FIELD DOCUMENTS AND WORK PLANS 2004-2014

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APPENDIX C Initial Study Checklist { PROJECT TITLE: Forrner Marley Cooling Tower Company Facility CALSTARS CODING: 11065- __ 100102-00 PROJECT ADDRESS: CITY:Stockton COUNTY: San Joaquin 200 N.Wagner Avenue PROJECT SPONSOR:MWH CONTACT: PHONE: 916.418.8354 Ton Mikecich APPROVAL ACTION UNDER CONSIDERATION BY DTSC: ❑ Initial Permit Issuance ❑ Permit Renewal ❑ Permit Modification ❑Closure Plan ❑ Removal Action Work Plan 9 Remedial Action Plan ❑ Interim Removal ❑ Regulations Other(specify): Remedial Action Plan Amendment STATUTORY AUTHORITY: ❑California H&SC, Chap. 6,5 0 California H&SC, Chap.6.8 ❑Other(specify): OTSC PROGRAM/ ADDRESS: 8800 Cal CONTACT:Steve Ross PHONE:916-255-3w Center Drive, Sacramento, Califomia 95826- 3200 PROJECT DESCRIPTION: The Department of Toxic Substances Control is proposing to approve a Remedial Action Plan Amendment (RAP Amendment) pursuant to the authority granted under Chapter 6.8, Division 20, California Health & Safety Code (H&SC) at the Marley Cooling Tower Company(MCTC) Site. The objective of this remedial action is 1) to modify the current groundwater remedy to implement in situ chromium reduction through injection of calcium polysutfide and ethanol (reductant solution); and 2) install horizontal wells and re- initiate flushing of deep soils to flush chromium to groundwater, where it will encounter the reductant solution. If groundwater data suggests favorable site-wide results, phase out groundwater extraction, treatment, and discharge to the Stockton Diverting Canal. The Draft RAP Amendment; August 2006, the Human Health Risk Assessment, and the Ecological Assessment of Clement Associates, 1990 are incorporated by reference. LOCATION: SPX, formerly MCTC is located at 200 North Wagner in Stockton, California. Figure 1, "Regional Map", Figure 2, "Site Location Map", and Figure 2-1, "Site Pian" are attached at the end of this document. Former operations were performed on two adjacent properties (referred to as North & South Yard) that are bisected by the Stockton Terminal & Eastern rail line. The facility is bounded on the north and east by light Industry and the Stockton Diverting Canal, on the west by Franklin High School's athletic field, and on the south and southeast by residential areas. PROJECT ACTIVITIES: Remediation of subsurface soils beneath the retort pit area and the underlying groundwater has not been completed and is the subject of this RAP Amendment. While the dissolved chromium plume has reduced from the maximum extent (August 1989) in the shallow and intermediate zone with the operation of the groundwater pump and treat system, remediation time is uncertain. A solution containing potable water, calcium polysulfide that is approved by State of California water agencies for well head rehabilitation activities and groundwater treatment of metals-impacted sites, and ethanol will be injected into groundwater to physically change the hexavalent chromium contamination in groundwater to the trivalent form, which is less toxic and not mobile in the subsurface environment. The approach proposed in the RAP Amendment has been successfully pilot-tested at the Site and is expected to clean up the groundwater in approximately three years as opposed to the current 17-year estimated cleanup time for the existing pump and treatment system.The injection solution application pilot-tested at the Site has been used at other multiple sites and has not displayed adverse effects on the long-term groundwater quality. Project activities include the following: 1. Enhance the existing soil flushing system which operated underneath the former retort pit area between 1992 and 2003.This enhanced system will be accomplished by the installation of an estimated five horizontal wells approximately 15 to 20 feat below the of the retortit cp ap,which is below the Page 1 of 25