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5.7 Biological Resources

Small Drainages
A number of short, isolated drainages originating at seeps occur on steep slopes on the
Project site, primarily west of the Aqueduct. Most of the smaller drainages either evaporate
or infiltrate within a short distance of the source. Because of the erosive character of the
soils, channels are often incised. In a few cases, one or several riparian trees or shrubs may
be present along the channel.

Ecological Functions Associated with Drainages and Wetlands in the Project Area
Potential Wildlife Habitat

A functional assessment of the drainages and other aquatic features on the Project site was
completed by Glenn Lukos Associates (GLA 2006b, 2009a) using a combined assessment
approach and subsequently refined by BonTerra Psomas (BonTerra Psomas 2015a) using
the California Rapid Assessment Method (CRAM). The results of these assessments indicate
that the wetlands on the site provide potentially suitable habitat for a variety of invertebrate
and vertebrate species. The riparian, palustrine, and small lacustrine systems also provide
potential wildlife habitat for several species. For the wetland functional assessment, the
functional capacity of jurisdictional resources was determined using a Functional Capacity
Index, which is a ratio of the functional capacity of a wetland under an existing condition,
and the functional capacity of a wetland under attainable conditions. The Functional
Capacity Index provides a measure of a wetland’s ability to perform a function relative to
similar wetlands in the region, as evaluated in the field based on multiple metrics (indicators
of wetland function). Functional capacity units, therefore, provide a measure of a wetland’s
ability to perform a function and are calculated by multiplying a Functional Capacity Index
by the area of wetland it represents.

The wetland vegetation includes monkeyflowers, which provide nectar resources for adult
hawkmoths (feeding on nectar) and other pollinators. The hawkmoths (white-lined sphynx
moth [Hyles lineata] and tobacco hornworm sphinx [Manduca sexta]) are abundant during
the summer, and were observed visiting flowers for nectar. Dragonfly and damselfly species
(e.g. common green darner [Anax junius] and damselfly [Enallagma sp.]) are abundant
around open water. Several pools appear to be densely populated by microcrustaceans
(Impact Sciences 2003).

The drainages, ponds, and pools provide potentially suitable habitat for a number of frog and
toad species. In turn, a number of snakes and lizards have been observed adjacent to open
water feeding on the frogs, toads, and their tadpoles. The sand deposition downstream has
created potential habitat for coast horned lizards (which were observed) along the lower
reaches of dry sandy streambeds, and continuing into the alluvial fans. Waterbirds (mallard
[Anas platyrhynchos], bufflehead [Bucephala albeola], black-necked stilt [Himantopus
mexicanus], Wilson’s phalarope [Phalaropus tricolor], and lesser yellowlegs [Tringa flavipes])
and a variety of swallow species [e.g. violet-green swallow [Tachycineta thalassina],
northern rough-winged swallow [Stelgidopteryx serripennis], cliff swallow [Petrochelidon
pyrrhonota], and barn swallow [Hirundo rustica]) have been observed on or using open
water on the site. Bullock’s orioles have been frequently observed among the mature valley
oaks adjacent to Oso Creek. Livestock and other mammals also utilize the ponds as water

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Draft EIR