dam cover.jpeg

Water surges through three floodgates at Duke Energy’s Cowans Ford Dam.

(RELATED: Deadly flooding more than a century ago inspired today's lake system)


STANLEY – Stand atop the Cowans Ford Dam, and the deluge-induced mismatch that led to recent flooding in the Mountain Island area begins to make sense.

To the north, under blue skies on a recent breezy morning, the waves of Lake Norman lap along the concrete wall just a few feet below. Distance makes the lakefront mansions on Bell Isle seem more like cottages, a reminder that the 56-year-old dam turned what once was a river into a 50-square-mile reservoir with more than 500 miles of shoreline.

Brissie.JPG

Michael Brissie, Duke Energy’s regional director for hydroelectric operations, stands atop the Cowans Ford Dam.

But turn 180 degrees, and the perspective shifts just as much. Now it is blue sky, not lake and shoreline, on the horizon. Here, the water is more than 100 feet below the dam’s summit, and it more resembles the original Catawba River than it does the lake above.

Cowans Ford Island is perfectly centered downstream in the flowing green water, as if placed there by design like the concrete behemoth that looms over it. In the distance, vehicles pass on the N.C. 73 bridge unheard against the sound of the lake’s waves and the hum of a single hydroelectric unit as its turbine sends churning discharge to the surface below.

Downstream, the river flows into the sixth of 11 reservoirs in Duke Energy’s Catawba-Wateree river system, where a smaller, decades-older dam controls the fate of Mountain Island Lake, which at less than 3,300 acres, is dwarfed by Norman above it.

This transition point is where reality trumped man’s attempts to control the whims of nature earlier this month, Duke Energy officials say.

“It’s a huge swimming pool dumping into a bucket,” Michael Brissie, Duke’s regional manager for hydroelectric operations, said in describing the relationship between Lake Norman and Mountain Island Lake.


Open the gates

On June 9, as runoff from days of rain in Catawba County filled that “pool,” Duke was left to take an unprecedented step.

“We had never opened the floodgates fully to deal with a weather event,” Brissie said.

Mountain Island Dam.jpeg

Water surges over the Mountain Island Lake Dam after floodgates were opened on the Cowans Ford Dam. The Mountain Island Dam is designed to overflow.

In the dam’s more than half-century in operation, the only time the company had lifted any of its 11 gates completely was to comply with five-year testing requirements by the Federal Energy Regulatory Commission, he added.

On June 9, Duke opened two of the gates completely, and lifted another partially.

The company also moved water through the three working generators at Cowans Ford (a fourth is shut down for maintenance). The hydroelectric units also send water downstream, but help ease the pace of overall flow because the release is less intense than the torrents crashing into the river from the elevated gates.

Based on the water moving through the gates, it was like having 4.5 additional generators operating, Brissie said.

Spillover.JPG

Water from Lake Norman laps over the edge of a window above a floodgate at the Cowans Ford Dam.

At its peak flow June 9, 76,000 cubic feet of water per second surged through the dam’s generators and floodgates combined. That water had only one place to go: into the “bucket.”


Fickle forecast

Duke knew earlier in the week that heavy rain was likely, and began moving water through the system in preparation on June 5, Brissie said.

The company created capacity above Lake Norman and in Mountain Island Lake, which was 4.2 feet below its “full pond” level by June 7. Keeping Mountain Island Lake low meant maintaining Lake Norman at 1.5 feet below its maximum level – slightly higher than Duke’s target.

Based on forecasts, Brissie said the company was prepared for 4-6 inches of rain. When as much as a foot of rain ultimately fell in places like Catawba County, it had to go somewhere when it moved downstream.

That somewhere eventually was Mountain Island Lake, where 4 feet below full pond became nearly 7 feet above by June 10, leading to flooding that damaged more than 100 homes.

“Even at 4 feet down, it doesn’t take (Mountain Island Lake) long to fill,” Brissie said.

Critics have suggested that Duke should have lowered Lake Norman more significantly ahead of the rain. But Brissie noted that the forecast also could have been 6 inches off in the other direction.

“That gets risky,” Brissie said in response to the notion that the company should have moved more water out of Norman in advance. “(The rain) could have gone a little east or a little west, and we wouldn’t have had enough water for operations, including flow releases, recreation, cooling water for McGuire and Marshall stations, and generating electricity.”

Dam calm.JPG

Small amounts of water flow down the Cowans Ford Dam a week after three floodgates were opened after heavy rain upstream.

Some Mountain Island-area homeowners also have suggested that the location of the damage is evidence of a bias in Duke’s water-management strategy.

“People say, ‘You’re flooding me (in the Mountain Island Lake area) because you like those people (on Lake Norman) more,’” Brissie said. “That’s not the case at all.”


No ‘overtopping’

Why couldn’t Duke have let Lake Norman property owners feel the pain of flooding along with – or rather than – those on Mountain Island? Because in the case of Cowans Ford, “Water over the dam” is not a phrase Duke – or the Federal Energy Regulatory Commission – wants to hear.

“Dams with floodgates are not designed to allow ‘overtopping,’” explained Duke spokeswoman Kim Crawford. “If this were allowed, it could damage the dams – and in the worst case, could result in dam failure.”

FERC requires Duke to keep Lake Norman no more than 5 feet below full pond, while the company sets 2 feet below full pond as its target “to balance (energy) generation, recreation and flow releases,” Brissie said.

A week after the floodgates were closed, Lake Norman was still at 99.3 Feet , which meant small waves sent splashes of water through windows of space left open above the dam’s floodgates. As of June 18, Lake Norman was 1.25 feet below full pond, while Mountain Island Lake was a little more than a foot below capacity.

1
0
0
0
0

(0) comments

Welcome to the discussion.

Keep it Clean. Please avoid obscene, vulgar, lewd, racist or sexually-oriented language.
PLEASE TURN OFF YOUR CAPS LOCK.
Don't Threaten. Threats of harming another person will not be tolerated.
Be Truthful. Don't knowingly lie about anyone or anything.
Be Nice. No racism, sexism or any sort of -ism that is degrading to another person.
Be Proactive. Use the 'Report' link on each comment to let us know of abusive posts.
Share with Us. We'd love to hear eyewitness accounts, the history behind an article.