This is the fourth in a series of articles reproduced from the National Small Flows Clearinghouse publication, Pipeline.
Morgantown, W.V., April 12, 2002--In most communities, before a homeowner or developer can obtain a permit to install any type of onsite wastewater system, a professional site evaluation of the lot is required. In a site evaluation, a sanitarian, soil scientist, or other wastewater professional examines the characteristics of the soils, landscape features, and past surveys of the site. He or she also may consult public records, such as soil surveys or maps prepared by the National Resource Conservation Office or by a state geological survey office.
Before approving a site for onsite treatment, the evaluator notes the location of nearby drinking water wells, neighboring homes and onsite wastewater systems, and the minimum vertical and horizontal separation distances to these and other features as required by law. He or she also examines the slope of the land and the depth to groundwater and impermeable layers, such as bedrock. The evaluator also considers the natural drainage patterns and boundaries of the lot.
An important feature of a site evaluation is a thorough study of the soil. The sanitarian digs and observation pit at the most likely location of the soil absorption field to examine the soil layers for texture, structure, and color patterns which give clues regarding its permeability and potential for seasonal water saturation. The sanitarian usually performs a percolation or "perc" test to measure how quickly water moves through the soil. Some states require additional methods for testing soil permeability.
For a detailed look at site evaluations, contact the National Small Flows Clearinghouse and request item #WWPLN21 or visit www.nsfc.wvu.edu to download the information.
Coming up next: More on the installation of chamber systems, a type of gravelless drainfield becoming increasingly popular.
