We are frequently asked about the most common ways underground storage tank leaks are discovered. Our company has over 25 years of experience cleaning up leaks from underground storage tanks (USTs), so we have a lot of information to share about how leaks are discovered.
One thing that is always true—the earlier UST leaks are discovered, the easier they are to clean up. And, if we know where leaks are usually discovered, we can monitor those areas for early detection.
For this article, we compiled data from the hundreds of leaking underground storage tank (LUST) projects we’ve managed over the years. These LUST sites included residential properties containing heating oil tanks, service stations with multiple tanks and varying levels of spill protection and leak detection systems, and other diverse commercial and industrial facilities that utilized USTs. Below are the 10 most common ways we have discovered leaks from USTs.
1. Phase I /II Environmental Site Assessments Related to Property Transfer Investigations
In 1980, Congress passed the Comprehensive Environmental Response, Compensation, and Liability Act –otherwise known as CERCLA or Superfund.
Through CERCLA, the EPA was given power to seek out those parties responsible for any release of contaminants and assure their “cooperation” in the cleanup.
The courts have applied a strict liability standard under CERCLA. Liability is imposed regardless of fault and can be imposed retroactively (i.e., before CERCLA was enacted). The liability is also joint and several, meaning that liability for contaminants can be imposed regardless of relative contribution, including merely purchasing a property.
Since CERCLA made purchasers potentially liable for past environmental contamination, most buyers of properties with USTs will conduct an Environmental Site Assessment to determine if past leaks or spills have contaminated the property.
The Phase II Environmental Site Assessment will usually include installation of soil borings and temporary monitoring wells. Site information is used to locate the borings and wells adjacent to existing or former tank, line, dispenser, and fill port areas.
Soil and groundwater samples are delivered to a testing laboratory for analysis of components of the liquids stored in the USTs. Environmental professionals compare the results with state and Federal standards and use this information to determine the existence, degree, and extent of contamination.
It is not uncommon for properties with a long history of UST use to have some degree of contamination. Astute buyers utilize the environmental site assessment results to quantify the potential liability and/or have it addressed as a condition of the purchase of the property.
2. Product or Product Components in Monitoring Wells
Product is a term we use to refer to whatever material is stored in the USTs. At a gasoline station, for example, product may refer to various grades of gasoline, diesel fuel, kerosene or waste oil. Other types of facilities may have any number of different fluids stored in tanks that are referred to as “product.” 
Most modern UST system installations will include four perimeter monitoring wells. The monitoring wells are used to detect the presence of leaked product from the tanks.
The monitoring wells can be inspected manually for the presence of product or may have automated detection devices to detect product fluids or vapors.
Products like gasoline are actually made up of hundreds of different types of hydrocarbon compounds and groundwater can be tested to determine the presence of those compounds.
3. Inventory Reconciliation
UST owners are required by law to reconcile the amount of product delivered to a tank vs. the amount of product dispensed from the tank.
Inventory reconciliation can be complicated by issues such as multiple deliveries of product, differing amounts of product delivered, and expansion and contraction of the volume of product related to differing temperatures of the product delivered and after it sits in the tank(s).
4. Recognized Customer Errors
Customers make fueling mistakes. Customers have been known to become inattentive while fueling and overfill their vehicles. They have also been known to drive off with the dispenser nozzle still attached to their vehicles!
Vehicles have also crashed into dispensers. Dispensers have shear valves that are supposed to shut off the supply of product in the event that the dispenser is moved. However, there have been occasions where the impact to the dispenser was so severe that the shear valves did not operate effectively.
5. Tank and Line Tightness Testing
State and Federal laws require periodic tank and line tightness testing. Owner/operators are also required to test leak detection and spill containment devices. Test failures prompt further assessment to determine the cause or presence of a leak.
6. Vapors in Buildings
Vapors from product leaks can travel along utility lines, through soil and gravel pathways, or from product components dissolved in groundwater.
The vapors can accumulate in building spaces and, depending upon concentration, can constitute an explosive hazard or an indoor air quality hazard. These vapors are most commonly reported as odor problems noted by building occupants.
7. Contamination Discovered During Closure/ Upgrade
State regulations require testing for contamination when tanks or product piping is removed.
As part of the closure process, states have specific soil and/or groundwater sampling and testing requirements in the vicinity of the tanks and product lines to determine if there has been an impact to the environment.
8. Potable Well Impact
Product leaks can migrate to groundwater sources and may impact drinking water sources. Initial impact may be detected by taste or odor.
Laboratory testing may indicate levels of contamination that exceed EPA drinking water standards.
When potable wells are determined to have been impacted, regulators automatically look for adjoining properties with USTs.
9. Leak Detectors
Modern leak detectors are designed to alert the operator of a loss of integrity in product lines.
Modern leak detectors can detect leaks ranging from catastrophic to very minor.
10. Observed Product Discharges
Product discharges have been observed due to errors in filling of the tanks. Tanker trucks have devices to shut off the flow of fuel when the tanks are full, but there are occasional fueling errors. There have also been discharges observed from damaged dispensers.
Preventive Measures
Properly managing underground storage tank systems can help decrease the probability of leaks or spills. By adhering to your state and federal UST regulations and employing the proper, leak detection systems, spill and overfill protections, and regular inspection programs, you can minimize your potential liability and mitigation costs.
Are you interested in finding out more about release detection and prevention? Do you need assistance with tank management or inspections? Do you need help with a leaking UST? Ambipar Response EMS has the experience to keep you in compliance with environmental regulations and decrease your potential liabilities. Contact us today to learn more!
To learn more, check out these other articles about underground storage tanks:
Top 10 Causes of Underground Storage Tank Leaks
Small Gasoline Leaks on Your Property Can Cause Big Problems
How Do I Make a Claim for North Carolina Leaking Underground Storage Tank Cleanup Costs?
How Do I Make a Claim for Pennsylvania Leaking Underground Storage Tank Cleanup Costs?
It’s good to know that modern leak detectors exist to help alert to any issues. The sooner you know that there is a leak, the sooner you can act on it and repair it if necessary. It would save money by being able to catch the leak before it becomes catastrophic.