Page 878 - anf1995elsmere_deis

evaporates, and the structure collapses. Clay minerals particularly susceptible to this type
of expansion and shrinkage include montrnorillonite, beidellite, nontronite, hectorite and
saponite (Dana, 1977).

In general, soils at the property have low to moderate shrink-swell potential (Table 3). Soils
with low shrink-swell potential include: Gaviota, Hanford, Ojai, and Saugus soil series. Soils
with moderate shrink-swell potential include Castaic, Millsholm, and Yolo. These latter
soils are primarily located in the extreme western, west-central, and southwestern portions
of the property (Figure 11).

10.2.2 Emsign

As discussed in Sections 5.5.1 and 5.5.2, the potential for erosion varies across the project
property. The majority of the property is underlain by soils with moderate to very high
erosion hazard ratings and moderate to high sheet and rill erosion potential. Factors

contributing to the rate of erosion include: soil type, slope length and steepness, vegetation
cover, root development, and climatic factors such as precipitation. Slope length and
steepness are critical factors that control the velocity of runoff and therefore contribute
directly to the potential for sheet and rill erosion.

Areas within the project property identified as being highly sensitive to erosion due to
disturbance include the eastern portion of the property, the northwestern portion of the

property, and a small area near the west-central portion of the property (Figure 11). Two
soil types in the eastern portion of the property underlie the majority of the proposed
landfill footprint area. These include Caperton-Trigo, granitic substratum-Lodo families
complex and Trigo-Modesto-San Andreas families complex, both which have very high

erosion hazard ratings. Fairly extensive erosion was observed on aerial photographs in the
southeastern portion of the project property underlain by Caperton-Trigo, granitic
substratum-Lodo families complex. Castaic and Saugus mixture soils located in the
west-central portion of the property also have a very high erosion hazard rating and very
high sheet and rill erosion potential. Ojai soils located in the northwestern portion of the
property are also very susceptible to sheet and rill erosion (Figure 11).

150

21351-006428
009/708