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Mr. Michael Kalish - 2 - 15 May 2001 groundwater, or uppermost aquifer. Additionally, the groundwater zone is impacted by VOCs. The California Code of Regulations, Title 27 §20415 states: "(b) Ground Water Monitoring System. (1) General—Except as provided under¶(e)(3),the discharger shall establish a ground water monitoring system for each Unit. This ground water monitoring system shall include: (A) For All Programs—for all monitoring and response programs, a sufficient number of Background Monitoring Points (as defined in §20164)installed at appropriate locations and depths to yield ground water samples from the uppermost aquifer that represent the quality of ground water that has not been affected by a release from the Unit; (B) For DMP—for a detection monitoring program under§20420: 1. a sufficient number of Monitoring Points (as defined in §20164) installed at appropriate locations and depths to yield ground water samples from the uppermost aquifer that represent the quality of ground water passing the Point of Compliance and to allow for the detection of a release from the Unit; 2. a sufficient number of Monitoring Points installed at additional locations and depths to yield ground water samples from the uppermost aquifer to provide the best assurance of the earliest possible detection of a release from the Unit; 3. a sufficient number of Monitoring Points and Background Monitoring Points installed at appropriate locations and depths to yield ground water samples from portions of the zone of saturation, including other aquifers, not monitored pursuant to¶(b)(1)(B)1. and¶(b)(1)(B)2.,to provide the best assurance of the earliest possible detection of a release from the Unit; 4. a sufficient number of Monitoring Points and Background Monitoring Points installed at appropriate locations and depths to yield ground water samples from zones of perched water to provide the best assurance of the earliest possible detection of a release from the Unit; and 5. Monitoring Point locations and depths that include the zone(s) of highest hydraulic conductivity in each ground water body monitored pursuant to this subsection [i.e.,under¶(b), inclusive]." These sections clearly indicate the need to monitor the first groundwater that underlies the waste unit, so for the southwestern half of the landfill, deeper groundwater monitoring wells are needed. In addition, adequate background monitoring is needed for any groundwater monitoring system. During our meeting on 1 May 2001, the County requested clarification as to the schedule for monitoring the Five-Year Constituent of Concern(COCl) analytes. The COCs may still be collected in opposite quarters (eg., first quarter and third quarter) alternating every five years, as has been done previously. Additionally, if the County wishes to propose monitoring the three, currently dry, deeper wells for sampling soil pore gas from the vadose zone; the Regional Board would be amenable to considering that as part of the required vadose zone monitoring. Based on our internal review, the Regional Board also has made revisions to the Site Location Map (Attachment A). These revised WDRs will be presented to the Board for approval on 14 June 2001. As indicated in the "Notice of Public Hearing"previously mailed to you,the Board meeting is scheduled for 9:00 AM at the