|(a) If a 100-year flood plain is located within 1,000
feet of the site of a wastewater treatment facility, the 100-year
flood plain must be shown on the site plan. A flood plain determination
must be based on a superimposition of the 100-year flood elevation
on the most accurate available topography and elevation data for the
(1) A 100-year flood plain must be based on the Federal
Emergency Management Agency (FEMA) Flood Insurance Study in effect
at the time the plans and specifications are submitted to the executive
director. FEMA maps are prima facie evidence of flood plain locations.
(2) An appropriate flood insurance rate map or Flood
Insurance Study profile, adjusted to the site's vertical data, may
be used to determine flood elevations.
(3) If a site is adjacent to a FEMA 100-year flood
delineation, but has no flood elevation published, a 100-year flood
elevation may be determined by overlaying the effective FEMA delineation
over a United States Geological Survey Quadrangle Map and interpolating
a flood elevation.
(4) If FEMA flood plain information is not available,
the engineering report shall include a 100-year flood elevation based
on the best information available.
(b) The 100-year flood plain must be shown on the profile
(1) The FEMA 100-year water surface elevation must
be marked on a hydraulic profile of a wastewater treatment facility
in accordance with the vertical scale of the drawing.
(2) If a wastewater treatment facility will occupy
less than 1,000 feet of shoreline along a flood plain, the profile
must show a single line coincident with the elevation of the centerline
of any outfall pipe.
(3) If a wastewater treatment facility will occupy
1,000 feet or more of shoreline along a flood plain, the profile must
show the water surface elevation at both the upstream and downstream
limits of any protective structure for the wastewater treatment facility.
(c) The executive director will not approve a design
of a proposed treatment unit within a 100-year flood plain, unless
the design provides protection for all open process tanks and electric
units from inundation during a 100-year flood event.