SAFFORD — Out in the San Simon Valley, a railroad bridge rises high above a streambed that may or may not have a name.
The few vehicles to travel this area kick up dust clouds in some spots; in other places, the ground can give way underfoot, eroded from below in a process called piping.
Widespread erosion in the form of downcutting, headcutting and piping has scarred the San Simon Valley for more than 100 years and continues to advance. Some of the area’s arroyos, carved by headcutting, are more than 20 feet deep; others, just getting started, are only inches in depth.
The problem was recognized as early as 1919, in F. H. Olmstead’s report to Congress, “Gila River Flood Control.” Nothing came of this until the 1930s, when the first erosion control dams were built by such agencies as the Civilian Conservation Corps (CCC).
Today, the San Simon Valley boasts 18 large dams and hundreds of smaller structures built through the years.
Maintenance and repair of the large dams are handled by the Safford Bureau of Land Management Office. When the HX Retention Dam, north of Bowie, was breached in 2014, the Safford BLM worked with state and national offices to secure funding for its repair.
Safford Field Manager Scott Cooke said the work, finished in 2016, cost approximately $1.3 million. “We wanted to get that fixed so it could continue to serve its purpose of holding back those large flows and slowly releasing them,” he added.
Another example is the 79-year-old Goat Well drop structure, installed to stop headcutting up Slick Rock Wash. Goat Well was built by the CCC and Soil Conservation Service in 1940 at a cost of $13,000 — around $238,000 in today’s money. It has done its work well, effectively halting erosion up the Slick Rock floodplain.
A new concrete face was installed on the structure, which was developing cracks, in 2010 using American Recovery and Reinvestment Act funds. More recently, mesquite trees and other vegetation were removed from the side of the retention dam associated with the drop structure.
“We pay particularly close attention to Goat Well because it’s so large,” Cooke said.
Piping remains a concern around Goat Well, with a ground cavity running parallel to one edge of the drop structure.
“If we don’t go in there and fix it, it could erode through and basically take away the functionality of that whole retention structure,” Cooke said.
The BLM is also working with the University of Arizona Cooperative Extension and Gila Watershed Partnership on a plan to assess the valley’s hundreds of smaller dams, many of which were also CCC projects.
“I have proposed for years to look at this system out here, make an evaluation of significant structures and say which ones are in need of maintenance, which ones are most important and which ones we’ll just forget about,” said Cooperative Extension Director Bill Brandau.
Cooke said the three organizations are discussing a study that would include an overall structure assessment, and that the BLM and GWP are working on an agreement that could potentially provide funding for that study.
“The San Simon has been an area that we’ve been interested in working on for a long time,” said GWP Executive Director Melanie Tluczek. “It’s got some major erosion issues; and from what I understand, it’s one of the most challenging places to try to do restoration.”
This is the second in a series on erosion and erosion control in the San Simon Valley. Next: A bit of history on the San Simon Valley’s dams and a closer look at restoration plans.