Clear Creek Watershed Authority
Routine maintenance is ongoing, with Fall and Winter mowing, Spring weed and brush control, and Summer fence and gate repair.
Engineering inspections are generally conducted following Winter mowing, and after all major storms. Special maintenance needs are identified at that time. Items deemed "urgent" by the engineers are scheduled for immediate repair, with other items scheduled for repair as budgeted funds are available.
Remote Video Pipe Inspections
Brian Wenberg, PE, of the NRCS, and Allan Colwick, PE, consulting engineer for the CCWA, performing an internal inspection of the principal outlet pipe on Site 51. Six sites were analyzed this year.
This robotic remote-control camera is part of a $50,000 system used by the NRCS, in cooperation with the CCWA, to inspect the interior condition of pipes and pipe joints. It can penetrate up to 600 feet and transmit video back to the receiving unit and recording device.
Recently Completed Special Maintenance Work
The inlet tower of Site 8 was plugged due to action of beavers. After piling sediment around the base of the tower, beavers packed the interior of the tower with mud and branches, preventing operation of the principal spillway pipe. This is a dangerous condition that could result in overtopping of the dam and possible dam failure. Emergency action was taken to open the slide-gate and lower the water level in preparation for maintenance.
In the photo above, a hydraulic excavator clears the area surrounding the inlet tower.
It was then necessary to enter the tower and manually clear out the interior.
Two weeks later, after heavy rains, the reservoir was full again and the outlet pipe was properly functioning as seen in the photos above and below.
The outlet works of Site 9 were heavily overgrown with briars and brush, and the outlet pipe was buried and submerged. The track-hoe is engaged in clearance of the area above the outlet pipe and plunge basin.
The equipment moves downstream, clearing the outlet channel to permit proper drainage.
The water level has been lowered and the outlet pipe carefully excavated and exposed, with proper functioning restored. Additional clearance of the area around the outlet pipe and in the plunge basin will be undertaken later in the summer.
Site 34 had been badly abused. The fences were cut in numerous places to allow free access by cattle. Overgrazing by the cattle resulted in loss of grass cover and weed dominance. The top of dam was also used as a road, with resultant deep ruts and depressions. A cattle guard, shown below, had been installed, without authorization and in violation of CCWA Rules, in the top-of-dam in the foreground of the picture. An old property-fence can be seen crossing the dam in the background, that prevented proper maintenance of the dam faces. All of these violations are serious, and in the future will result in heavy fines.
The cattle guard, after removal from the top-of-dam.
In order to secure and protect the site, re-fencing was first undertaken. This JD 332 with construction bucket and hydraulic brush-wolf was used to remove the old fence and clear the overgrown fence row.
The site has now been completely re-fenced, and repairs to the top-of-dam and dam faces are underway.
Immediately downstream of Site 104, seen in background, a county road was built across the outlet channel. A culvert pipe was placed too high in the road bed to permit drainage from the dam, blocking the plunge basin and burying the outlet pipe of the dam under six feet of water, and an additional two feet of mud. In a cooperative effort with Montague County Precinct 1 Commissioner Dickey Cox, the CCWA lowered the culvert pipe, exposed the outlet pipe, and restored proper functioning to the dam.
After draining the blocked plunge basin, the area is excavated to expose the principal spillway pipe of the dam.
County maintenance crew extends the length of the culvert pipe prior to excavation and lowering by the CCWA.
The culvert pipe is then lowered to permit proper downstream drainage.
The downstream channel was cleared, and a headwall was installed over the lowered culvert pipe.
The road was then repaired and restored to its original level.
Less than a week after the repairs, heavy rains filled the reservoir and activated the principal spillway pipe. The dam and its outlet works are now functioning properly. Additional clearance of sediment from the plunge basin will be performed when weather conditions permit.
Additional Scheduled Repairs
Broken 6" foundation-drain pipe on far side of cantilevered outlet pipe, angled down into water Second foundation-drain pipe on near side is also broken-off and is under water. This plunge basin is difficult to access and will require machine clearance prior to attempted repair.
Extensive damage to the emergency spillway of Site 45 occurred during the extreme storm events of June and July 2007. This headcut was created by rapidly flowing water passing around the dam to prevent over-topping, as designed. While preventing downstream flooding, the flood control structure absorbed the damage. NRCS engineers are currently preparing repair plans and specifications. The project has been approved for federal cost share under the NRCS Emergency Watershed Protection program, but no federal funds are available. The cost is estimated to exceed $44,000 and may have to be absorbed entirely by the CCWA.
Slope slippage and slumping was first observed in three separate areas on the upstream face of Site 48 in February 2006. In March of 2008, the slippage accelerated and significantly worsened. The embankment is unstable and still moving. Engineers are presently investigating the cause and repair methodology. This repair project, originally estimated to exceed $250,000, was approved for federal cost share in 2007 under the NRCS Emergency Watershed Protection program, but no federal funds are available. The NRCS EWP program presently has some $110 million in approved projects for which no funding is available. Pending repair, the slide-gate has been opened and the water level in the reservoir has been lowered.