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• The upstream limit of the alluvium as mapped (based on flood <br />plain and channel meander features) terminates at approximately the <br />confluence of the North Fork and Middle Fork of Bolton Draw. There <br />is not a precise upstream contact between the alluvium and the surr- <br />ounding uphill terrain in this vicinity, but rather the contact is <br />very gradiational. However, from this point (approximately 300 feet <br />upstream from Weir #1), the North Fork of Bolton Draw has no recog- <br />nizable channel for a distance of at least 300 feet. The channel <br />picks up again at this point and continues up to the vicinity of the <br />M&T access road where it has become deeply incised. This is probably <br />the result of the reduced sediment load of surface runoff because <br />the road has acted as a dam causing sediment to drop out of suspension <br />before being discharged from the culvert. <br />The channel continues upstream past the M&T access road contin- <br />ually narrowing until it again disappears about 500 feet before it <br />reaches the southern boundary of the lease area (C-30168). Although <br />• the North Fork of Bolton Draw exhibits a definite channel in some <br />places upstream of Weir #1, it does not exhibit any active or <br />inactive flood plains, terraces, abandoned oxbws or other similar <br />geomorphic characteristics indicative of alluvial valley floors. <br />Partially within Pit 2 and extending downstream to about the <br />M&T access road, there is mapped a second unit of alluvium which is <br />isolated from the unit further downstream. This area has been <br />mapped as an unnamed alluvium (Unit 8 on the soil map, Appendix E). <br />This soil which is composed of thick quantities of silt, has a large <br />water holding capacity and does contain some groundwater. This <br />minor pocket of perched alluvial groundwater is, however, isolated <br />from the main water table aquifer occuring downstream in the vicinity <br />of Well 2. This soil type was probably formed as the result of <br />water enhanced erosion off the steep P,illsides on the north side of <br />the draw. As the runoff (which is laden with suspended solids) <br />reaches the break in slope near the bottom of the hill the heavier <br />~ • <br />-109- <br />