SITE INFORMATION AND CORRESPONDENCE

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Spingolo Trucking - 2 - 25 November 2014 1011 N. Broadway Ave., Stockton San Joaquin County 3) The following USTs were removed from three locations (Figure 3) at the Site: • December 1986, two 6,000-gallon diesel (USTs 4 and 5), • May 1990, one 500-gallon waste oil UST (UST 3) • April 1992, one 500-gallon gasoline (UST 1) and one 2,000-gallon gasoline (UST 2) 4) Soil contamination was not reported at USTs 2 and 3. SJCEHD records do not state the volume of soil removed nor give the fate of stockpiled soil for any of the five USTs. 5) A March 1989 Unauthorized Release Form (URF) issued by the San Joaquin County Environmental Health Department (SJCEHD) indicated diesel fuel contamination in confirmation soil results (not found in SJCEHD records) taken in December 1986. SJCEHD stated contaminated soil from USTs 4 and 5 was over-excavated to 27' below ground surface (bgs), and clean soil was used to backfill the excavation. 6) A SJCEHD inspection report noted a failed gasoline precision test for UST-1 in November 1990. In June 1992, a URF for UST 1 noted that confirmation soil sample results (Table 1 below) indicated a release of gasoline. Soil at UST 1 was over-excavated (depth not stated by SJCEHD) and a SJCEHD inspection report states stockpile results were too high for reuse as fill. 7) Between October 2001 and June 2007, a number of soil and groundwater investigations were conducted (Figure 4). Investigation soil boring results (P1) taken from beneath USTs 4 and 5 indicated the presence of total petroleum hydrocarbons as diesel (TPHd) from 25' bgs to 45' bgs, up to 4,700 milligrams per kilogram (mg/kg) at 25' bgs (Figure 5). Samples from P-6 (just outside of USTs 4 and 5 excavation) noted TPHd from 15' bgs to 50' bgs up to 11,000 mg/kg (40' bgs), and TPH as motor oil (TPHmo) up to 1,400 mg/kg (25' bgs). Soil samples P-2 and P5 results below UST 1 reported TPH as gasoline (TPHg) up to 18 mg/kg from 15' bgs to 25' bgs. One grab groundwater sample (P-2), taken at 55' bgs, reported TPHd, 200 micrograms per Liter(ug/L); toluene, 1 ug/L and tert butyl alcohol (TBA), 8.1 ug/I (Table 2 below). 8) Three shallow monitoring wells (MW-1 through MW-3) were installed in 2006. Quarterly groundwater monitoring, conducted from April 2006 until April 2007, did not detect petroleum hydrocarbons. The consultant recommended additional vertical delineation of contaminated soil below the water table, however, in June 2007 all work stopped at the Site. 9) SJCEHD transferred the case to the Regional Water Board on 28 September 2010 for failure to comply with their 25 June 2008 directives to complete the soil investigation and install one well towards the southwest of the USTs, and for failure to meet with the SJCEHD in September 2010 to discuss their directives. Regional Water Board staff(Staff) contacted and met with the Responsible Party on 26 October 2010. Staff determined that the additional work to conduct a limited soil and groundwater investigation was not cost effective or necessary, as the monitoring wells were deemed adequately located around the USTs, and the groundwater data did not indicate an impact from residual soil contamination. The work proceeded to assess threats to nearby sensitive receptors, namely two of the domestic wells (#28 and#29).