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S E C 0 R 7-Eleven Store #19976 Quarterly Groundwater Monitoring and Remediation Progress Report (1 Q2006) May 16, 2006 . Page 5 On April 9, 2004, SECOR submitted a request with the SJCEHD to reduce sampling of MW-4 and MW-4A from quarterly to annually Approval was received in a letter from the SJCEHD dated July 28, 2004 On June 2, 2004 a 22-hour SVE event was conducted on the horizontal tank pit wells Based on sod vapor samples collected during the test it is estimated that approximately 0 10 pound of TPHg was removed in soil vapor during the 22-hour test No recordable amount of benzene or MtBE was removed during the test On November 23, 2004, an additional SVE test was conducted on monitoring well MW-2 Based on the soil vapor samples collected during the five hour test, approximately 1 79 lbs of TPHg was removed No recordable amounts of benzene or MtBE were removed during the test On March 15, 2005, SECOR submitted a Work Plan for OZ Sparge Well Installation to the SJCEHD This work plan details the proposed installation of three oxygen infection wells to improve the remediation at the site In a letter dated May 3, 2005, the SJCEHD stated that the work plan would have to be approved by the CRWQCB before the SJCEHD could comment on it The letter also directed 7-Eleven, Inc to sample MW-4 semi-annually and MW-4A quarterly In response, SECOR submitted a work plan for evaluation of oxidation capacity of groundwater to the CRWQCB on July 8, 2005 The CRWQCB approved the work plan in an email dated August 9, 2005 On June 27, 2005, SECOR submitted a work plan for additional site assessment to the SJCEHD The work plan proposed the addition of MW-8 to the west of MW-2 The work plan was approved in a letter dated July 11, 2005 MONITORING AND SAMPLING PROCEDURES The depth to water was measured to within 0 01 foot in monitoring wells MW-1 through MW-7, MW-1A, MW-4A, and MW-5A from the top of casing (TOC) using a water level indicator Dissolved oxygen concentrations were measured in wells MWA through MW-7, MW-1A, MW-4A, and MW-5A using a YSI Model 550A dissolved oxygen meter equipped with a down hole sensor Well purging and sampling equipment was thoroughly cleaned prior to purging and sampling each well The sampling procedure for each well included measuring the water level and checking for the presence of liquid-phase hydrocarbons (LPH), using an electronic indicator and a clear Teflon® bailer Wells not containing LPH were purged of approximately three casing volumes of water (or to dryness) using a submersible pump or bailer The equipment and purging methods used for the current sampling event were noted on the field data sheets shown in Attachment A During purging, temperature, pH, and electrical conductivity were monitored After purging, water levels were allowed to recover to 80% of the original levels prior to collection of the water sample Groundwater samples were collected using a disposable Teflon bailer, placed into appropriate EPA- 19976 06-1Q Report doc SECOR international incorporated