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1 <br />Il <br />B. Subsurface Soil and Drainage Investigation - In general, the greatest <br />influences on the success or failure of an underground crossing are the <br />existing subsurface soil and water conditions. To correctly plan individual <br />crossing procedures such as dewatering, use of cutting heads, <br />positioning of auger within the casing and to accurately locate potential <br />problem areas, subsurface investigation must be made by the permittee <br />or his contractor. <br />C. Dewatering - Evacuation of ground and surface water from jacking and <br />receiving pits and from path of proposed crossing. Where the ground <br />water level is above the invert of the proposed crossing, or above the <br />floor level of the jacking pits, dewatering is necessary to reduce the <br />water level to below the jacking pit floors and the invert of the proposed <br />crossing, and must be designed, installed and in operation prior to <br />beginning the crossing as follows: <br />1) Except where rock is present throughout the length of the bore <br />and no likelihood of sand pockets exists. <br />2) Where the existing ground water level and particular soil type <br />involved indicates that excessive flowback of spoil material, as the <br />jacking progresses is likely. <br />Dewatering shall not be necessary where remote - powered <br />hydraulic equipment is used to make the crossing underwater. <br />When dewatering is necessary, and if requested, a plan showing <br />the proposed method must be submitted to the Local Maintenance <br />Engineer prior to beginning work. It must be in writing and should <br />be included with the subsurface investigation report. <br />t <br />� 0so, <br />The dewatering report shall contain where appropriate: <br />1) Plan and profile drawing of area to be dewatered, showing: <br />i) Location on plan view of pumps, headers, well <br />points, berms, sump holes, discharge points and their <br />relationship to the roadway, jacking pits and path of <br />proposed crossing. <br />Elevations or depths on profile view of same features <br />and equipment as above. <br />2) Project identification and system design information. <br />16200 -8 <br />03- 1438.A -R <br />