ARCHIVED REPORTS_PRELIMINLARY SUBSURFACE INVESTIGATION

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Preliminary Subsurface Investigation City of Stockton, former Western Pacific Railroad Property, Stockton, CA May 27, 1992 W0601.1D ' • The shallow groundwater has been impacted by intrusion of poor quality waters from deltaic sediments, deep connate water from marine sediments, leakage from improperly abandoned gas wells and infiltration from the deep water channel and other surface ' waters. • Laboratory analyses of the shallow subsurface soils reported levels of metals well below maximum total and soluble threshold limit concentrations. • Shallow groundwater flow at the former WPRR property is controlled by influx from the ' tidally influenced deep water channel. Influx of this water through dredge spoils adjacent to the channel may also contribute to poor water quality. ' • Sampling of the three wells on the former WPRR site has shown water chemistry consistent with that throughout the south-central Stockton area. The laboratory analyses ' on the two wells across the deep water channel detected selenium at higher concentrations than found at the former WPRR Property. This shows that the groundwater in the downtown Stockton area has poor water quality and past practices on the former WPRR Property have not degraded water quality. • The results of this investigation indicate that former site operations have not significantly ' impacted beneficial use of the groundwater beneath the site. 8.0 RECOMMENDATIONS RF-SNA recommends performing the following work at the site: ' No further investigation is warranted based on the results of this investigation and the one concurrently performed at the adjacent Banner Island Property. This report should be forwarded to the Central Valley Regional Water Quality Control Board and San Joaquin County for concurrence. Thereafter, all wells on-site should be properly abandoned prior to site development. R041392.SAY 13