COLUMBIA — The developers of the BullStreet District — a development of homes, stores and offices that sprawls across more than 180 acres near downtown Columbia — had crafted plans to revamp how water moves across the site after the city's historic 2015 flood.
That presented a challenge for developers who wanted to bring a creek going through pipes back above ground and planned to add a number of buildings, streets and parking lots that do not absorb water. The solution includes a design that has never been done before in the Southeast, its builders say.
To clean up and bring Smith Branch Creek back to the surface, BullStreet developers are spending about $5 million as part of their deal with the city of Columbia.
The plan included adding a grassy buffer to absorbs water if it flows over the banks, as it can happen annually, and using the existing underground piping to whisk away water from a worse flood.
"I felt like it was an opportunity for us to do something above and beyond what was required, and to set a precedent, really, for the way in which stormwater and flood could be managed,” said Robert Hughes, president of Hughes Development, which is overseeing the BullStreet project.
The grassy areas along with a park, dog park and even a wet meadow will function as a way for the system to absorb more groundwater.
“It’s flood management, but most people on most days are going to have no clue that they are in the middle of a flood-management project,” said Joshua Robinson, a hydrologist and member of the adjunct faculty at the College of Charleston who has consulted on the project.
BullStreet had little choice but to address the issue.
After storms four years ago dumped up to 2 feet of rain, breaking dams and flooding neighborhoods, the city's position on flood control hardened, Hughes said.
Even with all the development planned, "there can be no impact from BullStreet on stormwater downstream," Hughes said the planners were told.
Major economic development projects like this, which is designed to become a popular destination with recreation, shopping and an inviting city park, often get some leeway under certain flood scenarios.
After Oct. 3, 2015, Columbia wasn't giving any.
The flood of 2015 highlighted the importance of the smaller waterways around the community, Congaree Riverkeeper Bill Stangler said. With several restorations of creeks, including the Smith Branch project underway, the Midlands is paying more attention to the quality of these waterways, he said.
BullStreet developers were dealing with an infrastructure put in place some 60 years ago.
During the 1950s, the site's owners, the state Department of Mental Health, wanted to make more of its land usable. It decided to push the creek underground across much of the site, installing two 7-foot diameter pipes and eventually putting softball fields atop them. The goal of such huge pipes, far bigger than necessary for everyday flow, was to ensure that flooding would be a very unlikely occurrence, Robinson said.
Instead of just digging up the pipes, the BullStreet project is implementing a design that has been done rarely in the United States. Even after sizable downpours, the creek will flow over the surface and even widen out across the park.
During a more severe flood, however, the kind that would only come to the city once per five or more years on average, the creek would rise higher and surge over a wall, sending extra water flowing through the underground pipes. This would provide extra capacity for floodwater to get across the site during more severe storms.
Essentially, the new system is a hybrid of a creek that helps to hold and even absorb groundwater and the current underground pipe system, Robinson said.
The surface section of the creek had consisted mostly of broken concrete and other construction debris that had been dumped, Robinson said. That mess has been removed and its banks rebuilt.
It’s beneficial to have a stream that has been in pipes for decades on the surface and flowing through a setting for the public to enjoy it, Stangler said. Bringing Smith Branch to the surface also should have benefits for water quality and wildlife, he said.
The outline of BullStreet's plan was created before the 2015 flood, but afterward, the design had to be evaluated under the city's more strict guideline of doing no harm. To test its plans, Hughes Development hired the same consulting firm doing the city's assessment to measure its impact on the flood maps.
Those tests found that the work from the BullStreet project did not make flooding worse, Hughes said. And with the creek and park adding some absorption of stormwater flows, some areas saw less flooding, he said.
With some tweaks to the design, Hughes and his team went forward bringing the stream to the surface.
To do so meant planning a path for the restored creek across the site and its parks, which was done carefully to preserve the best and healthiest of the trees on the site, Hughes said. It would have been been impossible to build the park without taking out some trees. The shape of the creek and pond were altered to preserve oaks and other shade trees, while more diseased and invasive nonnative trees were removed, Hughes said.
“It’s been an unfortunate reality that a lot of the trees out here are in poor and dangerous condition, which is never something you want to hear from your arborist,” Hughes said.
This fall will be a time of planting new trees, wildflowers and grasses across the park and creek banks. The creek's full flow should be restored through the structure in the spring, with the hope that the park will be lush and welcoming next year.
Wildlife is not waiting to be invited, however. On a recent morning, a great blue heron was prowling the shore of the cleaned-up surface section among the cattails, looking for a meal while birds and tadpoles thrive in the area.
Other visitors were less welcome. Somehow a pair of beavers found their way onto the site, probably coming all the way from where the Smith Branch Creek joins the Broad River just above its meeting with the Saluda, Robinson said.
The developers already had been planting dozens of trees, such as willows, along the banks of the creek, which became a perfect food source for the two newcomers. They ate thousands of dollars worth of young trees. “That’s like Snickers bars sticking out of the banks for beavers.” Robinson said.
Because the waters are supposed to flow across and not create an unplanned pond, the two beavers had to be relocated.