Marshall Municipal Utilities

Inflow and Infiltration

One of the problems we continue to have in the collection system is inflow and infiltration (I&I). The sources of the I&I are varied and many. Some of our manholes contribute to this problem. For a lot of years manholes were built using brick and mortar. Now, manholes are constructed with precast reinforced concrete. The old brick manholes are not watertight. The mortar has deteriorated to the point that groundwater can seep into the manholes and become part of the waste stream. National surveys say manhole leaks account for only about 10% of total infiltration, house services account for approximately 60%, and 30% is caused by mains. We are currently replacing manholes and mains determined to be in poor condition as new streets are built by Municipal Services or others.

A major source of I&I is the footing drains on many of the houses in town. We are in the process of disconnecting these drains from the sanitary sewer system. This is being accomplished in a piecemeal fashion as problems are found. We are also working with Municipal Services on a case-by-case basis by installing new 4" house sewer service laterals under new streets being constructed, to keep from having to cut streets after new construction. We will continue to repair known problems as they are found.