SITE INFORMATION AND CORRESPONDENCE

Home Browse Search

MEMORANDUM CALIFORNIA REGIONAL VV#R QUALITY CONTROL BOARAENTRAL VALLEY REGION 3443 Routier Road, Suite A Phone: (916) 361-5600 Sacramento, CA 95827-3098 ATSS Phone: 8-495-5600 TO: Antonia K. J. Vorster FROM: Camilla Williams Senior WRC Engineer Engineering Geologist DATE: 29 August 1991 SIGNATURE: 12 t4 SUBJECT: REVIEW OF INTERIM REMEDIAL MEASURE (IRM) PROVE-OUT PHASE REPORTS, DEFENSE DISTRIBUTION REGION WEST (DDRW), TRACY, SAN JOAQUIN COUNTY I have reviewed the reports for the Prove-Out Phase of the IRM. The reports were prepared by Ensotech, Inc. for the Corps of Engineers and were submitted on 10 July 1991 . Submittal of the following reports were required by required by Waste Discharge Requirements Order No. 90-275. "Prove-Out of the Interim Ground Water Remediation System", "Installation Data Report", "Geologic Well Logs", "Site Specific Quality Management Plan (SSQMP)", "Start-up Schedule" . My overall comment on the reports is that there appears to be a lack of an exchange of data between the different contractors for the IRM and the Remedial Investigation/ Feasibility Study (RI/FS) . Therefore, all of the available data are not being used in making technical decisions. Tracy needs to implement a system by which the data developed in the RI/FS can be used for the IRM and any future expansions of the IRM, and likewise, to use the data developed for the IRM for the site-wide RI/FS and final remedial design for the ground water cleanup. The major deficiency of the IRM, as reported in these documents, is that one of the injection wells does not perform as designed. There was no discussion in the reports on the possible reasons for the poor performance of this injection well . Tracy should evaluate all of the hydrogeologic data to determine if the poor well performance can be attributed to well design, construction, lithology, or some other factor. Tracy should use the evaluation of this well performance to avoid similar problems with future injection wells and to optimize the performance of the final ground water remedial action. My review concentrated primarily on the Prove-Out of the Interim Ground Water Remediation System, Installation Data and Geologic Well Logs Reports. My comments and concerns on these documents are discussed below. PROVE-OUT OF THE INTERIM GROUND WATER REMEDIATION SYSTEM REPORT 1. Page 4. The static water level (SWL) in the injection wells appears to have been monitored between 1500 and 1555 (about one hour) on 11 April 1991. The WDRs do not specify any requirements for monitoring of the SWL. Generally, a 24 hour period is used to monitor the SWL prior to conducting any aquifer test. Because the IRM