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CaalMet/wne Drarnoge Plnjee - Pane4 16-74 West E/k Mine f PoBe 3-6 characteristic understory vegetation or distinct vegetation changes. Based on these site-specific surveys, riparian areas typically extend along part or the entire bottoms of perennial and intermittent drainages, varying in width from 25 to 100 feet and, in some cases, including small ponds and small isolated wedand areas. Many of the smaller ephemeral drainages may have no flow for several consecutive yeazs and contain limited or no riparian areas. Appendix B displays Special Stipulations that apply to riparian areas (Section 15, Item (b)(2)). The stipulation states that "A 1/8 mile buffer zone (660 feet) will be protected on either side of riparian zones (or a buffer zone may be established in accordance with the surface management agency guidelines). No surface disturbances, except surface subsidence, will be permitted within these buffer zones, unless no practical alternatives exist" Fox this project, the USFS has replaced the 1,320 foot buffer zone with the buffer Zone that is prescribed in the Forest Service Watershed Conservation Practices Handbook (FSH 2509.25), the Water Influence Zone (WIZ). The WIZ includes the geomorphic floodplain, riparian ecosystem and inner gorge. Its minimum horizontal width (from top of each bank) is the greater of 100 feet or the mean height of nature dominant late-seral vegetation, It includes adjacent unstable and highly erodible soils (Reid and Ziemer 1994). WIZ azeas are shown on Map M1, Project Area Activities With Surface Stipulations 3.1.2 Environmental Consequences 3.1.2.1 Effects Common to Alternatives 2, 3, 4, and 5 Soil removal, stockpiling, and replacement, along with consequent compaction and erosion would change soil characteristics in affected areas. Although dismrbed areas can be reclaimed and rehabilitated, the soil productivity will be changed. The potential for impacts on subsurface geology from the proposed activities is considezed to be negligible. The drilling activity itself and proposed methane drainage measures would not affect geologic conditions or materials. The Conditions of Approval listed in Section 2.4 of this document include many measures designed to minirnize soil disturbance. Despite these practices, erosion, soil loss, and sediment transport from newly disturbed areas would still affect nearby drainages. Depending on proximity to streams and the amount of sediment cazried by runoff, surface water quality (turbidity and suspended solids) could be temporarily impacted. No bedrock aquifers aze expected to be intercepted during the proposed drilling operations, however, shallow colluvial or perched ground water could be encountered. Those drill pads located near drainage bottoms would be most likely to encounter ground water. Drilling operations would use circulation media including air, water; and biodegradable polymer foams. Gels, surfactants; and bentonite-based drilling muds would also be used to stabilize boreholes, if necessary. Other materials, including crushed peanut shells, cottonseed hulls, and cedaz fibers could also be added to the circulation medium to help seal the walls of the hole to maintain circulation and minimise loss of drilling fluids to the formation. These materials would normally maintain pressures in the boreholes adequate to prevent substandal ground water inflows to the boreholes if water is encountered. If substantial quantities of water were encountered in any borehole, high-density additives would be introduced with the circulation media to contain the water flows, and casing would be extended and cemented in place to case off the flow source. Casing of the MDWs would prevent deterioration of the borehole, and cementing [he casing in the borehole would prevent flow of either gas or water in the annulus between the casing and borehole and prevent contamination of ground water or mixing between ground water sources. It is anticipated that these standard drilling and completion measures would be effective in preventing or controlling any project-related effects to ground water quantity or quality. Enuironmenta/A.frexment W:¢'-/Nwv. GdG/E.1/ate )l!/0?l:'r VfFf i/1/OS iEr