(a) Introduction.      
        (1) Purpose. Hyacinths may be used for the removal of suspended solids from secondary effluent. Other proposed treatment applications, however, are not excluded by these criteria, and such proposals will be reviewed on a case-by-case basis.       
        (2) Other permits. The authority to use hyacinths is contingent upon obtaining a possession permit from the Texas Parks and Wildlife Department.       
        (3) Location. Uncovered hyacinth basins will be approved only in Cameron, Hidalgo, Kenedy, and Willacy Counties. Hyacinth basins elsewhere shall be covered with a greenhouse structure. A variance will be considered for systems which are designed for seasonal operation. Greenhouse design shall provide for adequate dike top width for equipment maneuverability, doors for personnel and equipment access, and openings for ventilation.       
      (b) Design.      
        (1) Multiple basins. Multiple basins shall be provided. Capacity to treat the design flow with one basin out of service shall be provided. A variance may be considered for systems which are designed for seasonal operation. Average water depth of basin shall not exceed 36 inches.       
        (2) Basin sizing and configuration. Multiple surface inlets and outlets shall distribute flow uniformly through the basin. This may be accomplished by a weir, openings in a baffle, by a perforated pipe, or other methods. Basins of one acre or less in size are required. The bottom of the hyacinth basin shall be sloped to facilitate draining. A surge basin or some other method of flow equalization to achieve a more constant rate of inflow to the basin is desirable.       
        (3) Barrier. A fixed barrier creating a clear zone shall be installed at the outlet to prevent the discharge of hyacinths or hyacinth seed. While screening may be used as a barrier material, a permeable rock barrier is preferred. Water depth within the outlet area shall not be more than 24 inches with the bottom covered by a layer of broken rock or washed gravel.       
        (4) Loading. Organic loading of hyacinth basins shall not exceed 100 pounds per acre per day of five-day biochemical oxygen demand (BOD                 5                ) unless supplemental aeration is provided to consistently maintain an aerobic surface water layer. The maximum hydraulic loading shall not exceed 0.20 million gallons per day per acre.       
        (5) Natural aerators and mosquito control. Exclosures shall be placed at intervals along basin edges to provide clear zones for aeration and to enhance fish production for mosquito control. Total area of exclosures should be approximately 20% of total basin area. Exclosures shall have a uniform depth of not more than 24 inches, with bottoms lined with broken rock or washed gravel. Plastic sheeting covered with a layer of broken rock or washed gravel, extending above and below operating water level, shall be placed all along inner basin berms to prevent weed growth and eliminate a mosquito breeding habitat.       
      (c) Operation.      
        (1) Harvesting. Adequate provisions for access, removal, and disposal of the hyacinth plants shall be provided. Removal shall be done mechanically.       
        (2) Cleaning. Each basin shall be cleaned once each year by dewatering and removing plants and sludge.       
        (3) Coverage. Plant coverage shall be limited to 90% of the basin area.       
     Source Note:        The provisions of this §317.11 adopted to be effective November 26, 2015, 40 TexReg 8341