Yelm Field YHS Stormwater Memo - 2200807 Page 1 of 3
TO: City of Yelm Community Development
106 2nd Street
Yelm, WA 98597
DATE: March 19, 2021
FROM: Todd Sawin, PE
Tacoma - (253) 383-2422
PROJECT NO.: 2200807.10
PROJECT NAME: Yelm High School Field Maintenance
SUBJECT: Stormwater Requirements Memo
The purpose of this memo is to discuss the Minimum Requirements required as part of the proposed maintenance
improvements at the existing Yelm High School baseball and softball field area. Yelm High School is located at
1315 Yelm Avenue W, Yelm, WA 98597 on Tax Parcel 21724210500. The project parcel totals 36.60 acres and
houses Yelm High School; maintenance improvements are located in the southwest corner of the site and will
cover approximately 4.02 acres. The proposed Yelm High School field maintenance project includes replacing the
existing underdrained grass baseball and softball fields with an underdrained artificial turf fields along with
replacing the existing batting cages and bullpens with new artificial turf areas. There are no proposed changes to
the site’s existing domestic water and fire service or sanitary service. The proposed improvements will discharge
to the existing discharge location of the ball field area on the west side of the site where it will disperse through
the adjacent property until it disperses into Thompsons Creek; this matches existing conditions. No pollution
generating surfaces are proposed as part of the ball field improvements. This memo demonstrates that the
stormwater design for this project complies with the requirements of the 2019 Department of Ecology (DOE)
Stormwater Management Manual for Western Washington (SWMMWW) (July 2019 Amended Edition), as
adopted by City of Yelm.
This project is subject to the 2019 SWMMWW. The project is a redevelopment that will result in greater than
7,000 square feet of land disturbing activity and less than 5,000 square feet 5,000 square feet of new hard
surfaces, ¾ acres of vegetation to lawn or landscape, and 2.5 acres of native vegetation to pasture. The project
site also results in less than 5,000 square feet of new plus replaced hard surfaces. Therefore, Minimum
Requirements (MRs) #1 through #5 apply to the new and replaced hard surfaces and the land disturbed (see the
attached Flow Chart for Determining Requirements for Redevelopment).
MR 1: Preparation of the Stormwater Site Plan
This Stormwater Requirements Memo has been prepared in accordance with III-3 Stormwater Site Plans
of the SWMMWW with all of the technical information and analysis necessary for the City of Yelm to
evaluate the proposed maintenance improvements for compliance with stormwater requirements.
MR 2: Construction Stormwater Pollution Prevention
A Construction Stormwater Pollution Prevention Plan (CSWPPP) complying with the 13 Elements
identified in the SWMMWW is included as part of this submittal package. This CSWPPP has been
prepared for both the Ridgeline Middle School and Yelm High School sites. A copy of this CSWPPP must
be kept at each project site.
MR 3: Source Control of Pollution
The proposed project is required to provide source control of pollution. The following are proposed
measures to be implemented as part of the civil plans:
· All pollutants, including waste materials and demolition debris created onsite during construction,
shall be handled and disposed of in a manner that does not cause contamination of surface
water.
Project Memo Page 2 of 3
Yelm High School Field Maintenance
2200807.10
March 19, 2021
· Cover, containment, and protection from vandalism shall be provided for all chemicals, liquid
products, petroleum products, and non-inert wastes present on the site (see Chapter 173-304
WAC for the definition of inert waste).
· Maintenance and repair of heavy construction equipment that may result in discharge or load of
pollutants into nearby surface waters shall be prevented utilizing proper spill prevention
measures.
· All Best Management Practices (BMPs) specified in the CSWPPP must be maintained throughout
the construction process.
The CSWPPP is included as part of this submittal package and provides details on the control of pollution
during construction.
MR 4: Preservation of Natural Drainage Systems and Outfalls
The existing Yelm High School baseball and softball field area discharges runoff west to the adjacent
private property (Tax Parcel 21724220000). The proposed maintenance improvements will maintain this
existing discharge location of the existing ball field area. Underdrains are proposed within the artificial turf
fields to collect runoff from the ball fields and discharge runoff west to disperse through the adjacent
private property. The proposed underdrainage pipes discharge to perforated pipes that run along the
outfield of these two fields. A solid wall pipe discharges runoff from the perforated pipe along the outfield
of the softball field, discharging to the perforated pipe along the baseball field outfield.
The proposed artificial turf fields will discharge runoff at a rate similar to the existing underdrained grass
fields therefore the proposed maintenance improvements will not increase flows discharging form the
proposed improvements. Existing discharge rates are expected to be maintained to the existing discharge
location.
MR 5: Onsite Stormwater Management
The project site triggers MRs 1-5 and is therefore exempt from Flow Control, MR 7 and the LID
Performance Standard has not been chosen as a way to meet the requirements of MR 5. Per the Flow
Chart for Determining MR #5 Requirements, attached, for each surface, BMPs found in List #3 must be
considered in the order listed for each type of surface; the first BMP that is considered feasible must be
used.
All stormwater runoff generated on the proposed project site will discharge to the existing outfall location
at rates similar to existing conditions. No roof surfaces, other hard surfaces, or lawn/landscape areas are
proposed as part of the proposed improvements therefore, no onsite stormwater management BMPs are
applicable to the proposed improvements therefore, stormwater form these proposed surfaces will
continue to discharge directly to the existing outfall location on the west side of the site and ultimately
Thompsons Creek.
Soils Report
Landau Associates, Inc. prepared a Summary of Geotechnical Engineering Services, dated February 5, 2021,
which is included as part of this submittal package. The Yelm High School portion of the investigation, test pits 5-
9, found that subsurface conditions mainly consist of fill soils consisting of gravel with variable silt, sand, and
cobble content or of sand with silt and gravel at medium dense to dense, moist condition and extending 1.1 to 5.3
feet below existing ground surface elevation. Glacial outwash consisting of gravel with variable sand, silt, and
cobble content in a medium dense to very dense, moist to wet condition was found below these fill soils. No true
groundwater table was observed at the Yelm High School site.
Project Memo Page 3 of 3
Yelm High School Field Maintenance
2200807.10
March 19, 2021
Wells and Septic Systems
To our knowledge, there are no existing wells or septic systems within the proposed Yelm High School
maintenance project limits. No onsite domestic water service or sewer services will be affected as part of the
proposed improvements.
Fuel Tanks
To our knowledge, there are no existing fuel tanks within the proposed Yelm High School maintenance project
limits.
Analysis of the 100-Year Flood
According to the FEMA Map 53067C0353E the site is not located within the 100-year floodplain (see attached).
Covenants, Dedications, and Easements
To the best of our knowledge, no known covenants, dedications, or easements are associated with this project.
Conclusion
This analysis is based on data and records either supplied to or obtained by AHBL. These documents are
referenced within the text of the analysis. The analysis has been prepared utilizing procedures and practices
within the standard accepted practices of the industry. We conclude that this project, as schematically
represented, will not create any new problems within the downstream drainage system. This project will not
aggravate any existing downstream problems due to either water quality or quantity.
CHS/
c: Charles Stout, AHBL Inc.
Attachments:
Flow Chart for Determining Requirements for Redevelopment
Flow Chart for Determining MR #5 Requirements
FEMA Flood Insurance Rate Map Number 53067C0353E
Q:\2020\2200807\10_CIV\NON_CAD\REPORTS\YHS\20210318 YHS Memo (SSP) 2200807.10.docx
Figure 1-3.1: Flow Chart for Determining Requirements for New
Development
Start Here
See Redevelopment Project
Does the Site have 35% Yes
Thresholds and the Figure Flow
or more of existing hard 10 Chart for Determining
surface coverage? Requirements for Redevelopment".
No
Does the Project convert %
IF
acres or more of vegetation to
Does the Project result in
lawn or landscaped areas, or
5,000 square feet, or No
convert 2.5 acres or more of
greater, of new plus
native vegetation to pasture?
replaced hard surface
area?
I
\ No
Yes
Yes Does the Project result in 2,000
IF square feet, or greater, of new plus
All Minimum Requirements replaced hard surface area?
apply to the new and replaced
hard surfaces and converted
vegetation areas. Yes/ No
Does the Project have land
Minimum Requirements #1 disturbing activities of 7,000
through #5 apply to the new Yes square feet or greater?
and replaced hard surfaces
and the land disturbed. No
Minimum Requirement #2
applies.
Flow Chart for Determining Requirements for
New Development
DEPARTMENT OF Revised March 2019
ECOLOGYPlease see http.lAvww.ecy.wa.gov/copyright.html for copyright notice including permissions,
State of Washington limitation of liability, and disclaimer.
2019 Stormwater Management Manual for Western Washington
Volume 1- Chapter 3 - Page 89
Figure 1-3.2: Flow Chart for Determining Requirements for
Redevelopment
2019 Stormwater Management Manual for Western Washington
Volume 1- Chapter 3 - Page 90
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?
Ilr Yes No
IF
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 %4 acres or more of vegetation to lawn or landscaped areas?
OR
Convert 2.5 acres or more of native vegetation to pasture?
Yes IF No
All Minimum Requirements apply Next Question Is this a road
to the new hard surfaces and the related project? NO
converted vegetation areas.
Yes
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 IF
AND
surfaces add 50% ordoes
No No
the value of the proposed improvements -
No additional
more to the existing
including interior improvements - exceed 50% of the
requirements.
hard surfaces within
assessed value (or replacement value) of the:
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
Yes
hard surfaces and converted vegetation areas.
Flow Chart for Determining Requirements for
Redevelopment
DEPARTMENT OF
Revised March 2019
ECOLOGYPlease
see http.lAvww.ecy.wa.gou/copyright.html for copyright notice including permissions,
State of Washington
limitation of liability, and disclaimer.
2019 Stormwater Management Manual for Western Washington
Volume 1- Chapter 3 - Page 90
Figure 1-3.3: Flow Chart for Determining MR #5 Requirements
Does the entire project qualify as Flow Control exempt (per MR #7)?
Yes
Did the project developer choose to meet
the LID Performance Standard?
No
Yes REQUIRED: For each
surface, consider the BMPs
in the order listed in List #3
for that type of surface. Use
the first BMP that is
considered feasible.
NOT REQUIRED:
Achievement of the LID
Performance Standard.
REQUIRED: For each
surface, consider the
BMPs in the order
listed in List #1 for that
type of surface. Use
the first BMP that is
considered feasible.
NOT REQUIRED:
Achievement of the LID
Performance Standard.
No
Does the project trigger
only MRs #1 - #5? (Per
the Project Thresholds in
Applicability of the
Minimum Requirements
Section).
Yes
No
(the project triggers
MRs #1 - #9)
No
Did the project
developer choose to
meet the LID
Performance
Standard?
N/
Yes
REQUIRED: Meet the LID Performance
Standard through the use of any Flow Control
BMP(s) in this manual.
REQUIRED: Apply BMP T5.13 Post
Construction Soil Quality and Depth.
NOT REQUIRED: Applying the BMPs in Lists
#1, #2, or#3.
DEPARTMENT OF
ECOLOGY
State of Washington
REQUIRED: For each
surface, consider the BMPs
in the order listed in List #2
for that type of surface. Use
the first BMP that is
considered feasible.
NOT REQUIRED:
Achievement of the LID
Performance Standard.
Is the project outside
the UGA on a parcel
that is 5 acres or larger?
Did the project
developer choose to
meet the LID
Performance
Standard?
No
Yes
REQUIRED: Meet the LID
Performance Standard through
the use of any Flow Control
BMP(s) in this manual.
REQUIRED: Apply BMP T5.13
Post -Construction Soil Quality
and Depth.
NOT REQUIRED: Applying the
BMPs in Lists#1, #2, or#3.
Flow Chart for Determining MR #5
Requirements
Revised March 2019
Please see http.lAvww.ecy.wa.govlcopyright.html for copyright notice including permissions,
limitation of liability, and disclaimer.
2019 Stormwater Management Manual for Western Washington
Volume I - Chapter 3- Page 118
NOTES TO USERS LEGEND
1110000 FT SPECIAL FLOOD HAZARD AREAS (SFHAS) SUBJECT TO
This maps for use in administering the National Flood Insurance Program. It does 122° 37'30* 1115000 FT INUNDATION BY THE 1% ANNUAL CHANCE FLOOD
not necessarily identify all areas subject to flooding, particularly from local drainage I M1ancefloat (100 -year flood), alw kmwn u Me base flood s [M1e flootl the[ M1as
sources of small sm. The community map repository should be consulted for 46'58'07'5" JOINS PANEL 0355 a 110—or berg,gmled or AaeaM n any given year TM Spedal Rood Haurd Area s
possible updated or additional flood hazard nformal on PIERCE 122' 35' 37.5" Meares sugeN m noodr a by the 1%annual Nance nom Areas of Speaal Flood Hamm
\ COUNTY 46' 58' 07.5' Mud, Zones A, AE, AH, A0, AR, A99, V, ate VF The Base Fkwd Ekvation Is the water-wrface
To obtain more detailed information in areas where Base Flood Elevations (BEES)ZONE A , devotion of the 1%annual mance flood.
and/or floodwusers am have been determined, useare encouraged to consult the Flood 12 , \ 7 ZONE A No Base Flood Elevations defermirral.
Profiles and Floodway Data and/or Summary or Stillwater Elevations tables contained-1<tyrrwll),� ` ZONEAE ease Hood Elevations demmined.
within the Flood Insurance Study (FIS) Report that accompanies this FIRM. Users THURSTON
should be aware that BEES shown on the FIRM represent rounded whole -foot COUNTY ZONE AN Fl O,pNAix1W3feet(usuallym,A,dxxdng); Base Flom Elevations
elevations. These BFEs are intended for flood insurance rating purposes only and --in..
should not be used as the Sale source or flood elevation information. Accordingly, THURSTON COUNTY '' n ZONEAo Rood delaMsdl max [(usually sheer now on skgng [main); average
flood elevation data presented in the FIS Report should be utilized in conjunction welt UNINCORPORATED AREAS rc tic Ay �� d,pths determined. F 11, df allwlal ran flooding, vele -also d- min x.
me FIRM for purposes of construction and/or floodplain management. $ORA
30188 AZED ZONEAR Special Road Harem Areas mrmedy pAxaaar from the l%annual dance
Coastal Base Flood Elevations shown on this map apply only landward of 0.0' hood by a note mmrd system Nat vas subsequently demur".. Zom
North Amencen Vertical Datum of 1988 (NAVD 88). Users of this FIRM should be OUY COUIT ss AR Indian -that the former flood control sysmn is being -mai mp W,
aware that Coastal flood elevations are also provided in the Summary of Stillwater OeiR. protection fm,, Me 1%annual Nana or greater flood.
Elevations table in the Flood Insurance Study Report for this jurisdiction. Elevations ZONE— Pres m be protectM from 1%annual chance flood by a Faleral flood
shown in the Summary of Stillwater Elevations table should be used for construction protxtion system under oambumon; m Base — Ekvatiom detemined.
and/or fbodplain management purposes when they are higher than the elevations -
ZONE V Coastal flood cone wind vclodry wmm (wave allon); rg Base Flood Elevatkns
shown on this FIRM.
` ZONE VE determined.
Uastel flood cone wIN veloory harem (wavy aNm); Base Food Eleva[bns
Boundaries of the floodways were computed at cross sections and interpolated I-.
between cross sections. The floodways were based on hydraulic considerations with N.A. FLOODWAY AREAS IN ZONE AE
regard to requirements of the National Flood Insurance Program. Roadway widths
and other pertinent floodway data are provided in the Flood Insurance Study Report CARLAMUNTSE4y nooaway is me manner da m,am plusam adjamm flmdplaln areas mat must tie rept tree or
for this junsdlcllon. SE Fln o„chmen wt an., annual .plus amn be fro w...,substantialimrmusin
Certain areas not in Special Flood Hazard Areas may be protected by flood control '� �_4" grin.[
structures. Refer to Section 2.4 "Flood Protection Measures' of the Flood Insurance orae' O OTHER FLOOD AREAS
Study Report for information on flood Control structures for this jurisdiction. "uE sE m a`
The projection used in the preparation of this map was Washington State Plane 8 ZONE x —a0.2%annual Nmm nova; areas a 1%annual chance flood wpm
avenge owns of less Man t foot or with dmimge ares, —Nan 1 ai—
South Zone (FIPS zone 4602). The horizontal datum was NAD 83, GRS 1980 mile; and areas Poteoed by levers fa,, t%annwl chance nxA.
spheroid Differences in datum, Spheroid, projection or UTM Zones used in the a s'0100poN OTHER AREAS
production of FIRMS for adjacent jurisdictions may result in slight positional
differences in map features across jurisdiction boundaries. These differences do not W Ex Areas demmlmato be comae Ne o.2%annual Name nvoegaln.
affect the accuracy Of this FIRM.
20NE D Arms in wM1ldi flood M1awms are unaeterminea but possible.
Flood elevations on this map re referentl to the North American Vertical Datum of
1988. These flootl elevationsace
cemust be compared to structure and ground elevations E 13 sE ZONE A 1$ ® COASTAL BARRIER RESOURCES SYSTEM (CBRS) AREAS
referend to the same vertical datum. For information regarding Conversion
between the National Geodetic Vertical Datum of 1929 and the North American _ = OTHERWISE PROTECTED AREAS (OPAS)
Vertical Datum of 1988, visit the National Geodetic Survey website at — -
httD://www.nas.n0aa.eOv or Contact the National Geodetic Survey at the following 600000 FT +F-
0.2%
I y + ®RS anti.,, aM OM are normally b w Min a adjamnt m Spetlal Fbod Harem Areas.
address: 1% Armco, Oenm Fkodpwnboundary
NGS bfonnallOn Services 0.2%Annual Q --PMI, BouMaN
NOAA, N/NGS72 Bmre Fbaaway boundary
National Geodetic Survey of
SSMC -3, i{9202 I A 305 O eO--
1315 East-West Highway 9,e �� ....... CBRS rd OPA boundary
Silver Spring. Maryland 20910-3282 E w+Ai
(301) 713-3242 o i I C ; 3B "CAO SE Ci1NpL (EL 9o])µ` eau depths, o n9 Special Rood Harem Area IDrres and boundary
a a d
g Sm I Fond Harem Areas of diRaert Base FIOM Elewtkns,
To obtain current elevation, description, and/or location information for bench marks B Hood r flood v ndev.
shown on Mia map, please Contact the Information Services Branch of the National Flood Ek2uon litre ate value; elevatkn in feet
Geodetic Survey at (301) 713-3242, or visit its website at htto://vivow nas.noaa.eov. B SeeFbod Elevi tim value wnere unnam within mm; elevation in
Base map information shown on this FIRM was derivedfrom multiple sources. C
Thu
CITY OF YELM rete
Base map files were provided in digital format by Thurston w
n County Geodata a 37� C 530310 -W--a to this norM Amra
enn .—Il Dammdl9ae
Center, WA DNR and USGS. This information was Compiled at scales of _ pclEVlswoe,Am I 'e
1:2400 to 1:24000 during the time Period of 19% to 2007. - 1 I O �9 ZONE AE :gyp i A A crass sawn IIM
This map reflects more detailed and up -toddle stream Channel configurations 1 I Yelm Crrek pF's$ q O - - - - - 23 Tana[ Ilne
man laymeshow, on the previous FIRM for this jurisdiction. The floodplain and _ r 322 D {c I THURSTON COUNTY -.'ii 93.02'12' C,ographic cpordlnates referenmdm Me rvplh AmMmn paWm of
floodways that were transferred from the previous FIRM may have been adjusted a `_ _ ` 1983 (NAD 03) Westem Hanlsphere
to conrorm to mese new stream channel configurations. As a result me » I cowl UNINCORPORATED AREAS u
Flood Profiles and RoadwayData tables for multiple streams in the Flood 530188 3100000 FT FNIS of tl65: ),I.A. [on State Plane Slu p.j e
dm u� TALCWmNW < (FlPB IDrIe 9802), lambert Cmforrml Conic prole tion
Insurance Study Report (which contains authoritative hydraulic data) may reflect c a 324 '">z o_ w —mTONcounr D. -agora" N 1000 -meter Universal Tmnmm Nermmr grid values, mm 1%
stream Channel distances that differ from what is shown on this map. U I a Z Bergh mark (see exganatlm In Nates m Users sectlm orals FlRM
10 X`
Corporate limits shown on this map are based on the best data available at the time ¢ 325 <� w F av1EW coUfi I D' M155 River Mlle
of publication. Because changes due to annexations or de -annexations may have Z F TONCWRi Nwa MAP REPOSITORIES
occurred after this map as published, map users should Contact appropriate o - 327 Refer W Mep Rep -de, III- MAP Ind.
Communky officials to verify current corporate limit locations.
s'00°0°aN EFFECTIVE DATE OF COUNTYWIDE
Please refer to the separately printed Map Index for an overview map of the i cou—
X FLOODINSURANCE RATEMAP
county showing the layout of map panels; Community map repository addresses; °`mbar 18'2012
and a Listing of Communities table Containing National Flood Insurance Program 328 EFFECTIVE DATE(S) OF REVISION(S) TO THIS PANEL
dates for each community as well as a listing of the panels on which each Community:DUE XE
is located. I
For information on available products associated with this FIRM visit the Map 329
Service Center (MSC) website at htto://msc.fema.cov. Available products may
include previously issued Letters of Map Change, a Flood Insurance Study Report, -
E
and/or digital versions of this map. Many of these products Can be ordered o F 3
obtained directly from the MSC website. I 330 yA - Fa wmmunlry map-kkn hiAx,p1or k wur"de mepping, refer k the Community
Mep ftux, rade kmted in Me Faad Ineuranm Study repA1 for Mk iurkdid-
If you have questions about this map, how to order products, or the National 330me°: To dnarmina nnwdinsumnm is availadaM mis wmmunlry, contact your insumnm agent
Flood Insurance Program In general, please call the FEMA Map Information y wcell me N—ml Flmdlnsurence P—et1-638-8620.
eXchwebsaenge at to 11 at 14a77FEMA-MAP (1-877-336-2627) or visit the FEMA
websiteat httoMIX) at 1m 1177TEMA-M /nfiD. C'
rA' ZONEAE ry
CITY OF YELM '3
530310r s C O 250 0 MAP SCALE500 500' 1000
`qq. _9 332 / ?� P METERS
4'� 150 0 150 300
595000 FT
46` 56' 15" ZONE A
122" 37'30"
24
NOTE: MAP AREA SHOWN ON THIS PANEL IS LOCATED
WITHIN TOWNSHIP 17 NORTH, RANGE 1 EAST AND
TOWNSHIP 17 NORTH, RANGE 2 EAST.
s2S""E
JOINS
s30ama'E
30
19
ZONE AE
THURSTON COUNTY
UNINCORPORATED AREAS
530188
PANEL 0353E
FIRM
FLOOD INSURANCE RATE MAP
R�
THURSTON COUNTY,
®
WASHINGTON
D
AND INCORPORATED AREAS
a1�pm„N
D
PANEL 353 OF 625
(SEE MAP INDEX FOR FIRM PANEL LAYOUT)
CONTAINS:
D
IGID
cOMMDN NUMBER PANEL suFFlx
LM,cITyDF wool. m,3 E
Ale
`S
Notice to User: The Map Number shown below
should be used when placing map orders; the
Community Number shown above should be
used on insurance applications for the subject
mmunity.
1A MAP NUMBER
46' 5V 1e•
®
53067CO353E
122' 35'37.5"
c
F EFFECTIVE DATE
aA'ask��` OCTOBER 16,2012
Federal Emergency Management Agency