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STATE OF CALIFORNIA - Environmental Prot _ m Agency PETE WILSON, Governor CALIFORNIA REGIONAL WATER QU ITY CONTROL BOARD CENTRAL VALLEY REGION 3443 Routier Road, Suite A Sacramento, CA 95827-3098 PHONE: (916) 255-3000 DOD FAX: (916) 255-3052 rn i£? ;< 4 February 1994 ;r1 ✓ r w - Mr. Mike McIlvoy f=_ Environmental Protection Division osy Sharpe Facility, Building S-108 m" a Defense Distribution Region West J µ P. O. Box 96001 Stockton, CA 95296-0710 IRRIGATION OF LEASED PROPERTY, DEFENSE DISTRIBUTION REGION WEST (DDRW), TRACY, SAN JOAQUIN COUNTY By letter dated 25 January 1994, you requested our position on leasing a portion of the property adjacent to and northeast of the DDRW, Tracy site. The purpose of leasing the property, formerly owned by Mr. Raspo, is to maintain the walnut orchards and row crops through continued irrigation by either flood or spray irrigation. We also understand that the lack of water will stress the orchards if the property is not quickly leased for continued farming. Because a large portion of the property in question is down gradient of the volatile organic constituent (VOC) plume and because the hydraulic affects from infiltration are anticipated to be very low in the area overlying the plume, the continued use of either flood or spray irrigation, as has been conducted historically, should not pose a detrimental affect on the ground water cleanup. We have, however, two concerns regarding leasing the property for farming. First and foremost, the farming activities must not hinder any activities conducted as part of the ground water remedial action. Specifically, DDRW, Tracy must be guaranteed any access to the leased areas, regardless of the farming use, should the cleanup warrant it. Secondly, the application rate of the irrigation water should be controlled so as not to prevent excessive runoff. Finally, we encourage DDRW, Tracy to consider use of the treated ground water for irrigation of the leased property. The previous source for irrigation was ground water which had to be discontinued as the agricultural well pumpage exacerbated the plume extent. Considering this, use of the treated ground water is appropriate in lieu of using water for irrigation from another source. The disposal of the treated ground water in this manner may require that DDRW, Tracy perform an Explanation of Significant Difference (ESD), amendment to the Operable Unit No. 1 (OU-1) Record of Decision (ROD) or some other regulatory process under the Comprehensive Environmental Response, Compensation and