Reliable drilling investigations are the cornerstone of geotechnical work. The soil data our drill teams gather is the basis of most of GeoEngineers’ geotechnical designs and recommendations. Even in ideal conditions, drilling operations can be challenging and unpredictable. But when we need soil information from below a river bottom it requires a team of exceptional drillers—and we have them here at GeoEngineers.
I’ve been drilling along and in the Mississippi River for more than 40 years. During that time, we’ve completed more than 6,000 projects in and around the river—from the delta and the Gulf South to as far north as Dubuque, Iowa. Our drill team has the equipment, knowledge and experience to efficiently and safely drill boreholes in water of 50-100 feet and even deeper. These geotechnical investigations are most often for trenchless pipeline crossings, bridges, docks, ports or other industrial projects. Besides handling our own investigations, our team is often subcontracted by other geotechnical firms up and down the river.
Over-water drilling brings a long list of specific challenges. It starts with acquiring permits and permission. We’ve been performing over-water drilling on the bustling Mississippi for a long time, and the process is easier when you know all the stakeholders. The United States Army Corps of Engineers (USACE) issues a Nationwide Permit 6 (or NWP No. 6)—the permit required for in-river drilling in the Mississippi or elsewhere. Although the permitting process is relatively straightforward, it can be lengthy. It may take up to a month or more to receive permit approval from the USACE, so starting early is critical.
Drilling in the Mississippi also requires coordination and permission from local pilot’s associations, which have authority over river traffic and flow. We most often work with the Maritime Navigation Safety Association and the Crescent River Port Pilots Association. We’re also required to notify the U.S. Coast Guard of our activities. They put out a “Notice to Mariners” to make other barge and ship traffic aware of our presence. Our subcontracted marine support team has been around as long as we have and also helps our operation stay safe.
With permits in hand, our crew must mobilize to the drill site. GeoEngineers owns and operates several drill rigs, but for over-water operations we mount our equipment on a barge or elevating boat in port. In remote locations or lakes without a commercial rental fleet of barges, we need to truck in a barge or build a modular platform with solutions like the Flexifloat™ system. Once on the river, we work closely with surveyors to pinpoint the drilling location with precise GPS technology, then position the barge over the right section of river.
Drilling requires an extremely stable platform. GeoEngineers sometimes uses barges equipped with extendable spuds, or legs, that can be used to anchor the vessel to the bottom of the river. In deeper water, we’ll use a system of up and downstream anchors to hold position on the drill site. Both of these solutions also require us to be positioned above an area of the channel bottom that is free from obstacles.
The strong current in the Mississippi is another challenge. A typical length of drill pipe extending from our barge to the river bottom can bend unless protected by additional pipe casing. Our crew usually begins by placing sturdy 8-inch casing down to the mudline, and then drops smaller casing through it to help strengthen the outer casing. This casing also allows us to push in and out of the same borehole and return drilling fluid to the surface.
Weather conditions are also a constant adventure while drilling on the river. Fog, extreme heat, extreme cold, thunderstorms and nighttime activities can all magnify safety concerns when drilling over water.
Despite the challenges, GeoEngineers’ drill team has become one of the leaders in over-water drilling in Louisiana and the larger Gulf Coast region. We believe that our combined years of over-water drilling experience make our team one of the most experienced in the country. If you need over-water geotechnical drilling, we’d be happy to discuss your needs and how GeoEngineers’ years of experience can help you accomplish your project goals.