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MEMORANDUM • CALIFORNIA REGIONAL WATER QUALITY CONTROL BOARD - CENTRAL VALLEY REGION 3443 Routier Road, Suite A Phone: (916) 755-3000 Sacramento, CA 95827-3098 CALNET: 8-494-3000 TO: Antonia K. J. Vorster A4 FROM: James Taylor Senior WRC Engineer Engineerinq Geologist DATE: 12 March 1993 SIGNATURE: SUBJECT: SUBSISTENCE WAREHOUSE STOCKPILED SOIL, DEFENCE DISTRIBUTION REGION WEST, (DDRW), TRACY, SAN JOAQUIN COUNTY On 26 January 1993, Regional Water Quality Control Board (RWQCB) staff Camilla Williams and I met with Marshall Cloud and Mark Phillibur of DDRW, Tracy to discuss the stockpiled soil excavated from the foundation for the Subsistence Warehouse. The purpose of the meeting was to present the results of two different methods used for evaluating the threat to water quality from the stockpiled soil , and decide on an appropriate method of disposal based on these evaluations. This memorandum presents the results of the stockpiled soil evaluations. Approximately 200 cubic yards (cy) of soil has been stockpiled onsite since construction of the Subsistence Warehouse in August/September 1991 . The source of the soil is from the overexcavation of the areas immediately beneath and surrounding the deteriorated drums found in the excavation of the foundation for the Subsistence Warehouse. Six in-situ (i .e. , before excavation and stockpiling) soil samples collected from beneath the drums exceeded the Soluble Threshold Limit Concentration (STLC) for lead and one in-situ soil sample exceeded ten times the STLC for arsenic. To determine the appropriate method of disposal , 17 soil samples were collected of the stockpiled soil . Approximately 1 grab sample per 25 cy of stockpiled soil was collected on 15 December 1992 and analyzed for soluble concentrations of lead and arsenic using the deionized Waste Extraction Test (DI-WET) as per RWQCB recommendations. The analytical results and a map of the soil sample locations are included as an attachment. "Designated waste" is defined in §2522(a) of Title 23 of CCR, Division 3, Chapter 15 as: "1) nonhazardous waste which consists of or contains pollutants which, under ambient environmental conditions at the waste management unit, could be released at concentrations in excess of applicable water quality objectives, or could cause degradation of waters of the State" or "2) hazardous waste which has been granted a variance from hazardous waste management requirements pursuant to Section 66310 of Title 22 of this code. " (In July 1991, §66310 of Title 22 of CCR was repealed and replaced with §66260.210. ) The second part of this definition pertains to those wastes granted a variance from Class I disposal by The Department of Toxic Substances Control (DTSC) . The first half of the "designated waste" definition includes non-hazardous wastes which have the potential to impair water quality at the site of discharge. Due to their threat to water quality, "designated wastes" are to be discharged to Class II waste management units (WMUs) which have engineered containment features, liners, leachate collection systems and caps. These WMUs act to isolate the wastes from the ground