ARCHIVED REPORTS XR0009635 - Laserfiche WebLink

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City of Stockton A68104 01A October 25, 1995 Page 8 September 1995 did not detect PPCs in groundwater above the detection limits Based on this data it would appear that PPCs have not migrated from the impacted soil into ' groundwater Findings from this work suggest that there are no PPCs in soil below 20 feet BSG in the ' immediate vicinity of the former UST location It is Twining's understanding, from information provided by the City of Stockton Public Works Department, that soil between the surface and 19 5 feet BSG was excavated and removed at the time of the UST removal action. The area of the former UST location was capped with Portland cement concrete after the UST removal Based on this information and the findings of this investigation, future migration of PPCs into groundwater appears unlikely 7,0 CONCLUSIONS • The soil profile at the site consists of interbedded strata of sand, silty sand with clay, P tY Y sand with clay, and clayey sand, • Groundwater was encountered beneath the site ata approximately 25 feet BSG on PP Y June 22, 1995, and 22 feet BSG on June 29, 30, and September 26, 1995, • PPC migration in soil appears to have extended vertically no deeper than 20 feet g PP Y P BSG beneath the former UST location, • PPC migration in soil appears to have extended laterally no more than 10 feet from the former UST location, • Based on analytical results of groundwater sampling analysis, it does not appear that PPCs in soil have migrated to groundwater below the former UST location 8.0 RECOMMENDATIONS • Copies of this report should be forwarded to SJCPHS for review and comment • A quarterly groundwater monitoring plan should be formulated and implemented If PPCs are not detected in the groundwater samples collected over one year, the City of Stockton may consider requesting a "no further action" letter for this project site from the SJCPHS,