Improving Capacity through Sewer Replacement – Potomac Interceptor Project

The Arlington County, Virginia Potomac Interceptor Sanitary Sewer System is one of two large interceptors that convey wastewater to the County's water pollution control plant. To serve long term growth in the service area, and avoid potential overflows during large storm events, expansion of the Potomac Interceptor was required to increase sanitary sewer capacity and protect the Potomac River from sanitary sewer overflows.This long term project was initiated by performing extensive hydraulic modeling, which determined the required increase in peak flow capacity for sewer improvements. Alternatives were developed and gravity sewer replacement was selected given the lower costs and ease of maintenance, which outweighed the implementation issues of performing construction work within Arlington National Cemetery and other properties. Several design and construction challenges were overcome including right-of-way and permit acquisition, utility relocation, deep excavation, and tunneling through mixed face soil and bedrock conditions for crossing under two major thoroughfares.