PORTLAND — A $2.2 million restoration of the city’s largest freshwater pond gained Planning Board approval last week.
The work to remove three acres of invasive cat tails in Capisic Pond, above and below the Capisic Street bridge, still needs state and federal permits and funding from the city.
But city Stormwater Coordinator Doug Roncarati said he hopes work can begin in the summer or early fall.
The pond, which flows to the Fore River, has lost almost three quarters of its open water to cat tails; from an estimated 7.7 acres more than 60 years ago, to less than two acres at present. The area is enclosed by a city park.
Plans created by engineering firm Woodard and Curran call for mechanically removing almost 213,000 square feet of cat tails and more than doubling the open water space from an estimated 84,500 square feet to 197,000 square feet.
Because the scope of the work is more than three acres, permits from the U.S. Army Corps of Engineers and Maine Department of Environmental Protection will also be required. The funding is part of the city Public Service Department request for the fiscal year 2015 capital improvements plan.
By removing the cat tails and replanting the area with native species, Roncarati said a more varied ecosystem can be created. But results will not be immediate, and the pond will have to be monitored to prevent a fresh invasion of cat tails in the future.
“It will take time for this to recover, should we go ahead with this project,” Roncarati said.
According to the project application, plans call for excavating to at least a 3-foot depth to remove 16,000 cubic yards of material. Slightly less than half the sediment, 7,500 cubic yards, will be reused for the new plantings.
Suggested new plantings in the application include buttonwoods, winterberry, mountain holly and speckled alders.
The growth of cat tails can also be attributed to increased development and subsequent runoff in the watershed. Some areas of cat tails north of the project area will be left intact because the plants provide a habitat.
“It is always going to be a give and take,” Roncarati said.
According to the application, the pond dates to the 17th century and was last dredged in the 1950s. Changes to the dam south of the bridge on Capisic Street in the last two decades may have accelerated the rate of cat tail growth over the last 10 years, while also managing flooding problems upstream.
The cat tails are conducive to some species of water fowl, but Roncarati said the new plantings could create a better ecosystem for species of wading and migratory birds, as well as turtles and fish.
A second project to improve storm water flow into the pond near Rockland Avenue is expected to alleviate erosion problems, Roncarati said. The waste water and storm water flows were separated over the last 15 years.
Invasive cat tails last week at Capisic Pond have reduced open water to about two acres. A plan to remove most of the growth and replace it with native species was initially approved by the Portland Planning Board on March 25.