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Reply #2 on: November 29, 2020, 01:26:49 pm »
The ECNA posts have mentioned this Phreatic Line quite a bit, but to some it might still be a mystery. So I have a couple nice pictures to explain it and also show what happens when the phreatic line starts to fail on an embankment dam. These pictures & videos are taken in my own backyard which has a 20 foot tall leaking canal embankment in the eastern corner of our two acre lot.
Go to this webpage to see a great explanation of the Phreatic Line - https://ecna.us/canal-facts/the-embankment-dam-phreatic-line-where-the-water-goes/
Basically all earthen dams work the same way. They leak LOTS of water from the water-filled side of the dam, through all of the earth used to build the embankment. Dam Leaking starts BELOW the waterline of the impounded water, and will eventually leak away at the base of the earthen dam known as the Toe of Slope. Along the Erie Canal any embankment that is about 16-18' tall should have water coming out where the outside slope of the earthen dam meets the original level ground.
Most places along the Erie Canal embankment collect this leaking water in a ditch called the Toe Drain. This drain carries leaking canal water back into culverts or creeks and into the general aquifer system. After awhile the lower sections of all earthen dams become so saturated that the top soil becomes full of water and can't even take even a normal rainfall. All of this water will eventually find it's way into these Toe Drains.
Normally the leak is very slow, like in the image below that shows a 20' tall dam section with a leaking Phreatic Line.
There are three marked leaks in this embankment and all 3 leaks are located about 24-30" above the bottom floor of the canal. If you look across the pink marked stakes that were placed in this section, by the NYS Canal Corporation in 2019 during their first canal inspection in 75 years, you will note that this leak is about 25-35 feet long as well.
In 2019 the NYS Canal Corporation Embankment Restoration Project removed trees that had died on the embankment and were over 80 feet tall. This leak is most likely caused by old roots and piping that is now moving water along old dead roots and that water has breached out of it's normal Phreatic Line.
So there you have it, a brief explanation of the Phreatic Line and why it's critical to be able to see if it's working properly.
This Phreatic Line in this section if dam is compromised and is now being monitored by the NYS Canal Corporation to see if flow eventually slows. If it gets worse, there are ways to insure the embankment will not break using steel barrier walls.
The most important part of any Erie Canal Embankment is most likely this "unseen" part that can cause an entire dam to collapse if not maintained properly or identified with line of sight inspections. Those inspections are IMPOSSIBLE to perform with canal embankment covered with trees & underbrush, which is why the Canal Corporation has now undertaken a new Embankment Integrity Program to clear these old dams, and perform proper inspections to identify more leaks like these three.
Here's our leak when it's full and ready to become our winter skating pond.
Our canal leak went "unclaimed" for 20+ years, while the NYS Canal Corporation denied it was "their water" flooding our yard. Once the NYS Canal Ownership changed in 2017, to the New York Power Authority, the new owners have not only taken ownership of this leak, they have also cleared 27 miles of other leaking canal embankment sections, that are keeping many canal neighbors in danger.
These new owners, NYPA, seem to be putting Erie Canal Safety & Sustainability, and the safety of Canal Neighbors FIRST on their list, which is a welcome change for many neighbors who have complained about overgrown embankments and leaky water for years and have gone unheard until now.
It is no secret that the amount of active Erie Canal leaks being monitored by the NYSCC, since they have started their Embankment Integrity Program, has grown five-fold. Those leaks are now being monitored, and corrective action can be taken, if and when needed, to avert a catastrophic flood in many areas west of Rochester. Many leaks like this are still undetected and growing worse over time. Each has the potential to be the next Erie Canal disaster that makes the National News cycle
There are still 100 miles of unsafe canal embankments that still need to be cleared though, many in the towns & villages that fought to stop the canal embankment work in their own communities. Those people who stopped the Embankment Integrity Program said they were doing it for the good of the public. Sadly they didn't hear the words of the OWNERS of the Erie Canal, who was saying the exact same thing, the embankments were being cleared for the SAFETY of the Public.
Time will tell who was correct... those who wanted to run a Public Safety Program on the Erie Canal or those who chose to stand in the way of Erie Canal Safety and fought to keep these leaking embankments from being cleared, and having all these leaks discovered and repaired.
Maybe want to ask yourself which side of that decision YOU want to be on?
« Last Edit: December 03, 2020, 11:14:48 am by Doug K »
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