Page 943 - trc_centennial_deir201705

5.7 Biological Resources

areas. GAP vegetation maps indicate that grasslands are relatively abundant in the Project
region and in the closely associated surrounding regions. As shown in Table 5.7-11, Impacts
to Vegetation Types, the Project would impact 6,415 acres of the Native Perennial
Grassland/California Annual Grassland vegetation type on site. Due to the loss of
approximately 11 percent of the grasslands in general in the Mojave Desert region, the loss
of thousands of acres of grassland at least potentially containing a native perennial
component (a special status vegetation type) is significant. Loss of wildflower fields,
considered to be a subset vegetation type within the grasslands, is similarly considered a
significant impact due to their rarity and status as a special status vegetation type (CDFG
2010; Holland 1986). Implementation of MM 7-10 would reduce these impacts to less than
significant levels through preservation of 14,375 acres of on-site and off-site grasslands. The
proposed preservation reflects greater than a 2:1 ratio of preservation acreage to impact
acreage. This ratio has been applied to all impacted grasslands (undifferentiated) although
typically is only applied to native grasslands. Due to the intent and objective of preserving a
mixed community similar to that which is impacted by the project, areas selected for
preservation are similarly mixed. Furthermore, studies indicate a high degree of similarity
between impacted grasslands and preserved grasslands assuring a sustained community
throughout the region.

The grassland mitigation is based on site-specific characteristics including, for example, the
existence of native grasslands in the 27,408-acre on-site (unimpacted/SEA lands) and off-
site preserve areas. The availability of native grassland in the vicinity of the Project site is
unique and allows for the implementation of the preferred preservation mitigation approach
(existing native grasslands to be preserved), which generally results in better quality habitat
with higher potential for long-term stability, rather than the implementation of creation
mitigation (new native grasslands are created as mitigation), which has a higher degree of
uncertainty.

Other factors considered in determining the grassland mitigation ratio include the size, scale,
and biological diversity of the contiguous preserve. The preserve is designed to maximize
the potential for success by creating a contiguous large open space with minimum potential
for edge effects from regional development. This program is described in the Mitigation
Measures section below. Specifically, the Project proposes to preserve 14,375 acres of
grasslands within the 27,404 -acre on-site (unimpacted/SEA lands) and off-site mitigation
preserve, which is part of a larger 240,000-acre conservation area (including dedication and
acquisition areas). Regardless of the status of the acquisition areas in the future, the
grassland mitigation area will remain contiguous with the larger dedicated open space areas.
The contiguity of the preserve with the larger Tejon Ranch open space dedication areas
ensures that the preserved grasslands are not “islands” surrounded by development but
rather part of a larger, contiguous natural landscape that will be preserved in perpetuity.

Other Special Status Vegetation Types

In addition to grasslands and wildflower fields, several special status vegetation types on the
Project site would be directly impacted by Project implementation, as quantified in
Table 5.7-11 and detailed below (see Exhibit 5.7-12, Vegetation Type Impacts). Due to the
status of these special status vegetation types as high priority and the additional protection

R:\Projects\PAS\CEN\000306\Draft EIR\5.7 Bio_051117.docx 5.7-160 Centennial Project
Draft EIR