Animal, Vegetable, Mineral
An unusual mix of species inhabits a 231-acre corner of Los Angeles, CA, housing the Wilmington Drain and Machado Lake. There is a diversity of plant, animal, and mineral species in residence, but the trouble is many of them don’t belong there at all. Animals dropped off by disillusioned pet owners include snapping turtles and snakes of various species, exotic banded water snakes that have bred freely there, and even an alligator that eluded capture for two years have been found plying the wetlands. The animals eat everything they can digest, throwing out of balance the fine interplay between native species and their natural predators.
The area housing the Wilmington Drain and Machado Lake is incorporated in Ken Malloy Harbor Regional Park in just north of the Port of Los Angeles. The waterways drain an area of about 15,553 acres into a natural wetland that had been previously known as part of Bixby Slough.
Invasive plants such as ludwigia thrive, clogging the channels of Wilmington Drain and choking the lake and the nearby wetlands. Mineral interlopers too have made their way into Machado Lake’s ecosystem, to deleterious effect. Sediments rich in nitrogen and phosphorus, introduced via stormwater runoff from the lawns of Los Angeles area residences, roads, land uses upstream, and creek banks, have altered the ecology of the lake. Settling to the bottom of Lake Machado, they deliver a biostimulating stream of nutrients that support the growth of excess algae and other biomass that clouds the bottom, middle, and surface of the water column.
From time to time domesticated rabbits, ducks, and geese have appeared at the lake grounds, abandoned by owners who perhaps harbor the illusion that the untamed surroundings will provide sustenance to their former companions, and that they might be able to eke out an existence in what looks to be a wild and pristine habitat. It looks natural, as though the animals would stand a fighting chance, but it isn’t, and they don’t. Helpless to fend for themselves in the wild, these animals, experts say, generally fall victim to predators or succumb to–or spread–disease.
But saddest of all, displaced persons have sought refuge in the park, sometimes along with their pets and whatever little they can salvage of their lives and carry with them as they camp in the elements.
Trash, nutrients, and fecal matter introduced via stormwater runoff, unauthorized camping, and animals, and amplified by changes in the watershed that reduced the volume of water received, have added up to make the lake and surrounding Ken Malloy Harbor Regional Park rather inhospitable.
All of this notwithstanding, Machado Lake and the community of plants and animals surrounding the Wilmington Drain is still considered by many to be one of the most pristine areas of natural beauty anywhere in the vicinity of Los Angeles. People familiar with the region say the terrain likely appears the way wetlands in the entire Los Angeles region would have looked for millennia before the sudden eruption of the megacities that have come to dominate the land and its functions today.
It is home to the least Bell’s vireo, a riparian dwelling bird on the endangered species list, as well as a varied community of native plants and animals. The park has been revered by anglers, who say it offers some of the best fishing in the city, and treasured by residents of the surrounding community, although some say in recent years some trepidation has been required to enjoy its charms.
While the situation facing Wilmington Drain and Machado Lake might sound chaotic, Mark Gold describes it rather as “complex” and amenable to resolution through an equally intricate process, which, he says, is now underway with primary funding through Proposition O, the $500 million bond issue that has financed dozens of water-quality and water infrastructure projects in the city of Los Angeles. (See a related article, “Los Angeles’s Proposition O,” in the May 2014 issue of Stormwater.) Gold, who has been on Proposition O Citizens Oversight Advisory Committee since the beginning more than 10 years ago, has helped oversee water quality improvement projects all over Los Angeles, but he says the $140 million Machado Lake ecosystem restoration “is a very different project.”
“There’s a bunch of TMDLs [total maximum daily loads], there’s an the issue of contaminated sediments–what do you do with those sediments?” In addition, he says, the Endangered Species Act constrains restoration activity around habitat in the park favorable to the rare least Bell’s vireo and one of the last willow forests in southern California. Furthermore, Gold says, there is an issue of adding hardship to area residents by taking the park out of commission for the three years it will take to renovate, in a neighborhood already known as “one of the most industrialized areas of the city.”
The city of Los Angeles however, chose the to take on the challenge and restore ecological function to Ken Malloy Harbor Regional Park, with the goal of eventually opening it for public enjoyment. And Proposition O offered, for the first time, the opportunity to address all of the major ecosystem restoration issues for Wilmington Drain and Machado Lake through a unified approach.
It is the latest and the final installment of major project initiatives to be funded through Proposition O.
Gold says that when the project is complete, he expects the Machado Lake restoration to be “one of the highlights of the entire Proposition O initiative.”
But “it’s a huge challenge,” he adds.
The depth of the complexity is not lost on Los Angeles Bureau of Engineering Wilmington Drain Project engineer Naushin Kamal, who says the restoration effort also includes some very important humanitarian considerations. According to Kamal, before construction could really get started, one of the key action items was to work with the displaced people residing on the property to help them find alternatives to living at the drain. “We worked hard with the LAPD and the local sheriff’s office, and we were able to safely and appropriately relocate them.”
Fresh Creek Technologies designed a trash netting system for the project.
Out With the Bad, In With the New
Although they are technically two separate projects, Wilmington Drain and Machado Lake are inseparably joined, says Julie Allen, Proposition O assistant division engineer. “It’s considered a phase one and a phase two of a combined project, because Machado Lake’s biggest source of water is through the Wilmington Drain; it’s a combined ecosystem rehabilitation project.”
According to the Los Angeles Regional Water Quality Control Board (LARWQCB), Machado Lake was originally listed as an impaired water body under the Clean Water Act in 1998, based in part on nutrient data collected during the 1990s. Additional data, collected in 2006 and 2007, indicated that nutrient loading was increasing at an accelerating rate.
For instance, although phosphorus concentrations of 1.0 milligram per liter recorded during the 1990s were already high enough to begin to promote eutrophication, they continued to rise and by 2007 were reported to be 1.35 milligrams per liter in the lake. Total nitrogen, another major factor in algae blooms and eutrophication, increased as well during that period from 2.9 milligrams per liter to maximum levels of 4.2 milligrams per liter, in spite of growing public awareness and concern about water quality.
Algal blooms in the lake in recent years had begun to make it an unpleasant place to be at certain times of the year, Allen says, and the decomposition of the tons of excess algae placed an oxygen burden on the lake that made things difficult for fish and other aquatic life.
However, close examination of Machado Lake showed that the largest sources of excessive nutrients in the lake were not ongoing discharges and sediments flowing into the lake, but rather legacy sediments and biological matter mixed with silt on the bottom, much of which had begun its journey to the lake’s ecosystem during the era predating Clean Water Act regulations. These sediments, built up over time, and came to comprise a large proportion of the soft bottom of both Machado Lake and Wilmington Drain, and they kicked up a fresh supply of nutrients whenever perturbed by changing currents or other disturbances.
A major step toward restoring ecological balance to the lake was to remove these sediments by dredging. Unfortunately, the dredged sediments would also hold other reminders of the way things were in California, and in fact throughout the United States, before clean water regulations came into effect.
The LARWQCB noted that in addition to nutrients, the sediments also contained organic pollutants such as pesticides like the now-banned chlordane, DDT and its breakdown products, and dieldrin, as well as PCBs left over as legacy pollutants at levels predicted to adversely affect the health and vitality of benthic communities. Organic pollutants have even been detected in fish from the lake, making it inadvisable to bring the day’s catch to the dining room table. But the contaminants also created a dilemma for the restoration project.
According to Gold, much of the 230,000 cubic yards of dredge material were considered hazardous and could not simply be disposed in a local landfill. Planners contemplated using it as slip fill for a port construction project, which could have been permitted, but according to Gold, it turned out that the mushy sediments lacked the structural integrity needed for that task.
The earliest bids on the disposal alone threatened to “bust the budget” for the entire project, he notes. “That sediment and dredging process has taken a lot of time to figure out.”
But eventually, he says, “There were some modifications allowing more flexibility to the contractors on how to do the dredging and disposal to see what creative ideas the contractors could come up with, and they ended up saving a significant amount of money taking that route.” Ultimately however, he says, “They are going to have to send a large portion of it to a class I landfill.” With that decision, the project could finally move forward with the award of the dredge and disposal contract.
Kamal explains that to achieve the flow regime described in the hydraulic model that would accommodate the heavier storms in the region, crews dredged and reshaped the bottom along 3,300 linear feet of the 100- to 140-foot-wide Wilmington Drain channel to smooth out the bumps to allow for a better flow rate. “The problem was we weren’t getting a lot of rain, and we had a lot of sediment collecting at the bottom of the channel, so the water was essentially stagnant on the bottom and not flowing into Machado like it should have been. But after removing the invasives and grading the channel, we hope, with Mother Nature’s help of course, that it will definitely improve the water quality–and the quantity of water going into Machado Lake.”
To reduce the likelihood of future onsite erosion adding to channel and lake sediments, she says, “We’ll be putting in a combination of turf reinforcement mats and jute netting to stabilize the banks of the channel as well as the island.” A sediment capture basin dredged from one of the deeper parts of the lake will help keep the sediment that manages to enter Machado Lake under control.
Rounding off the source control measures from Wilmington Drain, technicians will install a trash netting system designed exclusively for this project by Fresh Creek Technologies Inc. Composed of 11 two-net support frames and multi-sectioned precast concrete chambers 16 feet long by 8 feet high, the system will include a “disposable synthetic mesh material to capture floatable materials,” and will use a LiftMaster structure to discharge the trash into a dumpster. “We’ll be working with our partners at the Department of Sanitation to maintain the trash net and remove all the sediments that are collected,” says Kamal.
The system is certified by the LARWQCB as a full-capture device. It features a 750-cubic-foot-per-second (cfs) design flow and a peak flow of 5,700 cfs, which meets Los Angeles County’s requirement for a 50-year storm event. The system’s high design flow capability and low head loss ensure no flooding of any upstream water elevations.
The Netting Trash Trap System is the world’s largest stormwater trash capture system.
Add Water and Stir
Removing contaminated sediments and addressing pollutant sources are just the first steps toward revitalizing the ecological viability of Machado Lake downstream of Wilmington Drain. Getting the lake to function as a living entity will also require putting something into it that has gradually been disappearing: water. In southern California that often can be hard to come by.
Allen says that prior to the project, the Recreation and Parks Department customarily supplied potable water “to keep the lake full during the summertime when there aren’t a lot of natural flows into the lake.” However, now under persistent regional drought conditions, the Recreation and Parks Department stopped providing any water augmentation, and the results illustrate how big a water deficit the lake can run up. The depth, usually hovering around 5 or 6 feet, fell by about 3 feet, presenting a dramatic contrast to the lake’s normal appearance.
With potable water at a premium, the city intends to turn to water reuse to supplement the lake’s needs, with plans to expand the Terminal Island treatment plant, “which provides high-quality treatment water,” says Allen.
She says the city will pipe in “essentially distilled-level water” from the plant several miles distant, which will deploy “microfiltration, reverse osmosis, or a combination of the two, to keep lake water levels up without having to use potable water.”
Continuous Deflection Separator (CDS) units installed on the storm drain inflows that feed directly into the lake will perform a filtering function, capturing sediments, oil and grease, and trash. Bioswales that will be installed at a different storm drain inflow will help clear the water coming from that source.
To provide treatment to address phosphorus in the lake, a water recirculation system will take water out of the lake put it through an inline treatment wetlands to be injected with dissolved oxygen generated onsite. The water will then pass through a phosphorus removal system before being returned to the lake.
“It is a very high-tech, innovative way to keep the water clean,” she says. “Basically it’s fed just from urban stormwater runoff, so you can imagine it gets a lot of contaminants in it.”
Excess phosphorus not captured by the treatment wetlands will be addressed through a technology that binds the nutrient to a media substrate. According to Allen, the water flows through the system and the phosphorus adsorbs to the media, which will be replaced every six months or so.
The other element lacking in the lake is oxygen, Allen says. However, unlike water, the oxygen can be sourced locally. The city has experience with artificial aeration at the Echo Park Lake as part of a separate Proposition O ecological restoration project. “That installation uses compressed air to generate bubbling throughout the lake, and we’ve had very good results in our dissolved oxygen in that lake.”
She says the Machado Lake project will deploy a device called a Speece Cone SuperOxygenation system by ECO2 to inject oxygen generated onsite into the lake water. “It’s intended to keep the oxygen level in the lake at a healthy level for the animals, fish, and other species that live in the lake.”
The entire complex will be unnoticeable to the public visiting the park. “The piping is all under the lake; the vault is underground. The only portion on the surface, the oxygen generator building, would be inside an enclosed recreation and maintenance yard.”
The most the public would see would be “bubbles in the water–if there are. But the oxygen is intended to be dissolved in the water–we don’t want it all to escape through bubbles, so you may not see anything from the surface.”
While absolute loadings of nutrients are important, what matters more from an ecological standpoint is their bioavailability. To address that concern, Allen says that as a one-time treatment during construction a dose of alum will be added to the lake to neutralize and bind residual nutrients, permanently sequestering them from the biological cycle, turning the lake sharply but safely away from the brink of eutrophication.
It includes precast concrete chambers, each 16 feet long and 8 feet high, and 22 capture nets.
Closeup of the trash capture system
No Lake Is an Island
Perhaps the most complex task at hand during the rehabilitation effort involves not technical enhancements to the infrastructure of the park, but bringing together the people and institutions that will sustain it into the future.
According to Allen, Machado Lake’s watershed is fed “mostly by non-city of Los Angeles water.” Although the construction will be complete in a few years, the ultimate outcome of the makeover of Machado Lake hinges perhaps in large part on what happens much farther up in the watershed over the course of many years, in communities that were beyond the scope of Proposition O’s and the city of Los Angeles’ water-quality projects.
Gold says, “The question is will there be adequate source reduction from the surrounding communities?”
“Getting the upstream communities to do their part is always difficult,” he says, but he adds that, as a result of all of the Proposition O projects, “One lesson the city has learned very well is the importance of the community and working with the community.” In the case of Machado Lake, that applies to an entire watershed and not just the citizens residing within the boundaries of the city of Los Angeles itself.
However, the community seems to be rallying as news of the changes at the park spread. The Los Angeles Times reports that local nonprofits, such as the International Environmental Service Club that reaches out to school students, have joined the effort reintroducing native plantings to restore bird habitat in the park.
Daniel Apt, an engineering consultant and vice president with RBF Consulting, working with Harbor College, an institution located squarely within the lake’s watershed, says the college and has begun thinking about ways to restore additional parts of the historic Machado drainage area that run through its grounds. At about the one-year mark after the start of construction, Kamal says, the Wilmington Drain portion of the project slated to span 830 calendar days was about three months ahead of schedule.
“We’re moving forward, and if the rain and the environment work with us, hopefully we’ll be able to finish sooner than anticipated.”
Machado Lake ecosystem rehabilitation is scheduled for completion by April 2017. But Allen says the completion of construction would not mark the end of the Bureau of Engineering’s involvement with the project; management and maintenance will continue long afterward.
“There are some components that we will manage because they are part of the permit requirements, such as maintenance of the habitat restoration areas, and we’ll work with the Bureau of Sanitation maintaining the treatment facilities that are there. It will be a combined effort for a few years to make sure everything is functioning properly and we’re getting the water-quality results we expect.”
Kamal also emphasizes the collaborative nature of the project. “We’ve had to partner with LA County because certain portions of Wilmington Drain area are owned and operated by them. We’ve also had to work with multiple agencies, including the Army Corps of Engineers and the California Department of Fish and Wildlife. In addition, we worked with the LARWQCB, and we were able to partner with all of them to meet all the permit conditions and satisfy our ultimate goal of creating an urban park with both passive recreation elements as well as elements for urban use.”
“We have a biologist that is part of our team that will be onsite everyday to make sure that environmental conditions are complied with by the contractor,” adds Allen. “We do surveys for the birds–we have multiple conditions in the project for staying away from the berm during certain seasons, because we have an endangered California least tern that brings its babies there after they hatch to find food. We have the least Bell’s vireo, which is an endangered bird, on each project, so we watch for them. We watch for bats, different nesting birds, and other creatures and stay out of their way and work around them. One of the reasons the duration of the project is so long is that we have to slow down progress of the work to avoid impact to the species that are there.”
Kamal is pleased to report that so far no birds have been harmed, and no complicating nesting sites have so far been encountered in the remaking of Wilmington Drain. She says when it is done, “It will be a nice area; there are so many homes nearby it will be natural, cleaner–it will be nice to have a mix of urban and natural elements.”
“I am optimistic that it will lead to the attainment of the beneficial uses of the lake and the channel,” says Gold. But he adds, “It’s a huge challenge. It’s a super-complicated project. The amount of thought and design that goes into this is equal in complexity to building a large sewage treatment plant.”Musing on the future scenario, Allen offers, “The water has been degraded in the lake so much that it’s murky and a lot of vegetation has grown into the lake. The goal is to bring it back to something that people are interacting with more–we’re putting in fishing piers and fishing platforms. We want people to really interact more with the water and appreciate the cleanness of the water.” Once the Echo Park Lake restoration was completed in an earlier Proposition O project, she says, “We saw a greater pride from the community in having that park in their neighborhood. So many more people showed up; people would even come and pick up trash that other people had left. We’re hoping a similar effect happens with this project.”