Lake Ladore Dam Repairs and Improvements Three Dam Wrongs Do Not Make A Dam Right

摘要

Man-made Lake Ladore was constructed in the mid-1800s as a "feeder" supply to the Delaware and Hudson Canal Company's coal transport canal. The Salvation Army acquired the property in 1967 and uses it as the centerpiece of a Retreat and Conference Center. HIGH hazard Ladore Dam impounds the Lake. The dam is a 330-foot long, 28-foot high hybrid structure made from connecting an original upstream earth and dry masonry structure to a downstream concrete gravity dam by ultimately filling the 50 feet between the two dams with soil. The original earth and dry stone masonry structure was constructed circa 1860. The concrete gravity dam, built circa 1907, is approximately 280 feet long and approximately 24 feet high. Fill between the dams was placed in the 1920s. Longstanding issues/major deficiencies at the dam include: 1. Spillway incapable of passing the SDF without overtopping. 2. Inadequate stability in sliding and overturning. 3. Hydraulic connections existed between the low-level outlet pipe and the surrounding embankment soils. 4. Significant uncontrolled seepage under the dam and through the upper portion of the sandstone foundation. 5. Significant surficial deterioration of the dam's concrete. 6. Discovery of an unknown pipe (likely a former pond drain) during low-level pipe replacement work. Initial recommendation was to keep the low-level outlet open at the downstream end/closed at the upstream end to mitigate severe seepage, soil loss and potential sliding failure. Overall design/construction objective was to address safety deficiencies in light of minimizing demolition/removal and replacement costs by maximizing the advantage of the existing mass of the "three dams." Solutions included: 1. A grouting program to fill seems in the fractured bedrock and deteriorated concrete/bedrock interface. 2. Tie-down anchors to improve stability. 3. A reinforced concrete structural facing, doweled into the downstream side of the dam and foundation bedrock. 4. Articulated block matting to mitigate erosion if overtopping occurred. 5. An innovative approach to grout the unknown pipe resulting in a stoppage of flow. Construction was executed in step-wise fashion over a period of 20 months. The over $2,000,000 invested on rehabilitation/remediation has resulted in a structure having a GOOD condition rating. Safe performance is expected under all loading including the SDF.