Section 18 AAC 72.630 - Construction requirements for alternative wastewater systems(a) All alternative wastewater systems installed, modified, or operated under 18 AAC 72.600 - 18 AAC 72.660 must meet the minimum construction requirements of this section unless a waiver of a provision is approved under 18 AAC 72.640.(b) Design flow for an alternative wastewater system must be calculated based on (1) 150 gallons per day for each bedroom in a residential dwelling; and(2) typical daily flow rates for each unit of a specific type of facility publicly identified by the department under 18 AAC 72.070.(c) Each component of an alternative onsite wastewater system, including all sewer lines, tanks, treatment units and absorption areas, must have the minimum freeze protection that meets the following insulation requirements in this subsection: INSULATION REQUIREMENTS* |
Geographical Area | Depth of Soil Cover or Insulation Equivalent** |
Southwest Alaska (Kodiak Island Borough and all areas southwest of Chignik, including Chignik) | two feet of soil cover |
Southeast Alaska (east of 141° West longitude), the coastal area south and east of Valdez between (to 141° West longitude), and the Valdez corporate boundary | three feet of soil cover |
All remaining areas of the state | four feet of soil cover |
*Minimum depth of soil cover does not apply to treatment units or package plants designed by the manufacturer to be installed in arctic conditions with less soil cover. |
**For every one inch of insulation installed over a system component, the soil cover may be reduced by one foot. |
(d) Private and community sewer lines must meet the material specifications publicly identified by the department under 18 AAC 72.070 and must meet applicable plumbing codes. In addition to these requirements, (1) gravity flow sewer lines must (A) have a minimum nominal diameter of four inches; and(B) be laid at slopes that maintain a minimum flow velocity of two feet per second and a maximum flow velocity of 10 feet per second when flowing full;(2) the 10 feet immediately preceding the primary treatment tank, treatment unit, or package plant may not exceed a two percent slope;(3) solid pipe without joints must span an excavation onto undisturbed earth, or the soil must be backfilled and compacted in six-inch lifts before laying the pipe;(4) sewer lines must be connected to the inlet and outlet of any tank, treatment unit, or package plant in accordance with manufacturer specifications;(5) all pipe-to-pipe joints must be glued with cement appropriate for the pipe material; and(6) cleanouts must be constructed using a sanitary wye, combination wye, or long-sweep wye fitting that has the same diameter of the sewer line to which it is attached, and extended to at least one foot above the ground surface; a single cleanout must be installed with the sweep in the direction of flow; a double cleanout must be installed with the upstream sweep in the direction of flow and the downstream sweep against the flow; cleanouts must be capped and installed (A) within five feet of the outside wall of the building foundation;(B) at intervals not to exceed 100 feet in continuous runs; and(C) before each aggregate horizontal change in direction of 45 degrees or more where the sewer line is located before primary treatment.(e) An advanced treatment unit or package plant must be designed and installed in accordance with manufacturer specifications, and documented (1) to have current certification from an accredited third-party testing organization; or(2) as meeting or exceeding secondary treatment standards through a one-year monitoring and sampling plan demonstrating that the design has successfully treated wastewater under similar installations.(f) Wastewater must meet minimum treatment requirements of 18 AAC 72.050 and be discharged to (1) a conventional soil absorption system constructed in accordance with 18 AAC 72.530;(2) an alternative soil absorption system constructed in accordance with a method publicly identified by the department under 18 AAC 72.070 as an approved best management practice, protective of public health, public and private water systems, and the environment;(3) the land surface in accordance with a method that is publicly identified by the department under 18 AAC 72.070 as an approved best management practice, protective of public health, public and private water systems, and the environment; or(4) an alternate method that is presented to and approved by the department in accordance with 18 AAC 72.615 and 18 AAC 72.200 - 18 AAC 72.290.Eff. 10/1/2023, Register 247, October 2023Methods publicly identified by the department as approved best management practices for alternative wastewater systems may be obtained at a department office or on the department's website.
Authority:AS 44.46.020
AS 46.03.020
AS 46.03.050
AS 46.03.100