One of the nicer nature trails in town is around Black Bass Lake. But if you park at the base of the dam and look at the crumbling pile of rocks and leaks on its face, it can make you say a little prayer before you take a hike or ride a bike around the lake.
It has long been known that Black Bass Dam is in poor physical condition. So, it is no wonder that recently the Eureka Springs City Council voted unanimously to support applying for an 80/20 percent matching grant for repairs. Mayor Butch Berry said the city could apply for grant funds to rehabilitate the dam through the 2018 Disaster Supplemental program of the Economic Development Administration. The city’s cost share of a maximum $625,647.86 grant would be $156,411.96 for a total project cost of $782,059.82.
But rehabilitating the dam is not the only option. Dr. James Helwig, a retired geologist who was co-chair of the Eureka Springs Committee, recently sent an email to city officials, including members of the Eureka Springs Parks Commission, recommending they attend a workshop “Dam Removal and River Restoration” Thursday, Sept. 20, in Fayetteville, sponsored by the Beaver Watershed Alliance.
“It’s a very impressive and comprehensive one-day event that should be attended by the City of Eureka Springs and Parks leaders,” Helwig said of the Beaver Lake Watershed 6th Annual Symposium. “Here is an opportunity that those interested in the future of Black Bass Dam should not miss. The choice of modification or removal of old dams is an alternative environmentally sound solution to expensive renovation, repair and maintenance for needless or dangerous dams.”
Helwig said the long-term vision of restoration of free-flowing streams is a major movement in “our overly dammed country.” He recommends a cost-benefit analysis of the alternatives as a part of any decision about what to do about Black Bass Dam. He also suggested city leaders consider a site visit to the dam removal project at Bella Vista.
Mayor Berry said the repair of Black Bass Dam has been on the city agenda for at least 8-10 years.
“There is a big difference between what is happening at Bella Vista Dam and Black Bass Dam,” Berry said.
The question about how the dam would be rehabilitated has been under discussion for years, and Berry said repair of the dam has different designs based on money available.
He also said the repair work could help prevent a major disaster.
“One of the major water distribution pumps for the western portion of the city is installed at the base of the dam,” he said. “If the dam fails, it would wipe out the pump station and the water supply for at least half of the city, if not more.”
Engineer and former alderman Dee Purkeypile, P.E., said loss of the pump station would also impact the ability to provide water to fight fires in the city.
“If the dam were to fail, for any reason, it would be expected that the lift station would be damaged or possibly destroyed, which would subject the city to an unacceptable level of health and safety risks,” Purkeypile said. “In my professional opinion, as a dam safety engineer with 33-years’ experience in the field, the dam should either be repaired or removed.”
There have been several reports written regarding the dam. Purkeypile said one was a detailed inspection report that was performed after a major 2008 rainfall where FEMA provided funding to improve two elements of the dam. One item of repair was raising the existing spillway’s sidewall and adding concrete and rock rip rap below the spillway.
“Additionally, an effort was made to seal off the voids in the mortared rock in a three-foot wide band along the length of the dam where the seepage was suspected of flowing through the mortared rock section of the dam,” Purkeypile said. “That effort was not successfully implemented by the contractor. As part of the repair project, the lake level was lowered and it was discovered that a concrete face exists from a point about three feet below the crest of the spillway. Once the lake level was lowered three feet, the seepage almost completely stopped.”
His recommendation is to lower the lake, apply an adhesive sealant and adhere an impervious barrier such as EPDM (Firestones’ Pond Guard) rubber liner or HDPE (thick plastic sheeting), which is also used for sealing ponds. He said the materials would be expected to last between 30 to 50 years, in place.
The first time Purkeypile looked at the dam in 2004, it was already showing signs of stress. When he moved to town in 2007, he saw the dam had deteriorated quite a bit in three years’ time.
“I brought that to the attention of Butch Berry, who informed the city council of my concerns,” Purkeypile said. “I have photo-documented the progressive failure of the dam up to this point.”
Some environmental groups say that when dams are no longer needed for flood control or other purposes, consideration should be taken to removing them. But Purkeypile said removing Black Bass Dam wouldn’t have a substantial environmental benefit.
“Regarding removal of the dam, it’s located at the headwaters of West Leatherwood Creek and removing it would not provide any substantial or quantifiable enhancement to the stream,” Purkeypile said. “The spring flows that keep Black Bass Lake full pass through the spillway and move downstream, ultimately entering Lake Leatherwood.
“Eureka Springs Parks has developed a series of walking, hiking and biking trails around the lake. The lake is a serene backdrop to the trails. If the dam were to be removed, the lake would be gone and the trails would not be as aesthetically attractive to recreationists. The repaired dam and the lake will provide a recreational asset for the community and for the many recreationists who are coming to Eureka Springs on a more frequent basis.”
Purkeypile said he recommended to Mayor Berry that the city obtain the services of McClelland Engineering to do the proposed work.
“Although I provided three conceptual designs to stabilize the dam in 2009, McClelland Engineering will be responsible for the final design to stabilize and rehabilitate Black Bass Dam,” he said.