SITE INFORMATION AND CORRESPONDENCE

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Ms. Lauri Cotulla September 25, 1990 Public Health Services Page 2 San Joaquin County concentration of up to 61. 3 mg/Kg. An organolead analysis was conducted on one of the tank excavation_ samples with non- detectable results. At the request of San Joaquin County, one additional soil sample was collected on January 24, 1990 from a depth of 15 ' below grade and analyzed for soluble lead. Theme County�d d—not=specify-any�pa tticula mr ethod_of-ana]Lysi-mss. The soil sample, identified as "T-2 15-16.5 A,BI (the sample was taken from the T-1 area even though it was labeled 'IT- 2. . . ". } , was analyzed for soluble lead by leachate extraction f by the acidic EP Toxicity Test and analyzed by EPA Method _ 6010. The entire analytical report for this test is attached. The results for lead were non-detectable at a detection level of 500 ug/L. As you know, there are numerous methods available to analyze just r. about any parameter. -1WESTON_,.-in�the=.absence—of;any=method specificat_on,-choose=to-use the-acidid:EP::T.axic'ity�proc_edure for -eextractiori. This procedure is significantly more rigorous than common distilled water leaching as it tends to mobilize metals t :better due to , the low pH. Hence, if soluble lead was present in the Laura Scudders samples, the EP Toxicity procedure was more likely to quantify it. Because of the nature of the EP Toxicity procedure, the leachate must be analyzed by EPA Method 6010 which .is an ICAP method. EPA .Method 7421, which is compatible only with the less effective distilled water leaching procedure, will not work with the EP Toxicity test due to interferences. While we certainly agree that consistency of methods for use in .programs such as your UST program is a desirable goal, we feel that it is scientifically reasonable to use a method which meets or exceeds the criteria of a preferred method. Per the above discussion, we believe that the EP Toxicity/Method 6`010 procedure meets these qualifications beyond any reasonable .-doubt. As the T-1 tank' soil sample was collected by appropriate methods and analyzed by methods exceeding the EPA. Method 7421 performance, we believe that the lack of a soluble lead concern in the T-1 tank area has been well documented. Hence, we feel that there is no ..need,. to resample the T-1 tank area again. :We request, in the interest of completing this project, that the County reconsider its position on the T-1 tank area in light of the information presented herein and issue a closure recommendation.