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Navy reports limited sludge, stepped‑up groundwater monitoring at Red Hill; data show no clear off‑site plume
Summary
At the Sept. 17 CWRM meeting Navy task force members reported tank inspections and limited sludge removal at Red Hill, a ramp‑up of groundwater monitoring and biweekly sampling, and said current data indicate contaminant detections remain largely within the facility and have not migrated off‑site; the Navy announced more sentinel wells, pilot remediation studies and public webinars. DOH will hold an open house Oct. 8.
Navy task force representatives briefed the commission Sept. 17 on Red Hill decommissioning, groundwater sampling and remediation planning.
Navy presenters said they began air quality monitoring in May and have degassed and entered Tanks 7 and 8 for inspection and cleaning preparations. Contrary to historical expectations of roughly 2,000 gallons of tank sludge per tank, presenters reported a much smaller recovery: 'we pulled 38 gallons of sludge combined out of the 2,' and said sludge removal took about a day and a half per tank.
The Navy described an expanded groundwater monitoring network comprised of wells sited inside the tunnel (to detect facility‑proximate contamination), peripheral compliance wells placed around the facility boundary, and a less mature sentinel network that will require coordination with multiple landowners. They said a regional groundwater flow model informed site planning and that an independent University of Hawaii modeling effort is expected next year to refine localized understanding.
Sampling frequency was shifted from monthly to biweekly with geographically dispersed sampling so that at least five wells are sampled each day; overnighted samples are processed in Denver with a two‑to‑three‑week laboratory turnaround. On data, the Navy presented heat‑map views for total petroleum hydrocarbons (TPH) and said the monitoring network does not show migration of a TPH plume off‑site: 'we're not seeing detections that move from location to location that would indicate... plume migration,' a Navy representative said. The Navy told commissioners the method detection limit for TPH is roughly 48 parts per billion and that non‑detects fall below laboratory reporting thresholds; they offered to provide mapping and geostatistical method details as follow‑up.
Navy staff also described concurrent site‑assessment activities and pilot remediation studies (soil vapor extraction and passive soil vapor monitoring) and said a PFAS remedial investigation aligned with CERCLA is scheduled to begin within about 30 days. Public engagement plans include an interactive dashboard/app, webinars on the groundwater network and groundwater flow model, and an open house being organized by the Department of Health on Oct. 8 at Aliamanu Middle School.
Commissioners and members of the public asked technical questions about laboratory reporting limits, mapping methodology and the possibility that detections in sentinel wells could reflect non‑Navy sources (asphalt runoff or historic agriculture). Navy presenters acknowledged those complexities, said site characterization will be iterative, and committed to data transparency through the Safe Waters/EDWMS portal and published model deliverables.
Next steps: additional sentinel wells as feasible, publication of an updated groundwater model, pilot studies to inform field investigation early next calendar year, and continued coordination with DOH and EPA.
