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Effective April 28, 2015 Chapter Four Subsurface Sewage Treatment System Regulations ii. Organic soil textures or mineral soil textures with an organic modifier; iii. Dominance of hydrophytic vegetation; iv. The soil treatment area at or near the elevation of the ordinary high water level of a surface water or in a concave hill slope position; V. Redoximorphic accumulations or depletions; or vi. The soil expressing indicators of seasonal saturation as determined in Field Indicators of Hydric Soils in the United States: A Guide for Identifying and Delineating Hydric Soils, USDA Natural Resource Conservation Service (2006 and subsequently amended). This field book is incorporated by reference, is available through the Minitex interlibrary loan system, and subject to frequent change. (6) Depth to periodically saturated soil for all existing systems, determined by redoximorphic features in item (5), except subitems (B), unit (i), and (C), units (i), (iii), and (iv), as measured outside the area of the system influence in an area of similar soil. (7) Depth of standing water in the soil observation excavation, measured from the soil surface, if observed. (8) Any other soil characteristics that needs to be described to design a system, such as hardpans or restrictive layers. These other characteristics must be classified according to the Field Book for Describing and Sampling Soils, which is incorporated by reference under Section 2.2 (46). 9.7 Determination of loading rate and absorption area size. The effluent loading and absorption area size must be determined by either item (1) or (2). (1) The loading rate based on an examination of soil texture, undisturbed soil structure, and soil consistence at the depth of either the proposed absorption area or the most restrictive layer within three feet of the proposed soil absorption area using the United States Department of Agriculture (USDA) soil classification system as specified in the Field Book for Describing and Sampling Soils, which is incorporated by reference under Section 2.2 (46); or (2) The loading rate based on the percolation procedure described in subitems (A) to (H). (A) Each test hole must be six to eight inches in diameter, and have vertical sides. For mounds and at -grade systems, the bottom of each test hole must be in the upper 12 inches of the original soil. For trenches and seepage beds, the bottom of each test hole must be at the depth of either the proposed absorption area or the most restrictive layer within three feet of the proposed soil absorption area; (B) Soil texture descriptions for percolation test holes must note the depths from the ground surface where texture changes occur; (C) The bottom and sides of the hole must be carefully scratched to remove any smearing and to provide a natural soil surface into which water penetrates. The scarification must not result in the hole having a diameter of greater than eight inches; (D) All loose material must be removed from the bottom of the test hole and two inches of one- fourth to three -fourths inch gravel or clean sand must be added to protect the bottom from scouring; (E) The hole must be carefully filled with clear water to a minimum depth of 12 inches from the bottom of the test hole and maintained for no less than four hours for saturation to occur. The soil must then be allowed to swell for at least 16, but no more than 30, hours. In sandy soils, the saturation and swelling procedure is not required and the test is allowed to proceed if the initial filling of the hole with 12 inches of water seeps away in less than ten minutes; (F) In sandy soils, water depth must be adjusted to eight inches over the soil at the bottom of the test hole. From a fixed reference point, the drop in water level must be measured in inches to the nearest 1/16 inch at approximately ten-minute intervals. A measurement is also allowed to be made by determining the time it takes for the water level to drop one inch from an eight inch reference point. If eight inches of water seeps away in less than ten minutes, a shorter interval between measurements must be used, but water depth must not exceed eight inches. The test must continue until three consecutive percolation rate measurements do not 36 Washington County Development Code