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Slopes shall extend from proposed casing invert elevation to existing ground level. Slopes are not required in solid rock. In lieu of constructing slopes as above, the pit walls may be shored, sheeted, braced or otherwise supported by means of sufficient strength to protect the employees and inspectors working within them. 2) Pit Floor Stabilization - Where necessary to ensure a solid, stable base for boring machinery, some means of stabilizing the pit floor rmust be provided. Stabilizing may vary depending upon job site condition, from timber supports under tracks, addition of clean sand or gravel to pit floor, or in some cases the construction of concrete slabs on the pit floor. Al stabilizing materials other than sand, gravel and like materials must be removed upon completion 1 of the project. E. Equipment Set Up 1) Aligning and leveling of auger tracks - To properly control line and grade during the crossing operation, it is imperative that the jacking unit tracks be rigidly set to the predetermined level and alignment requirements of the job. Control should be ensured by the use of appropriate engineering instruments. 2) Auger and casing section lengths should be determined prior to beginning the crossing operation to ensure that the leading end of ithe first casing section will not be under, or within three (3) feet of any Roadway Pavement when the crossing operation is halted to joint new auger and casing sections. As an exception, in areas where jacking pit space is restricted by narrow right -of -way, or obstructions and will not allow continuous operations under paved areas as stipulated in this section, all preparations for adding additional casing and augers should be made prior to stopping under the pavement and the joint made as quickly as possible. Crossings made by closed end jacking method or crossings made in materials other than loose unstable soils, are not subject to the provisions of this section. 3) Methods of Reducing Skin Friction - Friction between the outer surface of the casing and the surrounding soil may be reduced by increasing the diameter of the casing hole by nor more than 3/4 I09/03 16200 -10 03- 1438.A -R