Bells Mill

Philadelphia Water Department | Philadelphia County, PA

The Philadelphia Water Department (PWD) and Fairmount Park Commission tasked AEG to provide watershed inventory and reconstruction design for Bells Mill Run, a tributary to Wissahickon Creek and part of the Wissahickon Valley, which is listed as a National Natural Landmark by the National Park Service. This stream was severely degraded and contributed large volumes of sediment to the Wissahickon Creek, as well as threatened adjacent Bells Mill Road and the parallel sanitary sewer line. The channel restoration design was intended to reduce sediment loads to the Wissahickon Creek, helping to meet the goals for Total Maximum Daily Load for Sediment and Nutrients. Channel restoration/stabilization also removed threats to local infrastructure, including roadways, substructure utilities, and manholes. This project is the largest stream restoration undertaken in the history of the PWD.

Upon completion of the construction activities for the original restoration, the PWD realized the effects of improper construction oversight by on this project. A conditions assessment of the rehabilitated stream found that the means, methods, and materials utilized by the awarded contractor were inadequate or incorrect, resulting in a final product that did not function to reduce sediment load, stabilize the stream channel, nor adequately protect the adjacent infrastructure.

Two years later, PWD found the condition of the stream to be intolerable and tasked AEG to assist with rehabilitative design and construction-phase efforts to properly restore the stream to function as the original design had intended. The post-construction condition of the stream offered a variety of challenges for devising an effective rehabilitative plan, planning the cost and materials, and documenting the effort. AEG was able to collaborate with PWD to forge success in all these areas.

AEG field staff performed on-site assessments and provided design initiatives, recommendations, and budget estimates for rehabilitation of the insufficient post- construction stream condition. Once the plan was in place, AEG staff provided oversight of the daily construction activities, coordinated with subcontractors, ensured compliance with E&S plans, tracked the budget, and most importantly, ensured that the final product met the goals of the project.

The post-rehabilitation condition of Bells Mill Run was monitored quarterly and measured bi-annually and was found to meet or exceed the stated goals for stream stability and sediment load reduction. AEG, when given the opportunity to be directly involved with the construction-phase oversight, lead the effort to re-design and properly construct a stable and functional stream channel within the allocated budget.