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Comprehensive Plan SEPTIC TANKS Sanitary Sewer Sub -Element The third type of sanitary sewer system utilized in the county is the individual system or septic tank. Septic systems are generally small and designed to serve one or a limited number of land uses. Despite major expansion of the wastewater collection network, many residents within the unincorporated portion of the county do not have access to regional wastewater treatment facilities or package treatment plants. For those land uses, wastewater treatment and disposal is provided by individual septic systems. According to the Indian River County Health Department (IRCHD), there were an average of 658 new septic systems constructed annually within the unincorporated county between 1995 to 2006. Of those septic tanks, 5% to 8% were for commercial uses. Most of the residential septic systems are concentrated in Roseland, Sebastian, Vero Lake Estates, and the older platted subdivisions south of the City of Vero Beach. Septic tank systems provide on-site wastewater treatment for both residential and small-scale commercial developments. Generally, residential septic tanks range in capacity from 900 to 1000 gallons. Commercial septic tanks usually have a larger capacity. Since effluent from septic tanks is discharged to a drainfield where it is allowed to percolate into the soil, soil permeability and depth to the water table are limiting factors for septic tank use. To ensure adequate performance and protection of groundwater quality, elevation of septic tank drainfields is often required. A septic tank system consists of two components. One is the septic tank, while the other is the drainfield. The tank receives sewage from the dwelling unit or commercial establishment and provides a period of settling, during which time a significant portion of the solids settle out. The treatment process is accomplished by bacteria which gradually decompose the solids which have settled to the bottom of the septic tank. The remaining liquids are discharged through underground drainage pipes into the drainfield and percolate into the soil. Once in the soil, microorganisms and filtration processes purify the liquids. Every three to five years, the accumulated solids must be removed from the septic tank. These solids, called septage, are generally transported to regional sanitary sewer facilities for treatment prior to disposal. According to the IRCHD, Indian River County is a difficult county in which to install septic tank systems. There are several factors which account for this difficulty. These factors are: • a high water table found in almost all areas of the county; and • soil conditions consisting of an underlying hardpan strata in much of the county. While a high water table impedes the discharge of liquids into the drainfield, an underlying hardpan strata may prevent the filtration of effluent into the soil. Community Development Department Indian River County 19