Laserfiche WebLink
RULE Z PERMITS <br />The majority of the springs with bedrock sources appear to be contact springs. A contact spring results <br />from the infiltration of water from the surface to a porous zone (such as sandstone) above a horizontal <br />hydrologic barrier (such as shale) where the water preferentially flows along the contact to the exposure. <br />This type of spring is common in areas where alternating sequences of lithologies exist that exhibit <br />differential hydraulic conductivities, such as the Williams Fork Formation. <br />Table 2.05.6-4 lists the springs and seeps found in the vicinity of the proposed mining area. The locations <br />of the investigated springs and seeps are presented on Map l OB. Data collected for the springs and seeps <br />were previously summarized in Table 2.04.7-49. <br />The potential impacts to springs and seeps listed below are evaluated for each of the three surface <br />drainage areas that will be affected by the mine: <br />• Elimination of springs and seeps <br />• Changes in flow <br />• Formation of new springs and seeps <br />Little Collom Gulch Area <br />Two springs (SPRLC-01 and SPRLC-02) maintained flow during July and August 2005 in Little Collom <br />Gulch, and produced a total of 0.30 cfs during spring runoff in June 2005, and 0.045 cfs during August <br />2005 base flow. (Table 2.04.7-49) Spring/seep SPRLC-03 produced a minor flow of 0.009 cfs in <br />December 2004, and produced no measurable flow for any other sampling event. Springs/seeps V 11 and <br />V29 produced no measurable flow for any sampling event. All Little Collom Gulch spring and seep <br />flows subsequently infiltrated into the valley fill or were captured by stock ponds. Streamflow monitoring <br />point LLCG located near the mouth of Little Collom Gulch was dry throughout the 18 month sampling <br />period. <br />Spring SPRLC-01 (V24) is located at an elevation of about 7270 ft in Little Collom Gulch within the pit <br />footprint area and will be eliminated by the mining operations. The bedrock groundwater elevation in this <br />area is about 7150 ft so the source of this spring is probably from perched groundwater. Spring V 11 was <br />mapped in the Little Collom Gulch drainage area at an elevation of about 7230 ft in the footprint area of <br />the facilities but had no measurable flow during the 2005 and 2006 monitoring events. It may reflect <br />localized discharge from snowmelt but is not a significant spring. It likely will be eliminated by the <br />facility construction. <br />Spring SPRLC-02 (V30) is located at an elevation of about 6926 ft in Little Collom Gulch near the toe of <br />the temporary spoil pile and in the area of the Section 25 sediment pond. Construction of the sediment <br />pond may affect the discharge zone of this spring. Also, the mine dewatering operations may intercept <br />groundwater that normally discharges at the spring and placement of the temporary spoil may intercept <br />local recharge sources for the spring. As a result, spring flow may decrease during mining operations. <br />Springs SPRLC-03 (V31) and V29 are located at elevations of about 6691 ft and 6845 ft, respectively, in <br />Little Collom Gulch north of the temporary spoil pile and Section 25 sediment pond. Similar to SPRLC- <br />02, they may experience reduced flows as a result of the dewatering operations and placement of the <br />temporary spoil over potential recharge areas. Neither of these springs is a significant feature and V29 <br />was dry during the 2005 and 2006 monitoring events. <br />In Little Collom Gulch, the springs potentially affected by mining operations produced a combined <br />average flow of about 0.16 cfs with a maximum flow of about 0.30 cfs and a minimum flow of about <br />0.015 cfs during the baseline monitoring period. <br />Collom — Rule 2, Page 111 Revision Date: 12/30/16 <br />Revision No.: TR -108 <br />