During its Oct. 24 meeting, the San Diego City Council allocated an additional $5 million for the Replacement of Stormwater Infrastructure on Avenida de la Playa (RSIAP) in La Jolla Shores. According to the request for action, $6,362,508 had already been spent on the project, which brings its pricetag to $11,362,508.
According to the City’s website, the calculated cost of the project is $10,862,507, but as City’s public information officer Anthony Santacroce said, “This number will continue to be refined as the project progresses.”
After years of construction, the RSIAP was finished in May 2015. Six months later, in January 2016, a large storm event collapsed the infrastructure, creating a sinkhole that extended almost half a block to the beach and flooding the Avenida de la Playa businesses between Camino del Sol and El Paseo Grande.
Engineer Hany Elwany of Coastal Environments, who works out of La Jolla Shores, explained that, in his opinion, the project had engineering and construction safety problems. “This is troubling for the people living in the area because you can’t continue closing and reopening the ground, and this costs the City a lot of money,” he said.
The explanation for why new stormwater infrastructure failed completely is not an easy one to come by. As City Senior Engineer Steve Lindsay reported at the Sept. 14 La Jolla Shores Association (LJSA) meeting, logs and debris coming down the system clogged the recently installed outfall structure (which replaced the old storm drain). Allegedly, that’s what caused the sinkhole that appeared close to the beach in the area known as “boat launch.”
In the 2012 Mitigated Negative Declaration document on the original project, this part of the infrastructure replacement was described as follows: “For the storm drain portion of the project, approximately 0.26 miles of (dual) 51-inch by 90-inch and (single) 72-inch by 72-inch Reinforced Concrete Boxes would be installed along Avenida De La Playa from Paseo Del Ocaso west toward the seawall within and adjacent to the beach area.”
At the Nov. 9 LJSA meeting, Lindsay stated, “The original design did not hold up with the first large event we had. It was a cast structure with a heavy lid that just sat on top. As soon as it got pressure, the lid blew off, there was nothing holding it down. This new structure is going to be cast in place; there’s no way this thing is going to suffer the damages that the original structure did.”
At the same time, a biofilter box installed under El Paseo Grande didn’t have the capacity to process the amount of water it received and it, too, blew up during the same storm event, causing flooding in that area of the street. When revisiting the project, Lindsay said they decided to leave the biofilter box out. “Unfortunately, what was there was working fine and we put something in that didn’t work, so we go back to the original design,” he explained.
Area of Special Biological Significance
La Jolla Shores is one of 34 Areas of Special Biological Significance (ASBS) along the California coastline. Coastkeeper lab coordinator Meredith Meyers explained that the designation was created in the 1970s to protect the water quality of those areas. “La Jolla Shores is home to several important habitats — kelp beds, rocky reefs, sandy flats and the canyon — and it’s special because gets a high level of use and it’s in the proximity of a highly urbanized area that makes it very vulnerable,” she said.
In 1983, Meyers continued, a no-discharge requirement for ASBS was included in the State’s Ocean Plan. However, “The cities were already there, so there were some exemptions granted on a case-by-case basis.”
The City of San Diego secured an exemption, but has been working since then to reduce urban runoff and low-flow discharges. As Lindsay pointed out, the low-flow has been directed to the sewer system for 15 years.
“Once the water gets to Camino del Sol, there’s a diversion, so we take the low flow and put it into the sewer, so it doesn’t go to the beach. The sewer goes down to the Point Loma Wastewater Treatment Plan, gets cleaned, and pumped into the ocean,” he explained.
However, the City had reports that indicated low-flow discharges during the dry season.
As the original budget, included in the 2014 Fiscal Year City Budget, states, “Reports indicated low-flow diversion was not functioning as needed resulting in dry weather flow reaching the beach, which is out of compliance with the California Oceans Plan. Additionally, the current pipe is vastly undersized which results in street flooding every year.”
The current construction, which eliminated the biofilter box, will replace the box culvert that failed in the storm event and add a baffle box on La Jolla Shores Drive. The baffle box, as Lindsay described it, will eliminate some of the contaminants for smaller storm events. “If you have a big stream coming down La Jolla Shores Drive, we are not going to put the baffle box right in the middle, we are going to have a pipe going to the side, so there’s no risk of losing that again,” he said.
Lindsay said the original design was to blame for the failure, and that was done by Tetra Tech Inc. A new company was hired for the new construction.
The Avenida de la Playa storm drain system and outfall structure drains approximately 820 acres (1.28 square miles) into a protected area of the Pacific Ocean. The highly-urbanized watershed, mainly for residential and commercial uses, has a large amount of impervious surfaces that contribute to the urban runoff. The failure of the stormwater system in January 2016 endangered low flow and wet weather discharges. But, even when the current construction is completed, the ASBS will still be subject to urban runoff from large storm events.
As Meyer put it, “By protecting urban runoff, you protect the biological communities that are valuable there, but you are also protecting the dozens of humans swimming there every day.”