FOR REFERENCE BLD2024-0518+Storm_Drainage_Report+4.17.2024_3.29.09_PM+4203294=JC JACOBSON
RECEIVED
Apr 23 2024
BLD2024-0518 CITY OFEDMONDS
DEVELOPMENT SERVICES
DEPARTMENT
ENGINEERING REPORT
Storm Drainage Report
Edmonds School District
Edmonds-Woodway High School Portable Placement
7600 212st ST SW
Edmonds, WA 98026
March 26, 2024
Prepared for
Edmonds School District
20420 68' Ave W
Lynnwood, WA 98036
Prepared through
Hutteball + Oremus Architecture
4010 Lake Washington Blvd NE #320
Kirkland, WA 98033
Prepared by
Jacobson Consulting Engineers
Sascha Eastman
206.426.2600
sascha@jacobsonengineers.com
255 S. King Street, Suite 800, Seattle, WA 98104 1 206.426.2600 1 JACOBSONENGINEERS.COM
Storm Drainage Report for
EDMONDS-WOODWAY HIGH SCHOOL PORTABLE PLACEMENT
,JACOBSON
mi� CO NSU LTIN G ENGINEERS
Project No. C230008-0180
March 26, 2024
TABLE OF CONTENTS
I. PROJECT OVERVIEW............................................................................................................. 2
GENERAL DESCRIPTION......................................................................................................................2
EXISTING CONDITIONS.........................................................................................................................2
PROPOSEDCONDITIONS.....................................................................................................................2
II. DRAINAGE ANALYSIS............................................................................................................ 3
EXISTING SITE HYDROLOGY...............................................................................................................3
DEVELOPED SITE HYDROLOGY.........................................................................................................3
UPSTREAMANALYSIS..........................................................................................................................4
DOWNSTREAM ANALYSIS....................................................................................................................4
III. DISCUSSION OF MINIMUM REQUIREMENTS.......................................................................... 4
MR 1: PREPARATION OF STORMWATER SITE PLANS....................................................................4
MR 2: STORWMATER POLLUTION PREVENTION PLAN (SWPPP).................................................4
IV. --MPORARY EROSION AND SEDIMENT CONTROL.................................................................. 6
APPENDICES
Appendix A Figures
EDMONDS-WOODWAY HIGH SCHOOL PORTABLE PLACEMENT
PROJECT OVERVIEW
GENERAL DESCRIPTION
The following Drainage Report provides the design analysis for the Edmonds-Woodway High School Portable
Placement project. The stormwater design for the project was based on the requirements set forth in the 2019
Washington State Department of Ecology Stormwater Management Manual for Western Washington (2019
WSDOE SWMMWW) as adopted by the City of Edmonds.
The Edmonds-Woodway High School Portable Placement project is located at 7600 212" St SW, Edmonds, WA
98026 (see Appendix A Figure 1, Vicinity Map). The project site area is located in the NE corner of the existing
track and field (Parcel #27043000104800) on the west side of the school campus. The property is bounded
by 216" St SW to the south, 76" Ave W to the east, 2212" St SW to the north, and multifamily residential
properties to the west. The site is in the NE 1/4 of the NE 1/4 of Section 30, Township 27 North, Range 4 East,
Willamette Meridian. The project's limits of work area within the property boundary is approximately 1,867
square feet (-0.04 acres). See Developed Site Hydrology in Section II below.
The project proposes to relocate (1) one existing portable building currently located at the school district's Oak
Heights Elementary School campus, to Edmonds-Woodway High School, that will replace an existing portable in
the same location in the northeast corner of the track and field. Work will consist of installing new concrete
foundations for the portables, concrete and gravel pads/landings for stairs and accessible ramps as required, and
metal grated landings, ramps, and stairs. Storm drainage for the proposed portables will consist of a building
downspout that will discharge stormwater onto a splash block, which will then sheet flow across the grass on the
south side of portable building towards the field, maintaining the natural drainage course for this area (see civil
plan sheet C2.00, CIVIL SITE PLAN).
EXISTING CONDITIONS
The existing Edmonds-Woodway High School property (Parcel #27043000104800) is currently developed with
school building in the northeast corner of the campus, asphalt parking lots to the west and south of the building,
and athletic facilities on the west side of the campus, including a baseball field to the south, track and football
field to the north, and softball field in the northwest corner of the campus. There is also an existing portable
classroom building located at the southwest corner of the classroom building and another portable building
located at the northeast corner of the track and field. The campus is also vegetated with grass and trees around
the parking lots and classroom building and on the west side of the athletic facilities along the west property
line. There is also an existing fire lane on the south and west side of the classroom building with access from
both 76t" Ave W and 212t" St SW.
The project site currently sheet flows stormwater across existing grass from north to south towards the track and
field. See Proposed Conditions discussion below.
PROPOSED CONDITIONS
The project proposes to relocate (1) one existing portable building currently located at the school district's Oak
Heights Elementary School campus, to Edmonds-Woodway High School, that will replace an existing portable in
the same location in the northeast corner of the track and field. Work will consist of installing new concrete
foundations for the portables, concrete and gravel pads/landings for stairs and accessible ramps as required, and
metal grated landings, ramps, and stairs.
There is an existing 6-inch storm drainage pipe that runs east -west under a portion of the southeast corner of
the proposed portable that will be maintained as it is at least 5-ft deep below the portable. The storm line
changes direction and drains the stormwater south from the southeast corner of portable and continues through
a series of 12-inch storm pipes south along the east side of the track and field. Storm drainage for the proposed
portables will consist of a building downspout that will discharge stormwater onto a splash block that will flow
along a proposed shallow grass lined swale towards the south, then sheet flow naturally towards the southeast
across the grass and collect in a catch basin located approximately 80-ft to the south.
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EDMONDS-WOODWAY HIGH SCHOOL PORTABLE PLACEMENT
II. DRAINAGE ANALYSIS
EXISTING SITE HYDROLOGY
The existing project limits area is approximately 1,867 square feet or —0.04 acres, with roughly 1,172 square
feet of area being disturbed for the portable to install the concrete foundation, concrete and gravel
pads/landings for stair and accessible ramps, as well as proposed downspout and splashblock, power, comm,
and fire alarm conduits. All utility work will be installed in the existing grass area on the west and north sides of
the proposed portable classroom building, except for downspout and splashblock being installed on the south
side of building. Most of the project site where the proposed classroom portable will be installed is grass
(pervious).
Stormwater runoff is generally conveyed via sheet flow from north to south around the existing portable
classroom building towards the track and field and collects in a catch basin located approximately 80-ft to the
south that then conveys the stormwater south through a series of 12-inch storm pipes located on the east side of
the existing track and field. See civil plan sheet C1.00, Civil Site Plan, which indicates the land cover
characteristics of the existing project site.
DEVELOPED SITE HYDROLOGY
The project proposes to relocate (1) one existing portable building currently located at the school district's Oak
Heights Elementary School campus, to Edmonds-Woodway High School, that will replace an existing portable in
the same location in the northeast corner of the track and field. Work will consist of installing new concrete
foundations for the portables, concrete and gravel pads/landings for stairs and accessible ramps as required, and
metal grated landings, ramps, and stairs.
There is an existing 6-inch storm drainage pipe that runs east -west under a portion of the southeast corner of
the proposed portable that will be maintained as it is at least 5-ft deep below the portable. The storm line
changes direction and drains the stormwater south from the southeast corner of portable and continues through
a series of 12-inch storm pipes south along the east side of the track and field. Storm drainage for the proposed
portables will consist of a building downspout that will discharge stormwater onto a splash block that will flow
along a proposed shallow grass lined swale towards the south, then sheet flow naturally towards the southeast
across the grass and collect in a catch basin located approximately 80-ft to the south that then conveys the
stormwater south through a series of 12-inch storm pipes located on the east side of the existing track and field.
Table 1 below summarizes the land cover characteristics of the proposed redevelopment (see Appendix A Figure
3, New + Replaced Impervious Areas).
TABLE 1 — DEVELOPED PROJECT SITE CONDITIONS
Land Cover
Impervious Area (sf)
Pervious Area (sf)
Total (sf)
New + Replaced Concrete
26
0
New+ Replaced Roof
1,172
0
New + Replaced Gravel
25
0
Metal Ramps/Stairs/Landings
*64
Total New & Replaced Hard Surface
*1,287
0
Landscaping (Grass Restoration)
0
580
Total Site
*1,287
580
1,867
% of Site 68.9% 31.1% 100%
From Table 1 above, 1,287 square feet of new + replaced impervious surface represents new concrete and
gravel pads/landings for stairs and accessible ramps, as well as proposed portable building roof. The metal
ramps, stairs, and landings, per drainage code, can be considered 50% impervious and 50% pervious. This
results in a revised new hard + replaced impervious surface area of 1,255 square feet. Since the project will add
less than 2,000 square feet of new plus replaced hard surface, it is therefore required to only evaluate minimum
=iC JACOBSON
EDMONDS-WOODWAY HIGH SCHOOL PORTABLE PLACEMENT
requirements (MR) 1 & 2 per Volume 1 Figure 1-3.2 of the DOE Stormwater Management Manual for Western
Washington (see Appendix A Figure 2, Project Minimum Requirements Flow Chart). The project will also not be
subject to flow control and runoff treatment requirements. Both MR#1 and MR#2 will be addressed below in
Section III of this report.
UPSTREAM ANALYSIS
Stormwater runoff for the project site will continue to sheet flow across the site from approximately north to
south and be drained to the existing catch basin located approximately 80-ft to the south that then conveys the
stormwater south through a series of 12-inch storm pipes located on the east side of the existing track and field,
maintaining its current drainage course.
DOWNSTREAM ANALYSIS
The project will maintain existing threshold points of discharge with stormwater runoff continuing to mimic the
existing drainage path and sheet flow stormwater across the project site where it will be collected and conveyed
in a series of catch basins located on the east side of the track and field. The project will create 1,255 square
feet of new hard + replaced impervious surface and does not anticipate any adverse effects to the existing
downstream storm system because of the proposed site improvements. In addition, there are no known drainage
concerns downstream of the proposed project site.
III. DISCUSSION OF MINIMUM REQUIREMENTS
The 2019 DOE Stormwater Management Manual for Western Washington references Figure 1-3.2 (Flow Chart for
Determining Requirements for Redevelopment), as the method to determine which Minimum Requirements are
required to be addressed for the proposed project redevelopment (see appendix A Figure 2, Project Minimum
Requirements Flow Chart).
The proposed Edmonds-Woodway High School Portable Placement project will install less than 2,000 square
feet of new + replaced hard surface and does not result in land disturbing activity of 7,000 square feet or
greater. As a result, the project will therefore only will be subject to Minimum Requirements 1 & 2 for the new
and replaced hard surfaces and all disturbed land. In addition, per section 1-3.4.2 of Volume 1 of the
Stormwater Management Manual, the project is "not required to prepare a Construction SWPPP, but must
consider all of the Construction SWPPP listed below (in MR 2) and develop controls for all Construction SWPPP
Elements that pertain to the site".
A discussion of these Minimum requirements is discussed in the following sections:
MR 1: PREPARATION OF STORMWATER SITE PLANS
Project shall provide Concurrence and Coordinated Civil Plans in accordance with all local requirements.
A Storm Water Site Plan drainage report has been prepared for this project and conforms to the requirements set
forth in the 2019 SWMMWW Section III-3.
MR 2: STORWMATER POLLUTION PREVENTION PLAN (SWPPP)
The project is not required to prepare a Construction SWPPP, but must address all 13 Elements of the CWWPP.
A breakdown of each element of the SWPPP is provided below:
Element 1: Preserve Vegetation / Mark Clearing Limits
Clearing Limits are noted on plans and will be implemented prior to any offsite impacts or damage
due to construction.
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EDMONDS-WOODWAY HIGH SCHOOL PORTABLE PLACEMENT
b. Element 2: Establish Construction Access
The Contractor, per the plans, shall implement necessary BMP measures to ensure sediment does
not leave site onto streets or adjacent properties. The existing asphalt parking lot area to the east of
the project site shall be utilized to mitigate sediment laden stormwater or sediment and debris from
leaving the site.
Element 3: Control Flow Rates
Flow rates from the project site will be controlled through a series of BMPs, including, but not
limited to, Straw Wattles and Catch Basin Protection.
Element 4: Install Sediment Controls
Sediment removal BMPs shall be implemented, and are anticipated per plans, to include, but not
limited to, Straw Wattles and Catch Basin Protection.
Element 5: Stabilize Soils
Soils shall be stabilized through a series of BMPs. Typical stabilization methods are temporary
seeding, mulching, and providing temporary "hog fuel" during wet weather work, and dust control
during drier weather conditions.
f. Element 6: Protect Slopes
All slopes will incorporate the applicable BMPs per the plans and as required during construction,
as field conditions dictate. BMPs such as plastic sheeting, slope roughening, and compost
blanket, could be utilized where appropriate and as applicable.
Element 7: Protect Permanent Drain Inlets
Existing drains shall be protected with Catch Basin Protection where applicable throughout the
project site.
Element 8: Stabilize Channels and Outlets
Channels and outlets shall be protected and stabilized where applicable throughout the project site.
Element 9: Control Pollutants
BMPs shall be implemented to prevent or treat contamination of stormwater runoff by pH modifying
sources. In addition, all waste materials from the site will be removed in a manner that does not
cause contamination of stormwater runoff.
j. Element 10: Control De -Watering
No De -Watering is anticipated as part of this project.
k. Element 11: Maintain Best Management Practices (BMPs)
BMPs indicated on plans shall be maintained and supplemented as needed throughout the project.
As portions of the project get completed, portions of the established BMPs shall be adjusted to
other areas of the project site until their completion.
Element 12: Manage the Project
The contractor / owner will employ a project CESCL to manage the site and ensure construction
BMP's are properly implemented and maintained.
M. Element 13: Protect On -Site Stormwater Management BMPs for Runoff from Roofs and Other
Hard Surfaces
The project will protect the Stormwater BMPs proposed for the project site until the site is
stabilized.
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EDMONDS-WOODWAY HIGH SCHOOL PORTABLE PLACEMENT
IV. TEMPORARY EROSION AND SEDIMENT CONTROL
Erosion control systems will be implemented throughout the construction process until the site is stabilized. All
temporary erosion and sedimentation control requirements will follow the Department of Ecology (DOE) Best
Management Practices (BMPs). Best Management Practices are defined as physical, structural, and/or
managerial practices, that when used singly or in combination, prevent or reduce pollution of storm water runoff
caused by construction activities. The Temporary Erosion and Sedimentation Control plan for the proposed site
has been designed to protect off -site properties, as well as to prevent sediment -laden water from entering the
public storm system.
Additional information of the BMPs implemented for the project and locations on -site can be found on the civil
engineering plans (see civil plan sheet C1.00, DEMOLITION AND TESC PLAN).
=iC JACOBSON
EDMONDS-WOODWAY HIGH SCHOOL PORTABLE PLACEMENT
Appendix A — Figures
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Edmonds
Dayton St
1p Marina Beach Park
a
3
a
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s Pine St
L
Woodway
v,
3
Q
t
rn
220th St SW
-
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High School
0 ty 228th St SW Esperance
9g
y
04
99
212th Sts'14
3
a'
L
10
Project Site
E
CASCP
Mountlake
Terrace
FRUITLAND ACRES
FIRDALE 99
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - los - - - - - - - -
N 200th St BALLINGLIi
ao w
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7 Saltwater Park z
FIGURE 1: VICINITY MAP
99 SCALE: NTS
255 S. King Street, Suite 800, Seattle, WA 98104 1 206.426.2600 1 JACOBSONENGINEERS.COM
Figure 1-3.2: Flow Chart for Determining Requirements for
Redevelopment
Does the Project result in 2,000 square feet, or more, of new plus replaced hard surface area?
OR
Does the land disturbing activity total 7,000 square feet or greater?
Yes No
Minimum Requirements #1 through #5
apply to the new and replaced hard Minimum Requirement #2 applies.
surfaces and the land disturbed.
Next Question
Does the Project add 5,000 square feet or more of new hard surfaces?
OR
Convert % acres or more of vegetation to lawn or landscaped areas?
OR
Convert 2.5 acres or more of native vegetation to pasture?
Yes
All Minimum Requirements apply
to the new hard surfaces and the
converted vegetation areas.
No
Next Question Is this a road
related project?
Yes
LM
Does the Project add 5,000 square feet or more of new hard surfaces?
Yes No Is the total of new plus replaced hard surfaces 5,000
square feet or more,
Do the new hard AND
surfaces add 50% or does the value of the proposed improvements -
No No additional No including interior improvements - exceed 50% of the
more to the existing assessed value or replacement value of the:
hard surfaces within requirements. ( P )
the Site? • existing Project Site improvements (for
commercial or industrial projects) OR
• existing Site improvements (for all other projects)
Yes All Minimum Requirements apply to the new and replaced
hard surfaces and converted vegetation areas. Yes
Flow Chart for Determining Requirements for
Redevelopment
Revised March 2019
DEPARTMENT OF
ECOLOGYPlease see http://www.ecy.wa.go✓%opyright.html for copyright notice including permissions,
State of Washington limitation of liability, and disclaimer.
2019 Stormwater Management Manual for Western Washington
FIGURE 2: PROJECT MINIMUM REQUIREMENTS FLOW CHART
NE 1/4 OF THE NE 1/4 OF SECTION 30, TOWNSHIP 27 NORTH, RANGE 04 EAST, W.M.
"�\ ® Call before You
iBM 'C' Dg�B-I-I
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0 5 10 20
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SCALE 1"=10'
SS y
„ _ l Legend
BASEBALL FIELD PROPERTY LINE Mnaras•e sae
„a
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P(PJ l 8 $fip u%
/ STORM DRAINAGE PIPE
— - BM 'B YD/CO/CR/CR 2/MH
■ ■
,FFE:425. CHISELED SQUARE ON
- GRATED STAIRS/RAMPS
i TOP BACK CURB
u ELEV:423.81 GRAVEL PAD
CB RIM:424.51 - I FFL, 475.89
E, 422.41 6°ADS(N W)� \ NOTE:SEEELECTRICAL PLANS FOR
rn
IE:421.66 6"�CMP(N) IXPAR LNG LOT -
� i � y. I ,.-' \\ � POWER AND COMM FEEDS TO PORTABLE
IE 421.61 6 4DS(VV) [
-----A
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BASEBALL FIELD
EDGE OF TURF i �o
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--- - - --
r _
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o
EX TRACK AND FIELD Il 1 y�'/ 4 4zz�3 �)y 154 � � /
1 _ 4(. 33 az39a1E+1
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/-P.$-REQUIRSOTO INSTALL
EDGE OF CONC ROOF OVERHANG (TYP) _
.tom CROPOSED MODULAR
-- 0 BUILDING. REINSTALL FENCE
LONG JUMP PIT ANDPOSTS UPON COMPLETION
— —
/ �az.33 OFCONSTRUCTION ACTIVITY. -- -- —/Y—
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� o _
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IE:41874 4"CP(N) j //
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T 41504 6 GP(U✓) MANHOLE TO RBMAIN. RAISE /
->• IL 414.94 6 N �'' / IX V420.3 (-1 ORAOE_—
( / / ^ �i ELEV 420.31 (+1'-9")
\ 414
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PROTECT TTOREMAI
EN ASPHAI-T
PAVEMENT TO REMAIN
New/Repaoedlmpervious Areas: LANDING Quantity Unit SEE DETAIL moo (CUT TO FIT)
AT DOWNSPOUT
• laf 5'X5'GRAVEL CONCRETESPLASHBLOCK /
DescriptionSEE
Y 2 \ s
BUILDING ROOF (NEW +REPLACED IMPERVIOUS) 1,172 sf PRQTECT XL2•
CONCRETE (NEW + REPLACED IMPERVIOUS) 26 sf PIPETOREmr�v GRATED METALLaNDING
AND STAIRS PER PORTABLE
GRASS (NEW + REPLACED PERVIOUS) *580 sf \ \ \\ MANUFACTURER
GRAVEL (NEW + REPLACED IMPERVIOUS) 25 sf SWAESEEDDETAa „s
METAL RAMP/STAIRS (OVER REPLACED PERVIOUS) * 64 sf /e --� --- - T
00 �
w�
ASPH I I
*GRASS EXCLUDED FROM TOTAL IMPERVIOUS Total 1,255
AREA CALCULATION; METAL RAMPS 50% -
IMPERVIOUS PER DRAINAGE CODE IXTRACKANDNED w� I o � DE g„RI,�/
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STAFF /
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/ PARKING .�PARKIpo LOT
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ELEV: 422.12
NOTE:
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CIVIL SITE PLAN
FIGURE 3: DISTURBED AREA MAP