January 24, 2008
Repairing the Mathews Drop Structure

Photo by Dave Mawell View of Mathews Drop Structure

By Dave Maxwell, Staff Writer

Not too far east of U.S. Highway 93 in the Panaca area is the Meadow Valley Wash. A good part of it today is filled in with sediment, but once it was a deep channel in the ground, about 25 feet deep and about 35-40 feet wide. Today looking out across the fields from the highway nearing Panaca, you probably wouldn’t see it. It simply drops off in front of your feet once you walk up to it. At one point there is a cement structure referred to as the Mathews Drop Dam, also known as the Cold Springs Dam.

According to Lincoln County Flood Control District Chairman, Glenn Zelch, of Pioche, it was intended to be a sedimentation basin. It was built in the mid-1930s, probably by the Civilian Conservation Corp. Zelch said that when the structure was first built across the deep wash, the upstream side was just as deep and wide as the south side (downstream) is today, and extended through Meadow Valley northward and got progressively smaller and shallower until it led all the way up to the end of Condor Canyon, northeast of Panaca. However, he said, “Between 1937 and 2007 the upstream part all filled in with silt.” At present there does not even appear to be much of a depression in the ground on the upstream side giving any impression a deep channel once existed there. “It did its job, it retained the silt,” Zelch said, “but nobody ever cleaned it out and now it’s completely full.”

He said there is no provision built into the drop structure that allows water to go through slower, allowing it to act as a flood control dam. Water just goes right over the top and onto the concrete bottom about 25 feet below and on down the wash. “If it was intended back in the ‘30’s for flood control, it couldn’t do today what it was intended to do.”

On the west side of the concrete structure is a small channel eroding away at the land touching the structure. County Engineer Charles Brechler expressed concerns a heavy flood would erode away the side even more and create a deep wash next to the cement structure rather than in line with it, and eventually erode the ground back upstream again. Commissioner Paul Mathews said that would create problems because it would affect ranching operations for ranchers on whose land the old wash is located.

Brechler said at the Feb. 4 Commission meeting he would present a request for $8,000 to do emergency repairs to stabilize the drop structure. County Building Director Ken Dixon said, “At this point in time, the best way to do that would be go in from the existing road to the top of the dam itself, cap that with a gravel base to get the water to go over the top of the dam like it’s supposed to, and fill in the existing hole that is going around the cement structure, so all the water will flow over the top of the dam.”

Zelch said the County Flood Control District also wants Commissioners to decide whether the structure is to be a sedimentation basin or flood control? “What is the purpose of it?,” he asked “If it is a sedimentation basin, do the Commissioners want to clean out behind it and continue to use it that way, or think about building a new structure down stream further?” Those questions were not addressed at the January 22 meeting.

He also said later plans by the Flood Control District may include grading off the filled in upstream section and spreading pretty good size rip rap on it, possibly six-inch river rock a foot or so deep, to discourage small animals from digging in the ground. Glenn said once the County decides what they want the structure to be: either a sedimentation basin or a flood control dam, then planning what needs to be built and where, would be the next step. Digging out the upstream part to the way it once was, Zelch thought, would involve a lot of excavation. Also what to do with all the dirt removed could be a problem. However, building a new structure further downstream, be it a flood control dam or sedimentation basin, he said, “could cost anywhere from $250,000 to $500,000.”

Phyllis Robistow, County Grant Administrator reported she had learned that the grant money to help stabilize the structure she had applied for “wasn’t for the type of thing we were trying for.” She said the grant would not work for “dams, levies and sediment structures.” Rather, it was for “pre-disaster help in getting people to move their houses if they were in the middle of a flood plane, not for fixing up things, “she said. She was optimistic there are other types of grant available, and said she will continue searching, “for some FEMA flood control stuff out there that we can look at.”