Mattabassett District Sewage Treatment Plant in Cromwell. Wilcox Island and the Arrigoni Bridge are visible at the top of the photo.
As described in a previous post, a sewage spill of 3.6 million gallons from the Mattabasset District plant on October 30, 2017, raised some obvious concerns and questions. In early January, John Hall met with the Mattabassett’s Executive Director Art Simonian to get some answers.
According to Mr. Simonian, the October 30 “bypass event” occurred after heavy rain forced storm water into the pipes via the seams that connect one pipe to another. This produced a larger volume (a mixture of storm water and sewage) reaching the treatment plant. As a consequence and to avoid flooding the plant itself, 3.6 million gallons of partly treated sewage needed to be discharged into the Connecticut River over a period of hours while the heavy rain and storm runoff continued.
In addition to water leaking into sewage pipes through the seams, storm runoff enters the system via catch basins and other storm drains that empty directly into the sanitary sewer system. This situation is known as “combined sewer overflow” (CSO). Middletown has been addressing this condition over a period of years, separating storm sewers from sanitary sewers, but there are still some remaining CSO projects to be completed. It is possible that some other municipalities within the Mattabassett District have not completed their CSO work, but we don’t have information on that issue.
An obvious question is: if water leaks into the pipes during heavy rainfall, doesn’t sewage leak out of the pipes and into the environment and groundwater at other times? Mr. Simonian said that is not generally the case, and that leakage is more often into the pipes due to the greater ground water pressure outside the pipes.
While a discharge or bypass 3.6 million gallons of partially treated sewage is not something we like to see happen, it should be viewed in context. The plant treats 12-20 million gallons of sewage per day, on average, and as many as 70 million gallons on a peak day. In the course of a year, 3.6 million gallons is about ½ of 1% of the total 6.5 billion gallons of sewage treated annually. Not something we like, but not catastrophic. Last fall, a power failure at a treatment plant in Waterbury resulted in a spill of 5 million gallons into a river with much less volume of water than the Connecticut River.
The main question that led to our investigation, however, involves reporting and public notice. The Mattabassett District reported the October 30 spill electronically to CT DEEP, but there are many smaller plants in the watershed that do not report electronically. One has to wonder if their reporting is in compliance with regulations. How can we make the public, especially boaters, fishermen, swimmers, and anyone else who uses the river become aware that a spill has occurred?
Apart from reporting and public notice requirements, which we are working to pursue, everyone should be aware that, during and after rainfalls, bacterial levels rise in any pond, stream, or river. Fecal bacteria from wildlife, livestock, pets, and poorly functioning septic systems will end up in the nearby rivers and streams. It usually takes a few days after rainfall for these bacterial levels to drop to safer levels.
The Jonah Center plans to arrange for a tour of the Mattabassett District plant some weekday afternoon in the spring, probably April or May, at 4 p.m. This is an extremely important facility for the protection of our environment, and the process of transforming raw sewage into clean water is quite interesting, educational. Let John Hall know (through email or the “contact us” feature on this website if you would like to be on a list of potential participants. The tour will be limited to about 12 individuals.