Hidden infrastructure kept flooding in Cape to minimum

Keeping Cape Girardeau's downtown safe from floodwaters is no small task.

While some of the protective measures are easily visible -- the floodwall, for example -- most are hidden.

"[Flood protection] is a little bit different downtown because of the floodwall and the way that has to work," said assistant public works director Stan Polivick. "If you're out by Independence and Silver Springs, that water all runs to Cape LaCroix Creek and runs on out to the river south of town. You can see all of that, but you can't see all of the stuff downtown. It's all underground."

Some people may have wondered what systems were at work -- or whether any were at work -- when pockets of downtown experienced flash flooding in early July. Parking areas near Broadway and Water Street were covered for a brief time, leaving the area inaccessible temporarily.

Behind the scenes, consistent rain, with the closed floodwall holding back the swollen Mississippi River, kept public works staff busy.

"The pumping stations along the river ... We've had people in there 24/7 and around the clock," public works director Steve Cook said in a July interview. "Any rain that falls will have to be pumped out to the river."

Two stations are available to service downtown -- the Mill Street station near Isle Casino Cape Girardeau and the Merriwether pump station on South Main Street north of the Red House Interpretive Center. There's also more than 6,000 feet of levee and floodwall that offers protection from the casino to the River Campus.

Polivick said there's a prevalent misconception the purpose of the two pumping stations is to pump out river water. In reality, they are the area's best tool to pump out rain, especially when the floodgates are closed.

"Today, those gates are open, and the rain that falls just goes by gravity into the river and it doesn't have to be pumped," he said. "Once the river approaches 32 feet, we'll close the gates, which keeps the river water in the river but also traps the water on the inside so it can't get out. Then we have to open gates within the pump station itself to let that water get in to where the pumps are, and then we can pump it out."

The recent flooding in downtown was a rarity, Polivick said, as the area has experienced only a few issues with stormwater flooding over the years. Sudden, heavy downpours, such as those that hit downtown in early July, can represent a problem, but he said the area has a strong system in place.

"We don't really have much evidence to say, 'Gee, we need to double the capacity of these pumps,'" Polivick said. "If you're only getting one of those occurrences every 10 or 15 years, that's a pretty good clue that you've got a pretty capable system in place."

The Merriwether pump station alone is capable of pumping about 3 million gallons per hour, according to calculations from the public works department.

Besides the pump stations, the area also has an extensive underground drainage system. Inlets placed in curbs and connected to drain pipes allow for drainage off the roadways. There are five underground pipes that run directly to the river, and everything else goes directly to the pump stations. Pipes range from 15 inches in diameter to 40 inches.

In general, Cook said smart decisions in flood-protection efforts in the past have saved the city and its residents a lot of grief this year. Polivick said forward thinking is evident even in downtown's drainage system.

"Over the years, when the system was put in during the original construction, they did a good job of sizing the pipes," he said. "We've done some enhancements and things over the years to address some localized problems ... but from what we've observed, it seems we don't have any severe deficiencies where we would need to say, 'Go change this 20-inch pipe and put in a 40-inch pipe.'"

The same can't be said for other areas of the city. Areas that suffer from flooding at times, such as Arena Park, are being evaluated for possible future stormwater projects, Polivick said.

Other areas that need better drainage already have received assistance. The recently completed Broadway stormwater tunnel, for example, helped relieve some of the stormwater that collects along the eastern part of the street.

And all of the pipes, which run as far east as Ellis Street, hook back up to the Merriwether pump station, Polivick said.

Despite the obstacles, from closed floodgates to runoff to the steep hill behind the Common Pleas Courthouse, public works officials believe downtown is well-equipped to handle stormwater flooding. They keep watch over the system and run the math to check for deficiencies in case any problems arise. Polivick said the system in place gets the job done, but he keeps his expectations realistic.

"There's no perfect system," he said. "In this business, in public works and dealing with weather, there's always a bigger rain coming."

srinehart@semissourian.com

(573) 388-3641

Pertinent address:

Broadway and Water Street, Cape Girardeau, Mo.