PE-1885 PRAIRIE ORCHARD DRAINAGE REVIEW FINAL REPORT (2)
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CLG A55OCIATES
D E N V E R
5 P O K A N E
5ALT LAKE CITY
1~~~~~oz
FI~AL
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OPER►A►TION & M~INTENANCE
MAN UAL
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Prairie Qrchard
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STo~MWArER CONvEVANCE
AND
DRaINAGE PoNDS
' OPERATION & MAINTEIVANCE
NiANUAL
Prairie Orchard
CLC #S02016Q
[]ctgber, 2002
_ BY
C.L.C. ►Associates, Inc.
707 W. ith Avenue, Suite 200
Spokane, WA 89204
, (509) 458-6840
; SrfiORMWATER CQNVEYANG'E ANf] DRAINAGE PONDS
' OPERATI[7N & MAINTENANCE MANl7AL"
1.0D PURPOSE
, Thrs document is intended to prcrvide general operations and rnaintenance guidelines for the drainage
, canveyance systems, Pands and ather drainage facilities lacated within the Prairie qrchard p4at.
fmplementation of these guideimes will insure that the drainage facilities installed will functign as intended
in the design.
;
2.00 INTRaDkJCTIORI
Generaily, the drainage system is intended to callect upgradient storrnwater runoff and convey it through
the development iv one of seven af the s#orage ponds. The drainage facdities consist primarily of a se►ies
of onsite drainage structures, starm pipes, treatmenllstflrage ponds, and tnfsltralion structures. if 9s of dhe
utmost ieraportance tcs provide adequate aperatians and maintenance actiuities to msure thaf the drainage
facilitres remain silt or dirt free, as this silt or dirt loading will afifect the perfarmance of the storm pipes,
ponds arrd infltration structures. [f tYaese faalities were to become corrsple#ely clogged, the anly femedy
would be cornpiete reconstruction tFse drainage facditses Therefore, periadic mamtenance +s a rnust A fufl
seC of sngineering drawmgs is avadabCe for review at Spakane Caunty Pubfic ►JVorks Asite layou# exhibit
is provided in the Appendix vf this document.
3.00 GENERAL C}PERATiONAL CHARp►CTERISTIGS
The drainage facilities for Prairie Orchard are very simple, funct9ona[, and have low maintenance
requirements. A periodic visua4 inspection at the tiaGifities will sdentify any reqvired maintsnance. Mast
maintenance will Corrsist o$ keeping the pipes, structures and' ponds free of debcis and sedirnent. A
specific inspection schedule should be fallowed See Sectian 4 Ci fnr rec❑mrriended rnaintenance
schedules.
3.10 Drainaoe Strwctures and 5torm Piaes
The ansite drainage conveyance system includes concrete gutters, curb inlets, concrete mlets,
arsd 12" PVC storrn pipe. ConGrete gutters convey the ransite runoff, cpllected in the streets, ro the
treatrnenUstorage swales, located on 3 of the 7 resiclenEial Iots.
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CLC Associates Page ? af 5 Prarrie CJrcl7ard
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STQRMWATER CONVEYANGE ANU DRAIN►4+GE POND5
OPERATION & MAIIVTENAhECE MAN13AL
3 26 ❑rainacie Pands
5tormwaier starage pands were used 3n the design of the Prairie Orchard plat ta provide starage
for the runoff created by the der+elopment. The storag$ volume for each porad was designed to
' adequately coniain the runaff created 50-year storm everrt within the dramage basin it serves.
Each pond is enclased withm earthen berms. The pvnd volume 3ncfudes the ievel portian nf the
iloor of the swale and the sideslcapes up tv the Qutlet mr nver-flow elevation. The svil Imcated in #he
ilaor of the swale shalE be a rnedium to weil drainirrg r-naterial, wifh a rniraimum infltraiiarr rate pf
0.5 inches per hour
- Porsd specificatians are provided irr TabPe 3 20A Additional informafion is prflvided in the
engineering drawings on fle at Spokane Caunty Public Warks, fde P-1885.
Tahfe 3.20p - Pond Specificatinns
p~id Pa~c! ~t~rn. Pvrrd S'tm. Treatrr`re~t O~utl`~t ' B+e~m
Lab.effl E vgIIIIIIIIIIIIIIIi r!~rea(+;SF) Ko~uWe (CF} Eleu. Elev.
A 2034.32 340 284 2035.00 2035.59
B 2051.00 75(] ~ 583 ~ 2051.66 I 2{]52.32
C ' 2037.77 340 277 2{]38.44 2039.62
_ 3 30 InTltratian Structures
Ponds RI and B each have one double-depih (Spakane County Standard Type B) drywell, that are
used ta infiltrate stormwater runaff beyantf the required treaCsnent volume. A capy af ths Spokane
County Standard F'lan B-aa Precast DryweJls Placecf irr Swales is prouided in the Appendrx tar
refererrce. These s#ructures corrsist of a grated inlet, perforated concrete barrel sections, and buried
washed drain rock, wrapped in porvus flier fahric. 7he grate inlet eleVation is set eight inches
aboVe the swale bottom to proaide a stilling basin bel6w the rsverftow e1evation o€ the drywell grate.
The barrel sec4ions and washed drain rock provide additiona9 starage during unfiltration
4.00 MAINTENANCE REQFJIREMENTS AN❑ SCHEDULES
BefQw is a maintenance description fvr each of tYre drainage system elerraents coniamed vvifhin the Rrairie
Drchard plat, including fhe drainage structures, pipes, grate inlets, ditches and ppnds Afl drainage facrlitiss
IoGated outside of the County road right-of-way, are expected ta be maintained by the homeowner's
assvciation. 5hould ths hvrneowner's associatiqrr be terminated for any reasQn, #he mairrtenanGe
respansibilities wi31 beceame that og the 'sndividual hameawners, Iocated within the Praicie Orchard plat
The hameowner's association shalE provide to the Spokane County Parks Dsparfment and the Spokane
Gounty Errgineer the name, address, and 24-hvur telephone number #or the entity respansible far
performing routine and emergency rnaintenance inspections and repairs Thris infarmatian shal1 be
eonfirmed on a yearfy basis. `fhe hQmecswner's association sha91 ,pravide natice of any changes tca the
Spakane Counfy Parks ❑eparEment and the Spokane CQUnty Engineer within 15 days of said changes.
~ CLC Associates Page 2 of 5 F'rarrie Qrchard
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STORMWATER CaNVEYANCE AND DRAINAGE PONDS
- (JPERATIQN & MAIN~ENAiVCE MANU►4L
Generaf
Praper maintenance procedures are necessary for the corrtinued functioning of fhe drainage facdities
Improper rnarntenance, or iack of attentive maintenance rneasures, rnay resuft in negative drainage
impacts ft is strangly recommended that the homeowner's assaciatian designate an individual who wili be
respansible fnr mafeing sure 3he maintenance measures are implemented
Generafly, maintenance personnel ase to conduct a Visual inspectian rsf fhe drainage facifities imrnediately
faflowing a substantial rainfaN event nr snvwmelt event SubsEantial events include
■ Nnticeably hard rain for a short period {30 minutes or more},
• Steady rain for a long period (6 haurs or rnnre), or
' ► Significant rainfalE andlor snowmelt when the ground is frozen
For long duration starms, fonger than 24 hours, maintenance persannel are to inspect ihe drainage
fscdities durirtg the storm event ta identrfy any deve4aping problems and correct them before they becorne
majar problems.
; 1 fnspect ail roadside tiilches and drainage structures {catch basons arid drywells} t❑ ensure
they are csear oE debris and obstructions.
2. Inspect a!I pond berms and retaining walls fos breaches. Emmediately repair any berrn
breaches with native sandy svil, campacted in place, and wall breaks with new concrete
block5.
' The above noted sform refated Visuak InSpeCtIpf15 are in addition to lhe maintenance schedules n4ted
beiow faE each ife►n.
, 410 Drainaae Strractures and Sform Piqes
Catch basins arrd pipes shauld be irrspected every 3 monthS, or after evEry 5ignificant starm evenf
andlor snowmelt event, whichever is mnre frsquent Visually inspect the pipes, 9nlets and
outlets, making sure they are clear nf debris and checking that the pipe is m good condition, without
breaks or cracks. If there is any obstruction pcesent it should he rernoved immediateCy,
- A f[ow test in the pipe can be used to readily detect majnr obstructivrss or breaks in the pipe. This
test requires awater source (hydrant or water truck) and a persnn at the downstream end of the
pipe nbserving the flow exiting ❑ut of the pipe section,
' all cateh basins shauld be cfeane[f (vacuumed) every 3 months
CLC Assoc►aiss Page 3 of 5 Prairre C?rchard
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i i STORNfWATER Cq'NVEYANCE AND l3RA[NAGE PONaS
OPERATiON & MAIiVTEIVAHGE MANUAL ,
~ 4.20 ❑rainaoe Pnnds
Yhe drainage ponds shouid be inspected every 3 m4nths, or after every signifrcant rainfall andlor
snvwmelt eWent, whichever rs more frequent The ponds consrst of earthen depressioRS cvnstructed
from native soies, enclosed withirr soil berms andior block retainmg walls. Each pond shouCd be
- svdded andlor hydro-seedsd wi#h a dryfand grass mixture, a6 a mmimum A lawn sod can be used if
regufar irriga#ing is implemented.
_ Routins mamtenance and inspectians of the pond will include removal Qf any acc€amusated debris,
such as Ieaves, weeds and trash Any obstructions that wauld nnt allaw waker to flow freely frarn the
ponds uia the outEet structures ❑r oVerflaw berms should he remoaed or repaired. Addilionafly, the
berms and b1cack walls of the ponds should be inspected to irrsure that #hey are in gond repair and
structurally competent and that nv ouiflow has occurred ather than thrnugh the outlet stnacture or
overflow berm.
The homeovvner's assacration shall be responsihle fvr replacement of any grass lurf and underlyirsg
1-foot clepth of soil in pvnds vvheneuer the aegefatEon appears tQ indicate a probZem due to
, cnntamination The turf and underlying soif shail meet Spakane County requirements for
perrneability and cation exchange capacitylorganic cantent in effect at the time of replacement.
_ 430 Infiltration Structures
' The in#iltratian structures shvuld be inspected every 3 months, or after ewery significant rainfall
andlor snowrnelt event, whichever is rr-rore €requeni. These structures consist of a grated iniet,
- perFarated concrete barrsl seetinns, and buried washed drain rock, wrapped in porocss filter fabric
- Qurmg roukine inspec#ion, if standing water is found 72 hours or more after the last significant
rair+fall event, the infiltrafivn structure ss masE likely cCogged due to sslt and sedirnent The structtare
shall be reacuumed of sfanding water and sediment.
5.00 Recommended 5et-Aside Funds
far Mairrtenance 8 Future Replacement Casts
There wdl be annual maintenance Gosfs, majar renavation costs and future replacement costs af the
drainage facifities. These costs are the responsibdity o# the horrseowner's associatian or successors in
interest. Major renQvaiion and future replacement costs have been converted to annual costs, rn the forrin
Qi recomrnended set-aside funds. C# is assurrred that %of ihe pipe and one drywell will neQd to be replaced
within 20 years.
CLC Assocrates Page 4 of 5 Prairie Urchard
STORMWATEE: CD'NVEY►4'NCE AMD aRAINAGE PQNDS
OPERaaFON a MA:NrENANcE MaNuaL
Tabfe S.OClA - Pipe Replacement
Pipe Y2 To#af Present Vaiue pnnual Set-
Size Length Per L.F. Total Aside Cost
12" P11C 10 $ 3.3D $33.00 $2.00
' roraL $2.00
- The estimated annual mamtenance costs and recommended annual set-aside costs are fisted he[aw in
Table 5.0013. Et is recommended fhe hvmeflwner's association set-aside these amount of funds annually,
tv ensure that adequate maintenance and replacernent measures 4f the drainage (acilities will be
implernented
7abPe 5OflB - Mairrienance asad Fufure Replacement Costs
Drainage Facility Annual Mainienance Annual 5et-Aside Funds for
Cvsts Future Replacement ar
Majvr Renvvativn
C3nsi4e Pipes & arainage Structures I $100 I $84.00
flryvveNs - 5pokane County Type B I $ 1QQ I $ 6D.a0
5ub-total Annual Cos#s
$200 $124.00
- Note: (1) assume repfacement ira 20 yrs, with 4% irrflahon and a 5°/o rate vf return crn Envestmenfs
for set-aside account.
{Grand Tvta1lyear = $ 32B.Q0
Cost per lotlyear _ $ 46.57 (7 Ints)
CLC Assocr"afes Page 5 rsf 5 Prairie grchard
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Tl'PE 'B' - 40 CU91C TARpS A11N1MUN / g$ '{ONg, PVC PIPE ADAPTEfdS AHp CASiiET MAY VARY
Oi AS SPECJFIE4 OH R0+1D PLAl15. _ PN SHAPE ANO SIIf AS ILLUSTRATEp fk
a SPECIAL gApCfYLL MqTEUA1. FOt QRyyEL,5 SiALL GONSISY OF DETAIL BY ACCEP4ABLE ALTERNATE !N
AGCORDANCE W1TH
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RRECAST CCiAlCdifTE DET►uLS. F~ T~ }'RARSE TYFE a ~
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IUYICK spaems. +r.k mve 456-36m n~ y.PRECAST 0Ft'fYlEl,LS PL'a4CED 1N SWALES B-1a
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SPOKANE
707 200 SFIOKANE 99204 - 509 458 6840 509 4SB 61344