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i <br />3.5 oints <br />~• <br />Joints, bedding planes, and intersections of these planes define weaknesses in the <br />l rock. They create potential hazards if their orientations are adverse with respect to the cliff <br />l face. <br />This section deals with general observations on jointing. The details of the <br />1 mapping program are given in Section 4 and summarized in Tables 1, 2 and 3. Seven <br />relatively strong joint sets were observed and measured. Two weaker sets were also <br />2 identified. All joint have similar characteristics. A11 sets contain joints that are both tight or <br />open, both filled or not filled, and both planar or wavy. Engineering analyses of these joints <br />1 and stability calculations with respect to the cliff face and to subsidence are described in <br />l Section 5.0. <br />1 <br />In this general discussion of joint sets, reference may be made to Figure 6 and <br />,• Table 2. A prominent joint set is oriented approximately N59E, 81E (Set No. 2). The set is <br />parallel to and controls the orientation of the cliff's face and its near-vertical slope along its <br />northeast strike (Hazard Zones Sb, Sc and 6). To the west, where the ridge is eroded, the <br />dip of the rocks controls the topographic expression although the joint set is still present. <br />The faces of these joints range from planaz to irregulaz to wavy. The amplitudes of the <br />waviness range up to an estimated 3 feet, peak to peak. The origin of this joint set is <br />unknown, but there are additional parallel extension joints along the free surface of the <br />1 northwest-striking cliff face suggesting that this set may be related to stress relief. <br />Another joint set oriented N66W, 84W (Set No. 7) is also present throughout the <br />area, but appears to be prominent in the western area (Hazard Zones 1 and 2). This joint set <br />J has the same approximate strike and dip as the faults and may be related to them. The <br />higher frequency of these joints in the western area suggests the presence of a fault but it <br />1 may be buried in the alluvium farther to the west. <br />,~ 9 <br />