FINGERPRINTING OF DNAPL FROM A FORMER MGP SITE AND NEARBY PROPERTY IN ASHLAND, WISCONSIN

摘要

The Gas Technology Institute has conducted a comparative study of nonaqueous phase liquid (NAPL) samples collected from three well locations in the town of Ashland, Wisconsin. These locations include the Northern States Power Company former manufactured gas plant facility (MW-15), the Copper Falls aquifer (EW-1) and the Ashland Lakefront Property (Kreher Park, MW-7). Samples were tested and evaluated against known standards for similarities and dissimilarities in tar composition and in quantity (percent content) of middle weight petroleum distillates (fuel oils). A literature search was performed to further corroborate results of testing with typical industry standards for identification of the NAPL samples. Using GC/FID fingerprinting techniques, results concluded that NAPL material from MW-15 and EW-1 are very similar in tar composition, both exhibiting a pattern typical of carburetted water gas (CWG) tars. The composition of samples MW-15 and EW-1 are also highly similar in the small percentage of middle weight petroleum distillates (average 8 percent aliphatic component). These samples are likely from the same source. This result is consistent with the fact that EW-1 is directly below the former MGP facility and may have been affected by site operations. Sample MW-7 is distinctly different from samples from MW-15 and EW-1. Sample MW-7 contains an MGP-type tar and a substantial fraction of middle weight petroleum distillate. The tar from MW-7 does not exhibit a pattern typical of the CWG standard. Nearly 30 percent of the sample from MW-7 is middle weight petroleum distillate. Data indicate that the MW-7 NAPL is derived from a source separate from that of samples derived from MW-15 and EW-1, and that the sample from MW-7 may represent an intentional mixture of petroleum-derived material and tar, such as a cresosote. Middle petroleum distillates may include diesel fuel, #2 fuel oil, gas oil and other fuel oils and were typically used as carriers in wood treatment operations. Material found in MW-7 is consistent with the US EPA definition of a wood treating mixture, "consisting of 35% by weight aliphatic hydrocarbon (oil) and 65% by weight polynuclear aromatic".