Control Structures and Interconnecting Piping

1. Interconnecting piping and overflow piping should be of cast iron, corrugated metal, or other suitable materials of at least eight (8) inches in diameter. Piping shall have capacity to permit transfer of water at a minimum rate of six (6) inches of pond water depth per day at the available head.

2. Control structures shall be provided for each cell. No discharge structure will be permitted for a single cell installation. The control structure should provide a positive visual means of

directing and controlling the flow and be accessible for maintenance and adjustment of controls. The control structure should consist of a manhole or box equipped with multiple-valved pond drawoff lines or an adjustable overflow device so that the liquid level of the pond can be adjusted to permit operation between the minimum and maximum operating levels. At least one drawoff line shall be located at the two (2) foot level. The lowest of the drawoff lines to

of bottom deposits. Erosion protection should be provided at the inlet and discharge end of the piping. The overflow from the pond during ice-free periods should be taken near, but below, the water surface to release the best effluent and insure retention of floating solids. A locking device should be provided to prevent unauthorized access to and use of the level control facilities. The outlet structure should be located to minimize short-circuiting within the cell, if possible, on the windward side. Consideration must be given in the design of all structures to protect against freezing or ice damage under winter conditions.

3. Interconnecting piping for multiple unit installations operated in series should be valved or provided with other arrangements to regulate flow between structures and permit flexible depth control. Interconnecting piping to secondary cells should discharge horizontally near the pond bottom to minimize the need for erosion control measures and should be located as near the dividing dike as construction permits. Consideration must be given in the design of all piping to protect against freezing or ice damage under winter conditions. Interconnecting piping shall be provided with splash pads. Anti-seep collars may be necessary on pipes penetrating the dikes, to discourage seepage and scouring.

4. The outlet end of the discharge pipe should be screened to prevent the entrance of wildlife.

H. Miscellaneous

1. Access Roads

An all-weather access road to the pond site shall be provided to carry out the routine inspections and maintenance which are required year-round on even the smallest installations.

A minimum 30 foot easement is recommended and not less than 20 feet should be provided. This minimum easement will permit light shaping and gravel surfacing for a ten foot roadway. Such minimums may only be satisfactory where the drainage is good and the distance from a maintained roadway is less than one-half mile. Minimum access fulfilling these requirements should be provided in all cases.

2. Fencing

The entire pond area shall be enclosed with a suitable fence to provide for public safety, to exclude livestock, and to discourage trespassing. The pond area should be fenced with at least 4 foot woven wire and two strands of barbed wire at the top. Where ponds are located near schools, parks, trailer courts, etc., the pond area shall be entirely enclosed with 6 foot high non- climbable chain-link fence. A vehicle access gate of minimum 12 foot width to accommodate mowing equipment should be provided unless the installation is small; then 8 foot will be satisfactory. All access gates shall be provided with locks. Fences shall be located away from the outside toe of the dike to facilitate dike mowing and maintenance operations.

Appropriate signs should be provided along the fence around the pond to inform the public of the facility and advise against trespassing. A minimum size of 20 inches by 12 inches with a minimum size letter of two inches is recommended. There shall be at least one such sign on each side of the pond and every 500 feet along the fence.

4. Flow Measurement

Provisions for flow measurement devices shall be provided at the inlet and outlet of controlled- discharge systems. Flow measurement devices shall be capable of measuring the maximum anticipated flows. Recording equipment shall be protected from the weather and flow conditions.

5. Depth Measurement

Pond depth indicators shall be provided. Due to ice conditions, a calibrated, inclined concrete section anchored into the dike slope is the most desirable. The outlet structure of each cell may also be utilized if properly and permanently calibrated. The depth indicator shall allow easy observation and shall be permanent. It is recommended that the depth indicators be

permanently etched in the concrete.

6. Synthetic Liners

a. The minimum lining thickness shall be 30 mils. The liner material shall be resistant to sunlight and organic materials typical of wastewater.

b. Where the bottom of pond is below the seasonal high groundwater, the liner shall be stabilized to prevent it from rising. An air-release system may be required.

c. Liners shall be installed and securely anchored to resist movement from wave and ice conditions.

7. Laboratory Equipment and Service Building

Equipment for wastewater analyses should be provided as outlined in Chapter 40, Recommended Standards for Sewage Works, 1978 or the latest edition.

A minimum amount of equipment may be provided if the owner utilizes the wastewater analyses provided by the Municipal Effluent Sampling Program (MESP) of the South Dakota Department of Water and Natural Resources or any other acceptable public or private

wastewater laboratory.

Consideration in design should be given to a service building to house laboratory and maintenance equipment.

The Department may consider and allow deviations where adequate documentation is provided to prove the need for such deviation.

CHAPTER V: Recommended Design Criteria For Aerated Ponds