S.C. Code Regs. § ch. 61, 61-56, 61-56.400, app 61-56.400.I
(1) Site/Permitting Requirements
(a) Soil conditions, the depth to rock and other restrictive horizons, the depth to the zone of saturation (ZOS), and the elevation differential between the septic tank outlet and the highest wastewater infiltration trench(es) must meet applicable standards for conventional or alternative onsite wastewater systems.
(b) There shall be a replacement area equivalent to at least fifty (50) percent in size of the original system area held in reserve for system repair. This area shall have a suitable configuration and shall meet the minimum soil and site conditions of this regulation.
(c) This system cannot be considered for facilities with peak flow rates in excess of fifteen hundred (1500) gpd unless the trench width is three (3) feet and the aggregate depth is between fourteen (14) and twenty-eight (28) inches.
(d) The linear footage requirement for an alternative width and depth system shall be determined by first figuring the conventional (thirty-six (36) inch wide with fourteen (14) inch aggregate depth) linear footage requirements and then multiplying by the appropriate factor based on desired trench width and aggregate depth. (See table below system illustration for multiplication factors.)
(2) Installation Requirements
(a) Trench widths shall not exceed ten (10) feet.
(b) The aggregate depth shall be between six (6) inches and twenty-eight (28) inches when considering trench widths ranging from one and one-half (11/2) to ten (10) feet (see chart). The aggregate depth may be increased to a maximum of forty-two (42) inches, provided the trench width does not exceed thirty-six (36) inches (Note: In these cases, the equivalency formula should be utilized to determine the appropriate factor (F) when considering aggregate depths between twenty-eight (28) and forty-two (42) inches). All trenches shall be covered with at least nine (9) inches of backfill.
(c) Methods of construction which preclude vehicular compaction of the trench bottom must always be utilized.
(3) Final Landscaping and Drainage
(a) Installation of drainage swales, ditches, diversion drains, or rain gutters may be required to divert or intercept water away from the onsite wastewater system location. The septic tank and subsurface wastewater infiltration area shall be backfilled and shaped to promote surface water runoff.
(b) A barrier to preclude parking and vehicular traffic over the area of the system may be required.
(c) Following final landscaping, seeding or sodding may be required to prevent erosion.
(d) Final approval shall be withheld until all landscaping and drainage improvements have been satisfactorily completed.
S.C. Code Regs. ch. 61, 61-56, 61-56.400, app 61-56.400.I