Page 31 - Careers & Stuff 2021

Closer Look
Hockessin-based Kuhn Construction was the lead contractor on a project to build a substructure for a new pump station in Richardson Park.
The project’s construction and engineering requirements were unusual, says Larry Kuhn, owner of Kuhn Construction: “It was a rectangular structure, which would normally require a rectangular cofferdam that holds back the earth and keeps water out of the excavation.”
However, to build the substructure, Kuhn Construction had to dig 40 feet deep, “and to fill a cofferdam that big in
a rectangular fashion, you would need internal bracing. Because the structure was going in the center of this [dam], you could not put internal bracing in.”
Jennifer Peirce Brandt, of Pennsylvania-based Peirce Engineering, instead designed a circular cofferdam, seen in images 1 and 2. Image 1 shows an excavator inside the cofferdam while excavation was still ongoing. Image 2 shows the rectangular structure going up in the center.
Another challenge with this project was related to the excavation. “We were excavating down to 40 feet. The first 20 feet was just soil, but the last 20 feet was granite rock,” Kuhn says. “We had to blast the rock from inside the cofferdam, which took roughly 15 blasts because we can only do a small area at a time. Each time, we had to lift our equipment in and out of that hole with a crane.” (As seen in Image 3.)
Image 4 shows workers pouring concrete for one of the floors of the structure, approximately 20 feet up from the bottom. Today, there is no outward sign of the construction, Kuhn says. “It’s just grass because the structure is all underground.” (See Image 5.)
IMAGES TAKEN BY LARRY KUHN. WE THANK THE DELAWARE CONTRACTORS ASSOCIATION FOR ITS KIND ASSISTANCE IN OBTAINING IMAGES AND INFORMATION ON THIS PROJECT.
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DelawareBusinessTimes.com | CAREERS & STUFF 29