By Markus Winkler and Karen J. Williams
Editor’s note: This is the second in a two-part Landscape Techniques feature on planning, designing, and building a natural swimming pool (NSP). The first article, ‘Designing A Rustic Backyard Escape’ appeared in Pool & Spa Marketing’s February issue.
After finalizing the plans and design with the clients for the Okanagan gold rush project, the next step was a massive cleanup and preparation of the land where this approximately 7.74 m2 (12,000 sf) backyard feature would be created. The general plan outlined the gold rush cabin, outdoor kitchen structure, putting green, and the natural swimming pool (NSP)/pond. The land preparation had to be performed in an environmentally sensitive manner not only to be less invasive in general, but also to try and save as many of the existing plants, shrubs, and trees as possible to incorporate them into the final landscape plans.
In the heat of the moment
During the cleanup process, the weather became warmer and quite dry, which made it necessary to start excavating the land sooner rather than later. During the decision process of what plant life could be saved and re-used, a 36.5-m (120-ft) tree needed to be prepared for the construction phase and the eventual changes in the yard.
To do this, an arborist was hired to properly prepare the tree by trimming it and analyzing its root structure not only to protect the tree during the construction process, but also to prepare it for a long future after the NSP was constructed.
Before excavation commenced, it was documented that within a very short period of time, water started collecting, which eventually amounted to approximately 0.3 m (1 ft) sitting on the proposed area where the NSP was to be built, despite the fact the drier weather had come.
At this point, the crew had not yet broken ground so a test dig was performed to determine the structure of the underground area as well as the possible respective water flow. At this point it became clear that the crew would be forced to work with an extensive dewatering process to contain the water and direct it into the storm sewer to facilitate a proper excavation. The company hired to handle the dewatering process during this project were proven professionals in their field with references to the Kelowna H2O public swimming facility. For this project, the dewatering process took place 24-hours a day, which meant the team had to work on the filtration and the swim zone areas at the same time. This is not always the case on each project; therefore, 24 well points, located 4.8-m (16-ft) deep with a 6.1-m (20-ft) deep manhole was needed to take the pressure off the entire construction area. This drainage system was installed beneath the NSPs’ membrane.
Figuring out the filtration pond
Before executing the filtration field in the filtration pond, another test was performed with regards to the water quality to ensure the calculation of the final filtration depth remained accurate and was still within the quality range of the original design. These test results, which are done for each project, cost in the range of a few hundred dollars, depending upon the area, and are well worth the investment.
The results for this test took approximately a week to receive; this timeline again is dependent upon each area, so it is best to conduct this test as early as possible to avoid any construction delays. In cases where the water quality has changed, modifications can take place to avoid unnecessary challenges at a later date. The test for this project came back with the identical values as in previous tests, which allowed the project to be foreseen in a balanced environment.