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STAFF REPORT • • 7 MUSCO FAMILY OLIVE COMPANY AND THE STUDLEY COMPANY CONSIDERATION OF WDRS AND A C&A ORDER 6 September 2002 Regional Board Agenda Background Water Quality Background water quality data is limited and due to the limited availability of the data, conclusions based on the data are tentative. The Discharger installed groundwater monitoring wells in 1985 for WDR Order No. 96-075 (the Title 27 WDRs). The wells have been reported as dry in most monitoring events. In April 2002 when the Discharger was required to install groundwater monitoring wells per the Time Schedule Order, Well W-2 was inspected and reported to contain groundwater. That well was added to the recently installed groundwater monitoring network. In April 2002, the Discharger installed 13 groundwater monitoring wells; however, Well MW-9 went dry during well development and has not recovered. The wells were to be installed in the first saturated interval; however, staff are concerned that some saturated intervals may have been drilled through without detecting groundwater. Because of the anticipated depth of some of the wells,the Discharger's consultant selected air rotary as the drilling technique. Because air rotary drilling might prevent installation of groundwater monitoring wells in the first saturated interval, staff required the Discharger to submit additional information describing how the wells would be constructed. The Discharger submitted a workplan addendum and the wells were installed. However, based on the results of the investigation, staff remains concerned that the first saturated interval may have been missed while drilling the deep wells. The first sample event for all the wells was performed in April 2002; a second sample event was performed in June 2002. The data collected in the two sample events is presented below. Well Date TDS Chloride Sodium NO, as N Sulfate MW-1 4/10/02 690 67 240 11.0 45 6/24/02 770 110 250 19.0 53 MW-2 4/10/02 9,800 130 2,400 1.2 2,800 6/24/02 10,000 4,200 2,500 1.9 2,700 MW-3 4/10/02 2,700 880 770 0.91 150 6/24/02 3,100 72 790 ND 160 MW-4 4/10/02 1,200 92 330 3.7 440 6/24/02 1,200 210 350 3.5 410 MW-5 4/10/02 2,200 670 600 ND 330 6/24/02 2,200 540 560 ND 360 MW-6 4/10/02 2,600 830 780 16 ND 6/24/02 Well was dry. MW-7 4/10/02 2,400 540 550 3.3 1,300 6/24/02 2,300 430 530 8.4 1,000 MW-8 4/10/02 1,300 130 280 5.2 460 6/24/02 1,300 270 290 14.0 390 MW-9 4/10/02 Well was dry.