It’s not every day you see a helicopter flying over the Potomac River carrying a 14-ton drill rig and workers suspended midair to work on DC Water’s sewer lines. The typical equipment used on sewer lines includes vacuum trucks, backhoes, excavators, and trenchers, but when you’re working in the middle of a river only a helicopter will do.

Workers began drilling in the Potomac this week at Great Falls, to remove rock core samples as much as 50-feet deep at five different boring locations. It’s part of the planned rehabilitation of the Potomac Interceptor, a 54-mile sanitary sewer system that