Monday, October 30, 2000

Downtown Drainage System Stressed Out; Overhaul in Works

Commercial Appeal
By Tom Charlier

Memphis plans a multimillion-dollar overhaul of a downtown drainage system officials say is too small to prevent floods and too prone to disgorging pollution on the city's waterfront.

In the midst of a downtown building boom, city officials want to clean up and improve the critical culverts and reservoirs funneling storm water to the Bayou Gayoso Pumping Station and into Wolf River harbor.

A new engineering study concluded the system can't store enough rainwater to prevent flooding when the Mississippi River rises to high stages.

The system also washes litter and debris from streets into the downtown Wolf River harbor, spoiling the scenery for boaters and threatening wildlife.

Details of the project haven't been developed. But likely solutions include the expansion of a network of reservoirs - possibly creating a park-like setting for them - and the installation of mechanical bar screens to extract litter from water.

"It'll take care of three problems - it'll remove litter from the storm water, it'll give us more storage capacity and it'll make the retention basins more esthetically pleasing," said Memphis public works director Jerry Collins.

Although design work is about to begin, actual construction isn't likely to start before the 2005-06 fiscal year. The project will appear on the five-year capital budget plan to be reviewed by the City Council later this year.

Whatever its eventual design, the overhaul project will cost "tens of millions" of dollars, Collins said.

It will be focused on a once-prominent stream - Bayou Gayoso - that has been largely sealed underground in culverts. The bayou flows to the pumping station at 35 W. Saffarans.

Under normal conditions, the stream runs under the plant and pours over a small spillway into the Wolf River harbor. But when the Mississippi is at high stages, blocking the bayou's flow, the station pumps the water into the harbor.

During these high stages, the bayou backs up into a series of five reservoirs, or storage basins, north of Auction and east of Front.

A study completed last spring by PDR Engineers Inc. concluded the basins are insufficient to keep downtown areas dry if a heavy storm were to occur when the Mississippi is within 4 feet of flood stage.

The reservoirs can hold 196 acre-feet of water - enough to cover 196 acres a foot deep.

However, to absorb a five-year storm event - the heaviest rain that can be expected in any five-year period - 209 acre-feet of storage is needed. And to retain a 10-year flood, 252 acre-feet of capacity would be required.

Collins said that in addition to expanding the basins, the project will make them more attractive. Covering entire city blocks, the barren, unsightly reservoirs are surrounded by chain-link fences.

"Those basins are extremely functional, but they weren't designed and built many years ago to be an attractive feature of the downtown area," Collins said.

City officials also want to deal with the pollution problem traceable to the bayou. Litter washing off streets and gutters often makes its way into the reservoirs and the bayou, eventually ending up in the harbor.

Boaters, environmentalists, tourists and others occasionally have complained about the trash problem.

Jeffrey Laper, a boater who moved to Memphis from Seattle five years ago, said it's common to find litter ranging from plastic bottles and buckets to syringes, diapers and tires in the harbor.

"It goes on and on. It gets real disgusting," he said.

Laper said the city should give the cleanup project a high priority. He said the pollution is a threat to the ducks, cranes, turtles, beavers and other creatures he sees in the harbor.

"It just boggles my mind how this isn't being taken care of," Laper said.

Terry Templeton, the regulator overseeing Memphis-area water-pollution problems for the Tennessee Department of Environment and Conservation, said his office has received two or three complaints about harbor pollution in the past two years. "Typically, they're the result of some storm event washing stuff downstream," Templeton said.

Collins said litter in storm water is a problem that's not confined to Bayou Gayoso. The city has begun a public education campaign focusing on the causes and prevention of storm water pollution.

But to deal with the litter problem in the bayou, Collins said, the project likely will include the installation of mechanical bar screens, which filter and remove debris from water. The overall design for the expanded retention basins will determine where bar screens are placed.

The devices aren't cheap - the city just paid $2 million to replace eight bar screens at a wastewater-treatment plant.

Given the high cost of the drainage-overhaul work, Collins acknowledged it might take several years to complete.

"The emphasis we'll give it will largely be determined by what the city perceives is the biggest problem," he said.

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Copyright 2000 The Commercial Appeal, Memphis, TN

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