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Cumming to extend intake pipes in effort to reach water

POSTED: November 15, 2007 5:03 a.m.
If the water will not come to the pipe, the pipe will come to the water.

At least that is the stance the city of Cumming took after the level in Lake Lanier dropped too low for it to withdraw water from the shallower of its two intake pipes, which was supplying one-third of the city’s water.

"We’re going to chase the water no matter how far it goes," said Jonathon Heard, head of the Cumming public utility department.

The lake, which was at 1,054.11 feet above sea level as of Saturday, is barely one foot above the city of Cumming’s cast-iron, shallow-water intake valve. It is no longer being used.

Cumming officials worked quickly last month to install two high-density polyethylene pipes that now serve as a substitute for the city’s existing shallow water intake valve in Lake Lanier.

The HDPE pipe is a flexible, yet rigid pipe with a diameter of 16 inches that stretches 50 feet into the lake from the shoreline.

Though it is nearly four inches smaller in diameter than the regular raw water intake valve, Heard said the HDPE can carry just as much water, because the pipe is pressurized. In other words, the water is pumped through the pipes.

"The 16-inch pipe is like a great big hose out there," Heard said.

When it was in use, the raw water intake valve at 1,053 feet above sea level supplied about one-third of Cumming’s water. The HDPE pipe is supplying the same amount of water to the city, Heard said. The rest of Cumming’s water is supplied by a deeper intake.

Cumming officials have closed off the valve on their 1,053-foot intake to keep the water coming in through the HDPE from flowing back into Lake Lanier, Heard said.

Cumming has two HDPE pipes in the lake, but one is a back-up pipe used for emergencies, Heard said.

The HDPE pipes, as is, can draw water until the lake drops to 1,040 feet above sea level, Heard said.

If the lake gets near that level, Cumming officials can add on to the HDPE by fusing additional segments to the end. Essentially, the pieces of pipe are melted together, Heard said.

"When you’re through with it, it becomes one long piece of pipe," Heard said.

Officials can continue adding on, but with the next addition will have to move the pumps, currently sitting on shore, into the lake to push water to the standing intake pumps.

"We’ll be watching the lake levels closely and the drought situation," Heard said. "At some point in the not too distant future, we’ll make the determination as to whether or not we need to go ahead with Phase 2, which would be to move the pumps closer to the water and extend the pipe out further."

So far, Cumming has spent between $200,000 and $300,000 on the process, Heard said.

Cumming officials will begin dredging the lake in the next week to supplement the water flowing to the city’s other existing intake, which is located at 1,033 feet above sea level. The dredging process will remove some of the silt on the bottom of the lake, thus making the lake deeper at the intake’s opening.

Cumming had to get an easement from the U.S. Army Corps of Engineers in order to dredge the bottom of the lake, but officials started that process long before the drought began to threaten the city’s water supply.

In June 2006, Cumming officials put in requests for an easement to build a redundant raw water intake facility. The new facility will draw water from as low as 1,018 feet above sea level when it is complete, and will be similar to the ones Gainesville and Gwinnett County have, Heard said.

Cumming’s population had grown to the point that the existing pipes were at full capacity on the hottest days of the summer, and the city was beginning to need a back-up pump, Heard said.

"There was no extra pump there to fall back on in case of an emergency," Heard said. "We would prefer to have a stand-by pump that is not in use that is available for use in case of an emergency."

The easement the city acquired for the new intake also allowed them to dredge to protect the water supply to the city’s deeper intake at 1,033 feet above sea level. That deeper intake supplies about two-thirds of the city’s water supply.

"Unfortunately, the drought came," Heard said. "Fortunately, we were almost to the end of the process by the time we began to see we had a problem with our first shallow intake ... we were ahead of the game."



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