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I I I I I I I I I I I I I I I I I I I Mr. David W. Walker October 30, 1989 Page 8 The results of this research indicate no utility conflicts within the project area other than the city of Englewood raw water intake, a local drainage swale outfalling at the end of the Englewood outlet sluice channel, and a local drainage culvert outlet and headwall on the west bank approximately 800 feet downstream of the existing USACE dam. Utility crossings of the South Platte River at the project site are at the Union Avenue bridge and will not be directly affected by the proposed construction. MODIFICATIONS TO USACE DAM CREST The drawings show the modifications to be made to the crest of the existing USACE dam. These modifications have been discussed with representatives of the USACE from both the Chatfield and Omaha offices. They are in agreement that the present integrity of the dam and safety to boaters and the public will not be impaired by the modifications needed to accommodate the boatchute and the sill. Model runs have shown that important hydraulic characteristics of the crest would not be changed by the addition of the sill just downstream of the crest. ESTIMATE OF COSTS The preliminary engineering estimated construction cost of the improvements shown on the attached drawings is $1,300,000. A copy of the preliminary cost estimate is included as Appendix D. This cost estimate is not guaranteed. It may change with additional study. ADDITIONAL GEOTECHNICAL INFORMATION Geotechnical information and analysis is needed before final design at locations both upstream and downstream of the existing USACE dam. These data are needed to determine the suitability of the existing materials as a foundation for the proposed solid wall and open barrier upstream of the existing dam. They are also needed to determine the adequacy of the existing material as a foundation for the proposed earth and rock embankments downstream of the existing dam, its weathering and erosional characteristics, the stability of various embankment fill material configurations, and the needs for channel bank protection. We will recommend a suitable geotechnical engineer for your consideration.