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Shallow overburden Unit 4 material (Tab 13, p. 13-3a) displays geochemical and <br />lithologic characteristics which indicate that this material will be <br />unsuitable as a plant growth medium. Therefore, this material will not be <br />placed within four feet of the backfilled area surface. Mixing of this <br />material with other overburden zones upon backfilling of each mining pit will <br />mitigate any potential ground water recharge contamination. <br />Deep overburden Class 4 material (Tab 13, p. 13-3) displays geochemical and <br />lithologic characteristics which make this material unsuitable as a plant <br />growth medium. This material will not be placed within four feet of the <br />backfilled area surface. This material also displays acidity limitations <br />which may degrade ground water recharge. Therefore, the Class 4 material will <br />be placed not less than ten (10) feet from the bottom of any mining pit. <br />To ensure the adequacy of the special handling plan, Peabody will conduct a <br />spoil quality sampling program in the backfilled areas of the mine. The upper <br />three feet of spoil will be sampled on a 300 foot grid for pH, acid base <br />potential, salinity, and particle size. If unsuitable material is identified, <br />appropriate mitigative measures will be implemented, as described in Volume 2, <br />Tab 6 of the permit application. <br />The operation is in compliance with the requirements of this section. <br />V. Surface Water Hydrology - Rules 2.04.5, 2.04.7, 2.05.3(4), 2.05.6(3) and <br />4.05 <br />Information on surface water hydrology can be found in Tab 7, Volumes 3 <br />through 6 of the permit application. Section I (Volume 3, p. 7-1 to 7-41A) <br />provides a description of regional hydrology and baseline monitoring data. <br />Section Y (Volume 3, p. 7-69 to 7-191) provides an updated discussion and <br />evaluation of data collected through 1986. <br />Surface water at the Nucla Mine drains into Tuttle Draw, a tributary of the <br />San Miguel River in west-central Colorado. Irrigation return flow is an <br />important component of runoff from the mine site in terms of water quality <br />considerations. The Lower Second Park Irrigation Ditch traverses the site <br />above most of the mining disturbance. Seepage losses from the ditch arise as <br />Springs and seeps at lower elevations and contribute to baseflow in surface <br />streams. The drainage from the northern portion of the permit area is <br />referred to as the West Return Ditch. This drainage meets Tuttle Draw to the <br />south before it leaves the permit area. Tuttle Draw flows in a southwesterly <br />direction about 2.5 miles before it enters the San Miguel River. <br />Runoff from the disturbed area within the Nucla Mine is controlled by a number <br />of sedimentation ponds at the mine. As a part of the Permit Revision No. 1 <br />application review, all of the ponds on site were reevaluated as to sizing <br />requirements, discharge structures and detention time provided in the design. <br />Previously, Peabody was granted a variance from the design requirements of <br />Rule 4.05.6 for Ponds 002-007 because they were located below areas of pre-law <br />disturbance or previous reclamation activities. With the change in mining at <br />the site, these ponds (except Pond 003) were upgraded and now meet the design <br />requirements of Rule 4.05.6. Pond 003 has not been upgraded and will still <br />-11- <br />