STOCKBRIDGE — On a clear mid-June day, as kayaks, canoes, sailboats, rowing shells, fishing boats and other watercraft ply the pristine waters of Stockbridge Bowl, the town's largest natural resource, it's hard to imagine that the 372-acre "Great Pond," as the state calls it, is in dire straits, with its future health in jeopardy.
But within a few weeks, the annual summer infestation of Eurasian watermilfoil weeds will be choking areas of the lake, stark evidence of the urgent need to complete the nearly $3.9 million "lakelift" project conceived seven years ago by the nonprofit Stockbridge Bowl Association.
With about $300,000 in support still to be raised this summer to close the gap and complete its Save Stockbridge Bowl campaign, the association is approaching the finish line for the crucial, $2,750,000 second phase of its cleanup project.
The mechanical dredging operation by earth-moving equipment to remove up to 70 years of silt buildup will be followed by a major winter drawdown to snuff out the roots of the invasive plants clogging ever-expanding portions of the lake's perimeter.
"The weed growth has been persistent and the sediment filling critical parts of the lake is getting to the point where it will be Stockbridge Bog instead of Stockbridge Bowl soon," said association President Richard Seltzer.
With crucial town backing, the association devised what Seltzer described as a "3-D plan" — installing a diversion drain, dredging and drawing down the lake.
Pending state approval of environmental permits being drafted by GZA Environmental of Springfield, the dredging project to remove 22,000 cubic yards of sediment from the bottom of a quarter-mile long, 7-foot-deep channel to be cleared between the lake and the Interlaken outlet dam is now slated for the winter of 2017-18, Seltzer said.
The 5.5-foot drawdown before subsequent winters would expose the roots so they would freeze and die before the first protective blanket of snow. The Town of Stockbridge Lake Management Plan has been approved by the state Department of Environmental Protection and the Stockbridge Conservation Commission.
The town is expected to put the project out to bid next summer, Seltzer said. According to state law, total funding must be in the bank before the work begins.
The excavated sediment, 8 to 10 feet deep, will be deposited in a 30-acre meadow within Bullard Woods, owned by the association off the northern shore of the lake. The area will then be restored to its natural state.
Major project funding includes $825,000 approved by annual town meeting voters in recent years and from Community Preservation Act support. Seltzer emphasized that the backing of the taxpayers has been crucial to the success of the fundraising campaign, and also has triggered significant state support.
The state Department of Environmental Protection has kicked in $910,000 in grants through the U.S. Clean Water Act.
The 400-member association has taken in $265,000 from private foundations, notably the Jack and Jane Fitzpatrick Trust, as well as several hundred thousand dollars from local businesses including Berkshire Bank, Canyon Ranch and Camp Mah-Kee-Nac as well as nonprofits such as the Kripalu Center for Yoga & Health and the Boston Symphony.
But private donations have been the greatest source of funding — more than $1 million from individuals who live on or near the lake.
Seltzer, a lakeshore resident, minces no words when he describes what's at stake for the town's primary recreational calling card: "If Stockbridge cannot dredge a half-century of accumulated sediment and enable a winter drawdown to kill the invasive Eurasian watermilfoil, Stockbridge Bowl will die," he said.
If left untreated, portions of the mile-wide, two-mile long bowl, originally known as Lake Mahkeenac, could turn into an unsightly marsh, hampering boating and threatening the idyllic beauty of the much-photographed and filmed setting.
At least 6,000 watercraft use the lake every year, according to a count at the town's boat launch off Route 183. The annual Josh Billings Runaground triathlon in mid-September includes a twice-around-the-lake race by more than 500 kayaks and canoes.
Although it's owned by the state, maintenance and preservation of the lake is primarily the responsibility of the town. About 400 seasonal and year-round property owners live on or near the Bowl.
The association, which has watched over Stockbridge Bowl since 1946 and first identified the invasive weed threat in 1958, has already spent $1.1 million on Phase One — installation in 2013 of a 250-foot-long, 4-foot-wide concrete drainage pipe under the town sewer line in the narrow outlet portion of the lake.
The dredging operation along 5 percent of the shoreline will be concentrated on the three most troubled sectors of the lake: The public beach and the outlet section behind the mid-lake island first, followed by the Hawthorne Road causeway area.
Why has the lake been so threatened by seven decades of silt buildup?
Seltzer explained that the town's storm drainpipe installed at the bottom of the lake's outlet section, along with three Tennessee Gas pipelines dating from the 1950s to the 1970s parallel to the town sewer line, combined to block the natural washing-out of the bowl. The Eurasian watermilfoil plants started encroaching on the shoreline because some residents used to dump their aquarium water into the lake.
The state DEP's Natural Heritage and Endangered Species Program is completing its final review of the project. The program protects the lake's rare Pilsbry's-Spire Snail.
"It's highly likely that our dredging project will not imperil the survival of the snail in the rest of the lake," Seltzer said.
Contact Clarence Fanto at 413-637-2551.
By the numbers . . .
The Stockbridge Bowl Association has raised about $3.5 million toward its nearly $3.9 million "lakelift" project from the following sources:
• Private donations: $1,150,000
• State Department of Environmental Protection: $910,000
• Town of Stockbridge (annual budget and CPA): $825,000
• Foundations: $265,000
• Berkshire Bank, other businesses and nonprofit organizations: $250,000
• Association's general fund: $100,000