PC: Ryan Kopp
The ponds in Roger Williams Park are a great resource for visitors and Providence residents alike. They have historically provided opportunities to fish, boat, and sightsee in the park.
The ponds were carved into the park landscape in the 19th century, and water flow was channeled from an upper watershed consisting of the Mashapaug, Tongue, and Spectacle Ponds. When the park was first established, the area surrounding it in southern Rhode Island was relatively vacant. However, as more people moved to this area, the surroundings became dense residential neighborhoods. About 58% of the watershed surrounding the park ponds is developed and has residential, commercial, and transportation uses. In comparison, only 9% is undeveloped, and 9% consists of wetlands and other surface waters. Urban drainage infrastructure channels stormwater runoff directly into the ponds. The runoff, which comes both from the ponds’ surroundings and from the upper watershed, often carries with it pollutants from impervious surfaces, such as dirt, sediment, pet waste, fertilizers, and trash.
As a result of this pollutant runoff and other conditions, the water quality in the Roger Williams Park ponds is poor. Part of the problem is due to the shallow nature of the park’s man-made ponds. Since the ponds are not natural and geographically-formed, they can heat up easily. A quickly rising temperature in the pond, as well as nutrients (i.e. phosphorus and nitrogen) channeled into the ponds by stormwater runoff, encourages the growth of bacteria and algae. During six months out of the year, the park ponds are clear and do not have algae and weed growth. But, these months are the least popular for tourist visitations due to the colder weather. As the temperature increases, the amount of weeds, algal blooms, and bacterial colonies increase. These populations decrease the ponds' aesthetic quality and biodiversity and prevent recreational activities such as boating and fishing. Toxic cyanobacteria blooms make the ponds potentially harmful to humans and animals.
Historic efforts attempted to “reset” the ponds, including a dredging project in the 1980s. Unfortunately, this project proved ineffective, as the sources of nitrogen and phosphorus pollution were not removed. One possible issue could be that sediment and phosphorus flow into the park pond from the upper watershed. Due to contributions from the park watershed’s surroundings, the park ponds have lost the additional pond depth that was achieved after the 1982 dredging.
As a result, more modern studies were performed in the ponds. In 2007, a TMDL (a total maximum daily load) for phosphorus was published by the Department of Environment Management as a result of data collected by the URI Watershed Watch team. At the time, the Roger Williams Park Ponds needed a phosphorus load reduction between 68%-73% in order to reach the RIDEM target concentration of 25 ug/l. The ponds had become eutrophic. This indicates that the ponds’ high nutrient concentrations caused the growth of too many plants. These plants threatened the survival of other aquatic life by decomposing and depriving the environment of necessary dissolved oxygen.
In 2011, another TMDL was published to address high bacteria levels in the ponds. In this study, it was shown that the level of fecal coliform exceeded Rhode Island’s water quality criteria. However, the amount of bacteria was higher under wet-weather conditions than in dry weather.
Based on the information provided in these TMDLs, a consent agreement was signed in 2017 between the Rhode Island Department of Environmental Management and the City of Providence. As a result of the decree, Providence agreed to monitor maintenance practices and construct structural stormwater controls. The City also agreed to clean remaining catch basins and stormwater infrastructure and hold programs such as a pollution prevention program and the Downspout Disconnection program. Many of the City’s projects have deadlines from 2017-2020, and are provided with environmental projects funding. One of the projects inspired by this consent decree was the Providence Stormwater Innovation Center.
Another control for water quality is the Clean Water Act (CWA). It was originally enacted in 1948, and was reorganized and expanded in 1972. This national act regulates discharges of pollutants into bodies of water and sets quality standards for surface waters. The CWA water quality regulations for Rhode Island were updated by EPA in 2020, and included further regulatory standards for freshwater ponds.
The Roger Williams Park Ponds have an EPA class of B, so they “are designated for fish and wildlife habitat and primary and secondary contact recreational activities.” For this reason, the water should have good aesthetic qualities. Criteria provided in the Clean Water Act regulations for Rhode Island include a required pH level of 6.5-9.0, and temperatures no higher than 83 degrees F. Any chemical constituent should remain at an ambient, and therefore not potentially harmful, level.
As required by the Clean Water Act and Rhode Island State Law, the Rhode Island Department of Environmental Management (RIDEM) developed a Stormwater Program. This stormwater permitting program meets regulations and laws from the Clean Water Act, Freshwater Wetlands Regulations, RIPDES regulations, and the RI Stormwater Management, Design, and Installation Rules, among others. This permitting program keeps different groups accountable for stormwater control and drainage.
The RIDEM program provides permits for three major categories of stormwater runoff: construction activities, municipal separate storm sewer systems (MS4s), and industrial activities. For example, operators of sewer systems and industrial sites may have to obtain authorization to discharge stormwater. If an entity has a wetlands on-site, they must consult with the Freshwater Wetlands Permitting Program to determine if the project needs to comply with stormwater requirements. All of these efforts are improving water quality in Rhode Island and the US, and involving others in the pursuit of cleaner water.
The aforementioned regulations inspired the growth of the Providence Stormwater Innovation Center. The Center achieves the goals explained in both national and state-wide legislation by using green infrastructure and buffer plantings to purify stormwater runoff. The Center is continuing to meet wider goals for maintenance and outreach as well.