25272 PE-1206D SUMMERFIELD EAST .
RECEIVED
rt6 19 2001
SPOKANE COUNN ENGINEER
; STORMWATER TREATMENT
AND
- DRAINAGE FACILITIES
OPERATION & MAINTENANCE
MANUAL
SUMMERFIELD EAST, 4`h ADDITION, SUBDIVISION
Spokane County Plat No. PE 1206-78
USKH No. 679300
February, 2002
By
Wyatt Engineering, Inc.
1220 N Aoward St
Spokane, WA 99201
(509) 328-5139
4
STORMWATER TREATMENT AND DRAINAGE FACILITIES
OPERATION & MAINTENAIVCE MANUAL
~
1.00 PURPOSE
This document is intended to provide general operations and maintenance guidelines for the drainage
facilities located within the Summerfield East, 4`h Addition, Subdivision. Implementation of these
guidelmes will insure that the drainage facilities installed will function as intended in the design.
2.00 INTRODUCTION
Generally, the drainage system is intended to collect uphill offsite and developed onsite stormwater
runoff for treatment and subsurface discharge. The drainage facilities consist primarily of continuous
swales, catch basins, pipes and drywells. It is of the utmost importance to provide adequate operations
and maintenance activities to insure that the drainage facilities remain silt or dirt free, as this silt or dirt
loading will affect the performance of the drainage structures. If these facilities were to become
completely clogged, the only remedy would be complete reconstruction the drainage facilities.
Therefore, periodic maintenance is a must. A full set of engineering drawings is available for review at
Spokane County Public Works, under County file PE 1206-78. A site layout exhibit is provided in the
Appendix of this document.
3.00 GENERAL OPERATIONAL CHARACTERISTICS
The drainage facilities for Summerfield East, 4`h Addition are generally very simple, functional, and have
low maintenance requirements. A periodic visual inspection of the facilities will identify any required
maintenance. Most maintenance will consist of keeping the pipes, structures and swales free of debris
and sediment. A specific inspection schedule should be followed. See Section 4.0 for recommended
maintenance schedules.
3.10 Drainaee Structures and Storm Pioes
The onsite drainage structures include concrete gutters for collection and transport of
stormwater from the roadway, curb inlets for passage of stormwater into the swales, catch
basins for collection of excess runoff and pipes far transport of stormwater to discharge
structures.
The offsite drainage structures include a one foot interceptor berm along the north boundary of
the plat, two type B drywells, and 6" deep sump areas around each of the drywells. These
measures are for an additional factor of safety against flooding from the Zone B flood plain to
the north. These facilities are located in a 20 foot wide temporary natural drainage easement.
In the event that the boundary of the flood plain is revised or development occurs north of the
plat boundary, these drainage features may be vacated and abandoned.
STORMWATER TREATMENT AiND DRAINAGE FACILITIES
OPERATION & MAINTENANCE MANUAL
3.20 Stormwater Treatment Swales
Stormwater treatment swales were used in the design of the Summerfield East, 4' Addition to
provide treatment and storage for the runoff created by the development. The storage volume _
for each swale was designed to adequately treat the runoff created by the first 1/2" of rainfall on
the street impervious areas and driveway areas draining directly to the streets, within the
drainage basin it serves. The individual swale volumes provide water quality treatment to a
depth of 0.50 feet, in accordance with the '208' treatment requirements specified in the
Sookane Countv Guidelines for Stormwater Manaeement.
Each swale is enclosed within earthen berms. The floor of a"208" swale includes the level
portion of the floor of the swale and the sideslopes up to the outlet or overflow elevation. The
soil located in the floor of the swale shall be a medium to well draining material, with a minimum
infiltration rate of 0.5 inches per hour.
Swale specifications are provided in Table 3.20A. Additional information is provided in the
engineering drawings on file at Spokane County Public Works, file PE 1206-78.
Table 3.20A-Swale Specifications
Swale Swale Btm. Swale Btm. Treatment Outlet Berm
Label Elev. Area Volume Elev. Elev.
1 Varies 100 100 ' 2034.50 Varies
2 Varies 164 164 2033.90 Varies
3 Varies 166 166 2033.90 Varies
4 Varies 474 474 2035.25 Varies
5 Varies 190 190 2036.10 Varies
6 Varies 198 198 2036.10 Varies
7 Varies 212 212 2037.15 Varies
8 Varies 1,782 1,782 2036.45 Varies
9 Varies 1,316 1,316 2036.45 Varies
10 Varies 750 750 2034.50 Varies
STORMWATER TREATMENT AND llRAINAGE FACILITIES
OPERATION & MAINTENANCE MANUAL
3.30 Discharge Structures
Discharge structures include single and double-depth (Spokane County Standard Type A& B)
drywells, and are used to discharge stormwater runoff beyond the required treatment volume.
A copy of the Spokane County Standard Plan B-la Precast Drywells Placed in Swales is
provided in the Appendix for reference. These structures consist of a grated inlet, perforated
concrete barrel sections, and buned washed drain rock, wrapped in porous filter fabric. The
grate inlet elevation is set six inches above the swale bottom to provide "208" treatment storage.
The barrel sections and washed drain rock provide additional storage during infiltration. ,
4.00 MAINTENANCE REOUIREMENTS AND SCHEDULES
Below is a maintenance description for each of the drainage system elements contained within the
Summerfield East, 4`h Addition development, including the drainage structures, pipes, and swales. All
drainage facilities located outside of the County road right-of way, are expected to be maintained by
the homeowner's association; any drainage facilities located on individual residential lots are to be
maintained by the respective homeowners. Should the homeowner's association be terminated for any ~
reason, the maintenance responsibilities will become that of the individual homeowners, located within <
the Summerfield East, 4" Addition. ~
The homeowner's association shall provide to the Spokane County Parks Department and the Spokane
County Engineer the name, address, and 24-hour telephone number for the entity responsible for
perfornung routine and emergency maintenance inspections and repairs. This information shall be
confirmed on a yearly basis. The homeowner's association shall provide notice of any changes to the
Spokane County Parks Department and the Spokane County Engineer witYun 15 days of said changes.
General
Proper maintenance procedures are necessary for the continued functioning of the drainage facilities.
Improper maintenance, or lack of attentive maintenance measures, may result in negative drainage
impacts. It is strongly recommended that the homeowner's association designate an individual who will
be responsible for making sure the maintenance measures are implemented.
Generally, maintenance personnel are to conduct a visual mspection of the drainage facilities
immediately following a substantial rainfall event or snowmelt event. Substantial events include:
► Noticeably hard rain for a short period (30 minutes or more),
► Steady rain for a long period (6 hours or more), or
► Sigmficant rainfall and/or snowmelt when the ground is frozen.
STORMWATER TREATMENT AND DRAINAGE FACII.ITIES
OPERATION & MAINTENANCE MANUAL
For long duration storms, longer than 24 hours, maintenance personnel are to ulspect the drainase
facilities during the storm event to identify any developing problems and correct them before they ~
become major problems.
1. Inspect all roadside swales and drainage structures (pipes, catch basins and drywells)
to ensure they are clear of debris and obstructions.
2. Inspect all swale berms for breaches. Immediately repair any berm breaches with native
sandy soil, compacted in place.
The above noted storm related visual inspections are in addition to the maintenance schedules noted
below for each item.
4.10 Drainaee Structures and Storm Pipes
Catch basins and pipes should be inspected every 3 months, or after every significant storm
event and/or snowmelt event, wliichever is more frequent. Visually inspect the pipes, inlets and
outlets, making sure they are clear of debtis and checking that the pipe is in good condition,
without breaks or cracks. If there is any obstruction present it should be removed immediately.
A flow test in the pipe can be used to readily detect major obstructions or breaks in the pipe.
This test requires a water source (hydrant or water truck) and a person at the downstream end
of the pipe observing the flow exiting out of the pipe section.
All catch basins should be cleaned (vacuumed) every 3 months.
4.20 Drainage Swales
The drainage swales should be inspected every 3 months, or after every significant rainfall
and/or snowmelt event, whichever is more frequent. The swales consist of earthen depressions
constructed from native soils, enclosed within soil bernis. Each swale should be sodded and/or
hydro-seeded with a dryland grass mixture, at a minimum. A lawn sod can be used if regular
imgating is implemented.
Routine maintenance and inspections of the swale will include removal of any accumulated
debris, such as leaves, weeds and trash. Any obstructions which would not allow water to flow
freely from the swales via the discharge structures should be removed or repaired. Additionally,
the berms should be inspected to insure that they are in good repair and structurally competent
and that no outflow has occurred other than through the outlet structure.
STORiYIWATER TREATMENT AND DRAINAGE FACILITIES
OPERATIOlV & MAINTENANCE MANUAL
The homeowner's association shall be responsible for replacement of any grass turf and AV
underlying 1-foot depth of soil in swales whenever the vegetation appears to indicate a problem
due to contamination. The turf and underlying soil shall meet Spokane County requirements for
permeability and cation exchange capacity/organic content in effect at the time of replacement.
The Spokane County Engineer requires soil tests where average swale depths are greater that
six inches. One test each for cation exchange capacity and soil organic content per swale
bottom area 1500 square feet or less. Tests shall be performed on a well-mixed composite
sample consisting of the top six inches of soil from at least four cores uniformly distributed over
the percolarion area. If the average cation exchange capacity of the soil is 15 milliequivalents or
more per 100 grams, or the soil is 2% or more organic carbon, the soil will be considered
suitable for stormwater treatment.
4.30 Dischame Structures
The discharge structures should be inspected every 3 months, or after every significant rainfall
and/or snowmelt event, whichever is more frequent. These structures consist of a grated inlet,
perforated concrete barrel sections, and buried washed drain rock, wrapped in porous £lter
fabric. •
During routine inspecrion, if standing water is found 72 hours or more after the last significant
rainfall event, the infiltration structure is most likely clogged due to silt and sediment. The
structure shall be vacuumed of standing water and sediment.
5.00 Recommended Set-Aside Funds for Maintenance & Future Renlacement Costs
There will be annual maintenance costs, major renovation costs and future replacement costs of the
drainage facilities. These costs are the responsibility of the homeowner's association or successors in
interest. Major renovation and future replacement costs have been converted to annual costs, in the
form of recommended set-aside funds. It is assumed that '/z of the pipe and 5 of the 11 drywells will
need to be replaced within 20 years.
STORIVIWATER TREATMENT AND DRAINAGE FACILITIES
OPERATION & NIAINTENANCE MANUAL
Table S.OOA - Structure Replacement
%z Total Present Value I Future
Units Value~
Per Unit I Total I
5 $2,000 $10,000 $21,911
TOTAI.. I $21,911
Table S.OOB - Pipe Replacement
PVC 1/2 Total Present Value Future
Size Length Value'
Per L F. I Total
10" 55 $12 $660 S1,446
I TOTAL I $1,446
The estimated annual maintenance costs and recommended annual set-aside costs are listed below in
Table S.OOB. It is recommended the homeowner's association set-aside these amount of funds annually,
to ensure that adequate maintenance and replacement measures of the drainage facilities will be
implemented.
Table S.OOC - Maintenance and Future Replacement Costs
Drainage Facihty Annual Maintenance Annual Set-Aside Funds
Costs for Future Replacement or
vlajor Renovation
Drywells $500 $595
Pipes & Drainage Structures I$200 I$39
Sub-total Annual Costs I$700 I$634
Note (1) Assume repiacement in 20 yrs, wrth 4% mFlanon and a 6% rate of return on mvestments for set-aside accounG
Grand TotaUyear = $ 1,334
Cost per lot/year 53.36 (25 lots)
' Assume replacement in 20 yrs, with 4% inflation and a 6% rate of return on
investments far set-aside account.
TECHNICAL APPENDIX
SITE MAP
SWALE SECTION DETAIL
PRECAST DRYWELL DETAIL
CATCH BASIN DETAIL
INTERCEPTOR BERM DETAIL
. - - ~
~ ry
OOm
mMmN
INIERCFPTOtli AERM o z °p a m
-r
/Ip1 ~ GRAPHIC SCALE w sz~ o
~k ~ ± f~~, / ~ • ~
1 ~ fL
I L.'~~i! o ~ an tso ~y.
LDT 1 I i LOT 6 LOT 5 LOT 4 . LOT 3 Uy
~ - 4.1 { ~f F'EE'P )
- ~ 1 inch = 80 it. Q
4 18
LOT 2 ~
~ ~ ~ ~
.
~~,~p . ~ ~N~
~ ~~O,
~ ~A~y C
~
LOT 1 Ur =WO"
_ ~ y I oq ~b y z
LOT 3 ~I
: Q I LOT ZO LOT 9
Q ~ LOT 8
. 0 I LOT 7
l.flT 2 LOT 6
F-,,
LOT 31 i,o x U~
39 Fr RW LOT 5 E z ~
, a Ff SMENIx ,n rr cw„r .or. ; J I~ U] R4
10 Fr 511WE lY~'A
LOT 1 LOT 12 , LOT 4 ~ ~ H
z to w
smEWAIX , J J ~ ~ • ~ LOT 3 Z ~
~ I
swr~ #,3 \ MI D
fe+aa E
ST LOT 13 a 4 ~ \ ~ ~ W z ~
. . \ . / c~ . ~
DRAINAGE ANO SIDEWALK
EASEMENT
13.0' ALONG BURNS RD.
13.0' ALONG QUEEN AVE.
} 14.0' ALONG CROWN ROAD ~
n ~ 3
Z~ 0 8.0' ALONG BURNS RD. '
8.0' ALONG QUEEN AVE.
S2 8.0' ALONG CROWN RD. _
DRAINAGE EASEMENT
na
r~ 10.0' 5.0' OR 6.0'
Z CONCRETE
TYPE B CURB 5.0' FINISH SURFACE TOP OF SIDEWALK - IS 0.2' BELOW IS 0.1' BELOW
TOP OF CURB TOP OF CURB J
' NORMAL
LINE
0.5'wBELOW SIDEWALK
TOP OF CURB ' y- 4•~ , ~ ) ~ !'t _ 2% ~
i
.,::i ,,``"~,~1~ I~t~ `~'1
r~w A, 1
~ , / • ' • - • '
FINISH SURFACE OF ~ TOP OF SIDEWALK
SWALE IS 0.2' BELOW IS 0.0' BELOW
TOP OF CURB TOP OF CURB
~ BOTTOM OF SWALE
IS 1.2' BELOW IF SIDEWALK NOT
TOP OF CURB AND INSTALLED, CONTINUE
2.0' WIDE SLOPE AT 4:1 TO MATCH
' EXISTING GROUND.
~ ~ NORMALL~ OW LINE
SWALE CROSS-SECTION
NOT TO SGU.E
i
CSaENERAL NOTES pRYWELL BARREL OR
WATERPR0C7F CAiCH BASi14 WALL f GRAVEL BACI(FILL pUAFfTITY FDR URY1VELl,S . IJOiJ-SHfINIC PIPE {TYP } NdT~.
1'i'PE 'A' - 30 CLtBIC YARdS AqINIldl1Al ] 42 iCt15 GRQUT
TYPE "9" - 40 GY181C YRHpS MINIMLfhI ~ 56 TONS PVC PIPE ApkR7ER5 kEdD GASKET MAY VpRY
08 AS SPECiFIEp ON R0,4p pLANS IN SHApE Ah1L7 SPZE AS itLU$'fRATEp IN
2, SPELYAL 9ACkFRL kfATEiiIRL F[1R ORYI4ELL5 SfiALL CONSISi OF DETAI~ BY AGCEPTA~LE ALT~RNATE IN
WASF[ED CRAVEI. GRAOEp FFiQA1 1" Tp 3" Ik171{ A MAXI6A11F~ 4F SN, -9 a ACGORDANCE 153T}{ p g T y,~ _C_428
PASS€NG illE ll g yn 200 SCRE£N, A5 MEASUREb 9Y WEICHi GRSKET
A MAkI~tUM 0F fOx oF THE ACGREGATE, ,4S AiEASl1REp @Y VrEIGHT,
AIRY SE CR415HEp OR FRACiIIREO ROCK Y11E RE1AAiNING 9[]X VC AOqFTER ~s
SHALL BE NATURAI.I.Y QGCURRIPlG lJ}IFRACTUREo lAATERIAL PV1,~ AD AP TER
3 FABRIC SHALL BE !Ap[3ERA7E SlJRN7VR61L17Y AS 4llT1.1NEd ~~AI'YQ ~VLLA~}
IN STANpAFip SPECIFICATI6N$ 9-33
4 SEE 57ANDAR❑ pLANS SHEET5 6-2 AN❑ 0-3 FOft
PRECqST CONCRETE OETAILS
FA rAL FRkME TYPE 4
5 ADJUSTAtENT BI.OCXS SHA~.L 9E CEMENi CQNCRETE PAY LIMITS G ASE 7TpE 4 ~ MORTqft IN PLACE
6 PRECAST RISEft h{AY BE USfC} IN COMB1NqTIDN METkL FRAME
VATN OR IN LlEU OF ADJl15T1NG 13LpCl(5 dc GRATE ~ 7 WFiEhi PVC PIPE IS USEd A pVC ApAPiER SHALL BE INSTAiLED ~ ~ -
x `
YW ,
H PtP~S SFiALL BE 9ROUTEh Ih}TP URYWE~I.$ 70P 5011. ~ E_.~~MORTARE6 ApJCISTl.iENT
RIHG5
GRATE T1PE E 4 r5'PE 4
GFiAVEL 9ACI[FiLL
FAORiAR IN pLAr„E TD BE EQMPLEFELY 0
~ CO Ep YYli1-d FAARIC ,
-IHLET PiPE
-TOP SAIL
i•'-; , -~.-MORCARED
~ _ • z kD.kJSFAiEHT RINGS , I
CFiAV€L BAEKFILL
17-1
7Li BE COlAPLElELF'/ - 2
~y ~ A9RIC WITN ~ '-4' ~.-SEE N03E 7
GVER
SEE GEN r.
NOTE 1 dc ~tu
- .-INL.ET FIPE ~ GRqVEL I SEEPAGE Pf]R75
lo 9ACHFlLL, • ~ 5£E DE7RlL. SHT B-2 a
co
SEE GEN
HOiE 1 Ac 2 FRaRiC LINER
GRAVEL
BAGKFIIL,
~ r
~gE~pp p T E; serrI r
" t 5EE PETRIL~ESHE~i e-2 CL
jr FA6RIC LINER
7 6~ ~ MIM ° ~ ~C, 1
` `h ~ f ' ! ~ I - I
wNpISTUR9E0
SUfL ~Nll STl1R9ED
dRYWELL - TYpE 'R' SWALE ~ dR„YWELL - TYPE 'B' SWALE
SPO}CANE CpLIN7Y
~ ~ ~ ~to.Tl-~6b
~ ~ DEPART,+tEMT nF PLI~LEC W~RKS AoPPRO~VED d STAN[aHRp~ `aFiEEr
QATE cxo nPP i ~ saOc.we. Wti aasue 45e-saoa llllll PRECAST dRYYYELL5 PLACED !N SWALES
F ~~r"vr L ~-1Q
GENERAL NOTES
~ 1 CATCH BASIN SHALL BE CONSTRUCIED IN ACCORDANCE WiTH ASTM C 478 (AASHTO M 199) d~ AST)d C 890
UNLESS OTHERMASE SNOriN ON PUNS OR NOTED IN i}1E PROJECT SPEqAL PROV1510NS,
2. AS AN ACCEPTABLE ALTERNATE TO REBAR, NELDED 1MRE FABRIC HAVINC A MINIMUM AREA OF 012 SOUARE
VNCHES PEfi FOOT MAY BE USED. N£LDED W1RE fABRIC SHALL COMPLY TO ASi/A A 497 (AASHTO M 221)
o VARE fABRIC SHALL NOT BE PUCEO IN TI1E KNOCKOUTS.
1 N A A J PRECAST BASINS SHALL BE FURNISNED YAi11 CUiW15 OR KNOCKOUTS KNOCKOUTS SHALL HAVF A WALL
iHICKNESS OF 2' MINIMUM.
tV ~
4 KNOCKOUTS SHALL BE ON ALL 4 SIDES N1iH MAXIMUAI DIAMEiER Of 20". KNOCKOUTS SHALL 8E RWNO.
NO 3 BARS (TYPICM.) F1PE SHALL BE INSTALLEO IN FACTORY SUPPUED KNOCKOUiS.
(NORIZONiAL) 5 KNOCKWT OR CUTWT HOLE SIZE IS EWAL TO PIPE WTER DIAAIETER PLUS CATCH BASIN WALL THICKNESS
L--..1 6. 1HE MA)tl1AU1A DEPT1i FROM THE FlNISNED GRADE TO THE PIPE INVERT IS 5'-0'.
1
I 7 1NE TAPER ON 1HE SIOES OF THE PRECAS[ BASE SECRON AND RISER SEC110N SHALL NOT EXCEEO I/2'/FT
~ S. CATCN BASiN fRAME AND GRATE SHALL BE IN ACCORDANCE YA1H 5lANDARD SPECIFlCAt10h AIATINC SURFACES
-~-i o~ SHALL BE Fl~JISHED TO ASSURE NON-ROq(ING FlT.
V 9. FRAME AND qtATE MAY BE INSTALLED VAiN FLANGE DOWN OA CAST INTO RISER.
1'-10' ~ 4 =
• 10. YMEN PVC PIPE IS USED, A PVC ADAPTER SHALL BE INSTALLED.
2-8• . ~ 11. PYC ADAPtER SHALL BE CRWTED INTO CATCN BAS1N.
PLAN
--F- ~ -
NO 3 BARS (TYPICAI)
/ o J \ N0. 3 BARS (TYPICAI.)
(YERi1CAL) (vERncnL) .
10' PIPE
loo ro (AIIN )
n n ~
- - _ ~
~ ~
z '
~ in
-Z. N I Z_ -Z. ~
2-
-i- ,
-4' C-10' -44 Z•_y' I..44
2'-6' 2'-10'
SECTION A-A SECTION B-B
SPOKANE COUNTY APPROVE S7ANOARD sHEe~'
DEPARTMENT OF PUBLIC WORKS c-~~ ~ CATGH 6ASIN TYPE 1 B-4
~ 51'OK1JlE. NA. VY20E I3E-3600 OA m.n~.~
}
~
CONSTRUCT 1.0' ~ o
HIGH BERM AT ~ m
LOC P11~ONN SHOWN Z g
~ a
0
/
/
EXIS77NG
GROUND
/ 5' MINIMUM ~
0 INTERCEPTOR BERM DETAIL
N TS
SP
i