How Contaminated Soil Affects Construction Projects

The presence or identification of contaminated soil during construction projects is always problematic due to the consequential time delays in properly identifying and classifying the contaminated area and the costs involved to ensure the safe and compliant management of the contaminated material.

The following summary aims to provide some background to fully understand the issues that contaminated soil can present during a construction works.

What is Soil Contamination?

Soil contamination is when the concentration of pollutants in the soil are higher than would be naturally, specifically due to the impact of past activities that were undertaken on the site and have consequentially impacted on the underlying soil.

What Causes Soil Contamination?

Soil contamination can arise as result of a wide and varied range of activities. Mining can release sulphuric acid, arsenic and mercury into the soil; hydrocarbons can be released during fuel storage, and lead by steel works, asbestos fibres can be released during demolition works. Human, agricultural and industrial waste can contaminate soil when leaks, spills and pipeline ruptures occur.

Historically, varieties of different wastes were used as general backfill in low lying urban areas, such as metal can and/or coal slags or contaminated dredge spoil. Again this can lead to issues with contaminated soil when modern day construction projects disturb and/or excavate from these areas of historical contaminated backfill.

Simply being located next to a site with contaminated soil has caused many unexpected issues for project managers and engineers, as flooding or groundwater flow can transfer soil contamination – a site boundary such as a wall or fence is not sufficient to act as a barrier to prevent the migration of contaminants to adjacent properties or sites.

The Impact of Contaminated Soil on Construction Projects

If not managed correctly, contaminated soil has the potential to harm the environment or anyone that may come into contact with it.  Legally, the responsibility rests firmly on the shoulders of all property owners and/or their nominated developers to manage contaminated soil arisings from construction projects in accordance with all relevant legislation and best practice guidelines.

As a result, contaminated soil must be first classified as per legal requirements, then be removed offsite by a suitable contractor. This process can be expensive – especially if not undertaken during the preliminary stage of development.

Handling Contaminated Soil

If you are undertaking development works on contaminated land, the first step it to have soils tested at a certified laboratory, so the soil can be correctly classified relative to the level of contamination and appropriate offsite remediation procedures can then be established. When tackling contaminated soil removal, try to avoid stockpiling any contaminated materials. If temporary stockpiling is necessary, always cover the pile with plastic sheeting or tarpaulin, install a berm around the perimeter to prevent run-off, and never position the pile near storm drains or public water infrastructure.

Ensuring no contaminated materials are carried off-site by employees and vehicles is critical. Personal Protective Equipment (PPE) should be stored on-site and anything that isn’t reusable should be properly disposed of. All areas with contaminated materials should be protected by a securely fenced-off exclusion zone. Air quality should be monitored on-site at all times, to ensure people aren’t inhaling contaminants. Any excavation, transportation or disposal of contaminated soil must be carried out in accordance with local regulations, and you must be sure to procure all the relevant licenses and pay any fees due.

Remediating Contaminated Soil

Contaminated soil remediation can either be carried out on-site, or it can be taken off-site for treatment. Generally on construction projects, material is removed offsite for remediation as it is surplus to requirements. If materials are transported off-site, they must be transported in appropriate vehicles that have been specially licensed to carry hazardous materials. A good environmental contractor will have all required equipment and vehicles to transport contaminated materials, and they will have an accredited transfer station to store materials for decontamination. They will also handle the mandatory permits and licensing requirements for you.

The options for treating contaminated soil include biological treatment options, like biopiles, which use indigenous bacteria to break down hydrocarbons from petroleum storage in the soil. Alternatively, there are chemical options to treat the soil, including soil stabilisation, which uses reduction and oxidation to convert contaminated soils into non-hazardous soils. Lastly there are physical methods, like soil washing or thermal treatment, which use water or heat to separate or remove contaminants.

There are many different approaches to contaminated soil remediation, and the appropriate treatments vary depending on the type of chemicals present in the soil, as well as the extent of the contamination. If being removed from the site and destroyed, contaminated soil disposal must be carried out at an accredited facility, in accordance with local regulations.

Don’t Ignore the Threat of Contaminated Soil

The growing global population combined with increasing migration to urban centres means more brownfield sites are being redeveloped to meet demand. Without proper due diligence at the preliminary stages of pre-planning and development to properly assess for the potential of contaminated soil on a site, these projects run the risk of major budget over-runs or else could have serious health implications for both employees and the eventual occupants.

If you believe there to be any threat of contaminated soil on your construction project site, contact soil remediation experts such as Enva immediately. Contamination experts can generally be on-site immediately, and have affected soil analysed and classified in days, thus keeping downtime to a minimum and removing the threat of some potentially costly legal and financial repercussions down the line.