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C.R.S. 34-33-114(2)(c) and Rule 2.07.6(2)(c), that the operation has been <br />designed to prevent material damage outside the permit azea. <br />III. ~ snil-Rule 4.Ofi <br />Soils resource information is found in Volume 3, Section II.I, of the permit application. <br />Removal, storage and redistribution of topsoil is addressed in Section V, of Vol. 4, with <br />supplemental information regazding refuse azea topsoil and subsoil salvage volumes <br />presented in Appendix IV A, of Section N, Vol. 4, of the application. <br />Topsoil replacement thickness is presented in Table V-4. Replacement thickness will <br />vary among different facility azeas depending on quantity available for salvage. Within <br />the refuse areas, a minimum of 1 foot of topsoil will be replaced, with a minimum non- <br />toxic cover (topsoil plus subsoil) thickness of 30 inches. The operator has committed <br />within Section IV.D.3 of the application, to document topsoil cover soil material balance <br />as future refuse area development and reclamation occurs, to ensure that sufficient <br />quantities of suitable topsoil and subsoil aze being salvaged. <br />Vegetation cover within a significant portion of the acreage to be affected by future refuse <br />azea development is dominated by cheatgrass (Bromus tectorum), an aggressive, weedy <br />annual brome. cheatgrass infestation has been noted on several of the long-term topsoil <br />stockpiles in the refuse disposal azea, and has also been a problem on RP-1 permanent <br />reclamation. cheatgrass is notably less prevalent on subsoil stockpiles (appazently due to <br />seedbank chazacteristics, or specific soil factors). In order to minimize the potential for <br />cheatgrass establishment and dominance on future reclaimed areas at the refuse disposal <br />site, the operator has committed, within Section V.H, to reverse the sequence of soil <br />replacement (i.e. replace subsoil over cheatgrass infested topsoil) during refuse area final <br />reclamation. In order to evaluate the factors that may be limiting to cheatgrass <br />germination and establishment, the operator has committed to initiate studies, which will <br />include field trials as described on page V-33. It is possible that intemal topsoil from <br />long-term stockpiles could be used as topdressing, due to the minor component of viable <br />cheatgrass seed that would persist at depth in the piles. The field trial plots, which will <br />include "subsoil over topsoil", "intemal stockpiled topsoil over subsoil", and a "blended <br />mixture of live topsoil and subsoil over subsoil", will be constructed during the next <br />available cycle of refuse area reclamation. Handling of cheatgrass infested soils will be <br />modified in the future if field trial results demonstrate that an alternative approach is more <br />appropriate. <br />The Division finds that the proposed "reverse sequence soil replacement" plan, in <br />conjunction with the proposed field trials, is appropriate for refuse area reclamation, <br />pursuant to 4.06.2(4)(a). This finding is based on field observations of topsoil and subsoil <br />stockpile vegetation cover, evaluation of topsoil and subsoil chemical and physical <br />chazacteristics, and observation and evaluation of RP-1 revegetation data. The subsoil will <br />be more suitable for sustaining desired vegetation than is the available cheatgrass infested <br />topsoil. <br />34 <br />