How to Pour Foundation Concrete Under Water

Save

When building a boat ramp or a bridge you will have to learn how to pour foundation concrete underwater. The important thing to remember is that while the finished product will be underwater, the construction technically is not. Through the use of a cofferdam you can create a dry space in which to work even in the middle of a river. While constructing a cofferdam for a project such as a bridge is enormously complex and requires special engineering, the principles are the same as creating a cofferdam for a shallow water boat ramp.

Things You'll Need

  • Building plans
  • Tape measure
  • Metal stakes
  • Sledge hammer
  • String line
  • Sheet metal
  • Welder
  • Water pump
  • Shovel
  • Pea Gravel
  • Hydraulic Cement
  • Concrete forms
  • Rebar cage (if needed)
  • Concrete finishing tools
  • Lifting eyes
  • Lifting machine
  • Potash (if needed)
  • Cow manure (if needed)
  • Drive a metal stake into the ground on the shore with a sledge hammer as a reference point from which to start all of your measurements. The location of this reference point will be detailed on your print (typically there will be measurements from the property line or other such permanent marker to help you locate where it needs to be placed).

  • Measure out from the stake to the farthest corner of your foundation. Drive a metal stake in that location making sure that at least one foot of it is sticking above the water level.

  • Drive two more stakes into the ground, one will be in the water representing the opposite corner to the stake you set in Step 2 and the other will be opposite the reference stake. Measure diagonally between the stakes and make sure that the diagonal measurements (from corner to corner) are the same. Adjust the stakes until they are, this will ensure that your foundation will be squared (have 90 degree angles).

  • Tie string line between the tops of the stakes so you can see where the walls of your cofferdam will be placed.

  • Drive stakes into the ground every 2 feet along the string line. These stakes will brace and support the inside of the sheet metal walls of your cofferdam.

  • Weld your sheet metal into a box, using angle iron to reinforce the outside of the corners. You are going to want your finished box to be large enough to slip over the stakes you have set in place.

  • Lift the box and lower it over the stakes. The weight of the box will allow it to sink to the bottom of the water bed. Use a sledge hammer to drive the box into the bed at least six inches.

  • Set up your water pump and begin to pump the water out of the inside of the box. As the water level begins to lower, weld the stakes to the inside of the box. When the water is completely drained from the interior of the box, remove the water pump.

  • Dig out 4 inches of the mud bottom. Pour in a 1 inch layer of pea gravel and then cover that with a 3 inch layer of hydraulic cement. This forms a "mud slab" which gives you a solid surface to place your foundation forms on. When the mud slab has cured, go onto the next step.

  • Form your foundation as you would on land. Install any required rebar cage and then pour and finish your concrete as you would normally. When the concrete has cured go on to the next step.

  • Weld lifting eyes to each corner of the box. Connect your lifting machine to the eyes and pull the box out of the water.

Tips & Warnings

  • If you are going to be working in your cofferdam for a while, mix up some potash and cow manure and have a helper shovel it into the water around the outside of the box as you work. This is an old school trick to plug the leaks that will invariably occur at your welds and prevent the inside of the box from filling with water again. Your helper will have to do this continuously as the mix will plug the leaks and then wash away so make sure you have enough on hand.
  • Do not attempt to construct a cofferdam that is deeper than 2 feet with an engineer's design. The force of the water can easily collapse a cofferdam, causing serious injury if not death, the cofferdam must be designed to withstand the pressure and only a certified engineer is capable of doing this.

References

  • Photo Credit Bridge image by Hedgehog from Fotolia.com
Promoted By Zergnet

Comments

Resources

You May Also Like

  • Thin Pour Concrete Recipes

    Thin concrete forms a smooth product suitable for use in garden decorations, concrete overlays and other non-load-bearing products. Thin concrete recipes use...

  • How to Quikrete an Underwater Post

    All hydraulic cements cure underwater, including Quikrete. A common misconception about concrete is that the curing process is dependent upon water evaporation....

  • How to Fix a Slab Leak

    In homes that do not have basements or crawl spaces, one of the most dreaded things is the slab leak: a water...

  • How to Pour a Concrete Mono Slab

    A slab is always monolithic, which means it is made from a single pour of concrete. Usually when the term monolithic is...

  • How to Cure Concrete Under Water

    The short answer is, all concrete cures under water without the need for you to do anything special. However, you can purchase...

  • How to Pour Concrete Under Old Foundation

    Old foundations can become weakened by air or water getting underneath them and over time eroding either the soil supporting the foundation...

  • How to Pour Concrete on Wet Ground

    Pouring concrete is a straightforward job. You dig, form the mix and pour. Sometimes, however, you may hit a snag that will...

  • How to Pour Concrete in the Marine Environment

    A marine or saltwater environment is devastating to normal concrete. The salt in the air or water degrades the integrity of normal...

  • How to Pour a Concrete Boat Ramp

    Sources like the Mississippi State University Extension Service explain why concrete is the best surface to use for a boat ramp because...

  • How to Pour a Concrete Ramp Onto a Slab

    Concrete can be used to build any number of different kinds of ramps. Among the uses for ramps are handicapped access, boat...

  • How Does Hydraulic Cement Work?

    Adhesive materials such as hydraulic cement are used in the building industry in order to bind building blocks together. Hydraulic cement contains...

  • Concrete Planking Boat Ramp Installation

    The construction of a boat ramp in a body of water is easier using pre-stressed concrete planks. Made just for the purpose,...

Related Searches

Check It Out

22 DIY Ways to Update Your Home on a Small Budget

M
Is DIY in your DNA? Become part of our maker community.
Submit Your Work!