Seawalls by Rick Fender
The water is up higher than I have ever seen it on Lake Holden and my dock is underwater. My dock was installed prior to the Orange County Environmental Protection Department, “OCEPD” requirement that the dock be constructed 1’ minimum above the Normal High Water Elevation. We will apply for a permit later this year to raise the dock about a foot. Hopefully that costly modification will allow us to use the dock year round. Luckily our seawall is still standing and protecting our property from the wave action of the storms and wakes of boats.
There are several options when it comes to protection of your lakeshore. Here is Orange County, you can use wood, concrete, steel, vinyl, fiberglass or aluminum for a vertical seawall. You could also choose to utilize a stone revetment to protect your shoreline. For a revetment you could use Florida Filed Stone, quarried lime stone, coquina, granite or any other durable stone. For a revetment it is preferable to use an angular stone that locks together with the other stone as opposed to a round stone like a river bed stone as they don’t stay in place as well when faced with wave action.
In Orange County, even if you choose to build a vertical seawall, you will still need to have a minimal 1’ tall by 2’ wide stone revetment at the toe of the waterward side of the new seawall. The exception is in canals where the County does not require a stone revetment at the toe of a new seawall. We install a geotextile against the seawall panels and under the stone revetment before installing the stone to further stabilize the stone. I can tell you that even that small amount of revetment makes a huge difference in the prevention of scour (erosion of the soil at the toe of the seawall associated with wave action) at your seawall. One seawall we constructed on the Western side of Lake Holden was 4’ high vinyl with an aluminum cap. Before we installed the required stone revetment at the toe of the new seawall, we witnessed the waves created by the passing wake board boats crashing into the seawall and creating vertical splashes of 6’ to 8’ above the top of the wall. After the 1’ high by 2’ wide stone revetment was constructed at the toe of the new wall, the wave action was totally dissipated when the wave hit the face of the wall and the revetment at the toe.
The Lake Holden website has a great deal of information regarding the historical data of the lake elevations. Knowing this information is important when planning a seawall or a boat dock. When we plan a seawall, we are careful to make sure that we have a slope from the home to the seawall so that the seawall does not hold water behind it. Orange County and the City of Orlando follow a State requirement known as “Compensating Storage”. This means that if your seawall is located below the 100 year flood plane, which most are, and you add backfill landward of the seawall to smooth the transition of the original contour of your yard to the top of the new seawall that you must compensate for the lost storm water holding capacity of Lake Holden that you have caused. If your seawall requires backfill be added below the 100 year flood plain, then you are taking away the overall capacity of Lake Holden to hold storm water during a 100 year storm event. The County and the City require that you compensate for the backfill that you added by building swales or mini-retention ponds on your property below the 100 year flood plain.
In Orange County when you install a new vertical seawall within 1’ waterward of an existing vertical seawall, the compensating storage rule is not applied. However, the City of Orlando, it is still applied. Most homeowners do not want to have retention swales around their property so you have another choice in the City of Orlando. What we have been able to do on a project in the City of Orlando, where there was an existing failing vertical seawall, was to remove a portion of the existing seawall and soil landward of the old seawall. Then we installed the new seawall further landward of the existing seawall and utilized a portion of the existing soil to backfill against that portion of the seawall and behind the other portion of new seawall where the new seawall could not be moved landward. The amount of backfill required for the project had to balance as no import fill could be used.
Back on the different types of seawalls. We install mostly vinyl tied back seawalls with steel reinforced concrete caps. Te panels are usually from either CMI or Everlast. Some projects are flat panel with a wood grain look and the other vinyl are corrugated. In the photo you can see a concrete cap with the formed and poured joints that are one of our signature details. No saw cut control joints for us. Our customers deserve and demand better.
The tiebacks on the above project are epoxy coated steel reinforcing bar connected from the concrete cap to the concrete deadmen at 8’ on center and some 12’ landward of the wall. Notice the stone revetment at the toe. You cannot see the prefabricated weep-holes in this photo but they are there on the other sides of the corrugations.
Another way to build a vertical seawall is to install approximately 2/3 of the panel in the ground leaving 1/3 above the ground. This is called a cantilevered seawall and must be engineered for the correct length of panel, amount of embedment, grade of panel and panel material to work properly. It looks just like our normal seawalls but does not have tiebacks or deadmen. We use these when there is some kind of obstruction landward of the proposed seawall such as the home, a pool or a patio.
We don’t recommend using wood for a seawall ever since the EPA outlawed the use of CCA (Chromate Copper Arsenate) in fresh water. So now the other seawall builders are using CA and ACQ treatment many times on the wood they use for a seawall and it does not last.
Probably the least expensive and best seawall system is all aluminum. The aluminum seawall panels are stiffer than the vinyl and the seawall can be install through roots a little easier. Further, you can have an aluminum cap, aluminum tiebacks and plate aluminum deadmen for a very clean easy to install all aluminum seawall that requires very little maintenance(just need to clean the weep-holes once a year). Below is a photo of an aluminum seawall.
Last word on seawalls. Always get a permit, even if you are building it yourself. It is a pain to do but you will be happy that you did. A seawall is different than a boat dock, in that the dock is an item that provides you access to the water and pleasure while the seawall is there to protect your investment. I have known homeowners on other lakes that hired unlicensed contractors to build their seawalls. The unlicensed contractors convinced the homeowners that they didn’t need permits for the seawalls. The unlicensed contractors built the walls over the neighbor’s property lines causing great heartache and lawsuits for all. If they had gotten a permits, the County and the City would have required site plans showing exactly where the seawalls were going. If the contractors had been licensed, they would have checked the surveys and the site plans and property corners to make sure that they were not building onto the neighbor’s property. During the inspection process, the County or the City inspectors may have found the encroachments of the seawalls onto the neighbor’s properties and corrected the issues before the walls were too far along.
If you plan to build a seawall by using a contractor, please make sure they have at least a Residential Contractor’s license with general liability insurance and State Act Worker’s Compensation Insurance with the code 6006F which is specific for seawall construction so you know their employees are covered.
If you plan to build one yourself, please let me know and I will send you to a friend who is a permit tech that helps you with the engineering and getting permitting in your name legally and she knows all about seawalls.