18 AAC 72.265. Soils analysis and report

The soils report must meet the following criteria:

(1) test holes and percolation tests must be located and conducted to yield data representative of the initial and replacement soil absorption system;

(2) the number of test holes and percolation tests must be sufficient to adequately evaluate subsurface characteristics of the area planned for the soil absorption system;

(3) soil borings and soil analysis must show that the vertical separations between the lowest part of the system and both the seasonal high water table and the impermeable strata conform to

(A) the provisions of 18 AAC 72.020, if the report is for a conventional soil absorption system; or

(B) Chapter 7 of the Design Manual: Onsite Wastewater Treatment and Disposal Systems, adopted by reference at 18 AAC 72.070(a) (4), and Chapter 10 from A 1979 State of the Art Manual of On-Site Wastewater Management, adopted by reference at 18 AAC 72.070(a) (2), if the report is for an alternate soil absorption system;

(4) if the water table is encountered in a test hole, the depth to the seasonal high water table must be determined by

(A) monitoring test holes or soil borings taken between June 1 and September 30;

(B) soil mottling analyses;

(D) the knowledge and experience of the engineer, based on past subsurface investigative work in the vicinity of the project; or

(E) a combination of these methods;

(5) the depth to seeps, if any, must be provided to the department; as necessary to protect public health, public and private water systems, and the environment, the department will require subsequent monitoring;

(6) the minimum test hole depth must be

(A) six feet below the lowest part of the soil absorption system; and

(B) in areas of known or suspected permafrost, the lesser of

(i) 20 feet below ground surface; or

(ii) the depth at which permafrost or an impermeable layer is encountered;

(7) soils in the usable wastewater disposal area for a conventional soil absorption system must be shown by a percolation test to have a percolation rate between

(A) one and 30 minutes per inch for seepage pits;

(B) one and 60 minutes per inch for trenches or beds; or

(C) faster than one minute per inch if the department has given its approval on a case-by-case basis under footnote 'b' of Table C at 18 AAC 72.260(a) (4)(D);

(8) soils in the usable wastewater disposal area for an alternate soil absorption system must be shown by a percolation test to have a percolation rate meeting the recommendations for that type of system found in Chapter 7 of the Design Manual: Onsite Wastewater Treatment and Disposal Systems, adopted by reference at 18 AAC 72.070(a) (4);

(9) percolation tests must be

(A) performed by a registered engineer, or a person under the direct supervision of a registered engineer;

(B) performed in accordance with applicable procedures contained in Table 3-8 of the Design Manual: Onsite Wastewater Treatment and Disposal Systems, adopted by reference at 18 AAC 72.070(a) (4);

(D) provided to the department; and

(E) confirmed to be accurate by a correlation of the observed soil texture in the test hole with the range of soil texture types associated with the observed percolation rate in Table C in 18 AAC 72.260(a) (4)(D);

(10) in areas known or suspected to contain permafrost,

(A) a soil moisture content profile analysis derived from laboratory testing methods, and taken from each test hole used for soils testing, must show that the soils are adequately drained throughout the usable wastewater disposal area; and

(B) the results of a geotechnical study must show that the area can successfully be used for the system proposed;

(11) the soils report must be sealed by a registered engineer.

History: Eff. 4/1/99, Register 149

Authority: AS 44.46.020

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