In the natural gas industry, PCBs were first discovered in natural gas pipeline liquids in the early 1980s. Soon afterwards, the United States Environmental Protection Agency (U.S. EPA), state governments and natural gas transmission companies began extensively sampling pipeline liquids to address the problem. As a result, 13 major natural gas companies were found to have transmission lines that were contaminated with PCBs at concentrations greater than 50 parts per million (ppm).
Although this amount was prohibited under these circumstances, the U.S. EPA instituted a Compliance Monitoring Program (CMP) for the 13 companies, rather than bring about enforcement actions. Established in 1981, the CMP required each company to develop remedial plans with four objectives:
- to ensure the proper storage and disposal of PCBs;
- to contain PCB contamination to limited areas of the transmission system;
- to eliminate any further entry of PCBs into the pipeline system; and,
- to remove remaining PCB contamination from the pipeline system.
The 13 CMP companies were still required to comply with all other aspects of state and federal PCB laws and regulations. However, the CMP did allow for the use of PCBs in natural gas transmission lines under certain conditions.
In 1998, the CMP was replaced by the PCB Disposal Amendments. Also known as the “Mega Rule”, these new regulations revised the use authorization to allow the use of PCBs in natural gas pipelines (in concentrations that exceed 50 ppm) under certain conditions. Additionally, the Mega Rule forced natural gas transmission companies to comply with many new sampling and characterization requirements.
In 2010, the U.S. EPA published an Advance Notice of Proposed Rule Making to modify the Mega Rule by reducing the current use authorization from 50 ppm to 1 ppm, virtually eliminating the permitted use of PCBs in the natural gas industry. The rule is anticipated to go into effect in the fall of 2017.
A major source of PCB contamination in the natural gas industry is from the historical use of PCB oil as a compressor lubricant. During machine startup and gas stream compression, compressor units were designed to release a small amount of oil into the housing seal that is connected to the transmission pipeline. Although this design reduced the leaking of natural gas into the atmosphere, it allowed PCBs to come in contact with the gas, causing small amounts to enter the gas stream. Additionally, air compressors that used PCB oils have been known to emit microscopic PCB particles into the air, causing nearby painted surfaces and equipment to become contaminated.
Other sources of PCB impacts could include older electrical equipment (such as transformers or capacitors), machine parts, valve sealants and other products that may have contained PCBs prior to the ban. Furthermore, although many products used in pipeline systems were not specifically manufactured with PCBs, they may have inadvertently contained small amounts of PCBs or become impacted from outside sources.