Infiltration and Inflow Reduction Plan Study

The City of Hallsville has recently been awarded a grant through the Department of Natural Resources and has retained the services of TREKK Design Group, LLC to assist in detecting storm water infiltration and inflow (I/I) sources entering the sanitary sewer collection system. Storm water infiltration and inflow (I/I) entering the sanitary sewer collection system not only may result in overflows and backups, but the increased costs of transporting and treating this storm water reflected in the individual sewer bills.  As part of this study, TREKK Design Group will be conducting manhole inspections, flow monitoring, smoke testing, and sanitary sewer system inspection activities throughout Hallsville. The purpose of the survey is to locate existing and potential sources of I/I and recommend a removal, replacement, or rehabilitation method to eliminate the source. The manhole inspections will be performed on all manholes including those on private property. These inspections have already begun. All TREKK Design Group employees have company IDs, wear clothing with TREKK Design Group on it and drive vehicles with TREKK Design Group decals. If you have doubts that a person is an employee of TREKK Design Group, contact the City Hall.  Prior to beginning the smoke testing of the sanitary sewer system additional information will be posted on the City’s web site and individual door hangers will be distributed.
What is Inflow and Infiltration?

Inflow & Infiltration or I&I, are terms used to describe the ways groundwater and stormwater enter the sanitary sewer system.

Inflow: Inflow is stormwater that enters the sanitary sewer system directly through connections such as roof downspouts, driveway drains, sump pumps, and cross connections with storm drains. Peak inflow can occur during heavy storm events or snow melts causing sanitary sewer surcharges resulting in sanitary sewer overflows and basement backups. Infiltration: Infiltration is groundwater or groundwater that is influenced by surface water that enters sanitary sewer pipes and manholes through holes, breaks, joint failures, connection failures and other openings. Infiltration quantities often exhibit seasonal variation in response to groundwater levels. Storm events can trigger a rise in groundwater levels and increase infiltration flows. The highest infiltration flows are observed following significant storm events or following prolonged periods of precipitation.

What is being done to find a solution?

The City of Hallsville has contracted with TREKK Design Group LLC to conduct a Sanitary Sewer Evaluation Study (SSES).  The purpose of an SSES is to identify issues with the sanitary sewer system that could cause problems that lead to sanitary sewer overflows (SSO’s) and basement backups (WIB’s) caused by a surcharged  sanitary sewer system (overload due to stormwater runoff in system). During surcharge conditions, sewer can back up into homes that are lower in elevation with respect to the sanitary sewer or it will overflow at the sanitary sewer manholes. The ultimate goal of the SSES is to find the sources of inflow and infiltration (I & I); this will lead to the improvement in sanitary sewer capacity.

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