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Street. the top of the dike would be two to three feet above the tOO-year flood elevation. No modification of the Boulder and Weld County Ditch siphon would be required. I I The existing arch bridge at County Line Road has little effect on the overall flooding situation, (PlateU). Thisbridgeconveysapproxilllately 1050 cfs of the 1950 cfs ~ieh flows to it. The excess flow is diverted along the east side of the road. Much of the diverted flow overtops the channel banks well upstream from the County Line Road bridge. No roadway inundation will occur due to the bridge. Increasing its si~e will only serve to transfer additional crop damage from One side of the road to the other. No overall economic benefit would be gained from increasing the size of this bridge. In the event the proposed improvements are not constructed, it is re- commended that appropriate floodplain management procedures be implemented. . , Floodplain regulations restrIcting future development of this area are conaidered to be the most economical plan. D. Reach 3 - Brixxs Street to Kenosha Road This reach is similar to Reach 1 with no buildings or other habitable structures in the flooded area. Potential damages include loss of topsoil, destructiGn of crops and inundation of roads. The basic consideration in thisreachwasdeterminingthefeaaibilityofimprovingroadcrossings. E. Reach 4 - Kenosha Road tG Downstream Limit of Study The first road crossing studied for this reach waS Briggs Street whlCh is a gravel road with light traffic vol~me. Under present conditions the major pGrtiGn Gf the lOO-ycar flood would flow ocross the road to the east of the bridge. Without any improve~ents to Griggs Street, the improvements proposed for Reach 2 will adequately prOt<'Ct th.. Town of Erie from Hooding. Shallow flooding through the Westview Estates aubdivision is the most serious problem in this reach. Several farm buildings slso will be inundated on the west side of County Line Road. All plans for this resch considered aiternatives for preventing flood damage to these improvements. With or witho~t improvements at Briggs Street, the major portion of the flood downstream will flow norrh along the east side of the Burlington Northern railroad. This situation cannot be altered without a major channel i~provement effort. Also rhe Burlington Nnrthern railroad bridge at the main channel could not convey the entire loo-year flood without increasing its size. No advantage is gained by forcing the flood to the west side of the railroad at this point as si~ilar damage to "gric~ltural land would occur on either sidc of the rail- road. To protect Weatview Estates, two alternate plans were considered. The first plan included an excavated channel to convcy the flooding to Boulder Creek. The channel w~uld begin downstream from th~ L~w~r a~uld~r Dilch aL the east side of County Line Road. Alignment would parallel the Burlington Northern railroad on the west side to a point represented by tha intersection of the extended Wastview Road and the railroad, then due north to Mineral Resd, then along the south aide of Mineral Road to Boulder Creek. A bridge at the point where the channel crosses County Line Road is required . Tratlsi- tional channel sections WQuld have to be provided where a change of channel direction is needed. This alternative would provide protection for properties downstream from Wcstview Estates and convey the storm runoff to Boulder Creek in a controlled ~anncr. To convey the entire lOO-year flood under Briggs Street without damage to the road,a major bridge would be required with a length of 100 to 120 feet. Channel improvements would also be roquired for several hundred feet upstream and downstream to provide adequate transitions through the bridge. This alternative would not significantly change flood elevations upstream. It would only protect the Briggs Street aCCcsS into Erie. -76- -79-