Drip Irrigation for On-Site Disposal of Wastewater in Serpentine Derived Soil.

The soils of the Piedmont region of southeastern Pennsylvania, Northern Delaware and Maryland exhibit pockets of serpentinite bedrock outcropping near the surface. The soils that form from this bedrock are unique and not well understood. They are low in fertility and contain unique clay minerals that are expansive. In addition they typically exhibit bedrock and often seasonal high water tables at depths of less than 60 cm. Very slow permeabilities, often less than 0.5 cm/hr are not uncommon in these soils.

 Economic pressures have forced residential development into some of these “serpentine barrens”, which are often in areas lacking public sewerage. Until recently, regulatory standards for individual on-site sewage disposal (septic) systems have limited their use in these challenging soils. The adaptation of drip irrigation technology to on-site sewage disposal has been applied to some of these sites with significant success rates. The use of this technology has allowed development of sites exhibiting these serpentine-derived soils. It has also facilitated the repair of malfunctioning on-site sewage disposal systems on existing sites that previously were forced to resort to holding tanks. The implications of the use of individual drip irrigation on-site sewage disposal systems in expansive clays may apply to other areas that have more wide-spread manifestations of these soils.