTHMOSESAVENUE¥k405
ST
SSMITHERSAVENUE S WYGRANTMORRIS4TH
LANE SSSTREET
AVENUE530088 CEDAR4TH
AVENUES
ZONE AH MILLS
HIGHRENTONS AVENUEAVENUEWHITWORTHSMORRISAVEAVENUEMILLS
PedestrianBridge
S GRADYSG R A DYAVENUE S9THAVENUEWAY S5TH
S
S 10TH STR
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A
D RAILRO ADLOGA
WILLIAMSTALB
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T
ZONEX
AVENUECITY OF RENTON BURNETTSSTREET
AVENUE7TH
SSMITHERSAVENUESTREETSS3RDSTREETSS R
AILROAD
AVENUEAVENUEWHITWORTHSS
41
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STREET SS
19 AVENUEMAINW
AY
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WATERSHED AFFORDABLE HOUSING APARTMENTS
DRAWING_TITLE
EXHIBIT
3-6
OTHER AREAS
ZONE X
ZONE D
mile; and areas protected by levees from 1% annual chance flood.
Areas determined to be outside the 0.2% annual chance floodplain.Areas in which flood hazards are undetermined, but possible.
250 10000FEET
150 3000METERS
MAP SCALE 1" = 500'500
150
COMMUNITY NUMBER PANEL SUFFIX
CONTAINS:
(SEE MAP INDEX FOR FIRM PANEL LAYOUT)
Federal Emergency Management Agency
FLOOD INSURANCE RATE MAPFIRM
Notice to User: The Map Number shown belowshould be used when placing map orders; theCommunity Number shown above should beused on insurance applications for the subject community.
MAP REVISED
MAP NUMBER53033C0977G
KING COUNTY,WASHINGTONAND INCORPORATED AREAS
KING COUNTY 530071 0977 GRENTON, CITY OF 530088 0977 G
NFIP
NATIONAL FLOOD INSURANCE PROGRAMPANEL 0977G
PANEL 977 OF 1700
PRELIMINARY
9/15/2017
PROJECT SITE
FEMA FLOOD INSURANCE RATE MAP
9,0281505
CRITICAL AREA MAP
This map is a user generated static output from an Internet mapping site and
is for reference only. Data layers that appear on this map may or may not be
accurate, current, or otherwise reliable.
THIS MAP IS NOT TO BE USED FOR NAVIGATIONWGS_1984_Web_Mercator_Auxiliary_Sphere
Notes
None
06/05/2020
Legend
1023 0 512 1023Feet
Information Technology - GIS
RentonMapSupport@Rentonwa.gov
Parcels
Erosion Hazard - High
Floodway
Special Flood Hazard Areas (100 year flood)
Other Flood Areas (Zone X - 500 year flood)
Channel Migration Zones (CMZ) as mapped by
King County
Moderate Hazard Area
Potential Hazard Area
Severe Hazard Area
Landslide
Very High
High
Moderate
Unclassified
Slope City of Renton
>15% & <=25%
>25% & <=40% (Sensitive)
>40% & <=90% (Protected)
>90% (Protected)
Environment Designations
Natural
Shoreline High Intensity
Shoreline Isolated High Intensity
Shoreline Residential
Urban Conservancy
Jurisdictions
Streams (Classified)
<all other values>
Type S Shoreline
Type F Fish
Type Np Non-Fish
Type Ns Non-Fish Seasonal
Unclassified
Not Visited
Wetlands
Seismic Hazard Areas
Faults
Streets
Parks
Waterbodies
Map
PROJECT SITE
DISCHARGE TO
BLACK RIVER
APPROXIMATELY
1.4 MILES
DOWNSTREAM
EX 3-7
Soil Map—King County Area, Washington
Natural Resources
Conservation Service
Web Soil Survey
National Cooperative Soil Survey
6/5/2020
Page 1 of 35257500525770052579005258100525830052585005258700525890052575005257700525790052581005258300525850052587005258900557300557500557700557900558100558300558500558700558900559100559300559500559700559900
557300 557500 557700 557900 558100 558300 558500 558700 558900 559100 559300 559500 559700 559900
47° 28' 54'' N 122° 14' 27'' W47° 28' 54'' N122° 12' 15'' W47° 28' 5'' N
122° 14' 27'' W47° 28' 5'' N
122° 12' 15'' WN
Map projection: Web Mercator Corner coordinates: WGS84 Edge tics: UTM Zone 10N WGS84
0 350 700 1400 2100
Feet
0 100 200 400 600
Meters
Map Scale: 1:7,400 if printed on B landscape (17" x 11") sheet.
Soil Map may not be valid at this scale.
EXHIBIT 3-8 SOIL SURVEY
MAP LEGEND MAP INFORMATION
Area of Interest (AOI)
Area of Interest (AOI)
Soils
Soil Map Unit Polygons
Soil Map Unit Lines
Soil Map Unit Points
Special Point Features
Blowout
Borrow Pit
Clay Spot
Closed Depression
Gravel Pit
Gravelly Spot
Landfill
Lava Flow
Marsh or swamp
Mine or Quarry
Miscellaneous Water
Perennial Water
Rock Outcrop
Saline Spot
Sandy Spot
Severely Eroded Spot
Sinkhole
Slide or Slip
Sodic Spot
Spoil Area
Stony Spot
Very Stony Spot
Wet Spot
Other
Special Line Features
Water Features
Streams and Canals
Transportation
Rails
Interstate Highways
US Routes
Major Roads
Local Roads
Background
Aerial Photography
The soil surveys that comprise your AOI were mapped at
1:24,000.
Warning: Soil Map may not be valid at this scale.
Enlargement of maps beyond the scale of mapping can cause
misunderstanding of the detail of mapping and accuracy of soil
line placement. The maps do not show the small areas of
contrasting soils that could have been shown at a more detailed
scale.
Please rely on the bar scale on each map sheet for map
measurements.
Source of Map: Natural Resources Conservation Service
Web Soil Survey URL:
Coordinate System: Web Mercator (EPSG:3857)
Maps from the Web Soil Survey are based on the Web Mercator
projection, which preserves direction and shape but distorts
distance and area. A projection that preserves area, such as the
Albers equal-area conic projection, should be used if more
accurate calculations of distance or area are required.
This product is generated from the USDA-NRCS certified data as
of the version date(s) listed below.
Soil Survey Area: King County Area, Washington
Survey Area Data: Version 15, Sep 16, 2019
Soil map units are labeled (as space allows) for map scales
1:50,000 or larger.
Date(s) aerial images were photographed: Jun 29, 2019—Jul
25, 2019
The orthophoto or other base map on which the soil lines were
compiled and digitized probably differs from the background
imagery displayed on these maps. As a result, some minor
shifting of map unit boundaries may be evident.
Soil Map—King County Area, Washington
Natural Resources
Conservation Service
Web Soil Survey
National Cooperative Soil Survey
6/5/2020
Page 2 of 3
Map Unit Legend
Map Unit Symbol Map Unit Name Acres in AOI Percent of AOI
Py Puyallup fine sandy loam 0.4 0.8%
Ur Urban land 30.6 58.4%
Wo Woodinville silt loam 21.4 40.8%
Totals for Area of Interest 52.5 100.0%
Soil Map—King County Area, Washington
Natural Resources
Conservation Service
Web Soil Survey
National Cooperative Soil Survey
6/5/2020
Page 3 of 3
Water Quality Atlas Map
Sources: Esri, HERE, Garmin, Intermap, increment P Corp., GEBCO, USGS,FAO, NPS, NRCAN, GeoBase, IGN, Kadaster NL, Ordnance Survey, EsriJapan, METI, Esri China (Hong Kong), (c) OpenStreetMap contributors, and
June 5, 2020
0 0.25 0.50.125Miles
K
AssessedWaters/Sediment
WaterCategory 5 - 303dCategory 4CCategory 4BCategory 4ACategory 2Category 1
SedimentCategory 5 - 303dCategory 4CCategory 4BCategory 4ACategory 2Category 1DRAINAGE PATH
PROJECT SITE
APPROXIMATELY
1.4 MILES DOWN
STREAM
EXHIBIT 3-9 WA DOE Clean Water Act Section 303(d) Map
4,800 400
City of Renton Wetland Inventory
This map is a user generated static output from an Internet mapping site and
is for reference only. Data layers that appear on this map may or may not be
accurate, current, or otherwise reliable.
None
6/9/2020
Legend
2720136
THIS MAP IS NOT TO BE USED FOR NAVIGATION
Feet
Notes
272
WGS_1984_Web_Mercator_Auxiliary_Sphere
Information Technology - GIS
RentonMapSupport@Rentonwa.gov
City and County Labels
City and County Boundary
Parcels
Environment Designations
Natural
Shoreline High Intensity
Shoreline Isolated High Intensity
Shoreline Residential
Urban Conservancy
Jurisdictions
Streams (Classified)
<all other values>
Type S Shoreline
Type F Fish
Type Np Non-Fish
Type Ns Non-Fish Seasonal
Unclassified
Not Visited
Wetlands
Streets
Points of Interest
Parks
Waterbodies
2019.sid
Red: Band_1
Green: Band_2
Technical Information Report Watershed Affordable Housing Apartments
2200335.10
Section 4
Flow Control and Water Quality Facility Analysis and
Design
Technical Information Report Watershed Affordable Housing Apartments 4-1
2200335.10
4.0 Flow Control and Water Quality Facility Analysis and Design
Flow Control
4.1.1 Existing Site Hydrology (Part A)
Based on a geotechnical report dated June 10, 2020, in general, site soils beneath the topsoil,
consist of very loose to medium dense alluvial and floodplain deposits consisting of non-plastic
silt (ML). Silty fine sand (SM) and sand (SP, SP-SM) were encountered extending to the
maximum exploration depth of 46.5 feet. Per the King County Soil Survey Map (Figure 1-4) site
soils consist primarily of Urban Land (Ur) soils. Per the geotechnical report, seasonal high
groundwater was observed at 6 to 9 feet below grade. The existing site was modelled as till grass
and impervious area.
MGSFlood was used to design the storm drainage facilities. The predeveloped site was modeled
in the existing condition because the site is in the peak rate flow control area shown on the City of
Renton GIS map.
Refer to Figure 1-3A for the Predeveloped Site Area Map.
The annual peak flows were determined using the information above and the surface conditions
below.
Table 1 - Existing Site Hydrology
Description Target Area (Acres) Total Area (Acres)
Till Grass 0.98 0.98
Impervious 0.30 0.30
Total Area 1.28 1.28
4.1.2 Developed Site Hydrology (Part B)
The project proposes to construct storm detention facilities to the Peak Rate Flow Control
standard. The developed inflow to the detention facility includes all developed target areas
tributary to the facility. Additionally, bypass areas were developed for target areas that are not
physically capable of being conveyed to the detention facility.
Bypass of target areas meets all five of the requirements found in Section 1.2.3.2 E of the
RSWDM, as listed below:
1. The point of convergence for runoff discharged from the bypassed target surfaces is within
one-quarter mile downstream of the facility’s project site. The point of convergence is at the
southwest corner of the site.
2. The increase in the existing site conditions’ 100-year peak discharge from the area of
bypassed target surfaces does not exceed 0.4 cfs because the bypassed target surfaces
are the same type as the existing surfaces. There will be no increase in the 100-year
existing site conditions’ 100-year peak flow.
3. There will be no increase in peak flow; the bypass will not create an adverse impact to
downstream drainage systems.
Technical Information Report Watershed Affordable Housing Apartments 4-2
2200335.10
4. There are no water quality requirements for the bypassed target areas.
5. The existing site conditions’ 100-year peak discharge from the area of bypassed target
surfaces will not increase more than 0.15 cfs. The bypassed target area matches the area
type of the existing conditions. In addition, Onsite BMPs are applied in all areas of bypass.
The flow control system has been designed to match the 2-, 10-, and 100-year flows from
the existing conditions at the southwest corner of the site.
Site soils are modelled as till soils. The project proposes to design a 36-inch pipe tank to address
the Peak Rate Flow Control requirements.
The site proposes grass pave in strips totaling 0.02 acre. The grass pave area was modeled as
100 percent grass per the RSWDM, Table 1.2.9.A. In addition, the project will use vegetated roof
totaling 0.05 acre, with depths less than 8 inches. The vegetated roof will be modelled as
50 percent grass, 50 percent impervious per the RSWDM, Table 1.2.9.A.
The detention facility will release surface water runoff to the existing public stormwater
conveyance system.
The annual peak flows for the proposed site were determined using the basin information above
and the surface conditions below. Refer to Figure 4-2 for the Proposed Area Map.
Table 2 - Developed Site Hydrology
Description
Target
Detained Area
(Acres)
Target
Bypass Area
(Acres)
Total
Area
(Acres)
Till Forest -- -- --
Till Grass (Grass Pave (0.02ac) + ½
Vegetated Roof (0.025ac))
0.145 0.02 0.165
Impervious (½ Vegetated Roof (0.025ac) +
New + Replaced Imp (1.06ac))
1.105 0.01 1.115
Total Area 1.25 0.03 1.28
4.1.3 Performance Standards (Part C)
Area-Specific Flow Control Facility Standard
This project is in a Peak Rate Flow Control Standard area, which requires matching developed
discharge rates to the existing peak discharge rates for the 2-, 10-, and 100-year return periods.
Refer to Section 4.1.4 for flow calculation results. Existing site conditions are assumed to be till
grass and impervious area.
Flow Control BMP Requirements
Flow Control BMPs are required per CR 9. The project site totals 1.28 acres, including all parcels.
The developed site includes 1.08 acres of impervious area, including new and replaced
impervious areas and bypass areas. This results in 84 percent impervious in the proposed
conditions. Onsite BMPs will be applied to a minimum of 10 percent of the target impervious
surfaces per the RSWDM. The project falls under the Large Lot BMP Requirements. Refer to
Figure 4-2 for the Proposed Area Map, which includes the total imperious surface for the site.
Technical Information Report Watershed Affordable Housing Apartments 4-3
2200335.10
Below is a summary of the Flow Control BMPs (per RSWDM Section 1.2.9.2.2) that the project
will assess:
1. Full dispersion: This is infeasible because there is not enough native vegetated surface.
2. Target Impervious Surface Flow Control BMPs: Per the RSWDM, Onsite BMPs will be
applied to a minimum of 10 percent of the site area (0.128 acre). The total acreage of
proposed impervious area treated with BMPs is 0.02 acre (grass pave) + 0.05 acre (green
roof) + 0.10 acre (pervious paving) = 0.17 acre.
o Full Infiltration: This BMP is infeasible because we cannot meet the minimum
design requirements. Per Section C2.2.2 1a. of the RSWDM, these soil conditions
must be met: existing soil must be coarse sands or cobbles or medium sands. In
general, the soils layers that could be used for infiltration consist of silty sand and
inorganic silts.
o Limited Infiltration: This BMP is infeasible because we cannot meet the minimum
design requirements. Per Section C2.2.2 1a. of the RSWDM, these soil conditions
must be met: existing soil must be coarse sands or cobbles or medium sands. In
general, the soils layers that could be used for infiltration consist of silty sand and
inorganic silts.
o Basic Dispersion: This BMP is infeasible. The minimum distance of vegetated flow
path (50 feet) cannot be met. In addition, this project is on very flat terrain and
surrounded by impervious area.
o Bioretention: Bioretention is infeasible, per infeasibility criteria 18, which states:
“Where a minimum vertical separation of 1 foot to the water table…or other
impervious layer would not be achieved below bioretention” that would serve a
drainage area that is less than 5,000 square feet of PGIS, less than 10,000 square
feet of impervious area, and less than 0.75 acre of pervious surface.
It is documented in the geotechnical report that the site is underlain by 3.5 feet of fill
in the only location for siting bioretention, which is west of the building. In this area,
we will be filling the site by approximately 2 to 3 feet. Depth of the bottom of the
gravel layer for bioretention is approximately 4 feet deep. The bottom of bioretention
would be less than 1 foot from fill soils, which is considered impervious.
o Permeable Pavement: The project proposes the use of permeable pavement
totaling 4,100 square feet (0.10 acre) for the northern parking area shown on the site
plans.
o Rainwater Harvesting: This BMP is infeasible; no irrigation systems are proposed.
o Vegetated Roof: The project will have a vegetated roof.
o Reduced Impervious Surface Credit: This BMP is not achievable because none of
the proposed techniques are feasible for the site’s intended use.
o Native Growth Retention Credit: This BMP is not achievable because there is no
presence of native growth in the existing conditions to retain.
o Perforated Pipe Connection for Roof Drains: Perforated pipe connections were
not provided for the roof drain connections due to the non-infiltrative soil type that
characterizes the site.
Technical Information Report Watershed Affordable Housing Apartments 4-4
2200335.10
The project is not required to mitigate any area according to Table C1.3.A of the RSWDM.
Conveyance System Capacity Standards
The onsite stormwater networks have been sized to adequately convey the fully developed,
25-year storm event, as stipulated by the RSWDM, and to not overtop during the 100-year storm
event.
Area-Specific Water Quality Treatment Menu
In accordance with the RSWDM, onsite flows will be treated to the specifications provided by the
Enhanced Basic Water Quality standards. The goal of this treatment menu is to reduce total
suspended solids (TSS) by 80 percent and to reduce zinc concentration by 50 percent for a
typical rainfall year. This goal will be accomplished by providing a proprietary system approved by
Ecology, a BioPod system.
Source Controls
The proposed project consists of a new parking lot, portable classrooms, and a covered play
area. The RSWDM will be referenced for source control measures, in addition to erosion and
sediment control measures, during construction. For construction source controls, refer to
Section 8.0 CSWPPP Analysis and Design. For post-construction source controls, refer to
Section 10.0, Operations and Maintenance Plan.
Oil Controls
Not applicable.
4.1.4 Flow Control System (Part D)
Flow Control BMPs
A vegetated green roof will be used.
Detention Sizing
Detention and control structure requirements were designed using the MGSFlood program and
hydrology summarized in Sections 4.1.1 and 4.1.2. For the results, refer to Figure 4-1, MGSFlood
Report. The system requirements are summarized as follows:
Table 3 – Detention Pipe Requirements
Required Provided
Live Detention Volume 2, 626 cf 2,757 cf
Live Storage Depth 2 ft 2 ft
Outlet Control Structure
Orifice #1 Diameter 2-5/8 in 2-5/8 in
Rectangular Weir 2.5 in x 6.84in 2.5 in x 6.84in
Orifice #1 Elevation 100.50 ft 100.50 ft
Rectangular Weir Elevation 101.93 ft 101.93 ft
Technical Information Report Watershed Affordable Housing Apartments 4-5
2200335.10
Point of Compliance Review
The developed peak flows for the 2-, 10-, and 100-year storms match that of the existing peak
flows. Refer to Figure 4-1, MGSFlood Report for results.
Discharge Requirements
The project meets the natural discharge location requirement and is not subject to discharge
requirements 1 through 3, per the following:
1. The project discharges to a manmade conveyance system.
2. The project is not located within a Landslide Hazard Drainage Area.
3. The project is not adjacent to or does not contain a landslide, steep slope, or erosion
hazard area.
Water Quality System (Part E)
The new target PGIS for the proposed site includes 13,940 square feet (0.32 acre). Roughly
4,790 square feet (0.11 acre) of target pollution generating surface cannot feasibly be conveyed
to the water quality facility. The project site is being filled and no further area can be conveyed to
the water quality systems. The area that cannot be treated is less than the 5,000 square feet of
new plus replaced PGIS.
A treatment trade is infeasible; the storm in the right-of-way is too shallow and does not have
adequate elevation to be treated. Storm pipes in the right-of-way are sloped less than 0.5 percent
in the existing condition. There are no areas that can be routed to our water quality system
because we are raising the site to allow for flow control and water quality. The area cannot be
treated by filter strip, bioswale, or linear sand filter for the following reasons:
• The design water elevation for flow control would be above the linear sand filter sand
elevation. The highest elevation of the bottom of the sand filter sand would be at elevation
27.81. The design water surface for flow control is at elevation 28.19. As stated in the
Applications and Limitations section for sand filters Basic and Large, “…Sand filters are
designed to prevent water from backing up into the sand layer (the underdrain system must
drain freely).” The underdrain system would be flooded frequently and likely will keep the
sand saturated (creating anoxic conditions) and release pollutants.
• There is no feasible location to site a bioswale or filter strip. This portion of the site is
draining to the southeast. There is a 5-foot wide planter strip located north of the parking
area, which would be the only location to consider. The top elevation at freeboard elevation
would be at elevation 29.24. As stated above, the design water surface elevation is at
28.19. Considering the treatment depth, freeboard, and growing medium, it is infeasible to
provide these systems. In addition, to get drainage to this area, the slopes will have to drain
toward the north, which will create slopes exceeding 6 percent in the parking area, which
would render parking at this location infeasible.
Onsite runoff from PGIS will be treated to the Enhanced Basic Water Quality standards of the
RSWDM using two BioPods, a proprietary system with Ecology approval to treat enhanced basic
water quality. MGSFlood was used to determine the online flows, and a chart from the
manufacturer was used to size the BioPod system. Refer to Figure 4-3 for the Water Quality Area
Map and Figure 4-4 for the BioPod Sizing Chart.
Technical Information Report Watershed Affordable Housing Apartments 4-6
2200335.10
A summary of the results is tabulated below:
Area from WQ
Area Map
Required Online
Discharge Rate
Provided
Size from BioPod
Sizing Chart
Treatment Flow
Capacity from
Figure 4-5, BioPod
Sizing Chart
WQ #1 0.01 cfs 4’ x 6’ 0.074 cfs
WQ #3 0.03 cfs 4’ x 6’ 0.074 cfs
Technical Information Report Watershed Affordable Housing Apartments
2200335.10
Section 4.0 Figures
Figure 4-1 ......... MGSFlood Report
Figure 4-2 ......... Proposed Area Map
Figure 4-3 ......... Water Quality Area Map
Figure 4-4 ......... BioPod Sizing Chart
—————————————————————————————————
MGS FLOOD
PROJECT REPORT
Program Version: MGSFlood 4.57
Program License Number: 201710010
Project Simulation Performed on: 02/27/2022 5:16 PM
Report Generation Date: 02/27/2022 6:16 PM
—————————————————————————————————
Input File Name: Grady Way 3' Tank.fld
Project Name: Water Shed Apartments
Analysis Title: Preliminary Model
Comments:
———————————————— PRECIPITATION INPUT ————————————————
Computational Time Step (Minutes): 15
Extended Precipitation Time Series Selected
Climatic Region Number: 3
Full Period of Record Available used for Routing
Precipitation Station : 95004005 Puget West 40 in_5min 10/01/1939-10/01/2097
Evaporation Station : 951040 Puget West 40 in MAP
Evaporation Scale Factor : 0.750
HSPF Parameter Region Number: 3
HSPF Parameter Region Name : USGS Default
********** Default HSPF Parameters Used (Not Modified by User) ***************
********************** WATERSHED DEFINITION ***********************
Predevelopment/Post Development Tributary Area Summary
Predeveloped Post Developed
Total Subbasin Area (acres) 1.280 1.280
Area of Links that Include Precip/Evap (acres) 0.000 0.000
Total (acres) 1.280 1.280
----------------------SCENARIO: PREDEVELOPED
Number of Subbasins: 1
---------- Subbasin : Existing Predeveloped ----------
-------Area (Acres) --------
Till Grass 0.980
Impervious 0.300
----------------------------------------------
Subbasin Total 1.280
EX 4-1
----------------------SCENARIO: POSTDEVELOPED
Number of Subbasins: 4
---------- Subbasin : NEW IMP PGIS BYPASS AND PASTURE AND GRASS PAVE ----------
-------Area (Acres) --------
Till Grass 0.145
Impervious 0.885
----------------------------------------------
Subbasin Total 1.030
---------- Subbasin : Bypass ----------
-------Area (Acres) --------
Till Grass 0.020
Impervious 0.010
----------------------------------------------
Subbasin Total 0.030
---------- Subbasin : WQ 1 ----------
-------Area (Acres) --------
Impervious 0.050
----------------------------------------------
Subbasin Total 0.050
---------- Subbasin : WQ 2 ----------
-------Area (Acres) --------
Impervious 0.170
----------------------------------------------
Subbasin Total 0.170
************************* LINK DATA *******************************
----------------------SCENARIO: PREDEVELOPED
Number of Links: 1
------------------------------------------
Link Name: POC 1
Link Type: Copy
Downstream Link: None
************************* LINK DATA *******************************
----------------------SCENARIO: POSTDEVELOPED
Number of Links: 4
------------------------------------------
Link Name: TDA 1
Link Type: Copy
Downstream Link: None
------------------------------------------
Link Name: Pipe Tank
Link Type: Structure
Downstream Link Name: TDA 1
User Specified Elevation Volume Table Used
Elevation (ft) Pond Volume (cu-ft)
100.00 0.
100.10 26.
100.20 91.
100.30 154.
100.40 226.
100.50 334.
100.60 422.
100.70 515.
100.80 645.
100.90 747.
101.00 852.
101.10 996.
101.20 1106.
101.30 1217.
101.40 1367.
101.50 1480.
101.60 1593.
101.70 1743.
101.80 1854.
101.90 1964.
102.00 2108.
102.10 2213.
102.20 2315.
102.30 2445.
102.40 2538.
102.50 2626.
102.60 2734.
102.70 2806.
102.80 2869.
102.90 2934.
103.00 2960.
Hydraulic Conductivity (in/hr) : 0.00
Massmann Regression Used to Estimate Hydralic Gradient
Depth to Water Table (ft) : 100.00
Bio-Fouling Potential : Low
Maintenance : Average or Better
Riser Geometry
Riser Structure Type : Circular
Riser Diameter (in) : 18.00
Common Length (ft) : 0.210
Riser Crest Elevation : 102.50 ft
Hydraulic Structure Geometry
Number of Devices: 2
---Device Number 1 ---
Device Type : Circular Orifice
Control Elevation (ft) : 100.50
Diameter (in) : 2.63
Orientation : Horizontal
Elbow : Yes
--- Device Number 2 ---
Device Type : Rectangular Weir that Intersects the Riser Top
Invert Elevation (ft) : 101.93
Length (ft) : 0.210
------------------------------------------
Link Name: WQ 1
Link Type: Copy
Downstream Link Name: Pipe Tank
------------------------------------------
Link Name: WQ 2
Link Type: Copy
Downstream Link Name: Pipe Tank
**********************FLOOD FREQUENCY AND DURATION STATISTICS*******************
----------------------SCENARIO: PREDEVELOPED
Number of Subbasins: 1
Number of Links: 1
********** Subbasin: Existing Predeveloped **********
Flood Frequency Data(cfs)
(Recurrence Interval Computed Using Gringorten Plotting Position)
Tr (yrs) Flood Peak (cfs)
======================================
2-Year 0.208
5-Year 0.305
10-Year 0.380
25-Year 0.493
50-Year 0.600
100-Year 0.626
200-Year 0.693
500-Year 0.783
********** Link: POC 1 ********** Link Outflow 1
Frequency Stats
Flood Frequency Data(cfs)
(Recurrence Interval Computed Using Gringorten Plotting Position)
Tr (yrs) Flood Peak (cfs)
======================================
2-Year 0.208
5-Year 0.305
10-Year 0.380
25-Year 0.493
50-Year 0.600
100-Year 0.626
200-Year 0.693
500-Year 0.783
----------------------SCENARIO: POSTDEVELOPED
Number of Subbasins: 4
Number of Links: 4
********** Subbasin: NEW IMP PGIS BYPASS AND PASTURE AND GRASS PAVE **********
Flood Frequency Data(cfs)
(Recurrence Interval Computed Using Gringorten Plotting Position)
Tr (yrs) Flood Peak (cfs)
======================================
2-Year 0.356
5-Year 0.445
10-Year 0.526
25-Year 0.626
50-Year 0.765
100-Year 0.928
200-Year 0.943
500-Year 0.961
********** Subbasin: Bypass **********
Flood Frequency Data(cfs)
(Recurrence Interval Computed Using Gringorten Plotting Position)
Tr (yrs) Flood Peak (cfs)
======================================
2-Year 5.758E-03
5-Year 7.885E-03
10-Year 9.962E-03
25-Year 1.245E-02
50-Year 1.479E-02
100-Year 1.669E-02
200-Year 1.799E-02
500-Year 1.968E-02
********** Subbasin: WQ 1 **********
Flood Frequency Data(cfs)
(Recurrence Interval Computed Using Gringorten Plotting Position)
Tr (yrs) Flood Peak (cfs)
======================================
2-Year 1.907E-02
5-Year 2.482E-02
10-Year 2.790E-02
25-Year 3.250E-02
50-Year 4.196E-02
100-Year 4.886E-02
200-Year 5.029E-02
500-Year 5.214E-02
********** Subbasin: WQ 2 **********
Flood Frequency Data(cfs)
(Recurrence Interval Computed Using Gringorten Plotting Position)
Tr (yrs) Flood Peak (cfs)
======================================
2-Year 6.483E-02
5-Year 8.437E-02
10-Year 9.487E-02
25-Year 0.111
50-Year 0.143
100-Year 0.166
200-Year 0.171
500-Year 0.177
********** Link: TDA 1 ********** Link Inflow
Frequency Stats
Flood Frequency Data(cfs)
(Recurrence Interval Computed Using Gringorten Plotting Position)
Tr (yrs) Flood Peak (cfs)
======================================
2-Year 0.200
5-Year 0.305
10-Year 0.380
25-Year 0.477
50-Year 0.536
100-Year 0.622
200-Year 0.704
500-Year 0.811
********** Link: Pipe Tank ********** Link Inflow
Frequency Stats
Flood Frequency Data(cfs)
(Recurrence Interval Computed Using Gringorten Plotting Position)
Tr (yrs) Flood Peak (cfs)
======================================
2-Year 0.441
5-Year 0.555
10-Year 0.650
25-Year 0.768
50-Year 0.950
100-Year 1.143
200-Year 1.164
500-Year 1.190
********** Link: Pipe Tank ********** Link Outflow 1
Frequency Stats
Flood Frequency Data(cfs)
(Recurrence Interval Computed Using Gringorten Plotting Position)
Tr (yrs) Flood Peak (cfs)
======================================
2-Year 0.197
5-Year 0.302
10-Year 0.376
25-Year 0.470
50-Year 0.528
100-Year 0.610
200-Year 0.691
500-Year 0.796
********** Link: Pipe Tank ********** Link WSEL
Stats
WSEL Frequency Data(ft)
(Recurrence Interval Computed Using Gringorten Plotting Position)
Tr (yrs) WSEL Peak (ft)
======================================
1.05-Year 101.184
1.11-Year 101.294
1.25-Year 101.402
2.00-Year 101.777
3.33-Year 102.033
5-Year 102.190
10-Year 102.327
25-Year 102.475
50-Year 102.515
100-Year 102.534
********** Link: WQ 1 ********** Link Inflow
Frequency Stats
Flood Frequency Data(cfs)
(Recurrence Interval Computed Using Gringorten Plotting Position)
Tr (yrs) Flood Peak (cfs)
======================================
2-Year 1.907E-02
5-Year 2.482E-02
10-Year 2.790E-02
25-Year 3.250E-02
50-Year 4.196E-02
100-Year 4.886E-02
200-Year 5.029E-02
500-Year 5.214E-02
********** Link: WQ 1 ********** Link Outflow 1
Frequency Stats
Flood Frequency Data(cfs)
(Recurrence Interval Computed Using Gringorten Plotting Position)
Tr (yrs) Flood Peak (cfs)
======================================
2-Year 1.907E-02
5-Year 2.482E-02
10-Year 2.790E-02
25-Year 3.250E-02
50-Year 4.196E-02
100-Year 4.886E-02
200-Year 5.029E-02
500-Year 5.214E-02
********** Link: WQ 2 ********** Link Inflow
Frequency Stats
Flood Frequency Data(cfs)
(Recurrence Interval Computed Using Gringorten Plotting Position)
Tr (yrs) Flood Peak (cfs)
======================================
2-Year 6.483E-02
5-Year 8.437E-02
10-Year 9.487E-02
25-Year 0.111
50-Year 0.143
100-Year 0.166
200-Year 0.171
500-Year 0.177
********** Link: WQ 2 ********** Link Outflow 1
Frequency Stats
Flood Frequency Data(cfs)
(Recurrence Interval Computed Using Gringorten Plotting Position)
Tr (yrs) Flood Peak (cfs)
======================================
2-Year 6.483E-02
5-Year 8.437E-02
10-Year 9.487E-02
25-Year 0.111
50-Year 0.143
100-Year 0.166
200-Year 0.171
500-Year 0.177
***********Groundwater Recharge Summary *************
Recharge is computed as input to Perlnd Groundwater Plus Infiltration in Structures
Total Predeveloped Recharge During Simulation
Model Element Recharge Amount (ac-ft)
-----------------------------------------------------------------------------------------------
Subbasin: Existing Predevelope 116.029
Link: POC 1 0.000
_____________________________________
Total: 116.029
Total Post Developed Recharge During Simulation
Model Element Recharge Amount (ac-ft)
-----------------------------------------------------------------------------------------------
Subbasin: NEW IMP PGIS BYPASS 17.168
Subbasin: Bypass 2.368
Subbasin: WQ 1 0.000
Subbasin: WQ 2 0.000
Link: TDA 1 0.000
Link: Pipe Tank 0.000
Link: WQ 1 0.000
Link: WQ 2 0.000
_____________________________________
Total: 19.535
Total Predevelopment Recharge is Greater than Post Developed
Average Recharge Per Year, (Number of Years= 158)
Predeveloped: 0.734 ac-ft/year, Post Developed: 0.124 ac-ft/year
***********Water Quality Facility Data *************
----------------------SCENARIO: PREDEVELOPED
Number of Links: 1
********** Link: POC 1 **********
2-Year Discharge Rate : 0.208 cfs
15-Minute Timestep, Water Quality Treatment Design Discharge
On-line Design Discharge Rate (91% Exceedance): 0.06 cfs
Off-line Design Discharge Rate (91% Exceedance): 0.03 cfs
Infiltration/Filtration Statistics--------------------
Inflow Volume (ac-ft): 346.11
Inflow Volume Including PPT-Evap (ac-ft): 346.11
Total Runoff Infiltrated (ac-ft): 0.00, 0.00%
Total Runoff Filtered (ac-ft): 0.00, 0.00%
Primary Outflow To Downstream System (ac-ft): 346.11
Secondary Outflow To Downstream System (ac-ft): 0.00
Volume Lost to ET (ac-ft): 0.00
Percent Treated (Infiltrated+Filtered+ET)/Total Volume: 0.00%
----------------------SCENARIO: POSTDEVELOPED
Number of Links: 4
********** Link: TDA 1 **********
2-Year Discharge Rate : 0.200 cfs
15-Minute Timestep, Water Quality Treatment Design Discharge
On-line Design Discharge Rate (91% Exceedance): 0.13 cfs
Off-line Design Discharge Rate (91% Exceedance): 0.08 cfs
Infiltration/Filtration Statistics--------------------
Inflow Volume (ac-ft): 541.65
Inflow Volume Including PPT-Evap (ac-ft): 541.65
Total Runoff Infiltrated (ac-ft): 0.00, 0.00%
Total Runoff Filtered (ac-ft): 0.00, 0.00%
Primary Outflow To Downstream System (ac-ft): 541.65
Secondary Outflow To Downstream System (ac-ft): 0.00
Volume Lost to ET (ac-ft): 0.00
Percent Treated (Infiltrated+Filtered+ET)/Total Volume: 0.00%
********** Link: Pipe Tank **********
Basic Wet Pond Volume (91% Exceedance): 6286. cu-ft
Computed Large Wet Pond Volume, 1.5*Basic Volume: 9429. cu-ft
2-Year Discharge Rate : 0.197 cfs
15-Minute Timestep, Water Quality Treatment Design Discharge
On-line Design Discharge Rate (91% Exceedance): 0.17 cfs
Off-line Design Discharge Rate (91% Exceedance): 0.10 cfs
Infiltration/Filtration Statistics--------------------
Inflow Volume (ac-ft): 530.66
Inflow Volume Including PPT-Evap (ac-ft): 530.66
Total Runoff Infiltrated (ac-ft): 0.00, 0.00%
Total Runoff Filtered (ac-ft): 0.00, 0.00%
Primary Outflow To Downstream System (ac-ft): 530.66
Secondary Outflow To Downstream System (ac-ft): 0.00
Volume Lost to ET (ac-ft): 0.00
Percent Treated (Infiltrated+Filtered+ET)/Total Volume: 0.00%
********** Link: WQ 1 **********
2-Year Discharge Rate : 0.019 cfs
15-Minute Timestep, Water Quality Treatment Design Discharge
On-line Design Discharge Rate (91% Exceedance): 0.01 cfs
Off-line Design Discharge Rate (91% Exceedance): 0.00 cfs
Infiltration/Filtration Statistics--------------------
Inflow Volume (ac-ft): 22.60
Inflow Volume Including PPT-Evap (ac-ft): 22.60
Total Runoff Infiltrated (ac-ft): 0.00, 0.00%
Total Runoff Filtered (ac-ft): 0.00, 0.00%
Primary Outflow To Downstream System (ac-ft): 22.60
Secondary Outflow To Downstream System (ac-ft): 0.00
Volume Lost to ET (ac-ft): 0.00
Percent Treated (Infiltrated+Filtered+ET)/Total Volume: 0.00%
********** Link: WQ 2 **********
2-Year Discharge Rate : 0.065 cfs
15-Minute Timestep, Water Quality Treatment Design Discharge
On-line Design Discharge Rate (91% Exceedance): 0.03 cfs
Off-line Design Discharge Rate (91% Exceedance): 0.02 cfs
Infiltration/Filtration Statistics--------------------
Inflow Volume (ac-ft): 76.85
Inflow Volume Including PPT-Evap (ac-ft): 76.85
Total Runoff Infiltrated (ac-ft): 0.00, 0.00%
Total Runoff Filtered (ac-ft): 0.00, 0.00%
Primary Outflow To Downstream System (ac-ft): 76.85
Secondary Outflow To Downstream System (ac-ft): 0.00
Volume Lost to ET (ac-ft): 0.00
Percent Treated (Infiltrated+Filtered+ET)/Total Volume: 0.00%
***********Compliance Point Results *************
Scenario Predeveloped Compliance Link: POC 1
Scenario Postdeveloped Compliance Link: TDA 1
*** Point of Compliance Flow Frequency Data ***
Recurrence Interval Computed Using Gringorten Plotting Position
Predevelopment Runoff Postdevelopment Runoff
Tr (Years) Discharge (cfs) Tr (Years) Discharge (cfs)
----------------------------------------------------------------------------------------------------------------------
2-Year 0.208 2-Year 0.200
5-Year 0.305 5-Year 0.305
10-Year 0.380 10-Year 0.380
25-Year 0.493 25-Year 0.477
50-Year 0.600 50-Year 0.536
100-Year 0.626 100-Year 0.622
200-Year 0.693 200-Year 0.704
500-Year 0.783 500-Year 0.811
** Record too Short to Compute Peak Discharge for These Recurrence Intervals
MATCHING
PREDEVELOPED
RUNOFF
DISCHARGE
FOR 2, 10, AND
100 YR EVENTS
1200 6th Avenue
Suite 1620
Seattle, WA 98101
206.267.2425 TEL
206.267.2429 FAX DRAWN BY:DATE:JOB NO.:
EG: 30.14
UP
UP
32
3232 323
2
3133
3332UP
UP
Grady Way Apartments
Developed Conditions Map
JN 10/11/2021 2200335
EX-1-3B
GRAPHIC SCALE
0 40 80
1" = 40 FEET
20
N
LEGEND
Description Quantity Unit
BYPASS IMPERVIOUS 0.01 ac
BYPASS TOTAL AREA 0.03 ac
GRASS PAVE 0.02 ac
NEW + REPLACED IMPERVIOUS 1.08 ac
TOTAL PROJECT SITE AREA WITH DEDICATION 1.28 ac
VEGETATED ROOF 0.05 ac
LIMITS OF
DEVELOPMENT
3-FOOT FLOW
CONTROL
TANK
LONGEST
PATH TO FC
FACILITY
APPROX 100'
DISHARGE
LOCATION
Bypass Grass
Bypass Landscape
0.03 ac (Bypass Total Area)
-0.01 ac (Bypass Impervious)
0.02 ac
Flow Control Grass (exclusding BMPs)=
1.28 ac (Total Project Site Area With Dedication)
- 0.03 ac (Bypass Total Area)
- 0.02 ac (Grass Pave)
- 0.05 ac (Vegetated Roof Area)
-1.08 ac (New + Replaced Impervious)
0.10 ac
Total grass including BMPs
0.10 ac (Flow Control Grass)
+ 0.02 ac (Grass Pave)
+0.025 ac (1/2 Vegetated Roof Area)
0.145ac
New + Replaced Impervious Total
1.08 ac (New + Replaced Impervious)
+0.025 (1/2 Vegetated Roof Area)
1.105 ac
WQ #1 WQ#2
1200 6th Avenue
Suite 1620
Seattle, WA 98101
206.267.2425 TEL
206.267.2429 FAX DRAWN BY:DATE:JOB NO.:
EG: 30.14
UP
UP
32
3232 323
2
3133
3332UP
UP
Grady Way Apartments
Water Quality Area Map
Name Date Job No.
EX 4-3
GRAPHIC SCALE
0 40 80
1" = 40 FEET
20
N
LEGEND
Description Quantity Unit
PGIS- BYPASS 0.10 ac
PGIS WQ 1 0.05 ac
PGIS WQ 2 0.17 ac
DISCHARGE
LOCATION
LIMITS OF
DEVELOPMENT
PROPOSED
BUILDING
3-FT DIAMETER
FLOW CONTROL
TANK
WQ #1
BIOPOD
PEDESTRIAN
WALKWAY,
ONLY VEHICLE
TRAFFIC
DURING
EMERGENCIES
BOLLARDS
BOLLARDS
WQ #2
BIOPOD
DRAWN BY:DATE:JOB NO.:
1200 6th Avenue, Suite 1620
Seattle, WA 98101
206.267.2425 TEL 206.267.2429 FAX
Watershed Affordable Housing Apartments
Biopod Sizing Chart
Jesse N 07/01/2020 2200335.10
FIG
4-4
Technical Information Report Watershed Affordable Housing Apartments
2200335.10
Section 5
Conveyance System Analysis and Design
Technical Information Report Watershed Affordable Housing Apartments 5-1
2200335.10
5.0 Conveyance System Analysis and Design
Conveyance has been sized to convey the 25-year storm event and checked for adequate
capacity for the 100-year event. The site has very few pipes to analyze; for this reason, in lieu of
a backwater analysis, a manning’s calculation has been performed to determine the full flow
capacity of the pipe with the smallest slope. The pipe with the smallest slope was an 8-inch pipe
with a 1 percent slope. The 100-year flow for the entire site is 1.10 cfs (see Figure 5-1). The full
flow capacity of an 8-inch pipe, with a manning’s coefficient of 0.012, is 1.31 cfs (see Figure 5-2).
In addition, following the flow control device, there will be a slight reduction in flow compared to
the existing conditions.
Technical Information Report Watershed Affordable Housing Apartments
2200335.10
Section 5.0 Figures
Figure 5-1 ................................... MGS Flood 100-Year Flow Calculation
Figure 5-2 ................................... Manning’s Full Flow Calculation
—————————————————————————————————
MGS FLOOD
PROJECT REPORT
Program Version: MGSFlood 4.57
Program License Number: 201710010
Project Simulation Performed on: 02/27/2022 7:44 PM
Report Generation Date: 02/27/2022 7:47 PM
—————————————————————————————————
Input File Name: Grady Way 3' Tank.fld
Project Name: Water Shed Apartments
Analysis Title: Preliminary Model
Comments:
———————————————— PRECIPITATION INPUT ————————————————
Computational Time Step (Minutes): 15
Extended Precipitation Time Series Selected
Climatic Region Number: 3
Full Period of Record Available used for Routing
Precipitation Station : 95004005 Puget West 40 in_5min 10/01/1939-10/01/2097
Evaporation Station : 951040 Puget West 40 in MAP
Evaporation Scale Factor : 0.750
HSPF Parameter Region Number: 3
HSPF Parameter Region Name : USGS Default
********** Default HSPF Parameters Used (Not Modified by User) ***************
********************** WATERSHED DEFINITION ***********************
Predevelopment/Post Development Tributary Area Summary
Predeveloped Post Developed
Total Subbasin Area (acres) 1.280 1.280
Area of Links that Include Precip/Evap (acres) 0.000 0.000
Total (acres) 1.280 1.280
----------------------SCENARIO: PREDEVELOPED
Number of Subbasins: 1
---------- Subbasin : Existing Predeveloped ----------
-------Area (Acres) --------
Till Grass 0.980
Impervious 0.300
----------------------------------------------
Subbasin Total 1.280
----------------------SCENARIO: POSTDEVELOPED
Number of Subbasins: 4
---------- Subbasin : NEW IMP PGIS BYPASS AND PASTURE AND GRASS PAVE ----------
-------Area (Acres) --------
Till Grass 0.145
Impervious 0.885
----------------------------------------------
Subbasin Total 1.030
---------- Subbasin : Bypass ----------
-------Area (Acres) --------
Till Grass 0.020
Impervious 0.010
----------------------------------------------
Subbasin Total 0.030
---------- Subbasin : WQ 1 ----------
-------Area (Acres) --------
Impervious 0.050
----------------------------------------------
Subbasin Total 0.050
---------- Subbasin : WQ 2 ----------
-------Area (Acres) --------
Impervious 0.170
----------------------------------------------
Subbasin Total 0.170
************************* LINK DATA *******************************
----------------------SCENARIO: PREDEVELOPED
Number of Links: 1
------------------------------------------
Link Name: POC 1
Link Type: Copy
Downstream Link: None
************************* LINK DATA *******************************
----------------------SCENARIO: POSTDEVELOPED
Number of Links: 4
------------------------------------------
Link Name: TDA 1
Link Type: Copy
Downstream Link: None
------------------------------------------
Link Name: Pipe Tank
Link Type: Structure
Downstream Link Name: TDA 1
User Specified Elevation Volume Table Used
Elevation (ft) Pond Volume (cu-ft)
100.00 0.
100.10 26.
100.20 91.
100.30 154.
100.40 226.
100.50 334.
100.60 422.
100.70 515.
100.80 645.
100.90 747.
101.00 852.
101.10 996.
101.20 1106.
101.30 1217.
101.40 1367.
101.50 1480.
101.60 1593.
101.70 1743.
101.80 1854.
101.90 1964.
102.00 2108.
102.10 2213.
102.20 2315.
102.30 2445.
102.40 2538.
102.50 2626.
102.60 2734.
102.70 2806.
102.80 2869.
102.90 2934.
103.00 2960.
Hydraulic Conductivity (in/hr) : 0.00
Massmann Regression Used to Estimate Hydralic Gradient
Depth to Water Table (ft) : 100.00
Bio-Fouling Potential : Low
Maintenance : Average or Better
Riser Geometry
Riser Structure Type : Circular
Riser Diameter (in) : 18.00
Common Length (ft) : 0.210
Riser Crest Elevation : 102.50 ft
Hydraulic Structure Geometry
Number of Devices: 2
---Device Number 1 ---
Device Type : Circular Orifice
Control Elevation (ft) : 100.50
Diameter (in) : 2.63
Orientation : Horizontal
Elbow : Yes
--- Device Number 2 ---
Device Type : Rectangular Weir that Intersects the Riser Top
Invert Elevation (ft) : 101.93
Length (ft) : 0.210
------------------------------------------
Link Name: WQ 1
Link Type: Copy
Downstream Link Name: Pipe Tank
------------------------------------------
Link Name: WQ 2
Link Type: Copy
Downstream Link Name: Pipe Tank
**********************FLOOD FREQUENCY AND DURATION STATISTICS*******************
----------------------SCENARIO: PREDEVELOPED
Number of Subbasins: 1
Number of Links: 1
********** Subbasin: Existing Predeveloped **********
Flood Frequency Data(cfs)
(Recurrence Interval Computed Using Gringorten Plotting Position)
Tr (yrs) Flood Peak (cfs)
======================================
2-Year 0.208
5-Year 0.305
10-Year 0.380
25-Year 0.493
50-Year 0.600
100-Year 0.626
200-Year 0.693
500-Year 0.783
********** Link: POC 1 ********** Link Outflow 1
Frequency Stats
Flood Frequency Data(cfs)
(Recurrence Interval Computed Using Gringorten Plotting Position)
Tr (yrs) Flood Peak (cfs)
======================================
2-Year 0.208
5-Year 0.305
10-Year 0.380
25-Year 0.493
50-Year 0.600
100-Year 0.626
200-Year 0.693
500-Year 0.783
----------------------SCENARIO: POSTDEVELOPED
Number of Subbasins: 4
Number of Links: 4
********** Subbasin: NEW IMP PGIS BYPASS AND PASTURE AND GRASS PAVE **********
Flood Frequency Data(cfs)
(Recurrence Interval Computed Using Gringorten Plotting Position)
Tr (yrs) Flood Peak (cfs)
======================================
2-Year 0.356
5-Year 0.445
10-Year 0.526
25-Year 0.626
50-Year 0.765
100-Year 0.928
200-Year 0.943
500-Year 0.961
********** Subbasin: Bypass **********
Flood Frequency Data(cfs)
(Recurrence Interval Computed Using Gringorten Plotting Position)
Tr (yrs) Flood Peak (cfs)
======================================
2-Year 5.758E-03
5-Year 7.885E-03
10-Year 9.962E-03
25-Year 1.245E-02
50-Year 1.479E-02
100-Year 1.669E-02
200-Year 1.799E-02
500-Year 1.968E-02
********** Subbasin: WQ 1 **********
Flood Frequency Data(cfs)
(Recurrence Interval Computed Using Gringorten Plotting Position)
Tr (yrs) Flood Peak (cfs)
======================================
2-Year 1.907E-02
5-Year 2.482E-02
10-Year 2.790E-02
25-Year 3.250E-02
50-Year 4.196E-02
100-Year 4.886E-02
200-Year 5.029E-02
500-Year 5.214E-02
********** Subbasin: WQ 2 **********
Flood Frequency Data(cfs)
(Recurrence Interval Computed Using Gringorten Plotting Position)
Tr (yrs) Flood Peak (cfs)
======================================
2-Year 6.483E-02
5-Year 8.437E-02
10-Year 9.487E-02
25-Year 0.111
50-Year 0.143
100-Year 0.166
200-Year 0.171
500-Year 0.177
********** Link: TDA 1 ********** Link Inflow
Frequency Stats
Flood Frequency Data(cfs)
(Recurrence Interval Computed Using Gringorten Plotting Position)
Tr (yrs) Flood Peak (cfs)
======================================
2-Year 0.200
5-Year 0.305
10-Year 0.380
25-Year 0.477
50-Year 0.536
100-Year 0.622
200-Year 0.704
500-Year 0.811
********** Link: TDA 1 ********** Link Outflow 1
Frequency Stats
Flood Frequency Data(cfs)
(Recurrence Interval Computed Using Gringorten Plotting Position)
Tr (yrs) Flood Peak (cfs)
======================================
2-Year 0.200
5-Year 0.305
10-Year 0.380
25-Year 0.477
50-Year 0.536
100-Year 0.622
200-Year 0.704
500-Year 0.811
********** Link: Pipe Tank ********** Link Outflow 1
Frequency Stats
Flood Frequency Data(cfs)
(Recurrence Interval Computed Using Gringorten Plotting Position)
Tr (yrs) Flood Peak (cfs)
======================================
2-Year 0.197
5-Year 0.302
10-Year 0.376
25-Year 0.470
50-Year 0.528
100-Year 0.610
200-Year 0.691
500-Year 0.796
********** Link: Pipe Tank ********** Link WSEL
Stats
WSEL Frequency Data(ft)
(Recurrence Interval Computed Using Gringorten Plotting Position)
Tr (yrs) WSEL Peak (ft)
======================================
1.05-Year 101.184
1.11-Year 101.294
1.25-Year 101.402
2.00-Year 101.777
3.33-Year 102.033
5-Year 102.190
10-Year 102.327
25-Year 102.475
50-Year 102.515
100-Year 102.534
********** Link: WQ 1 ********** Link Inflow
Frequency Stats
Flood Frequency Data(cfs)
(Recurrence Interval Computed Using Gringorten Plotting Position)
Tr (yrs) Flood Peak (cfs)
======================================
2-Year 1.907E-02
5-Year 2.482E-02
10-Year 2.790E-02
25-Year 3.250E-02
50-Year 4.196E-02
100-Year 4.886E-02
200-Year 5.029E-02
500-Year 5.214E-02
********** Link: WQ 1 ********** Link Outflow 1
Frequency Stats
Flood Frequency Data(cfs)
(Recurrence Interval Computed Using Gringorten Plotting Position)
Tr (yrs) Flood Peak (cfs)
======================================
2-Year 1.907E-02
5-Year 2.482E-02
10-Year 2.790E-02
25-Year 3.250E-02
50-Year 4.196E-02
100-Year 4.886E-02
200-Year 5.029E-02
500-Year 5.214E-02
********** Link: WQ 2 ********** Link Inflow
Frequency Stats
Flood Frequency Data(cfs)
(Recurrence Interval Computed Using Gringorten Plotting Position)
Tr (yrs) Flood Peak (cfs)
======================================
2-Year 6.483E-02
5-Year 8.437E-02
10-Year 9.487E-02
25-Year 0.111
50-Year 0.143
100-Year 0.166
200-Year 0.171
500-Year 0.177
********** Link: WQ 2 ********** Link Outflow 1
Frequency Stats
Flood Frequency Data(cfs)
(Recurrence Interval Computed Using Gringorten Plotting Position)
Tr (yrs) Flood Peak (cfs)
======================================
2-Year 6.483E-02
5-Year 8.437E-02
10-Year 9.487E-02
25-Year 0.111
50-Year 0.143
100-Year 0.166
200-Year 0.171
500-Year 0.177
***********Groundwater Recharge Summary *************
Recharge is computed as input to Perlnd Groundwater Plus Infiltration in Structures
Total Predeveloped Recharge During Simulation
Model Element Recharge Amount (ac-ft)
-----------------------------------------------------------------------------------------------
Subbasin: Existing Predevelope 116.029
Link: POC 1 0.000
_____________________________________
Total: 116.029
Total Post Developed Recharge During Simulation
Model Element Recharge Amount (ac-ft)
-----------------------------------------------------------------------------------------------
Subbasin: NEW IMP PGIS BYPASS 17.168
Subbasin: Bypass 2.368
Subbasin: WQ 1 0.000
Subbasin: WQ 2 0.000
Link: TDA 1 0.000
Link: Pipe Tank 0.000
Link: WQ 1 0.000
Link: WQ 2 0.000
_____________________________________
Total: 19.535
Total Predevelopment Recharge is Greater than Post Developed
Average Recharge Per Year, (Number of Years= 158)
Predeveloped: 0.734 ac-ft/year, Post Developed: 0.124 ac-ft/year
***********Water Quality Facility Data *************
----------------------SCENARIO: PREDEVELOPED
Number of Links: 1
********** Link: POC 1 **********
2-Year Discharge Rate : 0.208 cfs
15-Minute Timestep, Water Quality Treatment Design Discharge
On-line Design Discharge Rate (91% Exceedance): 0.06 cfs
Off-line Design Discharge Rate (91% Exceedance): 0.03 cfs
Infiltration/Filtration Statistics--------------------
Inflow Volume (ac-ft): 346.11
Inflow Volume Including PPT-Evap (ac-ft): 346.11
Total Runoff Infiltrated (ac-ft): 0.00, 0.00%
Total Runoff Filtered (ac-ft): 0.00, 0.00%
Primary Outflow To Downstream System (ac-ft): 346.11
Secondary Outflow To Downstream System (ac-ft): 0.00
Volume Lost to ET (ac-ft): 0.00
Percent Treated (Infiltrated+Filtered+ET)/Total Volume: 0.00%
----------------------SCENARIO: POSTDEVELOPED
Number of Links: 4
********** Link: TDA 1 **********
2-Year Discharge Rate : 0.200 cfs
15-Minute Timestep, Water Quality Treatment Design Discharge
On-line Design Discharge Rate (91% Exceedance): 0.13 cfs
Off-line Design Discharge Rate (91% Exceedance): 0.08 cfs
Infiltration/Filtration Statistics--------------------
Inflow Volume (ac-ft): 541.65
Inflow Volume Including PPT-Evap (ac-ft): 541.65
Total Runoff Infiltrated (ac-ft): 0.00, 0.00%
Total Runoff Filtered (ac-ft): 0.00, 0.00%
Primary Outflow To Downstream System (ac-ft): 541.65
Secondary Outflow To Downstream System (ac-ft): 0.00
Volume Lost to ET (ac-ft): 0.00
Percent Treated (Infiltrated+Filtered+ET)/Total Volume: 0.00%
********** Link: Pipe Tank **********
Basic Wet Pond Volume (91% Exceedance): 6286. cu-ft
Computed Large Wet Pond Volume, 1.5*Basic Volume: 9429. cu-ft
2-Year Discharge Rate : 0.197 cfs
15-Minute Timestep, Water Quality Treatment Design Discharge
On-line Design Discharge Rate (91% Exceedance): 0.17 cfs
Off-line Design Discharge Rate (91% Exceedance): 0.10 cfs
Infiltration/Filtration Statistics--------------------
Inflow Volume (ac-ft): 530.66
Inflow Volume Including PPT-Evap (ac-ft): 530.66
Total Runoff Infiltrated (ac-ft): 0.00, 0.00%
Total Runoff Filtered (ac-ft): 0.00, 0.00%
Primary Outflow To Downstream System (ac-ft): 530.66
Secondary Outflow To Downstream System (ac-ft): 0.00
Volume Lost to ET (ac-ft): 0.00
Percent Treated (Infiltrated+Filtered+ET)/Total Volume: 0.00%
********** Link: WQ 1 **********
2-Year Discharge Rate : 0.019 cfs
15-Minute Timestep, Water Quality Treatment Design Discharge
On-line Design Discharge Rate (91% Exceedance): 0.01 cfs
Off-line Design Discharge Rate (91% Exceedance): 0.00 cfs
Infiltration/Filtration Statistics--------------------
Inflow Volume (ac-ft): 22.60
Inflow Volume Including PPT-Evap (ac-ft): 22.60
Total Runoff Infiltrated (ac-ft): 0.00, 0.00%
Total Runoff Filtered (ac-ft): 0.00, 0.00%
Primary Outflow To Downstream System (ac-ft): 22.60
Secondary Outflow To Downstream System (ac-ft): 0.00
Volume Lost to ET (ac-ft): 0.00
Percent Treated (Infiltrated+Filtered+ET)/Total Volume: 0.00%
********** Link: WQ 2 **********
2-Year Discharge Rate : 0.065 cfs
15-Minute Timestep, Water Quality Treatment Design Discharge
On-line Design Discharge Rate (91% Exceedance): 0.03 cfs
Off-line Design Discharge Rate (91% Exceedance): 0.02 cfs
Infiltration/Filtration Statistics--------------------
Inflow Volume (ac-ft): 76.85
Inflow Volume Including PPT-Evap (ac-ft): 76.85
Total Runoff Infiltrated (ac-ft): 0.00, 0.00%
Total Runoff Filtered (ac-ft): 0.00, 0.00%
Primary Outflow To Downstream System (ac-ft): 76.85
Secondary Outflow To Downstream System (ac-ft): 0.00
Volume Lost to ET (ac-ft): 0.00
Percent Treated (Infiltrated+Filtered+ET)/Total Volume: 0.00%
***********Compliance Point Results *************
Scenario Predeveloped Compliance Link: POC 1
Scenario Postdeveloped Compliance Link: Pipe Tank
*** Point of Compliance Flow Frequency Data ***
Recurrence Interval Computed Using Gringorten Plotting Position
Predevelopment Runoff Postdevelopment Runoff
Tr (Years) Discharge (cfs) Tr (Years) Discharge (cfs)
----------------------------------------------------------------------------------------------------------------------
2-Year 0.208 2-Year 0.441
5-Year 0.305 5-Year 0.555
10-Year 0.380 10-Year 0.650
25-Year 0.493 25-Year 0.768
50-Year 0.600 50-Year 0.950
100-Year 0.626 100-Year 1.143
200-Year 0.693 200-Year 1.164
500-Year 0.783 500-Year 1.190
** Record too Short to Compute Peak Discharge for These Recurrence Intervals
100 year flow
Project Description
Friction Method Manning Formula
Solve For Full Flow Capacity
Input Data
Roughness Coefficient 0.012
Channel Slope 0.01000 ft/ft
Normal Depth 0.67 ft
Diameter 0.67 ft
Discharge 1.31 ft³/s
Results
Discharge 1.31 ft³/s
Normal Depth 0.67 ft
Flow Area 0.35 ft²
Wetted Perimeter 2.09 ft
Hydraulic Radius 0.17 ft
Top Width 0.00 ft
Critical Depth 0.54 ft
Percent Full 100.0 %
Critical Slope 0.01021 ft/ft
Velocity 3.75 ft/s
Velocity Head 0.22 ft
Specific Energy 0.89 ft
Froude Number 0.00
Maximum Discharge 1.41 ft³/s
Discharge Full 1.31 ft³/s
Slope Full 0.01000 ft/ft
Flow Type SubCritical
GVF Input Data
Downstream Depth 0.00 ft
Length 0.00 ft
Number Of Steps 0
GVF Output Data
Upstream Depth 0.00 ft
Profile Description
Profile Headloss 0.00 ft
Average End Depth Over Rise 0.00 %
Worksheet for 8 inch Full Flow
10/7/2021 4:55:04 PM
Bentley Systems, Inc. Haestad Methods Solution CenterBentley FlowMaster V8i (SELECTseries 1) [08.11.01.03]
27 Siemons Company Drive Suite 200 W Watertown, CT 06795 USA +1-203-755-1666 2of1Page
Full flow of 8-inch
pipe
GVF Output Data
Normal Depth Over Rise 100.00 %
Downstream Velocity Infinity ft/s
Upstream Velocity Infinity ft/s
Normal Depth 0.67 ft
Critical Depth 0.54 ft
Channel Slope 0.01000 ft/ft
Critical Slope 0.01021 ft/ft
Worksheet for 8 inch Full Flow
10/7/2021 4:55:04 PM
Bentley Systems, Inc. Haestad Methods Solution CenterBentley FlowMaster V8i (SELECTseries 1) [08.11.01.03]
27 Siemons Company Drive Suite 200 W Watertown, CT 06795 USA +1-203-755-1666 2of2Page
Technical Information Report Watershed Affordable Housing Apartments
2200335.10
Section 6
Special Reports and Studies
Technical Information Report Watershed Affordable Housing Apartments 6-1
2200335.10
6.0 Special Reports and Studies
“Updated Geotechnical Engineering Study” dated June 10, 2020, by Earth Solutions NW.
Technical Information Report Watershed Affordable Housing Apartments
2200335.10
Section 6.0 Figures
Figure 6-1 ......... Geotechnical Report
EarthSolutionsNWLLC
EarthSolutionsNWLLC
15365 N.E. 90th Street, Suite 100 Redmond, WA98052
(425) 449-4704 Fax (425) 449-4711
www.earthsolutionsnw.com
Geotechnical Engineering
Construction Observation/Testing
Environmental Services
UPDATED
GEOTECHNICAL ENGINEERING STUDY
PROPOSED RENTON APARTMENTS
615 AND 617 WILLIAMS AVENUE SOUTH
RENTON, WASHINGTON
ES-5946.03
PREPARED FOR
GMD DEVELOPMENT, LLC
June 10, 2020
_________________________
Adam Z. Shier, L.G.
Project Geologist
_________________________
Kyle R. Campbell, P.E.
Principal Engineer
UPDATED
GEOTECHNICAL ENGINEERING STUDY
PROPOSED RENTON APARTMENTS
615 AND 617 WILLIAMS AVENUE SOUTH
RENTON, WASHINGTON
ES-5946.03
Earth Solutions NW, LLC
15365 Northeast 90th Street, Suite 100
Redmond, Washington 98052
Phone: 425-449-4704 | Fax: 425-449-4711
www.earthsolutionsnw.com
06/10/2020
Geotechnical-Engineering Report
Important Information about This
Subsurface problems are a principal cause of construction delays, cost overruns, claims, and disputes.
While you cannot eliminate all such risks, you can manage them. The following information is provided to help.
The Geoprofessional Business Association (GBA) has prepared this advisory to help you – assumedly a client representative – interpret and apply this geotechnical-engineering report as effectively as possible. In that way, you can benefit from a lowered exposure to problems associated with subsurface conditions at project sites and development of them that, for decades, have been a principal cause of construction delays, cost overruns, claims, and disputes. If you have questions or want more information about any of the issues discussed herein, contact your GBA-member geotechnical engineer. Active engagement in GBA exposes geotechnical engineers to a wide array of risk-confrontation techniques that can be of genuine benefit for everyone involved with a construction project.
Understand the Geotechnical-Engineering Services Provided for this ReportGeotechnical-engineering services typically include the planning, collection, interpretation, and analysis of exploratory data from widely spaced borings and/or test pits. Field data are combined with results from laboratory tests of soil and rock samples obtained from field exploration (if applicable), observations made during site reconnaissance, and historical information to form one or more models of the expected subsurface conditions beneath the site. Local geology and alterations of the site surface and subsurface by previous and proposed construction are also important considerations. Geotechnical engineers apply their engineering training, experience, and judgment to adapt the requirements of the prospective project to the subsurface model(s). Estimates are made of the subsurface conditions that will likely be exposed during construction as well as the expected performance of foundations and other structures being planned and/or affected by construction activities.
The culmination of these geotechnical-engineering services is typically a geotechnical-engineering report providing the data obtained, a discussion of the subsurface model(s), the engineering and geologic engineering assessments and analyses made, and the recommendations developed to satisfy the given requirements of the project. These reports may be titled investigations, explorations, studies, assessments, or evaluations. Regardless of the title used, the geotechnical-engineering report is an engineering interpretation of the subsurface conditions within the context of the project and does not represent a close examination, systematic inquiry, or thorough investigation of all site and subsurface conditions.
Geotechnical-Engineering Services are Performed for Specific Purposes, Persons, and Projects, and At Specific TimesGeotechnical engineers structure their services to meet the specific needs, goals, and risk management preferences of their clients. A geotechnical-engineering study conducted for a given civil engineer
will not likely meet the needs of a civil-works constructor or even a
different civil engineer. Because each geotechnical-engineering study
is unique, each geotechnical-engineering report is unique, prepared solely for the client.
Likewise, geotechnical-engineering services are performed for a specific
project and purpose. For example, it is unlikely that a geotechnical-
engineering study for a refrigerated warehouse will be the same as
one prepared for a parking garage; and a few borings drilled during
a preliminary study to evaluate site feasibility will not be adequate to
develop geotechnical design recommendations for the project.
Do not rely on this report if your geotechnical engineer prepared it:
• for a different client;
• for a different project or purpose;
• for a different site (that may or may not include all or a portion of
the original site); or
• before important events occurred at the site or adjacent to it;
e.g., man-made events like construction or environmental
remediation, or natural events like floods, droughts, earthquakes,
or groundwater fluctuations.
Note, too, the reliability of a geotechnical-engineering report can
be affected by the passage of time, because of factors like changed
subsurface conditions; new or modified codes, standards, or
regulations; or new techniques or tools. If you are the least bit uncertain
about the continued reliability of this report, contact your geotechnical
engineer before applying the recommendations in it. A minor amount
of additional testing or analysis after the passage of time – if any is
required at all – could prevent major problems.
Read this Report in Full
Costly problems have occurred because those relying on a geotechnical-
engineering report did not read the report in its entirety. Do not rely on
an executive summary. Do not read selective elements only. Read and refer to the report in full.
You Need to Inform Your Geotechnical Engineer About Change
Your geotechnical engineer considered unique, project-specific factors
when developing the scope of study behind this report and developing
the confirmation-dependent recommendations the report conveys.
Typical changes that could erode the reliability of this report include
those that affect:
• the site’s size or shape;
• the elevation, configuration, location, orientation,
function or weight of the proposed structure and
the desired performance criteria;
• the composition of the design team; or
• project ownership.
As a general rule, always inform your geotechnical engineer of project
or site changes – even minor ones – and request an assessment of their
impact. The geotechnical engineer who prepared this report cannot accept
responsibility or liability for problems that arise because the geotechnical engineer was not informed about developments the engineer otherwise would have considered.
Most of the “Findings” Related in This Report Are Professional Opinions
Before construction begins, geotechnical engineers explore a site’s
subsurface using various sampling and testing procedures. Geotechnical engineers can observe actual subsurface conditions only at those specific locations where sampling and testing is performed. The data derived from
that sampling and testing were reviewed by your geotechnical engineer,
who then applied professional judgement to form opinions about
subsurface conditions throughout the site. Actual sitewide-subsurface
conditions may differ – maybe significantly – from those indicated in
this report. Confront that risk by retaining your geotechnical engineer
to serve on the design team through project completion to obtain
informed guidance quickly, whenever needed.
This Report’s Recommendations Are Confirmation-Dependent
The recommendations included in this report – including any options or
alternatives – are confirmation-dependent. In other words, they are not
final, because the geotechnical engineer who developed them relied heavily
on judgement and opinion to do so. Your geotechnical engineer can finalize
the recommendations only after observing actual subsurface conditions
exposed during construction. If through observation your geotechnical
engineer confirms that the conditions assumed to exist actually do exist,
the recommendations can be relied upon, assuming no other changes have
occurred. The geotechnical engineer who prepared this report cannot assume
responsibility or liability for confirmation-dependent recommendations if you
fail to retain that engineer to perform construction observation.
This Report Could Be Misinterpreted
Other design professionals’ misinterpretation of geotechnical-
engineering reports has resulted in costly problems. Confront that risk
by having your geotechnical engineer serve as a continuing member of
the design team, to:
• confer with other design-team members;
• help develop specifications;
• review pertinent elements of other design professionals’ plans and
specifications; and
• be available whenever geotechnical-engineering guidance is needed.
You should also confront the risk of constructors misinterpreting this report. Do so by retaining your geotechnical engineer to participate in prebid and preconstruction conferences and to perform construction-phase observations.
Give Constructors a Complete Report and GuidanceSome owners and design professionals mistakenly believe they can shift unanticipated-subsurface-conditions liability to constructors by limiting the information they provide for bid preparation. To help prevent the costly, contentious problems this practice has caused, include the complete geotechnical-engineering report, along with any attachments or appendices, with your contract documents, but be certain to note
conspicuously that you’ve included the material for information purposes only. To avoid misunderstanding, you may also want to note that
“informational purposes” means constructors have no right to rely on
the interpretations, opinions, conclusions, or recommendations in the
report. Be certain that constructors know they may learn about specific
project requirements, including options selected from the report, only
from the design drawings and specifications. Remind constructors
that they may perform their own studies if they want to, and be sure to
allow enough time to permit them to do so. Only then might you be in
a position to give constructors the information available to you, while
requiring them to at least share some of the financial responsibilities
stemming from unanticipated conditions. Conducting prebid and
preconstruction conferences can also be valuable in this respect.
Read Responsibility Provisions Closely
Some client representatives, design professionals, and constructors do
not realize that geotechnical engineering is far less exact than other
engineering disciplines. This happens in part because soil and rock on
project sites are typically heterogeneous and not manufactured materials
with well-defined engineering properties like steel and concrete. That
lack of understanding has nurtured unrealistic expectations that have
resulted in disappointments, delays, cost overruns, claims, and disputes.
To confront that risk, geotechnical engineers commonly include
explanatory provisions in their reports. Sometimes labeled “limitations,”
many of these provisions indicate where geotechnical engineers’
responsibilities begin and end, to help others recognize their own
responsibilities and risks. Read these provisions closely. Ask questions.
Your geotechnical engineer should respond fully and frankly.
Geoenvironmental Concerns Are Not Covered
The personnel, equipment, and techniques used to perform an
environmental study – e.g., a “phase-one” or “phase-two” environmental
site assessment – differ significantly from those used to perform a
geotechnical-engineering study. For that reason, a geotechnical-engineering
report does not usually provide environmental findings, conclusions, or
recommendations; e.g., about the likelihood of encountering underground
storage tanks or regulated contaminants. Unanticipated subsurface
environmental problems have led to project failures. If you have not
obtained your own environmental information about the project site,
ask your geotechnical consultant for a recommendation on how to find
environmental risk-management guidance.
Obtain Professional Assistance to Deal with Moisture Infiltration and Mold
While your geotechnical engineer may have addressed groundwater,
water infiltration, or similar issues in this report, the engineer’s
services were not designed, conducted, or intended to prevent
migration of moisture – including water vapor – from the soil
through building slabs and walls and into the building interior, where
it can cause mold growth and material-performance deficiencies.
Accordingly, proper implementation of the geotechnical engineer’s recommendations will not of itself be sufficient to prevent moisture infiltration. Confront the risk of moisture infiltration by
including building-envelope or mold specialists on the design team. Geotechnical engineers are not building-envelope or mold specialists.
Copyright 2019 by Geoprofessional Business Association (GBA). Duplication, reproduction, or copying of this document, in whole or in part, by any means whatsoever, is strictly prohibited, except with GBA’s specific written permission. Excerpting, quoting, or otherwise extracting wording from this document is permitted only with the express written permission of
GBA, and only for purposes of scholarly research or book review. Only members of GBA may use this document or its wording as a complement to or as an element of a report of any kind. Any other firm, individual, or other entity that so uses this document without being a GBA member could be committing negligent or intentional (fraudulent) misrepresentation.
Telephone: 301/565-2733
e-mail: info@geoprofessional.org www.geoprofessional.org
June 10, 2020
ES-5946.03
GMD Development, LLC
520 Pike Street, Suite 1010
Seattle, Washington 98101
Attention: Mr. Thomas Geffner
Dear Mr. Geffner:
Earth Solutions NW, LLC (ESNW) is pleased to present this report titled “Updated Geotechnical
Engineering Study, Proposed Renton Apartments, 615 and 617 Williams Avenue South, Renton,
Washington”. This report was updated to reference the most current plans and provide additional
subsurface exploration.
Based on the conditions observed during our fieldwork, the site is underlain primarily by a
relatively thick layer of very loose to medium dense alluvial sediments consisting predominately
of silt and sand layers. The seasonal groundwater level was observed at depths of about six to
nine feet below existing grades. Groundwater levels fluctuate and may become shallower during
the wetter winter months.
Based on the results of our study, the proposed apartment building should be supported by a pile
foundation system advanced through the loose soils to bear on firm native soils, or on
conventional shallow foundations after completion of a ground improvement program (rammed
aggregate piers, etc.). Recommendations for foundation design and other geotechnical
recommendations are provided in this study.
The opportunity to be of service to you is appreciated. If you have any questions regarding the
content of this geotechnical engineering study, please call.
Sincerely,
EARTH SOLUTIONS NW, LLC
Adam Z. Shier, L.G.
Project Geologist
15365 N.E. 90th Street, Suite 100 • Redmond, WA 98052 •(425) 449-4704 • FAX (425) 449-4711
Earth Solutions NW LLC
Geotechnical Engineering, Construction
Observation/Testing and Environmental Services
Earth Solutions NW, LLC
Table of Contents
ES-5946.03
PAGE
INTRODUCTION ................................................................................. 1
General..................................................................................... 1
Project Description ................................................................. 2
SITE CONDITIONS ............................................................................. 2
Surface ..................................................................................... 2
Subsurface .............................................................................. 2
Groundwater ................................................................. 3
Geologically Hazardous Areas .............................................. 3
Seismic Hazard Areas .................................................. 4
Coal Mine Hazard Areas .............................................. 4
DISCUSSION AND RECOMMENDATIONS ....................................... 4
General..................................................................................... 4
Site Preparation and Earthwork ............................................. 5
Foundations ............................................................................ 6
Ground Improvement ................................................... 6
Pile Foundations .......................................................... 6
Building Slabs ......................................................................... 7
Retaining Walls ....................................................................... 7
Seismic Considerations ......................................................... 8
Drainage................................................................................... 8
Utility Trench Backfill ............................................................. 8
Pavement Sections ................................................................. 9
LIMITATIONS ...................................................................................... 9
Additional Services ................................................................. 9
Earth Solutions NW, LLC
Table of Contents
Cont’d
ES-5946.03
GRAPHICS
Plate 1 Vicinity Map
Plate 2 Subsurface Exploration Plan
Plate 3 Retaining Wall Drainage Detail
Plate 4 Footing Drain Detail
APPENDICES
Appendix A Subsurface Exploration
Boring and Test Pit Logs
Appendix B Laboratory Test Results
Earth Solutions NW, LLC
UPDATED
GEOTECHNICAL ENGINEERING STUDY
PROPOSED RENTON APARTMENTS
615 AND 617 WILLIAMS AVENUE SOUTH
RENTON, WASHINGTON
ES-5946.03
INTRODUCTION
General
This updated geotechnical engineering study was prepared for the proposed apartment building
to be constructed at 615 and 617 Williams Avenue in Renton, Washington. The purpose of this
study was to prepare geotechnical recommendations for the proposed development. Our scope
of services for completing this geotechnical engineering study included the following:
Subsurface exploration and laboratory testing of soil samples obtained during subsurface
exploration;
Engineering analyses, and;
Preparation of this report.
As part of our report preparation, the following documents were reviewed:
Architectural Site Plan, prepared by Studio19 Architects;
Geologic Map of the Renton Quadrangle, King County, Washington, 1965, by D.R.
Mullineaux;
Geologic Structure Map of Renton Coal Mine, 1920, by Watkins Evans;
Amendments to the King County Surface Water Design Manual, February 2010, Provided
by the City of Renton, and;
The Natural Resources Conservation Service Web Soil Survey (WSS).
GMD Development, LLC ES-5946.03
June 10, 2020 Page 2
Earth Solutions NW, LLC
Project Description
We understand the site will be developed with an apartment building and associated
improvements. A preliminary site layout plan was available to us at the time of this report
preparation, and we anticipate the building will be six stories in height with one level of concrete
and five levels of wood frame supported on a post-tensioned concrete slab. No grading plans
were available at the time of writing this report; however, we anticipate the parking area will have
a finish floor elevation matching the existing grade. The building will likely incorporate a post-
tensioned slab configuration. If grades will be raised more than one foot, the recommendations
herein must be re-evaluated by ESNW.
We anticipate foundation loads will be on the order of 4 to 6 kips per lineal foot for continuous
footings, column loads on the order of 300 to 500 kips and slab-on-grade loading will likely be on
the order of 150 pounds per square foot (psf). A preload program to reduce settlement on site
will likely be necessary due to the soil conditions encountered.
If the above design assumptions are incorrect or change, ESNW should be contacted to review
the recommendations in this report. ESNW should review the final design to verify that our
geotechnical recommendations have been incorporated.
SITE CONDITIONS
Surface
The site is located at 615 and 617 Williams Avenue in Renton, Washington. The site is irregular
in shape and is bordered to the north and west by mixed commercial and residential properties,
to the south by South Grady Way and to the east by Williams Avenue South. The 617 address
is currently occupied by a billboard, and the 615 address contains a single-family residence. The
overall site topography is relatively flat with little discernible elevation change and vegetation
consists primarily of field grass with sparse trees near Williams Avenue. The limits of the property
are approximately delineated on the Subsurface Exploration Plan (Plate 2).
Subsurface
Two test pits were excavated across accessible areas of the site for purposes of assessing soil
conditions and characterizing the site soils on March 20, 2018. A boring was completed on April
5, 2018 to further classify the site soils. Three additional borings (B-101, B-102, and B-103) were
advanced across the subject site on May 22, 2020 as part of this updated geotechnical
engineering study. Please refer to the test pit and boring logs provided in Appendix A for a more
detailed description of the subsurface conditions. Additionally, two groundwater wells were
installed at boring locations B-101 and B-102 to monitor groundwater throughout the 2020-2021
winter season.
GMD Development, LLC ES-5946.03
June 10, 2020 Page 3
Earth Solutions NW, LLC
At our test sites, a relatively deep topsoil layer was encountered extending up to about two feet
below existing grades. The topsoil was characterized by a dark brown color and organic content.
fill was not encountered; however, fill may be present in areas where former structures were
removed. Underlying the topsoil, very loose to medium dense alluvial and floodplain deposits
consisting of non-plastic silt (ML), silty fine sand (SM) and sand (SP, SP-SM) were encountered
extending to the maximum exploration depth of 46.5 feet. A thin layer of peat (PT) was
encountered at boring location B-1 and B-101 from about 21 to 21.5 feet below existing grade.
Soil conditions improved to a medium dense state at depths of about 20 to 30 feet. The
referenced geologic map of the area identifies alluvial soil deposits modified by widespread
artificial fill throughout the site and surrounding areas. The referenced WSS resource indicates
the site is underlain predominantly by Urban land (Ur) soils. This soil unit is used in areas of
extensive grading.
The soil conditions observed at our test sites generally correlates with historic fill underlain by
alluvial deposition.
Groundwater
The seasonal groundwater table was observed at an average depth of about six to nine feet
below existing grades during our fieldwork (March and April 2018) which occurred during a record
rainfall season and between 9 to 10 feet during our May 2020 fieldwork. However, the seasonal
high groundwater elevation may rise to a shallower depth than the elevation observed during our
fieldwork depending on the seasonal rainfall.
It should be noted that groundwater elevations fluctuate depending on many factors, including
precipitation duration and intensity, the time of year, and soil conditions. In general, groundwater
levels are generally higher during the wetter, winter months. With respect to the proposed
development activities, groundwater should be expected in site excavations, particularly
underground utility and vault excavations. We understand underground building levels are not
planned as part of the proposed construction. In this respect, extensive measures for controlling
groundwater and temporary dewatering are not anticipated. However, temporary dewatering of
underground utility excavations should be expected throughout some areas of the site. Flowing
sand condition may be encountered depending on the time of year deeper excavations occur.
Additionally, two groundwater wells were installed at boring locations B-101 and B-102 to monitor
groundwater throughout the 2020-2021 winter season.
Geologically Hazardous Areas
As part of this study, the site and proposed development areas were evaluated for the presence
of geologically hazardous areas. As part of our evaluation, Chapter 4-3-050 of the Renton
Municipal Code was reviewed.
GMD Development, LLC ES-5946.03
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Earth Solutions NW, LLC
Seismic Hazard Areas
Liquefaction is a phenomenon where saturated or loose soils suddenly lose internal strength in
response to increased pore water pressures resulting from an earthquake or other intense ground
shaking. The liquefaction susceptibility for the subject site in the current configuration is high.
We used the Liquefy5 computer program to assess the overall susceptibility of the site to
liquefaction and associated settlement resulting from the maximum credible earthquake event for
this area. We determined the peak ground acceleration (PGA) using the USGS online calculation
program that provides current information for a particular address location. Using this resource,
a design PGA of 0.4g was used. The computer model predicted significant settlement may occur
from liquefaction occurring after the site is subjected to the design PGA. We used this
assessment to aid in developing foundation support recommendations that would adequately
mitigate differential settlement and maintain adequate levels of life-safety subsequent to a design
earthquake event. We would expect total settlements in the range of five to ten inches and
differential settlements of between two to four inches may result from strong seismic shaking to
occur within the existing soils.
Providing a uniform subgrade and foundation support using either piles or a ground improvement
program will reduce the potential for differential settlement that may result from a strong seismic
event. With foundation support as recommended in this report, we do not anticipate life-safety
will be compromised resulting from liquefaction; however, damage should be expected from
seismic shaking.
Coal Mine Hazard Areas
We reviewed the referenced coal mine hazard mapping collection to classify existing coal mine
hazard areas on the site in general accordance with chapter 4-3-050 of the Renton Municipal
Code. Based on our document review, it appears that a mine opening located southwest of the
subject property was likely used as an access-way which trended south toward seam workings.
The mine entrance is located southwest of Parcel Number 172305-9069, and is not present on
the property. Based on the reviewed information, the site should be considered a “Declassified”
coal mine hazard because no records of coal mine activity are present on or within 500 feet of
the identified mine opening. The risk of subsidence or related damage associated with coal mine
hazards does not exist on this site.
DISCUSSION AND RECOMMENDATIONS
General
Based on the results of our updated study, construction of the proposed apartment building is
feasible from a geotechnical standpoint. The primary geotechnical considerations associated
with the proposed development include foundation support, minimizing post-construction
settlements, structural fill placement, and the suitability of the on-site soils for use as structural
fill.
GMD Development, LLC ES-5946.03
June 10, 2020 Page 5
Earth Solutions NW, LLC
The proposed apartment building should be supported by a pile foundation system advanced
through the loose soils to bear on firm native soils, or on conventional shallow foundations after
completion of a ground improvement program (rammed aggregate piers, etc.).
The presence of groundwater in excavations that extend below about six to nine feet should be
anticipated. The groundwater table will likely fluctuate throughout the year, depending on many
factors and may rise above the depth where it was observed during the fieldwork. Appropriate
de-watering measures should be incorporated into site designs prior to construction.
ESNW should review final site layout and plans to confirm the geotechnical recommendations in
this report have been incorporated into the plans and to provide supplemental recommendations,
as appropriate.
This study has been prepared for the exclusive use of the GMD Development, LLC and their
representatives. No warranty, expressed or implied, is made. This study has been prepared in
a manner consistent with the level of care and skill ordinarily exercised by other members of the
profession currently practicing under similar conditions in this area.
Site Preparation and Earthwork
With respect to earthwork, the primary considerations at this site are related to structural fill
compaction, moisture sensitivity of the site soils, and foundation support. From a geotechnical
standpoint, the soils encountered at the test sites may not be suitable for use as structural fill
depending on the moisture content at the time of grading. Successful use of the on-site soils will
largely be dictated by the moisture content of the soils at the time of placement and compaction.
The soils encountered at the test sites above the groundwater table were generally in a moist to
wet condition at the time of the exploration (March and April 2018). Soils encountered during site
excavations that are excessively over the optimum moisture content may require moisture
conditioning prior to placement and compaction.
Successful placement and compaction of the on-site soils during periods of extended
precipitation will likely be difficult. If the on-site soils cannot be successfully compacted, the use
of an imported soil may be necessary. Imported soil intended for use as structural fill should
consist of a well graded granular soil with a moisture content that is at or near the optimum level.
During wet weather conditions, imported soil intended for use as structural fill should consist of a
well graded granular soil with a fines content of 5 percent or less defined as the percent passing
the #200 sieve, based on the minus three-quarter inch fraction.
Structural fill is defined as compacted soil placed in foundation, slab-on-grade, and roadway
areas. Fills placed to construct permanent slopes and throughout retaining wall and utility trench
backfill areas are also considered structural fill. Soils placed in structural areas should be
compacted to a relative compaction of 95 percent, based on the maximum dry density as
determined by the Modified Proctor Method (ASTM D-1557) and placed in maximum 12 inch lifts.
Temporary construction entrances and drive lanes, consisting of at least 12 inches of quarry
spalls can be considered in order to minimize off-site soil tracking and to provide a relatively firm
temporary road surface. Erosion control measures should consist of silt fencing and surface
water runoff controls.
GMD Development, LLC ES-5946.03
June 10, 2020 Page 6
Earth Solutions NW, LLC
Foundations
The soils underlying this site are relatively weak and contain compressible layers. Groundwater
was observed at a depth of about six to nine feet below existing grade. Foundations must be
designed to reduce the effects of liquefaction-induced settlement and provide adequate static
support for the new building.
Based on the results of our study and our understanding of the project, the proposed apartment
building should be supported by a pile foundation system advanced through the loose soils to
bear on firm native soils, or on conventional shallow foundations after completion of a ground
improvement program (rammed aggregate piers, etc.). Differential settlement between pile and
non-pile supported elements will occur.
Ground Improvement
Rammed aggregate piers (RAPs) stone columns or other vibro-installation intermediate elements
can be considered as ground-improvement for foundation support. Vibro-installed elements
provide ground improvement between elements, essentially providing ground improvement over
a uniform area. This method provides increased resistance to liquefaction-induced settlement
and would immediately improve the surrounding soil where installed. For preliminary design
considerations, we recommend ground improvement elements be installed to a minimum depth
of 40 feet. ESNW should review proposed designs to confirm the soil parameters used are
representative of the site conditions. For preliminary considerations, foundations supported by
ground improvement elements can be designed 4,000 pounds per square foot (psf) of allowable
bearing capacity.
Pile Foundations
If piles will be pursued for foundation support, we provide capacities for 18 inch diameter
augercast piles. Other pile diameters can also be considered, and should be assessed by ESNW.
The following allowable capacities for 18 inch diameter augercast piles should be used for
foundation design.
Allowable Capacities
* Allowable uplift capacity does not include weight of the pile or pier.
The above allowable capacity is based on a pile length of 40 feet to bear within the medium dense
to dense soil deposits. A higher pile capacity is possible, however, an additional boring would be
necessary to confirm soil conditions at depth. A representative of ESNW should observe the
installation of the foundations and assess pile foundation lengths based on the soil conditions
encountered during the installation.
Lateral Capacities
Diameter
(in.) Compression (kps) Uplift (kps)* 0.5 Inch (kips)
Deflection
1.0 Inch (kips)
Deflection
18 100 55 10 16
GMD Development, LLC ES-5946.03
June 10, 2020 Page 7
Earth Solutions NW, LLC
Building Slabs
Building slabs should be structurally supported by the pile foundation system if piles are used. If
the ground improvement option is used for foundation support, building slabs can be supported
on grade provided ground improvement program includes slab areas. A capillary break
consisting of a minimum of four inches of free draining crushed rock or gravel should be placed
below the slab. The free draining material should have a fines content of five percent or less
(percent passing the #200 sieve, based on the minus three-quarters inch fraction). In areas
where slab moisture is undesirable, installation of a vapor barrier below the slab should be
considered.
Retaining Walls
If retaining walls will be used for this project, they should be designed to resist earth pressures
and applicable surcharge loads. For design, the following parameters can be assumed for
retaining wall design:
Active earth pressure (yielding condition) 35 pcf (equivalent fluid)
At-rest earth pressure (restrained condition) 55 pcf
Traffic surcharge (passenger vehicles) 70 psf (rectangular distribution)*
Passive earth pressure 300 pcf (equivalent fluid)
Coefficient of friction 0.40
Seismic surcharge 8H psf**
* Where applicable
** Where H equals the retained height (in feet)
Additional surcharge loading from foundations, sloped backfill, or other loading should be
included in the retaining wall design. Drainage should be provided behind retaining walls such
that hydrostatic pressures do not develop. If drainage is not provided, hydrostatic pressures
should be included in the wall design.
Retaining walls should be backfilled with free draining material that extends along the height of
the wall, and a distance of at least 18 inches behind the wall. The upper one foot of the wall
backfill can consist of a less permeable soil, if desired. A perforated drain pipe should be placed
along the base of the wall, and connected to an appropriate discharge location.
GMD Development, LLC ES-5946.03
June 10, 2020 Page 8
Earth Solutions NW, LLC
Seismic Considerations
The 2015 IBC recognizes ASCE for seismic site class definitions. If the project will be permitted
under the 2015 IBC, in accordance with Table 20.3-1 of ASCE, Minimum Design Loads for
Buildings and Other Structures, Site Class E, should be used for design.
In our opinion, liquefaction susceptibility at this site is high due to the soil gradation and
groundwater conditions. Foundations must be designed to resist or reduce the effects of
liquefaction-induced settlement, which can be mitigated using either ground improvement or
piles, as discussed earlier in this report.
Drainage
The seasonal groundwater table was observed at an average depth of approximately six to nine
feet below existing grades during our fieldwork (March and April 2018). As such, the presence
of groundwater should be expected in deeper site excavations, such as those required for utility
improvements or detention vault areas. Temporary measures to control groundwater seepage
and surface water runoff during construction will likely involve interceptor trenches and sumps,
as necessary. Where heavy seepage conditions are encountered, particularly in deeper
excavations, conventional dewatering methods such as pumping wells or well points may be
necessary.
Perimeter drains should be installed below the invert of foundations or pile caps and grade
beams. A typical perimeter drain detail is provided on Plate 3.
Utility Trench Backfill
In our opinion, the soils observed at the test sites are not suitable for direct support of utilities in
the current condition and will require stabilization prior to installing utilities. Moderate to heavy
caving of the site soils should be expected during deeper site excavations. Means of shoring or
sloping excavation walls should be accounted for prior to construction. Organic or highly
compressible soils encountered in the trench excavations should not be used for supporting
utilities. Subgrade stabilization will likely be required and may consist of quarry spalls placed
over a woven geotextile such as Mirafi 500X or approved alternative. In general, the on-site soils
observed at the test sites are not suitable for use as structural backfill in the utility trench
excavations due to the predominately fine-grained texture. Moisture conditioning of the soils may
be necessary at some locations prior to use as structural fill. Utility trench backfill should be
placed and compacted to the specifications of structural fill provided in this report, or to the
applicable specifications of the city or county jurisdictions, as appropriate.
GMD Development, LLC ES-5946.03
June 10, 2020 Page 9
Earth Solutions NW, LLC
Pavement Sections
The performance of site pavements is largely related to the condition of the underlying subgrade.
To ensure adequate pavement performance, the subgrade should be in a firm and unyielding
condition when subjected to proofrolling with a loaded dump truck. Structural fill in pavement
areas should be compacted to the specifications detailed in the Site Preparation and Earthwork
section of this report. It is possible that soft, wet, or otherwise unsuitable subgrade areas may
still exist after base grading activities. Areas containing unsuitable or yielding subgrade
conditions may require remedial measures such as overexcavation and thicker crushed rock or
structural fill sections prior to pavement. Cement treatment of the subgrade soil can also be
considered for stabilizing pavement subgrade areas if allowed by local jurisdictions.
For relatively lightly loaded pavements subjected to automobiles and occasional truck traffic, the
following sections can be considered:
Two inches of asphalt concrete (AC) placed over four inches of crushed rock base (CRB),
or;
Two inches of AC placed over three inches of asphalt treated base (ATB).
Heavier traffic areas generally require thicker pavement sections depending on site usage,
pavement life expectancy, and site traffic. For preliminary design purposes, the following
pavement sections for occasional truck traffic areas can be considered:
Three inches of asphalt concrete (AC) placed over six inches of crushed rock base (CRB),
or;
Three inches of AC placed over four and one-half inches of asphalt treated base (ATB).
The AC, ATB and CRB materials should conform to WSDOT specifications.
ESNW can provide appropriate pavement section design recommendations for truck traffic areas
and right-of-way improvements, as necessary. Additionally, the City of Renton Pavement Design
Standards may supersede the recommendations provided in this report.
LIMITATIONS
The recommendations and conclusions provided in this geotechnical engineering study are
professional opinions consistent with the level of care and skill that is typical of other members in
the profession currently practicing under similar conditions in this area. A warranty is not
expressed or implied. Variations in the soil and groundwater conditions observed at the test pit
and boring locations may exist, and may not become evident until construction. ESNW should
reevaluate the conclusions in this geotechnical engineering study if variations are encountered.
Additional Services
ESNW should have an opportunity to review the final design with respect to the geotechnical
recommendations provided in this report. ESNW should also be retained to provide testing and
consultation services during construction.
Geotechnical Engineering,Construction
Observation/Testing and Environmental Services
Drwn. CAM
Checked AZS Date June 2020
Date 06/09/2020 Proj. No. 5946.03
Plate 1
Earth Solutions NWLLCEarthSolutionsNWLLC
EarthSolutionsNWLLC
Vicinity Map
Renton Apartments
Renton, Washington
Reference:
King County, Washington
OpenStreetMap.org
NORTH
NOTE: This plate may contain areas of color. ESNW cannot be
responsible for any subsequent misinterpretation of the information
resulting from black & white reproductions of this plate.
Renton
SITE
Plate
Proj. No.
Date
Checked By
Drwn. ByEarth Solutions NWLLCGeotechnical Engineering,ConstructionObservation/Testing and Environmental ServicesEarthSolutionsNWLLCEarthSolutionsNWLLCss..gg rr aa dd yyww aa yywwiilllliiaammssaavveennuueess..TP-1
TP-2
B-1
B-101
B-102
B-103
NOTE: This plate may contain areas of color. ESNW cannot be
responsible for any subsequent misinterpretation of the information
resulting from black & white reproductions of this plate.
NOTE: The graphics shown on this plate are not intended for design
purposes or precise scale measurements, but only to illustrate the
approximate test locations relative to the approximate locations of
existing and / or proposed site features. The information illustrated
is largely based on data provided by the client at the time of our
study. ESNW cannot be responsible for subsequent design changes
or interpretation of the data by others.
LEGEND
Approximate Location of
ESNW Boring, Proj. No.
ES-5946.03, May 2020
Approximate Location of
ESNW Boring, Proj. No.
ES-5946, April 2018
Approximate Location of
ESNW Test Pit, Proj. No.
ES-5946, March 2018
Subject Site
Proposed Building
Existing Building
TP-1
NOT - TO - SCALE
NORTH Subsurface Exploration PlanRenton ApartmentsRenton, Washington
B-101
B-1
CAM
AZS
06/09/2020
5946.03
2
Drwn. CAM
Checked AZS Date June 2020
Date 06/09/2020 Proj. No. 5946.03
Plate 3
Earth Solutions NWLLCEarthSolutionsNWLLC
EarthSolutionsNWLLC Geotechnical Engineering,Construction
Observation/Testing and Environmental Services
Retaining Wall Drainage Detail
Renton Apartments
Renton, Washington
NOTES:
Free-draining Backfill should consist
of soil having less than 5 percent fines.
Percent passing No. 4 sieve should be
25 to 75 percent.
Sheet Drain may be feasible in lieu
of Free-draining Backfill, per ESNW
recommendations.
Drain Pipe should consist of perforated,
rigid PVC Pipe surrounded with 1-inch
Drain Rock.
LEGEND:
Free-draining Structural Backfill
1-inch Drain Rock
18" Min.
Structural
Fill
Perforated Rigid Drain Pipe
(Surround in Drain Rock)
SCHEMATIC ONLY - NOT TO SCALE
NOT A CONSTRUCTION DRAWING
Drwn. CAM
Checked AZS Date June 2020
Date 06/09/2020 Proj. No. 5946.03
Plate 4
Earth Solutions NWLLCEarthSolutionsNWLLC
EarthSolutionsNWLLC Geotechnical Engineering,Construction
Observation/Testing and Environmental Services
Footing Drain Detail
Renton Apartments
Renton, Washington
Slope
Perforated Rigid Drain Pipe
(Surround in Drain Rock)
18" Min.
NOTES:
Do NOT tie roof downspouts
to Footing Drain.
Surface Seal to consist of
12" of less permeable, suitable
soil. Slope away from building.
LEGEND:
Surface Seal: native soil or
other low-permeability material.
1-inch Drain Rock
SCHEMATIC ONLY - NOT TO SCALE
NOT A CONSTRUCTION DRAWING
Earth Solutions NW, LLC
Appendix A
Subsurface Exploration
Boring and Test Pit Logs
ES-5946.03
The subsurface conditions at the site were explored by excavation two test pits and drilling four
boring. The approximate exploration locations are illustrated on Plate 2 of this report. The logs
are provided in this Appendix. The subsurface exploration was completed in March and April
2018 and May 2020. The boring was excavated to a maximum depth of 46.5 feet below existing
grades.
Logs of the borings excavated by ESNW are presented in Appendix A. The final logs represent
the interpretations of the field logs and the results of laboratory analyses. The stratification lines
on the logs represent the approximate boundaries between soil types. In actuality, the transitions
may be more gradual.
GRAVEL
AND
GRAVELLYSOILS
CLAYEY GRAVELS, GRAVEL - SAND -
CLAY MIXTURES
WELL-GRADED SANDS, GRAVELLYSANDS, LITTLE OR NO FINES
POORLY-GRADED SANDS,GRAVELLY SAND, LITTLE OR NO
FINES
SILTY SANDS, SAND - SILTMIXTURES
CLAYEY SANDS, SAND - CLAYMIXTURES
INORGANIC SILTS AND VERY FINESANDS, ROCK FLOUR, SILTY OR
CLAYEY FINE SANDS OR CLAYEYSILTS WITH SLIGHT PLASTICITY
INORGANIC CLAYS OF LOW TO
MEDIUM PLASTICITY, GRAVELLYCLAYS, SANDY CLAYS, SILTY CLAYS,LEAN CLAYS
ORGANIC SILTS AND ORGANICSILTY CLAYS OF LOW PLASTICITY
INORGANIC SILTS, MICACEOUS OR
DIATOMACEOUS FINE SAND ORSILTY SOILS
INORGANIC CLAYS OF HIGHPLASTICITY
SILTSANDCLAYS
MORE THAN 50%
OF MATERIAL ISLARGER THANNO. 200 SIEVE
SIZE
MORE THAN 50%OF MATERIAL IS
SMALLER THANNO. 200 SIEVESIZE
MORE THAN 50%OF COARSEFRACTION
PASSING ON NO.4 SIEVE
MORE THAN 50%OF COARSEFRACTION
RETAINED ON NO.4 SIEVE
SOIL CLASSIFICATION CHART
(APPRECIABLEAMOUNT OF FINES)
(APPRECIABLE
AMOUNT OF FINES)
(LITTLE OR NO FINES)
FINEGRAINEDSOILS
SAND
AND
SANDY
SOILS
SILTS
AND
CLAYS
ORGANIC CLAYS OF MEDIUM TO
HIGH PLASTICITY, ORGANIC SILTS
PEAT, HUMUS, SWAMP SOILS WITHHIGH ORGANIC CONTENTS
LETTERGRAPH
SYMBOLSMAJOR DIVISIONS
COARSE
GRAINEDSOILS
TYPICAL
DESCRIPTIONS
WELL-GRADED GRAVELS, GRAVEL -SAND MIXTURES, LITTLE OR NO
FINES
POORLY-GRADED GRAVELS,
GRAVEL - SAND MIXTURES, LITTLEOR NO FINES
SILTY GRAVELS, GRAVEL - SAND -
SILT MIXTURES
CLEANGRAVELS
GRAVELS WITH
FINES
CLEAN SANDS
(LITTLE OR NO FINES)
SANDS WITH
FINES
LIQUID LIMITLESS THAN 50
LIQUID LIMITGREATER THAN 50
HIGHLY ORGANIC SOILS
DUAL SYMBOLS are used to indicate borderline soil classifications.
The discussion in the text of this report is necessary for a proper understanding of the nature
of the material presented in the attached logs.
GW
GP
GM
GC
SW
SP
SM
SC
ML
CL
OL
MH
CH
OH
PT
Earth Solutions NW LLC
SS
SS
SS
SS
SS
33
33
50
50
67
2-2-2
(4)
1-2-2
(4)
1-1-1
(2)
1-6-1
(7)
2-2-2
(4)
MC = 26.40%
MC = 30.30%
MC = 58.40%
MC = 41.20%
Fines = 68.20%
MC = 30.10%
SM
ML
SM
Brown silty SAND, very loose, moist
Gray sandy SILT, very loose, moist to wet
[USDA Classification: LOAM]
Gray silty SAND, very loose, wet
-groundwater table
6.0
13.0
NOTES Surface Conditions: field grass
GROUND ELEVATION
LOGGED BY AZS
DRILLING METHOD HSA
HOLE SIZE
DRILLING CONTRACTOR Boretec1, Inc.GROUND WATER LEVELS:
CHECKED BY KRC
DATE STARTED 5/22/20 COMPLETED 5/22/20
AT END OF DRILLING ---
AFTER DRILLING ---
AT TIME OF 14.5 ft
(Continued Next Page)SAMPLE TYPENUMBERDEPTH(ft)0
5
10
15
20
PAGE 1 OF 3
BORING NUMBER B-101
PROJECT NUMBER ES-5946.03 PROJECT NAME Renton Apartments
GENERAL BH / TP / WELL - 5946-3.GPJ - GRAPHICS TEMPLATE.GDT - 6/10/20Earth Solutions NW, LLC
15365 N.E. 90th Street, Suite 100
Redmond, Washington 98052
Telephone: 425-449-4704
Fax: 425-449-4711
RECOVERY %BLOWCOUNTS(N VALUE)TESTS
U.S.C.S.MATERIAL DESCRIPTION
GRAPHICLOG
SS
SS
SS
SS
SS
100
100
100
100
100
1-2-2
(4)
2-3-2
(5)
5-3-8
(11)
7-11-11
(22)
8-15-11
(26)
MC = 35.10%MC = 108.90%
MC = 24.60%
MC = 11.90%
MC = 9.50%
MC = 15.80%
Fines = 4.10%
SM
SP
Gray silty SAND, very loose, wet (continued)-1"-2" sand lens
-6" organic lens (peat)
Gray poorly graded SAND, loose, wet
-trace organics
-becomes poorly graded sand with gravel
-becomes medium dense
[USDA Classification: gravelly coarse SAND]
25.0
42.9
(Continued Next Page)SAMPLE TYPENUMBERDEPTH(ft)20
25
30
35
40
PAGE 2 OF 3
BORING NUMBER B-101
PROJECT NUMBER ES-5946.03 PROJECT NAME Renton Apartments
GENERAL BH / TP / WELL - 5946-3.GPJ - GRAPHICS TEMPLATE.GDT - 6/10/20Earth Solutions NW, LLC
15365 N.E. 90th Street, Suite 100
Redmond, Washington 98052
Telephone: 425-449-4704
Fax: 425-449-4711
RECOVERY %BLOWCOUNTS(N VALUE)TESTS
U.S.C.S.MATERIAL DESCRIPTION
GRAPHICLOG
SS 100 9-8-10
(18)MC = 23.90%
SP
Gray poorly graded SAND with gravel, medium dense, wet (continued)
Boring terminated at 46.5 feet below existing grade. Groundwater tableencountered at 14.5 feet during drilling. 2" PVC standpipe installed to bottom of
boring. Lower 20.0 feet slotted. Well ID: BJZ554. Boring backfilled withbentonite/sand.
46.5SAMPLE TYPENUMBERDEPTH(ft)45
PAGE 3 OF 3
BORING NUMBER B-101
PROJECT NUMBER ES-5946.03 PROJECT NAME Renton Apartments
GENERAL BH / TP / WELL - 5946-3.GPJ - GRAPHICS TEMPLATE.GDT - 6/10/20Earth Solutions NW, LLC
15365 N.E. 90th Street, Suite 100
Redmond, Washington 98052
Telephone: 425-449-4704
Fax: 425-449-4711
RECOVERY %BLOWCOUNTS(N VALUE)TESTS
U.S.C.S.MATERIAL DESCRIPTION
GRAPHICLOG
SS
SS
SS
SS
SS
33
50
33
50
67
2-2-1
(3)
1-1-0
(1)
1-1-1
(2)
1-0-1
(1)
1-1-0
(1)
MC = 13.30%
MC = 43.60%
MC = 82.30%
MC = 37.30%
MC = 92.90%
SM
ML
Brown silty SAND, very loose, moist
Gray SILT, very loose, wet
-wood debris
-wood debris
-groundwater table
4.5
NOTES Surface Conditions: grass
GROUND ELEVATION
LOGGED BY AZS
DRILLING METHOD HSA
HOLE SIZE
DRILLING CONTRACTOR Boretec1, Inc.GROUND WATER LEVELS:
CHECKED BY KRC
DATE STARTED 5/22/20 COMPLETED 5/22/20
AT END OF DRILLING ---
AFTER DRILLING ---
AT TIME OF 13.0 ft
(Continued Next Page)SAMPLE TYPENUMBERDEPTH(ft)0
5
10
15
20
PAGE 1 OF 3
BORING NUMBER B-102
PROJECT NUMBER ES-5946.03 PROJECT NAME Renton Apartments
GENERAL BH / TP / WELL - 5946-3.GPJ - GRAPHICS TEMPLATE.GDT - 6/10/20Earth Solutions NW, LLC
15365 N.E. 90th Street, Suite 100
Redmond, Washington 98052
Telephone: 425-449-4704
Fax: 425-449-4711
RECOVERY %BLOWCOUNTS(N VALUE)TESTS
U.S.C.S.MATERIAL DESCRIPTION
GRAPHICLOG
SS
SS
SS
SS
SS
100
100
100
100
100
2-2-4
(6)
2-4-9
(13)
4-6-5
(11)
2-4-4
(8)
3-4-6
(10)
MC = 30.00%
MC = 16.90%
Fines = 4.10%
MC = 26.90%
MC = 18.30%
MC = 20.70%
ML
SP-SM
SP
Gray SILT, very loose, wet (continued)
Gray poorly graded SAND with silt, loose, wet/saturated
[USDA Classification: very gravelly coarse SAND]
Gray poorly graded SAND with gravel, medium dense, wet/saturated
-becomes loose
-becomes medium dense
20.5
25.5
(Continued Next Page)SAMPLE TYPENUMBERDEPTH(ft)20
25
30
35
40
PAGE 2 OF 3
BORING NUMBER B-102
PROJECT NUMBER ES-5946.03 PROJECT NAME Renton Apartments
GENERAL BH / TP / WELL - 5946-3.GPJ - GRAPHICS TEMPLATE.GDT - 6/10/20Earth Solutions NW, LLC
15365 N.E. 90th Street, Suite 100
Redmond, Washington 98052
Telephone: 425-449-4704
Fax: 425-449-4711
RECOVERY %BLOWCOUNTS(N VALUE)TESTS
U.S.C.S.MATERIAL DESCRIPTION
GRAPHICLOG
SS 100 5-5-7
(12)MC = 16.20%
SP
Gray poorly graded SAND with gravel, medium dense, wet/saturated(continued)
Boring terminated at 46.5 feet below existing grade. Groundwater tableencountered at 13.0 feet during drilling. 2" PVC standpipe installed to bottom of
boring. Lower 20.0 feet slotted. Well ID: BJZ555. Boring backfilled withbentonite/sand.
46.5SAMPLE TYPENUMBERDEPTH(ft)45
PAGE 3 OF 3
BORING NUMBER B-102
PROJECT NUMBER ES-5946.03 PROJECT NAME Renton Apartments
GENERAL BH / TP / WELL - 5946-3.GPJ - GRAPHICS TEMPLATE.GDT - 6/10/20Earth Solutions NW, LLC
15365 N.E. 90th Street, Suite 100
Redmond, Washington 98052
Telephone: 425-449-4704
Fax: 425-449-4711
RECOVERY %BLOWCOUNTS(N VALUE)TESTS
U.S.C.S.MATERIAL DESCRIPTION
GRAPHICLOG
SS
SS
SS
SS
SS
33
67
50
100
2-1-0
(1)
1-1-0
(1)
1-1-1
(2)
2-5-7
(12)
2-2-2
(4)
MC = 38.70%
MC = 38.00%
MC = 77.20%
MC = 40.40%
Fines = 64.40%
MC = 27.50%
ML
SP
Brown sandy SILT, very loose, moist to wet
-wood debris
-becomes gray
-wood debris
[USDA Classification: LOAM]
Gray poorly graded SAND, very loose, wet
-groundwater table
13.0
NOTES Surface Conditions: grass
GROUND ELEVATION
LOGGED BY AZS
DRILLING METHOD HSA
HOLE SIZE
DRILLING CONTRACTOR Boretec1, Inc.GROUND WATER LEVELS:
CHECKED BY KRC
DATE STARTED 5/22/20 COMPLETED 5/22/20
AT END OF DRILLING ---
AFTER DRILLING ---
AT TIME OF 13.5 ft
(Continued Next Page)SAMPLE TYPENUMBERDEPTH(ft)0
5
10
15
20
PAGE 1 OF 3
BORING NUMBER B-103
PROJECT NUMBER ES-5946.03 PROJECT NAME Renton Apartments
GENERAL BH / TP / WELL - 5946-3.GPJ - GRAPHICS TEMPLATE.GDT - 6/10/20Earth Solutions NW, LLC
15365 N.E. 90th Street, Suite 100
Redmond, Washington 98052
Telephone: 425-449-4704
Fax: 425-449-4711
RECOVERY %BLOWCOUNTS(N VALUE)TESTS
U.S.C.S.MATERIAL DESCRIPTION
GRAPHICLOG
SS
SS
SS
SS
SS
100
100
100
100
100
2-2-1
(3)
4-5-9
(14)
4-4-3
(7)
2-3-3
(6)
4-6-6
(12)
MC = 14.50%
MC = 23.50%
MC = 19.00%
MC = 34.20%
MC = 24.00%
SP
ML
SM
Gray poorly graded SAND, very loose, wet (continued)
-4" silt lens
-becomes loose
Gray SILT, loose, wet
Gray silty SAND, medium dense, wet
35.0
38.0
(Continued Next Page)SAMPLE TYPENUMBERDEPTH(ft)20
25
30
35
40
PAGE 2 OF 3
BORING NUMBER B-103
PROJECT NUMBER ES-5946.03 PROJECT NAME Renton Apartments
GENERAL BH / TP / WELL - 5946-3.GPJ - GRAPHICS TEMPLATE.GDT - 6/10/20Earth Solutions NW, LLC
15365 N.E. 90th Street, Suite 100
Redmond, Washington 98052
Telephone: 425-449-4704
Fax: 425-449-4711
RECOVERY %BLOWCOUNTS(N VALUE)TESTS
U.S.C.S.MATERIAL DESCRIPTION
GRAPHICLOG
SS 9-15-10
(25)MC = 21.90%
SM
Gray silty SAND, medium dense, wet (continued)
Boring terminated at 46.5 feet below existing grade. Groundwater tableencountered at 13.5 feet during drilling. Boring backfilled with bentonite.
46.5SAMPLE TYPENUMBERDEPTH(ft)45
PAGE 3 OF 3
BORING NUMBER B-103
PROJECT NUMBER ES-5946.03 PROJECT NAME Renton Apartments
GENERAL BH / TP / WELL - 5946-3.GPJ - GRAPHICS TEMPLATE.GDT - 6/10/20Earth Solutions NW, LLC
15365 N.E. 90th Street, Suite 100
Redmond, Washington 98052
Telephone: 425-449-4704
Fax: 425-449-4711
RECOVERY %BLOWCOUNTS(N VALUE)TESTS
U.S.C.S.MATERIAL DESCRIPTION
GRAPHICLOG
SS
SS
SS
SS
SS
22
94
78
100
67
6-4-3
(7)
1-1-1
(2)
3-3-3
(6)
1-1-1
(2)
2-3-4
(7)
MC = 38.10%
MC = 31.60%
MC = 28.90%
MC = 28.70%
MC = 30.50%
SM
TPSL
SM
SM
SP-SM
ML
1.0
1.5
3.5
8.0
15.5
Brown silty SAND, loose, damp (Fill)
TOPSOIL (Fill)
Brown silty SAND, loose, damp (Fill)
Brown silty SAND, very loose, wet
Gray poorly graded SAND with silt, loose, wet
-groundwater seepage at 9'
-becomes very loose
Gray SILT with sand, loose, wet
NOTES
GROUND ELEVATION
LOGGED BY SES
DRILLING METHOD HSA
HOLE SIZE
DRILLING CONTRACTOR Holocene Drilling GROUND WATER LEVELS:
CHECKED BY SSR
DATE STARTED 4/5/18 COMPLETED 4/5/18
AT TIME OF DRILLING ---
AT END OF DRILLING ---
AFTER DRILLING ---
(Continued Next Page)SAMPLE TYPENUMBERDEPTH(ft)0
5
10
15
20
PAGE 1 OF 2
BORING NUMBER B-1
PROJECT NUMBER ES-5946 PROJECT NAME Renton Mixed-Use
GENERAL BH / TP / WELL - 5946.GPJ - GINT STD US.GDT - 6/10/20Earth Solutions NW, LLC
15365 N.E. 90th Street, Suite 100
Redmond, Washington 98052
Telephone: 425-449-4704
Fax: 425-449-4711
RECOVERY %BLOWCOUNTS(N VALUE)TESTS
U.S.C.S.MATERIAL DESCRIPTION
GRAPHICLOG
SS
SS
100
100
3-5-9
(14)
7-10-16
(26)
MC = 64.10%
Fines = 98.80%
MC = 196.00%
MC = 38.10%
Fines = 56.60%
ML
PT
ML
21.0
21.5
26.5
Gray SILT with sand, loose, wet (continued)[USDA Classification: LOAM]
PEAT, wood debris
Gray SILT with sand, medium dense, wet
[USDA Classification: LOAM]
Boring terminated at 26.5 feet below existing grade. Groundwater seepageencountered at 9.0 feet during drilling. Boring backfilled with bentonite.SAMPLE TYPENUMBERDEPTH(ft)20
25
PAGE 2 OF 2
BORING NUMBER B-1
PROJECT NUMBER ES-5946 PROJECT NAME Renton Mixed-Use
GENERAL BH / TP / WELL - 5946.GPJ - GINT STD US.GDT - 6/10/20Earth Solutions NW, LLC
15365 N.E. 90th Street, Suite 100
Redmond, Washington 98052
Telephone: 425-449-4704
Fax: 425-449-4711
RECOVERY %BLOWCOUNTS(N VALUE)TESTS
U.S.C.S.MATERIAL DESCRIPTION
GRAPHICLOG
MC = 15.00%
MC = 26.60%
Fines = 12.80%
MC = 35.80%Fines = 52.50%
MC = 63.70%
SM
SP-SM
ML
Dark brown silty SAND, medium dense, damp (Fill)
-large debris
Brown poorly graded SAND with silt, dense, moist
Gray SILT with sand, dense, wet
-caving from 5.5' to BOH[USDA Classification: LOAM]
-groundwater table at 7'
Test pit terminated at 9.0 feet below existing grade. Groundwater table encountered at 7.0 feetduring excavation. Caving observed from 5.5 feet to BOH.
3.5
5.5
9.0
NOTES Surface Conditions: grass
GROUND ELEVATION
LOGGED BY SES
EXCAVATION METHOD
TEST PIT SIZE
EXCAVATION CONTRACTOR NW Excavating GROUND WATER LEVELS:
CHECKED BY SSR
DATE STARTED 3/20/18 COMPLETED 3/20/18
AT END OF EXCAVATION ---
AFTER EXCAVATION ---
AT TIME OF 7.0 ft
SAMPLE TYPENUMBERDEPTH(ft)0
5
PAGE 1 OF 1
TEST PIT NUMBER TP-1
PROJECT NUMBER ES-5946 PROJECT NAME Renton Mixed-Use
GENERAL BH / TP / WELL - 5946.GPJ - GRAPHICS TEMPLATE.GDT - 6/10/20Earth Solutions NW, LLC
15365 N.E. 90th Street, Suite 100
Redmond, Washington 98052
Telephone: 425-449-4704
Fax: 425-449-4711
TESTS
U.S.C.S.MATERIAL DESCRIPTION
GRAPHICLOG
MC = 23.30%
Fines = 58.40%
MC = 25.50%
MC = 42.70%
Fines = 46.50%
MC = 27.50%
SM
ML
SM
Brown silty SAND, medium dense, damp (Fill)
Brown SILT with sand, medium dense, moist
Black silty SAND, dense, wet
-groundwater table at 6'
-bedded with ML
Test pit terminated at 7.0 feet below existing grade. Groundwater table encountered at 6.0 feet
during excavation. No caving observed.
2.0
5.0
7.0
NOTES
GROUND ELEVATION
LOGGED BY SES
EXCAVATION METHOD
TEST PIT SIZE
EXCAVATION CONTRACTOR NW Excavating GROUND WATER LEVELS:
CHECKED BY SSR
DATE STARTED 3/20/18 COMPLETED 3/20/18
AT END OF EXCAVATION ---
AFTER EXCAVATION ---
AT TIME OF 6.0 ft
SAMPLE TYPENUMBERDEPTH(ft)0
5
PAGE 1 OF 1
TEST PIT NUMBER TP-2
PROJECT NUMBER ES-5946 PROJECT NAME Renton Mixed-Use
GENERAL BH / TP / WELL - 5946.GPJ - GRAPHICS TEMPLATE.GDT - 6/10/20Earth Solutions NW, LLC
15365 N.E. 90th Street, Suite 100
Redmond, Washington 98052
Telephone: 425-449-4704
Fax: 425-449-4711
TESTS
U.S.C.S.MATERIAL DESCRIPTION
GRAPHICLOG
Earth Solutions NW, LLC
Appendix B
Laboratory Test Results
ES-5946.03
Earth Solutions NW, LLC
Report Distribution
ES-5946.03
EMAIL COPY GMD Development, LLC
520 Pike Street, Suite 1010
Seattle, Washington 98101
Attention: Mr. Thomas Geffner
Technical Information Report Watershed Affordable Housing Apartments
2200335.10
Section 7
Other Permits
Technical Information Report Watershed Affordable Housing Apartments 7-1
2200335.10
7.0 Other Permits
A Construction Stormwater NPDES Permit is necessary for the proposed construction.
Technical Information Report Watershed Affordable Housing Apartments
2200335.10
Section 8
CSWPPP Analysis and Design
Technical Information Report Watershed Affordable Housing Apartments 8-1
2200335.10
8.0 CSWPPP Analysis and Design
The proposed development will comply with guidelines set forth in the RSWDM and in
conformance with the required Construction Stormwater NPDES Permit. The plan will include
erosion/sedimentation control features designed to prevent sediment-laden runoff from leaving
the site or from adversely affecting critical water resources during construction.
ESC Plan Analysis and Design (Part A)
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.
The following measures will be used to control sedimentation/erosion processes:
• Clearing Limits: Areas of clearing will be delineated on a TESC plan. Areas will be
delineated in the field with high visibility construction flags or temporary construction
fencing.
• Cover Measures: Disturbed areas shall be permanently or temporarily covered, as
required in Section D.4.2 of the RSWDM. Temporary measures include plastic sheeting
and mulch. Permanent measures include hydroseed.
• Perimeter Protection: Silt fencing and straw wattles will be used for perimeter protection.
• Traffic Area Stabilization: Existing paved surfaces will be used for the construction
entrance to the maximum extent feasible. A construction entrance will be supplied in areas
that are unpaved. Wheel washing and/or street sweeping will be provided as necessary to
prevent tracking of sediment onto adjacent surfaces. Dust control measures will be
implemented when exposed soils are dry to the point that wind transport is possible.
• Sediment Retention: Inlet protection will be provided on all new and existing catch basins
downstream of construction activities.
• Surface Water Control: Stormwater will be collected and conveyed in swales to a
sediment trap. Refer to Figure 8-1 for the sediment trap sizing.
• Wet Season Requirements: Construction activities will occur during the months of May
through August and will thus not trigger wet season requirements. The Contractor shall
ensure that the site is stabilized prior to a predicted storm event with plastic sheeting or
mulch.
• Critical Areas Restrictions: No critical areas are located onsite.
8.1.1 ESC Maintenance
All ESC measures shall be maintained and reviewed on a regular basis, as prescribed in the
maintenance requirements of each BMP.
Technical Information Report Watershed Affordable Housing Apartments 8-2
2200335.10
8.1.2 ESC Supervisor
The Contractor shall designate an ESC supervisor who shall be responsible for maintenance and
review of ESC and for compliance with all permit conditions relating to ESC. The ESC supervisor
must be available for rapid response to ESC problems. The ESC supervisor is required to be a
Certified Erosion and Sedimentation Control Lead (CESCL) with demonstrated expertise in ESC
to perform these reviews and to be responsible for ESC implementation.
8.1.3 Documentation
The ESC supervisor shall review the site at least once a month during the dry season, weekly
during the wet season, and within 24 hours of significant storms. Written records of these reviews
shall be kept onsite, with copies submitted to the King County Department of Development and
Environmental Services (DDES) within 48 hours.
If DDES requires that a written record be maintained, a standard ESC Maintenance Report will be
included closer to final design. A copy of all required maintenance reports shall be kept onsite
throughout the duration of construction.
8.1.4 Review Timing
During the wet season, weekly reviews shall be carried out every 6 to 8 calendar days. During the
dry season, monthly reviews shall be carried out within 3 days of the calendar day for the last
inspection (e.g., if an inspection occurred on June 6, then the next inspection must occur between
July 3 and July 9). Reviews shall also take place within 24 hours of significant storms. In general,
a significant storm is one with more than 0.5 inch of rain in 24 hours or less. Another indication
that a storm is “significant” is if gullies form as a result of the runoff.
Stormwater Pollution Prevention and Spill (SWPPS) Plan Design (Part B)
The below SWPPS Plan shall be completed by the Contractor for use during construction of the
project. Blanks are intentional because they are part of the Contractor’s means and methods.
The SWPPS Plan includes three elements: a site plan, a pollution prevention report, and a spill
prevention and cleanup report. This report includes identifying the expected sources of potential
pollution and spills that may occur during construction, and works to develop a plan to prevent
pollution and spills. It also develops a plan to mitigate spills that may occur. The SWPPS Plan will
be kept onsite at all times during construction. The general contractor will be responsible to
ensure that subcontractors are aware of the SWPPS Plan and a form or record will be provided
stating that all subcontractors have read and agree to the SWPPS Plan. An employee training
worksheet will be provided for the Contractors use.
A SWPPS Site Plan will be developed by the Contractor. The SWPPS Site Plan, Pollution
Prevention Report, and Spill Prevention and Cleanup Report have been preliminarily developed
and BMPs have been selected based on Section 2.3.1.4 of the RSWDM and the KCSPPM.
8.2.1 Pollution and Spill Prevention Source Controls and BMPs
The sources of pollution and spills have been identified below, and the BMPs to be used for each
source for prevention of both pollution and spills have been listed below:
Technical Information Report Watershed Affordable Housing Apartments 8-3
2200335.10
Liquids that will be handled or stored onsite are the following: _________. Containers will be
stored as shown on the SWPPS Site Plan and include the following types and sizes:
___________. Tight-fitting lids shall be placed on all containers containing liquids. Containers
shall be covered with plastic sheeting during rain events. Drip pans or absorbent materials shall
be placed beneath all mounted container taps and at all potential drip and spill locations during
filling and unloading of containers. Containers shall be stored such that if a container leaks or
spills, the contents will not be discharged, flow, or be washed into the storm drainage system,
surface water, or groundwater. Appropriate spill cleanup materials shall be stored and maintained
near the container storage area. Storage area shall be swept and cleaned as needed. Area shall
not be hosed down such that water drains to the storm drainage system or neighboring areas.
Containers shall be checked daily for leaks and spills and replaced, as necessary. All spilled
liquids will be collected and disposed of properly. Spill control devices shall be routinely inspected
on a weekly basis.
Dry pesticides and fertilizers shall be covered with plastic sheeting or stored in a sealed
container. Materials shall be stored on pallets or another raised method to prevent contact with
stormwater runoff. Alternatively, the materials shall be contained in a manner such that if the
container leaks or spills, the contents will not discharge, flow, or be washed into the storm
drainage system, surface waters, or groundwater. Maintenance requirements are the same as
liquid materials described above.
Chemicals that will be handled or stored onsite are the following: _________. Containers will be
stored as shown on the SWPPS Site Plan and include the following types and sizes:
___________. BMPs and maintenance requirements are the same as liquids with the addition of
the following ______.
Soil, sand, and other erodible materials shall be stored onsite in a contractor-designated
location. Materials shall be covered with plastic sheeting per standard detail. Perimeter controls
shall be constructed as shown on the TESC plan to prevent eroded materials from leaving the
project site.
Fueling shall not occur onsite. If fueling does occur onsite, the Contractor shall develop a
containment plan for spills and provide lighting and signage if fueling occurs at night in
conformance with the KCSPPM.
Maintenance and repair of vehicles shall not occur onsite. If maintenance or repair of vehicles
does occur onsite, the Contractor shall develop a spill prevention plan in conformance with the
KCSPPM.
Truck wheel washing shall occur in a controlled manner, such that runoff is collected and
disposed of in a legal manner.
Rinsing of hand tools shall occur in a designated location and water for washing shall be
collected and disposed of in a legal manner.
Contaminated soils shall be covered with plastic sheeting or contained to prevent stormwater
from carrying pollutants away to surface or ground waters. Appropriate spill cleanup materials,
such as brooms, dustpans, vacuum sweepers, etc., shall be stored and maintained near the
storage area. Storage area shall be swept and cleaned as needed. Area shall not be hosed down
such that water drains to the storm drainage system, groundwater, surface water, or neighboring
areas.
Technical Information Report Watershed Affordable Housing Apartments 8-4
2200335.10
During concrete and asphalt construction, the Contractor shall provide the following BMPs or
equivalent measures, methods or practices as required:
1. Drip pans, ground cloths, heavy cardboard, or plywood wherever concrete, asphalt, and
asphalt emulsion chunks and drips are likely to fall unintentionally, such as beneath
extraction points from mixing equipment.
2. Storm drains shall be covered to prevent concrete and asphalt from entering the storm
system.
3. Concrete, concrete slurry and rinse water shall be contained and collected and shall not be
washed or allowed to discharge into storm drain, ditch, or neighboring parcels. All collected
runoff shall be properly disposed of.
4. Contractor shall designate an area where application and mixing equipment cleaning will
be conducted. Rinse water and slurry shall be collected, contained, and disposed of in a
legal manner.
5. Routine maintenance: the pouring area shall be swept at the end of each day or more
frequently if needed. Loose aggregate chunks and dust shall be collected. Areas shall not
be hosed down.
The Contractor may provide the following optional BMPs if the above do not provide adequate
source controls:
1. Cover portable mixing equipment with an awning or plastic sheeting to prevent contact with
rainfall.
2. Provide catch basin inserts configured for pollutant removal.
pH elevated water shall not be discharged from the site. Contractor shall monitor stormwater for
pH prior to discharging from the site. Contractor shall implement a pH treatment plan if pH is not
within the natural range.
8.2.2 Responsible Personnel and Contact Information
The Contractor shall designate a CESCL and post their contact name, company, and phone
number and/or email in a readily visible location onsite.
[name] with [company] shall be responsible for pollution and spill prevention and
cleanup and can be contacted at [phone] or [email] .
Contractor shall fill out a Pollution Prevention Team Worksheet that will be supplied later.
8.2.3 Pollution and Spill Prevention Worksheets
Pollution prevention, BMP implementation reports, material inventory worksheets, pollutant
source identification worksheet, and spill/leak report will be supplied closer to final design.
8.2.4 Disposal Methods
Contractor shall dispose of contaminated soils and water in a legal manner. Options include the
following: _______________.
Technical Information Report Watershed Affordable Housing Apartments
2200335.10
Section 8.0 Figures
Figure 8-1 ......... Sediment Trap Sizing Calculation
Civil Engineers
Structural Engineers
Landscape Architects
Community Planners
Land Surveyors
Neighbors
SEATTLE
1200 6th Avenue
Suite 1620
Seattle, WA 98101-3117
206.267.2425 TEL
www.ahbl.com
Project__________________________
Subject _________________________
With/To_________________________
Address_________________________
Date____________________________
Project No.______________________
Phone__________________________
FAX # _________________________
# Faxed Pages ___________________
By_____________________________
Page _____ of _____
Calculations
Fax
Memorandum
Meeting Minutes
Telephone Memo
If this does not meet with your understanding, please contact us in writing within seven days. THANK YOU.
Q= 2-Year Design Inflow = 0.572 CFS
Per City of Renton Stormwater Drainage Manual (2017, D.2.1.5.1, Page 817) Sediment Traps
shall be sized per the following:
SA = 2 x Q/0.00096
SA = Design Surface Area of Sediment Trap (Measured at Invert of Weir)
SA = 2 x 0.572/0.00096
SA = 1,191.67 = 1,192 Square Feet
Grady Way Apartments 2200335.10
TESC Calcs
09/14/2021 KB
4
Technical Information Report Watershed Affordable Housing Apartments
2200335.10
Section 9
Bond Quantities, Facility Summaries, and Declaration
of Covenant
Technical Information Report Watershed Affordable Housing Apartments 9-1
2200335.10
9.0 Bond Quantities, Facility Summaries, and Declaration of Covenant
Refer to Figure 9-1 for the draft Declaration of Covenant, Figure 9-2 for the Stormwater Facility
Summary Sheet, and Figure 9-3 for the draft Bond Quantity Worksheet.
Technical Information Report Watershed Affordable Housing Apartments
2200335.10
Section 9.0 Figures
Figure 9-1 ......... Declaration of Covenant (Draft)
Figure 9-2 ......... Stormwater Facility Summary Sheet
Figure 9-3 ......... Bond Quantity Worksheet (Draft)
Page 1 of ___
Return Address:
City Clerk’s Office
City of Renton
1055 S Grady Way
Renton, WA 98057
DECLARATION OF COVENANT
FOR INSPECTION AND MAINTENANCE OF DRAINAGE FACILITIES AND
ON-SITE BMPS
Grantor:
Grantee: City of Renton, a Washington municipal corporation
Legal Description:
Assessor's Tax Parcel ID#:
IN CONSIDERATION of the approved City of Renton (check one of the following)
Residential Building Permit Commercial Building Permit
Clearing and Grading Permit Civil Construction or Utility Permit
for Permit(s)_____________________ (Construction/Building/Utility Permit #) relating to the real property
("Property") described above, the Grantor(s), the owner(s) in fee of that Property, hereby
covenants (covenant) with the City of Renton (“City of Renton” or “City”), a municipal corporation
of the state of Washington, that he/she (they) will observe, consent to, and abide by the conditions
and obligations set forth and described in Paragraphs 1 through 9 below with regard to the
Property, and hereby grants (grant) an easement as described in Paragraphs 2 and 3. Grantor(s)
hereby grants (grant), covenants (covenant), and agrees (agree) as follows:
1.The Grantor(s) or his/her (their) successors in interest and assigns ("Owners ") shall at their own
cost, operate, maintain, and keep in good repair, the Property's drainage facilities constructed
as required in the approved construction plans and specifications __________________ (Project
Plan #) on file with the City of Renton and submitted to the City of Renton for the review and
approval of permit(s) _____________________________ (Construction/Building/Utility Permit #). The
Property's drainage facilities are shown and/or listed on Exhibit A – Site Plan. The Property’s
drainage facilities shall be maintained in compliance with the operation and maintenance
schedule included and attached herein as Exhibit B – Operations and Maintenance. Drainage
facilities include pipes, channels, flow control facilities, water quality facilities, on-site best
management practices (BMPs) and other engineered structures designed to manage and/or
4
See Exhibit C
172305-9069, 172305-9136, 182305-9115, 182305-9282
Page 2 of ___
treat stormwater on the Property. On-site BMPs include dispersion and infiltration devices,
bioretention, permeable pavements, rainwater harvesting systems, tree retention credit,
reduced impervious surface footprint, vegetated roofs and other measures designed to mimic
pre-developed hydrology and minimize stormwater runoff on the Property.
2.City of Renton shall have the right to ingress and egress over those portions of the Property
necessary to perform inspections of the stormwater facilities and BMPs and conduct
maintenance activities specified in this Declaration of Covenant and in accordance with the
Renton Municipal Code. City of Renton shall provide at least thirty (30) days’ written notice to
the Owners that entry on the Property is planned for the inspection of drainage facilities. After
the thirty (30) days, the Owners shall allow the City of Renton to enter for the sole purpose of
inspecting drainage facilities. In lieu of inspection by the City, the Owners may elect to engage
a licensed civil engineer registered in the state of Washington who has expertise in drainage to
inspect the drainage facilities and provide a written report describing their condition. If the
engineer option is chosen, the Owners shall provide written notice to the City of Renton within
fifteen (15) days of receiving the City’s notice of inspection. Within thirty (30) days of giving this
notice, the Owners, or engineer on behalf of the Owners, shall provide the engineer’s report to
the City of Renton. If the report is not provided in a timely manner as specified above, the City
of Renton may inspect the drainage facilities without further notice.
3.If City of Renton determines from its inspection, or from an engineer’s report provided in
accordance with Paragraph 2, that maintenance, repair, restoration, and/or mitigation work is
required to be done to any of the drainage facilities, City of Renton shall notify the Owners of
the specific maintenance, repair, restoration, and/or mitigation work (“Work”) required
pursuant to the Renton Municipal Code. The City shall also set a reasonable deadline for the
Owners to complete the Work, or to provide an engineer’s report that verifies completion of
the Work. After the deadline has passed, the Owners shall allow the City access to re-inspect
the drainage facilities unless an engineer’s report has been provided verifying completion of
the Work. If the Work is not completed within the time frame set by the City, the City may
initiate an enforcement action and/or perform the Work and hereby is given access to the
Property for such purposes. Written notice will be sent to the Owners stating the City’s
intention to perform such Work. This Work will not commence until at least seven (7) days after
such notice is mailed. If, within the sole discretion of the City, there exists an imminent or
present danger, the seven (7) day notice period will be waived and Work will begin
immediately.
4.The Owners shall assume all responsibility for the cost of any Work, or any measures taken by
the City to address conditions as described in Paragraph 3. Such responsibility shall include
reimbursement to the City within thirty (30) days of the receipt of the invoice for any such Work
performed. Overdue payments will require payment of interest at the maximum legal rate
allowed by RCW 19.52.020 (currently twelve percent (12%)). If the City initiates legal action to
enforce this agreement, the prevailing party in such action is entitled to recover reasonable
litigation costs and attorney’s fees.
5.The Owners are required to obtain written approval from City of Renton prior to filling, piping,
cutting, or removing vegetation (except in routine landscape maintenance) in open vegetated
stormwater facilities (such as swales, channels, ditches, ponds, etc.), or performing any
alterations or modifications to the drainage facilities referenced in this Declaration of Covenant.
Page 3 of ___
6.Any notice or consent required to be given or otherwise provided for by the provisions of this
Agreement shall be effective upon personal delivery, or three (3) days after mailing by Certified
Mail, return receipt requested.
7.With regard to the matters addressed herein, this agreement constitutes the entire agreement
between the parties, and supersedes all prior discussions, negotiations, and all agreements
whatsoever whether oral or written.
8.This Declaration of Covenant is intended to protect the value and desirability and promote
efficient and effective management of surface water drainage of the real property described
above, and shall inure to the benefit of all the citizens of the City of Renton and its successors
and assigns. This Declaration of Covenant shall run with the land and be binding upon
Grantor(s), and Grantor's(s') successors in interest, and assigns.
9.This Declaration of Covenant may be terminated by execution of a written agreement by the
Owners and the City that is recorded by King County in its real property records.
IN WITNESS WHEREOF, this Declaration of Covenant for the Inspection and Maintenance of
Drainage Facilities is executed this _____ day of ____________________, 20_____.
GRANTOR, owner of the Property GRANTOR, owner of the Property
STATE OF WASHINGTON )
COUNTY OF KING )ss.
On this day personally appeared before me:
, to me known to be the individual(s)
described in and who executed the within and foregoing instrument and acknowledged that they
signed the same as their free and voluntary act and deed, for the uses and purposes therein stated.
Given under my hand and official seal this _____ day of ___________________, 20_____.
Printed name
Notary Public in and for the State of
Washington, residing at
My appointment expires
TITLE PARCEL B
APN. 172305-9136
TITLE PARCEL DAPN. 182305-9282
TITLE PARCEL AAPN. 172305-9069
TITLE PARCEL CAPN. 182305-9115 3131
3232 323232 3232
3333
3333
SOIL AMMENDMENT
GRASS PAVE
3 FOOT DIAMETER FLOW
CONTROL TANKBIOPOD WQ SYSTEM
BIOPOD WQ SYSTEM
GRASS PAVE
PEDESTRIAN
WALKWAY/
EMERGENCY
ACCESS
PARKING LOT
GRAPHIC SCALE
0 60 120
1" = 60 FEET
30
PROJECT PARCEL NUMBERS:
172305-9069,172305-9136, 182305-9115, 182305-9282
PROJECT ADDRESS: 615 WILLIAMS AVE S
TOTAL SITE ACREAGE: 1.28ac
TOTAL IMPERVIOUS AREA: 1.13 ac
BMPS USED: GRASS PAVE, DETENTION TANK, AND
BIOPOD PROPRIETARY WQ SYSTEM, VEGETATED
ROOF, SOIL AMMENDMENTN
PROPOSED BUILDING, WITH
VEGETATED ROOF
SOUTH TGRADY WAYWILLIAMS AVE S.ROOF OVERHANG
ROW DEDICATION LINE
EXHIBIT A-ONSITE BMP SITE PLAN
MAINTENANCE INSTRUCTIONS FOR VEGETATED PERMEABLE PAVEMENT (GRASSED MODULAR GRID PAVEMENT)
Your property contains an on-site BMP (best management practice) called “grassed modular grid
pavement,” which was installed to minimize the stormwater quantity and quality impacts of some or all of the paved surfaces on your property.
Grassed modular grid pavement has the runoff characteristics of a lawn while providing the weight-
bearing capacity of concrete pavement. The grassed surface not only minimizes runoff quantity, it
helps to filter pollutants generating by vehicular use of the surface.
MAINTENANCE RESTRICTIONS
The composition and area of grassed modular grid pavement as depicted by the site plan and design details must be maintained and may not be changed without written approval from the City of Renton
or through a future development permit from the City of Renton.
INSPECTION FREQUENCY AND MAINTENANCE GUIDELINES
• Grassed modular grid pavement must be inspected after one major storm each year to make
sure it is working properly. More frequent inspection is recommended.
• Prolonged ponding or standing water on the pavement surface is a sign that the system is
defective and may need to be replaced. If this occurs, or if any modification, surface restoration or stabilization is planned (except for mowing and periodic maintenance), contact
the pavement installer or the City of Renton for further instructions.
• The grassed surface of the pavement must be regularly mowed and maintained in a good
condition. Bare spots must be replanted in the spring or fall.
RECORDING REQUIREMENT
These vegetated permeable pavement on-site BMP maintenance and operation instructions must be
recorded as an attachment to the required declaration of covenant and grant of easement per Requirement 3 of Section C.1.3.4 of the City of Renton Surface Water Design Manual. The intent of these instructions is to explain to future property owners, the purpose of the BMP and how it must be
maintained and operated. These instructions are intended to be a minimum; the City of Renton may require additional instructions based on site-specific conditions. See the City of Renton’s Surface Water Design Manual website for additional information and updates.
MAINTENANCE INSTRUCTIONS FOR SOIL AMENDMENT
Your property contains an on-site BMP (best management practice) called “soil amendment,” which
was installed to mitigate the stormwater quantity and quality impacts of some or all of the pervious
surfaces on your property.
Soil amendment is a method of regaining greater stormwater functions in the post development
landscape by increasing treatment of pollutants and sediments, and minimizing the need for some
landscaping chemicals. To be successful, the soil condition must be able to soak water into the ground for a reasonable number of years. This on-site BMP shall be maintained per Appendix A of the City of
Renton’s Surface Water Design Manual.
MAINTENANCE RESTRICTIONS
The size, placement, and composition of these devices as depicted by the site plan and design details
must be maintained and may not be changed without written approval from the City of Renton or through a future development permit from the City of Renton.
INSPECTION FREQUENCY AND MAINTENANCE GUIDELINES
To be successful, the soil must be able to soak water into the ground for a reasonable number of years.
• Return leaf fall and shredded woody materials from the landscape to the site when possible in order to replenish soil nutrients and structure.
• On turf areas, “grasscycle” (mulch-mow or leave the clippings) to build turf health.
• Maintain 2 to 3 inches of mulch over bare areas in landscape beds.
• Re-seed bare turf areas until the vegetation fully covers the ground surface.
• Avoid using pesticides (bug and weed killers) which damage the soil.
• Where fertilization is needed (mainly turf and annual flower beds), a moderate fertilization program should be used which relies on compost, natural fertilizers, or slow-release synthetic balanced fertilizers.
RECORDING REQUIREMENT
These on-site BMP maintenance and operation instructions must be recorded as an attachment to the
required declaration of covenant and grant of easement per Requirement 3 of Section C.1.3.4 of the
City of Renton Surface Water Design Manual. The intent of these instructions is to explain to future property owners, the purpose of the BMP and how it must be maintained and operated. These
instructions are intended to be a minimum; the City of Renton may require additional instructions based on site-specific conditions. See the City of Renton’s Surface Water Design Manual website for additional information and updates.
MAINTENANCE INSTRUCTIONS FOR VEGETATED ROOFS
Your property contains an on-site BMP (best management practice) called a “vegetated roof,” which
was installed to minimize the stormwater runoff impacts of the impervious surfaces on your property.
Vegetated roofs (also called green roofs) consist of a pervious growing medium, plants, and a moisture barrier. The benefits of this device are a reduction in runoff peaks and volumes due to the storage
capabilities of the soil and increased rate of evapotranspiration. This on-site BMP shall be maintained
per Appendix A of the City of Renton’s Surface Water Design Manual.
MAINTENANCE RESTRICTIONS
• The composition and area of vegetated roof as depicted by the site plan and design details must be maintained and may not be changed without written approval from the City of Renton or
through a future development permit from the City of Renton.
• Vegetated roofs must not be subject to any use that would significantly compact the soil.
INSPECTION FREQUENCY AND MAINTENANCE GUIDELINES
Vegetated roofs (also called green roofs) consist of a pervious growing medium, plants, and a moisture
barrier:
• Vegetated roofs must be inspected annually for physical defects and to make sure the vegetation is in good condition.
• If erosion channels or bare spots are evident, they should be stabilized with additional soil similar to the original material.
• A supplemental watering program may be needed the first year to ensure the long-term survival of the roof's vegetation.
• Vegetation should be maintained as follows:
(1) Vegetated roofs must not be subject to any use that would significantly compact the soil;
(2) Replace all dead vegetation as soon as possible;
(3) Remove fallen leaves and debris;
(4) Remove all noxious vegetation when discovered;
(5) Manually weed without herbicides or pesticides
RECORDING REQUIREMENT
These vegetated roof on-site BMP maintenance and operation instructions must be recorded as an
attachment to the required declaration of covenant and grant of easement per Requirement 3 of Section C.1.3.4 of the City of Renton Surface Water Design Manual. The intent of these instructions is to explain to future property owners, the purpose of the BMP and how it must be maintained and
operated. These instructions are intended to be a minimum; the City of Renton may require additional instructions based on site-specific conditions. See the City of Renton’s Surface Water Design Manual website for additional information and updates.
TYPICAL VEGETATED ROOF CROSS-SECTION
Page 6 of ___
Exhibit C – Legal Description
Please replace this page with “Exhibit C – Legal Description” if the property legal
description does not fit within the space provided on Page 1 of the Declaration of
Covenant. Add reference to “Exhibit C” in the legal description field on page 1 of the
Declaration of Covenant document.
2016 KING COUNTY SURFACE WATER DESIGN MANUAL, REFERENCE D
4/24/2016
Page 1
STORMWATER FACILITY SUMMARY SHEET DPER Permit No.___________________
(provide one Stormwater Facility Summary Sheet per Natural Discharge Location)Date ___________________
OVERVIEW:NPDES Permit No.___________________
Project Name
Parcel No.____________________________
Project Location Retired Parcel No.____________________________
Downstream Drainage Basins:Project includes Landscape Management Plan?yes
Major Basin Name ______________________________________________(include copy with TIR as Appendix)no
Immediate Basin Name ______________________________________________
GENERAL FACILITY INFORMATION: Leachable Metals
Infiltration Impervious Surface Limit
Type # of Type # of Type # of facilities Flow Control BMPs
Ponds ______ Ponds ______ Ponds ______ Basic Clearing Limit
Vaults ______ Tanks ______ Vaults ______ Conservation Drainage Facility
Tanks ______ Trenches _____ Tanks ______ Flood Problem Landscape Management Plan
If no flow control facility, check one:
Project qualifies for KCSWDM Exemption (KCSWDM 1.2.3):
Basic Exemption (Applies to Commercial parcels only)Area % of Total
Redevelopment projects
Cost Exemption for Parcel Redevelopment projects
Direct Discharge Exemption
Other _____________________ Total impervious surface served by
Project qualifies for 0.1 cfs Exception per KCSWDM 1.2.3 flow control facility(ies) (sq ft)
Impervious surface served by flow
KCSWDM Adjustment No. ___________________control facility(ies) designed
1990 or later (sq ft)
approved KCSWDM Adjustment No. __________________ Impervious surface served by
Shared Facility Name/Location: _________________________ pervious surface absorption (sq ft)
No flow control required (other, provide justification): Impervious surface served by approved
____________________________________________________ water quality facility(ies) (sq ft)
Flow Control
Performance Std
Declarations of Covenant Recording No.
Water QualityDetention
TREATMENT SUMMARY FOR TOTAL IMPERVIOUS SURFACES
-----
Total Impervious Acreage (ac)
No flow control required per approved
Flow control provided in regional/shared facility per approved
PROVIDE FACILITY DETAILS AND FACILITY SKETCH FOR EACH FACILITY ON REVERSE. USE ADDITIONAL SHEETS AS NEEDED FOR ADDITIONAL FACILITIES
Impervious Surface Exemption for Transportation Total Acreage (ac)
Watershed Apartments
615 Williams Avenue S, Renton Wa
Green River North Basin
172305-9069, 172305-9136, 182305-9115,182305-9882
1
Peak Rate Flow Control
1.115 ac 100 %
1.085 ac 97.3 %
1.085 ac 97.3 %
.21 ac 18.8 %
Black River
2016 KING COUNTY SURFACE WATER DESIGN MANUAL, REFERENCE D
4/24/2016
Page 2
STORMWATER FACILITY SUMMARY SHEET DPER Permit No.___________________
(provide one Stormwater Facility Summary Sheet per Natural Discharge Location)
Project Name Downstream Drainage Basins:
Major Basin Name _______________________________
Project Location Immediate Basin Name ___________________________
FLOW CONTROL FACILITY:Basin:
Facility Name/Number _______________________________________ New Facility Project Impervious
Facility Location ____________________________________________ Existing Facility Acres Served ________
UIC? □ yes □ no UIC Site ID:% of Total Project Impervious
cu.ft.Volume Factor Acres Served ________
_____________ ac.ft.____________of Safety _______No. of Lots Served ________
Control Structure location: _______________________________________________
Type of Control Structure:No. of Orifices/Restrictions __________
Riser in vault Size of Orifice/Restriction (in.) No.1 ______ cu.ft.
Riser in Type II CB (numbered starting with lowest No.2 ______ ac.ft.
Weir in Type II CB orifice): No.3 ______
(inches in decimal format)No.4 ______
WATER QUALITY FACILITIES Design Information
Indicate no. of water quality facilities/BMPs for each type:Water Quality design flow (cfs)
_______Flow dispersion Water Quality treated volume (sandfilter) (cu.ft.)
_______Filter strip Water Quality storage volume (wetpool) (cu.ft.)
_______Biofiltration swale regular, wet or Landscape management plan Farm management plan
continuous inflow
_______Wetvault combined w/detention ______High flow bypass structure (e.g., flow-splitter catch basin)
_______Wetpond basic large combined w/detention ______Oil/water separator baffle coalescing plate
_______Pre-settling pond ______Storm filter
_______Stormwater wetland ______Pre-settling structure (Manufacturer:______________________)
_______Sand filter basic large Sand bed depth ______Catch basin inserts (Manufacturer:________________________)
regular linear vault (inches)______________Source controls _________________________________________
● Is facility lined? yes no If so, what marker is used above liner?_____________________________________________________
Facility Summary Sheet Sketch: All detention, infiltration and water quality facilities must include a detailed sketch (11"x17" reduced size plan sheets preferred).
Dam Safety Regulations (WA State Dept of
Ecology):
Reservoir Volume
above natural grade
Depth of Reservoir
above natural grade (ft)
Live Storage
Volume
Live Storage
Depth (ft)
1.085 ac
97.3 %
3
2193 cf 2 ft 1.05
Watershed Apartments
615 Williams Avenue S, Renton Wa
Black River
Green River River North Basin
See Strm Rprt
1 OLD CASTLE BIOPOD
Planning Division |1055 South Grady Way – 6th Floor | Renton, WA 98057 (425) 430-7200••Section I: Project Information•••Section II: Bond Quantities Worksheets••Section II.a EROSION CONTROL (Stabilization/Erosion Sediment Control (ESC))•Section II.b TRANSPORTATION (Street and Site Improvements)•Section II.c DRAINAGE (Drainage and Stormwater Facilities): •Section II.d WATER - ONLY APPLICABLE IF WATER SERVICE IS PROVIDED BY CITY OF RENTON•Section II.e SANITARY SEWER - ONLY APPLICABLE IF SEWER SERVICE IS PROVIDED BY CITY OF RENTON••••••Section III. Bond Worksheet• This section calculates the required Permit Bond for construction permit issuance as well as the required Maintenance Bond for project close-out submittals to release the permit bond on a project. All unit prices include labor, equipment, materials, overhead and profit. Complete the 'Quantity' columns for each of the appropriate section(s). Include existing Right-of-Way (ROW), Future Public Improvements and Private Improvements.The 'Quantity Remaining' column is only to be used when a project is under construction. The City allows one (1) bond reduction during the life of the project with the exception of the maintenance period reduction.Excel will auto-calculate and auto-populate the relevant fields and subtotals throughout the document. Only the 'Quantity' columns should need completing.Additional items not included in the lists can be added under the "write-in" sections. Provide a complete description, cost estimate and unit of measure for each write-in item. Note: Private improvements, with the exception of stormwater facilities, are not included in the bond amount calculation, but must be entered on the form. Stormwater facilities (public and private) are required to be included in the bond amount.BOND QUANTITY WORKSHEET INSTRUCTIONSThis worksheet is intended to be a "working" copy of the bond quantity worksheet, which will be used throughout all phases of the project, from initial submittal to project close-out approval. Submit this workbook, in its entirety, as follows:The following forms are to be completed by the engineer/developer/applicant as applicable to the project: The Bond Worksheet form will auto-calculate and auto-populate from the information provided in Section I and Section II.This section includes all pertinent information for the projectSection II contains a separate spreadsheet TAB for each of the following specialties: (1) electronic copy (.xlsx format) and (1) hard copy of the entire workbook for civil construction permit submittal. Hard copies are to be included as part of the Technical Information Report (TIR).(1) electronic copy (.xlsx format) and (1) hard copy of the entire workbook for final close-out submittal.This section must be completed in its entiretyInformation from this section auto-populates to all other relevant areas of the workbookPage 1 of 14Ref 8-H Bond Quantity WorksheetINSTRUCTIONSUnit Prices Updated: 06/14/2016Version: 04/26/2017Printed 3/18/2022
Planning Division |1055 South Grady Way – 6th Floor | Renton, WA 98057 (425) 430-7200Date Prepared: Name:PE Registration No:Firm Name:Firm Address:Phone No.Email Address:Project Name: Project Owner:CED Plan # (LUA):Phone:CED Permit # (U):Address: Site Address:Street Intersection:Addt'l Project Owner:Parcel #(s):Phone:Address: Clearing and grading greater than or equal to 5,000 board feet of timber? Yes/No:NOWater Service Provided by:If Yes, Provide Forest Practice Permit #:Sewer Service Provided by: SITE IMPROVEMENT BOND QUANTITY WORKSHEETPROJECT INFORMATIONCITY OF RENTONCITY OF RENTON1 Select the current project status/phase from the following options: For Approval - Preliminary Data Enclosed, pending approval from the City; For Construction - Estimated Data Enclosed, Plans have been approved for contruction by the City; Project Closeout - Final Costs and Quantities Enclosed for Project Close-out SubmittalPhoneEngineer Stamp Required (all cost estimates must have original wet stamp and signature)Clearing and GradingUtility ProvidersN/AProject Location and DescriptionProject Owner InformationWatershed ApartmentsSEATTLE WA 981011723059069, 1723059136,1823059115GMD DEVELOPMENT21-000239Phone10/10/2021Prepared by:FOR APPROVALProject Phase 1dtapp@ahbl.comDoug Tapp35702AHBL Inc.1200 6th Avenue, Seattle WA 98101206-267-2425625 Williams Avenue520 PIKE ST #1010Additional Project OwnerGrady Way Avenue S and Williams Avenue S.21005115AddressAbbreviated Legal Description:THAT PORTION OF THE SOUTHWEST QUARTER OF THE SOUTHWEST QUARTER OF SECTION 17, TOWNSHIP 23 NORTH, RANGE 05 EAST, WILLAMETTE MERIDIAN, CITY OF RENTON, KING COUNTY, WASHINGTON AND THAT PORTION OF THE SOUTHEAST QUARTER OF THE SOUTHEAST QUARTER OF SECTION 18, TOWNSHIP 23 NORTH, City, State, ZipPage 2 of 14Ref 8-H Bond Quantity WorksheetSECTION I PROJECT INFORMATIONUnit Prices Updated: 06/14/2016Version: 04/26/2017Printed 3/18/2022
CED Permit #:21005115UnitReference #PriceUnitQuantity CostBackfill & compaction-embankmentESC-16.50$ CY Check dams, 4" minus rockESC-2SWDM 5.4.6.380.00$ Each180.00Catch Basin ProtectionESC-335.50$ Each14497.00Crushed surfacing 1 1/4" minusESC-4WSDOT 9-03.9(3)95.00$ CY DitchingESC-59.00$ CY20180.00Excavation-bulkESC-62.00$ CY4080.00Fence, siltESC-7SWDM 5.4.3.11.50$ LF500750.00Fence, Temporary (NGPE)ESC-81.50$ LF Geotextile FabricESC-92.50$ SY Hay Bale Silt TrapESC-100.50$ Each HydroseedingESC-11SWDM 5.4.2.40.80$ SY Interceptor Swale / DikeESC-121.00$ LF Jute MeshESC-13SWDM 5.4.2.23.50$ SY Level SpreaderESC-141.75$ LF Mulch, by hand, straw, 3" deepESC-15SWDM 5.4.2.12.50$ SY10702,675.00Mulch, by machine, straw, 2" deepESC-16SWDM 5.4.2.12.00$ SY Piping, temporary, CPP, 6"ESC-1712.00$ LF1401,680.00Piping, temporary, CPP, 8"ESC-1814.00$ LF Piping, temporary, CPP, 12"ESC-1918.00$ LF Plastic covering, 6mm thick, sandbaggedESC-20SWDM 5.4.2.34.00$ SY Rip Rap, machine placed; slopesESC-21WSDOT 9-13.1(2)45.00$ CY Rock Construction Entrance, 50'x15'x1'ESC-22SWDM 5.4.4.11,800.00$ Each Rock Construction Entrance, 100'x15'x1'ESC-23SWDM 5.4.4.13,200.00$ Each13,200.00Sediment pond riser assemblyESC-24SWDM 5.4.5.22,200.00$ Each Sediment trap, 5' high berm ESC-25SWDM 5.4.5.119.00$ LFSed. trap, 5' high, riprapped spillway berm section ESC-26SWDM 5.4.5.170.00$ LFSeeding, by handESC-27SWDM 5.4.2.41.00$ SY Sodding, 1" deep, level groundESC-28SWDM 5.4.2.58.00$ SY Sodding, 1" deep, sloped groundESC-29SWDM 5.4.2.510.00$ SY TESC SupervisorESC-30110.00$ HR404,400.00Water truck, dust controlESC-31SWDM 5.4.7140.00$ HR405,600.00UnitReference #PriceUnitQuantity Cost EROSION/SEDIMENT SUBTOTAL:19,142.00SALES TAX @ 10%1,914.20EROSION/SEDIMENT TOTAL:21,056.20(A)SITE IMPROVEMENT BOND QUANTITY WORKSHEETFOR EROSION & SEDIMENT CONTROLDescription No.(A)WRITE-IN-ITEMS Page 3 of 14Ref 8-H Bond Quantity WorksheetSECTION II.a EROSION_CONTROLUnit Prices Updated: 06/14/2016Version: 04/26/2017Printed 3/18/2022
CED Permit #:21005115ExistingFuture PublicPrivateRight-of-WayImprovementsImprovements(D) (E)DescriptionNo. Unit PriceUnitQuant.CostQuant.CostQuant.CostQuant.CostGENERAL ITEMS Backfill & Compaction- embankmentGI-16.00$ CY60360.00Backfill & Compaction- trenchGI-29.00$ CYClear/Remove Brush, by hand (SY)GI-31.00$ SYBollards - fixedGI-4240.74$ Each163,851.84Bollards - removableGI-5452.34$ EachClearing/Grubbing/Tree RemovalGI-610,000.00$ AcreExcavation - bulkGI-72.00$ CY60120.00Excavation - TrenchGI-85.00$ CY100500.005002,500.005152,575.00Fencing, cedar, 6' highGI-920.00$ LFFencing, chain link, 4'GI-1038.31$ LFFencing, chain link, vinyl coated, 6' highGI-1120.00$ LFFencing, chain link, gate, vinyl coated, 20' GI-121,400.00$ EachFill & compact - common barrowGI-1325.00$ CY200050,000.00Fill & compact - gravel baseGI-1427.00$ CYFill & compact - screened topsoilGI-1539.00$ CYGabion, 12" deep, stone filled mesh GI-1665.00$ SYGabion, 18" deep, stone filled mesh GI-1790.00$ SYGabion, 36" deep, stone filled meshGI-18150.00$ SYGrading, fine, by handGI-192.50$ SYGrading, fine, with graderGI-202.00$ SYMonuments, 3' LongGI-21250.00$ EachSensitive Areas SignGI-227.00$ EachSodding, 1" deep, sloped groundGI-238.00$ SYSurveying, line & gradeGI-24850.00$ Day54,250.00Surveying, lot location/linesGI-251,800.00$ AcreTopsoil Type A (imported)GI-2628.50$ CYTraffic control crew ( 2 flaggers )GI-27120.00$ HRTrail, 4" chipped woodGI-288.00$ SYTrail, 4" crushed cinderGI-299.00$ SYTrail, 4" top courseGI-3012.00$ SYConduit, 2"GI-315.00$ LFWall, retaining, concreteGI-3255.00$ SF90049,500.00Wall, rockeryGI-3315.00$ SFSUBTOTAL THIS PAGE:360.004,870.00105,851.842,575.00(B)(C)(D)(E)SITE IMPROVEMENT BOND QUANTITY WORKSHEETFOR STREET AND SITE IMPROVEMENTSQuantity Remaining (Bond Reduction) (B)(C)Page 4 of 14Ref 8-H Bond Quantity WorksheetSECTION II.b TRANSPORTATIONUnit Prices Updated: 06/14/2016Version: 04/26/2017Printed 3/18/2022
CED Permit #:21005115ExistingFuture PublicPrivateRight-of-WayImprovementsImprovements(D) (E)DescriptionNo. Unit PriceUnitQuant.CostQuant.CostQuant.CostQuant.CostSITE IMPROVEMENT BOND QUANTITY WORKSHEETFOR STREET AND SITE IMPROVEMENTSQuantity Remaining (Bond Reduction) (B)(C)ROAD IMPROVEMENT/PAVEMENT/SURFACINGAC Grinding, 4' wide machine < 1000syRI-130.00$ SYAC Grinding, 4' wide machine 1000-2000syRI-216.00$ SYAC Grinding, 4' wide machine > 2000syRI-310.00$ SYAC Removal/DisposalRI-435.00$ SY50217,570.00Barricade, Type III ( Permanent )RI-556.00$ LFGuard RailRI-630.00$ LFCurb & Gutter, rolledRI-717.00$ LFCurb & Gutter, verticalRI-812.50$ LF4305,375.00Curb and Gutter, demolition and disposalRI-918.00$ LF4307,740.00Curb, extruded asphaltRI-105.50$ LFCurb, extruded concreteRI-117.00$ LFSawcut, asphalt, 3" depthRI-121.85$ LFSawcut, concrete, per 1" depthRI-133.00$ LF5001,500.00Sealant, asphaltRI-142.00$ LFShoulder, gravel, 4" thickRI-1515.00$ SYSidewalk, 4" thickRI-1638.00$ SY40015,200.00Sidewalk, 4" thick, demolition and disposalRI-1732.00$ SY35411,328.00Sidewalk, 5" thickRI-1841.00$ SYSidewalk, 5" thick, demolition and disposalRI-1940.00$ SYSign, Handicap RI-2085.00$ EachStriping, per stallRI-217.00$ Each43301.00Striping, thermoplastic, ( for crosswalk )RI-223.00$ SF220660.00Striping, 4" reflectorized lineRI-230.50$ LFAdditional 2.5" Crushed SurfacingRI-243.60$ SYHMA 1/2" Overlay 1.5" RI-2514.00$ SYHMA 1/2" Overlay 2"RI-2618.00$ SYHMA Road, 2", 4" rock, First 2500 SYRI-2728.00$ SYHMA Road, 2", 4" rock, Qty. over 2500SYRI-2821.00$ SYHMA Road, 4", 6" rock, First 2500 SYRI-2945.00$ SY51022,950.00HMA Road, 4", 6" rock, Qty. over 2500 SYRI-3037.00$ SYHMA Road, 4", 4.5" ATBRI-3138.00$ SYGravel Road, 4" rock, First 2500 SYRI-3215.00$ SYGravel Road, 4" rock, Qty. over 2500 SYRI-3310.00$ SYThickened EdgeRI-348.60$ LFSUBTOTAL THIS PAGE:43,513.0038,810.00301.00(B)(C)(D)(E)Page 5 of 14Ref 8-H Bond Quantity WorksheetSECTION II.b TRANSPORTATIONUnit Prices Updated: 06/14/2016Version: 04/26/2017Printed 3/18/2022
CED Permit #:21005115ExistingFuture PublicPrivateRight-of-WayImprovementsImprovements(D) (E)DescriptionNo. Unit PriceUnitQuant.CostQuant.CostQuant.CostQuant.CostSITE IMPROVEMENT BOND QUANTITY WORKSHEETFOR STREET AND SITE IMPROVEMENTSQuantity Remaining (Bond Reduction) (B)(C)PARKING LOT SURFACINGNo.2" AC, 2" top course rock & 4" borrowPL-121.00$ SY2" AC, 1.5" top course & 2.5" base coursePL-228.00$ SY3208,960.004" select borrowPL-35.00$ SY1.5" top course rock & 2.5" base coursePL-414.00$ SYSUBTOTAL PARKING LOT SURFACING:8,960.00(B)(C)(D)(E)LANDSCAPING & VEGETATIONNo.Street TreesLA-1450.00$ EA73,150.00Median LandscapingLA-2Right-of-Way LandscapingLA-38.00$ SF178014,240.00Wetland LandscapingLA-4SUBTOTAL LANDSCAPING & VEGETATION:17,390.00(B)(C)(D)(E)TRAFFIC & LIGHTINGNo.SignsTR-1Street Light System ( # of Poles)TR-2Traffic SignalTR-3Traffic Signal ModificationTR-425,320.00$ LS125,320.00SUBTOTAL TRAFFIC & LIGHTING:25,320.00(B)(C)(D)(E)WRITE-IN-ITEMSLighting Lump sum180,450.00$ LS180,450.00Pervious Pavemet100.00$ SY50050,000.00Heavy Asphalt Pavement40.00$ sy72929,160.0072929,160.00SUBTOTAL WRITE-IN ITEMS:29,160.0080,450.0079,160.00STREET AND SITE IMPROVEMENTS SUBTOTAL:73,033.00175,800.00185,312.842,575.00SALES TAX @ 10%7,303.3017,580.0018,531.28257.50STREET AND SITE IMPROVEMENTS TOTAL:80,336.30193,380.00203,844.122,832.50(B)(C)(D)(E)Page 6 of 14Ref 8-H Bond Quantity WorksheetSECTION II.b TRANSPORTATIONUnit Prices Updated: 06/14/2016Version: 04/26/2017Printed 3/18/2022
CED Permit #:21005115ExistingFuture PublicPrivateRight-of-WayImprovementsImprovements(D) (E)DescriptionNo. Unit PriceUnitQuant.CostQuant.CostQuant.CostQuant.CostDRAINAGE (CPE = Corrugated Polyethylene Pipe, N12 or Equivalent) For Culvert prices, Average of 4' cover was assumed. Assume perforated PVC is same price as solid pipe.) Access Road, R/DD-126.00$ SY* (CBs include frame and lid)BeehiveD-290.00$ EachThrough-curb Inlet FrameworkD-3400.00$ EachCB Type ID-41,500.00$ Each23,000.00CB Type ILD-51,750.00$ EachCB Type II, 48" diameterD-62,300.00$ Each49,200.00 for additional depth over 4' D-7480.00$ FTCB Type II, 54" diameterD-82,500.00$ Each410,000.00 for additional depth over 4'D-9495.00$ FTCB Type II, 60" diameterD-102,800.00$ Each12,800.00 for additional depth over 4'D-11600.00$ FTCB Type II, 72" diameterD-126,000.00$ Each16,000.00 for additional depth over 4'D-13850.00$ FTCB Type II, 96" diameterD-1414,000.00$ Each for additional depth over 4'D-15925.00$ FTTrash Rack, 12"D-16350.00$ EachTrash Rack, 15"D-17410.00$ EachTrash Rack, 18"D-18480.00$ EachTrash Rack, 21"D-19550.00$ EachCleanout, PVC, 4"D-20150.00$ EachCleanout, PVC, 6"D-21170.00$ EachCleanout, PVC, 8"D-22200.00$ EachCulvert, PVC, 4" D-2310.00$ LFCulvert, PVC, 6" D-2413.00$ LFCulvert, PVC, 8" D-2515.00$ LFCulvert, PVC, 12" D-2623.00$ LFCulvert, PVC, 15" D-2735.00$ LFCulvert, PVC, 18" D-2841.00$ LFCulvert, PVC, 24"D-2956.00$ LFCulvert, PVC, 30" D-3078.00$ LFCulvert, PVC, 36" D-31130.00$ LFCulvert, CMP, 8"D-3219.00$ LF2504,750.00Culvert, CMP, 12"D-3329.00$ LF9261.00SUBTOTAL THIS PAGE:12,000.0024,011.00(B)(C)(D)(E)SITE IMPROVEMENT BOND QUANTITY WORKSHEETFOR DRAINAGE AND STORMWATER FACILITIESQuantity Remaining (Bond Reduction) (B)(C)Page 7 of 14Ref 8-H Bond Quantity WorksheetSECTION II.c DRAINAGEUnit Prices Updated: 06/14/2016Version: 04/26/2017Printed 3/18/2022
CED Permit #:21005115ExistingFuture PublicPrivateRight-of-WayImprovementsImprovements(D) (E)DescriptionNo. Unit PriceUnitQuant.CostQuant.CostQuant.CostQuant.CostSITE IMPROVEMENT BOND QUANTITY WORKSHEETFOR DRAINAGE AND STORMWATER FACILITIESQuantity Remaining (Bond Reduction) (B)(C)DRAINAGE (Continued)Culvert, CMP, 15"D-3435.00$ LFCulvert, CMP, 18"D-3541.00$ LFCulvert, CMP, 24"D-3656.00$ LF30016,800.0015840.00Culvert, CMP, 30"D-3778.00$ LFCulvert, CMP, 36"D-38130.00$ LFCulvert, CMP, 48"D-39190.00$ LFCulvert, CMP, 60"D-40270.00$ LFCulvert, CMP, 72"D-41350.00$ LFCulvert, Concrete, 8"D-4242.00$ LFCulvert, Concrete, 12"D-4348.00$ LFCulvert, Concrete, 15"D-4478.00$ LFCulvert, Concrete, 18"D-4548.00$ LFCulvert, Concrete, 24"D-4678.00$ LFCulvert, Concrete, 30"D-47125.00$ LFCulvert, Concrete, 36"D-48150.00$ LFCulvert, Concrete, 42"D-49175.00$ LFCulvert, Concrete, 48"D-50205.00$ LFCulvert, CPE Triple Wall, 6" D-5114.00$ LFCulvert, CPE Triple Wall, 8" D-5216.00$ LFCulvert, CPE Triple Wall, 12" D-5324.00$ LFCulvert, CPE Triple Wall, 15" D-5435.00$ LFCulvert, CPE Triple Wall, 18" D-5541.00$ LFCulvert, CPE Triple Wall, 24" D-5656.00$ LFCulvert, CPE Triple Wall, 30" D-5778.00$ LFCulvert, CPE Triple Wall, 36" D-58130.00$ LFCulvert, LCPE, 6"D-5960.00$ LFCulvert, LCPE, 8"D-6072.00$ LFCulvert, LCPE, 12"D-6184.00$ LFCulvert, LCPE, 15"D-6296.00$ LFCulvert, LCPE, 18"D-63108.00$ LFCulvert, LCPE, 24"D-64120.00$ LFCulvert, LCPE, 30"D-65132.00$ LFCulvert, LCPE, 36"D-66144.00$ LFCulvert, LCPE, 48"D-67156.00$ LFCulvert, LCPE, 54"D-68168.00$ LFSUBTOTAL THIS PAGE:16,800.00840.00(B)(C)(D)(E)Page 8 of 14Ref 8-H Bond Quantity WorksheetSECTION II.c DRAINAGEUnit Prices Updated: 06/14/2016Version: 04/26/2017Printed 3/18/2022
CED Permit #:21005115ExistingFuture PublicPrivateRight-of-WayImprovementsImprovements(D) (E)DescriptionNo. Unit PriceUnitQuant.CostQuant.CostQuant.CostQuant.CostSITE IMPROVEMENT BOND QUANTITY WORKSHEETFOR DRAINAGE AND STORMWATER FACILITIESQuantity Remaining (Bond Reduction) (B)(C)DRAINAGE (Continued)Culvert, LCPE, 60"D-69180.00$ LFCulvert, LCPE, 72"D-70192.00$ LFCulvert, HDPE, 6"D-7142.00$ LFCulvert, HDPE, 8"D-7242.00$ LFCulvert, HDPE, 12"D-7374.00$ LFCulvert, HDPE, 15"D-74106.00$ LFCulvert, HDPE, 18"D-75138.00$ LFCulvert, HDPE, 24"D-76221.00$ LFCulvert, HDPE, 30"D-77276.00$ LFCulvert, HDPE, 36"D-78331.00$ LFCulvert, HDPE, 48"D-79386.00$ LFCulvert, HDPE, 54"D-80441.00$ LFCulvert, HDPE, 60"D-81496.00$ LFCulvert, HDPE, 72"D-82551.00$ LFPipe, Polypropylene, 6"D-8384.00$ LFPipe, Polypropylene, 8"D-8489.00$ LFPipe, Polypropylene, 12"D-8595.00$ LFPipe, Polypropylene, 15"D-86100.00$ LFPipe, Polypropylene, 18"D-87106.00$ LFPipe, Polypropylene, 24"D-88111.00$ LFPipe, Polypropylene, 30"D-89119.00$ LFPipe, Polypropylene, 36"D-90154.00$ LFPipe, Polypropylene, 48"D-91226.00$ LFPipe, Polypropylene, 54"D-92332.00$ LFPipe, Polypropylene, 60"D-93439.00$ LFPipe, Polypropylene, 72"D-94545.00$ LFCulvert, DI, 6"D-9561.00$ LFCulvert, DI, 8"D-9684.00$ LFCulvert, DI, 12"D-97106.00$ LFCulvert, DI, 15"D-98129.00$ LFCulvert, DI, 18"D-99152.00$ LFCulvert, DI, 24"D-100175.00$ LFCulvert, DI, 30"D-101198.00$ LFCulvert, DI, 36"D-102220.00$ LFCulvert, DI, 48"D-103243.00$ LFCulvert, DI, 54"D-104266.00$ LFCulvert, DI, 60"D-105289.00$ LFCulvert, DI, 72"D-106311.00$ LFSUBTOTAL THIS PAGE:(B)(C)(D)(E)Page 9 of 14Ref 8-H Bond Quantity WorksheetSECTION II.c DRAINAGEUnit Prices Updated: 06/14/2016Version: 04/26/2017Printed 3/18/2022
CED Permit #:21005115ExistingFuture PublicPrivateRight-of-WayImprovementsImprovements(D) (E)DescriptionNo. Unit PriceUnitQuant.CostQuant.CostQuant.CostQuant.CostSITE IMPROVEMENT BOND QUANTITY WORKSHEETFOR DRAINAGE AND STORMWATER FACILITIESQuantity Remaining (Bond Reduction) (B)(C)Specialty Drainage ItemsDitching SD-19.50$ CYFlow Dispersal Trench (1,436 base+)SD-328.00$ LF French Drain (3' depth)SD-426.00$ LF2105,460.00Geotextile, laid in trench, polypropyleneSD-53.00$ SYMid-tank Access Riser, 48" dia, 6' deepSD-62,000.00$ Each36,000.00Pond Overflow SpillwaySD-716.00$ SYRestrictor/Oil Separator, 12"SD-81,150.00$ EachRestrictor/Oil Separator, 15"SD-91,350.00$ EachRestrictor/Oil Separator, 18"SD-101,700.00$ EachRiprap, placedSD-1142.00$ CYTank End Reducer (36" diameter)SD-121,200.00$ EachInfiltration pond testingSD-13125.00$ HRPermeable PavementSD-14Permeable Concrete SidewalkSD-15Culvert, Box __ ft x __ ftSD-16SUBTOTAL SPECIALTY DRAINAGE ITEMS:11,460.00(B)(C)(D)(E)STORMWATER FACILITIES (Include Flow Control and Water Quality Facility Summary Sheet and Sketch)Detention PondSF-1Each Detention TankSF-265,000.00$ Each 165,000.00Detention VaultSF-3Each Infiltration PondSF-4Each Infiltration TankSF-5Each Infiltration VaultSF-6Each Infiltration TrenchesSF-7Each Basic Biofiltration SwaleSF-8Each Wet Biofiltration SwaleSF-9Each WetpondSF-10Each WetvaultSF-11Each Sand FilterSF-12Each Sand Filter VaultSF-13Each Linear Sand FilterSF-14Each Proprietary FacilitySF-1530,000.00$ Each 260,000.00Bioretention FacilitySF-16Each SUBTOTAL STORMWATER FACILITIES:125,000.00(B)(C)(D)(E)Page 10 of 14Ref 8-H Bond Quantity WorksheetSECTION II.c DRAINAGEUnit Prices Updated: 06/14/2016Version: 04/26/2017Printed 3/18/2022
CED Permit #:21005115ExistingFuture PublicPrivateRight-of-WayImprovementsImprovements(D) (E)DescriptionNo. Unit PriceUnitQuant.CostQuant.CostQuant.CostQuant.CostSITE IMPROVEMENT BOND QUANTITY WORKSHEETFOR DRAINAGE AND STORMWATER FACILITIESQuantity Remaining (Bond Reduction) (B)(C)WRITE-IN-ITEMS (INCLUDE ON-SITE BMPs)WI-1WI-2WI-3WI-4WI-5WI-6WI-7WI-8WI-9WI-10WI-11WI-12WI-13WI-14WI-15SUBTOTAL WRITE-IN ITEMS:DRAINAGE AND STORMWATER FACILITIES SUBTOTAL:28,800.00161,311.00SALES TAX @ 10%2,880.0016,131.10DRAINAGE AND STORMWATER FACILITIES TOTAL:31,680.00177,442.10(B) (C) (D) (E)Page 11 of 14Ref 8-H Bond Quantity WorksheetSECTION II.c DRAINAGEUnit Prices Updated: 06/14/2016Version: 04/26/2017Printed 3/18/2022
CED Permit #:21005115ExistingFuture PublicPrivateRight-of-WayImprovementsImprovements(D) (E)DescriptionNo. Unit PriceUnitQuant.CostQuant.CostQuant.CostQuant.CostConnection to Existing WatermainW-12,000.00$ Each24,000.00Ductile Iron Watermain, CL 52, 4 Inch DiameterW-250.00$ LFDuctile Iron Watermain, CL 52, 6 Inch DiameterW-356.00$ LFDuctile Iron Watermain, CL 52, 8 Inch DiameterW-460.00$ LF60036,000.00Ductile Iron Watermain, CL 52, 10 Inch DiameterW-570.00$ LFDuctile Iron Watermain, CL 52, 12 Inch DiameterW-680.00$ LFGate Valve, 4 inch DiameterW-7500.00$ EachGate Valve, 6 inch DiameterW-8700.00$ EachGate Valve, 8 Inch DiameterW-9800.00$ Each97,200.00Gate Valve, 10 Inch DiameterW-101,000.00$ EachGate Valve, 12 Inch DiameterW-111,200.00$ EachFire Hydrant AssemblyW-124,000.00$ Each28,000.00Permanent Blow-Off AssemblyW-131,800.00$ Each11,800.00Air-Vac Assembly, 2-Inch DiameterW-142,000.00$ EachAir-Vac Assembly, 1-Inch DiameterW-151,500.00$ EachCompound Meter Assembly 3-inch DiameterW-168,000.00$ EachCompound Meter Assembly 4-inch DiameterW-179,000.00$ EachCompound Meter Assembly 6-inch DiameterW-1810,000.00$ Each110,000.00Pressure Reducing Valve Station 8-inch to 10-inchW-1920,000.00$ EachWATER SUBTOTAL:67,000.00SALES TAX @ 10%6,700.00WATER TOTAL:73,700.00(B) (C) (D) (E)SITE IMPROVEMENT BOND QUANTITY WORKSHEETFOR WATERQuantity Remaining (Bond Reduction) (B)(C)Page 12 of 14Ref 8-H Bond Quantity WorksheetSECTION II.d WATERUnit Prices Updated: 06/14/2016Version: 04/26/2017Printed 3/18/2022
CED Permit #:21005115ExistingFuture PublicPrivateRight-of-WayImprovementsImprovements(D) (E)DescriptionNo. Unit PriceUnitQuant.CostQuant.CostQuant.CostQuant.CostClean OutsSS-11,000.00$ Each33,000.00Grease Interceptor, 500 gallonSS-28,000.00$ EachGrease Interceptor, 1000 gallonSS-310,000.00$ EachGrease Interceptor, 1500 gallonSS-415,000.00$ EachSide Sewer Pipe, PVC. 4 Inch DiameterSS-580.00$ LFSide Sewer Pipe, PVC. 6 Inch DiameterSS-695.00$ LFSewer Pipe, PVC, 8 inch DiameterSS-7105.00$ LF202,100.00232,415.00Sewer Pipe, PVC, 12 Inch DiameterSS-8120.00$ LFSewer Pipe, DI, 8 inch DiameterSS-9115.00$ LFSewer Pipe, DI, 12 Inch DiameterSS-10130.00$ LFManhole, 48 Inch DiameterSS-116,000.00$ EachManhole, 54 Inch DiameterSS-136,500.00$ EachManhole, 60 Inch DiameterSS-157,500.00$ EachManhole, 72 Inch DiameterSS-178,500.00$ EachManhole, 96 Inch DiameterSS-1914,000.00$ EachPipe, C-900, 12 Inch DiameterSS-21180.00$ LFOutside DropSS-241,500.00$ LSInside DropSS-251,000.00$ LSSewer Pipe, PVC, ____ Inch DiameterSS-26Lift Station (Entire System)SS-27LSSANITARY SEWER SUBTOTAL:2,100.005,415.00SALES TAX @ 10%210.00541.50SANITARY SEWER TOTAL:2,310.005,956.50(B) (C) (D) (E)SITE IMPROVEMENT BOND QUANTITY WORKSHEETFOR SANITARY SEWERQuantity Remaining (Bond Reduction) (B)(C)Page 13 of 14Ref 8-H Bond Quantity WorksheetSECTION II.e SANITARY SEWERUnit Prices Updated: 06/14/2016Version: 04/26/2017Printed 3/18/2022
Planning Division |1055 South Grady Way – 6th Floor | Renton, WA 98057 (425) 430-7200Date:Name:Project Name: PE Registration No:CED Plan # (LUA):Firm Name:CED Permit # (U):Firm Address:Site Address:Phone No.Parcel #(s):Email Address:Project Phase: Site Restoration/Erosion Sediment Control Subtotal (a)Existing Right-of-Way Improvements Subtotal (b)(b)80,336.30$ Future Public Improvements Subtotal(c)269,390.00$ Stormwater & Drainage Facilities (Public & Private) Subtotal(d)(d)209,122.10$ (e)(f)Site RestorationCivil Construction PermitMaintenance Bond111,769.68$ Bond Reduction2Construction Permit Bond Amount 3Minimum Bond Amount is $10,000.001 Estimate Only - May involve multiple and variable components, which will be established on an individual basis by Development Engineering.2 The City of Renton allows one request only for bond reduction prior to the maintenance period. Reduction of not more than 70% of the original bond amount, provided that the remaining 30% willcover all remaining items to be constructed. 3 Required Bond Amounts are subject to review and modification by Development Engineering.* Note: The word BOND as used in this document means any financial guarantee acceptable to the City of Renton.** Note: All prices include labor, equipment, materials, overhead and profit. 206-267-2425dtapp@ahbl.comWatershed Apartments21-000239625 Williams Avenue1723059069, 1723059136,1823059115FOR APPROVAL210051151200 6th Avenue, Seattle WA 98101346,434.00$ P (a) x 100%SITE IMPROVEMENT BOND QUANTITY WORKSHEET BOND CALCULATIONS10/10/2021Doug Tapp35702AHBL Inc.R((b x 150%) + (d x 100%))S(e) x 150% + (f) x 100%Bond Reduction: Existing Right-of-Way Improvements (Quantity Remaining)2Bond Reduction: Stormwater & Drainage Facilities (Quantity Remaining)2T(P +R - S)Prepared by:Project InformationCONSTRUCTION BOND AMOUNT */**(prior to permit issuance)EST1((b) + (c) + (d)) x 20%4,248.75$ MAINTENANCE BOND */**(after final acceptance of construction)21,056.20$ 80,336.30$ 329,626.55$ 21,056.20$ 2,832.50$ 209,122.10$ -$ Page 14 of 14Ref 8-H Bond Quantity WorksheetSECTION III. BOND WORKSHEETUnit Prices Updated: 06/14/2016Version: 04/26/2017Printed 3/18/2022
Technical Information Report Watershed Affordable Housing Apartments 10-1
2200335.10
10.0 Operations and Maintenance Plan
The drainage facilities detailed in this report will be privately owned and maintained.
Facility Descriptions
Control Structure
The control structure is a manhole on the downstream end (south end) of the pond. The control
structure includes a flow restrictor attached to the outlet pipe that looks like a tee. The bottom of
the tee has an orifice plate, and one downturned elbow also has orifice plates attached to the
bottom. The top of the tee is open. The purpose of the flow restrictor is to control the release of
flows to the downstream system, which prevents flooding and excessive erosion. The manhole
also includes a jailhouse overflow, which is an opening with vertical bars set on the side and near
the top of the structure.
In order to function properly, the control structure should be kept free of excessive accumulated
sediment, trash, and debris. Damage to the structure or the flow restrictor should be repaired or
replaced. The orifice plates and flow restrictor tee should be free of obstructions. If the orifice
plates are damaged or missing, it should be repaired or replaced. The inlet and outlet pipes
should be free of sediment accumulation, trash, and debris. The jailhouse should be clear of
blockages and the grates should be intact.
Conveyance Systems
Pipes transport stormwater runoff from developed portions of the property to the detention pond,
and then to the downstream points of connection. To work properly, pipes must be kept free of silt
and other debris. If pipes become blocked, surface flooding will occur.
Debris Barrier
Debris barriers are a metal trash rack located over the entrance to a pipe or culvert. A debris
barrier may also be a conical structure constructed of metal bars and/or rods placed over a catch
basin. Trash and debris should be removed so that the barrier is clear to receive stormwater
flows. Damaged or missing bars should be repaired or replaced.
Catch Basins and Area Drains
Catch basins collect surface drainage and direct it into storm conveyance pipes. They help
prevent downstream drainage problems by trapping sediment and other debris that would
otherwise flow downstream with the runoff. It is important to keep catch basins clean so that
accumulated silt is not flushed out during a significant storm. In addition, if the outflow pipe
becomes blocked with debris, surface flooding will occur. All catch basins should be inspected at
least once each year and after major storms.
Area drains convey runoff directly into conveyance pipes. To prevent surface flooding, their
surface grates must be kept free of litter and debris. If dirt or other sediment gets into the pipes
and they become blocked, the pipes will need to be cleaned, either manually or using a Vactor
truck.
Technical Information Report Watershed Affordable Housing Apartments 10-2
2200335.10
BioPod Water Quality System
The BioPod™ Biofilter System (BioPod) is a stormwater biofiltration treatment system used to
remove pollutants from stormwater runoff. Impervious surfaces and other urban and suburban
landscapes generate a variety of contaminants that can enter stormwater and pollute downstream
receiving waters unless treatment is provided. The BioPod system uses proprietary StormMix™
biofiltration media to capture and retain pollutants, including total suspended solids (TSS), metals,
nutrients, gross solids, trash, and debris, as well as petroleum hydrocarbons. It is important to
follow the operations and maintenance manual to ensure the BioPod is functioning properly. All
BioPods shall be inspected twice per year and after major storms.
Maintenance Tasks
Refer to Figure 10-1 for the Stormwater Facility Checklist.
Maintenance Requirements
Refer to Figure 10-2 for the Operations and Maintenance (O&M) manual.
Technical Information Report Watershed Affordable Housing Apartments
2200335.10
Section 10.0 Figures
Figure 10-1 ....... Stormwater Facility Checklist
Figure 10-2 ....... Operations and Maintenance (O&M) Manual
Page 1 of 3
STORM FACILITY MAINTENANCE CHECKLIST
Property: Watershed Apartments
Property Owner:
Property Address: 615 Williams Avenue South
Inspection Date:
Completed by:
The following items shall be inspected. Further detailed instructions for maintenance can be
found in the Operations and Maintenance Manual provided in the Technical Information Report.
1. Detention Tank
COMPLETED ITEM
Vault is clear of:
1. Trash and debris
2. Contaminants and pollution
3. Cracks/damage in structure
4. Sediment accumulation (removed if greater than 1.5 foot in depth)
The following are in satisfactory working condition:
5. Cover/metal grate lid (in place, free of obstructions)
6. Cover locking mechanism (bolts are present and pose no difficulty
in removal)
7. Ladder (no missing or damaged rungs)
TAC O MA
2215 North 30th Street
Suite 300
Tacoma, WA 98403-3350
253.383.2422 TEL
253.383.2572 FAX
SEA T TL E
1200 6th Avenue
Suite 1620
Seattle, WA 98101-3117
206.267.2425 TEL
206.267.2429 FAX
SPO KAN E
827 West First Avenue
Suite 301
Spokane, WA 99201-3912
509.252.5019 TEL
509.315.8862 FAX
www.ahbl.com
Civil Engineers
Structural Engineers
Landscape Architects
Community Planners
Natural Resource Ecologists
Land Surveyors
Neighbors
Storm Facility Maintenance Checklist Page 2 of 3
2. Catch Basins/Area Drains
COMPLETED ITEM
Clear of:
1. Trash and debris
2. Sediment
3. Structural damage to frame and or top slab
4. Cracks in basin walls or bottom
5. Vegetation
6. Chemicals or pollution
+ 7. Settlement/misalignment
The following are in satisfactory working condition:
8. Cover/metal grate lid (in place, free of obstructions)
9. Cover locking mechanism (bolts are present and pose no difficulty
in removal)
10. Ladder (no missing or damaged rungs)
3. Conveyance Pipes
COMPLETED ITEM
Clear of:
1. Trash and debris
2. Sediment
3. Vegetation
4. Damage
Storm Facility Maintenance Checklist Page 3 of 3
4. Grounds (Landscaping)
COMPLETED ITEM
Clear of:
1. Trash and debris
2. Weeds in excess of 20% of the landscaped area
3. Poisonous or noxious vegetation
4. Damage to trees and shrubs
APPENDIX A MAINTENANCE REQUIREMENTS FOR STORMWATER FACILITIES AND ON-SITE BMPS
12/12/2016 2017 City of Renton Surface Water Design Manual A-6
NO. 3 – DETENTION TANKS AND VAULTS
MAINTENANCE
COMPONENT
DEFECT OR
PROBLEM
CONDITIONS WHEN
MAINTENANCE IS NEEDED
RESULTS EXPECTED WHEN
MAINTENANCE IS PERFORMED
Site Trash and debris Any trash and debris which exceed 1 cubic foot per 1,000 square feet (this is about equal to the amount of trash it would take to fill up one standard size office garbage can). In general, there should be no visual evidence of dumping.
Trash and debris cleared from site.
Noxious weeds Any noxious or nuisance vegetation which may constitute a hazard to City personnel or the public.
Noxious and nuisance vegetation removed according to applicable regulations. No danger of noxious vegetation where City personnel or the public might normally be.
Contaminants and pollution Any evidence of contaminants or pollution such as oil, gasoline, concrete slurries or paint.
Materials removed and disposed of according to applicable regulations. Source control BMPs implemented if appropriate. No contaminants present other than a surface oil film.
Excessive growth of grass/groundcover Grass or groundcover exceeds 18 inches in height. Grass or groundcover mowed to a height no greater than 6 inches.
Tank or Vault Storage Area Trash and debris Any trash and debris accumulated in vault or tank (includes floatables and non-floatables).
No trash or debris in vault.
Sediment accumulation Accumulated sediment depth exceeds 10% of the diameter of the storage area for ½ length of storage vault or any point depth exceeds 15% of diameter. Example:
72-inch storage tank would require cleaning when sediment reaches depth of 7 inches for more than ½ length of tank.
All sediment removed from storage area.
Tank Structure Plugged air vent Any blockage of the vent. Tank or vault freely vents.
Tank bent out of shape Any part of tank/pipe is bent out of shape more than 10% of its design shape. Tank repaired or replaced to design.
Gaps between sections, damaged
joints or cracks or tears in wall
A gap wider than ½-inch at the joint of any tank sections or any evidence of soil
particles entering the tank at a joint or through a wall.
No water or soil entering tank through joints or walls.
Vault Structure Damage to wall, frame, bottom, and/or top slab
Cracks wider than ½-inch, any evidence of soil entering the structure through cracks or qualified inspection personnel determines that the vault is not structurally sound.
Vault is sealed and structurally sound.
Inlet/Outlet Pipes Sediment accumulation Sediment filling 20% or more of the pipe. Inlet/outlet pipes clear of sediment.
Trash and debris Trash and debris accumulated in inlet/outlet pipes (includes floatables and non-floatables).
No trash or debris in pipes.
Damaged inlet/outlet pipes Cracks wider than ½-inch at the joint of the inlet/outlet pipes or any evidence of soil entering at the joints of the inlet/outlet pipes.
No cracks more than ¼-inch wide at the joint of the inlet/outlet pipe.
Access Manhole Cover/lid not in place Cover/lid is missing or only partially in place. Any open manhole requires immediate maintenance.
Manhole access covered.
APPENDIX A MAINTENANCE REQUIREMENTS FOR STORMWATER FACILITIES AND ON-SITE BMPS
2017 City of Renton Surface Water Design Manual 12/12/2016 A-7
NO. 3 – DETENTION TANKS AND VAULTS
MAINTENANCE
COMPONENT
DEFECT OR
PROBLEM
CONDITIONS WHEN
MAINTENANCE IS NEEDED
RESULTS EXPECTED WHEN
MAINTENANCE IS PERFORMED
Access Manhole (cont.) Locking mechanism not working Mechanism cannot be opened by one maintenance person with proper tools. Bolts cannot be seated. Self-locking cover/lid does not work.
Mechanism opens with proper tools.
Cover/lid difficult to remove One maintenance person cannot remove cover/lid after applying 80 lbs of lift. Cover/lid can be removed and reinstalled by one maintenance person.
Ladder rungs unsafe Missing rungs, misalignment, rust, or
cracks.
Ladder meets design standards. Allows
maintenance person safe access.
Large access
doors/plate
Damaged or difficult
to open
Large access doors or plates cannot be
opened/removed using normal equipment.
Replace or repair access door so it can
opened as designed.
Gaps, doesn't cover completely Large access doors not flat and/or access opening not completely covered. Doors close flat; covers access opening completely.
Lifting rings missing, rusted Lifting rings not capable of lifting weight of door or plate. Lifting rings sufficient to lift or remove door or plate.
APPENDIX A MAINTENANCE REQUIREMENTS FOR STORMWATER FACILITIES AND ON-SITE BMPS
12/12/2016 2017 City of Renton Surface Water Design Manual A-8
NO. 4 – CONTROL STRUCTURE/FLOW RESTRICTOR
MAINTENANCE
COMPONENT
DEFECT OR
PROBLEM
CONDITION WHEN MAINTENANCE
IS NEEDED
RESULTS EXPECTED WHEN
MAINTENANCE IS PERFORMED
Structure Trash and debris Trash or debris of more than ½ cubic foot which is located immediately in front of the structure opening or is blocking capacity of the structure by more than 10%.
No Trash or debris blocking or potentially blocking entrance to structure.
Trash or debris in the structure that exceeds 1/3 the depth from the bottom of basin to invert the lowest pipe into or out of the basin.
No trash or debris in the structure.
Deposits of garbage exceeding 1 cubic foot in volume. No condition present which would attract or support the breeding of insects or rodents.
Sediment accumulation Sediment exceeds 60% of the depth from the bottom of the structure to the invert of the lowest pipe into or out of the structure or the bottom of the FROP-T section or is
within 6 inches of the invert of the lowest pipe into or out of the structure or the bottom of the FROP-T section.
Sump of structure contains no sediment.
Damage to frame and/or top slab Corner of frame extends more than ¾ inch past curb face into the street (If applicable).
Frame is even with curb.
Top slab has holes larger than 2 square inches or cracks wider than ¼ inch. Top slab is free of holes and cracks.
Frame not sitting flush on top slab, i.e., separation of more than ¾ inch of the frame from the top slab.
Frame is sitting flush on top slab.
Cracks in walls or bottom Cracks wider than ½ inch and longer than 3 feet, any evidence of soil particles entering structure through cracks, or maintenance person judges that structure is unsound.
Structure is sealed and structurally sound.
Cracks wider than ½ inch and longer than 1 foot at the joint of any inlet/outlet pipe or
any evidence of soil particles entering structure through cracks.
No cracks more than 1/4 inch wide at the joint of inlet/outlet pipe.
Settlement/ misalignment Structure has settled more than 1 inch or has rotated more than 2 inches out of alignment.
Basin replaced or repaired to design standards.
Damaged pipe joints Cracks wider than ½-inch at the joint of the inlet/outlet pipes or any evidence of soil entering the structure at the joint of the inlet/outlet pipes.
No cracks more than ¼-inch wide at the joint of inlet/outlet pipes.
Contaminants and pollution Any evidence of contaminants or pollution such as oil, gasoline, concrete slurries or paint.
Materials removed and disposed of according to applicable regulations. Source control BMPs implemented if appropriate. No contaminants present other than a surface oil film.
Ladder rungs missing or unsafe Ladder is unsafe due to missing rungs, misalignment, rust, cracks, or sharp edges. Ladder meets design standards and allows maintenance person safe access.
FROP-T Section Damaged FROP-T T section is not securely attached to
structure wall and outlet pipe structure should support at least 1,000 lbs of up or down pressure.
T section securely attached to wall and
outlet pipe.
Structure is not in upright position (allow up to 10% from plumb). Structure in correct position.
APPENDIX A MAINTENANCE REQUIREMENTS FOR STORMWATER FACILITIES AND ON-SITE BMPS
2017 City of Renton Surface Water Design Manual 12/12/2016 A-9
NO. 4 – CONTROL STRUCTURE/FLOW RESTRICTOR
MAINTENANCE
COMPONENT
DEFECT OR
PROBLEM
CONDITION WHEN MAINTENANCE
IS NEEDED
RESULTS EXPECTED WHEN
MAINTENANCE IS PERFORMED
FROP-T Section (cont.) Damaged FROP-T (cont.) Connections to outlet pipe are not watertight or show signs of deteriorated grout.
Connections to outlet pipe are water tight; structure repaired or replaced and works as designed.
Any holes—other than designed holes—in
the structure.
Structure has no holes other than designed
holes.
Cleanout Gate Damaged or missing cleanout gate Cleanout gate is missing. Replace cleanout gate.
Cleanout gate is not watertight. Gate is watertight and works as designed.
Gate cannot be moved up and down by one maintenance person. Gate moves up and down easily and is watertight.
Chain/rod leading to gate is missing or damaged. Chain is in place and works as designed.
Orifice Plate Damaged or missing
orifice plate
Control device is not working properly due
to missing, out of place, or bent orifice plate.
Plate is in place and works as designed.
Obstructions to orifice plate Any trash, debris, sediment, or vegetation blocking the plate. Plate is free of all obstructions and works as designed.
Overflow Pipe Obstructions to
overflow pipe
Any trash or debris blocking (or having the
potential of blocking) the overflow pipe.
Pipe is free of all obstructions and works
as designed.
Deformed or damaged lip of overflow pipe
Lip of overflow pipe is bent or deformed. Overflow pipe does not allow overflow at an elevation lower than design
Inlet/Outlet Pipe Sediment accumulation Sediment filling 20% or more of the pipe. Inlet/outlet pipes clear of sediment.
Trash and debris Trash and debris accumulated in
inlet/outlet pipes (includes floatables and non-floatables).
No trash or debris in pipes.
Damaged inlet/outlet
pipe
Cracks wider than ½-inch at the joint of the
inlet/outlet pipes or any evidence of soil entering at the joints of the inlet/outlet pipes.
No cracks more than ¼-inch wide at the
joint of the inlet/outlet pipe.
Metal Grates (If applicable) Unsafe grate opening Grate with opening wider than 7/8 inch. Grate opening meets design standards.
Trash and debris Trash and debris that is blocking more
than 20% of grate surface.
Grate free of trash and debris. footnote to
guidelines for disposal
Damaged or missing grate Grate missing or broken member(s) of the grate. Grate is in place and meets design standards.
Manhole Cover/Lid Cover/lid not in place Cover/lid is missing or only partially in place. Any open structure requires urgent maintenance.
Cover/lid protects opening to structure.
Locking mechanism
not working
Mechanism cannot be opened by one
maintenance person with proper tools. Bolts cannot be seated. Self-locking cover/lid does not work.
Mechanism opens with proper tools.
Cover/lid difficult to remove One maintenance person cannot remove cover/lid after applying 80 lbs. of lift. Cover/lid can be removed and reinstalled by one maintenance person.
APPENDIX A MAINTENANCE REQUIREMENTS FOR STORMWATER FACILITIES AND ON-SITE BMPS
12/12/2016 2017 City of Renton Surface Water Design Manual A-10
NO. 5 – CATCH BASINS AND MANHOLES
MAINTENANCE
COMPONENT
DEFECT OR
PROBLEM
CONDITION WHEN MAINTENANCE
IS NEEDED
RESULTS EXPECTED WHEN
MAINTENANCE IS PERFORMED
Structure Sediment accumulation Sediment exceeds 60% of the depth from the bottom of the catch basin to the invert of the lowest pipe into or out of the catch basin or is within 6 inches of the invert of the lowest pipe into or out of the catch basin.
Sump of catch basin contains no sediment.
Trash and debris Trash or debris of more than ½ cubic foot which is located immediately in front of the catch basin opening or is blocking capacity of the catch basin by more than 10%.
No Trash or debris blocking or potentially blocking entrance to catch basin.
Trash or debris in the catch basin that exceeds 1/3 the depth from the bottom of basin to invert the lowest pipe into or out of the basin.
No trash or debris in the catch basin.
Dead animals or vegetation that could generate odors that could cause complaints or dangerous gases (e.g., methane).
No dead animals or vegetation present within catch basin.
Deposits of garbage exceeding 1 cubic foot in volume. No condition present which would attract or support the breeding of insects or rodents.
Damage to frame and/or top slab Corner of frame extends more than ¾ inch past curb face into the street (If applicable).
Frame is even with curb.
Top slab has holes larger than 2 square inches or cracks wider than ¼ inch. Top slab is free of holes and cracks.
Frame not sitting flush on top slab, i.e., separation of more than ¾ inch of the frame from the top slab.
Frame is sitting flush on top slab.
Cracks in walls or bottom Cracks wider than ½ inch and longer than 3 feet, any evidence of soil particles entering catch basin through cracks, or maintenance person judges that catch
basin is unsound.
Catch basin is sealed and is structurally sound.
Cracks wider than ½ inch and longer than 1 foot at the joint of any inlet/outlet pipe or any evidence of soil particles entering catch basin through cracks.
No cracks more than 1/4 inch wide at the joint of inlet/outlet pipe.
Settlement/ misalignment Catch basin has settled more than 1 inch or has rotated more than 2 inches out of alignment.
Basin replaced or repaired to design standards.
Damaged pipe joints Cracks wider than ½-inch at the joint of the inlet/outlet pipes or any evidence of soil entering the catch basin at the joint of the inlet/outlet pipes.
No cracks more than ¼-inch wide at the joint of inlet/outlet pipes.
Contaminants and pollution Any evidence of contaminants or pollution such as oil, gasoline, concrete slurries or paint.
Materials removed and disposed of according to applicable regulations. Source control BMPs implemented if appropriate. No contaminants present other than a surface oil film.
Inlet/Outlet Pipe Sediment accumulation Sediment filling 20% or more of the pipe. Inlet/outlet pipes clear of sediment.
Trash and debris Trash and debris accumulated in
inlet/outlet pipes (includes floatables and non-floatables).
No trash or debris in pipes.
APPENDIX A MAINTENANCE REQUIREMENTS FOR STORMWATER FACILITIES AND ON-SITE BMPS
2017 City of Renton Surface Water Design Manual 12/12/2016 A-11
NO. 5 – CATCH BASINS AND MANHOLES
MAINTENANCE
COMPONENT
DEFECT OR
PROBLEM
CONDITION WHEN MAINTENANCE
IS NEEDED
RESULTS EXPECTED WHEN
MAINTENANCE IS PERFORMED
Inlet/Outlet Pipe (cont.) Damaged inlet/outlet pipe Cracks wider than ½-inch at the joint of the inlet/outlet pipes or any evidence of soil entering at the joints of the inlet/outlet pipes.
No cracks more than ¼-inch wide at the joint of the inlet/outlet pipe.
Metal Grates (Catch Basins) Unsafe grate opening Grate with opening wider than 7/8 inch. Grate opening meets design standards.
Trash and debris Trash and debris that is blocking more than 20% of grate surface. Grate free of trash and debris. footnote to guidelines for disposal
Damaged or missing grate Grate missing or broken member(s) of the grate. Any open structure requires urgent maintenance.
Grate is in place and meets design standards.
Manhole Cover/Lid Cover/lid not in place Cover/lid is missing or only partially in place. Any open structure requires urgent maintenance.
Cover/lid protects opening to structure.
Locking mechanism not working Mechanism cannot be opened by one maintenance person with proper tools. Bolts cannot be seated. Self-locking cover/lid does not work.
Mechanism opens with proper tools.
Cover/lid difficult to remove One maintenance person cannot remove cover/lid after applying 80 lbs. of lift. Cover/lid can be removed and reinstalled by one maintenance person.
APPENDIX A MAINTENANCE REQUIREMENTS FOR STORMWATER FACILITIES AND ON-SITE BMPS
12/12/2016 2017 City of Renton Surface Water Design Manual A-12
NO. 6 – CONVEYANCE PIPES AND DITCHES
MAINTENANCE
COMPONENT
DEFECT OR
PROBLEM
CONDITIONS WHEN
MAINTENANCE IS NEEDED
RESULTS EXPECTED WHEN
MAINTENANCE IS PERFORMED
Pipes Sediment & debris accumulation Accumulated sediment or debris that exceeds 20% of the diameter of the pipe. Water flows freely through pipes.
Vegetation/root growth in pipe Vegetation/roots that reduce free movement of water through pipes. Water flows freely through pipes.
Contaminants and pollution Any evidence of contaminants or pollution such as oil, gasoline, concrete slurries or paint.
Materials removed and disposed of according to applicable regulations. Source control BMPs implemented if appropriate.
No contaminants present other than a surface oil film.
Damage to protective coating or corrosion Protective coating is damaged; rust or corrosion is weakening the structural integrity of any part of pipe.
Pipe repaired or replaced.
Damaged pipes Any dent that decreases the cross section area of pipe by more than 20% or is determined to have weakened structural integrity of the pipe.
Pipe repaired or replaced.
Ditches Trash and debris Trash and debris exceeds 1 cubic foot per 1,000 square feet of ditch and slopes. Trash and debris cleared from ditches.
Sediment accumulation Accumulated sediment that exceeds 20% of the design depth. Ditch cleaned/flushed of all sediment and debris so that it matches design.
Noxious weeds Any noxious or nuisance vegetation which may constitute a hazard to City personnel or the public.
Noxious and nuisance vegetation removed according to applicable regulations. No danger of noxious vegetation where City personnel or the public might normally be.
Contaminants and pollution Any evidence of contaminants or pollution such as oil, gasoline, concrete slurries or paint.
Materials removed and disposed of according to applicable regulations. Source control BMPs implemented if appropriate. No contaminants present other than a surface oil film.
Excessive vegetation growth Vegetation that reduces free movement of water through ditches. Water flows freely through ditches.
Erosion damage to
slopes
Any erosion observed on a ditch slope. Slopes are not eroding.
Rock lining out of place or missing (If applicable)
One layer or less of rock exists above native soil area 5 square feet or more, any exposed native soil.
Replace rocks to design standards.
APPENDIX A MAINTENANCE REQUIREMENTS FOR STORMWATER FACILITIES AND ON-SITE BMPS
2017 City of Renton Surface Water Design Manual 12/12/2016 A-15
NO. 9 – FENCING
MAINTENANCE
COMPONENT
DEFECT OR
PROBLEM
CONDITIONS WHEN
MAINTENANCE IS NEEDED
RESULTS EXPECTED WHEN
MAINTENANCE IS PERFORMED
Site Erosion or holes under fence Erosion or holes more than 4 inches high and 12-18 inches wide permitting access through an opening under a fence.
No access under the fence.
Wood Posts, Boards
and Cross Members
Missing or damaged
parts
Missing or broken boards, post out of
plumb by more than 6 inches or cross members broken
No gaps on fence due to missing or broken
boards, post plumb to within 1½ inches, cross members sound.
Weakened by rotting
or insects
Any part showing structural deterioration
due to rotting or insect damage
All parts of fence are structurally sound.
Damaged or failed
post foundation
Concrete or metal attachments
deteriorated or unable to support posts.
Post foundation capable of supporting
posts even in strong wind.
Metal Posts, Rails and Fabric Damaged parts Post out of plumb more than 6 inches. Post plumb to within 1½ inches.
Top rails bent more than 6 inches. Top rail free of bends greater than 1 inch.
Any part of fence (including post, top rails, and fabric) more than 1 foot out of design alignment.
Fence is aligned and meets design standards.
Missing or loose tension wire. Tension wire in place and holding fabric.
Deteriorated paint or protective coating Part or parts that have a rusting or scaling condition that has affected structural adequacy.
Structurally adequate posts or parts with a uniform protective coating.
Openings in fabric Openings in fabric are such that an 8-inch diameter ball could fit through. Fabric mesh openings within 50% of grid size.
APPENDIX A MAINTENANCE REQUIREMENTS FOR STORMWATER FACILITIES AND ON-SITE BMPS
12/12/2016 2017 City of Renton Surface Water Design Manual A-16
NO. 10 – GATES/BOLLARDS/ACCESS BARRIERS
MAINTENANCE
COMPONENT
DEFECT OR
PROBLEM
CONDITIONS WHEN
MAINTENANCE IS NEEDED
RESULTS EXPECTED WHEN
MAINTENANCE IS PERFORMED
Chain Link Fencing Gate Damaged or missing members Missing gate. Gates in place.
Broken or missing hinges such that gate cannot be easily opened and closed by a maintenance person.
Hinges intact and lubed. Gate is working freely.
Gate is out of plumb more than 6 inches and more than 1 foot out of design alignment.
Gate is aligned and vertical.
Missing stretcher bar, stretcher bands, and ties. Stretcher bar, bands, and ties in place.
Locking mechanism does not lock gate Locking device missing, no-functioning or does not link to all parts. Locking mechanism prevents opening of gate.
Openings in fabric Openings in fabric are such that an 8-inch diameter ball could fit through. Fabric mesh openings within 50% of grid size.
Bar Gate Damaged or missing cross bar Cross bar does not swing open or closed, is missing or is bent to where it does not prevent vehicle access.
Cross bar swings fully open and closed and prevents vehicle access.
Locking mechanism does not lock gate Locking device missing, no-functioning or does not link to all parts. Locking mechanism prevents opening of gate.
Support post damaged Support post does not hold cross bar up. Cross bar held up preventing vehicle access into facility.
Bollards Damaged or missing bollards Bollard broken, missing, does not fit into support hole or hinge broken or missing. No access for motorized vehicles to get into facility.
Bollards do not lock Locking assembly or lock missing or cannot be attached to lock bollard in place. No access for motorized vehicles to get into facility.
Boulders Dislodged boulders Boulders not located to prevent motorized vehicle access. No access for motorized vehicles to get into facility.
Evidence of vehicles
circumventing boulders
Motorized vehicles going around or
between boulders.
No access for motorized vehicles to get
into facility.
APPENDIX A MAINTENANCE REQUIREMENTS FOR STORMWATER FACILITIES AND ON-SITE BMPS
2017 City of Renton Surface Water Design Manual 12/12/2016 A-17
NO. 11 – GROUNDS (LANDSCAPING)
MAINTENANCE
COMPONENT
DEFECT OR
PROBLEM
CONDITIONS WHEN
MAINTENANCE IS NEEDED
RESULTS EXPECTED WHEN
MAINTENANCE IS PERFORMED
Site Trash and debris Any trash and debris which exceed 1 cubic foot per 1,000 square feet (this is about equal to the amount of trash it would take to fill up one standard size office garbage can). In general, there should be no visual evidence of dumping.
Trash and debris cleared from site.
Noxious weeds Any noxious or nuisance vegetation which may constitute a hazard to City personnel or the public.
Noxious and nuisance vegetation removed according to applicable regulations. No danger of noxious vegetation where City personnel or the public might normally be.
Contaminants and pollution Any evidence of contaminants or pollution such as oil, gasoline, concrete slurries or paint.
Materials removed and disposed of according to applicable regulations. Source control BMPs implemented if appropriate. No contaminants present other than a surface oil film.
Excessive growth of grass/groundcover Grass or groundcover exceeds 18 inches in height. Grass or groundcover mowed to a height no greater than 6 inches.
Trees and Shrubs Hazard tree identified Any tree or limb of a tree identified as having a potential to fall and cause property damage or threaten human life. A hazard tree identified by a qualified arborist must be removed as soon as possible.
No hazard trees in facility.
Damaged tree or
shrub identified
Limbs or parts of trees or shrubs that are
split or broken which affect more than 25% of the total foliage of the tree or shrub.
Trees and shrubs with less than 5% of total
foliage with split or broken limbs.
Trees or shrubs that have been blown
down or knocked over.
No blown down vegetation or knocked over
vegetation. Trees or shrubs free of injury.
Trees or shrubs which are not adequately supported or are leaning over, causing exposure of the roots.
Tree or shrub in place and adequately supported; dead or diseased trees removed.
APPENDIX A MAINTENANCE REQUIREMENTS FOR STORMWATER FACILITIES AND ON-SITE BMPS
12/12/2016 2017 City of Renton Surface Water Design Manual A-44
NO. 36 – VEGETATED ROOF BMP
MAINTENANCE
COMPONENT
DEFECT OR
PROBLEM
CONDITIONS WHEN
MAINTENANCE IS NEEDED
RESULTS EXPECTED WHEN
MAINTENANCE IS PERFORMED
Preventive Vegetation Vegetation to be watered and pruned as needed to maintain healthy growth. Healthy vegetation growth with full coverage as designed.
Site Trash and debris Trash and debris has accumulated on the vegetated roof. Vegetated roof free of any trash or debris.
Waterproof Membrane Leaking waterproof membrane Waterproof membrane breached. Waterproof membrane has no tears or holes allowing water through it.
Drainage Layer Drainage pathway plugged/obstructed Drainage layer flow plugged or obstructed. Drainage layer passing water with no obstruction.
Drainage Overflow obstructed Drainage of overflow is obstructed. Overflow has no obstruction.
Growth Media Compaction Soil in the growth media area compacted. No part of the growth media is compacted.
Erosion Growth media washed out. Growth media is not being washed away.
Insufficient nutrients Plants are not thriving. Growth media has proper nutrients to support plant growth.
Vegetation Insufficient vegetation Vegetation species not succulents, grass, herbs,
and/or wildflowers adapted to harsh conditions.
Correct species of vegetation is used.
Poor vegetation coverage Healthy vegetation covers less than 90% of vegetation area. Healthy vegetation covers more than 90% of vegetation area.
Undesirable vegetation Weeds and other undesirable plants are invading more than 10% of vegetated area. No undesirable vegetation occurs in the vegetated area. No herbicides or pesticides used to control undesirable vegetation.
Poor vegetation
growth
Special vegetation not thriving. Special vegetation is kept healthy and
inspected on frequent schedule.
Border Zone Access restricted Border zone limited by vegetation overgrowth or other means. Border zone is kept open so vegetated area is accessible.
Gravel Stop Overflow uncontained Gravel stop does not contain overflow or divert it to a designed outlet. Overflow water is only exits from the designed outlet.
APPENDIX A MAINTENANCE REQUIREMENTS FOR STORMWATER FACILITIES AND ON-SITE BMPS
2017 City of Renton Surface Water Design Manual 12/12/2016 A-47
NO. 38 – SOIL AMENDMENT BMP
MAINTENANCE COMPONENT DEFECT OR PROBLEM CONDITIONS WHEN MAINTENANCE IS NEEDED RESULTS EXPECTED WHEN MAINTENANCE IS PERFORMED
Soil Media Unhealthy vegetation Vegetation not fully covering ground surface or vegetation health is poor.
Yellowing: possible Nitrogen (N) deficiency. Poor growth: possible
Phosphorous (P) deficiency. Poor flowering, spotting or curled leaves, or weak roots or stems: possible Potassium
(K) deficiency.
Plants are healthy and appropriate for site conditions
Inadequate soil nutrients and
structure
In the fall, return leaf fall and shredded woody materials from the landscape to the
site when possible
Soil providing plant nutrients and structure
Excessive vegetation growth Grass becomes excessively tall (greater than 10 inches); nuisance weeds and other
vegetation start to take over.
Healthy turf- “grasscycle” (mulch-mow or leave the clippings) to build turf health
Weeds Preventive maintenance Avoid use of pesticides (bug and weed killers), like “weed & feed,” which damage
the soil
Fertilizer needed Where fertilization is needed (mainly turf and annual flower beds), a moderate
fertilization program should be used which relies on compost, natural fertilizers or slow-release synthetic balanced fertilizers
Integrated Pest Management (IPM) protocols for fertilization followed
Bare spots Bare spots on soil No bare spots, area covered with
vegetation or mulch mixed into the underlying soil.
Compaction Poor infiltration due to soil compaction
• To remediate compaction, aerate
soil, till to at least 8-inch depth, or further amend soil with compost and
re-till
• If areas are turf, aerate compacted areas and top dress them with 1/4 to
1/2 inch of compost to renovate them
• If drainage is still slow, consider investigating alternative causes (e.g.,
high wet season groundwater levels, low permeability soils)
• Also consider site use and protection
from compacting activities
No soil compaction
Poor infiltration Soils become waterlogged, do not appear to be infiltrating. Facility infiltrating properly
Erosion/Scouring Erosion Areas of potential erosion are visible Causes of erosion (e.g., concentrate flow entering area, channelization of runoff) identified and damaged area stabilized (regrade, rock, vegetation, erosion control
matting).For deep channels or cuts (over 3 inches in ponding depth), temporary
erosion control measures in place until
permanent repairs can be made
Grass/Vegetation Unhealthy vegetation Less than 75% of planted vegetation is
healthy with a generally good appearance.
Healthy vegetation. Unhealthy plants
removed/replaced. Appropriate vegetation planted in terms of exposure, soil and soil
moisture.
Noxious Weeds Noxious weeds Listed noxious vegetation is present (refer to current County noxious weed list). No noxious weeds present.
Inspection and Maintenance Guide
BIOPODTM SYSTEM
WITH STORMMIX™ MEDIA
BioPod™ Biofilter with StormMix™ Biofiltration Media
Description
The BioPod™ Biofilter System (BioPod) is a stormwater biofiltration treatment system used to remove pollutants
from stormwater runoff. Impervious surfaces and other urban and suburban landscapes generate a variety of contaminants that can enter stormwater and pollute downstream receiving waters unless treatment is provided. The BioPod system uses proprietary StormMix™ biofiltration media to capture and retain pollutants including
total suspended solids (TSS), metals, nutrients, gross solids, trash and debris as well as petroleum hydrocarbons.
Function
The BioPod system uses engineered, high-flow rate filter media to remove stormwater pollutants, allowing for a smaller footprint than conventional bioretention systems. Contained within a compact precast concrete vault, the
BioPod system consists of a biofiltration chamber and an optional integrated high-flow bypass with a contoured
inlet rack to minimize scour. The biofiltration chamber is filled with horizontal layers of aggregate (which may or
may not include an underdrain), biofiltration media and mulch. Stormwater passes vertically down through the mulch and biofiltration media for treatment. The mulch provides pretreatment by retaining most of the solids or sediment. The biofiltration media provides further treatment by retaining finer sediment and dissolved pollutants.
The aggregate allows the media bed to drain evenly for discharge through an underdrain pipe or by infiltration.
Configuration
The BioPod system can be configured with either an internal or external bypass. The internal bypass allows both
water quality and bypass flows to enter the treatment vault. The water quality flows are directed to the biofiltration
chamber while the excess flows are diverted over the bypass weir without entering the biofiltration chamber. Both
the treatment and bypass flows are combined in the outlet area prior to discharge from the structure. BioPod units without an internal bypass are designed such that only treatment flows enter the treatment structure. When the system has exceeded its treatment capacity, ponding will force bypass flows to continue down the gutter to
the nearest standard catch basin or other external bypass structure.
The BioPod system can be configured as a tree box filter with tree and grated inlet, as a planter box filter with shrubs, grasses and an open top, or as an underground filter with access risers, doors and a subsurface inlet pipe. The optional internal bypass may be incorporated with any of these configurations. In addition, an open
bottom configuration may be used to promote infiltration and groundwater recharge. The configuration and size
of the BioPod system is designed to meet the requirements of a specific project.
Inspection & Maintenance Overview
State and local regulations require all stormwater management systems to be inspected on a regular basis and
maintained as necessary to ensure performance and protect downstream receiving waters. Without maintenance,
excessive pollutant buildup can limit system performance by reducing the operating capacity of the system and
increasing the potential for scouring of pollutants during periods of high flow.
Some configurations of the BioPod may require periodic irrigation to establish and maintain vegetation. Vegetation
will typically become established about two years after planting. Irrigation requirements are ultimately dependent
on climate, rainfall and the type of vegetation selected.
2
INSPECTION AND MAINTENANCE GUIDE
3
Maintenance Frequency
Periodic inspection is essential for consistent system performance and is easily completed. Inspection is typically conducted a minimum of twice per year, but since pollutant transport and deposition varies from site to
site, a site-specific maintenance frequency should be established during the first two or three years of operation.
Inspection Equipment
The following equipment is helpful when conducting BioPod inspections:
• Recording device (pen and paper form, voice recorder, iPad, etc.)
• Suitable clothing (appropriate footwear, gloves, hardhat, safety glasses, etc.)• Traffic control equipment (cones, barricades, signage, flagging, etc.)• Manhole hook or pry bar
• Flashlight
• Tape measure
Inspection Procedures
BioPod inspections are visual and are conducted without entering the unit. To complete an inspection, safety
measures including traffic control should be deployed before the access covers or tree grates are removed. Once the covers have been removed, the following items should be checked and recorded (see form provided on page 6) to determine whether maintenance is required:
• If the BioPod unit is equipped with an internal bypass, inspect the contoured inlet rack and outlet chamber
and note whether there are any broken or missing parts. In the unlikely event that internal parts are broken or missing, contact Oldcastle Stormwater at (800) 579-8819 to determine appropriate corrective action.
• Note whether the curb inlet, inlet pipe, or – if the unit is equipped with an internal bypass – the inlet rack is blocked or obstructed.
• If the unit is equipped with an internal bypass, observe, quantify and record the accumulation of trash
and debris in the inlet rack. The significance of accumulated trash and debris is a matter of judgment. Often, much of the trash and debris may be removed manually at the time of inspection if a separate maintenance visit is not yet warranted.
• If it has not rained within the past 24 hours, note whether standing water is observed in the biofiltration chamber.
• Finally, observe, quantify and record presence of invasive vegetation and the amount of trash and debris and sediment load in the biofiltration chamber. Erosion of the mulch and biofiltration media bed should also be recorded. Sediment load may be rated light, medium or heavy depending on the conditions.
Loading characteristics may be determined as follows:
o Light sediment load – sediment is difficult to distinguish among the mulch fibers at the top of the
mulch layer; the mulch appears almost new.
o Medium sediment load – sediment accumulation is apparent and may be concentrated in some areas; probing the mulch layer reveals lighter sediment loads under the top 1” of mulch.
o Heavy sediment load – sediment is readily apparent across the entire top of the mulch layer; individual mulch fibers are difficult to distinguish; probing the mulch layer reveals heavy sediment load under the
top 1” of mulch.
Often, much of the invasive vegetation and trash and debris may be removed manually at the time of inspection if a separate maintenance visit is not yet warranted.
4
Maintenance Indicators
Maintenance should be scheduled if any of the following conditions are identified during inspection:
•The concrete structure is damaged or the tree grate or access cover is damaged or missing.•The curb inlet or inlet rack is obstructed.•Standing water is observed in the biofiltration chamber more than 24 hours after a rainfall event (use
discretion if the BioPod is located downstream of a storage system that attenuates flow).
•Trash and debris in the inlet rack cannot be easily removed at the time of inspection.
•Trash and debris, invasive vegetation or sediment load in the biofiltration chamber is heavy or excessiveerosion has occurred.
Maintenance Equipment
The following equipment is helpful when conducting BioPod maintenance:
•Suitable clothing (appropriate footwear, gloves, hardhat, safety glasses, etc.)•Traffic control equipment (cones, barricades, signage, flagging, etc.)
•Manhole hook or pry bar
•Flashlight
•Tape measure•Rake, hoe, shovel and broom•Bucket
•Pruners
•Vacuum truck (optional)
Maintenance Procedures
Maintenance should be conducted during dry weather when no flows are entering the system. All maintenance
may be conducted without entering the BioPod structure. Once safety measures such as traffic control are
deployed, the access covers may be removed and the following activities may be conducted to complete maintenance:
•Remove all trash and debris from the curb inlet and inlet rack manually or by using a vacuum truck as
required.
•Remove all trash and debris and invasive vegetation from the biofiltration chamber manually or by using avacuum truck as required.•If the sediment load is medium or light but erosion of the biofiltration media bed is evident, redistribute
the mulch with a rake or replace missing mulch as appropriate. If erosion persists, rocks may be placed in
the eroded area to help dissipate energy and prevent recurring erosion.
•If the sediment load is heavy, remove the mulch layer using a hoe, rake, shovel and bucket, or by using avacuum truck as required. If the sediment load is particularly heavy, inspect the surface of the biofiltrationmedia once the mulch has been removed. If the media appears clogged with sediment, remove and
replace one or two inches of biofiltration media prior to replacing the mulch layer.
•Prune vegetation as appropriate and replace damaged or dead plants as required.
•Replace the tree grate and/or access covers and sweep the area around the BioPod to leave the site clean.•All material removed from the BioPod during maintenance must be disposed of in accordance with localenvironmental regulations. In most cases, the material may be handled in the same manner as disposal
of material removed from sumped catch basins or manholes.
Natural, shredded hardwood mulch should be used in the BioPod. Timely replacement of the mulch layer
according to the maintenance indicators described above should protect the biofiltration media below the
mulch layer from clogging due to sediment accumulation. However, whenever the mulch is replaced, the BioPod should be visited 24 hours after the next major storm event to ensure that there is no standing water in the biofiltration chamber. Standing water indicates that the biofiltration media below the mulch layer is
clogged and must be replaced. Please contact Oldcastle Infrastructure at (800) 579-8819 to purchase the
proprietary StormMix™ biofiltration media.
5
BioPod Tree Module BioPod Media Module
BioPod Planter Module BioPod Media Vault
6
Curb Inlet or Inlet Rack Blocked Notes:
Yes No
BioPod Inspection &
Maintenance Log
BioPod Model__________________________ Inspection Date________________________
Location______________________________________________________________________________
Condition of Internal Components Notes:
Good Damaged Missing
Standing Water in Biofiltration Chamber Notes:
Yes No
Trash and Debris in Inlet Rack Notes:
Yes No
Trash and Debris in Biofiltration Chamber Notes:
Yes No
Maintenance Requirements
Yes - Schedule Maintenance No - Schedule Re-Inspection
Invasive Vegetation in Biofiltration Chamber Notes:
Yes No
Sediment in Biofiltration Chamber Notes:
Light Medium Heavy
Erosion in Biofiltration Chamber Notes:
Yes No
BIOPODTM SYSTEM
WITH STORMMIX™ MEDIA
BUILDINGSTRUCTURES
OUR MARKETS
TRANSPORTATION
WATER
ENERGYCOMMUNICATIONS
December 2018 v.1
www.oldcastleinfrastructure.com
800-579-8819
Technical Information Report Watershed Affordable Housing Apartments
2200335.10
Section 11
Conclusion
Technical Information Report Watershed Affordable Housing Apartments 11-1
2200335.10
11.0 Conclusion
This site has been designed to meet the 2017 RSWDM. The site incorporates detention and
water quality facilities to treat stormwater draining from the site. Flow calculations/modeling used
City of Renton standards for sizing stormwater conveyance networks and treatment facilities.
It was determined using these criteria that:
• Detention facilities have been designed to meet the required Peak Rate Flow Control
Standard.
• Water quality facilities have been designed to meet the required Enhanced Basic Water
Quality Treatment Level for the site.
• Pipe networks will be designed to be of adequate size to effectively convey the 25-year
storm event and to contain the 100-year storm event. Calculations will be supplied closer to
final design.
This analysis is based on data and records either supplied to or obtained by AHBL. These documents are
referenced within the text of the analysis. The analysis has been prepared using procedures and
practices within the standard accepted practices of the industry. We conclude that this project, as
schematically represented, will not create any new problems within the downstream drainage system.
This project will not noticeably aggravate any existing downstream problems due to either water quality or
quantity.
AHBL, Inc.
Jesse Newman, EIT
Project Engineer
JN/lsk
November 2020
Revised May and October 2021
Revised February 2022
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