REVIEWED RESUB1 BLD2024-0134+Storm_Drainage_Report+5.14.2024_11.49.55_AM+4255826RESUB BLD2024-0134
May 14 2024
CITY OF EDMONDS
DEVELOPMENT SERVICES 10429240 t" P i sw
DEPARTMENT
Single Family Residence
10429 240th PI SW
Edmonds, WA 98020
BLD 2024-0134
Stormwater Site Plan Report
Prepared for:
Select Homes
Date: January 30, 2024
Revised: May 13, 2024
go WASI l�
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36508W
0A� ��GISTER�'� i
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5/13/2024
Prepared by: Rob Long, PE
RAM Fnginininring, Inr,
19109 36'" Ave W, Suite 103, Lynnwood WA 98036
(425) 678-6960 RAMengineeringinc.com
Job No. 23-035
10429 240th PI SW
Single Family Residence
Introduction: This summary report provides site design information for a single-family residence
at 10429 240th PI SW. This report includes stormwater analysis to support permit review and
approval. The property is located on the north side of 240t" PI SW in the Southwest 1/4 of Section
36, Township 27N, Range 3E, W.M.
Site Address: Applicant:
10429 240th PI SW Select Homes
Edmonds, WA 98020 8304 212th St SW
Edmonds WA 98026
Tax Parcel Number: Contact: Kayla Clark Nichols
00564900100500 (425) 742-6044
TABLE OF CONTENTS
SECTION PAGES
A. Project Overview.............................................................................................................................. 5
B. Existing Conditions Summary........................................................................................................... 1
C. Developed Site Hydrology.............................................................................................................. 18
D. Soils Reports................................................................................................................................... 18
E. Construction SWPPPP Requirements................................................................................................ 2
F. Operation and Maintenance Guidelines............................................................................................ 8
RAMEngineering, Inc.
RAM No. 23-035
10429 240th P1 SW SFR
Stormwater Site Plan Report
Page
A. PROJECT OVERVIEW:
This report provides engineering information for the proposed construction of a single family residence on
a 0.263 acre parcel; the project is located on the north side of 2401h PI SW at 10429 2401h PI SW in the City
of Edmonds. The applicant, Select Homes proposes to remove the existing residence to construct a new
single family residence with an attached garage on the subject site. This report provides the evaluation for
the new single family residential development.
Summary of Minimum Requirements for Category 1 Project:
Minimum Requirement #1 — Preparation of Stormwater Site Plan. The proposed site development
consists of disturbing a majority of the 0.263 acres site while retaining the existing detached garage and
pavement area (2,078 sf) off the back alley of site. The project will create/replace about 3,972 sf of hard
surface area; thus, the project is classified as a Category 1 project per the City's classification system. Per
ECDC 18.30, Category 1 projects must comply with Minimum Requirements No. 1 through No. 5. The civil
site development plans and this report have been prepared to address the project's impacts.
Minimum Requirement #2 — Construction Stormwater Pollution Prevention (SWPPP). A construction
Stormwater Pollution Prevention Plan (SWPPP) has been incorporated into the site development plans. A
summary of the site's erosion control measures that evaluates the typical 13 elements of a SWPPP are
included in section E. The total site disturbance area (0.263 ac) of the project will not exceed one acre,
thus a formal Notice of Intent application for NPDES coverage will not be made to the Department of
Ecology.
Minimum Requirement #3 —Source Control of Pollution. Specific source controls are not required for
single family residential sites. General requirements for these sites include preventing the discharge of
pollutants to the City's storm drainage system per Edmonds City Code Chapter 7.200 (Illicit Discharges).
This includes common household items such as pesticides, herbicides, fertilizers, detergents and fluids
from vehicle maintenance.
Single family residences shall incorporate DOE's S411 BMPs for landscape and lawn vegetation
management. Lawn and vegetation management can include control of objectionable weeds, insects,
mold, bacteria, and other pests with pesticides. Examples include weed control on golf course lawns,
access roads, and utility corridors and during landscaping; sap stain and insect control on lumber and logs;
rooftop moss removal; killing nuisance rodents; fungicide application to patio decks, and residential
lawn/plant care. It is possible to release toxic pesticides such as pentachlorophenol, carbamates, and
organometallics to the environment by leaching and dripping from treated parts, container leaks, product
misuse, and outside storage of pesticide contaminated materials and equipment. Poor management of the
vegetation and poor application of pesticides or fertilizers can cause appreciable stormwater
contamination.
RAMEngineering, Inc.
RAM No. 23-035
10429 240th PI SW SFR
Stormwater Site Plan Report
Page A-1
Minimum Requirement #4 — Preservation of Natural Drainage Systems and Outfalls. Most of the site
slopes in a southerly direction towards 2401h PI SW, however the back detached garage and pavement
area flows northerly towards the adjacent alley. The local underlying soils in the area consist of outwash
sands and stormwater runoff disperses and infiltrates into the soils; due to the local well -draining soils,
there are no existing stormwater pipe and catch basin systems in 240th PI SW or the adjacent alley to the
north.
Most hard surfaces in the area dissipate and infiltrate stormwater runoff. Additionally, there are no public
stormwater pipe and catch -basin system in most of the surrounding roads. The % mile downstream path
(gravity flow path) for runoff if it was not infiltrated generally flows in a south/southwest direction
towards King County/City of Shoreline within the Storm Creek basin. See the Downstream Drainage
Facility Map provided in Section C below.
The site development will utilize the well -draining on -site soils and use an infiltration system onsite to
manage stormwater runoff. Runoff flows from the new hard surfaces of the site will be collected and
infiltrated in an onsite infiltration system. The infiltration system will have an overflow system that will be
directed to 240th PI SW. The site is located within the upper reach of the Southwest Edmonds A watershed
basin per the City of Edmonds maps (see section C).
Minimum Requirement #5 — Onsite Stormwater Management. The proposed project is a category 1
project, thus is subject to the City's on -site stormwater management BMPs found in "List No. 1" in the
City's code. A site -specific geotechnical evaluation of the site's soil demonstrates that infiltration is a
viable option for stormwater management onsite. Therefore, the project will install an infiltration system
that will fully mitigate (100% infiltration) the new and replace hard surface together with 25% of the
existing hard surface to remain onsite. See the full stormwater design included in Section C below; a
summary table of the project Stormwater Management BMPs are provided below.
RAMEngineering, Inc.
RAM No. 23-035
10429 240th P1 SW SFR
Stormwater Site Plan Report
Page A-2
MR#5 Stormwater Management BMP List No. 1 Evaluation
Lawn and landscaped areas:
BMP
Viable
Limitations / Infeasibility Criteria
BMP T5.13: Post -Construction Soil Quality and Depth
Yes
BMP T5.13 shall be applied to the site post construction.
(Volume V, Chapter 11)
Roofs:
BMP T5.30: Full Dispersion
Infeasibility: A viable vegetated flow path 50 or 100 feet and
(Volume V, Chapter 3)
No
less than 20% is not achievable onsite.
BMP T5.10A: Downspout Full Infiltration Systems
The project will install an infiltration system that will fully
(Volume V, Chapter 4)
Yes
mitigate (100% infiltration) the new and replace hard surface
together with 25% of the existing hard surface to remain
onsite
BMP T5.14 Rain Gardens
However, the project will install an infiltration system that will
(Volume V, Chapter 11) or
fully mitigate (100% infiltration) the new and replace hard
BMP T7.30: Bioretention
Yes
surface together with 25% of the existing hard surface to
(Volume V, Chapter 7)
remain onsite
BMP T5.1013: Downspout Dispersion Systems
Infeasibility: A viable vegetated flow path 50 or 100 feet and
(Volume V, Chapter 4)
No
less than 20% is not achievable onsite.
However, the project will install an infiltration system that will
Detention Vaults or Pipes
fully mitigate (100% infiltration) the new and replace hard
(Edmonds Stormwater Addendum)
Yes
surface together with 25% of the existing hard surface to
remain onsite
However, the project will install an infiltration system that will
BMP T5.10C: Perforated Stub -out
fully mitigate (100% infiltration) the new and replace hard
(Volume V, Chapter 4)
Yes
surface together with 25% of the existing hard surface to
remain onsite
Other Hard Surfaces:
BMP T5.30: Full Dispersion
Infeasibility: A viable vegetated flow path 50 or 100 feet and
(Volume V, Chapter 3)
No
less than 20% is not achievable onsite.
BMP T5.10A: Full Infiltration
The project will install an infiltration system that will fully
(Volume V, Chapter 4)
mitigate (100% infiltration) the new and replace hard surface
BMP T5.15: Permeable Pavement
Yes
together with 25% of the existing hard surface to remain
(Volume V, Chapter 5)
onsite
BMP T5.14 Rain Gardens
However, the project will install an infiltration system that will
(Volume V, Chapter 11) or
fully mitigate (100% infiltration) the new and replace hard
BMP T7.30: Bioretention
Yes
surface together with 25% of the existing hard surface to
(Volume V, Chapter 7)
remain onsite
BMP T5.12: Sheet Flow Dispersion
Infeasibility: A viable vegetated flow path 50 or 100 feet and
(Volume V, Chapter 3)
No
less than 20% is not achievable onsite.
However, the project will install an infiltration system that will
Detention Vaults or Pipes
fully mitigate (100% infiltration) the new and replace hard
(Edmonds Stormwater Addendum)
Yes
surface together with 25% of the existing hard surface to
remain onsite
RAMEngineering, Inc.
RAM No. 23-035
10429 240th P1 SW SFR
Stormwater Site Plan Report
Page A-3
Parcel (Vicinity) Map:
SW
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RAN Engineering, Inc.
RAM No. 23-035
10429 240th PI SW SFR
Stormwater Site Plan Report
Page A-4
Site Plan:
240TH STREET SW
— — — - N 8806'41 W 70.
DOW 47' It
CONN�CAON
IlE 32 .3t
i I EX GARAGE
--
TO REMAIN ;]
FF 327.3t
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I I i
1 ,
� I
H K SCHROEDERS R� r
OF FOREST GLEN \\ -------
LOT 6-------
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F0077NG DRAIN
CONNEC770M O 20X MIN
g AT
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I
J I °
I n
I I i
c
SDCO 2
IE 324.0t
I
INSTALL 1-1/2' PE (160 PSI)
FROM WA7ER METER TO
L — — ._HOUSE DETAILS _(TRACER — —
INSTALL NEW MAILBOX
WiR£ TO BE INSTALLED Wf7H I
WATER LINE)
ON EXIS77NG STAND
(REMOVE DAMAGED
I 13 -4" PVC O 2.00X—
MAILBOX DESIGNATED
17'-6' PVG O 5.85X
FOR 10429).
INFIL iRA710N TRENCH
17(L)xIO'(K9x3(D) ? 1
SEE DETAILS SHT DT--42
I
-- --- —
INSTALL i' WATER METER PEEL
OVWSD S7D DETAIL W-IA
¢ 1' PE (160 PSI) FROM WATER
®
MAIN TO METER & 1-1/2' PE
(160) FROM METER TO HOUSE
(SEE DETAIL. ON SHEET DT-: 02)
(TRACERWTRE TO BE
_ ---SS --=
SS }INSTALLED WITH WATER LINE) EX 8' SEWER
---------------
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CONSTRUCTION W77H1N THE TREE
PR07EC77ON AREA. THE PRO CT
ARBORIST SHALL BE CONSULTED
AND SUPERWSE ALL WORK WITHIN
THE RETAIN TREE CRITICAL ROOT
ZONE/CANOPY.
JEL DRAIN
y
0' MAX
'— POWER POLE
W/STREET LIGHT
——-%-W ---
SSMH RIM=324.88
INSTALL T SANITARY SEWERPERT
CLEANOUT AT THE PROPERTY
IE 8' Z(W))=316.58
If 8' PVC(E)=316.68
UNE PER OVWSD STD DETAIL S-3
(SEE DETAIL ON SHEET DT-02)
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—SS----�
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TYPE I INSTALL CHANNEL DRAIN
O RIM 325.50 TOP 325.0
W 6' if 322.70 (IN -NW) NOS PRO CHANNEL GRAIN _..
6,IE 321.00 (OUT-W) OR APPROVED EQUAL
4' IE 323.00 (OUT—S) (SEE DETAIL SHT DT-02)
240TH PL SW
---I----------------
fXIS7iNG WATER METER TO B£ R£MOVE�.
(EXISTING WATER METER SHALL BE
RETAINED NEW METER IS
INSTALLED.UNTIL HOSE SPIGOT & AM SHAL[�
BE INSTALLED FOR USE DURING
CONS7RUC77ON)
I
RAN Engineering, Inc.
RAM No. 23-035
.Ot _
APPROX. LOCATION OF EXIST SEWER
LATERAL CONTRACTOR TO VERIFY
LOCA77ON PRIOR TO CON57RUC77ON.
(SEE SIDE SEWER N07ES) I
`INSTALL ASPHALT DRIVEWAY
APPROACH PER CITY STD
DWG NO:. TR-,W
(SEE SHEET DT-01)
`S WWCM & REMOVE EXISTNG PAVEMENT
AS TOUIR£D. NEAT LINE CUT, CLEAN,
HEAT AND 7'ASp�C ,EEXRISTTNG PAVEMENT
EDGES W7HSEAL
WflHH AAR4000 AND,,S4ND. SAWCUT -9iALL
BE MINIMUM 1-FT INTE THE EXISTING
EDGE OF PAVEMENT.
10429 240th PI SW SFR
Stormwater Site Plan Report
Page A-5
B. EXISTING CONDITIONS SUMMARY
Existing Conditions. The total site consists of 11,455 sf (0.263 acres) and is currently occupied by an
existing single-family residence and detached garage. The existing house caught on fire and is currently
vacant. The site's existing detached garage is accessed via an alley along the north boundary of the
subject site. The existing house is surrounded by grass lawn and landscape areas. The site is surrounded
by single family residences to the east, west, and north; and 240th PI SW along the southern boundary (see
aerial photo below).
The site generally slopes in a southwesterly direction at a relatively flat to moderate slope with only 5 feet
of drop across the site. No defined drainage courses are found on -site, and most of the stormwater runoff
would sheet flow southwesterly to 240th PI SW along the southerly boundary of the site. However, the
existing detached garage and access driveway to the alley do slope northwesterly towards the alley. No
known stream or wetlands are located on or adjacent to the site. Additional discussion of the local
drainage basin and downstream path is discussed in Section C of this report.
Soils: In accordance with the project's site -specific geotechnical engineering evaluation by Earth Solutions
NW, LLC the on -site soils consist of outwash sands and gravels deposits (Everett series soil). As outlined in the
geotechnical evaluation, the native sand outwash soils exhibit good infiltration characteristics and can be
utilized for on -site infiltration. The geotechnical evaluation performed a small-scale PIT test on -site and
measured an initial infiltration rate of 35.4 in/hr and recommends a design rate of 11.1 in/hr. A full soil
description is included in the project's site specific geotechnical engineering study by Earth Solutions NW, LLC
(attached below).
Aerial Photo (City of Edmonds —GIIS, 2022 photo)
�h!•�'�►a�c �i1a�i�
RAMEngineering, Inc.
RAM No. 23-035
2,40 9
10429 240th PI SW SFR
Stormwater Site Plan Report
Page B-1
C. DEVELOPED SITE HYDROLOGY.
Developed Conditions. The proposed project includes the replacement and construction of a single family
residence with an attached garage, and associated driveway and utilities. The existing detached garage
and access driveway off the alley will be retained. The proposed new construction will create and/or
replace 3,972 sf of hard surface. Per ECDC 18.30.060.D.5.b, a minimum of 25% of existing hard surfaces
that are not controlled by existing approved stormwater management facility shall provide on -site
stormwater management BMPs. Thus, the project site development will install an infiltration system
along the south (lower) portion of the site to mitigate the new and replaced hard surfaces (3,972 sf) and a
portion of the existing hard surface to remain (existing roof garage = 628 sf). The proposed infiltration
trench system has been sized to mitigate a total hard surface area of 4,600 sf (0.106 ac). The following is
a summary of the projects hard surface areas:
New and Replaced Hard Surfaces = 3,972 sf (0.092 ac)
Roof Area = 2,662 sf
Walkway/Patio Area = 70 sf
Driveway Area = 1,240 sf
Existing Hard Surfaces (existing detached garage) = 628 sf (0.014 ac)
Total Existing Hard Surface to Remain = 2,078 sf
(Existing Detached garage, walk and driveway)
Percent Retrofit Stormwater Control = 30.2% (628 / 2,078)
Total Hard Surface Mitigation Area = 4,600 sf (0.106 ac), 3,972 sf + 628 sf
In accordance with the Edmonds City Code (18.30) Category 1 projects shall meet MR#5 (see discussion in
Section A above) and provide on -site stormwater management. To meet these criteria, the proposed hard
surfaces of the site shall implement BMPs from "List No. 1" or meet the LID performance standard.
As discussed above in the MR#5 evaluation above in Section A, an on -site infiltration trench system will be
utilized to manage (full 100% infiltration) the project's new/replaced hard surfaces and a minimum of 25%
of existing retrofit hard surface to remain. BMP T5.13: Post -Construction Soil Quality and Depth will be
applied to the disturbed pervious areas of the site development.
The project proposes to implement full (100%) hard surface infiltration onsite. The on -site infiltration
trench will be sized using the DOE 2012 Western Washington Hydrology Model (WWHM2012) continuous
runoff model. To mitigate the 4,600 sf of project hard surface area, the project will install a trench 10 feet
wide, 17 feet long and 3.0 feet deep; filled with 1%z" to 3" washed drain rock (35% voids). A site specific
geotechnical evaluation was made to assess the use of infiltration onsite. The evaluation determined
infiltration is feasible onsite and recommends a long-term infiltration design rate of 11.1 in/hr.
The developed runoff rates and storage calculations were performed using the DOE 2012 Western
Washington Hydrology Model (WWHM2012) continuous runoff model. The below calculations
demonstrate that the trench will fully mitigate (100% infiltration) the increased hard surfaces, see
WWHM2012 input/printout on the following pages.
RAMEngineering, Inc.
RAM No. 23-035
10429 240th P1 SW SFR
Stormwater Site Plan Report
Page C-1
WWHM2012
PROJECT REPORT
Project Name: 23-035 SFR Infiltration
Site Name: 10429 240th SFR
Site Address: RAM 23-035
City : Edmonds
Report Date: 1/29/2024
MGS Regoin Puget East
Data Start 1901/10/1
Data End : 2058/09/30
DOT Data Number: 03
Version Date: 2021/08/18
Version : 4.2.18
Low Flow Threshold for POC 1 : 50 Percent of the 2 Year
High Flow Threshold for POC 1: 50 year
PREDEVELOPED LAND USE
Name : Basin 1
Bypass: No
Groundwater: No
Pervious Land Use
acre
A B, Forest, Flat
.106
Pervious Total
0.106
Impervious Land Use
acre
Impervious Total
0
Basin Total 0.106
Element Flows To:
Surface Interflow
IaIYY[!I VY2IIla4GIIIslam]9
Name : Basin 1
Bypass: No
Groundwater: No
Pervious Land Use
acre
Pervious Total
0
Impervious Land Use
acre
ROOF TOPS FLAT
0.076
DRIVEWAYS MOD
0.028
SIDEWALKS FLAT
0.002
Impervious Total
0.106
Basin Total 0.106
Groundwater
Element Flows To:
Surface Interflow Groundwater
Gravel Trench Bed 1 Gravel Trench Bed 1
PAN Engineering, Inc. 10429 240th PI SW SFR
RAM No. 23-035 Stormwater Site Plan Report
Page C-2
Name : Gravel Trench Bed 1
Bottom Length: 17.00 ft.
Bottom Width: 10.00 ft.
Trench bottom slope 1: 0 To 1
Trench Left side slope 0: 0 To 1
Trench right side slope 2: 0 To 1
Material thickness of first layer: 3
Pour Space of material for first layer: 0.35
Material thickness of second layer: 0
Pour Space of material for second layer: 0
Material thickness of third layer: 0
Pour Space of material for third layer: 0
Infiltration On
Infiltration rate: 11.1
Infiltration safety factor: 1
Total Volume Infiltrated (ac-ft.): 39.284
Total Volume Through Riser (ac-ft.): 0.001
Total Volume Through Facility (ac-ft.): 39.285
Percent Infiltrated: 100
Total Precip Applied to Facility: 0
Total Evap From Facility: 0
Discharge Structure
Riser Height: 2.9 ft.
Riser Diameter: 8 in.
i ' Schematic ���
RAN Engineering, Inc.
RAM No. 23-035
E3
Facility Name Gravel -Trench Bed 1
Outlet 1 Outlet 2 Outlet 3
Downstream Connection 10 110 0
Facility Type lGravel Trench/Bed
r Precipitation Applied to Facility Quick Trench
r Evaporation Applied to Facility Facility Dimension Diagram
Facility Dimensions
Trench Length (ft)
117
Trench Bottom Width (ft)
10
Effective Total Depth (ft)
0
Top and bottom slope (HN)
0
Left Side Slope (HN)
0
Right Side Slope (HN)
0
Material Layers for Trench/Bed
Layer 1 Thickness (ft)
0
Layer 1 porosity (0-1)
0,35
Layer 2 Thickness (ft)
0
Layer 2 porosity (0-1)
0
Layer 3 Thickness (ft)
0
Layer 3 porosity (0.1)
0
Infiltration Yes
Measured Infiltration Rate (in/hr)
Reduction Factor (infilt'factor)
Use Wetted Surface Area (sidewalls)
Total Volume Infiltrated (ac-ft)
Total Volume Through Riser (ac-ft)
Size Infiltration Trench
Target %: 100 -:I
Outlet Structure Data I
Riser Height (ft) 2.9 . _-'
Riser Diameter (in)
Riser Type Flat
Notch Type
Orifice Diameter Height
Number (in) (ft)
1 Fo----H Fo----H
2 fo --t-! to -!
3 Fo----d Fo--- --ld
Trench Volume at Riser Head (ac-ft) .004
11.1 ^-1
Show Trench 10pen Table
NO -�-i
Initial Stage (ft) 0
39.284
Total Volume Through Faa ity act 39.285
0.001
Percent Infiltrated 100
10429 240th PI SW SFR
Stormwater Site Plan Report
Page C-3
Element Flows To:
Outlet 1
Outlet 2
Gravel
Trench Bed
Hydraulic
Table
Stage(feet)
Area(ac.) Volume(ac-ft.)
Discharge(cfs)
0.0000
0.003
0.000
0.000
0.000
0.0333
0.003
0.000
0.000
0.043
0.0667
0.003
0.000
0.000
0.043
0.1000
0.003
0.000
0.000
0.043
0.1333
0.003
0.000
0.000
0.043
0.1667
0.003
0.000
0.000
0.043
0.2000
0.003
0.000
0.000
0.043
0.2333
0.003
0.000
0.000
0.043
0.2667
0.003
0.000
0.000
0.043
0.3000
0.003
0.000
0.000
0.043
0.3333
0.003
0.000
0.000
0.043
0.3667
0.003
0.000
0.000
0.043
0.4000
0.003
0.000
0.000
0.043
0.4333
0.003
0.000
0.000
0.043
0.4667
0.003
0.000
0.000
0.043
0.5000
0.003
0.000
0.000
0.043
0.5333
0.003
0.000
0.000
0.043
0.5667
0.003
0.000
0.000
0.043
0.6000
0.003
0.000
0.000
0.043
0.6333
0.003
0.000
0.000
0.043
0.6667
0.003
0.000
0.000
0.043
0.7000
0.003
0.001
0.000
0.043
0.7333
0.003
0.001
0.000
0.043
0.7667
0.003
0.001
0.000
0.043
0.8000
0.003
0.001
0.000
0.043
0.8333
0.003
0.001
0.000
0.043
0.8667
0.003
0.001
0.000
0.043
0.9000
0.003
0.001
0.000
0.043
0.9333
0.003
0.001
0.000
0.043
0.9667
0.003
0.001
0.000
0.043
1.0000
0.003
0.001
0.000
0.043
1.0333
0.003
0.001
0.000
0.043
1.0667
0.003
0.001
0.000
0.043
1.1000
0.003
0.001
0.000
0.043
1.1333
0.003
0.001
0.000
0.043
1.1667
0.003
0.001
0.000
0.043
1.2000
0.003
0.001
0.000
0.043
1.2333
0.003
0.001
0.000
0.043
1.2667
0.003
0.001
0.000
0.043
1.3000
0.003
0.001
0.000
0.043
1.3333
0.003
0.001
0.000
0.043
1.3667
0.003
0.001
0.000
0.043
1.4000
0.003
0.001
0.000
0.043
1.4333
0.003
0.002
0.000
0.043
1.4667
0.003
0.002
0.000
0.043
1.5000
0.003
0.002
0.000
0.043
1.5333
0.003
0.002
0.000
0.043
1.5667
0.003
0.002
0.000
0.043
1.6000
0.003
0.002
0.000
0.043
1.6333
0.003
0.002
0.000
0.043
1.6667
0.003
0.002
0.000
0.043
1.7000
0.003
0.002
0.000
0.043
1.7333
0.003
0.002
0.000
0.043
1.7667
0.003
0.002
0.000
0.043
1.8000
0.003
0.002
0.000
0.043
1.8333
0.003
0.002
0.000
0.043
1.8667
0.003
0.002
0.000
0.043
1.9000
0.003
0.002
0.000
0.043
1.9333
0.003
0.002
0.000
0.043
1.9667
0.003
0.002
0.000
0.043
2.0000
0.003
0.002
0.000
0.043
2.0333
0.003
0.002
0.000
0.043
RAN Engineering, Inc.
RAM No. 23-035
Infilt(cfs)
10429 240th PI SW SFR
Stormwater Site Plan Report
Page C-4
2.0667
0.003
0.002
0.000
0.043
2.1000
0.003
0.002
0.000
0.043
2.1333
0.003
0.002
0.000
0.043
2.1667
0.003
0.003
0.000
0.043
2.2000
0.003
0.003
0.000
0.043
2.2333
0.003
0.003
0.000
0.043
2.2667
0.003
0.003
0.000
0.043
2.3000
0.003
0.003
0.000
0.043
2.3333
0.003
0.003
0.000
0.043
2.3667
0.003
0.003
0.000
0.043
2.4000
0.003
0.003
0.000
0.043
2.4333
0.003
0.003
0.000
0.043
2.4667
0.003
0.003
0.000
0.043
2.5000
0.003
0.003
0.000
0.043
2.5333
0.003
0.003
0.000
0.043
2.5667
0.003
0.003
0.000
0.043
2.6000
0.003
0.003
0.000
0.043
2.6333
0.003
0.003
0.000
0.043
2.6667
0.003
0.003
0.000
0.043
2.7000
0.003
0.003
0.000
0.043
2.7333
0.003
0.003
0.000
0.043
2.7667
0.003
0.003
0.000
0.043
2.8000
0.003
0.003
0.000
0.043
2.8333
0.003
0.003
0.000
0.043
2.8667
0.003
0.003
0.000
0.043
2.9000
0.003
0.004
0.000
0.043
2.9333
0.003
0.004
0.043
0.043
2.9667
0.003
0.004
0.121
0.043
3.0000
0.003
0.004
0.219
0.043
RAN Engineering, Inc.
RAM No. 23-035
10429 240th PI SW SFR
Stormwater Site Plan Report
Page C-5
ANALYSIS RESULTS
Stream Protection Duration
Predeveloped Landuse Totals for POC #1
Total Pervious Area:0.106
Total Impervious Area:O
Mitigated Landuse Totals for POC #1
Total Pervious Area:O
Total Impervious Area:0.106
Flow Frequency Return Periods for Predeveloped. POC #1
Return Period
Flow(cfs)
2 year
0.000053
5 year
0.00007
10 year
0.00008
25 year
0.000084
50 year
0.000084
100 year
0.000085
Flow Frequency Return Periods for Mitigated
Return Period
Flow(cfs)
2 year
0
5 year
0
10 year
0
25 year
0
50 year
0
100 year
0
® Analysis
®
.0
I-,
-
Cumulative Probability
POC #1
1.0
0.1 xxxxx x x x -x - 0.1
x x x xxxxxxwoorak°
001
+ 50'
0 001
x 70'
LL
0.0001
0.5 1 2 5 10 20 30 50 70 80 90 95 98 160
Stream Protection Duration LID Duration Flow Frequency Water Quality Hydrograph
Welland Input Volumes I LID Report Recharge Duration Recharge Predeveloped I Recharge Mitigated
Analyze datasets Compact WDM Delete Selected I r Monthly FF
501 POC 1 Redeveloped flow
r
0 s•
1000 Gravel Trench Bed 1 ALL OUTLETS Mitigated
1001 Gravel Trench Bed 1 OUTLET 1 Mitigated
1002 Gravel Trench Bed 1 OUTLET 2 Mitigated
All Datasets Flow Stage Precip Evap POC 1
Flood Frequency Method
(" Log Pearson Type III 17B
Weibull
Cunnane
(: Gringorten
RAN Engineering, Inc.
RAM No. 23-035
9
Flow Frequency
Flow(cfs) 0501
15m
0701 15m
0801 15m
2 Year =
0.0001
0.0316
0.0000
5 Year =
0.0001
0.0431
0.0000
10 Year =
0.0001
0.0514
0.0000
25 Year =
0.0001
0.0645
0.0000
50 Year =
0.0001
0.0766
0.0000
100 Year =
0.0001
0.0938
0.0000
Annual Peaks
1902
0.0000
0.0379
0.0000
1903
0.0000
0.0413
0.0000
1904
0.0001
0.0451
0.0000
1905
0.0000
0.0228
0.0000
1906
0.0000
0.0250
0.0000
1907
0.0001
0.0296
0.0000
1908
0.0001
0.0268
0.0000
1909
0.0001
0.0344
0.0000
1910
0.0001
0.0294
0.0000
1911
0.0001
0.0357
0.0000
1912
0.0001
0.0586
0.0000
1913
0.0000
0.0241
0.0000
1914
0.0001
0.0941
0.0000
1915
0.0000
0.0212
0.0000
1916
0.0001
0.0408
0.0000
1917
0.0000
0.0196
0.0000
1918
0.0000
0.0320
0.0000
1919
0.0000
0.0193
0.0000
1920
0.0001
0.0276
0.0000
1921
0.0000
0.0211
0.0000
1922
0.0001
0.0314
0.0000
1923
0.0001
0.0268
0.0000
1924
0.0000
0.0451
0.0000
1925
0.0000
0.0199
0.0000
1926
0.0001
0.0407
0.0000
1927
0.0001
0.0309
0.0000
1928
0.0000
0.0246
0.0000
1929
0.0001
0.0431
0.0000.
10429 240th PI SW SFR
Stormwater Site Plan Report
Page C-6
Stream Protection Duration
Annual Peaks for Predeveloped and Mitigated
Year
Predeveloped
Mitigated
1902
0.000
0.000
1903
0.000
0.000
1904
0.000
0.000
1905
0.000
0.000
1906
0.000
0.000
1907
0.000
0.000
1908
0.000
0.000
1909
0.000
0.000
1910
0.000
0.000
1911
0.000
0.000
1912
0.000
0.000
1913
0.000
0.000
1914
0.000
0.000
1915
0.000
0.000
1916
0.000
0.000
1917
0.000
0.000
1918
0.000
0.000
1919
0.000
0.000
1920
0.000
0.000
1921
0.000
0.000
1922
0.000
0.000
1923
0.000
0.000
1924
0.000
0.000
1925
0.000
0.000
1926
0.000
0.000
1927
0.000
0.000
1928
0.000
0.000
1929
0.000
0.000
1930
0.000
0.000
1931
0.000
0.000
1932
0.000
0.000
1933
0.000
0.000
1934
0.000
0.000
1935
0.000
0.000
1936
0.000
0.000
1937
0.000
0.000
1938
0.000
0.000
1939
0.000
0.000
1940
0.000
0.000
1941
0.000
0.000
1942
0.000
0.000
1943
0.000
0.000
1944
0.000
0.000
1945
0.000
0.000
1946
0.000
0.000
1947
0.000
0.000
1948
0.000
0.000
1949
0.000
0.000
1950
0.000
0.000
1951
0.000
0.000
1952
0.000
0.000
RAN Engineering, Inc.
RAM No. 23-035
POC #1
10429 240th PI SW SFR
Stormwater Site Plan Report
Page C-7
1953
0.000
0.000
1954
0.000
0.000
1955
0.000
0.000
1956
0.000
0.000
1957
0.000
0.000
1958
0.000
0.000
1959
0.000
0.000
1960
0.000
0.000
1961
0.000
0.000
1962
0.000
0.000
1963
0.000
0.000
1964
0.000
0.000
1965
0.000
0.000
1966
0.000
0.000
1967
0.000
0.000
1968
0.000
0.000
1969
0.000
0.000
1970
0.000
0.000
1971
0.000
0.000
1972
0.000
0.013
1973
0.000
0.000
1974
0.000
0.000
1975
0.000
0.000
1976
0.000
0.000
1977
0.000
0.000
1978
0.000
0.000
1979
0.000
0.000
1980
0.000
0.000
1981
0.000
0.000
1982
0.000
0.000
1983
0.000
0.000
1984
0.000
0.000
1985
0.000
0.000
1986
0.000
0.000
1987
0.000
0.000
1988
0.000
0.000
1989
0.000
0.000
1990
0.000
0.000
1991
0.000
0.000
1992
0.000
0.000
1993
0.000
0.000
1994
0.000
0.000
1995
0.000
0.000
1996
0.000
0.000
1997
0.000
0.000
1998
0.000
0.000
1999
0.000
0.000
2000
0.000
0.000
2001
0.000
0.000
2002
0.000
0.000
2003
0.000
0.000
2004
0.000
0.000
2005
0.000
0.000
2006
0.000
0.000
RAM Engineering, Inc.
RAM No. 23-035
10429 240th PI SW SFR
Stormwater Site Plan Report
Page C-8
2007
0.000
0.000
2008
0.000
0.000
2009
0.000
0.000
2010
0.000
0.000
2011
0.000
0.000
2012
0.000
0.000
2013
0.000
0.000
2014
0.000
0.000
2015
0.000
0.000
2016
0.000
0.000
2017
0.000
0.000
2018
0.000
0.000
2019
0.000
0.000
2020
0.000
0.000
2021
0.000
0.000
2022
0.000
0.000
2023
0.000
0.000
2024
0.000
0.000
2025
0.000
0.000
2026
0.000
0.000
2027
0.000
0.000
2028
0.000
0.000
2029
0.000
0.000
2030
0.000
0.000
2031
0.000
0.000
2032
0.000
0.000
2033
0.000
0.000
2034
0.000
0.000
2035
0.000
0.000
2036
0.000
0.000
2037
0.000
0.000
2038
0.000
0.000
2039
0.000
0.000
2040
0.000
0.000
2041
0.000
0.000
2042
0.000
0.000
2043
0.000
0.000
2044
0.000
0.000
2045
0.000
0.000
2046
0.000
0.000
2047
0.000
0.000
2048
0.000
0.000
2049
0.000
0.000
2050
0.000
0.000
2051
0.000
0.000
2052
0.000
0.000
2053
0.000
0.000
2054
0.000
0.000
2055
0.000
0.000
2056
0.000
0.000
2057
0.000
0.000
2058
0.000
0.000
RAM Engineering, Inc.
RAM No. 23-035
10429 240th PI SW SFR
Stormwater Site Plan Report
Page C-9
Stream Protection Duration
Ranked Annual Peaks for Predeveloped and Mitigated
Rank
Predeveloped
Mitigated
1
0.0001
0.0130
2
0.0001
0.0000
3
0.0001
0.0000
4
0.0001
0.0000
5
0.0001
0.0000
6
0.0001
0.0000
7
0.0001
0.0000
8
0.0001
0.0000
9
0.0001
0.0000
10
0.0001
0.0000
11
0.0001
0.0000
12
0.0001
0.0000
13
0.0001
0.0000
14
0.0001
0.0000
15
0.0001
0.0000
16
0.0001
0.0000
17
0.0001
0.0000
18
0.0001
0.0000
19
0.0001
0.0000
20
0.0001
0.0000
21
0.0001
0.0000
22
0.0001
0.0000
23
0.0001
0.0000
24
0.0001
0.0000
25
0.0001
0.0000
26
0.0001
0.0000
27
0.0001
0.0000
28
0.0001
0.0000
29
0.0001
0.0000
30
0.0001
0.0000
31
0.0001
0.0000
32
0.0001
0.0000
33
0.0001
0.0000
34
0.0001
0.0000
35
0.0001
0.0000
36
0.0001
0.0000
37
0.0001
0.0000
38
0.0001
0.0000
39
0.0001
0.0000
40
0.0001
0.0000
41
0.0001
0.0000
42
0.0001
0.0000
43
0.0001
0.0000
44
0.0001
0.0000
45
0.0001
0.0000
46
0.0001
0.0000
47
0.0001
0.0000
48
0.0001
0.0000
49
0.0001
0.0000
50
0.0001
0.0000
51
0.0001
0.0000
RAN Engineering, Inc.
RAM No. 23-035
POC #1
10429 240th PI SW SFR
Stormwater Site Plan Report
Page C-10
52
0.0001
0.0000
53
0.0001
0.0000
54
0.0001
0.0000
55
0.0001
0.0000
56
0.0001
0.0000
57
0.0001
0.0000
58
0.0001
0.0000
59
0.0001
0.0000
60
0.0001
0.0000
61
0.0001
0.0000
62
0.0001
0.0000
63
0.0001
0.0000
64
0.0001
0.0000
65
0.0001
0.0000
66
0.0001
0.0000
67
0.0001
0.0000
68
0.0001
0.0000
69
0.0001
0.0000
70
0.0001
0.0000
71
0.0001
0.0000
72
0.0001
0.0000
73
0.0001
0.0000
74
0.0001
0.0000
75
0.0001
0.0000
76
0.0001
0.0000
77
0.0001
0.0000
78
0.0001
0.0000
79
0.0001
0.0000
80
0.0001
0.0000
81
0.0001
0.0000
82
0.0001
0.0000
83
0.0001
0.0000
84
0.0001
0.0000
85
0.0001
0.0000
86
0.0001
0.0000
87
0.0001
0.0000
88
0.0001
0.0000
89
0.0001
0.0000
90
0.0000
0.0000
91
0.0000
0.0000
92
0.0000
0.0000
93
0.0000
0.0000
94
0.0000
0.0000
95
0.0000
0.0000
96
0.0000
0.0000
97
0.0000
0.0000
98
0.0000
0.0000
99
0.0000
0.0000
100
0.0000
0.0000
101
0.0000
0.0000
102
0.0000
0.0000
103
0.0000
0.0000
104
0.0000
0.0000
105
0.0000
0.0000
RAM Engineering, Inc.
RAM No. 23-035
10429 240th PI SW SFR
Stormwater Site Plan Report
Page C-11
106
0.0000
0.0000
107
0.0000
0.0000
108
0.0000
0.0000
109
0.0000
0.0000
110
0.0000
0.0000
111
0.0000
0.0000
112
0.0000
0.0000
113
0.0000
0.0000
114
0.0000
0.0000
115
0.0000
0.0000
116
0.0000
0.0000
117
0.0000
0.0000
118
0.0000
0.0000
119
0.0000
0.0000
120
0.0000
0.0000
121
0.0000
0.0000
122
0.0000
0.0000
123
0.0000
0.0000
124
0.0000
0.0000
125
0.0000
0.0000
126
0.0000
0.0000
127
0.0000
0.0000
128
0.0000
0.0000
129
0.0000
0.0000
130
0.0000
0.0000
131
0.0000
0.0000
132
0.0000
0.0000
133
0.0000
0.0000
134
0.0000
0.0000
135
0.0000
0.0000
136
0.0000
0.0000
137
0.0000
0.0000
138
0.0000
0.0000
139
0.0000
0.0000
140
0.0000
0.0000
141
0.0000
0.0000
142
0.0000
0.0000
143
0.0000
0.0000
144
0.0000
0.0000
145
0.0000
0.0000
146
0.0000
0.0000
147
0.0000
0.0000
148
0.0000
0.0000
149
0.0000
0.0000
150
0.0000
0.0000
151
0.0000
0.0000
152
0.0000
0.0000
153
0.0000
0.0000
154
0.0000
0.0000
155
0.0000
0.0000
156
0.0000
0.0000
157
0.0000
0.0000
RAM Engineering, Inc.
RAM No. 23-035
10429 240th PI SW SFR
Stormwater Site Plan Report
Page C-12
Stream Protection Duration
POC #1
The Facility PASSED
jW Analysis
ijF
w 0.00
0
v
0.00
O
J
0.00
501 POC 1 Predeveloped
801 POC 1 Mitigated flow
0.00 r 6 1
10E-5 10E-4 10E-3 10E-2 10E-1 1 10 100
Percent Time Exceeding
Stream Protection Duration LID Duration j Flow Frequency I Water Quality I Hydrograph f
Welland Input Volumes I LID Report I Recharge Duration I Recharge Redeveloped I Recharge Mitigated
Analyze datasets Compact WDM Delete Selected i F Monthly FF
501 POC 1 Predeveloped flow
801 POC 1 Mitigated flow
All Datasets I Flow Stage _E!!S!Lj Evap POC 1
Flood Frequency Method
(' Log Pearson Type III 17B
C Weibull
(- Cunnane
6 Gringotten
The Facility PASSED.
Flow(cfs) Predev Mit Percentage Pass/Fail
0.0000
4538
2
0
Pass
0.0000
4407
2
0
Pass
0.0000
4246
2
0
Pass
0.0000
4082
2
0
Pass
0.0000
3948
2
0
Pass
0.0000
3803
2
0
Pass
0.0000
3670
2
0
Pass
0.0000
3525
2
0
Pass
0.0000
3379
2
0
Pass
0.0000
3266
2
0
Pass
0.0000
3118
2
0
Pass
0.0000
2995
2
0
Pass
0.0000
2909
2
0
Pass
0.0000
2793
2
0
Pass
0.0000
2702
2
0
Pass
0.0000
2627
2
0
Pass
0.0000
2546
2
0
Pass
0.0000
2462
2
0
Pass
0.0000
2379
2
0
Pass
0.0000
2280
2
0
Pass
0.0000
2212
2
0
Pass
0.0000
2129
2
0
Pass
0.0000
2058
2
0
Pass
RAN Engineering, Inc.
RAM No. 23-035
F9
Facility PASSED I
'lov(cfs)
Predev
Mit
Percentage
Pass/Fail
1.0000
4538
2
0
Pass
1.0000
4407
2
0
Pass
1.0000
4246
2
0
Pass
I.0000
4082
2
0
Pass
I.0000
3948
2
0
Pass
1.0000
3803
2
0
Pass
1.0000
3670
2
0
Pass
I.0000
3525
2
0
Pass
1.0000
3379
2
0
Pass
1.0000
3266
2
0
Pass
1.0000
3118
2
0
Pass
1.0000
2995
2
0
Pass
I.0000
2909
2
0
Pass
1.0000
2793
2
0
Pass
1.0000
2702
2
0
Pass
1.0000
2627
2
0
Pass
I.0000
2546
2
0
Pass
1.0000
2462
2
0
Pass
1.0000
2379
2
0
Pass
1.0000
2280
2
0
Pass
1.0000
2212
2
0
Pass
1.0000
2129
2
0
Pass
1.0000
2058
2
0
Pass
I.0000
1983
2
0
Pass
I.0000
1884
2
0
Pass
1.0000
1810
2
0
Pass
1.0000
1741
2
0
Pass
1.0000
1674
2
0
Pass
1.0000
1595
2
0
Pass
1.0000
1515
2
0
Pass
I.0000
1424
2
0
Pass
I.0000
1341
2
0
Pass
1.0000
1307
2
0
Pass
1.0000
1237
2
0
Pass ,
10429 240th PI SW SFR
Stormwater Site Plan Report
Page C-13
0000
1983
2
0
Pass
0000
1884
2
0
Pass
0000
1810
2
0
Pass
0000
1741
2
0
Pass
0000
1674
2
0
Pass
0000
1595
2
0
Pass
0000
1515
2
0
Pass
0000
1424
2
0
Pass
0000
1341
2
0
Pass
0000
1307
2
0
Pass
0000
1237
2
0
Pass
0000
1187
2
0
Pass
0000
1151
2
0
Pass
0000
1099
2
0
Pass
0000
1068
2
0
Pass
0000
1017
2
0
Pass
0000
971
2
0
Pass
0000
939
2
0
Pass
0001
887
2
0
Pass
0001
867
2
0
Pass
0001
836
2
0
Pass
0001
816
2
0
Pass
0001
792
2
0
Pass
0001
765
2
0
Pass
0001
744
2
0
Pass
0001
719
2
0
Pass
0001
690
2
0
Pass
0001
634
2
0
Pass
0001
610
2
0
Pass
0001
591
2
0
Pass
0001
550
2
0
Pass
0001
505
2
0
Pass
0001
489
2
0
Pass
0001
481
2
0
Pass
0001
455
2
0
Pass
0001
435
2
0
Pass
0001
415
2
0
Pass
0001
399
2
0
Pass
0001
386
2
0
Pass
0001
364
2
0
Pass
0001
348
2
0
Pass
0001
333
2
0
Pass
0001
319
2
0
Pass
0001
310
2
0
Pass
0001
303
2
0
Pass
0001
295
2
0
Pass
0001
273
2
0
Pass
0001
258
2
0
Pass
0001
243
2
0
Pass
0001
240
2
0
Pass
0001
232
2
0
Pass
0001
225
2
0
Pass
0001
211
2
0
Pass
0001
189
2
1
Pass
0001
187
2
1
Pass
0001
185
2
1
Pass
0001
175
2
1
Pass
0001
163
2
1
Pass
0001
158
2
1
Pass
0001
137
2
1
Pass
0001
127
2
1
Pass
0001
124
2
1
Pass
0001
118
2
1
Pass
0001
113
2
1
Pass
0001
99
2
2
Pass
0001
96
2
2
Pass
0001
88
2
2
Pass
0001
78
2
2
Pass
RAN Engineering, Inc.
RAM No. 23-035
10429 240th PI SW SFR
Stormwater Site Plan Report
Page C-14
0.0001
73
2
2
Pass
0.0001
58
2
3
Pass
0.0001
54
2
3
Pass
0.0001
49
2
4
Pass
0.0001
47
2
4
Pass
0.0001
34
2
5
Pass
0.0001
30
2
6
Pass
0.0001
21
2
9
Pass
0.0001
10
2
20
Pass
LID Report
a - LID Report
s POC TI
:........... _..
LID Technique
Usedfor
Total Volume
Volume
Infiltration
Cumulative
Percent
Water Quality
Percent
Comment
Treatment?
Needs
Through
Volume
Volume
Volume
Water Quality
Treatment
Facility
(ac-ft)
Infiltration
Infiltrated
Treated
(ac-ft)
(ac-ft)
Credit
Gravel Trench Bed 1 POC
❑
35.75
❑
100.00
Total Volume Infiltrated
35.75
0.00
0 OU
100.00
0.00
0%
No Treat.
Credit
Compliance with LID
Duration
Standard 8% of 2-yr to 50% of
Analysis
2-yr
Result =
Passed
Perind and Impind Changes
No changes have been made.
This program and accompanying documentation are provided 'as -is' without warranty of any kind. The entire risk
regarding the performance and results of this program is assumed by End User. Clear Creek Solutions Inc. and
the governmental licensee or sublicensees disclaim all warranties, either expressed or implied, including but not
limited to implied warranties of program and accompanying documentation. In no event shall Clear Creek Solutions
Inc. be liable for any damages whatsoever (including without limitation to damages for loss of business profits,
loss of business information, business interruption, and the like) arising out of the use of, or inability to use
this program even if Clear Creek Solutions Inc. or their authorized representatives have been advised of the
possibility of such damages. Software Copyright 0 by : Clear Creek Solutions, Inc. 2005-2024; All Rights
Reserved.
RAN Engineering, Inc.
RAM No. 23-035
10429 240th PI SW SFR
Stormwater Site Plan Report
Page C-15
Additionally, all disturbed pervious (lawn and landscape) areas will preserve or restore the health and water -
holding capacity of the soils by compost -amending (Per DOE BMP T5.13: Post -Construction Soil Quality and
Depth). See attached City of Edmonds Standard Detail SD-642 criteria for BMP T5.13: Post -Construction Soil
Quality and Depth.
UNDISTURBED
NATIVE VEGETATION
UNDISTURBED NATIVE SOIL
2" ORGANIC MULCH
3" OF COMPOST
INCORPORATED INTO 5" OF
SITE SOIL (TOTAL AMENDED
DEPTH OF 9.5 FOR A
SETTLED DEPTH OF 8")
SUBSOIL SCARIFIED 4" BELOW
COMPOST AMENDED LAYER
(12" BELOW SOIL SURFACE)
2" ORGANIC
MULCH
6" IMPORTED
TOPSOIL MIX
(COMPACTED
DEPTH)
SUBSOIL IS
SCARIFIED 6"
BELOW
IMPORTED
TOPSOIL MIX
UNDISTURBED PLANTS UNDISTURBED TURF (LAWN)
(SEE NOTE 1) AREAS (SEE NOTE 1)
PLANTING BEDS TURF (LAWN) AREAS
0"
8"
UNDISTURBED
TURF/LAWN/LANDSCAPE
UNDISTURBED NATIVE SOIL
STEEP SLOPE NOTE:
AMENDED SOILS SHOULD NOT BE
INSTALLED ON FINISHED SLOPES
EXCEEDING 33%. AREAS EXCEEDING
337. SHALL BE STABILIZED PER THE
ENGINEER/GEOTECH OF RECORD.
;RASS: SEED OR SOD
.75" OF COMPOST INCORPORATED
NTO 6.25" OF SITE SOIL (TOTAL
4MENDED DEPTH OF 9.5", FOR A
SETTLED DEPTH OF 8")
SUBSOIL SCARIFIED 4" BELOW
;OMPOST AMENDED LAYER
;12" BELOW SOIL SURFACE)
OPTION 2 — AMEND IN PLACE OR STOCKPILE AND AMEND
GENERAL NOTES:
PLANTING BEDS
TURF (LAWN) AREAS
III�III�III��
GRASS: SEED
OR SOD
11-III=111-III=III11 I
1I 1 11=1 I I —I 11 1I M I I I I I
111911-1I1=1IMINI
-III=III=III=II�IIL�I
6" IMPORTED
1=1 I I-1
Ell
III II—III-11 11 I
16 41M=1f�I 1=1
TOPSOIL MIX
COMPACTED
iEiTRI 1 I11111 1111
Ti >
DEPTH)
-P ;I_?v
i
SUBSOIL IS
SCARIFIED 6"
BELOW
IMPORTED
TOPSOIL MIX
OPTION 3 — IMPORT TOPSOIL
1. AREAS OF NO DISTURBANCE
SHALL BE FENCED AND EXISTING
VEGETATION AND SOIL SHALL BE
PROTECTED FROM CONSTRUCTION
IMPACTS.
2. TO MEASURE SETTLED DEPTH,
WATER SOIL SUFFICIENTLY TO
FULLY SATURATE WITHOUT
CAUSING EROSION.
3. COMPOST SHALL MEET SPEC.
REQUIREMENTS IN THE 2017
EDMONDS STORMWATER
ADDENDUM (CHECKLIST 7).
4. COMPACTION OF TOPSOIL (WHERE
REQUIRED) TO BE TO 85% (MAX)
OF THE MAXIMUM DRY DENSITY
PER MODIFIED PROCTOR TEST
(ASTM D1557).
REVISION DATE
CITY OF EDMONDS POST CONSTRUCTION SOIL APRIL 2021
QUALITY AND DEPTH
PUBLIC WORKS STANDARD
DEPARTMENT DETAIL
4's t 189�j APPROVED BY: R. ENGLISH S D — 6 42
RAMEngineering, Inc.
RAM No. 23-035
10429 240th PI SW SFR
Stormwater Site Plan Report
Page C-16
Offsite Basin Analysis. The site is located in the Southwest Edmonds A watershed basin; the Southwest
Edmonds A basin is a developed urban basin that primarily consists of single-family residences. The local
area underlying soils consists of outwash sandy soils that are well -drained and create little to no stormwater
runoff. Most hard surfaces in the area dissipate and infiltrate stormwater runoff. Additionally, there are
no public stormwater pipe and catch -basin system in most of the surrounding roads. The % mile
downstream path (gravity flow path) for runoff if it was not infiltrated generally flows in a south/southwest
direction towards King County/City of Shoreline within the Storm Creek basin.
Due to the fact the site's underlying soils are sandy and well -draining and there are no formal collection and
conveyance system adjacent to the site, the project will utilize on -site infiltration to control stormwater
runoff. The project does not propose to directly discharge to the city stormwater system (MS4). See the
Downstream Drainage Facility Map and Watershed Basin Map delineating the local stormwater system and
basin.
Downstream Drainage Facility Map (City of Edmonds GIS)
o � o
I ,' • imir
pi
a
ile Downstream Point 9 + .
RAMEngineering, Inc.
RAM No. 23-035
10429 240th PI SW SFR
Stormwater Site Plan Report
Page C-17
Watershed Basin Map:
F I G U R E B- 1
CITY OF EDMONDS
WATERSHEDS
Deer Creek
Perrinville
Edmonds Marsh
Puget Sound
Edmonds Way
`- Puget Sound Piped
Fruitdale
®_ Shell Creek
Good Hope Pond ` Shellabarger
Halls Creek
Southwest Edmonds A
- Hindley Creek
C Southwest Edmonds B
Lake Ballinger
L - Stilthouse Creek
Lund's Gulch
Talbot Park A
Meadowdale A
® Talbot Park B
Meadowdale B
® Terrace Creek
Northstream
i�� Westgate Pond
Dutfall Creek
1000 2,000
Willow Creek
4,000 6.000
1 in = 2,000 ft
Ne —rly of arty sort, ind.dirg accuracy, fitness, of me,chaMabilnv
acwmpanythis protluR.
March 30, 2010
N
A
A
Lund's Gulch'"
Meadowdale A
s
Mea2lowdale B "
Z �
-iamot°' \\\
Terrace Creek
8,000
;reet Puge
; albotParkA
aLb k
lb1t Park B IF
rl .uitdale
Ssi
Creek
A
pY �y I
Good Hope Pond s3
hY
1
I
----loam so sw
—' 1_7
B-- wy i
If Shell Creek uah s, sw i
barged .t i
es Pe
/ 3
/ a
Westgate Pond Halls Creek /
a
-----------------
ill�w Creek ,• < 3
T; m zzam sisw
JO
•I _ i a i.-- \ i
Creek ! -------
Edmonds Way I
SITE Southwest Edmonds A
- Lake Ballinger
240!h 51 S W O
E
Sbuthwest Edmonds B
1
L--------------------�—
RAN Engineering, Inc.
RAM No. 23-035
10429 240th PI SW SFR
Stormwater Site Plan Report
Page C-18
D. SOILS REPORTS:
1. Geotechnical Response to City Comments Letter
Prepared by: Earth Solutions NW, LLC
Date: May 10, 2024
Pages: 2
2. Geotechnical Evaluation Letter
Prepared by: Earth Solutions NW, LLC
Date: January 15, 2024
Pages: 15
MAN =ngineering, Inc.
RAM No. 23-035
10429 240th PI SW SFR
Stormwater Site Plan Report
Page D-1
May 10, 2024
ES-9558.01
Select Homes, Inc.
8304 — 212' Street Southwest
Edmonds, Washington 98026
Attention: Kayla Nichols
Subject: Response to Comments
Proposed Single -Family Residence
10429 — 240t" Place Southwest
Edmonds, Washington
Dear Kayla:
Earth
Solutions
NW«C
Earth Solutions NW LLC
Geotechnical Engineering, Construction
Observation/Testing and Environmental Services
As requested, Earth Solutions NW, LLC (ESNW) has prepared this letter responding to the City
of Edmonds review comments. The comments pertinent to the geotechnical aspects of the
project are provided below, followed by our responses. ESNW prepared the referenced
geotechnical evaluation for the subject project.
Storm Drainage Report 2. — The Geotech report states that temporary storm mitigation will likely
require interceptor trenches and sumps. Please provide a note in the SWPPP and/or the TESC
plan.
ESNW Response — Based on the permeability of the native soil, we anticipate storm runoff to
infiltration on site, and the need for interceptor trenches or sumps is unlikely.
Storm Drainage Report 3. — The geotechnical report states zones of perched groundwater
seepage may be encountered within site excavation. Please suggest a BMP or method for
dewatering for Element 10 of the SWPPP.
ESNW Response — Based on the permeability of the native soil, it is unlikely that seepage is
encountered and it is our opinion that project plans do not need to incorporate dewatering
methods.
Civil Plans 3. — It appears that the estimated finished grade over the infiltration facility is
approximately 325.5' and the bottom of the proposed drywell is 319'. The Geotechnical report
states that they encountered groundwater seepage at 6.5' below grade. Please confirm that the
infiltration facility base is at least 1 foot above the seasonal groundwater table.
15365 NE 90" Street, Suite 100 • Redmond, WA 98052 • (425) 449-4704
3130 Varney Lane, Suite 105 Pasco, WA 99301 • (509) 905-0275
esnw.com
Select Homes, Inc.
May 10, 2024
ES-9558.01
Page 2
ESNW Response — The light groundwater seepage noted was a result of the high volume of
water infiltrated during the pilot infiltration test completed within that test pit. Review of a boring
that was completed near the intersection of 244th Street Southwest and 13th Avenue Northwest
indicates that groundwater is present at depths of about 28.3 feet to 29.8 feet below the ground
surface elevation (approximately 300 feet). Based on the subsurface conditions observed on site
and the review of nearby deep subsurface data, it is our opinion that groundwater will not
negatively impact the proposed drywell. ESNW shall be present on site during construction of
the drywell to confirm anticipated subsurface conditions.
Should you require additional information, or have questions, please call.
Sincerely,
EARTH SOLUTIONS NW, LLC
05/10/2024
Henry T. Wright, P.E.
Associate Principal Engineer
cc: RAM Engineering, Inc.
Attention: Rob Long, P.E.
References:
• Stormwater Review Comments, provided by City of Edmonds, dated March 18, 2024
• Geotechnical Evaluation, prepared by ESNW, ES-9558, dated January 15, 2024
• Civil Plans, prepared by RAM Engineering, Inc.
Earth Solutions NW. LLC
January 15, 2024
ES-9558
Select Homes, Inc.
8304 — 212th Street Southwest
Edmonds, Washington 98026
Attention: Kayla Nichols
Subject: Geotechnical Evaluation
Proposed Single -Family Residence
10429 — 240th Place Southwest
Edmonds, Washington
Greetings:
Earth
Solutions
NW«c
Earth Solutions NW LLC
Geotechnical Engineering, Construction
Observation/Testing and Environmental Services
As requested, Earth Solutions NW, LLC (ESNW) has prepared this geotechnical evaluation for
the proposed single-family residence. A summary of our subsurface exploration, laboratory
analyses, and recommendations are provided in this letter report.
Project & Site Description
The subject site is located north of 240th Place Southwest, approximately 200 feet east of the
intersection with 105th Place West, in Edmonds, Washington, as illustrated on the attached
Vicinity Map (Plate 1). The site consists of a single tax parcel (Snohomish County Parcel No.
00564900100500) and totals about 0.26 acres of land area. The site is currently developed with
a single-family residence and a detached garage building. Existing topography descends gently
to the southwest, with less than five feet of elevation change across the parcel. Vegetation across
the subject site consists of moderately sized trees along the property margins and landscaping
elements.
We understand the proposed project includes the removal of the existing single-family residence
and the construction of a new single-family residence. Based on conceptual plans discussed
with the client, the proposed residential structure will be two to three stories and will consist of
relatively lightly loaded wood framing supported on conventional foundations. Based on our
experience with similar developments, we estimate wall loads on the order of 1 to 2 kips per linear
foot, column loads of less than 20 kips, and slab -on -grade loading of 150 pounds per square foot
(psf).
15365 N.E. 90th Street, Suite 100 0 Redmond, WA 98052 6 (425) 449-4704 • FAX (425) 449-4711
Select Homes, Inc.
January 15, 2024
Subsurface Conditions
ES-9558
Page 2
An ESNW representative observed, logged, and sampled two test pits on November 16, 2023.
The test pits were excavated at accessible areas of the site using a mini-trackhoe and operator
provided by the client. A hand -auger exploration was completed in the front yard area to
supplement the data collected with the excavator. The approximate locations of the test locations
are depicted on Plate 2 (Subsurface Exploration Plan). Please refer to the attached soil logs for
a more detailed description of subsurface conditions. Representative soil samples collected at
the locations were evaluated in general accordance with Unified Soil Classification System
(USCS) and United States Department of Agriculture (USDA) methods and procedures.
Topsoil
Topsoil was observed extending to a depth of approximately six inches below the existing ground
surface (bgs) at the test locations. The topsoil was characterized by dark brown color and the
presence of fine organic material.
Fill
Fill was not encountered during our subsurface exploration.
Native Soil
Underlying the topsoil, native soil encountered at the test locations consisted primarily of soils
consistent with the makeup outwash deposits, including poorly graded sands and gravels (USCS:
SP-SM, SP, and GP). The native soil was generally encountered in a damp condition at the time
of exploration. The maximum exploration depth was approximately six and one-half feet bgs.
Geologic Setting
Geologic mapping identifies advance outwash (Qva) across the site and the nearby area.
Advance outwash deposits consist primarily of a nonsorted mixture of silt, sand, and sub -rounded
to well-rounded gravels. Outwash deposits are typically observed in a semi -compacted state as
a result of glacial processes.
USDA soil mapping identifies the Alderwood-urban land complex, 0 to 5 percent slopes, as the
primary soil unit underlying the site. Alderwood series soils formed in glacial deposits. The urban
land designation denotes areas that have been subject to historical mass grading.
Based on our field observations, on -site native soils are representative of advance outwash
deposits and Everett series soil.
Earth Solutions NW. LLC
Select Homes, Inc.
January 15, 2024
Groundwater
ES-9558
Page 3
Light groundwater seepage was observed at a depth of six and one-half feet bgs in TP-2.
Groundwater seepage rates and elevations fluctuate depending on many factors, including
precipitation duration and intensity, the time of year, and soil conditions. In general, groundwater
flow rates are higher during the winter, spring, and early summer months.
Critical Areas Evaluation
A review of Edmonds Municipal Code Chapter 23.80 — Geologically Hazardous Areas (GHAs)
was completed to evaluate whether GHAs recognized by the City of Edmonds (including erosion,
landslide, and seismic hazard areas) exist on or near the subject site. Based on review of the
Edmonds interactive parcel viewer, the subject site contains a potential erosion hazard area on
the northwestern property boundary. Based on our on -site evaluation of the subject site,
gradients within mapped potential erosion hazard area were observed to be roughly five percent
slopes and do not classify as an erosion hazard area. Based on our site -specific field
observations, it is our opinion the site does not contain, and is not immediately adjacent to, any
geologic hazard areas.
Structural Fill
Structural fill is defined as compacted soil placed in foundation, slab -on -grade, roadway,
permanent slope, retaining wall, and utility trench backfill areas. Structural fill placed and
compacted during site grading activities should meet the following specifications and guidelines:
• Structural fill material
• Moisture content
• Relative compaction (minimum)
• Loose lift thickness (maximum)
Granular soils*
At or slightly above optimum**
95 percent (Modified Proctor)
12 inches
The existing soil may not be suitable for use as structural fill unless the soil is at (or slightly above) the optimum
moisture content at the time of placement and compaction.
"* Soil shall not be placed dry of optimum and should be evaluated by ESNW during construction.
Site Excavations
Temporary site excavations over four feet in height should be sloped at a maximum inclination of
1 H:1 V (Horizontal:Vertical). If temporary site excavations cannot be achieved with the above
slope inclination, ESNW should provide additional recommendations and shoring may be
necessary. ESNW should observe site excavations to confirm adequate excavation stability.
Earth Solutions NW. LLC
Select Homes, Inc.
January 15, 2024
Foundations
ES-9558
Page 4
The proposed residential structure can be constructed on conventional continuous and spread
footing foundations bearing on competent native soil, compacted native soil, or new structural fill
placed directly on competent native soil. Competent native soil suitable for support of foundations
will likely be encountered beginning at depths of two to three feet bgs. Compaction of the
foundation subgrade areas may be prudent depending on the condition of the native soil exposed
during construction. ESNW should be retained during construction to perform a foundation
subgrade evaluation prior to formwork. Where loose or unsuitable conditions are encountered at
foundation subgrade elevations, compaction of the soils to the specifications of structural fill, or
overexcavation and replacement with structural fill will be necessary.
Provided the proposed structures will be supported as recommended above, the following
parameters can be used for foundation design:
• Allowable soil bearing capacity 2,500 psf
• Passive earth pressure
• Coefficient of friction
300 pcf
M1
The passive earth pressure value provided above assumes the foundations will be backfilled with
structural fill. A factor -of -safety of 1.5 has been applied to the passive earth pressure and
coefficient of friction values provided in this section. For short-term wind and seismic loading, a
one-third increase in the allowable soil bearing capacity may be assumed.
With structural loading as expected, total settlement in the range of one inch is anticipated, with
differential settlement of about one-half inch. The majority of the settlements should occur during
construction, as dead loads are applied.
Slab -on -Grade Floors
Slab -on -grade floors for the proposed structures should be supported on a well -compacted, firm,
and unyielding subgrade. Where feasible, native soils exposed at the slab -on -grade subgrade
level can likely be compacted in situ to the specifications described in this section. Unstable or
yielding areas of subgrade should be recompacted, or overexcavated and replaced with suitable
structural fill, prior to slab construction.
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 5
percent or less (where the fines content is defined as the percent passing the Number 200 sieve,
based on the minus three -quarter -inch fraction). In areas where slab moisture is undesirable,
installation of a vapor barrier below the slab should be considered. If a vapor barrier is utilized,
it should be a material specifically designed for use as a vapor barrier and should be installed in
accordance with manufacturer specifications.
Earth Solutions NW. LLC
Select Homes, Inc.
January 15, 2024
Retaining Walls
ES-9558
Page 5
Retaining walls must be designed to resist earth pressures and applicable surcharge loads. The
following parameters can be used for retaining wall design:
• Active earth pressure (unrestrained condition)
• At -rest earth pressure (restrained condition)
• Traffic surcharge (passenger vehicles)
• Passive earth pressure
• Coefficient of friction
• Seismic surcharge
* Where H equals the retained height.
35 pcf
55 pcf
70 psf (rectangular distribution)
300 pcf
0.40
8H*
The passive earth pressure and coefficient of friction values include a safety factor of 1.5.
Additional surcharge loading from adjacent foundations, sloped backfill, or other loads 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 or sheet drainage 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 approved discharge location.
Earth Solutions NW. LLC
Select Homes, Inc.
January 15, 2024
Seismic Design
ES-9558
Page 6
The 2018 International Building Code (2018 IBC) recognizes the most recent edition of the
Minimum Design Loads for Buildings and Other Structures manual (ASCE 7-16) for seismic
design, specifically concerning earthquake loads. Based on the soil conditions encountered at
the test locations, the parameters and values provided below are recommended for seismic
design per the 2018 IBC.
Parameter
Value
Site Class
D*
Mapped short -period spectral response acceleration, Ss (g)
1.281
Mapped 1-second period spectral response acceleration, S1 (g)
0.449
Short period site coefficient, Fa
1.000
Long -period site coefficient, Fv
1.851 **
Adjusted short -period spectral response acceleration, SMs (g)
1.281
Adjusted 1-second period spectral response acceleration, SMi (g)
0.831 **
Design short -period spectral response acceleration, SIDS (g)
0.854
Design 1-second period spectral response acceleration, SID, (g)
0.554**
Assumes medium dense to dense native soil conditions, encountered to a maximum depth of six and one-half
feet bgs during the November 2023 field exploration, remain medium dense to dense to at least 100 feet bgs.
** Values assume Fv may be determined using linear interpolation per Table 11.4-2 in ASCE 7-16.
Drainage
Zones of perched groundwater seepage may be encountered within site excavations. Temporary
measures to control surface water runoff and groundwater during construction would likely involve
passive elements such as interceptor trenches and sumps. ESNW should be consulted during
preliminary grading to identify areas of seepage and to provide recommendations to reduce the
potential for instability related to seepage effects.
Finish grades must be designed to direct surface drain water away from the structure. Water
must not be allowed to pond adjacent to the structure. Grades adjacent to the building should be
sloped away from the building at a gradient of either at least 2 percent for a horizontal distance
of 10 feet or the maximum allowed by adjacent structures. In our opinion, footing drains should
be installed along building perimeter footings. However, elimination of footing drains can be
considered if relatively free -draining soil is exposed at footing subgrade elevations.
Earth Solutions NW. LLC
Select Homes, Inc.
January 15, 2024
Infiltration Evaluation
ES-9558
Page 7
ESNW completed a small-scale Pilot Infiltration Test (PIT) to evaluate the feasibility of on -site
infiltration BMPs from a geotechnical standpoint. In general, the native sand outwash deposits
exhibit good infiltration characteristics and can be utilized for on -site infiltration to the extent
practicable. In opinion, based on the results of in -situ infiltration testing, field observation, and
laboratory analyses, full infiltration is feasible from a geotechnical standpoint.
The small-scale PIT was completed in general accordance with the Department of Ecology
Stormwater Management Manual for Western Washington, as adopted by the City of Edmonds,
at test location TP-2. The PIT was completed at a depth of roughly two and one-half feet bgs
and within a representative section of sand outwash deposits. For infiltration facilities interfacing
with the native sand outwash deposits, the following design values (based on the results of the
PIT) may be used:
Test Pit ID
Test Depth
Ksat initial
CFv
CFT
Um
Ksat design
TP-1
2.5 ft
35.4 in/hr
0.7
0.5
0.9
11.1 in/hr
ESNW should review final drainage plans as well as observe infiltration facility excavation to
confirm anticipated soil types are exposed in the facility subgrade.
Limitations
This report has been prepared for the exclusive use of Select Homes, Inc. and their
representatives. The recommendations and conclusions provided in this report 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 sites may exist
and may not become evident until construction. ESNW should reevaluate the conclusions in this
report if variations are encountered.
Additional Services
ESNW should be retained to provide additional geotechnical services in association with this
project, including testing and consulting services during construction. ESNW should have an
opportunity to review final project plans with respect to geotechnical recommendations provided
in this letter.
Earth Solutions NW. LLC
Select Homes, Inc.
January 15, 2024
ES-9558
Page 8
We appreciate the opportunity to be of service to you and trust this letter meets your current
needs. Should you have any questions, or require additional information, please call.
Sincerely,
EARTH SOLUTIONS NW, LLC
Samuel E. Suruda, L.G.
Senior Staff Geologist
�lT•W
WA
Z.Ir
53803
�FGISTER��
FSS/ONAk-
01 /15/2024
Henry T. Wright, P.E.
Associate Principal Engineer
Attachments: Plate 1 — Vicinity Map
Plate 2 — Subsurface Exploration Plan
Subsurface Exploration Logs
Grain Size Distribution
References:
• Geologic Map of the Edmonds East and Part of the Edmonds West Quadrangles,
Washington, prepared by James P. Minard, dated 1983
• Edmonds Municipal Code Chapter 23.80 — Geologically Hazardous Areas, updated
August 2, 2023
• Edmonds Municipal Code Chapter 18.30 — Stormwater Management, updated July 1,
2022
• 2019 Stormwater Management Manual for Western Washington, endorsed by the City of
Edmonds
Earth Solutions NW. LLC
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Reference: NORTH
Snohomish County, Washington
Open StreetMap.org
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.
m ry
v
"'�- _--�-- North 188th Street¢'
Northwest 185th Street v \ LL
O. D
Vicinity Map
10429 — 240th Place S.W.
Edmonds, Washington
Drawn MRS I Date 01 /03/20241 Proj. No. 9558
Checked SES Date Jan.2024 Plate 1
c
ALLEY
TP-21
I TP-1
24OTH PLACE S.W.
LEGEND
_ TP-1 Approximate Location of
— ■ — ESNW Test Pit, Proj. No.
ES-9558, Nov. 2023
HA-1 I Approximate Location of
— • — ESNW Hand Auger Boring,
Proj. No. ES-9558, Nov. 2023
Subject Site
Existing Building
NORTH
NOT - TO - SCALE
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.
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.
Subsurface Exploration Plan
10429 — 240th Place S.W.
Edmonds, Washington
Drawn MRS Date 01/03/2024 Proj. No. 9558
Checked SES Date Jan.2024 Plate 2
W
I
,1� ��
Well -graded gravel with
Moisture Content
Symbols
m
CU >
GW
or without sand, little to
0
c
no fines
Dry - Absence of moisture, dusty, dry to
Cement grout
U U
j L
11
the touch
ATD = At time
surface seal
0
O
o
o
of drilling
g
Bentonite
o p
o01 00(lo
Poorly graded gravel with
Damp Perceptible moisture, likely below
chips
o Z
v
UU
o 0 0 0
GP
or without sand, little to
optimum MC
Static water
i
LO C
o
Q�oQ
no fines
level (date)
eall
Co °
Moist - Damp but no visible water, likely
o
a)
H a)
at/near optimum MC
-
Filter pack with
65
0
a) tav,
0
0
uD
op
o
GM
Silty gravel with or without
Wet - Water visible but not free draining,
blank casing
section
o
0
2 �
O
Q
0
sand
likely above optimum MC
Screened casing
o
or Hydrotip with
U) °
0 .0
o
Saturated/Water Bearing - Visible free
filter pack
o
U)
0
�
Clayey gravel with or
water, typically below groundwater table
End cap
O
-0-0
�
° L
L LL
C7
^
GC
without sand
Terms Describing Relative Density and Consistency
_ 0
co Z
Coarse -Grained Soils: Test Symbols & Units
Well -graded sand with
u�
O
SW
or without gravel, little to
=
Density SPT blows/foot Fines Fines Content
( )
oo
N
o
c
IL
o°o°o°o°o°o
°°°°°°°°°°°
no fines
Very Loose < 4
O LO
U
._
U (n
o
MC =Moisture Content (%)
Loose 4 to 9
'::
ca
�
0
to
,
•:: •..:•.;: , .
Poorly graded sand with
DD = Dr Density cf
Medium Dense 10 to 29 Y Y (P )
a)o
v
Sp
or without gravel, little to
o Z
no fines
Dense 30 to 49 Str = Shear Strength (tsf)
0
a)Very
Dense _> 50
O U)
PID = Photoionization Detector (ppm)
co
a�
'.:'
.
SM
Silty sand with or without
o
Lo c
c
:;:
.::'•:.
;..
gravel
Fine -Grained Soils: OC = Organic Content (%)
e
.
•;.
Consistency SPT blows/foot CEC = Cation Exchange Capacity (meq/100 g)
:
Very Soft < 2
�
�
SC
Clayey sand with or
LL = Liquid Limit (%)
Soft 2 to 3
^
without gravel
Medium Stiff 4 to 7 PL = Plastic Limit (%)
(%)
Stiff 8 to 14 PI = Plasticity IndexLO
CD
Silt with or without sand
IVIL
or gravel; sandy or
Very Stiff 15 to 29
gravelly silt
Hard _> 30
0
0 0
U 0
F///
Clay of low to medium
Y
Component Definitions
>
a)—.1
plasticity; plasticity; lean clay with
cn
M t.
or without sand or gravel;
Descriptive Term Size Range and Sieve Number
00
cn E
sandy or gravelly lean clay
Boulders Larger than 12"
— —
_
�
rn .
— J
U .5
Cobbles 3" to 12"
�o
_
OL
Organic clay or silt of
Zo
—
low plasticity
Gravel 3" to No. 4 (4.75 mm)
-0 to
J
�_
—
Coarse Gravel 3" to 3/4"
Fine Gravel 3/4" to No. 4 (4.75 mm)
Elastic silt with or without
d
Sand No. 4 (4.75 mm) to No. 200 (0.075 mm)
0
0
o
MH
sand or gravel; sandy or
Coarse Sand No. 4 (4.75 mm) to No. 10 (2.00 mm)
c O
(n g
gravelly elastic silt
Medium Sand No. 10 (2.00 mm) to No. 40 (0.425 mm)
IL 2
>, -
Fine Sand No. 40 (0.425 mm) to No. 200 (0.075 mm)
0 °o U O
Clay of high plasticity;
Silt and Clay Smaller than No. 200 (0.075 mm)
o
-0 LO
CH
fat clay with or without
Modifier Definitions
o
E
sand or gravel; sandy or
J
gravelly fat clay
—_
Percentage by
fn
Weight (Approx.) Modifier
CY
OH
Organic clay or silt of
medium to high plasticity
< 5 Trace (sand, silt, clay, gravel)
5 to 14 Slightly (sandy, silty, clayey, gravelly)
o>
ca o
PT
Peat, muck, and other
15 to 29 Sandy, silty, clayey, gravelly
=
�U)
— =
highly organic soils
Q
_> 30 Very (sandy, silty, clayey, gravelly)
Classifications of soils in this geotechnical report and as shown on the exploration logs are based on visual
—
field and/or laboratory observations, which include density/consistency, moisture condition, grain size, and
ii
FILL
Made Ground
plasticity estimates, and should not be construed to imply field or laboratory testing unless presented herein.
Visual -manual and/or laboratory classification methods of ASTM D2487 and D2488 were used as an
identification guide for the Unified Soil Classification System.
Earth
Solutions
NW L�c
Earth Solutions NWLLC
Geotechnical Engineering, Construction
Observation/Testing and Environmental Services
EXPLORATION LOG KEY
Earth Solutions NW, LLC
15365 N.E. 90th Street, Suite 100
Redmond, Washington 98052
Telephone: 425-449-4704
Fax: 425-499-4711
BORING NUMBER HA-1
PAGE 1 OF 1
PROJECT NUMBER ES-9558 PROJECT NAME 10429 — 240th Place S.W.
DATE STARTED 11/16/24 COMPLETED 11/16/24 GROUND ELEVATION
DRILLING CONTRACTOR ESNW Rep LATITUDE 47.78080 LONGITUDE-122.37370
LOGGED BY SES CHECKED BY HTW GROUND WATER LEVEL:
NOTES SZ AT TIME OF DRILLING
SURFACE CONDITIONS Grass AFTER DRILLING
w
ww
H w
CO
TESTS
2
J
0-
o
Q z
c7
U)
SP-
SM
MC = 9.2 2.5
.inac = Q
MATERIAL DESCRIPTION
Dark brown TOPSOIL, minimal root intrusions
Brown poorly graded SAND with silt and gravel, medium dense, damp
[USDA Classification: very gravelly loamy coarse SAND]
Hand auger boring terminated at 2.5 feet below existing grade. No groundwater encountered during
excavation. No caving observed.
LIMITATIONS: Ground elevation (if listed) is approximate; the test location was not surveyed.
Coordinates are approximate and based on the WGS84 datum. Do not rely on this test log as a
standalone document. Refer to the text of the geotechnical report for a complete understanding of
subsurface conditions.
Earth Solutions NW, LLC TEST PIT NUMBER TP-1
15365 N.E. 90th Street, Suite 100
Redmond, Washington 98052 PAGE 1 OF 1
Telephone: 425-449-4704
Fax: 425-499-4711
PROJECT NUMBER ES-9558 PROJECT NAME 10429 — 240th Place S.W.
DATE STARTED 11/16/24 COMPLETED 11/16/24 GROUND ELEVATION
EXCAVATION CONTRACTOR Client Provided LATITUDE 47.78129 LONGITUDE-122.37340
LOGGED BY SES CHECKED BY HTW GROUND WATER LEVEL:
NOTES SZ AT TIME OF EXCAVATION
SURFACE CONDITIONS Grass AFTER EXCAVATION
w
H w
2
ww
CO
0-
TESTS
J
MATERIAL DESCRIPTION
o
Q z
j
c7
U)
0.0
TPSL
Ta• :
Dark brown TOPSOIL, roots intrusions to 3'
0.5
Brown poorly graded SAND with silt and gravel, medium dense, damp
GB MC = 5.7 SP- .:
SM
2.5
IT
3.0
Gray poorly graded SAND with gravel, medium dense, damp
SP
GB MC = 2.4
[USDA Classification: extremely gravelly coarse SAND]
5.0 Fines = 0.4
GB MC = 5.7 5 5
Test pit terminated at 5.5 feet below existing grade. No groundwater encountered during excavation.
No caving observed.
LIMITATIONS: Ground elevation (if listed) is approximate; the test location was not surveyed.
Coordinates are approximate and based on the WGS84 datum. Do not rely on this test log as a
standalone document. Refer to the text of the geotechnical report for a complete understanding of
subsurface conditions.
Earth Solutions NW, LLC
15365 N.E. 90th Street, Suite 100
Redmond, Washington 98052
Telephone: 425-449-4704
Fax: 425-499-4711
TEST PIT NUMBER TP-2
PAGE 1 OF 1
PROJECT NUMBER ES-9558 PROJECT NAME 10429 — 240th Place S.W.
DATE STARTED 11/16/24 COMPLETED 11/16/24 GROUND ELEVATION
EXCAVATION CONTRACTOR Client Provided LATITUDE 47.78130 LONGITUDE-122.37325
LOGGED BY SES CHECKED BY HTW GROUND WATER LEVEL:
NOTES SZ AT TIME OF EXCAVATION
SURFACE CONDITIONS Grass AFTER EXCAVATION
w
ww
H w
CO
TESTS
2
J
0-
o
Q z
c7
U)
0.5
SID
SD
2.5 0110
GB MC = 4.0 o p
Fines = 2.3 GP O
o
(�R M('=5d o D
MATERIAL DESCRIPTION
Dark brown TOPSOIL, minimal root intrusions
-probed 6"
Brown poorly graded SAND with silt and gravel, medium dense, damp
Gray poorly graded GRAVEL with sand, medium dense, damp
[USDA Classification: extremely gravelly coarse SAND]
-probed 2"
-becomes wet post test
Gray poorly graded SAND with gravel, medium dense, damp
-light groundwater seepage at 6.5'
[USDA Classification: very gravelly coarse SAND]
Test pit terminated at 6.5 feet below existing grade. Light groundwater seepage encountered at 6.5
feet during excavation. No caving observed.
LIMITATIONS: Ground elevation (if listed) is approximate; the test location was not surveyed.
Coordinates are approximate and based on the WGS84 datum. Do not rely on this test log as a
standalone document. Refer to the text of the geotechnical report for a complete understanding of
subsurface conditions.
r Earth Solutions NW, LLC
15365 NE 90th Street, Suite 100
Redmond, WA 98052
Telephone: (425) 449-4704
GRAIN SIZE DISTRIBUTION
PROJECT NUMBER ES-9558 PROJECT NAME 10429 — 240th Place S.W.
U.S. SIEVE OPENING IN INCHES U.S. SIEVE NUMBERS I HYDROMETER
100
95
90
85
80
75
70
65
H
c3 60
w
m
55
tY
w 50
z
LL
1-- 45
z
w
ry 40
w
a
35
30
25
20
15
10
5
0
III■■■■����■■off■III■11■■■■■■�■■111■■■■�■■��III■1
100 10 1 0.1 0.01 0.001
GRAIN SIZE IN MILLIMETERS
COBBLES
GRAVEL
I SAND
SILT OR CLAY
coarse fine
coarse medium fine
,ecimen Identification
Classification
Cc
CU
HA-01 2.50ft.
USDA: Brown Very Gravelly Loamy Coarse Sand. USCS: SP-SM with Gravel.
0.75
32.92
TP-01 4.50ft.
USDA: Gray Extremely Gravelly Coarse Sand. USCS: SP with Gravel.
0.92
10.48
TP-02 2.50ft.
USDA: Gray Extremely Gravelly Coarse Sand. USCS: GP with Sand.
0.87
38.57
TP-02 6.50ft.
USDA: Grav Very Gravelly Coarse Sand. USCS: SP with Gravel.
0.64
8.03
Specimen Identification
D100
D60
D30
D10
LL
I PL
PI
%Silt
I %Clay
•
HA-01 2.5ft.
37.5
3.493
0.529
0.106
9.2
m
TP-01 4.5ft.
37.5
5.152
1.522
0.491
0.4
A
TP-02 2.5ft.
37.5
12.968
1.948
0.336
2.3
*
TP-02 6.5ft.
19
2.793
0.791
0.348
0.3
E. CONSTRUCTION SWPPP REQUIREMENTS:
The project will require grading to construct the proposed building and utilities (including the stormwater
control facilities). Standard erosion control measures are proposed to be used during construction. The
primary erosion and sediment control BMP during construction will be proper soil stabilization methods.
Exposed soils shall be stabilized by application of effective BMPs that protect the soil from the erosive forces
of raindrops, flowing water, and wind. Applicable practices include, but not limited to, temporary and
permanent seeding, sodding, mulching, plastic covering, erosion control fabrics, matting, the early
application of gravel base on areas to be paved, and dust control. The contractor shall select a soil
stabilization method best suited for the particular situation. Stockpiles must be stabilized and protected
with sediment trapping measures. In addition, site containment of exposed soils shall be sustained by using
silt fence barriers along the down -slope boundaries of the site's disturbance areas. See the site
development plan for details.
Construction Stormwater Pollution Prevention Plan (SWPPP): The following is a summary of the site's
erosion control measures that evaluates the typical DOE 13 elements of a SWPPP:
Element 1: Mark Clearing Limits: Clearing limits have been delineated on the engineering site development
plans.
BMP Recommended: Utilized: BMP C233: Silt Fence
Element 2: Establish Construction Access: A construction access has been delineated on the engineering
site development plans.
BMP Recommended: BMP C105: Stabilized Construction Access
Element 3: Control Flow Rates: Due to the relatively small size of the site's disturbance areas (less than 0.5
ac); it is recommended to maintain sheet flow dispersion (through downslope perimeter silt
fencing) and not install collect swales and a sediment trap that would concentrate runoff flows.
During construction silt fencing will provide attenuation of site runoff and upon project
completion and stabilization (established lawns and landscape of exposed soils).
BMP Recommended: No site specific BMP prescribed.
Element 4: Install Sediment Controls: Filter fabric fence has been delineated and detailed on the
engineering site development plans. At a minimum, silt fence will be installed along the down
gradient perimeter of the disturbed area that will receive sediment -laden runoff.
BMP Recommended: BMP C233: Silt Fence
Element 5: Stabilize Soils: Soils will be stabilized per the TESC notes listed on the engineering site
development plans.
BMP Recommended: BMP C120: Temporary and Permanent Seeding and BMP C123: Plastic
Covering
Element 6: Protect Slopes: Exposed slopes shall be stabilized per the TESC notes listed on the engineering
site development plans.
RAMEngineering, Inc.
RAM No. 23-035
10429 240th PI SW SFR
Stormwater Site Plan Report
Page E-1
BMP Recommended: BMP C120: Temporary and Permanent Seeding and BMP C123: Plastic
Covering
Element 7: Protect Drain Inlets: Drain inlet protection will be installed on all catch basins that will receive
sediment -laden runoff. See the engineering site development plans for locations and detail.
BMP Recommended: BMP C220: Inlet Protection
Element 8: Stabilize Channels and Outlets: This element is not applicable since there are no temporary
channels or outlets proposed.
BMP Recommended: BMP C209: Outlet Protection
Element 9: Control Pollutants: Pollutants shall be managed as described in the TESC notes listed on the
engineering site development plans.
BMP Recommended: BMP C151: Concrete Handling
Element 10: Control De -Watering: Highly turbid or contaminated de -watering water shall be handled
separately from stormwater. The water from all de -watering systems for trenches and
foundations shall be treated or disposed of prior to discharging from the site.
BMP Recommended: No site specific BMP prescribed.
Element 11: Maintain BMPs: BMPs shall be maintained and removed at the end of the project as follows:
i. All temporary and permanent erosion and sediment control BMPs shall be inspected,
maintained and repaired in accordance with the Drainage Manual or as approved or
required by the City to assure continued performance of their intended function in
accordance with BMP specifications.
ii. The applicant may remove temporary BMPs when they are no longer needed.
iii. All temporary erosion and sediment control BMPs shall be removed within 30 days after
construction is completed and the City has determined that the site is stabilized.
BMP Recommended: BMP C150: Materials on Hand
Element 12: Manage the Project: The owner of the site is responsible for managing the installation and
maintenance of the site BMPs.
BMP Recommended: BMP C150: Materials on Hand and BMP C162: Scheduling.
Element 13. Protect Low Impact Development BMPs: Compaction (i.e. vehicle and equipment traffic or
storage; and/or placement of stockpiles) to the soils in the area of the stormwater BMPs (Post -
Construction Soil Quality and Depth BMP T5.13 and Perforated Stub -out Connections BMP
T5.10C) shall be avoided during construction.
BMP Recommended: BMP C233: Silt/Protection Fence
Conclusion: The total site disturbance area (0.263 ac.) of the project is less than one acre, thus a formal
Department of Ecology Notice of Intent application for NPDES Construction Stormwater Permit coverage is
not required. The final site development construction plans include specific grading and drainage
improvement notes and details. With proper installation, maintenance, and inspections of the proposed
construction the project should have minimal impact on the surrounding environment.
RAMEngineering, Inc.
RAM No. 23-035
10429 240th PI SW SFR
Stormwater Site Plan Report
Page E-2
F. OPERATION AND MAINTENANCE GUIDELINES:
These guidelines are intended to provide operation and maintenance instructions for the project's storm
drainage control facilities. The owner is responsible for maintenance of storm drainage facilities within
the property (private property owner system); the owner is not responsible for maintenance within the
public right-of-way (City system).
The private property owner is responsible for properly maintaining the stormwater infrastructure on their
property to ensure it operates as designed. The City has developed an inspection program to ensure
private property owners are properly maintaining their stormwater systems.
This manual is not comprehensive; although it explains the intended operation of the various
components of the drainage system, and suggests a routine of inspection and maintenance, it cannot
anticipate every problem. Once a historical record of maintenance is established, it may be prudent to
alter the routine. It is recommended that maintenance records be kept, and that the records be
reviewed periodically.
The private on -site infiltration trench system consists of excavated trench filled with drain rock. The
infiltration trench system has been designed to infiltrate most storm event; if an extraordinary event
was to occur or multiple back to back large storm events occurred the connected catch -basins may
overtop and overflow into the street system. If regular overtopping of the catch basin is experienced
the system shall be thoroughly cleaned and inspected. Over a period of time siltation of the infiltration
bed can occur (especially if the system and upstream catch basin are not inspected and cleaned
regularly) and replacement of the rock in the infiltration system may be required. Regular inspection
and maintenance of the infiltration system should occur according to the attached maintenance tables
from the Washington State Department of Ecology Stormwater Manual (2019- Volume V).
Semi-annual inspections shall be conducted to ensure proper operations of the drainage system. The
inspections should occur prior to the winter rain season (Oct/Nov), leaving sufficient time to correct any
detected maintenance problems, and at the end of the season (April/May) to determine the effect of
the season's runoff. Once a historical basis is developed the frequency of inspection may be modified as
necessary. Sediment can build up inside control structures and catch basins, blocking or restricting flow
to the inlet. To prevent this problem, these structures should be routinely cleaned. Regular inspections
of control structures should be conducted to detect the need for non -routine cleanout.
MAINTENANCE REQUIREMENTS
ECDC Section 18.30.090 requires privately -owned
stormwater management facilities, such as LID
BMPs be properly maintained. The owner of the
property is the responsible party for such
maintenance. The system must be kept in good
working order. The entire system should be
inspected once per year. An improperly maintained
BMP may cause private property or street flooding.
RAMEngineering, Inc.
RAM No. 23-035
Contact the City Engineering Division for
maintenance information.
The City may make periodic inspections of BMPs to
ensure they are operating properly. ECDC Section
18.30.100 contains the enforcement provisions the
City can use to ensure the system is properly
maintained.
10429 240th P1 S W SFR
Stormwater Site Plan Report
Page F-1
Washington State Department of Ecology
2019 Stormwater Management Manual for Western Washington (2019 SWMMWW)
Publication No.19-10-021
Appendix V-A: BMP Maintenance Tables
Ecology intends the facility -specific maintenance standards contained in this section to be
conditions for determining if maintenance actions are required as identified through inspection.
Recognizing that Permittees have limited maintenance funds and time, Ecology does not
require that a Permittee perform all these maintenance activities on all their stormwater BMPs.
We leave the determination of importance of each maintenance activity and its priority within the
stormwater program to the Permittee. We do expect, however, that sufficient maintenance will
occur to ensure that the BMPs continue to operate as designed to protect ground and surface
waters.
Ecology doesn't intend that these measures identify the facility's required condition at all times
between inspections. In other words, exceedance of these conditions at any time between
inspections and/or maintenance does not automatically constitute a violation of these standards.
However, based upon inspection observations, the Permittee shall adjust inspection and
maintenance schedules to minimize the length of time that a facility is in a condition that
requires a maintenance action.
Table V-A.1: Maintenance Standards - Detention Ponds
Maintenance
Defect
Conditions When
Results Expected When
Component
Maintenance Is Needed
Maintenance Is Performed
Any trash and debris which
exceed 1 cubic feet per 1,000
square feet. In general, there
should be no visual evidence of
Trash &Debris
dumping.
Trash and debris cleared from
site
If less than threshold all trash
General
and debris will be removed as
part of next scheduled
maintenance.
Any poisonous or nuisance
No danger of poisonous
Poisonous
vegetation which may constitute
vegetation where maintenance
Vegetation and
a hazard to maintenance
personnel or the public might
noxious weeds
personnel or the public.
normally be. (Coordinate with
local health department)
RAM-7inaarinq, Inc,
RAM No. 23-035
10429 240th PI SW SFR
Stormwater Site Plan Report
Page F-2
Table V-A.1: Maintenance Standards - Detention Ponds
Maintenance
Defect
Conditions When
Results Expected When
Component
Maintenance Is Needed
Maintenance Is Performed
Any evidence of noxious weeds
Complete eradication of noxious
as defined by State or local
weeds may not be possible.
regulations.
Compliance with State or local
eradication policies required
(Apply requirements of adopted
IPM policies for the use of
herbicides).
Any evidence of oil, gasoline,
contaminants or other
pollutants
Contaminants and
No contaminants or pollutants
Pollution
present.
(Coordinate removal/cleanup
with local water quality
response agency).
Any evidence of rodent holes if
Rodents destroyed and dam or
facility is acting as a dam or
berm repaired. (Coordinate with
Rodent Holes
berm, or any evidence of water
local health department;
piping through dam or berm via
coordinate with Ecology Dam
rodent holes.
Safety Office if pond exceeds 10
acre-feet.)
Facility is returned to design
function.
Beaver Dams
Dam results in change or
function of the facility.
(Coordinate trapping of beavers
and removal of dams with
appropriate permitting agencies)
Insects destroyed or removed
When insects such as wasps
from site.
Insects
and hornets interfere with
maintenance activities.
Apply insecticides in compliance
with adopted IPM policies
Tree growth does not allow
Trees do not hinder
maintenance and inspection
maintenance activities.
Tree Growth and
access or interferes with
Harvested trees should be
Hazard Trees
maintenance activity (i.e., slope
recycled into mulch or other
mowing, silt removal, vactoring,
beneficial uses (e.g., alders for
or equipment movements). If
firewood).
trees are not interfering with
RAMEngineering, Inc.
RAM No. 23-035
10429 240th P/ S W SFR
Stormwater Site Plan Report
Page F-3
Table V-A.1: Maintenance Standards - Detention Ponds
Maintenance
Defect
Conditions When
Results Expected When
Component
Maintenance Is Needed
Maintenance Is Performed
access or maintenance, do not
remove
Remove hazard Trees
If dead, diseased, or dying
trees are identified
(Use a certified Arborist to
determine health of tree or
removal requirements)
Slopes should be stabilized
using appropriate erosion
Eroded damage over 2 inches
control measure(s); e.g.,rock
deep where cause of damage is
reinforcement, planting of grass,
still present or where there is
compaction.
Side Slopes of Pond
Erosion
potential for continued erosion.
If erosion is occurring on
Any erosion observed on a
compacted berms a licensed
compacted berm embankment.
engineer in the state of
Washington should be
consulted to resolve source of
erosion.
Accumulated sediment that
exceeds 10% of the designed
Sediment cleaned out to
Sediment
pond depth unless otherwise
designed pond shape and
specified or affects inletting or
depth; pond reseeded if
Storage Area
outletting condition of the
necessary to control erosion.
facility.
Liner (if Applicable)
Liner is visible and has more
Liner repaired or replaced. Liner
than three 1/4-inch holes in it.
is fully covered.
Any part of berm which has
settled 4 inches lower than the
design elevation
If settlement is apparent,
Ponds Berms
Settlements
measure berm to determine
Dike is built back to the design
(Dikes)
amount of settlement
elevation.
Settling can be an indication of
more severe problems with the
berm or outlet works. A
licensed engineer in the state of
Washington should be
RAMEngineering, Inc.
RAM No. 23-035
10429 240th P/ S W SFR
Stormwater Site Plan Report
Page F-4
Table V-A.1: Maintenance Standards - Detention Ponds
Maintenance
Defect
Conditions When
Results Expected When
Component
Maintenance Is Needed
Maintenance Is Performed
consulted to determine the
source of the settlement.
Discernable water flow through
pond berm. Ongoing erosion
with potential for erosion to
continue.
Piping
Piping eliminated. Erosion
potential resolved.
(Recommend a Goethechnical
engineer be called in to inspect
and evaluate condition and
recommend repair of condition.
Tree growth on emergency
Trees should be removed. If
spillways creates blockage
root system is small (base less
problems and may cause failure
than 4 inches) the root system
of the berm due to uncontrolled
may be left in place. Otherwise
Tree Growth
overtopping.
the roots should be removed
and the berm restored. A
Tree growth on berms over 4
licensed engineer in the state of
feet in height may lead to piping
Washington should be
Emergency
through the berm which could
consulted for proper
berm/spillway restoration.
Overflow/ Spillway
lead to failure of the berm.
and Berms over 4
feet in height
Discernable water flow through
pond berm. Ongoing erosion
with potential for erosion to
continue.
Piping
Piping eliminated. Erosion
potential resolved.
(Recommend a Geotechnical
engineer be called in to inspect
and evaluate condition and
recommend repair of condition.
Only one layer of rock exists
above native soil in area five
square feet or larger, or any
Emergency
Emergency
exposure of native soil at the
Rocks and pad depth are
Overflow/Spillway
Overflow/Spillway
top of out flow path of spillway.
restored to design standards.
(Rip -rap on inside slopes need
not be replaced.)
Erosion
See "Side Slopes of Pond"
RAMEngineering, Inc.
RAM No. 23-035
10429 240th P/ S W SFR
Stormwater Site Plan Report
Page F-5
Table V-A.2: Maintenance Standards - Infiltration
Maintenance
Conditions When Maintenance Is
Results Expected
Component
Defect
Needed
When Maintenance Is
Performed
See Table V-A.1:
Trash & Debris
See Table V-A.1: Maintenance
Maintenance
Standards - Detention Ponds
Standards - Detention
Ponds
See Table V-A.1:
Poisonous/Noxious
See Table V-A.1: Maintenance
Maintenance
Vegetation
Standards - Detention Ponds
Standards - Detention
Ponds
General
See Table V-A.1:
Contaminants and
See Table V-A.1: Maintenance
Maintenance
Pollution
Standards - Detention Ponds
Standards - Detention
Ponds
See Table V-A.1:
Rodent Holes
See Table V-A.1: Maintenance
Maintenance
Standards - Detention Ponds
Standards - Detention
Ponds
Water ponding in infiltration pond after
rainfall ceases and appropriate time
allowed for infiltration. Treatment
basins should infiltrate Water Quality
Design Storm Volume within 48 hours,
Sediment is removed
and empty within 24 hours after
and/or facility is
Storage Area
Sediment
cessation of most rain events.
cleaned so that
infiltration system
works according to
(A percolation test pit or test of facility
design.
indicates facility is only working at 90%
of its designed capabilities. Test every
2 to 5 years. If two inches or more
sediment is present, remove).
Filter Bags (if
Filled with Sediment
Sediment and debris fill bag more than
Filter bag is replaced
applicable)
and Debris
1/2 full.
or system is
redesigned.
By visual inspection, little or no water
Gravel in rock filter is
Rock Filters
Sediment and Debris
flows through filter during heavy rain
replaced.
storms.
Side Slopes of
Erosion
See Table V-A.1: Maintenance
See Table V-A.1:
Pond
Standards - Detention Ponds
Maintenance
RAMEngineering, Inc.
RAM No. 23-035
10429 240th P/ S W SFR
Stormwater Site Plan Report
Page F-6
Table V-A.2: Maintenance Standards - Infiltration
Maintenance
Conditions When Maintenance Is
Results Expected
Component
Defect
Needed
When Maintenance Is
Performed
Standards - Detention
Ponds
See Table V-A.1:
Tree Growth
See Table V-A.1: Maintenance
Maintenance
Standards - Detention Ponds
Standards - Detention
Ponds
Emergency
Overflow Spillway
and Berms over 4
feet in height.
See Table V-A.1:
Piping
See Table V-A.1: Maintenance
Maintenance
Standards - Detention Ponds
Standards - Detention
Ponds
See Table V-A.1:
Rock Missing
See Table V-A.1: Maintenance
Maintenance
Standards - Detention Ponds
Standards - Detention
Ponds
Emergency
Overflow Spillway
See Table V-A.1:
Erosion
See Table V-A.1: Maintenance
Maintenance
Standards - Detention Ponds
Standards - Detention
Ponds
Pre -settling Ponds
Facility or sump filled
6" or designed sediment trap depth of
and Vaults
with Sediment and/or
sediment.
Sediment is removed.
debris
Table V-A.S: Maintenance Standards - Catch Basins
Maintenance
Results Expected When
Component
Defect
Conditions When Maintenance is Needed
Maintenance is
performed
Trash or debris which is located immediately in front of
the catch basin opening or is blocking inletting capacity
No Trash or debris
of the basin by more than 10%.
located immediately in
front of catch basin or on
Trash or debris (in the basin) that exceeds 60 percent of
grate opening.
the sump depth as measured from the bottom of basin
General
to invert of the lowest pipe into or out of the basin, but in
No trash or debris in the
Trash & Debris
no case less than a minimum of six inches clearance
catch basin.
from the debris surface to the invert of the lowest pipe.
Inlet and outlet pipes free
Trash or debris in any inlet or outlet pipe blocking more
of trash or debris.
than 1/3 of its height.
No dead animals or
Dead animals or vegetation that could generate odors
vegetation present within
that could cause complaints or dangerous gases (e.g.,
the catch basin.
methane).
RAM E, .
RAM No. 23-035
10429 240th P/ S W SFR
Stormwater Site Plan Report
Page F-7
Table V-A.S: Maintenance Standards - Catch Basins
Maintenance
Results Expected When
Component
Defect
Conditions When Maintenance is Needed
Maintenance is
performed
Sediment (in the basin) that exceeds 60 percent of the
sump depth as measured from the bottom of basin to
invert of the lowest pipe into or out of the basin, but in
No sediment in the catch
Sediment
no case less than a minimum of 6 inches clearance from
basin
the sediment surface to the invert of the lowest pipe.
Top slab has holes larger than 2 square inches or
Top slab is free of holes
cracks wider than 1/4 inch. (Intent is to make sure no
and cracks.
Structure Damage
material is running into basin).
to Frame and/or
Top Slab
Frame not sitting flush on top slab, i.e., separation of
Frame is sitting flush on
more than 3/4 inch of the frame from the top slab.
the riser rings or top slab
and firmly attached.
Frame not securely attached
Maintenance person judges that structure is unsound.
Basin replaced or
Fractures or
Grout fillet has separated or cracked wider than 1/2 inch
repaired to design
standards.
Cracks in Basin
and longer than 1 foot at the joint of any inlet/outlet pipe
Walls/ Bottom
or any evidence of soil particles entering catch basin
Pipe is regrouted and
through cracks.
secure at basin wall.
Settlement/
If failure of basin has created a safety, function, or
Basin replaced or
repaired to design
Misalignment
design problem.
standards.
Vegetation growing across and blocking more than 10%
No vegetation blocking
of the basin opening.
opening to basin.
Vegetation
Vegetation growing in inlet/outlet pipe joints that is more
No vegetation or root
than six inches tall and less than six inches apart.
growth present.
Contamination and
See Table V-A.1: Maintenance Standards - Detention
No pollution present.
Ponds
Pollution
Cover Not in Place
Cover is missing or only partially in place. Any open
Cover/grate is in place,
meets design standards,
catch basin requires maintenance.
and is secured
Locking
Mechanism cannot be opened by one maintenance
Mechanism opens with
Catch Basin
Mechanism Not
person with proper tools. Bolts into frame have less than
proper tools.
Cover
Working
1/2 inch of thread.
One maintenance person cannot remove lid after
Cover Difficult to
applying normal lifting pressure.
Cover can be removed by
Remove
(Intent is keep cover from sealing off access to
one maintenance person.
maintenance.)
Ladder Rungs
Ladder is unsafe due to missing rungs, not securely
Ladder meets design
standards and allows
Ladder
Unsafe
attached to basin wall, misalignment, rust, cracks, or
maintenance person safe
sharp edges.
access.
Grate opening
Grate with opening wider than 7/8 inch.
Grate opening meets
Unsafe
design standards.
Trash and Debris
Trash and debris that is blocking more than 20% of
Grate free of trash and
Metal Grates (If
grate surface inletting capacity.
debris.
Applicable)
Grate is in place, meets
Damaged or
Grate missing or broken member(s) of the grate.
the design standards, and
Missing.
is installed and aligned
with the flow path.
RAMEngineering, Inc.
RAM No. 23-035
10429 240th P/ S W SFR
Stormwater Site Plan Report
Page F-8
ENGINEERING, INC.
Civil Engineering /Land Planning