SITE INFORMATION AND CORRESPONDENCE_2

Home Browse Search

1 Ron Rowe Registered Environmental Specialist February 2, 2000 Page 9 2. New Evidence Points to a More Recent Release on the Property The finding of elevated levels of TBA indicates that the gasoline released at the site was formulated after 1979. Because Del Monte was in complete control of the Property from April, 1976 through the present, one can only conclude that Del Monte used or allowed the USTs to be used by others subsequent to Calpak's purchase of the Property in 1976. According to United States Environmental Protection Agency ("USEPA"), TBA was used as a carrier solvent for other fuel additives and was present only at very low concentrations (e.g., parts per million) in petroleum products between 1969 and 19798. In 1979, ARCO received a waiver from the USEPA to blend up to 7.0 percent TBA by volume in unleaded gasoline. Other producers subsequently received similar waivers to blend even higher concentrations in the early 1980s9. As of 1992, USEPA allows up to 3.5 percent oxygen by weight for a combination of TBA and methanol, provided the TBA concentration is greater than I or equal to the methanol concentration by volume10. TBA at blended concentrations (e.g., percentage concentrations of TBA) can enhance fuel octane, act as a co-solvent for methanol, and prevent carburetor icing in cold weather. More recently, TBA has been used as a fuel oxygenate". TBA is completely miscible in water,is biodegradable and can be utilized as a primary substrate by adapted microorganisms 12. TBA has previously been detected in groundwater samples from the Property at concentrations ranging from 31 to 82 µg/1. Although TBA is not present at concentrations that appear to adversely affect the beneficial uses of the groundwater at this site, TBA concentrations are relatively high in comparison to the reported concentrations of total petroleum hydrocarbons as gasoline (TPHg). The reported concentrations of TBA average 0.15 percent of the TPHg concentrations (10,900 to 145,000 µg/1) reported for the same samples. Thus, the ratio of TBA to TPHg is several orders of magnitude greater than would be expected if the product had originated from gasoline formulated before April, 1976. If pre-1979 product had been released at this site, TBA concentrations would be well below the method detection limit (even in the absence of natural weathering processes). 8 Fernandes, Joseph, U.S. Environmental Protection Agency Fuels Section, personal communication, 1998. J 9 Gibbs, L.M., Gasoline Additives—When and Why, SAE 1990 Transactions: Journal of Fuels fI &Lubricants, 1990, Section 4, Volume 29,Participant. 618-30. 10 Fernandes, 1998. 11 Owen, K. and Coley, T.,Automotive Fuels Handbook, 1990, Participant. 45-51. 12 Verschueren, K.,Handbook of Environmental Data on Organic Chemicals, Third'Edition, 1996, Participant. 354-57. E 1 .761778.3 I