CARLSBAD — Epic rains during the week of April 6-10 resulted in a giant sinkhole in Carlsbad.
During the April 10 storm, which dumped 3.45 inches of rain, according to the National Weather Service, a 21-inch sewage pipe ruptured and led to a massive sinkhole in a parking lot in the 6300 block of Yarrow Drive on April 12.
A parked van was consumed by the sinkhole, although the owner, a transient, was not injured, according to Elmer Alex, Vista’s sewer engineer division manager.
The pipeline is owned by the Buena Vista Sanitation District, an entity of the city of Vista. On April 16, the Vista City Council held a special meeting to approve $575,000 in repairs, which began on April 12.
“We are fortunate it did not cause a spill and the driver was able to remove himself from the vehicle,” Alex said during the special meeting. “If a spill had occurred, the city may have been subject to a fine. The vehicle had been parked illegally in the lot. It is believed to be a transient vehicle.”
Alex said sewer meters had high peaks of 7,000 gallons per minute during the storm, leading to unstable soil and the break. Due to stay-at-home orders because of the COVID-19 pandemic, the district is averaging 3 million gallons of sewage per day, an increase of 1.2 million gallons per day before the orders.
Repairs, though, were delayed a bit when 40,000 gallons of residual water were unknowingly released by construction crews, according to the site superintendent. The water was in an abandoned pipe, which was then pumped out.
The hole is 30 feet deep and crews have expanded the site hole around the original sinkhole according to safety regulations as they moved in heavy equipment and began cementing the floor with 12 inches of concrete on April 17. Work was completed on April 20, although crews must complete some additional repairs, Alex said.
The outflow pipe carries raw sewage, which then is pumped to a treatment facility on Avenida Encinas before being expelled into the Pacific Ocean, according to Vicki Quiram, general manager of the Carlsbad Municipal Water District.
Crews, though, ran numerous temporary lines and two pumps to bypass the sewage water to another manhole and back into the system.
“We share ownership in multiple wastewater facilities,” Quiram said. “Some of our pipes connect into the line.”
The cost, meanwhile, will come from the district’s reserves fund, which is currently at $13 million.