Jefferson County - East-West Gateway Coordinating Council

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Jefferson County – Section 1
the basement, elevated to two feet above the base flood elevation. The building envelope
must be filled to an elevation one foot above base flood elevation; (2) new construction or
substantial improvement of any commercial, industrial or nonresidential structures,
including manufactured homes, must have the lowest floor, including basement elevated
to one foot above the base flood elevation, together with utility and sanitary facilities
floodproofed so that below the base flood elevation, the structure is watertight with walls
impermeable to water with structural components with the capability of resisting
hydrostatics and hydrodynamic loads, an engineer must certify that the structure has met
these standards; and (3) for all new construction and substantial improvements, that all
fully enclosed areas below the lowest floor used only for parking of vehicles, building
access, or storage in an area other than the basement must be designed to equalize
hydrostatic flood forces, and the design must be certified by a registered engineer or
architect.
Manufactured homes to be placed within all unnumbered and numbered A zones on the
community’s FIRM must be installed using methods to minimize flood damage. The
homes must be elevated and anchored to resist movement. These homes must be placed
on elevated permanent foundations so that the lowest floor of the home is elevated two
feet above the base flood elevation and securely attached to prevent movement.
Manufactured homes that are not subject to provisions of Article 4 Section C(2) of the
ordinance must be elevated so that the lowest floor of the home is two feet above the base
flood elevation, or the home chassis is supported by reinforced piers so that there are no
less than 36 inches above the grade and securely attached.
The floodplain ordinance also requires that the community select and adopt a regulatory
floodway, that the community prohibit encroachments (fill, construction) in the floodway,
unless it had demonstrated through standard engineering practices that the encroachment
would not result in flood levels. The community, in unnumbered A zones will obtain and
use base flood elevation data from sources in Article 4, Section A(2).
Recreational vehicles, as stipulated in the floodplain ordinance, can only be placed on sites
within unnumbered and numbered A zones on the community’s FIRM for fewer than 180
consecutive days, and fully licensed for use or meeting the permitting, elevating and
anchoring requirements for manufactured homes.
The floodplain damage prevention ordinance has variance procedures and conditions for
approving floodplain management variances, for agricultural structures, accessory
structures, and penalties for violation of the ordinance.
Jefferson County has stormwater management plans in place. The Rock Creek Watershed
Management Plan is a comprehensive, small area-planning project being conducted
through a partnership between the Jefferson County Planning Division, the Missouri
Natural Resource Conservation Service (NRCS), and the Great Rivers Alliance of Natural-
Resource Districts (GRAND). The first of twelve watershed management plans to be
conducted in Jefferson County, the Rock Creek Watershed Management Plan will address a