Leaky Dam Overflow Assembly

[NM_Shooter]

Not sure if this belongs here or not!

Looking for advice on fixing an overflow tube that has developed a hole in the side of the riser.  Trying to see if there is a way to do this without draining the pond.   

We have a 2 acre pond on our property.  The means for controlling overflow is pretty clever.  There is a vertical riser with a trash rack on top, but the water typically comes from below as the discharge tube is double walled.  Here is a sketch of the assembly.  The red lines indicate normal overflow water path.  The pond is spring fed year around, and in the winter, the top freezes.  This assembly lets the pond flow in to the creek below it, which allows the fish in the stream to survive and keeps the pond from washing out the overflow in the spring. 

Note the red lines indicate normal overflow water path.  Unfortunately, we have developed a hole in our riser.  The last few years we have had lower than normal rain, so we noticed that the pond level was dropping and the hole was found.

We are trying to figure out if there is a clever way to fix this, or if we are just going to have to bit the bullet and drain the pond.  Hate to do that, as there are hundreds of native fish in the pond.  Some brook trout to 15". 

Anybody have any ideas for a long term fix? 



Here is the actual dimension dwg that was created in 1969 when the pond was constructed :

[UK4X4]

mmm something to think of on the plane in 20 mins

mean while just for a giggle 

[Redoverfarm]

Frank is the the material (metal-plastic) in the riser?  Have you pinpointed the leak location (depth)? 

[NM_Shooter]

Well, I'm not sure.  I think the leak is about 4' down from the top.  I have asked the person who took this picture to clarify :



I found another picture... we had a different failure 10 years ago or so, and they drained the pond to make repairs.  This is what the tube looks like:

[Redoverfarm]

It looks like the inside has a good bit of rust considering that it is galvanized   The location of the leak would obviously dictate the amount of drainage that would need to be done to repair it.  They make unions for that style culvert to join two pieces together .  Maybe able to make a boot with one of those and heavy rubber to repair.  But then again how long would it last.  Hopefully you will not have to drain it that far to repair as it was done previously still allowing enough water for the fish to survive.  If you had someone with some SCUBA gear they could install the boot w/o draining.

But then again if the hole has developed because the pipe is rusting a fix would only be short term and the riser probably will have to be replace eventually.

[rick91351]

So the stand pipe for the 'glory hole' is a galvanized culvert.

Does the drain valve still work?  If so drain it down to that level.  If done in the winter time or early spring that fish would have less stress.  They make collars to join galvy culverts.  You could use one or two of those and some heavy membrane or belting to patch it.  Close the gate and fill.  Or if it is rotting and rusting which is my guess what is going on just replace the stand pipe.  WOW I want photos of that........  I would look at using concrete culvert or forming and pouring a standing structure.  The last two of above equals big $$$   Is this owned by a subdivision or irrigation district or is it yours.  Or am I going some place I should not ...........     

[NM_Shooter]

I am one of about 10 families that own this ranch.  We have some funds in a ranch maintenance account to do this, although we may just do it ourselves. 

I was trying to figure out if there was a way to do some sort of cast-in-place assembly.   Thought about trying to seal the hole (mostly) from the outside using a sheet of EPDM rubber too. 

I have seen some good replacements for this... google "wetland water level control structure".  One of the big problems is that the standpipe goes a pretty good way under the soil to the drain tube. 

I am hoping the valve is still operable.  Otherwise, we are in a bind for getting water out of the lake 

[Redoverfarm]

I was looking at the sketch and it indicated that the riser is 13 feet to the bottom of the drain pipe but it doesn't have the demensions of how much is sticking out of the ground.  There is a figure but that may be just the trash rack.  If you have to replace you might consider pouring your riser.  You can use two different size poly pipe sort of like a double wall and reinforce the void with rebar and pour concrete.  Just leave both pieces of poly in place.  But     I would pour them on top of a bolted plate or platform so that at some later time you had to do maintenance on the drain pipe that it could be removed.

Stainless is the way to go under water but you would probably have to sell the ranch (no pun intended) to afford it.  I have inspected some underwater drains, filters, screens, structures and water will play havoc even to what was installed to last a lifetime.  And yes things do rust under water w/o the presence of air.

[Bob S.]

How about just leaving the present pipe and sliding a larger diameter pipe over it and filling the voide with concrete? You would not have to drain the pond that way, as I think you can pour the concrete in the water.

Bob

[rick91351]

Bob S you are correct about concrete and water. 

But WOW you are still going to have to patch.  Then get the outer form out there some how, and lifted into place.  Lowering down into place is no small feat either.  This would require maintaining equal spacing  or some what equal spacing creating the form, and still be straight up and down to the other pipe that might not be straight to the world while all while underwater without  damaging the rusty failing inner pipe.   
 
  Not impossible but is it cost effective?

[NM_Shooter]

Yeah, this is tricky, huh?

About as much of it is below the ground as is above.  And I don't know how the saddle attachment is made between the riser and the drain line, or what condition that drain line is in.  Last thing we need is for it to rot out and for the dam to start to erode.

Making it concrete puts a lot of weight on the thing.  Better be plumb for sure!  I'm also not sure how much longer we can get out of that tube given that it is rusted. 

I have called a contractor in Albuquerque called Aquatic Consultants.  http://www.aquaticconsultants.com/

I'm going to see what they suggest.  Maybe see if I can get our board of directors to agree to swapping out some elk tags in exchange for some work to get the price down to the "extreme" level.

[rick91351]

So this is at the hunting or recreational property.  I did not know if there is two ranches in your life or......

[NM_Shooter]

Nah... this is the one and only!  Established in the 60's by a small group of Los Alamos Scientists as a place to hunt.  Set up as an ownership corporation rather than a collective individual ownership.  They set it up so that you had to have a 10% ownership in the corporation to use the property, and with that you get to pick a 30 to 40 acre parcel to call your own.  You can improve the parcel (cut trees, build a cabin, etc.).  Other corporation members still have access to your parcel to hunt / fish / recreate.  There is also a bunch of "common" area of meadows and woods, as it is over 1500 acres of land.  Over time, shares have become available for sale.

About half of the owners are widely distributed and out of state, so the ranch does not get used much.  We are frequently the only ones out there.  It is deep in the NM woods, and both refreshing but a little spooky when you think how far away from pavement you are.  We also pass through 3 other private ranches to get to our land, and we back up to a 50,000 acre Jicarilla Indian hunting preserve.  Lots of elk, grouse, turkey, deer, porcupines, weasels, fox, coyotes, trout etc.  Got about 1/2 mile of trout river on the property, and another 3/4 mile of trout "creek" plus tiny pocket water streams that start then drain into the earth but oddly also hold fish.  We also lease out the grazing for some income, and to keep an agri exemption.  It is nice in that we don't have any annual fees at all.  Actually, once every 10 years or so, our treasury gets to the point where we distribute funds to shareholders.  It is a crazy nice setup.  Bad with the good is that the access is bad.  I can see town 7 miles away from the west ridge of the ranch (nice to have cell phone access there) but it takes 90 minutes to get to town.  It is also at 10,000 feet and snow covered half the year.  No utilities.  This is high country back woods living.  You either hate this or love it, no in-between. 

Here are some pix, including one of my crew chief and me near a fire pit outside my cabin where you can see the lake.  My nearest "neighbor" is about 1/3 mile away : http://countryplans.com/smf/index.php?topic=4782.msg158044#msg158044

[NM_Shooter]

Thinking about trying this...

Opening up the drain valve and dropping the water level 3 or 4 feet.

Removing outer culvert and debris screen.

Putting a repair band on the outside of the inner culvert.

Inserting a 14" PVC sleeve on the inside of the inner drain tube.

Ramming some fiberglass insulation or similar inbetween the pvc sleeve and the drain tube... packing it down as far as possible to seal the annulus around the pvc.

Pouring 2 part expanding foam between the sleeve and inner tube. 

Replacing the outer culvert with 24" pvc tube.

I suspect that the culvert inside the dam is also getting rusty, so this may only get us another few years before it fails.  But if we can get 5 or more years out of it, it will allow us to build up our treasury a little to invest in a robust water level control mechanism. 

Meeting with a contractor at lunch this week to discuss options.

[rick91351]

The 24 inch inch PVC replacement seem like a good option if 'do able'.  Being so this was developed in 1969 I would think the hands of time have done a real work on the whole of it.  As you say this might need are real fix in a few years. 

[UK4X4]

Long term- repairing that steel duct will be like the dutch kid sticking his finger in the dyke

Patch one rusty bit and the bit next door will rust out and fail

From the dwg looks like you have 5 ft from top of dam to the planned water level

being that its leaking lower down presumably the water level is presently lower

I would simply build a new drain to install at the 13ft level in plastic valves at both ends- redundancy and a garbage grate

Build a small bund- to protect the dam 4ft by 4ft  by as deep as needed- this bund is to stop water flow into the trench and errosion
add a pump inside if it leaks

Dig a trench across the dam into that bund

Install your new plastic "100year" drain system

Refill and pound down securely

Open up a small entry way through the bund to limit flow

Open your new drain and let her flow

After a season the dam should be structualy sound and the bund can be removed fully

[mgramann]

How much water does this pipe handle?  If it is significantly oversized, would it be worth it to PVC line the entire assembly?  The amount of water volume the system could handle would drop significantly, but it would definitely be a more permanent solution.  Could the joints and liner be installed from the outlet side, "fished" in place using the existing pipe as a chase?

[NM_Shooter]

We think that there is a significant amount of corrosion in the main drain pipe that runs horizontally through the dam too.  Right now we are trying to figure out if we patch it for the next few years, then make a permanent fix, or if we bite the bullet and rip up the dam now and put in a concrete water level control structure.  That thing does not flow a lot of water, except in spring during runoff. 

I would guess that it flow through the lake is at about 150 gallons per minute. 

Unfortunately, the vertical riser meets the drain pipe a significant distance under the ground, and there is quite a bit of concrete poured around it. 

When it comes to the permanent fix, this is going to be no fun. 

[JJYJR]

Did you complete the repair of this leaky dam?  I have a similar situation, and I am wondering what you did.  Did you consider a horizontal drain pipe at the pond/lake/pool level through the dam - something contractors are suggesting to me?  Thanks.