TreePeople’s L.A. Pilot Project Is Testing the Waters

Wouldn’t it have been great if we could have saved some of the rain that fell last winter to use in our gardens right now, when things are beginning to look a little parched?

Think of how happy the plants would be to get fresh, pure rainwater instead of municipal water, which often comes from sources high in mineral salts (such as the Colorado River).

Those salts cause the edges of the leaves on some plants to turn brown at this time of year, and they affect the health of plants in other ways too.

If we had our own backyard supplies, water companies would be happy because they’d have to find and store less water. Even flood control agencies would be tickled because any water saved on your property would not be surging down their over-taxed storm drains. Think of how much water simply rushes to the sea each winter.

That’s some of the thinking behind the TreePeople’s latest project garden on a typical urban lot in South-Central Los Angeles.

TreePeople has designed and built a landscape that captures and saves rainwater.

A panel of experts came up with the goals and ideas, engineers did the planning and design and two designer-contractors--Karen Bragg and Bob Cornell--made it all work.

Some of the water coming off the roof is stored on the property in huge cisterns, and some of the water is contained by berms or captured in dry wells, where it can slowly soak into the ground. In combination, these systems let very little rainfall leave the property.

In a city where so much of the land is paved or roofed over and where gutters run freely, TreePeople’s ideas make good sense.

A number of interested agencies and foundations sponsored the project, including the city of Los Angeles, the Department of Water and Power, the U.S. Forest Service, the Environmental Protection Agency, the Metropolitan Water Department and the L.A. County Department of Public Works.

TreePeople estimate that retrofitting a typical Los Angeles garden to save and store water would cost in the neighborhood of $7,500 to $15,000.

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Andy Lipkis of TreePeople thinks that much of this cost might be born by such public agencies as water departments and flood control districts.

Lipkis believes that retrofitting gardens might be cheaper than building new drainage systems, dams and aqueducts.

In Australia and in several island countries, individuals routinely capture and save rainwater, so it is not a new idea, though the flood control aspects of this project are a new twist, and this is the first system I’ve seen that saves rainwater exclusively for the garden.

The heart of the water-storing system is two cisterns that collect water from the roof like giant rain barrels. Together they hold about 3,200 gallons.

The cisterns take up very little room in the garden because most of their bulk is underground. Above ground, each is 2 feet wide, 5 feet tall and 10 feet long. This above-ground portion could do double-duty as a garden wall. The project’s designers figure that they could line up along one property line to store about 20,000 gallons.

That’s far short of the 60,000 to 70,000 gallons a year used to water the typical garden in city of Los Angeles, but it would make a nice dent.

Below ground, the cisterns are 10 feet long, but each becomes 4 feet wide and extends 6 feet below ground.

The tanks are made of recycled polypropylene with a fiberglass coating. When I saw them, TreePeople had not yet figured out how to put a finish coat on the fiberglass, so the containers looked a little raw.

Before the water gets to the cisterns, it runs though an elementary filter that takes out much of the particulate matter that settles on roofs, from brake lining dust to pigeon droppings.

From the interconnected tanks, the water is pumped directly into the automatic irrigation system.

The system was completed only in May but managed to “grab 300 gallons” from the last freak storm, which dropped about two inches of rain on May 12 and 13, according to Lipkis.

For the pilot project, the two tanks drain only a quarter of the roof (about 250 square feet). The water can also be pumped to the street if the cisterns are too full and a big storm is approaching.

In TreePeople’s pilot project, the rest of the water from roof downspouts is directed down “swales,” gentle 2% slopes that drain water away from the house but at such a slow rate that it has time to soak into the soil.

Rainwater that soaks into the ground is almost as useful as water that is saved for summer. It thoroughly waters trees and other deep-rooted plants and it eventually ends up as part of our ground-water supply. Plenty of water running down through the soil also pushes out those harmful salts that tend to accumulate from fertilizers and municipal irrigation water.

The swales are covered with either lawn grass or bark mulch, and they all slope toward the front lawn, where the water is temporarily trapped behind low berms.

In the middle of one lawn in the pilot project there is a dry well, which is simply a big hole filled with gravel where water can collect and soak into the soil. The dry well is hardly visible, only a small, round drain hole shows.

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The lawns would become like little lakes during a storm, holding water behind the low, mounded berms. If the water got too deep, an overflow would let it run to the street.

Rain falling on the driveway is also sent to these lawn “lakes” and the dry well.

In nearly rainless years (which is what’s being predicted for the coming winter), every drop that gets into the ground counts.

Last winter and spring, it was quite clear in most gardens how helpful deep, soaking rains can be. Some of the clever devices in this experimental garden make any rain a soaking rain, while the others stash water away for those rainless days and months.