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VI <br />J &T Consulting, Inc. <br />November 22, 2013 <br />Mr. Tyler O'Donnell <br />Environmental Protection Specialist <br />State of Colorado <br />Division of Reclamation, Mining, & Safety <br />1313 Sherman Street — Room 215 <br />Denver, CO 80203 <br />c'iZ� 1p13 <br />Np� 21 <br />RE: GP Aggregates, LLC. — West Farm Pit — Technical Revision No. 2 Request <br />File No. M- 2008 -078 — Response to Second Adequacy Review <br />Mr. O'Donnell, <br />We have received the Division's Technical Revision No. 2 Second Adequacy Review comments <br />relating to GP Aggregates, LLC's (GP) permit number M- 2008 -078. GP offers the following <br />responses addressing the Division's comments. <br />1. Please commit to monitoring groundwater elevations upgradient and downgradient of the West <br />Farm Pit. Please depict on a map a few possible locations for groundwater monitoring wells. <br />Please commit to monitoring groundwater elevations quarterly and reporting the results to the <br />Division annually. <br />GP commits to monitoring groundwater elevations upgradient and downgradient of the pit. <br />Attached is a map that was included in the original application that depicts where four <br />monitoring wells are currently installed around the perimeter of the pit. GP has installed three <br />wells (GP MW -1, GP MW -2, & GP MW -3) on the south, west, and east sides of the pit <br />respectively. The Town of Lamar has a monitoring well located on the north side of the pit. The <br />Town of Lamar has agreed to provide their groundwater depth readings for this well to GP. <br />GP commits to monitoring groundwater elevations quarterly and reporting the results to the <br />Division annually. <br />5. Where are the subsurface utility lines in relation to the critical surface on the cross section? Please <br />provide discussion for how this area between the two reservoirs (and the utilities /roadway) were <br />analyzed. Identify and discuss the potential failure scenarios that could impact these structures. <br />There are no subsurface utility lines within this cross - section or anywhere between the two <br />proposed reservoir cells. <br />The stability analysis for the condition of the two adjacent reservoirs was conducted by <br />maintaining one reservoir at the maximum water elevation and lowering the water level in the <br />adjacent reservoir in a rapid drawdown condition. This represents the worst case scenario for <br />S', 305 Denver Avenue, Suite D • Fort Lupton, CO 80621 • Ph: 303 - 857 -6222 • Fax: 303 - 857 -6224 <br />