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Mr. Harlin Knoll Checklist for No Further Action Request and Monitoring Well Destruction Work Plan LSeptember 29,2010 Page 3 LTable 1 (continued) Checklist of Required Data for No Further Action Request Western Oil and Spreadin Inc.,Acampo Plant Site,Acampo,California L Site Name and Location: Western Oil and Spreading,Inc.,Acampo Plant Site 19356 N.Highway 99,Acampo,San Joaquin County,California L 9. Zone o influence calculated and assumptions f fl The zone of influence was not calculated due to the limited extent ® used for subsurface remediation system and the of TPHD contamination at the site. No active remediation system zone of capture attained for the soil and is in use at the site due to decreasing concentration trends groundwater remediation system; LThe Unauthorized Release form is included in Attachment D; 10. Reports/information copies of report covers(Quarterly Monitoring Reports,Work ® Unauthorized Release Form Plans,etc.)are included in Attachment E;boring logs are included ® in Attachment F. As discussed earlier,historical analytical data, L ® QMRs ❑ PAR ❑ FRP cross sections,tables,and figures are contained in Attachment B ® Well Boring Logs ® Other and have been previously presented in the March 2010 first half 2010 groundwater monitoring report and request for closure. The USTs and ASTs have been removed and the soil containing L petroleum hydrocarbons is isolated under a cap. All petroleum hydrocarbon concentrations have been below the laboratory L 11. Best Available Technology(BAT)used or an detection limits for groundwater samples collected in all site wells explanation for not using BAT; during the last four quarters of groundwater monitoring when samples were subjected to the silica gel cleanup procedure. Natural attenuation will continue to degrade the remaining residual contaminants at the site(not economically beneficial to L conduct active remediation). The remaining petroleum hydrocarbons in soil at the site will not pose a long-term threat to groundwater quality as evidenced by the decreasing concentrations of petroleum hydrocarbons detected ® 12. Reasons why background waslis unattainable in site monitoring wells,the vertical separation of identified soil using BAT; impacts and the highest groundwater elevations recorded in site wells,and the low mobility and toxicity of longer chain petroleum hydrocarbons that comprise the soil contamination identified at this site. ® 13. Mass balance calculation of substance treated Insignificant mass to calculate and perform a mass balance L versus that remaining; calculation. Trend analyses of historic groundwater analytical results from wells MW-1,MW-2,MW-3,MW-5,and MW-6 indicate that concentrations of TPHD in these wells should reach the Water L 14. Assumptions,parameters,calculations and model used in risk assessments,and fate and Quality Objective(WQO)of 100 ug/V(RWQCB,2004)within a ® reasonable time. The trends predict a conservative estimate of time transport modeling; to WQO achievement because only results not subjected to the L silica gel cleanup procedure were used when applicable. This information was presented in the March 26,2010 report. Based on our evaluation of site data and as described in State 15. Rationale why conditions remaining at site will Water Resources Control Board Resolution No.2009-0042,we t ® not adversely impact water quality,health,or conclude that no significant benefit to human health or the Lother beneficial uses;and environment would be achieved through additional investigation, monitoring,or remediation at this site. L ® 16. WETS or TCLP9 results WET and TCLP was not performed due to the low concentrations of contaminants in the soil and groundwater. 1. AST: Aboveground Storage Tank 5. TPHMO: Total Petroleum 7. ug/L: micrograms per Liter 2 UST: Underground Storage Tank Hydrocarbons as Motor Oil 8. WET: Waste Extraction Test L 3. BGS: Below Ground Surface 6. TPHD: Total Petroleum 9. TCLP: Total Characteristic Leaching 4. NFA: No Further Action Hydrocarbons as Diesel Procedure \\Eureka\Projects\2007\007152-WOS\PUBS\rpt\20100929-NFA.doc