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Consultants find Stevens Lake sediment benign but warn dam leakage may need up to $750,000 to breach; URA renews Oasis on-call contract
Summary
Oasis Consulting reported sediment samples at Stevens Lake are largely benign but a dam inspection showed leakage and potential spillway issues; the URA approved renewal of Oasis’s $65,000 on-call environmental contract and discussed a $67,000 design study and a possible $750,000 capital cost to breach or repair the dam.
Oasis Consulting told the URA that sediment sampling at Stevens Lake returned largely benign results, but a field inspection and geotechnical borings revealed leakage in the dam’s spillway and areas that could undermine the structure if left unaddressed.
"The sediments at the bottom of Stevens Lake actually turned out to be fairly benign or innocuous," said the Oasis representative, who also reported that soil borings and a visual inspection identified leakage and a compromised emergency spillway. Oasis and the dam specialty firm Walden Ashworth recommended further geotechnical and hydraulic studies and proposed an initial design budget of about $67,000 to develop plans for a controlled breach or rehabilitation. The consultant provided a ballpark estimate that breaching or large repairs could cost about $750,000.
The URA voted unanimously to renew Oasis’s on-call environmental contract (the amount noted in the consultant’s request was $65,000), a contract the consultant said is used only as needed for services such as MEC (munitions of explosive concern) awareness training, specialized sampling and site assistance. The motion to approve the on-call contract was moved by Dr. Patrick and seconded by Miss Sutton and passed by voice vote.
Board members noted the possibility of seeking cost-sharing with adjacent property owners because Stevens Lake is surrounded by development; staff said decisions on capital remediation are on hold until design and hydraulic analyses are completed.
Next steps: Oasis and Walden Ashworth to complete a condition assessment and a hydraulic study if funded; staff will bring proposals and potential cost-sharing options back to the URA.
