State Route 58 Widening Project - Bakersfield Freeways

Chapter 4 Results: Biological Resources, Discussion of Impacts and Mitigation
the design plans for SR-58 Widening. Final project design modifications intended to
reduce potential adverse effects on kit fox will be approved by USFWS during the
final design phase.
The primary objective of the project design modifications is to maintain opportunities
for kit foxes to cross over the road surface while reducing the potential for an increase
in vehicle strike. Limited research indicates that kit foxes infrequently use culverts to
cross under a roadway, even when a culvert is present nearby; foxes tend to continue
to cross over the roadway surface opportunistically (Cypher 2009). Therefore, project
design modifications do not emphasize the creation of new culverts, especially when
the project is not anticipated to disrupt a known movement corridor (e.g., canal and/or
railway corridor). However, some use of culverts has been documented by ESRP, and
use has increased with increasing culvert size (Cypher 2000). Because there are
culverts in the project BSA and no data to suggest whether or not kit fox use these
features, project design modifications recommend retaining existing culverts in the
BSA to the extent feasible in the event that these passageways are used, or may be
used in the future, by kit fox in the project area.
• SJKF – 6 Fencing
Fencing is not proposed for any portion of SR 58 Widening project ROW. If fencing
is required during a later planning stage, permeable fencing will be installed. One or a
combination of the following three design options may be adopted to provide kit fox
with movement opportunities: elevating the bottom of the fence 5 inches above
ground to allow unobstructed movement by kit foxes under the fence; installing
ground-level 8-x-8-inch-wide gaps no more than 100 feet apart for the length of the
fence, which would allow kit fox movement at regular intervals along the ROW; and
installing fencing with a minimum mesh size of 3½ x 7 inches, preferably
5 x 12 inches, which would allow unlimited movement by kit fox through the fence.
Permeable fence design is expected to reduce the potential to disrupt north-south kit
fox movement and habitat fragmentation in the project area, when implemented in
conjunction with all project design modifications, by allowing unlimited kit fox
movement.
• SJKF – 7 Curbed Medians and Median Barriers
Curbed medians are proposed as part of project design. The height of curbed medians
will be no greater than 10 inches. Ten-inch curbed medians will remain un-vegetated
38 State Route 58 Widening Project Biological Assessment