R 323.2235 Overland flow treatment.

Rule 2235. (1) Overland flow treatment of wastewater is the application of wastewater to the upper reaches of grass-covered slopes with excess wastewater collected at the end of the slopes for reapplication. A facility utilizing an overland flow system for the land treatment of wastewater shall design and construct the system under this rule. (2) A system may be constructed on a site that has slowly permeable soil, which is soil that has 50% or more of the soil particles pass through a no. 200 sieve, except that more permeable or coarser textured soil may be approved on a case-by-case basis depending on system design and wastewater strength. Suitable soil shall extend not less than 3 feet below the soil surface. (3) The system shall consist of an adequate number of cells that can be alternately loaded and rested, unless there is adequate storage or pretreatment, to allow loading and resting of a single cell. (4) The shape of each cell within the system shall be designed to minimize soil disturbance when constructing the system. (5) For a system utilizing more than 1 cell, the wastewater distribution system shall be designed and constructed so that individual cells within the system can be taken out of service for resting or other purposes without disruption to the remaining cells. (6) The header ditch drainage and the grading of the furrows, where utilized, shall be tested for equal liquid distribution before seeding. (7) All embankments and dikes shall be properly seeded in order to establish appropriate vegetative cover for the purpose of erosion prevention. (8) All furrow side slopes, where present, shall be designed and constructed to allow for the periodic maintenance and mechanical harvesting of vegetative cover. (9) The depth of the furrows of a ridge and furrow system, when utilized, shall be adequate to contain the highest proposed furrow stream. The furrow stream is the volume, in gallons per unit time, usually per minute, of wastewater discharged into the furrow. (10) The system shall be seeded with perennial grass, or other vegetation approved by the department as capable of high nutrient uptake, and be suited to the climate and soil moisture conditions created by the operation of the system. Vegetative cover, not less than 2 inches in length and capable of preventing significant erosion to furrows or embankments, shall be established before the system is used for wastewater treatment.