Polluted Ponds at Roger Williams Park a Problem

By KEVIN PROFT/ecoRI News staff

PROVIDENCE — “In trying to improve the quality of the ponds we are trying to change 100 years of development.” That is how Tom Ardito, the restoration program manager at the Narragansett Bay Estuary Program (NBEP), recently described the challenge facing the team of wide-ranging partners attempting to restore the health of the Roger Williams Park watershed.

In the second public meeting of the Roger Williams Park Ponds Restoration Program, held Feb. 7, speakers from the state Department of Environmental Management (DEM), the city’s Parks and Recreation Department and the NBEP updated a group of concerned community members about the program’s progress.

Twenty-five percent of the total acreage of Roger Williams Park is ponds. Because of the park's location within a highly urbanized setting, those ponds have become polluted with nitrogen and phosphorus. The high levels of these pollutants result from a number of factors.

Outdated stormwater management practices often funnel runoff either directly into the ponds or into drainage pipes that empty into the ponds. This runoff, from the time it hits the ground to the time it enters the ponds, absorbs nitrogen and phosphorous from a number of sources, such as lawn treatments and impervious surfaces like roads and sidewalks.

Another source of nitrogen and phosphorus pollutants is the artificially high population of geese in the park. As many as 400 geese call Roger Williams Park home, and many no longer migrate south during the winter because they are being fed by park-goers year-round. Geese droppings release phosphorus and nitrogen into the water.

Sedimentation of ponds also adds to the watershed’s pollution problems. Since it was last dredged in the 1980s, Roosevelt Pond, located directly behind the Casino, has lost two-thirds of its depth. The sedimentation is mostly the result of road sanding, but also from the erosion of the watershed due to overtaxed waterways and the natural process of organic matter such as leaves decomposing in the pond. Much of the sediment entering the pond system is already contaminated with high levels of phosphorous.

The high level of phosphorous and nitrogen in the ponds has dramatically altered the ecosystem and caused a slew of environmental problems, according to Roger Williams Park Ponds Restoration Program members. Aquatic plants, fed by the fertilizing pollutants, are choking waterways that used to be plant free. Algae outbreaks, which used to occur only during June, are now a fixture in the ponds throughout the summer. Last summer, the appearance of toxic algae, dangerous if touched by humans, caused a three-week ban of all recreational water activities such as paddle boating.

The pollutants have caused a sharp fall in the ponds’ biodiversity, while simultaneously stimulating the populations of some organisms, such as carp, to explode to environmentally unhealthy levels. Carp are well adapted to live in water with low levels of dissolved oxygen, and are notorious for eating other fish until their populations have been depleted.

DEM Director Janet Coit said urban communities deserve parks that can be used for boating, fishing and other forms of recreation. Under the current circumstances at Roger Williams Park, many of those water activities are being hindered.

Restoration work underway
Since the group’s first meeting in November, the restoration team has drafted a water quality management plan that is under review by the steering committee, DEM and the Parks and Recreation Department. It also has identified best-management practices that can be applied within and around the park.

To manage the park’s goose population, the team has entered into a $4,000 contract with the U.S. Department of Agriculture, and is employing a number of different strategies, ranging from public education campaigns to egg addling. The group also has begun to develop new signage for the park to help educate the public about the history of the park and dissuade people from feeding the geese.

“These ponds are a dynamic system which have sustained many years of assault by stormwater runoff from a heavily urbanized surrounding,” said Bob McMahon, the superintendent of Roger Williams Park. It will take many small activities, some short term and some long term, to reverse the damage that has been done, according to McMahon.

The restoration team is attacking the pollution problem on three different geographic fronts. It is considering solutions that can be implemented inside the park’s boundaries; within the pond system’s lower watershed, which includes urban areas surrounding the park; and the within the system’s upper watershed, which is to the west of the park and is responsible for 40 percent of the phosphorous currently entering the ponds.

Inside the park, the team has identified more than 30 sites where best-management practices can be implemented. Many of the sites require improved stormwater management. One such area is near the park’s carousel, where impervious road surfaces are causing runoff to enter the pond directly. McMahon expects to begin improvements near the carousel area as early as this year, noting that it is a popular area of the park and will be an ideal place to get the word out about what the restoration program is attempting to do.

Other best-management practices within the park are expected to be implemented. One is to reduce the use of curbs, which would allow stormwater from roadways to infiltrate the ground and be filtered by the soil rather than being drained and piped directly into the ponds. Another practice would divert some stormwater runoff to large grassy swales, where it would infiltrate the ground. Planting native plants along pond edges is being considered as a way to create a barrier against stormwater runoff that runs directly from the park’s manicured grassy fields and into the ponds.

Planting around the ponds’ edges would also help with the waterfowl problem. Currently, the park’s geese are able to easily hop out of the water and onto the grassy fields that stretch out from the ponds’ edges. Taller grasses and plants along the waters’ edge would make their transition from water to land more challenging and less appealing, and would limit their interaction with humans eager to feed them.

By the end of the year, the restoration team hopes to have implemented three of these best-management practices within the park.

Community outreach important
Implementing solutions in the lower and upper watersheds of Roger Williams Park could pose more of a hurdle for the restoration team than doing so within the park’s boundaries. On these two fronts, the team will also target stormwater runoff by encouraging smarter road and sidewalk design, but much of the work will concentrate on public outreach and education. 

A major source of the nitrogen and phosphorous leaking into the Roger Williams Park pond system is the fertilizer used on the lawns of residents living within the upper and lower watersheds. When it rains, water falls on these lawns and absorbs the pollutants. If it rains hard enough, lawn runoff finds its way into drains and gets piped into the ponds, bringing nitrogen and phosphorous with it.

The restoration team plans to reach out to local residents, who in many cases don’t realize lawn fertilizer is a park pollution problem, and teach them how their behaviors are affecting the park’s ecosystem. Among other things, the team hopes to reduce littering, fertilizer use and goose feeding.

Perhaps the most costly plan to reduce the ponds’ pollution level comes in the form of a small-scale treatment facility that would remove phosphorous from the water as it travels from the upper to the lower park watershed. While this approach could reduce phosphorous levels in the ponds by as much as 50 percent, it is an expensive initial capital cost and comes with long-term operation and maintenance costs. A treatment facility also could be used as a short-term fix, over about three to five years, and be phased out as more sustainable solutions, geared at reducing pollutants in the upper watershed, are implemented.

Another obstacle comes in the form of municipal boundaries. Both Cranston and Providence own land within the boundaries of the Roger Williams Park watershed. As McMahon said, whatever plan the team comes up with will require Providence and Cranston to work together.