Laserfiche WebLink
Californiafegional Water Quality Coal Board - <br /> Central Valley Region W�cFVE <br /> Robert Schneider,Chair <br /> Dan Skopec Arnold <br /> Acting Secretary Sacramento Main Office PR 1 9 "[QO15chwarzenegger <br /> 11020 Sun Center Drive 1!200,Rancho Cordova,California 956766114 A Governor <br /> Phone(916)464-3291•FAX(916)464.4645 <br /> http://www.waterbouds.ca.gov/mntralvalley ENVIRONMENT HEALTH <br /> PERMITISEWCES <br /> 14 April 2006 <br /> Mr.Bob Hopkins Mr. Jay Allen <br /> Union Oil Company of California Stone Brothers Management Company <br /> 276 Tank Farm Road,P.O.Box 1069 1024 W. Robinhood Dr. <br /> San Luis Obispo, CA 93406 Stockton, CA 95207 <br /> REQUEST FOR RED UCTION IN SAMPLING AND TEMPORAR Y SUSPENSION OF REMDJA TION, <br /> CLEANUP AND ABATEMENT ORDER (CAO)NO. 5-00-0707, FORMER UNOCAL STATION#5098 AT <br /> 5606 PACIFIC AVENUE,AND FORMER MONTGOMERY WARDS AUTO SERVICE AT 5400 PACIFIC <br /> AVENUE, STOCKTON,SAN JOA Q UIN CO UNTY <br /> Background: On 29 July 2005 and 10 January 2006,ENSR International Inc. (ENSR,UNOCAL's consultant) <br /> submitted two requests for modifications to CAO No. 5-00-0707, in Request for Reduction in Sampling <br /> (Report 1) and the Updated Site Conceptual Model, Quarterly Monitoring And Remediation Status Report, <br /> 4'6 Quarter 2005(Report 2),respectively. <br /> Report 1 <br /> The rational for the requested changes to the Monitoring and Reporting Program (MRP) are stated in the <br /> Report 1 conclusions: <br /> • "The existing groundwater monitoring well network defines the limits of the SCM(Site Conceptual <br /> Model). The TPHg and benzene plumes appear to be reducing in size, stable, and well defined within the <br /> groundwater monitoring well network. Groundwater is not considered to bean exposure pathway <br /> because there no(sic)drinking water wells exist within the well network" <br /> • "The nearest surface water body is the Calaveras River and is located over 4,000 feet to the south- <br /> southeast. Based on the distance from the site, surface water is not considered to be a potential exposure <br /> pathway." <br /> • The majority of dissolved and residual concentrations of petroleum hydrocarbons is located <br /> approximately <br /> 50 to 70 feet below ground surface (bgs) and the site and surrounding areas are predominantly paved. <br /> Therefore, soil and biota are not considered to be exposure pathways. <br /> • In ENSR's opinion, inhalation of vapors through indoor air vapor intrusion is considered the only <br /> potential exposure pathway to receptors at this site. ... <br /> The Report 1 specifically asks for four modifications to the CAO No. 5-00-0707 monitoring and reporting <br /> program (MRP). <br /> A. Removal of 25 monitoring wells and one air sparge well(listed on Enclosed Page 2)from the MRP,because <br /> groundwater-to-indoor air screening levels(Enclosed Table A-1)have not been exceeded. <br /> California Environmental Protection Agency <br /> pia Recycled Paper <br />