Thursday, August 30, 2012

Crosstown drainage fix: Phase 1 of 4 nearing completion

Riley says Tuesday's flooding would have been worse without preliminary improvements

Posted by Paul Bowers on Thu, Aug 30, 2012 at 12:18 PM

Some of the streets in downtown Charleston looked like the canals of Venice on Tuesday, only with college kids on air mattresses instead of docents in gondolas. And while S.C. Democratic Party Chairman Dick Harpootlian took the flooding as an opportunity to make some jabs at Gov. Nikki Haley for leaving the state to speak at the GOP Convention, the rest of us out here in the sopping-wet real world were left to wonder: What is the city doing to fix this daggone flooding?

click to enlarge Morris Street falls within the drainage basin for the city's planned improvements around the Crosstown. On Tuesday, it obviously wasn't draining very well. - COURTESY OF CAMILLE KEY
  • Courtesy of Camille Key
  • Morris Street falls within the drainage basin for the city's planned improvements around the Crosstown. On Tuesday, it obviously wasn't draining very well.

In a press conference Wednesday, Mayor Joseph P. Riley Jr. said the flooding would have been even worse on Tuesday if the city had not already begun its improvements on and around the Septima P. Clark Expressway — the perennially flooded downtown stretch of U.S. 17 also known as the Crosstown.

The project will help solve an essential problem of drainage physics that has plagued Charleston since its founding. Hydrologists call the difference in elevation between two connected water surfaces the hydraulic head, and in Charleston, the head between storm drains and the river is often fairly small — especially at high tide. The smaller the head, the slower the drainage, so when a maelstrom hits the city at high tide, we end up with a lot of drowned sedans.

Now, 48 years after the Crosstown was built, the Big Drainage Fix is underway. After years spent fixing smaller drainage issues, including in Ardmore and on East Bay Street, the city has finally secured the funding to fix the Crosstown from sources including the State Infrastructure Bank, state matching funds, the American Recovery and Reinvestment Act, and tax increment financing related to the Gaillard Auditorium improvements.

According to Riley, the first of four phases in the $154 million Crosstown project is set to be completed in November. In this first phase, inadequate 18-inch underground drainage pipes are being replaced by pipes up to 48 inches in diameter.

"It would have been even worse yesterday if we had not had the 48-inch pipes underground," Riley said on Wednesday.

Phase 2, which will begin in November, will include drainage improvements from the end of the Crosstown to the Ashley River, south along President Street to Bee Street, and up President Street to Fishburne Street.

Phase 3 will feature a series of tunnels dug by robotic machines 140 feet under the city (yes, you read that correctly) leading to an underground reservoir system that carries stormwater to the Ashley River.

Phase 4 will be the construction of three massive pumps between the two Ashley River bridges, capable of pumping 360,000 gallons per minute into the river.

The city has also secured $25 million in bond money to connect drainage pipes under the City Market to a pump station on East Bay Street, although construction has not yet begun. On Tuesday, shoppers and vendors could be seen slogging through knee-deep water in the outdoor market.

Riley wrapped up the conference with a word of common-sense advice to drivers: "If you're driving into what looks like a street that might be flooded, just don't proceed. Don't take the gamble. Try to wait and back out and find another route."

Click here (PDF) for a map of the planned improvements on the Crosstown.

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