Agenda - 03-10-1987 - Laserfiche WebLink

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5; SOIL STABILITY I . DESCRIPTIVE DATA Soils was one of the three environmental parameters addressed in the preparation of the Joint Planning Land Use Plan. 40 soil types were identified in the Joint Planning Area using the Soil Survey of Orange County_ Four constraining factors were evaluated . These were slope, plasticity (shrink-swell) , depth to bedrock, and depth to groundwater. Slope(s) is expressed in percent, i .e., ( rise/ run) x 100. Plasticity is expressed in terms of a numeric index . In the evaluation, soils with a Plasticity Index (PI) > 30 were viewed as having moderate constraints and those with a PI > 55 were rated as posing severe con- straints to development . Depth to bedrock is expressed in inches and soils where the average depth to rock was < 24" were rated severe. Depth to groundwater (GW) is expressed in feet and soils where the depth was < 2 ' were viewed as posing problems . Evaluation of soils was done by pairing the constraining factors (except for bedrock < 24" which stood alone) as follows : S < 5 and PI > 30, S < 5 and PI > 55, and S > 10 and GW < 2 . The constraints were combined with the 40 soil types in a matrix . Soils that did not possess any of the above factors received a score of zero and were rated as posing "slight" Limitations. Any soil that possessed one of the four constraint pairings was rated as posing "moderate" limitations . Soils having two or more of the constraint pairings were rated as posing "severe" constraints to devel- opment . II . QUANTITATIVE DATA Acreages and percentages of moderate and severe soils relative to the Joint Planning Area were as follows: CLASSIFICATION ACREAGE PERCENT OF JPA Moderate 2,676 7% Severe 1 ,138 3% TOTAL 3,814 10% • III . ISSUES AND IMPLICATIONS Most of the soils coded as severe on the University Lake Watershed map were code incorrectly. These are Chewacla (Ch) soils and according to the evaluation matrix should have received a rating of "slight" .