CS13C - Concurrent Session 13C: Improvements at Flat Rock Dam

Abstract Description: More than two hundred years ago, the Schuylkill Navigation Company was formed to construct and operate Schuylkill Canal, to transport coal, the energy source that would fuel the Industrial Revolution, from the mines to the markets. Constructed between 1815 and 1828, the Schuylkill Canal was a sophisticated system of low head dams, slack water pools, pound locks, and aqueducts created to form a continuous navigable waterway stretching along the Schuylkill River from its headwaters near Port Carbon, Pennsylvania to Fairmount Dam in Philadelphia. Schuylkill Canal’s Lock 68 structure is the left abutment of Flat Rock Dam, which includes the historical Feeder Gatehouse, both forming the head-end structure of Manayunk Schuylkill Canal, a 1.5-mile canal section along Venice Island, in the Philadelphia’s Manayunk neighborhood.

The Philadelphia Water Department engaged Ramboll Americas Engineering Solutions (Ramboll) to provide a full suite of engineering services for major improvements to the Lock 68 structures as a key component in a series of public and private investments that are transforming this former industrial area into a vibrant urban space. Ramboll provided site investigations, design, permitting and construction administration assistance to create an efficient and resilient design for construction of new Diversion and Overflow Spillway structures including measures for retaining wall rehabilitation, stormwater conveyance, green stormwater features, landscaping, maintenance equipment access roadways, debris control, site security, and historical preservation. Critical design elements included mandatory sequencing for construction phasing, temporary cofferdams for control of water, seasonal restrictions, preservation of historical artifacts, drilled anchors, bulk excavation, select backfill, structural concrete, concrete rehabilitation, masonry restoration, and site improvements. For controlling flow into the Manayunk-Schuylkill Canal, hydraulic gates were installed that should only require infrequent adjustments to moderate flow during extreme conditions such as droughts or floods. As the construction phase is nearing completion (expected late spring 2025), the design fundamentals, which include incorporating safeguards to protect assets at risk during construction and meeting Pennsylvania Dam Safety and Army Corps of Engineers regulations, have proven appropriate. As anticipated, there have been field issues that had to be addressed. Overall, the design concepts that were selected have resulted in an economical and sustainable solution. These physical improvements at Flat Rock Dam are being realized throughout this urban environment and will be a positive asset to the Manayunk and Philadelphia communities by continuing the benefits these waters have been providing for the last two centuries.