High-Flow Preparedness at Orange County Sanitation District

On January 22-23, 2017, OCSD saw influent flows that had not been seen since 1995. OCSD experienced peak flows of up to 586 million gallons per day (mgd) coming into both of their wastewater treatment plants. As events started to unfold, OCSD staff worked tirelessly to ensure that its facilities could handle the unprecedented flows that OCWD staff worked to ensure that the Groundwater Replenishments System (GWRS) would continue to run at its normal 100 mgd flow rate. This alleviated any concerns that flows would exceed their discharge capacity of the five-mile outfall line and force OCSD to use its one-mile outfall, which would have resulted in beach closures.

Preparing for high-flow emergencies: the OCSD program

Just when California water and sewer utilities were getting used to managing lower than normal flows, along came the “Pineapple Express” and the other atmospheric rivers.  With little warning, utilities have had to adapt to high flows caused by the seemingly endless march of rain events across the state.

Orange County is typical. The mid-January storm dumped more than seven inches of rain in certain areas of the County— more than normally falls in a calendar year during the multi-year drought.

But the response by the Orange County Sanitation District (OCSD) to the wet weather may not be typical. The Sanitation District has developed an effective system of color-coded categories for managing higher flows. The system includes check lists and ranges from preparedness, to action, to recovery. Training and communication techniques assure that everyone is on board.


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The OCSD operates two wastewater treatment plants, receiving a combined average dry weather flow of 185 mgd; combined design capacity is 660 mgd. The Sanitation District serves about 2.6 million people, encompasses 479 square miles, and maintains about 400 miles of separated sewer lines and 15 off site pump stations. Treated effluent from the District’s Fountain Valley Reclamation Plant is provided to the nearby Groundwater Replenishment System (GWRS)–a joint effort between the Sanitation District and the Orange County Water District providing indirect potable water to 850,000 Orange County residents.

“This year’s rainy season has provided more than three times the average rainfall in the last five years,”  says Ed Torres, OCSD Director of Operations and Maintenance. “It’s a whole new paradigm for our staff—especially in operations. It seems like every week there’s a new storm coming in. We’ve had to take a different perspective on high-flow preparedness.”

That’s where the color codes come in. The OCSD system consists of code blue for preparedness; yellow, orange, red, for various wet weather conditions; and finally purple for recovery. The color codes are communicated via a call back system, text messages and emails throughout the OCSD plant staff and management in various departments.


Torres explains the coding:

“Code blue triggers a series of activities in preparation for high flows,” he says. That includes making sure tunnels are clear, sandbags are on hand, gate and valve actuators are staged and in working order. “We prepare all standby basins and tanks to receive flow for storage, we review Prado Dam emergency procedures, make sure we have access to any contractor sites, and put our maintenance staff on standby. “

OCSD also readies its fleet of portable pumps and hoses–some on carts, larger units on trailers. “We get these stationed at critical areas,” Torres explains.

Yellow is the threat phase and is flow-dependent. “When we get to 125 mgd above our normal flow for that time of the day,  we notify and coordinate with other agencies that can send water to us, or that we rely on to provide relief,” Torres says.  That includes the Orange County Water District, Irvine Ranch Water District, and the Santa Ana Watershed Project Authority member agencies. “We notify these agencies of rising flows in our district and advise them not to send water to us.”

Orange triggers several actions, as stormflow rises above 125 mgd over the normal flow. Standby units, such as the extra primary and secondary clarifiers at the treatment plants, should be brought into operation, while influent and outfall wet wells are brought down to their lowest levels. Staff is dispatched to critical locations such as the Santa Ana River when the Army Corp of Engineers releases higher flow from Prado Dam into the river.

Red means the system is at or has exceeded capacity. “All main sewage pumps would be operating,” explains Torres, “and we would be trying to get every extra ounce of water into the plant.” The Sanitation District would also prepare to deal with a potential spill or to bring its emergency ocean and river outfalls into play. “We would try to minimize the public health and environmental impact while ensuring the reliable operation of our facilities,” Torres says.

The purple code means the storm has passed and the Sanitation District is putting its facilities back into normal operation.

Management and training.

Depending upon the severity of the storm an ICS (Incident Command System) may be enacted, including formation of an Emergency Operations Center to provide management and coordination of the event.

Training is a key. “Two and a half years ago we invested in a three-day training program, involving real-life exercises,” says Torres. “We really brought the whole ICS system into play.  We assumed various roles and practiced how to react and interact (during emergencies).”

On-going training is a challenge because of staff turnover, he notes. “We do desk-top exercises conducted by our risk management group two or three times a year. Our operations staff goes through the emergency response plan, and we look at critical processes, making sure our emergency generators and our sump pumps are ready to go.”

Torres says the Sanitation District’s ICS training has been conducted through FEMA (Federal Emergency Management Agency), with certification through the Department of Homeland Security. Other training is handled in-house.

Foresight pays off.

In addition to emergency preparedness, Torres credits the OCSD board of directors for foresight in resisting the temptation to scale back facilities in view of the recent multi-year drought and substantial reductions in flow. “They have been committed to rehabilitating facilities to the original design capacity,” he says. “With the drought, conservation, and the economics of water purveyors, policy-makers could have made facilities smaller, but they’ve continued to invest in infrastructure.”

Torres also applauds the partnership with the GWRS–as not only a great source for potable water in the area, but as a sort of relief valve for high flows from the OCSD treatment system. “Without the GWRS,” he says, “we would have had to use our emergency outfall during the Jan. 18-22 storm. That would have resulted in closing of beaches due to high bacteria levels.”

Lessons learned.

As it’s shifted from low-flow to high-flow conditions, what valuable lessons has OCSD learned from the wettest winter in recent recorded history?

“We’ve learned that our preparation has really paid off,” says Torres. “All the upfront planning, review of procedures, the storage facilities, and the emergency equipment – it’s really valuable.”

Some lessons are more specific. “During the Jan. 18-22 storm, we had some challenges getting people into the plant and responding, particularly at a pump station where the emergency generator failed and all power was lost.”

Torres says it’s not enough just to have key people available. You should bring them onto the site proactively. “Don’t risk a half hour travel time during storms,” he says. “In any storm event, have your storm watch people at the plant, rather than just on-call.”


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Jim Force

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