Laserfiche WebLink
<br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br /> <br />older medium grained granite. Near the contact, dikes ranging from a <br />few feet to a few inches in width can be traced in irregular patterns <br />through the older rock. The texture of this unit varies erratically <br />from very fine grained, to irregular clusters of macro crystals. In <br />addition to the regional jointing described above for the older gran- <br />ite, the intrusive granite has been intensely fractured, probably as a <br />function of the rate of cooling of the intrusive material. Swarms of <br />fine, closed incipient joints occur parallel to the contact with the <br />country rock with chaotic1y oriented discontinuous joints distributed <br />perpendicular to it. Even though the rock exposed in the outcrops is <br />massive it breaks easily along the closed joint planes when impacted by <br />a hanmer. <br /> <br />A third granitic unit was identified in several locations in the form <br />of dikes cutting through the two older units. The rock is a dark grey, <br />medium grained granite composite of about 50 percent biotite. The <br />dikes are thin, up to 1 foot, and are not highly fractured. <br /> <br />The valley floor is composed of recent stream alluvium consisting of <br />angular to subangular cobbles and sand derived from the adjacent <br />igneous/metamorphic complex. The alluvium is overlain by up to three <br />feet of black, highly organic top soil. <br /> <br />B. Initial Materials Investigations <br /> <br />1. Subsurface Investigation - The subsurface investigation at <br />Site B consisted of seismic refraction lines along the axis and perpen- <br />dicular to the axis in the valley floor. This was supported by three <br />rotary boreholes drilled along the centerline, one on each abutment and <br />one in the valley floor. The location of the seismic lines and bore- <br />holes at Site B are shown in Exhibit 3-6. In addition a seismic <br />refraction survey was made of the left abutment and spillway alignment <br />at Site A. The locations of these lines are also shown in Exhibit <br />3-6. The borehole logs, field test data and interpretation of the <br />seismic refraction are illustrated in cross section in Exhibits 3-7 and <br />3-8 respectively for Sites A and B and are discussed below. <br /> <br />3 - 9 <br /> <br />6819W/502OW <br />