From our April 2003 newsletter

The TR9 modified with a 1-inch bolt-on flat plate and a pile driving guide welded to the plate

The Missionary Ridge Fire which started onJune 9, 2002, 10 miles northeast of Durango, Colorado, burned for over 40 days, causing one death and many injuries. Over 2,000 people were forced to evacuate their homes and 73,000 acres were severely burned.

Newscasts show vivid images of the devastation caused by major forest fires while they are ongoing, but few of us are aware of the serious problems that arise after the fire is put out. Burned out mountainsides, like those resulting from the extraordinary Rocky Mountain fires of this past summer, are subject to severe mudslides from heavy rain and melting snow, and the debris carried by the slides – rocks, boulders, trees, ash – destroys everything in its downhill path.

At Missionary Ridge, the mudslides pose an immediate threat to the reservoir and the spillway behind Lemon Dam. Accumulating debris could seal off the discharge of the spillway and dam water levels, causing water to rise to a dangerously high level. In addition, debris from mountain runoffs form debris dams. These dams grow as more rocks, tree trunks, etc. wash downhill, impounding an ever larger volume of water. Eventually the dams must break, releasing heavy flows and debris downstream. As an immediate stopgap, log erosion barriers have been used to stabilize the hillside which in spots are a steep 70% grade.

The TR9 installing 6-inch vertical pipes using downward force from the excavator. Vertical pipes had to be perfectly aligned.

Engineers assessed the situation and maderecommendations for emergency flood control and water quality protection. Among the many measures that the Florida Water Conservancy District (Durango, CO) are undertaking is the construction of five trash racks. The racks are being constructed on site in runoff areas, using 6" diameter steel tubes placed in the ground vertically and welded to a horizontal support pipe. The racks will trap debris as it runs downhill. From time to time it will be necessary to bring in heavy duty equipment to clean them out.

Battling Deadlines and Weather
Work on the trash racks had to be completed before the heavy snows made it impossible to get construction equipment to the sites and before the spring thaws result in a massive downpour of debris. Unfortunately, Colorado received an early blast of winter and snow this fall.

When we spoke to John Ey, Superintendent of Lemon Dam for the Florida Water Conservancy District, in mid-November, two racks had been completed, another had the vertical tubes in place, and the two biggest had not been started. Snow had been falling on and off for weeks and more was in the forecast. John had been listening intently to the weather forecasts. It was a difficult situation, and he described how they proceeded on a daily basis. A trail was cut to the sites. At 6:00 AM, while the ground was still hard, equipment was moved in and work was done until mid-morning. When the sun hit, the ground softened and the equipment got mired in. Workers then had to hike the return trip.

Recently, we checked back with John Ey who reported that the weather held and all the racks were completed by the first week in December. So far, they have not been put to the test because they have not had heavy snow or rain but, it’s good to know, they’re ready for the spring thaw.

Completed trash rack

Getting It Done
For the trash racks project, the contractor, R&M Construction & Services, LLC of Montrose, CO rented a Tramac hydraulic plate compactor (the TraPac TR9) mounted on a Mustang ME8002 excavator. Dale Bourelle of Valley Crane & Equipment, also in Montrose, is their Tramac representative.

TraPac vibratory plate compactors are designed to handle tough compaction tasks in granular and moderately cohesive soil. With their powerful vibratory forces, they easily double as pile drivers, which is the way they were used at the Missionary Ridge site. They are easy maintenance attachments – the bearings run in an oil bath, no greasing required – and kits are available for all carrier models, allowing easy replacement of the carrier bucket with a TraPac compactor. There are five basic models. Each can be equipped with a custom bolt-on mounting bracket.

For the Missionary Ridge project, the TR9 was modified by welding a pipe guide – customized for the 6" pipes – to a bolt-on 1" flat plate. This made it easy to maintain a straight downward path as the pipes were pushed to a depth of up to 6' below ground. Accurate depth is of the utmost importance since the tops of the vertical pipes have to align properly for the horizontal cross pipe to connect. The TR9 did the job!