Trip Blank Hits, Duplicate Failure, and a Lender Deadline at a Former Dry Cleaner
A Phase II investigation is under way at a former dry cleaner, now a vacant retail building being sold. The purchaser's lender requires confirmation that perchloroethylene has not migrated off the 0.4-acre parcel. The consultant's scope was four soil borings to 4 m, two temporary groundwater wells, and six VOC samples analyzed by EPA 8260B. The draft report shows PCE at 85 µg/L in MW-2, 3.4 µg/L in MW-1, and no soil detections; the federal MCL for PCE is 5 µg/L. Three problems appear in the data package: the trip blank contains PCE at 2.4 µg/L; the field duplicate pair at MW-2 came back at 85 and 18 µg/L (relative percent difference of 130%); and the MW-2 sample was analyzed 16 days after collection. Field notes show both wells were purged with a bailer, and MW-2 was turbid at 480 NTU. The property owner wants the report finalized by Friday so the closing can proceed, and the state voluntary cleanup program coordinator will not accept the report without a defensible data quality assessment.
1. Which results in this package are usable for decision-making, and what do you do before the report is finalized?
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Almost none of it is usable as a definitive basis for a closure decision, and the report cannot be finalized as written.
- Trip blank at 2.4 µg/L. This is the most serious defect. A contaminated trip blank means VOCs entered the sampling train or the containers somewhere between the lab and the field, so every VOC detection in the package carries a positive bias of unknown size. The 3.4 µg/L result in MW-1 sitting below the 5 µg/L MCL cannot be distinguished from method contamination. It is also large enough, relative to a 5 µg/L standard, that it cannot be dismissed as a trace artifact.
- Duplicate RPD of 130%. Precision has failed badly. Even a generous aqueous VOC data quality objective is 30-40% RPD at these concentrations. A 4-to-1 spread between co-located samples means the result is not reproducible, so 85 µg/L is not a defensible concentration.
- Holding time. The 14-day holding time for preserved aqueous VOC samples was exceeded at 16 days. The 85 µg/L figure may be used as a screening indicator that PCE is present near MW-2, but not as a validated result.
- Bailer purging and 480 NTU are not disqualifying for VOCs, which are dissolved-phase; they are a lesser issue here, though they would invalidate metals or SVOC results.
Before finalizing: issue a data quality assessment that flags the affected results as rejected or estimated, and do not certify the report to the lender until MW-2 is resampled.
2. Redesign the sampling program to satisfy both the lender and the state program, given that you will get one more mobilization.
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Design for defensibility, because a second resample is not in the budget.
Groundwater:
- Resample MW-1 and MW-2 using low-flow purging with dedicated tubing and a bladder pump; stabilize water quality parameters before sampling and record them.
- Add at least one well between the site and the downgradient property boundary plus one sentinel well at or just beyond the boundary. Two wells cannot demonstrate that a plume has not migrated - that is the lender's actual question, and the current scope does not answer it.
- Full QC: one trip blank per shipping cooler per day, one field duplicate per ten samples, one matrix spike/matrix spike duplicate, and equipment blanks if reusable gear is used.
- Ship on ice, confirm the lab's 14-day holding time in writing, and require the lab to report the method reporting limit and any dilution.
Soil:
- Discrete samples at the capillary fringe and smear zone beneath the former dry-cleaning equipment area rather than a composite; a composite dilutes a narrow hot interval into a non-detect, which is likely what produced the clean soil results.
- Analyze the highest-foam or highest-odor interval first; add a soil-gas or sub-slab sample if a building remains.
Schedule and money: one mobilization, roughly two weeks of field time, additional wells are the largest cost line. Present it as the minimum scope that supports a closure the state will accept, and note that the alternative - a rejected report - costs a second mobilization plus the closing delay anyway.
3. The owner argues that 3.4 µg/L is below the MCL and the site should be closed. How do you respond, and what is your recommendation on the Friday deadline?
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Separate the chemistry from the transaction.
The chemistry argument: 3.4 µg/L is below the 5 µg/L MCL as a number, but a result that sits inside the uncertainty created by a contaminated trip blank and a 130% duplicate RPD carries no weight. A standard is a threshold applied to a valid measurement, not to any number that appears on a lab report. The 85 µg/L result, even unvalidated, is inconsistent with a clean site.
The transaction argument: the lender's requirement is confirmation that PCE has not migrated. A report built on rejected data does not provide that confirmation, and a purchaser relying on it may later find the data unusable under the All Appropriate Inquiry requirements - a Phase II with a defective data quality assessment does not support the bona fide prospective purchaser defense. A reopener or a failed closing after the fact is far more expensive than a two-week delay now.
Recommendation: do not finalize Friday. Deliver a short interim memorandum by Friday that states clearly what is known, what is rejected and why, and the resampling plan with dates. Most lenders and state coordinators accept a documented data gap with a corrective plan; what they do not accept is a certified report that papers over one.
If the owner presses, offer the middle path: close with an escrow holdback conditioned on the resampling results, with the environmental professional's opinion expressly limited to the validated data.