City officials approved a plan for a new groundwater sustainability project, hoping it will be a solution to increase the supply of groundwater and find a place for excess effluent water coming to the Tehachapi Waste Water Treatment Plant. The benefits will not appear for decades, when the project is complete.
The Tehachapi City Council unanimously approved this second of five phases at its April 1 meeting.
“It will change the way the city uses our water and wastewater in the future,” said Don Marsh, city public works director.
The study will look at the costs and project scoping to eliminate wastewater reclamation at the airport and at the Tehachapi Waste Water Treatment Plant.
The water would be allowed to percolate into the ground at Blackburn Dam, after a more extensive cleaning and filtering process to treat the wastewater to a tertiary level.
The goals are to increase water supply, maximize recycled water use, improve water quality and decrease reliance on imported water from the State Water Project, Marsh said.
The project work plan that outlines the scoping, overview of pipeline alignment of Blackburn Dam, permitting, design and construction will be handled by the Engineering firm, MKN & Associates, Inc. a company that specializes in wastewater reuse. The city will pay about $698,611 for this work.
“As we discussed, the city is in a unique situation to be able to develop probably one of the more cost-effective indirect potable reuse systems we have seen, just because you have all the right conditions,” said Mike Nunley, professional engineer of MKM Associates, Inc. who addressed the council at the meeting.
The city began an evaluation of an Indirect Potable Reuse and Groundwater Replenishment Reuse Project project in 2015, exploring different options for recycling water.
Some ways to expand the city's reuse of water were very costly. This could have meant upgrading the Tehachapi Waste Water Treatment Plant, existing effluent pump station, constructing a new discharge structure behind Blackburn Dam and new booster pump station and pipeline to Blackburn Dam — all at the same time.
The estimated initial cost was expected to be about $24.5 million for the required planning, design, construction and regulatory approvals, according to the Indirect Potable Reuse Conceptual Study Summary Report from 2016. The number is expected to change in the future.
Reductions in growth for Tehachapi and average daily flow of wastewater have been re-evaluated, meaning that the city will not have to upgrade the WWTP at this time, according to the Indirect Potable Reuse Evaluation Technical Memorandum-Addendum to the Conceptual Study Summary Report 2018.
The plant has the capacity of 1.25 million gallons per day, but only processes 750,000 gallons a day.
If the entire Indirect Potable Reuse and Groundwater Replenishment Reuse 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.
Local groundwater in the Tehachapi area is scarce and may not support future demand.
In 2018, the city went over the allotted 1,847 acre of feet of annual pumping of native groundwater within the Tehachapi Basin. When this happens, the city may need to purchase water from the Tehachapi-Cummings County Water District or lease water rights from other private individuals, said Marsh.
Water is pumped more than 4,500 vertical feet from the California Aqueduct by the TCCWD to supply the area with water for agricultural and residential customers and the project could supplement the area's resource.
“We look forward to working alongside the city and one of the tasks between the two agencies is to move forward with this project. We see this as a great resource, not only for the city, but for the area as well,” said Tom Neisler, general manager for TCCWD. “We are a regional agency and we have to take care of everybody and the city having this additional supply available takes some of the burden off of some of our imported resources.”
Residents and airport users raised some concerns and opinions about the wastewater being removed from reclamation land at Tehachapi Municipal Airport.
A 2018 Annual Report for Tehachapi's Wastewater Treatment Plant shows that treated effluent was applied to 53 acres of farmland, as in years past, at the airport.
“I think it's a smart move," city business owner Scott Baker said. He added, “Your sewer treatment plant would be considered part of your critical infrastructure and so you are now separating these two items into individual critical pieces of infrastructure, which can be maintained better. You don’t want to keep tying these two entities up like that. The airport is a critical piece of the infrastructure.”
Baker suggested the city consider using more water for landscaping, especially when the Sage Ranch development, a housing tract of more than 1,000 dwellings, is built near Tehachapi High School.
Mike Lerner, secretary of the Tehachapi Airport Hangar Owners Association, asked about future development of the north side of the airport. He requested information about how long it would take for the land where the effluent wastewater is spread to be encumbered from the state, and if there would be a lengthy clean-up process to allow development.
Marsh said it could take more than two years for any future use, depending on when the water discharge permit is removed.
Jay Schlosser, development services director for the city, said that information on water samples is sent to the state for testing and the city is in compliance with state standards.