14 CAR § 21-707. Capping fill systems

(a)(1) Standard onsite wastewater systems shall not be installed in fill material. (2) However, fill material may be used as a cap over the natural soil surface to increase the volume available for the storage of effluent. (b) Where capping fill is incorporated in the design of a standard onsite wastewater system, the distribution system shall be capable of storing effluent to the top of the settled cap. (c)(1) The absorption trenches on capping fill systems shall be designed and installed in natural soil. (2) However, a variance as provided in 14 CAR §§ 21-201 and 21-202 can be requested to install the absorption trenches partially in the fill, no less than four inches (4”) into the natural soil, to overcome bedrock separation requirements. (3) Systems utilizing capping fill shall have a minimum six inches (6”) of settled cover above the gravel bed or gravel substitute. (d)(1) The slope of the absorption area cannot exceed twelve percent (12%). (2) Submitted plans shall indicate both the original and the finished elevations referenced to a benchmark. (e)(1) For absorption areas exhibiting slopes of six percent (6%) or less, the full depth of fill shall extend a minimum of ten feet (10’) beyond the edge of the absorption trench then graded at a three (3) to one (1) or less slope. (2)(A) The fill area shall be seeded and watered regularly to prevent erosion. (B) See Appendix G, Figures 4 and 5. (f)(1) For absorption areas exhibiting slopes greater than six percent (6%) the full depth of fill shall extend: (A) One foot (1’) beyond the absorption area on the uphill side; (B) Ten feet (10’) on the sides of the absorption area; (C) Twenty feet (20’) on the downhill side of the absorption area; and (D) Then all sides graded to a three (3) to one (1) slope or less thereafter. (2)(A) The fill area shall be seeded and watered regularly to prevent erosion. (B) See Appendix G, Figures 6 and 7. (g)(1) For absorption areas exhibiting slopes greater than six percent (6%), a berm and/or drainage ditch to divert surface water is required. (2) The berm and/or drainage ditch shall be: (A) Constructed no more than ten feet (10’) up slope from the absorption area; and (B) Extended a minimum ten feet (10’) beyond the applied capping fill. (h) On slopes of greater than twelve percent (12%), a variance for capping fill systems may be granted in accordance to 14 CAR §§ 21-201 and 21-202. (i)(1) The fill material used shall be a: (A) Uniform loamy soil with maximum clay content of twenty-seven percent (27%); and (B) Maximum sand content of sixty percent (60%). (2) The depth of fill above the original ground surface is measured after settling. (3) Loamy soils can be expected to settle twenty-five percent (25%). (j)(1) The absorption area shall be scarified to destroy and remove the vegetative material. (2) The absorption area shall be tilled to a minimum depth of four inches (4”). (3) Stumps should be left in place at the absorption area to prevent extensive disruption of the soil. (k) Where capping fill is incorporated into the design of a system, only track equipment may be utilized when applying the cap. (l) The soil cap is a part of the standard onsite wastewater system and shall meet all the setbacks outlined in 14 CAR § 21-502.