uch is dependent upon the type of soil present. The standard septic tank and drain field are quite up to this cleansing under many different situations. However, there are many areas in the country where septic tanks and standard drain fields will not work properly. These areas, if they are to be protected from pollution, require alternative liquid waste disposal systems. Typical areas where such systems are used include those with high water tables, steep slopes, tight soils, very coarse soils, and shallow bedrock. The choice of system is based upon the specific situation encountered. Each potential alter- native probably costs more than a standard system, is more difficult to design and construct, and is more subject to being upset by misuse and lack of maintenance. Selection of Site and System SITE EVALUATION If you do not know well the area where the septic system will go, the local health department or the neighbors may be able to tell you if problems with septic tanks are common in the neighborhood. A site inspection must be made before the system is designed in order to note potential problems and to perform necessary onsite tests. Keep in mind that conditions for onsite sewage disposal can change from excellent to impossible over very short distances. Neighbors on adjacent lots may need entirely different types of disposal sys- items. Since location of the septic system can be more restricted than the house location, it is best to site the septic system before the house and any on-lot water well are located. A sketch of the lot is very useful for planning the location of the disposal system. Building locations and driveways should be noted as well as trees, wells, water lines, and surface depressions that must be avoided. The degree and direction of land slope should be shown. Figure 3.1 is an example of a useful sketch. Local or state regulations may define how close parts of the liquid waste system may be to various features on or proposed for the lot. Once the best location for the drain field is ident