-
01
What happened
A depression appeared on the grounds of an active water reclamation facility. At a plant that cannot be taken offline, the question was whether the ground beneath critical structures could still be relied on.
-
02
The investigation
25 standard penetration test borings to depths between 48 and 115 feet, reaching limerock. The samples and field data revealed a solution cavity at several locations, with a raveled soil zone above it.
-
03
Recommendation
Compaction grouting to compact and stabilize the loose and soft soils in the raveled zone. A sealed grout injection point location plan set the location, depth, and sequence of each point, monitored through installation.
-
04
Verification
Grouting without verification proves nothing, so we remobilized and drilled again in the treated zone. The soils that had shown sinkhole activity were significantly strengthened and stabilized.
-
05
Why it mattered
The facility stayed in service. The city got a documented before-and-after record rather than an assurance, which is what allows a public agency to close out a problem like this on the record.
