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5 become established, flood debris has accumulated azound their trunks. All of these chazacteristics indicate episodic, but not seasonal, flood scouring of the canyon floors. All of the slopes on the south side of the river valley aze dominated by slide slopes and colluvial fans. Bedrock outcrops aze present, but tend to be less prevalent and higher above the valley bottom than on the north side of the valley. The present course of the river is deeply -incised into Quaternary gravel terraces in a moderately narrow canyon, and Holocene terrace development is present only in a small azea of the extreme northwest comer of the study azea. Most of the valley floor within the study azea has been disturbed by recent landslides or highway construction. Slopes outside the river valley aze generally precipitous. Except for the top of the West Flatiron, most of the study azea is dominated by slopes of 10° to 40°, punctuated by narrow bedrock ridges and deeply incised gulches. Several azeas have slopes in excess of 60°, including sheer cliffs along the western edge of the West Flatiron. There are few azeas of stable sediment, and little potential for in situ cultural deposits. The bedrock mesa of the West Flatiron contrasts with the general pattern. The northwest section of the West Flatiron is more gently sloping bedrock surface, mantled by thin residual soils and oak chaparral. The remaining portions of the flatiron aze crosscut by two drainage catchments, low ridge azeas and open flats. Scrub oak is patchy to open in this area, and sage meadows or wet meadow aze common. This azea includes • extensive azeas of deposition and poor surface visibility neaz seasonal water sources, and is considered the most likely setting for cultural resources in the study azea. The latter azea includes a lazge part of the southeast quarter of Section 23. Recommendations The proposed permit expansion is for underground mining that will involve minimal surface disturbance, including exploratory drilling and surface vents. Previous cultural resource surveys within and near the proposed permit expansion azea were reviewed to assess the likelihood of significant resources within the potential area of effect. The previous) investigations have included samples of all of the environmental settings and terrain types in the expansion azea. The existing sample is adequate for the cultural resources portion of an environmental assessment and for the identification of physical settings that merit additional investigations. In past cultural resource investigations, the general azea outside the principal river valleys has exhibited a very low potential for significant cultural resources. Consequently, it is unlikely that the proposed expansion will threaten significant cultural resources. The narrow canyons and steeply sloping areas in the proposed permit expansion area, including the slide features along the south side of the river valley, have yielded no evidence of in situ cultural resources. A block survey of these azeas would be impractical and unproductive because of the steep slopes, absence of deposition, dense brush and access difficulties. The few historic mines and buildings close to the project azea have been recorded. Cultural resource clearance is recommended for these azeas.