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b. Mounds and At-Grades. Mounds and at-grades must meet <br /> specifications per Minnesota Rules Chapter 7080 and may not be located on soils with percolation <br /> rates slower than 120 mpi. Mounds or at-grades may be placed on slopes up to 12% with soils <br /> having a percolation rate of 0.1-30 mpi and a soil texture of sand, fine sand, sandy loam, or loam. <br /> Mounds or at-grades may be placed on slopes up to 9%with soils having a percolation rate of 31-45 <br /> mpi and a soil texture of loam or silt loam. Mounds or at-grades may be placed on slopes up to 6% <br /> with soils having a percolation rate of 46-120 mpi and a soil texture of clay loam or clay. <br /> C. Compliance Standards. <br /> 1. A new system shall be located, designed and constructed as a code system. <br /> 2. When an e�cisting code system is repaired or expanded,such ISTS shall remain <br /> a code system. Compliant systems, when repaired, shall be upgraded to a code system status <br /> whenever such classification is reasonably attainable. <br /> 3. Existing non-compliant systems shall be replaced by code systems whenever <br /> such classification is reasonably attainable. If a code system is not achievable due to soil, water <br /> table, or lot limitations, the ISTS may be replaced or repaired such that it becomes a compliant <br /> system. <br /> D. Construction Procedures. <br /> 1. Protect Drainfield Area: Proposed drainfield areas shall be identified and <br /> marked off on the lot at the time of the site evaluation and prior to any construction or grading <br /> occurring in the area. The drainfield area shall remain undisturbed until drainfield construction is <br /> commenced. No vehicular traffic shall be allowed in the drainfield area either before or after <br /> drainfield installation. <br /> 2. Favorable Weather Required:Drainfield area or trench construction must not <br /> proceed if the area is wet or has had rain within 48 hours. Mound or trench construction shall not <br /> proceed unless the soil moisture content is below the plastic limit. <br /> 3. Construction Inspection Required: The contractor issued a permit for ISTS <br /> construction shall perform all work according to the design specifications approved by the City for <br /> each particular ISTS. All subsurface work including building sewer, sewage tanks, distribution <br /> system and soil-treatment area shall be inspected by the City Inspector prior to backfilling or <br /> covering of any portion thereof. It shall be the responsibility of the contractor to notify the City at <br /> least 24 hours prior to the time an inspection will be required,and it shall be the responsibility of the <br /> contractor to ensure that the inspection is accomplished and the construction is approved prior to any <br /> backfilling, covering or continuation of the construction. <br /> Page 10 of 17 <br />