Their leaking underground storage tanks, also referred to with the amazingly ironic acronym of LUSTs, contain hazardous liquids, primarily petroleum products such as gasoline, diesel, kerosene or oil. Many of these old tanks are leaking and forming hydrocarbon plumes that contaminate groundwater, drinking water and the surrounding soil. As of March 2012, over 504,000 leaks had been recorded from federally-regulated LUSTs in the USA. For the grassroots remediator, cleaning up and regenerating gas stations is not easy and poses some significant challenges.
Contaminants at Old Gas Station Sites
From volatile organic compounds and polyaromatic hydrocarbons to heavy metals, see the list below for some of the many contaminants that you may find lurking in the soil and water on gas station sites.
- Benzene, Toluene, Ethylbenzene, Xylenes. Lead
- Lead and other heavy metals
- MTBE (gasoline additive)
- Ethylene dichloride (EDC)
If there is an autoshop too, you may also find: Trichloroethylene (TCE), Perchloroethylene (PCE or PERC), Methylene chloride, Carbon tetrachloride, oils, blended oils and glycol solutions, heavy oil distillates (motor oil, hydraulic fluid), Ethylene glycol, detergents, acid solutions, and more.
Conventional Gas Station Clean-Up
Contamination found at these sites, like the hydrocarbon plumes that contaminate groundwater, drinking water and the soil, can run deep and spread over an area that extends well beyond the border of the site itself. This makes earth repair challenging because you can’t always get at the contamination, especially if you are in a densely built and populated area where that hydrocarbon plume may have migrated and now extends under the road, houses, other businesses. In situations like these, some high-tech conventional technologies try to aerate and encourage bioremediation under these areas, or off-gas the contamination. Other conventional clean-up strategies include fencing and sealing up the site or excavating the contaminated soil, trucking it off to a landfill and filling the site with “clean soil.”
Grassroots Bioremediation Options
Due to their concern over liabilities, companies that own these sites may not allow you to engage in grassroots bioremediation work there, especially if it involves digging in the soil. But if you are able to get permission to do this work, or the company is long gone leaving only their toxic legacy behind, there are a few grassroots bioremediation options you could try.
When it comes to using PLANTS to phytoremediate toxic sites, plants can clean up the soil only as far as their root systems reach. Using fast growing trees, such as poplars, willows or black locust, to access deeper contamination with their longer roots would be ideal. Following that with more surface soil remediators would also be great, though the main focus would be on working with the trees to access contamination deeper down. This approach would take time, and success would depend on how deep the contamination or the hydrocarbon plume was and where it was in relation to the site.
If there is more shallow contamination, there are quite a few plants that have shown promise for remediating some common gas station contaminants. For example, when it comes to PAH’s, the following plants could be helpful: Poplar, Pine, Tall Fescue, Red Fescue, Black Locust, Willow, Sunflower, White Clover, Yellow Sweet Clover, Red Clover, Bermuda grass, Western Wheatgrass, Blue Grama Grass, Buffalograss, Canada Wildrye, Perennial Ryegrass, California White Sage , Switchgrass, Red Mulberry, Alfalfa, Apple, Cat Claw, and Pumpkin.
Some projects working with old gas station sites lay down some sort of cap of clean soil, wood chips or other protective barrier, and then use raised beds on the site to avoid digging into the ground at all. This allows the site to be utilized in a rather safe way, but does not deal with the underlying material which may continue contaminating water sources. A mixed approach involving some trees to engage in remediating the deeper contamination with raised beds (which would not be affected by the closed tree canopy in the early years) could be a good place to start.
MICROBES can also be used to assist with hydrocarbon contamination in the soil. Some professional bioremediators take hydrocarbon contaminated soil and compost it down in windrows. Compost tea can be applied as well, either to the composting contaminated soil (between turning it), or directly to the soil on site. Note, microbes can break down hydrocarbons, but not heavy metals.
When it comes to hydrocarbon contamination (PAH’s and VOC’s), FUNGI have shown a lot of promise – especially species like the Oyster mushroom. If the contamination is very shallow/close to the surface, you could use some mycoremediation to break down some of the contaminants. However, if it is deep contamination, which can often be the case at old gas stations, than mycoremediation will be challenging as your fungal allies need oxygen to do their work. There are some neat experiements being conducted to address this challenge. One promising technique that is being worked on comes from a few of the folks at the Amazon Mycorenewal Project – they are using an installation called a “mycoreactor” to get oxygen down to deeper contamination and create conditions more conducive for mycoremediation.
Safety and health concerns
The contaminants found at gas stations are serious ones and can impact your health if you are not careful. If you choose to engage in any remediation work, you need to take the proper precautions to protect your health and those of folks you are working with. Look into purchasing a respirator, with the correct filter, as well as a tyvek or tychem suit if you can. Wear gloves, closed toed boots, eye protection, and make sure to not wear your cleanup gear off the site.