National Dam Inspection Program. Mahanoy Dam Number 2 (NDS ID Number PA-667, DER ID Number 54-11), Susquehanna River Basin, Tributary to North Mahanoy Creek, Schuylkill County, Pennsylvania. Phase I Inspection Report

摘要

The assessment of Mahanoy Dam No. 2 is based upon visual observations made at the time of inspection, review of available records and data, hydraulic and hydrologic computations and past operational performance. Mahanoy Dam No. 2 appeared to be in poor condition. Vegetation consisting of brush and small trees were observed on the upstream and downstream slopes. Erosion was noted on the downstream embankment near the maximum section of the dam. Several wet areas were located on the downstream face of the embankment during the inspection. One seepage point was noted at the right abutment contact and two other seepage points were observed near the left abutment. The reservoir drain valves have not been operated in the recent past. Maintenance of the dam and operating facilities is considered poor. Mahanoy Dam No. 2 is a high hazard-small size dam. The spillway design flood is the 1/2 PMF to PMF (Probable Maximum Flood). Based on the downstream potential for loss of life the spillway design flood for this dam has been selected as the PMF. Mahanoy Dam No. 2's spillway is capable of controlling approximately 12% of the PMF without overtopping the embankment. Based on criteria established by the Corps of Engineers, the spillway is termed seriously inadequate. If Mahanoy Dam No. 2 should fail due to overtopping, hazard to loss of life and property downstream of the dam would be significantly increased from that which would exist prior to the overtopping. Mahanoy Dam No. 2 is classified as unsafe, non-emergency.