Transportation Corridor Agencies (TCA) commissioned an alignment planning team for road and rail planning optimization to assist them in the complex environmental process associated with the 16-mile Southern California Foothill Transportation Corridor-South (FTCS) project. After spending two years developing alternative route options for the toll road using conventional CAD and GIS systems, TCA and their appointed consultant, the Corridor Design Management Group, had been unable to satisfy the multiple interests of different project stakeholders.
When TCA compared the results achieved with the alignment system against the alignments previously developed using conventional CAD and GIS systems, it was readily apparent that the new alternatives were far superior to many of the 19 previously selected alternatives. This allowed for a systematic elimination of many of the alternatives and reduced the number of alignments presented in the project DEIS/SEIR from 19 to eight.
Figure 1 shows three Quantm refined alternatives (green, red and yellow) as compared to two seed alignments (black and blue) developed using the conventional approach.
Figure 3 shows how the alignment derived using the new methodology avoids the Talega development and moves the alignment behind the ridge line to reduce visual impacts of the new facility.
The improvements to the environmental and social outcome included:
Reduced impact to riparian ecosystems (wetlands) from 107 acres to 39 or 49 acres for two options in one corridor, and 60 acres to 43 acres for alternatives in another corridor;
Reduced impact to sensitive species by completely avoiding the Pacific Pocket Mouse habitat and limiting the grading in the area by use of retaining walls;
Reduced the landslide risk/disturbance limits by avoiding many of the existing landslides and reducing the amount of earthworks by identifying roadway geometry that more closely follows the natural terrain;
Reduced residential displacement in one corridor from 32 to zero; and
Minimized impact on existing utilities and avoided them to be relocated to undisturbed areas with associated environmental impact.