West Roxbury Low Level Sewer I/I Study
Boston Water & Sewer Commission
BETA conducted comprehensive infiltration/inflow (I/I) study for the West Roxbury Low Level Sewer (WRLLS) subsystem. The WRLLS experiences excessive I/I within its 25 miles of combined and separated sewers. The Commission wanted to use the full range of I/I investigation methods to find and quantify the sources of I/I.
This investigation program included:
- Bilingual public information program to gain local support for this effort.
- Sewer manholes inspection.
- Internal and external inspection of the WRLLS’s 2,400 buildings to identify: sump pumps connected to the separated system; suspect inflow sources such as yard drains; and roof leaders piped into the foundations of homes.
- Implementation of a hotline to facilitate setting up appointments for building inspections.
- Flow metering of 10 subareas within the system.
- Closed circuit television inspection of 5 miles of high infiltration sewers.
- Smoke testing of 25 miles of sewer.
- Dye testing of 870 suspect inflow sources.
The results of these investigations were used to determine the sources of peak infiltration and inflow within the WRLLS subsystem. Field inspection data was recorded in a GIS database compatible with the Commission’s system-wide database to facilitate follow-up I/I removal programs, assist in sewer system maintenance and focus Commission funds towards cost-effective I/I removal. BETA also provided supplemental hydraulic modeling services to determine how the WRLLS interacts with other Commission service areas.