California Utility Keeping I&I at Bay

Richmond Municipal Sewer District sets an example with its work to reduce SSOs and protect San Francisco Bay.
California Utility Keeping I&I at Bay
City of Richmond Water Pollution Control Plant.

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Richmond, California, enjoys 32 miles of coastline, the most of any city in the San Francisco Bay Area, but this geography has its downside.

“During heavy or prolonged rain events, our treatment plant flow can increase from 5 mgd to 40 mgd,” says Dan Duffield, source control inspector for the Richmond Municipal Sewer District.

The I&I comes from direct tidal inflow in the southern basin near the Bay, groundwater infiltration from tidal saturation, storm runoff inflow from connections between stormwater sources (downspouts and sumps) and the sewer system, and rainfall-dependent infiltration. Many Bay Area communities experience similar issues.

“The goal of our sewer collections system master plan is to eliminate SSOs during conditions up to a 10-year 24-hour storm event,” Duffield adds. “That equates to 4.2 inches of rain in 24 hours, and could send 70 mgd to the plant. As our collections system is repaired and I&I is reduced, that reduction will be the measure of our success.”

Baykeeper agreement

In 2002, the district contracted with Veolia North America (formerly U.S. Filter), a provider of environmental services in cleaning, energy, waste and water. Beginning in September 2014, Veolia now runs the treatment plant and collections system. It was an auspicious start to I&I management, but more was soon to be needed.

The original master plan was conceived in 2006, when RMSD entered into an agreement with San Francisco Baykeeper, an NGO founded in 1989 to protect water quality in the Bay Area. Baykeeper wields considerable power with extensive grass-roots support — and it was threatening a lawsuit.

“That was a controversial time,” recalls Richmond Mayor Tom Butt. “I’ve always supported the Clean Water Act, knew we had some problems, and wanted to do what was right for the Bay. And the law was on Baykeeper’s side. The EPA counts on local organizations to do their enforcement, so that’s where Baykeeper came in.”

As a result of this agreement, RMSD was required to reduce SSOs by 90 percent by 2016, and to eliminate overflows into the Bay from their two engineered overflow weirs. The 5-million-gallon wet weather storage facility (see sidebar) was also a result of this agreement.

The two weirs separate the sanitary and stormwater systems. During high tide and associated rain events, the stormwater system often backs up. This can result in flow discharging into the sanitary system at rates exceeding 200,000 gph, or cause untreated sewage to enter the stormwater system, which then goes out into the Bay.

Keeping tabs on I&I

In 2010, West Yost Associates was retained to complete a wastewater collections system master plan, delivered in 2011. In 2012, the city contracted with Infrastructure Engineering Corporation to monitor flows at the two overflow weirs, as well as other locations in the system.

“We installed flow monitors on the weirs,” says IEC project manager George Elaro. “Now, if we get close to an overflow on either the sanitary or stormwater pipelines, an alarm is triggered. The I&I is dependent on both rain intensity and tidal events. So tracking rain gauge data and NOAA tidal data is very important to us.”

During a storm event, when the influent flow rate exceeds 22 mgd, wastewater flow is diverted to two basins with a capacity of 1.8 million gallons. “When those basins are full, a ‘blending event’ occurs,” says operations supervisor Russ Clifton. “Primary treated wastewater is sent to chlorine contact basins and discharged to the Bay. If the flow reaches 40 mgd, then wastewater is diverted to our 5-million-gallon wet weather storage facility. That shaves the peaks off extreme flows during heavy rain events.”

In 2014, IEC contracted with FlowWorks to host the flow data on their servers. This allows RMSD staff to view the data on a near-real-time basis during storm events. Initially, FlowWorks supplemented the monitoring of plant data such as influent and effluent flow rates, wet well level, and the time, duration and volume of bypass or diverted wastewater.

FlowWorks now incorporates data from the flow monitors, a rain gauge, NOAA tidal charts, and SCADA output from the treatment plant. What RMSD gets is a real-time graph incorporating all that information. With this data, the operations staff gets a better picture of a storm’s impact on their system.

“The goal is to utilize more real-time data, as well as historical trend data, when making operational decisions at the plant,” Duffield says. “The data also guides planning capital improvements to our infrastructure. A peripheral benefit is that FlowWorks allows multiple users access from any location with an internet connection.”

Lateral program

RMSD also initiated a residential sewer lateral inspection program in 2006. All property owners must obtain a Certificate of Lateral Compliance at the time and in the manner required by the Richmond Municipal Code. That includes:

  • Title transfers
  • Subdivision of properties containing one or more structures
  • Remodels adding two or more sanitary plumbing fixtures

“On a first-come, first-served basis, the city will reimburse residents 50 percent of the cost of the lowest bid submitted,” says Mary Phelps, RMSD source control inspector. “Three bids are required, and reimbursement can be up to $3,000, but the program is ultimately subject to our annual budget of $100,000.”

The district subsequently approached 30 major industrial facilities in the southern basin near the Bay to evaluate and replace their antiquated private sewer systems. Many of them had been installed before 1970. Tidal infiltration in this area was causing sewer capacity issues. This effort, along with targeted point repairs, resulted in a significant reduction of inflow at the treatment plant — from 7 mgd to 5 mgd. The ongoing drought has also played a role in that reduction.

“We’ve seen a big reduction in SSOs this year,” says Duffield. “In 2012, we had 47 SSOs. The Baykeeper limit was then 114. In 2015, we had 21. The Baykeeper goal is 16. We amended our lateral ordinance in 2014, and now require property owners to evaluate their laterals if the system is more than 15 years old.”

Part of the master plan was to enact the ordinances conferring RMSD the authority to require inspections. The City Council granted that power in 2006. RMSD now issues compliance certificates after vetting any inspection or new build.

Of course, keeping point-source stormwater out of the system is also important, and some customers are still diverting downspouts and sumps into the sewer lines. “We have a credit program that allows customers to save on their rates, and we require approved drainage plans on all new builds,” Phelps says.

RMSD offers customers three-year credits of up to 50 percent on their stormwater rates for installation of rain gardens, vegetated filter strips, on-site storage (such as rain barrels and cisterns) and pervious pavement. It’s a popular program, promoted with bill inserts and featured prominently on the RMSD website.

Strategies for success

Duffield says there are a few things worth noting from the district’s experience, including the development and implementation of their master plan, and their lateral program with residential, commercial and industrial property owners.

“The data is also a large part of our success. Doing all the monitoring and pulling it into a web-based platform like FlowWorks really helps us understand what our system is doing, and to make the right decisions.”

Infrastructure Administrator Patrick Phalen notes that the process includes incorporating sewer lateral data into the GIS with existing maps, and requiring maps to be submitted for new sewer laterals.

“We have the size, type and condition of pipes, manholes, clean-outs, lift stations, elevations, connections to the public sewer system, as-built diagrams, historic documents, inspection videos and modeling software,” Phalen says. “It’s our geodatabase repository.”

RMSD operates a continuous collections system inspection program, utilizing flow monitoring, video inspection and situational smoke testing. The rough schedule is 10 percent of their system each year. Their service area is essentially “built out,” so they rarely need to incorporate additional infrastructure.

“Here’s what it comes down to,” says Duffield. “We educate the public to treat their sewer laterals like any other asset — it might not be as visible as the roof on your house, but if it’s leaking you still gotta fix it.”

Storing storms for future flow

Even a “normal” rainstorm can dump a lot of water on the San Francisco Bay Area. The Richmond Municipal Sewer District recently invested $18 million in a storage system to hold much of that water, and keep it out of their treatment plant.

It was pushed on an aggressive timeline. The district used a design-build approach to facilitate the project. Carollo Engineers, the city’s design-build contractor, prepared a number of construction packages that were publicly bid to ensure the lowest cost for the project. Construction began in June 2014.

The RMSD wet weather storage facility, completed in September 2015, has a 5-million-gallon capacity. During a rain event, wastewater is diverted when the flow at the treatment plant exceeds 40 mgd. When the plant returns to a normal flow rate, water held in the facility is directed to the plant’s influent lines for treatment.

The system includes a diversion box, pump station, pipeline and an above-ground circular prestressed concrete tank approximately 150 feet in diameter and 53 feet tall. The tank is located near the treatment plant. It is covered for odor containment, to reduce algae growth and keep out insects and birds.

“We’ve engineered the system for a 10-year 24-hour storm event,” says Aaron Winer, project manager for Veolia North America (contracted by RMSD). “To date, we have not exceeded that capacity.”


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