Monterey Peninsula targets ASR well conversions to ease injection bottleneck amid water surplus

Monterey Peninsula targets ASR well conversions to ease injection bottleneck amid water surplusWith the expansion of the Pure Water Monterey potable reuse project pushing the region into a rare water surplus, the Monterey Peninsula Water Management District is urgently seeking to restore lost injection capacity at its Aquifer Storage and Recovery facilities.

The district injected 835 acre-feet into ASR this water year, falling short of the 1,210 acre-foot long-term average due to disabled injection wells.

ASR Wells 3 and 4 were previously converted to production-only to maintain regulatory distance from Pure Water Monterey injection paths.

MPWMD is using an ongoing CPUC rate case to pressure California American Water to convert Well 4 back to injection mode.

The district is also evaluating the feasibility of drilling a third, district-owned injection well in the Santa Margarita area.

The Monterey Peninsula Water Management District (MPWMD) is navigating a historic transition to a "water surplus mode" driven by the expansion of the Pure Water Monterey project, but infrastructure constraints are limiting the district's ability to maximize groundwater storage. During the district's April 20, 2026, Board of Directors meeting, the General Manager reported that MPWMD had injected 835 acre-feet (AF) of water into the Seaside Groundwater Basin during the current Aquifer Storage and Recovery (ASR) season. While the region experienced an above-normal precipitation year—reaching 115% of the long-term average—ASR injection fell short of the 1,210 AF historical average. The bottleneck is located entirely on the Seaside Basin end, where the district currently lacks sufficient injection capacity. According to the General Manager, ASR Wells 3 and 4 are currently disabled for injection purposes. The wells were converted to production-only after the launch of the Pure Water Monterey potable reuse project. ASR Well 1 was initially taken offline for production to ensure sufficient underground travel time for virus log removal credits from the Pure Water Monterey injection site. To compensate for the lost production, Wells 3 and 4 were converted to extraction, removing the valve components necessary for injection. To restore optimal storage capabilities, the district is pursuing multiple infrastructure solutions. MPWMD is utilizing the current California Public Utilities Commission (CPUC) general rate case to push California American Water (Cal-Am)—the region's primary retail purveyor—to convert Well 4 back to an injection well. District staff noted that they are actively working with Cal-Am engineers to plumb two new extraction wells, Bayonet 1 and 2, which would allow treatment at the Santa Margarita facility and enable Well 4 to return to injection mode. Concurrently, MPWMD is evaluating the feasibility of drilling a third, district-owned injection well in the Santa Margarita area. However, the identified location sits beneath high-voltage power lines, creating logistical challenges for deploying a deep-drilling rig. Resolving the injection bottleneck is critical as the district finalizes its 2025 Urban Water Management Plan. With the Pure Water Monterey expansion coming online, the General Manager noted that Cal-Am will be in a supply surplus for the next several years, requiring complex operational decisions to balance the new potable reuse supplies with Carmel River water rights and Seaside Basin adjudication limits.