As the saying goes, when it rains it pours – and our team at Industrial One in Chattanooga, Tennessee dealt with quite the downpour last winter while beginning earthwork.
Winter construction can present many challenges that we expect to encounter and understand how to address. However, there are times when we encounter the unexpected, such as a more than 1,000-foot natural, underground swale in the middle of our Industrial One building pad. Every time there was significant rainfall, the swale turned into an underground stream. It was clear the water was an issue, and we had to quickly find a solution so work could continue.
Our team investigated several options, including the following:
- Chemically treating all building materials. This option was ruled out because it was too wet, costly and temperature dependent.
- Installing auger-cast piles underneath the building pad. For this method, a piece of equipment drills multiple 18-inch-wide, 10- to 30-foot-deep holes and fills the holes with stone. This option could have worked but was very costly and would have taken too long to implement.
- Installing a french drain and shot rock. With the help of a geotechnical engineer, GEOServices, our team ultimately decided to pursue this option, because it provided the most viable, timely and cost-efficient solution.
Our team installed a 1,300-foot-long by 6-foot-wide by 3-foot-deep french drain wrapped in fabric to direct the natural swale to a structure beyond the building footprint. The french drain was then covered by an 800-foot-long by 40-foot-wide area of shot rock to bridge the unsuitable soils for the remainder of the building pad. These unforeseen conditions led to roughly $1 million in additional earthwork cost that still had to be completed under the original schedule constraints. Our team and sitework trade partner, Brown Bros, worked tirelessly – including after hours and on weekends – for two months to complete this challenging sitework package and deliver the project on-schedule.