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HomeMy WebLinkAboutDrainage Reports - 11/04/1994 (3)FINAL DRAINAGE REPORT for KNUTSON STORAGE BUILDING City of Fort Collins, Colorado October 31, 1994 prepared for: Knutson Construction prepared by: Northern Engineering Services, Inc. 420 S. Howes, Suite 202 Fort Collins, Colorado 80521 (303)221-4158 Project Number: 9454.00 Northern Engineering Services, Inc. October 31, 1994 Mr. Glen Schleuter Stormwater Utility City of Fort Collins 235 Mathews P.O. Box 580 Fort Collins, Colorado 80521 RE: KNUTSON DRAINAGE City of Fort Collins, Colorado Project No. 9454.00 Dear Glen: Northern Engineering is pleased to submit this Final Drainage Report for your review. The proposed site occupies O. 135 acres on the corner of Jefferson and Chestnut Streets. The owner proposes to construct a 24' x 45' storage building on the site. The addition of this building would increase the site imperviousness from 50% to 68% which is still below the 80% imperviousness assumed in the "Old Town Master Drainage Basin Plan". The site is fairly flat and drains primarily to Chestnut Street. The proposed building would not interfere with any existing major drainageways. Developed runoff would increase to 0.36 cfs and 1.2 cfs from historic rates of 0.32 cfs and 1.1 cfs for the 2 and 100-year storms respectively. The location at which the proposed building is to be constructed is currently unimproved parking with a runoff coefficient of 0 .50. Gutter capacity in Chestnut Street was also analyzed with a tributary basin of 0.64 ac(See Exhibit "A", Pg.3). Both the initial and major storms are well below allowable capacities. Based on the very minor amount of additional runoff this project would generate, it would appear the existing drainage system adjacent to the site would not be unduly stressed. 420 S. Howes • Suite 202 • Fort Collins, Colorado 80521 • (303) 221-4158 • Fax (303) 221-4159 Final Drainage Report Knutson Storage Building November 3, 1994 Page 2 This report was prepared in compliance with technical criteria set forth in the, City of Fort Coll ins, Storm Drainage Design Criteria and Construction Standards manual. A variance is requested for erosion control due to the minimal amount of disturbance expected in the construction of the proposed building. A second variance is request-e<l for drainage certification upon completion of the pro1ect. No drainage structures are proposed to be constructed as part of this project, and final grading will resemble existing grading. If you should have any questions or comments as you review this report, please feel free to contact me at your earliest convenience. Sincerely, NORTHERN ENGINEERING SERVICES, INC. I E ~ 0 t1l !II z t.> ~ la C I ~ i~ t, If~ I z-oz I~ I I I '· ' I I I I I A~A = 0. 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Q L. = o . e,.s l 1 . o ) ~. z.-=; , .., ; ... .. ( o. w4-,..,_ ) ... 0. ..... '& o. e5"( ,. 2-.6") •=;,o , ... ; ... ,.. l o.~4-=-) = I.~-,& <c:::. A~-.,,(-i: s. t:> e..-F,.; < < ~~:!>Le c::; .... ~ c::::::-.~....-.'1"""i"" = ~2-'-e.fs (fa.{, - - - - -----------. .. ~ . ~ . ' -~~--~ ... ~:~~~\,~~-.. ., . ., / ., , --~ .. " V .................. ~. . , . ~ . . ......... . >.. l; . ..., ..,. " ... . · c-,,16.,.·-1· ~-· ·~-~_l\\\\\\\~._ .. ~ . . ' ' . . .............. . ' ~-, '.} . ·':.--•~---•~,.. .. · .... _\, · .......... . ,i/ I . ,. 's.. ' ~~ /·~~·-, '~,,-.•-..-_-..-_-_"f ,, 1· , . . ') . . ...... . l>' •• •• •• ' /' ' ~ ~ ~ -'--•'!.~•· '!.., ; ,.i,. ,, -. ., ,., \ <\0.~~ / _,, ' . -~~-,J~""~ ,. '41, .. } . " f ".-~ L ... GI II I • z 0 .... :E , ':1; ; ~ t i< f I 0 '1 ~,n '~-.i_);:: _._i_ ~ .•• i '., ~ ~ . , .. :_-._. . . II 1 · •""Jl't: ,'· :..J . . . ..,. ' . . . I • • ~ . . ~:' ·, ... . ~ , , . . .. .,, . ~ l~..,...:, ... · . ' .:--. , ft[ ~ Cl) (;' I I ,.: . . f_ i-:-_11 f ' f 'i , .. ;OZ\;;;, . . rr ·. " , l\, .. , ~ • • r ... .. j ' , I . ·. I ;·, . , • ii ' ,U 1\_ '' --~ '1J .:' . ! " ~ l ; ·Cl)! ' =--_1 ':-:1,: ~ !~, ~ t,.,:J\l~•1·; E11 ' , 1 1 ('. .. v , ~ r . , •< ~-), . .. l ,.. a. ._ .;;... :::• ; ~--i.., ! ~ ~ .. ~ <! . ..,, ~: • !'! t ' -" ~ ~ \ ·""'· ~ ',,, "' -' . , .. ' ·, \. . ,, •-.... :-. , 9NORTB GRAPHIC SCALE SCALE: 1 • = 200' NORTHERN ENGINEERING SERVICES ( KNUTSON PROJECT 411 IDUII --_... ... n. ~ maaDO IDlll (..., __ _ EXHIBIT "J;' )(E] G I I I I I I I I I I I I I I DRAINAGE CRITERIA MANUAL RUNOFF I I I I ' / / ' / / I I ' I / / .5 ._ __ .._.,_ ...................................... _..__ .. ___ .._ .......... __ ... .1 .2 .3 .5 1 2 3 5 10 VELOCITY IN FEET PER SECOND FIGURE 3-2. ESTIMATE OF AVERAGE FLOW VELOCITY FOR USE WITH THE RATIONAL FORMULA. • MOST FREQUENTLY OCCURRING "UNDEVELOPED" LAND SURFACES IN THE DENVER REGION. 20 REFERENCE : "Urban Hydrology For Small Watersheds" Technical Release No . 55, USDA, SCS Jan . 1975. 5 -1 -84 URBAN DRAINAGE & FLOOD CONTROL DISTRICT 0 -- -Project n..cription: ICnlDOII Drainage Project Number: MS4.00 Pile Number: VRTC&G.WQl 31-0ct-94 10:29AM STREET: CHESTNUT STREET DESIGN POINf: DJ DESIGN CRrrERIA: 1) Mi-Storm 2) No curb OYertoppiag. 3) Sueet width from crowa 10 no.tine s lS' = Ar1erial Street; 100' RO w. 4)n = 0.016 Gutter Width = 2.0' NPUT W = from CL of street to face of gutter (ft) WW = width from BOC to BOW (It) z 1 = 1 / street cross slope z2 = 1 / gutter cross slope z3 = 1 / gutter cross slope z4 = 1 / sidewalk cross slope s = longitudinal street slope (ft/ft) y = depth at the flowllne of gutter (ft) northern engineering services, inc. -CITY OF FORT COLLINS GUTTER CAPACITY FOR VERTICAL 6' CURB AND GUITER 0 = 0.56 z/n s'0.5 y'2.67 SLOPE% 33.00 4.00 50 2.00 12 8.33 12 8.33 100 1.00 0.01 1.00 0.5 -- - -OUTPUT Oc = depth of water al the crown (ft) = Ow = depth of bock of walk (ft) = Flow Spread from Flowina (ft) = 01 02 03 {-) 04 OTOTAL ~ 2-YR THEORETICAL CAPACITY -F = REDUCTION FACTOR FOR ALLOWABLE GUTTER CAPACITY = (Sea Figure 4-2) ACTUAL ALLOWABLE GUTTER CAPACITY = OTOTAL fcTs)' 2-YR ALLOWABLE CAPACITY - ----0.327 --0.040 18.65 9.289 6.599 2.229 0.000 :::] 0.8 i3.66 • 0.8 10.93 I ~) ----Project Deocription: KnUDOD Drawee Project Nwnl>er. 9454.00 Pile NWlll>er. VKJ'C&O.WQI 3!-0cl-94 10:26AM STREET: aIBSTNlJf STREET DESIGN POINT: DI DESIGN CRITF.RIA: I) Major Storm -----CITY OF FORT COLLINS GUTIER CAPACITY FOR VERTICAL 6' CURB AND GUITER Q = 0.56 z/n s'0.5 y'2.67 -----2) Depth of water al the crown lllall ool exceed t;' and depd, of wala' al the flowllne shall not --.I tr. 3) Street Mdtb from Gl'OW1I lo llowline z 35' = Arterial Street; 100' RO.W. ◄)n =0.016 5) Outkr Width = 20' INPUT W = from CL of street to face of gutter (ft) WW = width from BOC to BOW (fl) z 1 = 1 / street cross slope z2 = 1 / gutter cross slope z3 = 1 / gutter cross slope z, = 1 / sidewalk cross slope s = lon!jtudinol street slope (fl/fl) y = depth ol the llowline of gutter (fl) northern engin•erlng services, inc. 33.00 4.00 50 12 12 100 0.01 1.32 SLOPE% 2.00 8.33 8.33 1.00 1.00 OUTPUT De = deplh of waler ol the crown (fl) = Ow = depth ol bock of wol< (fl) = Flow Spread from Flowline (fl) = Qt 02 03 (-) 04 QTOTAL (els 100-YR THEORETICAL CAPACITY r = REDLCTION FACTOR FOR ALLOWABLE GUTTER CAPACITY = (See Figure .t-2) ACTUAL ALLOWABLE GUTTER CAPACITY = QTOTAL (els 100-YR ALLOWABLE CAPACITY -255.931 88.142 61.423 206.040 282.65 282.65 226.12 -O . .t93 0.780 59.65 0.8 0.8 -© I I I I I I I I I I I I I I MAY1964 1.0 .9 .8 .7 "- a: .6 0 ... u ~ ~ z .5 0 ... u ::> 0 l.&J .4 a: .3 .2 .I ( I" ,' I I I I ' I I I I ' I / - 0 ~s=O 6 °le Fs 0 .8 \ \ ' : ~-4% \ VF• ~-5 \ I\ i f\. eElow MINIMUM ~ A:.LOWABL E ' "' ST~EET GRADE "' I - 2 ·. ... 4 6 8 SLOPE OF GUTTER (¾) Figure4-2 "' 10 r---r---. 12 REDUCTION FACTOR FOR ALLOWABLE GUTTER CAPACITY r---. I 4 Apply reduction factor for applicable slope to the theoretical gutter capacity to obtain allowable gutter capacity. (From: U.S. Dept. of Commerce, Bureau of Public Roads, 1965) 4-4 DESIGN CRITERIA