Grandview and Last Chance Mines Gating Project
Horseshoe Mesa, Grand Canyon National Park

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The production part of the project only began after first hiking down to the mines and taking measurements of the adits. The site inspection was instrumentental in planning project logistics at such a remote and challenging site. Our goal was to install the gates quickly in a safe and secure manner, thus limiting our impact to the park. We chose to install the gates in September so that most of the roosting bats would not be present at the site. Our project also focused on making our gates designs blend into the historic feel of this unique site.

Back at our shop in Tucson, we began production of the three gates. We started by building gate template tools to facilate quicker and more accurate construction of the gates. In this photo we are measuring bar gaps to ensure that they are 5 3/4 inches wide needed for easy bat flight passage. This is the optimum bat gate bar-gap size determined by research from BCI and other bat researchers.


Designing Bat Gate in Workshop


Trimming Bat Gate


Once the gate is framed up we weld the bars and braces into place. To increase gate security and strength we apply continuous welds to each intersecting piece. The gates for this project weighed around 350 pounds each, so we used chain hoists to move the gates around the shop. By building the gates in a shop instead of onsite, we were able to reduce the time in the field. This greatly reduced our impact in the park.

The entrance section of the gate is designed to have easy access when open, and allow enough space to pass a rescue litter through the gate entryway. On each gate we installed our secure P-Locking system, along with a heavy duty Medico high security lock. Final modifications to the gate are made onsite to fit the specific mounting location.

The upper adit of the Grandview mine required a culvert gate to help support the ceiling from further cave-ins. The culvert gate contains gating bars similar to the adit gates, but must be entered via crawling through the 30 inch diameter culvert.


A project of this size required significant logistical planning. We would be working at a remote site where we would only have one chance to get this project done correctly. Since we would be working on three gates concurrently, we decided to have three workers at each gate, and two more team members for running materials and tools between the sites. This team size of 11 experienced workers proved just right for this project. We also brought duplicate tools in case something broke or did not work properly. This was most fortunate because one of our two cutting torches and fuel bottles got damaged during transport.

To prepare the tools, gear and gates for helicopter transport our group had to weigh and mark each specific item. Then the items were organized by the four different drops points, and then placed on cargo nets as shown. Each load must weigh less than 800 pounds for the helicopter to safely tranport. This project required seven loads brought in, and five loads removed at the end of the project.

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Organizing Gear into Helicopter Cargo Nets


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