S.C. Code Regs. § ch. 61, 61-56, 61-56.400, app 61-56.400.P
(1) Site/Permitting Requirements
(a) The texture in the upper eighteen (18) inches of naturally occurring soil must be Class I or Class II.
(b) The filter shall not be placed on slopes greater than three (3) percent.
(c) This system cannot be considered for facilities with peak flow rates in excess of four hundred eighty (480) gpd. This system shall not be considered for facilities requiring grease traps.
(d) There shall be a buffer of at least fifty (50) feet surrounding and separating the system from all adjacent property lines. This buffer shall be measured from the retaining wall.
(e) 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.
(f) No part of this system can be installed within one hundred twenty-five (125) feet of the critical area line or tidal waters as determined by the Department or within one hundred twenty-five (125) feet of the ordinary high water elevation within the banks of non-tidal, environmentally sensitive waters.
(g) The total bottom area of the filter must be increased by fifty (50) percent above that required for conventional trenches.
(h) 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 retaining wall intersects the naturally occurring soil surface.
(2) Installation Requirements
(a) Site Preparation
(i) If present within eighteen (18) inches of the naturally occurring soil surface, organic material and restrictive horizons must be removed from beneath the filter and replaced with USDA medium sand, washed concrete sand, or an equivalent material approved by the Department.
(ii) The naturally occurring soil surface underlying the filter shall be thoroughly tilled and mixed with the imported filter material to a depth of six (6) inches.
(b) System Requirements
(i) The filter must be constructed to a height of at least thirty-six (36) inches above the original grade with the sewage effluent passing through at least twenty-four (24) inches of filter material.
(ii) The filter material shall be USDA medium sand, washed concrete sand, or other material approved by the Department.
(iii) The filter retaining wall shall extend at least four (4) inches above the surface of the filter material and shall penetrate the naturally occurring soil surface at least four (4) inches.
(iv) The filter retaining wall shall be constructed in accordance with the accompanying design illustrations.
(v) 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).
(vi) The top of the filter shall be capped with Class II or Class III soil and shall slope from center to edges in order to promote surface runoff.
(c) Distribution Requirements
(i) Low Pressure Pipe Distribution (LPP) must be utilized to preclude localized hydraulic overloading of the imported fill material and to minimize the impact on the shallow zone of saturation.
(ii) Low Pressure Pipe Distribution (LPP) must be designed and installed in accordance with Department standards or equivalent designs. The size and layout of each distribution system will vary based on the size of the filter and the needed dosing.
(iii) Pump design shall be in accordance with Department standards.
(3) Final Landscaping and Drainage
(a) Fill material shall be placed around the outside of the filter to a depth of one (1) foot, and shall slope to original grade at a point five (5) feet from the retaining wall.
(b) The septic tank and filter area shall be backfilled and shaped to promote the runoff of surface water.
(c) Where natural surface drainage does not exist, a swale shall be constructed adjacent to the filter to divert surface water away from the onsite wastewater system to a positive outfall. The installation of ditches, curtain drains, and/or rain gutters may be required to intercept and divert water away from the onsite wastewater system location.
(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.
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S.C. Code Regs. ch. 61, 61-56, 61-56.400, app 61-56.400.P