Friday, October 19, 2007

Pile Driving and Jetting for Marine Construction of Docks, Boathouses and Seawalls

Pile Driving and Jetting in Marine Construction

When you are thinking of building your own dock or seawall or hiring a contractor, here are some problems to watch out for.
In general, do now hire unlicensed or uninsured contractors. This practice is wide spread in marine construction as there are plenty of people with a pickup truck and the ability to sell. If the marine builder does not have a license, he has (3) choices.

1- He can build the structure without a permit and hope he does not get caught.
2- He can get you to pull the permit for him as the homeowner. This is somewhat tricky as you have to swear to the permitting agency that you or your family will be constructing the project.
3- He could ask a friend with a license to pull the permit for him.

The last (2) of these options are third degree felonies. So really none of these options should be acceptable to you.

When you actually start installing either wood piling for a dock or sheet piles for a seawall, you must make sure that the post rests on a good foundation. This is accomplished by using water pressure from say a 2” trash pump with a steel wand reduced down to a ¾” pipe. The post or sheet is placed in position on the bottom of the lake and the water is used to wash the sand away from the base, allowing the post or sheet to settle slowly downward. When the bottom of the post reaches the hardpan or so much friction at say 4’ to 6’ below the mudline, the post will not go any further, you have reached a good foundation for the post. For the sheet pile, unless the sheet hits a void or deleterious materials at the pre-described amount of sheet penetration below the mudline, then it is considered to have been set to a good foundation.

The reason this good foundation is important is that if the post is not seated correctly, it will drop after a load is placed on it. Further, the post will be more susceptible to wave and wind uplift during high wind or wave conditions.

For the seawall sheet, the correct amount of penetration below the mudline will prevent the panels from kicking out at the bottom. If you have someone else setting the posts or the sheets, measure them before they are installed. That way when they are done, you can measure the length of the post or sheet above the mudline and calculate the length of post or sheet embedded below the mudline.

Sometimes you will find a root or rock or other obstruction impeding your way to getting the proper penetration. Don’t give up! Either jet or cut or dig the obstruction out of the way and continue down with your sheet or post. If you leave it up higher than required, you will have trouble in the future.

Until next time, “You’ve got to build on a good foundation!”

Rick Fender- Cloud 9 Services, Inc.

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