“Atmospheric River” is a meteorological term coined in the 1990s that’s recently entered common public usage. They are bands of concentrated moisture traveling in the air over a region. Atmospheric rivers can contain as much moisture as major river, such as the Amazon.
On February 5th, the Scripps’ Center for Western Weather and Water Extremes released a new rating scale, categories 1 thru 5, depicting the level of strength for atmospheric rivers.
On February 14th, weather stations in California were tracking a large atmospheric river heading into Southern California. It became known as the Valentine’s Day storm and was eventually designated a category 4 atmospheric river.
For many CWEA members in Southern California, it was one of the worst storms they’ve seen.
At the Coachella Valley Water District, Juan Martinez, Collections System Supervisor, and Nahúm Padilla, Collection Systems Crew Chief, were keeping a close eye on weather forecasts.
“We knew it was coming, but we didn’t know if it would go around or if we would be a direct hit,” said Juan.
Coachella Valley is below sea level, and normally very dry, with storm fronts usually hitting the Santa Rosa mountains to the west and going around the valley towards the higher desert to the north.
CVWD is responsible for 28 lift stations and over 1100 miles of sanitary sewers. 85 miles is forcemain, and over 22,300 manholes. The sewer lines feed into five separate CVWD water resource recovery facilities.
On February 13th, in advance of the storm, all 21 CVWD Collection System operators were put on notice of emergency standby. In the end about 80% of the operators were called into service.
The rain didn’t go around, and according to Juan, “It got us, and it got us pretty good.”
In preparation for the storm, operators were redirecting several sewer force mains from one side of the valley to the other so they could manage incoming water. Shifting the flow helped alleviate pressure on the system. The ability to redirect flow allows managers to distribute flow evenly to all the treatment plants, and not overwhelm them.
As the storm progressed on February 14th, storm channels began to fill to capacity and came within a few inches of overflowing. It was only the second time in over 30 years operators have ever seen the main channel that full.
“That was a sight to see, because normally you only see a small stream going down the center,” said Juan.
As part of the District’s emergency preparedness planning, several scenarios were anticipated and team members trained for them. Although they were busy during the storm, crews with Vactor trucks kept drains clear and using flow mitigation efforts, there were no unpleasant surprises. Just long hours.
Juan & Nahúm agree everything went well during one of the worst storms to hit the area.
“We had a few things going on. Being proactive and doing training really paid off,” said Juan.
Andy Keller, Sewer Department Foreman for Big Bear City Community Services District (BBCCSD) was watching the weather too. Big Bear is a mountain resort community at 6,000 feet, and BBCCSD is responsible for 116 miles of main sewer line, 2900 manholes and 12,000 service connections. They also operate seven pump stations, feeding into a main trunk line going to the water resource recovery facility operated by Big Bear Area Regional Wastewater Authority.
A preventive cleaning & CCTV inspection plan has been in place at the BBCCSD for many years. Over the past eleven months they were inspecting lower laterals.
Andy was the operator on call when he received a pump station alarm early February 14th. At 4:00 am he headed over to the Kern pump station to check the system for excessive pump run time. He found both pumps running because higher flows were entering the station.
At 6:30 am, high winds knocked over multiple power poles and the entire community of Big Bear City lost power. All seven pump stations are equipped with back up generators, so operators were dispatched to the pump stations to monitor their operation. Andy remained at the Kern station to coordinate activities, while monitoring the system on SCADA with the IT manager.
“We were forecast for 3” of rain for the day, which is a lot,” Andy said. “But in reality we ended up getting 4-10” with this storm. In my 36 years up here, I’ve never seen anything like it.”
The rains came on top of snow which had fallen earlier in the week, compounding problems.
As the levels continued to rise at the Kern pumping station, Andy called out the larger of the BBCCSD’s two Vactor trucks to deal with the flow. As the morning progressed more and more of the pumping stations alarmed with high levels. The other, smaller, BBCCSD Vactor truck was put into service at another pumping station. As additional pumping stations needed help, local septage pumpers were called in to vacuum up the excess flow.
Due to high winds, downed trees, extreme flooding and rockslides, all three roads leading up to Big Bear were closed. There was no way to bring in additional pumps.
At 3:00 pm the Kern station came within 3” of overflowing. At 3:30 the rain subsided and at 4:30 pm, the rain turned to snow.
By this time Andy had been working at the pump station for 12 hours. His team had been working for over 10 hours, all without a break. The BBCCSD is also responsible for solid waste collection, so they called in their solid waste workers, provided on-the-fly cross training, and rotated people so those on duty the longest could get warmed up and put on dry clothes.
As the evening wore on, the roads became slippery, so the Vactor trucks had to be chained up. While chaining up the larger Vactor a leaking tire was detected, rendering the truck temporarily out of service while the tire was repaired. Fortunately, the storm flows had receded enough so the smaller Vactor could keep up with the flow.
The contract pumper trucks left about 7:00 pm as roads became impassable.
As the flows receded more operators were released, and at about midnight, the last of the BBCCSD crew was sent home.
As a result of the extreme flows experienced during the Valentine’s Day storm, and anticipating future storms could be similar, Andy has added a new bypass pump into the District’s upcoming budget.
“There were a lot of manholes submerged underneath flood waters, mostly easements in natural drainages,” said Andy. “In the areas that were flooded we’re looking at changing out the lids to a sealing type lid.”
“We did have our flat tire issue, so I’ve already ordered mounted spare tires for our Vactors.”
Longer term, Andy plans to do more investigation and remediation of the infiltration and inflow issues upstream of the Kern pumping station.
Andy has high praise for all of his crew.
“One of our operators had the day off and was heading off the mountain. He got turned around because the road was closed. He knew we’d need help so he came in for the rest of the day.”
“Our IT guy was out at the pumping station all day, even though he didn’t have proper raingear, monitoring the SCADA system, getting soaked.”
“The guys from the trash department were eager to help. Every crew member had a great attitude, despite being soaked and frozen, working hard non-stop.”
“We’re very proud of our system and the limited spills that we do have,” said Andy. “The last (sewer overflow) spill was in March of 2009, so everyone was determined not to let anything spill, doing everything we can.”
At the Santa Margarita Water District in southern Orange County, rain started falling early in the morning. Per standard practice, the District’s crews were out in the days before the storm, ensuring all the equipment was functional and standby pumps available.
Daily peak flow at the water resource recovery facility typically happens 8 am and 10 am. The storm infiltration & inflow started reaching pump stations between 6 am and 7 am.
Don Bunts, Deputy General Manager for SMWD, commented, “We could see the rippling effect from our lift stations that was pumping the water and bringing it towards the treatment plant. It was one of those situations where the rain hit when the peak flow for our normal diurnal events took place. That was a fairly strong combination of peak flows happening.”
The combination of peak daily flow and storm flows hit at the same time, and the facility hit 4.2xs its average flows, higher flow than the plant had ever experienced before. It could have rapidly overwhelmed the capacity of the plant.
Operators quickly diverted flow from the primaries into empty secondary clarifiers for temporary storage.
“The plant operators were really sharp in coming up with that,” Don explained. “We had not anticipated that we would experience that high of flow.”
The intense storm was over in 2-3 hours, so after the surge had passed, operators pumped wastewater out of the secondaries and back to the headworks for treatment. An extra crew was also called in to help out around the plant.
According to Don, “They got caught up later that same day.”
SMWD’s collection system runs through the rolling hills and canyons of rural Orange County. In some areas, sewer lines are buried in parallel to creek beds. During the storm, the creeks and canyons filled and some overflowed their normal boundaries.
Normal operating procedure is an employee drives along the access roads to check the sewer lines. During a routine inspection on February 15th a crew member discovered the rushing waters of the Trabuco Creek had scoured the bank away, leaving a gravity sewer line intact but exposed, 20’-30’ above the normal creek level.
Knowing the environmental importance of preventing a spill, a contractor was hired, and the appropriate agencies contacted to let them know work was being done on the creek bank. The contractor worked over the President’s Day holiday weekend to restore the bank and protect the sewer line. The project was completed in two days.
“We had contingency plans in case the stabilization couldn’t be done,” said Don, “but they weren’t required.”
Despite the severity of the storm, the advance preparation, training, cross-training, and the quick thinking and actions of the workers during the event paid off.
“It’s our new normal,” said Don. “We need to re-evaluate what our peaking factors are at our facilities so we don’t get into this situation again.”
On February 28th, Governor Gavin Newsom declared a state of emergency for several counties in relation to the Valentine’s Day storm, allowing local communities to receive State and Federal aid..
The atmospheric rivers are categorized based upon the amount of water vapor carried in the plume in combination with the duration of the event.
The precipitation brought by atmospheric rivers is generally beneficial, but as the intensity increases the potential for hazardous side effects such as flooding or landslides increases. Category 1 thru 2 are considered to be primarily beneficial, while category 3 is considered to be a balance of beneficial and hazardous. Category 4 is more hazardous than beneficial, while category 5 is primarily hazardous, causing significant damage.
According to analysis of past weather, the Oregon coast receives on average one atmospheric river in the Category 4 level once per year, while Washington State receives a Category 4 level once every two years, the Bay Area once every three years, and Los Angeles every 10 years. A well known atmospheric river is the ‘Pineapple Express’, famous for bringing warm water vapor plumes from the Hawaiian Islands area and depositing them along the west coast of North America, from California to Canada.
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