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5.7 Biological Resources

populations within the Mitigation Preserve and promoting the distribution of this species in
the Project region through the propagation of new or expanded populations in the Mitigation
Preserve. The expansion of the local population of this species is expected to increase its
potential to be sustained in perpetuity.

Sylvan scorzonella is a CRPR 4.2 species. Numerous occurrences (roughly approximated at
500), were identified on the Project site in 2004 and, in 2008 the number of individuals
observed across the site likely exceeded 100,000 plants. This species was observed in
scattered patches in grasslands predominately east of the Aqueduct. It was most commonly
found on the upper north sides of ridges and hills, and on slopes and flats immediately
bordering ephemeral drainages. Nearly all occurrences were located within grasslands; a
few were in areas bordered by oak woodland (Vollmar Consulting 2004). In 2015, estimated
population counts exceeded 100,000 and, as in previous years, it was observed
predominately in grasslands, but was also noted to occur in scrub habitat. Project
implementation would remove most occurrences of this species on the site. As discussed
above, the County of Los Angeles Department of Regional Planning typically does not require
mitigation for impacts to CRPR 4.2 species. However, due to the lack of botanical knowledge
in the region for this species, the level of impact is difficult to ascertain and therefore the
impact is considered potentially significant. Implementation of MM 7-1, proposed to mitigate
for impacts to special status plants, would reduce the level of impact by preserving existing
populations within the Mitigation Preserve and promoting the distribution of this species in
the Project region through the propagation of new or expanded populations in the Mitigation
Preserve. The expansion of the local population of this species is expected to increase its
potential to be sustained in perpetuity.

Piute Mountains navarretia is a CRPR 1B.1 species. It was observed on the Project site in
2004 at 3 locations, with approximately 20,100 total plants. Occurrences on the site were all
located in the hills in the far western region of the Project site, associated with clay soils in
areas that had been recently disturbed by feral pigs. These occurrences represent the only
known occurrences for this species in Los Angeles County and the southernmost known
occurrences. However, this population is outside the Project impact area; as such, impacts to
this species are not expected to occur and no mitigation for this species would be required.

Adobe yampah is a CRPR 4.3 species. In 2004, one occurrence of this species with
approximately 16 individuals was identified on the Project site. It was found in native
grassland habitat on a dry, moderately steep slope with bare soil and low total vegetation
cover south of SR-138 (Vollmar Consulting 2004). In 2006, three occurrences were identified
including approximately 15 individuals. In 2008, approximately 108 individuals were
observed. In 2015, approximately 100 occurrences were recorded in the survey area, with
an estimate of 3,100 individuals. Project implementation would result in impacts to
approximately 1,490 individuals. On Liebre Mountain, this species has been described as
“generally infrequent and scattered in open chaparral and grassland on the higher ridges,
but locally common in clay-rich openings on the north face of Sawmill Mountain” (Boyd
1999); Sawmill Mountain is located about ten miles southeast of the Project site. Like CNPS
4.2 species, although CRPR 4.3 species are considered special status species, impacts on
CRPR 4.3 species often do not meet the significance criteria under CEQA to require
mitigation. However, due to the lack of botanical knowledge in the region for this species, the

R:\Projects\PAS\CEN\000306\Draft EIR\5.7 Bio_051117.docx 5.7-144 Centennial Project
Draft EIR