Final Environmental Impact Statement - New Federal Courthouse

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Biological Resources Fenders blue butterfly is one of about a dozen subspecies of Boisduval's blue butterfly. Recent surveys indicate that the butterfly is confined to 32 prairie sites in the Willamette Valley. The ~ l majority of these sites are dry upland prairies characterized by Festuca species. ' Kincaid's lupine almost always serves as the sole source of oviposition sites and larval food for these butterflies. Because neither dry upland prairies nor Kincaid's lupine occur at any of the alternative sites, Fenders blue butterfly is not expected to be affected by courthouse construction'activities. Significant Adverse Impacts Impacts Common to Alternatives 1 and 2 The following analysis addresses the potential impacts from the lazger site option for both Alternatives 1 and 2 (i.e., site option A in each case). The impacts would not be significantly different for the smaller site option (i.e., option B in each case). - Loss of landscaped areas on any of the alternative sites would have minimal impact upon wildlife present, which consists predominantly of small mammals and birds adapted to urban habitats. Construction of the proposed courthouse facility would require land clearing and removal of some landscape trees on the majority of the alternative sites under consideration. Preliminary siting studies have been initiated for each of the alternative sites to enable assessment of these impacts. The sketches shown in Figure 6 provide preliminary estimates of the size and placement of the courthouse building footprint at each of the alternative sites. Based on those general estimates, the tree removal requirements at each of the sites aze described below. Fish habitat for threatened and endangered species occurring in azeas downstream of the alternative project sites may be affected during construction and long-term operation of the proposed courthouse facility. The potential impacts aze common to both alternative sites, although the degree of impact is dependent on the proximity of the building site to a water body, as well as the design of stormwater collection and treatment facilities. Construction impacts can result from stormwater runoff carrying sediment and nutrients, and from accidental chemical spills. Long-term impacts on fish involve changes in the amount of impervious surface azea and water quality degradation. Stormwater runoff during construction may transport sediment, nutrients, and pollutants into water bodies, thereby affecting fish habitat. Excessive sediments can harm fish by clogging spawning gravels, reducing benthic invertebrate populations, and filling in pools used as juvenile reazing habitat. Excessive nutrient loading can harm fish by causing algal blooms that reduce dissolved oxygen levels and by reducing the diversity of benthic invertebrate populations. Accidental spills of pollutants (fuel, oil, chemicals, and concrete leachate) during construction may harm fish in the immediate azea, although the impact is dependent on the effectiveness of containment and cleanup procedures. ~_ Final EIS 58 New Federal Courthouse ,__,