| (a) Areas of emergent vegetation in a free water surface
(FWS) wetland must have a maximum water depth less than or equal
to 24 inches at design flow.
(b) Plants.
(1) Emergent plant spacing must be no more than 66
inches on center.
(2) If floating plants are used in a FWS wetland,
the wetland must also contain emergent plants.
(c) Multiple Cells. An FWS wetland must include multiple
cells that can be operated independently, allowing an individual
cell to be removed from service while maintaining system operations.
(d) System Size. An FWS wetland system must be sized
to meet permit effluent limits, even when any single cell is removed
from service.
(e) Bottom slope.
(1) An FWS wetland cell must have adequate bottom
slope, or other means such as strategically placed deep-water zones,
to facilitate drainage for maintenance.
(2) Plants selected for an FWS wetland cell shall
be compatible with the water depths under all anticipated operational
flow conditions.
(f) Parallel trains. An FWS wetland must have parallel
treatment trains to increase operational flexibility.
(g) Wind protection. An FWS wetland cell must either
be oriented to avoid prevailing winds perpendicular to the process
flow direction, or must use elevated berms or vegetative windbreaks.
(h) Inlets and Outlets.
(1) The inlets and outlets of an FWS wetland cell
must ensure uniform distribution of influent flow and uniform collection
of effluent flow across the entire cell cross section.
(2) An FWS wetland must have multiple inlet and outlet
devices designed to minimize scouring of wetland substrate caused
by locally high velocity effluent flow.
(3) Each inlet and outlet device in an FWS wetland
must be adjustable to allow variations in the operational water level.
(4) Submergence. An FWS wetland inlet must be submerged
under normal operational conditions.
(5) Inspection and Cleaning. An FWS wetland must be
designed to allow for the inspection and cleaning of inlet and outlet
devices.
(i) Organic Loading and Treatment Efficiency.
(1) The design of an FWS wetland must be based on
the design organic loading of the influent to the FWS wetland.
(2) Organic removal efficiency for FWS wetlands must
be calculated from the area-based loading rate equation found in
Figure: 30 TAC §217.210(i)(2), unless the engineering report
justifies an alternate method to determine the organic removal efficiency
by identifying a method, the sources of the method, and all supporting
calculations.
Attached Graphic
(j) Vector Control.
(1) The design of an FWS wetland must include mosquito
control by:
(A) using mosquito fish (Gambusia
spp.) or other natural predators;
(B) maintaining aerobic conditions; or
(C) using other biological controls.
(2) A design must minimize the potential for damage
to wetlands caused by mammals such as nutria and muskrats.
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