WORK PLANS_PART 1 FILE 1 - Laserfiche WebLink

Home Browse Search

GE®MA" RIX Section 20415 of Title 27 states that a DMP must have a sufficient number of monitoring points that are "installed at appropriate locations and depths to yield ground water samples from the uppermost aquifer," and that"provide the best assurance of the earliest possible detection of a release from the Unit." As seen on cross-sections A-A' and B-B' (Figures 3 and 4,respec- tively), the existing groundwater monitoring wells have screens that are about 20 to 50 feet below current groundwater levels (measured on October 5, 2000). The compliance wells are apparently screened below the uppermost part of the aquifer, and may be screened in two different water bearing zones, which are separated by a thick clay layer. In a December 18, 2000 meeting with RWQCB staff, Simplot proposed to install a new moni- toring well system to more fully comply with the detection monitoring provisions of Title 27. The RWQCB replied with a letter dated December 22, 2000, requesting the submission of a work plan by March 1, 2001 for the installation of additional monitoring wells and a background well. 3.0 GROUNDWATER OCCURRENCE IN EXISTING WELLS Groundwater occurrence in the existing monitoring wells has implications for the placement and construction of the DMP network. 3.1 GROUNDWATER ELEVATION AND DEPTH TO GROUNDWATER Since late 1994, groundwater elevations in monitoring wells adjacent to the surface impound- ments (LP-1, LP-2, and LP-3) have ranged from about -1 to 11 feet from mean sea level (fmsl) (Figure 5). During this time the depth to groundwater in these wells ranged from about 8 to 17 feet below ground surface (bgs). Intra-well groundwater level fluctuations have been about 6 to 7 feet. Water levels have been measured in several nearby monitoring wells (PW-1-48, PW-2-40, and PW-3-49, see Figure 2) since 1983. The historical groundwater elevation range in these wells has been about 12 to 17 feet (Figure 6). 3.2 GROUNDWATER GRADIENTS Current groundwater elevation data derived from existing wells implies that groundwater beneath the surface impoundments flows generally to the west (Figure 7). The gradient in the uppermost portion of the aquifer may be different because the effects of deeper pumping wells 1APROJECM741.000\6741-06.doc 2