Lotus blossoms have returned to Echo Park Lake in Los Angeles following a $45-million rehabilitation project. Courtesy of Black & Veatch
A $45-million project restores the lake to pristine conditions and marks a return of the famed lotus blossoms.
August 20, 2013—The City of Los Angeles had approximately 5,700 residents when leaders created Echo Park Lake as a drinking water reservoir in the late 1860s. The sprawling metropolitan area that is now home to nearly 10 million people literally grew up around the park. Residents in the 1920s and 1930s flocked to the sparkling lake, drawn by picturesque views of the burgeoning city, paddle boating, and the emblematic lotus blossoms.
By 2006, the lake had fallen into a state of decline and was identified by the State of California as an impaired water body, placing it on the U.S. Environmental Protection Agency 303(d) list. The lake was impaired by algae, ammonia, copper, eutrophication, lead, odor, PCBs, pH, and trash.
The city recently completed a $45-million rehabilitation of the 79 acre-foot body of water that has returned it to the pristine condition of its halcyon days. The project included elements to capture and treat storm water and eliminate seepage issues that were forcing the city to replenish the lake with potable water during the dry season.
The project was accomplished with funding from Los Angeles’s Proposition O Clean Water Bond. In 2004, voters authorized the city to issue a series of general obligation bonds for up to $500 million for watercourse and ocean pollution remediation projects. The Echo Park Lake rehabilitation was designed by Black & Veatch, in Overland Park, Kansas, in collaboration with contractor Ford E.C., Inc., of Los Angeles. The clients were the City of Los Angeles Department of Recreation and Parks and the Department of Public Works, Bureau of Sanitation. Project management was provided by the city’s Department of Public Works, Bureau of Engineering.
“There is a very famous lotus festival that happens every year in July in the park,” says Hala Titus, P.E., A.M.ASCE, the project director for Black & Veatch. “The lake is very close to the residents’ hearts. Giving it back to them was very important for all of us.”
The team performed a hydraulic analysis and an evaporation loss study of the lake to determine the best solution to minimize its dependency on potable water.
“We calculated the evaporative loss and correlated it to the lake,” Titus says. “So we were able to account for exactly how much was lost to exfiltration and how much from seepage.”
Early in the design work the team learned there were valuable natural clay formations beneath much of the lake. By excavating this clay, mixing it with bentonite, and compacting it, the team was able to eliminate the need for an expensive synthetic liner, reducing the project budget by $12 million.
The lake offers dramatic views of the city and is popular with local
residents, seen here enjoying paddle boating in 2008, before the
rehabilitation. Wikimedia Commons/Sterling Davis
“It was a very good finding,” Titus says. “We actually achieved a highly impervious layer, so we were able to minimize greatly the level of exfiltration around the lake. Also, this was more sustainable and a lot less expensive than a synthetic liner.”
To further reduce the need for the inflow of potable water, engineers designed a system to introduce storm water flow from the area into the lake. The influent first enters two new hydrodynamic separators, to remove fat, oil, grease, and trash.
The water flows from the separators into 2.7 acres of constructed wetlands, which includes plants chosen for drought tolerance and homogeneity with the natural habitat that remove such nutrients as phosphorous and nitrogen. The lake includes recirculation and aeration to further improve the water quality.
The system is designed to accept 100 percent of the dry weather flow and the majority of the first flush during storm events, amounting to approximately 13.2 cu ft/sec.
“We modeled the water quality and we proved that with these steps in place, the improvements would take care of the pollutants,” Titus says. “We handed over a healthy lake to the city.”
Also early in the design work the team discovered that the lake was considered to be within the jurisdiction of the California Division of Safety of Dams (DSOD).
“The number one design challenge was the DSOD,” Titus says. “They gave us three options. One of them was backfilling the lake and forgetting there was a lake. The second option was to bring it into compliance, which was a very expensive solution. The third was to take it out of their jurisdiction. So this was a key design challenge for us.”
Engineers took the lake out of DSOD jurisdiction by developing a submerged berm, effectively dividing the lake into two smaller cells, both of which are beneath the 50 acre-foot threshold to be considered a dam.
The lake was drained to accomplish the two-year construction, which presented a challenge for the team. The lake serves a vital storm water control function for the city and need to remain available for that purpose. Titus says the team developed a solution that included partitioning measures and bypassing flows.
“We were lucky,” Titus says. “We had dry winters the last two seasons. The team completed the project on schedule and under the cost estimate we had provided.” The park officially reopened on June 15, and the city has reintroduced lotus plants to the restored lake.
“It was wonderful to hear the comments from the community at the grand opening event,” said Kendrick Okuda, P.E., the program manager for the city’s Proposition O Program, in written comments to Civil Engineering online. “Not only were they excited to have such a beautifully renovated park, but they were astonished that the water in the lake was so clean and clear.”