Targeted Brownfields Assessment of a Former Power Plant Using the Triad Approach

Abstract

A Targeted Brownfields Assessment of a former power plant was conductedusing the Triad approach, through the efforts of EPA Region I andMetcalf & Eddy, the Brownfields Technology Support Center, and the townof Greenwick Connecticut. The Triad approach is an integrated strategyfor managing decision uncertainty at hazardous waste sites that is beingpromoted by EPA, along with other Federal agencies. The Triad approachconsists of three elements: systematic project planning, real-timemeasurement technologies, and dynamic work strategies(http://www.triadcentral.org). The Triad approach recognizes thatoverall decision uncertainty is generally governed more by samplinguncertainty (that is, the uncertainty that the samples collectedadequately represent site contamination), than by analytical uncertainty(that is, the accuracy and precision of the analytical method)(Crumbling et al., 2001). The town plans to redevelop the nine-acre siteas a waterfront park, and needed to decide whether this plan wasfeasible, and if so, what remedial measures might be necessary beforethe park could be constructed. Because coal ash was historicallydisposed at the site, it was considered probable that site surface soilthroughout the entire nine acres would show concentrations ofcontaminants that exceed Connecticut residential direct exposurecriteria. Historical information also suggested the possibility oflocalized petroleum and polychlorinated biphenyl (PCB) releases. Thegoal of the investigation was to obtain sufficient data, in onemobilization, to determine the nature and extent of surface soilcontamination. Attaining this goal was judged to be infeasible using atraditional approach of soil sampling with analyses in off-sitelaboratories, and evaluation of results several weeks later. The Triadapproach, with its focus on development of a conceptual site model,evaluation of decision uncertainty, use of field/real time analyticalmethods, and field decision-making, was selected over a traditionalapproach. Field analytical techniques included siteLAB (R) test kits fortotal petroleum hydrocarbons (TPH) and total polyaromatic hydrocarbons(PAHs), EPA's X-ray fluorescence instrument for metals, and the EPAmobile laboratory for PCBs. Soil samples were also analyzed by anoff-site laboratory for arsenic with 48-hour turnaround. Samplinglocations were added based on feedback from the field analyses. The useof field methods allowed for sampling using a random-grid approach, withmany more locations sampled than would have been possible by relyingsolely on the more costly off-site laboratory analyses. The team locatedan area of PCB contamination that might have gone undiscovered if arandom grid sampling approach had not been used. A correlation wasdeveloped between the TPH/PAH test-kit results and off-site laboratoryresults, which enabled use of the test-kit results to define the extentof soil contamination with TPH and PAHs. The results showed that sitesurface soil contains concentrations of arsenic, TPH, and PAHs at levelsexceeding Connecticut residential direct exposure criteria. The observedconcentrations are partially from the coal ash that is co-mingled withsite soil. PCBs were also identified near an area where transformers hadbeen located. The Triad approach yielded an estimated cost savings ofapproximately 35 percent, when compared with a traditional approachinvolving two mobilizations of 20 borings each, with locations selectedjudgmentally, and off-site laboratory analytical methods alone.