Underground storage tanks: uses, hazards, and remediation 
Posted June 18, 2020

According to the United States Environmental Protection Agency (EPA), underground storage tanks, or USTs, are storage tanks and any underground piping connected to the tanks that have at least 10 per cent of their combined volume underground. Typically, USTs are used to store toxic substances such as gasoline and oil. In fact, one of the most common applications for USTs is at gas-filling stations.

It’s difficult to get an accurate picture of how many USTs are present around the world, but a 2019 year-end report from the EPA suggests that there are over 546,000 active USTs at about 197,000 different facilities in the United States alone. Apart from the petroleum industry, they’re commonly used in locations such as dry cleaners, schools, churches, manufacturing facilities, airports, and even, homes.

Potential hazards of USTs
There are inherent hazards that come with the use of USTs, including but not limited to, fire and explosion. However, most pertinent to our industry and one of the most significant hazards from an environmental perspective is leaking. Leaks may be the result of several factors, including corroding steel, faulty installation, and/or inadequate maintenance, commonly occurring at subsurface points along the delivery system, and the piping from the tank to your dispenser nozzle at the gas station.

Leaking USTs can allow hazardous substances to seep into soil and groundwater, contaminating the surrounding environment. Considering that many communities — particularly rural ones — rely on groundwater for drinking, this contamination poses a serious threat to public health.

UST regulations now mandate specific leak prevention and detection requirements, yet the widespread use of these tanks means that incidents still happen, and regulated materials like gas, diesel, dry cleaner solvents and home heating oils enter the subsurface and contaminate the soil and groundwater. Older USTs which have been replaced represent the biggest concern, since they were installed prior to the regulations, (typically single walled), and over time corrode while buried unprotected in the soil resulting in small, but long-term releases, which over time become significant environmental liabilities.

Remediation of UST leaks
Once a leak is identified, it’s important to put a stop to it as quickly as possible, but that isn’t always possible nor does it remedy the contamination that already occurred. Biostimulation enhances the natural conditions of a contaminated site, removing stresses to microbial growth, development and communication, so that the soil and groundwater can be treated right there, in-place (in-situ) without having to excavate and haul away, without aboveground support equipment eliminating fuel costs, nuisance noise and emissions, and reducing overall remedial costs. TerraStryke’s biostimulation additives support the establishment of soil conditions that allow microorganisms to do what nature intended: degrade contaminants (utilize available energy sources) as efficiently as possible.

Case in point – In one instance, TerraStryke biostimulation additive TPHenhanced was used to enhance the organic remediation of groundwater after a petroleum fuel oil release occurred in Philadelphia, Pennsylvania. The site was a manufacturing facility where USTs where used to store regulated materials naphthalene and 1,2,4-trimethylbenzene. After the treatment zone was amended by the consulting group using TPHenhanced, concentrations of naphthalene decreased by 92 percent and 1,2,4-trimethylbenzene by 83 percent in less than six months, and closure was allowed after Risk Assessment identified that no further action was required.

Additionally, in Seattle a former UST site amended with TPHenhanced realized >95% and >98% reductions in 9 months. We see the same at site after site – by enhancing the subsurface habitat and looking at treatment zones as the ecosytems they are, our biostimulation products expedites residual mass and dissolved-phase contaminant destruction sustainably and completely to realize long-term site remediation objectives sustainably and cost-effectively.