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70 year old masonry dam repair considerations and advise? 2

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Mannyou

Civil/Environmental
Aug 5, 2008
4
Got a very beautiful old dam that is leaking and beginning to lose mortar. Currently draining the lake and I intend to build an interior concrete liner to serve as a concrete gravity dam sealing and relieving pressure on the old masonry. I’m forced to build a temporary road through the lake that has several feet of silt and muck. I have several concerns:
1. What kind of road design should I consider for the several feet of muck I have to work with?
2. What is the best and most inexpensive cofferdam out there in the market or can I make my own?
3. How do I design concrete cold joints to prevent leakage?
4. At what point do I need to add cooling tubes to the concrete to prevent overheating?
5. Any other considerations I need to think about?

Any suggestions or advice would be great.
 
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3. How do I design concrete cold joints to prevent leakage? - use waterstops
4. At what point do I need to add cooling tubes to the concrete to prevent overheating? - ACI has guidance for mass concrete design and construction

If you are in the U.S., get ahold of your state dam safety engineer and scope the project with him. Your construction permit will be issued by him.

 
1. Floating dock, if the mud is deep and difficult to dredge out. The dick can be supported on posts & stringers, or on barrels as seen in river dredging projects, or the combined.

Old dam repair is not a simple task. As cvg suggested, get permit agency and dam safety personnel involved as early as you can to go over the 'musts". In my opinion, you need to expose the dam to its foundation to check erosions, scours, leakage from soil-foundation interface, as well as leakage from the wall (crack width, condition of reinforcing, if used, are important features).

Prior to lining, I think you will need to address all the issues above, and have plan to repair the old concrete dam to bring the strength to the desirable level.
 
Is this what you really meant?

"The dick can be supported on posts & stringers, or on barrels as seen in river dredging projects, or the combined."

This is HUGE!

Mike McCann
MMC Engineering
 
Glad you asked that question first Mike.
Size and depth of dam and lake will factor into approach.
 
Sorry - but not sure that is what Mike meant. [bigsmile]
 
oops, hope it does not offend anybody, just make myself looks like a fool. Mike, thanks.
 
Permeation Grouting would fill any holes.Might be possible to grout and seal existing structure without any additional
construction. Depend on location and environmental considerations as you may have some grout leakage into downstream water.

Intrusion Prepakt /marineconcrete.com
 
The problem may be a little more complicated. Often mortar for earlier masonry work lacked the proper hydraulic characteristics for longevity. It may be that over the decades, the binding materials have been leached out and you have mortar consisting essentially of lime. Intrusion prepact may be workable, but there may be areas that aren't encapsulated with new concrete/mortar and it may be necessary to repair the dam again. Also, damage can be done to existing masonry by using a 'hard' mortar, one that doesn't permit 'plastic' deformation.

Dik
 
First off, you need to talk to a competent geotechnical engineer as well as an competent dam engineer.

If the dam fails, you have life safety issues. You should not be rely on undocumented internet comments for your design.
 
Thank you to all for the good responses.

Bimr: I am gathering as much info to complete this project and I am definitely talking to a geotech and a dam engineer.

For the construction road I have been researching geogrid material topped off with coarse aggregate. Got a DOT friend that had a similar project where he used geogrid by the Tensar company succesfully.

cvg: good advice on the mass concrete and the state dam safety consultation. My project is in Oklahoma and I will be talking to those folks. Also I am considering for mass concrete overheating.

dik: We have considered the issues you brought up concerning the mortar. Also, our historical protection folks are giving us constraints on the mortar color.

kslee1000: We are now leaning towards draining the lake and letting the hot oklahoma summer bake the lake bottom until August, hopefully harden it somewhat. Then we'll excavate what we have to and lay a geogrid on the baked silt and muck topped of with gravel

Has anyone ever set up a small concrete plant and used conveyors to deliver the mud? If so what was the approxiamte cost?

We are open fo any other thoughts.. thanks
 
batch plant with conveyers is used for large projects, but mobilization cost is quite high. unless the dam is very remote, let the contractor determine means and methods of supplying concrete.

draining the lake as well as building your road and building your dam will definitely trigger a 404 permit. environmental mitigation may be less if you don't drain the lake...
 
It's not the colour of the mortar that may cause you problems, but the hardness of it. The US as well as the Canadian Parks departments likely have a lot of information on historic mortars.

Dik
 
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