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' Quarterly Groundwater Monitoring Report Exxon Station 7 3330 ' STANDARD OPERATING PROCEDURES Monitonna Well Sampling ' Prior to groundwater sampling, initial water level and floating liquid hydiocaibon measurements ate recorded for each well Each well is sounded for depth to ascertain if silting has occurred and to verify the well's actual depth below ground surface These measurements are used to calculate each well's volume At this time, all non-dedicated pumping and sampling supplies are washed with an Alconox solution, rinsed with clear water, and final iinsed with either distilled or detonized water to prevent any cioss contamination from other sampling events Then each well is purged by evacuating a minimum of three well-casing volumes of groundwater from each well The well water may be evacuated either by bailing, or pumping Any of the following may be used for bailing a dedicated pvc bailer, sterile disposable Teflon bailer, or a stainless steel bailer For pumping the groundwater out of the well, a downhole impeller type pump (dedicated or removable), a downhole dedicated bladder pump, of a surface peristaltic pump is used After three to four well volumes are pumped, each well is permitted to iecharge to ?80% of original capacity or two hours, whichever occurs first The water is then measured to verify whether the well has stabilized Stabilization is deterrmned by measuring the parameters of pH, ' tempetature, and electrical conductivity Stabilized measuzements indicate that formation watei has entered the well When two subsequent measurements of these three parameters are within 10% of each other, the well is considered stabilized and is ready to be sampled The samples are collected using a new polyethylene bailer with a bottom siphon and nylon cord The bailers are disposable, and therefore, never reused The groundwater sample is visually inspected foi the presence of free product in the sampling bailer Agitation is rmnitnized during sample retrieval to prevent aeration during the transfer from the well to the laboratory prepared sample containers Duplicate water samples are collected from the well and siphoned into three, 40 ml, VOA, septum top vials, with additional 950 ml samples collected in an amber glass bottles of polyethylene bottles depending on the analyses to be pet formed The VOA vials aie filled completely, leaving no headspace, and are Sealed with Teflon-lined lids All samples ate labeled, placed on crushed ice in an ice chest, and sent to a Caizfoinia State Certified hazardous mate[ials ' testing laboiatory under chain-of-custody documentation (attached) All groundwater samples ate collected in accoi dance with Califoi nia Regional Watei Quality ' Control Board (RWQCB) piocedures described in the Leaking Undeigiound Fuel Tarek (LUFT) Field Mamial, the Ti i-Regional Bom d Staff Reconilneiidatinit 5 fof Pt elinunai y Ei,aluation ulid l,ii,ertiglattojj of Undeigiound Tank Sites, and local te4Uulatozy guidelines ' Standaid Envuonmental Protection Agency (EPA), San Fiancisco Bay Regional Watei Quality Control Board (SFBRWQCB), and Department of Health Set-vices (DHS) methodologies for sampling and analyses ate routinely utilized Chain of Custody documentation accompanies all samples to the laboratory A copy of the Chain of Custody documentation is attached to the Certificate of Analysis Monitor well purge water is piopet ly stored and labeled on site in DOT 17-H containers pending off site disposal 3175 Kerner Boulevard Suite lw • San Rafael CA 94901 • (415) 257 4801 • FAX (415) 257-4805 1�