City officials in Tehachapi are investigating ways to move treated effluent water coming from Tehachapi’s Waste Water Treatment Plant. More potable water could be available if a groundwater reuse project becomes reality, opening more land at Tehachapi Municipal Airport for potential growth.
“We want to capture that water and put it back in the aquifer and receive a credit. We can only pump as much as we own or control,” City Manager Greg Garrett said. “It’s certainly an event changer, so the city of Tehachapi can be self-sufficient, but it’s really a visionary at this point.”
Treated water could recharge in the Tehachapi aquifers, although pipes would have to be placed to pump it up the hill to Blackburn Dam, near Tehachapi Mountain Valley Airport. It's estimated to cost more than $10 million. Plans to bring it before the City Council are being made, Garrett said.
If the project became reality, the potential to spread up to 1,500 acre-feet per year at Blackburn Dam would require an upgrade at the wastewater plant to produce tertiary disinfected effluent, according to the city of Tehachapi’s 2018 Annual Report for the Summary of Reclamation Operations at the WWTP.
Tertiary disinfected effluent is a high level of treated water and comes after a primary and secondary process, said Scott J. Hatton, supervising engineer for the California Regional Water Quality Control Board.
Effluent treated water is the final product at a facility, but it's not disinfected and cannot be used to grow crops for human consumption.
“The city has executed a conceptual study to investigate our current and future wastewater treatment and reclamation practices. At this point, no project or funding has been approved by the City Council to move forward with the project,” city Public Works Director Don Marsh wrote in an email.
In 2016, the city completed an Indirect Potable Reuse Conceptual Study to evaluate the "feasibility of indirect potable reuse of its treated WWTP effluent," according to the city of Tehachapi’s 2018 Annual Report for the Summary of Reclamation Operations at the WWTP.
Airport users are concerned that reclamation land at TMA is not being used for aeronautical purposes. Now the city is investigating other ways to remove the treated effluent water.
“The plant here processes 750,000 gallons a day. And basically we discharge wastewater at the airport from April to October,” Marsh said in an interview. He added, “The other six months we have to store 750,000 gallons a day, times six months' worth of wastewater. That is a lot of wastewater.”
Wastewater storage at the plant consists of 39 acres of effluent reclamation areas, according to a 2018 Reclamation Area Soil Sampling report for the WWTP from BSK Associates. Treated effluent was applied to 53 acres of farmland at the TMA in 2018. A borrow pit is also used for storage off of Tehachapi Boulevard.
About 65 percent of the capacity of the treatment plant is being used. Land at the wastewater facility needs to be left open in case residents start using more water, or a catastrophic event occurs, said Tyler Napier, utilities manager for the city in an interview.
“Our plant capacity currently, and the way the plant is designed and built, we can handle 1.25 million gallons per day,” Napier said. “We are not at full capacity, but we have to be available for that.”
He added, “Storage is not just for what we use today, but what we could potentially use.”
Hatton said, "Any wastewater plant has to work around the clock and it’s always good for them to have backup area for the storage of the any waste water.”
The city's access to water is limited.
Tom Neisler, general manager for the Tehachapi Cummings-County Water District, said, “Under the adjudication, the city owns 2,770 acre feet of base water rights. These rights equate to 1,847 acre of feet of allowed annual pumping of native groundwater within the Tehachapi Basin.”
He added, “If the city needed more water than what they were allowed to extract under the adjudication, they would need to utilize another supply. They could use banked water that TCCWD had previously stored for them. They could purchase imported water that TCCWD would bank for them or they could develop an alternate supply. TCCWD stands ready to assist the city or any of our customers to meet their needs.”