HINKLEY, San Bernardino County — October 24, 2026. Residents following the Hinkley groundwater cleanup have access to official maps, but the lines on those maps require careful interpretation. The Lahontan Regional Water Quality Control Board’s current public project page links to a second-quarter 2026 upper-aquifer chromium plume map, a grid-book version and older maps. They document a regulated cleanup area; they are not certificates of drinking-water safety for an individual household.
Where the latest maps are published
Start with the board’s PG&E Hinkley Chromium Cleanup portal and expand its Map of Chromium Plume section. The agency lists 2026 and 2025 upper-aquifer maps, including larger-format and grid-book versions. Maps may be designed for print and detailed viewing, so a small phone display can hide well numbers, line styles and explanatory legends.
What a plume boundary does and does not represent
A plume map shows estimated contamination based on available groundwater sampling, hydrogeology and agency-defined thresholds. It does not mean there are measurements at every point inside or outside the lines. The board describes historical chromium-6 releases associated with the compressor station, alongside ongoing cleanup orders and monitoring. Changes from one quarter’s map to another should be assessed with their legends, methods, sampling dates and agency explanations before drawing conclusions about improvement or worsening at a particular address.
Why private wells need a different kind of answer
Household exposure can depend on which well serves a residence, how deep the well is, whether it is connected to an affected aquifer, the quality of recent sampling and whether treatment is in place. A public map is a starting point for questions, not a substitute for certified laboratory testing or direct advice from the relevant water authority. People concerned about a private supply should ask the board which records relate to the specific well and whether any protective program or separate notice applies. California58 cannot determine that a specific home has safe or unsafe water from a general map.
Finding monitoring reports and correspondence
The agency points readers to GeoTracker for project filings and reports and lists the Lahontan Water Board’s contact as amanda.lopez@waterboards.ca.gov, telephone 760-241-7373. Relevant questions include which map is the most recent, what dates laboratory samples cover, which wells were not sampled and what the agency’s most recent written findings establish.
Read Hinkley News’s related report on the 2026 cleanup-feasibility investigative order. Submit public documents, personal experiences or corrections to Hinkley News.
Sources: Lahontan Regional Water Board Hinkley cleanup portal, 2026 upper-aquifer map list, GeoTracker and California State Water Board chromium-6 information page; checked October 24, 2026. The edition has not undertaken independent well testing.
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