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E. Acid-forming and Toxic-forming Spoil <br />1. Pre-law spoil material was utilized to achieve the post-mining <br />topography and cover the underground development waste pile with <br />four feet of cover. A 1988 renewal adequacy issue concerned the <br />validity of the use of two chemical analyses of pre-law spoil <br />samples which had been taken from the top four inches (4") and <br />showed no elevated parameter levels. The operator sampled three <br />additional sites, compositing the top three feet of material. <br />One of these samples had a pH of 4.6 and an electrical <br />conductivity of 9150 umhos/cm. The results of this testing led <br />to the Division's request that the operaCOr develop a plan to <br />mitigate the presence of acid-forming spoil on the regraded <br />surface. <br />The Division approved the applicant's plan for disposal of <br />debris, acid-forming or toxic materials, or materials <br />constituting a fire hazard in a manner designed to prevent <br />contamination of ground or surface waters. The operator <br />committed to bury known acidic spoils, per their plan in Rule <br />2.05.4 (2)(e)(vi), and amend the regraded spoil if necessary. <br />Regraded spoil samples taken by the Division in 1989, as well as <br />subsequent quantitative and qualitative assessment of vegetation <br />establishment, have not indicated the presence of deleterious <br />root zone materials. <br />2. The Division proposes to approve the method and design <br />specifications for covering of acid-and toxic-forming materials <br />in order to prevent leaching into surface and ground water and to <br />ensure backfill stability. The operator will bury known acidic <br />spoils below the rooting depth and above the water table, per <br />their plan in Rule 2.05.4 (2)(e)(vi) (4.14.3(2)). <br />F. Impoundments <br />1. Refer to the section regarding sediment ponds (4.05.9). <br />2. The Division has approved retenCion of the existing sediment pond <br />as a permanent impoundment, and makes the following specific <br />findings pursuant to Rule 4.05.9(1), on the basis of information <br />provided by the applicant: <br />(a) The quality of the impounded water will be suitable on a <br />permanent basis for its intended use, and discharge of water <br />from the impoundment will meet applicable State and Federal <br />water quality standards. The source of impounded water is <br />primarily irrigation runoff from agricultural fields located <br />higher in the watershed. The operator collected a water <br />sample from irrigation water stored in the pond in the <br />summer of 1997, and submitted analyses to the Division in <br />August, 1997. Based on the data submitted, water quality is <br />suitable for the postmining use, with all applicable <br />15 <br />