3 Major R.I. Waterbodies Show Signs of Improvement
March 1, 2021
As a result of stringent permitting and long-term investments in pollution abatement infrastructure and practices, segments of upper Narragansett Bay, Mount Hope Bay, and the Blackstone River now meet water quality standards, according to the Rhode Island Department of Environmental Management (DEM).
Every state, tribe, and territory are required under the federal Clean Water Act to assess and report on the condition of its waters. As part of the process, DEM identifies those surface waters that don’t meet water-quality criteria and requires the development of a restoration study. The state agency also recommends waters or impairments that should be removed from the list because they meet water-quality standards.
Segments of three major Rhode Island waterbodies have demonstrated significant improvements, according to DEM. The following is a look at the waterbodies removed from the state’s 2018-2020 impaired waters list:
Portions of upper Narragansett Bay
The investments made to address combined sewer overflows from the Narragansett Bay Commission (NBC) sewer system have resulted in increased shellfish harvesting opportunities in the upper bay, according to DEM.
In 2017 DEM lifted rainfall-related shellfishing restrictions on one portion of upper Narragansett Bay that had been in place for more than 70 years. The completion of Phases I and II of the NBC’s combined sewer overflow (CSO) project eliminated a significant volume of sewage and stormwater that previously entered the upper bay via the Providence River.
The resulting improvement in water quality has allowed the area previously identified as Conditional Area B by the DEM shellfishing program to operate on an approved status and Conditional Area A to close at 1.2 inches of rainfall vs. 0.5 inches since May 2017. DEM said it expects further improvements in water quality once Phase III of the CSO project is completed.
Mount Hope Bay
In 1996 DEM included Mount Hope Bay on its impaired waters list because of the sharp decline in the number and diversity of fish associated with operations of the Brayton Point Power Station in Somerset, Mass.
DEM’s Division of Marine Fisheries conducted a review analysis of historical and recent available Mount Hope Bay and Narragansett Bay finfish data to evaluate abundance and species composition prior to and after construction of the power plant’s cooling towers. The analysis showed that the large reduction in water withdrawn from and heat discharged to the bay was followed by a realignment of the Mount Hope Bay finfish community with that of Narragansett Bay.
The impairments were identified in 1996 (dissolved oxygen) and 1998 (total phosphorus) from extensive monitoring, which led to stringent phosphorus limits at five wastewater treatment facilities (WWTF) in Rhode Island and Massachusetts.
Continuous dissolved oxygen data collected in 2017 and documentation of phosphorus reductions at the WWTF plants and data collected in the river during the past 10-15 years showed a significant drop in phosphorus levels, according to DEM. The data show that TP and DO are no longer impairments for the Rhode Island portion of the Blackstone River, protecting aquatic life.
In October, DEM held a virtual public workshop to present findings of the full statewide assessment of water-quality conditions, including the draft impaired waters list. The agency’s Office of Water Resources biennially assesses the quality of the state’s surface waters by comparing available monitoring data against the state’s established water-quality criteria to determine whether the waters are suitable for such uses as swimming, fish/shellfish consumption, and aquatic life.
The results of this assessment are presented in the state’s Integrated Water Quality Monitoring and Assessment Report, which documents the overall quality of the state’s waters. It includes a five-part integrated list that provides information on each of the state’s lakes, ponds, rivers, streams, and estuarine waters.
As part of the process, DEM identifies those surface waters that don’t meet water-quality criteria for which a restoration study known as a Total Maximum Daily Load (TMDL). These impaired waters are placed on the state’s 303(d) list.