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GECHVIATUIX Mr.Robert Mihalovich Chevron Environmental Management Company May 9,2002 .Page S contaminants at a site or multiple pathways of exposure." The le rick level is the point of departure" Acceptable risk levels are generally between 1194 and 104,;however the actual level of acceptable risk is u site-spee fe risk management decision: l'herefore,In conformation with the NCP,1.x1Or6 is the point ofdeparture for acceptable risk in the health risk assessment. A11 diseussions with respect to -wacceptable-levels ofrlsk;in the.HI?A'shoxild be based on thispoint of departure.. Comment noted. 7 Attachment 2,page 10,of the updated risk evaluation only.includes equa tans for calculation of risk due to inhalait do ex posures.ofgroundwater. Although the report appears not to include all the exposurepathways,HE"verified that all exposure pathways were included in the calculated risk values. Specifically,the risk table results do include risks due to oral and dermal exposures ofgroundwater. 1n addition,page 17 ofA1tachment2,includes the risk for inhalation,oral and dermal groundwater exposurex Comment noted. &. Using the maximum,dewected concentrations, as in Attachment 2, the screening level risk evaluation iden if ed total risks to residential receptors±of 3xl 0,with the potential future groundwater exposure contributing a risk of 2xlli"�and pottial soil exposure contributing a risk of 1x1 e.4. The total hazard index was 0.4. No response required. 9 The most appropriate means of applying the data is using the 95%2'TCL soil concentrations and the maximum detected groundwater concentration. HERD compiled this information by drawing from. Afrachment 4 forsotl and Attachment 2 for � groundwater. The resulting screening level risk evaluation identified total risks to J residential recet'tors IT;of2x1with potential future groundwater exposure contributing a risk of 2xl; and potendat.soil exposure contributing a risk of 2x10' . The total hazard indev was 0.1. No response required. CortC'LUSIOM ]HERD evaluated the October 2,2001 "Results of the Updated Human Health Screening Risk Evaluation Pombo Property(San Joaquin CountyAFN232-170-a7), 1755 West 11th .Stree4 Tracy, California.." Using the 95% UCL soil concentration and the maximum detectedgroundwater concentration, the total screening level risk to residential receptors is of 2xi r is ith potential future groundwater ccposure contributing a risk of Z:v1O and potential soil exposure contributing a risk of 2x1 Q'7 71ie total hazard index is less than 1.