Air Emission Sources

Evaluating possible sources of PFAS air emissions that could potentially affect groundwater or surface water.

The NHDES Air Resources Division regulates and limits air emissions from a variety of industrial sources within New Hampshire through a statewide permitting program. In 2016, when perfluorooctanoic acid (PFOA) was first detected in a tap water sample at the Saint-Gobain Performance Plastics facility in Merrimack, NH, the Air Resources Division began to investigate potential sources. While this search led to further site investigations for localized PFAS issues, thus far only Saint-Gobain has been identified as an active PFAS emitting source large enough to cause groundwater contamination above AGQS. The Air Resources Division has been actively involved with investigations of other industrial and municipal facilities to ensure PFAS emissions are not contributing to groundwater contamination in New Hampshire.

Saint-Gobain Air Emissions History 

In 2004, Saint-Gobain conducted stack tests using testing and analytical methods that had recently been developed to evaluate the potential PFOA emissions from three coating towers at the facility. Upon review of the emissions detected, Saint-Gobain reported to NHDES that the emissions from the entire facility were predicted to exceed the ambient air limits (AALs) established in Env-A 1400, Regulated Toxic Air Pollutants. NHDES issued an Administrative Order by Consent to Saint-Gobain, which required reformulation of coatings to reduce PFOA content by the end of 2006. Additional stack testing was conducted in 2007, at which time Saint-Gobain demonstrated compliance with the AALs using the information from the stack test and air dispersion modeling. As a result, PFOA emissions were reduced by more than 96% from 2004 levels. See Saint-Gobain Performance Plastics site investigation history page.

Air Emission Controls

a Regenerative Thermal Oxidizer
The Regenerative Thermal Oxidizer (RTO) was brought online July 14, 2021.

In 2018, the New Hampshire Legislature passed legislation that added Section RSA 125-C:10-e to the Air Pollution Control statute. As a result, NHDES made a determination that Saint-Gobain was subject to the regulation and required to install Best Available Control Technology for PFAS emissions. After a year-long permitting process, NHDES issued a permit for the construction, installation and operation of a Regenerative Thermal Oxidizer (RTO) for the control of PFAS with specific emission limitations for PFOA and PFOS – the two PFAS that had AGQS standards at the time of permit issuance. Saint-Gobain failed to complete the construction by the February 2021 deadline required by statute and permit. NHDES and Saint-Gobain entered into a Consent Decree in 2021, which required Saint-Gobain to complete construction and installation of the RTO by July 31, 2021, conduct more extensive stack testing, a material balance to determine potential hydrogen fluoride emission rates and conduct an Env-A 1400 compliance demonstration, and a rainwater study as well as limit operations and pay a penalty. The RTO was brought online July 14, 2021.

Current Status of Operations

saint-gobain bypass stack
A bypass stack at Saint-Gobain.

In September 2021, Saint-Gobain, in conjunction with their consultant Barr Engineering, conducted stack testing as required by the permit and Consent Decree to evaluate the operation of the RTO. During the stack test, NHDES observed that the main header associated with conveying the coating towers and auxiliary equipment exhaust streams to the RTO had been built with a bypass stack. Therefore, NHDES issued a Letter of Deficiency to Saint-Gobain on November 18, 2021. The LOD required Saint-Gobain to submit, among other information, a permit application requesting a significant permit amendment to Temporary Permit TP-0256 regarding the bypass stack. NHDES is currently evaluating the information contained in both the significant permit amendment application along with the state permit to operate application submitted on June 1, 2022. Saint-Gobain operates the RTO in accordance with the revised monitoring plan submitted to and approved by NHDES. Stack testing was conducted at Saint-Gobain on August 24 and 25, 2022. NHDES had two experienced staff members present to observe the method in which samples were collected and the operation of the towers at the facility during the stack test. The RTO did not encounter any issues and the stack test was completed as designed. NHDES received a final stack test report from Saint-Gobain on October 24, 2022, and is currently reviewing the document.