Can You Dig It? (aka Blacktail Bridge Part 2) - Sara Griffith, GY

This is the phrase that kept running through my head during our crew's third hitch in the Yellowstone backcountry. We finally started hands-on work on the Blacktail bridge and our first order of business was to dig out around the concrete abutments. We dug down until we reached the bed (about 6-7 feet on the south side, much less on the north). This allowed Kevin, the engineer to evaluate the concrete and determine how much needed to be replaced and if the bridge needed to be jacked up. We discovered that most of the concrete was okay on the south side, but quite crumbly on the north. It took us about two days to dig down far enough.

The old concrete was broken-up and removed through the use of the Pionjar and the Hilti. We then transferred the old concrete to the pit we dug on the south side and used it as crush around that abutment.

The concrete and bedrock was then cleaned to remove as much dirt and biological material as possible. On the final day of the hitch, we were prepared to actually pour concrete. Half of the crew put the finishing touches on the north pit, while the rest started prepping the concrete operations. In the pit, we created a grid of rebar interwoven and tied together in a fashion that was strong enough to walk on. The pieces of rebar had been cut to specific sizes and angles on a previous day.

Duraprep was then applied to the faces of the remaining concrete and bedrock. The purpose of the Duraprep is to help the new concrete bond to the old. With the pit prepared, the concrete race was on.

We are equipped with two small concrete mixers that operate on the south side of the bridge. The wet concrete is then wheelbarrowed over to the north pit. To say that working with concrete is a dirty dusty operation would be a serious understatement. Fortunately, after a while, we found our rhythm and progress started being more more noticeable. This continued for the rest of the work day. The new concrete reached a level that provided support back to the bridge. When we removed the old concrete it weakened an already weak structure. Obviously, it couldn't be left like that.

Our new slab should provide us a base to jack up the north side of the bridge and finish the repairs on that side. Our crew only has one more hitch on the Blacktail trail. It'll be a little odd to move to a new location. But, at the same time I think our crew will welcome the continuing of a new aspect of our MCC experience.