National Grid/NYSEARCH achieve success with EPA confirmation of MDPE being treated as ‘Non-Porous’ Material

Excerpts from recent EPA acceptance letter regarding MDPE classification.

In December 2018, after many years of work and discussions facilitated by AGA with EPA, a decision has been made to classify MDPE in a similar way to HDPE as having a non-porous surface. This EPA decision was based on a series of studies that National Grid led through NYSEARCH and conducted by John Woodyard and Jana. The work focused on Assessment of PCBs in Medium Density PE and High-Density PE used in the gas distribution sector. The project tested a range of pipes particularly new and older generation MDPE and utilized mass transport theory.

Prior to an Advanced Notice of Proposed Rulemaking in 2010, the EPA regulations that govern PCBs in natural gas systems were based largely on the assumption that all gas pipes are metal. PCBs are present in some gas distribution PE pipes as condensate from historical use of PCBs. The new EPA classification, as discussed in the December 14, 2018 letter from Barnes Johnson of EPA, is defined in 40 C.F.R. 761.3 and may be wipe sampled for waste profiling under 40 C.F.R. 761.60 and for decontamination under 40 C.F.R. 761.79. EPA concludes that the study demonstrates that medium and high-density polyethylene used in natural gas distribution piping “meets the definition of a ‘non-porous surface’ under 40 CFR 761.3 because the pipe is a ‘smooth, unpainted solid surface that limits penetration of liquid containing PCBs beyond the immediate surface.” This finding translates into better use of resources when de-commissioning older PE pipe and reduced costs in storage and disposal.

NYSEARCH Senior Project Manager, Joseph Mallia led the project with funding, materials and SME input from National Grid. In a true cross-industry effort, AGA’s Chief Regulatory Counsel Pam Lacey led the interactions and aided communications regarding iterations of responses over several years with EPA. NYSEARCH and its contractors worked iteratively to answer EPA questions and demonstrate that the worse-case scenarios that were requested by EPA were tested sufficiently.

The report from the study and the EPA acceptance letter have been made available to the EPA and is available through the following links.

View / Download National Grid / NYSEARCH Report: "Assessment of Polychlorinated Biphenyls (PCBs) in Polyethylene (PE) Gas Distribution Piping"

View / Download EPA Acceptance Letter


For over thirty years, NYSEARCH has worked as a consortium of natural gas Local Distribution Companies (LDCs) who have a common interest and need for research and technology development and demonstration. Today, as part of the Northeast Gas Association (NGA), NYSEARCH manages over (30) projects in various stages of development for LDCs, transmission companies, federal agencies and their manufacturing and commercial partners. NYSEARCH is located in Parsippany, NJ and NGA is headquartered in Needham, Massachusetts.