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In the State of Minnesota, soil mottling has become the key factor in determining <br />the higlKst level of seasonal saturation in the soil. In Orono's loam arid clay loam <br />soils, soil mottling and seasonal saturation are commonly found from 2* to 5’ below <br />the grouiKi surface. In order to meet the 3' separation requirement, a majont> of <br />IKW septic systems are mounds, which maintain the 3 separation. <br />The use of soil mottling for determining seasonal saturation is subjective at best <br />but is the only practical method identified by the State for determimng seasonal <br />saturation. However, in some years saturation may not occur at the mottlmg level, <br />and in other years saturation may occur at mottling level for only a few days <br />weeks or months in a given year. The State has taken the position that even though <br />the system might be too close to the water table for a short period during any given <br />year, that system is not conforming. <br />Very few septic systems in Orono are faiiilUi at any given time, perhaps 3 5% or <br />1 in 25 However, as many as 500-600 of the 1 100 e.xisting systems are estimated <br />as fitting the definition of "non-conforming ”. While these might treat sewage quite <br />adequately most of the time, during some periods they might not. <br />3. Evaluation Methods. <br />Each neighborhood was evaluated in terms of soil and water conditions, proximity <br />to lakeshore or other water bodies, and lot sizes. Within each neighborhood, <br />individual systems were analyzed to determine system type (trench, mound, bed <br />or cesspool), system condition (working, marginal or failing), conformity with 3 <br />separation requirement (conforming or nonconforming), whether the system is in <br />the "shoreland", and whether or not an alternate drainficld site is available. <br />Note that in analyzing system conditions, systems exhibiting no surface discharge <br />and generally in working order were considered as "working", systems obviously <br />discharging to the surface were considered as failing, and systems with a drainlield <br />area saturated but not discharging were considered as "marginal". It is, therefore, <br />possible and quite common to have a system that is work ing but is still IML <br />rnnformimi . <br />4. Individual Neighborhood Data Sheets & Summary (Attached) <br />5. Summary of Results/Prioritization <br />Evaluation of the accumulated data suggests that some neighborhoods are more <br />critical than others in terms of ability to continue using septic systems on a long