Why geotube installations fail, and what we do about each cause

What is true about the objection

The objection is short: a geotube will not last. Part of it is true.

A geotube is a large sleeve of woven geotextile. We fill it with a slurry of sand and water. The water drains out through the fabric and the sand stays inside. Sod covers it down to the water.

Sunlight on bare fabric is what ends a geotube. Covered by sand and sod, or under water, the fabric is out of the sun. So a tube fails where its fabric is left bare.

The City of Miramar installs geotubes on residential lake banks through its own program, and it tells its residents the same thing: a tube left exposed to the sun for a long time deteriorates and will eventually break.

One more part is true. Florida lakes drop every dry season, and a submerged tube can show for a while. That cannot be fully prevented.

The three ways a geotube fails

1. Bare fabric

Sod dies at the waterline, the fabric shows, and the sun does the rest.

Our answer: no fabric faces the sun on the day we finish, and we tell you what to watch for.

2. The wrong fill

The tube lets water through and holds sand. Pump clean sand and it packs solid. Pump lake muck and the fines wash out through the fabric, leaving hollows the tube settles into. The crew can hear it happen: the pump changes its note when it starts pulling silt.

Our answer: we pump from your lake when it is shallow enough and the bottom is clean sand. When the lake is deep (we will not dredge it deeper) or the bottom is silt, we truck in clean sand. That adds to the price, and the work goes faster.

3. A cut at the waterline

The top of the bank has plenty of sand over the tube, so a mower cannot hurt it. The face of the tube at the water’s edge does not. A landscaper’s edger, or a boat, can slice it, and a sliced tube loses its sand. It is rare, but it is real.

Our answer: a one-page guide for your landscaping crew and a walk-through at handover. Mow here, never edge there.

What covers the fabric: the build, from the water up

1. Base tube. It is set to a laser level. With sand and sod on top, the finished edge comes to about a foot.
2. Backfill tube. A second tube on top. Once it is full we cut it open, spread its sand into the slope, and fold the fabric back over the rounded edge of the base tube, the bullnose, so that no fabric is left facing the sun.
3. Graded sand. Shaped to match the existing bank.
4. Coconut erosion blanket. It holds the slope while the grass roots in.
5. Sod. From the water’s edge up to your lawn.

The build, with a drawing, is on the geotube page.

What published sources say about lifespan

We do not promise a number of years. Here is what the published sources say.

• A geotextile manufacturer. Propex states it plainly in its engineering bulletin: once a geotextile is covered, the potential for UV damage is removed.
• The data sheet of our fabric. The tube is made of Mirafi® FW404, a woven polypropylene fabric from Solmax (formerly TenCate). The manufacturer’s data sheet gives its UV resistance as 90% of strength kept after 500 hours in a laboratory test. That figure is a laboratory comparison between fabrics. It says nothing about years in service.
• A city that installs geotubes. The City of Miramar states that they “normally last upwards of twenty (20) years if properly maintained”, and it requires residents to keep the tube covered with grass. That is our expectation too, under the same condition.
• The oldest example we can point to. It is not a pond tube. It is a line of large geotextile containers built into a dune at Atlantic City in the mid-1990s and covered with sand. Their distributor reports that the protected stretch performed as designed in Superstorm Sandy in 2012.

What to watch for at the waterline

The grass is the tube’s armor against the sun. On any geotube bank, look at the edge of the water.

• Fabric showing. If fabric ever shows, it should be covered again.
• A cut. A cut at the waterline from an edger or a boat is another way a geotube fails, so look for that too.
• Edging. Mowing on top is fine. Edging at the waterline is the one thing to stop.
• Low water. Where we expect the level to fall, we cover the submerged tube with a protective fabric, and the care guide tells your crew what to look for at the waterline.

The City of Miramar adds two rules for its residents: do not cut or perforate the tube, and do not plant hedges or trees in it.

When we would not recommend a geotube

Three things decide whether a geotube fits: the drop-off, the shelf and the water control structure. We check all three on the free site visit.

A tube needs a flat ledge under the water to sit on: about five feet wide and about six inches below the surface. We check it with a grade rod. If your lake has a structure that holds the water level steady, a geotube is a strong candidate.

We would not recommend a geotube in two cases:

• The level swings about two feet or more between the rainy and the dry season.
• There is no shelf and the drop-off runs past five or six feet. That is bulkhead or sheet-pile work, and we will quote it that way.

The other methods are compared in Geotubes vs. riprap vs. concrete mats.

What we put in writing

• Five-year workmanship warranty on what we build: the fill and placement of the tube, the stakes, the blanket and the laying of the sod.
• No handover until the sod has rooted. We water it until then, and we check it before you sign off.
• A walk-through with your landscaping crew at handover, and a one-page guide: mow on top, never edge at the waterline.
• What it does not cover: damage done by others after handover, such as an edger or a boat cutting the tube, or fabric left bare. After handover, watering and mowing are your landscaping contractor’s job.

Does a geotube repair need a permit?

Which rules apply depends on where the lake is. The South Broward Drainage District, for one, requires a district permit for any erosion restoration work, and lists geotubes among the methods used successfully in the district. We prepare and file the paperwork, and the proposal says which permit your lake needs and how long it should take. More in our guide to permits for lake bank repair in Broward County.

Next step

The free site visit covers one lake, and we come within 7 days (usually sooner). A written proposal with a price range follows within 2 days of the visit. Most jobs fall between $50,000 and $500,000; what moves the price is in our guide to cost.