The successful installation of any utility using the horizontal directional drill (HDD) method begins with early planning and thoughtful design. We’ve heard from numerous HDD contractors that many of the HDD designs they receive with bid packages often lack adequate subsurface information, are geometrically infeasible, pose a high risk of inadvertent returns or pose other construction risks. Ultimately, the designer needs to consider each project’s feasibility and identify potential construction risks and work to mitigate those risks to the extent possible.
The Importance of Historical Data
The first phase in the HDD design process should include a desktop study of all available information and development of a conceptual design. The designer should first gather as much information as possible from the client regarding the proposed pipe specifications, planned project alignment, workspace limits and environmental and cultural constraints to consider during design. During this stage, designers can also utilize many publicly available sources of information ranging from USGS geology and topographic maps, USACE bathymetric data, state well log databases, aerial imagery, national wetland databases and state and local geologic hazard maps, to name a few. Spending a few hours researching the available data can give the designer a useful head start in understanding the potential construction risks and what design criteria to consider when developing geotechnical recommendations. Building off this basic information, the designer can then develop a conceptual alignment and profile for the crossing and determine the best location and depths for the explorations.