LaSalle officials outline well‑drilling problem, casing and grout plan; city to use sewer funds for mitigation

LaSalle Mayor Jeff Grove updated the council on complications at a municipal well site and described an engineering plan to stabilize the borehole, then told aldermen the city will use sewer funds to cover the immediate mitigation costs.

Nut graf: The city’s drilling contractor encountered a subsurface void while drilling a municipal well; the mayor said contractors will case the borehole, inject grout and issue a change order for the additional work. Council members asked technical questions and staff said they are reviewing aquifer connections and related risks.

What the mayor told the council: Mayor Grove summarized a recent site incident that engineers characterized as a “loss of flow” while drilling — an indication the drill hit a void in the subsurface. He said the contractor will install an outer casing around the original well pipe (Mayor Grove described it as an approximate 24‑inch outer casing with a 20‑inch inner pipe, with the annulus grouted) and that the contractor will issue a change order for the extra work. Grove cautioned that a casing and grout mitigation is not guaranteed to resolve every subsurface uncertainty; “no matter what you’re doing, there’s still no guarantee that it’s gonna work,” he said.

Funding and risk: Grove told the council the immediate mitigation costs will come from sewer funds. He said contractors reduced the original estimate (the mayor said a negotiated reduction was achieved with Ryan, a staff negotiator) but that the city still faces an unavoidable change order to install casing and grout. Grove and council members discussed the possibility that the void could be a natural cave, an old mine or other subsurface feature; staff said the subsurface geometry (depth vs. lateral extent) may be unknown until further investigation.

Questions and next steps: Council members asked for a brief technical summary and for staff to check regional aquifer connections (the mayor mentioned Joliet and Morris in the context of aquifer use). Mayor Grove said he had contacted outside geologists and engineers and that the contractor’s mitigation follows the engineering guidance he had obtained; he also said the city will monitor the site and update the council. Grove noted the contractor has taken steps to prevent the drilling discharge from reaching the Vermilion River by containing flows in temporary tanks while mitigation proceeds.

Ending: Mayor Grove said staff will continue to pursue technical follow‑up with engineers and to provide the council with updates; council members asked that the matter return to the council if the mitigation plan changes or additional risks emerge.