History of PCBs in the natural gas pipeline industry
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. At one time, there were liquids that were intentionally added to natural gas pipelines; these included 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. Intentionally adding liquids to the pipeline is no longer a common practice in the industry.
In January 1981, PCBs were discovered in some natural gas pipeline liquids in Long Island, New York. Due to the discovery of PCBs, the federal Environmental Protection Agency, state agencies and the natural gas pipeline industry formed a task force to address the PCB problem and to coordinate national activities. Under this task force, the EPA took responsibility for addressing the PCB problem in major interstate natural gas transmission companies, while the EPA regions were tasked with coordinating with state commissions and local distribution companies. Extensive sampling of the major transmission facilities found 13 companies with PCB contamination greater than 50 parts per million (ppm), a rate high enough to cause concern. PCB pipeline liquids contamination also was found at a number of local distribution companies.
In late 1981 - more than 30 years ago - the EPA instituted a Compliance Monitoring Program (CMP) for the pipelines found to have PCBs greater than 50 ppm. The 1981 CMP required each company to develop remedial plans with four basic objectives: (1) ensure the proper storage and disposal of PCBs; (2) contain PCB contamination to limited areas of the transmission system; (3) eliminate any further entry of PCBs into the pipeline system; and (4) 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 pipeline interconnections with major natural gas purchasers, and large volume condensate collection points. Individual monitoring plans were finalized with each company by early 1982.
The EPA required the pipelines to participate 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 requested the EPA to declassify the southern portion of its pipeline system from the CMP because PCB levels were either low or non-existent. The southern portion of the pipeline system consists of the pipeline south of the Beatrice, Nebraska, compressor station. Northern’s request was granted 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 were required to comply with sampling and characterization requirements.
In 1999, following the installation of the Mega Rule, Northern 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 by the Gas Research Institute in 2001 indicated that PCBs travel through a pipeline in liquid form. Therefore, the study concluded, if liquids in the pipelines are controlled, the PCBs will be controlled. When the gas stream drops in pressure and velocity, the liquids fall out and remain in the pipeline. Accordingly, gas delivered to residential homes should not have liquids entrained in the gas. Any liquids will drop out prior to reaching the resident’s home.
PCBs in Northern Natural Gas' pipeline system
The PCBs found in Northern's pipelines entered the system many 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 into Northern’s system from another pipeline company through an interconnection. Northern did not use turbine oil that contained PCBs. The other type of PCB is from valve sealant that Northern used in its pipeline system on segments north of Beatrice, Nebraska.
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 downstream the pipeline in the gas stream and can pick up the PCB-contaminated valve sealant. To address this situation, Northern treats all of its liquids found north of the Beatrice station as PCB-contaminated, and follows all applicable regulations to test and remediate the presence of PCBs.
Northern rarely finds liquids that have concentrations above EPA's threshold levels that require the liquids to be treated as PCB-contaminated. Most of the liquids collected on Northern's system are well below these limits. Therefore, Northern handles the liquid wastes as it does 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 the pipeline and the range of the gas stream velocity. Northern also is 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 any PCBs from the system.