LAWRENCE — A local nonprofit group has started a comprehensive water testing program aimed at shedding new light on one of the Merrimack River's most important and complex environmental problems: the impact of combined sewage overflows.
Combined sewage overflows, or CSOs, often occur during significant rain storms. Sewage treatment facilities in Haverhill, Lawrence, Lowell, Nashua and Manchester, New Hampshire, are older systems that are not designed to fully treat all of the sewage and storm water that flow into them during rain storms. They are permitted to release excess flow into the Merrimack.
Last year approximately 650 million gallons were released into the river. CSO water typically contains bacteria that can be harmful to people and animals.
Merrimack River Watershed Council will be testing the river this summer at a variety of locations ranging from Lowell to Newburyport. The tests will focus on sections where people tend to come in contact with the river, such as boat ramps and popular swimming areas. This is the first time that tests focused primarily on CSOs have been conducted on the Merrimack.
Merrimack River Watershed Association Executive Director Matthew Thorne said the organization is "proud to rally this community effort to develop a high-precision approach to gauging the water quality of our Merrimack River. We saw significant progress out of Manchester this week through the agreement with EPA to invest $231 million to bring that cities' infrastructure into the 20th century. We have to be vigilant and build on this momentum."
The tests will collect a variety of data on water quality, including bacteria levels, which are key indicators of CSO pollution. Tests will be conducted on a regular schedule, with additional ones conducted when sewage overflows occur.
A key goal is to track the flow of bacteria down the river in the aftermath of a CSO. The river's flow is complex, and bacteria levels can change substantially as water moves downriver. For instance, it's not known whether a large CSO release in Lowell will lead to significant spikes in bacteria levels in Newburyport. The testing is intended to generate data that will shed light on how bacteria levels change.
Ultimately the data collected will aid a notification system that will alert the public when the Merrimack is unsafe. A similar system, based on collected data and a mathematical model, is used to alert the public when bacteria levels are too high in the Charles River.
CSOs are not the only source of bacteria in the river. During rain storms, storm drains and runoff can send significant amounts of bacteria into the river.
MRWC is seeking additional volunteers and financial contributions to support the testing. If you are interested, contact the Merrimack River Watershed Council at www.merrimack.org.