Terragone Engineering

We Are Here To Help Residents With Seawall & Dock Damage From Hurricane Ian & Nicole

You don’t always get what you pay for, but you will always pay for what you get…..

Terragone Engineering is a qualified engineering firm for seawall, marine, marina, and dock engineering, both public and private.  We have over 30 years of engineering experience.  Terragone Engineering has focused experience in marine and seawall specialization for 15 years.  We employ sound engineering practice coupled with state of the art tools for evaluation

Causes of Seawall Failure

Aging Seawalls - typical concrete seawalls have underlying steel corrosion caused by chloride (salt ) exposure and stresses the concrete panels.

Aging & Corroding Tieback Rods- Seawalls installed prior to 1980 almost universally, and indeed seawalls built earlier were constructed with steel anchor rods.  These anchor rods rust overtime and weaken.  Eventually, they fail and the wall fails.

Poor Design – Undersized anchors and improper anchors.  Few people understand how anchors work and use ad hoc approaches.  Very few engineers even know how to evaluate the holding power of an anchor or understand the loads they need to support.  The anchors perform ok until maximum conditions are placed on the wall,  low water on the front side and high water table, and saturated soils on the backside.   Anchors will drag through the weak soils trying to support massively increased loads.   A Buried piling anchor's design is a telltale sign of very poor thinking on any but the shortest of walls.   

More Poor Design – Not understanding forces on walls.   In Florida, maximum service loads occur at low tides and massive downpours.   In all instances, the designer should be asked about the service conditions considered.  In low-lying coastal areas, it should always be assumed the wall will be filled to the top of the cap with water.   We have recently seen walls installed in the 1960’s fail only because the maximum service loads were not experienced until the recent heavy rain.   The anchors were shallow and undersized and the wall failed only because of loading

More Poor Design – Poor consideration of soils supporting and loading the wall.    If a wall is designed without the benefit of soil testing, ask why.  Soils represent the total load and support.   Frequently we have experience in an area and are comfortable with local understanding, other times we know an area is subject to bad or sometimes very good soils.   Muck layers are very difficult because they add large loads and no support.  On the other hand, rock and marl layers are good for support but can be a difficult situation for installation.    Your designer should demonstrate a good understanding of the soils on your project or should be asking for soil tests.

More Poor Design – Short panels, weak panels.  Often contractors push to limit panel size in order to drop the price of a wall in order to get the job.  This will cause the wall to bow, soil to escape out from under panels, and walls to develop a ‘belly’ because panels are undersized.   Unfortunately, these problems usually manifest several years after installation, and the contractor and engineer are long gone.

More Poor Design – Cap loads poorly understood.   The seawall cap is a very important structural member.  It acts as a beam with point supports and ties the top of the wall together and holds the entire system back and in line.   If the cap is poorly designed or poorly constructed

More Poor construction practices – The most frequent poor practice is the construction of a cap using a ‘bag cap’, where a concrete cap is not formed to the wall but simply fabric is draped over the top of the panel.  Thus the concrete does not properly ‘grab’ the top of the panel.   Also, the concrete section is reduced, resulting in improper material

Why use an Engineer for Seawall Design?

Engineers are bound by a code of ethics to protect the public, protect clients' interests and practice only in their areas of competence and expertise.

Engineers are paid for the product design, not a margin.   Unlike contractors who typically have every interest in reducing costs which in marine contracting often comes at the expense of a poorly constructed seawall.   An engineer should design and specify seawall components based on loads, physics, and service conditions.

Seawalls typically cost $400 - $1100 per foot depending on conditions.  For a 100 foot property, that translates to $40,000 to over $110,000.   The cost of a good competent design is a fraction of that.

Most marine contractors are not insured for construction failures, which means you have to sue to recover for a failure.  In that time, the contractor can close the business, or have no attachable assets and reform under a different name.  Check SunBiz.org to see how many times a principal contractor (by name of owner) has formed and closed a business.

It is our experience that contractor-specified walls are terribly designed.  We estimate that 20-30% of contractors are reputable and most of these employ a competent experienced engineer for specifications.  Others just are not competent for building seawalls.

Often contractors are trying to give a lower price and still make money on the seawall.  They will notoriously install cheaper panels, shorter panels, fewer tieback anchors, improperly installed tieback anchors, and other cost-cutting measures.   The result will typically be a seawall that looks pretty good and performs for a few years until severe conditions are placed on the seawall.

Building Departments offer little protection.  Building reviewers typically do not understand wall design, loads, and stresses. 

They invariably review plans only to check it is signed and sealed and assume everyone has proper insurance and competence.

They often accept plans designed by environmental permitting people not competent in engineering or even engineers who do a seawall design just every so often.  The reviewers are not responsible for design math, only to check the proper certifications are in place.

Many permitting experts have no design training.  They can do drawings, they can obtain permits but normally don’t understand the physics.   Often the plans will be prepared and then sealed by an engineer they pay to seal drawings without review.

Good Contractors

The problems caused by shoddy contracting are myriad.   Many components of a wall can fail, often after the statute of limitations (responsibility ) has expired.   A modern seawall should have a design service life of at least 40 years, and often in excess of 75 years for very good quality walls.

A good contractor will have been in business for many years under the same name.  A new good contractor will have a handful of references and should be known by your engineer.  If you have a new contractor, pay an engineer to go see the last few projects by the contractor, or a wall under construction.  A very good contractor will have both errors & omission insurance and good liability insurance.  This guarantees if a wall does not perform, you as the owner has recourse to rectify the situation with minimal attorney involvement or very few if any court claims.  Also check the building department records for projects that your contractor has completed.

Good Engineering

A good Engineer will charge a fair price for good work.  There are no ‘deals’, only low-cost headaches and failures in your backyard.  If you are quoted pricing under $400 a foot for a 4-5 foot wall, be wary.  Unfortunately, there are a lot of engineers who are legally qualified to design a wall but don’t have the training or practical experience to serve you.

Good engineers carry a valid professional engineers license in the state of service rendered.  A good engineer will design a solid wall to the most extreme anticipated service condition with an appropriate factor of safety.  The engineer will be able to discuss these readily and competently.  A good engineer will not unnecessarily over design a wall to protect themselves.  A good engineer will have design tools and be able to discuss how anchors are designed, tie rods, soils work and panels are designed.  

Designs should be cost-effective, a good engineer should have an understanding of soil conditions, including the presence of muck, rock, marl layers, and weight and structure parameters of sand, they should ask for soil boring and survey will carry errors and omissions insurance to give you recourse in case of design failure, explain anchors work by area opposing soils and know deep anchors, helical and plate anchors.  Normally a competent engineer designs more than 5 seawalls per year.

What to Avoid?

Environmental consultants, permitting agents, or other unqualified personnel purporting to be seawall designers unless they are operating in direction of a properly licensed engineer.  It is illegally and potentially very costly to you

Anyone selling ‘design services’ for very low fees or seal sellers.   The real design takes real professional work and there is a reasonable cost to that.

Big design firms – normally they don’t have a lot of in-house experience and their big fees are a result of a lot of work due to inexperience and administrative costs.

Good Design work does cost a reasonable amount but doesn’t warrant extraordinary fees.

The construction of seawalls does not simply entail dumping rock on a foreshore.  We often draw a parallel with the construction of a house.  You don’t build a house by simply tipping a truckload of timber onto a vacant block of land.  Individual components must be assembled appropriately so as to sustain external loads in order to fulfill the intended purpose of the structure.  That is also the case for seawalls.

A properly designed seawall will provide robust protection to foreshore assets and require a minimal commitment to future maintenance.  Coastal Engineering Solutions has considerable expertise and experience in designing and supervising the construction of seawalls.

Design Life

Most seawalls are designed and constructed for a design life which would be specifically selected according to the intended purpose of the wall.  Temporary works having a relatively short structural purpose would normally be a fairly simple design.  Such structures may be removed or demolished when no longer required.  A more permanent structure such as that fronting essential coastal infrastructure will typically have a longer design life of 50 to 100 years.

The design life of the structure would also be selected on economic aspects – such as the cost of replacing the seawall and/or the design life of the infrastructure it is protecting.  Clearly, the components of the seawall must have adequate durability to last to the end of its design life.