North Dakota Administrative Code › Title 62 - State Board of Plumbing › Article 62-03.1 - Plumbing Installation Standards › Chapter 62-03.1-03 - Private Sewage Disposal Systems › Section 62-03.1-03-12 - Alternative systems

Current through Supplement No. 393, July, 2024
1.
Mounds.
Mounds may be constructed on soils having a percolation rate faster than
				one hundred twenty minutes per inch [2.54 centimeters]. For soils slower than
				one hundred twenty minutes per inch [2.54 centimeters], either the system must
				be moved to more amenable soil or see subsection 2 on lagoons.
a. Location. Mounds may not be located on
				sites of greater than twelve percent slope. For moderately permeable soils, the
				administrative authority may approve construction on slopes over six percent.
				Mounds may not be built in areas where water may pond.
b. Design. The basal sand area of the mound
				must be sized on the basis of eighty-three hundredths gallons [3.12 liters] per
				square foot [0.09 square meter] per day. The basal sand may be twelve inches to
				twenty-four inches [30.48 centimeters to 60.96 centimeters] deep and must
				extend at least five feet [1.52 meters] beyond the rock filter material in all
				directions. The rock layer may be twelve inches to twenty-four inches [30.48
				centimeters to 60.96 centimeters] deep and may not exceed ten feet [3.05
				meters] in width. Only pressure distribution may be used in the mound, so
				piping shall be one and one-half-inch to two-inch [38.10-millimeter to
				50.80-millimeter] diameter rigid ABS or PVC. A one and one-fourth inch [31.75
				millimeters] hole must be drilled every thirty-six inches [91.44 centimeters]
				and the ends of the lateral must be capped. A one-fourth inch [6.35
				millimeters] hole shall be drilled in the top of the cap to serve as a siphon
				break. Laterals shall be spaced no further than forty inches [101.60
				centimeters] on center and no further than twenty inches [50.80 centimeters]
				from the edge of the filter rock. Surface water must be diverted by a berm
				located uphill from the base of the mound.
c. Specifications. Sand must be uniformly
				graded, with no more than fifteen percent fines. Filter rock must be one inch
				to three inches [25.40 millimeters to 76.20 millimeters] in diameter, washed or
				screened to less than ten percent fines.
A jar test should be used to determine sand suitability. In
				  a one quart [.95 liters] jar, place two inches [50.8 millimeters] of the sand.
				  Add water to three-fourths level, cap, shake, and set aside to settle. If a
				  layer of silt is present on top which is more than one-eighth inch [3.18
				  millimeters] thick, the sand is not suitable for mound construction.
d. Construction.
(1) Scarify the area with backhoe teeth or a
				cultivator. Do not remove topsoil. Bring outlet pipe from pump up into the
				center of the mound area.
(2) Lay
				sand on scarified area. Do not compact the soil with machinery tires. Level
				sand to desired depth.
(3) Lay
				filter rock down the center of the sand layer. Level.
(4) Connect piping to manifold and lay pipe
				on rock. Cover pipe with rock and level by hand. Holes must be on bottom of the
				pipe.
(5) Lay sand up to the top
				of the rock on all sides, sloping sand away at a three-to-one or four-to-one
				slope.
(6) Cover rock with red
				rosin paper, hay, or filter fabric.
(7) Backfill entire mound to a three-to-one
				or four-to-one grade. Downhill side of mound on slopes must be backfilled at a
				four-to-one or longer grade. Cover mound with topsoil.
(8) Seed grass over mound. Trees and shrubs
				may be planted on the toe and up the sides of the mound, but do not plant
				shrubs or trees on top. If vegetation is not established before winter, cover
				mound with hay or straw to prevent freezing.