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(8/14/2008) Brian Taylor- NuStar Stockton Terminal Page 1 <br /> i <br /> From: "Amanda Spencer"<aspencer@ashcreekassociates.com> <br /> To: 'Brian Taylor'<betaylor@waterboards.ca.gov> <br /> CC: "Goodenow,Vicki"<Vicki.Goodenow@nustarenergy.com>,"Aldridge,Joe"<Jo... <br /> Date: 8/8/2008 1:22 PM <br /> Subject: NuStar Stockton Terminal <br /> Hi Brian-As requested in our telephone conversation on Wednesday, <br /> August 6, 2008,the following documents our discussion of two Water <br /> Board comments/questions remaining on the Vertical Characterization Work <br /> Plan. <br /> 1) Provide more specifics on how we are going to use the field <br /> screening and analytical data to determine whether impacts seen in the <br /> B-zone are from an additional off-site source and not the facility. As <br /> discussed,the decision would be based on a preponderance of the <br /> evidence and cannot be strictly determined prior to conducting the field <br /> work and reviewing the data. However,some of the guidelines we will be <br /> using include: <br /> ' presence of separate phase hydrocarbons(SPH)based on visual <br /> observations and/or field sheen tests in A-zone soil in the borings <br /> located east(or on)Stork Road or upgradient of the facility; <br /> ' elevated soil concentrations(indicative of the presence of SPH) <br /> in A-zone soil in the borings located east(or on)Stork Road or <br /> upgradient of the facility, <br /> ' pattern and distribution of soil and groundwater concentrations <br /> in the A-and B-zones support the presence of an off-site source;and/or <br /> composition of the fuel compounds in soil or groundwater in <br /> off-site borings. <br /> As discussed in our telephone conversation on August 6,2008,the above <br /> criteria would be used together to determine,with reasonable <br /> confidence, that an off-site source is present. The first item <br /> (presence of SPH in soil column in a location that could not reasonably <br /> be from a release at the facility)is the only criteria that could be <br /> used as stand-alone evidence of an off-site source. The other criteria <br /> listed would be evaluated in conjunction with each other. If,based on <br /> the preponderance of the evidence,we feel that it is likely that <br /> currently observed off-site B-zone impacts are not due to the releases <br /> at the facility,we would present and discuss this data with you before <br /> terminating the investigation and preparing the results report. <br /> 2)Chemical Analysis TAT for soil samples from the A-zone? As <br /> discussed,this will be a field decision: if the sample results will be <br /> critical to informing the next steps of the B-zone investigation or <br /> whether the investigation should proceed to the C-zone,they would be <br /> analyzed on a 24-hour TAT. If the data will only assist in completing <br /> the characterization but is not needed for decision-making purposes <br /> during the investigation,the analyses will be performed on a normal <br /> TAT. <br /> Please do not hesitate to contact me if you have further questions or <br /> comments. <br /> thanks, <br /> amanda <br />