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<br />'~c..-- & A:mociates, Inc. <br /> <br /> <br /> <br />~to, ,.'ou", coo,cl'o". <br /> <br />April 10, 1992 <br /> <br />2995 Centargreen Cou1 South. Sulta C <br />l?oOuld'~r, Cclorado 803'Jl-5<121 <br />Phone, (.303) d4Q.3439 <br />fAX.(3J3)44'J-.3335 <br /> <br />Dr. John Liou, P.E., P.L.S. <br />Fl:deral Emergency Management Agency <br />Region VIII <br />Denver Federal Center - Building 710 <br />Box 25267 <br />Denver, Colorado 80225-0267 <br /> <br />N.iT. Ken Brugh <br />Clty Manager <br />Town of Florence <br />City Hall <br />300 West Main <br />Florence, Colorado 81226 <br /> <br />lli'. Larry Lang, P.E. <br />l:.xex::utive Director <br />-:Olorado Wawr Conservation Board <br />:721 CentenniaI Building <br />1313 Shermaa Street <br />)envcr, Colorado 80203 <br /> <br />REF: 8924D - CROSS SECTIONS FOR OA:C: CREEK LMMP IN FLORENCE, <br />COLORADO <br /> <br />Dear Sirs: <br /> <br />We have completed a preliminary review of the hydJ lull!: aaalysis for Oak: Creek~ The hydrology <br />has been flllalized and approved with a 100-year flo vof 16,000 cfs. The Oak: Crl~k study limits <br />for this aaalysis extend from its confluence with the ,.:rkansas River to the irrigation ditch crossing <br />of Oak: Creek upstrelun of the Denver and Rio Grand 'estern (D&RGW) Railroad. <br /> <br />T~e attached maps show the location and orienta,tion of the cross sections we propose to use in the <br />hydraulic aaalysis. We currently do not have suffici 'Ilt mapping at the downso-e:IIlD end to extend <br />east of Maple A venue. Ken Brugh is trying to obtair detliled mapping for this area. Downstream <br />of the D&RGW Railroad, the floodplain is hydrdulic lily connected; thus, no split tlow model will <br />bl: used in this area. The bridge crossings for 2nd: treet, 3rd Street, and the D,~RGW Railroad <br />will be included in t:~e HEC-2 model. The foilowinl' is a. description of the hydr,lulic aaalysis we <br />propose for Oak: Creek (see Figure 1). <br /> <br />The D&RGW Railroad crossing is a barrier to flow i1the main charmel. A portion of the flow will <br />bl: conveyed through the bridge opening and will spi lover the raili'oad at the bridl~e aad a portion <br />will split east along the railroad. The split flow conti ues east along the railroad to the low point in <br />the tracks at Frazier A venue. Flow will spill over the raihoad continuously along this alignment. <br /> <br />A t the irrigation ditch crossing, at the upstream stud~ limit, a portion of the flow will split from the <br />main channel aad flow east along the irrigation ditch alignment. This flow retwns in the split flow <br />1'e:ach upstream of the D&RGW Railroad. <br />