In the event of poorly drained soil, one with a high clay content or else low-lying, a standard leach field will not work very well, especially when the ground is already saturated with rain water or snow melt. One can't drain wastewater into soil that is saturated with water. That's when the sand mound sewage disposal system is employed. When the septic tank isn't draining properly, a pump will kick in and pump the effluent into a pile of sand and gravel above ground (although sometimes a pump isn't necessary and gravity does the job). A perforated pipeline in the pile of sand allows the effluent to drain down through the mound. Sand mounds are usually covered with soil and grass. In Pennsylvania, sand mounds must be at least one hundred feet downslope from a well or spring, fifty feet from a stream, and five feet from a property line.2 According to local excavating contractors, sand mounds cost $5,000 to $12,000 to construct. They must be built to exact government specifications, and aren't usable until they pass an official inspection (see Figure 5.8).
Source: The Humanure Handbook. Jenkins Publishing, PO Box 607, Grove City, PA 16127. To order, phone: 1-800-639-4099.