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9 <br /> On-Site Sewage Maintenance and <br /> Operation <br /> Snohomish County is responsible for ensuring that stormwater discharged from stormwater <br /> management systems we operate does not harm or impair the use of the receiving waters (creeks, <br /> rivers, lakes, groundwater or Puget Sound). Sample tests of stormwater discharges and receiving <br /> water occasionally indicate high levels of fecal coliform bacteria. <br /> One potential source of bacteria in surface water is malfunctioning onsite sewage systems(septic <br /> systems). Septic tank failures have been documented on private property in Snohomish County. <br /> Septic systems vary widely in their design and complexity. Owners of septic systems should contact the <br /> Snohomish County Department of Public Health and Social Services (Environmental Health Division) <br /> to request an as-built of their system. <br /> In its simplest design the septic tank is the first stage of a private sewage disposal system. The septic tank <br /> is a water-tight tank below ground that is usually made of concrete but may be fiberglass,plastic or steel. <br /> Septic tanks have one or two access ports for inspection and maintenance which are usually buried a few <br /> inches below the ground. <br /> The tank receives household wastewater through an inlet pipe at one end,settles out larger material to the <br /> bottom, breaks down waste material with bacteria present in the tank and delivers the partially treated <br /> wastewater out another pipe on the opposite end of the tank to the disposal field. <br /> The disposal field is the second stage of the private sewage disposal system and completes the final <br /> breakdown of wastewater with organisms in the soil. <br /> The disposal field consists of narrow trenches filled with gravel and perforated pipes that distribute the <br /> wastewater to the field. With proper maintenance, a well designed system can last a long time;however, <br /> disposal fields will clog if forced to handle large particles that should settle out in the bottom of the septic <br /> tank. <br /> One potential source of bacteria in surface water is <br /> malfunctioning onsite sewage systems. <br /> 22 <br />