Understanding Water Quality

Norwalk River Watershed Association
How Riverwater Is Monitored

The Norwalk River is lucky to have been monitored consistently since 1998 by the Earthplace HarborWatch Program, which runs two state-certified labs for testing water samples. Volunteers and staff from HarborWatch collect riverwater samples from over 20 sites along the Norwalk River and in its major tributaries (Silvermine River, Comstock Brook and Cooper Brook). The group tests for dissolved oxygen, conductivity and E. coli levels. HarborWatch has also conducted limited nutrient research for total nitrogen (TN) and total phosphorus (TP) at the major tributaries to the Norwalk River and at the outflows of the three wastewater treatment plants that discharge treated effluent into the Norwalk River. Harborwatch submits monthly reports to the CT Department of Energy and Environmental Protection (DEEP) for review and comment.

How Is Our Water Quality?

The CT DEEP rates the water quality in the state’s rivers to determine which water is safe to use for drinking and for recreation, such as for swimming and fishing. To set standards for water quality, the CT DEEP considers several factors including the levels of contaminants present in water samples. The Norwalk River is a Class B river, which means the water is not safe enough to use as drinking water, but is generally safe for recreational use.

Based upon the water quality data collected by HarborWatch, which monitors the Norwalk River, the water quality in the Norwalk River Watershed is moderately impaired. In other words, it doesn’t always meet the Class B standards set by the state. Water Quality Reports from HarborWatch, available here, indicate that bacteria levels frequently exceed the state’s water quality criterion for Class B waters at a number of sites along the Norwalk River. Most sites meet the dissolved oxygen level criterion, and conductivity levels are consistently higher in the upper reaches of the watershed than in the lower watershed.

Signs of Improvement?

The Environmental Protection Agency (EPA) included the Norwalk River on its recent list of “Water bodies Improved” because of reduced bacteria levels and improved water quality. The EPA reclassified two sections of the river, one near Old Mill Road in Wilton and one in the Stonehenge area of Ridgefield, removing them from its “Impaired Waters” list. Crediting the work of NRWA, Harbor Watch, Norwalk River Watershed Initiative and Trout Unlimited in its report, the EPA recognizes the importance of the work these organizations and their volunteers do to protect and restore the watershed. The EPA lists pollution sources in the watershed as including, “permitted municipal wastewater and storm water discharges, runoff from impervious surfaces, failing septic systems, pet and domestic animal waste, and wildlife.” The results from data collected from 1998 to 2011 showed levels of e-coli above those that meet water quality standards for recreational use and aquatic life support. Our community changed that through years of helping to “educate schoolchildren, garden club members, and the public about household pollution prevention, domestic animal waste management, management of non-migratory Canada geese, organic land care, and the use of LID (Low Impact Development) practices such as rain barrels and rain gardens.”

Norwalk River Water Quality Reports