Characteristics of Aesthetic Enhancements
It is immediately realized by anyone examining the topographic setting of most highway projects that it is impossible to exactly replicate natural land forms in engineered rock cuts. In nature, stable, natural land forms almost always comprise flatter slopes than highway departments wish for their rock cuts. Where the natural landscape is sufficiently rugged that it incorporates cliff faces and natural rock slopes approximating the desired cut slope angles, the condition of the natural rock slopes is generally much more degraded than is desired in the highway cuts. For these reasons, cut slopes cannot be made to exactly look â€œnaturalâ€, even if that is what is required in construction bid documents.
To the construction contractor bidding on a rock excavation project, this means that, at the very least, he will not have to make the cut slopes indistinguishable from the backdrop. More problematically, a bidder may also believe that since the required appearance is not strictly attainable, under the pressures of actual construction the door will be open to negotiate a far lesser degree of compliance. Often, to the dismay of many (including the other, unsuccessful bidders whose estimates reflect a nobler intent), he is correct. To avoid this undesirable situation, several things must happen:
- The bid documents must require a standard of performance that is defined as much as possible in terms of measurable physical characteristics;
- The land use agency and the highway engineering team must work together to determine what those physical characteristics will be;
- The land use agency must commit to accepting the standard of aesthetic attainment implied by the criteria in the bid documents;
- The highway department must commit to inspection, measurement, and enforcement of aesthetic criteria as stridently as for more traditional elements of inspection;
- A process needs to be developed to review, and if necessary, attain consensus on modifications if and only if geologic conditions differ materially from those assumed during design.
The processes of achieving consensus, developing working relationships, and performing joint reviews during construction have been successfully accomplished through partnering. Partnering is now well known and accepted in the highway engineering community and will not be discussed further here. The remainder of this subsection will deal with what criteria have been found suitable and attainable on prior projects.
It is important to conduct visual prioritization to distinguish aesthetic enhancements that will actually be of benefit from those that are only a needless expense. The visual prioritization process is normally carried out by a landscape specialist working as part of a multidisciplinary highway design team, and in close coordination with the land management agency. Through the visual prioritization process, the team not only recognizes the various levels of visual impact that will occur due to highway construction, but agrees to eliminate from consideration those visual impacts that are not significant. The visual impacts must be considered in terms of the location, duration, and range of view. In general, the most significant visual impacts to the highway user are those that will be apparent for longer than 10 seconds or so. The pedestrian will generally have a narrower scope of view but hold it for a longer period. Two categories of visual impact emerge from the visual prioritization, the short range view, and the long range view.