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<br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br /> <br />The site i nspecti ons showed the dam crest and upstream face of the dam to be <br />in re1 atively good shape. The downstream face, however, is vari abl e with <br />alternating steeper and flatter slopes. The steep slope at the toe of the dam <br />is contained by a hand-built, loose masonry rock wall. <br /> <br />One of the concerns at Twin Lakes Dam is uncontrolled seepage. Seepage <br />measurement weirs have been in place for years, and the City inspects the dam <br />on a dai 1y basi s when the reservoi r is in operati on. Al though the reservoi r <br />was empty at the time of the i nspecti ons, seepage i nfonnati on was gathered <br />from inspection reports on file at the State Engineer's Office, from <br />moni tori ng data gathered by the City, and from a vi sit to the dam by MKE <br />personnel when the reservo; r was full in 1982. Consi derabl e seepage emerges <br />at the toe of the dam render; ng the area irrrnedi ate1y downstream a bog, as <br />evidenced by the lush growth of grass. <br /> <br />The high phreatic level evidenced by the seepage, in conjunction with the <br />steep downstream slope discussed previously, places the stability of the slope <br />; n question. <br /> <br />The primary reason for the zero storage restriction at Twin Lakes Reservoir is <br />the condition of the outlet works. Due to the diameter of the outlet conduit, <br />it was impossible to physically inspect the interior; however, MKE viewed a <br />tape of a conduit inspection, made by the City uSing a remote controlled video <br />camera. The tape showed the conduit to be in extremely poor condition, with <br />spa11ed and deteriorated concrete in the upstream section and the steel lining <br />wi thi n the condui t irrrnedi ate1y do~mstream of the gate severely damaged and <br />partially torn away. The gate valve itself is corroded and partially worn, <br />maki ng the val ve unab1 e to properly seat and stop the flow of water through <br />the conduit. The inlet structure and dry well was in satisfactory shape, but <br />the outlet structure is cracked, partially separated and severely eroded. <br /> <br />At the spillway there are no man-made structures to control elevation or <br />resi st erosi on. It is doubtful that 1 arge di scharges woul d flow through the <br />channel, due to the high density tree growth downstream of the control section. <br /> <br />iii <br />