Frequently asked questions about sand slit drainage
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Q. Do the channels eventually fill with material from the surrounding soil?
A. Examination of older systems indicates that silting is not a problem. To our knowledge, no systems have ever failed because the channels filled with silt or clay and could no longer conduct water. Most water enters the channels from the surface, not the surrounding soil. Particle size differences limit the lateral movement of water from the native soil into the channels. This also limits the movement of the fines suspended in the water. Some industry experts have further suggested that particle bridging serves to block the lateral movement of fines from the soil to the sand.
Q. Do roots ever clog the channels?
A. There is no observed evidence that roots have ever created a problem in the channels. Roots will grow into the channels, but not to the extent that they restrict the movement of water through the channels.
Q. Does the Sand Channel system create additional runoff?
A. No. Runoff originates from two principal sources: natural precipitation and irrigation. During a significant rain event or heavy irrigation, if water falls on the field faster than it can infiltrate the soil, surface runoff will occur. When a sand channel drainage system is installed, much of the water will make its way through the system; the balance remains at the surface and is removed as runoff. The total discharge remains basically the same.
Q. Does the Sand Channel system increase the risk of contamination from fertilizers or pesticides?
A. No. In fact, in many cases, the system will actually help to reduce the potential for contamination. Contamination occurs as a result of two processes - surface runoff and leaching.
- The system is designed to minimize surface runoff, so it should actually reduce problems from this source. Water that enters the system will pass through the sand in the channels, which will act as a quasi filter/scrubber to help remove some contaminants before they reach a water source.
- For a couple of reasons, the system should also help to reduce the level of contaminants that leach into ground water sources. First, most users adjust their irrigation practices, to capitalize on the system's ability to deliver water deep in the root zone. They reduce the amount of water applied during each irrigation cycle, but increase the frequency of the cycles, to apply the same amount of water. The net result is that the soil in the root zone rarely gets beyond field capacity; meaning that there is little if any excess water available to carry contaminants into ground water supplies. Fertilizers and pesticides will stay in the root zone, where they are available to the plants. Second, USGA sponsored studies have shown that pesticides applied to turf are much less likely to cause contamination problems than pesticides applied to bare soil. This is due to the intense microbial action associated with healthy turf. Since Sand Channel Drainage is known to contribute to healthy turf, it also contributes to a reduced risk of contamination.
Q. Are the channels visible through the turf?
A. No. After the system is installed, turf should completely cover the channels and hide them from view. Depending on the time of year and the type of installation, this may take a few weeks. Specifically, in situations where the channels are created by cutting through existing turf, the channels will be visible until new turf has established itself over the channels. Once turf has covered the channels, it is possible for "striping" to occur in the form of subtle color differences between the turf immediately over the channels and the turf on the surrounding soil. Striping can be controlled by aerifying and top-dressing to create more uniformity between the channels and the surrounding soil. Close monitoring and management of irrigation schedules will also help. On a comparative note, Sand Channel drainage systems are much less prone to striping than most competitive systems. Other slit drainage systems use wider channels - some as wide as 2 inches, or more. These wider channels have little impact on performance, but take much longer to heal and are much more prone to striping than the 1" channels used in our systems.
Q. Does the system require any special maintenance?
A. No. The system doesn't require any maintenance beyond what is normally needed to sustain a healthy stand of turf. Two maintenance procedures impact the performance of the system: aerifying and top-dressing. Ideally, users should aerify and top-dress at least a couple of times per year. Top-dressing improves the lateral movement of water at the surface, helping it reach the areas above the channels. Aerifying promotes good infiltration - moving water from the surface into the network of channels. When aerifying, hollow tines are preferred, but solid tines are also acceptable.
Q. Are there any limitations when it comes to aerifying?
A. Yes. Aerifying with deep tines could potentially damage the existing irrigation and drainage pipes. Also, it is inadvisable to use a machine that is designed to "break" or "fracture" the soil. The "kicking action" of certain aerifiers can move soil into the channels, thereby reducing their efficiency. Our recommendation is to aerify to a depth of 3"- 5", and to use a machine that inserts and extracts the tines or knife blades without creating major displacement. We are comfortable recommending a shallower, less aggressive form of aerification, because the network of channels accomplishes many of the objectives of deep-tine aerifying. The channels reduce compaction and provide a way for water, air and nutrients to move deeper into the soil profile. Consequently, once the drainage system is in place, the basic reasons for aerifying are limited to controlling compaction in the near-surface area and to maintaining good infiltration rates.