PE-1885 PRAIRIE ORCHARD DRAINAGE REVIEW FIRST SUBMITAL
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SMKME COUNlY 'S OFFHC'0 TION & MAINT ~ ~
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DR~~NAVE PVNDS
OPERATIC?N & 1VIAINTENANCE
MACV UA'L
Prairie Orchard
CLC #5Q24180
►4ugust, 2002
By
' C.L.C. Asseciates, lnc.
' 707 W. 7t' Avenue, 5uite 200
5pakane, VVA 99204
(509) 458-6840
STORMWATER CON►JEYANCE AND L7RAFNAGE P0NDS
vPERATIoN & MAINTENANcE nnANuAL
1.00 F'lJRP05E
This document is intended fo proVide general 6perations and maintenance gutdelines for the tlrainage
canueyance systems, pands and ofher drautage faciGties Iracaied within the Prairie Orchard plat
lmplementatian of these gu"sdelines wdl insure that the drainage facilities installed will functtvn as intended
in the dessgn.
2,00 INTRC70l3CTlC]N
General6y, the drairrage system is jnte-ndd to collect upgradient stacrnwater runofF and convey it through
the deaelapment to one of~even of the starace nds The drainage facdities consist primarily of a series
of ansite drainage skructures, starm pipes, treatmenstorage ponds, and infiltration structures It is of tfae
utmost importance ta provide adequate aperations and mamtenance actiutties to insure that the drainage
facilities remain 5ilk Dr dirt tree, as this silt or d'srt loading wili affect the performance of the starrn pipes,
ponds and mfiltration structures. If these fac'slities were #a became cQmpletefy clogged, the Qn9y remedy
wcauld be complete reconstruction the drasnage fac"slsties. Therefore, periodic maintenance [s a must. Afull
se# of engineering drawings is available for review at Spokane Coursty Public Works. A site layaut exhibit
is pravided in the Rppend6x of th'ss document
3.40 GENERAL C3PERAYfDNAL CHARAGTERISTlCS
The drainage faGilities for Prairie Orchard are very sirrrple, funct'svnal, and have fow maintenance
- requirements A perrodie visual inspection of the faciiities wdl identify any required rnaintenance Mosf
mainfenamee wdl consESt of keeping the pipes, structures and ponds free of debris and sediment A
specifie inspeetEOn schedule should be followed See Section 4 0#or recommended maintenance
schedules.
110 Drainaae Structures and Storm PcaeS
The onsite drainage con►reyance system includes concrete gut#ers, curb inlefs, concrete infets,
and 12" PVC starm pipe. Concrete gutters cflnuey the onsite runoff, collec#ed En the streets, ta the
treatmentlstorage swales, lacated on 3 of the 7 residential iats.
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iICLC.4ssocrafes Page ? of 5 Prairie Qrchard
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STDRMWATER G€]NVE1(ANCE ANQ DRAINAGE P'vNdS
OPERATION R MAIN7ENANCE MAhIIJAL
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3.20 Dramacie Ponds
Stormwater storage pands were used in the design of the Prairie C}rchard plat to proaide starage
for ihe runoff created by #he deveEaprrrent. The storage volume for each pQnd was designed to
adequateiy cvntain the runaff created 50-year storm eaent within 4he drainage basin it senres
Each pand is enclosed within earthen berms The pand uaEume includes the level partion vi the
flave of the swale and the sscieslopes up to the outlet Dr overflow eleuatian. The sail located irr the
flooc af ttse swaee shall be a medium to well draining material, with a minimurn infi3tration rate of
fl 5 mches per hour.
Pond speei#icat'sons are provided in Table 320A. Additional in#or is pravic3ed gn fhe
ersgirseering drawings on file at Spokane County Pubfic Works, fde PN 1658-9~
Tab1e 3 20A - F'and Specificatians
Pvn~ WEle Btm 6tm. Treater~utlet Bern~
Label v. ~~SF~~ Volume(§jFA) Eleu, Efer~.
A 2033.59 v~ 34{} ~ 284 ~ 2034.2+6 2035.49
B 2051.00 VI 750 f 583 I 2051.66 I 2052.32
C I 2037.54 \II 340 " 277 I 2039.00
330 Infd#ratian S#ructures
Ponds A and Beach have one dvuble-depth (Spo9caroe Cnurrty 5tandard Type B) drywell, and are
used to infiltrate starmwater rianoff beyond the required treatment aalume. A copy of the Spvkarte
County Standard Plan B-1a Precast Qrywells Placed in SwaPes is prflvided in fhe Appendix far
reference. These structures cortsist of a grated irrlet, perforated corscrete krarrel sections, and buried
washed drain rock, varapped in porous flter fabric. The gra#e inlet elevation is set eight InChE5
aboae the swale bottom fa provide a stifling basin below the overfEor+v elevatinn of the drywel6 grate.
The barrek sections and washed drain rack prvvEde additional stvrage during 'snfil€ration.
4.00 1VI►41NTENAIdCE REflUIRE{YIEhITS AND SCHEDCJLES
8elaw is a maintenance description for each of the drainage system elements cnntained within the Prairie
Orchard plat, including fhe drainage structures, pipes, grate: inlets, ditches and ponds AiC drainage facilities
Qacated outside af the County road nght-of-way, are expected to be maintained by the homecawner's
aS5[7Cfr3tlOf1a any drainage bwAAL-s lacated on individual reside 'r~f~a1 lQts are o t~e maintairsed by the
respectiue V~ameovuners. ould the homeowner's association be terminat~d for any reasan, the
maintenance responsi4ilities will hecame ~tCl~ in ivditl~ '~r~or~ae~ , ted within the Prairie
Orchard pfat
The harneowner's associatirsn shall provide to the Spokane County Parks aepartmen# and the Spokane
- +County Engineer the nar'ne, address, and 24-hour telephone number for the entity respansible for
CLC Assacrates Page 2 af 5 Prarrle Orchard
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' STORNfWATER CC]NVEYANCE AN0 L]RAINAGE PQND5
❑PERATION 8 MAfNTEtiANCE MANI]AL
perForming routine and ernergency maintenance irrspections and repairs. This information shafl he
eonflrmed dn a yearly basis The hQmeowner's assaciatian sha91 prodide notice of any changes to the
Spokane County Parfcs Depar#rnent and the Spokane County Engineer within 15 days of said changes
, General
Proper maintenance proeedures are necessary for the continued functianing of the drainage faCIIItleS.
lrnproper rnaintenance, ar lack of attentive maintenance measures, may result in negative drainage
' impacts. It is strongly recomrriended that the homeawraer's associatEon designate an individual who wdl be
respnnsible for making sure the maintenance measures are implemented.
Generally, maintenance persflnnel are tv conduct a visual inspection of the dramage facdifies rmmediatefy
fallflw"sng a substantial rainfall euent or snowmelt event Substantial euents incaude:
• Noticeabfy hard rain for a short period (30 minutes or more),
■ 5teady rain for a long period (6 hours ar more), or
► 5ignrficant ramfall andlor snowmelt when the ground is frvzen.
Ferr [ong duratiora storrnS, 9pnger than 24 hours, maintenance personnel are ta inspect the dramage
facdities during the storm euent ta identify any developing problems and corceci them before they became
majar problems
1 Inspect aE[ roadside ditches and drainage structuFes (catch basins and drywelfs) ta ensure
they are cfear af debris antl obstructions.
2. Irsspec# all pond berms and retaining wa1ls for breaches. Imrnediately repair any berm
breaches with native sant€y soil, carnpac€ed in piace, and wall breaks wi3h rsew eoncrete
black5
The above noted storrri related visual snspectivns are in addition to fhe maintenance schedules noted
below far each item.
4.10 ❑rainaae 5tructures and Storm PaDes
Cateh hasins and p'spes shauld be inspected every 3 months, ar aTter every significant starm eaen#
('la') andlcsr srrowmelt event, whichever is more fcequent Uisually inspect the pipes, infets and
outlets, making sure they are clear of dehns and checking that the pspe is in good conditian, withou#
breaks Qr cracks. If there is any obstruction present i4 should be rernoved immediately,
Aflow test in th€: pipe can be used to readily detect rnaJar obstructions ❑r breaks in the pipe. This
test requires a water source (hydran# or water truck) and a person at the downstceam end af the
pipe Qbseruing the fPaw exoting out af the pipe secfion.
E#fl catch basins should be cleaned [vacuumed] every 3 mortths,
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CLC Assocrates Page 3 of 5 Prarrie C7,rchar[`f
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~ STC3'FtMWATERC{3NVEYANCE ►4NCI DRAINAGE P[3N'DS
{3F'EF2AT!❑IV & MAINTENANCE MANUAL
, 4.20 Drainaae Ponds
The drainage ponds shoufd he mspected every 3 m[anths, or affer eyery significarr3 fainfall andlor
snowmelt event, whschever is more frequent. The pQnds cansist of earthen de,pressiorts eonstructed
fro►n natiVe soils, enclosed within soil berms andlor black retaining walls. Each porcd should be
sadded andfor hydra-seeded with a drylancf grass mixture, at a minirraum A lawn sod can be used if
regufar irrigating ss implemented.
Routirre mamtenance and inspections af the pond wilf inolude removal af any accumulated debris,
, such as Ieaves, weeds and trash. Any+ nbstructions that wouEd nnt a1faw water to ffaw freely from the
ponds via the outlet structures or overflow berms shauld be rerrooved or repaired Additionally, the
berms and block walls o€ fihe ponds shauld be inspected to insure khat they are in goad repair and
structurally competent and that n❑ oui#low has occurred a'lher than through the outlet structure ar
overflow berm
The homeawner's association shall be respflnsible fer replaceri'ient of any grass turf and underlying
'i-fomt depth of soib sn pands whersever the vegetation appears to mdicate aprob9em due to
contaminatton. The turf arrd underlying soil shall rriest 5pokane County requirements far
permeability and cation exChange capacitylorganic cantent irs effect at the tame of replacement
430 fnfiltratian Struciures
The infiliration structures should be inspected every 3 months, or after every signifiCant rainfall
andior snowmelt event, whicheuer is more frequent Thsse structures consist flf a grated inCet,
perforated cancrete barrel seGtions, and buried washed drain rack, wrapped in pornus f3lter fabric.
During routine inspect4on, if standmg water is found 72 hours or more after the East significant
rainfaH euent, the infiltratian struct+sre is rnast likely clogged due ta siBt and secliment The structure
shall be aacuumed of standing water and sedimen#
5.00 Recommended Set-Aside Funds
for Maintenance 8 Future Replacement Costs
There v+nll be annual maintenance costs, major ren4vafion costs and future replaeernent eosts of the
drainage facilities. 7hese costs are the responsibil'sty of the hameowner's assoc'sation or swccessors in
interest. Major renovatiorr and future replacement costs have been converted to annual costs, in the forrn
of recommended set-aside funds. !t is assumecf that %x of the pspe and one dcyweEl wall need to be replaced
, within 20 years
CLC Associates Page 4 of 5 Pra►rre Orchard
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STORNlWATER CONVEYANCE AND DRAINAGE P[7ND5
(3PERATION & MAINTERIANCE MANI!AL
Tabls 5 ODA - Pipe Replace~ent -
Pipe I'2 Tota1 Present Valrae Annuak Set-
5ize Length Per L. F. Total Aside Cost
12" PVG I 10 I $3.30 $ 33.D0 $ 2.00
f
TCD7AL $ T.40
The es#imated annual maintenarsce costs and recornmended annual set-aside costs are listed below in
Table 5 L30B lt is recorr►mended fne homeawner's associaEion set-astcie 1hese amount of funds annually,
to ensure that adequate enaintenance and replacement measures af the drainage facilities will be
implemented.
Table 5.C1(3B - Maintenance artd Future Reqlacement Costs
Drainage Facility Annual Maintenance Annual Sek-Aside Funds for ~
Cmsts Future Replacement or
Major Renovation
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Onsite Pipes & 'Drainage StruGtures I $100 I $64.00
Drywefls - Spakane Coun#y Type B I $ 1oCD I $ 60.0t]
Sub-total ►4nnuak Costs
$2047 $1 24.(10
iVate: (1) Assurne replacement in 20 yrs, wiCh 4°Ia inflation and a6°'o rate of return on investments
for set-aside accaunt.
Grand Tvtallyear = $ 326.00
Cast per Iotlyear = $ 46.57 (7 lats)
CLC Assacrafes Page 5 of 5 Prairie Drchard
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GENERAL. NOTES CATpH BASIH 4YALt
WATERRRObF ~ PIPE ~~'1'P.)
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1. GRRVEL BAC7CF7LL OllAkT1T1' Fot DRYwELtS : MC]N-SHRIH!( J
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£ "A' r SD ~91C YAR05 AIIHIAd1JM / 42 '~Ot1S, GR~T ~r 1 PVC PtPE AI3lIpdERS ANO CASKET AlRY VARY ,
TY~E *B' -+l0 C11~G YARQS AtIH1hIl7Ai TDHS. ~ IN SHAPE ,~tp $IZE A3 Il.LUSTRATF[) !M
flR A$ SPE~F1~p pH q9Ap RIAH$. ~ QETAIL gY ACfEPTABCE ALTFRNRTg W 2'5PEdAl BApfflLL MA§ER1AL F'qR ORYME4L3 SHhU, CONSI5T OF AGC(7RaANCE WEiH A 5 T ki -C-428
WASHEQ GidVEl GRADEfl FRaFI k' TD 7' WI'!}E A fdA3(IlAi7Ai OF Sx -
PASSINC THE U.S. Ne. 200 SiRE£H. AS kFA5URE0 BY NEfpi7 11S14~T
A YAJGIACJdi (PF' 10X ~ THE kCCRECAiE, +A5 IrtEkStl~ 9Y lVE1L~l?. 'IAC AdAPTER
~i u e~N r ~~a~~ u~Ac~ ~~A~~~u..~°" F VC ADAPTER
J. FA9MC SHAS.L 8E IdOOp3ATE 511R►RVABtIJTY AS OJTLINE4 ( LL A
aN STAMdkRO SPe~'iF7CA11Ck5 9-33 ,S N D
4. SEE STRFIpARp PLAHS SHEETS 8-2 ANp 9-3 FOR
RRECAST CDNCtETE OETAllS. I fET~ FflAAIE T1?E 4
S. ApJ615Tl~IENT BLOC.lSS SHAL1 6E CEkIE'IT G~CRETE. PAY LdA[ITS CRA TYPE 4--- 1.4ORTAR IN PLA{E
8. PRECA$7 RISEI! 6AAY BS VSED IN L4Al91HkTiOH METAL FRAME -
W1TH (1R fH LIEU OF IUldFSTIHC SLOCfS. k CRATE
7, wHQN PVC PfPf 15 i1SED A PVC AORPTER Si+141, BE IHSiAL.1.E0. 3
TOP SOIL faRTAREf1 ADXST}aE~lT
PfPES SkA11. R~ GROl1TEG fHTD f1FiY4jiELLS. ;RUNCS
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CRAti T1'P~ iTYPE 4
I CRAVEL BAdCFIIL 2''0'
AIORTA11 W FLACE TO BE SOAfPL.EiELT
~ a GO Et] M1TH FABRIC ;
~ }Y [NLET pIPE
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cxlAVEI BACKFILL C3 ~ .
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FABRIC LI~tER
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S~L SNRHEiS sruReco
DRYWELL ~ TYPE 'A' SWALE D YWELL TYPE '8' SWALE
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sPVKArrE caurrrr
DEPARTTAdENT ~]F PU6LIC WaRKS ~ IRO~ sTANQ~RD sHesr
1cm i ~I'~f14 ~e+a~c. ~+0acs 4se-~ o~~, , PRECAST DRYWELLS PLACED IN SWALES e'~e