Rain, Sheen, and a Missing Fill Cap at a Two-Tank Retail Site
A technician responds to a 12-year-old retail fueling site with two 10,000-gallon double-wall tanks, one turbine (STP) sump per tank, two dispenser sumps, and a spill bucket at each fill. It rained heavily for five days. The technician finds:
• Tank 1 STP sump: about 3 inches of clear, odorless liquid. The tank's interstitial sensor is dry; the sump liquid sensor has been in alarm for two days. • Island 2 dispenser sump: about 4 inches of liquid with a bright rainbow sheen and a strong gasoline odor. The store manager has reset the alarm three times without removing the liquid. • Tank 2 spill bucket: roughly 2 gallons of liquid gasoline standing in the bucket. The fill cap is missing and the bucket drain appears plugged with debris.
The ATG shows no water in either tank and no unexplained loss over the past 30 days. The owner asks whether the site can stay open and whether anything must be reported to the state.
1. Classify each of the three conditions: which are releases, which are maintenance issues, and which require notification? Explain your reasoning, not just the category.
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Tank 1 STP sump - not a release, but not acceptable either. Clear, odorless liquid after a week of heavy rain, a dry interstitial sensor, and no inventory loss all point to surface water entering through the lid gasket, a conduit seal, or an unsealed penetration. The sump sensor is doing its job. But a sump that holds water cannot hold product, so the 3-year containment sump test is now in doubt, and the infiltration path must be sealed before the water is removed and forgotten.
Island 2 dispenser sump - treat as a suspected release. A sheen plus strong product odor means petroleum, not rain. Candidate sources are the dispenser pan, a flex connector, a shear valve, a swivel, or the piping termination. Resetting the alarm three times without removing the liquid is exactly the 'unusual operating condition' that must not be normalized into routine. If the source cannot be immediately identified and attributed to a one-time spill, notify the implementing agency within 24 hours; many state rules also require reporting any product found in secondary containment.
Tank 2 spill bucket - a spill, not a tank release. Two gallons of product in a bucket with a plugged drain and no fill cap violates spill prevention. The product must be removed, the drain cleared, and the bucket tested for tightness. The missing cap is both a vapor release and a water-intrusion path.
Priority order: Island 2 first, Tank 2 second, Tank 1 third.
2. What must be done at Island 2 before those dispensers are returned to normal service, and what tests would you order?
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Isolate before you investigate. Close the shear valves at Island 2, lock out and tag the STPs, and remove the liquid into approved containers. Trace the source before the sump is wiped down, because cleaning destroys the evidence: inspect the dispenser pan, flex connectors, shear valve, piping termination fittings, and the sump penetration seals.
Once the source is identified, run the tests that prove containment is intact:
• Line tightness test at 0.1 gph on the affected line. • Hydrostatic tightness test of the dispenser sump. • Functional test of the sump sensor, including confirmation that it reports to the tank monitor. • Line leak detector test at 3 gph.
If no source is found, dry the sump, leave the dispenser locked out, and observe for 24 hours. A sheen that reappears confirms an active leak, which triggers reporting and a release investigation rather than another reset.
The dispenser goes back into service only when the sump is dry, the sump passes a tightness test, and the line has passed its tightness test. Preserve the alarm history - the manager's repeated resets will be the first thing the regulator asks about.
3. How should the liquid in the Tank 1 STP sump be removed, and what should be checked before pumping?
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Identify the liquid before you move it. Use water-finding paste or a hydrocarbon test on a sample to confirm it is water rather than product, and cross-check the tank's ATG water level and the interstitial sensor reading. A sump holding water while the annulus is dry is reassuring; a sump holding product is a different event entirely.
Do not pump to a storm drain, a sanitary sewer, or the ground. Use a vacuum truck or approved container. If the liquid is clean water, some states allow discharge under permit or after treatment - but that determination belongs to the state, not to the technician on site.
After removal: clean and dry the sump, inspect the lid gasket, penetration seals, and conduit seals, and reseal the actual source of infiltration. Then re-test the sump for liquid tightness to satisfy the 3-year containment sump requirement. Verify the sensor is set at the correct height and is the right technology for the expected liquid - a hydrocarbon sensor would have stayed silent on water, while the conductivity sensor alarmed, so sensor selection must match the design intent.
Record the event, the volume removed, the disposal method, and the repairs, and file it with the site's release detection and inspection records.