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SP-811-92 S P (D K A N E o,a C O U N T Y - OFFiCE OF THE COUNTY ENGINEER • A DMSION OF THE PUBLIC WORKS DEPARTMENT Ronald C. Hormann, P.E., County Engineer Dennis M. Scott, P.E., Director December 9, 1993 Steve Hanson Ramer & Associates, Inc. SUBJECT: SP811 - Staley Short Plat Approval Gentlemen: I am enclosing a blueline set of the road and drainage plans for this project with the County's approval stamp; the originals are on file at the Public Works Department. A copy of the drainage calculations (stamped "Approved") are also enclosed. In accordance with Section 2.02.A.3 of the SCRS, th.is approval is valid wntil December 9, 1995. If the facilities are not constructed, you may request an extension for an additional two years; the plans shall be revised to reflect current standards prior to granting the extension. Please be advised that if you construct the road and drainage facilities without posting surety, that the plat cannot be finalized until either: a) the road and drainage facilities are constructed and accepted, and the roads established by the County Commissioners; or b) adequate surety for any remaining work is posted. If you have any questions, please contact me at 456-3600. Thank you. Very truly yours, Ronald C. Hormann, P. E. Spokane County Engineer ~ Edward J. Jr., P. E. Plans Review Engineer encis: Plans (1 set) Calculacions (1 copy) cc: v4ject file reviewer (comments only) W. 1026 Broadtivay Ave. Spokane, WA 99260-0170 (509) 456-3600 FAX (509) 456-4715 MAILINO ADORESS: OFFICE LOCATION: P.O. BOX 18779 N. 10115 NEWPORT HWY. SPOKANE, WASHINGTON 99208 SPOKANE, WASHINGTON 99218 PHONE (509) 467•5261 J. PAUL RAMER & ASSOCIATES, INC. CONSULTINa CIVIL ENGINEERS S LAND SURVEYORS WASHINGTON • IDAHO • MONTANA NEVADA • CAUFORNIA OREGON r• - (Revised Nov. 1, 1993) . (Revised July 19, 1993) April 1, 1993 . Project #93029 STORMWATER MANAGEMENT PLAN for SHORT PLAT NO. SP-811-92 Portion of Section 27, T25N, R44E, W.M. Spokane County, Washington ?ROVr--~ ~ O~ ~ sPoa ra~ coU;ffl~ E;~~. a~f........ . c. ~...,0 u c\0 ~ Prepared for P~~~IT R► 7.. lJlR:ED ! HELEN STALEY NOTIFY THE PER?,•;~1' ENGINEER P.O. Box 790 456-3600 Spokane, WA 99037-0790 24 NRS. P,RIOR TO CONSTRUCTION OFFICIAL PUBIIC DOCUMENT SPOKANE COUNTY ENGINEER'S OFFICE OR G NAPROJECT # -r?P t' < < . QP%JL SUBMITTAL # 3 , df'" ~ RE7URN TO COUNTY ENGINEER _ , RECEIVED 9 ~ 1001e N OV 0 1 1993 ~ ~GtaTEwt qL SPOKANE COUNTY ENGlNEER EXPtRE$ J. PAUL RAMER CNIL ENGINEER - LAND SURVEYOR . ST{]RMWATER MANAGEMENT RLAN The Short Plat s[te 1 s located ad,jacent to Evergreen Street between 21st and 23rd. Svl Ts in this viclnity are g ene ral1 y 5pringda1 e g rave l 1 y sandy T oarr3 wh i ch 1 s poraus and naG generally knawn for runvff problemsi The site i nc 1 udes three parce 1s 3/4 Acres + T n s ize . Th I s low dens ity wi1 1 nat have a substant lal +ef fect on runoff quanLfties compared.to the existing open field. One, drainage basin has been outlined ulhich 1ncl udes most of the proposed pr Ivate road and i s genera 1ly i n the area of Parce l 'Tp,'T. 7he 1and i s genera 1] y flat, but has a 1 oca 1 low poi nt Y n the area of the proposed drywei 1 and "T208" swale, We propose to col 1ect runoff from a 10 year storm at that pay nt and d i spose of i t i n t,he drywel1. Some runoff may also enter the basin fram Evergreen Street but there Z s na def's neci gutter or slope to drai n any s i gn i f icant amau nt to the plat. Evergreen Street has only a slight grade to the north i n the area of the pl at. A cul vert woul d not be p rac t i ca 1 i n th is proj ect, sa the runo-f f w1 1 1 be coilected in the "208" swa]e vla the proposed o'n-sQte raad di tch . The easement be i ng estab ]ished for i ng re ss and eg ress wil1 be suff ici ent to hand 1 e thi s srrra ll runoff. Runoff fram other off-si te 5ources wi 1l be neg 1 i g ib1e, The proposed pr ivate road s1 apes toward Ghe d i tch and swa le at 2% and w w] 1 prevent on-s i te f 1 ows fram f1 ow1 ng no rt h, The natu ra 1 contours af the area are otherw, se fl at to slapi ng away from Che p]at. ,INGTON - SHEET NUMBER 75 R. 44 E. (Joins sheet 66) - i , f s~ • " ~ J f - 1C Y ' ir ~ ' , _ ~ . . ti '►,y' ~ -A',.' + . ~y ~S~ti wer ~1 ~F . 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X Iftl SO 10 90 110 130 150 I I ~ I I LL, -----F-~---T-,~O . 0 ~ ~ ~--0 - ----a - ~ - ~ ~ j I ,f~ o ft) P h o - ~,__--~Q~p - - - - - -U Q ~ w ~0 - - - - - Q - I y I / ~ ---h ~ _ M - - ~ - I I Q. 2 I - ~ I ~ ~ I ~ I 1 I I • - - ~ AtCEIERATION ~er~s OND1TlONS S.D. j= j1.4T V(2 +ta) I I I i 1 200 400 00 900 iooo i:oo 1400 1600 1e00 ~j tIGHT DIStANCE REOiIIRED lffl IS.D.1 . ~ z Slght Distence tor Grade Intersectlon With Stop Control ng" 9iaisa , . - Orslgn A/anual Prgo 01041 aipamDW 1902 - '-1RAINAGE POND CALCULATIONS ' Required grassy swale pond storage volume = Impervious Area x.5 in./ 12 in./ft. = 363 cu. ft. provided: 370 cu. ft. DRYWELL REQUIREMENTS - 10 YEAR DESIGN STORM Maximum storage required by Howstring= 732 cu. ft. provided: 740 cu. ft. Depth of storage swale = 1.00 ft Number and type of Drywells Required = 1 Single 0 Double TIME OF CONCENTRATION (minutes) Tc (overland) Tc (gutter) Ct = 0.15 L2 = 100 Z1 = 3 L1(A) = 220 Z2 = 3 N(A) = 0.4 B = 0 S(A) = 0.005 n = 0.025 s = 0.1 Tc (A) = 10.79 d = 0.27 ,1(B) = 0 Tc (gu) = 0.35 J(B) = 0.4 Tc(A+B) = 10.79 S(B) = 0.15 Tc(tot.) _ -11.14 Tc (B) = 0.0 Intensity 2.13 Areas "C" A*C A = 0.2187 WP = 1.7076 1.16 0.25 0.29 R= 0.1281 0.22 0.90 0.198 V= 4.77 0.00 0.00 0 Tc(gu) = 0.35 0.00 0.00 0 Q(est) = 1.04 0.00 0.00 0 0.00 0.00 0 Holding = 3.56 0.00 0.00 0 Total A Comp "C" 1.38 0.35 Q=C*I*A= 1.04 Q(est.) = 1.04 30WSTRING METHOD (TEN YEAR STORM DESIGN) PROJECT: 93029 )ETENTION BASIN DESIGN HASIN: A DESIGNER: S. Hansen NUMHER OF DRYWELLS PROPOSED DATE: 01-Nov-93 1 Single (type A) 0 Double (type B) Total Area (calc.) 1.38 (see following sheet) Time of Conc. (calc.) 11.14 (see following sheet) Composite "C" (calc.) 0.35 (see following sheet) Time of Conc. (min) 11.14 Area (Acres) 1.38 C' Factor 0.35 Impervious Area (sq. ft.) 8700 Volume Provided 208: 370 storm: 740 Outflow (cfs) 0.3 Area * C" Factor 0.49 #1 #2 #3 #4 #5 #6 #7 Time Time Intensity Q dev. V in V out Storage Inc. Inc. ' (min.) (sec.) (in./hr.) (cfs) (cu. ft.) (cu. ft.) (cu. ft.) (#1*60) (A*C*#3) (Outf.*#2) (#5-#6) 11.14 668.46 2.13 1.04 932 200.54 732 5 300 3.18 1.55 ~624 90 534 10 600 2.24 1.09 879 180 699 15 900 1.77 0.86 974 270 704 20 1200 1.45 0.71 1010 360 650 25 1500 1.21 0.59 1020 450 570 30 1800 1.04 0.51 1029 540 489 35 2100 0.91 0.44 1033 630 403 40 2400 0.82 0.40 1051 720 331 45 2700 0.74 0.36 1057 810 247 50 3000 0.68 0.33 1071 900 171 55 3300 0.64 0.31 1102 990 112 60 3600 0.61 0.30 1139 1080 59 65 3900 0.60 0.29 1208 1170 38 70 4200 0.58 0.28 1253 1260 -7 75 4500 0.56 0.27 1292 1350 -58 80 4800 0.53 0.26 1300 1440 -140 85 5100 0.52 0.25 1352 1530 -178 90 5400 0.50 0.24 1373 1620 -247 95 5700 0.49 0.24 1417 1710 -293 100 6000 0.48 0.23 1459 1800 -341 c (total) = Tc (overland) + Tc (gutter) c (overland) = Ct*(L1*N/S-0.5)"0.6) Ct 3 0.15 L1 =Length of Overland Flow N= friction factor of overland flow (.4 for average grass cover) S= average slope of overland flow Tc (gutter) = Length (ft.)/Velocity (ft./sec.)/60 H= Bottom width of gutter or ditch Z1 = inverse of cross slope one of ditch Z2 = inverse of cross slope two of ditch d= depth of flow in gutter (estimate, check estimate with Flow) Area = d*B+d-2/2*(Z1+Z2) Wetted perimeter = B*d+(1/sin(atn(1/Z1))+1/sin(atn(1/Z2))j Hydraulic Radius = R= Area/Wetted Perimeter Velocity = 1.486/n*R".667*s'.5 Flow = Velocity*Area n = 0.016 for asphalt s= longitudinal slope of gutter ~„r, . ~ . ~ r~~ - . - . ~ - ~ F ~ I ~ ~ 1 ~ ~ , , ~ ♦ ~ ~ ~ 1 ~ r , ~ , • ~ o ~ e . . ' P r ' ~ ~ ~ ~ ~ ~ , ~ ~ H . e . ~ ' ~ L ` ♦ , . ~ . f . y ~ ; w ~ ;a~ . , ' ~ ~ ^ ~ , ; ~ V , k"~t~i r ~3 : . " l~ ~i ~ ! i~~ ~ ~ ~ • ~ f l l / ~ ~ 1 I" r ~ ' " ; ~ ~ ~ ` ~ ~ • ~ i ~ 1 I i ~ i ~ r , ~ . o q ~ ' ~ $ ~ ~ ~ , ~ ~ 1, . . , Vl , , ~ 1~ ~ ~ ~ ~ ~l, N ~ " 1~ . ~ 7J 3~~I.~~ ' ' ' ~f~fr • ~ ~ ` . , . ~ r ~ 1f.~ ~ ia~yr" ~ ~ ~ ~ ylSS ~ ,~9rtSs, ~oee~ ~~f;/;~y'~eserntn~'-~- ' ~ 'T V • ~ •:C ~L~ ~M,I~I . ~~St1i'~t'nl ~ _ ~ ~ ~ ~ ~ ~ _ I- - ~ ~ ~ M' . . " . r , ~ ~ ~ I~f. M ~ Hr h ~~"v f " - Ya . . ~ . . ~,_~r ~ ~ ` ~ ► ~ , ~ ~ o;nc c ~ ~ ~ 1V~(~ r /~Rft/P1el~ ~ U~f~ll ~ ~ ` '1 , ~ II ~1 ~ e ~as[mP~t : 1 ~ 1 ~ ~ u ~ 0 11~ Ak~'A = ~l, 3S6 S~'~ 8~;1~~ ~~d~ _ ~ ~ ~1~ ' ~ scfbric~ ; ~ ~ ~ . ~ 1 ~ '1 . / ~ ~y , , ~ , t ~ ~y~~~~~~ ~e ~ ~ ,~,✓~d~~d ~ 0 .'~"'r". ~ ~ . ' , ' ~ M . ' Fc~ fi~ "~Prb~. w G~ ~ ~ . . . ~~s ~eryi „ •i . ~ ' ~ , . ~ /G' ~"~/urt R/W ~ ~ rl . • qc9~~Si ~%on Are4 Lti1 , S r, i , ~ ~ ~ r~ ; ; ~ ~ r ~ ;'~1r~t ~ ~ . t t ~O ~ i • R ~ ~ ~ y ~ I ~ ~ ~ ~ r i ~u ac~ ~ B 1 B 7O0 S H i ~ ~ r n e v S s ~ r P rG; n1 e ~s~n A~Qq = . a ~ l~ 3 ~ - slo~e -o.s v_ i ~ L : 2Z0 _ -I ~ ~ ~ , ~ ~ ~1 d. l ♦ ~ 1 ~ ~ 1 l l / ~ 631.z8' C~Pe~oi ' : = See'so ~qi~~ .zg~ _ , _ f ~ - • _ . ~ , f ~ j ~ . ~ Fd R~6~+. /~4 s , I P Fd / ~eb~r / ~ ~ , ~ ( . o~~e ~5 ~81N~ I o ~ D 1. 5 i Ty~ o ~ ~ . , ~ ~ ~ . s ~ ~ ~ , ~ ~~~/r~n 0 ~ 1 3y 30 , 9 p ; . . _ 1~ . ;e/b►<k ~ . ~ ~ ~ ~ ~ „ . . ~ „ r ~ ~ ~ p • , - ~ • - ~ - _ ~ ~ , ~ ~ ~ ~ , ~ , , , . ~ , w-~. ; , . ~ ~ , y 1 ~ o 2 , ~ x.. o h . . ~ ~ I ~ + . ~ i.K, y~ v . r ~ , v , ~ ~ ~r "~p% \ . ~ . ~ AREA . 310, 395 SF- 1 ~ - - - p ~ , ~ 1 ~ ~ • ~ ~ ~ , ~ , ~ , . ~ ~ . \ l 11 , 1 ~ Q ~ ~ q ~ I ~ ~ M , ~d P; c ~i~ rn knorun 11 ~ ~v~ : . ~ ~ ~ , 7 , , ~ ~ . R' ~ . ~ i,oo~/, .08 ~ ~ s . , . I. ~ N~ s~ ~ ~W ~IG. DD 'k~ ~Pf6vr ~ , ~ ~ i . ~ ( ~ ' , r~ ~ • t~/ ~G~ ~ ' ~ 1 C~~ , _ ~ ~ ~ ~ . , , s~~ So ~j j 3~5, ~ ~.I ~ ~ 1~l ~ ~ ~ , ial~i,. ~ ~ f + / i~~ ~~i ~ ;i Q , ~ l6 _ ~►J ~ ~ / - _ 1 h res ~~tSS ~ it~oa U~~~%l ~aSement 0 , ~ , , ~ S ~ 9 ~ ~ ~ ~ i , i . i ' . 25 ~ -^M--+ ~ ewe~ ~oSt»~fF, T pC ~ D~ wefl , r , „ • ~ f ~a s~ - - - - - - - - - - - - - - - - - - y y ,i ~ ~ ' 1 1 , ~ ~'Y'"o ~ / 0 I ~ _ ' _ - r~~, , ~ I • . ~ ~ ~ ~ ♦1 . ~ ~ , ' ~Y ~ „ I • ~ . \1 ~ o , ~ i ; . i ti o , hn~ - ~ . , D~x3 . ~ c JS - . , ~ , ~ h~ ~ ~ry~ ~ \ , 1 . .t 3 V f • ` . ~ r ~ ~ / ` r, I. t \ Y . . . . ~1 37' ~ ~ ; • , . , ~ ; • ~ 1~ , ~ i` ' ' , • . ~ ~ , / ~ o a N , h , ~ ~ - ~ • , t ~0 ' ~ ~ t' i`1 . • praln aq t s ~ , / ~ , - , ~ 0~8 . ~ ~ O~o I 5 ''1 , ~ ofa9 ~ 1~ ~~~e' ,En~r.~nc~ t M u- r ~ _ . ti Bu;lc~'n X ~ (1!~l,l~ ~ ~ ~ ~ , A A- 3G, 3 8~S 1~,,2 c~ I , ~ ~a ~ r I , - _ ~ s ~ascment , ~ 1 ( ~ ' \ ~ efbnc~ • . 9 o~x _ , i L I ~ , 1 n~' \^c r 25 ' . , 3 ~ AR,~A = q! 35~0 SF'j d ~ ~~1 0 ~ , / B~~ ~l ~r~ ~ . o , ~ G , ~ . ,Nj ~ • I I 16 + , 6,g.~ s~~t~~,~ : . . n-~ ~ . i - ~ . . • j ~ ,i i , 1 ~ 3~5. /9 ~ ~ ~ s ~ ~ ~ A~.' I ' - D ~ J ~ W 1 lob, l~- , ~.ov I 9 ao , _ _ _ ~ 2,y N/ % .r ~.u r , R . , . ~ ,~~kl4~U - ~ ( x , ~ ~ - - - - S' , w ~ N~B sl 3/ 6,3/~ /y 0 . ' M Fd /B ~Peb~ / C ~ ~~11~ . / . 0 i~ ~ M ~ , 1 F~ s W ~a „ ~ ,P~b~ / ,o ,csid~yl o,/d~ , 1 ~ ~ ~LS ~BJyI 1 ~ , , ~ / '7 ~ ~ I ~ ( ~ (o ~ ~ r ~ ~ fu/vit ~~k/ ~ i ~ . ~ Ac u;}~ ~;on Aie4 Lt ~ ~ ~ ~ ~ A / 1 ~ . ~ • ~ ~ ' ~ ~ ~ ~ r ~ ~l y ~ ~ ~ ~ i (C' il i~ 1 I i ~ ~~~r: I ~ i• / ~ : . ~ ~ ~ i ~I l~f~ ~ . ~•I 1..~.~~ ~ .L ~4 l i I ~I ~ ~ 1 ~ Jo' 30' ~ . r`r - • i ~ t - - i ~ ~ ; . . ~ ~ ~ J PAD MOUNT T 13815 MOUNT TRANS. ~ z ~ 13807 ~ . 13713 1„7 , 9 ~ ~y1 _Cl . ~3a2~ , 3 PHASE SEt -IASE SECTOR 137U5 ~ ~ sECr , I PHASE SEC IASE SECTOR A • ♦ , VERA'S POWE I 1 l , 1'S POWER POLE 1 j ~ NEW POWER P+ ~ ~ w POWER POLE U CI 0 ~ C90 I S ~ FUSED CUT C =D CUT OUT UG STREET L 3TREET LIGHT ~ b~ ~ 0 ~ ~ OH STREET L >TREET LIGHT T ~ r.-T' T' A D L I GHTN I NG A 1 i T ~i ~ T~~ R~ ~ ~t r, r~ r,~~r T 1' i iTNING ARRESTOR ` l~ i d L. ~I FAULT I ND I C .T INDICATOR - ' ~ ' ' Q : CABLECON !P FIRE TRUCK TURN AROUND . , . .ECON (PRIMARY) ; ~ ~ r: ° e ~ UG SECGNDAR S ~ ' ,ECGNDARY (4/0) ~ ~ L , R ~ 1 ~ ;j V „ ; STREET LIGH ' ~ , ~ , n :ET ~I~IJT W( RE C 0 DU I ~ ~ ~r ll' , ~U~ ~ ~ 4 I NCH COND i ~ . ICH CONDUiT ~ \ ~rn . ■~~F - . . , 2 INCH COND \ ~ ~ C ~ - ~ :Q VALVE ~ , ~ WATER VALVE ~ , - ~ ~ ' ~ - ' ` ~ - : HYDRANT ~ , - ~ _ F I RE HYDR,~,N , ~ , ---------------,---~r-----.--- ~ EL - RC , A P ~ L _ ~ ~ » , ~ _L~ IST 3LOCK ar , ~ THRUST BL C , ~ ~ ~ . 4 ~ . . ~ ~ >HING P01N~ O ~ ~ ~ i ~ ~ (Y ~ ~~USH I NG PO ~ DRHNhGE EASt~B~(f , , I ~ ~ ~ P ~ TAP , , z , S w i =..~.r= _w . ~ . . ~ n ~ ~ . ~ , - , 0 N ~ w ~ w l. ~ , . > > - C SPOKANE COUNTY ENGINEEI ~ ~ ~ ~ W ~ ~ i . 1 ~cKe I' - 70' ~~r' I ~~s ~-19-93 lNTY ENGINEER ~ Y , AT 81-92 MwN eir: BKD. mmm ft J. Paul Ramer & Associates, Inc. LETTEF~ TF~A~VSfiVIITTAL Consu/ting Civil Engineers & Land Surveyors N. 10115 Newport Highway ` Mailing Address: P.O. Box 18719 DATE JOB NO. b Spokane, Washington 99208•0179 ~eC, (o . 9.~ 7 3n2q Phone (509) 467-5261 • FAX 461-5262 ATTcNTION ' _ / ~ ti ~.L t'~ ~ In M~ ►J G V RE ~ To S~o kah e (fouv%+U Chcii neer S -,z>A4ee Y 50 -RZ Iw M ~ A~ I~. GENTLEMEN: WE ARE SENDING YOU ❑ Attached 0 Shop drawings C-J Prints!-~- o ,oE~lans ❑ Samples O Specifications 0 Copy of letter El Chanqe order ❑ COPIFS I DATE I PAGES I DESCRIPTION 7-11-iTy p THESE AFiE TRANSMITTED as checkeci below: ~ For approval ,Q=Fef your use ❑ Ns requested C For review and comment ❑ REMARKS A5 B y ,6Z4 G✓4T~ a~ ~6 t-~~~ COPY TO . SIGRFD . ~ If ericlosures are noP as nated, kindly notify us at once. 4 SUBMITTAL CHECKLIST PROJECT # t REVIEW # 3 REV I EWER : t~f~llA DATE : 10 I&vember 93 PROJECT : PROJECT SPONSOR: TEL PROJECT ENGINEER (Road & Drainage Plans ) M%& 1Z Assce /57ewt wr4v~--w4 TEL # 4~7~5z~ r PROJECT SURVEYOR (Plat) TEL # GENERAL ITEMS YES NO N/A 1. The $100.00 fee for plat review has been paid to Spokane County for this submittal / 2. An agreement to pay fees has been submitted to ~ Development Engineering Services ~ 3. The fee agreement has been signed by the project owner or a principal of the developer's firm. If signed by an agent of the owner, written authorization from the owner is attached to the fee agreement ~ 4. Review fee account is Current (no invoices over 30 days outstanding) J 5. I have noted the plans in, plans out dates on the pink sheet in the file ~ 6. If the project is a mobile home park, were the plans reviewed by Planning? 7. 2 copies of the plans were submitted i i i 8. 2 copies of the calculations were submitted / 9. The plans are on 24" x 36" sheets ~ GENERP,L ITEMS (cont' d) ~ 10. The calculations are bound together / 11. The plans and calculations are stamPed and signed by a Professional Engineer 12. The developer has signed and approved the road and drainage plans ° 13. Are there any conflicts between the proposed drainf ields and any drainage ditches on the plat 14. Bowstring calculations by developer are in the file for this review. ~ 15. Vertical curve stopping sight distance calculations by developer are in file for this review ~ 16. Horizontal & vertical alignment sight distance calculations by developer are in file for this review • ~ 17. The engineer/developer has provided evidence of coordination with the electric utility servicing the project 18a. The file contains a Spokane County Section Map 18b. The file contains a Spokane County Assessors's Map 18c. The file contains an aerial photo of the proposed proj ect area 18d. The file contains a corrected preliminary of the final plat map 19. The project is located in urban boundary area 20. The project is located in the Aquifer Sensitive Area 21. The project plan name matches the plat name i ~ 22. Is the entire project located outside of an i identified Flood Plain Area? i i ~ 23. Is the entire project is located outside of an identified Stormwater Management Problem Area? cklistv3.0/Aug93 2 GENERAL ITEMS (cont' d) 24. List any design deviation requests and their , status: rafx k~o,,w~.~~ dc eY~~'.r ~ 66~~'~~~,'l 25. Locate the Findings and Order for the project and list any unusual conditions: (eMIAWG~ . J i 9 Z #A dv Arll - E1r~~ (40/W v P,A~4 Mad -3 l~'A . ' 23. Backcheck of previous comments completed ~ 24. All previous comments adequately addressed ~ cklietv3.0/Aug93 3 FIELD REVIEW 1. Field investigation trip made on 2. Report completed and put into file on 3. Are there any existing utilities on the project site? (Overhead power, fire hydrants, etc.) If yes, describe. 4. Are the drainage basins on the ground the same as those that are presented in the drainage report? 5. Are there any drainage channels directed toward property? 6. Are there any drainage channels directing water through the property? 7. Do County roads cut off drainage as per drainage calculations? 8. If there are culverts under county roads, does the flow go away from or toward the project? 9. What kind of ground cover exists? 10. Describe any existing channel conditions: 11. Describe channel cross section: 12. Existing Curb Type: ck1iatv3.0/Aug93 4 ROAD PLANS l. List any roads that must be designed and constructed on the project. ROAD REQ'D WIDTH DESIGN MIN./MAX. STOPPING SIGHT MIN. CURVE NAME CLASS. PAVED R/W TERRAIN SPEED GRADE DISTANCE HORIZ. VERT. ~ 2. Planning conditions require submission of a landscape plan. (NOTE: Usually associated with PUD' s ) 3. I have checked the landscape plan against the ' road and storm drainage design and there are the following conflicts: / 4. The following road Plans have a bearing on the / design of roads for this proj ect and a copy is in the f ile : ~ 5. I have sent an "R" value and percolation test ~ request to the Construction Section with soils information and a layout of the project. "R" value test request to Designer (date). cklistv3.0/Aug93 5 ROAD PLANS (cont'd) ✓ 6. Is the bench mark shown on the plans? lei 04tv ~7. Are stationing equations shown? ~ _X/ 8. Is stationing correct (south to north, west to ~ ading lef t to right on the plan) ? ~ 9. Are existing utilities shown on the plans (or an ~ information copy of the utility plans submitted) ? ~ 10. Are proposed utilities shown on the plans (or an ' information copy of the utility plans submitted) ? ~ 11. Does the note "Any conflicting utilities shall be relocated prior to construction of roads or drainage facilities." appear on the plans? 12. STREET WIDENING 12a. Are curb design sheets provided for widening of existing streets? 12b. Does the curb design conform to Spokane County Standards of section cross slope (Between 2o and 4.50)? 12c. Is there a street cross section shown for widening existing streets? _ 12d. Does the proposed new width match the width required in the Findings and Order? 12e. The cross-section shows: existing R/W proposed R/W future setaside 12f. 100' (min.) pavement taper into project is shown (1) There is adequate R/W f or the taper to extend from the new paving width to existing pavement. (2) There is inadequate R/W for the taper to extend from the new paving width to existing pavement; taper extends from existing paving to R/W. 12g. Length of pavement taper out of project meets: WS2 = 60 for design speeds s 40 mph WS for design speeds > 45 mph ; ft. min. taper length approved by County i Traf f ic Engineer 12h. Transition from end of curb to existing paving is shown (curb should nose down in 1211) ck1i8tv3.0/Aug93 6 ROAD PLANS ( cont' d) 12i. A 411-wide, white painted fogline at 12" from the edge of paving is indicated (tapers or tangents) 12j. Are the curb grades above the county minimum of 0.8%? , 12k. If curb grades are below 0.80, has a special note been added which requires a licensed land surveyor to verify that the curb forms are at the correct plan grade prior to construction? 13. NEW STREETS 13a. Does the proposed alignment meet Spokane County Standards? vertical slopes ~Rt~W vertical curve length horizontal ~ curve radius intersection separation ~ ✓ 150' on local access 300' on arterials / 13b. The plans show the typical cross section for streets ~ 13c. Does the proposed street width match the Findings and Order? 13d. The cross-section shows: / existing R/W ~ proposed R/W / future setaside 13e. Does the typical section on the plans meet Spokane County Road Standards? cross slope is shown cross slope is within standards cross slope is correct when checked on profile , 13 f . Curb type /10 aw~ ~j~ shown ~ proper type for the road classification I meets Spokane County Road Standards for curbs within the public right-of-way consistent with the curb type in the general , area , 13g. Are the curb grades above the county minimum of 0.80? ck1istv3.0/Aug93 7 ROAD PLANS ( cont' d) ! 13h. If curb grades are below 0.80, has a special note been added which requires a licensed land surveyor to verify that the curb forms are at the correct plan grade prior to construction? 14. Has an "R" value test been performed for each soil group? 14a. The pavement section is adequate for the R-value and Traffic Index for the road type ~ 15. Locations where water is intended to flow through an inlet or curb cut are at the low point in vertical curve 16. SIGNAGE PLAN ~ 16a. Stop signs are shown for all streets which intersect an arterial (Check with County Traffic Engineer if there is a question) 16b. Street name signs are shown at all intersecting r streets ~ 16c. Is there a need for barriers at the end of dead end streets? 16d. Is there a need for other special signing? (Check with the County Traffic Engineer) 17. Has the Fire District approved all proposed private road turnarounds that are substandard according to our Spokane County Road Standards? 18. CURB RETiTRNS 18a. Are BCR, MCR, and ECR stations/elevations on curb / returns shown on the plan? / in the prof ile? i 18b. Are the curb return elevations correct? / 18c. Is there positive drainage from the road intersection to the MCR? ~ ~ _ 18d. Curb return radius meets County Standard minimum ~i of 20' (to back of curb for rolled/wedge curbs, to face for vertical curb face types) / 18e. BCR, MCR, and ECR elevations are set to allow drainage from the centerline to the curbline ckli9tv3.0/Aug93 8 ROAD PLANS ( cont' d) ~ 18f. BCR, MCR, and ECR elevations are set so that the ~ superelevation between the intersection and the curbline is banked properly for right-hand turns into and out of the intersection roads (the road slopes from the intersection down to the flowline) ~ 18f. BCR, MCR, and ECR elevations at intersections ~ without stop sign control are set so that the superelevation between the intersection and the curbline does not exceed: (ref. AASHTO) 100 (flat terrain) 80 (rolling terrain) 60 (mountainous terrain) 19. CUL-DE-SACS J._ 19~~,,/ The cul -de- sac grades (top of curb) meet county WW"' cul -de- sac standards (1 o min.) ~b. The cul-de-sac curb is shown in profile 20. INTERSECTIONS _ -41' 20a. Do the intersections meet the 2o grade requirements? I 20b. wheelchair ramps are provided at intersections with sidewalks 20c. If there is a change of direction at the wheelchair ramps, are the ramps oriented so that: a 51x5' pad is provided at the top of the ramp? the required 51x5' landing zone at the bottom ~ of the ramp is located inside of a line drawn 1' inside a line extended between the curb faces of the adjoining street at intersections? any drainage structures are located outside of the landing zone? J 20d. The intersection horizontal sight distance analysis shows that sight triangle encroachment on private property is 2' or less / 21. Is there a need for slope easements? 22. Is there a need for erosion protection? ckliatv3.0/Aug93 9 ROAD PLANS (cont' d) 23. DRIVEWAYS , 23a. Can a driveway slope of 80 or less be maintained between the edge of pavement and the right-of- way? 23b. Can a driveway slope of 12 0 or less be maintained between the right-of -way and the building setback - line? ckliatv3.0/Aug93 10 DRAINAGE PLANS 1. Has a plat map been submitted which shows lot dimensions, street widths, etc.? ; 2. Was a map with ✓ contours spot . ; elevations submitted to properly determine ; drainage basins? / 3. Were all existing drainage courses shown? ~ 4. Were all the ProPosed drainage courses shown? , 5. Were Hydrologic calculations submitted for each basin? (Bowstring if area s 10 acres, SCS TR-55 if area > 10 acres) Offsite (50-yr storm if undeveloped, 10-yr storm if developed) ~ Onsite (10-yr storm) Q for entire area Q for roads only INFILTR.ATION POND ~ Actual pond volume provided DETENTION POND ; Release to pipe system: i contain 50-yr developed release at 50-yr pre-developed ; I secondary overflow to pipe in control i ~ structure for 100-yr developed emergency overflow weir for 100-yr developed i sump prior to outlet to control structure i ~ 1' min. f reeboard ; I grassed sides/floor for publicly-maintained ~ ponds i sprinkler system for publicly-maintained ponds ; Retained on site, no drywell: ; contain 100-yr developed emergency overflow for 100-yr developed i i 208 SWALES ~ 208 swale floor area, volume requirements 208 swale floor area provided 208 swale volume provided , ckliatv3.0/Aug93 y 1 DRAINAGE PLANS ( cont' d) ~ UNDERGROUND GRAVEL GALLERIES ~ ~ ~ 1. .3 void ratio for gravel free space volume is ~ used ~ i i ; 2. Perc rate from field test is used to develop ~ outflow rate i i i 3. 10-yr event volume is contained entirely i ' underground i i ~ 4. 100-yr event volume is contained by a combination i of underground storage and above ground storage i up to 8" depth i i 5. 100-yr event volume is contained by a combination ; of underground storage and above ground storage ; exceeding 8" depth i 5a. Soil mixture is specif ied for water depth in pond i exceeding 8" i ~ ; 6. Entire gallery is wrapped in filter fabric CONVEYANCE Conveyance - ~ pipes ~ ~ ditches ~-t~t.`~r f ow de~h is less than er height Qold`' WtAA- Backwater - pipes, ditches Headwater - culverts ~ Curb drop/curb inlets , on grade ( f ig 16), sump ( f ig 17) Grates - sump ( f ig 15), continuous grade ( f ig 16) Riprap - stone gradation, pad dimensions 7. Soils type is "pre-approved" (Garrison, etc.,) ~ for drywells without percolation tests ~ 8. Does the drainage report identify the SCS soil groups for the project area and for the proposed roads to be built in the project area? 9. The drainage design maintains sheet flow patterns ~ in natural watercourses i i i i / 10. The drainage design maintains existing sheet flow i patterns without concentrating flows cklistv3.0/Au993 12 DR.AINAGE PLANS (cont' d) i -11. Does the entire plat lie outside of designated i 100-year Flood Plain Area? i i ; 12. Does the entire plat lie outside of Zone "B" of ; the designated Flood Plain Area? 13. Is the max. street ponding in any part of a Zone "B" less than 1'? 14. Does the plat contain appropriate language ~ limiting the lowermost opening in a structure located in a Zone "B" to not less than 1' above the lowest road elevation? / 15. The drainage concept is compatible with planning commission requirements. 16. The difference between present and future flows is retained on the site. INZETS / 1. The inlets shown are within the stream flow. ~ 2. Inlets are shown on the low side of a road or at the low point of a vertical curve ~ 3. Curb type inlets are shown at sags and are properly sized. Perimeter does not include the side of the grate against the curb face (all grate types). Perimeter is divided by 2 for calculations where no curb opening (Type 1) is provided. Area = clear area = 2 for Type 1 grates) 4. There are no long curves with flat grades ~ which pose a problem. ~ 5. The centerline road stations, offsets, and invert i ~ elevations for all inlets are shown on: i i plans i prof ile . ~ 6. Grate type is shown on the plan and is acceptable. (Spokane County Standard inlets in county ROW, on private property other inlet type may be specified) (Type 1: D-2; Type 2: D-4) 7. A detail drawing of the grate/curb installation is shown on the plans and includes the 2" depression and transitions as per county standards for grates that are located within county ROW, or referenced to SCRS std. detail D-8 Ck113tv3.0/Aug93 13 I DR.AINAGE PLANS ( cont' d) 8. A curb cut detail is shown on the plans with the new county back drop with transitions and a 2" depression for curb cuts inside county ROW, or referenced to SCRS std. detail B-15 9. The plans shows acceptable curb cut details and grate details for installations which lie within private road easements. 10. If inlets are in a gravel road or a dirt ditch a 6' x 6' A.C. apron is shown around the inlet. / 11. Catch basin or special manhole details are shown or a standard drawing is specified. 12. Critical low points in the drainage system have been provided with overflow easements. 208 SWALE SYSTEMS ~ 1. Is the swale located outside a future set aside ~ area? See Findings and Order for where setasides are required. ~ 2. The swale bottom and sides have sod or grass turf specified. ~ 3. Swale side slopes do not exceed a 3:1 side slope. (A 2:1 side slope is allowed if swale depth is less than 1211 deep. Should only be allowed where constrained by obstacles) ~ 4. If depth of water from bottom to drywell rim is ~ between 6 and 8 inches, soil mixture has been specified which meets Spokane County Guidelines. 5. Drywell is: i ~ I located within 8 feet of the curb line, or i a maintenance access route and easement are i ~ provided ~ 6. Drywell stationing is staggered from the inlet by at least 4' 7. Multiple drywells are located more than 30' (center-center) apart ck1ietv3.0/Aug93 14 DR.P,INAGE PLANS ( cont' d) 8. Soil tYPe is aPPropriate for drYwells (Perc rate ~ i a 72"/hr) ~ if not : i 8a. overflow from a swale at a low point will be i i directed away from building pads by i an identified easement over improved ground an existing natural drainage channel covered by ~ an easement i I 9. Drywell location does not conflict with underground utilities. 10. Drywell type is specified. 11. Drywell grate type is specified (Type 3-std. detail D-7) 12. Drywell grate elevation is: below the invert at the curb inlet between 6" and 8" above the swale floor elevation / 13. Does the note: "Wrap the drywell with a filter fabric (Amoco 4545 or equivalent)" appear on the plans? 14. Swale floor elevation is: specified between 6" and 8" below the drywell grate elevation " at least 6" below the normal gutter flowline at the curb inlet for swale without a drywell ~ at least 8" below the normal gutter flowline at the curb inlet for swale with a drywell 15. Swale floor dimensions are shown ~ minimum area is shown i , / the area matches the required area from the 208 calculation for impervious areas. 16. Easements for the 208: ~ are shown on the drainage plans are shown on the subdivision plat are of adequate size to contain at least 6" ~ freeboard above the max. water surface elevation for the design storm are tied to the lot corners. / 17. The side of the swale that is the furthest distance from the street should have a top of swale elevation that is higher than the highest water level of the swale. ck1iatv3.0/Aug93 15 DRAINAGE PLANS (cont' d) ~ 18. The invert at the curb inlet is at or above the max. water surface elevation for the design storm 19. Filter fabric is specified for the gravel envelope around the drywell ; is specif ied between the drywell and the gravel i envelope installation specification is adequate. i ~ 20. Irrigation plan for County-maintained 208 swales i Lot plans submitted on ' 208 LOT PLANS ~ 1. Lot plans are required; submitted on 2. The 208 lot plans show: the lot number, block number, subdivision name, date drawn, scale, and north arrow. dimensions to lot corners drainage easements setback requirements swale floor elevation swale floor dimensions rim elevation if drywells are present curb cut station, offset, invert and length any drainage ditches shows depth f rom the top of the curb an attached cross section of the swale or ditch 3. Lot plans have been stamped by a professional engineer on all pages 4. Lot plans are of sufficient scale to maximize the lot size to the 8 1/2" x 11" paper size. (Drawings may be on plain white paper) 5. 208 lot plans were approved on CULVERTS AI1D PIPE SYSTEMS 1. The road culverts are at the low points of stream ~ flow. 2. The headwater was calculated for culvert ~ entrances and is under 2 diameters for culverts under 18" in diameter and 1.5 diameters for culverts greater than 18". ~ 3. There is a minimum of 12" of cover for all ~ culverts and storm sewer pipes ckliatv3.0/Aug93 16 DRAINAGE PLANS (cont'd) 4. The designer has provided a letter f rom the pipe manufacturer certifying that the intended pipe is suitable for cover less than 3' (PVC), 2' (CMP, RCP), 1' (HDPE/ADS) or the engineer has provided trench details for upgraded pipe bedding for these areas 5. The minimum velocity within the pipe system is 4 feet per second at design flow in a backwater condition. (Note: The County Engineer may permit lower velocities) 6. The backwater calculations show a minimum freeboard of 0.75 feet for each catch basin or manhole. 7. The minimum culvert and pipe slope is 0.5% and all pipes meet or exceed this standard. 8. All angle points in the storm sewer system have suitable access such as a manhole for cleaning. 9. At locations where two different pipe sizes enter the same manhole the 0.8 diameter points of each pipe are at the same elevation. (Note: Exception allowed for drop manholes) ~ 10. Is there any downsizing of pipes in a systems of pipes that are 18" in diameter and smaller. 11. There is a downsizing of pipes in the amount of 3" f or a minimum of 100 f eet in a pipe sys tem that contains pipes that over 18" in diameter. 12. Al1 pipes in the pipe system are 12" and larger as per Spokane County Standards; (10" pipe that is allowed for connection of inlets to catch basins or drywells, if the length does not exceed 44 LF and the velocity is at least 4 fps). 13. Al1 storm sewer pipes are located a minimum of 5 feet from a rear or side property line and have adequate easements for maintenance. ~ 14. Inlets on the same slope are located so that the ; maximum width of spread for the gutter flow does ; not exceed 6' (from curb face for Type "A" or f rom back of curb f or Type "R" ) 15. The plans and profiles show all culvert pipe types, stations, offsets, lengths, and inverts cklistv3.0/Aug93 17 DRAINAGE PLANS (cont'd) 16. Pipe materials meet county standards for systems that lie within county ROW. (Note: The type of pipe in private systems may be as specified by the design engineer) 17. The culverts shown are properly stationed from centerline stationing. 18. Does the drainage system configuration avoid conflicts with underground utilities? 19. Is there a need for energy dissipation on any of the culvert outlets shown on the plans? 20. Is there a need for rip rap around the culvert outlet at any of the culverts as proposed on the drainage plans. 21. The rip rap that is shown for the drainage plans is adequate for the culverts where erosion is a concern and the engineer has submitted acceptable rip rap design calculations. 22. Pipe anchors are shown for pipe grades greater ti than 150. ~ 23. There are no instances where water is trapped against a fill with no culvert shown. ~ 24. Profiles and cross sections are shown on the plans for all proposed channels and ditches. ~ 25. Ditches with eroding velocities have pr p r ' lining for erosion protection.L 1545 ~ 26. Water will properly flow from ine isting or proposed ditch on to the pavement as proposed on the drainage plans. 27. Where the ditch profile passes from cut to fill the flow has been properly disposed of. ck1iatv3.0/Aug93 3.8 EASEMENTS 1. Adequate drainage easements are shown for maintenance of drainage ditches or pipe systems. 2. There are easements proposed or existing for natural channels which cross the property. ~ 3. An easement was provided where street drainage was diverted onto private property. pN~J1~ 4. The perpetual maintenance of private systems has ~ properly been provided for. ALI 5. The maintenance of drainage systems within Spokane County ROW has been properly provided for. ~ 6. Appropriate drainage language has been provided by the reviewing engineer to the surveyor and/or engineer who is involved with the platting work. i ~ 7. Pre-existing drainage easements on this parcel i are not affected by this plat i i ; 8. Overflow easements are provided from swales/ponds ; located in low points MISCELLANEOUS 1. QC check of review completed (date) (init. ) J 2. Bond uantities for draina e item calculated g to~ R~ V (date) (init.) 3. Vertical curve sight distance worksheets done ~ (date) (init. ) ~ 4. Vertical curve geometry worksheets done (date) (init. ) 5. Draina e v ume worksheets done ~ ~ ~ (date) ( init . ) 6. Stamped road mylars to Permit Tech. (Sylvia/Suzanne) 7. Stamped lot plans to Admin. Asst. (Sandy) ckli3tv3.0/Aug93 19 ~w toi__) xEv~w c oMW lvr rs ~ A SPOKANE COUNTY DIVISION OF ENGINEERING & ROADS 1026 W BROA.DWAY, SPOK:ANE WA 99260-0710 PHONE (509)456-3600 FAX (509)324-3478 REVIEW 2 REVIEWER: Ed Parrv PROJECT SP811 DATE: 5 August 93 PROJECT NAME: Short Plat 811 PREVIOUS COMIVIENTS: . Indicate Section, Range, Township of project site (for future reference: should show at top of page - see 1981 SCRS std. detail S-19) ~,~rntersection should be located to maintain at least 300' separation from other intersections on vergreen (a design deviation request should be submitted) 00"60 "I~COP ~~as the Fire District approved the non-standard turnaround? (Fire District approval or design deviation request is needed to approve non-standard turnarounds. If this has been aa "approved" coafiguration for several years, then there should be no problem obtaining Fire District approval) / #/!,ri08 swale section: d. DrYwell should be wraPPed inside & outside with a filter fabric (Amoco #4545 or e ual) (see attached detail) Please provide an information copy of the utility plans for this project, so that we may Oc'-onlfirm ~ that there are no interferences between the drainage facilities and other utilities (pending submittal) CALCULATIONS: E~eProvide a contour map to support the drainage basin map (enough spot elevations to define ; the dcainage break, as a muiimum, should be provided if a contour map is not available) mo~wale floor area is insufficient for 208 floor area requirements (8700 ft2 impervious area ~requires 363 fe of volume for 208; 725 ftz of surface area is required to provide this volume at a 6" depth. the 30' x 19' floor d.imeasions of the swale provide only 570 ftZ of area) 7 Provide 208 lot pians - see attached guidelines (pendi.ng finalized plans) af I~~~fm M2 Bla, ff.c~IAs -wuc. Pl-ff li;"D( t~ m VA~°► muc D/P*~ t%* REVIEW COMIVIENTS Page 2 of 2 5 August 93 REVIEW 2 PROJECT SP811 9. 4An easement will be needed if runoff from the R/W is conveyed/stored/disposed in private rainage system facilities (pending finalized plans) tot, 'e ie,~ w A. /Dxk✓ W C01VIlV1ENTS: Aff . LT profile: Indicate vertical curve length between 1+25 and 1+75 w RT profile: Indicate vertical curve length between 1+25 and 1+75 ~3~Developer's signature needed 4. Where ' station 0+00 on Evergreen Road? E"6Wf11PA . REVIEW COMMENTS SPOKANE COUNTY DIVISION OF ENGINEERING & ROADS 1026 W BROADWAY, SPOKANE WA 99260-0710 PHONE (509)456-3600 FAX (509)324-3478 REVIEW 2 REVIEWER: Ed Parrv PROJECT SP811 DATE: 5 August 93 PROJECT NAME: Short Plat 811 PREVIOUS CONIlVIENTS: ,,00~~ndicate Section, Range, Township of project site (for future reference: should show at top of page - see 1981 SCRS std. detail 5-19) G K, intersections on //~Vp ntersection should be located to maintain at least 300' separation from ot~ rgreen (a design deviation request should be submittedwp"o'; S~ 4Y ,Jv2.Has the Fire District approved the non-standard turnaround? (Fire District approval or design deviation request is needed to approve non-standard turnarounds. If this has been cw an "approved" configuration for several years, then tbere sbould be no problem obtaining Fire District approval) dK ' . 208 swale section: ~ d. Drywell should be wrapped inside & outside with a filter fabric (Amoco #4545 or equal) (see attached detail) ~~ee r~ o 4,. 20. Please provide an information copy of the utility plans for this project, so that we may confirm that there are no interferences between the drainage facilities and other utilities (pending submittal) CALCULATIONS: 72~. 'Provide a contour map to support the drainage basin map (enough spot elevations to define the drainage break, as a minimum, should be provided if a contour map is not available) 5. Swale floor area is insufficient for 208 floor area requirements (8700 ft2 impervious area requires 363 ft3 of volume for 208; 725 ftz of surface area is required to provide this volume oe~ at a 6" depth, the 30' x 19' floor dimensions of the swale provide only 570 ft2 of area) ~k(A t& 6@pa v i~~"C~ 20I y( 37 ~ Sw~h2 7. Provide 208 lot plans - see attached guidelines (pending finalized plans) 7 1 ~ REVIEW COMMENTS Page 2 of 2 5 August 93 REVIEW 2 PROJECT SP811 ...`'An easement will be needed if runoff from the R/W is conveyed/stored/disposed in rivate drainage system facilities (pending finalized plans) 1#4, NEW COMMENTS: , LT profile: Indicate vertical curve length between 1+25 and 1+75 G~C- RT profile: Indicate vertical curve length between 1+25 and 1+75 0~ . Developer's signature needed C> . Where is station 0+00 on Evergreen Road? . MAILING AODRESS: OFFICE LOCATION: P.O. BOX 18779 N. 10115 NEWPORT HWY. SPOKANE, WASHINGTON 99208 SPOKANE, WASHINGTON 99218 PHONE (509) d67-5261 J. PAUL RAMER & ASSOCIATES, INC. CONSULTING CIVIL ENGINEERS & LAND SURVEYORS WASHINGTOM • IDAHO • MONTANA PJEVADA • CAUFOfiNIA OREGON (Revised July 19, 1993) April 1, 1993 Pro j ect #93029 STORMWATER MANAGEMENT PLAN for SHORT PLAT N0. SP-811-92 Portion of Section 27, T25N, R44E, W.M. Spokane County, Washington gou RECEivED (d 0 V 0 1 1993 Prepared for UPvPJ HELEN STALEY SPOKANE COUNTY ENGINEER P.O. Hox 790 Spokane, WA 99037-0790 ° ~ . p11L AA~1 CqM1uAST ~P~v~ w fftVg%c, ~ d~ v gEVcew tk y - ~ X : Cc~t~1►~f ~'~i'''~ ~ ~ooie ~v ~ S~ON At. EXPIREt 111,f/9s = JuL Z ~ 1 ~qR~ ~ ,i SGtE~~%E ~ - -a-a-- - - - J. PAUL RAMER ed F, v ~ CIViI ENGINEER - LANO SURVEYOR ~ STORMWATER MANAGEMENT PLAN The Short Plat site is located adjacent to Evergreen Street between 21st and 23rd. Soils in this vicinity are generally Springdale gravelly sandy loam which is porous and not generally known for runoff problems. The site includes three parcels 3/4 Acres + in size. This low density will not have a substantial effect on runoff quantities compared.to the existing open field. One drainage basin has been outlined which includes most of the proposed private road and is generally in the area of Parcel "A". The land is generally flat, but has a local low point in the area of the proposed drywell and "208" swale. We propose to collect runoff from a 10 year storm at that point and dispose of it in the drywell. Some runoff may also enter the basin from Evergreen Street but there is no defined gutter or slope to drain any significant amount to the plat. Evergreen St reet has on 1 y a s 1 i ght g rade to the north in the area of the plat. A culvert would not be practical in this project, so the runoff will be - collected in the "208" swale via the proposed on-site road ditch. The easement being established for ingress and egress will be sufficient to handle this small runoff. Runoff from other off-site sources will be negligible. The proposed private road slopes toward the ditch and swale at 2% and will prevent on-site flows from flowing north. The natural contours of the area are otherwise flat to sloping away from the plat. i f - - INGTON - SHEET NUMBER 75 R 44 E. 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Volume Provided 208: 370 storm: 740 Outflow ( cfs ) 0.3 Area * C" Factor 0.44 , ~ #1 #2 #3 #4 #5 #6 #7 Time Time Intensity Q dev. V in V out Storage . Inc. Inc. (min.) (sec.) (in./hr.) (cfs) (cu. ft.) (cu. ft.) (cu. ft.) (#1*60) (A*C*#3) (Outf.*#2) (#5-#6) ' 11.64 698.48 2.09 0.91 855 209.54 645 ' S 300 3.18 1.39 560 90 470 , 10 600 2.24 0.98 789 180 609 15 900 1.77 0.78 882 270 612 20 1200 1.45 0.64 913 360 553 ~ 25 1500 1.21 0.53 921 450 471 30 1800 1.04 0.46 928 540 388 35 2100 0.91 0.40 932 630 302 40 2400 0.82 0.36 947 720 227 45 2700 0.74 0.32 952 810 142 50 3000 0.68 0.30 964 900 64 55 3300 0.64 0.28 992 990 2 60 3600 0.61 0.27 1025 1080 -55 65 3900 0.60 0.26 1087 1170 -83 = 70 4200 0.58 0.25 1127 1260 -133 75 4500 0.56 0.25 1162 1350 -188 ' 80 4800 0.53 0.23 1169 1440 -271 85 5100 0.52 0.23 1216 1530 -314 90 5400 0.50 0.22 1235 1620 -385 95 5700 0.49 0.21 1274 1710 -436 100 6000 0.48 0.21 1311 1800 -489 ~ • y _ t DRAINAGE POND CALCULATIONS • Required grassy swale pond storage volume = Impervious Area x.5 in./ 12 in./ft. = 363 cu. ft. provided: 370 cu. ft. DRYWELL REQUIREMENTS - 10 YEAR DESIGN STORM ~ ~ Maximum storage required by Bowstring = 645 cu. ft. provided: 740 cu. ft. Number and type of Drywells Required = 1 Single TIME OF CONCENTRATION (minutes) , , ' Tc (overland) Tc (gutter) - Ct = 0.15 L2 = 100 Z1 = 3 L1(A) = 220 Z2 = 3 N(A) = 0.4 H = p S(A) = 0.005 n = 0.025 - s = 0.01 Tc (A) = 10.79 d = 0.4 . ~ L1(e) = 0 Tc (gu) = 0.85 ' N(B) = 0 Tc(A+B) = 10.79 . . S(B) _ 0 Tc(tot. ) = 11.64 Tc (B) = 0.0 Intensity 2.09 Areas "C" A*C A = 0.48 WP = 2.5298 . 0.96 0.25 0.24 R= 0.1897 - 0.22 0.90 0.198 V= 1.96 0.00 0.00 0 Tc(gu) = 0.85 0.00 0.00 0 Q(est) = 0.94 0.00 0.00 0 0.00 0.00 0 Holding = 3.56 0.00 0.00 0 . Total A Comp "C" 1.18 0.37 Q=C*I*A= 0.91 Q(est.) = 0.94 , Tc (total) = Tc (overland) + Tc (gutter) • Tc (overland) = Ct*(L1*N/S'0.5)-0.6) Ct = 0.15 ' L1 = Length of Overland Flow N= friction factor of overland flow (.4 for average grass cover) " S== average slope of overland flow Tc (gutter) = Length (ft.)/Velocity (ft./sec.)/60 B= Bottom width of gutter or ditch . Z1 = inverse of cross slope one of ditch Z2 = inverse of cross slope two of ditch d= depth of flow in gutter (estimate, check estimate with Flow) Area = d*B+d-2/2*(Z1+Z2) 'Wetted perimeter = B*d+(1/sin(atn(1/Z1))+1/sin(atn(1/Z2))) ' Hydraulic Radius = R= Area/Wetted Perimeter ' Velocity = 1.486/n*R~.667*s.5 Flow = Velocity*Area - n = 0.016 for asphalt . s= longitudinal slope of gutter ~ t ; x Ib }l Z tz0 =~2~+ rnr.rwctla:-ia r Cc~ = I0 i-Z`i 2-0 - 5 y i t J ~ . ~ 4 S.D. rlqht ~ S.D. left ' S- h 5~9h ~ ne ''o X~ ~ I V -y- XR wR-~ V EXAMPLE ~ L Civeni JL L - VALUES 2- 12' lanes to be crossed by o r'8-50 Ii I Approximately 90' Intersect3on ~ I P= 19 ft ' Thru highwoy desiqn speed = TO NPH SU = 30 ft Findi WB-50 = 55 ft Minimum required sight distance V8-63 = 69 ft Solutiont V=,De~T gn on Thru Highwoy Enter Charts as shown to = Time for Acceferation for X r 1 flht = 10 + MR+ L= 10 + 24 + 55 = 99 X left = 10 + wL+ L = 10 + 12 + 55 = 77 L= Vehiculor Lengttti Required Ninimum S.D. = 1260 ft. right S.D. = Slght Dlstance anG 1180 ft. left X= Crossin9 Distance NOTE: If the minor road Qpprooch ts not level, adjust ta using the applicable foctor from Figure 910-3. 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