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RULE 4 PERFORMANCE STANDARDS <br />! 4.05.10 Underground Mine Entry and Access Discharges <br />Colowyo currently conducts surface coal mining exclusively. <br />4.05.11 Groundwater Protection <br />There are no aquifers or continuous sources of groundwater within the stratigraphic section from <br />which the Colowyo Mine mines coal using surface mining techniques. This is also noted in <br />Section 2.04.7. In addition, there are no continuous aquifers of regional extent within the entire <br />Williams Fork Formation in the location of the Colowyo Mine. Occasionally, a minimal amount <br />of water is found under perched conditions in noncontiguous lenticular sandstones and in <br />fractured coal under the sandstones. No toxic concentrations of acid - forming materials have been <br />found in the overburden, reclaimed slopes or surface and groundwater system associated with the <br />Colowyo Mine. No adverse effects on groundwater quality are expected to occur due to mine <br />excavations or backfilling. <br />4.05.12 Protection of Groundwater Recharge Capacity <br />The reclamation plan as described in 2.05.4 will return the disturbed lands to approximately the <br />pre- mining condition; therefore, groundwater recharge capacity is expected to approximate the <br />pre- mining condition. Also, because of the minimal existence of ground water in the mining area, <br />the mining operation and subsequent reclamation should have no adverse effect on the existing <br />groundwater recharge capacities. <br />0 4.05.13 Surface and Groundwater Monitoring <br />The proposed monitoring program below will supplement the existing monitoring program to <br />enable assessment of the effects of mining in the Collom permit expansion area. This section is a <br />supplement to Section 4.0 5.13 of Volume 1, as amended. Colowyo proposes monitoring the <br />following sites: <br />Sedimentation Ponds - The proposed surface water monitoring plan includes monitoring <br />required under the NPDES) Permit Number CO- 0045161 issued by the Colorado Department <br />of Public Health and Environment. Colowyo will measure the quantity and quality of any <br />discharges from the permit area in compliance with the NPDES Permit and in accordance <br />with permit requirements. Please refer to Colowyo's discharge permit for a list of monitored <br />parameters. <br />Colowyo will report the discharge in accordance with the Clean Water Act of 1977 under the <br />NPDES Permit on a quarterly basis; therefore, Colowyo will plan to use the NPDES report <br />for filing with the Division. All surface water and shallow groundwater monitoring data is <br />submitted in an annual report. Annual Hydrologic Reports for the period of January 1 S ` <br />through December 31 will be submitted by April 1" of the following year. <br />At various times, due to unforeseen circumstances, Colowyo will obtain and discharge water <br />under a CDPS minimal discharge permit. In the event that water is discharged under a <br />minimal discharge permit, Colowyo will report the discharge in the corresponding Annual <br />Hydrologic Report. <br />Collom — Rule 4, Page 11 Revision Date: 1/23/09 <br />Revision No.: PR -03 <br />