Mississippi River Levee Pipeline Crossings

A large pipeline company planned to use horizontal directional drilling (HDD) to install three pipelines beneath the Mississippi River and its levees near Empire, Louisiana. The US Army Corps of Engineers (USACE) has become more restrictive in its regulation of construction around Louisiana’s levee system in recent years, especially with images of Hurricanes Katrina and Rita fresh in the nation’s memory.

GeoEngineers worked with the pipeline company to create HDD engineering designs to specifically evaluate hydraulic fracture and inadvertent returns and their effects on the levees. GeoEngineers also provided HDD construction consulting services for the project. Hydraulic fracture occurs when the pressure required to keep drilling fluid flowing through the hole underground causes the surrounding soil to expand and eventually fracture, allowing drilling fluid to escape the HDD hole. When these drilling fluid leaks reach the ground surface, they are known as inadvertent returns.

Factors contributing to project success included:

• Constant communication
• Adjustments to standard HDD design and construction procedures
• Careful monitoring of drilling fluids and down-hole annular pressures

GeoEngineers’ engineering recommendations and construction mitigation techniques demonstrated that even the most difficult HDD installations beneath levees are possible—without reducing the levees’ ability to protect coastal environments, economies and the general public.

Approach

• GeoEngineers worked with USACE and the pipeline company to create HDD engineering designs that could obtain permitting at the two sites.
• GeoEngineers discovered that the USACE’s original factor of safety requirement was nearly impossible for HDD design and construction at the proposed crossing locations. Instead of giving up, GeoEngineers continued discussing the anticipated soil properties and hydraulic fracture theory with the USACE. Finally, based on GeoEngineers’ engineering calculations and construction mitigation recommendations, the USACE issued the permits.
• Our HDD specialists met with the pipeline company’s chosen HDD construction contractor to address proposed construction mitigation techniques prior to construction.
• GeoEngineers was also on site to observe operations throughout the project and worked as a liaison to the USACE.
• GeoEngineers always kept the pipeline company’s and the public’s safety in mind.

Results

• GeoEngineers’ unique approach persuaded the USACE to permit the project and move forward. The precedent set by this successful project provides energy companies more latitude in the future to install infrastructure near sensitive river systems.
• Using constant communication, design adjustments and careful monitoring of drilling fluid, GeoEngineers demonstrated that even the most difficult HDD installations beneath levees are possible—without reducing the levees’ ability to protect coastal environments, economies and the general public.
• When the pipeline company faced challenges meeting USACE guidelines on the major river-crossing pipeline project, GeoEngineers developed a solution that satisfied both the pipeline company and USACE. By doing so, the pipeline company was able to complete its pipeline installation beneath the levee and continue transporting its product.