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5.7 Biological Resources

within the off-site mitigation areas is 3,102 acres and is expected to
substantially exceed the required 50 percent of mitigation as preservation.

Mitigation through creation is typically implemented on lands with minimal
habitat value (e.g., ruderal vegetation, graded slopes) rather than in areas with
a substantial component of existing native vegetation. However, evidence of
lack of naturally occurring recruitment on site indicates that the existing
woodlands are likely to be eventually replaced by non-woodland vegetation.
Based on the lack of naturally occurring replacement trees, it is anticipated
that oak woodland planting is necessary to sustain the oak woodlands.
Therefore, the goal of oak resource mitigation efforts will be to create and
enhance oak woodlands. To maximize potential for success, oak woodlands
will be created within and adjacent to the same areas where oak woodlands
currently exist. This method will create future generations of oak trees and
oak woodland on the site in these areas. Details of the oak woodland mitigation
program are described below in items 1–10.

1. To mitigate for impacts to oak woodland and oak trees, site-specific
native acorns will be collected. Acorns will be collected within the
watershed area of the Project site to ensure that acorns collected are of a
similar genetic stock to those existing on the site. Some acorns will be
planted and maintained in containers, and others will be stored and
planted directly on site within the Oak Mitigation Areas.
2. To maximize oak woodland biological values and the potential for long-
term success, some locally collected oak acorns will be planted directly
into the ground. These acorns will be planted in appropriate locations in
the Oak Mitigation Areas. The locations identified for acorn planting will
be reviewed by the County Forester.

3. Container plants will be propagated and maintained from locally
collected acorns. In this way, more established container plants will be
available for mitigation efforts, and they will contain the most suitable
genetic variability appropriate for the region to increase mitigation
success. The preferred method of propagation will include the
establishment of a temporary nursery on the Project site. The nursery
will include partial shade areas to reduce water loss and a constant water
supply to supplement planted trees. Using the acorns collected from
within the watershed area of the Project site, container plantings will be
cultivated at this location. Development of trees on site will ensure that
they are acclimated to the typical weather conditions at their eventual
permanent location. If necessary, and in consultation with the County
Forester, acorns collected from the site may be stored or propagated and
maintained under contract with a reputable native plant nursery off site.
4. To provide overstory, midstory, and understory tree/plant coverage,
some container plants and oak trees, grown from locally collected acorns,
will be installed in addition to the application of native seed mixes. Since
studies indicate that the younger the planting is, the more likely the

R:\Projects\PAS\CEN\000306\Draft EIR\5.7 Bio_051117.docx 5.7-183 Centennial Project
Draft EIR