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HomeMy WebLinkAboutMiscellaneous t1s McCLURE ENGINEERING, INC. July IE), 19,92 Mrs.JDeborahL.' 'K's'a:ting, P -. E. Project. Engineer 'CITY 'OFCOLLEGE .,S'TATliON P.O .,Box .99.60 -CollegeSt-ation,T.exas7'7:842 RE-: DRAIN-AGE EASEMENT .REQUIREMENT AMEN.DIN'G PLAT' .OF<LOT .5, .B-LOCK. .V,UNIVERSITY PAlm SECTI'ON''!'WO 'RESUBDIVISION .and ALL ..OF.......iBLOCK...]),...UNIVERSITY... PARK 'SECTION ONE TEXASA&Mr .UHIVERSITy.....SYSTEMS-SUI.LDING De.ar :Debbi.e.: As . per your .. request., we bave investigated the . requirements for drainage'eat;emEants ..in.....the. vicinity. ..,of .the.TEXAS...A&M lJNIVERSITY SYSTEMS IUJILDJl~G. . Using conservative calculations and comparing the 'results "with..the 'drain,age 'reports.,and.const.ructi,on...draw~Lngs that: you. made .avalla.J.jleto .us . from city EnqineE!ring< Departlnen.t. files,we,h,av.edetermin~dthatthe<:ea'sementsshown -on the Amen(iing Plat. .assubm.ittedare..... 'a.dequate. In making, tAiis determinatio-n, we made the following e.valuations ,a:md., :cal-c.ulati,ons:: 1. We have' f'ield ver i fied the> .crit.ical 'elevations on the -detention.' 'f.acility"outl:etcontrol'structure - Cflow~li'ne elevat.io:n ==211.091 ,ve;e-notchweir .eJ..evation= .277. :26' , top/structure elevation =282.:56' ), the flow line eleVat.ion .ofthe .1inedchannEaland the ..top of curb el-evations..alo.rl-gtbe-eastlineof .- parking-area (-t::urb eleV'atio-ns' . range .firom .284 .1' ..to'286. .6'. 2. Web.ave .cons-ervatively . computed ..the... .1-"OO-year-storIn]peak runof'f (905cfsl andvo.lumeo,f the watershed u~sing Rational .formul-avariables' .of'Tc .-=10 . minutes, Ar.e,a .:= '85 ac.;r.es.' ....and.coeffi.c.ient . ....I.-C" .=0.85. 3'. We have calculated the Rorm.a.l flow depths ( 2.7" max. ) in the lined, ,c'h.anne land o:notedthat in some areas, a s.upe.rcritical flow condition exists (typicalchaJtlnel propertieis: 'W='3-0',S= 1.--6-~,n== ,:O,.~035J. 4. We nave .noted. tbat.t:becnannel velocity ls. approxima"tely 1,Ofps,butweabserved' that t:heexisti.ngchannell ining iss-ound. . 5 .Wehavede'te.rminedthat. ..... the,p:arking lot top of4~urb el-ev.a.tioniscconsis.te-ntly .greaterthan'2,..7'.abovet:he channel flow 'line. 1722 Broadmoor, Suite 210 . Bryan, Texas 77802 · (409) 776-6700 TAMU SYSTEMS. .BUIL.DING D'RAINAGE .REQUIREMENTS .CON'T Julyl() ,.1992 PAC;E. 2 6 . 'Ffte.ro~t.i.Il~~at~int:!\e.. be:~br~ment.ioneddrainagerep()rts indicat.e <t.bat>tb:edeptb/of.fl()wof .t.he Q25 storm is5 . 7 feet..... .... Thisi.....::;t(}rm. ;event.. ....wi1.1 .. iOV'erflo'W. the. ..detention th~.. .size....oft;h,e.Oyerf"Low.. .w~ir. On <t';he .detiantion .iac ;ility , higbeJ:"( .fJ:'eqtlen~Y s;t.():r11l .e2'VeIltscoulclatt(iin >el evat.i.ones .of the. . ..28;J.,.0'-tP .-283.3Ir~nge. . . Even so, flows of this ma-gn i tude would not ..... inunda:tethe parking lot. In summary, from ."our'.. >an.alysis.......of .th,e........available drafIlag:e reports, '. cQnf!:t:t'~"t..i.~ndrawill9s.and:ei$~dj()bservationf:>' . we. . cOnclude tbat.. .t1;tere.... .i::;a~~uate >capacity.. .i.nt:he ...ce>{ist~n9 ...cb~l1nEalitO. .con1:ain established along the most easterly cu:rblirleoft,he '.existing parkingfaci.lity. ShOl.11d....yol.l.ha~re '.any qu'estion.s '.'or need additio.nal informat:ion con.cerningour ......analy.s is, please advise. Very truly yours, ::lae1. R.. MCClur~::::::R .P.L .s.. MRM/mlm