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#Post#: 1736--------------------------------------------------
What is HYDROSTATIC PRESSURE?
DIR By: Michael Caswell
Date: August 29, 2021, 6:38 am
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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.
[attachimg=1]
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.
HTML https://youtu.be/BNFQ1EJX4h0
HTML https://youtu.be/PC58mGG55io
Those 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.
HTML https://youtu.be/vy6mhgUZeIY
Control 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.
#Post#: 1738--------------------------------------------------
Re: What is HYDROSTATIC PRESSURE?
DIR By: Doug K
Date: August 29, 2021, 12:03 pm
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In practical terms the MAIN goals of the Erie Canal Embankment
Integrity work is to IDENTIFY where the Phreatic Line is
leaking, by allowing for proper, regular embankments inspection
of a cleared, turf covered, earthen dam surface and to MINIMIZE
the opportunity for the Phreatic Line to leak by removing the
invasive vegetation and root systems that cause the "piping"
that disrupts a normal Phreatic Line water flow.
That minimization the opportunity part is done by removing large
trees and root balls, and then replacing those tree roots with
turf grass roots.
Here's a section of cleared canal embankment at Canal Mile
Marker 278, note that this is in the Brockport section, where
barrier screen plantings have been added.
[attachimg=1]
So did you see the three leaks on this Earthen Embankment? Look
again, there's one right in the bottom foreground.
Hmm, you say you can't see it? Probably because you are not a
qualified Dam Safety Inspector.
It's a good thing the Canal Corporation hires those
professionals who DID see these leaks and marked them for
monitoring right after they cleared the vegetation, and
remediated the outboard embankment to the proper slope angles.
When water started running out they saw the phreatic line
integrity issue here and marked these leaks.
Go look again, I'll give a hint to what Mike is talking
about...phreatic line leaking.
[attachimg=2]
Still unsure it's a leak? Let's get a real CLOSE-UP look at it.
[attachimg=3]
I can assure you the canal embankment is leaking, one of 4 NEW
leaks that were found along our 400' of Canal Embankment Dam
frontage here in Brockport.
Thank God our Town Supervisors & Village Mayors on the Westside
decided to take care of the safety of their Village & Town
residents instead of sticking their heads in sandy embankments
and ignoring public safety, in the name of "pleasing voters".
This story is the same all along the western end of the Erie,
where in 27 miles of clearing embankments the Canal Corporation
reportedly found over 3-4 new canal leaks per mile of cleared
earthen structure.
And another fact about Phreatic Line Leaks... after watching the
Toe Ditches that collect the water from these leaks, these
Phreatic Leaks get stronger near the end of the Canal Navigation
season, normally start leaking visibly after 4-5 months of
having the canal filled each year. Which makes perfect sense as
the saturation level of the embankment dam increases over time,
with that 5-6 lbs of pressure at the BOTTOM of the canal,
pushing water outward through old dead roots, and poorly
maintained dams.
On the bright side, because there always is one.. we never have
to pay a bill to water our lawn, it's the rule of thumb when you
live below an earthen canal embankment, green grass, even in the
worst drought.
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