ge areas of the country. Many of these systems will be installed in areas of scenic beauty, suburban tranquillity, and envi- ronmental vulnerability. Where homesites are not amenable to stan- dard onsite disposal practices, the protection of human health and environmental quality demands the use of systems designed to overcome particular limitations of the site. Areas of high flooding potential, steep slopes, thin topsoil, high ground water tables, and clay soils can present problems which, if not solved by design, can result in angry neighbors, paranoid public health officials, and resentful grandchildren. The technology of onsite liquid waste disposal has rapidly advanced during the last decade. In addition to the rediscovery of very old and very satisfactory methods of disposal, new methods have been developed for application on difficult sites. These new methods have been in use long enough that some performance data are available. It is now possible to present design criteria, construc- tion methods, and maintenance requirements, as well as to identify potential problems for each of these systems. The designs presented in Part II of this book are tested and proven, are addressed by many states in their regulations, and are suitable for use both by persons living an isolated existence far removed from neighbors and by developers planning waste disposal systems for subdivisions. How- ever, each site has its own climatic and physical characteristics, each installer has his own techniques, and each user has his own habits. None of these designs can be guaranteed to function properly under all conditions. On the other hand, the designs are proven as pre- sented, and any change in design to conform to local conditions should be made with a clear understanding of the effect of that change. The purpose of this book is to provide information sufficient to allow a homeowner, potential homeowner, contractor, septic sys- tem installer, or consulting engineer to evaluate the future site of a ONSITE WASTEWATER DISPOSAL li