A scientific study of ways to control pollution and restore lower Malibu Creek and Lagoon offers possible solutions to the long-running controversy among environmentalists, surfers and creekside residents.
Along with targeting potential restoration sites, the Lower Malibu Creek and Lagoon Restoration study suggests using “eco-rafts” and chemicals to reduce excess nutrients and constructing a weir, an outfall pipe or a new route for the creek to control the water level in the lagoon, according to professor Richard Ambrose, director of the environmental science and engineering program at UCLA.
“There are no easy solutions [to controlling the water level in the lagoon],” Ambrose stressed. Instead of remaining low and salty, the water is high and more like fresh water, which is harmful to plants and animals in the lagoon and backs up nearby septic systems, he explained.
Lagoon water levels become unnaturally high in summer because of increased development in the upper Malibu Creek watershed, which includes Calabasas, Agoura Hills, Westlake Village and a small portion of Thousand Oaks, according to an already completed report from the California State Coastal Conservancy, which helped to fund the study.
When the water level rises, the sandbar at the mouth of the lagoon is breached, and polluted water from the upper watershed and from septic system failures flows out into the Santa Monica Bay, according to the conservancy report.
One option the study considers is to build a weir, a “little dam” that can be adjusted to a certain height, Ambrose said. While some of the water would be kept within the lagoon, the weir would be set at such a level that excess water would spill over its wall and into the ocean.
Another possibility is a pipeline that might pump water out of the lagoon during summer, Ambrose added. It’s an effective solution but expensive to run and to maintain, he cautioned. Also, pumping water directly into the bay would be controversial, especially among surfers, he said.
Bypassing the lagoon by rerouting the creek is an alternative, whereby water from the creek would be “shunted around,” but “that’s not likely to happen” because the engineering is too complicated and expensive, Ambrose said.
“Nutrients [that stimulate algal blooms] are going to be tough,” Ambrose admitted. The study will recommend both “source reduction,” from creekside septic systems and the Tapia Reclamation Facility, and treating the water with chemicals and biology such as “eco-rafts,” floating bales that suck nutrients out of the water.
“Decisions about what to do depend on a lot of things outside our control,” Ambrose said. For instance, “How much do Malibu residents want to pay?”
The cost for restoration depends in part on what properties the city is willing to purchase. The study, “ignoring ownership issues,” concludes that the lagoon has been “hugely reduced in size,” and suggests some vacant property might be turned back into a salt marsh. The Chili Cook-Off site at Webb Way and Civic Center Way “is not a good area for a salt marsh but it’s good for other types of wetlands,” Ambrose said.
The area between the Civic Center and the creek “is possible for treating waste water or storm water runoff,” according to Ambrose. Another option is creating a bird nesting island on public land by the Adamson House on the east side of the lagoon.
The final draft of the $280,000 study — $40,000 contributed by Malibu — is expected to be released before Oct. 20, when the multi-agency Malibu Task Force is scheduled to meet.