b'Eventually many densely settled areas needed wastewater management. Wastewater was collected and piped to a facility that separated the solids from the liquids, killed almost all of the human waste bacteria, while using other bacteria to further digest the waste, and released a clear effluent into the ground. This process is known as secondary treatment. Chatham chose that route when we built our Wastewater Treatment Plant offSam Ryder Road.Chathams only sewered area is the downtown area and along Crowell Road to serve Chathamsmiddle and high schools.In the rest of town, private and commercial users have underground septic systems on site.The septic tank contents, pumped from Chatham septic systems, are brought to one of several municipal septage treatment facilities in Barnstable, Chatham, Orleans or Yarmouth that treat the solids from our systems.The treated residue is pumped to huge leaching fi elds where it fl ows through the groundwater, eventually ending up in Nantucket Sound or Cape Cod Bay. Backyard disposal: The septic system and how it works The septic system is an adequate disposal technique where housing density is low and groundwater does not carry thedissolved contaminants into bays and ponds.However, septic systems are still used by the vast majority of homes in the region even though population densities are increasing. Newer systems consist of the tanka cement or fi berglass container with a T-shaped outlet pipe that keeps the fl oating grease layer in the tankand a soil absorption system that infi ltrates the liquid portion of the wastes into the ground. Older systems, cesspools and leach pits perform similar functions. The Board of Health oversees these systems and enforces the State sanitary regulations under Title 5, as well as local regulations.Of the approximate 6,700 housing Typical Septic Tank units surrounding our waters, the vast majority utilize backyard wastewater systems.Chatham residents and businesses release well over 1,000,000 gallons of wastewater into the environment each day. Septic Leachfi eldDrawing by Kassie FossPage 26 bluepages.indd 26 8/26/2009 1:50:28 PM'