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<br />.-. q. <br /> <br />November 3, 1997 <br /> <br />RECEIVED <br /> <br />NOV 7 - 1997 <br />Colorado W. <br />Conservati ater <br />On Board <br /> <br />MEMORANDUM <br /> <br />To: <br /> <br />File <br /> <br />From: <br /> <br />Dennis G. Miller ""?~ <br /> <br />Subject: <br /> <br />Lake Manchester Dam; W. Div. 1, DAMID: 060307 <br />Meeting with owner and engineer to discuss design issues <br /> <br />On October 30, 1997, Mark Haynes and 1 met, in the Denver office, with representatives from the <br />ownership group for Lake Manchester and with their engineer, Tim Dolen. The purpose of the meeting <br />was to discuss the noted deficiencies with the dam, as documented by my inspection report of 9/2/94 and <br />subsequent follow-up inspection memos, to evaluate design concepts, and to describe what is required to <br />be done with the dam to return it to satisfactory condition. A list of attendees is attached. <br /> <br />The meeting was scheduled in response to my letter of 7/9/97, requiring the owner to provide a <br />work plan for repairs to the dam by 12/31/97. Tim provided a copy of a report of observations and <br />recommendations prepared by Tom McDaniel, P.E., who will apparently serve as design engineer of <br />record for the repair work. Tim is currently employed by the USBR, and is therefore restricted in the <br />types of consulting activities he can certify. Tom is a fonner USBR geotechnical engineer, currently <br />retired, who has extensive dams experience. <br /> <br />The noted deficiencies with the dam were first discussed. These include the following: <br /> <br />· Non-functional low level outlet pipe which has been buried at the downstream end and has <br />no apparent operator at the upstream end; pipe condition is unknown. <br />. Seepage along the toe and lower slope of both the main dam and the north dike. <br />. Over-steep downstream slope on both the main dam and the north dike, which, when <br />considered with soft soil conditions caused by the observed seepage, leads to concerns for <br />embankment stability. <br />. Excessive tree (especially aspen) and brush growth on the north dike, which is a relatively <br />small embankment of narrow section, and along its downstream toe. <br />· Insufficient freeboard provided by the "emergency spillway" low area on the left abutment <br />of the north dike. <br /> <br />Tim is aware of all of these issues, and the design will address them. The intent is to properly abandon <br />the low level outlet by pumping it full of grout. Since the last time 1 observed the dam on 6/24/97, the <br />owner has located the downstream end of the outlet conduit and has uncovered it. It appears to be a 12- <br />inch diameter steel pipe, and it drained water readily once uncovered. We discussed what would need to <br />be done to accomplish grouting; the pipe will need to be cleaned thoroughly inside by jetting to ensure <br />removal of the sediment observed to have accumulated in the invert. Grouting will need to incorporate an <br />air vent pipe in the crown of the outlet conduit to ensure complete filling of the conduit interior. Grouting <br />would proceed from the downstream end. <br />