CHATHAM — Soil sampling around Homestead Lane shows no detectable levels of cancer-causing polychlorinated biphenyl, or PCB, following the failure of an electrical transformer during the July 23 severe storm.
The spill prompted town officials to prohibit shellfishing and swimming in Little Mill Pond, Mill Pond and part of the Mitchell River immediately after the storm. First responders noticed a sheen on the surface of the water, indicating that the transformer oil had reached the waterway. Under orders from the Massachusetts Department of Environmental Protection, the owner of the utility pole, Eversource, contracted with Clean Harbors, Inc., for the initial cleanup.
The cleanup crew used a solvent to clean storm drains, and then vacuumed the water from those drains, using absorbent booms to contain run-off. Officials recommended cleaning the pipe that leads from the storm drains to the waterway, but could not immediately locate the end of the pipe. By July 31, no sheen was visible on the waterway any longer, and the oily trail leading down Homestead Lane toward the water had become less visible.
“The oil never reached water, and the spill was immediately cleaned up,” Eversource spokesman Reid Lamberty said.
The spill happened after a tree fell on utility wires, causing the utility pole to snap and the transformer to break open. While modern electrical transformers contain mineral oil, older ones contain PCB, a carcinogen that persists in the environment for years and accumulates in living tissue. The substance is a neurotoxin, and the EPA has ruled that it is unsafe in drinking water at any level, even at trace amounts. About 17 gallons of fluid leaked from the Homestead Lane transformer, flowing about 150 feet downhill, where much of it ended up in storm drains.
“This transformer was roughly 50 years old which is in line with the normal life cycle of a transformer,” Lamberty said.
The production of PCBs was outlawed in 1978, but it’s unclear how many PCB-containing transformers are still on utility poles.
“Since the mid ‘80s, we have proactively removed tens of thousands of transformers containing PCBs near environmentally sensitive areas, such as schools, hospitals and libraries. To be clear, any distribution transformer that contains PCBs was the result of the manufacturing process and done without our knowledge,” Lamberty said. “The only transformers we know contain PCBs are industrial-sized transformers used at our substations or large industrial customers. Again, we have proactively replaced those transformers.”
First responders arriving at a damaged transformer may not immediately know what chemicals are in the spilled fluid. Information on the name plate of the transformer may indicate the presence of PCBs, but crews might need to use a field testing kit to know for certain. In the case of the July 23 spill, downed trees kept crews from reaching the scene for several hours.
An oily slick running down Homestead Lane, visible for more than a week after the spill, showed that the fluid reached the edge of the pavement and entered the marsh just east of the Mill Pond Road public dock.
Testing shortly after the spill showed no measurable PCBs in the waterway, and technicians from the Pocasset-based environmental engineering firm of Tighe and Bond sampled soil taken from three locations around the utility pole and two locations in the marsh near the end of the oily slick.
In a July 30 email to Chatham Shellfish Constable Renee Gagne, Environmental Scientist Emma Larkin of Tighe and Bond said the two samples closest to the shoreline were tested for PCBs and other chemicals consistent with transformer oil.
“The laboratory results indicate that PCBs were not detected above the laboratory detection limits, and therefore are also below the MassDEP Method I Standards,” Larkin wrote. Low levels of the indicator chemicals were found in those two soil samples from the marsh, “however, the concentrations were well below the MassDEP Method 1 Standards,” she wrote.
Based on those test results, town officials reopened the waterways to shellfishing and swimming.
Chatham Health and Natural Resources Director Robert Duncanson said it is hard to predict the environmental and public health risk from a release of PCBs into the environment.
“Obviously it’s a concern,” he said, but the spread of the chemical depends largely on factors like the amount of rainfall present, tides and currents. For that reason, such spills are always addressed by mitigation plans tailored to the particular circumstances involved, he said.
Are there other transformers with PCBs in Chatham today?
“I have no idea,” Duncanson said.
Neither does Eversource.
“We do not [know the] number of PCB transformers still in use today, but as we continue to make upgrades across our service territory, we replace transformers that we identify contain PCBs,” Lamberty said.