S.C. Code Regs. § ch. 61, 61-56, 61-56.400, app 61-56.400.L
(1) Site/Permitting Requirements
(a) There must not be a zone of saturation (ZOS) within twelve (12) inches of the naturally occurring soil surface.
(b) The depth to any restrictive horizon must be greater than twelve (12) inches below the bottom of the proposed wastewater infiltration trenches.
(c) No part of this system can be installed within one hundred twenty-five (125) feet of the ordinary high water elevation within the banks of environmentally sensitive waters.
(d) This system may be considered for installation on contiguous lots in new subdivisions approved after the effective date of this standard provided a setback of at least seventy-five (75) feet is maintained between the system and all adjacent property lines. The seventy-five (75) foot setback shall be measured from the point at which the fill cap taper intersects with the naturally occurring soil surface.
(e) This system cannot be considered for facilities with peak sewage flow rates in excess of four hundred eighty (480) gpd. In addition, this system shall not be considered for facilities requiring grease traps.
(f) 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.
(g) The long-term acceptance rate for system sizing shall be based upon the most hydraulically limiting naturally occurring soil texture from the ground surface to twelve (12) inches below the bottom of the proposed wastewater infiltration trenches.
(2) Installation Requirements
(a) Effluent discharged to this system must receive a higher degree of treatment than that provided by a conventional septic tank (e.g. two (2) compartment septic tank or two (2) septic tanks in series).
(b) Where gravity flow from the septic tank to the subsurface wastewater infiltration area is utilized, the invert elevation of the septic tank outlet shall be installed at an elevation at least equal to or higher than the top of the aggregate in the highest wastewater infiltration trench(es).
(c) The required fill cap must extend at least five (5) feet beyond the limits of the wastewater infiltration trenches, and it must taper to the original soil surface at a slope not to exceed ten (10) percent . The required seventy-five (75) foot property line setback shall be measured from the point at which the fill cap taper intersects with the naturally occurring soil surface.
(d) The required fill material must be soil texture Class I, Class II, or Class III and be void of extraneous debris such as organic matter, building materials, etc.
(e) The depth of the fill cap shall provide a minimum of twelve (12) inches backfill above the top of the wastewater infiltration trench aggregate.
(f) The wastewater infiltration trench width shall be thirty-six (36) inches.
(g) All tree and brush removal shall be done in a manner that minimizes the disturbance or loss of naturally occurring soil.
(3) Final Landscaping and Drainage
(a) The septic tank and fill cap area shall be backfilled and shaped to promote the runoff of surface water.
(b) Where natural surface drainage does not exist, a swale shall be constructed adjacent to the filled area to divert surface water away from the onsite wastewater system to a positive outfall. The installation of ditches, curtain drains, and rain gutters may be required to intercept and divert water away from the onsite wastewater system location.
(c) A barrier to preclude parking and vehicular traffic over the system area may be required.
(d) Following final landscaping, seeding or sodding may be required to prevent erosion.
(e) 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.L