As printed in The Memphis Business Journal | Author: Michael Sheffield
When excavation work began for the $6.5 million parking garage of the $20 million renovation of Overton Square, local engineering firm Powers Hill Design literally unearthed something unexpected.
Construction crews found an abandoned pumping station that had been paved over near Trimble and Florence, where the garage will go. Despite going through construction plans for that area going back almost 50 years, there was no record of the station, which hadn’t been in use and was forgotten about.
For engineers who are laying the literal groundwork for new projects, the more urban the area they’re working in, the more likely they’ll find something unexpected, says Nisha Powers, president of Powers Hill.
“You try to find out as much on the outside so you know what’s going on underground,” Powers says. “But things get paved or built over so much, you’ll find that someone didn’t take out what was there before. They just left it and covered it up.”
Because of underground surprises, there is often a contingency fund put into project budgets to handle anything that may have to be removed. In extreme cases, excavation may reveal contamination in soil, which causes a different set of problems, and could derail a project.
Steve Hill, chief operating officer of Powers Hill, says in cases where something is found underground, it’s often cheaper to remove the obstruction than to change the project.
These kinds of surprises occur because construction records are often misfiled or lost. And if an area has had a lot of construction over the years, it could take days to find everything that has been done.
“If you go into the basement at City Hall and see 200 drawers of plans and you’re trying to find information on one street, it’s hard to track everything down,” Hill says. “We can get plans from 1920, but the street has changed five times since then. You just try to find whatever is available.”
As the city gravitates more toward electronic filing, those problems could eventually be eliminated.
Vic Young, a geologist with Fisher & Arnold Inc., says contingency budgeting typically can cover the cost of whatever might be found. Young says one excavating crew swore they ran into bedrock during a project that was placing new sewer pipes near Sanga Road, which Young doubted because the closest bedrock is 3,000 feet underground. But to his surprise, the crew brought him samples of what was solid rock. The rock went down 12 feet underground and was 30 yards long. It all had to be removed before the project could be completed.
“We run into things like buried tanks all the time because there’s no record of them being there,” Young says.
Powers Hill was eventually able to track down plans for the pumping station and the Overton Square garage project is back on track. The best thing an engineer can do is make sure their information is as thorough as possible so 50 years from now, they don’t run into a similar surprise.
“Anybody that knew about it was dead, so you’ll have something everyone has forgotten about,” Hill says. “Any time you stick a backhoe in the ground in Downtown Memphis, you’re going to find something no one knew was there.”