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SECTION 4 – SANITARY <br />56 <br />3.) Verify the locations of all utilities and structures prior to any boring. Vacuum excavation or <br />hand excavation shall be used to spot verify locations of existing utilities to minimize <br />disturbance to surrounding facilities. <br />4.) The directional drilling system to be used shall have the following features: <br />i.The system shall be remotely steerable and permit electronic monitoring of bore/tunnel <br />depth and location. The system shall be able to control the depth and direction of the <br />pipes and must be accurate to a tolerance of plus or minus six (±6) inches. <br />ii.Track and plot the actual horizontal and vertical alignment of the pilot bore at intervals <br />not exceeding thirty (30) feet over the course of the entire horizontal directionally <br />drilled pipe installation. Provide and maintain instrumentation that will accurately <br />locate the pilot hole and measure drilling fluid flow pressure. The City Engineer shall <br />have access to all data and readouts pertaining to the position of the bore head and the <br />fluid pressures and flows. <br />The locating system shall, at a minimum, consist of an electronic transmitter (sonde) <br />positioned at the drill head and a receiver which displays the signal strength. The <br />transmitter shall also employ a pitch (inclination) and roll sensor. <br />iii.Calibrate the transmitter and receiver system per the manufacturer’s specifications for <br />signal strength and verify depth accuracy with a tape measure. Check other parameters <br />such as pitch, roll, battery life, and temperature according to the manufacturer’s <br />specifications. Calibration shall be conducted in an area which is clear of possible <br />interference sources. <br />After calibration of the transmitter and receiver system, walk the bore path to the extent <br />allowable with the receiver “on” and the transmitter “off” in order to check for signal <br />interference. Record the location and particulars of any unusual interference readings <br />and take adequate measures to ensure a proper installation. <br />iv.A swivel type apparatus shall be used to connect the sanitary force main pipe to the <br />drill pipe to prevent torsional stresses from occurring in the pipe during installation. <br />v.The system shall utilize a fluid cutting process, using liquid clay such as bentonite. <br />This clay shall be totally inert and contain no risk to the environment. Submit to the <br />City Engineer a Drilling Fluid Plan which details types of drilling fluids, cleaning and <br />recycling equipment, estimated drilling fluid flow rates, and procedures for minimizing <br />drilling fluid escape. This Drilling Fluid Plan shall be submitted to the City Engineer <br />before starting the horizontal directional drilling installation process. <br />vi.The liquid clay shall remain in the bore hole/tunnel to increase the stability of the bore <br />hole/tunnel and to provide a lubricant to reduce frictional drag when the pipe is <br />installed. <br />vii.The HDPE Pipe shall be filled with a fluid during pullback to offset buoyancy.