General: Elevated Sand Mound

General: Elevated Sand Mound. 1. Successful function of any on-site system is characterized by a two-fold process: treatment and disposal. The final treatment is accomplished predominantly by physical and microbiological/chemical processes within the soil environment. These processes are affected by: a. Wastewater strength and characteristics. b. Soil moisture levels. c. The nature of the receiving soil. d. The soil loading rate. 2. Disposal is primarily affected by the depth of the unsaturated receiving soils, their hydraulic conductivity, and the area available for disbursement. The mound system relies on a single-pass flow pattern in unsaturated flow conditions through specified filter media (sand) for sewage treatment. The elevated sand-mound system incorporates the disposal component by discharging directly into the underlying soil. 3. An elevated sand-mound system is characterized by: a. A pretreatment device (a septic tank with an approved filter, or a treatment plant). b. Pressure distribution components (pumping chamber, pump and controls, and distribution laterals). c. The “mound.” [See Figure 16.] The “mound” consists of: i. Filter media (sand). ii. An absorption area. iii. A distribution system. iv. A soil cap and topsoil cover. 4. A septic tank with an approved filter or an aerobic treatment unit may be used as the pretreatment for the elevated sand mound. The effluent, pumped from the pump chamber into the distribution network in the absorption bed area, flows through the filter media where it is treated through biological and chemical processes. The treated effluent then passes into the natural soil, which must have at least six (6) inches of unsaturated soil.