Page 903 - trc_centennial_deir201705

5.7 Biological Resources

entering from the north begin at seeps and springs on hillsides, while those from the south
emerge from hills south of SR-138 and flow northward through culverts under the highway.
The major creek from the south is Tentrock Canyon Creek, which crosses north
under SR-138 and joins the watershed near its eastern terminus.

Several segments of these drainages are dominated by willows, while a few localized sites
along the channels are dominated by large cottonwoods. Most of the channel reaches are
dominated by emergent vegetation, specifically watercress (Nasturtium officinale) and water
speedwell. Adjacent to the channels, several areas of the wet flats and depressions are
associated with Chino loam soils. These areas are dominated by Baltic rush, sedge, spike
rush, wild-rye (Elymus [Leymus] sp.), and dock. The wettest depressions, primarily where
berms have been created to provide water for cattle, support California bulrush
(Schoenoplectus [Scirpus] californicus) and broad-leaved cattail (Typha latifolia). In most of
the dry areas of this watershed, grasslands are present, with varying cover of native
perennial grasses, forbs, and non-native annual grasses.

To the north of this watershed are ten additional “blueline” streams (as indicated on the
USGS topographic quadrangle maps). Seven of these drainages have natural channels (bed
and banks), while the other three are broad swales between ridges. These drainages have
ephemeral or intermittent flows from west to east. Most of these drainages begin east of the
Aqueduct; however, two begin to the west, flowing through culverts under the Aqueduct.
These drainages vary from shallow and narrow, to wide and deep (when flowing), but all end
on the site, and infiltrate into the sandy alluvial fan to the east. Several springs are present
on slopes adjacent to the drainages, and several drainages have eroded deeply enough to
possibly reach groundwater. In both cases, these areas remain wet long into the summer.
The drainage systems beyond the first ridge north of SR-138 are less diverse botanically than
the watershed along SR-138, with increasing non-native vegetation to the north. In contrast
to the drainage along SR-138, these drainages lack willow riparian and rush vegetation.

Ponds and Impoundments

Surveys conducted on the Project site have identified ten seasonal pools/depressional
features in the Project site (GLA 2005a, 2005b, 2005c, 2006a, 2006b; see Appendix 5.7-B).
Most, if not all, these sites were created to provide water for livestock and some have been
disturbed by livestock grazing. These features are described in a fairy shrimp habitat
assessment, most as roadside depressions that receive local watershed runoff and direct
rainfall; the report contains detailed information on existing conditions, dimensions,
ponding depth, and common vegetation for each feature (GLA 2005b).

The ponding depth of the identified depressional features varies from a few inches to over
two feet. Ponding is associated with runoff, direct rainfall, slope discharge from shallow
subsurface groundwater, and overbank connection to adjacent creeks during high flows.
Although some depressional features are unvegetated, others support vegetation, including
black mustard, bromes, small-flowered melic grass (Melica imperfecta), willow-herb
(Epilobium pygmaeum), toad rush, common knotweed (Polygonum arenastrum), everlasting
(Gnaphalium sp.), Mexican rush (Juncus mexicanus), black willow, spike rush (Eleocharis
acicularis), perennial spike rush (Eleocharis macrostachya), alkali plagiobothrys
(Plagiobothrys leptocladus), and woolly-heads (Psilocarphus tenellus var. tenellus).

R:\Projects\PAS\CEN\000306\Draft EIR\5.7 Bio_051117.docx 5.7-130 Centennial Project
Draft EIR