WILLARD, Box Elder County (AP) — A leak in the Willard Bay dam has been plugged and water officials now plan to drop the bay's water level 10 feet so they can figure out what happened.

Water seepage from the Arthur V. Watkins Dam was discovered near the south end of the bay last week by a farmer. The Bureau of Reclamation dumped sand and gravel around the dam to seal it off. Part of the earthen dam was eroded by the leaking water.

"Over the long run we've still got to figure out why there was seepage, where it came from and what we're going to do about it long term," bureau spokesman Barry Wirth said.

That means pumping out more than half the amount of water in the reservoir — about 100,000 acre-feet — Wirth said. The project will take about 30 days. Officials are importing 10 irrigation pumps from New Mexico to speed up the process.

"It's a lot of water," he said. "The problem is, we have to get down to where we can examine the face of the dam and the reservoir base. Unfortunately, that means taking water out, and we need to do it sooner rather than later."

The 14.5 mile dam was built 43 years ago and encloses 10,000 acres of fresh water used for recreation and as water storage for the Wasatch Front. Willard Bay was at about 80 percent capacity before the leak was discovered, said Tage Flint, director of the Weber Basin Water Conservancy District.

Pumps will deposit bay water into the Great Salt Lake. Some water is already being released to the lake through an outlet.

Engineers will study a 2,000-foot strip of the dam to try to determine how the leak occurred.

The draw-down will leave enough water in the bay to protect its fishery. Boating on the bay has been prohibited since the leak was discovered Nov. 13.

Wirth says it's unclear how the repair project might impact the area water supply.

"The district can't run the facility until it's safe, and it won't be safe until we do what we have to do," Wirth said.