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(TSS) levels. Detention ponds will be used to detain runoff water from the disturbed areas to <br />allow the TSS to settle out and to attain acceptable concentrations for other parameters <br />consistent with the requirements of the NPDES Permit. Any Small Area Exemptions (SAE'S) <br />employed will be designed to minimize contributions of TSS to the hydrologic balance. <br />Infiltration and percolation of precipitation in the mine area may be enhanced by the <br />reclamation techniques of contour furrowing on hillsides and the continued excellent <br />revegetation success at Colowyo. Infiltration rates for the pre-mined and post-mine condition <br />of the land were presented earlier. Striffler and Rhodes (1981) showed through field <br />measurements, using an intense rainfall simulation, that infiltration capacities of the mulched <br />and revegetated areas were much greater than the pre-mine estimates. Runoff from the <br />revegetated and contour-furrowed areas has been minor to date, as documented by Colowyo <br />Mine personnel. Flows from Streeter Gulch will be moderated with the detention pond. <br />Moderated flows will continue to pass through the historic drainages. Recharge of the limited <br />groundwater systems in the mine will not be inhibited and may be enhanced through the use <br />of the above techniques. <br />Groundwater protection, per se, is not necessary in the permit area as essentially no <br />continuous groundwater system exists. Perched aquifers of limited nature will be impacted <br />only in the mine area property. This water will be evaporated. The quantity of groundwater is <br />minimal as evidenced by the lack of water in test holes and the dry active pit. <br />Protection of water quality will also be maintained at the present variable limits through the <br />use of the reclamation procedures listed above. Groundwater will not be affected as the <br />supplies are minimal. Surface water will not be significantly impacted in the mine area. An <br />ongoing monitoring program is maintained by the Colowyo Coal Company to verify the <br />conclusions in the permit application. Sampling stations are maintained and samples <br />collected in accordance with the water monitoring plan approved by the Division. Refer to <br />the annual reclamation reports for results of the sampling program. <br />Flow volumes in the Goodspring Creels Alluvial Valley Floor may be impacted by the <br />Colowyo Mine through exercise of water rights. However, the impact is expected to be <br />minimal as the water rights used are owned by the Colowyo Coal Company and are not an <br />integral part of any ranching or farming operation. The Colowyo Augmentation Plan will <br />mitigate the effects on any other water rights and will provide for flows downstream of the <br />affected area. Quality of water in Good Spring Creek will not be affected by the exercise of <br />the water rights. <br />As discussed under Hydrologic Balance-Permit Area, changes in flow volumes caused by <br />mining and reclamation operations will be less than the accuracy range of present day flow <br />measuring equipment. <br />In summary, the Colowyo Mine will not significantly affect the hydrologic balance or water <br />quality of the general area or the permit area and the affect to the hydrologic balance within <br />the permit area will be insignificant. Temporary increases in TDS and associated common <br />ions are expected to affect quality in backfilled spoils within the permit area. Refer to the <br />Annual Reports for additional information regarding hydrologic monitoring. <br />2.05-78 Revision Date: 3/14/08 <br />Revision No.: TR-72