FIELD DOCUMENTS AND WORK PLANS 1991

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STATE OF CALIFORNIA • • PETE WILSON. Governor ,CALIFORNIA REGIONAL WATER QUALITY CONTROL BOARD— 65� CENTRAL VALLEY REGION3443 ROUTIER ROAD, SUITE A SACRAMENTO, CA 95827-3098 PHONE: (916) 361-5600 FAX: (916) 361-5686 KECEIVEu'mk MAY Z 0 1991 13 May 1991 ENVIRONMENTAL HEALTH PERMIT/SERVICES Mr. David Bates Marley Cooling Tower Company 5800 Foxridge Drive Mission, Kansas 66201 REVISED REMEDIAL WELLFIELD DESIGN AND PERFORMANCE MONITORING PLAN FOR THE REMEDIAL WELLFIELD, MARLEY COOLING TOWER COMPANY, SAN JOAQUIN COUNTY We have reviewed the Remedial Wellfield Design and the Performance Monitoring Plan for the Remedial Wellfield submitted on 5 February 1991 by Hargis and Associates for the Marley Cooling Tower Company. Our review found these conceptual plans to be acceptable. We commend Hargis on the presentation of the data in these Plans. However, our review of these plans indicates that there appears to be inadequate performance monitoring of the extraction system. However, this inadequacy is due to the insufficient number of existing monitor wells to define the lateral and vertical extent of contamination. In our 14 November 1991 meeting, we agreed that monitor wells will be installed along Walker Lane. However, based on our review of the subject reports, we conclude that additional monitor wells are needed to define the eastern boundary of the plume due to the change in flow direction caused by the drought in recent years. Well clusters are needed to the east of MW-426 and MW-214. The installation of these wells may be deferred until after start-up of the full-scale ground water treatment system for the purposes of verification monitoring. We concur with your plans to combine the performance monitoring of the remedial wellfield with the quarterly ground water monitoring program. With this program, all of the monitor wells will be sampled in January and July. The key monitor wells for the performance monitoring program (located along the longitudinal axis and along the down gradient edges of the plume) will be monitored in April and October. This reduced monitoring, using only the key monitor wells, should be adequate to monitor the effectiveness of the extraction system and plume movement between the wet and dry seasons. The Plans state that an annual performance monitoring report will be submitted in addition to the quarterly/performance monitoring reports. The annual report will evaluate the progress of the ground water remediation and will include any recommendations for modifications to the pumping distribution.