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HomeMy WebLinkAboutDrainage Reports - 05/21/2008��QgOI oj-,b fi/(01/10ya, March 11, 2008 INTERWEST . CONSULTINGGROUP - Glen Schlueter City of Ft. Collins Ap rov Plans City of Fort Collins Stormwater Approved ay - 1h kvc--,_ 700 Wood Street Date ru a l -O$ Fort Collins, CO 80522-0580 RE: Drainage Design for Lot 7, CountryClub Corners Third Filing Replat (Subway) Dear Glen, Please accept this letter as an addendum to the drainage report for Country Club Corners Third Filing Replat and Fourth Filing. The original development' designed detention facilities and conveyance elements for the entire area prior to the City's change to the rainfall criteria and the addition of the requirement for water quality facilities. This project will construct a building on the pad site on Lot 7 (just east of the Burger King restaurant on North College Avenue). All of the parking and sidewalks on Lot 7 were installed with the original construction, so the only "new" pavement is the building roof and a patio. We have prepared this letter and attachments to discuss the affect of the rainfall change and the requirement for water quality. Landmark Engineering has prepared various studies on this land as development has occurred'. The Country Club Corners Third Report included Lot 7 and designed an interim and ultimate detention pond to the south of Lot 7. The Country Club Corners Fourth Drainage Report modified the interim pond and is the most recent report that includes Lot 7. In both reports, Lot 7 is within Basin A2 and has a "C" value of 1.00. This "C" value does not change with the proposed building, so the only affect on the detention pond is the change in the rainfall quantity. It appears that the interim pond shown in the Fourth Filing Report is the existing condition in the field. The area to be built upon is 3,300 square feet. The difference in 100-year rainfall between the 1996 design (2.89 inches) and the current 100-year rainfall (3.67 inches) is 0.78 inches. Since the "C" value was already 1.00 the theoretical additional water to the pond because of 'the construction on the 3,300 square feet is: . 3,300SF * 0.7.8inch * Ift = 215CF 12in In the Fourth Filing Drainage Report, it was calculated that the 100-year water surface of the pond is at elevation 4984.72 and at this elevation the water -surface area is 36,984 SF. Adding 215 cubic feet to the overall pond volume would increase the water surface elevation by 0.006 1218 WEST ASH, SUITE C WINDSOR, COLORADO 80550 TEL. 970.674.3300 • FAX. 970.674.3303 feet (less that one hundredth of a foot): 215CF 0.006 ft 36,984SF We feel this additional volume is negligible and that no changes to the detention pond are warranted with this project. Another illustration of the magnitude of this change is that the project area drains to an existing 30" storm sewer.. The additional 215 cubic feet. of storage would be accounted for in just 44 linear feet of this pipe. The pipe is lower than the detention pond water surface and none of the storm sewer was attributed to the pond volume. We have. attached copies out of the Fourth Filing Report for verification of these calculations. . In the original plans, this pad was designed to sheet flow south into the shared driveway and into the storm sewer system to the pond. The proposed construction mimics the original design with structure and patio encompassing the majority. of the site. It is not feasible for this project to modify the existing pond outlet to provide water quality, and there is no room on the site for a water quality pond. We propose adding water quality for the restaurant by increasing the contact time with landscaping. The attached grading plan shows_a shallow swale on the south side of the property. This swale will take flows from the proposed patio and the roof. The Swale is designed to be 2" lower than the existing sidewalk, so the capacity is minimal and any sizable storm will -quickly fill the Swale and flows will sheet to the south over the walk and to the storm sewer system. Minor storms will travel in the swale to the east. to a new curb cut and into the storm sewer system. We do not propose that this area be a technical bioswale, but a mulch bed with shrubs is proposed in this area and the minor storms will have significantly more contact time with the ground prior to reaching the pavement. With the original design, the entire site would sheet flow about 20' before reaching the pavement and then the storm sewer. With the proposed design, this contact time with the ground is increased to over 100' and the swale is at a shallow slope (1.2% to 1.8%). With the mulch and shrubs, the intent is to increase the time it takes for this water to leave the. site and give sediment an opportunity to drop out. We have called for an impervious membrane to be installed between the Swale and the building so that there will not be standing water that actually touches the foundation. The site is less than one acre, so no stormwater discharge permit is required. There is phically not room to install silt fence, so the plari calls out wattles in the proposed swale and at the two inlets that receive flow from this site. Please review this letter, grading plan and the attached excerpts from the Fourth -Filing Report. I appreciate your time and consideration in reviewing this submittal. Please call if you have any questions. . a OR SrF Sincerely, moo` . • a CA Michael Oberlander, P.E. 34 m a, U-0'�r�Q �ssian�n� eNc,�� N —�' NN I °T ' I LOT 7 .Q wNKs um aKms I I awa mP ,ID wE In Y: I I I aTF xuu ame sraP eE �: I . I I PIT �1 rwc 'arza rw m ec'AY Asp ' \`I. I �[ • /. Ain sYi ^ -•�I nns Y�PJP�r m�iwau ¢TYwi �A A •'�.�,— Oar pA _ _ _ __ _____ �\. I ❑❑ / J I I PLLIW T.V sDIT1' AP w R6TNL IQw TY Mlp 1' i1PC X I tI • w mM¢ raw wYY m RE1 Dam e NY OYSwG 12rER er . , I uar YISTALL I• SM4¢ s' Pwsr NEw KIEn I I - I i AWI 1' m 1565 SFA'W m (>o PAr6DI1DY1 RIYM a ND ITS .A' PIPOA05mBiNG FFo4(9T9.08J.OB —7 I . • i Fit 4Yq e wA I I _ I ... xrH Drwour •� / I M • w 1 1 '.. AJs. • I I �� \1 L r \ AYY I / S t \\\. Alb!. .' •. ))Af »» .- '. . F..• ' w Lor B---- -o. rs mM PUL ALL YPEIIMDS 100w1A11E OiME N0 BEIYEDI J M 1" /✓Y FDIYATIX NS R6 N SYUf Lail MUM WAMM i.— ...�.r... ® tetra — x -Mn . 1 �i •<®e.x�elo.v ��< Y[v.®e.as <M NmE xob vi0![<snL R..r��'err.4'e sru<ra Y��Fr lw4�P prP< ROW_ w am— r <rlrx vrsn �.y sew —YwrrfN VO s rI esm — wsil[ssr eso �mw m.es mi<c.. .solrol ' mmrw nbrtnbx smn xA rT�TTII e�TA= . � RPrteil.11 S[Te WATTLES ---------------- --- I INET iRl -Yet, r mWL MiF1 1.'u. bs1 1¢p fu PPS) Y. J/t FN OY I M -.FY nYr Mx ..Y 4 PR.' F MM Pi 1< a 4pNq rY4. ' 1 m-�iNecUa s spa 4teTV des— � IM,w N vewlM M PI IM M 1 l®4 we ee. me .NIA Pn swq Y n. we.Y mlry ewwga 4 w Op Y Iwsu4Y b. wN1sA\P w <II.�\ mpwllm Ny..Y <� PbYq s b YWby w N4 rlp. lr sne 4 net Ip .s/b Imm w w0 R40. YeA1P40 W. s141 m'gA9 b w CUY4p 1 No Oa4YP tlbw0 Mrs e/0 RIW N imle: s114y ' 6 Ys Ip R aqe Iw w sJs Den w —PwYb .w b e NnYa� M 1 M Pnl'w MII qL r. W ramyw (Mn� YeRYnN R4.} �nmMq m e Lea a.<e .num • Iwt ew Mey N�<le ML aM rq YRe rWn IP W MaNNiws YL TYPICAL WATER SERVICE r. mxm Orr6rCT fXU115 STORNWATER Uw116 CONSiRUCD. DETAILS PYs emle OETAA NOTES: - No DA'li DeacwanoN 1. ANY CURB. GUTT1 OR SIDEWALK DAMAGED WOH THE CONSTRUCTION T - SHALL BE REPAIR AND BROUGHT BACK TO TS EKISTNG CONDTON OR BETTER 1 2. WATERSERVICESFU.LLBET'PE^K•'COPPERINS ALLEDPERC(IY STANDARDS. - 3. SEWERS CESHALLBE4"SDR3SPVCINSTALLEDAT2%MINIMUM SLOPE ' 4. ALL DISTURBED AREAS SHALLBE SEEDED Mn MULCHED. S. THEMNISHEDFlAORELEVAMONISh E"MEASTHEMINIMUMOP ING ATTHE BURRING AND IS THE MINIMUM ELEVATION FOR PROTECTION FROM THE IODYR STORM - I 0. EROBION CONTROL FORTHE PROJECTSWILLCONSLST OF TNSTALUNIG ' WATTLES IN THE SWALE SOUTH AND EAST OFTHE BULKING AND ON THE TOWAOIACENTCURBINLETS. ]. ANY SEDIMENT DEPOSMM ON ADUACENT` DrdVESANOPARKING AREAS SHALLBECLEANEDDAILY. 10 S 0 10 20 SCALE I^- la CALL UTILITY NOBTCADON CENTER,OF COLORADO 8 DA feu ]- oAn Y UAW(¢ . Yell CK•. WADE m FY:INArz In BFM ' .. T FrIR me NAbPNG a NDFADIDYD ' w01aEn uwrYS , a. xP.e T DIRB OPEMNC NFTAM1. NP,a L 0. rol YVd w .rr....l wR P.4q R P<ro. .YM� .�T .la � YMYn rR4 ' a. s srwM IssN rw.a eU . nPww 4 r ww • -I N sN. Nnv x M M .AIM 1P 1e1 .1 wNr pa 1 4..Y4 M.wf^Y M. — aroI M'Y r IIn Iroa t. IY. s /unMY swrotlw (wa sP.T ec) M Grob Ya 6 M le W e..�a blFp b r e s�ns� M Y wl .w s4r .0 M r YYI .4\ 6 O.Y �qlw .M n<� .s A.IWtlw wM'ro M w w� .Y)sl •+1� Ls m< ,. n . Pdn .Yes r� N.wAY b N,..rN cra Nnlr .N. rr w we,d w.�.rYr EPrN w r N.N-.N .o— G = eET11NG M e/1 N1, EKD 1 0. W&M IRIt98 V v eI 0 U Hm C IL O�1 Z n Mo- 1W' a11 L 0U� d % o wwm one ow cnw M7 W og Ua a nm z_ UO Z �3 c U= F O J E m O Z � 1ho01 �21 b � o' u CITY OF FORT COLONS. COLORADO - UTILITY PLAN APPROVAL APPROVED: Olr EMOIEFA IYrz CHECKED'BY: ' urEn a wAsrzsrzA uwT IMrz CHECKED BY: sreYwrzA uwTr IMrz CHECKED BY: PMY(e A YCO1GP011 IMrz PRfAI. NO. IOBT4 CHECKED BY: murc rAOI¢m IMrz 2 OF 2 CHECKED 8r: V. i \ I I LOT LINEM I LOT % IX.RAMP I I I ALL IX WALKS. AND CURBS I 3 I I AROUND SITE SHALL REMAIN EXISTING CURB STOP AND METER PIT. I UNLESS OTHERWISE NOTED. I II CURB STOP TO BE REPLACED. I I=I \ I I METER PIT TO BE REUSED.L I I I I I I I z L> — UTILTY EASEMENT —.— - _— 4: ----- ��T d \ a .a n < ° d e e I a . " y , d �I WATER TAP TO BE ABANDONED. I a ° 7970 ., ? a, a 7893 7890 q 7872 78..68 a q a e 7857° I CORP STOP AND REMOVE 2' OF TR4 A s = =_ � -- — — 0 0 ° —-$�'—'— = — - — -- - - — — — ° 7i2B ADJACENT SERVICE LINE (MIN.) 49�g 7&93 79.05 79.05 I I ° I \ _ e 7&75 i &TER TAP 3 SOUTH OF EX AP • P\. 79.30. 79.20 :. ° �; : ' LOT j -W'TAP AND 1 TYPE K COPPER I m E FROM MAIN TO NEW CURB STOP w e. I e q . 79.03 7&85 7&81 79.03 7&81 I \ AND EXISTING METER PIT. i a ° I . :. \ \ _ 1' SERVICE 5' PAST NEW METER I I .. 77.50 \' \ j ZE TO 1-r SERVICE TO BUILDING. SERVICE, 15 LF OF 1-}' SERVICE) I I, 4 7&81 PROPOSED BUILDING I \ \ 76.73 FZ tIVE AND REPAIR CURB AND WALK ` I d I 77.26. FF=-•�979.08 \ ° OR EXCEED EXISTING CONDITIONS. e I e ° :� ::" 79.05 77.00 . 3 I q \ •a e IX STORM ; IX CURB INLE INSTALL WATTL INLET FILTE I EX 6 CONNECT TO EX4 SEWER STEPS I a-.76.65SERVICE WITH ClEANOUT AND -� I 178.81 - - 7&EXTEND INTO BUILDING FL 70 ' I 77.00 76.61 77.26 \ \ 7&95 - 78.80 a 7878 ( 79.05 79.05 °7476:0 I a &N \\ \ 3 77.05 �... 79.05 77.35 a 77.17 77.10 \ \ \ d a m 76.67 \ \ S 7844 \ \ ° ° 78.42.. j 7&00 77.80 77.25 7&95 .� \ yoov n.es----.-�-- n.�o �r. i6.94 ----- 76.78. ° 5 3 \ a .a7810 d .. e , e a. oq d a, _ e ° 7702 • a ' ° . . \\ ' 77.96 c e ° 77.5A - . d 7719 e b ° �'.a ------ a%L— THICKEN SOUTH — — — — EX C — 3 . LOT s FLOW PATH THROUGH PROPOSED — — EISTA VEGETATION (WATER QUALITY). _ NO TRICKLE PAN. INSTALL IMPERVIOUS MEMBRANE BELOW GRADE AND BETWEEN SHALLOW SWALE' AND FOUNDATION. INSTALL 3 WATTLES IN SWALE ntimin mNSTuurnnN 3 r - ;c FINAL DRAINAGE STUDY FOR LOT 1, COUNTRY CLUB CORNERS FOURTH FILING, P.U.D. p 'C POUDRE. HEALTH. SERVICES DISTRICT CENTER Prepared For: Poudre Health Services District 123 N. College Avenue, Suite 203: Fort Collins, CO 80524 January 8, 1997. Project.No. PHSD-611A-01-304 CONSULTING ENGINEER Landmark Engineering Ltd... . 3521 West Eisenhower Boulevard Loveland, Colorado 80537 -11 r to I HIM IIIIIIIIIIIIIINIIIINIIIIIII L�II�1 Runoff cgs oil --1 HIM No Text N C ava H5067-1A-01 Sc>4 II/ PC7-EkP5/D , . P000 VOLUt^ ;'!_t=V Drlrnl VOL. `7Z Io 31 f3 13-733,S - c�, 7t,.. I,0 �tt;ta, '73 Zslto9 3�� Uaz. 0, i 1.0 75. ? 7 C IRRCC,vLl+2' SID_5) glZaL IRuj:) DE=�,ISloN /1PPl�a�'Iti�h"'7= 100Yr -�i�Ji — 74 89?`f: -74, �= i oo y.,-- H w L - 7 <I 1-7z. � I E _ r • I `----- ;DRAINAGE PLAN EXHIBIT ; r I NORTH RT ANNEXATION COLLEGE ' I I I I NORTH I COLLEGE 'ANNEXATION 97021-0i 9]021-00-DI. I {\ ry'R II I I. , �I I I � � - , 0 ma\ `97021-M-004 r 9]@t-'0-001' .' p 9702lrOD-021 - 197021-00-012 I 97021-00-002 , 97021-13-001 ---9 01 -• �. T \ 'V9 - --- \ NORTH COLLEGE AVE. NORTH COLLEGE AVE. 8 r INTERIM DETENTION P 1,.r,-r-_-______T 'T . �--.' / 1/ -- \ la •br _ I' I•j i I ; 9 Ol/b SUMMARY I m rS1 I 1 L,JA+' / 1; ,_ i \ V % �I •au I - .r 1W Ma=UDU-]{.7R I u.TJ I 1( I I V' I I wIRDFR.IND I J 1 f= tm m lv r MW - am' crs M 1w 1 I r A P I I I ' I 1 -c = 5 IM L. a61 w11e.L1 KMc) Y I F. y m I VauME AT M1a' Irv¢ - tm AI•JE rm i m S'V.A _ I I t--_--J �_`1 i .� C i I ' f •lit a 3gj a i 1 z z 1.51 - /, IIg r I I p 1 'Fe I C I I' , O i a n dg- l ;47 k EXISTING .11 �fjt�, D I �' J I I D➢AI j \\ DETENTION r Z -FUTURE DET'ExNTIO C 1 705, rN " m ' I• i --- r yC 101 '•a 9 p m V A ��---_----_— I m—ram I a I a _ — _ _ _ I r ♦ ..:. I¢ ,/u \s�uT 1 ____ _-___ /� / ♦ , ' I. I I I O Q w 0o W All }J J � •, � I i •! it 7' i ` �i ---' �ti '7• W jj" ...ffjjj •J .:,1 J • �. -- I -` r_ __ W Z g•�• _- ;•Zvl I gg �i, I �-.:. _ \\ �'•�\`\�\. II•. Imo, �� a i - .li 'i�* �* I m 1 a : A h e i o i t 1 ,11{`-1 / i-!c sa "'{\ �\ I I i i 1•I I • f Qrd-aaT I U.. .N • .rscn �, LI / A I.V(� ...,. r �1 �� Y1..© L'D sTi�TiEr�r��'�•� \it'� _#r `LYg, DRAINAGE SUMMARY TABLE DEVELOPED CONDITION FOR PHASE 1 Df9GN A9MSYI Pura <as) (os) 1 M n.m uM l AW M.b )in ! AlA I0.b 112D A MAXIM W6 "AI ! 91M.91M 17M On l 61.10.1141,54 8aB1,h.p 7Ltl IA.7! - narsu law e�D - ORO ZA, 1A D, 01 0.01 N1]MDC _ - E u M C W W o __w Ro V W DATE: FEB. 1A, t99] SCME I' - 50' DRAWN: IA5 CHECKED: PM APPROVED: KM I Nt III RII I B8 f♦ � �. / 1J% i Ii R I LEGEND � `61 a W 1 I { Tf to \ 1186 1\ - _ M 3 raq / .4 A i I ® DOWMI Porn - o Fi lI j .60 i 87 Z 0 § /� ,• .I i I B5/Jc Any' Ruvc) H lJ ji PM- 83 b 7 -m I ' R I qm ZAe lm m IIMNOFT (Gis) Z ____ I I I IIII 9 I Q ♦ 11 -a G� _ ' , I I -1.60 to n, lll)or (OS) r w j I lii \ I 5 / - - 1Bii "R Cams To �i .i _ T-CD I I ; >, _ m ,GAR N7a�\ ' W •e:.m / z . ,• ■ cans L) L+- ()\ I 1 I i stm moroso sr6mr 6RAm y z algal MN-" L I 'll \ \ ` ^' E cwi N C ~ WX 'm I I^^i 1 - ,+ I ° _O LI = mr"" -'"C \° _�� I _ a,d.D.6D --,•-s,rl-__ EwmKc stmM DKNK L> m m PIPE)-1{.za - ,• awe - ♦ W X S101a, •� r� - �® ,,,ry /i B{ I 0 9. E3 I SU66A91 Bd1r6VfI fn W J w mAx ANCIMINI I .. i ; ID i,t _ I .r. .I' _ _ _ , / .el I� f.. -- 1 i 1 M C5 Z JS Ir _ - rm 1 II ,,.-R,..,- .aB-- -----L •. Lt— -'�- - o. _ .. - - - Cityof Fort Collins, Colorado Q ��a r �*�`. I rmk xwY )u .r / ,�' - TiLITY PLAN APPROVAL ,y¢j Z P asa ` L urY -M/ -- u Y- , W taAs aLLT w 1 , YYYY 1-....1.. :.o .n ..r .,. y,/ T -\ :• OY16 .•IpIIM ,. r a tm,.c uqL 1 :3Y' ' = x o w I I II I rRFT /17 I - 1 n 1 ' .� INUT /I! IaET /ID MII�O �_LJtSi9 •r'r.p,.n VK 1 0 I II II fnuY z) Q =28.30 I 1 LOCK 2 OrI ' AT NO-1.OF VER�REEN PARK 1 1 \ Tay 1 W U II II 1`jl' -oic la 1 I 11 APPROVED: J W Q I I I I 1{.2S _ 1 1 uv o[ Ja� f+iii v` / , I I C3 _ Z I I L Il .I I 1 LOT Il LOT 1 LOT'9L -1 LOT a 1) LOT 7 1 / 1 1 I-, a„•LOT 2 I LOT I 1 1 DM.eYr sl t.IY.M l4 Q FA LOT 12 ' r-� F I , LOT b I LOT 5 Ia I $* - 1 Q ^ - LOT {' LOT 5 r--T --Fb°L 1 1 � Q •y I 17 1 CHECKED BY: u• a.v.97 I- 1I I I III Wf am BP u 1 , i jl I I I I I/ r!,.)p- BLOCK 7 Or REPLAT NO. 1 Or-44(GREEN PARNI O O Pr ___________ - u CL ill J Q BRQILEWIF SMMM.R1' AT OP -a - 10 YElR BRISTLFT.ONE SUMMARY AT OP-6 - 100 YEAR r - 1 --i___�'♦♦ 11 I 1 1 r CHECKED BY: J J F sm6lma 6 x STRm D N PPE - GRAPHIC SCALE SY.m..Yr uuav o'L) u i R. SuaBAID2 0 N a1R¢T cow PFc Qm CHECKED BY: �A- JOB NO.: PH5G crs an cr.a I.M crs A. D.m cis &V crs 6a.! crs w am vs 0M ar.a LW c,r.a r Tm crs lab crs '6 crs P. • R..rr.M.. D.Y u uD crs Dm crs 0.m Cr.S 6 tuA vs am rss ,sue crs CHECKED BY: an Aot-3o{ roue aw cr,a msa c.r.a ll.87 crs TOT& 2a« crs EA,I Crs Im3l crs -� (a r¢t > ' D RDTAA {mV SRE (Im A.) - 2].M . 2lJl . )AI - m.w Cr.a SHEET f{ I I..a - 60 M1 . M.]IErBK S1R[R CAPAQIY . ,].77 Cr3.> l0.11 CR ()aa. CTS ONRrtE . ).!! D)a ORSRC CONMmUIR ro ems11S011q 0 TOTAL R]FASE - m.w . 0.l1 (RVROf11 KDIC) - !13! CHECKED BY: o➢rNSIRr7N PIP[ WACIIY 1.KeT. 10- . y CR 9 IOTK IN rPE . 24.11 , 0.01 (WRCF11 NrIC) Or 66