Maintenance Committee: Underground Water

We live in a large watershed where surface and underground water flow from the Santa Ana Mountains to the ocean. Most of the surface water flows in San Juan Creek to the Pacific Ocean at Doheny State Beach, while the underground water flows under Dana Point and its surroundings.
This underground water is mostly at significant depths, but some is flowing relatively close to the surface. Of concern to NSCA is water that flows just below the base material under our asphalt streets and concrete sidewalks and driveways. This ground water can and has caused serious damage to NSCA infrastructure over the years. When asphalt is exposed to water for an extended time, the solvent nature of water breaks down the asphalt leading to cracks, spalling and potholes.
On lower Manta Court there was an area where the gutters never dried and there was a perpetually wet area in the nearby street surface. This was determined to be caused by the capillary action of underground water. Capillary action refers to the ability of a liquid to flow in narrow spaces in opposition to the force of gravity. The Maintenance Committee decided that the best solution was to install a French drain. These have been used throughout the NSCA community over the years.
French drains are named after a 19th century American who developed a system to drain water from higher to lower areas. The earliest forms of French drains were simple ditches filled with gravel. Our drain used trenches to intercept the ground water with a layer of coarse gravel at the trench bottom. On this was placed a 4-inch diameter perforated pipe and another layer of gravel. The pipe and gravel were wrapped in a specialized geotextile designed to keep fine materials from entering the system, and the pipe was connected to a nearby storm drain. Several inches of gravel were put on top of the wrapped pipe, and the drain was finished with new surface asphalt.
At Manta Court, our successful, modern design, French drain was completed in March. Now the gutters are dry and the wet spot is gone.
—Bob Gregg

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