 Welcome to the Sibyla National Forest and to the Zuni Mountains, which are located in West Central New Mexico. Here in the Zuni Mountains, the U.S. Forest Service maintains about 600 miles of low-volume roads. Since 1988, the Forest Service has been changing some of the practices used to maintain these roads in the past. The purpose of these changes is to restore the water table in meadows that have been damaged by erosion. The change in erosion has created channels so deep that the water tables beneath the meadows have become too low to support vegetation. The changes have reduced the amount of sediment that is being carried away into streams and lakes, and it is now possible to trap sediment in channels that are eroded. This allows the channels to fill in naturally. The first idea for these changes started at this meadow, post office flats. There was a ford where the road crossed the bottom of the meadow. Over several years, traffic passing through the ford caused enough soil to be washed out of the crossing area that the channel was at least two feet lower than it had been when the road was constructed. This was enough of a drop in the water level to cause the meadow area to start dying out, and an erosion channel to start moving through the meadow. As engineers began looking for ways to stop the drying of the meadow, they thought of a simple solution to raise the water level. The idea was to fill in the channel and install two culverts that had inlets about 12 inches above the original surface of the meadow. The culverts were installed following customary procedures for this work, except the inlets were at an increased height. No extra effort for the compaction was necessary, and about two feet of fill was placed over the culverts. The results here were rapid and encouraging. The first year, the vegetation in the meadow was showing the water table had raised enough to sustain the entire original meadow area, and the erosion channel that had been moving up through the meadow was beginning to fill in. Six years after the culverts were installed, the entire meadow was restored, and the erosion channel was completely filled in. Since these culverts, with their raised inlets, were installed, several hundred logging trucks have passed over them, and there has been no problem with the road supporting these very heavy loads. As part of the regular maintenance program, several culverts have been replaced that were located in eroded channels. The Forest Service has been very pleased with the results of these installations. The outlet of the culvert is placed so that it discharges into the bottom of the existing channel. Ripwrap is placed around the outlet to dissipate the energy of the water as it leaves the culvert. Water table levels upstream from each culvert with an elevated inlet have been raised. In Deener Canyon, a wall in front of the culvert inlet was constructed using jersey barriers. This wall has been very effective in restoring the water table level in this meadow by stopping the erosion that was happening and using the existing culvert for drainage under the road. This wall has been in place for six years. It was installed so that the distance from the wall to the pipe is at least equal to twice the diameter of the pipe. This separation is adequate to allow for near the full hydraulic capacity of the pipe. An important factor in the stability of this wall is that the channel between the wall and the pipe was lined with grid blocks to keep the water falling from the wall from eroding this area. It is essential that ripwrap or something else is installed on the downstream side of the wall to prevent erosion. Geotextile material was placed on the upstream face of the wall to reduce seepage through the joints. At this location, the Forest Service wanted to maximize water storage behind the wall because the overland flow is intermittent. If this type of wall were constructed in a channel with perneal flow, filter fabric would probably not be needed. The jersey barriers used to construct this wall in Deener Canyon were new. However, used jersey barriers or barriers that have been shipped or cracked and not suitable for use as traffic barriers can be used. The other technique that can be used to raise the inlet of a culvert without having to replace it is to install a corrugated metal pipe elbow on the upstream end of the culvert. Shown here is an elbow that was installed on an existing culvert. It has been successful at raising the water table level upstream of the culvert. The elbows are easy to install. A two person crew can usually install a 24 inch diameter elbow at a cost of about $150. An elbow that raises the upstream water table by two feet can create a one to two acre meadow or wetland in areas of flat or gentle terrain. There are a few items to consider when installing the elbows. First, make sure the surface of the road is at least two feet higher than the invert of the elbow. This will assure that the road bed will not be saturated. The road will still be able to support the same loads without rutting. Second, make sure that the invert of the elbow is not so high that water will flow down the road rather than going through the culvert. This includes making sure that high flows will pass through the culvert rather than continuing on down the ditch. Again, at this installation, the erosion that was occurring in the channel upstream of the culvert has stopped. The elbows have been used to slow water so sediment will settle out of the water, thus storing the sediment in the area around the culvert. Shown here is a culvert in the six mile canyon area where the elbow has made it possible to store sediment. The sediment and the increased water storage behind the culvert help to create better growing conditions for plants. Keeping the sediment upstream of the culvert also improves the quality of water that flows downstream from it. Besides storing sediment that has been eroded upstream from a road, elbows and raised inlets have been used to trap sediment from the road itself. This has been an inexpensive solution to stopping sediment from roads that is causing water quality problems for nearby streams. This technique has also been used to impound water to create small ponds that wildlife and livestock can use. The idea of raising the inlets of culverts to restore or create meadows and to stop erosion has been very effective. It improves the condition of the land and water beside roads without having to make a large increase in funds used for road maintenance and construction. It is an activity that has shown how roads can be used to improve the environment. If you would like more information about the changes the Sibyla National Forest has been making in drainage design, contact the Sibyla National Forest Engineering Section 2113 Osuna Road, Northeast, Suite 8, Albuquerque, New Mexico, 8-7-1-1-3 or by calling 505-761-4650.