Norristown Municipal Waste Authority

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SSM has provided continuous assistance to the NMWA for over 15 years for compliance with a PA Department of Environmental Protection Consent Order and Agreement to eliminate combined sewer overflows (CSOs) and excessive Inflow/Infiltration from the sewage collection system. Approximately 10,000 customers are served by the NMWA WWTP. SSM has performed extensive Inflow/Infiltration (I/I) investigations and program management, including manhole inspections, building and outside property inspections, and some smoke and dye testing of roof leaders, foundation drains and parking lot storm drains. SSM prepared and calibrated the hydraulic model of the Norristown Municipal Waste Authority’s 60-mile sanitary sewer collection system.


Sewer System Hydraulic Modeling and I/I Remediation

  • Phase 1 utilized GIS capabilities to create a working database.

  • Utilized PCSWMM to create a calibrated hydraulic model.

  • Phase 2 utilized database and model to determine future flow impacts and provide rehabilitation recommendations to reduce infiltration and inflow.

  • Develop and implement I/I remediation projects based on closed circuit television inspections and field inspections. Manage all construction projects related to I/I remediation.

  • Collection system modeling to develop a relationship between rainfall patterns and inflow patterns at the WWTP.

  • Performed computer modeling simulations of the NMWA sanitary sewer system in order to predict how proposed changes to the sewer system and corresponding CSO-003 would affect the system’s hydraulic conditions during a heavy storm event, as well as estimate the storage capabilities in the system.

GIS Mapping for Sanitary Sewer Rehabilitation and Investigation

SSM provided extensive GIS Mapping of the NMWA’s sanitary sewer collection system to include 60 miles of sanitary sewer. The GIS database was used to prepare and calibrate a hydraulic model of the sewer system and to provide maps for use in Inflow/Infiltration (I/I) investigations and program management, including flow metering locations (pre- and post-rehabilitation), manhole inspections, building and outside property inspections, some smoke and dye testing of roof leaders, foundation drains and parking lot storm drains. GIS Database management was utilized in order to map the results of televising investigations and flow metering, as well as to provide recommendations for non-invasive inflow reduction methods for property owners. SSM provided guidance to NMWA staff for collecting data from property surveys which was then incorporated into the GIS database. This mapping was later incorporated into the NMWA’s Combined Sewer Overflow - Long Term Control Plan for submission to the PA DEP, including the Nine Minimum Controls update for CSO 003.