Building a Seawall / Bulkhead – 101s
With over 28 years of combined expertise Perfection Seawalls can assist you in your
need to build a seawall or Bulkhead. As a Florida marine contractor we know how to evaluate, estimate, plan, design, and build a seawall or bulkhead to provide your perfect coastal property solution. Browse from the below topics to learn more about building a seawall / bulkhead and marine construction. So What’s The Difference in Building a Seawall vs. a Bulkhead? Many people refer to all vertical shoreline structures as “Seawalls” but there is a difference.
Read below to learn more:
A more fortified structure both below and and behind wall or barrier that provides shoreline protection from waves but also retains soil. Usually seawalls are found directly exposed to open ocean.
A vertical shoreline stabilization structure that primarily retains soil, and provides minimal protection from waves. Bulkheads in Florida are typically located on inland waterways or canals, and are subject to storm surges and tidal action even though they are not exposed to ocean waves. A coastal engineering study can provide Bulkhead design information to ensure that they are designed properly to withstand the dynamic loading and over-topping effects of waves. The “rule of thumb” in bulkhead design is to account for wave impact with wave height at a project site expected to be in excess of three feet (1 meter). Unfortunately, many existing walls on the coast were simply designed as bulkheads, and did not account for coastal storm impacts.
Elements of Designing and Building a Seawall or Bulkhead:
Prior to building a Seawall or Bulkhead (Marine Construction) an evaluation needs to be done by a Florida marine contractor and the following design considerations need to be addressed to be able to properly assess the condition of the Seawall or Bulkhead to determine proper course of action for a new sea wall construction or bulkhead construction:
Topography: Elevations, grading, etc.
Soil Properties: Unit weight of soil, clay vs. sand, etc.
Embedment / Stability: Depth of wall for stability
Water Table: Differential water levels behind and in front of walls can introduce additional loading on the wall
Wall Material Properties: Strength and performance of materials in the marine environment
Surcharge: Live loads behind the wall such as ground water, runoff, vehicles, structures, etc.
These additional design considerations need to be addressed by a marine contractor for seawalls:
- Tidal Action
- Wave Over-topping
- Storm Surge
- Toe Scour
If a Seawall or Bulkhead is determined by the marine contractor to be damaged or deteriorated, the original design may not have accounted for the above-listed design considerations. Original or “as-built” Seawall or Bulkhead plans can provide a wealth of information including the age of the structure and many of the design elements listed in the above paragraphs. The deteriorated condition of a wall may also be an indication that the wall is in need of maintenance or that the sea wall construction / bulkhead construction has fulfilled it’s service life.
Seawall & Bulkhead Structural Evaluation Info:
The American Society of Civil Engineers (ASCE) Underwater Investigations Standard Practice Manual was released in 2001 for marine contractors and and provides guidance for the evaluation of walls. Procedures are also applicable for above-water structures. Most bulkheads are along the waterfront, and should be evaluated above and below the water, whereas seawalls typically are not exposed to water on a regular basis.
The following topics are covered related to structural integrity of Seawall construction / Bulkhead construction evaluation for marine construction:
- Qualifications of Inspection Personnel
- Types and methods of inspections
- Typical forms of deterioration
- Condition Rating
- Frequency of Inspection
A comprehensive marine construction report is essential to document a proper Seawall or Bulkhead evaluation. All of the above items should be included along with photographs and sketches of the observed configuration with notes regarding deterioration. Comparison of previous reports provides an indication of the rate of deterioration.
Repair recommendations, along with marine construction cost estimates, should be included to provide the property owner with sound engineering advice so they can plan for maintenance or repairs as necessary. The report should be sealed by a registered professional engineer experienced in the evaluation of in service marine structures.
Seawall & Bulkhead Construction Materials Info:
Seawalls and bulkheads are constructed of similar materials. The material of the wall must be properly identified prior to assessing the condition. The following table presents common Seawall construction / Bulkhead construction materials with comments regarding availability, construction issues, and general performance in the marine environment:
Concrete: Pile/panel and sheet piling configurations common in South Florida. Most common Seawall or Bulkhead material in South Florida due to the locally available aggregate; provides service life of 30+ years if correct mix design and proper marine structural design implemented.
Steel: Steel sheet piling is commonly used for Seawalls or Bulkheads. Material provides excellent strength characteristics for high wall exposure applications. Provides interlocking seal, and generally easy to install, even in harder substrate. Must be properly coated and maintained for long service life of 25+ years.
Aluminum: Aluminum sheet piling provides good corrosion resistance, but lighter sections allow for minimal exposed wall height. Recognize corrosion potential of dissimilar metal hardware, do not use in waters with low Ph or back-fill with clay-mucky soils. Difficult to install in hard substrates. Not often used in South Florida, but occasionally seen on inland waterways.
Vinyl: Relatively new economical product with service life of 50+ years. Available in different colors. Limited strength characteristics for wall heights. Difficult to install in hard substrates.
Timber: Timber pile/wale/sheet system is common structural configuration. Generally economical material, but limited strength characteristics for high wall heights. Preservative treatment is essential for marine organisms. Difficult to install in hard substrates. Relatively new economical product with service life of 50+ years. Available in different colors. Limited strength characteristics for wall heights.
Bulkhead and Seawall FAQs:
Q : Can I raise the grade of my property with the existing bulkhead?
A : The bulkhead must be evaluated by a Florida marine construction engineer to determine if the structure can withstand the additional loads from fill and structural modifications. Deterioration can severely weaken the structural capacity of the bulkhead, and the bulkhead was most likely designed for the existing conditions.
Q : What is the best material for bulkheads and seawalls?
A : Material selection is site-specific and dependent on design conditions. Concrete (if designed appropriately) generally provides a long service life, but it is not favorable from a first-cost basis. Vinyl sheet piling and other composite materials, where applicable, should be considered due to their resistance to the harsh marine environment and 50+ year service life.
Q : How long can I expect my wall to last?
A : Answers to this question are generally subjective. An experienced marine construction structural engineer can provide general assumptions as to the “expected remaining service life” of a Florida marine construction. Comparisons with observed deterioration over time can also provide an indication of material performance. Certain non-destructive and/or partially destructive exploratory excavations are good to evaluate condition of the tie backs. Underwater photographs of steel sheet piling materials testing can provide additional information for the assessment.
Q : What regulatory permits are required?
A : Bulkheads typically require an environmental resource permit from several agencies including the county environmental resource management agency, the DEP, and the U.S. Army Corps of Engineers. Depending on the jurisdiction, the local water management district may also issue a permit. Seawalls require a permit generally from the state agency such as the DEP.
Q : How often should I inspect the wall?
A : The ASCE Manual provides guidance for the frequency of inspections. Generally, Seawall or Bulkhead should be evaluated every 5 to 6 years by a Florida marine construction structural engineer.
Q : How do I repair my wall?
A : A qualified marine structural engineer should be consulted to evaluate the existing wall and to determine if rehabilitation or replacement is required. Options can generally be provided to provide an economical approach to meet budget constraints.
Q : Who can build a wall?
A : Marine structures are specialized structures, often requiring water-based construction equipment and techniques. The costs for waterfront construction are generally higher than for upland structures such as buildings. Bulkhead construction / Seawalls construction work should be reserved for a qualified and experienced Florida marine contractor.
Seawall – DER Requirements:
Seawalls on the coast of Florida come under the jurisdiction of the Florida Development of Environmental Regulation (DER) Division. In addition to evaluating the structural condition of a seawall, the DER has special requirements for seawalls at or near the Erosion Control Line (ECL). A coastal engineering analysis is required to determine if an existing seawall will be affected by a 30-year coastal storm event. If the existing wall is within the 30-year Erosion Projection, then the property owner must “provide scientific and engineering evidence that the armoring structure (seawall) has been designed, constructed, and maintained to survive the effects of a 30-year storm and provide protection to existing and proposed structures from the erosion associated with that event.” The DER requires certification by a professional engineer that the seawall was designed, constructed, and is in adequate condition to meet the following criteria:
- The top of the seawall must be at or above the predicted maximum wave crest elevation, considering the eroded beach profile, of the 30-year design storm.
- The seawall must be stable under the 30- year design storm including localized scour, with adequate penetration and toe protection to avoid settlement, toe failure, or loss of material from beneath or behind the armoring.
- The seawall must have sufficient continuity or return walls to prevent flanking under the design storm from impacting the proposed construction.
- The seawall must withstand the static and hydrodynamic forces of the 30-year design storm.
Required Documents to Build a New Seawall or Bulkhead:
Below are a list of documents that may be necessary for you in order to obtain permitting for a Seawall or Bulkhead, depending on your project.
- Current DER License and Approval
- Copy of Survey
- Notice of Commencement (signed and notarized)
- City or Municipality Building permit (if needed)
- County Building permit (if needed)
Seawalls / Bulkheads typically require an environmental resource permit from several agencies
including the county environmental resource management agency, the DER, and the U.S.
Army Corps of Engineers. Depending on the jurisdiction, the local water management
district may also issue a permit. Seawalls require a permit generally from the state
agency such as the DER.