GrokSurf's San Diego

Emergency repair work on the damaged and deteriorated dam at Lake Hodges Reservoir that the City of San Diego started doing last year is expected to be completed by April 2023, but even after spending an estimated $14.3 million on repairs, the City will need to keep the reservoir level lowered indefinitely, according to a report presented at the January 26 board meeting of the San Diego County Water Authority (SDCWA) by Eva Plajzer, SDCWA Director of Operations and Maintenance.

Because the dam’s risk factors will be excessive, even after repairs, the California Division of Safety of Dams requirement that the water level at Hodges should not exceed an elevation of 275 feet will apparently remain in effect (although the City of San Diego’s consultant recommends increasing the elevation limit to 280 feet). Normally, the reservoir’s water elevation would reach 315 feet if it were filled to capacity.

That means the City of San Diego will need to continue releasing excess water to the San Dieguito River in order to keep the Hodges reservoir level low enough, but according to SDCWA’s Plajzer, if we experience heavy rain again, like we recently had, runoff into the reservoir could be so great that it might not be possible to release water fast enough to prevent the water from rising above the 275 foot limit. That would potentially increase the risk of further damage to the dam or even a breach that would threaten people and structures downstream.

Plajzer said the quality of the released water is very poor and the downstream water agencies, San Dieguito Water District and the Santa Fe Irrigation District, are unable to treat and use the water, so the water will flow on to the ocean.

That’s bad enough, but there’s yet another problem:

The lower water level at Lake Hodges interferes with SDCWA’s ability to operate its pumped storage facilities located there. The pumped storage facilities, originally built at a cost of $200 million as part of SDCWA’s Emergency and Carryover Storage Project, connect Lake Hodges Reservoir (owned by the City of San Diego) to Olivenhain Reservoir (owned by SDCWA and the Olivenhain Municipal Water District) so that water can be moved between the two bodies of water for water storage purposes and for electricity generation.

During normal operations, water is pumped from Lake Hodges uphill to Olivenhain Reservoir for about 5 hours every day during periods of low energy demand, typically at night, when energy costs are lower. During daytime at peak hours, the flow is reversed, and the same amount of water is sent back downhill to Hodges through electric generators. This reverse flow generates 40MW of electricity which is sold to SDG&E at peak rates and provides on-demand power for up to 26,000 homes.

The problem is that the water intake system for the pumped storage facilities requires Lake Hodges water elevation to be 290 feet. Since the state has imposed a 275-foot limit, those facilities are therefore inoperable.

On top of SDCWA’s lost revenue of $3 million per year from the idled pumped storage electricity generation, it will be necessary to continue maintaining the idle facilities at a cost to SDCWA of another $3 million per year. It will also cost SDCWA an unspecified amount of money to maintain optimal water level at Olivenhain Reservoir with water transfers via a connection to the San Diego Aqueduct for as long as water from Lake Hodges is unreachable.

Plajzer also said that the pumped storage facilities are now operating under a “Force Majeure provision under the SDG&E Power Purchase Agreement.” According to Wikipedia, force majeure “…is a common clause in contracts which essentially frees both parties from legal liability or obligation when an extraordinary event or circumstance beyond the control of the parties…prevents one or both parties from fulfilling their obligations under the contract.”

And indeed, the situation is nobody’s fault: we’re talking about a well worn century-old dam that needs to be replaced.

SDCWA Board members expressed hope that some way might be found to allow the pumped storage facilities to restart operations even with the restricted water level, either by building a new water intake system or perhaps with some kind of containment structure around the water intakes where the water level could be kept at a higher elevation. Even if some workaround would be feasible, it could take years to implement.

As for the impaired dam at Lake Hodges, it must be replaced at a preliminary estimated cost of $275 million. The San Diego Public Utilities Department envisions a 12-year process for that. Our local news outlets will likely continue covering developments on that front.

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This story is based on the following agenda materials and the audio proceedings of SDCWA’s Engineering and Operations Committee at the January 26 board meeting.

The SDCWA Board January 26 meeting agenda and presentation materials: https://www.sdcwa.org/about-us/board-of-directors/meetings/?event=past.

The SDCWA brochure about the Lake Hodges Pumped Storage Facilities: https://www.sdcwa.org/projects-programs/facilities/lake-hodges/.