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Appendix D - MW9 Pumping Test 1 <br />• 1. INTRODUCTION <br />A 72-hour pumping test was performed in the alluvial aquifer at the Schwartzwalder Mine near Golden, <br />Colorado from March 29 to April 1, 1999. The purpose of the test was to determine the permeability of the <br />alluvium and to evaluate the hydraulic and chemical interaction between the alluvium and Ralston Creek. <br />Monitoring well MW9 was drilled specifically for this pumping test, in a location that was expected to have <br />relatively high uranium concentrations in groundwater. The location of MW9 is shown in Figure 1, along <br />with the locations of other wells and sumps completed in the alluvium and fill along Ralston Creek. <br />MW9 was pumped at a rate of approximately 30 gallons per minute (gpm) for approximately 72 hours. <br />Drawdown and recovery were monitored in nearby observation wells and sumps to assess the hydraulic <br />response of the fill and alluvial aquifer to pumping. Flow in Ralston Creek was monitored during pumping, <br />and water samples were collected regularly during the pumping test to assess the chemical characteristics of <br />the flow system. <br />2. TEST DESCRIPTION <br />2.1 Data Collection <br />Water levels were measured before, during, and after the pumping test in four sumps, seven observation <br />wells, and the pumping well. Plots of water level versus time are provided in Attachment 1. Water levels <br />were measured on intervals ranging from 1 minute to 30 minutes. Discharge was measured hourly at a <br />minimum, except the period from 11:00 p.m. to 7:00 a.m. on March 29, 30, and 31, during which time only <br />• one flow measurement was recorded. <br />Background water levels were monitored prior to the start of the pumping test. The pumps in all of the <br />sumps (Sump 1, 2, 3, and 4) were turned off prior to pumping, and remained off throughout the pumping <br />and recovery test to obtain accurate water level measurements. The water levels in the four sumps had <br />recovered to approximately 75% of pre-pumping conditions prior to the start of the MW9 pumping test. <br />Water levels in Ralston Creek were measured immediately prior to the start of the test and daily during the <br />test. <br />2.2 Pumping Test <br />The pumping test started at 10:00 a.m. on March 29, 1999. Monitoring well MW9 was pumped at a rate of <br />approximately 30 gpm. Water from the pumping test was routed to the onsite water treatment plant. <br />The pumping rate held relatively constant throughout the test, with the exception of 3:00 to 3:30 p.m. on <br />March 29, when the pump was stopped and started several times for repairs. The pump was restarted at <br />3:30 p.m. and ran for the remainder of the test. The pump was shut off at 7:30 a.m. on April 1. The <br />recorded flow rates are given in Table 1. <br />2.3 Recovery Test <br />Water level recovery was monitored in the pumping well, observation wells, and sumps for approximately <br />24 hours after the pump was shut off. Water level recovery data are presented on the water level plots in <br />Attachment 1. <br />0 <br />4109B.071116 Whetstone Associates