ENVIRONMENTAL CONSEQUENCES

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ALTERNATIVE C: PREFERRED ALTERNATIVE

This section evaluates the potential impacts of alternative C, the preferred alternative.

Soils and Geology

Roadway

The existing roadway covers approximately 26 acres (10.5 hectares). The total amount of previously undisturbed soil permanently affected by the switchback realignment would be approximately 2.5 acres (approximately 1.0 hectare) (FHWA, 30% design, 2002). This would have a long-term, negligible, adverse impact on soils.

The approximate area of existing roadway to be obliterated, then revegetated, due to realignment of the switchbacks and removal of the turnouts, would be 1 acre (0.4 hectare). Surface scarring, rehabilitation, and revegetation efforts would reduce loss of soil through erosion. Natural soil processes would be restored in rehabilitated areas only over the very long term, as soil structure slowly returned to a more natural condition. This would constitute a long-term, negligible beneficial effect on soils.

No blasting activities should be required. Some moving, covering, trampling, and compaction of soils by equipment and workers within the construction zone is expected, but soils in much of the construction zone have been previously disturbed by road-related activities (e.g., construction and maintenance). Local soil compaction would temporarily decrease permeability, alter soil moisture content, and diminish water storage capacity. Some excavation of rock in the upper switchback would be required for the new alignment. Construction activities associated with the preferred alternative would have long-term, negligible, adverse impacts on soils and geology.

Cumulative Impacts. Past, present, and reasonably foreseeable future actions that would have effects on soils and geology within the park include the waterline replacement from Munson Springs to Garfield and the lagoon project at Munson Valley. The effects of these projects would result in long-term, localized, adverse impacts. Alternative C would contribute a long-term and negligible, beneficial, cumulative effect on reclaimed sites, but a long-term, adverse, and negligible impact on soils. The cumulative impacts of these projects would be long term, adverse, and negligible.

Conclusion. Construction activities associated with the preferred alternative would have long-term, negligible beneficial effects on reclaimed areas, but a long-term, negligible to minor, adverse impact to soils and geology. Alternative C would contribute a negligible, adverse, and long-term, cumulative impact.

Because there would be no major adverse impacts to a resource or value whose conservation is (1) necessary to fulfill specific purposes identified in the park’s establishing legislation, (2) key to the natural or cultural integrity of the park or to opportunities for enjoyment of the park, or (3) identified as a goal in the park’s General Management Plan or other relevant National Park Service planning documents, there would be no impairment of park resources or values related to soils and geology at Crater Lake National Park.