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Gravity and sanitary drainage

January 25, 2014

A gravity fed drainage system relies on a gradient , an incline,
where one end of the pipe is at a higher level than another.

City of Warren storm drain

City of Warren storm drain

Over a distance of 1 mile (5,280 feet), one end of the pipe would have to be
100 feet deeper than the other for a 2 % slope in the drain pipe

It is expensive and time consuming to dig 100’s of feet
deep into the earth. Then crews have to make water tight connections
at 100’s of feet underground so that no leaks occur.
The deep pits would have to be safe and secure from cave-in
or collapse, preventing any possibility of death to a worker.

The 2 percent drainage slope

The 2 percent drainage slope

It all seems fairly straight forward and easy to comprehend.
Reality and economics come into play , gunking it all up.
Slopes which are slightly less than the recommended minimum slopes
— may be permitted —-.
The operating authority of the
sewer system will give written assurance to the
appropriate reviewing authority that any additional
sewer maintenance
required by reduced slopes will be provided.

Minimal slope for sewer pipes

Minimal slope for sewer pipes

http://10statesstandards.com/wastewaterstandards.html

The 10 states waste water standards

The 10 states waste water standards

Macomb County drain design criteria

Macomb County drain design criteria

In the end , it all comes down to COST, pure $$$ dollars.
A true statistical risk analysis of Mother Nature’s rainfall
on any given day, or week, is damn tough to predict.
Hopefully recent events and the in-inadequacies of 1950/1960 construction
methods can be overcome in the new projects and designs for the present day.
Tax payers need to realize infrastructure
is NOT the place for cutting corners or shortcuts.

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