1. (a) A Free Water System (FWS) wetland must be based on a maximum water depth of not greater than 24 inches in emergent vegetation areas at design flow.

2. (b) Plants.

   1. (1) Emergent plant spacing must be no more than 66 inches on center.
   2. (2) Floating plants are prohibited in an FWS.
3. (c) Multiple Cells. An FWS wetland must include multiple cells that may be operated independently, allowing an individual cell to be removed from service while maintaining system operations.
4. (d) System Size. An FWS wetland must be sized to meet permit effluent limits with any single cell removed from service.

5. (e) Bottom slope.

   1. (1) A FWS wetland cell must have adequate bottom slope or other means such as strategically placed deep-water zones to facilitate drainage for maintenance.
   2. (2) A design must require that a bottom slope maintain an appropriate range of wetland water depths along the entire cell length under all anticipated operational flow conditions.
6. (f) Parallel trains. An FWS wetland must have parallel treatment trains to increase operational flexibility.
7. (g) Wind protection. An FWS wetland cell must be oriented to avoid prevailing winds perpendicular to the process flow direction or use elevated berms or vegetative windbreaks.

8. (h) Inlets and Outlets.

   1. (1) The inlets and outlets of an FWS wetland cell must assure uniform distribution of influent flow and uniform collection of effluent flow across the entire cell cross section.
   2. (2) Inlet and outlet devices must minimize erosion of wetland substrate from locally high velocity effluent flow.
   3. (3) Each inlet and outlet device must be adjustable to allow variations in operational water level.
   4. (4) Submergence. An inlet must be submerged under normal operational conditions.
   5. (5) Inspection and Cleaning. A design must allow inspection and cleaning of inlet and outlet devices.

9. (i) Organic Loading and Treatment Efficiency.

   1. (1) Constructed wetland process design may be based on organic loading design for typical municipal wastewater primary or secondary effluent, whichever is the influent for the constructed wetland.
   2. (2) A design must be based on the organic removal treatment efficiency for FWS wetlands on the areal loading rate equation found in the following figure unless the report justifies an alternate method to determine the organic removal treatment efficiency by identifying a method, the sources of the method, and all supporting calculations.
      Attached Graphic
      

10. (j) Vector Control.

    1. (1) The design of an FWS wetland must include mosquito control:

       1. (A) using mosquito fish (Gambusia) and other natural predators,
       2. (B) maintaining aerobic conditions, or
       3. (C) using other biological controls.
    2. (2) A design must minimize the potential damage to wetlands caused by mammals such as nutria and muskrats.

Source Note:The provisions of this §217.210 adopted to be effective August 28, 2008, 33 TexReg 6843.