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EPA requires City of Great Falls to investigate sewer gas

Release Date: 04/04/2006
Contact Information: Rosemary Rowe, 406-457-5020 Julie DalSoglio, 406-457-5025

Denver, Colo. (04/04/06) The Environmental Protection Agency has issued an Administrative Order to the City of Great Falls requiring additional investigation of high levels of hydrogen sulfide, commonly known as "sewer gas," in the City’s sewer system. The Order requires the City to conduct additional monitoring and to submit a plan specifying actions to reduce levels of the toxic gas.

This action is being taken since hydrogen sulfide levels in the City’s sewer system remain high despite recent actions taken by one of its industrial users, Montana Refining Company, to reduce its discharge. While the sewer line in question goes through a residential area, the City of Great Falls reports that no homes are connected to the sewer line.

EPA is concerned that hydrogen sulfide poses both acute and long-term risks to the health and safety of municipal employees working in and near the sewer system. In addition, the highly flammable gas can corrode sewer lines and cause explosions that threaten human life and damage valuable public infrastructure.

"EPA is issuing this compliance order to ensure that the City of Great Falls takes immediate steps to identify and address the source of this persistent problem," said EPA's assistant regional administrator, Carol Rushin. "While data reported to date indicate that the risk of an explosion is minimal, EPA remains concerned that an explosion could occur if the underlying source of the gas remains unresolved and levels of hydrogen sulfide increase substantially."

The City of Great Falls has an EPA-approved pretreatment program designed to prevent impacts to the City’s publicly owned wastewater treatment plant from industrial sources. In November 2005, EPA issued Administrative Orders to the City of Great Falls and an industrial source citing violations of pretreatment regulations caused by discharges of hydrogen sulfide. While the City and the industrial souce have taken actions to reduce the levels of hydrogen sulfide, recent tests submitted to EPA indicate that high levels of the gas persist in segments of the sewer system and require the City's immediate attention.