Modern agricultural practices rely heavily on the use of pesticides to sustain high productivity. When pesticide containers and application equipment are rinsed after use, the contaminated water requires proper disposal. At Iowa State University in Ames, Iowa, dilute pesticide rinsates have been placed in a concrete-lined pit for more than ten years. The pit contains alternating layers of gravel and soil. Water evaporates from the pit surface while pesticide chemicals are adsorbed on soil particles destroyed by microorganisms or broken down chemically. Similar lined pits have been used at several locations around the nation. This investigation includes review of design criteria for lined disposal pits as well as descriptions of some of the pits now in use.