SITE INFORMATION AND CORRESPONDENCE

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Mr.M. Scott Mansholt—CEMC Second Quarter 2007 Groundwater Monitoring and Sampling Report July 24,2007 Vernalis Pump Station Page 3 of 5 SAMPLING Following depth-to-groundwater measurements,wells MW-6 and MW-7 were purged using the regulatory-accepted, low-flow minimal drawdown method. Well MW-5 was purged using the three well casing-volume purge method due to a slow recharge rate. A low-flow submersible pump with dedicated polyethylene tubing was used. During the purge process,pH, specific conductance,temperature, oxygen-reduction potential,turbidity, and dissolved oxygen water- quality parameters were recorded. After water-quality parameters stabilized groundwater samples were collected at wells MW-6 and MW-7. Stabilization criteria are presented on field data sheets(Attachment A). Groundwater samples were collected at well MW-5 following the three well casing-volume purge and after the groundwater recharged to 80 percent of the static depth to water level. Well MW-1 was not sampled due to the consistent historical presence of SPO and wells MW-2,MW-3, and MW-4 were not sampled due to insufficient groundwater recovery for sample collection. Laboratory-provided bottles were used to preserve the samples. The bottles were labeled, sealed, and placed immediately into an ice-cooled container for delivery to Lancaster Laboratories, Inc. (Lancaster),under SAIC chain-of-custody protocol. Lancaster is a California-certified laboratory (ELAP#2116). A sample was not collected from well MW-1 due to the presence of SPO in the well. GROUNDWATER ANALYTICAL RESULTS The groundwater samples from MW-5, MW-6,MW-7, and MW-7 field duplicate were analyzed for the following constituents: • Total petroleum hydrocarbons quantified as diesel(TPHd) (C10—C25),using U.S. Environmental Protection Agency(EPA)Method 8015B and TPHd with silica-gel preparation for samples with detectable concentrations of TPHd using EPA Method 8015B; and • Polynuclear aromatic hydrocarbons(PAHs)using EPA Method 8270C selective ion monitoring. The groundwater analytical results are summarized and compared with the RWQCB Region 2 Environmental Screening Levels (ESLs) and the numerical State Water Quality Objectives (WQOs)in Table 2 (TPHd)and Table 3 (PAHs).2 Results exceeding the most conservative ESL or WQO are highlighted in bold-type font. TPHd was non-detect below the laboratory method detection limit of<50 micrograms per liter(µg/L) in all the samples and there were no PAHs detected at concentrations exceeding the most conservative WQOs/ESLs. The data usability summary and a copy of the laboratory analytical report are presented as Attachment B. Please see Attachment B for details regarding data qualifiers. QUARTERLY OIL-ABSORBENT (OLEOPHILIC) SOCK REPLACEMENT In October 2005, an oleophilic sock was installed in well MW-1 due to the observation of SPO observed in the well consistently since 1998. The sock has been monitored and replaced as necessary on a quarterly basis. During the second quarter of 2007,the oleophilic sock from well 2. The ESLs(provided as a reference)are a tool based on conservative standard exposure factors for initial human health and the environment screening-level evaluations of analytical results. The WQOs are defined by the Porter- Cologne Act as"the levels or limits of water quality constituents or characteristics which are established for the reasonable protection of beneficial uses of water or the prevention of nuisance within a specific area."