Committee says south‑facing stormwater basin likely driving City Hall leaks; orders targeted tests and study of lot consolidation

The Building Committee on March 24 reviewed new geotechnical findings that staff said point to the stormwater basin behind City Hall as a major contributor to repeated leaks and seasonal wall movement, and authorized a program of targeted testing and engineering study.

Staff member (speaker 2) told committee members that studies in 2020 and 2024 and four test pits dug behind the municipal building show saturated soils and “fatty clays” along the south foundation and that only one pit reached the footer level; that single test did not locate a footer drain the project’s designs would normally include. “We have a very strong inclination that that drainage pipe just doesn't exist,” staff said, adding the missing drain plus the clay soils could cause subsurface water to swell and exert upward pressure on the foundation.

Why it matters: staff said the basin sits very close—about 4 or 5 feet—from the foundation and stores parking‑lot runoff plus roof and sidewalk water; when the basin fills during storms, the city has repeatedly seen leaks in the back storage closet, women’s restroom and the police station hallway. Staff noted that a waterproofing patch last year cost roughly $3,000 and temporarily eliminated a corner leak, but that larger rain events still produce seepage.

The committee approved two near‑term steps. First, staff will run a systematic “hose test,” placing a nozzle at marked foot intervals and running water an hour per quadrant along the south wall to see whether pressurized surface water produces seepage into the building. Staff said the test should be done during an upcoming dry spell and may be run with hired waterproofing contractors to ensure strategic placement of hose tests. Second, the committee endorsed a planning‑level study by civil/environmental engineers (CEC) to evaluate options if the three adjacent lots were consolidated so more stormwater could be stored upstream of the building rather than at the foundation.

Legal context: staff briefed the committee on a legal review of construction records. Attorneys raised concerns that a ten‑year limitation tied to the project’s 2014 completion could hamper recovery actions against designers or contractors; staff recommended an attorney‑client executive session should the committee want privileged legal advice.

What comes next: staff will run the water‑penetration tests, solicit contractor input as needed, and return with test results and CEC’s options for basin relocation or remediation. If tests identify a leak traceable to the basin, staff said excavation and installation of a footer drain and replacement of degraded waterproofing would likely be required.