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Parameter <br />Suspect Level <br />pH <br />Less than 5 or greater than 9 standard units <br />Electrical Conductivity <br />Greater than 12 millimhos/cm <br />Sodium Adsorption Ratio <br />Greater than 15 <br />Colowyo Coal Company <br />2011 Annual Reclamation and Hydrology Report <br />Figure 8 -1— Permit Requirements <br />Overburden Monitoring Program <br />Historically, beginning around 1983, Colowyo initiated overburden monitoring in both the pit <br />(truck/shovel materials) and on regraded overburden. See CDMG Permit Exhibit 6, Item 4 as <br />described in the associated January 4, 1983 Colowyo memo to Dan Mathews, CDMG, for an <br />overview of this initial program. Starting in 1990, Colowyo eliminated the in -pit sampling <br />program. Sufficient data had been collected to indicate that all weathered overburden <br />material (ie. within -- 50 feet of the ground surface) was suitable for replacement onto the <br />reclaimed surface prior to topsoil replacement. Three revisions were submitted to the <br />Division and approved on January 24, 1983, August 17, 1983, April 24, 1990, and PR -02 <br />respectively. The following summarizes the requirements of the current regraded overburden <br />(backfill) sampling program and supersedes all previous commitments. It is based on the <br />following limitations of the earlier program. <br />1. placing weathered overburden material onto reclamation areas prior to final regarding, <br />and <br />2. sampling regraded overburden at a density of one composite surface sample per 5 acres <br />of regraded spoil. <br />The regrading of overburden is an event that takes place sporadically during the year. Once <br />backfill areas are regraded, but prior to topsoil replacement, the new locations are identified <br />and sampled. A life-of-mine sampling grid has been established on 500 -feet centers, and <br />each sample location on the grid corresponds to a letter /number combination as established <br />on the sampling map. Using this grid interval, each sample location represents an area of <br />about 5.7 acres in size. A hand shovel is used to take small, representative surface samples of <br />spoil across the sample area. <br />Regraded Overburden Suspect Levels: <br />The laboratory results are kept at the mine site. Results of the sampling program are <br />provided in the appropriate Annual Reclamation Report and are periodically checked during <br />CDMO quarterly complete inspections. <br />If the results of the sampling indicate that one more of the parameter suspect levels is <br />reached, the Division will be contacted. At that point, Colowyo will resample the area to <br />determine the extent of the suspect material. If the problem area is greater than one acre in <br />size, it will be necessary to cover the area with at least five feet of acceptable material before <br />the application of topsoil. <br />2.05 -8 Revision Date: 03/30/07 <br />Revision No.: PR -02 <br />