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City staff outline geotechnical findings, three-step plan after new cracking and leaks at municipal building
Summary
City staff presented a geotechnical report showing fat clays and inadequate drainage under parts of the municipal building foundation, proposed immediate measures and a legal review, and warned repairs could be costly.
City staff told the Administration & Public Works Committee that a recent geotechnical study found fat clays and a likely missing drainage pipe under the footing behind the municipal building, a pattern the department believes is contributing to recent leaks and new cracks.
The study, summarized by staff member Thomas Lee, identified four elements: crack monitors on multiple floors, rain‑garden test pits, a piezometer monitoring groundwater, and nine slab cores. The core samples and test pits found clay in the engineered depth the 2006 geotechnical guidance had said should have been over‑excavated and replaced with compacted aggregate. Lee said investigators also found “there was not a drainage pipe where it should be,” allowing water to saturate soils behind the building and likely causing upward movement that shows in second‑floor crack monitors.
The discovery matters because the city has already repaired several leaks but still has one unresolved roof/garden area leak near the rear police station. The ad hoc building committee will ask the full council to approve a three‑step approach: hire a structural engineer to assess the issues; obtain a targeted engineering quote to rework the rain garden and install drainage under the footing; and request a legal review of prior design and construction records to identify any liabilities or process gaps. Lee reported crack‑monitor readings taken in winter showed up to about 5 millimeters of movement on the second floor; the first floor showed little change.
Committee members pressed for cost context. Staff said a firm estimate is not yet available; in discussion one participant referenced a rough range heard during committee meetings of roughly $500,000 to $2,000,000, but staff cautioned no final price exists and said quotes would be sought as part of the engineering step. The department said it would bring specific repair options, cost estimates, and any recommended legal steps back to the committee and to the council for decisions.
The department characterized the item as informational tonight; the committee did not approve construction funds at the meeting. Staff said the council will see a fuller recommendation at its next regular meeting.
