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Appendix G - Sump Shutdown Test Methods and Results <br />• <br />1. INTRODUCTION <br />:Four sumps were operated in the alluvium and fill adjacent to Ralston Creek. The sumps operated from <br />1990 to June 2002, and were designed to limit direct seepage of uranium-impacted water from the alluvium <br />into the creek. During that time, the sumps were effective in reducing uranium loading to Ralston Creek <br />because alluvial groundwater with higher concentrations of uranium and other dissolved solids was drawn <br />into the sumps and prevented from interacting with water in the creek. <br />The effect of groundwater in the alluvium and valley fill on water quality in Ralston Creek was evident <br />when the sumps were shut down. Two short-duration sump shutdown tests were conducted in 1998 and <br />1999, prior to the washing and reclamation of the fill. The sumps were permanently shut down in June <br />:2002. The sump shut down tests (described below in Sections 3.1 and 3.2) indicated that water quality in <br />]?,alston Creek would be affected after the sumps were permanently shut down. <br />2. SUMP PUMPING RA'Z'ES <br />Groundwater in the alluvium was intercepted and collected by four sumps, which were installed in 1990' <br />and operated until June 2002. Water drained into each sump by gravity and was pumped to the water <br />treatment plant near the western end of the mine facilities. The water was treated and discharged into <br />Ralston Creek, under Colorado Discharge Permit #CO-0001-244. The last Discharge Monitoring Report <br />1,DMR) was submitted on June 29, 2002. <br />Sump pumping records provide an indication of the interconnection between Ralston Creek and the <br />alluvium and fill material. Flow rates from the sumps were measured from 1995 to June 2002, when the <br />pumps were shut off. Monthly average pumping rates for the four sumps combined ranged from 59 to 404 <br />gpm, with an average of 104 gpm over the period of record (Table 1). A decline in sump pumping rates <br />was observed in 2000, which was most likely related to drought conditions. <br />Monthly average sump pumping rates clearly correlate with monthly average precipitation rates (Figure 2z). <br />A slightly weaker correlation exists between monthly sump pumping rates and monthly average flow rate <br />in Ralston Creek (Figure 3, Figure 4). Although flow rates in the creek peak in May, as do pumping rates <br />i:rom the sumps, the trend between creek flow and pumping rates differ during high flow (spring) months <br />i:rom the trend during low flow months. <br />1 Sump #1 went online in August 1990, sump #2 in April 1990, sump #4 in October 1990, and sump #3 went online January1992. <br />2 It should be noted that Figure 2 was generated using 26 years of precipitation data (May 1978 - November 2003), while the sump <br />pumping records span only about five years. Some of the sump flow records contain only one or two flow measurements exist <br />. for a given month (Jan, Feb, Mar, Sept, Oct, Nov, Dec.) While a longer span of data might make the correlation stronger, the <br />strong relationship between precipitation and sump flow (and the weaker relationship between stream flow and sump flow) is <br />significant. <br />4109B.071109 Whetstone Associates