The services of Beck Engineering, Inc. were retained to evaluate the existing sanitary sewer system for the City of Terril, Iowa due to several non-compliance notices they received from the Iowa Department of Natural Resources (IDNR). The City initially believed the issue was due to excessive infiltration/inflow (I/I) into the sanitary sewer collection system. After televising and smoke testing the sanitary sewer main and analyzing the size of the existing wastewater lagoons and outfall pipe, it was determined that the issue was not the I/I but the size of the wastewater lagoons and condition of the outfall pipe. The lagoons were constructed in the early 1970’s prior to the Clean Water Act of 1972. The lagoons are severely undersized for current IDNR standards. In addition, the existing outfall pipe on the southeast part of town was constructed very shallow and at a grade that would not allow the sewage to flow at a minimum cleaning velocity of 2 feet per second.
Improvements to the system included improvements to the main outfall pipe, increasing the capacity of the two existing lagoon cells, and construction of a new primary cell. The project was completed in 2012. Funding sources included a Community Development Block Grant (CDBG) and a State Revolving Fund (SRF) loan.
View of Excavation of the new Primary Cell for the Wastewater Lagoons