Trenchless Technology

NOV 2018

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46 T R E N C H L E S S T EC H N O LO GY N OV E M B E R 2018 T H E C I T Y O F R E V E R E, Massachusetts entered into a consent decree (CD) with the U.S. Department of Justice that required the removal of infiltration and inflow (I / I) to elimi- nate sanitary sewer overflows (SSOs). In response to the CD, the City imme- diately began a series of sewer system evaluations to determine the condi- tion of the collection system. In addition, a System Capacity As- sessment was conducted by install - ing 15 temporary flow meters, one rain gauge, and three groundwater gauges, as well as utilizing a perma- nent MWRA flow meter immediately downstream of Revere's service area, to monitor sewer flows in the collec- tion system. This phase of the project characterized the sewer system opera- tions during dry weather, wet weather and tidal conditions as a baseline. The data collected during the flow metering program was used to develop a SWMM model of the sewer system. A range of design storms were input into the SWMM model to simulate the ef- fects that these various storm events would have on the wastewater collec- tion system; one-year, five-year, 10-year, 25-year, 50-year, and 100-year design storms were simulated with varying results based on the size of the storm simulated. This step was crucial in relat- ing specific areas of flooding (SSOs) with sections of the collection system identi- fied as having capacity issues. This also formulated a baseline for the evaluation of alternatives which would ultimately reduce overflows in the system. The SWMM model indicated that a very large portion of the sewer col - lection system would need to be reha- bilitated to remove sufficient extrane- ous flow to mitigate SSOs and to meet requirements outlined in the CD. In fact , the model showed that in order to reach a 10-year level of protection against SSOs, approximately 40 to 50 percent of the extraneous flow would need to be removed citywide. C O M P R E H E N S I V E R E H A B I L I T A T I O N : M e a s u r i n g t h e Effe c t i ve n e s s o f P u b l i c vs . P r i vate I / I Re m ova l By Nicholas J. Rystrom, P.E., Jonathan E. Kunay, P.E., and Ahmad Habibian, Ph.D., P.E.

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