Grease causes So. Lake sewer jams
What goes in, must come out. And out again when it comes to sewage in South Lake Tahoe.
Thirty percent of a South Tahoe Public Utility District customer’s bill goes toward pumping effluent out of the basin to the Carson Valley. Once it is treated, it is sent through a maze of pipes over Luther Pass onto land used for cattle grazing.
Everything that goes down a drain comes out at the 44-year-old plant to be treated. Because there is no manufacturing in South Tahoe, about 99 percent is water and 1 percent sewage.
“It would pass many drinking-water standards,” lab director Terry Powers told Leadership Lake Tahoe as the group toured the site this month.
No one opted to take a swig of the murky water that had solids settled on the bottom of the container. What eventually gets shipped to Nevada is “sparkling,” according to Powers.
STPUD also provides the majority of drinking water for South Shore from wells. Chlorine is added to curb bacteria.
“Prior to us using chlorine, we had bacteria 4 percent of the time,” Powers said.
There was a time when it took four days to test for bacteria. Now it can be done in a matter of hours. The district continually monitors the water. One way is by sampling water from about 20 homes a week to ensure the purity.
E. coli has never turned up, though it is something scientists watch out for.
Throughout the treatment plant, there are water storage tanks, some with birds swimming on top. One vat is 30 feet deep with paddles at the bottom, where the solids collect.
Dennis Cocking, spokesman for the utility district, said it can be surprising what comes through a toilet. Diapers are not uncommon.
At the early stage, there is also a slab of grease on top of the water.
“It’s equivalent to cholesterol in sewage treatment,” Cocking said.
To combat this, he plans to educate people about the hazards of pouring liquid grease down a drain. Informational flyers have been sent with bills twice.
In a later interview, Cocking said he is impressed that Little Rock, Ark., is giving customers metal cans with liners that can absorb grease with a temperature of 2,000 degrees. All cooking grease goes into the container, which then can be tossed into the garbage because it is considered solid waste.
Grease does go down drains just with hot water. The problem starts when it arrives at STPUD’s tanks. In the process, the pipes are getting colder, and the fat is beginning to solidify.
It is the grease-diaper combo that often is the culprit in sewer spills. Though there has not been one in South Tahoe in three years, regular cleaning of pipes has shown the two together are a threat. Diapers either get stuck along the grease-filled pipes or lodged against sticks that have been shoved down manhole covers by curious kids, according to Cocking.
Cocking said a 5-year-old program to contain restaurant grease has decreased claims by 85 percent. Old grease traps have been replaced with grease interceptors at 30 area restaurants.
What grease still makes its way to the plant is sold to a company in a break-even proposition for the utility.
“The worst thing you will smell (here) is rancid grease,” Cocking said.
By March, the district expects to be the only plant of its size in the country to recycle all wastewater and bio-solids. Because South Tahoe PUD averages 5 million gallons of wastewater a day, the Environmental Protection Agency considers it a medium-size plant.
One-hundred percent of the wastewater has been recycled since 1968.