« ** on:** August 29, 2021, 07:38:48 am »

What is Hydrostatic Pressure?The deeper you go under water, the greater the pressure of the weight of the water pushing on you will be. For every 33 feet (10.06 meters) you go down, the pressure increases by 14.5 psi (1 bar).

Imagine a pile of bricks placed on your chest. Just one is say only a pound, put another on and its now 2 pounds, and the more you pile on top, the heavier it gets.

The Erie Canal was dug or built to a depth of twelve feet. so for every foot of water the pressure is 33/14.5 which equals .44 lbs per foot. At 12 feet deep, the pressure is therefore 12 x .44 = 5.28 lbs. It doesn't sound a lot, but that pressure is there twenty four hours a day. There is nothing stopping it except dirt.

Eventually, the water permeates through the soil and escapes. We all know water won't travel uphill, so where does it go? It seeps through the dam, until gravity pulls it toward the bottom of the dam and it drains away into the level ground. This leaves a line of wet soil below and dry soil above. It's called THE PHREATIC LINE.But, things can go wrong, and the phreatic line can move. If it is raised, say due to a steep slope, (as in most of our dams here) then there is a chance the water will exit above ground level and this can become catastrophic.https://youtu.be/BNFQ1EJX4h0https://youtu.be/PC58mGG55ioThose few pounds of constant hydrostatic pressure don't seem like much of a problem, but a small dribble can remove a few grains of soil, which allows a bigger volume of water to escape, taking more soil, so the path becomes bigger and bigger, until the dam collapses with just 5.28 lbs of pressure.https://youtu.be/vy6mhgUZeIYControl of the pressure and The Phreatic Line are crucial in keeping our residents safe.

Frequent inspections are crucial, and at this time, this is impossible (see Rizzo Engineering Reports) because of the trees and vegetation.
« *Last Edit: August 29, 2021, 12:37:42 pm by Doug K* »