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HomeMy WebLinkAbout3501 MT. VERNON AVENUE (4)Linda S. Adams Acting Secretary for Environmental Protection California Regional Water Quality Control Board Central Valley Region Katherine Hart, Chair 1685 E Street, Fresno, California 93706 559) 445 -5116 • FAX (559) 445 -5910 http: / /www.waterboards .ca.gov /centralvalley Mr. Nassri Jaber 3501 Mt. Vernon Avenue Bakersfield, CA 93306 Edmund G. Brown Jr. Governor 12 July 2011 CASE CLOSURE - UNDERGROUND STORAGE TANK RELEASE, MINIT STOP MARKET, 2900 UNION AVENUE, BAKERSFIELD, KERN COUNTY, RB CASE NO. 5T15000857 Dear Mr. Jaber This letter confirms the completion of a site investigation and corrective action for the underground storage tank formerly located at the above - described location. Thank you for your cooperation throughout this investigation. Your willingness and promptness in responding to our inquiries concerning the former underground storage tanks are greatly appreciated. Based on the information in the above - referenced file and with the provision that the information provided to this agency was accurate and representative of site conditions, this agency finds that the site investigation and corrective action carried out at your underground storage tank site is in compliance with the requirements of subdivisions (a) and (b) of Section 25296.10 of the Health and Safety Code and with corrective action regulations adopted pursuant to Section 25299.3 of the Health and Safety Code and that,no further action related to the petroleum release at the site is required. A summary of the information in the above - referenced file is included in the Case Closure Summary, a copy of which is enclosed. This notice is issued pursuant to subdivision (h) of Section 25296.10 of the Health and Safety Code. If you have any questions regarding this matter, 559) 445 -5504. C Pam la C. Creedon Executive Officer please contact Mr. John D. Whiting at Enclosure: Case Closure Summary cc w /enclosure' Ms. Barbara Rempel, SWRCB, UST Cleanup Fund, Sacramento Mr. Craig Perkins, City of Bakersfield Fire Department, Bakersfield Mr. Timothy Treloar, California Water Service, Bakersfield City of Bakersfield Public Works Department, Bakersfield Mr. Thomas Yoon, Bakersfield Mr. William Lawson, E2C Remediation, LLC, Bakersfield California Environmental Protection Agency C4Recycled Paper California Regional Water Quality Control Board Central Valley Region Katherine Hart, Chair 1685 E Street, Fresno, California 93706LindaS. Adams (559) 445 -5116 • FAX (559) 445 -5910 Acting Secretary for http: / /www. waterboards .ca.gov /centralvalleyEnvironmentalProtection TO: Lonnie M. Wass FROM: John D. Whiting Supervising WRC Engineer Engineering Geologist PG No. 5951 Clay L. Rodgers Assistant Executive Officer 0.0r; 1 Edmund G. Brown Jr. Governor DATE 12 July 2011 SIGNATURE: ' CASE CLOSURE SUMMARY, UNDERGROUND STORAGE TANK RELEASE, MINIT STOP MARKET, 2900 UNION AVENUE, BAKERSFIELD, KERN COUNTY, RB CASE NO. 5T15000857 Background Information Site Investigation A convenience store with retail motor fuel sales is currently and. has formerly been operated on the subject site, which is on the northeast corner of Union Avenue and Pacific Street, in a commercial and residential area. During May 2000, three 10,000 - gallon gasoline underground storage tanks (USTs) and associated dispensers and piping were removed. Two additional 5,000 - gallon gasoline USTs discovered during the removals were abandoned in- place. Moderate to high gasoline constituent concentrations were detected in soil samples collected beneath one 10,000 - gallon UST and one 5,000 - gallon UST. Low to trace concentrations were also detected in samples beneath the other USTs. The fueling facilities were later upgraded. The Bakersfield Fire Department (Fire Department) requested assessment of the release, which was conducted during 2001 and 2002. The investigation revealed that gasoline had migrated to the water table. One groundwater monitoring well screened to intersect the water table was also installed. Groundwater was encountered at 118 feet below ground surface bgs) during well installation. The local regulatory agency referred the case to the Central Valley Water Board by letter of 22 April 2002. Additional assessment was conducted during 2003 and 2004 to complete characterization and definition of impacted soil. The release was characterized by high to low gasoline constituent concentrations dispersed through a large soil volume, with some lateral spreading. The consultant estimated that approximately 22,000 cubic yards to 125 feet bgs beneath a surface area of approximately 100 feet by 80 feet was impacted. Total petroleum hydrocarbons as gasoline (TPH -g) up to 6,300 milligrams per kilogram (mg /kg), benzene up to 58.8, and methyl tertiary butyl ether California Environmental Protection Agency 0Recycled Paper Minit Stop Market Case Closure Summary -2- 12 July 2011 MTBE) up to 2,800 mg /kg were detected. TPH -g above 1,000 mg /kg was extended to approximately 115 feet bgs. Soil and Groundwater Remediation From April 2004 through October 2009, a soil vapor extraction (SVE) and air sparging (AS) system removed an estimated 178,847 pounds (lbs.) or 27,945 gallons of gasoline constituents. The unit was operated intermittently (cycled) and was operated in catalytic mode during the last three years of operation to reduce operating costs. Removal rate had decreased to below six lbs. per day during the last three months of operation. Frequent sampling during the last month of operation confirmed TPH -g, toluene, ethylbenzene, xylenes, and MTBE influent concentrations less than 1 part per million by volume (ppmv). The consultant concluded that little or no gasoline mass remained in subsurface soil. Groundwater Monitoring Four additional monitoring wells were installed during 2003 to evaluate the lateral extent of impacted groundwater. Thirty monitoring events were conducted from February 2002 until April 2009. Depth -to -water on -site ranged from approximately 114 to 118 feet bgs during most of the monitoring history, and increased to approximately 124 feet bgs during the last two events. Flow was generally toward the southeast with moderate gradients. TPH -g was detected in groundwater beneath the source area well MW -1 from approximately 5,000 to 67,000 micrograms per liter (pg /L) until June 2004, when concentrations declined to below 5,000 pg /L. TPH -g increased to 13,000 pg /L during October 2006, but again decreased, and was not detected in MW -1 during the last four monitoring events. High TPH -g concentrations (up to 68,000 pg /L) also persisted near the south site boundary in MW -3 until October 2007, but decreased, and were not detected during the last two events. Benzene was detected on -site at up to 3,550 pg /L during the early monitoring history, but decreased, and was not detected in the entire monitoring network during the last eight events. MTBE up to.74,600 pg /L was detected in MW -1; concentrations remained greater than 10,000 pg /L until June 2004. MTBE was not detected in MW -1 after December 2004, and was generally not detected in MW -3 after May 2005. MW -5 was installed approximately 180 feet south - southeast of MW -3. Closer installation was prevented by a building footprint. The lack of gasoline constituent detections during the monitoring history suggests that off -site migration was limited. TPH -g and benzene were not detected in MW -5 and MTBE,was detected during two events prior to 2006. Sensitive Receptors The consultant identified six municipal wells within 2,500 of the Minit Stop Market site, but none were within 1,800 feet. Two unlined irrigation canals are west of Union Avenue, approximately 150 to 600 feet west of the site. Minit Stop Market Case Closure Summary -3- 12 July 2011 Health Risk Assessment During 2009, the consultant determined that remaining gasoline mass in soil and groundwater was unlikely to threaten human health and recommended that the site be considered for closure. Public Participation and Well Destruction On 14 January 2010, 1 mailed a pre - closure Public Notice to vicinity landowners and tenants. Public comments were not received during the 30 -day comment period. Groundwater monitoring and SVE wells had not been destroyed when this document was prepared, due in part to access restrictions associated with a bankruptcy at an off -site property. Conclusions Gasoline constituents remaining in subsurface soil and groundwater are unlikely to impact the present or future use of groundwater and /or human health.. Most extractable hydrocarbons appear to have been removed by the SVE system. I estimate that as much as 1,000 lbs. of gasoline may remain in soil as low adsorbed concentrations that are expected to naturally degrade. Remaining effects of the release are unlikely to threaten groundwater or surface water quality. I recommend that a standard underground tank site closure letter be mailed to the responsible party. Groundwater monitoring and SVE wells should be destroyed in accordance with California Well Standards and local ordinances.