Dam Failure in Upstate New York

[dig1]

http://www.lakehadlock.org/broken_dam_7-2-05.htm

Above is a link to pictures of a dam failure in upstate New York (Fort Ann, approximately 50 miles north of Albany).

Hadlock Pond is (was) a 220 acre +/- pond used now for recreation.

Several homes were destroyed but not one injury due to the efforts of the local fire department who went door to door to get people out before it finally let go. Fortunately it happened early evening (about 6:30 pm) and not at 1:00 am.

Failure occurred right after the initial fill; the majority of the dam had been reconstructed during the past year and was only full for about 2 weeks.

There are many rumors, speculations, denials, running for political cover (the local government unit (Town of Fort Ann) owns the dam), etc.

My background is geotech so this is technically interesting but also troubling especially since I know the people in one of the houses that is covered with water.

Whatever was the root cause of this failure of a new construction; it is essential that when we design, inspect, monitor, construct facilities whether out of soil, steel, concrete, timber, or any other material our action or lack of action has serious potential.

Patrick

 

[VAD]

Very Interesting. Pictures tell a lot.

Here is my take on failure for what it is worth.

1. Failure occurred within vicinity of new spillway structure. Spillway was constructed to maintain level of water in lake. Any higher water level would be reduced by water moving over spillway into downstream channel.

2.The location of failure appears to be central to the downstream channel. This is a weakspot and in hindsight the width of the downstream channel should have been sheetpiled to form a seepage cutoff. This should have extended to the spillway which may have had this cutoff or at least its construction would have resulted in excavation and founding the spillway foundation in good ground i.e far below the
generally loose and pervious sediments that often are associated with channels.

3. It appears that prior to the spillway construction that slow seepage was occurring in the downstream channel. With the construction of the spillway and heightening of the dam, it is possible that the spill way construction now forced the seepage to occur along a smaller width of the downstream channel and hence leading to increased seepage pressure at a concentrated location. The spillway being intact supports this proposition. This may have been enough to cause piping or blow out to ocurr.

4. Was this weakpoint i.e the downstream channel properly examined during the initial study prior to reconstruction would be a question in my mind. While dams generally seep, one has to examine such an event if changes are to be made to their holding capacity etc.

Regards

 

[GeoPaveTraffic]

I would be interested to know what the post failure analysis determines the cause of the failure to be. It is not possible from the photos to tell what happened.

 

[dig1]

When the report is released I will post what I know.

This is going to take a long time to sort out.

 

[dickg]

Actually there were two failure points. The one that actually failed on the west end of the dam and the one that was about to fail east of the spillway. We were lucky that the west end failed first since that area was not as deep as the east side. Also the roller compacted concrete structure for the fuse plug spillway prevented the breach from opening furthur. If the east side had failed first there was nothing to stop the breach from running from the concrete spillway to the east bank. The depth of dam in that area is 29 feet vs 12 - 15 feet at the breach. From a down stream flow model, an east end failure flow would have resulted in 2 - 2.5 times more flow.

Clouth Harbour is investigating the failure for DEC. The report originally due in the end of August has been delayed until the end of September.

We have been attempting to FOIL the documntation and have met resistance from the Town and DEC.

 

[dgillette]

DickG and Dig1 - Does anyone know whether the breach initiated AT the fuseplug structure and progressed leftward (looking downstream), or did it start AWAY from the structure and progress rightward until it reached the structure? (Structures and conduits through embankments are common locations for initiation of piping failure.) Or, was that part of a segmented fuseplug as it appears it might be from some of the photos in the link provided by Dig1? I'm quite interested in hearing about this once the report is out. In Michigan a couple years back there was a case where a fuseplug operated when it really shouldn't have and since there was no base structure, it eroded a very large breach with similar results. (Silver Lake Dam - see FERC.gov.)

VAD - Did you walk on the site prior to the failure to see the seepage or have inspection reports that report on the seepage?

 

[VAD]

dgillette

Re your question, my opinions were based on the site photos provided via dig1's web reference. I would be interested as well to know of the outcome of the investigation.

Regards

 

[dgillette]

I had a little different take on it from the photos, particularly the ones by Doug Harwood and the aerials by Erin Coker. The breach appeared to be on the right abutment (using the convention of left and right seen as one looks downstream*) rather than at the maximum section. I'm not sure, but the breach MAY have been of the fuseplug embankment rather than the actual dam embankment. At the right side of the breach, one can see what looks like a concrete core wall, which may have stopped the breach from eating its way farther right. In the first picture by Coker, it looks like there is no core wall on the left side of the breach - perhaps the fuse plug embankment (which is designed to wash out when the auxiliary spillway is needed)? In that same photo, there is something that looks like a concrete slab with a big piece of grass-covered embankment on it. Could that be the floor slab of the auxiliary spillway?

It's hard to tell a whole lot from the photos, which were not taken for the benefit of our speculation from 2000 miles away. I should probably quit now before I go too far out on a limb.

*The convention, I'm told by an old draftsman, is based on the fact that engineers think they walk on water.

 

[dickg]

Based on what I observed and observations of those who whitnessed it the whirlpool formed some 50 feet from the front of the dam. If you take that elevation at that point it would be at the juncture from the base of the old dam to the new fill. Having watched them construct it they did not appear to key in the new dam to the old dam. There are a couple other possibilies. Secondly they started so early in the season the frost may have been still in the ground. It did not appear that they removed the top level of dirt off the dam when they started filling in. Since that area had been used for heavy equipment the surface ends up being more like dust than soil. Weakening the structure. Also from the pictures you can see the steel plates under the fuse plugs. As they are driven in you get liquid fraction creating another potential path. Core samples indicated there was a zone of "loose rocks" in the dam. I was not told at what level that was found. NYS DEC regulations have specific requirements for the interfaces between new and old dams. From the construction pictures it does not appear that these guidelines were followed. To make things worst the Engineer who designed the dam lives 4 hours from the site. He had requested the town to hire a local engineer to inpect the dam. The town responded by making the Town Attorney the "Project Manager" and hiring a testing company to be on site. We have heard that the engineer was on site very little. This was a complicated structure and there should have been an engineer on site daily.

If you want to see more pictures go to

http://www.lakehadlock.org.

 

[dickg]

The failure report is out.

http://www.dec.state.ny.us/website/dow/hadlock.html

 

[landscapepainter]

what happened to the linked photos? i'm sure they were there a while back. also, is it possible to find online, somewhere, the appendix with graphs photos etc that accompany the final report of the failure?

 

[dickg]

You can find some of the pictures on

http://www.hadlockpond.org.

The DEC report has a lot of pictures in the appendix. Some which haven't been on the net before. Unfortunately the PDF of the entire report with appendix is 38 MB. It is available on CD thru DEC or is available in Glens Falls, NY area libraries.

 

[justbuildit]

WOW.. very interesting reading

Thanks from California

 

[shockstressed]

Old lake ?
it sounds as if the base sediments were weak and somebody failed to assess the geotechnical works prior to in a thorough manner or somebody did not want to accept the site had gone permanently due to soak, and degradation, or nobody would pay what would have been a small cost compared to resultant loss.
Hey ho.
People here (England) spent months clearing up an old lake to the same extent
viscious, dangerous to children
full of rubbish
mud slump slide and slip
and days wading about in the muck collecting "semi-eutrophic" fish.
TV thought it was wonderful.
Should have been buried in rubble that allowed the water to filter and dry out with some effective stress.
It took three years for my garden pond to dry out, filled with shrub stem, dry waste that has rotted to compost, gravel, soil and given adequate drainage, and that was only ten feet long.
Having fallen down an organic mass stream subsurface Mendip arenaceous bedrock in 1970 I have become very careful to withdraw my leg from garden ponds filled in when it reaches about 2 feet down. You know not what the site is like underneath in an area once Somerset Levels silt and peat wetland drained. Wet and soggy is the answer.
That does not stop local authority and government and private contractors chucking waste rubble on it and cutting into it to plaster slum style housing on it (slum for the future at high cost, back to back but costs more than our normal house).
But they do not like it when you tell them and state you are neurotic, although too well qualified to bother with them normally,
like the neurotic state of the six foot long, one foot shear that opened up alongside a footpath and rhyne ditch, requiring a foreman to fill it in with one digger
as the crew had walked off downtown for lunch
in the sog and wet rain and winter cold
and it is still seeping water and sliding with the footpath not finished. It does have a nice geotechnical drain pipe sticking out of it. I expect if the river floods all the water will go under the dockside new housing and shops into the dock full of nice yachts
an old dock that should have been backfilled with Power Station Rubble some years ago as a flood soak and plants conservation zone
but then the contractor has gone now having left half a tonne of rubble concrete under the bridge (commonly referred to as cladding protection)
and the local authority politicians still want housing on the site. Only thing stopping them: traffic loads across motorway also built in wrong place thirty five years ago
and about which the malcontents moan endlessly.
They want results, they do not want good design, then they do not get results, then they complain.
Panic cost muddle and damp.

Sounds about a correct description.
Good job there are so many geotechs, geologists and hydro soils people these days who can see it.
Discouragement is no use. Go and work on something where you can be of use as you sound to me to be one of the few concerned who are good enough to note the real design needs. They will flail themselves like Paul the evangelist for decades and if you get caught in the middle they will beat you although you had nothing to do with it.
Believe me from experience
leave the lawyers to chew on it at this stage.
I went off to deal with earthquake seismic stress arc design and pivots and materials and enjoy myself helping people in need and use my qualified ability as my University seniors would have liked and solve fluid mechanics and atmospheric cold drain flows providing resource etc. Friends and family are the worse, they think you can form miracles after the event on something you have no control over and you will form them never hear the last of it.
Not nice leaving people but I gave up on "bogs" standard work items after the last lot fell in near here and they still put more housing on it !!
Mike Stagg
RD 1967 1969 appointed University Senior Lecturer 1978 College 1987 consultant
geology is better than mud shifting

University Research is alike the inverted pyramid design
the many supported by the few

it works but very hard to keep holding it up there.
And we need more graduates taught by ethical staff members. Boring at times but safe.
I worked in College of Art and Design and University research science
so I am now going off somewhere where I can work in peace and achieve some result
and I thought systematic research was a bit of a waste of time ! Planning is these days so leave it to lawyers.

 

[shockstressed]

shockstressed (Structural) 7 Mar 06 10:28
corrected error
Old lake ?
it sounds as if the base sediments were weak and somebody failed to assess the geotechnical works prior to in a thorough manner or somebody did not want to accept the site had gone permanently due to soak, and degradation, or nobody would pay what would have been a small cost compared to resultant loss.
Hey ho.
People here (England) spent months clearing up an old lake to the same extent
viscious, dangerous to children
full of rubbish
mud slump slide and slip
and days wading about in the muck collecting "semi-eutrophic" fish.
TV thought it was wonderful.
Should have been buried in rubble that allowed the water to filter and dry out with some effective stress.
It took three years for my garden pond to dry out, filled with shrub stem, dry waste that has rotted to compost, gravel, soil and given adequate drainage, and that was only ten feet long.
Having fallen down an organic mass stream subsurface Mendip arenaceous bedrock in 1970 I have become very careful to withdraw my leg from garden ponds filled in when it reaches about 2 feet down. You know not what the site is like underneath in an area once Somerset Levels silt and peat wetland drained. Wet and soggy is the answer.
That does not stop local authority and government and private contractors chucking waste rubble on it and cutting into it to plaster slum style housing on it (slum for the future at high cost, back to back but costs more than our normal house).
But they do not like it when you tell them and state you are neurotic, although too well qualified to bother with them normally,
like the neurotic state of the six foot long, one foot shear that opened up alongside a footpath and rhyne ditch, requiring a foreman to fill it in with one digger
as the crew had walked off downtown for lunch
in the sog and wet rain and winter cold
and it is still seeping water and sliding with the footpath not finished. It does have a nice geotechnical drain pipe sticking out of it. I expect if the river floods all the water will go under the dockside new housing and shops into the dock full of nice yachts
an old dock that should have been backfilled with Power Station Rubble some years ago as a flood soak and plants conservation zone
but then the contractor has gone now having left half a tonne of rubble concrete under the bridge (commonly referred to as cladding protection)
and the local authority politicians still want housing on the site. Only thing stopping them: traffic loads across motorway also built in wrong place thirty five years ago
and about which the malcontents moan endlessly.
They want results, they do not want good design, then they do not get results, then they complain.
Panic cost muddle and damp.

Sounds about a correct description.
Good job there are so many geotechs, geologists and hydro soils people these days who can see it.
Discouragement is no use. Go and work on something where you can be of use as you sound to me to be one of the few concerned who are good enough to note the real design needs. They will flail themselves like Paul the evangelist for decades and if you get caught in the middle they will beat you although you had nothing to do with it.
Believe me from experience
leave the lawyers to chew on it at this stage.
I went off to deal with earthquake seismic stress arc design and pivots and materials and enjoy myself helping people in need and use my qualified ability as my University seniors would have liked and solve fluid mechanics and atmospheric cold drain flows providing resource etc. Friends and family are the worse, they think you can form miracles after the event on something you have no control over and you will from them never hear the last of it.
Not nice leaving people but I gave up on "bogs" standard work items after the last lot fell in near here and they still put more housing on it !!
Mike Stagg
RD 1967 1969 appointed University Senior Lecturer 1978 College 1987 consultant
geology is better than mud shifting

University Research is alike the inverted pyramid design
the many supported by the few

it works but very hard to keep holding it up there.
And we need more graduates taught by ethical staff members. Boring at times but safe.
I worked in College of Art and Design and University research science
so I am now going off somewhere where I can work in peace and achieve some result
and I thought systematic research was a bit of a waste of time ! Planning is these days so leave it to lawyers.