Iron Ochre: The Toxic Enemy
Last modified: 2019/04/15 | Approximate reading time 12 mins
Due to the severe damage it can cause, iron ochre is an enemy to watch out for. This oxidizing iron substance deserves special attention, whether for the current homeowner who has dealt with its negative effects or for the potential homeowner, who fears having to deal with it. Regardless, here is all of the relevant information you’ll need to know the signs of iron ochre.
How does iron ochre form?
Iron ochre deposits are a result of the presence of iron, oxygen and water in the soil. Specifically, the appearance and growth of ochre depend on a biological reaction, a chemical reaction or a combined effect of the two. The chemical reaction that creates iron ochre happens due to the presence of iron in the soil and is drawn up when mixed with water. Iron hydroxide is created when this mixture meets the air.
The biological reaction creates the presence of an iron-containing bacterium within the water table, and this is known as Ferro-bacteria. Once this bacterium meets with air, the formation of a gelatinous substance is created by way of the oxidization of the iron. Note that the combination of the biological reaction and the chemical one will greatly increase the quantity of iron ochre.
Certain conditions will be favourable for the appearance of iron ochre, and these include:
- The presence of a filtered drain;
- If you have a drain that is warped;
- The presence of sandy soil;
- A soil which has a neutral pH level, or is close to neutral, and therefore around 7;
- A drain with a tip that has been punched rather than cut, as this creates a source for an accumulation of iron deposits;
- Living in a region where the water table is high;
- Lastly, living in an area with a substantial risk of flooding.
What are the consequences of the presence of iron ochre?
The presence of iron ochre in the soil underneath a home or building will cause many undesirable effects. Firstly, the presence of iron ochre will compromise how your drain and pump operates, as the deposits of this substance will cling to the inner and outer walls of the drain, as well as the water inlet of the pump. Further, iron ochre deposits will block drain openings, which will prevent proper drainage following water buildup, heavy rainfall or melting snow. As a result, water will begin to accumulate around the foundation of your home, as well as under the concrete slab.
Further, water may seep into the house by way of the foundation walls and will appear as a reddish-colour deposit with a sulphur-like smell. It's also worth noting that iron ochre can block your storm sewer line, as well as the water catchment area.
Another common cause of iron ochre is having very high humidity in your home. This will be visible by the appearance of mould and condensation on your windows, and moreover, traces of efflorescence can appear in the bottom of concrete walls.
7 ways to minimize the negative effects of iron ochre
Of course, after reading the consequences of iron ochre, one would instinctively ask: is there a method of prevention for this substance? Unfortunately, the Régie du bâtiment du Québec confirms that it's impossible to avoid the appearance of iron ochre. However, it only takes a few moments to minimize the consequences of its presence.
1- Raise the slab above the water level
The purpose of the assessment we mentioned earlier is not to give up on the construction project you’ve already undertaken, but instead, to take measures to avoid the negative effects that iron ochre causes. Considering the specifics inherent in each iron ochre case, your contractor may decide to raise the slab above the water table before construction begins. This will help to avoid water infiltration as well as complications related to drainage obstruction. Again, it's worth noting that it only takes a few years for obstruction to occur if the appropriate preventative measures are not taken accordingly.
2- Change your home's drainage system or location
To maximize drainage of the surrounding land as well as limit the accumulation of deposits inside the drain, your contractor may decide to change the intended location of your home's drainage system and its openings, as well as their size. A model which is less favourable to buildup, and as well as larger in size, may be installed inplace of your old one.
Also, some contractors may opt for the installation of a stack chimney to easily reach the drainage system, allowing it to be cleaned correctly. Further, cleaning chimneys can be installed to allow for the removal of iron ochre residue, and thus, to avoid plugging the drain. Modifications can be made to the type of granular fill used during the drain installation.
3- Bactericidal and chemicals treatments
Another way to deal with iron ochre is to opt for bactericidal and chemical treatments. These treatments will directly affect the elimination of the Ferro-bacterium present in the soil while controlling the pH of the soil. Nevertheless, it's important to remember that this is a costly treatment, and it will have to be completed once a year. In addition, the products used in this treatment are harmful to the environment, and, as a result, can have a direct affect by contaminating the water table.
4- Case the inside of your foundation
Another measure one can take against iron ochre is to case the inside of the foundation. This option is known for having a high success rate. The interior casing is aimed at dealing with high humidity levels on the interior walls of underground or semi-buried foundations due to the frequent use of cement as well as a water-repellent coating. However, like the previous treatment, this is an expensive project.
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6- Install a geotextile membrane
Moreover, the location of the geotextile membrane could be adapted based on the presence of iron ochre. Further, impermeable membranes can be installed around the walls of your foundation following the application of a bitumen coating. However, this type of work is expensive and will require an investment of between $10,000 and $15,000.
7- Change the slope of the land
The modification of the slope of your property could be the key to avoid any damage due to the presence of iron ochre. It's mainly a question of preventing water from reahcing the land that surrounds the foundation of your home.
Is iron ochre a contaminant?
In the case of a new home, your warranty may exclude damage that has been caused by soil contamination by way of iron ochre. This makes it imperative to use the expertise of a professional to detect the presence of iron ochre in the soil. Some homeowners, as well as new buyers, have defended their case in court by arguing that it is inaccurate to consider ferrous ochre (the other name of iron ochre) a contaminant. This is because when the soil is affected by iron ochre, humans are unable to intervene.
However, this is simply one interpretation, as the Quebec Association of Builders and Housing (APCHQ) would argue the contrary position (based on section 29 of the regulations.) The Régie du bâtiment du Québec has ruled that “this is a situation covered by the guarantee plan in the case of new construction.” Continuing this idea, they argued that “it’s not a contaminant problem, it’s a design problem.”
However, many consumers have succeeded in winning their court case, and have had the necessary work to eliminate hazards as well as the consequences of iron ochre covered by the guarantee plan, including the lifting or casing of their foundation. The Association of Consumers for Quality in Construction has also intervened to encourage the amendment of this regulation in support of consumers affected by the presence of iron ochre, deploring APCHQ’s position on the subject.
However, the decisions regarding this subject may vary based on the evidence submitted. Indeed, you must be able to prove that damage has been suffered. In this regard, the Canadian Center for Commercial Arbitration asserts that “arbitral jurisprudence usually requires foundations to be built in the groundwater to declare that an iron ochre problem constituted a major flaw.”
Some are even challenging the fact that houses can be built on iron ochre contaminated land, as there is no regulation to prevent this situation. This is a chapter to follow, as the regulation to this effect has yet to be changed.
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