May 8, 2008
"Dam" Repairs

Photo by Dave Maxwell Pahranagat National Wildlife Refuge Manager Merry Maxwell.

By Dave Maxwell, Staff Writer

Drawing down water in Upper Pahranagat Lake continues at the Pahranagat National Wildlife Refuge. Speaking at the May 5 County Commission meeting Merry Maxwell, Refuge Manager, said engineers asked her to keep the lake at a low 7-foot level all year. Now they are getting ready to replace the entire headwall structure below the fishing pier; that’s the location of the water outlet structure that was examined in 2007. Inspections done by the Corp of Engineers found the outlet culvert is partially crushed, the water release screw gate is not operating correctly, and the trash rack on the gate is full of large boulders. This allowed for a heavy water build up behind the dam, then large water releases at times when the dam broke free. Merry said the construction period is planned for July 14 to October 1. “My goal is to have the lake dry by July 1,” Merry said.

She said she slowly lowered the lake this spring, “so we could provide shorebird habitat during migration and not getting it too low so we can still take care of the fisherman and those who come to the campground as long as we can, but we are going to start getting aggressive about the draw down real quickly.”

In addition, Merry also said “We feel it’s time for us reclassify the hazard level of the dam…We also suspect it’s time for us to take a careful look at what a 100-year flood might do to the area, based in the proximity with U.S. Highway 93 and the Headquarters facilities.”

While all of this is taking place, it has created an unusual reverse effect: the re-emergence of water in Lower Pahranagat Lake, which is normally very dry. Two reasons have accounted for that Merry explained. “The first is we are trying to treat the Russian knapweed in Black Canyon, which means we can’t divert water over there, we’re trying to keep it dry…The second thing is we are trying to treat Salt Cedar and one of the ways to keep it from sprouting is to inundate it with water. Russian knapweed and Salt Cedar are both invasive species that adversely affect the habitats they invade.

Another problem Ms. Maxwell said they are facing is how to keep Upper Pahranagat Lake low and yet keep everything really wet so it didn’t dry out while we’re doing construction. The solution has been to fill up the South lake and “Keep the wetland area (between the two lakes, the middle marsh area) as wet as we could because we knew we were going to subject them to some pretty high temperatures during the summer without water in the Upper Lake,” she said.

In late June or early July, Merry said, the north marsh levy, the one that is visible going across the lake, will be boarded up to create a coffer dam to dry up the main lake. A second coffer dam will be built close to the south outlet. This will allow construction and replacement work on the headwall structure and removal of the fishing pier.

Having Upper Lake pretty much dry during the summer months, Merry said, may have impacts on campers at the lake this year. Most of the fish in the lake, except the Carp, have been moved or will be moved as conditions arise, to the Key-Pittman Refuge.

The fishing pier was constructed in 1937, probably by the Civilian Conservation Corp, and the water outlet for the Upper Lake is directly below it.