FLOOD00852 - Laserfiche WebLink

Home Browse Search

CHERRY CREEK RIVER RUN IMPROVEI1ENTS LETTER OF MAP REVISIONS ARAPAHOE COUNTY, COLORADO Job No. 5136717 September, 19116 PURPOSE OF STUDY The purpose of this report is to pre"ent the engineering calculations and transmit the technical back-up material which supports a revision of the cur- rent Federal Emergency Management Agen,:y Flood Insuran,oe Study for Arapahoe County, Colorado. PREVIOUS STUDIES In July of 1984, Greiner Engineering pr"pared a Letter of Map Revision Report for Cherry Creek which included the Rivet Run Development (Reference 1). The basis for the revision was a more technically supportive analysis using U.S. Army Corps of Engineers' hydrology and a very detailed hydraulic model which utilized detailed field surveys. This analysis was performed for the reach of Cherry Creek from Cherry Creek State Park to the Arapahoe-Douglas County line. In November of 1985, Greiner submitted a letter t,o FEMA to request that a letter of belief (conditional letter <,f map revision) be issued for all pro- posed channel improvements between Arapahoe Road and the Arapahoe-Douglas County line. The basis for this revision 1118S the proposed improvements as outlined in the Feasibility Study fOI the Cherry Creek Basin Drainageway (Reference 2). Both of the above requests ,;ere approved by FEMA. All pre- vious correspondence regarding these studies can be found in the Appendix of this report. BASIS OF REVISION The basis of this request for revision to the FEMA Flood Insurance Study is comple tion of grading per the grading plans, entitled IOWa 1 ters-Banbury I Grading" by Greiner Engineering for the River Run site. The River Run site is shown on the Vicini ty Map loca ted in t:1e Appendix of this report. Also lo- cated in the Appendix is a copy of the J.atest boundary survey. The grading plans were developed from the proposed improvements for Cherry Creek, as outlined in the above mentioned Feasibility Study, upon which the approved eond! tiona 1 Ie t ter of map revi~; ion was based. These pIa ns a re bas ie- ally in conformance with the feasibilit~ study; however, slight modifications were required due to the timing of the '.mprovements. Since the River Run si te was the first area to be improved along the reach of Cherry Creek from Arap- ahoe Road to the Arapahoe-Douglas County line, the floodway encroachment limits had to be reduced so as not to cause any adverse effects to the still undeveloped areas upstream and downstrl~am of the property. At such time as the adjacen t property owners deve lop thei r sites in conf ormance wI. th the Feasibility Study for the Cherry CreeL Basin Drainage'way (Reference 2) the floodplain encroachment within River Run may be extended. These adjacent