Retaining Walls Are Your First Line of Protection Against Shore Erosion
Seawalls, otherwise known as retaining walls, are a common sight along the shorelines of the Fox Waterway here in Illinois. If you’re a waterfront property owner, you may be wondering, “Do I need retaining walls? What do I need to know about them?”
Seawalls Unlimited wants you to have everything you need to make well-informed decisions about your shoreline. Here’s our comprehensive guide to retaining walls. The topics we’re going to cover are:
- What are the benefits of retaining walls?
- What are the different types of seawalls?
- How do you choose the right type of seawall for your property?
- What sort of maintenance and repairs might a retaining wall need?
What Are the Benefits of Retaining Walls?
So, why get a retaining wall in the first place? The most important reason to consider a seawall is to protect your shoreline against the forces of erosion, flooding, and more. Here’s a breakdown of those and other reasons to consider installing a retaining wall.
Retaining Walls Prevent Land Erosion
Over time, the waves from the natural flow of water as well as wakes from passing boats will push against the soil on your shoreline. This causes it to break up, disintegrating into the water. As time goes by, the shoreline will have much less land and much more water. That can be devastating for waterfront property owners.
A retaining wall, when properly designed and maintained, provides effective erosion control to prevent this from happening. It acts as a barrier to keep the land where it is, so your property has room to thrive.
Seawalls Protect Property from Flooding
You can predict how high the water rises near your shoreline during normal conditions. What about during a storm? Torrential rains can and do bring floodwaters which rise far above what we normally see, sometimes with very little warning.
When that happens, it can cause lots of property damage, and fast. Just check out what happened along the Fox River last year. Heavy rains up north brought water rushing downstream. It swept away people’s boats and other possessions, deteriorated their shorelines, and sent debris crashing into people’s docks and washing up on their shores.
A retaining wall will help protect your property from flooding, and buy you more time to prepare in the event of a storm or flood.
Some seawalls are hundreds of years old and still standing to this day. When properly designed, constructed, and maintained, your retaining wall will last you for many years to come. This makes it an effective way to protect your land for generations to come.
Read more about the advantages of seawalls here!
Types of Retaining Walls
Here at Seawalls Unlimited, we offer three main types of retaining walls. Those are steel seawalls, outcropping, and rip rap. Let’s take a look at each of these types of seawall.
This is a popular seawall design common throughout the Fox Waterway and the Chain O’Lakes. You’ve probably seen many of them along the shoreline. They’re the most plain-looking, but also the most versatile type of retaining wall.
Installing this type of retaining wall is a multi-step process. The crew first excavates the shoreline to ensure enough space to work. They then construct a “dead man” structure. They build this underground support system from five- and seven-gauge steel, galvanized steel, and steel round-stock tie-back rods. This structure braces the seawall against erosion.
Once the steel seawall is installed, they fill the area. Some contractors use soil, but it’s better to use medium-sized #8 stone. That’s because soil soaks up and holds water, while stone lets it pass through. Once the space is filled with stone, it’s covered with a vented plastic sheet, top soil, a straw blanket, and grass seed. The plastic sheet keeps soil from falling through the stone, and the grass regrows over the top to hide the fact the area was excavated.
If you don’t like the spartan look of steel seawalls, outcropping is a good alternative. Outcropping is a wall built out of rows of layered stone, usually in large flat pieces. When you use irregular stone, this gives the shoreline a more natural look.
The installation process starts a lot like it does with the steel seawalls. Our crew excavates the shoreline to the right grade. Then they lay down a filter fabric to prevent soil from eroding away from under or behind the outcropping.
Once that’s in place, we assemble the layers of stone like a jigsaw puzzle. These are generally big, flat pieces of limestone averaging between 1,000 and 1,800 pounds. They vary a lot in terms of height, shape, texture, and color, allowing us to create a unique look that fits your shoreline.
Rip rap is another alternative to steel seawalls, also made from stone. The term “rip rap” originally comes from the noun “rap,” meaning a series of knocks or strikes. So, rip rap is made of layers of fractured stones broken up into smaller pieces. Maybe you’ve seen rip rap lining the shores of ponds and streams. This is the most natural and eco-friendly option.
Installing rip rap starts a lot like installing other types of seawalls. Again, our crew excavates the earth to the right grade and covers the soil with a protective fabric. We then layer the stone on top. Rip rap with smaller 3” to 6” stones is best for small ponds and no-wake zones. In contrast, 6” to 12” stones are better for rivers and inland lake shorelines.
Check out our detailed breakdown of these three seawall designs here!
Which Type of Retaining Wall Is Right for Me?
So, how do you choose which type of seawall is right for your property? Here are some helpful guidelines.
What Sort of Body of Water Will It Border?
Your first consideration should be the body of water the retaining wall will border. Think about the size and depth of the water, as well as currents and salinity.
Smaller and calmer bodies of water are less demanding on the seawall. If you border a calm bit of lake or a small pond, you can use rip rap with stones as small as 3” to 6”. If you border an inland lake shoreline or a river, you can use 6” to 12” rip rap stones. You could also use outcropping or a steel seawall if the waters are rougher.
Also think about the water’s salt content. If you’re bordering a saltwater body like an inlet or even the sea, you might want to avoid steel seawalls, which are better for freshwater.
What Conditions and Activity Levels Will Be Near It?
The next thing you should think about is the environment around the shoreline. Consider the shoreline conditions as well as the level of nearby human activity.
Are boat wakes going to be an issue? Boat wakes are the waves which a boat or jet-ski creates in the water as it goes by. If lots of watercraft are always passing by at high speeds, the large wakes they create can significantly erode your shoreline over time. If there’s a no-wake zone you may be able to use small-stone rip rap, but areas with excessive wake may need a sturdier design like outcropping or a steel seawall.
You should consider the shoreline itself as well. Is the soil sandy? Is it mostly clay or silt? Is the incline gradual, or steep? You should learn about the installation process for each design to determine if it’d work for your property. Since steel seawalls penetrate any kind of soil, they may be your safest choice if you’re unsure about the stability of your shoreline.
There’s still potential for other designs in rough conditions, though. In areas with potentially dangerous currents, you can use large rip rap stones to create a barrier that’s hard to walk on. That’ll discourage people from wandering too close. The largest varieties of rip rap also effectively prevent soil erosion and restore banks in problem areas. In contrast, if you want convenient water access, outcropping can provide natural stone steps for you to use.
Does Eco-Friendliness and Appearance Matter to You?
Finally, you might want to give some thought to your seawall’s appearance and how much you want to focus on eco-friendliness.
If you want an environmentally friendly seawall, rip rap is the best option. Unlike other designs, rip rap doesn’t block organisms from moving in and out of the water. If you’re worried about harming organisms like turtles by impeding their ability to use the shoreline, rip rap offers a less intrusive solution. It can even be colonized by some native plan and insect species.
In addition, rip rap gives you the most natural look. The native plants and other vegetation can partially cover up the stones, which look pretty natural to begin with. It’ll almost like it isn’t a manmade structure, so it’s nice if you want something that blends in with the shoreline.
Outcropping looks more planned and manmade, but can still be beautiful. The irregularity of the stones leaves you a lot of possibilities depending on the mood you want to set.
However, if beauty and eco-friendliness aren’t high on your list of priorities, there’s nothing wrong with a practical and sturdy steel seawall.
Which Design Fits Your Budget?
Last but not least, you’ll want to evaluate which design best fits your budget.
The first point to address here is, do you care more about installation costs or long-term ownership costs? Rip rap is usually the most cost-effective design in the short term because the materials are simple and cheap. On the other hand, a steel seawall has the longest lifespan. That may save you money in the long run if you hold onto the property and maintain the retaining wall properly.
However, you should be aware that the relative costs of each design are also determined by your shoreline. Differences in incline, soil type, currents, and other factors will impact your seawall’s design specifications and determine what work needs to be done to ensure your wall is built to last.
See our full article on choosing the right seawall design here!
Seawall Maintenance and Repair
Like any other structure, retaining walls need upkeep if you want them to last. So, what does that entail? Here’s a primer on some of the basic elements of seawall maintenance and repair.
Basic Maintenance for Retaining Walls
To start with, there are a few basic tasks you should do on a regular basis to help prevent any issues with your retaining wall.
The first is to keep a close eye on any plant growth around your wall. Though some seawalls such as those made with rip rap incorporate landscape shrubbery and native plant matter to create a more natural and eco-friendly aesthetic, not all growth is good growth. Check for weeds. Their roots can bore deep into the ground, causing cracks and other penetrations in the liner and other parts of your seawall.
You should also be checking on weep holes. These are openings which allow water from behind the seawall to filter through instead of accumulating and putting pressure on the wall. Clear any blockages and make sure they have good flow and aren’t clogging. Otherwise, you’ll have increased risk of cracks and crumbling.
Finally, some owners apply spray-on waterproofing solution to their retaining walls. This provides an extra layer of protection against water erosion. Depending on your seawall design and shoreline, this might be a good item to add to your maintenance regimen.
Perform Minor Repairs
Some issues with retaining walls are simple enough that you can fix them yourself with a bit of DIY experience. Minor cracks and holes, for example, can be sealed with marine grout. That’ll keep water from flowing through and eroding away soil and sand from under or behind the seawall.
What issues you look for will vary depending on your seawall design.
- If you have a steel seawall, look for cracks, leaks, and rust.
- If you have rip rap, look for dislodged stones that need to be replaced.
- Finally, with outcropping, you should look for joint separation. This occurs as stones shift and settle over time and tidal shifts put different pressures on the wall. You can spot holes on the landward side where soil is spilling through the separation. Alternatively you can spot seawall backfill in the water, especially at low tide.
Check for Signs of Bigger Problems
On top of those smaller problems, you should also check for issues that can grow into more expensive problems. Look for these during your regular maintenance checks and especially after major runoff events like storms or flooding.
- Loss of soil or sinkholes behind the wall. These are caused by defects in the wall, leading to water seepage under or through the wall. This issue weakens the wall but also leads to further erosion issues and potentially property loss.
- Rust-colored cracks in the wall or sheeting. This is rebar eroding due to salt water damage. Rebar eroding is a very serious issue because it causes the rebar to expand. That creates more cracks and allows water to get through. When a storm comes, the seawall is at risk of failing.
- Rotating or sinking walls. This is usually caused by pressure from water caught behind the wall. It can cause immediate damage if not addressed, including total failure of the wall and major soil loss.
If you notice these issues, you should get a professional inspection to assess what repair work needs to be done. Often, minor separations and other issues can be fixed up with jointing sands or hydraulic cement. In more extreme cases though, the crew may need to do some excavation to address the underlying issue.
Read our complete introduction to seawall maintenance here!
What to Do When a Seawall Needs Serious Repairs
Sometimes, it’s too late for routine maintenance. If you discover your seawall is sagging, sinking, or bowing outwards, your retaining walls need serious repair work from a team of professionals.
For example, one type of repair for retaining walls is footer repair. This is when the seawall’s base no longer extends far enough into the soil, as a result of tidal erosion pushing sand fill out of the bottom of the wall. In that case, the bottom of the wall needs to be extended by adding pilings to the front of the wall and pouring concrete to form a new edge.
These aren’t repairs you can handle on your own. Seawalls Unlimited is a crew of professionals who have been installing and maintaining retaining walls in McHenry, IL and the greater Chicago area for years. If you have any questions about seawall repairs or any other aspect of retaining walls, just give us a call. We’ll assess your land and do our best to give you the service you deserve.