Laserfiche WebLink
<br />e <br /> <br />e <br /> <br />e <br /> <br />east half where the leaks occur was constructed with a blocky clay that was placed in loose, <br />uncompacted lifts. <br /> <br />The 1913 report states, "The water was allowed to rise three feet more to elevation 43, when the <br />seepage through the dam became rather alarming". The dam is in the same condition today and <br />when the water was allowed to rise above gage height 42 feet in 1996 it was still alarming and <br />prompted the irrigation company to seek some solution to the problem. <br /> <br />The spillway for the dam is located on the east side of the reservoir (right abutment) and is <br />approximately 300 feet in width. The spillway crest varies from gage height 47.4 feet to 43.3 <br />feet. The spillway is a depressed area with an earth channel. There are no erosion control <br />measures at the spillway and the spillway crest is not controlled with a concrete wall or any other <br />measures that would maintain a constant crest elevation. The historic drainage path for the basin <br />and that for the current spillway are not the same. The discharge from the reservoir spillway is <br />across Boulder County Road 10 then on to the north toward the St. Vrain River. The existing <br />spillway diverts the flows across private property prior to the discharge meeting the St. Vrain <br />flood plain. The historic drainage path was through the reservoir basin and discharged into the <br />St. Vrain flood plain approximately 'h mile to the west of the current location. <br /> <br />The deficiencies for the dam associated structures is as follows. <br /> <br />1. Seepage through the dam embankment and dam foundation. <br />2. Uncontrolled spillway crest with no erosion control measures. <br />3. Spillway that does not meet the State Engineer's requirements <br />to discharge into the historic drainage basin. <br /> <br />The intent of the Company is to address the above deficiencies and rehabilitate the dam such that <br />it meets current standards and requirements of the State Engineer. A more complete discussion <br />of the darn, its associated structures, and recommended repairs is included in Appendix H of this <br />report. <br /> <br />ALTERNATIVES EVALUATED <br /> <br />A range of alternatives were considered as outlined below. <br /> <br />Alternative 1) Includes placing a drainage blanket over the upstream face of the dam from <br />approximately gage height 40 feet to the dam toe, installing a toe drain at the downstream toe, and <br />constructing a spillway which meets the State Engineer's requirements. <br /> <br />Alternative 2) Includes placing a PVC liner on the upstream face of the dam, a toe drain at the <br />downstream toe, a narrow drainage blanket at the downstream toe, and constructing a spillway <br />that meets the State Engineer's requirements. <br /> <br />Foothills Dam- 96.014 <br /> <br />Page 4 <br />