SECTION 217.209. Constructed Wetlands

(a) Types of Constructed Wetlands. A constructed wetland may be either a free water surface system or subsurface flow system.

(b) Natural Wetlands. The use of natural wetlands for wastewater treatment is prohibited. For the purposes of this chapter, a natural wetland is an area which was not constructed for wastewater treatment that meets the definition of wetlands in 40 Code of Federal Regulations, Part 230.

(c) Constructed Wetland Design.

(1) A constructed wetland must be preceded by primary treatment or secondary treatment.

(2) A primary treatment system that precedes a constructed wetland must be designed to control odor and algae.

(3) A primary treatment system must produce an effluent quality with no more than 150 milligrams per liter of five-day biochemical oxygen demand to discourage anaerobic conditions and stress on vegetative communities in any subsequent wetland treatment unit.

(4) A wastewater treatment facility that uses a constructed wetland as the means of complying with a permit effluent limit must be sized and designed to ensure that the permit limitations will be met even when any one wetland cell is out of service. The engineering report must include water balance calculations and the potential effect of evaporation on the predicted effluent concentrations.

(d) Vegetation. A constructed wetland must have a diverse vegetative community of emergent and floating plants to minimize any adverse impact from potential disease, insect pests, or species-specific toxicity. A constructed wetland must include a diversity of plants selected from the following categories of emergent plants, floating plants, or both.

(1) Emergent plants for use in constructed wetlands include:

(A) Schoenoplectus spp. (bulrush);

(B) Sagittaria spp. (arrowhead);

(C) Phragmites spp. (reeds);

(D) Juncus spp. (rushes);

(E) Eleocharis spp. (spikerush);

(F) Carex spp. (sedges);

(G) Caladium spp. (elephant ear);

(H) various aquatic grass species (e.g., wild rice); and

(I) other appropriate emergent plant species approved in writing by the executive director.

(2) Floating plants for use in constructed wetlands include:

(A) Lemna spp. (duckweed);

(B) Hydrocotyle umbellata (water pennywort);

(C) Limnobium spongia (frogbit);

(D) Nymphaea spp. (water lily);

(E) Wolffia spp. (water meal); or

(F) other appropriate floating plant species approved in writing by the executive director.

(3) The vegetation used in a constructed wetland must be suitable for the local growing conditions. The use of indigenous plants is recommended if the species have been demonstrated effective in a constructed wetland wastewater environment. The engineering report must identify the plants that will be used in each constructed wetland.

(4) Plans for harvesting aquatic plants from water in the state must be reviewed with the United States Army Corps of Engineers to determine if regulatory coordination is required.

(5) Gathering seed plants from natural wetlands must minimize any impact on the harvested plant community and the natural wetlands.

(6) The use of any harmful or potentially harmful wetland plant or organism is subject to review by the Texas Parks and Wildlife Department, as required by 31 TAC §§57.111 - 57.118 and §§57.251 - 57.258 (relating to Definitions; General Rules; Exceptions; Health Certification of Harmful or Potentially Harmful Exotic Shellfish; Transportation of Harmful or Potentially Harmful Exotic Species; Exotic Species Transport Invoice; Exotic Species Permit: Application Requirements; Exotic Species Permit Issuance; Definitions; General Provisions; Permit Application; Denial; Renewal; Amendment; Reporting and Recordkeeping; and Prohibited Acts, respectively).

(e) Maintenance of a constructed wetland must not result in a deterioration of effluent quality.

(1) The use of herbicides, insecticides, and fertilizers in a constructed wetland is prohibited.

(2) Floating Material Removal.

(A) A constructed wetland must be designed to allow the removal of an algal mat or other floating material prior to the effluent entering each cell of the constructed wetland.

(B) A removal mechanism must be a screen, a submerged adjustable inlet, a baffle, or another method approved in writing by the executive director. The removal mechanism must be justified in the engineering report.

(C) The removed floating material must be stored and disposed of in a manner that minimizes odor and complies with the requirements of Chapter 330 of this title (relating to Municipal Solid Waste).

(3) The operation and maintenance manual for a wastewater treatment facility that has a constructed wetland must include a detailed description and schedule for maintaining the constructed wetlands. The maintenance plan must include a schedule and procedure for removing overabundant live plant material and dead plant material.

(f) A constructed wetland system must have an established plant community and must be functioning properly before wastewater effluent is processed. The engineering report must include a management and oversight program that specifies construction scheduling, plant species selection, planting practices, and start-up procedures.

(g) Liners.

(1) The liner for a constructed wetland system must comply with the requirements of §217.203(d) and (e) of this title (relating to Design Criteria for Natural Treatment Facilities).

(2) A layer of productive topsoil at least 6.0 inches thick must be placed above a liner to encourage root propagation.

(h) Berms. A berm of a constructed wetland must comply with the requirements of §217.203(f) of this title.

(i) Flood Hazard Analysis. A constructed wetland must be protected from flooding according to the requirements of §217.35 of this title (relating to One Hundred-Year Flood Plain Requirements).

(j) Nitrification. A constructed wetland that provides nitrification is an innovative and non-conforming technology and is subject to the requirements of §217.7(b)(2) of this title (relating to Types of Plans and Specification Approvals).

(k) Allowed Uses. A constructed wetland may be used as a secondary treatment unit, as an advanced secondary treatment unit, or for polishing wastewater effluent. A constructed wetland may not be used for primary treatment.

Source Note: The provisions of this §217.209 adopted to be effective August 28, 2008, 33 TexReg 6843; amended to be effective December 4, 2015, 40 TexReg 8254