An update of the Oxford Basin Improvement Project was presented at a meeting of the Marina Affairs Committee June 17th by Greg Jaquez, associate civil engineer with the Watershed Management Division of the Los Angeles County Department of Public Works.
The Marina Affairs Committee is a committee of the LAX Coastal Area Chamber of Commerce.
Jaquez said that the Watershed Management Division is relatively new in its organization, using a new approach of managing storm water not just as wastewater, but as a resource.
The formal name of the project is the Oxford Retention Basin Flood Protection and Multi-Use Enhancement Project, a title descriptive of everything the agency is attempting to do regarding flood protection and multi-use with the project, said Jaquez.
The Oxford Basin is part of the unincorporated area of Marina del Rey that is owned by Los Angeles County, and the Los Angeles County Flood Control District has rights on the parcel, he said. The project is estimated at just over $14 million. By September, a large general workshop/public outreach meeting will be held to develop some refinements of the concept, he said.
Jaquez said the focus of the project is for flood protection, operations and maintenance, water quality, aesthetics and recreation.
The tide gates and a culvert connect Oxford Basin to Basin E in the Marina. When storm water collects, the discharge goes out at low tide after a storm.
In the area of flood protection, the intent is to restore retention capacity of the Oxford Basin. After 40 years of operation, accumulated sediment has built up.
There are two storm drains off Washington Boulevard, one on the north end of the basin and one on the east end near Yvonne B. Burke Park (formerly Admiralty Park).
The storm drains have tide gates that are exit points to Basin E. Sediment contaminated from many years of runoff from the watershed drains into the Oxford Basin, said Jaquez.
Runoff is mostly from the City of Los Angeles to the north, several hundred acres in Venice, a portion from Culver City, and some of the California Department of Transportation (Caltrans) right-of-way. The county runoff drains into the basin after entering storm drains, he said.
Operations and maintenance is a concern, including trash cleanup and landscaping. An effort is under consideration to access the area to remove trash more easily by utilizing more modern devices on storm drain outlets and by adding a boat ramp for maintenance personnel to collect trash more easily.
Water quality is one of the biggest challenges — the Los Angeles Regional Water Quality Control Board administers water quality regulations that affect Marina del Rey — with impacts by bacteria and toxins, metals and organics identified as contaminants on Basins E, G and F, said Jaquez.
The project proposal is to address the installation of features in the Oxford Basin to help clean storm water runoff with an interchange of tidal flows into the basin during dry weather, letting out cleaner water from the basin than the water that came in, and excavating the sediment which is a major contributor of the discharge in Basin E, he said.
Jaquez said that a study will begin in the next few weeks to evaluate sediment and water quality, looking at different conditions, such as wet and dry, to get a better idea of what the problem is and how to treat it.
Another way to address the water quality is to put in some types of emergent traditional wetlands that would be planted in the bottom of Oxford Basin, he said.
Two tide gates and the construction of a berm-like structure would separate flows between the tide gates, allowing the tidal flows into one gate to circulate into the far back reaches of the basin and around the berm structure during dry weather, and flow in a circulatory manner in Basin E during dry weather, Jaquez said.
Water that is let into one gate would be released through the other gate through wetland features. This would help to absorb any contaminants, clarify the water, take up excess nutrients and algae, and expose the bacteria to the sun to cause it to die off, he said.
Another alternative would feature the same circulatory split between the tide gates, but instead, a wetland would be planted in the basin bottom to create a floating wetland island, complete with wetland plants having a root structure that would grow down into the water.
This would perform the same function as a wetland except that it would float, providing advantages such as lesser maintenance challenges, said Jaquez. This method is relatively new and shows promise, he said.
A third alternative would be to use the same floating wetland island with more of an open water scenario without the channelized berm structure splitting the water between tide gates. Wetland islands would be placed at various locations and a mechanical circulator in the middle of the water would create vertical overturning of the water, and cause it to circulate throughout the basin and throughout the wetland islands.
“We already have a treatment wetland along the Los Angeles River — the Dominguez Gap Wetlands — to treat diverting flows into the river,” Jaquez said.
Another optional feature would address water quality and maintenance at the east basin, where the two storm drains come in, by using a separate sedimentation forebay created through construction of a dam-like structure that would allow the inflow to come in during smaller storms, and slow down sediment and particulates, he said.
“This is important because the effect of sediment transfer, especially metals, is of concern. The water quality study over the next year should determine if that option is viable, and if so, may be part of the design,” he said.
“This alternative may effectively make the basin surface water area smaller on one side of the sediment barrier, but it would have a permanent pool of water on the other side of the barrier,” said Jaquez.
AESTHETICS, RECREATIONAL ENHANCEMENT, HABITAT AND LANDSCAPING —
The next component — aesthetics, recreational enhancement, habitat and landscaping — is also a challenge because there are many concerns from various stakeholders on how it could be done, he said.
Jaquez said questions of external visibility, whether or not to expand the potential habitat, and bird watching sensitivity toward bird species are important issues, and he expects a lot of community input at future public workshops on these issues.
After consultation with biologists, it was determined that certain types of trees should be removed, including the Myoporum laetum (also known as the Ngaio or mousehole tree), a native of New Zealand and considered extremely invasive. There will be select trees on the east end of the property and remaining landscape that is more friendly to birds, he said.
Public access, with some enhancements, possibly with a perimeter walking/jogging path around the property is also being considered. A perimeter fence is still required for security, Jaquez said.
The fence could be moved inward to make a walk/jog path available. Public outreach about how fencing coordinates with access needs and potential habitat will be also be solicited.
During the public comment period, Jim Fawcett, co-chair of the committee, said that the situation in the Oxford Basin is a “microcosm of what happens at the harbor entrance.”
He said that storms typically bring a lot of sediment that washes off the streets after eight months of a dry period — including brake linings and all the fine particles from vehicles that attach to sediment (metals, inorganic materials) — and the storm flow comes down Ballona Creek and hits the detached breakwater.
“When the water flow slows down, all the sediment settles. The harbor mouth is periodically dredged, and some of that sediment is contaminated and needs to be removed. It’s a natural process, happening in an arid climate every year,” Fawcett said.
“Here you have the advantage of building a wetland, which you can’t do at the harbor entrance,” he added.
Jaquez responded to a question about the odor from Oxford Basin, saying that even though there is a tidal inflow/outflow, the actual exchange is not complete and the stagnation combines with nutrient content in the water, allowing algae to bloom, along with decay and smell.
He said officials are seeking bids for scientific consultants to do bio-remediation work for the project. The goal is to use beneficial bacteria to consume the organic material, the source of the smell and clear up the algae problem, and officials hope to get a good sense of the effectiveness of bio-remediation.
In larger projects, sediment laden with lots of decaying organic material smells a lot worse when the basin is drained and exposed to air, and he said officials are concerned because they don’t want to have a project where they drain the basin, waiting for it to dry for mechanical excavation and having the smell create a big nuisance.
The use of bio-remediation to reduce the sludge content in the sediment is the answer to prepare for excavation, according to Jaquez.
One individual asked what land could flood in the area. Jaquez said that storm water runoff combined with high tides would cause flooding in areas upstream from the basin on the Venice side, with storm drains backing up. A local residential area near the Oxford Basin is also subject to flooding.
Beverly Moore, the executive director of the Marina del Rey Convention and Visitors Bureau, said that local business owners are happy about this project because it eradicates the visual blight that has been left to “fester” on the north border of the community.
Trash dumping, vans and campers proliferating in the area have given the impression that the community is not welcoming, Moore said. Tens of thousands of bicyclists accessing Washington Boulevard from the bike path, as well as numerous tourists entering the community every month, were confronted by this unsightly area, which has also affected residential areas nearby, she said.