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<br />WOOdward-Cly8t <br /> <br />. <br /> <br />The reservoir water is used for irrigation of alfalfa crop and orchards. For the last three <br />or four years, the dam has been maintained essentially full. In 1993, however, the <br />growing season was dry and calls were made on the reservoir for water releases. <br />Between mid-June and mid-August, the reservoir was drawn down, with the rate of <br />drawdownbetween about mid-July and mid-August exceeding I foot per day. In the <br />middle to latter part of August, the owner began hauling riprap to the dam to place on <br />the upstream slope to fill in some of the overly steep areas. As the rock was being <br />hauled in, the owner noted a crack on the downstream edge of the crest of the dam, <br />Approximately 160 tons of rock were hauled in and placed at six or seven places across <br />the dam before the work was stopped. The reservoir drawdown was also stopped at this <br />time. <br /> <br />The downstream slope of the dam is covered by scattered brush and some grass with <br />substantial areas that are not vegetated, However, there is very little, if any, erosion <br />evident on the downstream slope. The downstream slope is somewhat irregular; <br />however, this is apparently due to off-road vehicle traffic and subsequent placement of <br />some earth berms to minimize vehicle traffic on the downstream slope of the dam. The <br />crest is generally clear of vegetation in the center 8 feet, with tall weeds growing on the <br />shoulders. There is no apparent differential settlement, however, there is cracking on <br />the downstream slope of the dam. The cracking begins about 200 feet from the right <br />abutment of the dam. Cracks were noted about 18 inches and about 30 to 36 inches <br />below the crest of the dam. These two cracks generally occur over a total distance of <br />about 400 feet. A third crack, located about 6 feet below the crest of the dam, was <br />noted at 380 feet from the right abutment. The cracking becomes difficult to trace near <br />the crest control building. Mr. Graber (Colorado State Engineer's Office) indicated that <br />the cracking could extend over a total length of up to 600 feet. Mr. Graber has placed <br />stakes across the cracks and monitors movement periodically. The reservoir is currently <br />being maintained at a constant, low level with all inflow (approximately 20 cis) being <br />diverted into the irrigation system. <br /> <br />The upstream slope is fully covered with riprap, and there were no obvious signs that <br />would indicate recent movement, although observation is very difficult because of the <br />rock cover. At the extreme right abutment, the riprap appears to be in excellent shape <br />and consists of a very planar surface of hand-placed rock. If the entire dam was <br />Woodward-Clyde Consultants <br /> <br />23360/PRO.I 12-08-93(8:52am)/RPT <br /> <br />1-2 <br />