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amec- <br /> 3.1.2 <br /> Historical Onsite Groundwater Pumping <br /> Four groundwater production wells supplied the plant with process water (Figure 2): N-1 (the <br /> primary production well near the northern Site boundary near the water tower), N-2 (a backup <br /> well which reportedly was used scarcely because it produced water with high dissolved solids, <br /> N-3, the primary supply well supporting the production of soluble tea, and N-4, which was <br /> reportedly used as a backup supply well for soluble tea production. Wells N-3 and N-4 were <br /> both located in the Engine Room, near the central portion of the facility, and well N-2 was <br /> located near the southeast corner of the Site, south of the railroad spur that bisects the Site. <br /> Information on the screened intervals of these four wells is not available. Well N-1 was <br /> reportedly installed in the mid-1950's and drilled to at least 150 feet bgs with "open bottom" <br /> construction (John Meling, personal communication). Production wells N-2 and N-3 were <br /> installed in 1979 and 1962, respectively. N-2 was installed to a depth of 250 feet bgs. No <br /> construction information is available on N-3. Wells constructed as "open bottom" wells are <br /> constructed by advancing steel well casing to the total depth, and then perforating the casing <br /> with a tool such as a Mills Knife at depth intervals corresponding with major water production <br /> zones identified during drilling. Wells N-1 through N-3 were decommissioned by perforating <br /> the casing and filling the well with a neat cement slurry (grout) in 1995 (Weiss, 1995a). Well N- <br /> 4 was likely closed between 1974 and 1978 (John Meling, personal communication); details on <br /> how the well was closed (i.e. whether it was simply capped or filled with grout) are not <br /> available. <br /> From the 1950's to the 1970's, annual average groundwater production from onsite wells <br /> (primarily N-1 and N-3) ranged from approximately 300 to greater than 500 gpm (RUST, <br /> 1994a). A summary of plant water use between 1969 and 1982, based on available plant <br /> records, is provided in Table 1. The highest rates of groundwater use occurred during tea <br /> production between 1962 and 1974, with an average annual production of over 600 gpm in <br /> 1974 (Table 1). Instantaneous pumping rates were likely much higher, as the pumps would <br /> have cycled to maintain sufficient water in the onsite water tower used to supply plant <br /> operations. Groundwater production from well N-3 (and perhaps N-4) often exceeded 1,000 <br /> gpm (John Meling, personal communication). <br /> A portion of the total dissolved solids (TDS) was removed from extracted groundwater prior to <br /> plant use. Two water treatment towers located south of the boiler building (Figure 2) used a <br /> combination of steam and calcium and magnesium oxides to remove dissolved minerals <br /> (primarily silica and carbonate salts)from extracted groundwater. Water from the towers was <br /> transferred to treatment columns located inside the boiler room for additional solids removal <br /> with zeolite, prior to storage in tanks. The treated water was then used for the boilers or other <br /> plant processes. <br /> AMEC Geomatrix, Inc. <br /> I:\Doc_Safe\9000s\9837.005\4000 REGULATORY\SCM_01.30.09\1_text\SCM Report Final.doc 9 <br />