Lofty Dam Rehabilitation

Mahanoy Township Authority | Mahanoy Township, PA
Lofty Dam

The Lofty Dam is an earthen dam and serves as a Department of Environmental Protection (DEP)-permitted public water supply source. The dam is 1,100 feet long, has a maximum height of about 28 feet, and is classified as a C-2 dam by the Pennsylvania Department of Environmental Protection (PADEP). The embankment was reportedly constructed with clay and gravel taken from the reservoir area. The upstream and downstream slopes are grassed. The primary spillway consists of a 29-foot wide concrete ogee section located near the left abutment.

Recommended improvements included raising the dam elevation to 6 feet. Benesch performed survey at the remote location, engineering analyses, developed contract drawings and technical specifications, prepared a design report, submitted permitting and provided bidding, contract administration and construction phase services. Services included survey, environmental clearances, hydraulic spillway review, structural design of parapet wall, PADEP permitting, and a wetlands/drainage system.

Following the original bidding and the Notice to Proceed, cracks were found in the dam breast and modifications to the rehabilitation approach were required. After a geotechnical assessment, it was determined that the original dam material installed in 1896 included a weak fill zone and caused cracks. The additional improvements included the removal of undesirable fill and the reconstruction of the upstream slope using current design standards. Additional funds were acquired to complete these added modifications.

The project was funded through a $3.8 million PennVEST Loan and a $1.7 million Department of Community and Economic Development Commonwealth Financing Authority H2O Water/Sewer Grant.