Mercury detected in gym slab prompts targeted removal plan and hazardous disposal

Project managers reported that core sampling of the gymnasium slab produced mixed mercury test results, prompting a remediation strategy that prioritizes safety and structural integrity.

"The allowable amount is 0.2 milligrams per liter," a construction presenter said while summarizing laboratory results. Of six cores taken, three tested above the allowable threshold and three below; individual results ranged from 0.072 to 0.52 mg/L. Designers and remediation contractors recommended removing a 0.25-inch concrete topping in areas where slab cuts are needed — deeper removal would jeopardize rebar cover and structural integrity.

Because the test results varied significantly across short distances, the team said it is not feasible to sample every square foot. For any slab removed for plumbing or foundation work, crews will treat that material as hazardous: double-bagging and shipping it off-site (contractor noted shipment to Indiana) at increased cost. Project staff said this approach balances worker and occupant safety with the need to keep the project moving.

Construction management said the 0.25-inch topping removal exceeds amounts sometimes used in other projects (0.125 inch) and, combined with encapsulation and a cementitious topping, should reduce long-term exposure risk once new finishes are installed. The board was told the work will have a notable cost impact for affected cuts, and that cost estimates for addressing the north wall would be reviewed at the next OACM meeting.