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Section 02310 <br /> HORIZONTAL DIRECTIONAL DRILLING <br /> pressures the geological formations encountered will withstand to assess the performance of <br /> the HDD operations relative to inadvertent mud returns. <br /> Contractor shall verify that: <br /> 1. The drill rig and equipment can be set up at the entry point and that sufficient space <br /> is available. <br /> 2. Sufficient work area exists at the exit location. <br /> 3. There is sufficient area for pipe staging and stringing. <br /> 4. No interfering utilities conflict with the entry and exit points and the rig tie-down <br /> area. <br /> Contractor shall verify that the steel casing pipe and the HDPE pipe is suitable for the pull <br /> back stresses that will be imposed during pull back. <br /> The Contractor shall review the geotechnical report and the proposed geometry of the drill <br /> path shown on the plans and if deemed necessary, may propose minor deviations, subject to <br /> Construction Manager's approval and the minimum criteria specified herein and on the <br /> plans. <br /> Contractor shall determine the ultimate depth of the bore based on favorable geotechnical <br /> conditions for drilling, but the borehole depth shall be a minimum of 100 feet below the <br /> bottom of the levee, floodway, or slough. <br /> The entry point shall be plus or minus 20 feet of the designated location along the alignment <br /> line. The exit point shall be within a 10 foot radius of the designated location. <br /> Alignment tolerance shall be plus or minus 15 feet. <br /> Borehole entrance and exit angles shall consider the potential for frac-outs along the side <br /> slopes and ditches. Sufficient cover (25 foot minimum) shall be provided to minimize frac- <br /> out potential. <br /> Curves shall be drilled at a radius equal to or greater than that shown on the plans. The <br /> minimum curve radius shall be 2400 feet for the steel casing and 1000 feet for the HDPE. <br /> The drilled radius will be calculated over any three joint (range 2 drill pipe) segments using <br /> the following formula: <br /> Rdrilled = (Ldrilled/Aavg)*57.32 <br /> Walnut Grove Sewer Project(Conformed) 02310-9 SA0160401 <br /> March 2008 N1sa0160401\Specs\WG Conform\Div 2\02310.doc <br />