South Dakota Administrative Rules › Title 74 - Department of Environment And Natural Resources › Article 74:53 - Water supply and treatment systems › Chapter 74:53:01 - Individual and small on-site wastewater systems › Section 74:53:01:37 - Requirements for a mound or evapotranspiration system

Current through Register Vol. 51, page 10, July 15, 2024
A mound or evapotranspiration system may be designed for gravity or
	 pressure flows in accordance with the following criteria:
(1) Plans and specifications shall be
  submitted to the secretary by a registered professional engineer or licensed
  plumber for review and approval of any individual or small on-site mound or
  evapotranspiration system prior to construction;
(2) Mound and evapotranspiration systems
  shall not be constructed on sites located in a floodplain. Mound systems shall
  not be constructed on sites located on bedrock or on soils with percolation
  rates of 120 or more minutes per inch or 3 or fewer minutes per inch at a depth
  of 12 inches below the sand layer of the mound. Mound or evapotranspiration
  systems may not be located on natural slopes exceeding 12 percent under any
  soil percolation rate conditions. When a mound or evapotranspiration system is
  located on a slope, no buildings, driveways, other surface or subsurface
  obstructions, or future construction is permitted within 30 feet of the system
  on the down gradient side while the system is being used. The systems shall be
  located in open areas with maximum available sunshine. The area surrounding the
  systems shall be graded to provide for diversion of surface runoff
  water;
(3) The mound or
  evapotranspiration system may be constructed only upon undisturbed naturally
  occurring soils. The bottom of the system bed shall be excavated to a depth
  from 8 to 12 inches below the ground surface and shall be completely level. The
  system may be round or rectangular;
(4) The mound system shall be constructed so
  that the minimum distance between the seasonal high groundwater table and the
  invert elevation of the distribution system is 4 feet;
(5) The required bottom area of the bed shall
  be calculated on the basis of a recommended or design application rate with
  respect to the soil percolation rate. For mound systems receiving less than
  1,500 gallons of wastewater per day, an application rate of 0.6 gallons per
  square foot per day shall be used when the percolation rate is from 60 to 120
  minutes per inch and an application rate of 0.83 gallons per square foot per
  day shall be used when the percolation rate is 3 or more but less than 60
  minutes per inch. For mound systems receiving 1,500 or more gallons of
  wastewater per day, the application design rate shall equal the soil
  percolation rate plus the seasonal evapotranspiration rate as shown in Table 6.
  For evapotranspiration systems, the application design rate is the seasonal
  evapotranspiration rate shown in Table 6 as follows:
TABLE 6
Evapotranspiration Rate
Season of Use
Gallons per square foot per
				  day
Year Around
0.12
Summer
0.20
Winter
0.06
Soil Infiltration Rate
Percolation Time, Minutes per
				  inch
Gallons per square foot per
				  day
5 or more but less than 10
0.65
10 or more but less than 15
0.60
15 or more but less than 20
0.54
20 or more but less than 30
0.49
30 or more but less than 45
0.42
45 or more but less than 60
0.34
60 or more but less than 90
0.27
90 or more but less than 120
0.18
120
0.12
(6) The fill
  material for the interior portion of a mound or evapotranspiration system shall
  consist of sandy loam soil, medium-size pit run sand, and pea rock or washed
  gravel ranging in size from 1/2-inch to 2 1/2-inch diameter. The first layer of
  fill material placed on the excavated bed bottom shall be a minimum of 12
  inches of sand. The next layer of fill material shall consist of at least 9
  inches of the pea rock or washed gravel placed in the immediate area on which
  the distribution pipe system will be placed. After placement of the
  distribution pipe system, additional pea rock or washed gravel shall be added
  until there are at least 2 inches of cover over and around the entire pipe
  system. The rock or gravel layer shall be covered with untreated building
  paper. The finish fill shall consist of sandy loam soil placed on the untreated
  building paper to a depth of 1 foot in the center of the mound and to a depth
  of 6 inches at the sides tapered out onto the side of the sand filled
  layer;
(7) The exterior portion of
  mound shall consist of at least a 6-inch layer of loose marsh hay or straw over
  the sandy loam soil, covered with at least 6 inches of topsoil. Flax straw may
  not be used. The outside slopes may not be steeper than 3 feet horizontally to
  1 foot vertically (3:1). Where the terrain slopes more than 7 percent, the
  downward slopes may not be steeper than 5 feet horizontally to 1 foot
  vertically (5:1). The entire system shall be seeded, sodded, or otherwise
  provided with a grass cover. No shrubs, trees, or other woody vegetation may be
  planted on the top of the system;
(8) The distribution pipe network for an
  elevated mound or evapotranspiration system shall consist of a dosing chamber,
  pump or siphon, 1 1/4-inch to 3-inch diameter flexible plastic pipe from the
  dosing chamber to the mound, and a manifold connected to the perforated
  distribution pipe. The distribution lines shall be installed in accordance with
  subdivision 74:53:01:36(2). The pipe from the dosing chamber to the center of
  the mound shall be installed below the frost line or be sloped uniformly back
  to the dosing chambers. The dosing or pressure system shall be constructed in
  accordance with §
									74:53:01:27. The distribution
  lines shall have perforations spaced from 2 to 7 feet along the pipe with
  varying hole diameters from 3/16-inch to 1/2-inch to provide uniform pressure
  and distribution over the bed. All drilled holes shall have burrs removed. All
  distribution pipe ends shall be capped. For gravity flow systems, all
  distribution pipes shall be at least 4 inches in diameter and spaced not
  greater than 5 feet on center across the bed width or closer than 30 inches to
  the bed wall perimeter; and
(9)
  Livestock and heavy equipment shall not be allowed on the bed.
General Authority:
SDCL
		34A-2-93.
Law Implemented:
SDCL
		34A-2-20.