As the founder of Stonebridge Pond & Waterfall, I’m always thinking of ways to push the boundaries of design and craftsmanship and stretch my imagination beyond the ordinary. For this build, I combined a couple of thoughts I’ve been meditating on for several years.
First, I’d thought about the dark, cool depth of water in a typical bubbling urn fountain and wanted to supersize it. Second, digging in the limestone bedrock of Central Texas is always a challenge. Once all the effort has been spent excavating, filling in the entire space with Aqua Blox and gravel has often felt like a waste of energy.
So, why not capitalize on that deep, cool water with a structure made specifically for people to cool off and escape the dreadful summer heat? I had a vision for the project and was just waiting for the right clients to sell it to.
A Perfect Canvas
beautification phase.
As luck would have it, an existing client with a passion for native flora and fauna finally moved out of the city and into the Texas Hill Country. Their new property was the perfect canvas for something unique. The best part was that they gave me complete creative freedom to create a cool water natural plunge pool within their $100,000 budget. A lofty goal of creating a 6-foot-deep pool, broken excavator teeth and a hydraulic breaker rental made this dig especially time consuming. (And speaking of pushing the boundaries of what’s possible, our profit margin was slim on this one, too!)
Simplistically speaking, the project is basically a 5,000-gallon basin with a stone cistern in the middle and an 8-by-24-foot upflow wetland filter positioned on the backside. We used a Performance Pro external pump to power the recirculation and filtration system to keep the water crystal clear and the ecosystem well balanced. A small waterfall faces the picture windows of their kitchen and living areas, inviting all manner of wildlife into their field of view.
With the grade sloping away from the house, the excavation ended up about 7 feet down from the patio edge. The excavation footprint was about 25 by 35 feet, which allowed plenty of space for 150 large Aqua Blox stacked three tall. We tamped down the granite gravel to make the level surface, and a thin layer of sand and two layers of 16-ounce rock pad gave me that extra insurance I needed to feel comfortable with this build. The center trench accommodates a 3-inch plumbing return line, feeding the plunge pool and creating the upwelling sensation I wanted to capture. Extra care was taken to ensure that pipe was installed level and plumb. A vertical pipe was teed into it and used as the center of the compass for drawing the circle for the stone masonry layout.
The Masonry Circle
The masonry circle is the heart of the plunge pool project. The interior diameter of the masonry circle is 9 feet in diameter, and the exterior diameter is nearly 11 feet. A bib liner placed at the bottom ensures proper water retention. I decided to go with a double course of 4-by-6-inch sandstone chop blocks for both the inside and outside of the cistern. This decision wasn’t just about aesthetics; it provided strength and stability while also giving the structure a beautiful, natural look.
The through-stone ties helped bind the two sides together and created a thick, strong base to anchor the interior flagstone steps. The space between the walls is filled with rock chips and scraps, with every third course being fully grouted for extra strength and water retention. The recirculation basin and waterfall on the front side hides the exterior wall of the cistern as well as teh wetland filter on the back. The main focus remains on the beauty of the center of the center plunge pool itself.
Care was taken to determine the specific depth of each step for ingress and egress, which is also used for seating and standing. The lowest two steps are measured for the water level to fall right at the clients’ shoulder height. I actually had the clients stand in the hole while I held a tape measure, and we all had a good laugh, with his step an entire 12 inches deeper than hers. 2-inch PVC served as temporary support for the steps until more masonry courses were placed on top to pinch in the flagstone steps into place permanently. I took special care to round off the edges of the steps and grind them smooth to avoid sharp corners that could lead to injury.
Once the main plunge pool and basin were complete, it was time to tackle the filtration. I used a typical Aquascape wetland filter and back filled the hillside with soil from the excavation and yet another load of weathered limestone boulders.
Each time I try something new and ambitious, there’s always a lingering background worry of whether it’s all going to work. It’s a feeling that I think all builders, designers and craftsmen know well. This project was no different, but as with all my previous ventures, I had faith that the work would speak for itself.
Lessons Learned
I worried that the water pressure within the cistern would press too much out of the bib liner and not leave enough for the upwelling and waterfall, but sure enough, everything came together as planned. The upwelling sensation was exactly what I had hoped for, and the interior steps provided the perfect balance between form and function.
It’s always a relief when a project works out the way I envisioned — and even better when it surpasses expectations.
A particularly challenging but rewarding aspect of this project was creating the illusion that the water was coming from a dark, mysterious abyss. I wanted it reminiscent of a natural spring, welling up from the earth itself rather than artificially pumped. To achieve this, I built up a false floor about 5 to 6 feet deep, which I then capped with oversized flagstone. This created a visually striking contrast and gave the water that extra sense of depth.
In hindsight, 6 feet of depth was challenging, and perhaps unnecessarily so. A depth of 3 ½ to 4 feet could have provided the same cooling effect with significantly less time and effort required for installation. That would have resulted in a higher profit margin, too! Maybe next time I’ll dial it back a bit.
This project also reinforced an important lesson: embracing creative ideas is always worth the risk. Without pushing the envelope, I wouldn’t have these stunning photos or the valuable experiences now in my portfolio. Each project, each challenge, is a learning opportunity, and I already have more fun ideas for the next one.
About the Author
Eric Arntson a three-time winner of the Water Artisans of the Year contest, founded Stonebridge Landscape in 2003, with the goal of creating breathtaking outdoor spaces that make a lasting impression. His dedication to craftsmanship, simple flowing lines and use of natural material have informed his unique organic style of landscape design.
