Rule 15-18-77-5.6.3 - DesignUtilizing USDA soil groups as classified by textures is the most appropriate criteria on which to base loading rates for this system. The size of the disposal field shall be based on the most restrictive soil, naturally occurring within 2 feet of the ground surface or to a depth of 1 foot below the trench bottom, whichever is deeper. Criteria and techniques for soil and site evaluation can be found in Chapter 03 Regulation Governing Residential On-site Wastewater Disposal Systems: Soil and Site Evaluation.
1. Prior to the design of the Subsurface Drip Irrigation System, the suitability of the site must be demonstrated through acceptable soil permeability rates, acceptable soil conditions (Table I) and other topographic characteristics. The design and construction of the Subsurface Drip Irrigation System must conform to the drip tubing manufacturer's specification (Figure 1).2. A minimum of 6 inches of naturally occurring soil must be present above a restrictive horizon or a predominantly gray soil (50%) before placement of appropriate fill. Subsurface Irrigation System is not recommendable on hydric soils conditions.3. Except where hydric soils are present, a clean fill material may be used to overcome seasonal water table limitation. The fill material shall consist of a minimum of 50 percent sand particles equal to or greater than 0.25 mm. Clay content shall be 20 percent or less. Organic matter shall be removed from the native soil surface prior to placing and incorporating the fill. This fill must be incorporated into the native soil to prevent a textural interface from developing. When fill material is used the entire fill area must be sodded to prevent erosion, or other effective erosion control methods used. The full depth of fill material must extend at least 2 feet in all directions from drip tubing and at that point shall be sloped at a grade of no steeper than 3 to 1.4. In soils that contain a restrictive horizon, within 5 feet of the surface, there shall be a minimum of 12 inches of unsaturated soil between the bottom of the drip tubing and any perched or seasonal water table.5. In soils that do not contain a restrictive horizon, within 5 feet of the surface, there shall be a minimum of 24 inches of unsaturated soil between the bottom of the drip tubing and any perched or seasonal water table.6. Drip tubing must be installed a minimum of 6 inches deep. The maximum depth may not exceed 18 inches. In all cases there shall be a minimum of 12 inches separation between the water table and restrictive horizon.7. Minimum separation between drip emitter shall be 2 feet. A 2 foot horizontal separation must be between drip tubing lines for slopes of less that 20 percent for slopes of 20 percent or greater shall be a minimum of 3 foot horizontal separation. 8. Drip tubing shall either be placed 4 inches lower than the supply manifolds or water breaks shall be used to prevent effluent from flowing along the drip tubing to the supply manifold trenches.9. Valves, fittings, level control switches and all other components must be designed and manufactured to resist the corrosive effects of wastewater and common household chemicals.10. Electrical equipment shall be protected with safety devices (overload interrupting devices, fuses, etc.). Electrical equipment shall comply with appropriate National Electrical Manufacturer's Association (NEMA) requirements. Electrical component parts shall be covered by the manufacturer's limited warranty.15 Miss. Code. R. 18-77-5.6.3