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7080.2210 INDIVIDUAL SUBSURFACE SEWAGE TREATMENT SYSTEMS 48 7080.2200 TYPE I SYSTEMS. Systems designed according to parts 7080.2200 to 7080.2240 are considered Type I systems. Statutory Authority: MS s 115.03; 115.55 History: 32 SR 1347 Published Electronically: October 10, 2013 7080.2210 TRENCHES AND SEEPAGE BEDS. Subpart 1. Characteristics. To qualify as a trench or seepage bed system, the system must meet the requirements of items A to E: A. employ flow values in parts 7080.1850 to 7080.1885; B. meet applicable technical requirements of parts 7080.1900 to 7080.2030, 7080.2050, and 7080.2100; C. provide flow measurement if a pump is to be employed; D. meet the requirements of part 7080.2150, subparts 2 and 3, except subpart 3, item M; and E. meet the requirements of subparts 2 to 4. Subp. 2. General. Seepage bed placement must be limited to areas having natural slopes of less than six percent. Absorption areas for seepage beds and trenches must not be placed in soils with a loading rate of less than 0.45 gallons per day per square foot or as shown in Table IX or IXa in part 7080.2150, subpart 3, item E. Seepage beds must not be located in floodplains. Subp. 3. Sizing of trenches and seepage beds. A. The trench bottom absorption area is calculated by dividing the design flow by the appropriate soil loading rate in Table IX or 1Xa in part 7080.2150, subpart 3, item E. If gravity distribution is used in seepage beds, the seepage bed absorption area is calculated by dividing the design flow by the soil loading rate in Table IX or IXa in part 7080.2150, subpart 3, item E, multiplied by 1.5. If pressure distribution is used in seepage beds, the seepage bed absorption area is determined by dividing the design flow by the soil loading rate in Table IX or IXa in part 7080.2150, subpart 3, item E. B. The minimum sidewall absorption is six inches. The bottom absorption area is allowed to be reduced, for trenches only, by the following: Sidewall absorption - inches Bottom area reduction 12 to 17 20% 18 to 23 34% 24 40% A 40 percent reduction is not allowed with a loading rate of 1.2 gallons per day per square foot. Copyright ©2014 by the Rev so of Statutes, State of Minnesota. All Rights Reserved.