Reprinted with permission from: Rocky Mountain Caving, Colorado Grotto, v. 25, n. 4, August 2008, p. 10-12.

Portal Stabilization and
Bat-Gates at the Elephant Mountain Mines



Since 2005, the Aspen-Sopris District and Colorado Division of Wildlife
(CDOW) have monitored a colony of approximately 750 Townsend's big-eared bats that inhabit an inactive mine near Redstone, Colorado, called Elephant Mountain mine. The mine serves as a maternity roost for the Townsend's big-eared bat, and as such, represents one of 15 identified in Colorado, and is the only maternity roost on public land in western Colorado. From 2005 to 2008, the mine openings became increasingly blocked by material and continued to degrade. In all, three adits of the mine and an air-vent shaft have degraded nearing the point of being blocked. The adits are used by the bat colony during spring through fall, and the air-vent provides air to the lower adit; the one that is most used by bats.

The objective of the project is to stabilize the mine openings that provide bat habitat and protect the openings from potential human disturbance using culverts and bat-friendly gates. The Townsend's big-eared bat (Figure 1)

Figure 1. A Townsend'sBig-Eared bat.

Figure 2. A bat cupola protects the lower mine opening.
is a Forest Service Sensitive Species on the Rocky Mountain Regional Forester's Sensitive Species list. Cave bats are a Management Indicator Species on White River National Forest, and have a number of Forest Plan objectives, standards, and guidelines associated with their protection.


After conducting NEPA, in Fall 2008, under contract administered by Colorado Division of Reclamation, Mining, and Safety (DRMS), culverts and bat-gates were used to stabilize four mine openings. The collapsing openings of the lower and middle adit portal were excavated to insert culverts, which were sealed in place using rock and expanding self-hardening foam. The air-vent shaft was also sealed with foam and a metal air-flow gate was installed over the opening. Excavated material was replaced over the culverts. Attached to the lower adit
culvert is a large chamber, or "bat cupola," that is designed to allow bat egress through 5.75-inch gaps in the bars (Figure 2). Attached to the middle adit is a bat-friendly gate (Figure 3). The cupola and bat-gate prevent general human access due to the bar spacing, but allow bat and air movement. The structures have lockable doors, to allow entry of authorized personnel. The upper adit is equipped with a lockable air-flow gate to allow air

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movement, but restricts unauthorized human entry.

Work was conducted by a five-person crew.
A total of 40 man-hours were required to fabricate the cupola, bat-gate, and air-flow gate. Earth excavation, culvert installation, attaching the cupola, and installation of the vent shaft and air-flow gate took 150 man-hours. Site reclamation, seeding, and associated tasks took 54 man-hours. Equipment used included a trackhoe, portable welder and cutting torch, shovels and other hand tools, chainsaw, PPE, 300 lbs of mortar, 50 lbs of native seed mix, 6 weed-free straw bales, and 3 padlocks. All equipment and supplies except for seed mix and padlocks were provided by the contractor. I participated with the State project representative in overseeing the site construction. This required 7 days of my time, or $2,121 in funds.

White River National Forest contributed $6,500 in funds toward State contract reimbursement, or 13 percent of total contract cost. CDOW contributed $8,000 and DRMS contributed $36,596. Total cost was $51,096.

Figure 3. A standard bat-gate also protects the lower mine

Figure 4. The bat-gat project protecting the Townsend's big-eared bats in report in local community newspapers.


Installing the two bat-gates and air-vent shaft enhances approximately 30 acres of bat habitat, based on 20 acres representing the area for a mine opening heavily used by bats (lower adit) plus 10 acres representing the area for a mine opening used by few bats (middle adit and air-vent, each 5 acres). Characteristics of habitat that were enhanced are stabilized access to maternity roosting habitat, securing roost sites from human disturbance, improving air flow to roost sites in the cave and mine, and maintaining roost sites in close proximity to foraging habitat and water.


Colorado Division of Wildlife - Glenwood Springs, CO; Colorado Division of Reclamation, Mining, and Safety; Robert Congdon, Maree Love mineral claim holder; Pitkin County Open Space and Trails; and the Colorado Grottos
of the National Speleological Society.

All photos courtesy White River National Forest.

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