ARCHIVED REPORTS XR0001826 - Laserfiche WebLink

Home Browse Search

Harding Lawson Associates December 22, 1998 4034405 Margaret Lagorio, Supervising REHS San Joaquin County Public Health Services Environmental Health Division ' Page 5 Decontamination of Drilling and Sampling Equipment Drilling equipment was steam cleaned prior to use Groundwater sampling equipment and soil sampling egmpment were washed in a residue-fiee detergent (such as Alconox, Liquinox, TSP, etc ) and rinsed in tap water and deionized water prior to each use 1 Waste Disposal All drill cuttings and decontamination water generated during drilling activities was retained on Site in clean, Department of'I ransportation-approved, 55-gallon steel drums, which were sealed and then labeled with the boring number and accumulation date Upon receipt of the analytical results, disposition of the cuttings and decontamination water was performed in accordance with local, state, and federal environmental and transportation laws Assessment of Risk to Human Health and Safety To evaluate whether impacted soils at the Site pose a risk to human health and safety, a Risk Based Corrective Action(RBCA) process was utilized The RBCA process is not a formal risk assessment per se, but rather, a consistent decision-making process for the assessment and response to a petroleum release based on the protection of human health and the environment The RBCA assessment was performed consistent with the American Society for Testing and Materials (ASTM) guidance document ASTM E 1739-95 entitled Standard Guide for Risk-Based Corrective Action Applied at Petroleum Release Sites (ASTM), 1995) Terminology in the following discussion is consistent with definitions presented in ASTM 1? 1739-95 (ASTM, 1995) Once it has been determined that theie is no immediate threat to health and safety, the first step in the RBCA piocess is the identification of chemicals of concern (CDCs) and reasonable potential exposure scenarios (RPES) fol the Site These RPESs are characterized in teims of primary and/or secondary sources, transport mechanisms, exposure pathways, and potential receptors ' An example of an RPES is the ingestion of impacted surficial soils by staff of the Newark Sierra plant A Tier 1 RBCA evaluation is performed by comparing the maximum concentrations of COCl with the risk- based screening level (RBSLs) associated with each RPES identified A Tier 1 RBSL is a generic (non-site specific), and therefore conservative value, calculated from reasonable maximum exposure intake assumptions (RME), toxicological parameters, and non-site specific physical parameters for site-media as recommended by the United States Environmental Protections Agency (USEPA) An RBSL is associated i with a given level of risk (generally for carcinogens this is a range of one-in-ten thousand to one-in-one million and for non-carcinogens a hazard quotientl of one or unity), the acceptable level of risk adopted for this assessment is a conservative one-in-one million for carcinogens and a hazard quotient of one for 1 non-carcinogens If the maximum concentrations of COCs exceed the RBSLs associated with any of the RPES identified for the Site, then the Site can be remediated to below the exceeded RBSL or a Tier 2 analysis can be performed In a Tier 2 analysis, concentrations of COCs are compared with site specific target levels (SSTLs) which are calculated with the same fate and transport equations by substituting site- specific intake assumptions and site media physical parameters for the generic default parameters If the maximum concentrations of COCs are less than relevant RBSLs (and the user is confident that the 1 o€a COC(s)over a specified time period to a reference dose for that COC(s)derived • 1 Hazard quotients-the ratio of the loves o€exposure O P for a srrrvlar exposure period in equation form this represented as Hazard quotient= average intake Inig1 kg day)(reference dose [uiWkg-day](ASTM,1995) 'fir