Excavation of portal #2 completed months before gating, located 300 feet away from the main entrance.
John Audubon would be proud to know that even today rare animals are being discovered and protected on his property. Located at Audubon's Mill Grove Preserve in Audubon, Pennsylvania, old copper mine remnants house a bat colony throughout the winter. Though much of the mine cannot be physically entered by humans, physical evidence as well as historical accounts suggest extensive bat use at the site. When surveyed in winter of 1998-1999, temperatures inside the mine were too high to ever be suitable for a major hibernaculm. Mill Grove reopened a similar portal a few hundred feet away in hopes that air circulation between the entrances would alter the temperatures, making the site even more suitable for bats.
During the winter survey, a multitude of human evidence was found presumed to be left behind by local children. A 20' vertical climb rigged with rotting clothesline was particularly disturbing. In effort to eliminate safety hazards yet keep the copper mine open for habitat use, an ACCA style cave gate was installed in August 1999 by Bat Conservation and Management from Pennsylvania (Sanders, and Chenger). The installation took only two days, despite the gate location being 600 feet from a road.
