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Posted 6/6/2016

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By AnnMarie R. Harvie
USACE, New England

Members of the New England District Team have recently transformed an environmentally-degraded body of water and surrounding property into a rich, vibrant ecosystem so that birds and fish will return to the area and thrive.

Problems at the Milford Pond in Milford, Massachusetts, began as early as the 1970’s when town residents began to see the once-deep open water areas becoming much shallower and filling in with aquatic plants and organic sediments.  They also discovered the infiltration of an invasive aquatic weed species called milfoil start to take over the pond.  The town studied the decline over the 1980’s and 1990’s, and when the 120-acre pond was choked with milfoil and the depth of the water was less than two feet, the town requested the District’s assistance in 2001.  “The Corps engaged in the project as part of our Section 206 Aquatic Ecosystem Restoration Program,” said project manager Adam Burnett. 

The restoration has been years in the making.  The District completed a detailed project report along with an Environmental Assessment and Finding of No Significant Impact in July 2005, according to Burnett.  In August 2005, the District began preparing plans and specifications.  “The Corps of Engineers and the town of Milford as the local sponsor signed a project partnership agreement in 2013,” said Burnett.  “The designs, along with permitting and all necessary real estate acquisitions, were completed in 2014.”

The project benefits are many, including restoring the pond to an open-water habitat to emergent and wooded wetland habitats.  The basin is critical habitat for protected species of native birds, including the least bittern, pied-billed grebe, king rail, and common moorhen.  The birds need a combination of open water and emergent wetlands, such as cattail marshes.  “Prior to getting artificially impounded a century ago, the Charles River Valley through Milford had a large, complex native Atlantic White Cedar swamp, marshland, and open water bodies,” said Burnett.  “The restoration work is designed to restore this complex mix of aquatic ecosystems, and enhance the wetland habitats needed for the four protected bird species.”

To make that happen, the District hydraulically dredged a thick layer of bottom sediment from a 17-acre corridor in the pond and disposed of the sediment in a 30-acre shallow backwater area.  This disposal site had been a cedar swamp prior to being flooded with the impounded water behind the constructed dam.  Approximately 168,000 cubic yards of organic-rich sediments were hydraulically dredged and pumped through floating pipes to the disposal area, which was contained by an innovative design using large stacked coir (coconut fiber) rolls surrounding the containment area.  The 17-acre dredged area is now 12 to 13 feet deep and restored to open water and cleared of the choking milfoil.  The deeper water discourages milfoil from returning since it normally can’t root into deep water areas.  This restoration provides open water habitat for fish and waterfowl, including the four protected bird species that live in the basin.  “The 30-acre disposal area for the dredged material was designed within the impounded footprint of Milford Pond and will restore emergent and wooded wetlands, including the possibility of restored native Atlantic white cedar community,” said Burnett.

The environmentally-friendly design of the disposal area involved the use of 16-inch diameter coconut fiber rolls, stacked on top of each other around the disposal area perimeter within the pond to form biodegradable retaining walls for the sediment.  The rolls were installed during the middle of the winter when there was a thick layer of ice on the pond. 

“Now that the disposal area is completely filled with sediment, the coir rolls will decompose within a few years, and the entire disposal area including the coir rolls will become densely covered with native emergent wetlands plant species,” Burnett explained.

Palmer Federal Constructors, Inc., of Lawrence, Massachusetts, was the contractor on the project.  The cost of this $4 million project was split between the town of Milford (35-percent) and the Corps of Engineers (65-percent).

According to Burnett, the final surface of the filled area will naturally revegetate to support a combination of native emergent, shrub, and forested wetlands habitats. 

“We expect the disposal area to settle some, and after a year, we will plant Atlantic white cedar,” said Burnett.