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RULE 4 PERFORMANCE STANDARDS <br />4.15.8 Revegetation Success Criteria <br />Colowyo will meet the requirements of this Subsection to insure that the post- mining vegetation <br />in the Collom mining area will be adequate for final bond release. As delineated under Subsections <br />4.15.7 and 2.05.4, Colowyo will utilize established reference areas (see Section 4.15.7 above) for the <br />purpose of comparing vegetation information between the reclaimed area and the undisturbed area for the <br />variables of ground cover and production. For the variables of woody plant density and species diversity, <br />Colowyo shall compare revegetated area parameters against defined standards detailed later in this <br />section. Data to be used in these comparisons must be from statistically adequate sampling (where <br />necessary) as indicated in Rule 4.15.11. In instances where grazingland targeted reclamation areas <br />exhibit the characteristics of the sagebrush steppe areas and can meet the release standards for core or <br />ecotonal sagebrush steppe, Colowyo will seek release and credit for the creation of those areas towards <br />fulfillment of the minimum habitat development requirement (350 acres). In the unlikely but not <br />impossible event that areas targeted for sagebrush steppe display community characteristics that will not <br />meet the sagebrush steepe area release criteria but do for the grazingland criteria, Colowyo will designate <br />those acres as grazingland. Colowyo will have to specifically designate the location of both grazingland <br />and sagebrush steppe areas prior to the initiation of phase III bond release data collection. For descriptive <br />purposes, "evolved" sagebrush steppe areas refer to lands originally seeded to grazingland that exhibit <br />sufficient community characteristics of the sagebrush steppe community to be fully released as either core <br />or ecotonal areas. Areas defined as "targeted" sagebrush steppe are by definition the areas originally <br />seeded to the sagebrush steppe plant community that exhibit the characteristics of that community and <br />meet either the core or ecotonal requirement for full release. <br />Herbaceous Cover <br />For revegetation targeting (and achieving) the land use subcomponent of rg azin lg and herbaceous cover <br />of the revegetated area will be considered adequate for final bond release if it is not less than 90% of the <br />herbaceous cover as determined from the reference areas with a 90% statistical confidence utilizing a <br />standard students statistical t -test comparison of the means. As allowed under the rules promulgated on <br />9/14/05, these comparisons may utilize one of three methods detailed under Rule 4.15.11 (2) [(a), (b) or <br />(c)]. Also as allowed by Rule 4.15.7 (4), either weighted- average or individual protocols will be followed <br />depending on the resulting community that evolves (see Section 4.15.7 above). For grassland testing the <br />weighted average approach (Rule 4.15.7 (4) (b)) will be utilized where reference area data and <br />revegetated area data are "weighted" (each combined into single values for comparison) based on the <br />proportional acreage of pre -mine communities within the disturbance area footprint. Testing will then <br />follow procedures detailed under Rule 4.15.11 (2) with preference being given first to subsection (a) <br />[direct comparison], second to subsection (c) [reverse -null testing], and third subsection (b) [classic t- <br />test]. <br />For "targeted" sagebrush steppe revegetation ( targeting the land use subcomponent of wildlife habitat <br />herbaceous cover will be considered adequate for final bond release if it is not less than 70 % of the <br />sagebrush reference area's herbaceous cover with a 90% statistical confidence utilizing a standard <br />students statistical t -test comparison of the means. If necessary, a reverse -null hypothesis testing <br />procedure may be utilized in accordance with procedures detailed in Rule 4.15.11 (2) (c). As allowed <br />under Rule 4.15.8 (3) (ii), relaxation of the herbaceous cover standard for areas targeting wildlife habitat <br />• The value of 70% has been selected given the following rationale: 1) herbaceous competition must be significantly <br />restricted to facilitate emergence and growth of shrubs as indicated under Rule 4.15.11 (3) (ii); 2) the original value is <br />90 %; 3) a value of 50% seems too low to adequately control erosion; 4) by regulation (4.15.11 (3)(a)) a reduction to <br />70% is allowed for one of the demonstrations for revegetation success for woody plant density; and 5) 70% of the <br />herbaceous material in a native reference area should be adequate to control erosion on slopes 10% or less. <br />Collom — Rule 4, Page 34 Revision Date: 1/23/09 <br />Revision No.: PR -03 <br />