SITE INFORMATION AND CORRESPONDENCE

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Shell Mountain House Pipeline - 3 - 3 November 2011 Mountain House Parkway and C A Line Road, Tracy Semi-Volatile Organic Compounds Phenol Naphth 2- 1- acenapht fluoranth alene methylna methylnaph hene fluorene phenanthrene ene pyrene chrysene htalene talene 1.5 15 26 20 2.5 8.9 14 1.3 2.8 2.4 Groundwater beneath the Site fluctuates from 27 to 34 feet bgs and generally flows to the northwest, but does fluctuate to the northeast, at a gradient that ranges from 0.002 to 0.018 foot per foot. Shell collected grab groundwater samples during 2005 from borings where there was field evidence of hydrocarbon impact. Shell initially observed LPH in a groundwater sample from Neighborhood B and concentrations of petroleum constituents that are indicative of LPH were reported in Neighborhoods C and D. The greatest dissolved phase petroleum constituent concentrations detected from groundwater sampling are shown on Table 2. Table 2 - Greatest Groundwater Concentrations in micrograms per liter(pg/L)] TPH-c TPH-d Benzene Toluene Ethyl- Total Naphthalene' Sulfate' Sulfur' benzene Xylenes 570,000 330,000 18 30 21 279 <10 220 78.8 TPH-c and TPH-d =total petroleum hydrocarbons as crude and as diesel ' Monitoring well data. Between February and May 2009 and after Shell completed the excavations, Shell installed fifteen groundwater monitoring wells (MW-2 through MW-16) to depths ranging from 35 to 40 feet bgs in Neighborhoods C and D. Shell also installed nineteen groundwater monitoring wells (MW-1 through MW-19) at depths ranging from 37 to 38 feet bgs in Neighborhood B. Shell began conducting quarterly groundwater monitoring on 21 September 2009 and petroleum constituents have only been detected during a single monitoring event. In March 2010, TPH-d was detected in seven of the thirty-three wells monitored (Well MW-10 in Neighborhood C and D was dry) at concentrations ranging from 54 to 79 micrograms per liter (pg/L), which is below the water quality objective of 100 pg/L for TPH-d. These spurious detections have since not been observed and petroleum hydrocarbon concentrations have since been non-detect in groundwater. The results of the most recent quarterly groundwater sampling event, conducted on 23 December 2010, were below the reporting limits for analyzed constituents in the 34 groundwater monitoring wells at the Site (Table 3). Table 3 - Most Recent Groundwater Anal tical Results (in pg/L) Well TPH-c TPH-d Benzene Toluene benzenEthyl- Xylenes Naphthalene MW-1(B) to MW-19(B) < 250 < 50 <0.50 <1.0 < 1.0 < 1.0 < 10 MW-2(C&D) to MW- < 250 < 50 <0.50 <1.0 < 1.0 < 1.0 < 10 16 C&D Soil vapor samples were collected using direct push temporary soil gas probes within and adjacent to select backfill areas between 5 and 25 feet bgs, during December 2006 in Neighborhoods C and D and September 2007 in Neighborhood B. Results of the soil vapor sampling event are shown in Table 4.