Skinner spill forces temporary shutoff

A malfunction at the Metropolitan Water District of Southern California’s Skinner Treatment Plant forced a nine-hour shutdown of water deliveries June 22 and tested demand water management plans of nearby water agencies.

Delivery to wholesale and retail agencies was cut in half during the shutdown, although the agencies had sufficient storage to impact water users.

“There really wasn’t any noticeable shortage from what we can tell,” said Denis Wolcott, a spokesperson for the Metropolitan Water District.

The malfunction manifested itself in the form of a spill. “We had a valve suddenly close on us, a gate actually,” Wolcott explained. “When that closed it forced the water to back up into an emergency release valve.”

Approximately 33 acre feet, which equates to over 10 million gallons, of treated drinking water spilled into Tucalota Creek at the rate of 420 cubic feet per second before the flow could be stopped. The gate was re-opened in approximately one hour. “In the meantime we shut down about half of the treatment plant,” Wolcott said.

That shutdown put one of Skinner’s two water treatment units out of service. “Because we were at half capacity out at the Skinner plant, we were notifying our member agencies,” Wolcott remarked.

The Western Municipal Water District of Riverside County, the Eastern Municipal Water District, the Rancho California Water District and the San Diego County Water Authority were among the agencies involved along with the Metropolitan Water District. “It was the five agencies working together,” said San Diego County Water Authority general manager Maureen Stapleton.

Construction is under way for an additional module to meet increasing demands by water agencies in the Skinner service area, and the San Diego County Water Authority has implemented a demand management program in case the CWA’s demand exceeds available treated water capacity. That plan was intended for peak periods rather than outages, but it fared well when it was applied after the shutdown. “It was certainly envisioned it could be used for that,” noted Gary Eaton, the director of operations and maintenance for the County Water Authority.

“All of the agencies agreed to a substantial reduction in treated water delivery,” Stapleton remarked. “Everybody took a like hit. Everyone took a like reduction in treated water.”

The CWA was notified of the shutdown at approximately 10:00 a.m.

“Because we had the plan in place we were able to react to it very quickly,” Eaton said.

The CWA activated its emergency operations center and kept the County of San Diego, including the county’s health services departments, informed of the situation and any updates. The CWA also updated its member agencies. “We made sure the correct information got out to everybody and everybody was well-informed.”

Two of the CWA’s member agencies, the City of San Diego and the Helix Water District, have treatment capacity of their own and optimized their capacities. The CWA let the member agencies handle cuts to users. “The agencies can best figure out the conservation messages and the conservation actions they need to put into place,” Eaton explained.

MWD was assessing when the unit might return to service and whether any damage had occurred. “We were anxiously waiting for MWD to provide us with an update,” Eaton remarked.

No lasting damage occurred. “There was no water quality problem, either,” Wolcott added.

Full operations at the Skinner plant resumed at approximately 6:00 p.m. “By 8:30 we had restored flow to all member agencies,” Eaton noted.

The cause of the malfunction is under investigation. MWD will form a board of inquiry which will investigate the failure and provide a report.

“We don’t know why the valve malfunctioned, but it did,” Wolcott remarked.

“I really want to emphasize how impressed we were with the professionalism of the operations personnel and the public affairs personnel,” Eaton said. “It’s good to know that everybody was prepared, had a plan, and was ready to execute the plan.”