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The Newark Group, Inc. - 3- 27 February 2013 800 W. Church St., Stockton San Joaquin County The Report states Areas B-7 and B-15 were UST-related releases (tanks and piping), while the source of Area B-14 petroleum hydrocarbons remains unknown. Soil is generally reported as contaminated below 10' to 15', which is below typical worker exposure depths bgs. The one exception was boring B-33 in Area B-15, which reported TPHd, 390 milligrams per kilogram (mg/kg) and TPHg, 1.9 mg/kg at 4.5' bgs. Soil has been delineated in Areas B-14 and B-15, and the railroad yard limits further investigation at Area B-7. The Site buildings have been demolished down to the foundations, prior to the sale and redevelopment. The Report states the soil vapor pathway is incomplete due to the lack of buildings on the Site and that future buildings would mitigate the risk with a vapor barrier under the foundation slab; however, a potential for soil vapor inhalation from outdoor air exists. The Report states there are no operating water supply wells; the groundwater pathway is incomplete since the onsite supply wells have not been used since 2003, and investigations to date show there is little risk that groundwater will migrate to sensitive receptors. The Report states that while the soil pathway is incomplete at surface, there exists a risk to construction workers doing utility or excavation activities, that risk can be mitigated by restrictions on the use of shallow groundwater, and construction without vapor barriers restricted over the impacted soils in Areas B-7, B-14, and B-15. While degradation of TPHd and TPHg is probably occurring, the rate of degradation cannot be determined with the available data. The Report states that future usage of the Site will probably be industrial/commercial, and that shallow groundwater use could be restricted if groundwater was needed as a water resource at the Site. The Report recommends: • Not allowing construction of workspaces or residences in Areas B-7 and B-15 where soil and groundwater contamination are present; • Not allowing construction of workspaces or residences in Area B-14 where TPHd was detected at 15' bgs, and • Not conducting further investigation of Area B-7 within the Union Pacific Railroad Yard and industrial land, which extends offsite 2,000' to the south and southeast. Comments: 1. The Report recommendations to prohibit redevelopment in areas of contamination imply that this is not a low risk candidate for a USTs closure and that deed restrictions would be necessary to protect human health from contamination. The text of the Report does not support these recommendations and provides one construction mitigation measure (vapor barrier on foundation slab) during redevelopment. See Comment#4 below.