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EC ® 1R
<br /> 7-Eleven Store#19976 {
<br /> Quarterly Groundwater Monitoring and Remediation Progress Report (302003)
<br /> . November 26, 2003
<br /> Page 4
<br /> On May 27, 2003, one soil sample was collected under the northern fuel dispenser (131-4 5), and the
<br /> second sample was collected beneath the product line (1-1-4 0) during a fuel system upgrade The
<br /> sod samples collected beneath the dispenser and fuel delivery piping did not contain concentrations
<br /> of TPHg, BTEX, or fuel oxygenates above laboratory detection limits On June 9, 2003, three
<br /> 10,000-gallon double-walled fiberglass USTs were removed from the excavation and hauled offsite
<br /> On June 9 and 19, 2003, a total of six UST confirmation soil samples (T1N-15' through T3S-13')
<br /> were collected in native soil underlying the ends of the three USTs (Figure 2) at approximate depths
<br /> of 12 to 15 feet bgs TPHg, BTEX, and fuel oxygenates were not detected at concentrations above
<br /> laboratory detection limits in two of the six sod samples collected beneath the USTs Benzene and
<br /> TPHg were reported in the sod samples collected beneath the north ends of two USTs (T1 N, T2N) at
<br /> maximum concentrations of 0 0087 mg/kg and 9 3 mglkg, respectively MtBE and TBA were
<br /> reported at maximum concentrations of 33 mg/kg (T1 N@13') and 18 mg/kg (T3N@13'),
<br /> respectively
<br /> Between June 23 and July 7, 2003, Glacier Environmental installed two new double-walled fiberglass
<br /> USTs one 10,000-gallon premium unleaded gasoline UST, and one 15,000-gallon regular unleaded
<br /> gasoline UST, and associated piping and dispensers (Figure 2) In order to accommodate the new
<br /> 15,000-gallon UST, Glacier excavated approximately 288 cubic yards of soil, expanding the UST pit
<br /> to the west
<br /> MONITORING AND SAMPLING PROCEDURES
<br /> . The depth to water was measured in monitoring wells MW-1 through MW-7, MW-1A, MW-4A, and
<br /> MW-5A from top of casing (TOC) using a water level indicator to within 0 01 feet bgs Dissolved
<br /> oxygen readings were also collected from each well using a YSI Model 550A dissolved oxygen meter
<br /> equipped with a down hole sensor
<br /> Well purging and sampling equipment is thoroughly cleaned prior to purging and sampling each well
<br /> The sampling procedure for each well includes measuring the water level and checking for the
<br /> presence of liquid-phase hydrocarbons (LPH), using either an electronic indicator and a clear
<br /> Teflon° bailer or an oil-water interface probe Wells not containing LPH are purged of approximately
<br /> three casing volumes of water (or to dryness) using a submersible pump or bailer The equipment
<br /> and purging methods used for the current sampling event are noted on the field data sheets included
<br /> in Attachment A During purging, temperature, pH, and electrical conductivity are monitored in order
<br /> to document that these parameters are stable prior to collecting samples After purging, water levels
<br /> are allowed to recover to 80% of the original levels prior to collection of the water sample
<br /> Groundwater samples are collected using a disposable Teflon® bailer, placed into appropriate EPA-
<br /> approved containers, labeled, logged onto chain-of-custody documents, and transported on ice to a
<br /> California state-certified laboratory Copies of the field notes have been included in Attachment A
<br /> 4F f
<br /> GROUNDWATER SAMPLE ANALYSES AND RESULTS
<br /> The groundwater samples collected from MW-1 through MW-7, MW-1A, MW-4A, and MW-5A were '
<br /> analyzed for the presence of TPHg, BTEX, and fuel oxygenates MtBE, tert-butyl alcohol (TBA),
<br /> dusopropyl ether (DIPE), ethyl-tert-butyl ether (EtBE), and tert-amyl-methyl ether (TAME) using EPA
<br /> it,
<br /> Method 8260B The certified laboratory analytical report and chain-of-custody documentation are
<br /> presented as Attachment B
<br /> Groundwater analytical results are presented on Figure 3, and are summarized in Tables 1 and 2
<br /> . Chemical concentrations were generally consistent with historical data Benzene, TPHg, MtBE, and
<br /> TBA concentrations continue to decline in MW-2
<br /> 19976 03-30 Report doc SECOR International Incorporated
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