Drilling of the pilot hole along the designated route will be carried out commonly using a Tri-Cone drill bit and a bent sub assembly which is fixed just behind the drill head during drilling. In hard (rock) ground a down hole (mud) motor will be deployed instead.

The survey probe assembly that monitors the drill path will be positioned along with two non-magnetic drill collars behind the jetting assembly and forms part of the BHA.

Upon completion of the pilot hole, the borehole reaming process will be commenced. Launch pit and mud containment pit will be constructed at the exit position (details enclosed)

The staging and number of reaming passes will depend on the soil formations encountered and the diameter of the utility to be installed. Depending on actual soil conditions, various types of reaming tools can be utilized including barrel reamers, fly cutters and hole openers.

The final borehole size is depending on the product line diameter and should not be less than 1.3 x O.D of the product pipe as a general rule in normal cases. However, the exact reaming program will be defined for each crossing based on job-specific parameters.

To verify and ensure a borehole of suitable condition, the reaming process is followed by a borehole cleaning / calibration phase whereas the final reamer will be run again to guarantee conditioning of the borehole and removal of cuttings. This process may be repeated several times depending on actual borehole condition encountered.

Upon removal of each drill rod on the rig, another rod will be added to the drill string at the pipe site behind the reamer. After the reamer reaches the rig site, it will be dismantled from the drill string, cleaned, inspected and prepared for its next deployment

Upon completion of the final borehole cleaning path, the pulling assembly consisting of a suitable barrel reamer (min 4 inch larger than the product pipe diameter) and a swivel will be connected to the pipeline section through the pulling head.

Then the pipeline section will be pulled to the entry launch pit. A final test of the reamer and jets as well as final pipeline coating inspection will enable the pullback to commence.

Pulling operations will be paused at intervals only to remove drill rods as they are pulled. The removal of the pulling assembly which is consisting of the barrel reamer, the swivel, and the pulling head will take place upon completion of pullback process when the reamer and pulling assembly emerge from the borehole in front of the HDD rig.

During all phases of the drilling operations, a log is kept applicable to each drilled or pulled pipe. During pilot drilling a comprehensive survey data logs are produced for each installed drill pipe.

Together with the survey and drillers logs a daily reports are issued for recording all work progress and forwarded to the client subsequently. Further reports weekly / monthly will be submitted as per the contractual requirements.

Together with the “as-built” documentation, a final report will be issued for the client, containing all the relevant data for the drilling & installation process.