Wednesday, Dec. 17, 2008 | Last year, almost 1 percent of the city of San Diego’s drinking water supply — 635 million gallons — got sprayed on freeway shoulders to keep plants green.
The water was pumped hundreds of miles from Northern California and the Colorado River, pushed through a vast system of pumps and aqueducts and treated to be safe for human consumption. Then CalTrans bought it from the city for $2.2 million and sprinkled it on medians and shoulders to accomplish what, in this semi-arid region, Mother Nature couldn’t.
CalTrans says it uses the water to irrigate plants that beautify highways, block views into private homes, create buffers in medians, control erosion and provide fire protection. Many of the plants are drought-tolerant, requiring less water than others, but they would not survive without irrigation.
The transportation agency doesn’t use the water it buys as efficiently as it could. The agency doesn’t have smart irrigation controls on 75 percent of its roadside sprinklers. Those would allow one person to turn sprinklers on or off with the touch of a button on a central computer.
Instead, many sprinklers are manually programmed to water three times a week in summer, twice a week in spring and fall and once a week in winter. Because they’re not easily adjustable, the sprinklers can operate even during rainstorms unless CalTrans staff shut them off, one-by-one. The agency sends its workers to turn them off when more than one-quarter of an inch of rain is forecast, said Hayden Manning, a CalTrans spokesman.
As the region’s water supply gets restricted, attention is increasingly turning to CalTrans’ use of drinking water for maintaining roadside landscaping. The region’s two major supplies are crimped by drought and endangered species protections. Water agencies say residents must save water by reducing outdoor irrigation. And few in the region pour more water on plants than CalTrans. It’s the city of San Diego’s fourth-largest user; it’s the top user in the Helix Water District, which serves La Mesa.