The project includes planning-level engineering and environmental analyses needed to develop a rehabilitation plan for Lackawaxen Tributaries Dams PA-413, PA-415, PA-419, and PA-421 (“Lackawaxen Tributaries Dams”), located in Wayne County, Pennsylvania. The four dams were originally designed as significant hazard potential but are now high hazard potential dams. The objective of the project is to bring the four dams into compliance with the current State and Federal dam safety and performance standards.
The project is being conducted in accordance with the National Engineering Manual (NEM), National Watershed Program Manual (NWPM), The Principles, Requirements, and Guidelines for Federal Investments in Water Resources (PR&G), and United States Department of Agriculture Manual. PR&G is an interagency standard, effective in June 2015, that provides guidance to specific federal agencies on the development and evaluation of federal water resource investments. Ultimately, the goal is to develop a rehabilitation alternative for each dam that will extend its useful life for at least another 50 years.
Key projects tasks include topographic, bathymetric and sediment surveys; geologic and geotechnical investigation; inventory of watershed resources; hydrologic and hydraulic analyses (SITES, HEC-HMS, HEC-RAS); flood inundation mapping; dam breach analysis (WinDAM C) and hazard mapping; identification of resource concerns; and formulation and evaluation of alternatives. Dam rehabilitation alternatives studied in detail included structural roller compacted concrete spillway armoring, articulated concrete block spillway armoring, labyrinth spillways, riser rehabilitation and replacement. All engineering, environmental, and economic analyses have been completed and we submitted the first draft of the Supplemental Watershed Plan and Environmental Assessment for NRCS and Sponsor review.