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9.10. Mounded Systems 9.10.1 A mound system is a soil absorption system that is elevated above the natural soil surface. The purpose of the design is to overcome site restrictions that prohibit the use of conventional soil absorption systems. Such restrictions are slowly permeable soils, slowly permeable soils with high water tables, and permeable soils with high water table. 9.10.2 The mound system consists of a suitable fill material, an absorption area, a distribution network, a cap or cover and topsoil.The effluent is pumped or siphoned or gravity fed into the absorption area through a distribution network located in the upper part of the coarse aggregate. It passes through the aggregate and infiltrates the fill material. Treatment of the wastewater occurs as it passes through the fill material and the unsaturated zone of the natural soil. The cap, usually a finer textured material than the fill, provides frost protection and retains moisture for a good vegetative cover. The topsoil provides a growth medium for the vegetation. 9.10.3 Design of a mound system is to conform to the EPA Design Manual-Onsite Wastewater Treatment and Disposal Systems, October 1980 except for the following exceptions: a) Minimum size of the absorption area within the mound system: 1 bedroom—2000 sq ft bed area 2 bedroom—3000 sq ft bed area 3 bedroom—4000 sq ft bed area Add 1000 sq. ft bed area for each bedroom above 3 b) All individual homes will be required to install a minimum of a 1900 gallon tanks with 800 gallon lift station, (dosing chamber), if system is under pressure from a pump. System shall have a back flow device installed between raised bed and lift station where applicable; thus to prevent back flow when system is nearing total saturation. Lift station must have an automatic alarm installed to warn homeowner of lift pump failure. All wiring connections will be made outside of lift station in a water- proof type electrical junction box. All wiring will be done under applicable permits from County or State agencies. c) The perimeter of the absorption bed may require a 2" width redwood board retaining wall the height of the bed to maintain soil stability. 9.10.4.Variation in design and sizing of a mound system must be done by a Qualified Professional and approved by the Director of Environmental Health. 9.11. Sumps 9.11.1 Sumps are two (2) to four (4) foot wide trenches installed at depths greater than three and one-half feet to twenty-five (25) feet and are only installed at the terminal end of a leach line. EHD 42-014 Page 31 of 40 OWTS Standards 1/2017