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CARRIAGE HILLS NO. 2 DAM, Dam Failure Forensic Investigation Report Page 12 February 27, 2015 6. FILE REVIEW: CONSTRUCTION & FILE HISTORY The State Engineer approved construction plans for the Carriage Hills No. 1 and No. 2 dams on Jan. 5, 1967 (Construction File C‐1195). SEO files contain no documentation of construction and the drawings are not marked as‐built. The C‐1195 plans (see Appendix A) show the Carriage Hills No. 2 Dam as a zoned earth embankment with 2H:1V upstream and downstream slopes and a crest width of 10‐ft (Figure 5). The upstream slope is shown protected with 12‐inch thick riprap. An upstream embankment zone of “selected impervious fill” is shown, followed by a 10 MIL polyethylene membrane, and then a downstream zone of “clay and disintegrated granite”. The dam is shown founded on bedrock. No foundation treatment is shown. A 24‐inch diameter 12 gauge corrugated metal pipe (CMP) outlet conduit is shown with an upstream slide gate. The spillway was to have a 10‐ft bottom width excavated into bedrock with vertical slopes, and 5 feet of freeboard below the dam crest. The spillway capacity is given as 377 cfs. Figure 5: C‐1195 plans maximum section of the Carriage Hills No. 2 Dam. The first record of performance in the SEO files is from a 1983 dam inspection performed by a water commissioner. He notes trees and brush growing on the dam. In 1985 the water commissioner noted “no outlet found” and in 1986 the DSB Engineer’s Inspection Report (EIR) stated that willows were obstructing spillway flow. The Town of Estes Park took ownership of the dams in 1991. In July 1991 the DSB EIR required the Town to remove obstructions from the spillway, provide a minimum of 3‐ft of freeboard, and repair or replace the outlet works. The Town subsequently requested they be allowed to operate pumps for emergency drawdown purposes in lieu of replacing the outlet works, which the DSB agreed to with conditions.