What Happens in The Next Big Storm?

— Scott Tulloch, director of San Diego's Metropolitan Wastewater Department, believes that the 2.66 inches of rain on October 27 showed how effective improvements to the city's sewer system have been over the past three years. In a November 3 report to the California Regional Water Quality Control Board's executive officer, John Robertus, Tulloch wrote: "I am pleased to inform you that other than an issue with the influent screens, the system functioned as designed through a period of unprecedented high rains and flows." But the claim appearså in the middle of the second page of the three-page letter, whose main purpose is to describe a 2.26-million-gallon raw sewage spill.

Before the workday of October 27 was over, deputy city manager Richard Mendes had written to Mayor Murphy and the San Diego City Council describing what happened. "The most serious event occurred at the Point Loma Wastewater Treatment Plant around noon today when increased flows resulted in a shutdown of screens used to remove material from the incoming sewage." Mendes went on to note that 175 million gallons per day is the normal flow at the plant, and 432 million gallons is its capacity. "Flows had reached 428 MGD," he writes, "when the screens shut down.... (For reference, the previous historic peak flow at the plant was 413 MGD).

"Sewage overflowed into the ocean for approximately 21 minutes while emergency bypass gates were being opened.... In addition, an overflow structure in the San Diego River released an estimated 1200 gallons of sewage into the river adjacent to the Pacific Coast Highway bridge....

"Another incident," Mendes continues, "occurred in a canyon downstream from Marine Corps Air Station Miramar due to inflow from sewer and storm drain systems located on the base.... Crews responded to alarms early this morning, but while preparing the pumps, storm flows washed away a pump inlet hose, and an estimated spill of 10,000 gallons occurred while crews were restoring the bypass operation."

At the end of his letter, Mendes speculates that people opening manhole covers to relieve flooding in their neighborhoods might have caused the "enormous surge in flow" that caused all the problems. He finishes by telling councilmembers that the San Diego County Health Department was already posting signs alerting citizens to stay away from the spills. The rains on October 27 started at 1:00 in the morning. Documents on file at the wastewater department show that at Lindbergh Field they increased to their highest point of the day, a little over .7 of an inch per hour, between 4:00 and 5:00 a.m. After that the rains fell off rapidly but continued at a rate of approximately .2 of an inch per hour until close to 9:00 a.m.

In its November 6 edition, the San Diego Union-Tribune's Terry Rodgers quotes Dave Hanson, a sewer-spill investigator for the Regional Water Quality Control Board, as saying, "Any spill that goes to surface water [sic] and results in contamination postings would automatically get a notice of violation." And that means that the incident at the Point Loma treatment facility will cost San Diego's wastewater department a fine. The amount of the fine has yet to be determined.

In the opening paragraph of his report to the water-quality board on the October 27 sewage spill, the wastewater department's Tulloch says that he was taking the opportunity to "cover actions initiated to determine the cause(s) of the incident and to prevent further problems in the future." He starts by mentioning how rains earlier in the month had "already saturated the ground and established conditions that would magnify the effects of any additional rain." Indeed, at 4.98 inches, the month had the heaviest rainfall ever in San Diego history.

Tulloch then acknowledged the work of his staff on the day of the spill at such pump stations upstream from Point Loma as those in Sorrento Valley, on South Harbor Drive, and on Harbor Drive near Lindbergh Field. The references make the point that employees did all the right things. Tulloch finally gets around to the spill site. "At 0930 hours, Point Loma staff prepared for high flows by making both influent channels available to take flow. They also put all five of their influent screens on manual mode to insure constant cycling of the raking mechanism....

"Because of the very high flow level, debris started accumulating on the screens, slowing down the flow going through them," writes Tulloch. "When this happened, the control system to the plant went into a high-level alarm at the screens and shut them down to protect the motors. Within one minute, the screens had built up enough debris to limit the flow going through them, forcing flows to escape rapidly at the screen structure. Point Loma Operations personnel responded and manually released the bypass gates so that flows could go over the screen structure, thereby bypassing the influent screens.... Within 20 minutes, they had all five bypass gates open, and the spill ceased."

In other words, we should be grateful that the spill was not a lot worse. But what happens in the next big storm? At the time of this writing, no one at Metropolitan Wastewater was available to answer my question. But Tulloch's report does contain a hazy indication of the department's thinking. "[The Point Loma] staff," he says, "is assessing potential changes to the operation of the screens and/or bypass channel in extremely high-flow situations. Distributed Control System monitoring systems are also being evaluated for additions or operational changes that could reduce the possibility of overflows by additional alarms or modified operational protocols."

And what about the two other incidents that city manager office's Mendes called to the attention of the city council? Tulloch mentions the San Diego River spill in his report to the Water Quality Board but calls it "a small spill...as the system became surcharged." He fails to mention the 10,000-gallon canyon spill that resulted from storm drains and sewers emptying out of the Marine Corps Air Station Miramar. Perhaps that's because the spill didn't go into the ocean, and his department can't be fined for it.

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