Environmental Science & Forensic Chemistry

Perimeter Air Monitoring During MGP Site Cleanups
New air-monitoring methods are being investigated for use at former manufactured gas plant (MGP) sites during cleanup operations. Gas Technology Institute (GTI) is leading a research team in a field-demonstration project of a promising technology and in the development of a guidance document based on research results.

ORS applied during MGP site cleanup in Tennessee
ORS applied during MGP site cleanup in Tennessee
Utilities and other owners of former MGP sites have designed comprehensive programs to clean sites of potentially hazardous contaminants. However, air-monitoring efforts put in place to protect the downwind community during the site cleanup have historically been limited in their ability to conclusively measure all the constituents of concern. Researchers explain that designing an effective sampling program in a medium as complex as air has been a challenge. While current methods can be effective, they seldom develop the criteria (or what is called ”data representativeness”) necessary for demonstrating continual maintenance of acceptable off-site exposure levels.

Investigators addressing the issue have seen strong potential through the use of optical remote sensing (ORS) technology. During a cleanup of a former MGP site in Bristol, TN, Atmos Energy Corporation chose to address the air migration pathway by employing ORS to measure gaseous contaminants along the entire downwind portion of the site perimeter.

Building upon the successful results of a preliminary feasibility demonstration of this technology for EPRI, Atmos Energy’s application led to community acceptance, an environmental excellence award from the Southern Gas Association, and accolades from the Tennessee Department of Environment and Conservation. However, before other site owners opt for this alternative (called a “whole-plume” approach) over the traditional point-monitoring approach, several critical areas need to be addressed.

The objective of this project is to demonstrate the effectiveness of ORS to facilitate standardization and regulatory acceptance of the ORS approach for MGP site application.

Researchers identified three critical areas that need to be addressed to accelerate widespread usage of the ORS approach within the industry:
  1. Gaseous Emissions Methods Comparison - Development of controlled field-test data comparing open-path Fourier-transform infrared (FTIR) spectroscopy, open-path UV spectro-scopy, and point monitoring.
  2. Data-Management Software - Completion of next-generation data-management software and “beta testing” using the FTIR and UV.
  3. Methods Guidance - Completion of a guidance document or standard operating procedure for accurate and uniform ORS-based monitoring.

The ultimate benefit to the industry and the public through this project is the enhanced safety of former MGP site cleanup operations and the reduced risk of litigation to site owners.

Researchers expect that this project will serve as a catalyst either for the development of similar methods for open-path spectroscopy or for providing guidance to extend the application of the method to other ORS approaches.

Technical Approach
The demonstration of acceptable off-site air concentrations has typically relied upon analysis results from a network of fixed monitoring stations strategically positioned around the perimeter of the MGP site. Researchers have found that data from such networks have only limited value in field decision-making. Particularly problematic is the fact that no approved, real-time point-monitoring analysis method exists for naphthalene. In addition, a “data representativeness” issue arises from the combination of a highly variable distribution of coal tar in the soil and an air-contaminant plume, which can pass between monitoring stations undetected.

Atmos Energy Corporation completed the cleanup of a former MGP site using open-path Fourier-transform infrared FTIR spectroscopy to monitor benzene, naphthalene, and 12 other gaseous target contaminants, all in real time. Data-management software, developed by Atmos Energy’s air-monitoring contractor (Minnich and Scotto) was combined with requisite on-site meteorological data to calculate maximum fenceline and off-site (sensitive receptor) exposure within seconds of each 10-minute monitoring event.

GTI is further investigating FTIR spectroscopy as one type of ORS technology. (Currently, FTIR spectroscopy is the only formally recognized ORS-based approach for air monitoring.)

The research plan calls for the testing of proposed methods and software at two appropriate MGP sites. The site owners (in compliance with existing work plans and protocols, independent of the ORS monitoring) will perform all traditional point monitoring. Emphasis will be placed on the typically controlling contaminants (benzene and naphthalene).

Investigators are also evaluating the next-generation data-management software, converted from an EXCEL™ program to a Visual Basic™ program. All meteorological data and open-path FTIR data will be entered automatically on-site. Data will be collected over a four-day period at each site.

Research results will be assembled into a guidance document for ORS-based perimeter air monitoring during MGP site cleanups.

Results/Project Status
TThe project entered its data-collection phase, starting with ORS data gathered at two former MGP sites undergoing remediation activities. Data will be analyzed and researchers will develop a standard operating procedure for use of the ORS technique for monitoring purposes.

A Final Report on this project is expected to be available in early 2008.

January 2007