Anchor Dam

Anchor Dam in the spring before the water drains away.

THE DISAPPEARING WATERS OF THE OWL CREEK

Anchor Dam

Charles Blonde had built his homestead in the late 1800’s with high hopes of building his herds and growing plentiful crops. He had just left the Shoshone agency at Fort Washakie where he had worked as a herder and had moved into the the remote Big Horn Basin. Blonde's brand resembled an anchor and his spread was thus called Anchor Ranch.

Blonde's two-story ranch house was nestled in the cottonwoods on the South Fork of Owl Creek. He dug irrigation ditches to redirect this small creek to his fields. Despite all his backbreaking efforts, Blonde struggled with irrigation at Anchor Ranch.

Local residents witnessed large holes appearing in the ditches of this region and tried to fill these holes with straw. Despite their efforts, a considerable amount of the water would drain away before it could be used. Sinks were also reported to exist in the bed of Owl Creek itself.

All that remains of Blonde’s former homestead are the remnants of a cow camp and empty irrigation ditches that have grown over with grass and sagebrush. In place of the historic ranch, is a concrete dam.

Named after the former ranch, Anchor Dam has earned the dubious reputation as a boondoggle. Like the irrigation ditches, it has never been able to hold back the water from Owl Creek.

Nearly every year, the Owl Creek over flows its banks, swollen with snow melt and spring rains. By late summer, there is not enough water for the farmers and ranchers downstream to use for irrigation.

Over the years, many attempts were made to get water to the region and it was the U.S. Bureau of Reclamation who believed they could accomplish this momentous task. A geologic report and map of the proposed dam site at Blonde’s old homestead was prepared in 1935. It was based on one week of reconnaissance field work.

Local rancher, Henry Freudenthal, strongly opposed the early efforts to build a dam in the area because of “seepage”. He even went as far as measuring the water from the upper to lower end of the Owl Creek and discovered that seventeen percent of the water was lost along the way.

The government’s report did not include his observations. The state and federal geologists repeatedly gave cautious approval and suggested further studies and investigation.

Once it became clear that the federal government was prepared to spend large amounts of money on the project’s construction, Freudenthal dropped his opposition and declared he would “entrust this point to the judgment of the government engineers.”

Problems began almost immediately.

In 1958, the year work was to commence, a 300-foot circular crack appeared in the future reservoir area. Two other sinkholes were also discovered that were caused by “solution cavities”. Dolomite, a sedimentary rock that could be dissolved by groundwater over time, was discovered under the entire floor of the future reservoir. Sinkholes kept appearing.

Sinkholes #33 and #34

Eddie Shaffer, a longtime resident of Hot Springs County, was part of the 300-man crew that was hired to build the dam and said that the workers attempted to fill these holes with cement.

“We mined under that dam,” Schaffer said, “I couldn't go back in those holes. They were too far back and they narrowed down. I knew guys that were crawling to get into those things and then they pumped them full of cement.”

“They were pumping into the holes, one time, a foot apart, the full length of that dam. They might take part of a truckload of cement for one hole and 15 truckloads for the next one.”

The workers continued to fill the solution caves with cement and plugged the cavities they couldn’t successfully seal otherwise. Their efforts to stop all the leaks failed.

Despite the hardships, the 208-foot Anchor Dam was completed on Oct. 26, 1960. The following spring, they began filling the reservoir. The lake was to have a capacity of over 17,000 acre-feet.

However, within days, the reservoir began to drain. Water leaked through undiscovered sinkholes and permeable bedrock and emptied the lake before it reached capacity. Testing showed that the water drained deep underground through joints and fissures.

The 300-foot crack from 1958 collapsed, forming a sinkhole that drained the reservoir at a rate reaching 2,210 cubic feet per second. Multiple unsuccessful attempts to plug this hole led to a dike being constructed around it to isolate the sinkhole from the remaining reservoir. Since then, 54 sinkholes have developed in the reservoir, generally in an area 600 feet upstream from the dam.

According to historian Kathy Lindholm, over seven million dollars was spent trying to build the dam and plug the sinkholes. By the mid-1970s, the Bureau of Reclamation largely stopped throwing their money down a hole. They had spent four years building the dam and twenty-seven years trying to get it to hold water.

In the spring, for a few brief weeks, Anchor Dam will look like the reservoir it was meant to be. It won’t last long, though, and the water will drain down once more. By late summer, the reservoir is a small puddle and this tiny amount of water can occasionally be used for late season irrigation.

Today, a small campground and picnic area sit in the shadow of Anchor Dam, a reservoir that will never serve its intended use. Despite a century of efforts, the waters of the Owl Creek continue to disappear into sinkholes and cracks deep in the earth.

Workers survey solution cavities beneath the dam site, August 1958