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Starrtec November 28,2011 Page 2 of 5 Permits for Discharge: None Historic Range in Depth to Water, Q2-06 to Q3-11 MW-1, 6.28 to 10.52 feet (Measured Below Top of Casing) Current Quarter Monitoring Data (See Figure 2 and Table 1) Wells Monitored and Sampled: Eight wells, MW-1 through MW-8 Dissolved Oxygen Concentrations Measured In: Eight wells, MWA through MW-8 Depth to Groundwater(DTW)(Measured Below 8,57 to 9.93 feet Top of Casing) Average Change in Groundwater Elevation Since 1.74 foot decrease Last Event: Groundwater Flow Direction and Gradient: Southeast @ 0.0002 foot per foot (Figure 2) Current Quarter Analytical Data (See Figure 3 and Table 1) Maximum TPHg Concentrations MW-4, 980 pg/L Maximum Benzene Concentrations MW-4, 3.4 pg/L Maximum MtBE Concentrations MW-4, 6.3 pg/L Maximum TBA Concentrations MW-2, 44 pg/L BACKGROUND On July 17, 1998, three 10,000-gallon single-walled USTs were removed from the site. The UST excavation was extended to the east, and two new 10,000-gallon double-walled steel USTs were installed. The new tanks were installed in a tan pit locate eas of the origina oca ions. One te�nIn h diameter Schedule 40 polyvinylchloride (PVC) conductor casing was installed in the new UST pit between the new tanks for future installation of well MW-2. On September 29 and October 2, 1998, Fluor-Daniel GTI advanced six offsite (OSGP-1 through OSGP-6) and 11 onsite (GP-7 through GP-17) Geoprobe@ soil borings. The offsite borings were located north of the 7-Eleven site in an apartment complex. The offsite borings did not contain detectable concentrations of petroleum hydrocarbons. The on$te rin s contained benzene, total petroleum hydrocarbons as gasoline (TPHg), and methyl-tert-butyl ether (Mt almax m m concentrations of 12.5 milligrams per kilogram (mg/kg) (GP-17@20'), 42,900 mg/kq (GP-15@15'), and 234 mg/kg (GP-14@10'), respectively(Fluor Daniel GI, 1�-998). On May 13 and 14, 1999, four groundwater monitoring wells(MW-1 through MW-4)were installed to 25 and 30 feet below ground surface (bgs) (Table 3). Benzene, TPHg, and MtBE in soil were reported at maximum concentrations of 2.89 mg/kg (MW-3-15'), 429 mg/kg (MW-3-15'), and 0.119 mg/kg (MW-4-20'), respectively(IT Corporation, 1999). On October 30, 2001, three groundwater monitoring wells (MW-5, MW-6, and MW-7)were installed to 20 feet bgs. TPHg, benzene, toluene, ethylbenzene, xylenes (BTEX), and MtBE in soil were not detected above laboratory reporting limits, except for 0.006 mg/kg total xylenes (MW-7@20'). Selected halocarbons also present in the soil samples indicated possible dry cleaner plume contributions(IT Corporation, 1999). On August 14, 2003, deep groundwater monitoring well (MW-8) and one soil boring (SB-1) were advanced onsite. SECOR summarized this assessment in the February 27, 2004 Additional Site 14117 11-3Q Report.doc