Last week’s rains gave local surfers a familiar warning to avoid runoff by staying out of the water. But another flow of stormwater, earlier in the week, came without much notice.
More than 1.7 million gallons of stormwater emerged out of the Herondo storm drain near the beachside border of Hermosa Beach and Redondo Beach last Monday and Tuesday. The discharge came from a Torrance stormwater basin that had been partially emptied to repair a broken pump.
The resulting discharge may have contributed to elevated bacteria readings. It also shed light on the need for improved communication among the variety of agencies that oversee stormwater, and highlighted innovative efforts that cities in the South Bay are deploying to address one of the most vexing problems facing California municipalities.
The Henrietta Basin sits on some five acres of city-owned land, and looks more like a park than a city yard. The former vacant lot near West Torrance High School was initially built to prevent flooding, and takes in some of the millions of gallons of water that fall during rainstorms and would otherwise build up in the streets.
But since its completion in 2015, it has taken on added ecological importance as the South Bay increasingly turns to progressive methods of dealing with stormwater. Under the direction of the Los Angeles region of the state Water Quality Control Board, Henrietta and similar facilities retain stormwater so that it does not all flow to the ocean, and use it for eco-friendly purposes like groundwater recharge and habitat restoration.
The trouble began last month when an irrigation pump burned out at Henrietta. In order to access the pump, which at the time was submerged beneath several feet of water, the city had to drain a portion of the lake, said John Dettle, an engineering manager with the City of Torrance Public Works Department.
With last week’s rain forecasted to raise the water level at the facility even higher, the city began the diversion on Monday Dec. 12, during which an estimated 810,000 gallons flowed to the Herondo storm drain, Dettle said. On Tuesday, an estimated additional 972,000 gallons flowed to the drain.
The stormwater from the Henrietta Basin traveled northward along a tributary before meeting up with the main line of BI 1105 Line A, known the Herondo drain, and heading west under 190th Street to the beach, according to a map of the stormwater system from the Los Angeles County Flood Control District.
Henrietta was allowed to make the discharge because the facility is covered by a National Pollution Discharge Elimination System (NPDES) permit, a program administered by states and the Environmental Protection Agency, Dettle said. But the water was not sampled before discharging, and cities farther down the Herondo line like Hermosa were not notified of the unusually large volume of water.
Under existing rules, there was no obligation for cities down the pipe to be alerted to this discharge, said Kristy Morris, environmental analyst for Hermosa. The existing system provides for notifications in the case of discharges of industrial pollutants, or for discharges into potable water sources, like a reservoir, but there is no such obligation for discharging stormwater into oceans.
On the days of the discharge, a large amount of water pooled up at the Herondo outfall, collecting on the sand and flowing into the ocean. It was noticed and documented by Heal the Bay employees, including Hermosa resident Jose Bacallao. Craig Cadwallader, head of the South Bay chapter of the Surfrider Foundation, said that there had been no warning signs or beach-closure advisories, and noted that the fact that the discharge occurred during a period of sunny weather meant that people would be less likely to worry about bacteria levels.
“Our concern was, what’s the notification procedure?” Cadwallader said in an interview. “There was no rain, so no would equate this water as potentially bacteria-laden.”
Torrance did give advance notice to the Beach Cities Watershed Management Group, which includes Torrance, Hermosa, Redondo and Manhattan Beach, and implements a watershed management program to address stormwater and non-stormwater discharges, Dettle said.
According to Kathleen McGowan, a consultant who works with the watershed management group, regular monitoring is done Monday through Friday in front of the Herondo outfall from a point about ankle high in the ocean. Warnings are handled by the sampling agency, which is the county on Mondays, and the city of Los Angeles Tuesday through Friday.
“If readings are high, a warning will usually be posted,” McGowan said.
The samplings monitor levels of enterococcus, fecal coliform and ecoli. According to data from the city and county of Los Angeles, Monday readings from the Herondo drain and a monitoring station 50 yards to the north slightly exceeded state standards for enterococcus, a bacteria linked to ailments like urinary tract infections and meningitis. Although it is impossible to determine whether those readings were caused by the discharge from Henrietta, high water quality prevailed across much of the region that day, with only one other monitoring station in the county reporting excessive levels of any of the three measurements. By Tuesday, levels at Herondo had returned to normal.
To prevent the need for future draining at Henrietta, Torrance plans to install a new sled-mounted pump that can be raised and lowered into the water, Dettle said. But the stormwater project itself appears to be working: last year saw a decrease of about 25 percent in the number of days with elevated bacteria levels in the ocean.
“Since the project has gone in, bacteria exceedances are way down,” he said.
Morris, Hermosa’s environmental analyst, said the experience revealed the need for the region to remain focused on dealing with stormwater before it makes it to the coast.
“It was sort of eye opening as to why we should be doing these up-stream capture projects, and diverting that water away from the ocean as much as we can,” she said.
