The Murfreesboro Water Resources Department wanted to know whether odors in the North Murfreesboro area in early September were originating from manholes or pump stations along Compton Road.
"The city has been conducting hydrogen sulfide (H2S) testing at manholes and pump stations in North Murfreesboro along Compton Road to measure H2S levels and determine whether the unusually high odor originated from the City sewer system," said Water Resources Director Darren Gore. "No appreciable hydrogen sulfide levels have been measured at any of the city locations."
In response to complaints, the city conducted H2S testing at manholes beginning in early September and pump stations beginning Sept. 22 to monitor and record levels for any spikes. The city continues to monitor gas levels in the Compton Road area.
This is not the first time MWRD has monitored H2S levels. In summer and fall 2016, the city began receiving complaints along the Compton Road corridor. At that time, Maintenance technicians were not able to pinpoint whether that the odor was coming from the sewer system.
In October 2016, MWRD installed "odor control media units" on all pump stations along the corridor. Since 2016, when complaints are received, MWRD sends out technicians to investigate whether the odor could be originating from the city system.
"In the past, chronic odor complaints in other parts of the city have been pinpointed in a manhole, pump station, or broken vent pipe as the cause," added Gore. "In these recent odor complaints in North Murfreesboro, technicians can’t locate where the odor is emanating."
As a rule, sanitary sewer odors are more prevalent during very dry weather when solids build-up in gravity mains as a result of low flow and off-gas hydrogen sulfide. During wet weather, higher flows in the sewer collection system flush out solids build-up and surface runoff dilute odors.
"During my 25-year career, I do not know of any instance that odor emanating from the sewer can inundate an entire neighborhood and not be pinpointed," Gore added. "MWRD staff is committed to determine whether the sewer system is part of the problem."
There have been incidents in the past where that is the case. In July 2017, MWRD received odor complaints in the Saratoga Subdivision. The H2S levels were traced to a manhole that received discharge from the Kensington Square subdivision. Odor control chemicals were added to the Kensington Dr. pump station to mitigate odor and lower H2S levels. The hydrogen sulfide levels currently monitored at the Compton Road locations are below the post-mitigation levels at the Saratoga subdivision.