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Status Report, Robinson Seep Investigation Climax Molybdenum Company
<br />3.2 Initial Drilling Program
<br />A drilling program was implemented to investigate the distribution of groundwater constituents
<br />and identify potential migration pathways between Robinson Lake, Robinson Seep and the
<br />downgradient shallow hydrostratigraphic unit. As described in Section 3.1, field electrical
<br />conductivity values in the first occurrence of groundwater were used to map Robinson Lake type
<br />water to evaluate the extent of seepage. The electrical conductivity data were evaluated in the
<br />field to advance the drilling program in real time. The initial drilling program incorporated direct
<br />push drilling; however it was soon evident that this method was unable to achieve the required
<br />depths due to either coarse rock or indurated geological material. As a result, use of a solid
<br />stem auger was substituted on all but the initial borehole (EV -01). Drilling was conducted
<br />between August 19th and August 21St, 2013. Eighteen holes (EV -01 to EV -18) were drilled in
<br />various transects between the Robinson Lake Dam and the Robinson seepage collection cutoff
<br />wall. Of the 18 holes initially identified, two holes were not attempted due to their location and
<br />proximity to underground utilities. Of the remaining 16 locations, drilling at five locations was
<br />unable to penetrate to a sufficient depth to yield water due to the competency of the subsurface
<br />material. Depth to water in the remaining holes is presented in Table 3.3.
<br />Each boring remained open until sufficient water volume was recovered with a peristaltic pump
<br />operating at approximately 0.1 Umin to obtain field measurements of electrical conductivity and
<br />pH. Where sufficient water entered into the boring, 500mL of unfiltered water was collected and
<br />placed on ice. The samples were stored until the drilling phase was completed in order to select
<br />samples for analyses. During this phase, eight samples were collected for analysis (EV -01, and
<br />EV -06 to EV -12). Unfiltered samples were submitted to ACZ Laboratories under chain of
<br />custody for analysis of dissolved Al, Sb, As, Ba, Be, Cd, Ca, Cl, Cr, Co, Cu, CN, WAD CN, F,
<br />Fe, Pb, Mg, Mn, Hg, Mo, N, Ni, K, Se, SO4, Ag, Na, TI, V, Zn, alkalinity, total organic carbon,
<br />and TDS.
<br />Field parameter measurements, including pH and EC, are presented in Table 3.3 and analytical
<br />results for the samples submitted for analyses are presented in Table 3.4. Major ion
<br />classifications are shown in Figure 3.4. Discussion of the analytical results is provided in section
<br />3.3.
<br />3.3 Additional Drilling Program
<br />Additional drilling, incorporating an air rotary D -120 drill rig, was conducted between September
<br />18th and September 20th, 2013. A total of ten holes were drilled to record field parameters and
<br />collect water samples for further analysis. Additionally, field screening of near surface
<br />groundwater within sediments was conducted downgradient of EVMW -1 S by use of a hand
<br />auger to approximately 2.0 feet and collecting field parameters at six locations. Recorded field
<br />parameters, including depth to water, are provided in Table 3.3 and all EC values from the field
<br />investigations are presented in Figure 3.5. Water samples were collected following the method
<br />described in Section 3.2.
<br />3.4 Field Observations
<br />The following observations are made based on all field investigations:
<br />• The toe drain collects seepage with an approximate EC of 1,900 pS /cm.
<br />Tetra Tech, Inc. November 2013 32
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