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• Water level and chemistry data were collected by PHCI in May, August and <br />November 1998. Table 1 also presents an average static water level for each <br />monitor well based on three 1998 measurements, as well as well water levels <br />for late February 2005. The table shows there is some seasonal fluctuation, <br />but that it is only on the order of several feet. The 1998 static water <br />level data were used to develop a potentiometric surface for the Dry Creek <br />alluvial system in the vicinity of the Loadout (see Figure 2). The <br />potentiometric map shows the groundwater gradient is towards the north. The <br />1998 data indicate monitor wells DCAL-3A, -3B, SGAL-3, HGDALI, DCAL-5 and <br />DCAL-6 are upgradient of the Loadout, while HGDAL2, HGDAL3, DCAL-4A and -4B <br />are downgradient. The February 2005 water level data is generally similar. <br />Major ionic chemistry data measured during 1996 for the upgradient and <br />downgradient alluvial wells are presented in Figure 3. The anion and cation <br />points are grouped closely, indicating that water types are either the same <br />or very similar; the alluvial groundwater exhibit a sodium-sulfate or sodium- <br />magnesium-sulfate signature. <br />Table 2 summarizes select constituent concentrations for the PHCI wells and <br />monitor well HGDAL3 measured during 1996. The data indicates the alluvial <br />groundwater upstream o£ Stokes Gulch is of "potentially usable quality" - TDS <br />concentrations measured at DCAL-3A/B ranged from 4,200 to 4,880 mg/1. Boron <br />concentrations were at, or just below the agriculture use standard (0.75 <br />mg/1). Stokes Gulch appears to be a sign i£icant contributor of TDS. The TDS <br />concentrations in the Stokes Gulch alluvial groundwater were 33,000 and <br />39,200 mg/1 - significantly higher than the 10,000 mg/1 threshold used to <br />classify a groundwater as "limited use and quality." Concentrations of boron <br />(1.09 and 1,0 mg/1) and manganese (2.94 and 3.47 mg/1) also exceeded their <br />agriculture use numeric standards, 0.75 and 0.20 mg/1, respectively. <br />Monitor well DCAL-5, which is located downstream of the Dry Creek and Stokes <br />Gulch confluence and situated proximate to the facility area, also had <br />concentrations o£ boron, manganese and TDS that were higher than their <br />respective water quality thresholds, The chemistry in well DCAL-5 is <br />characteristic of Dry Creek alluvial groundwater quality at the permit area <br />boundary. Constituent concentrations in monitor well DCAL-6, which monitors <br />alluvial groundwater flowing from the area southeast o£ the Loadout, also <br />exceeded water quality thresholds. The boron concentrations were 2.1 and 2.9 <br />mg/1, manganese concentrations were 0,2 and 0.9 mg/1, and TDS concentrations <br />were 37,500 and 38,100 mg/1. These data indicate that alluvial groundwater <br />upgradient of the Loadout is of "limited use and quality." <br />TA-06 7-2.3 Aevis ed 06/05 <br /> <br />