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2. The Idaho Springs Reservoir is currently restricted by the Office of the State <br />Engineer, Dam Safety Branch, to a capacity of approximately 120 AF, at 7 feet below the <br />spillway crest. The original storage capacity of the reservoir is 227 AF. Restrictions were <br />imposed. due to structural damage of the spillway, and due to evidence of seepage below the dam. <br />3. Rehabilitation of the dam will include scope elements to minimize seepage and to <br />repair the structural damage of the spillway (see Figure 2 far plan view of the dam vicinity). The <br />actual rehabilitation scope will be determined during execution of the project based on additional <br />geotechnical investigations. The following scope elements are representative of the <br />rehabilitation work required, and provide a basis for the estimated costs of the project: <br />a. Updating the Emergency Preparedness Plan. <br />b. Reseating the oil gland nut on the outlet valve. <br />c. Installing survey monuments on the dam to monitor settlement. <br />d. Installation of 2 new piezometers in the new toe berm. <br />e. Dressing up the dam slopes and adding any supplemental rip-rap necessary to <br />cover the slopes. <br />£ Installing a cut-off wall at the end of the outlet pipe to eliminate back cutting. <br />g. Emptying the reservoir and borrow pit on the reservoir floor so that the <br />borrow pit can be sealed with concrete to minimize seepage. Also, any other sources of seeps <br />evident during the drawdown will be sealed. <br />h. If Item g does not mitigate the seepage problem, then hot asphalt injection <br />grouting will be undertaken. The grouting will be on the crest of the dam at zones of known <br />seepage. <br />i. If Items g and h do not mitigate the seepage problem, then the existing dirt <br />road on the dam toe will be removed. This dirt road likely acts as a hydraulic barrier to seepage <br />forcing water up into the dam. After removing the dirt road, a free draining rock berm will be <br />added at the dam toe so that seepage water is not forced upward in the dam. <br />j. Lining the existing ditch west of the concrete spillway to prevent surface <br />water from seeping into the ground behind the concrete spillway wall. <br />k. Rehabilitating the concrete spillway. Waterstops will be removed, weeps <br />installed, and the existing failing walls will be rock anchored. The walls and floor will then be <br />overlaid with a new 1 foot thick anchored reinforced concrete slab. <br />� <br />