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Sent By: BASELINE; d r 510 420 ,1707;1 Sep 5 f9:14; Page 10/i2 Mr. Steven Pinkerton March 17,'2000 , ` page 2 _ . t Soil samples analyzed indicated that the Site contains lead as high as 184 milligrams per kilograms (mg/kg or part per million), and lead in groundwater at 75.3 micrograms per liter (ug/1) (groundwater sample collected at south area of site). This lead value in groundwater exceeds Federal primary drinking water standards established as =Maximum Containment Levels (MCL). ' However; the sample was prepared absent j; filtering and the lead value may be overstated and not representative of lead in ,groundwater- Fpr, this reason at least, anoth6f Sample is required to determine the lead! ' levels in groundwater. + Soil samples also contained benzo(a) pyrene at 0.33 ppm. Sediment samples collected from the Stockton Channel below the pier-supported parking lot contained lead levels . as high as 200 ppm, arsenic at 22.1 ppm, and benzo(a) pyrene were detected as high = as 1.2 ppm. Samples collected from an offsite.monitoring well (Well #4) indicated components associated with the underground tank release at a former ARCO gas station including MTBE.at 53 ppb, benzene at 300 ppb, vinyl chloride at 61 ppb, and I, cis,.1,2-dichloroeth6ne.at 120 ppb, which significantly.exceed Federal MCL for drinking water. . A human health screening evaluation was completed as part of the PEA investigation Using the default residential land use scenario to calculate on site risk, the calculated #` s y' excess risk from soil ingestion-and dermal contact was 2.3 x 1 Q'S and the excess cancer: risk from groundwater ingestion and showering/bathing.as calculated using onsite groundwater was _1 1 x 10-5-'with a total cumulative risk of 33 x 10'x. s Based on the data presented in the PEA report, the Site poses a risk to human health S and the environment asevaluated under unrestricted land use activities_ Therefore DISC has determined that further action is necessary as outlined below to address investigative and remedial measure requirements associated with the hazardous substances at the Site , .9$ F. ' DTSC concurs with the recommendation in the PEA., Specifically. ' A....t k Recording a-deed restriction on theLpropertyto prevent future residential use and restrict use of the surface water and shallow groundwater underlying the Site. A ' supplementai risk assessment should ibe completed using future land 'use ,. F o scenarios which show that the site does not pose a risk to future occupants and€_ users including utility and construction workers.`' 4 • Continue to evaluate data being collected from the ARCO investigation to ' determine the need for.additional onsite remedial measures in the future to Y ,._ i ,'.,eliminate risk associated with the migration from the offsite SOUrcell. F ci