Enlighten Me: Wilmington water system's historic raceway gets a facelift

The city of Wilmington is about halfway through overhauling the signature feature of its water system: a 250-year-old stone raceway that runs through Brandywine Park.

Built to bring water to local flour mills in the 1700s, the raceway has a rich history, but it's also badly in need of repair. As Delaware Public Media's Annie Ropeik reports, the city is modernizing the literally crumbling structure -- while hoping to stay true to its roots.

The first sign that Wilmington's water system is a little out of the ordinary comes inside the Brandywine Pumping Station, on the south bank of the creek.

City water division director Sean Duffy is pointing to a three-story-tall iron steam engine. It's an imposing monument to this building's 19th-century roots. But it -- and the rest of the utility -- were built to fit something even older: the stone raceway that runs along the creek outside.

Duffy explains why the city chose to use it to carry water, both north of the city and into town, more than a century ago:

"I guess when you think about it, maybe the raceway seemed to be an efficient way of accomplishing two objectives," he says. "Instead of having to pump it down here, you utilize gravity, utilize the power of water to just flow itself."

Now, it supplies water to about 130,000 customers: city residents and bigger users, like DuPont, Noramco and the Port of Wilmington. Dams in Brandywine Creek divert water into the raceway, which has a one-foot grade spread out over a mile that leads into the city's system. It dates back to the flour mills that lined the creek when Wilmington was first founded in the 1700s.

In her book Brandywine Village, Delaware historian Carol Hoffecker writes that Wilmington was in a good spot for the milling industry -- with easy access to wheat, water power and the sea. Before and after the Revolutionary War, millers with familiar names like Tatnall, Shipley and Canby built the dams and raceways that bracketed the Brandywine for decades.

The superfine flour they made was top of its market in the early 1800s. But as the nation grew, competition began to increase. Families were already getting out of the business in 1827, when the city of Wilmington bought the mill system's water rights. A fire later that century hastened the mills' decline, as the city kept growing -- and along with it, its water system.

 In 1922, Hoffecker writes, the city filled in the raceway on the north side of the creek, leaving only the one on the south bank. But as it ages, the city is losing as much as 50 percent of its water flow to leakage -- and spending more and more on maintenance.

Now, the city is investing $6 million to make sure the raceway lasts at least another century.

"We're putting in a concrete bottom. And we have a very uniform slope from where the water enters the raceway to where it comes into the screen house over there," Duffy says. "So actually, hydraulically, it'll be much more efficient as far as water flowing by gravity from the river into the pumping station and plant."

"No obstructions or anything like that," adds city public works director Jeff Starkey. "It's just a straight flow, straight on in, and again, the reduction of the loss of water."

We drive up the creek, along the expensive townhouses on South Park Drive, to see the rest of the raceway. Starkey says most locals probably don't realize that all their water originates right from this part of the state park:

In the raceway, workers have just finished laying new concrete along the clay bottom and loosely stacked stone sides. Beyond that, Starkey says...

Sean Duffy says they worked with neighbors and nonprofits to make sure the raceway didn't lose its character in the redesign.

"The top of the concrete wall -- the new wall -- will just be around the top of the water level or a tiny bit below," he says. "So that way, when it's in service, all you'll see is water, and then the exposed part of the wall will be stone, just like it looks right now."

We drive up to the creek's north bank to see the head of the system. Beyond it, the Brandywine's drainage basin extends into Pennsylvania -- where Duffy say they're increasingly concerned about runoff and spill risks from new development.

"And actually, that's one of the reasons we went with the upgrade," he says. "We're replacing the head gates, which'll give us a positive shutoff. So when we close the head gates, no water's going to come into the raceway until we open them back up again." Right now, he says the gates tend to leak -- even when they're shut.

When these repairs are done, he says they'll be able to close the gates remotely, as opposed to with the current on-site mechanism.

The threat of pollution -- and changing regulations to control it -- are also why the city's whole filtration system is constantly evolving. New technologies are slowly replacing ones that have been in place as long as the city's existed. It creates odd juxtapositions like back at the pumping station, where 1930s-era water basins sit next to state-of-the-art, microscopic plastic filters.

But for now, the top of the raceway system looks a lot like it must have when the mills still stood here -- all quiet, clear water and towering trees, their leaves just starting to turn.

"It's odd -- I mean, you feel like you're in the city, and then you're out of the city. The city limits," says Jeff Starkey. He walks out onto an old wood-and-cable bridge, beneath a huge train crossing high overhead.

"We used to call it the swinging bridge when I was a kid," he says. "We used to dive off of here and swim."

The water beneath us is pooled against the city dam, a couple hundred yards away. It diverts anywhere from 15 to 24 million gallons of water out of the creek every day. That might sound like a lot, but Duffy says the creek's normal flow is well over 100 million gallons a day -- sometimes up to a billion, after heavy rain.

On the north side of the creek is the city's upper pumping station -- and on the south side is the raceway to the lower one, where our tour began. We cross the swinging bridge to get there and find a crude dam made of plastic sheets, blocking the creek from passing through the under-construction gates into the dry channel.

As we walk back up the creek, a flock of geese comes in to land on the water, and Duffy says the makeshift dam will stay there for the next several months.

"By the time we're done, all of these muddy areas -- we'll put the grass back, and we'll repair any of the walkway, any of the sidewalk here that got damaged during construction," he says.

"We're actually talking about exploring taking out one of the dams at the other end," adds Starkey. "We're working with [U.S. Fish and] Wildlife to get the fish back up here that migrate up. Some of them can't jump up over those dams."

Helping those shad return to the top of the creek is their next goal in continual upgrades to the water system. That's as Wilmington keeps working to maintain the Brandywine's balance of old, new and natural into the future.