February 9, 2012

City to Undertake Preliminary Engineering Review for Possible Lagoon Upgrades

Changes in state and federal regulations mean big changes are likely looming for the city of Memphis sewer system. On February 2nd, the Memphis City Council authorized the completion of a Preliminary Engineering Report (PER).

An agreement was entered with Allstate Consultants to provide the service, which will include evaluations of possible repairs or upgrades to the current lagoon system that could provide extended aeration, the installation of a membrane bioreactor or other simple conventional expansion.

The preliminary project evaluation is a requirement for qualification for any state or federal funding to finance water or wastewater system improvements. The PER is evaluated by the Missouri Water and Wastewater Review Committee, which consists of the Missouri Department of Economic Development, DNR and USDA Rural Development representatives.

Other options the Memphis PER will examine include the creation of a land application system, that would distribute the city's wastewater to be absorbed as soil moisture through either a slow rate irrigation system or standard overland flow application slow as opposed to confinement in lagoon treatment before release into stream flow.

The engineering study will also review the city's current inflow and infiltration problems that creating compliance issues with the Department of Natural Resources permitting process.

Within the DNR permitting process, inspectors have identified concerns the lagoon is exceeding its designed flow rates. The structure, which was originally built in 1969, was designed to serve a population of 2,143 with a design flow of 214,300 gallons per day. Actual flow at the lagoon according to DNR records is averaging 325,260 gallons.

While the I/I issue has been ongoing, a new change to the DNR permit process has made the biggest impact on the process. DNR has inserted limits on Ammonia generated in the lagoon system. Previously the permit had simply required regular testing for the possible pollutant. City officials as well as representatives of the city's engineering firm have indicated, the city's lagoon system will not be able to meet the ammonia requirements without major changes.

Engineer Cary Sayre estimated a new mechanical treatment facility would cost between $3.5 and $4 million. A land application system was expected to be significantly less costly, with more exact price estimates for both options as well as all other possibilities, to be provided by the completed PER report.

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