Channeling the raindrops
MY frontyard looked like a storybook American home -- a lavender-lined front walk, two oaks, grass paths, a driveway to the side -- but it was a textbook polluter. The gutter fed directly to the concrete driveway. This swept rain straight from the gutter, onto the driveway, into the street.
Rain, it turns out, is only pure until it hits the street. The minute it rolls off our properties, it becomes what engineers call storm water -- a toxic soup of water, pesticides, fertilizers, motor oil, cigarette butts, fast-food wrappers, batteries and dog droppings. During a rainy day, as much as 10 billion gallons of this urban concoction floods out of 65 outfalls into the Santa Monica and San Pedro bays, says Joyce Amaro from the City of Los Angeles Stormwater Program.It could not be a more complete perversion of the natural cycle, in which April showers feed lakes and springs, and are absorbed into the groundwater supply, or as the watery intelligentsia prefer, the aquifer.
I had been gardening in central Los Angeles and going swimming at Santa Monica beaches for six years before I made the connection. It was July 2004. I was standing before Garden/garden, a pair of test gardens that landscape designer Susanne Jett and City of Santa Monica Water Resources specialist Bob Galbreath had created to demonstrate the difference between a conventional frontyard with lawn, roses and concrete paving and a conservationist model with native plants and plumbed to capture rainfall. Jett began talking about something called “percolation pits,” Galbreath about how keeping rain on the property could capture the water in its pure state, feed plants and help save our coastline. I took notes, nodded appreciatively, went home and put my head in my hands.
And so 2005 became the year of chasing rain. As Southern California received 37 inches of rainfall -- the second heaviest drenching in more than a century -- and more than 20,000 gallons of rainfall poured off the front pitch of my roof alone, I began digging trenches to direct the water from the downspout, away from the driveway in channels around flowerbeds. This captured some water but also created a mud channel, adding soil to the runoff. When the skies cleared, the network of trenches amounted to a snaking, tripping hazard.
I studied the layout of Garden/garden to see if I could adapt it to my home. Its methods were so efficient that in a winter month, Galbreath’s and Jett’s model garden used 1 gallon of water, the conventional one next to it 8,000. “Eight thousand to 1 isn’t a bad ratio,” said Galbreath.
But it wouldn’t work for me: Its methods are perfect for unplanted sites but challenging for existing gardens with established trees. The water feeds through downspouts into submerged percolation pits. I had already planted oaks where the pits would theoretically go and their root zones would be badly damaged.
Other solutions recommended by the city of Santa Monica, the environmental group TreePeople and the Los Angeles storm water programs were interesting but not quite right either. Cisterns -- tanks by the downspouts -- were ugly, held only a fraction of what rolled off the roof, and I worried about mosquitoes. Basic advice to buy extensions for the drain pipes and redirect gutter water into planted areas was good and I used it in the backyard. Out front, however, the impromptu trenches were a mess.
One solution would have been to break up the driveway, creating a permeable quilt of broken stone. Or maybe the twin strips of concrete that garden designers call a “Hollywood drive”? No, the car could be moved to the street, the rainwater couldn’t. The driveway had to go. While I was at it, the front walk could also be broken up into a water-permeable path of pavers.
This required a landscaper. I chose Nick Tan, a specialist in native landscapes at the Eagle Rock company Urban Organics. I know Nick and thought his work the perfect mix of groovy and profound. My commission: zero runoff, near zero irrigation. He suggested terracing built around a dry streambed that could fill, and then gradually absorb the water.
On the first day, Nick showed up with a friend, another landscaper, Marco Barrantes, who has a master’s degree in planning from UC Berkeley and a unique flair for turning broken concrete into dry-stone terracing. They began by renting a jackhammer and a compressor so that it had the power to break but not shatter the concrete. They then sorted out reusable slabs of concrete from the rubble, and scraped up the latter to take to the dump. The viable pieces were laid out like a huge jigsaw puzzle so that they could be reused in dry-stone walls and new pathways.
Step two was creating a winding series of creeks to channel the water. Though these appear to be from 6-inches to 2-feet deep in the finished landscape, they actually run 1 to 2 feet deeper and have been refilled with gravel to create percolation traps. The key differences between these and the buried infiltration pits in the Santa Monica garden is that they are not hollow tanks, but snaking waterways with deep gravel beds designed to hold water while respecting the root zones of the oaks. Nick and Marco then scattered earth and river rocks over the gravel to give the pits the appearance of a streambed.
The strip where the solid concrete front walk had once been was cleared and dug 6 inches below grade, then lined with gravel and topped with a patchwork of the concrete pieces. Sand was then used to fill in the cracks. The gravel underlay would allow free drainage of water that percolated through the cracks. New paths of the same design swept around the western side of the property to create an elegant border to the adjoining lawn.
Out on the parkway, Nick rebuilt the curb-break and removed the grass and enough earth to create a 3-inch depression. This meant that whatever water ran off the main garden would be caught in this long, depressed bed. After planting, he mulched the parkway with a thick layer of pea gravel to bring it back up to grade. Important note: Do not use wood mulch on parkways. It floats and easily washes away.
Next came trips to nurseries that stocked native plants. Landscaped with the right plants, this garden would not only trap all the winter water, but also thrive without summer irrigation, other than the occasional spritz to rinse off smog. For the streambed portions, Nick chose riparian species: sedges, rush and bunch grass. We then planted the banks above with irises, coral bells, artemisia, manzanita, ceanothus, salvias and a Matilija poppy. To provide quick, lush cover come spring, I scattered poppy seeds.
The construction job took three weeks, cost $4,500 in labor, $1,000 in gravel and river rock and $500 in plant materials. Total cost: $6,000. For a do-it-yourself homeowner, it was a perfectly achievable task that would have cost more like $1,500.
What had been a source of water pollution was now a model of water conservation -- provided that it worked. Proof would only come when it rained. On Jan. 2, 3 inches of rain fell and the fourth pit did not overflow. Nick woke up on the third of January to an e-mail basket full of digital photographs showing how the rain trap that he designed and built for me had crested but not overflowed. Last week, as 2 inches of rain washed through Los Angeles, the gutter spill only made the third trench -- again, no runoff.
The relief was unquantifiable. For a gardener, there is no higher achievement than to manage nature without insulting it. There is nothing more frustrating than seeing spring showers become storm water, nothing more heartbreaking than to realize that the design of one’s garden is helping to poison our bays, and I can say from experience, nothing more gratifying than finally being able to say: The rain that falls on my property stays on my property.
Emily Green can be reached at firstname.lastname@example.org
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Most cities in Southern California leave the managing of rainfall in developed regions to their sewer engineers. Not so Santa Monica, where Neal Shapiro, urban runoff management coordinator, has developed one of the most aggressive public education programs for homeowners in the country. For those interested in shopping for a solution that fits their property, Santa Monica is the place to start.
Garden/garden is at 1724 Pearl St., Santa Monica. Park in a city lot and take a bus. For more information from Santa Monica, go to: santa-monica.org/epd/residents/UrbanRunoff/urban.htm.
The Virginia Avenue Project will be giving a tour of sustainable gardens in Santa Monica from 10 a.m. to 4 p.m. April 29. Most have water infiltration pit systems. Advance tickets, $30; seniors or per person rate for groups of four or more, $25; Tickets at the door, $35. 12 and younger, free. Call (310) 264-4224, e-mail email@example.com or go to www.virginiaavenueproject.org.
TreePeople offers quarterly tours of its South Los Angeles Rain-Harvesting Home. The next tour will be from noon to 1 p.m. May 20. Admission is free, but space is limited. Reservations are required. For information, call David O’Donnell, (818) 623-4884 or e-mail firstname.lastname@example.org. This autumn, the organization will open the La Kretz Urban Watershed Garden at Coldwater Canyon Park. For information, go to www.treepeople.org.
-- Emily Green