A study designed to pinpoint sources of pollution in Malibu Lagoon shows some surprising conclusions. This second phase of a study, mandated by the state Regional Water Quality Control Board and performed by URS Greiner Woodward Clyde, monitored levels of indicator microorganisms, nutrients and other wastewater markers at 23 sites along the beach, the lagoon and creek.
The study, paid for out of the city’s general fund at about $80,000, was released in April and contains lab analysis of water samples of surface water in the surf zone, groundwater and sediments at locations in and near Malibu Lagoon and Creek and along the beachfront of Malibu Colony and Malibu State Beach.
City Engineer Rick Morgan said there were some surprises for the RWQCB, which has assumed septic systems to be the primary pollution source, and Malibu residents, who have long blamed treated effluent from the Tapia Wastewater Treatment Plant upstream.
Neither of these, however, appear to be the primary source.
“The most dramatic finding is that storm drains are regular sources of contamination with high fecal coliform counts,” Morgan said. Sediment samples collected at the outfall of three storm drains that empty into the lagoon were shown to contribute significant bacteriological contamination to the lagoon.
The good news is that storm drain contamination is treatable. The city’s new “stormceptor” disinfection system was installed in May at Storm Drain No. 3 (formerly known as “the mystery drain”), which collects runoff from Malibu Colony Plaza, Malibu Road and the golf course and enters the lagoon just north of the Colony.
“I’m seeking funding to do the other two storm drains,” Morgan said.
MBAS (surficant) levels detected in samples collected at the storm drains do not provide evidence that wastewater from household or commercial septic systems are probable sources, the report states. Sources for the nutrient- and microbial-impacted water could be from excessively fertilized fields, surface water run-off containing animal feces and rinsing off of areas where septic leachate has daylighted due to a poorly operating system.
The other significant element of the study is the connection between water levels in the lagoon and groundwater levels when the lagoon sand berm is breached, leading Morgan to conclude that ongoing water-level management may be key to controlling water quality.
Morgan says they learned a lot from Phase I (formerly called “the dye study” and completed in June, 1999), which used a phage, or marker, to try to detect a hydraulic connection between septic leach fields and groundwater in the Cross Creek shopping center.
“As long as there was 1-1/2 feet separating the leach field from the groundwater, the soils filtered out pathogens,” Morgan said. “In this study, we found higher contamination in the ground water adjacent to the creek near the shopping center and near the Colony during a breach of the berm when the flow draws. When the berm was open, the levels went up and down with the tide.
“The difference was only about seven feet. It wasn’t real dramatic,” Morgan said. “That shows we need to manage the lagoon water levels.”
When lagoon levels begin to rise, measured amounts of surface water could be released onto the beach–where exposure to the sun would kill pathogens–reducing pressure on septic and groundwater levels before a full breach could occur and contaminate the surf zone.
The RWQCB has not commented on the findings since the study was released in April, even though there was considerable pressure to complete the project quickly. Executive Officer Dennis Dickerson said Monday that his staff has not yet given the board any information regarding the study, and that report was probably with the Santa Monica Bay Restoration Project.
“At our meeting on Aug. 31, we will be doing a comprehensive look at Malibu on a number of issues, and that will be one of them,” Dickerson said. “There are waste discharge permit requirements [for the City Hall site]. The city needs to obtain one.”
There is still some disagreement, however, over whether the city or Los Angeles County, which owns the property, is responsible for obtaining the permit.
Water officials had sued the city last year because they said Malibu hadn’t submitted its plan for Phase II promptly. The city said it was waiting for the results of a UCLA study on the entire watershed before designing its own plan.
The RWQCB is now asking for tests of the groundwater around City Hall, Morgan said. Phase I of the study reported pathogen transport quickly traveled 10 feet from contact, but nothing much was detected beyond that.
“What’s the chance of a pathogen getting from here [City Hall] all the way to the ocean?”