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TILE DEWATERING ALTERNATIVE ON-SITE SEWAGE SYSTEM A "Tile Dcwatefing' septic system means a system where a standard disposal field is installed and a dewatering trench is dug on all four sides of the disposal field. The purpose of the system is to lower the naturally occurring water table found on the property during the wet, winter months. This allows the disposal field to function properly in unsaturated soil conditions. General Cpnditions for Approval: On-Site system construction permits may be issued by this office for tile dewatering systems provided the following requirements can be met: (1) (2) (3) (4) The site h~ a natural outlet that will allow a field tile installed on a proper grade around thc proposed absorption facility to daylight above the annual high water. Soils must he silty clay loam or cea.reef texture and be dralnable, with a minimum effective soil depth of at least thirty (30) inches in soils with temporary groundwater; and at lea~t seventy-two (72) inches in soils with permanent groundwater. Slope in the area of the proposed disposal field does not exceed three (3) percent. All other requirements specific4 in the Department of Envkomuental Quality rules for the system, except depth to groundwater, can be met. However, after the field collection drainage tile is installed, the groundwater levels shall conform to the appropriate requirements of the D.E.Q. rules. C_qnstruction Requirements: (1) (2) (3) (4) (5) (6) (7) (8) (9) (lO) Field collection drainage tile shall be installed on a uniform grade of two-tenths to four-tenths (0,2-0.4) feet of fall per one-hundred (100) feet. and either: (a) A minimum depth of thirty~six (36) inches in soils with temporary groundwater, OR Co) A minimum depth of sixty-six (66) inches in soils with permanent groundwater. The maximum drainage tile spacing shall be seventy (70) feet, center to center. The minimum horizontal separation distance between the drainage tile and the absorption facility shall be twenty (20) feet. The field collection drainage tile shall be rigid, smooth wall, perforated pipe with a minimum diameter of four (4) inches. The field collection drainage tile shall be euveloped in clean drain media (drain rock) to within twelve (12) inches of the soil surface in soils with temporary groundwater, OR to within thirty (30) inches of the soil surface in soils with permanent groundwater. The drain media shall be cover*d with filter fabric, m~ated building paper or other nondegradable material approved by this office. The outlet tile dali be rigid, smooth wall solid PVC pipe with a minimum diameter of four (4) inches. The outlet end shall be protected by a short section of PVC pipe meeting or exceeding ASTM Standard D-B034, with a flap gate or grill to exclude rodents. A silt trap with a twelve (12) ir~eh minimum di~neter shall be installed between the field collection drainage tile and the outlet pipe. The bottom of the silt trap shall be a minimum of twelve (12) inches below the invert of the drainage pipe outlet. The drainage pipe and tile drainage system are integral parts of the septic system, but do not need to meet setback requirements to property lines, wells, streams, lakes, ponds or other surface waterbodies. Marion County ha~ the discretion of requiring demonstration that a proposed tile dewatering site can be drained prior to issuing a Constmctiun-Installation permit. The absorption facility shall use equal or pressurized distribution.