Inflow & Infiltration Study - East Haven CT

Phase I, Infiltration / Inflow Study

For the purposes of the Study, the entire Town was subdivided into 23 sub-areas. Flow metering was conducted in each sub-area for a period of 12 weeks. A total of 12 groundwater wells were installed to observe and correlate fluctuation of groundwater height with infiltration.

The amount of infiltration for each sub-area was determined by subtracting estimated sewage from the minimum flows measured during night-time hours. Inflow was estimated by comparing wet weather flows to normal dry weather flows. A cost effective analysis was done in each sub-area to determine which areas had excessive infiltration/inflow. Eight of the twenty-three sub-areas were found to have excessive I/I.

Phase II, Sewer System Evaluation Survey

A Phase II Sewer System Evaluation Survey was conducted for three of the eight sub-areas found to have excessive I/I. Funding was not available to complete the SSES for all areas. Once the sources were identified, a cost effective analysis was performed to determine if the cost of rehabilitation of sewers and manholes could be offset by savings in treatment plant costs. Using flow isolation, it was possible to eliminate 25 miles of total of 32 miles of sewers with excessive I/I from further study.

The SSES survey included the inspection of 600 manholes, cleaning and close-circuit television inspection of 32,000 linear feet of sewers and rainfall simulation.

Phase III, Sanitary Sewer Rehabilitation

After completion of the SSES Study, a sewer rehabilitation project was carried out. The rehabilitation consisted of a combination of spot repairs, chemical joint sealing and manhole repairs for over 17,000 linear feet of sewers.