14 CAR § 20-103. Site assessment

Subsurface drip system or systems may be utilized on sites that meet the following criteria: (1)(A) The drip tubing or installed trench bottom shall be above the seasonal water table, whatever the duration. (B) Brief seasonal water tables may be minimized or eliminated by the use of effective interceptor drains. (C) Any design that incorporates the use of an interceptor drain shall indicate the effective depth of seasonal water table reduction; (2)(A) Low hydraulic conductivity shall include soils with forty percent (40%) or greater clay. (B) Clay percentage shall be determined from in-depth zone extending six inches (6”) above and twelve inches (12”) below installed drip tubing depth; (3) No loading rates are available for low hydraulic conductivity soils with greater than sixty percent (60%) clay; (4) Systems utilizing drip dispersal must maintain a minimum of nine inches (9”) separation between drip tubing and any rock substrata, consolidated or fractured, for soils that exhibit a moderate and/or long SWT; (5) Systems utilizing drip dispersal must maintain a minimum of fifteen inches (15”) separation between drip tubing and any rock substrata, consolidated or fractured, for soils that: (A) Exhibit only a brief SWT; or (B) Do not exhibit an SWT; (6) Soils that are structureless or with massive structure shall not be approved for onsite subsurface treatment; and (7)(A) The lot size shall be of sufficient area to accommodate both the primary and secondary dispersal area. (B) Both the primary and secondary dispersal area shall be sized according to the respective loading rates. (C) If the lot can only support the primary dispersal field, a subsurface drip dispersal system shall not be installed.