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Joseph Mello, Jr. <br /> February 2, 2001 <br /> Page 2 <br /> facilities was common practice but is no longer employed at the two dry cleaning facilities <br /> currently operating at Lincoln Center. In 1999, a soil-vapor extraction treatment system <br /> (SVETS)was installed on the Lincoln Center site as part of an interim remedial action. The <br /> SVETS will continue operating until contaminant concentrations are below that which poses a <br /> human health threat. <br /> Scope of Review <br /> Our review focused on the methods and assumptions used in evaluating the potential <br /> human health risks associated with exposure to contaminants identified throughout the property. <br /> We understand that the Regional Water Quality Control Board, Central Valley Region has <br /> reviewed all relevant soil and groundwater analysis data to confirm the location of contamination <br /> throughout the site. <br /> Comments <br /> Risk Assessment Approach <br /> The risk assessment was conducted in accordance with the U.S. Environmental <br /> Protection Agency(USEPA) and California EPA(Cal/EPA)recommended methodologies and <br /> guidelines. Reasonable maximum exposures (RME) and central tendency exposures (CTE)were <br /> considered for each of four potential receptor populations. Potential receptor populations <br /> included commercial/industrial workers, maintenance/utility workers, shoppers and residents. A <br /> number of conservative assumptions were used to evaluate health risks based on the chemicals of <br /> potential concern identified at the site. For each exposure scenario (i.e., current shopping center <br /> and a hypothetical future residential scenario), it was assumed that contaminant concentrations <br /> have not changed over time. Therefore, exposure estimates were based on concentrations <br /> detected before remedial measures were in place. <br /> Risk Assessment Results <br /> The highest estimated potential cancer risk for each receptor population was associated <br /> with PCE exposure.RME assumptions for several potential exposure scenarios were estimated to <br /> be above regulatory threshold values. The target risk level of 1 x 10-5 was exceeded for the <br /> commercial/industrial worker exposed to soil vapors. A target risk level of 1 x 10'5 is appropriate <br /> for this scenario since the site is used for commercial purposes only. The RME estimates for the <br /> hypothetical residents (adult and child) exposed to soil vapors or with direct exposure to <br /> groundwater also resulted in values that exceed the target value of 1 x 10 "6. Additionally, a <br /> hazard index (HI) of one, estimating chronic noncancer adverse health risk for the hypothetical <br /> residential child receptor with direct groundwater use was also exceeded. However,health risk <br />