PITTSFIELD — Demolition of Building 12 on the former General Electric Power Transformer site has resumed as the company complies with requirements following a spike in airborne PCB levels last month.

Work was halted when an air quality sample taken on July 11 and 12 at one of eight monitoring stations near the site was found to exceed the U.S. Environmental Protection Agency’s “action level” of 0.1 ppm. The monitoring station in question is located on adjacent property owned by the Pittsfield Economic Development Authority.

GE contractor Brandenburg Industrial Service Co. of Bethlehem, Pennsylvania, is demolishing Building 12, where power transformers were built and tested, and Building 14, where insulation tanks were manufactured. Unlike adjacent properties awarded to PEDA, GE is retaining the sites of Building 12 and Building 14.

The sample was taken from a monitor on PEDA’s Site 9 property, where workers have been removing the foundations of former transformer buildings and preparing the site for future development.

The sample was the only one of 72 samples taken over a six-month period that exceeded EPA health and safety limits. PEDA reported this on July 25 when the test results were available, the EPA said.

State and federal environmental agencies believe the increase in PCB concentrations in the air – 0.2324 ppm – is due to the demolition of nearby Building 12, where the chemical was used for decades to make power transformers. PCBs (polychlorinated biphenyls) were used by GE and other electronics manufacturers in insulating fluids. They were banned in 1979 as a probable cause of cancer.

Following this discovery, the EPA ordered a halt to demolition work until GE could meet several conditions, including a new round of air quality tests that showed PCB levels below the action level and additional steps to limit dust from demolition waste.

“With approval from the U.S. Environmental Protection Agency (EPA), GE has conducted a new round of air sampling on our property and an adjacent PEDA property,” a GE spokesperson said Tuesday. “We have shared these results, which showed no detection of PCBs on any monitors, and the EPA has approved the resumption of demolition work. Air sampling will continue and all data will be shared with the EPA.”

This week, workers could be seen spraying debris with water to reduce dust.

As for the work, Building 14, which ran along the Tyler Street Extension, has been completely demolished, and Building 12, along the CSX rail line, is about 25 percent demolished, said EPA spokeswoman Jo Anne Kitrell.

“Since work began over the past six months, all asbestos-containing materials, liquids and waste, equipment and transformer materials have been removed,” she said. “After that, construction waste materials such as steel beams, concrete and bricks will be consolidated into secured underground vaults. Any excess construction material that exceeds the vault capacity will be removed from the site.”

Kittrell said a sample taken during subsequent air monitoring detected PCB concentrations in the air that were well below the agency’s reporting and action limits for the chemical.

Meanwhile, work is nearing completion on Site 9, the largest parcel of land in PEDA’s William Stanley Business Park. The $10.8 million project involved breaking and destroying existing foundations, installing utilities and curb cuts, and landscaping the site for future use.

Site 9 between Woodlawn Avenue and Tyler Street Extension is the site of the former “Teens” complex, as the buildings were numbered for power transformers.