Click HERE to view a PDF of project photos. (Photo Credit: Erin Witham & Karen Robbins)
Wildlife-safe culvert installed in Arrowsic
BY ROSANNA GARGIULO Times Record Staff – Weekend Edition, September 26, 27, 28, 2014
A roughly seven year-long project to restore the phosphorus-impaired Sewell Pond in Arrowsic made a significant step forward on Thursday with the successful installation of a wildlife-safe culvert.
The Arrowsic Conservation Commission worked in collaboration with the Kennebec Estuary Land Trust to obtain funding for the replacement, which cost approximately $166,200, from the Maine Natural Resource Conservation Program.
MNRCP uses state and federal funding to award grants “that restore and protect high-priority aquatic resources throughout Maine,” according to the MNRCP website.
Prior to this, grants were obtained from state and federal sources to contract Gartley & Dorsky Engineering Inc., based in Rockport, to design the final box culvert structure. The total project cost is estimated to be $200,200.
The new culvert design, which contains a pool and weir system for fish passage and a ramp for turtle and amphibian passage, as well as other species specific passageways, is unique in Midcoast Maine, said KELT project manager Erin Witham.
The 45-acre Sewell Pond “is an observed habitat for blueback herring, American eel, snapping turtle, painted turtle, bald eagle, osprey, blue heron” and several marine and upland mammals, according to a KELT report.
“One of the (Arrowsic Conservation Commission’s) main goals is to have a healthy pond,” said Witham. “They’ve approached it from an ecosystem management point of view and realized that these two issues, a phosphorus issue and an low alewife population issue, were connected.”
Elevated phosphorus levels in water is the premier factor contributing to algal blooms in lakes and ponds, according to a report from the Maine Department of Marine Resources. Though residential developments are often the predominant cause of elevated phosphorus levels in Maine lakes and ponds, most of the area surrounding Sewell Pond is in conservation, said Witham.
“It has naturally high phosphorus levels,” said Witham of Sewell Pond, noting that the conservation commission had surveyed to make sure runoff wasn’t a significant contributor. “In 2009, the DEP identified Sewell Pond as phosphorus impaired and issued a management plan.”
According to Maine Department of Environmental Protection studies conducted in more than a dozen lakes, water systems where alewife runs have been sustained or reintroduced have better water quality than systems where the run has dropped off.
Alewives and other migratory fish that live primarily in saltwater habitats and spawn in freshwater, are “net exporters” of phosphorus, according to a KELT report. Though alewives carry phosphorus with them when they enter freshwater systems, they also take phosphorus with them when they migrate back out to sea.
Juvenile alweives that begin their lives in freshwater also export phosphorus when they migrate to saltwater for the first time.
Between 1997 and 2007, the Arrowsic Conservation Commission received shipments of 500 alewives from the DMR each spring, which were released in Sewell Pond, according to a 2007 commission report.
In 2007, the commision undertook to determine the historical abundance of alwives in Sewell Pond. Responses to a survey indicated that the alewive harvest had decreased from 75 bushels in the 1960s to 53 bushels in the 1980s, after which point the harvest was closed for conservation and remains closed today.
The commission also instituted an alewife count, carried out by volunteers. Last April, volunteers contributed more than 200 hours to the annual effort.
“Alewife numbers were considerably lower than 2012 due to low water levels in the culvert which prohibited fish from entering the pond,” according to the commission’s report in the Arrowsic 2014 Annual Report.
“Only 3,800 fish made it to the pond during the season,” the report stated, “including 718 fish that were caught in the pool at the culvert outlet and carted across Route 127 in buckets.”
The old culvert was “rusted out and sunken in the middle,” said Witham. “The pond has a low flow — there isn’t a lot of water running out — and one of the main issues was that there wasn’t enough flow or velocity for fish to pass.”
The new culvert is designed so fish can access the pool and weir system under all conditions, said Witham, “not just a few lucky alewives who are there at the right time.”
The Arrowsic alewife restoration effort is one of many in the Mid-coast area. Construction of a new fish ladder at Nequasset dam in Woolwich — a project KELT is also involved in — is nearly complete. In late August, Phippsburg received an $18,000 Coastal Communities Planning Grant from the Maine Coastal Program to improve the Center Pond alewife run.
“Scientists are really starting to pay attention to the important role that alewives play,” said Witham. “Not everyone likes to eat alewives, but a lot of the fish that we do like to eat depend on alewives in their diet.”