Septic Tanks
In the investigation of potentials for contamination of soil and groundwater, we pay attention to septic tank systems.
Septic means putrefaction. A thing that causes putrefaction is septic.
(The word derives from Greek septikos which means putrefaction.)
Putrefaction is the decomposition of organic matter.
(The word derives from Latin putrere to be rotten + facere to make.)
A septic tank is a tank in which the solid matter of continuously flowing sewage is putrefied by bacteria.
Here is an illustration of a septic tank system. The two main parts are the tank and drain field.
And here’s a cross-sectional view of a typical septic tank:
(Illustration courtesy of the Maryland Department of the Environment)
Inside the tank, wastewater separates into layers. Bacteria begin to digest the solids that have settled to the bottom of the tank and break them up into liquids and gases. The liquids rise to the outflow pipe and enter the drainfield
The next schematic shows the drainfield:
(Illustration courtesy of the United States Environmental Protection Agency)
Through the perforated pipes, the liquids percolate into the soil. The soil absorbs and filters the liquids, and microbes break down the leftover waste into innocuous material. Solids that are not digested by bacteria accumulate in the tank and need to be removed periodically.
Sometimes, a seepage pit (dry well) serves instead of a drainfield.
(Illustration courtesy of the United States Environmental Protection Agency)
Septic systems were the order of the day years ago, before the widespread installation of public-owned sewage mains. To this day, septic systems are widely used in areas where the public-owned sewage systems have yet arrived.
Where septic tanks are or were in use, chemicals that would be dumped into toilette bowls and wash sinks would ultimately reach the soils and could percolate to groundwater.
In investigations of environmentally related risks in real estate transactions we at times find septic tank systems in properties that changed use from residential to commercial/industrial. As the use of chemicals is more prevalent in the commercial/industrial sectors, we indicate a potential risk to the parties involved in the transaction.
Acknowledgements:
Materials for this newsletter were borrowed from the following sources:.
Meriam-Webster’s Collegiate Dictionary.
http://www.septicare.com/
http://www.co.thurston.wa.us/health/ehoss/inspect_septic.html
http://www.abeeseptic.com/
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