The recent sewage spill into Monterey Bay, which started Jan. 19 and ended the next morning, was the worst in Monterey One Water’s history, and the only one to occur out of the agency’s 29-year-old wastewater treatment plant in Marina. The good news, if it can be called that, is the estimated volume of the spill is continually being revised downward as engineers make assessments.
Initially, the agency estimated that as much as 4.9 million gallons of raw sewage flowed out of the treatment plant’s outfall, which is two miles offshore of Marina. Within a day, the estimate was revised to 4.4 million gallons, and by Jan. 30, to 2.8 million gallons; the estimate is expected to go down further.
Nonetheless, Monterey One Water General Manager Paul Sciuto does not want to minimize the severity. “It’s unacceptable,” he says of the spill.
The agency is working with an outside firm to better understand what went wrong, how it went wrong and how it can be prevented in the future.
This is what is known: At 7:10pm on Jan. 19, a single component of a computer failed, leading to two problems. First was that a mechanical rake that clears debris from a screen covering the plant’s intake stopped working; waters eventually rose to a spillway that leads to the outfall. That component also failed to send data to the alarm system that should have gone off in the plant’s control room.
There are about 192 trillion gallons of water in the bay.
Why the component failed remains under investigation, but Monterey One Water has already put redundancies in place to ensure such an accident doesn’t happen again. The agency has installed an infrared camera focused on the headworks – essentially, the plant’s intake filter – and ultrasound sensors in the pipes leading into the headworks that will send a message via satellite if water levels rise to a certain height. And while the plant’s control room is always staffed, a temporary employee has been hired to walk around the plant from 6pm to 6am to look for any problems.
The spill started about an hour after the equipment failure on Jan. 19, and was only discovered around 5am the next morning because a plant employee walked outside to open a gate for a contractor and noticed raw sewage discharging from a concrete structure on the property (in addition to what was flowing into the bay).
Had the problem not been discovered then, the spill could have been far worse as people started using bathrooms in the morning and volume into the plant increased.
While Sciuto expects the state will fine the agency for the incident, the spill’s impact on the Bay’s water quality is likely negligible, although the composition of the sewage – and whether it contained chemicals that are harmful to marine life – is still being analyzed.
Context is also important: Bridget Hoover, the water quality protection program director at NOAA’s office in Monterey, estimates there are about 192 trillion gallons of water in Monterey Bay.
Additionally, the plant’s outfall has a diffuser with 171 different ports that discharge the water over a larger area, lessening the impact in any one location.
Tests conducted by Monterey One Water in the days after the spill showed elevated bacteria levels at only one location – Wharf 2 in Monterey – but it is not believed to be related.