05-06-1997 Council Packet - Laserfiche WebLink

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"Nonconforming" Versus "Failing" Systems. In 1989, MPCA Rules Chapter 7080 were revised to include in the definition of nonconforming systems, "systems with less than 3' of unsaturated soil or. sand between the distribution device and the limiting soil characteristics". This regulation defines limiting soil characteristics as "those soil characteristics which preclude the installation of a standard system, including evidence of water toble". Water table is defined as "the highest elevation m the soil where all voids are filled with water, as evidenced by presence of water or soil mottling or other information". In the State of Minnesota, soil mottling has become the key factor in determining the highest level of seasonal saturation in the soil. In Orono's loam and clay loam soils, soil mottling and seasonal saturation are commonly found from 2' to 5' below the ground surface. In order to meet the 3' separation requirement, a majority of new septic systems are mounds, which maintain the 3' separation. The use of soil mottling for determining seasonal saturation is subjective at best, but is the only practical method identified by the State for determining seasonal saturation. However, in some years samration may not occur at the mottling level, and in other years saturation may occur at the mottling level for only a few days, weeks or months in a given year. The State has taken the position that even though the system might be too close to the water table for a short period during any given year, that system is not conforming. Very few septic systems in Orono are failing at any given time, perhaps 3-5% or 1 in 25. However, as many as 500-600 of the 1150 existing systems are estimated as fitting the definition of "non-conforming". While these may treat sewage quite adequately most of the time, during some periods they may not. Evaluation Methods. Each neighborhood was evaluated in terms of soil and water conditions, proximity to lakeshore or other water bodies, and lot sizes. Within each neighborhood, individual systems were analyzed to determine system type (trench, mound, bed or cesspool), system condition (working, marginal or failing), conformity with 3' separation requirement (conforming or nonconforming), whether the system is in the designated "Shoreland" district, and whether or not an alternate drainfield site is available. Note that in analyzing system conditions, systems exhibiting no surface discharge and generally in working order were considered as "working"; systems obviously discharging to the surface were considered as "failing"; and systems with a drainfield area samrated but not dischargmg were considered as "marginal". It is, therefore, possible and quite conunon to have a system that is working but is still non-conforming.