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Mr.M. Scott Mansholt—CEMC 2008 Annual Groundwater Monitoring and Sampling Report April 16,2008 US Can-Welty Road Page 3 of 6 A 1.5-inch,4 foot-long heavy bottom polyvinyl chloride bailer was used. The pH, specific conductance,temperature,turbidity, and dissolved oxygen water-quality parameters were recorded during the purge process. Groundwater samples were collected at well MW-3 and MW-4 following the three well casing-volume purge and after the groundwater recharged to 80 percent of the static depth-to-groundwater level. Samples were not collected from MW-1 and MW-2 due to the presence of SPO. Samples were not collected from WFSMW-1 due to a request by RWQCB to discontinue sampling in a letter to CEMC dated August 21,2007. MW-5 could not be sampled due to limitations of the site access agreement with the property owner. Field data sheets are included as Attachment A. Laboratory-provided bottles were used to preserve the samples. The bottles were labeled, sealed, and placed immediately into an ice-cooled chest for delivery to Lancaster Laboratories,Inc. (Lancaster)under SAIC chain-of-custody protocol. Lancaster is a California-certified laboratory (ELAP#2116). GROUNDWATER ANALYTICAL RESULTS The groundwater samples from MW-3 and MW-4 were analyzed for the following constituents: • Total petroleum hydrocarbons quantified as diesel(TPHd) (Clo—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 801513; and • Polynuclear aromatic hydrocarbons(PAHs)using EPA Method 8270C with large-volume injection(MW-3 was analyzed using EPA Method 8270C with selective ion monitoring). Tables 2 and 3 summarize the groundwater analytical results and compare them with the RWQCB Region 2 Environmental Screening Levels(ESLs)and the numerical State Water Quality Objectives (WQOs).1 Results exceeding the most conservative ESL or WQO are highlighted in bold-type font in the tables. MW-3 had a TPHd detection of 1,600 micrograms per liter(gg/L; 1,300 gg/L after silica-gel cleanup). MW-3 also had the following PAHs exceeding their respective screening levels: benzo(a)anthracene at 0.059 gg/L,benzo(a)pyrene at 0.029 gg/L,benzo(b)fluoranthene at 0.032 gg/L,and chrysene at 0.37 gg/L. Well MW-4 indicated no detectable concentrations of TPHd or PAHs. A petroleum-hydrocarbon distribution map is presented on Figure 5. The laboratory analytical report and data usability summary, as well as details regarding data qualifiers, are presented as Attachment B. QUARTERLY OIL-ABSORBENT (OLEOPHILIC) SOCK REPLACEMENT An oleophilic sock was installed in 2005 in well MW-1 due to the presence of SPO, and in MW-2 due to petroleum odor. The socks in MW-1 and MW-2 have been monitored and replaced as necessary on a quarterly basis. Oleophilic sock monitoring and replacement was reduced from quarterly events to an annual event at the request of the RWQCB in August 2007. The oleophilic socks from MW-1 and MW-2 were replaced during the January 2008 event. Approximately 0.01 1. 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."