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17 <br /> will have the added benefit of decreasing the hydrostatic pressure exerted on the <br /> dam, and will consequently increase the safety level of the dam with regard to <br /> possible seepage or catastrophic structural failure. <br /> 4) After the water level is lowered, inspect the exposed dam face for evidence of <br /> beaver activity. Clear the backslope area of the dam and inspect it in a similar <br /> way. Repair any burrow holes that exist in the dam, by filling them with solid, <br /> compacted fill material or a grout mixture. <br /> 5) Take steps to protect the dam and outlet from further beaver activity. The <br /> beavers will probably always have a presence around the lake, since there is <br /> evidence of their work all along the downstream area below the railroad. A <br /> maintenance plan should be put into effect which would include regular inspection <br /> of the outlet pipe, spillway, and dam. Debris in or around the riser pipe should <br /> be removed and any burrow holes repaired. A drain valve or gate could be <br /> installed as part of the riser pipe base that would allow periodic manual drawdown <br /> of the lake level for. dam face inspection. A drawdown of 1 or 2 feet will <br /> probably be sufficient to expose any burrowing. <br /> Covering the face of the dam with a barrier to prevent burrowing may not be <br /> practical, either from a construction-ease perspective or a long-term durability <br /> perspective. Any partial protection near the top of the dam may promote <br /> burrowing at lower elevations, making detection more difficult and structural <br /> problems more severe. <br /> 6) Clear the top and backslope of the dam of small trees and brushy vegetation. The <br /> healthy, is better to <br /> but if they are h <br /> are not desirable, , <br /> ee o <br /> n the dam Y <br /> large tr s Y <br /> leave them in place. Any dead trees should be removed and their root stumps <br /> replaced with solid structural fill. If possible, the entire exposed surface of the <br /> dam should be covered with a dense grass, but that will be difficult to achieve due <br /> to the heavy tree cover around the dam. Maintenance procedures should include <br /> regular inspection of the dam for dying trees, and removal of any such trees. <br /> Also, the scrubby vegetation which readily grows in this area should be <br /> continually removed or prevented from growing. <br /> 7) Determine if the apparent low area near the southeast end of the dam is in fact <br /> more than a few inches lower than the rest of the dam. If so, fill it in to provide <br /> a consistent dam elevation. <br /> evidence of seepage.8) Regularly check the dam for any ev e. Since no construction p g <br /> records of the dam are available, neither the quality of the fill material nor the <br /> presence of a cut-off trench can be easily determined. The dam has apparently <br /> performed quite well, so there is no reason to think that there are major structural <br /> problems. However, the regular inspections for seepage are essential. <br /> Page 5 <br />