BULLWORK OF DEMOCRACY EXCLUSIVE COVERAGE: The Black Lagoon is a contaminated man-made pond near the corner of Maple and Walker streets in Marlborough, Mass. For more than a century, petroleum-product spills have plagued properties on a mile-long stretch of Maple Street. Toxins from those spills including lead now rest uneasily in The Black Lagoon, mingled in massive silt deposits that pose a threat to the nearby Sudbury Reservoir.
LAND OF THE DAMMED: A large meadow dominates the terrain immediately downstream from The Black Lagoon. If the man-made pond's dam fails during a storm, the floodgate spillway drainage ditch in the foreground of this photo and the field in the background would be covered with contaminated silt. The Sudbury Reservoir, which is a backup water supply for 2.2 million people in Greater Boston, is about a quarter-mile downstream. /Christopher Cheney photo
The dam holding back tons of contaminated silt at The Black Lagoon is structurally compromised and could fail catastrophically, according to a pair of engineers.
The dam has been poorly maintained over the past two decades, and the elements have taken their toll, says Joseph Landry, principal at San Francisco Bay Area-based Joseph Landry Architecture and Design. "It is easy to see that the structural integrity has been compromised from years of natural forces and maintenance neglect. The cracks in the concrete and the misalignment of the top stones will only further degrade at a more rapid speed because the foundation support is obviously deteriorated. Even by just viewing photos, one can see the severity of the situation."
A washout on the back side of The Black Lagoon's dam is at least 5-feet-wide and 10-feet long. The washout runs along the concrete portion of the structure's western abutment, which is constructed with carved stone and mortar. Poor maintenance over the past 20 years also has weakened the earthen portion of the the dam, below, which has trees growing along its entire surface. Tree roots compromise the structural integrity of packed-earth dams. /Christopher Cheney photos and bullworkofdemocracy illustrations
The damaged eastern abutment and tree growth on the earthen portion of the dam are serious structural problems that could lead to a collapse, says an engineer at the Connecticut Department of Transportation who also reviewed photographs of the site. "It is possible," he says of a dam failure at The Black Lagoon. "Like anything, it's not going to last forever. It has to be maintained."
The Black Lagoon, which is on state land managed by the Department of Conservation and Recreation (DCR), is filled with tons of contaminated silt from several properties upstream along Maple Street. Over the past three decades, at least 16 Maple Street properties have undergone state-supervised environmental cleanups, according to Massachusetts Department of Environmental Protection (DEP) records.
In an April 1996
story published in the
Middlesex News, a state official called The Black Lagoon a major source of contamination for the Sudbury Reservoir, which is a key element of the backup water supply for 2.2 million Greater Boston residents and 5,500 businesses. In the time since I wrote that newspaper story, the environmental threat has mushroomed, with alarming growth of the contaminated silt deposits in The Black Lagoon and the man-made pond's dam in disrepair.
This week, an official at the city of Marlborough told
Bullwork of Democracy that all of the known contamination along Maple Street has been removed or contained. "It's been cleaned up piece by piece," said Priscilla Ryder, the agent for the Marlborough Conservation Commission who has been monitoring Maple Street toxic waste sites for a quarter century. Some of the cleanup efforts have taken as long as 15 years to complete, she said.
There still could be contamination under the surface along Maple Street, in part because DEP denied requests from the city to conduct a comprehensive cleanup of the entire commercial strip. "They've cleaned up what we found," she said.
DCR bears responsibility for cleaning up The Black Lagoon, Ryder said. "I remember talking with DCR at the beginning [of the Maple Street cleanups in the late 1980s], and they said they were not going to clean up the pond until everything was cleaned up upstream."
DCR officials did not respond to email and phone requests for comment.
Most of The Black Lagoon is filled with contaminated silt. /Google Earth image and bullworkofdemocracy illustration
For more than a century, a mile-long stretch of Maple Street has been the scene of repeated oil and gasoline spills, according to DEP records. The Marlborough Fire Department
headquarters, a $2.4 million facility completed in 1995, is located on one of the most notoriously polluted properties: 215 Maple St.
A 1986
subsurface exploration study of 215 Maple St. focuses on the environmental impact of a coal gasification plant that operated on the property from about 1900 to 1940. The Black Lagoon, which is about a half-mile south, is fed by the Sudbury Reservoir tributary that flows through the 215 Maple St. parcel. "Flow in the Metropolitan District Commission ditch which bisects the site is ... in a southerly direction, towards Sudbury Reservoir," the 1986 study says.
The study documents a thin layer of coal-gasification sludge "found at a depth of about 16 to 18 feet in one area of the site." The study also says the discovery of "an abandoned underground gasoline storage tank on the site constitutes a violation of the State Fire Marshals Regulations." Despite these toxic hazard discoveries, the study fatefully concludes "The volume of hazardous material (coal tar) buried on the site appears to be small."
While preparing the property for the new fire department headquarters on Nov. 15, 1993, excavation workers hit an abandoned pipe from the coal gasification plant, releasing more than 100 gallons of thick black coal tar into the soil, DEP
documents say. "While performing construction activities at the new fire station, a pipe that was part of a former coal plant was ruptured, resulting in a release of 100-150 gallons of a tar-like substance," a DEP report on the spill says.
The day after the coal tar spill, a cleanup contractor estimated that 50 cubic yards of contaminated soil would have to be removed from the property and "approx 3000 gallons of coal sludge/water will be pumped out of the excavation," a DEP document says.
The Black Lagoon -- and the legacy of petroleum-product spills that it harbors in tons of contaminated silt -- is an environmental threat that has grown silently over time with no end in sight, Ryder says. "It's been a sleeping giant. Nobody's rattling the cage."
A recent photo of The Black Lagoon shows the largest contaminated silt deposits, which are located on the commercially zoned side of the man-made pond. A neighborhood with dozens of homes is on the eastern side of Marlborough's toxic waste "sleeping giant." /Christopher Cheney photo and bullworkofdemocracy illustration
DEP documents on Maple Street environmental cleanups:
Cleanup plan for former Texaco gas station, March 11, 1997
Cleanup report for 417 Maple St., April 1998
Cleanup report for 415 Maple St., June 1998
Cleanup report for gasoline spill, 146 Maple St., June 1999
Cleanup report for 146 Maple Street, July 2010
Waste oil cleanup
report for 417 Maple St., August 2013
