Philadelphia bypasses trouble in sewer rehab
Built in the 1950s, the Central Schuylkill East Side Interceptor Sewer runs parallel to the Schuylkill River in Philadelphia. It follows a path that includes Boathouse Row, Fairmount Waterworks and the city’s Museum of Art.
In 1999, the Philadelphia Water Department (PWD) began work to alleviate backup in the sewer. Because of the line’s location in a heavily visited and scenic part of the city, the department had to ensure that the project would not interrupt service, disrupt traffic or damage the aesthetics of the riverfront.
Enlarging the existing concrete sewer would have required excavation, disturbing the riverfront. Therefore, PWD decided to install a new sewer using microtunneling. The new line would run parallel to the existing one; then, the two lines would be connected, allowing the original line to be used for overflow.
In spring 2000, Wheeling, Ill.-based Kenny Construction tunneled for the new line and installed 1,100 feet of 48-inch pipe. Shortly thereafter, Springhouse, Pa.-based Driscoll Construction (the primary contractor for the improvement project) began patching the original sewer and constructing the overflow connection and distribution box.
To accomplish that portion of the job, the contractor had to divert flow — up to 29 million gallons of wastewater per day — from the site. It constructed a bypass that included eight Dri-Prime DPC300 pumps from Bridgeport, N.J.-based Godwin Pumps of America. Together, the 12-inch, diesel-driven pumps — six primary units and two backup units — could divert more than 35 million gallons of wastewater per day, providing a cushion for rain events.
Construction and site restoration (e.g., removal of temporary, above-ground pipe) were completed in summer 2000. However, in another segment of the sewer — downstream of the first phase of improvements — PWD soon discovered extensive debris buildup and severe deterioration of concrete pipe.
Launching a second phase of improvement, PWD hired Closter, N.J.-based En-Tech to restore 2,200 feet of 66-inch pipe. Using 10 hydraulic submersible pumps (the Heidra 250 from Godwin), the contractor again diverted up to 29 million gallons of wastewater per minute from the pipeline. It then removed debris and repaired the pipe using reinforced shotcrete and calcium aluminum cement.
Phase II repairs were completed early this year, and site restoration was finished in June. Combined, the improvements to the Central Schuylkill East Side Interceptor Sewer affected 3,300 feet of pipe.