Agenda - 10-08-1991 - Laserfiche WebLink

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III. Waste.-Treatment System Classification and Dencriation Much-confusion has been created by the varying methods of classification used to group types of waste treatment systems. Classifications have grouped systems according to tFie waste treatment technology involved, the regulatory agency involved in permitting the system, the number of people or residences served by a system, the type of ownership of a system or the manner of operation of a system. This report uses the classification system developed.by the Environmental Health Section of the Orange County Health Department, which classifies systems by responsible regulatory authority, treatment technology and number of users of the system. Class I System - Individual Conventional Systems - This is the most common type of non - municipal, non - discharging, individually -owned waste treatment system in Orange County and in the United States. It has been in use for at least fifty years. The conventional system consists of a septic tank and a nitrification field. Raw sewage and other waste water flows by gravity from a building into a large concrete tank with a capacity of approximately 1000 gallons. A wall with openings located below the water surface level separates the tank into two internal chambers. Floating and settleable solids are retained in the entrance or influent chamber while liquid wastes flow into the outlet or effluent chamber of the tank. While the septic tank provides some limited anaerobic bacterial decomposition of wastes, its primary purpose is the removal of solids from waste. From the outlet chamber of the tank, the liquid flows by gravity into a 4" perforated plastic pipe laid in a 3' wide trench filled with gravel and covered with 6 -12" of earth. Effluent drains into the gravel trenches and then seeps through the trench walls and bottom into the ground. Aerobic bacterial decomposition of suspended organic solids contained in the effluent occurs in the soil beneath the trenches. This process occurs until the soil beneath the trenches has been wet for so long that aerobic bacteria can no longer survive, the organic material can no longer be decomposed and collects to the extent that it forms an imvermeable "clogging mat" along the entire length of the existing trenches. This is referred to as a "progressive failure" of the system, because the clogging mat forms first in the section of line nearest the septic tank and then gradually spreads to the end. When the clogging mat has rendered the nitrification field unusable, it is repaired by extending the trenches or by moving them to another area with suitable soils. If no suitable repair area is available, the system is abandoned and another waste treatment methodology must be found. 4