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1 <br />alignment requirements of the job. Control should be ensured by <br />the use of appropriate engineering instruments. <br />2) Auger and casing section lengths should be determined prior to <br />beginning the crossing operation to ensure that the leading end of <br />' <br />the first casing section will not be under, or within three (3) feet of <br />any Roadway Pavement when the crossing operation is halted to <br />joint new auger and casing sections. As an exception, in areas <br />' <br />where jacking pit space is restricted by narrow right -of -way, or <br />obstructions and will not allow continuous operations under paved <br />areas as stipulated in this section, all preparations for adding <br />additional casing and augers should be made prior to stopping <br />under the pavement and the joint made as quickly as possible. <br />Crossings made by closed end jacking method or crossings made <br />in materials other than loose unstable soils, are not subject to the <br />provisions of this section. <br />3) Methods of Reducing Skin Friction - Friction between the outer <br />rsurface <br />of the casing and the surrounding soil may be reduced by <br />increasing the diameter of the casing hole by nor more than 3/4 <br />inch greater than outside diameter of casing itself. This may be <br />accomplished as follows: <br />1 a) Overboring - Use of a cutting head with an overall diameter <br />of no more than 3/4 inch greater than the casing diameter. <br />Maximum diameter includes wing cutters which must be <br />securely blocked to limit the overall diameter in order to <br />meet this requirement. <br />' b) Use of bands, couplings, collars or welds will be allowed, <br />providing the casing diameter is increased by no more than <br />3/4 inch. Any such device or method used shall be rigidly <br />affixed and shall in no way weaken the leading edge of the <br />casing. Collars and couplings used to reduce skin friction <br />on steel pipe must be welded in place when cutting heads <br />are used, eliminating the possibility of the cutting head <br />unscrewing or dislodging the collar or coupling during the <br />operation. <br />c) Use of lubricating materials on the outer surface of the <br />casing to reduce skin friction is also acceptable, subject to <br />1 07/03 16200 -11 03- 1438.A <br />