5a. Update on-site septic regulations

41 percolation rates faster than 15 minutes per inch (sandy loam) in the top 8 inch depth, disking may be used for surface preparation as a substitute for plowing. Mound construction must proceed immediately after surface preparation is completed. The original soil must not be excavated or moved more than one foot from its original location during soil surface preparation. I. A minimum of 12 inches of soil defined as sand must be placed where the drain field rock is to be located. This sand must be placed by using a construction technique that minimizes compaction. If the sand is pushed into place, a crawler tractor with a blade or unloaded bucket must be used to push the sand into place. At least 6 inches of sand must be kept beneath the equipment to minimize compaction of the plowed layer. When placing sand with a backhoe that has rubber tires, the tractor must not drive over the drain field rock or banks of the mound. The sand layer upon which the drain field rock is placed must be level. On slopes of 3% or greater, the long axis of the level drain field rock layer must not diverge up or down the slope by more than 12 inches of elevation from the natural contour line. The depth of the sand layer along the upper edge of the level drain field rock layer must not vary by more than 12 inches. On slopes of 3% or greater, and where the percolation rate in the top foot of original soil is in the 61 to 120 minutes per inch range, mounds must not be located where the ground surface contour lines directly below the long axis of the drain field rock layer represent a swale or draw, unless contour lines have a radius of curvature greater than 100 feet. Mounds must never be located in swales or draws where the radius of curvature of the contour lines is less than 50 feet.