Council approves grout injection plan to stabilize Swanson Trails trench backfill

Portage City officials voted to accept an engineering-backed plan to pressure-grout trench backfill in the Swanson Trails subdivision after staff and the developer described a targeted program to fill voids left by number-2 stone backfill.

Michael Prigge, representing Midland Standard and Lennar, told the council the contractor will core the binder pavement along the utility trench at intervals and inject a flowable-fill grout to fill voids, then patch the cores and place a final surface course. "We are proposing a solution to the trench backfill," Prigge said, specifying the work will be monitored by yield to estimate spacing and that the grout is excavatable for future maintenance. City engineering staff said the affected work includes about 2,670 feet of mainline and 70 laterals (28 feet each, totaling 1,960 linear feet of lateral), and that a geotechnical engineer prepared the report underpinning the approach.

Council members pressed staff on prior experience and long-term maintenance; engineers said the method has been used in analogous seepage and infiltration cases and that the material can be excavated if later repairs are necessary. After discussion the council accepted a motion to adopt the engineer's recommendation and to require a four-year maintenance agreement beyond the standard two-year maintenance period; the motion was seconded and approved with members indicating "Aye." Specific vote tallies were not provided in the record.