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Council forwards groundwater management plan after months of modeling and debate
Summary
Staff and consultants presented a near-final groundwater management plan that models island water balances and provides a range of sustainable-yield estimates; the council unanimously voted to advance the plan to a future meeting after hearing requests for more public engagement and additional monitoring.
City staff and consultants presented the 90%-level draft of the Bainbridge Island Groundwater Management Plan and a public engagement schedule. Interim city manager Ellen Schroer framed the plan as years in the making; Christian Berg (surface and groundwater resource specialist) summarized staff work and introduced consultants from Kettle Waters (Joel and Adam Massaman) to present steady-state equilibrium modeling and water-budget analyses.
The technical case: Joel Massaman reviewed how multiple groundwater models were used to compute equilibrium water balances; he emphasized that recharge (precipitation) is a primary driver, septic return flows meaningfully contribute to stream baseflow (roughly 8–10% on average per the consultants’ discussion), and deeper aquifers transmit a smaller share of pumped water to surface systems than shallower aquifers. The consultants noted uncertainty in off-island connections; some model scenarios suggest Kitsap Peninsula pumping could affect island availability but that connection remains uncertain.
Sustainability framing: Adam Massaman described sustainable yield as the level of pumping maintainable indefinitely without unacceptable environmental, economic, or social consequences, and presented a wide rule-of-thumb range for sustainable yield (quoted in the draft) alongside current consumptive-use estimates. Because the ranges overlap, the consultants said they cannot say definitively whether current pumping is sustainable and recommended improved metering, additional streamflow measurements, and targeted conservation strategies that could reduce per-person use (they cited a reference system achieving ~39 gallons per person per day as an example of conservation that would likely be sustainable).
Council concerns and direction: Councilmembers asked for population/ERU translations of acre-feet figures, the basis for the low/high range in sustainable-yield estimates (largely recharge uncertainty), and how to narrow uncertainty through monitoring. Consultants explained why system-level presentation preserves conservation policy flexibility, recommended improving metering and streamflow monitoring, and noted the city and KPUD hold many of the water rights on the island, limiting some legal lever options.
Outcome and next steps: Councilmember Franloy Johnson moved to forward the groundwater management plan to a future meeting for adoption; staff noted an open house scheduled for May 27 (6:00–7:30 p.m.) and the motion was amended to a future date to allow for public engagement. The motion passed unanimously (7–0). Staff and consultants will return with any edits and a public-comment summary prior to adoption.
Key quote: "It is not possible to say definitively whether current consumptive use is sustainable or unsustainable given current uncertainties in recharge," the consultants said, arguing for improved metering and monitoring to narrow the range of possible outcomes.
Next procedural step: A public open house is scheduled for May 27; the plan will return to council for formal adoption after that engagement and any final edits.
