By Karl Bremer, Versa-Lok Retaining Wall Systems

The stingray exhibit at the Milwaukee County Zoo features a temporary pool, which holds 10,000 ?EUR??,,????'??? 15,000 gallons of water. Versa-Lok products were used to construct the pool that was built on a concrete floor and had to be removable after the exhibit closed.

Versa-Lok retaining walls have held back a lot of earth, but a project at the Milwaukee County Zoo is the first time one of their walls has ever held up a pool full of stingrays.

Joe Kresl, owner of Hawks Nursery in Wauwatosa, Wis., has been involved with the Milwaukee County Zoo for many years and currently is president of the Zoological Society of Milwaukee County. When the zoo was planning to build a lagoon to hold a temporary exhibit of stingrays, he recalls, ?EUR??,,????'??We got called into the project by the company who was putting the exhibit together.?EUR??,,????'??

The exhibit was to feature a 10,000 – 15,000 gallon pool built on a concrete floor, but it had to be removable.

?EUR??,,????'??We do pools all the time, but this is the first time we ever did an above-ground pool?EUR??,,????'??+or a temporary one,?EUR??,,????'?? says Kresl. ?EUR??,,????'??But it wasn?EUR??,,????'???t all that different from what we usually build underground.?EUR??,,????'??

The wall of the stingray pool is three courses tall. To ensure its stability, the wall units were glued together using concrete adhesive in addition to a top-pinning connection system. The nature of the project limited its construction to approximately 2-feet-tall.

A curvaceous retaining wall was built for the perimeter of the pool. ?EUR??,,????'??The pool itself has a rubber membrane much like roofing material,?EUR??,,????'?? said Kresl. ?EUR??,,????'??It goes on the floor and is wrapped up the inside of the wall and over the top. Then we glued caps in place on top of it.?EUR??,,????'??

A curved form was installed along the inside bottom to keep the membrane lining from getting pinched between the wall and floor as well as to keep the full weight of the water from pushing laterally on the wall.

According to Keith Miller, an engineer with Versa-Lok, ?EUR??,,????'??The basic stability of a block wall with water behind it limits its construction to about 2 feet tall.?EUR??,,????'?? ?EUR??,,????'??Although water is lighter than soil, water has no strength, so all the weight of the water is pushing on the wall.?EUR??,,????'??

A smaller, upper pool was built featuring palms, ferns, boulders and a waterfall that cascades into the larger pool below. A curved retaining wall was built for the perimeter of the pool with a rubber membrane lining the bottom. The membrane is wrapped up inside of the wall and over the top. Caps were then glued in place on top of it.

The lagoon wall is three courses tall. To ensure better stability, the wall units were glued together using concrete adhesive in addition to a top-pinning connection system.

?EUR??,,????'??We did that because little kids would be leaning over the edge into the pond,?EUR??,,????'?? notes Kresl. ?EUR??,,????'??It?EUR??,,????'???s a lot more sturdy than we imagined, even with thousands of people leaning on it and sitting on it.?EUR??,,????'?? A smaller upper pond built on one end features plants, boulders and a waterfall cascading into the lagoon. The outside of the wall is faced with a stucco-type product and textured with different types of leaves and shells to give it an ocean-bottom appearance. Miller cautioned that such a finish probably would suffer some degradation in an outdoor installation.

?EUR??,,????'??You could expect to see some cracking of the finish to occur due to freeze-thaw shifting.?EUR??,,????'??

The Sting Ray Lagoon was stocked with spotted rays and Sea of Cortez rays and was the centerpiece of the zoo?EUR??,,????'???s exhibit on coral reefs of the Caribbean and South America. It was wildly popular, drawing over 365,000 visitors during its four-month run during summer 2005. So popular, in fact, that the ?EUR??,,????'??temporary?EUR??,,????'?? pool now is being left intact so the exhibit can return in 2007.

?EUR??,,????'??After building this one,?EUR??,,????'?? concludes Kresl, ?EUR??,,????'??we realized something like this could be built on a permanent basis.

This type of pool could actually be constructed as a fountain in someone?EUR??,,????'???s back yard or at a commercial business.?EUR??,,????'??

Bend Industries of West Bend, Wis., donated the products for the project and Hawks Nursery donated some of the labor.

Karl Bremer is a communications specialist with VERSA-LOK Retaining Wall Systems in Oakdale, MN. www.versa-lok.com