Efforts to expand Pacheco Reservoir receive boost with key step toward federal funding

Valley Water’s effort to expand Pacheco Reservoir in Santa Clara County received a significant boost in June with a recommended award of $1.7 million in federal funding to complete a feasibility study of the new dam.

The Pacheco Reservoir Expansion Project was identified last year as the preferred alternative to address an issue of algae growth that sometimes occurs in San Luis Reservoir. Algae growth can disrupt the delivery of water from San Luis Reservoir to Valley Water and the San Benito County Water District.

The effort to address the algae issue, known as the San Luis Low Point Improvement Project, is being led by the U.S. Bureau of Reclamation and Valley Water. Reclamation and Valley Water studied dozens of possible alternatives to address the low-point issue, narrowed that list to five choices, and identified the Pacheco Project as the preferred option.

In June, the Interior Assistant Secretary for Water and Science included the San Luis Low Point Improvement Project in a list of recommended surface water storage projects to receive federal funding under the Water Infrastructure Improvements for the Nation (WIIN) Act of 2016. Congress will make a final determination by naming the projects it wants Reclamation to fund. That could happen toward the end of this year.

If Congress approves the San Luis Low Point Improvement project for federal funding, those dollars will be spent by Reclamation to complete studies of the new dam at Pacheco Reservoir.

“This is a huge first step in the process to obtain federal funding for the proposed expansion of Pacheco Reservoir,” Valley Water Chair Nai Hsueh said. “We are thrilled that the San Luis Low Point Improvement Project was included in Reclamation’s list of recommended projects to receive federal funding.”

The proposed expansion of Pacheco Reservoir, located about 60 miles southeast of San Jose, is a collaboration between Valley Water, the San Benito County Water District and the Pacheco Pass Water District. The project will boost Pacheco Reservoir’s operational capacity from 5,500 acre-feet to up to 140,000 acre-feet, enough to supply up to 1.4 million residents with water for one year in an emergency.

A rendering of an expanded Pacheco Reservoir in south Santa Clara County.

The expanded Pacheco Reservoir will also reduce the frequency and severity of water shortages during droughts, preserve groundwater and protect infrastructure, and improve habitat for fish.

Valley Water and the Bureau of Reclamation also believe an expanded Pacheco Reservoir will solve the low-point issue at San Luis Reservoir in Merced County, located about 15 miles east of Pacheco Reservoir.

In summer and early fall, high temperatures and low water levels can foster algae growth in San Luis Reservoir. When water levels reach a certain “low point,” water in San Luis Reservoir becomes unsuitable for municipal and industrial use in Santa Clara and San Benito counties.

San Luis Reservoir has reached the low-point level seven times since 1968; with climate change, this is expected to increase.

During potential low-point events, Valley Water will utilize the expanded Pacheco Reservoir to receive and store its supply of water from San Luis Reservoir. This will allow Valley Water and the San Benito County Water District to receive water from the state and federal supplies before algae growth becomes an issue.

If Congress approves the San Luis Low Point Improvement Project to receive federal funds for the study, the project could receive federal funds in the future for costs associated to design, permitting and construction of a new Pacheco Dam.

Valley Water is presently conducting studies, investigations and surveys to design and evaluate potential environmental impacts for the Pacheco Project. The proposed expansion of Pacheco Reservoir includes the construction of a new, earthen dam a short distance upstream of the current dam. It also includes a connection to San Felipe pipeline that will allow Pacheco Reservoir to receive water from San Luis Reservoir.

Construction to expand Pacheco Reservoir is anticipated to begin in 2024.

To receive the latest information about the project or upcoming meetings, please sign up on the project’s webpage at valleywater.org/pachecoexpansion.

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