Soil testing
What it is, and when you actually need it
Everything else in the oil-tank problem is opinion until a lab weighs in. Testing means physical samples — pulled by hand auger or a geoprobe rig from specific depths at specific points around the tank — sealed under chain of custody and analyzed by a certified laboratory for petroleum compounds, with results compared against your state's numeric soil standard. The report is the only document that turns "the pit smelled like oil" or "the pit looked fine" into a fact.
Four situations genuinely call for it. During a removal or closure in place, where post-job samples are the point of the exercise and are usually bundled into the contract. As buyer due diligence on a property with a closed-in-place tank whose paperwork lacks lab data — common, and the gap that makes many old closures worthless. When there's specific evidence of a leak — oil odor in a sump, a dying patch of lawn over the tank, a failed tightness test — and you want the answer before scoping anything bigger. And before signing any remediation contract, because delineation data is what an honest remediation price is built on.
When you don't need it: a tank that was removed with clean lab results already in the closure report — retesting documented clean soil is paying twice for the same fact. And testing makes little sense as a substitute for a sweep when you don't yet know whether a tank exists; find the tank first, then decide whether its soil needs a lab.
What happens on the day
- Locating and layout (15–30 minutes). The technician marks the tank footprint and picks boring locations — typically at the tank ends and along its sides, where leaks concentrate.
- Borings (30–90 minutes). A hand auger or geoprobe advances each boring to just below the tank's base depth, since oil migrates down. Shallow samples from beside a deep tank prove little.
- Sample collection (15–30 minutes). Soil from the target depth goes into lab jars, labeled, chilled, and logged under chain of custody. Field observations — staining, odor, moisture — get recorded alongside.
- Lab analysis (3–7 business days; rush available at a premium). Standard petroleum analyses (TPH/EPH-type methods, state-dependent) quantify what's in each sample.
- Report (a few days after results). Lab certificates plus a summary comparing each result to the applicable state standard — NJDEP criteria in New Jersey, the equivalents under DEC, DEEP, MassDEP, and PA DEP elsewhere. Insist on the comparison, not just raw numbers.
What drives the price
| Driver | Effect on the $300–$1,000 range |
|---|---|
| Number of samples | The main variable — each boring and each lab analysis is a unit cost, so a two-sample screen sits at the bottom and a five-plus-sample delineation at the top. |
| Rig vs. hand auger | Geoprobe rigs reach deeper and through harder ground but mobilize at a higher day rate than a technician with an auger. |
| Analysis type | Basic petroleum screens are cheapest; fuller analyte lists required by some state programs cost more per sample. |
| Lab turnaround | Standard is 3–7 business days; 24–48 hour rush for a closing deadline carries a meaningful premium. |
| Depth and conditions | Deep tanks, rocky fill, or a high water table slow the borings and can force the rig option. |
One boring on one side of a tank can miss a leak entirely — oil travels down and with groundwater, not evenly in all directions. A one-sample "clean" result sold as proof the tank never leaked is the testing trade's version of the lowball quote: technically a lab report, practically an answer to a question nobody asked. A defensible screen samples multiple points at the right depth — below the tank base — and says in writing what standard the results were compared against.
Questions to ask before signing
- How many samples, at what locations and depths — and will the plan be in writing before the visit?
- Which laboratory do you use, and is it certified in my state?
- Which analysis method, and which state standard will results be compared against?
- What's the turnaround, and what does rush service cost if my attorney-review clock is running?
- Is your firm independent, or do you also sell remediation — and if results come back dirty, am I under any obligation to use you for the cleanup?
- Will the report be formatted so my attorney or the state agency can rely on it?
Reading the results
Clean results below the state standard end the inquiry — file the report with the house records; it's the document a future sale will ask for. Results above the standard don't automatically mean a five-figure dig: the next step is delineation (more samples to map the extent), then a scoped cleanup priced per ton — the remediation page covers what an honest version looks like, and the NJ leak guide covers the reporting obligations that follow a confirmed hit. Not sure testing is even warranted yet? The leak-risk calculator scores the probability from your tank's age, type, and history, and the timeline guide shows where lab days land in a transaction.
To get sampling priced by people who do it weekly, request quotes from licensed professionals and compare their sampling plans, not just their totals.