The challenge
Salinity drove much of the proposed scope. The question that mattered was whether the salt in the soil came from the plant's operations or was simply part of the natural setting, because the guidelines applied to the closure depended on the answer.
The approach
Statvis reviewed the salinity data across the site's historical documentation: decades of reports and laboratory results produced by different consultants for different purposes, read into one cited record.
Salinity fingerprinting compares the balance of the major ions in each sample, not just how much salt is present. Samples whose fingerprint matches naturally occurring background group together; samples that carry an operational signature stand apart. Laid out sample by sample, the record highlighted naturally occurring background concentrations, which supported adjusting the regulatory guidelines applied to the closure.
Every value in that comparison stayed linked to the report and page it came from, so the reasoning could be checked by the regulator rather than taken on trust.
The result
With revised, defensible guidelines in place, the site met closure criteria with 4,500 m³ of excavation, a 74% reduction from the 17,000 m³ in the earlier remediation plan.
The regulatory closure plan was approved in under 12 weeks instead of years. Reduced excavation, and no longer needing years of previously recommended sampling, saved an estimated $2.6 million against the original scope.