As the owner of a construction business, making sure that the land you choose is good enough for building is very important. In some cases, the site being evaluated for placing a building might need considerable amounts of improvement; maybe due to the land being polluted or contaminated. Thus environmental remediation is implemented to address the contaminants from the soil. Such action not only makes the land more suitable for construction, but also reduces or eliminates the risk of adversely affecting human health. One of the better-known forms of environmental remediation are in-situ stabilization and solidification, which are collectively referred to as ISS.
The term in-situ, which means “in original or natural place or position,” refers to treatment of the contaminated soil without removing the soil itself. This is contrasted with ex-situ, which involves excavation of the contaminated soil for treatment at the surface. Although stabilization and solidification are often grouped together, they actually do not mean the same thing. Stabilization refers to the addition of reagents to the soil, since they are substances that react to the chemicals found there and thus enable people to conduct an analysis of the contaminated area. Such analysis can then help in producing more chemically stable components in the soil. By contrast, with solidification, the reagents gather the contaminants together and solidify them, as well as reduce the amount of access that external agents like air and water have to the soil. In each instance, the reagents act as a binder that stops, prevents or reduces the mobility of contaminants.
Standards and Assessment
If you suspect a building site of being contaminated, you’d need to assess the level of contamination. This involves identifying potential or existing environmental contamination liabilities on the underlying land, as well as addressing the physical improvements to the site. This evaluation is referred to as an environmental site assessment, also referred to as an ESA. Phase I of the ESA usually involves preparing a report to highlight the existing and potential risks, while Phase II is a more detailed investigation that includes chemical analysis for hazardous substances. ESA standards are set by the U.S. Environmental Protection Agency.
With in-situ S/S, soil is mixed by putting them in augers, excavator buckets or rotary drum mixers. Of the three aforementioned mechanisms, the auger is the best for soil mixing, since it is the only device able to stabilize materials that are deeper than 15 feet below the work platform. With in-situ solidification in particular, Portland cement—which is renowned in the construction world for its strength, low cost, and versatility—is added to the mixture. In some cases, other additives—such as bentonite, blast furnace slag, fly ash, cement kiln dust, and activated carbon—can be tossed in with Portland cement.
In-situ solidification and stabilization has its detractors. There is still a dearth of authoritative technical guidance on S/S. Also, the method can lead to a significant increase in carbon dioxide emissions, due to the use of cement. Ultimately, though, solidification/stabilization has been able to maintain a remarkable track record on its reliability and efficiency, making it one of the most established and widely used remediation technologies in the world.