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THERESA LANCTOT EARTHGRAINS BAKING COMPANIES 8400 MARYLAND AVE ST LOUIS MO 63105-3668 RE: The Earthgrains Company Facility 2651 South Airport Way Stockton, California JAN 0 9 2004 SITE CODE 19093 RO: 0431 San Joaquin County Environmental Health Department (EHD) has reviewed Remedial Action Completion Report, dated 14 April 2003, prepared by Philip Services Corp. (PSC) on your behalf for the above -referenced site. In this report, PSC describes the history of the subsurface investigation of the unauthorized underground storage tank (UST) system release, property use, a water well survey, the physical and chemical characteristics of the subsurface, and a site conceptual exposure model with a risk-based corrective action model (RBCA). Briefly summarized, the findings and interpretations of PSC include: • The unauthorized release of fuel hydrocarbons was apparently from one of the 6,000 - gallon USTs removed in 1987; • The former UST facility is not within 1,000 feet of residential land use or within 900 feet of a surface water body; • Recent depths to water have been approximately 40 feet below surface grade (bsg); the inferred groundwater flow direction is toward the north-northeast at a gradient of approximately 0.0022; the measured hydraulic conductivity ranges from 1.04 x 10-5 centimeters per second (cm/s) to 4.15 x 10'6 cm/s; • There are no water supply wells located on the facility and none is planned; the only well identified during a receptor survey was an irrigation well located approximately 400 feet south of the facility; • Over 1,000 pounds of contaminants were removed by air sparging and soil venting between 25 April 2001 and December 2002; • Diisopropyl ether (D1PE) is the only oxygenate detected in groundwater on the site; • Overexcavation in 1987 removed most of the impacted soil in the former UST vicinity and it is PSC's opinion that the residual petroleum impact in soil is relatively limited; • Data indicate that lateral extent of impacted groundwater is limited to the subject site property and the vertical extent is less than 60 feet bsg; • Site remediation and natural attenuation have reduced the initial dissolved total petroleum hydrocarbons as gasoline (TPH-g) mass from 70 kilograms (kg) to 33 kg; • Natural attenuation of hydrocarbons on the site has been documented through identification of microbes and measurements of physical parameters; ENVIRONMENTAL HEALTH DEPARTMENT OPS. �.!N C .� - SAN JOAQUIN COUNTY �: �� c: ?� Donna K. Heron, R.E.H.S. Unit Supervisors " i Director 304 East Weber Avenue, Third Floor Carl Borgman, R.E.H.S. ' •�--�— AI Olsen, R.E.H.S. Stockton, California 95202-2708 Mike Huggins, R.E.H.S., R.D.I. 9u F6R°'� Pro iam,itanager g Telephone: 209 468-3420 Laurie A. Corolla, R.E.H.S. p ( ) Douglas W. Wilson, R.E.H.S. Margaret Lagorio, R.E.H.S. Program Manager Fax: (209) 464-0138 Robert McClellon, R.E.H.S. Mark Barcellos, R.E.H.S. THERESA LANCTOT EARTHGRAINS BAKING COMPANIES 8400 MARYLAND AVE ST LOUIS MO 63105-3668 RE: The Earthgrains Company Facility 2651 South Airport Way Stockton, California JAN 0 9 2004 SITE CODE 19093 RO: 0431 San Joaquin County Environmental Health Department (EHD) has reviewed Remedial Action Completion Report, dated 14 April 2003, prepared by Philip Services Corp. (PSC) on your behalf for the above -referenced site. In this report, PSC describes the history of the subsurface investigation of the unauthorized underground storage tank (UST) system release, property use, a water well survey, the physical and chemical characteristics of the subsurface, and a site conceptual exposure model with a risk-based corrective action model (RBCA). Briefly summarized, the findings and interpretations of PSC include: • The unauthorized release of fuel hydrocarbons was apparently from one of the 6,000 - gallon USTs removed in 1987; • The former UST facility is not within 1,000 feet of residential land use or within 900 feet of a surface water body; • Recent depths to water have been approximately 40 feet below surface grade (bsg); the inferred groundwater flow direction is toward the north-northeast at a gradient of approximately 0.0022; the measured hydraulic conductivity ranges from 1.04 x 10-5 centimeters per second (cm/s) to 4.15 x 10'6 cm/s; • There are no water supply wells located on the facility and none is planned; the only well identified during a receptor survey was an irrigation well located approximately 400 feet south of the facility; • Over 1,000 pounds of contaminants were removed by air sparging and soil venting between 25 April 2001 and December 2002; • Diisopropyl ether (D1PE) is the only oxygenate detected in groundwater on the site; • Overexcavation in 1987 removed most of the impacted soil in the former UST vicinity and it is PSC's opinion that the residual petroleum impact in soil is relatively limited; • Data indicate that lateral extent of impacted groundwater is limited to the subject site property and the vertical extent is less than 60 feet bsg; • Site remediation and natural attenuation have reduced the initial dissolved total petroleum hydrocarbons as gasoline (TPH-g) mass from 70 kilograms (kg) to 33 kg; • Natural attenuation of hydrocarbons on the site has been documented through identification of microbes and measurements of physical parameters;