Spoiler alert! No Spoils New Construction Foundation Successfully Installed

A large brownfield site stood three blocks from the center of Hartsville, South Carolina. Previously a railroad yard, the soil was contaminated with creosote and coal dust covered with 2.5 feet of clean fill. The town of Hartsville wanted to build on the site to help increase economic development in the area. The question was, how could the site be utilized without disturbing the hazardous substances hiding below the fill?

Royal Engineering, Inc. had an idea to build a hotel on the site without creating any spoils. Spoils are any excess materials that are excavated and removed from a building site.

Learn more about helical piles for new construction applications

Types of Deep Foundations

Broadly speaking, there are two different types of deep foundations:

• Replacement - soil is removed and replaced with a more structural material such as steel re-bar and concrete, or crushed stone. Two examples of replacement deep foundations are caissons, otherwise known as drilled shafts, and rammed aggregate piers.
• Displacement – as a displacement foundation is installed, soil is moved aside and compacts to make room for the foundation element. A few examples are timber piles, steel pipe piles, and helical piles.

Chance helical piles are a displacement foundation. As they are screwed into the ground the soil is displaced, making room for the steel shaft and bearing plates. The pitch of the helices on Chance helical piles are designed so that each helix follows the same path as the one before it, meaning the same “track” is followed for the installation of all helices, causing minimal soil disturbance.

Because of the minimal soil disturbance caused by helical piles, the building, a four-story hotel, could still be built on an engineered deep foundation. EST General Contractors, Dunn, NC got the job and contacted Carolina Foundation Solutions, LLC out of Charlotte, NC to install the piles.

Helical Piles vs. Concrete Slab

Chet Miller, President of Carolina Foundation Solution explains, “This was the new construction of a four-story hotel, which covers two city blocks in downtown Hartsville. While the contractor could dig down about two feet, no spoils could be generated, which is why the design called for helical piles.”

The only other option considered was pouring a massive concrete slab over the site and building on top of that. Unlike deep foundations, discussed earlier, a concrete slab is a shallow foundation, which transmits the structure load to the soil that is relatively close to the ground surface. While shallow foundations can be viable for lighter weight structures, the four-story hotel needed a foundation that wouldn’t settle or be affected by changes in the soil over time.

The concrete slab idea was rejected for several reasons. The first was cost. Secondly, that approach would have raised the building, changing the elevation with respect to the road frontage. With Chance helical piles, all of the material was on-site and ready to install, delivered from Foundation Technologies, Inc. (FTI), the local Chance distributor for the southeastern and western United States. FTI carries an abundant supply of in-stock inventory, ready to be mobilized exactly when it’s needed for a project. By utilizing Chance helical piles, no additional scheduling or waiting was required for concrete to be delivered and poured. Additionally, helical piles can be installed in any weather, avoiding further delays that may have been present with a concrete foundation.

Helical Piles offered other advantages, as Miller points out. “Noise was a consideration. This site was in the downtown section of a city with business and a college nearby. Helical Piles can be installed quietly, compared to other approaches. They can also be installed quickly, which is beneficial on any job. Also, we did not need to bring in big equipment. EST General Contractors dug numerous shallow trenches for footings around the site, but we were able to use a Bobcat Mini-Excavator and easily maneuvered around them.”

Deep Foundation Installation

Carolina Foundations installed the required 404 Helical Piles in 22 days, delivered on time to the worksite by FTI, allowing work to proceed on schedule.

Each pile was an SS5 with a 10 inch and 12 inch helix plates. On average, the piles were installed to a depth of 14 to 17 feet to reach the required torque of 3,500 foot-pounds. “We use an electronic digital torque indicator. So, we were able to monitor torque continuously throughout the pile installation. Royal Engineering also checked,” explains Miller.

Of the 404 piles, approximately 50, scattered throughout the structure, were installed with a slight batter from the vertical to better support the internal walls. Battering enabled some of the piles to resist both vertical and lateral loads where needed.

Carolina Foundations welded a 7 x 7” structural steel bearing plates to the top of each shaft and then the contractor poured a grade beam to support the hotel. The bearing plates embedded in the concrete grade beams provided a fixed

end condition to aid in load transfer to the pile head.

Occasionally, a job might call for minimal spoils, but on this project NO spoils could be generated. Helical piles were the perfect solution, and the project was completed without disturbing the underground contaminants present in the brownfield. If you have challenging jobsite conditions, get in touch with your local Chance distributor to see if helical piles are a viable solution.

If you are a contractor who would like to become a Certified Installer of Chance helical piles and resistance piers, contact civilconstruction@hubbell.com or reach out to your local distributor.