By Rob Sample
What’s the state of Lake Carmel and how can municipalities better protect lake water quality?
A.J. Reyes of Massachusetts-based GEI Consultants presented the Kent Town Board and attendees of its Nov. 19 meeting with an overview of what’s being done to preserve Lake Carmel for generations to come.
Reyes, an aquatic biologist and certified lake manager, noted that over many, many years, lakes will naturally evolve into wetlands, and then forests.
“Humans that live in these areas have greatly accelerated the rate by which these lakes move to wetland status and forest,” he said. “You have more impervious surface, you have increased runoff, roads bring more sediment into the lake… and lead to the eventual filling of the lake.”
The science of lake management aims to define what’s normal in a lake, what’s gone wrong, identify solutions, and implement and monitor such measures. According to Reyes, this slows down negative changes in a lake’s quality and prolongs its enjoyment by residents. However, even the best lake-management plans can be negatively affected by factors such as new invasive species in a lake, weather events, and nearby development.
“The do-nothing approach is really not viable – something has to be done, especially if you want to use it,” said Reyes. “I imagine this group wants to be actively using the lake and actively enjoying it to its fullest potential.”
Added to the mix is that Lake Carmel is man-made and shallow, creating conditions favorable for the growth of algae and other plant life. Reduction of algae blooms is a key focus of lake management because such plants can produce harmful toxins.
“The only thing we realistically have any control over when it comes to lake management are nutrients,” said Reyes. “This is basically the fuel for algae growth. And in freshwater lakes, phosphorus and nitrogen are considered the most important.”
Over the past 30 years, phosphorus in Lake Carmel has been shown to be consistently above the total maximum daily load set by the federal Environmental Protection Agency. The EPA, in turn, has required the state to identify some of its sources and to come up with mitigation measures.
The goal is to get Lake Carmel below 20 micrograms per liter.
Through computer modeling, streambank erosion has been shown to be the biggest culprit, accounting for 33 percent of the excess phosphorus in the lake. Reyes said the computer models for streambank erosion need to be verified by actual field tests, to avoid expensive measures that might have a limited impact on phosphorus levels.
Other significant sources of phosphorus include septic systems (22 percent), “internal loading” (19 percent), and groundwater (15 percent). According to the North American Lake Management Society, “internal loading” refers to phosphorus that comes from lake sediment. The contribution by municipal wastewater treatment plans is relatively small, at 3 percent.
Neighborhoods around Lake Carmel began as summer colonies, and the fact that they are now mainly year-round homes makes their septic systems worth attention. In Reyes’ view, expanding municipal sewer systems would be the best solution. Such a measure, however, would be quite costly.
Alternatively, towns can create grant funds to assist homeowners in replacing outdated septic systems, noting that effluent from these systems spreads throughout a lake, making this a community-wide issue. Reyes also called for a more aggressive pumping requirement, as the town currently only requires septic pumping to be conducted every five years.
Multiple sampling studies carried out at a variety of inflow points around Lake Carmel, all completed during periods of no precipitation for 72 hours or more, backed up Reyes’ statement. These tested phosphorus, nitrogen, and e-Coli bacteria.
“At the end of the day, the enforcement on this has to come from the health department,” he said.
Reyes also suggested greater attention be paid to storm drainage in nearby residential areas. These should be designed so that runoff isn’t directed straight into the lake during storms, but instead pass through a system of swales and other water-control systems, thus minimizing the entry of nutrients into Lake Carmel.
Katherine Doherty, a former town supervisor who is also on the sewer district committee, pointed out that 44 homes in Lake Carmel had a peat system put in 15 years ago that was supposed to help mitigate nutrient flow into the lake.
“But nobody seems to know where those records are,” she said.
“Our work with the health department has been collecting the data and using it to inspect the homes (with systems) that may be potentially failing,” explained Reyes.
Another attendee asked if the propagation of freshwater mussels would be feasible, as these aquatic creatures feed on the sediment at the bottom of lakes and thus help remove some of it.
Reyes, however, said evidence points to the results being negligible.
Councilman Shaun Boyd pointed out that Lake Carmel was last dredged in 1994, and asked if doing so again would be of benefit in removing sediment, which is one source of phosphorus.
“There are areas that could probably use some sediment removal, like right where Stump Pond comes in,” said Reyes, who agreed that some small-scale dredging would be quite beneficial.
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