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Foundation for a jetty

Foundation for a jetty

Foundation for a jetty

(OP)
I would like suggestions on the foundation for a jetty extending  50 to 150 feet out into a lake.  The lake bottom is located at a depth of approximately 9 feet.  The lake bottom subsurface is comprised of a 20 feet thick layer of very loose organic silt underlain by medium dense sand and gravel.  There is a stream that may intersect the jetty at times.

RE: Foundation for a jetty

That's a loaded question.   A lot more info on what you propose is needed for useful answers.

Off hand, I'd guess you will be creating two islands parallel to the jette after you have placed about 5 times or more of fill that you thought you would need.

Are there any nearby fills that could be used as an example of what works and what does not?

How much time do you have for this, say in years?.  How fussy does the final elevation have to be?

Any chance you will get law suits for changing the lake bottom?

Stand by for a bunch of ideas.

RE: Foundation for a jetty

(OP)
Sorry!  The question was poorly worded.  The jetty would simply extend out into the lake perpendicular to the shore.  The stream is a very small drainage system and does not intersect it and is about 300 feet away.  At the worse case scenario it may cause very slight water turbulence near the jetty  not enough to undercut it.  The fill would need to be trucked onto the site so it is possible to select the optimum type.  The final elevation is not critical—just enough to remain out of the water and walkable.

RE: Foundation for a jetty

(OP)
I have more details of the proposed jetty.   It is to be about 50 to 100 feet in length and 20 feet wide.  It is proposed to have concrete blocks along the sides and front.  The blocks are 2 x 3 x 4 feet and made from concrete.  The jetty will extend about 2 feet above the surface of the water.  The blocks will be placed along the sides of the jetty and compacted fill will be placed in the center.  The surface of the jetty will be bituminous concrete (asphalt).  The jetty will extend perpendicular from the shoreline of the lake.  The lake bottom ranges in depth from 2 feet at the shore to about 8 feet at the tip of the proposed jetty.  The lake bottom is comprised of an approximate 20 feet thick layer of vary loose organic silt overlying medium dense well graded fine to coarse sand and fine gravel.  There is a small stream of highway drainage/runoff coming into the lake in a direction that will intersect the jetty at a 90 degree angle.  The steam is very slow flowing unless there is a big rainfall.  The stream is approximately 200 feet away from the jetty.  I was told that during severe weather the stream shoots deposits out into the boat lane and the lane must be dredged.  The jetty will help to contain the deposits so that it can be easier to control. I would appreciate any suggestions you may have and thank you in advance for the advice.

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