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Larencim Can_YOn Mine - Graundmarcr Technical Repnrt <br />These velocities indicate that ground water seepage ranges from 2.56 z lOZ fr/yr to 0.82 fr/yr. <br />Transmissiviry value derived for this zone indicates that water production for domestic use is <br />infeasible. <br />Primero Coal <br />The Primero Coal in the Lorencito Canyon Permit area outcrops at approximately 6800 feet <br />AMSL. Total estimated thickness for this unit ranges from 0 to 9.3 feet with an average thickness <br />of 5.12 feet. Recharge to the Primero is via precipitation on outcrop surfaces, and from inflow <br />from fractures or overlying units. Infiltration rates for this unit are anticipated as low. <br />Examination of a flow net of the system (Figure GW-S), indicates that some of the recharge is <br />discharged at the outcrop surface area via evapotranspvation. In addition, springs would generally <br />be anticipated to emanate for the coal at the outcrop. Spring and seep surveys conducted during <br />the baseline period did not determine springs (with the exception of SPLJC-1) to exist at this <br />particular outcrop area. This may be the result of small amounts of recharge combined with the <br />high evapotranspiration in the area. <br />Groundwater in the Primero is characterized as being under confined conditions. Water was <br />apparent in all of the borings into the Primero; however, substantial flow increases through the <br />• Primero seam were not apparent. Groundwater in the Primero appears to be continuous <br />throughout the zone. <br />The potentiometric surface of the aquifer was determined from data from wells MW-4, MW-5, <br />and MW-6. The data indicates the flow direction to be to the east-northeast, with a gradient of <br />0.0078 ft/ft or 41.68 fr/mi. This tlow direction is relatively comparable to the direction <br />established in the region by Howard (1982). A map of the potentiometric surface of this unit is <br />included as Map 2.04.7-5. <br />Characteristics of the Primero were determined via slug testing. A slug test was performed in well <br />MW~-C, and recovery of the well to static was not accomplished in 17 hours of data collection. <br />Approximately 65 percent of the recovery did take place in this time. This indicates an extremely <br />low hydraulic conductivity for the Primero. Estimated hydraulic conductivity as determined via <br />this testing was 1.22 x 10"' ft/day. This value can be translated to transmissivity (T) by the <br />equation T = Kb, where T is transmissivity, K is hydraulic conductivity, and b is the aquifer <br />thickness. Therefore: <br />T=Kb <br />T = (1.22 x 10' fr/day) (5 ft) <br />T = 6.10 x 10' ftZ/day or 4.56 g/d/ft <br />• <br />Groundwazer 375\Dttcmber 9, 1996 42 <br />