PE-1885 PRAIRIE ORCHARD DRAINAGE REVIEW SUBMITAL 2
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CLC A55OCIATES
D E N V E R
S P D K A N E
SALT LAKE CITY
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~ ~~INTENAt4CE
+DPERA►TIt)I~
- MANIJAL
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prairie C~rchard
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_ STO'RMWATER CONVEYANCE
' Ahl D
DaAINAGE PONas
OPERAT[ON & MAINTEIVANCE
MANUAL
Rrai rie Orchard - GLC #5020160
- I • 5eptember, 2002
By
C.L.C. Associates, Inc.
707 W. 3'" ►4venue, Suite 200
Spakane, WA 99204
, (509) 458-6840
STORMWATER CONVEYAIdCE ANa ❑RAINAGE PONQS
OPERATIDN $ MAINTENANCE MANlJAE.
1.00 PURPVSE
This document is intended to prvvids generai aperatians and maintenance guidelines far the drainage
conveyance systems, ponds and other drainage facilities IQCated within the Prairie Orchartf pfat.
lmplernentatinn of these guidelines wdl irrsure that the drainage facilities irrstalled w61l €unction as intended
in #he design.
, 2.00 1NTi3OOUCTlOhl
~
Generally, fhe drasnage ska mtended ta coflect upgradient starmwater r~anoff and cnnVey it fhrough
the deVelopment to one o f the storage ponds. The ~iramage facilities consist prirnardy Qf 2r series
of onsite drainage structum pipes, treatmentfstarage ponds, and infiltration structures. I# is af the
, utmosf importance to prpvide adequate aperations and maintenance activFtiss ta insure that the drainage
facilities remain silt nr dirt free, as fhis silt or dirt loading will affect the performance of the storm pipes,
ponds and infiftratican structures. Ig these facilities were to become cvmpFetely cfngged, the an1y+ remedy
would he complete recQnstrucEiQn the drainag€; facdities. There6oce, periadic maintenance is a must. A full
' set of engmeering drawings is available for rev6ew at 5pokane County+Public WQrks A site layout exhibit
is provided in the Appendix of this documerrt
3.04 GEIdERAL OPEFiATI❑NAL CHARACTERISTiGS
The drainage facilities for Prairie Orchard are very simple, €unctional, arnd have inw maintenance
reguirements. A periadic Visual inspection of the facilities wEli iden#ify any required maintenance. Most
maintenance will consist of keeptng Ehe pipes, structures and parsds free Qf debris and sedimertt. A
specific inspecfion schedule shou1d be fo9lovaed. See 5ection 4.0 far recommended rnaintenance
SChBdLilES.
3.10 €7rainaqe Structures and Storrn Pioes
The ansite dramage cflnWeyance system includes corrcrete gutters, curb infe#s, cancrete inlets,
and 12" PVG storFn pipe. Concrete gutters convey the ansite runoff, collected in the streets, ta the
treatmentfstvrage swales, located ata 3of the 7 residentia9 lats.
- CLC Assactates Page I of 5 Prarrie Orchard
STORMWATER CONVEYANCE AN'D DRAINAGE PONDS
dPERATIOhf 8 MAINTEtiANCE 4VIAN4JRL
3.20 Drainarae Ponds
Stvrmwater storage pvnds were used in the design vf the Prairie OrGhard plat to provide stcrrage
for the rurraff created by fhe tteVelaprraent The starage uolume Tnr each pond was desigraed to
adequately contain the runoff created 50-year stvrm event within #he drainage basin it serves.
, Each pflnd is enclosed within earthen berms. 'Che pond vo3uri-ie incfudes the levef pariian of the
flaor of the swale and the sideslppes up to the ouflet or overflow elevatian. The soil lacated in the
flaor af fhe swale shall he a mediurxr to well drainmg materiaB, wi#h a minimum in#iffratiorr rate of
0.5 inehes per hour
Pond specifications are provided in Table 3 20A. Addifional indflrmat9an is prnvided in the
engineerirrg drawmgs on fite at Spakane County Public Works, file P-1885.
Table 3.20A - Pnnd Specifications
e"rm
Po 8#m'. Treatmen~ fl
Panci Pand Btm. nd
LaArvlu~~~►►. Ele+v.
' A 2033.59 I 340 284 ~ 2034.25 I2035 49
B 2051.00 I 750 I 583 2051.66 205232
- ~ C I 2037.86 I 340 I 277 I 2038.85 I 2039.470
3,30 InfltratiQn Structures
Ponds A and B each have vne dauble-depth (Spokane Cnunty Standard Type B) drywell, ihat are
used to infFltrate starmwa#er runflff beyond the required treatment Volume. A copy af the 5pvkane
Caunty 5tandard Plara B-1 a Precast Orywells ,Placed in Swafes is pravided in the Appendix far
reference These structures consist vf a grated inlet, perforated concrete barrel sections, and buried
washed drain rock, ►rurapped in porvus flter fabnc. The grate iNet elevatiDn is set eight inches
ahove the swale battom tv pravide a stiiling basin befQw the ouerflow elevation af the drywell grate,
The barrel sections and washed dram rock provide additional sfarage durirrg infiltration.
4.00 MAfIVTEtVANCE REQUIREMENTS AND SCHEmNLES
Below is a mainfenance descciptian for eac'h of 1he drainage system elements contained within the Prairie
❑rchard plat, incfuding the drainage structures, pipes, grate inlets, ditches and ponds. All drainage facili#Ges
located outsids aF the County road right-nf-way, are expected to be maintained by the homeowraer's
associafion, any drainage facilities locatsd on indiaidual residential lots are to be maintamed by the
respectiVe hQmeownees. 5hould the homeowner's assQCiation be terminated ior any reasan, the
maintenance responsibiEities will become fhat of the individual homeowners, located wifhin the Prairie
- Qrchard plat.
- The homeawner°s association shall provide to the Spokane Cvunty Parks Department and the Spokane
GvuntyEngineer° the name, address, and 24-hour tefephone number for the entily respansible for
CLC Associates Page 2 of 5 Prairie Orchard
S70RMWATEFt CONVEYANGE ►4fVD C)FtA1NAGE PONC]5
vPEFtATION &'MAINTENANCE M►4NUAL
perForming rauiine and emergency mainfenance inspeciiQns and repairs. This informatian shall be
confirmed an a yearly basis. The hvmeowner's asspciatian shall provide natice of any changes ta the
5pokane CQUnEy Parks ❑e,partmerrt and the Spokane Gaunty Engineer within 15 days og said changes
General
Proper maintenance prncedures are necessary far the cantinued functioning of the drainage facdities.
Improper maintenance, or Iack of attentEVe maintenance measures, may result in negatiae drairsage
'smpacts. It is sirnngly recommended tha# the homeowner's ass6ciatian designate an mdividual who will be
responsible for making sure the rrtaintenance measures are implemented.
Generally, maintenance personnei are to conduct a visual inspection of the drainage facil3ties imorsediately
falEaw4ng a substantial rainfap eWent or snowrrzelt ewent. 5ubstantiaf events include:
• Nnticeably harsi rain for a short period (30 minutes or rnare),
~ 5teady rain for a Irng perivd (6 haurs or more), or
• Significant rainfall andlor snowmeft when the grvund is frozen
For long duration storms, lDnger th2rn 24 hdurs, maintenance personnel are to inspect the clrainage
facilities during the stnrm eVent tQ identify+ any deve[oping problems and c6rrect them before they become
rnajor problems.
1. Inspect all readsEde ditches and drainage strucfures (catch basms and dryweEls) to erasure
they are dear of debris and obstructic+ns.
2 lnspect a1f pand herrns and retaining wa[Is for hreaches. lenmediately Tepair any berm
bceaches with nadive sandy soil, compacted in place, and wall breaks with new concrete
b1ocks.
The above noted storm relatecf visual ir3spections aee madditiarr to the maintenanee schedufes noted
helow for each item.
4.10 ❑rainaae Sfructures and 5tarm Pioes
Catch basins and pipes should be inspected every 3 months, nr after eaery significant storrn even#
(!z") andlva snovvmelt event, whichever is more firequent. Visually inspsct the pipes, inlets and
outlets, making sure they are clear vf debris and checking that the pipe is m gvad cnnditiorr, withaut
breaks or cracks. If there is any obsfruction present it should be removed immediateCy
Aflow test in the pipe can be used to readily detect major obstructions or breaks m the pipe. This
test requires a water saurce (hydrant ar ►n+ater truck) and a person at the dovarnstream end nf dhe _
pipe observ9ng the flaw exiting nut of the pipe sectsan.
AIE catch basirrs should be cPearred (vacuumed) eaery 3 months.
' CLC Associatss Page 3 of 5 Prarrie Orehard
STORMVIIATER CvNVEYANCE ANa DRAINAGE PaN'DS
OPERAYf0N S MAIHTENAAIGE a1AANUAL
4.20 ❑rainacie PQnds
The drainage pands should be inspected eaery 3 mvnths, or after every significant rainfall andlor
snawrnelt event, wh'scheVer is more frequent. The ponds cvnsist of earihen r4epressions constructed
from native sods, encfosed withira soil berms andlor block retaining waf[s. Each pond shvuPd be
sodded andlor hydro-seeded with a dryfand grass mixture, at a minimum. A la►!vn sad r-an be used if
regular irrigating is implernented.
Routine maintsnance and inspections vf the pond wiE6 include remaval of any accumulated debris,
such as leaves, weeds and trash. Any abstructions that would not allaw wrater ta flow freely firom the
pands via the vutlet structures or nuerFlerw berms should be removed ar repaired. Additionally, the
bercns and 61vck walls of the ponds shnuld be inspected ta insure that fhey are in goad repair and
structurafly campetent and that no outflaw has occurred other tharr thraugh the autlet structure or
overFlow herm
The homeowrner's association shafl be responsibls for replacement of any grass turf and underfying
1-fvot depth of soil tn ponds whenever the vegetation appears to indicate a problem due to
cvrrtaminafion The turf and underlying sod shall meet Spokane County requiresnents for
permeabality and cation exchange capacitylarganic content in efFect at the time of replacement.
430 fnfltration Structures
7he infiltration structures should be inspecfed eVery 3 months, or after every sigmfcant rainfall
andlar snowcnelt event, whichever is more frequent. These strucfures consist of a grated inset,
perforated concrete barrel sections, and buried washed drain rack, wrapped in parous filter fabric.
During rautirre inspection, i6 standing water is fourad 72 hours ar more after the last srgrnfcant
rainfa1l event, the irrfltratiDn structrsre is most kikely cfagged due tQ si[t and seefiment. The structure
shall be vacuumed of standing water and sediment
5A0 Recommended 5et-Asicfe Funds
_ for fVlaintenanee 8 Fwture ReplacEment Costs
There wifi be annual maintsnanee costs, rroajor renovation costs arad future replacement costs of the
drainage faci[ities. 7hese costs are the responsibdrty of the hameorNner's association or successvrs in
interest. Major rerrovattvn and future replacement casts have been converted to annual cosfs, in #he fnrm
nf recommended set-aside funds. ft is assumed khat'fa af fhe pipe and one dryvuell will need to be replaced
within 20 years.
GLCAssacr"ates Page 4 of 5 ,Prarrre nrchard
STORMWATER C[7NVE'ifANCE AfVO DRAINAGE P[]NDS
vPERAFIfJN & AAAINTENANCE MAIVUAL
Table S.UOA - Pipe Replacerrrent
Pape la Total Present Va'lue Annual 5et-
Size Length Per L. F. Total Aside Cast ('I
12" PUC 10 $ 3.30 $33.00 $ 2.0D
TvTAL, $2.00
The estimated annual maintenance cvsts and recommended annual set-aside costs are hsted below in
Table 5OO8. 1t is recornrnended the homeowner's assacGatatirr set-aside tfiese amaunt of funds annually,
to ensure tha4 adequate masntenance and replacement measures of the drainage facilities will be
implemented.
Table 5.006 - Maintenance and Future Replacement Gosts
Drainage Facifity Annual Maintenance Annual 5et-Aside Funds far
Costs Future Rep[acement or
Major Renavataon
Dnsite Pipes &Drainage Structures ~ $100 I $64.00
arywells - 5pokane County Type B ~ $ 1D0 ~ $ 60.00
5ub-tvtal Annual Costs
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$zvv $124.00
NQte. (1) Assume replacement m 20 7rrs, wifh 4°fa inilatian and a 6% rate of return on investments
far set-aside account.
Grand Totallyear = $ 325.00
Cost per lotlyear = $ 45.57 (7 lots)
CLC AssQCiates Page 5 of 5 Prairie flrchard
5TC?RMWATER GONIJEYANCE AND DRA►INAGE PONDS
vPERATEON & MA1NTENANCE M►4NUAL
TECHNICAL 14PPEND1X
SITE MAP
PRECAST DRYWEILL
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QYWELL eaRREL OR
GENERAL NO7ES warERPR CA1cH B~,SIN W~uL
tl~ PiPE (
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1. asAv~ BA~u. auawnrv F~ g~vrr~~s : wot~-sWRIr~x ,I NOTE:
`6YFE "A' - 30 CtJB1C YARDS kIlHlMllRi / 42 TONS. CROUt
'f5'RE 'B" - 40 LUBiC YAROS wIHIMUM / 98 iON5. PViC PIFE ACIAPTERS IINd CA5ISET MAY VARY
- IN SNAPE ►~r~0 ~rE A5 ILLUS1R~,iEa it~
OR A5 SP~pF7~ ~1 RUAO ~SHS. OETAIL BY ACCEP7ABLE ALiERNATE IN
2. SRED,At gACKflLL MATERIAI, FQR ORYMElL$ SHALL LON9ST OF ACCpRQYNCf WE7Fl A 5 T,id -C-4?B
1VA5HEO GRAYEi CRAOEO FRVId t' Td 3' WITH A AiAXIIAUAE QF SX
PdS51NC TH$ ll5 Na 208 SCREEN, A5 RI$A56lRED 8Y WEIGHf A$1(ET
A YA5pt11lld pF 10lC OF 7FYE ACpifCATE, AS RiEA$VFiELI BY Y4EIpiT, i1C ADAPTER y~ eB
SNALL BE~HATURAiIY OCCXIRFiiG l1HFRACNRECI~ATERI~AI..OX PVC ALdAPTCft
3. PABRfC SiiA1.L BE 1rfOpERATE SIJRNVASILl/Y AS fll11LIHED (SANQ COLLAR)
IN srAr+auRu SPeaRcAnaNs a-as
4. SEL STAHOARp PLIJIS S14EETS 8-3 AHt7 B-] FpR
PRfCAST COHp1ETE DETAtLS, i! TA FRAeE TYRE 4
S. Ap.R7511AEHT OLf~tRS SFiAIL BE Cf1a4ENT C~ICRETE. PAY tIRi1T5 0~~~ T"~ WOR AR IN PLACE
8. PRECAST RISER MAY BE USEa lM LDAIBIHATIOH METAL FRAeaE
iMTH pA IN llEV S!F A4JU5'dINC 9L~K5. l1a ~ATE
7 vMcN avc rCPE is usED A P►C AohaTER sHwu. eE iNsrALLEo.
rOP 5OIL ~ITAREi1 Ap,R15TAlENi
a. PiPES SHALL BE CRfJt1TED IF~TO RRY1kELtS, 'i t~~ R1MG5
c~iATE TYPE~ itYPE 4 ~ 0 B+E cAIIPI.ETEtV 2'!0•
hipRTRRW PLACE q CpVE ~ NpT{ FA9FtiC '
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Apdu5tuEriT aINCS
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p ~COVERED 151iY1 r SEE feOTE 7
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y r+4~'d aiP~ AVEL k r'-I ~EPAr;E P~t7s.
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DETJIEI., SIi7, 8-
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Spl 5TUR9ED H~iIISTl1RBEQ
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DRYWELL - TYPE 'A' SWALE D YWELL - TYPE '9° SWALE
I 5Pt7KANE CqUNTY ~.~-••p
ARPRpiVEQ: sH~Lr •
DE~PpRTMENT OF PUBLIC W~]R~45 c~ ~a STANDAE~o
"+Xr. w,. 11200 454-3eoo- PRECAST ❑Rl'WELLS PLACED IN SWALES B-~~