Rehabilitating a Dam Is NOT Just Piling Dirt!

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The work rehabilitating Millsite gets more and more technical as it advances.

Inspections continue regularly by NRCS, Dam Safety, county and local inspectors. Backfilling is starting as dewatering and excavation of the north end of the dam nears completion. The backfilling becomes very technical and every grain of sand and gravel is tested to make sure the compaction will be adequate to meet specifications. This happens in an onsite lab and also by radiation tests as the backfill is rolled into the foundation of the dam. The backfill completion date is Nov. 17. Once the backfill is in place, then levies will be used to layer sand and gravel on the surface of the dam. This sand and gravel is brought from Nielson Construction’s gravel pits and dumped in concrete and black-top lined and floored bunkers in order to avoid any contamination  All equipment used is also pressured washed before being used on the site. Much more equipment is now on the job site and is being used extensively.

One of the most time consuming and difficult areas of construction is the area of rebuilding the spillway. The fine-grained sandstone is so tightly compacted that a John Henry drill is being used to drill the holes. These are 11 foot holes every 6-12 inches. Expensive expansive grout is then driven into the holes that will expand, causing the rock to crack so that big track hoes can remove the rock. This must be done before the concrete work, which is scheduled for December, can begin. The floor and side walls of the spillway will be finished by March 30 but the weir on the front side cannot be finished until after the reservoir spills in the spring.

Old Howell-Benger valves are being replaced by Plunger Valves. The new valves are run by hydraulics and control the flow more accurately and easily. Ferron City, Ferron Canal Company and PacifiCorp have all purchased their own valves. They will be replaced temporarily and the hope is that will only take a couple of days so that the city will not run out of culinary water. City storage tanks hold enough water for two days of light usage. Citizens will be given notice and encouraged to use water sparingly during those times of valve replacements, both temporary and permanent. The golf course, camping area and boat ramp reconstruction will happen next summer and fall.

This rehabilitation was prompted to restore capacity and at the same time meet current safety standards. The reservoir, which is presently at an all-time low, will be four feet higher at maximum storage and a normal operational year is expected by the Ferron Canal and Reservoir company. In order to keep on schedule, construction working shifts have increased to 12 hours, sic days per week. Wall Concrete has subcontracted the concrete work.