The committee also uncovered numerous examples of small-scale projects that produced environmental benefits. These ranged from sensitive-species mapping and planting, stream habitat improvement, construction of stormwater treatment facilities, and improved aquatic habitat. Other small-scale projects focused on endangered species recovery and restoration, such as riparian and stream restoration for salmon in the Pacific Northwest and fencing for protection of the desert gopher tortoise. Other projects included attempts at decreasing habitat fragmentation by construction of multifunctional crossings, widening of bridges, and improving wildlife connectivity. These projects integrate a variety of objectives, such as improving fish passages and stormwater and noise management, in environmental retrofit programs and can lead to broader-scale, such as watershed scale, improvement of ecosystem functioning (Figure 4-7c,d).
This chapter has presented a set of existing and potential opportunities for mitigating the ecological effects associated with three major phases of road projects: planning, construction, and maintenance. At the national scale, the types of conclusions made in Chapters 3, 5, and 6 are all germane. Environmental issues should be addressed earlier in the planning and design phases. Interdisciplinary teams could be developed to share data, understanding, and expertise. At the medium and fine scales, many designs, activities, and projects have been done to mitigate effects. However, information, studies, and databases on the long-term functionality of these mitigation efforts are sparse. Long-term studies and a greater set of analytical tools are needed to help inform decision makers about the implementation of mitigation efforts, such as wildlife habitat connectivity structures. These tools could help to assess appropriate locations and design measures for these efforts. Many other opportunities exist for improving environmental conditions in road project operation and maintenance. Projects have addressed improving water quality, aquatic habitat, habitat for species of concern, control of nonnative plants and animals, and reestablishment of habitat connectivity.