Section 11-62-34 - Specific requirements for new and proposed disposal systems(a) Absorption trenches. (1) Location. (A) Absorption trenches shall be located in accordance with section 11-62-32.(B) Absorption trenches shall not be constructed in soils with a percolation rate slower than sixty minutes per inch or where rapid percolation may result in contamination of water-bearing formations or surface waters.(C) Absorption trenches shall be located on the property to maximize the vertical separation distance from the bottom of the absorption trench to the seasonal high groundwater level, bedrock, or other limiting layer, but under no circumstance shall the vertical separation be less than three feet. The director may require a greater vertical separation where water-bearing formations are in danger of contamination.(D) Absorption trenches shall not be constructed in unstabilized fill.(2) Design. (A) The minimum absorption area for any absorption trench system shall be based upon a flow of 20 0 gallons per bedroom per day and in accordance with Table III located in Appendix D, entitled Tables, dated July 1, 2014, and located at the end of this chapter.(B) The absorption area shall be computed using the bottom area of the absorption trench.(C) Each absorption trench system shall have a minimum of two trenches.(D) Each distribution line shall be equal in length.(E) The maximum length of any one trench shall be one hundred feet.(F) Absorption trenches shall be at least eighteen inches wide but no more than thirty-six inches wide.(G) The bottom of absorption trenches shall be at least eighteen inches below the finished grade.(H) Gravity fed absorption lines and trenches shall have a slope at the rate of two to four inches per hundred feet.(I) Absorption trenches shall not be installed on land with a slope gradient greater than twelve per cent.(J) On rolling or sloping land, each absorption trench shall approximate the land surface contour.(K) A distribution box or header shall be installed between the treatment unit and the absorption trenches.(L) Each distribution line shall connect individually to the distribution box.(M) If a header is used, there shall be an equal number of distribution lines on each side of the influent junction. An inspection port shall be provided on the header and shall be brought to grade and fitted with a screw type cap or cover.(N) If a distribution box is used, a permanent inspection port with a minimum interior diameter of six inches shall be secured to the box cover, brought to the finished grade, and fitted with a screw type cap or cover.(3) Materials. (A) The engineer shall be responsible for the choice of materials used in the soil absorption system.(B) Pipe used for distribution lines shall meet the appropriate ASTM standard or those of an equivalent testing laboratory. Fittings used in the absorption system shall be compatible with the materials used in the distribution lines.(C) Gravel or crushed stone shall be washed and shall range in size from three-fourths to two and one-half inches.(D) The material used to cover the top of the stone shall be a filter fabric material or equal.(4) Construction. (A) A distribution box or header shall be set level and arranged so that effluent is evenly distributed to each distribution line. Adequate provisions shall be taken to assure stability and provide access for inspection of the distribution lines.(B) The pipe connecting the distribution box to the distribution line shall be of a tight joint construction laid on undisturbed earth or properly bedded throughout its length.(C) If a header is used, it should be made of water-tight construction.(D) When the trenches have been excavated, the sides and bottom shall be raked to scarify any smeared soil surfaces. Construction equipment and other materials not needed to construct the system should be kept off the area to be used for the absorption system to prevent undesirable compaction of the soils. Construction shall not be initiated when the soil moisture is high.(E) At least six inches of gravel or crushed stone shall be placed in the bottom of the trench.(F) The distribution line shall be carefully placed on the bedding at a uniform slope and covered with at least two inches of gravel or stone.(G) The ends of the distribution lines shall be capped or plugged.(b) Deep absorption trenches. Deep absorption trenches may be considered where the depth of suitable soil is insufficient to permit the installation of a conventional trench system due to the presence of a limiting layer more than two feet in depth which overlies suitable soils of sufficient thickness. Requirements for location, design, slope, material, construction, and dosing system design contained in subsection (a) shall apply to deep absorption trenches except for depth of construction. In addition, the following design considerations shall apply: (1) The site evaluation procedure shall include soil profile observations of at least three soil observation pits constructed to a minimum depth of three feet below the proposed trench bottom. Monitoring to establish depth to seasonal soil saturation or high groundwater may be considered;(2) Deep absorption trenches shall be constructed at least one foot into the suitable soil,- and(3) The distribution piping in deep absorption trenches shall be installed with the invert of the piping at a depth of not more than thirty inches. Gravel or crushed stone shall be placed from the bottom of the trench excavation to a point two inches above the top of the distribution piping.(c) Absorption beds. (1) Location. (A) Absorption beds shall be located in accordance with section 11-62-32.(B) Absorption beds shall not be constructed in soils with a percolation rate slower than sixty minutes per inch or where rapid percolation may result in contamination of water-bearing formations or surface waters.(C) Absorption beds shall be located on the property to maximize the vertical separation distance from the bottom of the absorption bed to the seasonal high groundwater level, bedrock, or other Limiting layer, but under no circumstance shall the vertical separation be less than three feet. The director may require a greater vertical separation where water-bearing formations are in danger of contamination.
(D) Absorption beds shall not be constructed in unstabilized fill.(2) Design. (A) The minimum area for any absorption bed system shall be based upon a flow of 200 gallons per bedroom per day and in accordance with Appendix D, Table III dated July 1, 2014 and located at the end of this chapter.(B) The absorption area shall be computed using the bottom area of the absorption bed.(C) Each soil absorption bed system shall have a minimum of two distribution lines.(D) If more than one absorption bed is designed, each absorption bed shall be equal in area.(E) The maximum length of any distribution line shall be one hundred feet.(F) Distribution lines within an absorption bed shall be uniformly spaced no more than six nor less than four feet apart.(G) Distribution lines within an absorption bed shall be placed no more than three feet nor less than eighteen inches from the sidewall of the bed.(H) The bottom of absorption beds shall be at least eighteen inches below the finished grade.(I) Absorption beds shall not be installed on land with a slope gradient greater than eight per cent.(J) A distribution box or header shall be installed between the treatment unit and the absorption bed.(K) Each distribution line shall connect individually to the distribution box.(L) If a header is used, there shall be an equal number of distribution lines on each side of the influent junction. An inspection port shall be provided on the header and shall be brought to grade and fitted with a screw type cap.(M) If a distribution box is used, a permanent inspection port with a minimum interior diameter of six inches shall be secured to the box cover, brought to the finished grade, and fitted with a screw type cap or cover.(3) Materials. (A) The engineer shall be responsible for the choice of materials used in the soil absorption system.(B) Pipe used for distribution lines shall meet the appropriate ASTM standard or those of an equivalent testing laboratory. Fittings used in the absorption system shall be compatible with the materials used in the distribution lines.(C) Gravel or crushed stone shall be washed and shall range in size from three-fourths to two and one-half inches.(D) The material used to cover the top of the stone shall be a filter fabric material or equal.(4) Construction. (A) The floor of the absorption bed shall be level.(B) A distribution box or header shall be set level and arranged so that effluent is evenly distributed to each distribution line. Adequate provisions shall be taken to ensure stability and provide access for inspection of the distribution lines.(C) The pipe connecting the distribution box to the distribution line shall be of a tight joint construction laid on undisturbed earth or properly bedded throughout its length.(D) If a header is used, it should be made of watertight construction.(E) When the beds have been excavated, the sides and bottom shall be raked to scarify any smeared soil surfaces. Construction equipment and other materials not needed to construct the system should be kept off the area to be used for the absorption system to prevent undesirable compaction of the soils. Construction shall not be initiated when the soil moisture is high.(F) At least six inches of gravel or crushed stone shall be placed in the bottom of the bed.(G) The distribution line shall be carefully placed on the bedding with no slope and covered with at least two inches of gravel or stone.(H) The ends of the distribution lines shall be capped or plugged.(d) Seepage pits. (1) Location. (A) Seepage pits shall be located in accordance with section 11-62-32.(B) Seepage pits shall not be constructed in soils having a percolation rate slower than ten minutes per inch (weighted average) or where rapid percolation through such soils may result in contamination of water-bearing formations or surface water.(C) The seepage pit shall be located on the lot to maximize the vertical separation distance from the bottom of the seepage pit to the seasonal high groundwater table, bedrock, or other limiting layer. The vertical separation shall not be less than three feet unless otherwise approved by the director and the requirements of section 11-62-33.1(b)(5) are met. Where water-bearing formations are in danger of contamination, greater vertical separation may be required.(2) Design. (A) Seepage pits shall be used only when one of the following are met;(i) Slope of the finished elevation of the lot is greater than twelve per cent and the use of absorption beds or trenches is not feasible.(ii) The presence of a limiting layer more than seven feet in depth which overlies suitable soils of sufficient thickness.(iii) Insufficient land area exists to install absorption trenches or beds.(B) The minimum area in any seepage pit shall be based upon a flow of 200 gallons per bedroom per day and in accordance with Appendix D, Table III dated July 1, 2014 and located at the end of this chapter.(C) The surface dimension is measured as the mean distance of the clear opening below the inlet pipe.(D) The minimum surface dimension is six feet.(E) The effective depth of the seepage pit shall be measured from the bottom of the inlet pipe to the bottom of the pit, with the thickness of strata of soils having percolation rates slower than thirty minutes per inch deducted.(F) The minimum effective depth is ten feet and shall be greater than its widest surface dimension.(G) The effective area of the seepage pit shall be the vertical wall area of the areas corresponding to the effective depth of the pit excavation. No allowance shall be made for the bottom area.(H) When more than one seepage pit is used, a distribution box shall be installed between the treatment unit and all seepage pits. Each seepage pit shall individually connect to the distribution box.(I) When more than one seepage pit is used, each pit shall have an equal effective area.(J) If a distribution box is used, a permanent inspection port with a minimum interior diameter of six inches shall be secured to the box cover, brought to the finished grade, and fitted with a screw type cap or cover.(3) Construction. (A) Seepage pits shall include a sidewall lining constructed of durable material that will permit free passage of wastewater without excessive plugging while still excluding the entry of surrounding soil.(B) Seepage pits shall include a cover which extends at least twelve inches beyond the seepage pit excavation, unless a concrete ring is used.(C) The lining and cover of any seepage pit shall be capable of supporting the normal loads imposed. The engineer shall submit written justification for the deletion of any sidewall lining.(D) The distance between the outer diameter of the lining and the excavation diameter shall be at least six inches, but not more than twelve inches. The space between lining and the excavation diameter shall be filled with washed gravel or crushed stone ranging in size from three-fourths to two and one-half inches. The placement of the gravel or stone shall fill the annular space between the pit lining and excavation diameter. Gravel and stone shall not be placed within the seepage pit itself.(E) The watertight cover shall be provided and at least one watertight manhole either round or square, tapered to a minimum of twelve inches in dimension shall be provided in the cover for inspection or for emptying the contents when required.(F) The top of the seepage pit shall be within twelve inches of the final grade.(G) If the cover of the seepage pit does not extend to the finished grade, a permanent inspection port with a minimum diameter of twelve inches expanding through and secured to the cover shall be brought to the finished grade and fitted with a screw type cap or cover.(H) The distribution box shall be set level so that the effluent is evenly distributed to each seepage pit.(I) The distribution box shall connect to each seepage pit with pipe of watertight construction at least six inches in diameter, and sloped at least one-eighth inch per foot.(J) The material used to cover the top of the stone or gravel surrounding the lining shall be a filter fabric material or equal.(e) Elevated mound system. Elevated mound systems shall be reviewed on a case-by-case basis.(f) Other disposal systems.(1) Soil replacement system. (A) Soil replacement systems shall be used for sites with the following soils layers in the upper soil horizons: (i) Soils with percolation rates less than one minute per inch; (ii) Soils with percolation rates greater than sixty minutes per inch that occur within the upper five feet of the soil and underlain by more permeable soils. Installation guidelines shall comply with the requirements of very high permeability soils of subparagraph (B); or(B) Trenches may be excavated up to thirty-six inches in width to depths not to exceed five feet below grade nor closer than three feet to seasonal high groundwater level, provided any groundwater mounding induced by wastewater does not rise closer than one foot from the bottom of the excavation and bedrock is at least three feet below the bottom of the excavation.(C) Soil replacement absorption trenches and beds shall follow the applicable provisions of subsections (a), (b), and (c).(2) Evapotranspiration systems shall be reviewed on a case-by-case basis by the director. The director shall use the provisions of section 7.3.2 of the October 1980 edition of the EPA Design Manual on Onsite Wastewater Treatment and Disposal Systems as a guide for the review of evapotranspiration systems.(3) Gravelless systems. (A) Gravelless soil absorption systems may be used as an alternative to soil absorption systems as specified in subsections (a) and (b), except for sections 11-62-34(a) (3) (C), 11-62-34(a)(3)(D), ll-62-34(a)(4)(E), and 11-62-34(a)(4)(F), 11-62-34(c)(2)(F), 11-62-34(c)(2)(G), 11-62-34(c)(3)(C), 11-62-34(c)(3)(D), and 11-62-34(c)(4)(F).(B) Design criteria, material specifications, and other pertinent data shall be submitted to the director.(C) The total area of the soil absorption system for the gravelless system shall be the same as specified in subsections (a), (b), and (c), except for chambered system where the director may approve of a reduction factor as deemed appropriate.(D) If chambered systems are used, the chamber units shall be placed up against the sidewall of the excavation. In absorption beds, the adjacent chambers shall abut one another.(E) The use of filter fabric, unless specified by the director, shall follow the manufacturer's recommendation.[Eff 8/30/91; am and comp 12/09/2004] (Auth: HRS §§ 321-11, 342D-4, 342D-5) (Imp: HRS §§ 321-11, 322-1 to 322-4, 322-8, 342D-2, 342D-4, 342D-5, 342D-50)