Superfund Innovative Technology Evaluation (SITE)
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|Strategic Diagnostics Inc. EnSys Petro Test System
The EnSys Petro Test System developed by Strategic Diagnostics Inc. (SDI) was demonstrated under the U.S. Environmental Protection Agency Superfund Innovative Technology Evaluation Program in June 2000 at the Navy Base Ventura County site in Port Hueneme, California. The purpose of the demonstration was to collect reliable performance and cost data for the EnSys Petro Test System and six other field measurement devices for total petroleum hydrocarbons (TPH) in soil. In addition to assessing ease of device operation, the key objectives of the demonstration included determining the (1) method detection limit, (2) accuracy and precision, (3) effects of interferents and soil moisture content on TPH measurement, (4) sample throughput, and (5) TPH measurement costs for each device. The demonstration involved analysis of both performance evaluation samples and environmental samples collected in four areas contaminated with gasoline, diesel, or other petroleum products. The performance and cost results for a given field measurement device were compared to those for an off-site laboratory reference method, Test Methods for Evaluating Solid Waste (SW-846) Method 8015B (modified). During the demonstration, SDI required 39 hours, 35 minutes, for TPH measurement of 191 samples and 12 extract duplicates. The TPH measurement costs for these samples were estimated to be $10,210 for the EnSys Petro Test System compared to $41,290 for the reference method. The method detection limit for the reference method was determined to be 6.32 milligrams per kilogram; a method detection limit could not be determined for the EnSys Petro Test System because it is a semiquantitative device. During the demonstration, the device exhibited good precision and lack of sensitivity to soil spiked with humic acid. The device showed a mean response of at least 24 percent for interferents that are not petroleum hydrocarbons (neat materials, including tetrachloroethene; turpentine; and 1,2,4-trichlorobenzene). A significant number of the EnSys Petro Test System TPH results were determined to be inconclusive because the detection levels used by SDI were not appropriate to address the demonstration objectives. Overall, the devices results did not compare well with those of the reference method; in general, the device exhibited a high positive bias. Collectively, the demonstration findings indicated that the user should exercise caution when considering the device for a site-specific field TPH measurement application.