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Home My WebLink AboutDrainage Reports - 10/31/1997-Final e, Report P"RopTy of �( ... IVORY A4; z s. �TMTM1 DRAINAGE REPORT FOR PALMER OFFICE REMODEL AT 3636 AND 3700 S. COLLEGE AVENUE PREPARED FOR PALMER HOUSE FLORIST C/o THORP ASSOCIATES - ARCHITECTS SEPTEMBER 4, 1997 PREPARED BY STEWART & ASSOCIATES, INC. 103 SOUTH MELDRUM STREET FORT COLLINS, COLORADO 80521 970/482-9331 STEWART&ASSOCIATES ' Consulting Engineers and Surveyors September 4, 1997 ' Mr. Basil Hamdan Storm Water Utility ' City of Fort Collins P.O. Box 580 Fort Collins, CO 80522 1 Dear Basil, ' re.�Pahner Office Remodel - 3636 and 3700 S. College Ave. Mr. Roger Thorp of the Thorp Associates, Architects, requested that I provide an analysis of the effect of the proposed remodel on the storm drainage of this site. ' The proposed remodel includes the east portion of the existing building at 3636 S. College Ave. and the existing parking lot located directly east of 3636 S. College Ave. Also, a remodel of the existing parking lot located east of the Palmer Florist building at 3700 S. College Ave. is proposed. ' I have attached a copy of the architect's site plan showing the proposed remodel areas. There will be some relocation of landscaped parking lot islands, and the rear portion of the existing building at 3700 S. College Ave. will be removed and replaced with parking, but the amount of hardsurface remains approximately the same. There are two existing detention ponding areas on the site. The proposed remodel will not adversely effect the function of these ponds. It is planned to lower the bottom of the east part of the pond at 3636 N. College Ave. This is being done so that the parking lot will not be so steep from the east edge to the existing center pan. The capacity of the pond will be increased slightly, but not enough to make a noticeable difference in the high water lime. The existing detention pond at 3700 S. College Ave. was designed in 1987 by Stewart and ' Associates, and the existing detention pond at 3636 S. College Ave. was designed in 1995 by WESTEC. Copies of the drainage reports showing these designs are included in this report. The pond at 3636 S. College Ave. is referred to as "Pond A" in the WESTEC report. ' During the parking lot construction, rainfall erosion will be controlled by placing a sediment trap over the detention pond outlets. ' James H. Stewart and Associates, Inc. 103 S. Meldrum Street P.O. Box 429 ' Ft. Collins, CO 80522 970/482-9331 Fax 970/482-9382 The erosion control collateral should be the minimum of $1000. I believe that no further drainage designs or plans are necessary for this proposed remodel. Sincerely, Phillip I. Robinson, P.E. & L.S. s a 4502 rrc a g a cc: Mr. Roger Thorp JOMPUTAT IONS STEWART&ASSOCIATES Consulting Engineers and Surveyors 214 N. Howes St. Ft. Collins, CO 80521 (303) 482-9331 By: PIK Date !!-/g) 07 Client:PC? Im e I- -Sheet No. of P Ctd By: —Date —Project: ReyLlfar, of L g �-f e f rif Vject '5 fO r-" rqA 1 r-? at cf e R q rf' m V _ i qd_J__ io-Ii..- I 4),e I gi r es &I q+J ef7 0 L/P Ot es. J 0: C-U. P I lz! tg Ok� 10 �e �r) I.i4 -'CIIcn i .1 1 e4k_ I Ilue? 0+ 0 W 65 1 141,.faa;Icf '70 ICA r +v�� A-7 e ?Of X? OL�/ r % �zc J.A ��Vl. 1 4L A e; ie I ie r> 1-4L1Ir)!I V i �? , sAo rill e � e � r:e� f-I 6t 4i 4�1 I t — 1 1 I I W v PYi5tirg overflow I . I I --t --- Q' •^ . %wOf r I -- -- Tract-5 Observatory Hts. Palmerin ;�_ I , -K • Office _----T----- a Re 1 ocjeiiMao RM +.. ''�L�vwv: LY19f lrt3 I �� (lY I •rCC[ AVCKO ?''' YK1�b68D , I rct�wrq »eu G oat:rg n,r.:na !L remrlm 3 G 3 G r` Q C4 ?` I ..e I - ----,ram --rg ,i• •, Repl�.e L.Ix�rq A? are LYi i0 form, Kw W 2i' . I _ wide 'X1aC] NGC j I bast Ea lik Olilcarbs relccallca Mew srlpn goasxo :InL •.micas cLI LYUGrg c.lb W tv"enloveo (��. i� W 1 i G.i.AW4 'a oecapjn to rc ru.r a YXTI♦ / I // New I T I q)V Curb, 5a (�il I I • I � I / I'! �� j I I r'I� `�• wwmk Palmer . Flowers i, I I I I i I O re�,� " 3 700 ,a�smpL 1. ! � —.+arcs tlro cYlstlr9 % r� • a ! n grremarre 4snaterm nan ms • / I - /� I area to tre . m v /1 A -9I 9! / ' I � ' existing iamcapkn/ ', If � �W I •'-_ •ICw IaKl,tdpL Mjlald — _ ! e.go^g oars;r5 a ^enwn / — GYatlro "M G l.vUlw- pit to rL»layl 1 r [Yatufa Cr" swewaS, to renal ! I III Total Exlstiro Parkin I115 Total "'Cw Parg!nq ' 1 I _ Site Plan 1 NOR114 'FES .&OMPUTATIONS STEWART&ASSOCIA Cormlfiineers and Surveyors_: 214 N. Howes St. Ft. Collins, CO 80521 (303) 482-9331 By: Date Client: Sheet No. --2—.f �kdBy: —Date Project: gevi51'0n 0�- L-c-41C I F-e&' vie .I*bject -51 0 r-r-) rc;t i n ep r4- - 7L i 7 71 �- -Jd /4 CA INC. -SAO— ch 4LC s r-77 T:( 0 k4 %-4 k or I V"x �5;s It I I:O M PUTATI O N S STEWART&ASSOCIATES Consulting Engineers and Surveyors 214 N. Howes St. Ft. Collins, CO 80521 (303) 482-9331 ly: P j 9 Date 2 2 Client: S 1 'r0 P.M 1 rn er Sheet No.�3 of cc 'hkd By: Date Project: AQd l Pa jeer P1or fs - L.aa- 2 F een e v Svc cJ Subject U r rn ' I' In a to irk ' l,�o!Iv!.wG! -�-q i -� I I i..I ,..�.' I �Ohat/r I ! la—�c� i ! i ; yUii/rMiL = �T � I 25�7!4� 4..h ! ! I _.I Q I 3o Z j 333.0 I� I-'►✓L= 3ri.7 70 I_ I I2-77 U -�✓� -- 31i • i � 7 i .. 1. ' .., .. .'._. I ._.I .. .., ._ - - !-' -_ i.. _ _ I I -1 r j - I L_._ . - ! I • I ! I I V�nI I ' � I 1 UlW>� J • l � •tQ \� ' 4i'1. � ' . i 1 , �- -� .Z tr _ • Z .. .' 'N Qtr ul• m 11 y O 1 i o / tc I��ryr o;•.1 `2�may -c-__.... �..._...�._._..L..,._— . M � ,: i �7N%�t ', �. 1 .y telp 1''•.' '�' ��—�n.i. uti.�7...�a 1. •A'-1 46z. • „ ' •+'' �-' a •'I � � � i±�� I �� / Vo a. g. v AN tp rr � t .. 1 y •I I LW -- ---....� '. fN ✓r ".�' .' .�. :Uil ICI _t tir� .1 t l is M .I I I 'J / �o •/ •rl I: �I 1 Q C w W 04- S ki) Mu, in I ic J, COMPUTATIONS 1 Fort Collins, Colorado James H. Stewart & Assoc. 4 AL Date (,✓R qClient: -il na, Ax F6P o Sheet No. of —�- kd By: Date Project: Job No. bject CALGl1 ATlD,US /0,2 L-O--T.S...I,-Z, 3. 30 Q D = D• ..95 .. x 7 0 : Y. z, /.S = /� 3 .G..�s. _. ._ .:-------- 3 X .7. 0 X 2• is - S c- H. &o = - /O .. (/�.3 03rJ c I�ETe.yT/ou. _ REQtI/J2ED -...- (-µ _ �. 3 .x . ?•-S-_X Z./s. /.G. C•Fs..- -- ----- Pe.e�,AaE,vT C AP AC cry Or- Ro D = iz. 0 a 0 1 _ _ COMPUTATIONS James H. Stewart & Assoc. - — ;---- — -- ^-- ---—- - — ; Fort Collins, -Colorado _ - - By _ ---+2 A R----Date -1& _ _ , ._-- Client:- . 7 om -Sheet No. � of o� - ---- Chkd By: --- Date-- ; ---Project: �FFii%FY s v S Job No. --Subject ._ -Z F_ TEw TtoA.) - Po N a -- -- --- — ---------- — -- 50 ---- - i �o¢,09. _ _ zz,os6 2 3 2.S- /o -- i i j c ' I ' 1 Zo��,ic cv.GT � i l C t 3888 Cu, f T: zo -30 i i ' DRAINAGE AND EROSION CONTROL REPORT FOR ' MISCELLANEOUS STREETS MITCHELL DRIVE and J.F.K. PARKWAY FORT COLLINS, COLORADO t ' DEVELOPMENT LOCATION AND DESCRIPTION ' Location ' Mitchell Drive and John F. Kennedy Parkway will be completed along two segments between Horsetooth Road and Bockman Drive. The completed roadways will allow for through traffic between these two east -west drives. The street improvements areas are shown on the vicinity map Figure 1. The land on which the two street segments will be completed is owned by a number of entities. The Site is located within the northwest quarter of the northwest quarter of Section 36, T7N R69W, City of Fort Collins, Larimer County, Colorado. Prooerty Description 1 u Mitchell Drive will be completed from Larimer Canal Number 2 (the Canal) south to the existing segment of Mitchell Drive through Toys "R" Us and Western Auto P.U.D. and includes approximately 550 feet of new pavement. This segment will be on Right -Of - Way (ROW) previously dedicated or new ROW dedicated by Spiro Palmer owner of Lot 5 of the Observatory Heights Subdivision (Showtime Video). The contiguous properties to the west of the new pavement have all been developed and will have new access drives installed with this work. The contiguous properties to the east are undeveloped except for the very easterly end of the Showtime Video lot which will be separated from the west portion by the new street. The land drains generally to the north and east to the Canal. JFK Parkway will be completed from the existing segment traveling south from Horsetooth Road west of First National Bank to the existing segment east of the Toys "R" Us and Western Auto Stores P.U.D. which extends from Bockman Drive to a point north the Canal. This segment will include 560 feet of new pavement and will be located on various parcels of land. The only development on either side of this street segment is the south parking area associated with the Strachan - Continental Subdivision located along the west side.of the north 100 feet of the new road section. The land drains generally to the north away from the Canal. 1 I DRAINAGE BASIN IDENTIFICATION Descriotion ' The two street sections will be located within Foothills Drainage Basin. Mitchell drive is also located in the Heart Special Improvement District (SID) [11 and Attachment A. ' For purposes of analysis, Mitchell drive was divided into Basins A-E as shown on Figure 2 and The Drainage and Erosion Control Plan (Drawing 5) attached to this report. JFK Parkway was evaluated as four basins. DRAINAGE DESIGN CRITERIA ' Regulations The City of Fort Collins Storm Drainage Design Criteria 121 is being used as the basis ' for this report. Development Criteria Constraints ' The Mitchell Drive improvements falls within the area controlled by the Heart Special Improvement District (Attachment A). The Heart SID allows all properties east of ' College Avenue and west of Larimer Canal Number 2 to drain to the Canal at a rate equal to or less than 0.87 cubic feet per second (cfs) per acre. Improvements were made to the Canal under the Heart SID to allow for these storm flows. JFK Parkway, north of the Canal, has no drainage constraints other than the City of Fort Collins street encroachment criteria. The street improvements will be installed to ' allow drainage to flow to Horsetooth Drive at this time. Improvements to the land West and east of this roadway section will be responsible for the contiguous half street drainage in accordance with the drainage criteria set forth for the Foothills Drainage Basin. Hydrologic Criteria ' The Rational Method was used to predict the peak and cumulative runoff from the proposed development. The 100-year storm event was used as the basis of design of ' the drainage systems for . Calculations are included in Appendix I. Calculations ' All calculations for this report have been made in accordance with criteria established by the City of Fort Collins. ' Variances ' It is requested that the Stormwater Utility grant a variance to allow the depth of pondirig in Detention Pond B, located on the east side of Mitchell Drive, to be 18 inches maximum during the 100-year storm event. DRAINAGE DESIGN' Conce ' Mitchell Drive, Pond A: Drainage to the Canal from the eastern portion of Showtime Video will be collected in Detention Pond A (Pond A). Basin E, as shown on Figure 2 ' and Drawing 5, will be ponded and release in compliance with the Heart SID. Pond A will be formed by a high curb adjacent to the Canal and the Mitchell Drive Embankment. The outlet to the pond will be through a small orifice in the curb at the ' low point. ' Mitchell Drive, Pond B: Drainage from centerline of Bockman Drive to the -Canal will be conveyed and collected in two 4-foot curb inlets at the low point of the sag curve located just south of the Showtime Video lot. A 15 inch Reinforced Concrete Pipe ' (RCP) will convey drainage from the street to the Canal. Drainage from the combined Wendy's/Palmer Gardens detention pond, located in the east parking area of Palmer Gardens will be connected to the east curb inlet and storm sewer system to the Canal. ' The discharge to the Canal from the storm sewer shall be regulated by a orifice plate located in the area inlet in Pond B. The orifice plate will back water up in the storm sewer and up through an area inlet in a parking/detention pond (Pond B) located east of the road until the head in the pond roughly equals that of the curb inlets with a ' maximum elevation of 5030.5 feet. At this elevation, the ponding in Pond B will be equal to or greater than the volume required during the 100-year storm event in accordance with the Heart SID. Pond B will be formed by earthen berms on the north ' and south, the Mitchell Drive embankment to the west and an 15 inch wall to the east with ponding not exceed 18 inches. As the hydrograph to the curb inlets recedes and water in the storm sewer system drains to the Canal, both the Palmer Gardens Pond ' and Pond B will drain to the Canal. The orifice plate at the end of the storm sewer was designed to discharge during the ' 100-year storm event: • The allowable discharge of 1.6 cfs from the Palmer Gardens Pond (Attachment ' B), plus • The 100-year peak flow from the Mitchell Drive ROW between the centerline of Bockman Drive and station 3+50, plus (this drainage flows undetained to the curb inlets but is accounted for by the Toys "R" Us and Western Auto development, See Attachment C) ' • Discharge equal to 0.87 cfs/Ac for the remaining undetained area which has previously been developed or will be paved with this project. ' Storm drainage from the undeveloped properties to the east of the Mitchell ROW, when developed, will be detained on -site and flows discharged directly to the Canal. ' JFK Parkway. Basin A: Storm drainage from JFK Parkway between Boardwalk and Horsetooth Road splits at the high point just north of Boardwalk and flows north toward Horsetooth Road. Storm Drainage along JFK Parkway, south of the two 15- ' foot curb inlets, for events up to the 100-year storm will be collected and detained by the properties adjacent to the street. The hydrologic and hydraulic discussion and evaluation of this area is detailed in the Final Drainage and Erosion Control Report for JFK Parkway September 19, 1991 (Revised May 19, 1992) [3]. Pertinent pages of this report area included as Attachment D. Storm drainage north of the two 15-foot curb inlets will drain in the street gutters to Horsetooth Road and to Warren Lake. This ' drainage will be collected and detained on the contiguous properties when these properties develop. ' Details 1 Support for the following discussion will be found in the calculations in Appendix I and on the drawings furnished with this report. As stated above, the Rational Method was used for drainage estimates. Mitchell Drive. Pond A: Pond A was size based on a mass balance of the inflow and discharge from the pond. The tributary area to Pond A is included in Basin E as shown on Figure 2 and encompasses 0.253 acres. The allowable discharge from Basin E, in accordance with the Heart SID, is equal to 0.22 cfs. The runoff coefficient for Basin E in 0.902. Using the above parameters in a mass balance the required ponding is 1,694 cubic feet. The available volume in Pond A is 2,070 cubic feet. Discharge from Pond A will be through a 2.5 inch section of PVC pipe located in the northeast corner of the curb forming the pond. The maximum head on the pipe will be 1.5 feet. Using a orifice coefficient of 0.6, the discharge will be 0.20 cfs which does not exceeds the allowable discharge of 0.22 cfs. Drainage release to the north side of the wall will be routed to an existing rip rap drop structure located to the northwest, on the south bank of the Canal. ' Mitchell Drive, Pond B: Detention for Basins C and D will be provided in Pond B. Pond B was size based on a theoretical mass balance of the inflow and discharge from the pond. For the mass balance, Basins C and D, with a combined area of 1.0 acres ' and a runoff coefficient of 0.863, was used with an allowable discharge of 0.87 cfs. Using the above parameters in a mass balance the required ponding is 6,696 cubic feet. The available volume in Pond B is 6,726 cubic feet. ' The tributary area to the storm sewer system discharging to the Canal includes Basins A,B,C and D as shown on Figure 2 and encompasses 1.43 acres. The allowable ' discharge to the Canal is 6.47 cfs and is made up of the following flows during the 100-year storm event. ' • 4.00 cfs from Basins A and B • 0.87 cfs from Basins C and D, and ' • 1.60 cfs from the Palmer Gardens detention pond tDischarge from the storm sewer system will be through an 11 inch orifice plate ' mounted on the downstream wall of the area inlet to be constructed in Pond B. The n= maximum head on the pipe will be 4.0 feet. Using a orifice coefficient of 0.6, the discharge will be 6.35 cfs which slightly exceeds the allowable discharge of 6.33 cfs. Drainage release to the Canal will drop 2.5 feet to the bottom of the Canal down a rip Az rap drop structure. JFK Parkway: Gutter flow on JFK Parkway was evaluated to check that encroachment will not exceed that allowable. Encroachment was checked at the north end of the section to be constructed. This is where the flows will be the greatest and ' the street grades the least. The 100-year peak flow was evaluated assuming the peak flow will come from the paved section between the flowlines downstream of the 15- foot inlets. The minimum time of concentration equal to 5 minutes was used to ' estimate the rainfall intensity of 9.0 inches per hour. With these parameters, the 100- year peak flow at the end of the new roadway section is estimated to be 4.52 cfs per gutter. The computer model UDINLET was used to evaluate the depth of flow in the ' gutter and thus the spread in the street. Gutter flow encroachment is estimated to be less than 0.33 feet in the gutter and will leave 24.5 feet of street open for travel. 1 1 t No Text Air � d� '� ® ELKO, NEVADA zzos "'� WINNEMUCCA, NEVADA WELSH ENGINEERING SCIENCE & TECHNOLOGY, INC. ENGLEWOOD, COLORADO O 1 BY T'rj/ �` �� DATE T.�Z.Z SUBJECT SHEET NO. OF I CHKD. BY DATE / PROJECT 11-�`/ PROD. NO. ZlY-1 �'- ,�.-rr F IJ 7 CA CO �� L 0,��3 ray 4 f�_brl I c\jZ.: S'TJ p' oqc) s �� VV �� `■ ELKO, NEVADA WINNEMUCCA, NEVADA - WELSH ENGINEERING SCIENCE &TECHNOLOGY, INC. ENGLEWOOD, COLORADO O BY -DATE � SUBJECT - - - �^ �..) fl � SHEET NO. `OF CHKD. BY DATE PROJECT lyfr`C G%�`'� PROJ. NO.rZ 1 ca5 ✓ ; f�ET€ "1u-r.1 T � �P� _t`�:o _ � T) —U�_ -'I.E "�Ti�Jp �� V 6�� ✓A-TZZJAJ Zg• 50, Z'g,Do. 4291 , So w ,Ob r; WESTEC PROJECT: PRJ. NO.: POND: DATE: Mitchell Drive 94417 Pond A, East Pond 08/03/95 INPUT VALUES TRAPEZOIDAL AVERAGE END AREA INCREMENT CUMULATIVE INCREMENT CUMULATIVE ELEV AREA VOLUME VOLUME VOLUME VOLUME S CF 28.50 0 29.00 210 35 35 35 35 29.50 11370 353 388 395 430 30.00 5,900 1,686 2,073 1,818 2,248 W z 0 im U Q ¢ En Q I ti a z�Q mAa m C"j e-i in �c in M O M 0�0 N N 00 et O �o d' N 0000 o 0�0 N M M h r- -, 'n N N N N N N N N N (q N N 3 ac0i N N N N N N N N N N N C C O O G C G C C O C a E to �o CN �o Cl) 00 00 h M CA Moo�ct-vr "o Xa otnNIc O m to C - C\ N M in No 00 r-� N N N N N C c O O O O C O O C 0 � 0 0 0 0 0 0 0 0 0 0 00 = N In 00 l- \o IT N 0 N 00 vl M r-+ C 00 \o ,t M N u tV r4 r4 r4 ; r4 p C C C C y M M M M M M M M M M M J In to to to v1 to Wn Wn In to to a¢ N N N N N N N N N N N C C C C C C O C C G C to N 44q N M \o 00 -t O \C kn 4 v M N N N N N N N N N N N N O 0 0 0 0 0 0 0 0 0 0 0 gum C\ C\ M M 01 CN C1 ON C\ C\ �� O vi" O �n O Vf o O CD 00 LE � �-• �N N M v Z. o\ .N� CO