(A) Site evaluations consisting of preliminary and field evaluations according to parts this Section must be conducted for all proposed sites for SSTS, including both ISTS and MSTS. The site evaluation is considered the first phase of an SSTS design.
(B) A preliminary evaluation for individual subsurface sewage treatment systems shall consist of determination, location, or existence of the following items:
(1) Design flow for the dwelling, dwellings, or other establishments.
(2) Proposed or existing:
(a) Water supply wells within 100 feet of the proposed SSTS;
(b) Existing and proposed buildings or improvements on the lot; and,
(c) Buried water supply pipes within 50 feet of the proposed system.
(3) Easements on the lot.
(4) The ordinary high water level of public waters, if adjacent to the lot.
(5) Floodplain designation and flooding elevation from published data or data that is acceptable to and approved by the Department or local unit of government or the DNR, if applicable.
(6) Property lines.
(7) All required setbacks from the system.
(8) The soil characteristics at the proposed soil treatment and dispersal areas as obtained by the soil survey report, including the soil map, map units, landscape position, parent material, flooding potential, slope range, periodically saturated soil level, depth to bedrock, texture, color, depth to redoximorphic features, and structure and consistence of soil horizons.
(9) A geocode or property identification number.
(10) Names of property owners.
(11) The inner wellhead management zone or wellhead protection area of a public water supply, if applicable.
(C) A field evaluation for an individual subsurface sewage treatment system shall consist of the following items:
(1) Lot lines shall be confirmed in the field using the most recent document source. Lot improvements, required setbacks, and easements must be identified.
(2) The following surface features must be described:
(a) The percent and direction of the slope of the proposed system location.
(b) Vegetation types.
(c) Any evidence of cut or filled areas or disturbed or compacted soil.
(d) The flooding or run-on potential.
(e) A geomorphic description.
(D) For subdivision or lot approval testing, enough soil observations must be conducted to assure that suitable soil exists for each lot for long-term sewage treatment outlining an area with enough space on the lot for two soil treatment and dispersal areas. This tested area must be at least 10,000 square feet. Percolation tests are not required for subdivision or lot approval testing unless the permeability cannot be estimated or there is reason to believe the soil is not original or has been disturbed.
(E) Complete soil testing on each individual lot must be conducted prior to permit issuance independent of any prior subdivision or lot approval testing. For permit issuance, a minimum of four soil observations outlining an area of 5,000 square feet are required. At least one soil observation must be performed in the portion of the soil treatment area anticipated to have the most limiting conditions. Larger areas may be required where conditions of use, soils, topography, or vegetation require. Soil observations must comply with the following requirements:
(1) The soil observation must be conducted within or on the borders of the proposed site;
(2) The soil observations must be performed in an exposed pit or by hand augering or probing. The use of flight augers is not allowed;
(3) The soil observation method must allow observation of the different soil horizons that constitute the soil profile and, if determining the loading rate by use of Table IX in Minn. Rules Chapter 7080.21501 undisturbed soil structure must be observed;
(4) Soil observations must be conducted prior to any required percolation tests to determine whether the soils are suitable to warrant percolation tests and, if suitable, at what depth percolation tests shall be conducted;
(5) The minimum depth of the soil observations must be to the periodically saturated layer, to the bedrock, or three feet below the proposed depth of the system, whichever is less.
(F) Each soil profile observed at the proposed soil treatment and dispersal area must be evaluated under adequate light conditions with the soil in a moist unfrozen state for the characteristics in items (F)(1) through (8):
(1) The depth of each soil horizon measured from the ground surface. Soil horizons are differentiated by changes in texture, color, redoximorphic features, bedrock, structure, consistence, and any other characteristics that affects water movement or treatment of effluent.
(2) A description of all soil colors for each horizon according to the Munsell Soil Color Charts, Revised Edition, Munsell Color Corporation (1992), or equivalent. The color charts are incorporated by reference, are available through the Minitex interlibrary loan system, and are not subject to frequent change.
(3) A description of the soil texture, and structure 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 § 52.02.
(4) Depth to bedrock.
(5) Depth to periodically saturated soil for new construction or replacement as determined by redoximorphic features and other indicators, as determined in divisions (a) to (c) below:
(a) In subsoil and parent material, redoximorphic features include:
1. Distinct redoximorphic iron accumulation or distinct redoximorphic iron depletions;
2. A gleyed or depleted soil matrix or redoximorphic mottles having a color chroma of two or less or a depleted matrix or redoximorphic mottles having a color hue of 5Y and a chroma of three or less; or
3. Faint redoximorphic concentrations or faint redoximorphic depletions in subsoil or parent material with a hue of 7.5YR or redder.
(b) In lower topsoil layers that are deeper than 12 inches from the surface and are immediately followed in depth by a periodically saturated horizon, redoximorphic features include:
1. Soil colors with a redoximorphic chroma of two or less; or
2. Redoximorphic accumulations or depletions.
(c) In the upper 12 inches of the topsoil layer immediately below which occurs a periodically saturated horizon, the depth of seasonal saturation is determined by indicators in divisions 1. to 5. below:
1. Soil colors with a chroma of zero;
2. Organic soil textures or mineral soil textures with an organic modifier;
3. Dominance of hydrophytic vegetation;
4. 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; or
5. Redoximorphic accumulations or depletions.
(6) Depth to periodically saturated soil for all existing systems, determined by redoximorphic features in division (F)(5) of this section, except divisions (F)(5)(b)1. and (F)(5)(c)1., 3., and 5., 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 § 52.02.
(G) The effluent loading and absorption area size must be determined by either item (G)(1) or (2).
(1) The loading rate based on an examination of soil texture, undisturbed structure, and consistence at the most limiting layer within 12 inches below the proposed 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 § 52.02; or
(2) The loading rate based on the percolation procedure described in divisions (G)(2)(a) to (h).
(a) Each test hole must be six to eight inches in diameter, have vertical sides, and be located at the depth of the proposed soil absorption area. 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 shall be at the depth of the 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 vary by more than ten percent. In other soils, the 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 30-minute intervals and refilled between measurements to maintain an eight inch starting head. If water seeps away in less than 30 minutes, a shorter time 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 vary by more than ten percent. The percolation rate is also allowed to be determined by observing the time it takes the water level to drop one inch from an eight-inch reference point if a constant water depth of at least eight inches has been maintained for at least four hours prior to the measurement;
(g) The time interval must be divided in minutes by the drop in water level in inches to obtain the percolation rate in minutes per inch. The percolation rates that are within the ten percent provision determined for each test hole must be averaged to determine the final percolation rate for that hole. The slowest final percolation rate for all holes within the soil dispersal area must be used for design; and
(h) A percolation test must not be run where frost exists within 12 inches of the bottom of the percolation test hole.
(H) A written report on the site evaluation for an individual subsurface sewage treatment system must be prepared and include the following:
(1) Preliminary and field evaluation results from divisions (B) through (F) of this section.
(2) Dates of preliminary and field evaluations.
(3) A map drawn to scale or dimension, with a north arrow, and including:
(a) Horizontal and vertical reference points of the proposed soil treatment and dispersal areas, soil observations, percolation tests, and pertinent distance from the proposed SSTS to all required setbacks, lot improvements, easements, ordinary high water mark of public waters, property lines, and direction and percent slope.
(b) The location of any unsuitable, disturbed, or compacted areas.
(c) The access route for system maintenance.
(4) The estimated depth of periodically saturated soil layer, bedrock, or flood elevation, if appropriate.
(5) The proposed elevation of the bottom of the soil treatment and dispersal system.
(6) Anticipated construction related issues.
(7) The name, address, telephone number, and certified statement of the individual conducting the site evaluation.
(8) An assessment of how known or reasonably foreseeable land use changes are expected to affect system performance, including, but not limited to, changes in drainage patterns, increased impervious surfaces, and proximity of new water supply wells.
(9) A narrative explaining any difficulties encountered during the site evaluation, including, but not limited to, identifying and interpreting soil and landform features and how the difficulties were resolved.
(10) A notation of any differences between observed soil characteristics and those identified in the soil survey report.
(I) Applicants for subsurface sewage treatment system permits, site approvals or subdivision approvals will be required to submit soil test data from soil borings and percolation tests, or soil pits, for each proposed site or installation. The minimum testing shall be that necessary to verify suitable conditions for two complete soil dispersal and treatment areas.
(J) All soil testing shall be conducted in accordance with the requirements of this chapter and shall be conducted by appropriately licensed businesses and certified individuals in accordance with Minn. Rules Chapter 7083.
(K) Prior to and during construction or lot improvements, the proposed initial and replacement soil treatment and dispersal areas shall be protected from disturbance, compaction, or other damage by use of stakes and silt fence or snow fence.
(L) Underground utilities must be located before soil observations are undertaken. Required safety precautions must be taken before entering soil observation pits.
(M) Where soil tests require a mound, testing and design must clearly show suitable area for installation of two complete mounds. Where site conditions are such that the only backup mound will likely be disturbed, the Department, at its discretion, may require both mounds to be constructed at once.
(N) Designs for new construction or replacement SSTS must comply with all applicable requirements and any other applicable codes, rules, and laws.
(Ord. 2010-162, passed 5-17-2010)