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SAN JOAQUIN COUNTY PUBLIC HEALTH SERVICES <br /> ENVIRONMENTAL HEALTH DIVISION <br /> UGST SITE MITIGATION UNIT- GENERAL RISK APPRAISAL <br /> Explanation of the General Risk Appraisal: <br /> i to Address !l U ��- <br /> The general risk appraisal was developed using <br /> ite Code L/ ,3 Facility Name I environmental fate and chemistry data for BTX&E <br /> to evaluate the risk of groundwater pollution <br /> from LUFT sites under severe conditions. This <br /> risk appraisal requires a limited amount of site- <br /> . Is the site in a mountainous area? (Shaded NO YES specific information; conservative assumptions <br /> moist areas and/or areas with rocky subsurface have been substituted for other site-specific <br /> conditions) �( information. For these reasons, the general risk <br /> appraisal is more sophisticated than the Leaching <br /> 2. Is the site in an area that could collect surface Potential Analysis. <br /> runoff or intercept water from a source other than <br /> the natural precipitation? �( <br /> . Does the areal extent of soil contamination exceed <br /> 1000 ft2? <br /> Do the concentrations of fuel constituents in any <br /> soil samples exceed the following amounts? <br /> [benzene: 100 ppm; toluene: 80 ppm; xylene: 40 ppm; <br /> ethylbenzene: 40 ppm] <br /> 5. Are there any records or evidence of man-made or <br /> natural objects which could provide a conduit for <br /> vertical migration of leachate? [septic systems; x <br /> leaching fields; wells; soil borings) <br /> 5. Do any boring or excavation logs show the presence v <br /> of fractures, joints or faults that could act as a n <br /> conduit for vertical migration of leachate? <br /> 7. Do any boring logs show that contaminated soil could <br /> be within 5 feet of highest ground water? <br /> S. Do any boring logs show the presence of a layer of <br /> material, 5 feet thick or more, which is more than ` <br /> 75% sand and/or gravel (coarse soil)? �( <br /> Directions: <br /> 1. Boring logs drilling at the site can be used to answer questions <br /> 5 - 8. Analytical results of the soil samples collected during the <br /> borings can be used to answer questions 3 and 4. <br /> 2. Lateral migration of constituents to problem areas should also be <br /> considered in questions 5-8. <br /> NOTE: The above checklist contains questions which are designed to identify <br /> sites with environmental conditions which could produce a greater risk <br /> to groundwater than was modeled through the usage of the Leaching Potential <br /> Analysis. The results of the general risk appraisal are most applicable <br /> if all the questions on the checklist can be answered "no" with reasonable <br /> certainty. If any of the questions on the checklist cannot be answered <br /> "no", then the results of the general risk appraisal may be less valid. <br /> If answers to the checklist questions indicate that the general risk <br /> appraisal results are not valid enough to be practical, then the LUFT <br /> Environmental Fate Worksheet should be considered. <br /> EH UNIT VI 2/91 RISKASMT <br />