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April 28, 2004 <br />Page 4 of 5 Pages <br />Rule 4.05.14(4)(c)(iii): If required by the Division, a written interpretation of the data and <br />identification of mining related impacts to the hydrologic balance. <br />The report is in compliance with this rule. The Division required no written interpretation ofthe data. <br />However, Colowyo has provided a general discussion of where monitoring reports are, and general <br />trends of changes in water quality. <br />One of the stream classifications (Colorado Division of Public Health and Safety) for Good Spring <br />Creek and Taylor Creek is agriculture. The Division identifies 1000 umhos/cm conductivity of <br />irrigation water as a suspect level for damage to vegetation. From the report, laboratory values of <br />Good Spring Creek above mining (at the New Upper Good Spring Creek monitoring station) average <br />(linear) in the 1500 range. At the Lower Good Spring Creek monitoring station, below mining, <br />laboratory values average (linear) in the 1700 range. Historically, average linear values have run <br />about 200 umhos/cm higher at the lower monitoring station. Conductivity has been rising over time <br />at both monitoring stations, slightly faster at the lower site. Average (linear) laboratory values of <br />conductivity at the Lower Taylor Creek monitoring station have risen, over time, from 1400 to 1800 <br />umhos/cm. <br />The probably hydrologic impact (PHC) from mining activities [Permit, page 2.05-75; Rule 2.05.6(2)] <br />is that "Surface water will not be significantly impacted in the mine area". The PHC continues <br />(Permit, page 2.05-75) "In summary, the Colowyo Mine will not significantly affect the hydrologic <br />balance or water quality of the general area or the permit area and the affect to the hydrologic balance <br />within 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." From information <br />available at this time, this review concludes that the impacts on water quality and quantity from <br />mining activities as the Colowyo Coal Mine are within the probable hydrologic consequences as <br />permitted. <br />file: C-1982-0192003AHR <br />C:\bgw\My Documents\Colowyo\ahr & arr\ahr03rvw.doc <br />