SEWER: Strike Force

Emergency overflow response in the Sanitation Districts of L.A. County focuses on control and confinement. Speed and organization are critical.

The call comes in at 10:21 a.m. There’s an emergency at South White Avenue and Ninth Street in Pomona. Instantaneously, a team springs into action. Respond. Contain. Remediate. Report.

Trucks roll. Radio waves crackle. In the command center, computer screens beam up GPS points. Personnel are on-site within minutes and have the situation under control in hours, if not sooner.

Fire and rescue department? EMT squad? Police SWAT team? No, it’s the collections system emergency response team at the Sanitation Districts of Los Angeles County, racing to a sewer overflow, fixing the problem, and keeping wastewater from contaminating public waterways.

“We may be unique,” says wastewater collections section superintendent Doug Walton. “We not only focus on fixing the problem as quickly as possible, we’re also committed to containing the spill or overflow, confining it to the sewer system, and preventing it from getting into the public waterways — our rivers, and ultimately, the Pacific Ocean.”

Walton and Sam Espinoza, wastewater collections systems manager, explain that beach closures caused by high counts of indicator organisms in the water are the last thing the Los Angeles metropolitan area needs. “There can be a significant economic impact here should that happen,” they say.

State and federal regulations prohibit wastewater overflows. However, in the L.A. Districts’ vast system of sewers, some built in the mid-1920s, failures inevitably occur. The agency is committed to a comprehensive two-pronged program: Stop the overflow, then contain and recover the wastewater discharge. And do both as quickly as possible.

Staying out front

The Sanitation Districts of Los Angeles County serve 78 cities and unincorporated areas with 11 wastewater treatment plants. The collection system includes 9,500 miles of tributary sewers and 1,400 miles of sanitation districts sewers. About 50 percent of the pipes are concrete and 45 percent are clay.

The districts started building its emergency response system more than 10 years ago. “In the old days, we were sometimes accused of not letting the proper authorities know about a spill or overflow,” Walton says. “Or, in some cases, we were actually the last people to know about it.”

It’s much different now. Calls about possible overflows come in to the districts’ central alarm center at the Long Beach Main Pumping Plant. The message and the location are transmitted immediately to the Compton Field Office where Espinoza, Walton or the O&M crew on duty forward it via cell phone or handheld radio to the entire collections staff of more than 100 people.

The districts lease bandwidth and have a designated frequency on the county’s integrated radio network, and maintain an emergency contact list that includes home phone numbers and emergency 24/7 cell phone and pager numbers. Within minutes, the entire network of people is notified.

At the same time, the call is transmitted to the public health department and the Office of Emergency Services and logged into an electronic database as a service request.

Once the word goes out, “Everybody goes into action simultaneously,” says Walton. “Everybody has a role to play.”

Using ESRI ArcView maps of the entire sanitary and storm sewer systems, the response team pinpoints the location of the spill or overflow and identifies catch basins and storm drains where the overflow is likely to go. The database also reveals any previous incidents in the same area, so the crew can make an educated guess of where the spill is headed. “We’ve gotten pretty good at this,” says Walton.

All-inclusive

That’s crucial, because the districts’ goal is to respond to the scene within one hour of notification, assess the situation, and notify the responsible agency if the situation was not caused by a problem within the sanitation districts’ system.

When the alarm really is a districts sewer overflow, a practiced protocol kicks in:

• Prevent the overflow from reaching the storm drain, if possible.

• Limit public access to the overflow area to prevent public contact with wastewater and any areas contaminated by wastewater.

• Stop the overflow as soon as possible, preferably within one hour of arriving on-site.

• Completely contain the overflow as close as practical to the overflow location to prevent or minimize any environ-mental impact.

• Completely recover the contained overflow and return it to the sewer system.

• Clean up the area contaminated by the overflow.

• Repair damaged facilities that caused or contributed to the overflow.

• Gather and compile pertinent information pertaining to the overflow, simultaneous with response efforts, and notify appropriate regulatory agencies of the overflow and response status as soon as practical.

• Conduct investigations to determine the probable cause of the overflow, document the events during the overflow and response activities, identify and implement measures to prevent recurrence.

Although each overflow is unique, the districts respond to most overflows in a standard fashion. Several crews travel to the scene, each under a lead worker or supervisor. One crew is responsible for stopping the overflow, and the others for containment, recovery and cleanup.

Stopping the overflow

When they arrive on the scene, crew members investigate the cause of the overflow, then work to stop it and correct the condition that caused it. They clear pipe blockages using combination trucks, remove any debris from manholes, and divert upstream flows or use vacuum trucks or pumps to bypass wastewater around the blockage or break.

If a failure in a pumping station or force main has caused the overflow, the crew relies on its battery of engine-driven generators to restore power, and uses portable pumps and hoses for bypassing. The districts maintain an overflow response trailer, equipped with portable pumps and hoses, fittings and tools able to bypass up to 450 gpm. For higher flows, the crew uses larger trailer-mounted engine- driven pumps.

Many of the districts’ pumping plants are specially configured for installation and operation of emergency bypass pumps in case the normal sewage pumps are inoperable. These portable bypass pumps are powered by electrical generators and sized to handle peak wastewater flows. Crews can connect the pumps to the force main or to a temporary above-ground force main. If necessary, a portable generator can power the bypass pump.

Individual emergency procedures manuals cover the procedures specific to each of the districts’ 52 pumping plants. Repairs are made as quickly as possible, using the districts’ field engineering section or qualified outside contractors.

Containment and recovery

Just as vital as correcting the problem, the emergency response team works to contain and recover any wastewater overflow and prevent it from entering waterways. “Over the years,” says Walton, “we’ve done our best to keep overflows out of our public waterways.” Last year, for example, the districts experienced 10 overflows and in seven of those incidents prevented any wastewater from escaping.

The first line of defense is to keep the overflow from reaching the storm drain system. Crews dam the overflow path with sandbags in the street gutter and recover the impounded water with a vacuum truck or jet-rodder. They may use sandbags to divert the overflow into a nearby sewer manhole.

“We’re working against the clock,” says Walton. Sometimes, due to slow reporting of an incident, or the city’s infamous traffic congestion, overflows do enter the storm drain. When that happens, the response team identifies the best spot in the downstream storm drain system to contain the flow. That decision is based on the time of the overflow, its route through the storm drains, time needed to erect a containment dam, accessibility for personnel, and proximity to a sewer.

The team uses sandbags to build the containment and trap the overflow. “Ideally, we contain the overflow underground, rather than daylight it, but we don’t always have that luxury because of confined-space access and safety considerations,” says Walton. “Plus, we can enter a storm drain system in dry weather only.”

Once the overflow is under control, the crews recover all impounded wastewater and return it to the sewers. They remove debris and flush the affected areas with potable water from a vacuum truck or water truck, then direct that water to the sewers as well.

When necessary, additional potable flush water is marked with a nontoxic dye and is allowed to flow into the overflow site. When it arrives at the containment site, crew members note the travel time and know for certain that they have recovered all the overflow and flush water. “We want to be sure we’ve caught it all and nothing has escaped from the site,” says Walton.

Finally, the crew removes all sandbags and completes the cleanup in the storm drain system. In rare cases where wastewater has reached a natural watercourse or other area accessible to the public, the collections section works with other jurisdictional agencies on additional cleanup measures. Any private property contaminated by the overflow or spill is handled by a professional restoration company hired by the districts.

Concern for health

The sanitation districts cooperate with local law enforcement and public works officials to prevent public contact with overflows and to ensure security of spill sites. The response team contacts members of the public who may have been exposed to raw sewage, informing them of health risks and advising them if they should vacate their property as a precaution.

At the same time, team members determine the path and final destination of the spill and potential public exposure. If wastewater from an overflow is ponding in a location that can be isolated, personnel set up barricades. Traffic control keeps vehicles from entering locations where the overflow has contaminated streets.

If an overflow might reach receiving waters, samples are taken to evaluate the potential impact on water quality. The samples are analyzed for total coliform, fecal coliform, and enterococcus and other constituents as appropriate, based on the nature of the receiving water and the spilled wastewater.

The districts report all overflows to the several regulatory agencies having jurisdiction in California. After cleanup, districts personnel review the situation to determine if maintenance should be increased or altered. Follow-up CCTV inspection verifies complete removal of blockages.

So, what has been the biggest test for the districts’ emergency response team? Any five-alarm situations? “Three or four years ago a force main failed at one of our pump stations,” recalls Espinoza. “We couldn’t turn off the pumping station, as that would have flooded out the incoming lines.

“We put a crew in front of the catch basin to keep the flow out of the storm drain system and placed other crews at various locations to draw water from the incoming sewer lines to minimize the flow into the pump station.”

Then, a team rigged a 1,300-foot bypass line from the pump station to a downstream sewer and brought in a contractor to excavate under a parking lot to repair the force main. “We had a lot going on at once, building the bypass line, stopping the flow, setting up containment, getting the contractor on-site,” Espinoza says.

Walton and Espinoza point out, though, that whether the overflow is big or small, the approach is the same. “We’ll provide the same level of response on a 5-gallon spill as we will on one of 1,000 gallons,” says Walton. “That’s an indication of our dedication and commitment.”



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