2010-11-22_REVISION - M2009023 (6)

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Final Mitigation Plan for Long Hollow Reservoir La Plata River Mitigation Site (Permit No. 200375243) end of the pond. Weeds have been managed at the site by Skanska USA under the direction of the Colorado Division of Reclamation, Mining, and Safety (CDRMS) and the existing mine permit. The wetlands south of the site along the La Plata River are dominated by sedges (Carexspp), spikerush, Baltic rush, foxtail barley, horsetail (Equisetum arvense), narrow-leaf cottonwood (Popu/us angustifo/ia) and sandbar willow (Sa/ix exigua) (see Appendix C). Based on the Soil Survey of La Plata County Area. Colorado (NRCS 1981), soils in the wetlands and mitigation area include fluvaquents, sandy, frequently flooded, and Sycle fine sandy loam. The fluvaquents are described as a deep, somewhat poorly drained soil formed in recent alluvium. They are extremely variable in texture and have a fluctuating water table 12 to 40 inches deep. The Sycle soil is described as a deep, well-drained soil on terraces with a fine sandy loam surface horizon underlain by sandy clay loam and gravelly sandy loam. The water table is relatively deep beneath this soil. Most of the soil in the wetland creation area has been disturbed, and the existing soil is reportedly reject material from the mine along with some topsoil. Observations indicate that the soil in the area contains sand and gravel with some fines. 2.5 Credit Determination Methodology The mitigation being proposed at the LPRMS is wetland creation. Regulatory Guidance Letter 02-02 (RGL 02-02), which was issued on December 24, 2002, provides guidance for determining compliance of proposed mitigation projects with the national policy of "no overall net loss" of wetlands and aquatic resources under Section 404. RGL 02-02 requires that a watershed or ecosystem approach be taken when determining compensatory mitigation requirements, consistent with the "operational guidelines" developed by the National Research Council (NRC) in 2001. Furthermore, impacts and compensatory requirements should be determined through functional assessment, such as the Hydrogeomorphic Assessment Method, Wetland Rapid Assessment Procedure or other method. The functional assessment scores should demonstrate that the functions lost by the impacted wetlands (and other aquatic resources) will be fully replaced by the proposed mitigation. The following approach was taken to show compliance with RGL 02-02: 1) a functional assessment was completed to compare the functions of the impacted wetlands to the proposed mitigation and 2) the mitigation was evaluated for consistency with the guidelines in the RGL, August 2010 Bikis Water Consultants, LLC Page 6