Stormwater_Report.pdfWESTERN
ENGINEERS &
SURVEYORS
SURVEYORS • ENGINEERS • LAND USE CONSULTANTS
9740 Evergreen Way - Everett, WA 98204
P: (425) 356-2700 F: (425) 356-2708 W: WESI.CO
Targeted Stormwater Report
For
EVANS Short Plat
20020 — 83RD AVE W
EDMONDS, WASHINGTON
City of Edmonds Project # PLN2018.
Issue Date: May 18, 2018
Revision Date:
PREPARED BY:
ERIC HAINES, E.I.T.
REVIEWED BY:
JESSE JARRELL, P.E.
o5,lg-tS
CLIENT(S): SIMON EVANS WESTERN ENGINEERS, INC.
20020 — 83' AVE W Job No. 17-1701-A
EDMONDS, WA 98026
EVANS — 2 Lot S.P.
1. ATTACHMENT "A"
DRAINAGE INFORMATION SUMMARY FORM
Project Name: EVANS — 2 LOT S.P.
Project Engineer: WESTERN ENGINEERS, INC.
Project Applicant: SIMON EVANS
EDMONDS, WA
Project Total Area: 0.581 Acres
Project Development Area: 0.265 Acre Number of Lots: 2
Summary Table
Drainage Basin Information
Individual Basin
Designation
A
B
C
D
On -site Development Area
0.265 ac.
Type of Storage Proposed
NIA
DISPERSION
Approximate Storage Volume
NIA
Soil types
ALDERWOOD
Type C
WESTERN ENGINEERS, INC. PROJECT:17-1701-A
EVANS — 2 Lot S.P.
Minimum Requirement # 1: Stormwater Site Plan
Executive SuniniaH y
The proposed project is located at 20020 83RD AVE W in the City of Edmonds, within
Snohomish County, Washington. More generally, the site is located in Section 19,
Township 27 North, and Range 4 East of the Willamette Meridian in Edmonds,
Washington. Please refer to the Vicinity Map attached in the next section.
The project contains approximately 0.581 acres, which is covered by an existing house,
concrete patio, shed, detached garage, and asphalt driveway. The preliminary proposal is
to subdivide 0.581 acres into two housing lots with associated utilities. The existing '
house, patio, and the driveway on proposed Lot 2 will be retained, both proposed lots will
access 83" Ave W via a proposed 12' wide paved shared driveway along the northern
side of the property. The project is to be designed to the 2012 (With 2014 Updates)
WADOE Stormwater Design Manual and City of Edmonds 2017 Stormwater Codes.
Drainage management for new hardscape areas will primarily be provided by roof drain
perforated pipe stub out trenches (T5.1 OC) and driveway dispersion (T5.12) BMPs.
Disturbed vegetated areas will be amended per soil quality BMP T5.13. All utilities to be
provided by existing services on 83'd Ave W fronting the site.
Existinl! Conditions Summary
The site is partially developed with an existing house, concrete patio, shed, detached
garage and asphalt driveway on the western half of the. Existing on -site vegetation
primarily consists of residential lawn with tree cover. The site generally slopes northwest
to southeast at slopes ranging from 2% to 8%. From the Soil Conservation Service Map
of Snohomish County, the site contains Alderwood Urban Land Complex type soils.
Please refer to the soil map and descriptions attached later in this report.
WESTERN ENGINEERS, INC. PROJECT: 17-170 1 -A
EVANS — 2 Lot S.P.
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WE
MAP TAKEN FROM GOOGLE MAPS
WESTERN
ENGINEERS &
SURVEYORS
SURVEYORS • ENGINEERS • LAND USE CONSULTANTS
EVANS SHORT PLAT
EDMONDS, WA 98026
SCALE: DATE: 04/04/18 CHECKED: JAJ
9740 Evergreen Way, Everett WA 98204 1" =—1,000'
(425) 356-2700+ (425) 356-2708 (FAX) EMH JOB NUMBER: FILE NAME:
westernengineers.com BY: 17-1701-A 171701A/VICINITYMAP
WESTERN ENGINEERS, INC. PROJECT: 17-1701 -A
EVANS — 2 Lot S.P.
OFFSITE ANALYSIS
Site reconnaissance was done by Eric Haines, E.I.T. of Western Engineers Inc. on April
03, 2018. Weather during the investigation was mostly cloudy with a temperature around
45 degrees.
A: Upstream Analysis
It appears from the topography of the site that upstream sheet flows may occur from lawn
areas to the north and west. However, during the site visit, no evidence of any significant
flows was observed. Any contributions to surface flows from off -site are expected to be
minor and no other significant upstream flows appear to enter the property.
B: Downstream Analysis
Please refer to the Downstream Analysis Map attached in the next section for a detailed
depiction of the downstream drainage course.
The site is partially developed with an existing SFR, patio, shed, detached garage and
driveway. The majority of the site slopes from northwest to southeast towards the storm
system and sheet flows directly into an underground storm system on the west side of
83rd Avenue W (see photo 3). Intercepted flows enter a series of catch basins on the west
side of 83rd Avenue W. Flows entering the catch basins are routed approximately 1025
feet south in a storm system along the west side of 83rd Ave were it enters into an open
ditch system going through Pine Ridge Park(see photos 3 through 5). Access into the
ditch system was not possible due to dense vegetation.
No visible drainage problems were observed during the initial and follow-up field
inspections. Refer to the following pages for Aerial and Downstream Map.
Drainage Complaints
There are no found drainage complaints for this site.
WESTERN ENGINEERS, INC. PROJECT: 17-1701-A
EVANS — 2 Lot S.P.
BASIN AND AERIAL
MAPS
WESTERN ENGINEERS, INC. PROJECT:17-1701-A
EVANS — 2 Lot S.P.
AERIAL AND DOWNSTREAM MAP
TAKEN FROM GOOGLE EARTH
WE,
ENGINEERS &
SURVEYORS
SURVEYORS •ENGNEERS•LAND USE CONSULTANTS
9740 Evergreen Way, Everett WA 98204
(425) 356-2700 (425) 356-2708 (FAX)
westcrncnL'inccrs.com
EVANS SHORT PLAT
EDMONDS, WA 98026
SCALE: None DATE: 04/04/18 CHECKED: JAJ
BY: EMH JOB NUMBER: FILE NAME:
17-1701-A I Aerial Map
WESTERN ENGINEERS, INC. PROJECT:17-1701-A
EVANS — 2 Lot S.P.
DOWNSTREAM
PHOTOGRAPHS
WESTERN ENGINEERS, INC. PROJECT:17-1701-A
EVANS — 2 Lot S.P.
DOWNSTREAM PHOTOGRAPHS
PHOTO 2:
Figure to the Right:
Looking easterly along the proposed
driveway
WESTERN
ENGINEERS &
SURVEYORS
SURVEYORS • ENOWEERS • LAND USE CONSULTANTS
PHOTO 1:
Figure to the Left:
Looking southeast from the
existing driveway
EVANS SHORT PLAT
EDMONDS, WA 98026
9740 Evergreen Way, Everett WA 98204 SCALE: None DATE: 04/04/18 SHEET: 1 OF 3
(425) 356-2700 (425) 356-2708 (FAX) JOB NUMBER: FILE NAME:
westernengineers.com BY: EMH 17-1701-A Downstream LDOC
WESTERN ENGINEERS, INC. PROJECT: I7-1701-A
EVANS — 2 Lot S.P.
DOWNSTREAM PHOTOGRAPHS
PHOTO 4:
Figure to the Right:
Looking south at a catch basin
located along 83'd Ave W
WESTERN
. ENGINEERS &
SURVEYORS
SURVEYON$ - ENOMRS • LAND USE CONSULTANTS
9740 Evergreen Way, Everett WA 98204
(425) 356-2700 (425) 30-2708 (FAX)
westernengineers.com
PHOTO 3:
Figure to the Left:
Looking west at the
manhole on the east side of
the site
EVANS PROPERTY
EDMONDS, WA 98026
SCALE: None DATE: 4/04/18 SHEET: 2 OF 3
JOB NUMBER: FILE NAME:
BY: EMH I 17-1701-A D.S.PHOTOS.DOC
WESTERN ENGINEERS, INC. PROJECT: 17-1701-A
EVANS — 2 Lot S.P.
DOWNSTREAM PHOTOGRAPHS
PHOTO 6:
Figure to the Right:
Direction of flow into Pine
Ridge Park
WESTERN
ENGINEERS &
SURVEYORS
SURVEYORS • ENGINEERS - LAND USE CONSULTANTS
9740 Evergreen Way, Everett WA 98204
(425) 356-2700 (425) 39' -2708 (FAX)
PHOTO 5:
Figure to the Lcft:
Looking north along 83'�d
Ave W
EVANS PROPERTY
EDMONDS, WA 98026
SCALE: None DATE: 4/03/18 SHEET: 3 OF 3
JOB NUMBER: FILE NAME:
BY: EMH 17-1701-A D.S.PHOTOS.DOC
WESTERN ENGINEERS, INC. PROJECT: I 7-1701-A
EVANS — 2 Lot S.P.
Minimum Requirement # 2: SWPPP Narrative
Element #1: Mark Clearing Limits
Clearing limits have been shown on the Temporary Erosion and Sedimentation
Control Plans.
Element #2: Establish Construction Entrance
A temporary construction entrance has been shown at the location of the proposed
driveway that is to access 83`d Ave W. All vehicles shall be free of debris prior to
leaving the site.
Element # 3: Control Flow Rates
Flow rates during construction are to be contained through the installation of silt
fencing.
Element # 4: Install Sediment Controls
Sediment controls mainly consist of installing silt fencing along the western
boundary of the clearing/construction limits.
Element # 5: Stabilize Soils
All soils disturbed during site grading will be stabilized by use of the most
appropriate BMP method available. These consist of short-term and long-term
solutions. Short-term methods consist of compaction of the soils by vibratory roller
or bulldozer. Long-term methods consist of straw covering over the soils (this is in
the case of the project becoming dormant for greater than 1 month). At this time no
wintertime grading or construction activities will occur. During construction
periods longer than 1 working week (7 days) where the soils are exposed and un-
worked will use the proscribed methods in the Storm Water Management Manual
for Western Washington to reduce sedimentation transported offsite. If winter
grading is conducted, all exposed soils shall be covered within 2 days.
Element # 6: Protect Slopes
There are no known steep or significant slopes on -site; therefore, slope protection is
not necessary.
Element # 7: Protect Drain Inlets
The off -site catch basins along the west side of 83rd Ave W will be provided sediment
protection with catch basin inserts or equivalent.
Element # 8: Stabilize Channels and Outlets
Channels and drainage outlets are not needed around the proposed development
area on site. No stabilization is necessary. Existing channels or drainage outlets
located within 500-feet of the property of the property should be routinely inspected
for debris that may dam and/or aid erosion.
WESTERN ENGINEERS, INC. PROJECT:17-1701-A
EVANS — 2 Lot S.P.
Element # 9: Control Pollutants
All pollutants from construction vehicles will be contained and disposed of in the
approved manner consistent with state environmental policies. Any vehicle
maintenance will be performed by authorized mechanics using drip pans and waste
containment vessels. All pollutants will be disposed offsite at approved facilities.
Element # 10: Control De -Watering
De -watering of the site is not expected. If dewatering of the site is needed, all
groundwater removed shall be retained and recharged into the ground after de -
watering has been finalized.
Element # 11: Maintain BMP's
All Temporary Erosion and Sedimentation Control (TESC) devices and equipment
will be inspected and maintained on a weekly basis if not sooner, based on storm
events contributing to runoff. When construction is complete and the site is
stabilized, any existing sediment will be removed and stabilized onsite.
Element # 12: Manage the Project
A general construction manager will manage the project for or by the owners. The
construction manager shall maintain all of the above items in order to minimize
sediment transport and turbid water leaving the site. His job will entail continual
observation of the grading operations to ensure minimal effects to adjacent
properties and offsite waterways.
Element # 13: Protect Low Impact Development BMPs
Proposed dispersion flow path areas and soil amendment areas will be protected
from compaction when feasible.
Minimal Requirement # 3: Water Pollution Source Control
All proposed development is to consist of residential construction. No water
pollution source control is needed.
Minimum Requirement # 4: Preservation of Natural Drainage Systems
and Outfalls, and provisions of off -site mitigation
No changes to the existing drainage systems and outfalls are proposed with this
development.
Minimum Requirement #5 On -Site Storm Water Management
The project results in less than 5,000 square feet of new/replaced hard surfaces and is
considered a Category 2 project. Category 2 projects must evaluate Minimum
Requirements 1 through 9 and select on -site stormwater BMPs according to List 2 for
each proposed hard surface. Note that due to geometry, spacing between the property
lines and the site consisting of an erosion hazard in the southeast portion of the site,
WESTERN ENGINEERS, INC. PROJECT: 17-1701 -A
EVANS — 2 Lot S.P.
infiltration and dispersion BMPs are generally infeasible. Refer to List 2 below for
appropriate BMP selection or infeasibility description:
Lawn and landscaped areas:
• Post -Construction Soil Quality and Depth in accordance with BMP T5.13
in Chapter 5 of Volume V. (To be used in disturbed vegetated areas)
Roofs feasibility description:
1. Full Dispersion per BMP T5.30 or Downspout Full Infiltration per BMP
T5.1 OA.
i. Full Dispersion is infeasible due to insufficient flow path length
and lack of native forest vegetation. Full Infiltration is infeasible
due to lack of spacing between property line and proposed edge of
house
2. Bioretention per Volume V, Chapter 7.
i. Due to the fact that the entire site consists of inadequate soil depth
for roof drain infiltration, bioretention facilities are infeasible.
3. Downspout Dispersion Systems in accordance with BMP T5.1 OB.
i. Due to the fact that there is not enough space between the property
line and the proposed edge of house, along with the fact that the
southeastern portion of the site is considered an erosion hazard
area, downspout dispersion is infeasible for roof runoff.
4. Perforated Stub Out Connections BMP T5.10C
i. Perforated Stub Out has been selected for this project because it is
a feasible option and all high priority options are infeasible.
Other Hard Surfaces feasibility description:
1. Full Dispersion per BMP T5.30
i. As noted above, Full Dispersion is infeasible due to insufficient
flow path length and lack of native forest vegetation.
2. Permeable Pavement per BMP T5.15
i. Due to the fact that the entire site consists of inadequate soil depth
to provide adequate separation between pavement subgrade and the
hardpan layer, permeable pavement is infeasible.
3. Biorention per Volume V, Chapter 7.
i. Due to the fact that the entire site consists of inadequate soil depth
for infiltration, bioretention facilities are infeasible.
4. Sheet Flow Dispersion in accordance with BMP T5.12 or BMP T5.11.
i. Sheet Flow Dispersion BMP T5.12 has been selected for new
shared driveway and individual driveway areas.
Minimum Requirement # 6: Runoff Treatment
Due to the site proposing less than 5,000 sf. of new pollution generating
impervious surfaces, less than 3/ acres of forest to lawn conversion, and less than
2.5 acres of forest to pasture conversion, runoff treatment is not required.
WESTERN ENGINEERS, INC. PROJECT: 17-170 1 -A
EVANS — 2 Lot S.P.
Minimum Requirement # 7: Flow Control
ry
Due to the site proposing less than 5,000 sf of new/replaced impervious surface,
less than3/ acres of forest to lawn conversion, less than 2.5 acres of forest to
pasture conversion, flow control is not required.
Refer to the summary below for an overview of the hardscape calculations.
Total Area of the Site
Total Clearing Area
= 25,327 sf. (0.581 Ac.)
= 11,550 sf. (0.265 Ac.)
Existing Site Before Clearing
Impervious area:
Existing SFR Roof = 2,347 sf. ±
Existing Concrete Patio = 1,287 sf. ±
Existing Driveway to Remain= 1,874 sf. +
Existing Shed and Garage = 582 sf. ±
Total = 6,090 sf. (0.140 Ac.)
Pervious area:
Existing Lawn Area = 19,237 sf. (0.442 Ac.)
Prouosed Site
Impervious area:
Existing SFR Roof =
2,347 sf. ±
Existing Concrete Patio =
1,287 sf. f
Existing Driveway to'Remain=
1,874 sf. +
Existing Shed and Garage =
582 sf. ±
New Driveway Extension =
540 sf. ±
New Lot 1 SFR Roof =
2,800 sf. ±
New Lot 1 Parking Addition =
1,000 sf. +
Total =
10,430 sf. (0.239 Ac.)
New/Replaced Impervious Surface = 4,340 sf.
Pervious area:
Existing Lawn to Remain = 7,687 sf. (0.176 Ac.)
Proposed Amended Lawn = 7,210 sf. (0.165 Ac.)
WESTERN ENGINEERS, INC. PROJECT: 17-1701 -A
EVANS — 2 Lot S.P.
Minimum Requirement # 8: Wetland Protection
There are no known wetlands on -site. Note that defined clearing limits, silt
fencing, and large vegetated spaces shown on the LDA plan will protect any
downstream wetlands or streams.
Minimum Requirement # 9: Operation and Maintenance Manual
BMP T5.13 Post -Construction Soil Quality and Depth
Maintenance
• Soil quality and depth should be established toward the end of construction and once
established, should be protected from compaction, such as from large machinery use, and
from erosion.
• Soil should be planted and mulched after installation.
• Plant debris or its equivalent should be left on the soil surface to replenish organic matter.
WESTERN ENGINEERS, INC. PROJECT:17-1701-A
EVANS — 2 Lot S.P.
Table
V-4.5.2(5)
Maintenance Stanaaras - vaccn esasins
Results
Maintenance
Defect
Defect
Conditions When Maintenance is
Expected
ComponentMain-
p onent
Needed
tenance is
performed
No Trash or
debris loc-
Trash or debris which is located imme-
ated imme-
diately in front of the catch basin opening or
diately in
is blocking inletting capacity of the basin by
front of catch
more than 10%.
basin or on
Trash or debris (in the basin) that exceeds
grate open-
60 percent of the sump depth as measured
i ng.
from the bottom of basin to invert of the low-
No trash or
est pipe into or out of the basin, but in no
debris in the
Trash &
case less than a minimum of six inches
catch basin.
Debris
clearance from the debris surface to the
invert of the lowest pipe.
Inlet and out-
letpipes free
Trash or debris in any inlet or outlet pipe
of trash or
blocking more than 1/3 of its height.
debris.
Dead animals or vegetation that could gen-
No dead
General
erate odors that could cause complaints or
animals or
dangerous gases (e.g., methane).
vegetation
present
within the
catch basin.
Sediment (in the basin) that exceeds 60 per-
cent 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 case
No sediment
Sediment
less than a minimum of 6 inches clearance
in the catch
from the sediment surface to the invert of the
basin
lowest pipe.
Structure
Top slab has holes larger than 2 square
Top slab is
Damage to
inches or cracks wider than 1 /4 inch. (Intent
free of holes
Frame and/or
is to make sure no material is running into
and cracks.
Top Slab
basin).
Frame is sit
2014 Stormwater Management Manual for Western Washington
Volume V - Chapter 4 - Page 838
WESTERN ENGINEERS, INC. PROJECT: I 7-1701-A
EVANS — 2 Lot S.P.
Table V-4.5.2(5) Maintenance Standards - Catch Basins (continued)
Results
Maintenance
Defect
Conditions When Maintenance is
Expected
When Main-
Componenti
Needed
tenance is
performed
Frame not sitting flush on top slab, i.e., sep-
ting flush on
the riser rings
aration of more than 3/4 inch of the frame
or top slab
from the top slab. Frame not securely
and firmly
attached
attached.
Basin
Maintenance person judges that structure is
replaced or
unsound.
repaired to
Fractures or
rac in
Grout fillet has separated or cracked wider
design stand-
Basin Walls/
than 1/2 inch and longer than 1 foot at the
ards.
Bottom
joint of any inletloutlet pipe or any evidence
Pipe is
of soil particles entering catch basin through
regrouted
cracks.
and secure at
basin wall.
Basin
Settlement/
If failure of basin has created a safety, func-
replaced or
repaired to
Misalignment
tion, or design problem.
design stand-
ards.
No veget-
Vegetation growing across and blocking
ation block -
more than 10% of the basin opening.
ing opening
to basin.
Vegetation
Vegetation growing in inlet/outletpipejoints
No veget-
that is more than six inches tail and less
grown or root
than six inches apart.
growth
present.
Contamination
See "Detention Ponds" (No. 1).
No pollution
and Pollution
present.
Cover is missing or only partially in place.
Catch basin
Cover Not in
Any open catch basin requires main-
cover is
Catch Basin
Place
tenance.
closed
Cover
Locking Mech-Mechanism
cannot be opened by one main-
Mechanism
�anisrn Not
tenance person with propertools. Bolts into
opens with
2014 Stormwater Management Manual for Western Washington
Volume V - Chapter 4 - Page 839
WESTERN ENGINEERS, INC. PROJECT:17-1701-A
EVANS - 2 Lot S.P.
Tnhla V.d_5.2(5) Maintenance Standards - Catch Basins (continued)
Results
Maintenance
Defect
Conditions When Maintenance is
Expected
When Main -
Component
Needed
tenance is
performed
Working
frame have less than 1/2 inch of thread.
proper tools.
One maintenance person cannot remove lid
'Cover can be
Cover Difficult
after applying normal lifting pressure.
removed by
to Remove
(Intent is keep cover from sealing off access
one main -
tenance per -
to maintenance.)
son.
Ladder meets
design stand
Ladder is unsafe due to missing rungs, not
ards and
Ladder
Ladder Rungs
securely attached to basin wall, mis-
allows main -
Unsafe
alignment, rust, cracks, or sharp edges.
tenance per-
son safe
access.
Grate open -
Grate opening
Grate with opening wider than 7/8 inch.
ing meets
Unsafe
design stand-
ards.
Metal Grates
Trash and
'Trash and debris that is blocking more than
Grate free of
(If Applic-
Debris
:20% of grate surface inletting capacity.
trash and
debris.
able)
Grate is in
Damaged or
Grate missing or broken member(s) of the
place and
Missing.
grate.
meets design
standards.
WESTERN ENGINEERS, INC. PROJECT: 17-170 1 -A
EVANS — 2 Lot S.P.
Table V 4.5.2(7) Maintenance Standards - Energy Dissipaters
Results Expec
Maintenance Conditions When Maintenance is ed When Main
Components Defect Needed tenance is
Performed
External:
Missing or
Only one layer of rock exists above nat
Rock pad
replaced to
Moved
ive soil in area five square feet or lar-
design stand-
Rock
ger, or any exposure of native soil.
ards.
Rock Pad
Rock pad
Erosion
Soil erosion in or adjacent to rock pad,
replaced to
design stand-
ards.
Pipe
Pipe cleaned/ -
Plugged
Accumulated sediment that exceeds
flushed so that
with Sed-
20% of the design depth.
it matches
iment
design.
Not Dis-
Visual evidence of water discharging
Trench
Dispersion Trench
charging
at concentrated points along trench
(normal condition is a sheet flow of
redesigned or
Water Prop-
water along trench). Intent is to prevent
rebuilt to stand-
erly
erosion damage.
ards.
Perforations
Over 1/2 of perforations in pipe are
Perforated pipe
cleaned or
Plugged.
plugged with debris and sediment.
replaced.
2014 Stormwater Management Manual for Western Washington
Volume V - Chapter 4 - Page 841
WESTERN ENGINEERS, INC. PROJECT:17-1701-A
EVANS — 2 Lot S.P.
Table V-4.5.2(7) Maintenance Standards - Energy Dissipaters
(continued)
Results Expec-
Maintenance
Defect
Conditions When Maintenance is ,ted When Main
Components
Needed tenance is
Performed
Water
Maintenance person observes or
Flows Out ut
receives credible report of water flow-
Facility rebuilt
Top of
T ofibutor
ing out during any storm less than the
or redesigned
trop
design storm or its causing or appears
to standards.
Catch
likely to cause damage.
Basin.
Receiving
Water in receiving area is causing or
No danger of
Area Over-
has potential of causing landslide prob
landslides.
Saturated
lems.
Internal:
Worn or
Damaged
Structure dissipating flow deteriorates
Structure
post,
to 1/2 of original size or any con-
replaced to
Manhole/Chamber
Baffles,
centrated worn spot exceeding one
design stand -
Side of
square foot which would make struc-
ards.
ture unsound.
Chamber
Other
See "Catch Basins" (No. 5).
See "Catch Bas
Defects
ins" (No.5).
WESTERN ENGINEERS, INC. PROJECT: 17-1701 -A
EVANS — 2 Lot S.P.
APPENDIX I
Drainage Plan
WESTERN ENGINEERS, INC. PROJECT: 17-1701-A
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NEW DRIVEWAY
SECTION DETAIL
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�"� PLAN VIEW OF ROOF
m .. PERFORATED TIGHTUNE CONNECTION
�� 1om y •Am 41' El5E1 W WIDTH
2D' fir - 2r rAm" w m
—D' - 20' PAVEWEM WIDTH
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EVANS — 2 Lot S.P.
APPENDIX II
SOIL INFORMATION
WESTERN ENGINEERS, INC. PROJECT: 17-1701 -A
EVANS - 2 Lot S.P.
USDA SOIL MAP
m
Snohomish County Area, Washington (WA661)
Snohomish County Area, Washington
(WA661)
Map Acres percent
Unit Map Unit Name In of A0I
Symbol A0I
5 Alderwood-Urban 0.6 100.0%
land complex, 2 to
8 percent slopes
Totals for Area of 0.6 100.00/6
Interest
USDA SOIL MAP LEGEND
5—Alderwood-Urban land complex, 2 to 8 percent slopes
Map Unit Setting
• National map unit symbol: 2hz9
• Elevation: 50 to 800 feet
• Mean annual precipitation: 25 to 60 inches
• Mean annual air temperature: 48 to 52 degrees F
• Frost -free period: 180 to 220 days
• Farmland classification: Not prime farmland
Map Unit Composition
• Alderwood and similar soils: 60 percent
• Urban land: 25 percent
• Minor components: 6 percent
• Estimates are based on observations, descriptions, and transects of the
mapunit.
Description of Alderwood
Setting
• Landform: Till plains
• Parent material: Basal till
Typical profile
• H1 - 0 to 7 inches: gravelly ashy sandy loam
• H2 - 7 to 35 inches: very gravelly ashy sandy loam
• H3 - 35 to 60 inches: gravelly sandy loam
Properties and qualities
• Slope: 2 to 8 percent
• Depth to restrictive feature: 20 to 40 inches to densic material
• Natural drainage class: Moderately well drained
• Capacity of the most limiting layer to transmit water (Ksat): Very low to
moderately low (0.00 to 0.06 in/hr)
• Depth to water table: About 18 to 36 inches
WESTERN ENGINEERS, INC. PROJECT: 17-1701 -A
EVANS — 2 Lot S.P.
Frequency of flooding: None
Frequency of ponding: None
Available water storage in profile: Low (about 3.0 inches)
Interpretive groups
Land capability classification (irrigated): None specified
Land capability classification (nonirrigated): 4s
Hydrologic Soil Group: B
Other vegetative classification: Limited Depth Soils (G002XN302WA)
Minor Components
Mckenna
Percent of map unit: 2 percent
Landform: Depressions
Norma
Percent of map unit: 2 percent
Landform: Depressions
Terric medisaprists
• Percent of map unit: 2 percent
• Landform: Depressions
WESTERN ENGINEERS, INC. PROJECT:17-1701-A
EVANS — 2 Lot S.P.
APPENDIX III
SOIL AMENDMENT
WESTERN ENGINEERS, INC. PROJECT:17-1701-A