DEM reports: Scott Pond phosphorus levels too high
DEM reports: Scott Pond phosphorus levels too high
LINCOLN - Contaminated primarily from wastewater treatment facilities upstream on the Blackstone River, toxins in Scott Pond have been known to rise to levels that could harm or kill pets and cause skin rashes and throat irritations in humans, according to a scientist with the Department of Environmental Management.
Environmental scientist Scott Ribas gave a "Scott Pond Water Quality Restoration" presentation at Lincoln Town Hall along with Elizabeth Scott, DEM Office of Water Resources deputy chief, on Feb. 27, informing the 20 residents in attendance, as well as Town Council members John Flynn and Arthur Russo, that phosphorus levels at the Lincoln pond are more than double what they should be.
Statistics came from a study by the Louis Berger Group Inc. published in 2008 in association with University of Rhode Island and the University of Massachusetts School of Marine Science and Technology.
Samples of the pond, which has been known as a recreational place for fishing, boating and swimming, were taken between 2005 and 2006. While resources are not available to do more updated sampling, Scott said, she said she does not expect the water "would've changed that dramatically."
Ribas explained the majority of the pond's problems are caused by water flowing in through the canal by way of the Blackstone River that has been contaminated by wastewater treatment facilities in Woonsocket and Worcester, Mass. Just 3 percent of toxins are considered to be from the immediate environment, he said, so the problem would not be fixed by residents switching to phosphate-free laundry detergents, fertilizers or cleaning agents.
Michael Gagnon, Lincoln's department of public works director, raised concerns about the potential for DEM to issue violations for contamination. He told The Breeze he does not believe the town owns the canal, though town workers will empty the canal during periods of high rain to ensure residents homes are not flooded. Gagnon said he is confident the boards removed to empty the canal belong to DEM.
"The town's position is that we didn't do this and that other people are responsible for it," Gagnon said.
Scott said the presentation was "in no way a precursor to enforcement," but rather a way to identify problems.
She said there is not enough surface outflow in the pond, which keeps problems trapped there.
The presentation is one of about 20 ongoing throughout the state, Scott said, as part of the federal Clean Water Act, which has a goal to restore and maintain the integrity of the nation's waters to support wildlife and recreation. The presentation was given as part of the report's public comment period, which closes March 31.
Clean Water Act requirements include a water quality standards program that identifies bodies of water that do not meet water quality criteria so a TMDL, or total maximum daily load, can be established to determine the maximum amount of a pollutant that can exist while still maintaining water quality.
In Scott Pond, Ribas explained, the TMDL addresses excessive phosphorus concentrations, dissolved oxygen depletion in the water column, and excessive algal blooms that include cyanbacteria blooms.
Those blooms are what has caused the pond to turn a pea green color at times, like in 2012, when DEM issued a health advisory to keep residents and pets away. That has been the only issued advisory, Ribas told The Breeze, though he said that was the year the pond was first screened.
Algal blooms, Ribas said, cause oxygen depletion from preventing sunlight to reach underwater plants, thus limiting photosynthesis. As those plants die, bacteria increases in decomposition, he said, which further depletes oxygen until the water becomes uninhabitable by fish or other organisms.
Oxygen levels have been reported to drop to zero, Ribas said, at 4 meters down in the north part of the pond, and at 5-6 meters down in the south.
Ribas reported that phosphorus levels for lakes, reservoirs and ponds are not to exceed a mean value of 0.025 mg/l. Scott Pond has been measured at the surface of 0.5 to 1 meter, mid-depth at between 4.8 and 8 meters, and the bottom of 10 to 13 meters, for four locations: the inlet, Scott Pond-North, Scott Pond-South in the northern basin, and Scott Pond-South in the southern basin.
At its best, the surface of the Scott Pond-South southern basin had phosphorus levels of 0.055 mg/l. At the worst, mid-depth at Scott Pond-North registered 0.640 mg/l of phosphorus.
Ribas stated during the presentation, this means having to reduce levels by 86 percent.
Some of that is expected to come from placing more stringent limits on wastewater treatment facilities, which are now required to have a phosphorus limit of either 0.1 mg/l for major facilities or 0.2 mg/l for minor ones during the growing season of April through October.
Upgrades to the Woonsocket facility, considered a major facility, are slated for 2017.
"At that time, we expect to see a major improvement to the water quality of Scott Pond," Ribas said.
Though some residents took issue with the fact that improvements are still years off, Scott explained that it was negotiated as part of the permit so they can make necessary upgrades. She acknowledged that the wait can be frustrating, but she encouraged residents to monitor the status of upgrades, as she said it is important for advocates to be aware. She said she would also recommend forming a lake association.
Other fixes include imposing additional requirements for Lincoln and Rhode Island Department of Transportation to reduce runoff volumes and treat pollutants, and recommending a lake management study to determine the influence of internal phosphorus on algal growth, with mitigation if warranted.
Control measures, Ribas outlined, include public education and outreach, public involvement and participation, illicit discharge detection and elimination, construction site runoff control, post-construction runoff control, and pollution prevention and good housekeeping.
If the pond turns bright green again, Scott said, residents are urged to call DEM so a sample can be taken. She also cautioned to be careful when the water level drops, as it can leave behind some contaminants on shore.
Scott said DEM is interested in working with Massachusetts Department of Environmental Protection for a bi-state TMDL of the Blackstone River.