Two months ago I pointed out an issue about dock building and installing new work in front of an older seawall in the canals of Treasure Beach titled " Not all dock builders are created equal". Well, folks my article was too accurate and the job has taken the final turn I warned about last month. After Tropical storm Fay gave us heavy rains in our area. The seawall I spoke about, blew out while Fay drifted away, leaving a lot of rain in Treasure Beach. The damage is now more costly than the property owner expected and so he's now facing the full nightmare he insisted on having. I cannot convey how simple it would have been to avoid the now expensive mess of concrete laying in the canal up against the new pilings and boat lift systems. From our vantage point the wall dropped about 2feet and cracked open spilling dirt into our canal system. From the top to the bottom the wall is now at an angle and "pushing" against the new boat lifts that were installed. Already the owner has met with a dock builder to assess the cost to install a new seawall. Without any more surprises, some of the new work will have to be removed to access the wall and dig up the old wall's remains. The materials from the old seawall will create a cost with the job, and the site will run up over anything like just having a seawall repaired or a new one installed. The old wall could have been saved from this blow out, but again you need to know the truth about your own seawall and its depth into the mud line of the canal.
From my past experience with seawalls, they can run a life span from 20 to 40 years before failure occurs. This depends on the type of material used and job conditions, even weather plays a factor for the life of a good seawall. The specifications for a good seawall today are 50% below the mud line, or that is in layman's terms, half the wall should be below the mud line. For an example if your wall is going to be 8ft for exposure, then there should be 8ft of wall buried below the mud line. Basically there are several types of walls to choose from for holding the dirt back so I'll explain each in some detail.
Lets go with the lowest cost for most builders first, and that is wood. These are popular for several reasons, but mainly the price per foot to install them, a wood wall can run from about $200 per linear foot and up depending on soil condition's and job access. A good wood seawall is said to have about 20 to 25 years of life expected in its design, if its installed correctly. The wood walls to be installed are generally lined with piling, that is 2.5CCA rated poles. A good wooden seawall will have a whaler system at the top and about midway along its exposure, the whaler is a heavy timber you'll see running about mid way up on your exposed wall and then a second one at the top which is capped by a wide board to finish the job and tied back by galvanized rods or stainless steel cables. The tie back is very important but should be maintained by the property owner, if anything begins to show such as bowing or soil dropping down behind the wall. The sinking soil problem is generally the first thing a property owner will see when leaking starts. you can fill in the dirt lost, but the wall will continue to " leak out". The wooden walls have some good points at this level. Working to repair a wooden seawall can be cheaper than other materials used for seawalls and in some cases a section of the wall can be repaired without rebuilding the length of the wall thus saving the property owner the nasty headache of spending a large amount of money to rebuild a failed wall. Generally the piling will out last the rest of the structure and can even be reused for a new wall if all the boards are rotted and leaking soil to the canal. Inspection of the piling before hand is recommended before attempting anything like re-using the old piling for a new wall. Failure in wood walls can vary depending on the original job, so there's no hard fast rule to where or what might be involved in wooden pressure treated seawalls when it reaches the point of failure.
In speaking with some of the local dock and seawall builders I was very unhappy about their opinions when it comes to seawalls. Truth be known from my past experience, they offer the cheapest and fastest repairs, but not always the best. There are several ways to get around the builders, but the only simple way is to insist watching the job site, even more important on commercial rated composite sheets, these are expensive but will offer up to a 50 year warranty. Installed correctly these will out perform any other material, but again like wood, the installation is the key to a good strong wall. If the builder takes short cuts or doesn't get the proper depth, then its possible to have failure with even these walls. The composite type products offer several good construction points, one is that the entire wall only requires a top hold back system tied to the whaler. No piling is required for installation and you'll see these walls used in commercial areas anywhere in Florida. The down side is the dock builder will require the correct equipment to install these, and that may very well be where they try and talk the home owner away from this product, thus the problem begins. These walls by manufacturer's standard require 50% below the mud line. Anyone in Treasure Beach will hit hard coral before reaching 50% in most cases. It takes some heavy equipment to dig out the rock like coral here and thus the expense starts to run up. Its best to have some one on hand to supervise this part to insure the builder is getting it done correctly.
This past week I spoke with country rep Karen, who was doing an inspection on a seawall. I showed her some issues that are early signs of problems in seawalls, and how a leak might be detected at the top before anything at the bottom shows up. For most of us, a good wooden seawall will fall better in our budget. There are several areas that should concern anyone getting a new wooden seawall. The tie back system, also called the deadmen is very important and must be installed correctly to prevent early failure at the top of the wall. The best way to do this is concrete with reinforce rod, all heavy galvanized products, and a coating brushed or sprayed on before the concrete is poured to insure long life. The tie back rods should be galvanized with a space up to 20ft between the seawall and the deadmen connection buried in the ground. At this point the wall material will make a difference on spacing. The average space per connection should be every 5 to 6 feet, but this can vary depending on soil and height conditions and materials being used for the new wall. Generally if you don't think your builder is doing it right, ask questions, or even insist on getting the job checked before letting the contractor finish it.
L.Panchuk ( Author: The Devil's Magnet ) X zone radio reporter Treasure Beach
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