In Part Two of this series, “Preserving Abandoned Mines – Protective Closures,” I explored some of the methods used to preserve abandoned mines that support wildlife habitats, including fences, gates and cupolas. While simple fences are easily constructed with inexpensive materials, they do not prevent a determined individual from entering an abandoned mine. When it is appropriate to preserve the underground habitats, it becomes necessary to use materials and construction methods that are far more robust.
About fourteen miles south of Wickenburg there is an abandoned mine shaft popularly known as the “Whispering Ranch” Mine. Its real name is lost in the fog of history, but it is barely two miles south of the historic Vulture Mine, on BLM-administered land near Whispering Ranch Road.  Like all other abandoned mines on public lands, this shaft was slated for destructive closure. As part of their pre-closure assessment, the BLM engaged biologists from the Arizona Game and Fish Department  and Bat Conservation International (BCI)  in June 2009 to perform quick inspections of the underground workings at this and other area mines, including the Mammoth Spar.
Conservation biologists from both organizations discovered a summer roost of California Leaf-Nosed Bats (Macrotus californicus) in the Whispering Ranch Mine, but none in the five shafts at the Mammoth Spar. In preparing its recommendations to BLM, the Arizona Game and Fish Department concluded that the bats at Whispering Ranch could be “excluded” from the mine and plans for destructive closure could proceed. In this case, the exclusion was merited because the bats were not believed to be using the mine as a permanent habitat. In general, the process of exclusion involves covering the mine entrance to prevent bats from reestablishing a roost. This must occur at times of the year when the colony is active and necessarily requires adequate inspection to ensure that the underground workings have been vacated.
Arizona Game & Fish returned to the Whispering Ranch Mine in late 2009 to conduct the exclusion, but immediately discovered that another (or same) colony of bats was using the shaft during the winter season as well. This discovery triggered permanent protection and meant that protective closure was warranted. Underground surveys showed that Barn Owls (Tyto alba) were also roosting and nesting in the mine.
There are two drifts (underground tunnels that follow an ore vein) above the 180 foot level of the mine. Arizona Game & Fish and BCI biologists determined that the upper drift was occupied by the bats, while the lower drift was used by the owls.
The California Leaf-Nosed Bat does not hibernate in winter, as some species are known to do. Therefore, it must forage for insects throughout the year. That this mine is used in both the warm and colder months indicates that the subterranean conditions and area food sources are suitable for long-term colonization. Barn Owls feed primarily on rodents, but bats are occasionally part of their diet. However, co-colonization of a mine by these species is not as rare as you might think. According to Jason Corbett, the Conservation Biologist and Southwest Subterranean Program Coordinator for BCI,
… the owls and bats use the same site, just at different times of the year. I have been into roosts where I have actually seen owls eating bats and have found bat skeleton parts in owl pellets. This seems to be more common in caves and with Great Horned Owls as opposed to the Barn Owls that I see in the mines. However, I’m sure there is some overlap and I’d bet that predation does occur.
The partnership that exists between AGFD, BCI and BLM ensured that BCI would be contacted on the latest finding. Since this would be a protective closure, BCI took a project proposal to the Freeport McMoRan Company with a request for funding.  Freeport agreed to fund the project and BCI contacted MineGates Inc. in Tucson to request their availability. 
Before we review the project to install a cupola, let’s briefly examine the history of the mine.
Short Historical Record of the Mine Site
What little is known about the Whispering Ranch site depends upon physical evidence rather than historical documents, and can be summarized into the following statements:
- The shaft is at least 180 feet deep and contains two relatively short underground drifts.
- A complex wood cribbing, at what “appears” to be the bottom of the shaft, may have a trap door leading to a lower level.
- Except for the cribbing in the sump, the walls of the shaft are fully exposed and the country rock appears to be stable.
- The mine dump measures approximately 12,200 square feet in two sections 85′ X 90′ and 70′ by 65′. Its depth ranges from about 5 feet to more than 15 feet. Waste material is uniform in color and rock content; suggesting there were no cross cuts and that either a single vein or multiple veins containing similar ore was the objective. 
- The volume of waste material on the mine dump significantly exceeds the volume of the shaft and two drifts (by a factor of more than 4:1). This suggests that there is a working level beneath the crib at 180 feet.
- The mine dump contains abundant samples of mineralized copper, but shows no indication that gold, silver or other ores were present.
- There is no tailing pile, indicating that mill ready ore (if any) was shipped off-site.
- The head frame was constructed of wood, but was probably dismantled when operations ceased. Concrete footings for the frame and cable hoist have survived to the present day.
- An abundance of bent nails suggests there may have been one or two wood buildings; but no wood remains. There are no remains or evidence of concrete floors. A few pieces of corrugated metal siding remain on the site.
- Cans were found in the trash field near the mine that can be dated to the period between 1887 and 1904. All of the cans contain the characteristic solder top and were manufactured using the “Norton’s Side Seam” method.
- One meat can has been dated to the period between 1900 and 1904. It is likely this mine had its origins around the turn of the 20th Century.
- A BLM archaeologist found materials that could be dated to the early 1920’s, but it is not known if these items were incidental or proof of operation beyond the early 1900’s. For example, there is a small cluster of broken china plates and bowls near the site. One of them bears the name of The Wellsville China Company, which establishes a date of 1917 or later. Whether the plates were used during the operational phase of the mine is not known. There is very little glass in the vicinity of the mine site.
- Small, white porcelain insulators show that the mine workings had electricity during at least part of its operational existence.
- This mine is less than one mile from Vulture City, making it possible that workers lived at the town site rather than at the mine. This would account for the modest size of the trash dump.
- The date range of the trash suggests the mine could have been developed and worked intermittently over a period of years, rather than during a single, short period.
Figure 2 shows a can that is narrowly dated to the period between 1900 and 1904. This type of key opener was patented in Canada in 1900. The solder top (seen as a gray “blob” on the lid) was no longer used after 1904.
Figure 3 shows the concrete bases for the cable hoist. The Head Frame was located to the right of this photo and was positioned next to the shaft. Without historical photos or sketches of the mine workings, it is impossible to know the height of the Head Frame. The dimensions of the cable hoist foundations, their spatial separation, and anchor positions of the frame suggest that it was probably not more than twenty-four feet tall.
According to Jason Corbett, the apparent bottom of the shaft (the location of the cribbing at the 180 foot level) was remarkably free of trash and rock. In other words, the shaft had not been used for dumping trash, and very few rocks or soil had fallen to the bottom. Jason reported that the floor of the crib gave a hollow sound when he tested it. It is assumed that the shaft continues to an unknown depth beyond the false floor.
The Gating Project
Once the mine was confirmed as a habitat requiring permanent protection, a company that specializes in the protective closure of mines and caves was brought on site to help assess the mine opening and develop an appropriate gate design. Tom Gilleland and his company, MineGates, Inc., located in Tucson, completed a design that would provide vertical and horizontal flyways for bats, while also accommodating the requirements of Barn Owls. The design incorporated a three-dimensional cupola that looks like an inverted box with a large, flat base that would safely extend beyond the edge of the shaft in all directions. A month-long construction process began at their shop and the gate was finally ready for installation in early February 2010.
Figure 4 shows the condition of the mine entrance just before installation project commenced. A fence enclosure had been in place for several years. Before the protective gate could be installed, it was necessary to remove about five feet of overburden from the dump and clear a path to the shaft.
As the waste material was being removed to an adjacent holding area, we had the opportunity to examine numerous samples of mineralized copper ore – primarily chrysacolla.
Removal of the waste rock is necessary for three reasons. First, it is loosely compacted and subject to erosion. Second, the gate needs to rest on solid rock to prevent anyone from digging underneath the structure. Finally, high strength steel rods are driven into the bedrock and welded to the frame to prevent the cupola from being moved. Figure 5 shows the clearing stage underway.
Great care was taken to prevent rocks and soil from falling into the shaft. Working around a vertical shaft requires abundant precaution, as evidenced in Figure 6.
In this image Tom Gilleland (MineGates) and Jason Corbett (BCI) use shovels to clear loose soil from the edge of the mine portal. Safety is a paramount concern when you are this close to a shaft, and both are wearing safety harnesses and ropes. Each is a veteran of many hundreds of descents into caves and mines in Arizona and other western states. As a conservation biologist, Jason has conducted more than 500 underground mine surveys in Arizona and an equal number in other western states. Tom has been in more than 400 mines and caves in Arizona and more than 1000 worldwide.
After the waste material was removed from around the shaft, the next phase of the project was ready to begin. Because of its size, the cupola and stability aprons were transported to the site in three pieces. Final assembly typically occurs on site.
Each apron – which is designed to extend beyond the perimeter of the shaft – must be welded to the cupola before installation. In Figure 7, Bruce Lynn (MineGates) is completing the top weld on one of the aprons.
Weighing in at 5,000 pounds, and measuring 15 by 13 feet, positioning the assembled gate next to the shaft was no easy matter – and darkness was rapidly approaching.
In Figure 8, Bruce Lynn and Jason Corbett confer on the strategy for off- loading the gate next to the shaft. When work resumed the next morning, the cupola would have to be positioned so that it would not drag rocks into the shaft. Wood planks were inserted under the aprons to make it easier to drag into place.
Work resumed the next morning under the threat of rain, but by 9:30 a.m. the structure was in its final position over the shaft.
The high-strength materials used for construction of the gate include “manganal,” a type of hardened steel with high manganese content. The horizontal rods provide the openings necessary for bats and owls, but keep people out. Only a few tasks remained before completion of the project.
Next, manganal rods were driven into the bedrock and welded to the frame, and two perches were installed at the raptor opening for owls. Finally, a camera perch had to be attached to the inside edge of the cupola.
The camera perch is an important tool for studying bat and owl activity in the future. Motion activated devices will be installed periodically to learn more about roosting and nesting activity at different seasons.
Waste material that had earlier been removed to provide access to the shaft was moved back in place for landscaping around the aprons and to form berms that would discourage vehicle traffic. The installation project was now complete and one shaft had been saved for wildlife.
In Part 4 we will explore a few aspects of the economic and ecological importance of protecting bat habitats in abandoned mines, as well as the prospects for their preservation. Tom Gilleland and Jason Corbett will provide some reflections on the significance of their work.
Footnotes and References
 The mine can be reached by driving 13.2 miles south on Vulture Mine Road from the intersection of West Wickenburg Way (U.S. 60), until arriving at Whispering Ranch Road. Turn left and proceed 1.0 miles. The mine dump will be visible on your right, about 100 yards south of Whispering Ranch Road. Total driving distance is 14.2 miles. GPS coordinates are: N33 47.646′ by W112 49.812′ (WGS84).
 See the Arizona Game and Fish Department’s involvement in protecting bat habitats on the web at: http://www.azgfd.gov/w_c/bat_conservation.shtml
 Learn about Bat Conservation International on the web at: http://www.batcon.org/
 Freeport McMoRan is one of the world’s largest copper, gold and molybdenum producers. They are headquartered in Phoenix, Arizona.
 To learn more about MineGates, Inc., visit their website at http://www.minegates.com
 A contrasting example would be the Black Rock Mine on Constellation Road, east of Wickenburg. There, the mine dump shows two distinctly different types of waste rock in the pursuit of both silver and gold.
Last 5 posts by Allan Hall
- Wickenburg Hospitality Comes in Many Forms - December 15th, 2010
- Calliandra Eriophylla is Native to the Wickenburg Area - December 9th, 2010
- Goodbye, Old Bridge - November 29th, 2010
- Abandoned Mines Part II: Protective Closures - March 10th, 2010
- Abandoned Mines Part I: Preserve or Destroy? - March 4th, 2010