The New York State Office of Parks, Recreation and Historic Preservation operates Letchworth State Park in Wyoming and Livingston Counties, New York. The park is located along the Genesee River, which traverses a deep rock gorge. McMahon & Mann has provided geotechnical engineering for a variety of projects within Letchworth State Park including High Bridge Road, Middle Falls, and Letchworth State Park roadway. At High Bridge Road, the subsurface exploration and monitoring program included borings, and instrumentation consisting of piezometers and inclinometers. The ground anchors were tensioned to compress the soil and increase the resistance within the failure zone. The inclinometer was maintained throughout construction providing information on the slope movement during and after construction. The inclinometer and load cells installed on three ground anchors continue to be monitored providing data on the force applied to the reaction blocks and slope movement.

At Middle Falls, we developed plans to stabilize the rock face, scale loose rock from the gorge face, and install high strength bar anchors 40 feet into the slope to improve its stability. The rock anchors are equipped with strain gauges which allow measurements of slope movement with time.

McMahon & Mann evaluated the condition of the gorge face beneath the Letchworth State Park roadway. We found that a section of the rock face and a retaining wall built in the 1930s had fallen into the gorge undermining the road and threatening its stability. We developed a plan to stabilize this section of the gorge which included, scaling loose debris from the rock face and using shotcrete, rock anchors, rock nails and drains to stabilize it. Due to access restrictions, all of the work had to be completed by suspending crews and equipment from ropes.