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REFUSE P/LE EXPANSION pond and rock drain system will also be constructed in this area. Historical developments in this area are limited to an old jeep trail through the central portion. Other more recent developments include the building of the relocated Highway 133 in the 1980's. Geologic features identified in [his area include a shallow soil slump and associated hummocky terrain located above a culvert on the embankment of [he Hiehvvay 133 right-of--way. Proposed RPE construction activities will effectively reinforce this area and improve stabiliryas shown in Appendix K. The only hydrologic feature identified was a wetland immediately south of [he Highway 133 embankment. The depression is apparently an erosional feature of the North Fork of the Gunnison River which occurred earlier in the history of the Gunnison valley. The feature became isolated as a result of construction of the Highway 133 road embankment and formed a wetland. The approximate size of this wetland is 0.88 acres. Surface waterflovv through this area appears relatively stagnant, but moving in a northwest direction through a partially plugged culvert extending under Highway 133 and exiting into the ' 'North Fork of the Gunnison River. See Appendix M ~•''for the investigation of this wetland. Minor ephemeral hydrologic features were mapped within [he RPE staging area to include drainages extending from the north slope. 5.3.3.4 Upper RPE Area The upper RPE area extends from the base of the lower Wes[ Flatiron slope to the upper contour elevation of 6400 feet MSL. It is controlled by the ridge linesofthe Sylvester Gulch corridor on the west and the unnamed drainaee on the east. This area will be affected by [he upper advancing stages of [he RPE. There are no recognizable historical developments on (e.g. trails/roads)this slope. Fottr major gef7logical features were identified and mapped within the limits of the slope. All four geologic features can be described as block-type, deep seated landslide failures (4' to 16') located between the general elevation of 6200 and 6320 feet MSL. The general failure mechanism for these landslides is the movement of colluvial soils away ., •from the base of the outcropping sandstone bedrock located at a general elevation of 6300 feet. The overall failure mechanism for these landslides is the rapid movement of meteoric (rain or snow melt) water across the face of the exposed sandstone bedrock, saturating underlying colluvial soils. Springs noted on the north slope are associated with these large landslide failures. The springs tend to occur downgradient of the moving soil mass. Four minor soil disturbances were also noted on the north slope. Their locations were relativel}• unevenly distributed in reference to landsliding and were characterized by shallow surficial slump and erosion (12" to 21 ")with associated hummocky retrain. A geologic feature composed of loosely consolidated sandstone boulders was also mapped within the perimeter of the proposed RPE, along the east side of the north slope. This area is apparently a rockslide/landslide that failed much earlier in the geologic historyofthe Gunnison Valley. Hydrologic features observed on the north slope included five springs. The five springs were seeping at the time of the field investigation. As previously mentioned, [he five springs are associated with large landslide failures. Smaller hydrologic features are the ephemeral drainage's running perpendicular to the slope. 5.3.4 Summary The following is a summary of [he findings of the geologic engineering mapping of the proposed RPE shown on Figure J- l . • The proposed RPE site and topsoil/subsoil storage area is currently undeveloped. The two most prevalent obstructions are an overhead power line in the proposed topsoil/subsoil storage area, and [he wetland believed to have been created by the constructionof Highwav 133. • Onsite surface soils consist predominantly of colluvial clay, gravel and sandstone boulders and bedrock. Identified geologic features include four block-type deep seated landslide failures. These failures are located on the north slope of the West Flatiron. In addition there are six minor soil disturbances and two mudflows within the area designated for the Harding Lawson Associates 6