HomeMy WebLinkAboutBLD2016-00401 - 05 STORMWATER • • .; / f r',., %
--s°N Co DEPARTMENT OF COMMUNITY DEVELOPMENT
� ", 621 Sheridan Street,Port Townsend,AV 98368 k .4 -�`t ,o` er
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ti :< Web:w�v-cv.co.iefferson wa.us/convnunitydevelopment 44.-,... ~8 ow y
` E-mail:dcd(aJ,co.jefferson.wa.us �0 �{�'�� fr. , •
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STORMWATER CALCULATION WORKSHEET Oct)
MLA# 1 z - OoZ52 PROJECT/APPLICANT NAME: M s hiE-A 50A oft.-
DETERMINING
DETERMINING 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
required.
PARCEL SIZE(I.E.,SITE)
4y
Size of parcel , "T-3Oiacres -7 An acre contains 43,560 square feet. Multiply the acreage by this figure.
Size of parcel in square feet C- U� / sq/ft
Land-disturbing activity is any activity that results in movement of earth, or a change in the existing soil cover(both vegetative and
non-vegetative)and/or the existing soil topography. Land disturbing activities include, but are not limited to clearing,grading,filling,
excavation,and compaction associated with stabilization of structures and road construction.
Native vegetation is vegetation comprised on plant species, other than noxious weeds, that are indigenous to the coastal region of
the Pacific Northwest and which 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.
LAND DISTURBING ACTIVITY, CONVERSION OF NATIVE VEGETATION,AND VOLUME OF CUT/FILL
Calculate the total area to be cleared, graded,filled, Answer the following two questions related to
excavated,and/or compacted for proposed development conversion of native vegetation:
project. Include in this calculation the area to be cleared for:
�. .� Does the project convert%acres or more of
Construction site for structures /,3 sq/ft native vegetation to lawn or landscaped areas?
Drainfield,septic tank,etc(e)(t5 i A/4) 6-6 00 sq/ft Circle: YesNo
Well,utilities,etc_i E?(I S 7-7A/0 /t O V sq/ft Does the project convert 2 Y2 acres or more of
c. native vegetation to pasture?
Driveway, parking, roads, etc .'I$TM/6J 6 sq/ft
/ 0o ✓✓ Circle: Yes (No
Lawn,landscaping,etc#Z:A/if - ') ►�() sq/ft
Other compacted surface, etc. sq/ft Indicate Total Volumes of Proposed:
Total Land Disturbance /4. 3 Q sq/ft Cut >n Fill 10 (cu/yd)
i
Impervious surface is a hard surface that either prevents or retards the entry of water into the soil mantle as under natural
conditions prior to development. A hard surface area which causes water to run off the surface in greater 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,driveways, 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.
1
stormwater talc worksheet-REV.10/20/2014
i •
STORMWATER CALULATIONS—IMPERVIOUS SURFACE
NEW EXISTING
Structures(all roof area) 1300 sq/ft Structures(all roof area) / 2 0 0 $q/ft
Sidewalks C, sq/ft Sidewalks C3 sq/ft
Patios C) sq/ft Patios ''=� sq/ft
Solid Decks sq/ft Solid Decks sq/ft
(without infiltration below) (without infiltration below)
Driveway, parking, roads,etc r 0 ,nJ€t sq/ft Driveway,parking, roads, etc C..›Wo sq/ft
Other .—' sq/ft Other *---, sq/ft
Total New r 30C) sq/ft Total Existing 7 asq/ft
TOTAL NEW+TOTAL EXISTING* 8 S'oo sq/ft *This amount will be used to check total lot coverage.
The following questions will help determine whether the proposed project is considered development or redevelopment.
DEVELOPMENT v. REDEVELOPMENT
Divide the total existing impervious surface above by the size of the parce w,4 '.•• sapa percentage: 2 .9%
Does the site have 35%or more of existing impervious surface? i I .:..i Lsig iji No
IX
Sep ,
FURTHER INSTRUCTIONS: If the answer is yes, the proposal is considered rede e1opment and th4 ..t r ed Fi should be used
to determine the applicable Minimum Requirements. If the answer is no, the pl 's considere. ne - opment and the
attached Figure 1 should be used. At this juncture, the applicant should refer to thAb, e Flow Chart to determine the
Minimum Requirements for stormwater management. DCD staff will help verify the classification di ct and the application
requirements. ILIC,
For proponents of "small" projects who must comply only with Minimum Requirement #2—Construction Stormwater Pollution
Prevention—an additional submittal is not required. The proponent is responsible for employing the 12 Elements to control erosion
and prevent sediment and other pollutants from leaving the site during the construction phase of the project. Pick up the
Construction Stormwater Pollution Prevention (SWPP) Best Management Practices (BMPs) Packet. Proponents of "medium"
projects—those that must meet only Minimum Requirements#1 through#5—and for"large" projects—those that must meet all 10
Minimum Requirements—are required to submit a Stormwater Site Plan. DCD has prepared a submittal template of a Stormwater
Site Plan, principally for rural residential projects. Complete the template in the Stormwater Site Plan Instructions and Submittal
Template or prepare a Stormwater Site Plan using the step-by-step guidance in the Storm water Management Manual.
APPLICANT SIGNATURE
By signing the 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 being made with the full knowledge and consent of all owners of the affected
property.
A
. 20
(IANDOWNE••R AUTHORIZED REPRESENTATIVE SIGNAT RE) ' :'(DATE)
a
x
OR OFFICEUS ONLY VA �: , ,,,zc 'iata s� Mr "r �"x"�"' -
e �` ' £e s ' b t ti tL`y^sem € -r. .,'3 ' L E: g. :fr ri n x':ya* t.ec .2K
*t T .. ; € .. a-g, ,. � S i . .5➢ .-. y 4.... �� m. eMkO ,1 AVS_ , � Z 51. "to moi._; .
'SMA-j MEDIUM -s><' LARGE -,-s VITR REDEVELOPMENTS , , t StormwaterSite Plan Yes' to A .m,
stormwater calc worksheet—REV.12/30/2015 2
•
3.1.2 Downspout Dispersion Systems (BMP T5.10B)
Downspout dispersion systems are splash blocks or gravel-filled trenches,
which serve to spread roof runoff over vegetated pervious areas.
Dispersion attenuates peak flows by slowing the runoff entering into the
conveyance system, allowing some infiltration,and providing some water
quality benefits.
Applications& Downspout dispersion may be used in all subdivision lots where
Limitations downspout full infiltration, full dispersion,and bioretention/rain gardens
are not feasible.
Runoff Modeling In WWHM,roof areas may be modeled as grassed surfaces(landscape) if
for Roof roof runoff is dispersed according to the requirements of this section on
Downspout lots greater than 22,000 square feet, and the vegetated flowpath is 50 feet
Dispersion or larger through undisturbed native landscape or lawn/landscape area that
meets BMP T5.13. If the available vegetated flowpath is 25 to 50 feet,
use of a dispersion trench allows modeling the roof as 50%
impervious/50% landscape. This is done in WWHM on the Mitigated
Scenario screen by entering the roof area into one of the entry options for
dispersal of impervious area runoff. For WWHM2012,see Appendix 111-C
in this Volume.
Design Criteria I. Use downspout trenches designed as shown in Figures 3.1.5 and 3.1.6
for all downspout dispersion applications except where splash blocks
are allowed below.
2. Splash blocks shown in Figure 3.1.7 may be used for downspouts
discharging to a vegetated flowpath at least 50 feet in length as
measured from the downspout to the downstream property line,
structure,slope over 15%,stream,wetland,or other impervious surface.
Sensitive area buffers may count toward flowpath lengths.
3. Cover the vegetated flowpath with well-established lawn or pasture,
landscaping with well-established groundcover,or native vegetation
with natural groundcover. The groundcover shall be dense enough to
help disperse and infiltrate flows and to prevent erosion.
4. If the vegetated flowpath(measured as defined above)is less than 25
feet,a perforated stub-out connection per Section 3.1.3 may be used in
lieu of downspout dispersion. A perforated stub-out may also be used
where implementation of downspout dispersion might cause erosion or
flooding problems,either on site or on adjacent lots. For example,this
provision might be appropriate for lots constructed on steep hills where
downspout discharge could culminate and might pose a potential hazard
for lower lying lots,or where dispersed flows could create problems for
adjacent off-site lots. This provision does not apply to situations where
lots are flat and on-site downspout dispersal would result in saturated
yards. Perforated stub-outs are not appropriate when seasonal water
table is<I foot below trench bottom.
Volume III--Hydrologic Analysis and Flow Control BMPs—December 2014
3-11
S •
Setbacks
Local governments may require specific setbacks in sites with slopes over
40%, land slide areas,open water features, springs,wells,and septic tank
drain fields. Adequate room for maintenance Cess and equipment should
also be considered. Examples of setbacks c monly used include the
following:
1. All infiltration systems should b- .t least 10 feet from any structure,
property line,or sensitive area,(except slopes over 40%).
2. All infiltration systems must be at least 50 feet from the top of any slope
over 40%.This setback may be reduced to 15 feet based on a
geotechnical evaluation, but in no instances may it be less than the
buffer width.
3. For sites with septic systems,infiltration systems must be downgradient
of the drainfield unless the site topography clearly prohibits subsurface
flows from intersecting the drainfield.
Volume III—Hydrologic Analysis and Flow Control BMPs—December 2014
3-10
I •
Note: For all other types of projects, the use of a perforated stub-out in
lieu of downspout dispersion shall be as determined by the Local Plan
Approval Authority.
5. For sites with septic systems,the discharge point of all dispersion
systems must be downgradient of the drainfield. This requirement may
be waived if site topography clearly prohibits flows from intersecting
the drainfield.
Design Criteria for Dispersion Trenches
1. A vegetated flowpath of at least 25 feet in length must be maintained
between the outlet of the trench and any property line,structure,stream,
wetland,or impervious surface. A vegetated flowpath of at least 50 feet
in length must be maintained between the outlet of the trench and any
slope steeper than 15%. Sensitive area buffers may count towards
flowpath lengths.
2. Trenches serving up to 700 square feet of roof area may be simple 10-
foot-long by 2-foot wide gravel filled trenches as shown in Figure 3.1.5.
For roof areas larger than 700 square feet,a dispersion trench with
notched grade board as shown in Figure 3.1.6 or alternative material
approved by the Local Plan Approval Authority may be used.The total
length of this design must not exceed 50 feet and must provide at least
10 feet of trench per 700 square feet of roof area.
3. Maintain a setback of at least 5 feet between any edge of the trench and
any structure or property line.
4. No erosion or flooding of downstream properties may result.
5. Have a geotechnical engineer or a licensed geologist,hydrogeologist,or
engineering geologist evaluate runoff discharged towards landslide
hazard areas. Don not place the discharge point on or above slopes
greater than 15%or above erosion hazard areas without evaluation by a
geotechnical engineer or qualified geologist and jurisdiction approval.
6. For purposes of maintaining adequate separation of flows discharged
from adjacent dispersion devices,the outer edge of the vegetated
flowpath segment for the dispersion trench must not overlap with other
flowpath segments,except those associated with sheet flow from a non-
native pervious surface.
Volume III—Hydrologic Analysis and Flow Control BMPs—December 2014
3-12
• 0
level outlet
• a b oor6ea e
°
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7Da, Va0 v
60* 6 11D0 .. r 00
6"mln
.,•• 9 .1- 9A°:dn° cfo 4-morf nino
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..I 2 a ea Pv e De:e.°
18 min 0 7,.1).00°0 7°00
.• 7 v °:De . •,.,"^ 11/2"-314'washed rock
00 p 3 70 0 0 c
V '90 9 6 O'/"'S°00
0•V°0 OCOC°
0'0 ° V
is* 24'min .1
TRENCH X-SECTION
NTS
slope--*-
small catch basin or yard drain
111 2'x 1 CI
level trenches
c700 sq.ft.
Type I CB
>700 sq.ft. standard
U dispersion trench
w/notched grade board
length 10'per 700 sq.ft.
of roof area.
PLAN VIEW OF ROOF
AMC
L -
Figure 3.1.5-Typical Downspout Dispersion Trench
Source: King County
Volume III—Hydrologic Analysis and Flow Control Bitils—December 2014
3-13
0 •
f pipe O.D.
1%0 /1'43
.Ill-01. *
li:131. *qd ap or p log /1riy to F,...cond
,--- - dispersal trerc h
1111, 76; clean out vo,e from pipe rt neci*,---A.ry
= 0 *
Io 70 * 4"o r 6"perbraed pipe lad flatilevel
note hed 0 v,
=in .,
g rEcle board /4 4 Aa
2'`x 2"note Fes 7 0. v type I CI B 4v/solid coksas(loc kino,)
tr. a I CB
is'ci.G. 1, 1 I typ
..r.__ 5 D 111111=37 km/solid co\er
ix= s—i ainimm ..4_,
=
b 3 4 infli.ent pipe (max desgn
c, fkr0 r.. 0.5 C FS per trench)
/1111' 0 V4*
I ,,4 clear%out loye from pipe
illt o '
I.
in 0 b
d 11111116 9 t''
' ficvo to other
branching CB's
PLAN as neciary
NTS
I ,
„pipe 0.0.
galvanized boltsi
1%0 / r'o 11111V 6,1 i4-2"
,,....fc,sok •
T
_11111111,4vt,
0 x12- '.4--",-AN4.12It... .Or 2"grad*
pressure """Vtiri.41113 0 4,, i:•*.: board notches 2"
treated grade I g :.1iii 6 't %*. .', 4"orEr perforated
board - -''' •..41,49,:t7 a V .17 ,,4 pipe.lad flat
'i-.4 ro ',..1, ..., 0 „. ,C.,
•-• tet '4A;* oV''.1 .< NOTES:
zie' l',•k,..
4"x 4*suppc.rt post Illt.(104 Clean(c.5%1i nes) 1.This trench shall be condo
, 00-0---- 14/2*-3/4"towhed rock as b prevent point discharge anthbr
' • , '4'.4 "V ,..,,, erosion.
co , 42, 0• .i. .,s,
......?„,..
2.Trenches may be placed no closer
filter fabr than 50 feet t one anther.(100 feet
abrg lbw!'re)
'15% maximiow ccritroNater cpality
3.Trench and gpri. board must betreatrrert in rural areas. lel.Aldn to folbw contours of sit.
SECTIONAA 4.Support post spacing., required by
NTS soil conditions to ensure graJ_ board
remains level. '
Figure 3.1.6-Standard Dispersion Trench with Notched Grade Board
Volume III—Hydrologic Analysis and Flow Control BMPs—December 2014
3-14
• •
Design Criteria for Splashblocks
A typical downspout splashblock is shown in Fieure 3.1.7. In general, if
the ground is sloped away from the foundation and there is adequate
vegetation and area for effective dispersion,splashblocks will adequately
disperse storm runoff. If the ground is fairly level, if the structure includes
a basement,or if foundation drains are proposed, splashblocks with
downspout extensions may be a better choice because the discharge point
is moved away from the foundation. Downspout extensions can include
piping to a splashblock/discharge point a considerable distance from the
downspout,as long as the runoff can travel through a well-vegetated area
as described below.
The following apply to the use of splashblocks:
1. Maintain a vegetated flowpath of at least 50 feet between the discharge
point and,any property line, structure, slope steeper than 15%,stream,
wetland, l*e,or other impervious surface. Sensitive area buffers may
count toward flowpath lengths.
2. A maximum of 700 square feet of roof area may drain to each
splashblock.
3. For purposes of main aining adequate separation of flows discharged
from adjacent dispersir• devices, the vegetated flowpath segment for
the splashblock must not •verlap with other flowpath segments,except
those associated with sheet low from a non-native pervious surface.
4. Place a splashblock or a pad o rushed rock(2 feet wide by 3 feet
long by 6 inches deep)at each de spout discharge point.
5. No erosion or flooding of downstre., properties may result.
6. Have a geotechnical engineer or a lice ed geologist, hydrogeologist,
or engineering geologist evaluate runoff•.scharged towards landslide
hazard areas.Do not place Splashblocks o 9r above slopes greater
than 15%or above erosion hazard areas with%ut evaluation by a
professional engineer with geotechnical expert e or a licensed
geologist,hydrogeologist,or engineering geolog •t,and approval by
the Local Plan Approval Authority.
7. For sites with septic systems,the discharge point mus be downslope
of the primary and reserve drainfield areas. This requir • ent may be
waived if site topography clearly prohibits flows from int: secting the
drainfield or where site conditions(soil permeability, distan e between
systems,etc.) indicate that this is unnecessary.
Volume III—Hydrologic Analysis and Flow Control BMPs—December 2014
3-15
I
Design Criteria for Splashblocks
A typical downspout splashblock is shown in Figure 3.1.7. In general, if
the ground is sloped away from the foundation and there is adequate
vegetation and area for effective dispersion, splashblocks will adequately
disperse storm runoff. If the ground is fairly level, if the structure includes
a basement,or if foundation drains are proposed, splashblocks with
downspout extensions may be a better choice because the discharge point
is moved away from the foundation. Downspout extensions can include
piping to a splashblock/discharge point a considerable distance from the
downspout,as long as the runoff can travel through a well-vegetated area
as described below.
The following apply to the use of splashblocks:
I. Maintain a vegetated flowpath of at least 50 feet between the discharge
point and any property line,structure, slope steeper than 15%,stream,
wetland,lake,or other impervious surface. Sensitive area buffers may
count toward flowpath lengths.
2. A maximum of 700 square feet of roof area may drain to each
splashblock.
3. For purposes of maintaining adequate separation of flows discharged
from adjacent dispersion devices,the vegetated flowpath segment for
the splashblock must not overlap with other flowpath segments,except
those associated with sheet flow from a non-native pervious surface.
4. Place a splashblock or a pad of crushed rock(2 feet wide by 3 feet
long by 6 inches deep)at each downspout discharge point.
5. No erosion or flooding of downstream properties may result.
6. Have a geotechnical engineer or a licensed geologist, hydrogeologist,
or engineering geologist evaluate runoff discharged towards landslide
hazard areas. Do not place Splashblocks on or above slopes greater
than 15%or above erosion hazard areas without evaluation by a
professional engineer with geotechnical expertise or a licensed
geologist,hydrogeologist,or engineering geologist,and approval by
the Local Plan Approval Authority.
7. For sites with septic systems,the discharge point must be downslope
of the primary and reserve drainfield areas. This requirement may be
waived if site topography clearly prohibits flows from intersecting the
drainfield or where site conditions (soil permeability,distance between
systems,etc.)indicate that this is unnecessary.
Volume III—Hydrologic Analysis and Flow Control BMPs—December 2014
3-15
• •
/pipe O.D
i
r-o
ilow to second
min ipljt -,end cap or plug
dispersal trench
..,-clean out wile from pipe if nee0.---s.ary
.0...., . 0
0 7e, * 4"o r 6"pert:mated pipe lad flattlevel
0
4 6
notched
=a ,4
grade bcxard a A*
20.,2.notches A q 0 9 -type IC Bsmtso lid cover(locking)
type I GB
L
18'U.G. i_IL 1 wimiiid ociier
a imimmt
in=
b 1 a influent pipe(max thsqn
le)
1 4.c flow 0.5 C FS per*trench)
IIII 0 Se*
D c.A clean outwe from pipe
. ,
• ,411110.0 0 flow to other
branching CO's
P'AN as nece,- ary
NTS
I 13'O.C.
pipe O.D.
galvanized bolts 1%0 / 1%0 *ftliP401„` --ir-I 14-2"
IIIIII 00'10,,,ic°,, '
...--:. „,,,
--
Tx12" ••.....c),ZW!';.'im'''''** *.2. *1'''in''''X'
pressure :4".•‘:',214,".4.,-:,'lig e`a ao °.t4 board notches 2"
treated grade -g •,:.:..N.e.,,,,, fr . ,..k...,... 4-or EP perforated
1.- ' ' '''w 07 9 !x"i. pipe laxl. fiat
ic°3rci is) i '1.f4."4 • ,,,
•-•01 '713;: , 0D7 '" *;$k• NOTES:
411x 4support post 7 .1*.4: clean(s6%'fires) I.This tiench shall te constructed
icil . tile.Olt"iwashed rock
0 %,s.,..,
a a *0 ..,y`
as t.prevent point discharge andtor
ersion.
it "".Z....<1.:\".101 2.Trenp.-hes may be placed no closer
I fabric than 50 feet to one arrother.(100 feet
along flowline)
15% max for flow centrolAvater cpedity
3.Trench arid grad,* board must be
tin rural.areas. lexel AlOn to folio*,contours of si .
SECTION A-A 4.Su pport post spacing as required by '
NTS soil co nd itbns to ensu re g rade board
remains level.
Figure 3.1.6-Standard Dispersion Trench with Notched Grade Board
Volume Ill-Hydrologic Analysis and Flow Control BMPs-December 2014
3-14
0 0
i
house
Roof 1 -tff,2
downspout ' Dl
serves up to :4:9 -
700 st.Of roof
kgiiiiil, I
4E1E1 I
50min.
Vegetated M .......,:i.:
....„...._.
flow path
\Splash
block
———— 110111116"
• irsvillt,•—• Downspout extension
ticiok . :100TS
Splash
block
01.4-
Figure 3.1/-Typical Downspout Splashblock Dispersion
Vol? ne III-Hydrologic Analysis and Flow Control Bit1Ps-December 2014
3-16
3.1.3 Perforated Stub-Out Connections (BMP T5.10C)
A perforated stub-out connection is a length of perforated pipe within a
gravel-filled trench that is placed between roof downspouts and a
stub-out to the local drainage system. Figure 3.1.8 illustrates a perforated
stub-out connection. These systems are intended to provide some
infiltration during drier months. During the wet winter months, they may
provide little or no flow control.
Applications& Perforated stub-outs are not appropriate when seasonal water table is less
Limitations than one foot below trench bottom.
In projects subject to Minimum Requirement #5 (see Volume 1),
perforated stub-out connections may be used only whenil other higher
priority on-site stormwater management BMPs are not feasible, per the
criteria for each of those BMPs.
Select the location of the connection to allow/aaximum amount of
runoff to infiltrate into the ground (ideally a dry,relatively well drained,
location). To facilitate maintenance, do not locate the perforated pipe
portion of the system under impervious or heavily compacted(e.g.,
driveways and parking areas)surfaces. Use the same setbacks as for
infiltration trenches in Section 3.1.1.
Have a licensed geologist,hydrogeologist,or engineering geologist
evaluate potential runoff discharges towards landslide hazard areas. Do
not place the perforated portion of the pipe on or above slopes greater than
20%or above erosion hazard areas without evaluation by a professional
engineer with geotechnical expertise or qualified geologist and jurisdiction
approval.
For sites with septic systems,the perforated portion of the pipe must be
downgradient of the drainfield primary and reserve areas.This
requirement can be waived if site topography will clearly prohibit flows
from intersecting the drainfield or where site conditions(soil permeability,
distance between systems,etc.)indicate that th•. is unnecessary.
Design Criteria Perforated stub-out connections consist of at leas 10 feet of perforated
pipe per 5,000 square feet of roof area laid in a lev 2-foot wide trench
backfilled with washed drain rock. Extend the drain .ck to a depth of at
least 8 inches below the bottom of the pipe and cover e pipe. Lay the
pipe level and cover the rock trench with filter fabric an. 6 inches of fill
(see Figure 3.1.8).
Runoff Model Any flow reduction is variable and unpredictable.No compu -I-modeling
Representation techniques are allowed that would predict any reduction in fib rates and
volumes from the connected area.
Volume III Hydrologic Analysis and Flow Control BMPs—December 2014
3-17
• i
7131103
DEPARTMENT OF COMMUNITY DEVELOPMENT
ADMINISTRATIVE
WATER CONSERVATION MEASURES LIST
...
To Promote Aquifer Recharge
and Prevent Seawater Intrusion
Roof and other intercepted precipitation shall be routed to on-site detention ponds
1. roved means and allowed to be released to the soil slowly.
and/or other app
Water collected from storm water and roof catchments may be used for watering
2. gardens. Unless catchments water has been treated to meet drinking
la
w s a g rds,there shall be no cross connections allowed between the potable
watterer standa
supply and impounded water_
3_ Ground water withdrawn from each property should not exceed a rate of three(3)
gallons per minute.
4. Install water-conserving fixtures such as low flow toilets,faucets and shower
restrictors and other water saving plumbing fixtures-
5. Landscaping should include xeriscaping and native vegetation with minimal amounts
of irrigation.
6. Use drip irrigation, soaker hose systems and root irrigation.
7" Use water basin techniques to water plants, hrubs and trees.
8. Routinely water deeply and less
9. Weed control is an important part of water conservation_
10.For Y Y awa from
our landscaping select drought tolerant plants, shrubs and trees stay
heavy water consumers.
11.Limit the amount of irrigated lawn.
garden as well as isolated plants,trees and shrubs_
12.Mulch your 9
13.Use shade and windlbreaks showerheads and water to assist in water onserving dish and clothes
14.Use low flow water c
washers.
15.Use rainwater catchment systems that corral rainwater from manmade surfaces and
into storage. lumbin fixtures.
-volume toilets and
should be
16-Install water-conserving devices `vumped from all exep pt wellg in
17 .Only 400 gallons per day or less P
Seawater Intrusion Protection Zones(SIPZ).
18_Water softeners that contribute salt to groundwater through infiltration should not be
used in SIPZ.
19.hose bibs(outdoor spigots)for outdoor water use should not be used in SIPZ""tend]
PLEAS NOTE:THIS LIST MAA DE A TANY TIME. USE CURB NT LIST.K IN PROGRESSAND MAY HAVE ADDITIONS
DELETIONS
2.5 Minimum Requirements
This section describes the minimum requirements for stormwater
management at development and redevelopment sites. Section 2.4 should
be consulted to determine which requirements apply to any given project.
Figures 2.4.1 and 2.4.2 should be consulted to detei mine whether the
minimum requirements apply to new surfaces,replaced surfaces, or new
and replaced surfaces. Volumes II through V of this manual present Best
Management Practices(BMPs)for use in meeting the Minimum
Requirements.
Throughout this chapter,requirements are written in bold and
supplemental guidelines that serve as advice and other materials are
not in bold.
2.5.1 Minimum Requirement#1: Preparation of Stormwater
Site Plans
All projects meeting the thresholds in Section 2.4 shall prepare a
Stormwater Site Plan for local government review.Stormwater Site
Plans shall use site-appropriate development principles,as required
and encouraged by local development codes,to retain native
vegetation and minimize impervious surfaces to the extent feasible.
Stormwater Site Plans shall be prepared in accordance with Chapter
3 of this volume.
Objective
The 2,000 square feet threshold for hard surfaces and 7,000 square foot
threshold for land disturbance are chosen to capture most single family
home construction and their equivalent.Note that the scope of the
stormwater site plan only covers compliance with Minimum Requirements
#2 through#5 if the thresholds of 5,000 square feet of hard surface or
conversion of%acre of vegetation to lawn or landscape,or conversion of
2.5 acres of vegetation to pasture are not exceeded.
Supplemental guidelines
Projects proposed by departments and agencies within the local
government with jurisdiction must comply with this requirement. The
local government shall determine the process for ensuring proper project
review,inspection,and compliance by its own departments and agencies.
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thresholds.Local governments should be prepared to demonstrate that by
comparing the number and types of historical projects that would have
been regulated using the Ecology thresholds versus the local government's
thresholds.
Local governments are allowed to institute a stop-loss provision on the
application of stormwater requirements to replaced hard surfaces. A stop-
loss provision is an upper limit on the extent to which a requirement is
applied.For instance,there could be a maximum percentage of the
estimated total project costs that are dedicated to meeting stormwater
requirements.A project would not have to incur additional stormwater
costs above that maximum though the standard redevelopment
requirements will not be fully achieved. The allowance for a stop-loss
provision pertains to the extent that treatment,flow control and wetlands
protection requirements are imposed on replaced hard surfaces.It does not
apply to meeting stormwater requirements for new hard surfaces.
ti
Local governments can also establish criteria for allowing redevelopment
projects to pay a fee in lieu of constructing water quality or flow control
facilities,on a redeveloped site. At a minimum,the fee should be the
equivalent;of an engineering estimate of the cost of meeting all applicable
stormwater requirements for the project. The local government should use
such funds for the implementation of stormwater control projects that
would have similar benefits to the same receiving water as if the project
had constructed its required improvements. Expenditure of such funds is
subject to other state statutory requirements.
Ecology cautions local governments about the potential long-term
consequences of allowing a fee-in-lieu of stormwater facilities.Sites that
are allowed to pay a fee continue without stormwater controls. If it is
determined,through future basin planning for instance,that controls on
such sites are necessary to achieve water quality goals or legal
requirements,the public may bear the costs for providing those controls.
Underground utility projects that replace the ground surface with in-kind
material or materials with similar runoff characteristics should not be
subject to redevelopment requirements except construction site erosion
control.
Local governments are also encouraged to review all road projects for
changes in elevations or drainage flowpath that could cause flooding,
upland or stream erosion,or changes to discharges to,wetlands.For
example,adding curbs will result in redirecting flows and possibly causing
new downstream impacts. The local government should set project-
specific requirements to avoid or mitigate those impacts.
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2.5.2 Minimum Requirement#2: Construction Stormwater
Pollution Prevention (SWPP)
Thresholds
All new development and redevelopment projects are responsible for
preventing erosion and discharge of sediment and other pollutants
into receiving waters.
Projects which result in 2,000 square feet or more of new plus
replaced hard surface area,or which disturb 7,000 square feet or
more of land must prepare a Construction SWPP Plan (SWPPP) as
part of the Stormwater Site Plan (see Section 2.5.1).
Projects that result in less than 2,000 square feet of new plus replaced
hard surface area,or disturb less than 7,000 square feet of land are
not required to prepare a Construction SWPPP,but must consider all
of the 13 Elements of Construction Stormwater Pollution Prevention
and develop controls for all elements that pertain to the project site.
General Requirements
The SWPPP shall include a narrative and drawings.All BMPs shall
be clearly referenced in the narrative and marked on the drawings.
The SWPPP narrative shall include documentation to explain and
justify the pollution prevention decisions made for the project.Each
of the 13 elements must be considered and included in the
Construction SWPPP unless site conditions render the element
unnecessary and the exemption from that element is clearly justified
in the narrative of the SWPPP.
Clearing and grading activities for developments shall be permitted
only if conducted pursuant to an approved site development plan (e.g.,
subdivision approval)that establishes permitted areas of clearing,
grading, cutting,and filling.These permitted clearing and grading
areas and any other areas required to preserve critical or sensitive
areas,buffers, native growth protection easements,or tree retention
areas shall be delineated on the site plans and the development site.
The SWPPP shall be implemented beginning with initial land
disturbance and until final stabilization. Sediment and Erosion
control BMPs shall be consistent with the BMPs contained in chapters
3 and 4 of Volume II.
Seasonal Work Limitations-From October 1 through April 30,
clearing,grading,and other soil disturbing activities shall only be
permitted if shown to the satisfaction of the local permitting authority
that silt-laden runoff will be prevented from leaving the site through a
combination of the following:
1. Site conditions including existing vegetative coverage,slope, soil
type and proximity to receiving waters.
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2. Limitations on activities and the extent of disturbed areas.
3. Proposed erosion and sediment control measures.
The following activities are exempt from the seasonal clearing and
grading limitations:
I. Routine maintenance and necessary repair of erosion and
sediment control BMPs.
2. Routine maintenance of public facilities or existing utility
structures that do not expose the soil or result in the removal of
the vegetative cover to soil.
3. Activities where there is one hundred percent infiltration of
surface water runoff within the site in approved and installed
erosion and sediment control facilities.
Project Requirements -Construction SWPPP Elements
Element 1: Preserve Vegetation/Mark Clearing Limits
• Before beginning land disturbing activities, including clearing and
grading,clearly mark all clearing limits,sensitive areas and their
buffers,and trees that are to be preserved within the construction
area.
• Retain the duff layer, native top soil, and natural vegetation in an
undisturbed state to the maximum degree practicable.
Element 2: Establish Construction Access
• Limit construction vehicle access and exit to one route,if possible.
• Stabilize access points with a pad of quarry spalls, crushed rock,
or other equivalent BMPs,to minimize tracking of sediment onto
public roads.
• Locate wheel wash or tire baths on site,if the stabilized
construction entrance is not effective in preventing tracking
sediment onto roads.
• If sediment is tracked off site,clean the affected roadway
thoroughly at the end of each day,or more frequently as necessary
(for example,during wet weather).Remove sediment from roads
by shoveling,sweeping,or pick up and transport the sediment to a
controlled sediment disposal area.
• Conduct street washing only after sediment is removed in
accordance with the above bullet.
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. Control street wash wastewater by pumping back on-site, or
otherwise prevent it from discharging into systems tributary to
waters of the State.
Element 3: Control Flow Rates
• Protect properties and waterways downstream of development
sites from erosion and the associated discharge of turbid waters
due to increases in the velocity and peak volumetric flow rate of
stormwater runoff from the project site.
• Where necessary to comply with the bullet above,construct
stormwater retention or detention facilities as one of the first steps
in grading.Assure that detention facilities function properly
before constructing site improvements(e.g. impervious surfaces).
• If permanent infiltration ponds are used for flow control during
construction,protect these facilities from siltation during the
construction phase.
Element 4: Install Sediment Controls
▪ Design,install,and maintain effective erosion controls and
sediment controls to minimize the discharge of pollutants.
▪ Construct sediment control BMPs(sediment ponds,traps,filters,
etc.)as one of the first steps in grading.These BMPs shall be
functional before other land disturbing activities take place.
• Minimize sediment discharges from the site.The design,
installation and maintenance of erosion and sediment controls
must address factors such as the amount,frequency, intensity and
duration of precipitation,the nature of resulting stormwater
runoff,and soil characteristics,including the range of soil particle
sizes expected to be present on the site.
• Direct stormwater runoff from disturbed areas through a
sediment pond or other appropriate sediment removal BMP,
before the runoff leaves a construction site or before discharge to
an infiltration facility. Runoff from fully stabilized areas may be
discharged without a sediment removal BMP,but must meet the
flow control performance standard in Element#3,bullet#1.
• Locate BMPs intended to trap sediment on-site in a manner to
avoid interference with the movement of juvenile salmonids
attempting to enter off-channel areas or drainages.
. Where feasible,design outlet structures that withdraw impounded
stormwater from the surface to avoid discharging sediment that is
still suspended lower in the water column.
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Element 5: Stabilize Soils
• Stabilize exposed and unworked soils by application of effective
BMPs that prevent erosion.Applicable BMPs include, but are not
limited to: temporary and permanent seeding,sodding,mulching,
plastic covering,erosion control fabrics and matting,soil
application of polyacrylamide(PAM),the early application of
gravel base early on areas to be paved,and dust control.
• Control stormwater volume and velocity within the site to
minimize soil erosion.
• Control stormwater discharges, including both peak flow rates
and total stormwater volume,to minimize erosion at outlets and to
minimize downstream channel and stream bank erosion.
• Soils must not remain exposed and unworked for more than the
time periods set forth below to prevent erosion:
• During the dry season (May 1 -Sept.30): 7 days
• During the wet season (October 1 -April 30): 2 days
• Stabilize soils at the end of the shift before a holiday or weekend if
needed based on the weather forecast.
• Stabilize soil stockpiles from erosion,protected with sediment
trapping measures,and where possible, be located away from
storm drain inlets,waterways and drainage channels.
• Minimize the amount of soil exposed during construction activity.
• Minimize the disturbance of steep slopes.
• Minimize soil compaction and, unless infeasible,preserve topsoil.
Element 6: Protect Slopes
• Design and construct cut-and-fill slopes in a manner to minimize
erosion.Applicable practices include,but are not limited to,
reducing continuous length of slope with terracing and diversions,
reducing slope steepness,and roughening slope surfaces(for
example,track walking).
• Divert off-site stormwater(run-on)or ground water away from
slopes and disturbed areas with interceptor dikes,pipes and/or
swales.Off-site stormwater should be managed separately from
stormwater generated on the site.
• At the top of slopes,collect drainage in pipe slope drains or
protected channels to prevent erosion.
• Temporary pipe slope drains must handle the peak 10-minute
velocity of flow from a Type 1A,10-year,24-hour frequency
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storm for the developed condition.Alternatively,the 10-year
and 1-hour flow rate predicted by an approved continuous
runoff model,increased by a factor of 1.6, may be used.The
hydrologic analysis must use the existing land cover condition
for predicting flow rates from tributary areas outside the
project limits.For tributary areas on the project site,the
analysis must use the temporary or permanent project land
cover condition,whichever will produce the highest flow rates.
If using the Western Washington Hydrology Model(WWHM)
to predict flows,bare soil areas should be modeled as
"landscaped" area.
• Place excavated material on the uphill side of trenches,consistent
with safety and space considerations.
• Place check dams at regular intervals within constructed channels
that are cut down a slope.
Element 7: Protect Drain Inlets
• Protect all storm drain inlets made operable during construction
so that stormwater runoff shall not enter the conveyance system
without first being filtered or treated to remove sediment.
• Clean or remove and replace inlet protection devices when
sediment has filled one-third of the available storage(unless a
different standard is specified by the product manufacturer).
Element 8: Stabilize Channels and Outlets
• Design,construct,and stabilize all on-site conveyance channels to
prevent erosion from the following expected peak flows:
• Channels must handle the peak 10-minute velocity of flow
from a Type 1A, 10-year,24-hour frequency storm for the
developed condition. Alternatively,the 10-year, 1-hour flow
rate indicated by an approved continuous runoff model,
increased by a factor of 1.6,may be used.The hydrologic
analysis must use the existing land cover condition for
predicting flow rates from tributary areas outside the project
limits.For tributary areas on the project site,the analysis must
use the temporary or permanent project land cover condition,
whichever will produce the highest flow rates.If using the
Western Washington Hydrology Model(WWHM) to predict
flows,bare soil areas should be modeled as "landscaped area.
• Provide stabilization,including armoring material, adequate to
prevent erosion of outlets,adjacent stream banks,slopes and
downstream reaches at the outlets of all conveyance systems.
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Element 9: Control Pollutants
• Design,install,implement and maintain effective pollution
prevention measures to minimize the discharge of pollutants.
• Handle and dispose of all pollutants,including waste materials
and demolition debris that occur on-site in a manner that does not
cause contamination of stormwater.
• Provide cover,containment,and protection from vandalism for all
chemicals,liquid products,petroleum products,and other
materials that have the potential to pose a threat to human health
or the environment. On-site fueling tanks must include secondary
containment.Secondary containment means placing tanks or
containers within an impervious structure capable of containing
110% of the volume contained in the largest take within the
containment structure.Double-walled tanks do not require
additional secondary containment.
• Conduct maintenance,fueling, and repair of heavy equipment and
vehicles using spill prevention and control measures. Clean
contaminated surfaces immediately following any spill incident.
• Discharge wheel wash or tire bath wastewater to a separate on-site
treatment system that prevents discharge to surface water,such as
closed-loop recirculation or upland application,or to the sanitary
sewer,with local sewer district approval.
• Apply fertilizers and pesticides in a manner and at application
rates that will not result in loss of chemical to stormwater runoff.
Follow manufacturers' label requirements for application rates
and procedures.
• Use BMPs to prevent contamination of stormwater runoff by pH
modifying sources.The sources for this contamination include,but
are not limited to: bulk cement,cement kiln dust,fly ash,new
concrete washing and curing waters,waste streams generated
from concrete grinding and sawing,exposed aggregate processes,
dewatering concrete vaults,concrete pumping and mixer washout
waters.
• Adjust the pH of stormwater if necessary to prevent violations of
water quality standards.
• Assure that washout of concrete trucks is performed off-site or in
designated concrete washout areas only.Do not wash out concrete
trucks onto the ground,or into storm drains,open ditches,streets,
or streams.Do not dump excess concrete on-site,except in
designated concrete washout areas. Concrete spillage or concrete
discharge to surface waters of the State is prohibited.
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. Obtain written approval from Ecology before using chemical
treatment other than CO2 or dry ice to adjust pH.
Element 10: Control De-Watering
• Discharge foundation,vault,and trench de-watering water,which
has similar characteristics to stormwater runoff at the site, into a
controlled conveyance system before discharge to a sediment trap
or sediment pond.
• Discharge clean,non-turbid de-watering water,such as well-point
ground water,to systems tributary to,or directly into surface
waters of the State,as specified in Element#8,provided the de-
watering flow does not cause erosion or flooding of receiving
waters.Do not route clean dewatering water through stormwater
sediment ponds.Note that"surface waters of the State" may exist
on a construction site as well as off site; for example,a creek
running through a site.
• Handle highly turbid or otherwise contaminated dewatering water
separately from stormwater.
. Other treatment or disposal options may include:
1. Infiltration.
2. Transport off-site in a vehicle,such as a vacuum flush truck,
for legal disposal in a manner that does not pollute state
waters.
3. Ecology-approved on-site chemical treatment or other suitable
treatment technologies.
4. Sanitary or combined sewer discharge with local sewer district
approval, if there is no other option.
5. Use of a sedimentation bag with outfall to a ditch or swale for
small volumes of localized dewatering.
Element 11: Maintain BMPs
. Maintain and repair all temporary and permanent erosion and
sediment control BMPs as needed to assure continued
performance of their intended function in accordance with BMP
specifications.
• Remove all temporary erosion and sediment control BMPs within
30 days after achieving final site stabilization or after the
temporary BMPs are no longer needed.
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Element 12: Manage The Project
• Phase development projects to the maximum degree practicable
and take into account seasonal work limitations.
• Inspection and monitoring—Inspect,maintain and repair all
BMPs as needed to assure continued performance of their
intended function.Projects regulated under the Construction
Stormwater General Permit must conduct site inspections and
monitoring in accordance with Special Condition S4 of the
Construction Stormwater General Permit.
• Maintaining an updated construction SWPPP—Maintain,update,
and implement the SWPPP.
• Projects that disturb one or more acres must have site inspections
conducted by a Certified Erosion and Sediment Control Lead
(CESCL).Project sites disturbing less than one acre may have a
CESCL or a person without CESCL certification conduct
inspections.By the initiation of construction,the SWPPP must
identify the CESCL or inspector,who must be present on-site or
on-call at all times.
• The CESCL or inspector(project sites less than one acre)must have
the skills to assess the:
• Site conditions and construction activities that could impact the
quality of stormwater.
• Effectiveness of erosion and sediment control measures used to
control the quality of stormwater discharges.
• The CESCL or inspector must examine stormwater visually for the
presence of suspended sediment,turbidity,discoloration,and oil
sheen. They must evaluate the effectiveness of BMPs and determine if
it is necessary to install,maintain,or repair BMPs to improve the
quality of stormwater discharges.
Based on the results of the inspection,construction site operators must
correct the problems identified by:
• Reviewing the SWPPP for compliance with the 13 construction
SWPPP elements and making appropriate revisions within 7 days
of the inspection.
• Immediately beginning the process of fully implementing and
maintaining appropriate source control and/or treatment BMPs as
soon as possible,addressing the problems not later than within 10
days of the inspection.If installation of necessary treatment BMPs
is not feasible within 10 days,the construction site operator may
request an extension within the initial 10-day response period.
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Documenting BMP implementation and maintenance in the site log
book(sites larger than 1 acre).
. The CESCL or inspector must inspect all areas disturbed by
construction activities,all BMPs,and all stormwater discharge points
at least once every calendar week and within 24 hours of any discharge
from the site. (For purposes of this condition,individual discharge
events that last more than one day do not require daily inspections. For
example,if a stormwater pond discharges continuously over the course
of a week,only one inspection is required that week.)The CESCL or
inspector may reduce the inspection frequency for temporary
stabilized, inactive sites to once every calendar month.
Element 13: Protect Low Impact Development BMPs
. Protect all Bioretention and Rain Garden BMPs from
sedimentation through installation and maintenance of erosion
and sediment control BMPs on portions of the site that drain into
the Bioretention and/or Rain Garden BMPs.Restore the BMPs to
their fully functioning condition if they accumulate sediment
during construction.Restoring the BMP must include removal of
sediment and any sediment-laden Bioretention/rain garden soils,
and replacing the removed soils with soils meeting the design
specification.
• Prevent compacting Bioretention and rain garden BMPs by
excluding construction equipment and foot traffic. Protect
completed lawn and landscaped areas from compaction due to
construction equipment.
. Control erosion and avoid introducing sediment from surrounding
land uses onto permeable pavements.Do not allow muddy
construction equipment on the base material or pavement.Do not
allow sediment-laden runoff onto permeable pavements or base
materials.
. Pavement fouled with sediments or no longer passing an initial
infiltration test must be cleaned using procedures in accordance
with this manual or the manufacturer's procedures.
. Keep all heavy equipment off existing soils under LID facilities
that have been excavated to final grade to retain the infiltration
rate of the soils.
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Objective
To control erosion and prevent sediment and other pollutants from leaving
the site during the construction phase of a project. To have fully functional
stormwater facilities and BMP's for the developed site upon completion of
construction.
Supplemental Guidelines
If a Construction SWPPP is found to be inadequate(with respect to
erosion and sediment control requirements),then the Plan Approval
Authority I within the Local Government should require that other BMPs
be implemented,as appropriate.
The Plan Approval Authority may allow development of generic
Construction SWPPP's that apply to commonly conducted public road
activities,such as road surface replacement,that trigger this minimum
requirement. They may also develop an abbreviated SWPPP format for
project sites that will disturb less than 1 acre.
Based on the information provided and/or local weather conditions,the
local permitting authority may expand or restrict the seasonal limitation on
site disturbance.The local permitting authority shall take enforcement
action-such as a notice of violation,administrative order, penalty,or
stop-work order under the following circumstances:
• If,during the course of any construction activity or soil disturbance
during the seasonal limitation period, sediment leaves the construction
site causing a violation of the surface water quality standard;or
• If clearing and grading limits or erosion and sediment control
measures shown in the approved plan are not maintained.
Coordination with Utilities and Other Contractors-The primary project
proponent shall evaluate, with input from utilities and other contractors,
the stormwater management requirements for the entire project,including
the utilities,when preparing the Construction SWPPP.
Element#13,Protect Low Impact Development BMPs,is not yet included
as a permit condition in the NPDES Construction Stormwater General
Permit. That permit is not scheduled for reissuance until December,2015.
Until that permit is reissued with element#13 added as a permit condition,
the element may be enforceable only through the requirements of local
stormwater codes that may have been updated to include it.Municipal
Stormwater Permittees must incorporate this element into local
requirements per the timelines in their Municipal Stotinwater Permit.
'The Plan Approval Authority is defined as that department within a local government that has been delegated
authority to approve stormwater site plans.
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Standard Conditions for Residential Development in Jefferson County
1. LIGHTING: Lighting fixtures shall be designed and hooded to prevent the light source from being directly
visible from outside the boundaries of the property. The intensity or brightness of all lighting, during
construction and after project completion shall not adversely affect the use of surrounding properties or
adjoining rights-of-way.
Exterior lighting for residential uses shall not exceed twenty feet(20') in height from the finished grade,
excepting when such lighting is an integral part of a building or structure. Ground level lighting is
encouraged.
2. BUILDING HEIGHT: The building height is not to exceed 35 feet.
3. OUTDOOR STORAGE: Outdoor residential storage shall be maintained in an orderly manner and shall
create no fire, safety, health or sanitary hazard.
4. UNLICENSED VEHICLES: Not more than 2 unlicensed vehicles shall be stored on any lot unless totally
screened from view of neighboring dwellings and rights-of-way. Such screening shall meet all applicable
performance and development standards specific to the district in which the storage is kept, and shall be in
keeping with the character of the area. Screening shall meet the requirements of Chapter 18.30 JCC.
Outdoor storage of 3 or more junk motor vehicles is prohibited except in those districts where specified as
an automobile wrecking yard or junk (or salvage) yard and allowed as a permitted use in Table 3-1 or
Chapter 18.18 JCC, and such storage shall meet the requirements of JCC 18.20.100, Automobile wrecking
yards and junk (or salvage) yards. In no case, shall any such junk motor vehicles be stored in a critical
area.
5. PARKING: A minimum of two (2) on-site parking spaces shall be provided for the single family residence.
6. This permit has been reviewed consistent with JCC 18.40.130 & 140. Notice: this permit does not excuse
the applicant from complying with other local, state and federal ordinances, regulations or statues,
applicable to the proposed development, but consistent with RCW 90.58. Future development beyond
that specified in this permit shall require further review.
7. BMPs: The project shall adhere to the Best Management Practices (BMPs) to control stormwater, erosion
and sediment during construction. BMPs shall address permanent measures to stabilize soil exposed
during construction, and in the design and operation of stormwater and drainage control systems.
8. NOTICE: This permit does not excuse the proponent from complying with other local, state, and federal
ordinances, regulations, or statutes applicable to the proposed development, but consistent with RCW
90.58.
Development pursuant to this permit shall be undertaken subject to the applicable policies and
performance standards of the Jefferson County Shoreline Management Master Program and the Jefferson
County Unified Development Code.
If during excavation or development of the site an area of potential archaeological significance is
uncovered, all activity in the immediate area shall be halted, and the Administrator shall be notified at once.
The Federal Endangered Species Act rules to protect threatened Chinook and Summer-run Chum salmon
became effective on January 8, 2001. Bull trout have been listed as threatened since early 2000. Under
the ESA, any person may bring lawsuit against any individual or agency that "takes" listed species (defined
2013-03-07 SFR StdConditions 3/7/2013 1
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as causing harm, harassing, or damaging habitat for the listed species). In addition, the National Marine
Fisheries Service can levy penalties. Portions of Jefferson County, including marine waters, are included
as "critical habitat"for a listed species. Development of property along any marine shoreline, freshwater
shoreline,
or floodplains could harm habitat if protective measures are not taken. To minimize the potential to
damage habitat, all property owners developing adjacent to marine shoreline, freshwater shoreline, or
floodplains are advised to do the following:
All development activities should avoid unstable slopes, wetlands, and forested areas near surface
waters
Remove minimal vegetation for site development, especially large trees
Allow trees that have fallen into surface waters to remain there
Infiltrate stormwater from buildings and driveways onsite through drywells rather than discharging
directly into surface waters or roadside ditches
The Federal Bald and Golden Eagle Protection Act requires landowners within 660 feet (1/8th of a mile) of
an eagle nest to consult with the US Fish and Wildlife Service. This Eagle Act prohibits anyone from
"taking" bald eagles. This federal law defines the term "take" and describes the possible legal
consequences when a "take" occurs. Among other actions, "take" includes a disturbance of bald eagles or
their habitat. Under federal law a permit may still be required for activities that impact bald eagles or their
habitat. Contact the US Fish and Wildlife Service (http://www.fws.gov/pacific/eagle/)to learn more about
how this law affects your project.
Any individual, group, or agency can bring suit for a listed species "taking", even if you are in compliance
with Jefferson County development codes. The risk of a lawsuit against you can be reduced by consulting
with a professional fisheries habitat biologist, and following the recommendations for site development
provided by the biologist. For more information, contact the National Marine Fisheries Service in Seattle,
or the U.S. Fish and Wildlife Service.
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Standard Conditions for Residential Development in Jefferson County
1. LIGHTING: Lighting fixtures shall be designed and hooded to prevent the light source from being directly
visible from outside the boundaries of the property. The intensity or brightness of all lighting, during
construction and after project completion shall not adversely affect the use of surrounding properties or
adjoining rights-of-way.
Exterior lighting for residential uses shall not exceed twenty feet (20') in height from the finished grade,
excepting when such lighting is an integral part of a building or structure. Ground level lighting is
encouraged.
2. BUILDING HEIGHT: The building height is not to exceed 35 feet.
3. OUTDOOR STORAGE: Outdoor residential storage shall be maintained in an orderly manner and shall
create no fire, safety, health or sanitary hazard.
4. UNLICENSED VEHICLES: Not more than 2 unlicensed vehicles shall be stored on any lot unless totally
screened from view of neighboring dwellings and rights-of-way. Such screening shall meet all applicable
performance and development standards specific to the district in which the storage is kept, and shall be in
keeping with the character of the area. Screening shall meet the requirements of Chapter 18.30 JCC.
Outdoor storage of 3 or more junk motor vehicles is prohibited except in those districts where specified as
an automobile wrecking yard or junk (or salvage) yard and allowed as a permitted use in Table 3-1 or
Chapter 18.18 JCC, and such storage shall meet the requirements of JCC 18.20.100, Automobile wrecking
yards and junk (or salvage) yards. In no case, shall any such junk motor vehicles be stored in a critical
area.
5. PARKING: A minimum of two (2) on-site parking spaces shall be provided for the single family residence.
6. This permit has been reviewed consistent with JCC 18.40.130 & 140. Notice: this permit does not excuse
the applicant from complying with other local, state and federal ordinances, regulations or statues,
applicable to the proposed development, but consistent with RCW 90.58. Future development beyond
that specified in this permit shall require further review.
7. BMPs: The project shall adhere to the Best Management Practices (BMPs) to control stormwater, erosion
and sediment during construction. BMPs shall address permanent measures to stabilize soil exposed
during construction, and in the design and operation of stormwater and drainage control systems.
8. NOTICE: This permit does not excuse the proponent from complying with other local, state, and federal
ordinances, regulations, or statutes applicable to the proposed development, but consistent with RCW
90.58.
Development pursuant to this permit shall be undertaken subject to the applicable policies and
performance standards of the Jefferson County Shoreline Management Master Program and the Jefferson
County Unified Development Code.
If during excavation or development of the site an area of potential archaeological significance is
uncovered, all activity in the immediate area shall be halted, and the Administrator shall be notified at once.
The Federal Endangered Species Act rules to protect threatened Chinook and Summer-run Chum salmon
became effective on January 8, 2001. Bull trout have been listed as threatened since early 2000. Under
the ESA, any person may bring lawsuit against any individual or agency that "takes" listed species (defined
2013-03-07 SFR StdConditions 3/7/2013
• •
as causing harm, harassing, or damaging habitat for the listed species). In addition, the National Marine
Fisheries Service can levy penalties. Portions of Jefferson County, including marine waters, are included
as "critical habitat"for a listed species. Development of property along any marine shoreline, freshwater
shoreline,
or floodplains could harm habitat if protective measures are not taken. To minimize the potential to
damage habitat, all property owners developing adjacent to marine shoreline, freshwater shoreline, or
floodplains are advised to do the following:
All development activities should avoid unstable slopes, wetlands, and forested areas near surface
waters
Remove minimal vegetation for site development, especially large trees
Allow trees that have fallen into surface waters to remain there
Infiltrate stormwater from buildings and driveways onsite through drywells rather than discharging
directly into surface waters or roadside ditches
The Federal Bald and Golden Eagle Protection Act requires landowners within 660 feet(1/8th of a mile) of
an eagle nest to consult with the US Fish and Wildlife Service. This Eagle Act prohibits anyone from
"taking" bald eagles. This federal law defines the term "take" and describes the possible legal
consequences when a "take" occurs. Among other actions, "take" includes a disturbance of bald eagles or
their habitat. Under federal law a permit may still be required for activities that impact bald eagles or their
habitat. Contact the US Fish and Wildlife Service (http://www.fws.gov/pacific/eagle/)to learn more about
how this law affects your project.
Any individual, group, or agency can bring suit for a listed species "taking", even if you are in compliance
with Jefferson County development codes. The risk of a lawsuit against you can be reduced by consulting
with a professional fisheries habitat biologist, and following the recommendations for site development
provided by the biologist. For more information, contact the National Marine Fisheries Service in Seattle,
or the U.S. Fish and Wildlife Service.
2013-09-06_SFR_StdCond it ions 9/6/2013 2
• 0
p �S°N CO DEPARTMENT OF COMMUNITY DEVELOP .i+ ,.//'1.,,,-
.4.,
, , ' 621 Sheridan Street,Port Townsend,\V.�98.368
W Tel:360.379.4450 I Fax:360.379.4451 ��
` ���
aP
xoi .� . onunp
.f �� ir
4\E-mail:dcdCco.jefferson.wa.us ��
sw/p � c6`
NrNG000 (12
STORMWATER CALCULATION WORKSHEET 41
41
MLA# l . " 002 52 PROJECT/APPLICANT NAME: M M. ) EA/5c/V / ejA-4
DETERMINING 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
required.
:or PARCEL SIZE(I.E.,SITE)
Size of parcel , t_5/Nacres An acre contains 43,560 square feet. Multiply the acreage by this figure.
Size of parcel in square feet 6-S?/ 1' sq/ft
Land-disturbing activity is any activity that results in movement of earth, or a change in the existing soil cover(both vegetative and
non-vegetative) and/or the existing soil topography. Land disturbing activities include, but are not limited to clearing,grading,filling,
excavation, and compaction associated with stabilization of structures and road construction.
Native vegetation is vegetation comprised on plant species, other than noxious weeds, that are indigenous to the coastal region of
the Pacific Northwest and which 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.
LAND DISTURBING ACTIVITY, CONVERSION OF NATIVE VEGETATION, AND VOLUME OF CUT/FILL
Calculate the total area to be cleared,graded,filled, Answer the following two questions related to
excavated,and/or compacted for proposed development conversion of native vegetation:
project. Include in this calculation the area to be cleared for:
Does the project convert 3/4 acres or more of
Construction site for structures I .) sq/ft native vegetation to lawn or landscaped areas?
Drainfield,septic tank,etc(E)05 i 1NX) 5 00 sq/ft Circle: Yes (No
Well, utilities,etc.(E)(isT)/1/L,) 000 sq/ft Does the project convert 21/2 acres or more of
� native vegetation to pasture?
Driveway,parking, roads, etc(( /$TM/) G sq/ft
/ c / Circle: Yes No
Lawn, landscaping, etc{.1:X)574 ar sq/ft
Other compacted surface, etc. ``��� sq/ft Indicate Total Volumes of Proposed:
Total Land Disturbance / 3 5—C) sq/ft Cut /0 Fill 10 (cu/yd)
Impervious surface is a hard surface that either prevents or retards the entry of water into the soil mantle as under natural
:onditions prior to development. A hard surface area which causes water to run off the surface in greater quantities or at an
ncreased rate of flow from the flow present under natural conditions prior to development. Common impervious surfaces include,
put are not limited to roof tops,walkways, patios, driveways, 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.
stormwater cats worksheet—REV.10/20/2014 1
•
: STORMWATER CALULATIONS—IMPERVIOUS SURFACE
NEW EXISTING
Structures(all roof area) 1,300 sq/ft Structures(all roof area) / 2 C 0 5q/ft
Sidewalks Q sq/ft Sidewalks C3 sq/ft
Patios C sq/ft Patios (-5" sq/ft
Solid Decks C) sq/ft Solid Decks sq/ft
(without infiltration below) (without infiltration below)
Driveway, parking, roads, etc i'e) ,,,,/e t.,osq/ft Driveway, parking, roads, etc 6., sq/ft
Other sq/ft Other sq/ft
Total New / 300 sq/ft Total Existing 7 ar sq/ft
TOTAL NEW+TOTAL EXISTING* 85-co sq/ft *This amount will be used to check total lot coverage.
The following questions will help determine whether the proposed project is considered development or redevelopment.
DEVELOPMENT v. REDEVELOPMENT
Divide the total existing impervious surface above by the size of the parcel and convert to a percentage: 2 c y%
Does the site have 35%or more of existing impervious surface? Circle: Yes No
FURTHER INSTRUCTIONS: If the answer is yes, the proposal is considered redevelopment and r . .,(�► •i F �.uld be used
to determine the applicable Minimum Requirements. If the answer is no, the proposal is c', Isere.n tt �R; f 1/ �" e
attached Figure 1 should be used. At this juncture, the applicant should refer to the ape + e FI w Chart to e `1I . t
Minimum Requirements for stormwater management. DCD staff will helpverifythe classification of th c and the +t'
q g �i�J� � ,h
requirements. � 2015 f
For proponents of "small" projects who must comply only with Minimum Requirement #2—C• .'.n Stormwater Pc7r tion
Prevention—an additional submittal is not required. The proponent is responsible for employing the 12 Ele -pptrol erosion
and prevent sediment and other pollutants from leaving the site during the construction phase of the project.k'P ''pp the
Construction Stormwater Pollution Prevention (SWPP) Best Management Practices (BMPs) Packet. Proponents of "medium"
projects—those that must meet only Minimum Requirements#1 through#5—and for"large" projects—those that must meet all 10
Minimum Requirements—are required to submit a Stormwater Site Plan. DCD has prepared a submittal template of a Stormwater
Site Plan, principally for rural residential projects. Complete the template in the Stormwater Site Plan Instructions and Submittal
Template or prepare a Stormwater Site Plan using the step-by-step guidance in the Storm water Management Manual.
APPLICANT SIGNATURE
By signing the 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 being made with the full knowledge and consent of all owners of the affected
property.
(LANDOWNE R AUTHORIZED REPRESENTATIVE SIGNAT RE) :'(DATE)
FOR O'F.SFCk{S't ON:.x Y4 k u ,m 4 *,3 h fi� x 2 I � Y t : i x 5R , tS 4 4t e;4, r•+.."k a:#_ ** "w a M
=
�...
{
Y � ' 'w`�'.�s3�
a $ v. .�:. x. s - x .� ,P.k: � -e'3'sae. $ ;� "z
Ict
'SMALtx �:= MEDIUM �= 4,a; TARGE r e ° REDEVELOPMENT <=- >:s�Stormwater site Plan Yes ^^ w o t 4YR.4: k
stormwater calc worksheet—REV.12/30/2015 2
• •
- •
3.1.2 Downspout Dispersion Systems (BMP T5.10B)
Downspout dispersion systems are splash blocks or gravel-filled trenches,
which serve to spread roof runoff over vegetated pervious areas.
Dispersion attenuates peak flows by slowing the runoff entering into the
conveyance system,allowing some infiltration,and providing some water
quality benefits.
Applications& Downspout dispersion may be used in all subdivision lots where
Limitations downspout full infiltration,full dispersion, and bioretention/rain gardens
are not feasible.
Runoff Modeling In WWHM,roof areas may be modeled as grassed surfaces(landscape) if
for Roof roof runoff is dispersed according to the requirements of this section on
Downspout lots greater than 22,000 square feet,and the vegetated flowpath is 50 feet
Dispersion or larger through undisturbed native landscape or lawn/landscape area that
meets BMP T5.13. If the available vegetated flowpath is 25 to 50 feet,
use of a dispersion trench allows modeling the roof as 50%
impervious/50%landscape. This is done in WWHM on the Mitigated
Scenario screen by entering the roof area into one of the entry options for
dispersal of impervious area runoff. For WWHM2012, see Appendix Ill-C
in this Volume.
Design Criteria I Use downspout trenches designed as shown in Figures 3.1.5 and 3.1.6
for all downspout dispersion applications except where splash blocks
are allowed below.
2. Splash blocks shown in Figure 3.1.7 may be used for downspouts
discharging to a vegetated flowpath at least 50 feet in length as
measured from the downspout to the downstream property line,
structure,slope over 15%,stream, wetland,or other impervious surface.
Sensitive area buffers may count toward flowpath lengths.
3. Cover the vegetated flowpath with well-established lawn or pasture,
landscaping with well-established groundcover,or native vegetation
with natural groundcover.The groundcover shall be dense enough to
help disperse and infiltrate flows and to prevent erosion.
4. If the vegetated flowpath(measured as defined above)is less than 25
feet,a perforated stub-out connection per Section 3.1.3 may be used in
lieu of downspout dispersion. A perforated stub-out may also be used
where implementation of downspout dispersion might cause erosion or
flooding problems,either on site or on adjacent lots. For example,this
provision might be appropriate for lots constructed on steep hills where
downspout discharge could culminate and might pose a potential hazard
for lower lying lots,or where dispersed flows could create problems for
adjacent off-site lots. This provision does not apply to situations where
lots are flat and on-site downspout dispersal would result in saturated
yards. Perforated stub-outs are not appropriate when seasonal water
table is<1 foot below trench bottom.
Volume Ill-Hydrologic Analysis and Flow Control BMPs-December 2014
3-11
•
Setbacks
Local governments may require specific setbacks in sites with slopes over
40%, land slide areas,open water features, springs,wells,and septic tank
drain fields.Adequate room for maintenance cess and equipment should
also be considered.Examples of setbacks c monly used include the
following:
1. All infiltration systems should b- .t least 10 feet from any structure,
property line,or sensitive area(except slopes over 40%).
2. All infiltration systems must be at least 50 feet from the top of any slope
over 40%.This setback may be reduced to 15 feet based on a
geotechnical evaluation,but in no instances may it be less than the
buffer width.
3. For sites with septic systems, infiltration systems must be downgradient
of the drainfield unless the site topography clearly prohibits subsurface
flows from intersecting the drainfield.
Volume III—Hydrologic Analysis and Flow Control BMPs—December 2014
3-10
41) •
J.
Note: For all other types of projects, the use of a perforated stub-out in
lieu of downspout dispersion shall be as determined by the Local Plan
Approval Authority.
5. For sites with septic systems,the discharge point of all dispersion
systems must be downgradient of the drainfield. This requirement may
be waived if site topography clearly prohibits flows from intersecting
the drainfield.
Design Criteria for Dispersion Trenches
1. A vegetated flowpath of at least 25 feet in length must be maintained
between the outlet of the trench and any property line,structure,stream,
wetland,or impervious surface. A vegetated flowpath of at least 50 feet
in length must be maintained between the outlet of the trench and any
slope steeper than 15%. Sensitive area buffers may count towards
flowpath lengths.
2. Trenches serving up to 700 square feet of roof area may be simple 10-
foot-long by 2-foot wide gravel filled trenches as shown in Figure 3.1.5.
For roof areas larger than 700 square feet,a dispersion trench with
notched grade board as shown in Figure 3.1.6 or alternative material
approved by the Local Plan Approval Authority may be used.The total
length of this design must not exceed 50 feet and must provide at least
10 feet of trench per 700 square feet of roof area.
3. Maintain a setback of at least 5 feet between any edge of the trench and
any structure or property line.
4. No erosion or flooding of downstream properties may result.
5. Have a geotechnical engineer or a licensed geologist,hydrogeologist,or
engineering geologist evaluate runoff discharged towards landslide
hazard areas. Don not place the discharge point on or above slopes
greater than 15%or above erosion hazard areas without evaluation by a
geotechnical engineer or qualified geologist and jurisdiction approval.
6. For purposes of maintaining adequate separation of flows discharged
from adjacent dispersion devices,the outer edge of the vegetated
flowpath segment for the dispersion trench must not overlap with other
flowpath segments,except those associated with sheet flow from a non-
native pervious surface.
Volume III—Hydrologic Analysis and Flow Control BMPs—December 2014
3-12
• •
1.
o 0 ,2,
level outlet
•iu Q.
Od
. qD 96 de, d
a 0 0
•
v ye, vaa v
0 ao Ova
°
vv o°
° -------___
. • , . 0
:,,. o , • 9 •99 ,9 .
6 min
• .; 4....Ae0T 00L1- i 4-ped pipe
po.
..,5 o-4 07 d od 0 a
18*min 07a a .Da°a vot,
P,70a 7aClio°430%'..a; 11/2'-3/4'washed rock
00 v ° v D 0 0
7,00o
' D.>7°. Dil Op bo 7
0•-.° • a 9 , ,,, ,,.,
24'min ri
TRENCH X-SECTION
NTS
slope--.-
small catch basin or yard drain
II 2'x 10'
level trenches
g00 sq.ft.
Type I CB
>700 sq.ft standard
U dispersion trench
w/notched grade board
length 10'per 700 sq.ft.
of roof area.
PLAN VIEW OF ROOF
ITC
Figure 3.1.5-Typical Downspout Dispersion Trench
Source: King County
Volume 111—Hydrologic Analysis and Flow Control BMPs—December 2014
3-13
. • • I
Ai-
pipe O.D.
V0 1-0
low to Second
mut miT1 erd cap or plug
dispersal tre.rch
Ft,via: clean out wIte from pipe if reCil.rf
= 4 0
I0 0 Vo 0 4"o r el"pert raced pipe lad flat/level
a
notcheda-
..... .
g raie board .,na
2„ 2Ti x ,notches 7 ,. type I C B wVso lid co‘er(loc king)
A type I CB
ie.o.c, t.- 1
-----' 40/sot d coke r
A 11111011ME lic3:11
aIIIIIIMIIII -41--
b 1 4 influent pipe(max design
in
if.•
III- Sr°
flow-A_0.5 C FS per trench)
il ,7,14 clean out we from pipe
In Oa;
irri a
g , . ..
ocAy to other
brarching CB's
PLAN as necary
NTS
I is-cx.c.
, I ,
pipe O.D.
gaheinized bolts
1}....0i-.. ...„....... .i..e....wit,-- 2"gra.de
2"xi2" `74,:::„;-,..0.-11.-31:7—~ 41,;„ 4 ° :ii•i;',Ni.g.'„/,
pnassure 2441.-2.1N1AeS VA C,.ti tv,ilY.,'S board notches 2"
treated grade 1 q ,,,f,Z. :,.. . . % .c; 4-ore?perforated
,...- ^..) 7 ° e 4 ..9 ,,r ,.PPIaii flat
• 1'' -
NOTES:
1'7.1- °•el'' 'cl.0 / ii..
4"x4 support post 7:,, Art ett,. clean 0.5%.t nes) 1.Th trench shall be construced so
4,,,,..-- *A v Vie-.3/1''washed rock
as 13 prevent point discharge andior
erosion.
ii ,. ....1.S r•
, . ."...." - -re.ii,-• 2.Trenches may be pled no closer
filter fabric than 50 feet fo one another(100 feet
°15% max tor licw ccrittolAwater qalong fbwili re)uality
3.Trench and grarl0 board must be
treatmr#in rural areas.
Aei.A Ign to follow contours of sie.
SECTION A-A 4.Support post spa.c ing as required by
NTS soil conditions to ensure g rade board
remains level.
L .
Figure 3.t6-Standard Dispersion Trench with Notched Grade Board
Volume 111—Hydrologic Analysis and Flow Control BMPs—December 2014
3-14