Using old railroad ties for landscaping projects such as retaining walls, garden edging, and raised garden beds was once very common practice, and it was even regarded as a good environmental strategy. As old railroad lines became repurposed as hiking and biking trails, repurposing the huge railroad ties in landscape work seemed like a good way to use the wood.
But most railroad ties are soaked with creosote to give them longevity, and in your landscape, they pose a health hazard as the chemical gradually leaches into the soil. As with many outmoded practices we learned from our grandparents or parents (like spraying dandelions with herbicide), we now understand that railroad ties are an environmental danger.
The Dangers of Creosote
The main issue with railroad ties is the presence of creosote. Although an effective preservative against decay and insect damage, the substance has been banned for residential use due to its toxicity. Creosote is an oily by-product of the distillation of coal tar. Creosote treatment of railroad ties allows long-term preservation of the wood, which must obviously stand up to heavy pressure and harsh weather conditions.
You may also be familiar with creosote as a substance created by woodsmoke that can build up inside your wood stove chimney, as many wood stoves have gauges that indicate when creosote buildup may be happening. Creosote buildup in chimneys is dangerous because it can be flammable, potentially leading to a house fire. Exposure to creosote can be dangerous for a number of reasons:
- Risk of cancer
- Chemical burns to skin
- Eye irritation
- Respiratory problems
- Kidney or liver problems
- Mental confusion
Danger from creosote exposure is not merely a matter of direct contact. Creosote can dissolve in water and take many years to break down, contaminating groundwater in the meantime. This can affect humans, pets, wildlife, and beneficial insects. And creosote in soil can persist for decades.
Disposing of Old Railroad Ties
Railroad ties should never be burned. This is true for all treated wood products, which may release toxic gases through smoke and cause illness or other hazards. The ash resulting from burned wood containing creosote also has been shown to be toxic. Similarly, sawdust from cutting chemically treated wood (such as railroad ties) should not be inhaled as it can cause respiratory problems. Always use a mask or respirator when cutting wood of unknown origin.
In many communities, railroad ties can be disposed of in the same way as other solid waste—in standard landfills—but make sure to check your local county and municipal laws governing hazardous substances. Even in landfills, creosote will gradually leach out of the timbers and may eventually find its way into groundwater supplies, so communities are increasingly setting restrictions on the disposal of materials that may contain creosote or other toxic chemicals. You now may be required to take old railroad ties to a special site equipped to safely handle chemical-laden building materials.
Other Chemicals in Railroad Ties
Some commercial railroad timbers may use chromated copper arsenate (CCA), a compound intended to prevent microbial or insect damage in wood. This compound typically contains chromium, copper, and arsenic. CCA is the same chemical that has been used in other types of timbers for residential outdoor use. CCA was once the standard compound used to pressure-treat timbers that were intended for outdoor ground contact, though the dangers of the chemicals soon became evident.
In 2003, the EPA and lumber industry agreed to phase out CCA in favor of alternative preservatives. Because the dangers of this chemical are now understood, CCA is no longer commonly used. Instead, the most common preservative is now ACQ (alkaline copper quaternary), a water-based wood preservative with relatively low risks.
CCA-impregnated timbers currently in use are not regarded as hazardous if they remain undisturbed, and you are not required to replace them. But inhalation of sawdust can cause arsenic poisoning, and the ashes resulting from burning CCA-treated wood have been shown to cause poisoning in livestock. Don't grow food near CCA-treated wood, and, when disposing of CCA timbers, make sure to follow local guidelines.
Alternatives to Using Railroad Ties
Raised beds are great ways to add flower or vegetable beds to your garden. But it's important to use building materials that won't leach toxic materials into the soil or the water table. A much safer option than railroad ties is old barn beams, if you can find them, but occasionally barn beams may be contaminated with substances such as motor oil or machine oil.
Many communities now have groups interested in recycling or reusing salvaged architectural or building materials, so you may be able to locate wood or other materials to help you build your raised beds or create barriers for your plantings.
Modern pressure-treated lumber that uses ACQ rather than CCA is regarded as safe for building raised beds, even those used to grow vegetables. And any number of other materials are also used, including concrete building blocks, concrete retaining wall blocks, or river boulders.