How Does a Geomembrane Hold Up 18 Months After It Is Installed?

In April 2016, I wrote about what I learned watching a geomembrane installation at the World’s Fair Park Lake in Knoxville, Tennessee. Those lessons were fundamental, such as the importance of a stable and well-prepared subgrade, why you should minimize field seams and the ability to get a flexible geomembrane to fit a serpentine basin. Now, it is over 18 months later and I checked on the working installation and can offer five observations:

1. There are no leaks reported by the owner, the Knoxville Metro Building Commission. In spite of underwater connections and a layout that was somewhat complicated, all connections are secure.  That was a major priority for the installers.
2. The liner remains in place; no uplifting is occurring which would be the result of improperly prepared subgrade. The site was somewhat at a low point, surrounded by higher ground, and no springs or other water instructions had been noted in the past, so dirty subgrade would be the concern. With prefabrication, minimal field seams were necessary which would be a major potential source of leaks and subsequent uplift problems.
3. Perimeter battening is secure and has not been compromised by thermal expansion contraction of the membrane. The XR-5 geomembrane used in this installation has a negligible rate of thermal expansion contraction.
4. There is no evidence of chemical attack in the waterfall area, the point where water treatment chemicals, primarily solid and liquid chlorine-based products, are introduced.
5. Inspections are important. The Building Commission empties the pond about twice per  year, usually in the winter for cleaning and inspection. Also, the geomembrane installer returns for an inspection once per year.

A geomembrane represents an engineered alternative to natural materials, but like natural materials, there are lots of materials that will “work,” but often not many that will work properly. Consider the whole of the project along with the initial cost. This one is functioning well.

 
World’s Fair Park Lake, Knoxville TN, October 2016