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The Rains Are Coming—Are Your Street-side Basin Inlets Ready or Clogged?

By Brad Lancaster

Like much of the country, we are in a record drought with record heat that is drying us out even more; stressing many shade plants, and threatening our cooling soil-carbon sponges—so we should be doing all we can to capture and hold on to cooling, life-enhancing moisture.

But even as the summer rains have begun in my home of Tucson, Arizona; many people who have installed passive street-runoff harvesting earthworks are NOT ready to receive that free water because their basin inlets are clogged!

Are YOU ready or clogged?

BAD. Note how the street-side tree basin’s stormwater inlet—a curb core in the street curb—is clogged with debris as is the street gutter. Fix this! Photo: Brad Lancaster
GOOD. Note how the street-side tree basin’s stormwater inlet—a curb core in the street curb—has now been cleared of debris, along with the street gutter. This was easily done with a shovel.
Photo: Brad Lancaster
GOOD, but note what was previously BAD on the basin-side of the street curb inlet. The concrete curb is stained darker from the dirt that was removed to prepare the basin to receive the coming rains—there is now at least a 2-inch (50-mm) drop from the bottom of the street-curb core hole (or in another case could be a curb cut) to the top of the soil (or mulch) in the basin. This way, the flow of the in-coming water will speed up, NOT slow down. So, sediment carried by the in-coming water will flow through, instead of settling out and clogging the inlet.
Photo: Brad Lancaster
A well-built and planted street-side basin with cleared inlet and street gutter efficiently harvesting copious amounts of runoff.
Photo: Brad Lancaster

More important points:

  • Water flows downhill, so make sure the elevation of the entire bottom of your street-side basin (and the surface of any mulch within it) is well-below the street gutter and inlet elevation. The deeper the basin the more water you can collect.
  • See here for important elevation and slope relationships within street-side basins, and tips on how you can expand their capacity.
  • Observe your street-side basin inlets during and after rains, and throughout the rainy season. Clean as necessary.
Curb core partially clogged by asphalt after a repaving project. Photo: Brad Lancaster
Clog now cleared. The City did not unclog the street-side water-harvesting basin inlets after multiple requests, so citizen activists fixed the problem by chipping away at the asphalt clogs with caliche digging bars (pointed steel digging bars). The chipped out asphalt pieces were then placed and compressed on the downstream side (right hand side in this case) of the curb core to encourage more flow through the core hole to the basin.
Photo: Brad Lancaster

For more

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Neighborhood Food ForestryPassive SystemsStormwater & Street Runoff Harvesting