Jefferson County - East-West Gateway Coordinating Council

A Regional Overview All-Hazard Mitigation Plan
The Sonsac-Useful-Moko Association ranges from three to 55 percent slope. It covers
approximately 58 percent of the county. These soils are most commonly found on narrow
ridgetops, backslopes and summits. The parent materials are loess and residuum. Welldrained
Sonsac soils (gravelly silt loam-well drained) make up 44 percent of the association.
Useful soils (silty loam-moderately well drained) make up 30 percent of the association.
Well-drained Moko soils (stony soils) make up 15 percent of the association and the
remaining 11 percent are minor soils.
The Wrengart-Goss Association ranges from three to 55 percent slope. It covers about 13
percent of the county and consists of soils located on summits, ridgetops, and backslopes.
The parent materials are loess and residuum. The moderately well drained Wrengart soils
(silty loam) make up 47 percent of the association, well-drained Goss soils (cobbly silty
loam) make up 45 percent of the association and eight percent of minor soils make up the
balance.
The Menfro-Gasconade Association ranges from three to 50 percent slope. It covers about
five percent of the county and is located mainly in the summit and backslope areas. Parent
materials consist of loess and residuum. The well-drained Menfro soils (silty loam) make up
69 percent of the association. Excessively well-drained Gasconade soils (rubbly soils) make
up 17 percent and the remaining 14 percent are minor soils.
The Minnith-Pevely Association ranges from three to 50 percent slope. It covers about
eight percent of the county. These soils are commonly found on ridgetops and backslopes.
The parent materials consist of loess and residuum. The moderately well drained Minnith
soils (silty loam) consist of 51 percent of the association. The moderately well drained
Pevely soils (silty loam) make up 32 percent of the association and minor soils make up the
remaining 17 percent.
The Haymond-Freeburg-Horsecreek-Bloomsdale Association ranges from zero to five
percent slope. It covers about 15 percent of the county. It is commonly found in the
floodplains and terraces. The parent material is alluvium. The well-drained Haymond soils
(silty loam) make up 26 percent of the association. The somewhat poorly drained Freeburg
soils (silty loam) make up 25 percent of the association. The well-drained Horsecreek soils
(silty loam) make up 25 percent of the association and the well-drained Bloomsdale soils
(silty loam) makes up about 24 percent of the association. Refer to Figure J4 above.
Climate Climate - Surficial materials in Jefferson County consist of residuum from cherty limestone
(clay and gravel) up to 50 feet in thickness. These materials are located in the northern half
of the county. Surficial materials in the southern half of the county consist of residuum
from cherty dolomite (clay, silt and gravel). The materials are normally less than ten feet
thick, but can exceed 50 feet in thickness. Surficial materials in the southwest corner of the
county consist of residuum from sandstone and cherty dolomite (clay, silt, sand, gravel and
boulders) and can be up to 200 feet thick.
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