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- 11 - <br />• with a large amount of gravel, pebbles and boulders. Most <br />f <br />h <br />l <br /> t <br />e grave <br />o <br />material is derived from lava rock; the <br /> material has the appearance of a basalt. Many of the boul- <br /> ders are slightly rounded; their sub angularity has been <br /> probably caused rather by weathering than by transport. The <br /> diameter of the boulders frequently exceeds 1 foot. Typical- <br /> ly, one foot diameter is most frequent. <br /> The cut carries several signs of instability. Small <br /> slides and sloughs have developed both in rock and in soil <br /> along the cut face. The largest area of instability is con- <br /> centrated on the middle part of the cut which has been ex- <br /> cavated in colluvial soils. This area is indicated on the <br /> geotechnical map; it is located directly above the fan and <br /> the intake shaft. A series of minor slides developed in this <br /> cut portion; these slides are located in the upper third or <br /> half of the slope. They do not extend all the way down to <br />• the toe of the cut. <br /> A larger slide reaching to the toe of the cut has <br /> developed in a very similar manner above the proposed tank. <br /> A very small slide or slough is visible within the western <br /> buried channel, close to the crest of the cut. <br /> Two minor instability features can be documented also <br /> in the cut portion that was excavated in rock. Both of them <br /> are located close to the east end of the cut in a fairly sharp <br /> bend above the channel. Both of these features have a very <br /> similar character: they comprise a developing rock slope <br /> failure where a layer of a more competent sandstone deforms <br /> along the underlying, softer layer of shale. As a result of <br /> these deformations, the upper cut portion loses its support <br /> and a slide slowly develops. <br />1 <br />• All these instability features indicate that the over- <br /> ceo•NmQO coKwure. ANC. <br />