While an airport employee refueled the Apaches, the crews had lunch in the airport’s office.

These little shrubs are easily missed — until they begin blooming, that is. Wickenburg’s native variety may reach heights of only two feet, but produce many pink “puff-ball” flowers like those shown in the photo. These are extremely hardy plants. They are well adapted for survival in hot, dry conditions.

Photo 1, November 2009 photo of new bridge and south roundabout. The old north bridge is seen partially demolished. Photo courtesy of Flying M Air.

Wickenburg has seen several bridges come and go during the past 120 years or so. Unfortunately, the “going” part has occasionally meant they were carried away by floodwaters. February 22, 1890 was by far the most catastrophic event, when heavy rains and melting snowpack caused the upstream Walnut Grove dam to fail. One hundred twenty-eight people in Wickenburg and other points along the river died in that event. In Phoenix, the Salt River rose 17 feet in 15 hours from the same winter storm.

Wickenburg’s first concrete bridge was completed in 1914, but it did not survive long. Three days of intense rains in January, 1916 caused major flooding on the Hassayampa watershed. By the time the rains ended there wasn’t much left (see Photo 2).

Photo 2, Flood of 1916 destroyed the 1914 bridge. Archive photo.

For reasons that remain obscure, the bridge had still not been replaced after two years. In 1918, some enterprising Wickenburg residents constructed a cable suspension bridge across the river, providing much needed relief for foot traffic.

Photo 3, Cable foot-bridge built in 1918. Archive photo.

Wickenburg residents must have been a patient lot in those days, for the next bridge across the Hassayampa was not completed until 1926. It was designed specifically for motor vehicles, but remained in service for only ten years, until the north bridge replaced it.

While drilling shafts in the riverbed, construction crews discovered the remains of two, much older, bridges. One of them, built in the late 1800′s, was made of wood pilings and served as a telegraph bridge. The second, constructed with rock and mortar, dated to the early 1900′s. It was used for horse and carriage traffic, but was either destroyed in flooding or demolished and replaced by the 1914 bridge (shown in Photo 2).

On December 4th, 2009 the last support column for the old north bridge was pounded into rubble, bringing to a close the life of a bridge that served Wickenburg residents and countless travelers for seventy-three years. Demolition began at the west end the week before Thanksgiving and the jack hammer finally reached the east bank on December 3rd.

Photo 4, Demolition in progress.

As bridges go, it was not spectacular in any sense: It was not an architectural “statement”; but it did its job reliably, surviving even the flood of February, 2005, which caused major damage along Jack Burden Road.

Photo 5, The west end of pedestrian bridge, as seen from near the Wishing Well.

Thankfully, town officials and the Arizona Department of Transportation saw fit to retain the old south bridge for pedestrian traffic. Structural modifications (including raising the height) have been complete for several months now, but other landscaping touches remain unfinished. For example, boxed shade trees and a few benches would be attractive and encourage pedestrians to linger in the area.

One day, perhaps soon, this will be a place where community events will be enjoyed by residents and visitors alike. For now, at least, bring your own shade and folding chair.

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. [1] 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 [2] and Bat Conservation International (BCI) [3] in June 2009 to perform quick inspections of the underground workings at this and other area mines, including the Mammoth Spar.

Figure 1, California Leaf-Nosed Bat. (Photo by Jason Corbett, BCI; used with permission.)

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. [4] Freeport agreed to fund the project and BCI contacted MineGates Inc. in Tucson to request their availability. [5]

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. [6]
• 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 2, Key-type meat can with solder top, 1900-1904.

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.

Figure 3, Cable Hoist.

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.

Figure 4, Shaft Collar and Overburden.

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.

Figure 5, Removing the Overburden.

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.

Figure 6, Tom Gilleland and Jason Corbett.

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.

Figure 7, Bruce Lynn (MineGates) Welding Apron to Cupola.

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.

Figure 8, Positioning the Gate.

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.

Figure 9, Cupola in Place. Bruce Lynn and Tom Gilleland look down 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.

Figure 10, Installing Camera Perch.

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.

Figure 11, Dump Material Used for Berm.

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

[1] 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).

[2] 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

[3] Learn about Bat Conservation International on the web at: http://www.batcon.org/

[4] Freeport McMoRan is one of the world’s largest copper, gold and molybdenum producers. They are headquartered in Phoenix, Arizona.

[5] To learn more about MineGates, Inc., visit their website at http://www.minegates.com

[6] 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.

Other voices have spoken for moderation, cautioning that indiscriminate closures of shafts and adits can deprive certain wildlife species of needed habitat. In fact, regulations require federal agencies like the BLM and National Forest Service to assess underground mine workings to ensure that habitats are protected.[1] Not all abandoned mines are suitable for wildlife, but unrelenting pressure on traditional habitats makes these mine workings increasingly important and – in some cases – they may be the last alternative for the long-term survival of some threatened species. Solutions for preserving abandoned mines include fencing, barricades and steel grates or cupolas that permit access for wildlife while keeping humans out. Mines that serve as habitats have been destructively closed in the past, trapping entire colonies of bats in the underground workings. In other cases, excessive human visitation and vandalism have forced bats and other wildlife to abandon some mines and caves. In April 2009, an unknown number of individuals shot and killed up to 90 bats in an abandoned mine in the Superstition Mountains.

The BLM’s policy handbook, Abandoned Mine Lands Policy Handbook states:

Abandoned underground mines provide significant habitat for bats-more than half of North America’s 47 bat species are known to use mines. Acquiring even a basic understanding of bat use of abandoned mines often requires repeated surveys during different seasons. Sealing mines without first evaluating their importance to bats may be one of the single greatest threats to North American bats.”[2]

There are two broad categories of closures: (1) Destructive closure, where the shafts or adits are permanently sealed by blasting or backfilling, and (2) Protective closure, where the shafts or adits remain intact, but access to the underground workings is prevented using some type of barricade.

Protective closures actually have two objectives that frequently operate concurrently: First, to keep people out of a dangerous underground mine without resorting to destructive closure; and second, to protect wildlife that might be using the mine for nesting, birthing, hibernation, night roosting or migration, etc. Protective closure means that the subterranean workings are effectively closed to human visitors. For wildlife, it remains a seasonal or permanent habitat – but with the danger of human disturbance greatly reduced or eliminated.

Figure 1, Simple Fence at Mine Shaft

The simplest and least costly method of protective closure is a fence constructed with metal stakes and wire, as shown in Figure 1.[3] Although this type of structure can be defeated by a vandal with wire cutters, it provides several benefits, including:

• It is a visual warning to visitors.
• With proper signage it serves notice that entry into the workings is criminal trespass.
• It can at least partially relieve potential liability.
• Fences can be quickly installed on site.
• With periodic maintenance these structures can last for decades.
• The materials are not expensive.[4]

Warning signs like that shown above are generally effective for most visitors but unfortunately, are not a deterrent to the small minority of people who choose to enter an abandoned mine in spite of the risks. [5] Not surprisingly, very few fences have been erected – even around abandoned mine shafts that are difficult or impossible to see from a distance in daylight or darkness. In my experience, the mere mention of fencing is met with deprecating remarks from state and federal officials.

When underground mines serve as permanent or seasonal habitats for wildlife, more robust solutions must be considered. One type of barricade is a gate structure like the one shown in Figure 2. These purpose-built gates are installed inside the entrance of an adit and must be designed to conform to its dimensions as well as to the type and condition of native rock in the walls. The variability of these factors is almost limitless and requires customized solutions. There is no “shrink-wrapped” or “one size fits all” gate.

Figure 2, Vertical Gate for Adits – Grandview Mine

Notice that the sides and top conform to the shape of the roof and side walls of the adit. Understandably, vandal-resistant gates such as this require the use of materials that are more costly. However, quality materials and extensive anchoring, using super-strong rods, ensures that this gate will remain in place for a very long time.

Variations of the adit design include gates that incorporate the use of culverts when the entrance to an adit is at risk of future collapse. This type of protective closure is particularly important for maintaining air flow in existing secondary mine openings, as shown in Figure 3.

Figure 3, Culvert Gate

As with mine adits, shafts come in a seemingly endless variety of shapes and sizes. Surface conditions around the shaft entrance (collar) can further complicate design criteria and affect the choice and cost of materials. Shafts that are particularly large can limit the degree of off site construction; requiring that some assembly be performed at the mine site.

Figure 4 illustrates a type of protective closure known as a cupola that accommodates the requirements of bats and owls in the same mine. Clicking on the image will open a larger graphic.

Figure 4, Cupola Design for Mine Shaft

Protective closures with gates or cupolas are only used when populations of bats, raptors or tortoises have been confirmed. As we will see however, preserving these habitats is far from automatic.

In Part three we will examine a gating project that used the cupola design to protect a colony of California Leaf-Nosed Bats and Barn Owls at a mine shaft near Wickenburg. You will be introduced to two organizations that work with state and federal agencies to protect habitats in abandoned mines.

Footnotes and References:

[1] Access to BLM Abandoned Mine Lands policies and manuals can be reached via these web sites:
Abandoned Mine Land Program Policy Manual Section (MS-3720) http://www.blm.gov/nhp/efoia/wo/manual/manuals.html
AML National Strategic Plan http://www.blm.gov/nhp/efoia/wo/fy06/im2006-145attach1.pdf
AML Website http://www.blm.gov/aml
BLM Manual Sections http://www.blm.gov/nhp/efoia/wo/manual/manuals.html

[2] Bureau of Land Management H-3720-1 Abandoned Mine Lands Policy Handbook. 9.3.3.4. Bat Surveys. Page 61.

[3] The shaft shown in this photo is approximately 200 yards west of the Mammoth Spar Mine. It is one of two shafts in the immediate vicinity that are awaiting external surveys to determine if they serve as habitats.

[4] The approximate retail cost of materials shown in Figure 1 is less than $80.00 (8 metal stakes at $7.00 each and 288 feet of wire at 6 cents per foot, plus signage.)

[5] Infrared sensors placed in abandoned mines in Nevada before and after warning signs were installed revealed no significant reduction in human visitation. Bat Conservation International. 2009. “Managing Abandoned Mines for Bats.” Page 79.