With expanding student populations across the United States and aging facilities, many schools are undergoing renovations. One such facility is Fairfield High School in Fairfield, Iowa. Built in 1939, it currently enrolls more than 550 students.

The school received a new three-story addition in June 2014. This expansion included four new science classrooms, a new auto shop, wrestling room, common areas, stairwells, and an elevator for ADA accessibility. Adding on to a 75-year-old facility presented challenges, especially when the soil is composed of clay and sand. The site also had limited clearances for large equipment, which hindered the foundation solutions available to combat the loose soil composition.

As the general contractor for the school prepared to add on to the facility, the design engineer onsite discovered that the soils lacked the load bearing capacity to complete the addition. After reviewing the location, the design engineer contacted Structural Anchor Supply in Osseo, Minn., and requested help with this large project.

Structural Anchor Supply, a Hubbell Power Systems distributor for CHANCE Helical Piles, recommended Stumpf Construction Services, one of its CHANCE Certified Installers. Stumpf Construction Services, in Riverside, Iowa, is a general contractor that specializes in structural and waterproofing issues. This family-owned, third-generation company has been in business for 40 years.

Structures built on soils that consist of clay and sand create several challenges, including clay that swells during high-moisture conditions and shrinks when in a drought season and loose sandy soils that typically fail to support heavy loads.

Furthermore, the foundation solution had to follow a tight deadline to not delay the remaining construction. Therefore, traditional solutions, such as concrete and driven piles, would not work because of the lead time and higher cost.

“Apex Structural felt that helical piles were the best solution — considering time, limited access, and budget constraints,” said Chad Stumpf, vice president of Stumpf Construction Services.

The CHANCE Helical Pile Foundation System provides the performance of concrete without the lead time, and eliminates the drawbacks of driven piles and drilled shafts. Overall, helical piles are a segmented deep foundation system with helical bearing plates welded to a central shaft. The load is transferred from the shaft to the soil through the bearing plates.

The piles were chosen for Fairfield High School due to their true helical shape, which allows them to screw into the soil with minimal disturbance instead of auguring through the soil. Also, the piles require smaller installation equipment, which makes them ideal for construction sites with limited clearances. Construction activity on the site made the work area tight, but with the helical piles, Stumpf Construction Services was able to access the tight installation areas.

“It would have been difficult and significantly more expensive to pour a foundation under the existing footing with a good possibility of compromising the existing structure, and it would’ve taken longer,” Stumpf said. “Also, the design engineer wanted to minimize vibration, considering that the new footer had to go right against the existing structure. Helical pile technology is a preferred deep foundation solution when adding on to an existing structure.”

CHANCE Helical Piles were also selected for the Fairfield High School project because they provide fast installation with immediate loading. It is a pre-engineered system, which is easy to use in limited access sites and weak surface soils. Helical pile installation minimizes soil disturbance and does not produce vibration.

The Stumpf Construction Services crew installed 22, SS5 Helical Piles with a 10-12-14 helix configuration in an ‘L’ shape along the existing buildings. Extensions were added to reach the required torque of 40 kips at depths between 18 feet and 21 feet.

“We used a small track excavator to drive the helical piles in at a slight angle next to the existing footing,” Stumpf said. “The design called for a grade beam, so we cut off the extension rods and put bearing caps on them.”

The installation was scheduled for three days, but it only took one day to complete. They were on time and at budget without disrupting the remaining construction schedule. This was a crucial element because construction had to be completed prior to students returning in August 2014 for the new school year. 

Information provided by CHANCE Helical Piles (www.abchance.com).