(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 site.
  (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 drawings.
  (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.

Source Note: The provisions of this §217.35 adopted to be effective August 28, 2008, 33 TexReg 6843; amended to be effective December 4, 2015, 40 TexReg 8254