HomeMy WebLinkAboutBLD2021-00251 - 05 STORMWATERIile<ijvl-E
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DEPARTMENT OF COMMUNITY DBVELOPMENT
621 Shcrid.r St ect, Port Townsend, WA 98368
Tel: 360.379.4450 I Fex: 360.379.,1451
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STORMWATER CALCUI-ATION WORKSHEET
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DETERMINT G SToRMWATER MANAGEMENT REQUIREMENTS: This stormwater calculation worksheet should be completed first to
classify the proposal as "small," "medium," or "large." The size determines whether a Stormwater Site Plan is required in
conjunction with a stand-alone stormwater management permit application, building permit application, or other land use approval
application that involves stormwater review. The basic information will also be helpful for completing a Stormwater Site Plan, if
req uired.
bnd4isturbing octivity i5 any adivity that results in movement of earth, or a change in the €xisting soil cover (both vegetative and
non-vegetative) and/or the existinS soil topoSraphy. Land disturbing adivities include, but are not limited to clearing. grading, filling,
excavation, and compadion associated with stabilization of structures and road construction.
Natlve vegetation is vegetation comprised of plant species, other than noxious weeds, \rrhich reasonably could have been expected
to naturally occur on the site. Examples include species such as Douglas fir, western hemlock, western red cedar, alder, big-leaf
maple, and vine maple; shrubs such as willow, elderberry, salmonberry, and salal; herbaceous plants such as sword fern, foam
flower, and fireweed.
PARCEL SIZE II.E.. SITEI
Ao acre contains 43,560 square feet Multiply the acrEage by this figure
Size of parcel in squareteet ?2t 214 sqn
,74 ..,.,Size of parcel
/6oo
700
/4,275
sqlft
@
Cut
d
sq/ft
sq/ft
Driveway, parking, roads, erc.
-!fQQ--------=1;{ftLawn, landscaping. etc.7?47
Other compacted surface, etc
Drainfleid, septic tank, etc.
Well, utilities, etc.
lndicatc Total Volumes of Proposed:
(lncludBs BN4P T5. 13 Fill Volume)
I
en 2oo putyal
T€mDoralv construction area
5€?7E,ACCE1S RD
Total Land Disturbanco
sq/ft
sqm
sq/ft
sq/ft
Answer the tollowing two questions related to
conversion of native vegetation:
Calculale the total area to be d6ared, graded, filled,
excavated, and/or compacted for proposed development
project. lnclude in this calculation the area to be cleared for:
Construction site for structures 172 b Does the proiect convert 7. acres or more of
native vegeiation to lawn or landscaped areas?
Does the proie€l convert 2 72 acr6s or morB ot
native vegetation to pasture?
Circle: Y6s
LAND DISTURBING ACTIVITY. CONVERSION OF NATIVE VEGETATION. AND VOLUME OF CUT/FILL
Cirde: Y6s
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PRoJEcr/aPPUcam aME:
STORI'WATER CALCULANONS _ IMPERVIOUS SURFACE
lmpeMious sutfoce is a hard surface that either prevents or slows the entry of water into the soil as under natural
conditions prior to development. A hard surface area which causes water to run off the surface in Sreater
quantities or at an increased rate of flow from the flow present under natural conditions prior to development,
Common impervious surfaces include, but are not limited to roof tops, walkways, patios, drivewayt parking lots
or storage areas, concrete or asphalt paving, gravel roads, packed earthen materials, and oiled, macadam or other
surfaces which similarly impede the natural infiltration of stormwater.
270D
4420Total New Total Exisfrng
'Thi$ amount will b€ used to check total lot covorage.
d
b d sq/ftsqft
sq/ft
titEw
StructurBs (all roof ar€a)
Sidewalks
Patos
Driveway, parking, roads, etc
Other
Solid Decks
(wilhout infi ltration below)
OriYeway, parking, roads, etc
Other
EXlsNNG
Structures (all roof area)
Sidewalks
Patios
Solid Decks
(vrithout infi ltralion below)
Divide the total exrstno
impervious surface above by the
size of the parcel and @nvert to
ape?.enlage. d Yo
DEVELOPMENT v. REDEVELOPMENT
.>Does the site have > 35Yo or more
existina im Dervious surrace?+no
+
yes
The proposal is considered redevelopment Answer
questions in Ftgwe 2.4,2- Flow Chart for
Redevelopment to determine projed size (n€xt page).
- Applicants for "small" projects must comply only with Minimum Requirement f2-Construction Stormv{ater Pollution Prevention.
Please submit the Sma ll Project Certification (Worksheet "s). The proponent is responsibleror employing the 12 Elements to control
erosion and prevent sediment and other pollutants from leaving the site during the construdion phase of the project. Pick up the
Coaitruction Stormw.ter Pollution Prevertion (SWPPP) B€st Manag€ment P.actlces (8Mp5l Fact Sheet.
- Applicants for "medium" projects-those that must meet only Minimum Requirements S1 through #5 must submit Worksheet A1
and 81, a stormwater site plan and a construction stormwater pollution prevention site plan (see Reference A1A and BIA for
guidance).)-
- "Large" proiects-those that must meet all 9 Minimum Requirements- must submit Worksheet Al and 81, a stormwater site plan
and a coflstruction stormwater pollution prevention site plan (See Referenc€ A1A and B1A for guidance). Large projects also may
require engineering. See Worksheet L to determine additional large project requirements.
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APPLICANI SIGI{ATURE By signing th€ stormwater calculation worksheet, I as the applicant/owner attest that the information provided herein
is true and correct to the best of my knowledge. I also certify that this application is belnB made with the fullknowledge and consent ofallowners
2o2/
lL iloow{ER oR aur BoRuto IDArE)
4
the ded property.
1726 rqn
rorAL NEw + rorAL ExrslNG. 44 2 O ,rn
The proposal is considered new d€velopment. Answer
questions in Figure 2.4.1 Flow Chart for New
Oevelopment to determine project siue (netrt paSe).
,
a-.
,€WorlcsheetAl
Medium & targe Project Report
:: : - iement # 1 : Prepa ration of Stormwater Site PIan
Cor:rpele :ne Follgwing:
; -: - : . :l:e plan demonstrating the project. Refer to REFERENCE A1A for examples of Best Management
:":,:.es tBMP'r)that you can use. Remember that allsite plans submitted forthe projed must be consistent
:-:3acurate.
lescribe both existing and proposed site conditions for the following items as applicable in the space below each
bsllet point. Attach additional pages if needed.. sttudures
E 47r4C eD o-- 5tr€
5e€ A77A1' eD
Minimum Requ rement#2:Constru on Stormwater Po ution Prevention P n SWPPP
A SWPPP is designed to be a rtand-alone document that addresses !q!SE!g!ig! stormwater management concerns. This
document is required to be kept by the contractor performing the work at the jobsite for reference and update durinS
th€ life the proiect. Construction BMP's must be indicated on the stormwater site plan. REFERENCE B1A includes
dia s of common BMP'S that may be used on the site plan
My completed SWPPP (WORKSHEET B1 or equivalent) is included in this application packetl
Minimum Requirement f 3 : Source Control of Pollution (not construction related)
The intent of source control is to prevent Stormwater from cominB in contact with pollutants. Source control BMPs
can be operational or structural in nature. A roof over a material storage area is an example of a structural source
control BMP Washing your vehicle on the lawn rather than in the street is an operational gMP. This requirement
is generally not applicable to Single Family Residences (SFR5); however, ways to minimize pollution from moving
downstream should be considered during the design phase of every project. Specificafions on standard source control
SMPs that are applicable to various commercial and industrial-tvpe facilities can be found in Volume lV of the 2014
Stormwater Management Manual ior Western WashinSton (SWMMWW) (continued on page 2),
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DRIV€WAY ACCESS ss 2d/-oaoo?
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Minimum Requirement # 3 : Source Control of Pollution (continued from page 1)
Check ooe of the following boxes that best represents your project with regards to MR #3.
f{Uy groiea is asingle Family Residence (SFR} and after considering operational and structural measures to prevent
- stormlater from comin8 in contact with pollutants, I have:
t' determined this MR to not be applicable. ! made appropriate adjustments to my project.
T My project is not a sFR and after reviewing Vol- lV of the swMMww. I have determined that this MR is not
applicable because of the follo$ring reason:
T control BMPs are applicable to my proiect and shall be incorporated into the
My project is not a 5FR and after reviewinE Vol. lV of the SWMMWW I have determined that the following source
and
WorlsheetAl
Medium & laree ftoiect Report
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WorksheetAl
Medium & Larye Project Report
Minimum Requirement fl 4 : Preservation of Natural Drainage Systems
Creating new drainage patterns results in more site disturbance and more potential fot erosign and sedimentation during
and after construction. to the maximum extent possible, proponents must 1) maintain the naturalon-site drainage
pattern and concentrated discharge location at the downstream property boundary, and 2) prevent erosion at and
downstream of the discharge locatlon.
NOTEr All outfalls require energy dissipation. see lable 4,5.1 in Vol, V of the SWMMWW for minimum design standards
for rock protection at outfalls.
choose the option below that best describes your projed:
lEl The project site does not currently have any intermittent, seasonal, or contrnuous concentrated water
Ql moving across any part of the property and the proposed improvements to the site will not create new
cgncenrated flow paths or not dischar8ing to existing drainaSe systems.
The project site has existing concentrated flow drainage systems and outfalls. (NOTE: These items must
be graphically shown on the Site Plan or equivalent, to include: type, slope, dimensions, channel lininE,
direction of flow, buffet etc.) Select below how it will be addressed.
tr This project will not alter the existing drainage system in any way. lf the existinS outfall(s) show
signs of erosion and saour, enerSy dissipation measures will be installed or improved upon.
Construction activity of any kind will not occur within at least 10 ft. of the edge of the channelized
flow BMP c1o2: BUFTER ZONES will be implemented during the life of the proiect to include visible
fla8ging or other demarcation technique.
The existing concentrated drainage system traversing the property will be impacted as part
of this proiect, as described in the space below and shown on the site plans. EnSlne€rln8
calculations are requlrcd that show the altered drainage design can accommodate the existing
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WorkheetAl
Medium & targe Prcject Report
Minimum Requirement # 5 : On-site Stormwater Management
On-site stormwater management techniques shall be implemented where possible to accommodate the permanently
added stormwater runoff being generated by development. Some on-site stormwater management techniques provide
bettet stormwater detention and treatment than others; howevet they are not always appropriate for use due to varyihg
individual site characteristics. Therefgre, techniques are presented to applicants on the next pages in a hierarchical order
and shall be considered for uie in the order Iisted. The fir5t technique on the list that is determaned to be possible shall
be implemented. See WORKSHEET C to determine which techniques are feasible.
Runoff from developments occurring in drainage basins that drain diredly or indirectlv to a creek require a hiSher level
of stormwater management, thuS the techniques are presented in three lists below:
All p rties will be in one of these three categories:
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My project is located in a drainage subbasin that
drains to directly or indirectly to freshwater
PROCEED to Pase 5 to use L IST #1.
c My Project will discharge to a subasin draining to
salt wdter, Dosewallips River, or Hoh River.
PROCEED to Page 6 to use LlST #3.
My projed is a large proiect. Refer to Workheet L. lf full dispersion isn't feasible, use LIST S1
(List S2 and Ust S1 a.e the same except raingardens are not permitted in List #2).
(+)
tr
Minimum Requirement # 5 : On-site Stormwater Management (continued)
For category below proceed throuSh the LIST top down. Use WORKSHEET C to the
can be used- lf number 1 on the list is not possibte, document why on WORKSHEET C and move down to number
2, and so on.
INSTRUCTIONS: Check the 6rst option that will work for Each Catesorv Below:
I tr g:::,.:" 'oes
not have ditturbed soils not covered bv impervious
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L 14, Post-construction soil Quality and Depth
Drsturbed soilr shall be amended (BMP T5.13: ).
Category B: Roofs
I uv nroiect does not have Roofareas.
T-J .. Full Dispersion (BMP T5.30)l-.1 OR
Downspout Full lnfiltration (BMP T5.10A)
2. Rain Garden ILARGE PROJECTS CANNOT USE)
(BMP T5.14A)
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3. Downspout Dispersion System {BMP T5.1OB)
4. Perforated Stub-Out Connecfion (BMp 15.10)
5. Ea.h BMP above is infeasible, see WORKSHEET C.sToP
COMPLETE AND 5U8MIT WORKSHEET 81. NO OTHER
INFORMATION REQUIRTD AT THIS TIME,
Cat€gory Cr Oth€r Hard So.faces, e.g. graveland paved
driveways, solid decks and p.tios without infiltration below
f-l My project does not have Othet Hotd Surfoce areasI_l
n 1. Full daspersion (BMP T5.30)
T-.l 2. Permeable Pavement (8MP T5.15)L-J . oR/ Rain Garden (LARGE PROIECTS CANNOT USE) (BMP T5.14A)
ff1. Sfreet rlow Oispersion (BMP T5.12)
OR
Concentrated Flow Dispersion (BMP T5.11)
Tl 4. Each item above is infeasible. see WORKSHEET C. STOP.
COMPLETE AND SUSMIT WORKSHEET 81, NO OTHER
LIST # 1 : Applicable to projects that directly or indirectly drain to freshwater.
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WorksheetAl
Medium & Large Project Report
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ttlHfintinrffiWorkheet 81
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Construction Protection: Medium and Large Projects
(SWPPP: Stormwater Pollution Prevention Plan)
Submit a rite plan demonstrating the construction protective measure! or best management practices that will
be used for the project during the construction phase,
Refer to REFERENC€ B1A for examoles o, Construction Best Management Practices (BMP's) that you can use. The
activities that take place during construction are the highest risk for stormwater problems such as erosion and
sediment control (you may need to provide an additional site plan with greater detail for sto.mwater features. lf so,
make sure it is consistent with the primary site plan. Remember that all site plans submitted for the project must
be consistent and accurate).
Element 1: Preserve Vegetation / Mark Clearing Limits
The goal of this element is to preserve native vegetation and to clearly show the limits of disturbance
choose ony of the following that dpply:
The perimeter of the area to be cleared shall be marked prior to .learing operaion with visible flagging, orange
plastic barrier fencing and/or orange silt fencing as 5hown on the SWPPP site plan. Vehicles will only be allowed
in the areas to be graded. so no compaction ofthe undeveloped areas will occur. lf this option is selected check
It is necessary to disturb the enttre property during this project due to existinB site conditions, property
constraints, and proposed design. I understand that all disturbed land not covered by hard surface at the end of
the project is subject to soil amendment requirements per BMP T5.13 Post-Construction Soil Quality and Oepth.
The site was cleared as part of clearing activity that is subject to an enforcement action and will be re-vegetated.
Restoration mav be necersary to comply with Critical Area Regulations or stormwater .equiremenls. Buffer Zones-
BMP C102 may apply if Critical Areas exist on-site and buffer zones shall be protected.
Element 2: Constru ction Access
The goal of this element is to provide a stabilized construction entrance/exit to prevent or reduce or sediment
traak out.
Choase one of the following
The driveway to the construc6on area already exists and wall be uged for construction access. All equipment and
vehicles will be .estri.ted to stayinB on that existing imperviou5 5urface. lf sediment i5 tracked off 5ite, the road-
the 8tv'lP5 vor.r r'' us-o below:
WI
wlwill be cleaned thoroughly at the end of each dav.
l:-yfrtabilized ronstruction entrance will be installed prior to any vehicles entg
shown on the 9flPPP site plan. lf5ediment istrack€d off tite, the roadway
of each dav,rfthis option is relected check the BMPS you w{ll use below:
ff.,,,,a,',"i'",r.'., I t]u! \r-bstl
Cortslrui!,11': E$rq4ggr \\'asll
i.\!!
Cl03 Hieh \''isibilit!
Fcncc
ering the site, at the location
willbe cleaned thoroughly at the end
(ll0: (i)nstruction
Brrld-rfarkilg AreB
ltrtrlizctia!
)
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Workheet 81
Construction Protection: Medium and Large Projects
(SWPPP: Stormwater Pollution Pr€\rention Planl
Element 3: Control Flow Rates
The goal of this element is to construct retention or detention farilities when necessary to protecl properties
and waterways downstream of development sites from erosion and turbid discharges.
This element d@Sjg!opply to my project becduse (check ony that opply)
Site is mildly sloped (<5%),
There are no individually sloped se.tions greater than 10%,
The bulk of the project is sch€duled to of,cur during dry season (May 1-Sept 30)
Element 4: Sediment Control
The goal of this element is to construct s€diment control BMPs that minimize sediment discharges from the
site.
Select one of the two stotements opplicoble to the project
The site has already been stabilized and re-vegetated
Sediment control EMPs shallbe pla
check the EMPS you will use below
ced at the locati shown on the SWPPP Site Plan. lf this option is selected
C2-l I Erush Barder
C232 Gravel filter
Berm
Cl3.l Silt []ence
(il.]"l \esetated
Sldip
C235 U'attles
Element 5: Stabilize 5oils
The goal of this element is to stabilize exposed and unworked soils by implementing erosion control BMPs,
Select one ol the three stotements qpplicoble to the ptoject,
My project will en5ure the following;. Soil sto€kpiles will be located within the disturbed area shown on the SWPPP Site Plan.. Soil ex.avated for the foundailon will be backfilled against the foundaton and Sraded to drain away from the
building.. No soils shall remain exposed and unworked for more than 7 davs rrom May 1 to September 30 or more than
2 days from October 1 to April 30.. Once th€ disturbed landscape areas are graded, the grass areas will be amended.. All rtockpiles will be covered with plastic or burlap if left unworked.
Tl rh,s elemera dGjO! oppty to my project becquset_l ila 5*pteatt SorL
n My proiect must implement specific BMP! to ensure compliance. (Check BMP'S you will use on the next page)
page 2 of 5
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Element 6: Protect Slopes
The goal of this element is to design and construct cut-and-fill
select
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Cl05 Subsurface
f)rains
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Worksheet 81
Construction Protection: Medium and Large Projects
(SWPPP: Storn rater Pollutbn Prevention Plan)
TIL-J
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slopes n a rndnqe to minimire ercsior'.
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one ofthe two stotements opplicoble to the project.
No cut slopes over 4 feet high or slopes steeper than 2 f€et horizontal to 1 foot vertical. and no fill slopes over
4 feet high will exceed 3 feet horiuonta! to 1 foot vertical. Therefore, there is no requirement for additional
engineered slope protection.
The above checkbox is not checked. My submittal is designed by a liceosed geologist to protect slopes. Based on
the licensed professionals recommendation (please attach their evaluation), the following BMP's will be used:
Clf0 'femdorarv & Permanent
Seeding
C20-1 PiDe SloDe Drairrs
C207 Check Dams
(.108 'liiane ul ar Silt IJike
(Geotelitile- Encased CheELUud
Element 7: Protect Permanent Drain lnlets
The goal of this element is to protect storm drain inlets during construction to prevent stormwater runoff from
entering the conveyance system without being filtered or treated.
Sekcjde of the three stolemenls opphcoble to lhe p@ject.,g The site has open ditches in the right-of-way or private road right-of-way,
n There are no catch basins on or near the site.
Catch basinr on the site or immediately offsite in the riSht-of-way are shown on the SWPPP Site PIan. Storm dratn
inlet protection shall be installed. if this option is selected check the BMPS you will use below:
(ill0 Storm Driin lnlet Protection
pate 3 or 6
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Workheet 81
Construction Protection: Medium and LarBe Projects
(SWPPP: Stormwater hlution Pr€vertirn Planl
Select one of the thrce stotements opplicoble to the proiect.
Cgnstruction will occur during the dry weather No storm drainage channels or ditches shall be constructed either
temporary or p€rmanent,
There are no existing or proposed stormwater conveyance channels on the proiect site.
A wattle shall be placed at the end of the swale to prevent erosion at the outlet ofthe swale, lf this option ls
selected check the EMPS you will use below:
n r -',,1 (lh.rrrrel lrningl-l C:o:( hcili i)i!!!t [-l r.:oguutl"t Prot((tr(,r f t.:.iittulo
Element 9: Control Polluta nts
The goal of this element is to design, install, implement and maintain BMPs to minimize the discharge of
pollutants from material storage areas, fuel handling, equipment cleaning, management of waste materials, etc
This element does not opply to my project becsuse (ctcle onv thot opply - lf any box is un.hecked this element applies.
There will be no (oncrete work,
There will be no sawcuttin g work,
There will be no hazardous materials on-!ite,
The goal of this element is to design, construct, and stabilize on-site conveyance channels to prevent erosion
from entering existing stormwater outfalls and conveyance systems.
ffiThere wilt be no fertilirer or pesti(ide application,
n There will be no heavy equipment assooated with this project,
ffrhere wilt be no pressure washrng, equipment maintenance or dewatering
Element 8: Stabilize Channels and Outlets
lf gne or more of the checkboxes above are unchecked. Any and all pollutants. chemicals, liquid produds and other
materi6ls that have the potefltial to pose a threat to human health or the environment will be covered, contained, and
protected from vandalism. All such products shall be kept uflder cover in a secure location on-site. Concrete handling
:ndll folroyAMP C 151 4154. lr Ihrs opnon iq \FlFCtpd
t4
check the BMPS you will use below
l5f Sarvcuftin d Surfa crngt-
tion Pre\'ention
Cl5+ C0ncrete lvashout Areaalo[taiDrnent
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Worksheet 81
Construction Protection: Medium and Large Proiects
(SWPPP: Stormrirdter Hlution P]ercmion Plan)
Element 10: Control De-watering
The goal ofthis element is to handle turbid or contaminated water from dewatering (removal of water)
separately from stormwater.
Seleylne ol the two stotements opplicoble lo the proiecl.
l!{ No dewatering of the site is anticipated.
Dewaterin8 of the site is anticipated. lf this option is selected check the BM PS you
will use below:ntr
Element 11: Maintain Best Management Practices
The goal of this element is to maintain and repair ali temporary and permanent erosion and sediment control
BMPs to assure continued performance.
Descrbe the steps you will toke:
JBestManagement Practicer or BMPs shall be inspected and maintained during ronstruction and removed within
IIJ 30 d"vs aft", the County lnspector or determines that the lite is stabilized, provided that they may be removed
when they are no lon8er needed.
Element 12: Manage the Proiect
The goal of this element is to ensure that the owner and those performing the site work comply with the
SWPPP and properly coordinate to ensure that all BMPS are deployed at the proper time to achieve full
compliance with county reBulations throughout the proiect.
The SWPPP will be implemented at all times, lf applicable to the project, erosion controi BMPs will be
implemented in the following sequenrel
1. Mark clearing limits
2. lnstall stabilized constructron entrance
3. lnstall protection for existing drainaBe systems and permanent drain inlets
4. Establish staging areas for storage and handling polluted material and BMPs
S. lnstallsediment control SMPs
6. Grade and inrtallstabilization m€asures for disturbed areas
7. Maintain gMPs until site stabili2a6on, at which time they may be removed
oase 5 of 5
Element 13: Protect Low lmpact Development BMPs
The goal of this element is to protect permanent stormwater management BMPs from siltation and compaction
during construction. The permanent stormwater management BMPs used for runoff from roofs and other hard
surfaces include: full dispersion, roof downspout full infiltration or dispersion systems, perforated stubout
connections, rain gardens, bioretention systems, permeable pavement, sheetflow dispersion, and concentrated
flow dispersion.
Methods that will be used to protect permanent stormwater management BMPs include:
Sequencing the construction in a fashion to install these permanent BMPs at the latter part of the
construction tradinB operations,
I ExcludinB eouipment from the BMPS and the associated areas,
sing the erosion and sedimentation control BMPs listed below to protect facilities such as drywells,
raingardens, permeable pavement, or bioretention from accumulating sediment during construction and
before site restoration, lf this option is sele€ted check the BMPS you will use below:
Workheet 81
Construction Prctection: Medium and Large Projects
(sWPPP: Stonnwater Pollutbn Pre\r€ntioo Plan)
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g]llul-rrAu!
eflldtlerie
e?3-l-Bssh Barrier Other
Applicant or Representative Signature 7/
Worksheet C
lffiafs the best option for your siE?
high groundwater table or other impermeable Iayer.
Minimum Requirement #5 (On-Site Stormwater Management)
The following tables summarizelhe criteria that can be used to iustiry why you cannot us€ various stormwater
management best management practices (BMPs) for consideration for Minimum Reguirement #5. This information i8 also
included under the detailed descriptions of each BMP in the Department of Ecology's Stormwater Management Manual for
Westem Washington (SVVIVIMWW [2014]). Vvhere any inconsistencies or lack of clarity exists, the requirements in the main
text of the SVWMWW shall b€ applied.
HOW TO USE:
Evaluate the feasibility of the : in priority order based on Worksheet 41 page 5 (List #'l ) or 6 (List #3) or
Worksheet Lfor Large Projects (List#2). Only one critsrion needs to ba selected for a BUP before evaluating the
next flu t.' on the list.
of the above boxes are checked. This is the BMP that must be used for lawn and landscaped areas. On
WorksheetAl, indicate that lhis will be the BMP used. CONTINUE to complete the form for other surface types
applicable to the project. lf none, STOP
Downspout Full
lnfiltration
rsana rn system on IS or an nt
lot (mound, sand filter pressure distribution, Glendon, aerobic
treatment unit). Therefore, there is not at least 3 feet or
more of permeable soil from the proposed final grade to theBMP T5,1OA,
STAMMWW Volume
lll, Section 3.1.1
List #1, #2
and #3
There is not at least 1 foot or more of permeable soil trom
the proposed bottom of the infiltration syslem to the seasonal
high groundwater table or other impermeable layer.
Lawn and Landscaped Areas
Roason why the BMP will not work on site.Additional Comments
lf needed
EIVIP and
Applicabls
Lbts
Post-construction
Soil Quality
and Depth
(8MP T5.13
SVTiMM\,VW Votunle V
Soction 5.3)
List*), #2 and #3
Lawn and landscape area is on till slopes greater than 33
percent.
Siting and design criteria cannot be achieved on site
Roofs
BMP and
Applicable
List8
Reason why the BMP will not wod( on site.Additional Comments
lf needsd
Dts?A$lce 70 cL4
DEfresst oN U€7 -L*rtDs pnecL.)De S
,/ oo t7 rlow tAfl
Full Oispersion
List #1 and #2
A 65 to 10 ratio of forested or native vegetalion area to
impervious area cannot be achieved.
A minimum forested or native vegetation florrpath length of
100 feet (25 feet for sheet flow from a non-native pervious
,urface) and protected by easement cannot be achieved
ff sitng ,no design criteria cannot be achieved on site.
None of the above boxes are checked. This is lhe BMP that must be used for roofs. On Vt/orkshe€tAl, indicate that
this will be the BMP used. CONTINUE to complete the form for other surface typ6s applicable to th6 projecl. lf none,
STOP ,,
n TI
1
n
tr
BMP T5,30,
SV${MWW VolurE V
Seclion 5.3
tr
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WorksheetC
Whafs the best option foryoursite?
B[lP and
Applicabls
Lists
Reason why the BMP will not work on site.Additional Comments
lf nosded
Downspout Full
lnfiltration
(cont)
BMP T5,1OA.
SWMMWW VoIume
d
Slopes steeper than 25% or less than 200' from slope
steeper than 40%.
Siting and design criteria cannot be achieved on site.
stlaL..oto uA/4.
,A'IE , 84P,5, IOA*z(3
None of the above boxes are checked. This is the BMP that must be used for roofu. On \ brksheetAl, indicate that
this will be the BMP used. CONTINUE to complete the form for other surface types applicable to the project. It none,
STOP
BMP T7.30 or T5.'l44
SVltrMWW Volurrte V
Seclion 7.4
List #1 (both)
and List #2
(bioretention
onlY)
Note Ctitoia wrth satback distances are as measurBd ftom the
boltom edge of the bioretention soil mix.
Citation of any of the following infeasibility criteria must be
based on an evaluation of site-specific conditions and a written
recommendation from an appropriate licensed professional (e.9.,
engineer, geologist, hydrogeologist):
Where professional geotechnical evaluation recommends
infiltration not be used due to reasonable concems about
erosion, slope failure, or down-gradient flooding.
vMthin an area whose ground water drains into an erosion
hazard, or landslide haza(d arca.
Wtrere the only area available for siting would threaten the
safety or reliability of pre-existing underground utilities, pre
existing underground storage tanks, prlexisting structures,
or pre-existing road or parking lot surfaces.
V\rhere the only area available for siting does not allow for
a safe overflow pathway to stormwater drainage system or
private storm sewer system.
Where there is a lack of usable space for bioretention areas
at re.development sites, or where there is insufficient space
within the existjng public right-of-way on public road proiects
VVhere infiltrating waler would threaten existing below grade
basements.
Vvtere infiltrating water would threaten shoreline struclures
such as bulkheads.
Roofs (conl)
n
Bioretention or
Rain Gardens
tr
tr
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2
lrf:*
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WorksheetC
Whafs the best optaon foryour sib?
BiiP and
Applicable
Lists
Reason why tho BMP yvill not work on site Addilional Comments
lf needod
I Bioretention or
Rain Gardens
(cont.)
BMPT7.30 or T5.l4A
SV\rIt Mt A /Volume V,
Section 7.4
TnEEnowingAterU can be cited as reasons for infeasibility
without further justification (though some require professional
services to make the observation):
Wthin selback provided for BMP T7.30 (SVVMMVWV Volume
V, Section 7.4)
Where they are not compatible with surrounding drainage
system as determined by the county (e.9., project drains to
an existing stormwater collection system whose elevation
or location predudes coflnection to a properly funciioning
bioretention area) .
Vvhere land for bioretention is within an erosion hazard, or
landslide hazard area (as delined by PAMC 15-20)-
Vvhere the site cannot be reasonably designed to locate
bioretenlion areas on slopes less than 8 percent.
Wthin 50 feet from the top of slopes that are greater than 20
percent and over 10 feet of vertical relief.
Within 100 feet of an area known to have deep soil
contamination.
Vvhere groundwater modeling indicates intiltration
will likely increase or change the direction of the
migration of pollutants in the groundwater.
Vvherever surface soils have been found to be
contaminated unless those soils are removed within
'10 horizontal feet from the infiltration area.
Wthin 100 feet of a closed or active landfill
Within 10 feet of an underground storage tank and
connecling underground pipes when the c€pacity of the tank
and pipe system is 1,100 gallons or less. As used in these
criteria, an underground storage tank means any tank used
to store petroleum products, chemicals, or liquid hazardous
wastes of which 10 percent or more of the storage volume
(including volume in the connecting piping system) is
beneath the ground surface.
Vvithin '100 feet of an underground storage tank and
connecting underground pipes when the capacity of the tank
and DiDe system is qreater than 1.100 qallons.
3
Roofs (cont)
tr
tr
T
tr
tr For properties with known soil or groundwater contaminetion
(typically federal Superfi.rnd sites or state cleanup sites under
the Model Toxics ControlAct [MTCAI):
I
tr
WorksheetC
Whafs the best option fioryoursite?
Roofs (cont)
BMP and
Applicable
Lists
Reagon why the BMP will not work on site.
/)l
Additional Comments
lf needed
Bioretention ol
Rain Gardens
(cont)
Vvhere the minimum vertical separalion of 1 foot to the
seasonal high groundwater or other impermeable layer would
not be achieved below bioretention that would serve a d
area less than the above thresholds
Where field testing indicates potential bioretention/rain
garden sites have a measured (a.k.a., initial) native soil
saturated hydraulic conductivity less than 0.30 inches per
hour. A small-scale or large-scale PIT in accordance with
SVVITMVVW Volume lll, Seclion 3.3.6 (or an alternative
small scale test specilied by the local govemment) shall
be used to demonstrate infeasibility of bioretention areas.
lf the measured native soil infiltration rate is less than 0.30
in/hour, bioretention/rain garden BMPs are not required
to be evaluated as an option in List #1 or List #2. ln these
slow draining soils, a bioretention area with an underdrain
may be used to treat pollution-generating surfaces to help
meet Minimum Requirement*6, Runoff Treatment. lf the
underdrain is elevated within a base course of gravel, it will
also provide some modest flow reduclion benefit that will help
achieve Minimum Requirement #7.
Vvhere the minimum vertical separation of 3 feet to the
seasonal high groundwater elevation or other impermeable
layer would not be achieved below bioretention that would
serve a drainage area that exceeds the following thresholds
(and cannot reasonably be broken dourn into amounts
smaller than indicated):
o 5,000 square feet of pollution-generating impervious
surface (PGIS)
o '10,000 square feet of impervious area
o 0.75 acres of lawn and landscape
Vvrthin 100 feet of a drinking water well, or a spring used for
drinking water supply.
T
I
I Any area where these facililies are prohibited by an approved
cleanup plan under the state MTCA or Federal Superfund
Law, or an envlronmental covenant under Chapter 64.70
RCW.
u
!*F
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WorksheetC
Whafs the best option foryour sib?
Roofs (cont.)
BilP and
Applicable
Lists
Reason why the BirP will not wotk on site.Additional Comments
lf noeded
within '10 feet of small on-site sewage disposal draintield,
including reserve areas, and grey water reuse systems. For
setbacks from a 'large on-site sewage disposal system," see
Chapter 2,16-2728 WAC
None of the above boxes are checked. This is the BMP that must be used for roofs. On Woftsheet Al , indicate that
this will be the BMP used. CONTINUE to complete the form for other suriac€ types applicable to the proiecl. lf none,
STOP
Oowospout
Dispersion
Systems
BMP T5.IOB
SVVI4MWW Volurne
ul. Sedion 3.,!.2
List #1, #2
and #3
For trenches, a vegetated flowpath of at least 25 feet in
between the outlet of the trench and any property line,
structure, stream, wetland, or impervious surface is not
feasible. A vegetated flowpalh of at least 50 feet between the
outlet of the trench and any slope steeper than 15 percent is
not feasible.
For splash blocks, a vegetated flowpath at least 50 feet in
length from the downspout to the downstream property line,
structure, stream, wetland, slope over 15 percent, or other
impervious surface is not feasible.
7*" oi it " "bove
boxes are checked. This is the BMP that must be used for roofs. On Worksheet A1 , indicate that
M this will be the BMP used. CONTINUE to complete the form for other surbce types appticable to the proiecl. lf none,
STOP
Perforated
Stub-Out
Connections
8MP T5.10C
SV\,ttlMWW VolunE
lll, Section 3.1.3
List #1, #2
and #3
For sites with septic systemg, lhe only location available for
the perforated portion ofthe pipe is located up-gradient of
the drainfield primary ahd reserve areas. This requirement
can be waived if site topography will clearly prohibit floris
from intersecting the drainlield or where site conditions (soil
permeability, distance between systems, etc.) indicate that
this is unnecessary.
There is a mound, sandfilter, Glenden or aerobic treatment
device on this or an adiacent lot. Therefore, there is not at
least 1 foot of permeable soil from the proposed boftom (final
grade) of the perforated stub-out connection trench to the
highest estimated groundwater iable or other impermeable
leyer.
The only locetion available for the perforated stub-out
connection is under impervious or heavily compac-ted soils.
The only location available is on or above slopes greater than
200k
Sitinq and desiqn criteria canngt be achieled on slte.
None of the above boxes are checked. This is the BMP that must be used for roofs. On Worksheet Al , indicate that
this will be the BMP used. CONTINUE to complele the form ,or other surface types applicable to the project, lf none,
STOP.5
n
Siting and design criteria cannot be achieved on site.
tr
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WorksheetC
Whafs the best ofiion foryoursite?
Other Hard Surfaces
rlMP and
Applicable
Lists
Reason why the B IP will not !vo* on site.Additional Comments
lf needed
Full Dispersion
BMP T5,30
S\rvt MVWVVoturrle
V S€ction 5.3
List #1 and #2
A 65 to '10 ratio of forested or native vegetation area to
impervious area cannot be achieved.
A minimum forested or native vegetation flowpath length of
100 feet (25 feet for sheet flow from a non-native pervious
surface) cannot be achieved.
None ofthe above boxes are checked. This is lhe BMP that must be used for hard surfaces- On Worksheet 41,
indicate that this will be the BMP used. CONTINUE to complete the form for other surface types appliceble to the
proiect. lf none, STOP
Permeable
Pavement
BMP T5,15,
SVvlvlMl.rw Volurne
V Seclion 5.3
List #1 and #2
Citation of any of the following infeasibility criteria must be
based on an evaluation of site.specilic conditions and a written
recommendation ftom an appropriate licensed professional (e-9.,
engineer. geologist, hydrogeologist):
Vvhere professional geotechnical evaluation recommends
inliltration not be used due to reasonable concems about
erosion, slope failure, or downgradient flooding.
Wthin an area whose ground water drains into an erosion
hazard, or landslide hazard area.
Where infiltrating and ponded water below the new permeable
pavement area would compromise adjacent impervious
pavements.
V\ihere infiltrating water below a new permeable pavement
area would threatefi existing below grade basements.
Vvhere inllltrating water would threaten shoreline structures
such as bulkheads.
Down slope of steep, erosion prone areas that are likely to
deliver sediment to the area of pervious pavement.
Vvhere fill soils are used that can become unstable when
saturated.
Exc€ssively steep slopes where water within the aggregate
base layer or at the subgrade surface cannot be controlled
by detention struclures and may cause erosion and sfuctural
failure, or where surlace runofi velocities may predude
adequate inflltration at the pavsm€nl surface.
6
tr
n
l-l Siting ano design criteria cannot be achieved on site.
I
' Note that
Raingardens
may bs used
in lisu of
pormeable
pavement if
sublect to
List #1.
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Worksheet G
Whafs the best option foryoursite?
Other Hard Surfaces (cont)
i3[,1P and
Applicable
Lish
Reason yyhy the BMP tyill not work on site.Additional Comments
lf needed
Permeable
Pavement
(cont)
BMP T5.'5,
S\M/iMVVW\rol-
ume v. S€c1bn
5.3
' Note that
Raingardens
may be used
in lieu of
permeable
pavemant if
subjsct to
List #1.
VVhere permeable pavements cannot provide sufficient
strength to support heavy loads at industrial facilities such
as ports.
Vvhere installation of permeable pavement would threaten
the safety or reliability of pre.existing underground utilities,
per-existing underground storage tanks, or preexisting road
subgrades.
The following criteria can be cited as reasons for infeasibility without
further iustification (though some require professional services to
make the observation):
Vvithin an area designated as an erosion hazard, or
landslide hazard.
Wthin 50 feet from the top of slopes that are greater than
20 percenl.
For properties with known soil or groundwatar
contamination (typically federal Superfund sites or state
cleanup sites under MTCA):
Wthin 100 feet of an area known to have deep soil
contamination.
Vvhere groundwater modeling indicates inriltration
will likely increase or change the direction of the
migration of pollutanB in lhe groundwaler
Wherever surface soils have been found to be
contaminated unless those soils are removed
within 10 horizontal feet from the infiltration area
Any area where these facilities are prohibited by
an approved cleanup plan under the state MTCA
or Federal Superrund Law, or an environmental
covenant under Chapter 64.70 RCW
Wthin 100 feet of a closed or active landfill-
Wthin 100 feet of a drinking water well, or a spring used
for drinking water supply, if the pavement is a pollution-
generating surface.
7
tr
tr
T
tr
T
tr
tr
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l.,
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1IN
WorkslreetG
Whafs the best option for your sib?
Other Hard Surfaces (cont)
HMP and
Applicable
Lists
Additional Comments
lf ne€ded
* Note that
Raingardena
may ba used
in lieu of
p€rmeable
pavement if
subject to
List #1.
VMthin 10 feet of a small on-site sewage disposal drainlield,
including reserve areas, and grey water reuse systems. For
setbacks from a 'large on-site sewage disposal system,"
see Chapter 246-2728 WAC.
Within 10 feet of any underground storage tank and
connecting underground pipes, regardless of tank size. As
used in these criteria, an underground storage tank means
any tank used to store petroleum products, chemicals, or
liquid hazardous wastes of which 10 percent or more of the
storage volume (including volume in the connecting piping
system) is beneath the ground surface.
At muhi-level parking garages, and over culverts and
bridges.
Vvlere the site design cannot avoid putting pavement
in areas likely to have long-term excessive sediment
deposition after construction (e.9., construction and
landscaping material yards).
Vvhere the site cannot reasonably be designed to have a
porous asphalt surface at less than 5 percent slope, or a
pervious concrete surface at less than 10 percent slope, or
a permeable interlocking concrete pavement surfaca (where
appropriate) at less than 12 percent slope- Grid systems
upper slope limit can range from 6 to 12 percent, check with
manufacturer and local supplier.
Vvhere the subgrade soils below a pollution-generaling
permeable pavement (e.9., road or parking lot) do not
meet the soil suitability criteria for providing treatment.
See soil suitability criteria for treatment in the SWIVIMVVW
Volume lll, Section 3.3.7. Note: ln these instances, the
county may approve installation of a 6 inch sand filter layer
meeting county specificetions for treatment as a condition of
construclion.
\Mere undertying soils are unsuitable for supporting trafiic
loads when saturated. Soils meeting a Califomia Bearing
Ratio of 5 percent are considered suitable for residential
access roads.
Vvhere replacing existing impervious surfacds unless the
existing surfuce is a non-pollution generating surface over
an outwash soil with a saturated hydraulic conductivity of 4
inches oer hour or oreater
I
Reeson why the BMP will not work on site.
Permcable
Pavenlerlt
(conl)
BMP T5.15.
sr it4Mvrrw
Volume V
Sec{ion 5.3
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Worksheet C
What's the best option for your sib?
Other Hard Surfacos (cont)
RMP 3n6l
Applicable
Lists
Reason tyhy the BirP will not work on Site.Additional Commonts
lf needed
Permeable
Pavc[]ent
(contl
BMP T5.15.
Svrr'rMl A /
Volume V
S€ction 5-3
' Note that
Raingardsns
may be used
in lieu of
p€rmeable
pavement if
subiect to
List #r.
Vvhere app ro$iate ireld testing indicates soils have a
measured (a.k.a., initial) subgrade soil saturated hydraulic
conductivity less than 0.3 inches per hour- Only small-
scale PIT or large,scale PIT methods in accordance with
SVVMMVvW Volume lll, Section 3.3.6 (or an alternative small
scale test specilied by the local government) shall be used to
evaluate infeasibility of permeable pavement areas. (Note: ln
these instances, unless other infeasibility restrictions apply,
roads and parking lots may be built with an underdrain,
preferably elevated within the base course, if flow control
benetits are desired-)
Roads that receive more than very low trafiic volumes, and
areas having more than very lovv truck traffic. Roads with
a projecled average daily traffc volume of 400 vehicles
or less are very low volume roads (AASHTO 2001) (U.S.
Department of Transportation, 20'13). Areas with very low
truck traffc volumes are roads and other areas not subiect
to through truck trafiic but may receive up to weekly use by
utility trucks (e.9., garbage, recycling), daily school bus use,
and muhiple daily use by pick-up trucks, mailiparcel delivery
trucks, and maintenance vehicles- Note: This infeasibility
siterion does not extend to sidewalks and other non-trafiic
bearing surfaces associated with the collector or arterial.
At sites defined as'high-use sites' (refer to the Glossary in
the svvlvlMvvw volume l).
ln areas with "industrial activity" as identified in 40 CFR
122.26(bX14).
Vvhere the risk of concentrated pollulant spills is more likely
such as gas stations, truck stops, and industrial chemical
storage sites.
Vvtere routine, heavy applications of sand occur in frequent
snow zones to maintain traction during weeks ol snow and
ice accumulation.
Vwrere the seasonal high groundwater or an underlying
impermeable/low permeable layer would create saturated
conditions within I foot of the boftom of the lowest gravel
base course.
None ofthe above boxes are checked. This is the BMP that must bs used for hard surtaces. On Worksheet 41,
indicate that this will b€ the BMP used. (List #1 may use Raingardons in lieu of Permeable Pavement). CONTINUE to
complete the form for other surface types applicabl6 to the project. lf none, STOP
I
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tr
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IN
WorksheetC
Whafs the best option foryoursib?
Other Hard Surfacee (cont)
LIMP and
Applicable
Lists
Reason why the Bt P will not work on Eite.Additional Comments
lf needed
Bioretention or
Rain Gardens
BMP T7,30.
SV\rvlMWW Volurne V
Soclion 7.4
List #1 (both)
and List #2
(bioretention
only)
Note: Citeia with setback distances aro as msasurad from tho
bottom edge of the bioretention soil mix.
Citation of any of the following infeasibility criteria must be
based on an evaluation ol sits.specilic conditions and a written
recommendation from an appropriate licensed professional (e.9.,
engineer, geologist, hydrogeologist):
Vvhere professional geotechnical evaluation recommends
inliltration not be used due to reasonable concems about
erosion, slope failure, or down-gradient flooding.
Vvithin an area whose ground water drains into an erosion
hazard, or landslide hazard area.
Vvhere the only area available for siting would threaten the
safety or reliability of pre-existing underground utilities, pre-
existing underground storage tanks, pre-existing structures,
or pre-existing road or parking lot surfaces.
Vviere the only area available for siting does not allow br
a safe overflow pathway to stormwater drainage system or
private storm sewer system.
Vvhere there is a lack of usable space for bioretention areas
at re-development sites, or where there is insufficient space
within the existing public right-of-way on public road projects.
Vvhere infiltrating water would threaten existing below grade
basements.
Where infiftrating water would threaten shoreline structures
such as bulkheads.
Within setback provided for BMP T7.30 (SWI MVVW Volume
V, Section 7.4)
10
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T
tr
tr
T
The following criteria can be cated as reasons for infeasibility
without further iuslification (though some require professional
services to make the observation):
tr
Vvhere lhey are not compatible wilh surounding drainage
system as determined by the county (e.9., project drains to
an exisling stormwater colleclion system who6e elevation
or location predudes connection to a properly functioning
bioretention area).
n
B-:-\
o
i.r_
\
WorlsheetC
Whafs the best option foryoursite?
and
Applicable
Lists
Reason why the BMP will not work on site.Additional Comments
lf ne€ded
Riorctentior or
Rain Gardens
(cont)
8MP T7.30,
S\M,IMVVW Volume V
Section 7.4
Where land for bioretention is wilhin an erosion hazard, or
landslide hazard area (as delined by PAMC 15.20).
Vvhere the site cannot be reasonably designed to locate
bioretention areas on slopes less than 8 percent.
Vvithin 50 feet from the top of slopes that are greater than 20
percent and over 10 feet of vertical relief.
For properties with known soil or groundwater contamination
(typically federal Superfund sites or state cleanup sites under
the Model Toxics ConkolAct [MTCA]):
Wthin 100 feet of a closed or active landllll
VMthin '10 feet of an underground storage tank and
connecting undBrground pipes when the capacity of the tank
and pipe system is 1,100 gallons or less. As used in these
criteria, an undarground storage tank means any tank used
to store peAoleum producls, chemicals, or liquid hazardous
wastes of which '10 percent or more of the storage volume
(including volume in lhe connecting piping system) is
beneath the ground surface.
vMthin 100 feet of an underground storage tank and
connecling underground pipes when the capacity of the tank
and pipe system is greater than '1,100 gallons.
Wtere the minimum vertical separation of 1 foot to the
seasonal high groundwater or other impermeable layer
would not be achieved below bioretention that would serve a
drainage area less than the above thresholds
11
Other Hard Surtaces (conL)
l
tr
tr
tr
. Wthin 100 feet of an area known to have deep soil
contamination.. Vvhere groundwater modeling indicates infiltration
will likely increase or change lhe direction of the
migration of pollutants in the groundwater.
. Wherever surface soils have been found to be
contaminated unless tho6e goils are removed within
l0 horizontal feet from the intiltration area.
tr
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tr
WorksheetC
Whafs the best ffion foryoursib?
Oth6r Hard Surfaces (cont)
Bfrlr and
Applicable
Llsts
Reason why the BMP will not rvork on site.Additional Comments
lf neoded
Bioretention or
Rain Gardens
(cont)
BMPT7.30. l
SVII\,MWW Volume Vl
Section 7.4 ]
Vvhere fi eld testing indicates potential bioretention/rain
garden sites have a measured (a.k.a., initial) natve soil
saturated hydraulic conductivity less than 0.30 inches per
hour. A smalFscale or large-scale PIT in accordance with
SVVtIMVVW Volume lll, Seclion 3,3.6 (or an altemative
small scale test specified by the local govemment) shall
be used to demonstrate infeasibility of bioretention areas.
lf the measured native soil infiltration rate is less than 0.30
in/hour, bioretentioni rain garden BMPs are not required
to be evaluated as an option in List #1 or List #2. ln these
slow draining soils, a bioretention area with an underdrain
may be used to tIeat pollution-generating surfaces to help
meet Minimum Requirement #6, Runoff Treatment. lf the
underdrain is elevaied within a bas€ course of gravel, it will
also provide some modest flow reduclion benetit that will help
achieve Minimum Requirement #7.
Vvhere the minimum vertical separation of 3 feet to the
seasonal high groundwater elevation or other impermeable
layer would not be achieved belovv bioretention that would
serve a drainage area that exceeds the following thresholds
(and cannot reasonably be broken down into amounts
smaller than indicated):
o 5,000 square feet ot pollution-generating impervious
sudace (PGIS)
o 10.000 square feet of impervious area
o 0.75 acres of lawn and landscape
Any area where these facilities are prohibited by an approved
cleanup plan under the state MTCA or Federal Superfund
Law' or an environmental covenant under Chapter 64-70
RCW
Vvrthin 100 feet of a drinking water well, or a spring used for
drinking water supply.
Vvithin 10 feet of small on-site sewage disposal drainrield,
including reserve areas, and grey water reuse systems. For
setbacks from a 'large on-site sewage disposal system," see
Chapter 2116-2728 WAC.
None of the above boxes are checked, This is the BMP that must be used for hard surfaces. On Worksheet A1 ,
indicate that this will be the BMP used. CONTINUE to complete the form for other surfaca types applicable to the
project. lf none, STOP.
1?
n
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/
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lN(
Other Hard Surfacea (cont)
and
Applica ble
Lists
Roason why the BilP will not work on sita.
Positive drainage for sheet flow runofi cannot be achieved.
Area to be dispersed (e.9., driveway, patio) cannot be graded
to have less than a 15 percent slope.
For flat to moderately sloped areas, at least a l0 fooFwide
vegetation bufier for dispersion of the adjacent 20 feet of
contributing surface cannot be achieved. For variably sloped
areas, at least a 25 foot vegetated llowpath betvveen berms
cannot be achieved.
Sheet Flow
Dispersion
BMP T5,12,
SWMMVvWVolume
V Sectim 5.3
List #1, #2
and #3
A minimum 3 foot length of rock pad and 50 foot flowpath
OR a dispersion trench and 25 foot flowpath for every 700
sq. ff. of drainage area followed with applicable setbacks
cannot be achieved.
More than 700 sq. ff. drainage area drains to any dispersion
device.
Siting and design criteria 6annot be achieved on site
one of the above boxes are checked- This is the BMP that must be used for hard surfaces. On Worksheet A1.
indicate that this will be the BMP used. CONTINUE to complete the form for other surface types applicable to the
proiect. lf none, STOP
Concentrated
Flow
Dispersion
BMP T5,11.
S\^/t Mwwvolurn€
V Seclion 5.3
List #1, #2
and #3
None of the above boxes ar6 checked. This is the BMP that must be used for hard surfaces. On Worksheet 41,
indicate that this will be the BMP used. CONTINUE to complete th€ form for other surtace types applicable to lhe
proiect. lf none, STOP
13
WorksheetC
Whafs the best option foryoursite?
Additional Comments
lf needed
l-l siting ana oesign criteria cannot be achieved on site.
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SEPTIC SYSTEM, PARCEL
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9762001 I I CREATIVE DESIGN SOLUTIONS
Septlo Sr8te Doa/4,,/s, Pofnltr, , F qpaclions
P.0. Box 2787, PoRr TilGELES, WA$H rcror{ 08982
(800) 395-7296, (300) 457-6353. EIAI-, UKEoCD$4YoU.CoI
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