History of PCBs in the natural gas pipeline industry
In January 1981, PCBs were discovered in natural gas pipeline liquids in Long Island, N.Y. Pipeline liquids include pipeline condensate and other liquids that were intentionally or accidentally added to the pipeline. Pipeline condensates, primarily composed of hydrocarbon distillates, occur as a result of the movement of pressurized natural gas through a pipeline under varying temperature conditions. Examples of liquids that were intentionally added to natural gas pipelines include: methanol as an ice hydrate deterrent; inhibitor chemicals for corrosion protection; and waste oils sprayed into a pipeline (known as fogging the lines) for gasket protection. Adding liquids to the pipeline, intentionally, is no longer a common practice in the industry.
Due to the discovery of PCBs in some pipeline liquids, the EPA, state agencies and the natural gas pipeline industry formed a task force in January 1981 to address the PCB problem and to coordinate national activities. Under this task force, EPA headquarters took responsibility for major interstate transmission companies, while the EPA regions were asked to work with public service commissions and local distribution companies. Extensive EPA and industry sampling of the major transmission facilities found 13 companies with PCB contamination greater than 50 parts per million (ppm). PCB pipeline liquids contamination was also found at a number of local distribution companies.
In late 1981, EPA instituted a Compliance Monitoring Program (CMP) for the 13 companies found to have PCBs greater than 50 ppm. The 1981 CMP required each company to develop remedial plans with four basic objectives: (1) to ensure the proper storage and disposal of PCBs; (2) to contain PCB contamination to limited areas of the transmission system; (3) to eliminate any further entry of PCBs into the pipeline system; and (4) to remove remaining PCB contamination from the pipeline system. To achieve these objectives, most of the participants installed filter separators to collect condensate at several locations along their respective pipeline systems.
In addition, each company was asked to develop and submit PCB monitoring plans that included sampling key points within the contaminated area. Suggested sampling locations included major natural gas purchasers and large volume condensate collection points. Individual monitoring plans were finalized with each company in late 1981 and early 1982.
The EPA decided that it would not take enforcement action against such companies for the improper use of PCBs as long as they participated in an EPA compliance monitoring program. All companies were required to comply with all other aspects of the PCB rule, which included marking, record keeping, and disposal.
In 1992, Northern Natural Gas requested, from the EPA, to declassify the southern portion of the pipeline system, because PCB levels were either too low or non-existent. The southern portion consisted of everything south of, and including, the Beatrice, Neb., compressor station. This was eventually granted on June 24, 1992.
In 1998, the EPA issued the Mega Rule, which addressed how pipelines were to handle PCBs. In order to manage the PCBs remaining in the pipeline system, natural gas transmission companies must comply with many sampling and characterization requirements.
In 1999, following the installation of the Mega Rule, Northern Natural Gas sampled all PCB sources within its pipeline. These sources included natural gas compressors, natural gas scrubbers, natural gas filters, interconnects with other natural gas transmission companies, and pipeline liquid tanks and drips. The sampling has been repeated in subsequent years.
Characteristics of PCBs in the gas stream
A study published in 2001, conducted by the Gas Research Institute, indicates that PCBs travel in liquid form. Therefore, if liquids in the pipelines are controlled, the PCBs should be controlled. When the gas stream drops in pressure and velocity, the liquids fall out and remain in the pipeline. Therefore, gas delivered to residential homes should not have liquids entrained in the gas. The liquids will drop out prior to reaching the customer's home.
PCBs in Northern Natural Gas' Pipeline System
The PCBs found in Northern's pipelines entered the system several years ago. This is known because PCB use was discontinued in 1979. There are two types of PCBs that have been found in Northern's system. One type of PCB is from a turbine oil, which Northern suspects was delivered from another pipeline company through an interconnect because Northern did not use turbine oil that contained PCBs. The other type of PCB is from valve sealant that Northern did use on the north section of the pipeline system.
The valve sealant can enter the pipeline through the course of normal maintenance of the valves. Northern immediately ceased using valve sealant containing PCBs in 1979 when the EPA determined there were risks to public health.
Liquids that are introduced into the system through normal maintenance of the compressors, travel down the pipeline in the gas stream and can pick up the PCB contaminated valve sealant. Because of this action, Northern treats all of its liquids found north of the Beatrice station as PCB contaminated and follows all applicable regulations to test and remediate.
Northern rarely finds liquids that have concentrations above EPA's threshold levels that require the waste to be treated as PCB contaminated. Most of the liquids collected on Northern's system are well below these limits. Therefore, disposal of these wastes are handled as used oil.
In the rare event that the liquids test above EPA's threshold level, the waste is disposed of properly and the required testing and sampling is conducted according to the regulations.
Northern is focusing on removing these liquids from the system by using various types of equipment such as separators, drips, and coalescing filters. The type of equipment chosen depends on the size of pipeline and the range of the gas stream velocity. Northern is also removing liquids by pigging the lines throughout the northern half of the system. These pigs will sweep the existing liquids out through the pig receiver.
These filter installations and pig runs are ongoing and will continue to be performed to remove liquids, and therefore, PCBs from the system