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IAfilA MillER. ERNSTSEN AND ASSOC.. INC. CIVIL AND LAND DEVELOPMENT ENGINEERING LAND SURVEYING 7150 EAST PRENTICE AVE. #202 770-201 !5 ENGLEWOOD, COLORADO 80t 11 Cherry Vale Meadows Drainage Study Page 3 Since emergency access during conditions more adverse than are expected is a concern, the attached calculations include the force that would be exerted on a typical vehicle crossing perpendicular to the flow over the bridge. The numbers show that a vehicle with a ground clearance of 7.2" or greater, having tires with an outside diameter of 30" and weighing in excess of 1600 pounds would not be swept to the railing of the bridge. Thus any pickup truck, ambulance, fire truck, etc., could safely cross the bridge during a 100 year storm event even in the event that 25% of the open area under the road was blocked by debris. It should also+be noted that the existing bridges 1000':!" upstream at Be11e- view and 1500'- at University would intercept the larger debris from most of the upstream tributary area, and that the proposed Cherry Vale bridge has slightly more open area than the bridge at E. Be11eview Avenue. The existing sewer and encasement located at the proposed box location will be left in place and will be afforded increased protection from undermining as a result of the concrete boxes and cutoff walls upstream and downstream of the crossing. CONCLUSIONS This revised report is the result of meetings with the City of Cherry Hills, Village City Council, City Manager, and City Engineer, the developer of the project, and this office. Use of concrete box culverts for the stream crossing minimizes the visual impact of the crossing and also, due to the thinness of the top 0 f the bo x sect ions, will allow floods 0 f greater magni tude than the 100 year design frequency to flow over the top without a great increase in water surface elevation. Horse traffic on the bridle path in the flood plain will be accomodated by keeping the slopes on the east side of the bridge at 5:1 or flatter so that horses can go up"across the street, and back down. The drainage plan and bridge selection for this project has been designed in such a way as to meet or exceed the minimum requirements as stated in the City of Cherry Hills Village and in the DRCOG Drainage Criteria Manual. The bridge opening is larger than the theoretical minimum requirements and regrading has been kept to an absolute minimum. The majority of the regrading wi 11 be in proposed Tract B, whi 1 e proposed Tract A wi 11 be 1 eft in its