FLH PDDM Chapter 9 - Eastern Federal Lands Highway Division

9.4.F. Other Design Elements. (continued)Rock cuts can be designed to produce a staggered bench effect which will reflect natural terrain and accentnatural fracture lines in the rock. When presplitting is necessary to stabilize the rock slopes, the use ofstaggered benches will break up the vertical drill scars.Where slope stability is not a factor, nonpresplit blasting techniques will expose the natural rock fractures.In some instances, this produces the most pleasing results.Where practical, design planting pockets or benches in the slopes for the introduction of plant material. It isdesirable to spread topsoil on all rock benches to encourage grass growth and minimize the visual scar throughrevegetation. The planting of trees and shrubs will aid in reducing the size and scale of the rock cuts.d. Clearing Techniques. In heavily forested areas, usual clearing techniques may leave a vertical wall ofvegetation at the tops of cuts and toes of fills. In these cases, selective thinning methods will produce a softeredge by cutting out taller old trees in favor of younger ones. The object is to produce a natural forest edgeeffect.Selective thinning methods combined within scalloped clearing lines and vista clearing to promote and framescenic views will enhance the natural beauty of any project. There is, however, a point where excessiveclearing is not beneficial. In some areas, the emphasis should be on bringing the forest as close to the roadwayas safety permits. A balance is needed that emphasizes vegetation patterns above and below the highwayslope.e. Revegetation. Revegetated slopes are not only pleasing to view but are stabilized and require little or nomaintenance. Re-established vegetation is also important as cover and food for wildlife.Select grass seed that is native to or adaptable to the area. The seed mixture should satisfy criteria for elevationand slope exposure changes. Several seed mixtures may be required to satisfy all conditions on a relativelylong project. Use soil mulches and netting to stabilize and protect the ground until grass is established.Where practical, conserve topsoil from the project limits and replace it on the finished slopes. The topsoil notonly provides needed fertility and a growing medium for grasses, it contains an abundance of native seeds.These forbs, weeds, and grasses usually grow fast and dense and will blend in with the undisturbed vegetationwhich effectively brings the background vegetation onto the cut slope.Shrubs and trees can be planted to primarily beautify the disturbed roadside areas and blend them into theundisturbed areas. Using hydrophilic shrubs, such as willow and birch, grouped in areas of excess soilmoisture will aid in stabilizing the area. Locate all plant groupings in areas most visible to the motorist.It is FHWA and FLHO policy that at least one-quarter of 1 percent of funds expended for landscape projectsbe used to plant native wildflowers, except in ornamental landscapes, or unless a waiver is granted by theDivision Engineer.An ornamental landscape is one that is irrigated, has barked shrub beds, and has irrigated grass that is routinelymowed.9 - 103