Below you will find our guidelines for a successful HDD installation of the MitiGopher AC Mitigation System and the Iron Gopher cathodic protection system.

Site Geotechnical Investigation

Any discussion about horizontal directional drilling installation starts with a site geotechnical investigation.  Obtaining a geotechnical survey or as much geological information about the respective job site is very important.  A great amount of record information is available through sources including:

• United States Geological Society (USGS)
• National Geological Map Database
• Publications of the US Army Corps of Engineers
• Earth Explorer
• The National Soil Survey Center (NSSC) a division of the US Department of Agriculture
• State Departments of Transportation
• Highway Administrations
• Original construction records

In addition to record information, site-specific investigations (soil bores and soil sampling) by trained geologists and geotechnical service companies can provide valuable detailed data on the planned bore area geology.  The geotechnical analysis should identify a number of relevant items including:

• Soil identification along the bore route to locate rock, rock inclusions, gravely soils, loose deposits, discontinuities and hardpan
• Soil strength and stability characteristics
• Groundwater

Local drillers with experience in the identified area can often provide valuable insight based on similar projects in the same area.

Terrain and HDD Route Mapping

Collecting accurate topographical information of the bore route is another critical component in the planning phase.  Terrain and HDD mapping includes determining HDD bore hole entrance and exit locations, identifying and mapping elevation profile changes, ensuring that other utilities are appropriately identified and avoided, assessing the need for traffic control, evaluating any environmental considerations or limitations that might impact the use of drilling muds and hole conditioners.

Bore Planning Software

Several commercial bore planning software tools are available to assist in the planning phase.  These programs utilize the soil and geotechnical data combined with the terrain and route mapping information to provide a graphic visualization of the job helping the driller more accurately “see” and perform the job from start to finish.  These software tools help the contractor select the appropriate drill rig, drill bit type and backreamer based on the anticipated soil conditions and the total bore length.  By choosing the drill stem and length, the desired bore path depth, desired minimum cover, diameter and bend radius of the product being pulled, the software plots a proposed bore pitch, calculates setback distances, figures point to point bore paths, estimates hole volumes and calculates pullback time. The software can also provide a fluid–mixing process map that shows how much mud should be used based on soil conditions, drill unit and tooling used.If a bore planning software package is not used, field calculations should be performed to appropriately choose the correct drill rig, drill bit and backreamer tooling requirements, desired bore path and quantity and type of drilling fluids to be utilized.

Contingency Planning

Even with proper project planning and an experienced installation crew, some consideration should be given to contingency plans in the event that something unforeseen happens during the HDD boring and anode installation.

• Are alternate bits available if needed to complete the pilot hole?
• Is a larger boring machine available if needed?
• If drilling is more challenging than anticipated do we have ready access to HDPE pipe for sleeving if warranted?
• Does the project warrant having one or more spare anode assemblies in the event of an anode breakage during installation?

While these risks can be greatly minimized with proper planning, asking these questions before mobilizing to the site can help solve problems more quickly, saving time and money.

Download the HDD Installation Guide