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Iron Ocher

Iron ocher is the result of a bacteria that occurs naturally in the soil and manifests itself as a reddish, viscous, foul-smelling sludge. There may be no visual or physical signs to suggest its presence.

Land suitable for the development of new residential neighborhoods near major centers is increasingly rare. As a result, these are now emerging in rural areas.

This is how our entrepreneur found the rare pearl! A magnificent unforested site, with a flattened topography, a low water table, a soil typology made up of sand and provided with a municipal drainage network. In short, a winning combination to avoid problems associated with foundation drainage.

The project is underway and ten houses have been built and inhabited for about a year and a half when the contractor receives a call from one of his clients stressing the fact that water infiltration has occurred in the basement of the residence.
Following an episode of heavy rain, the access manhole to the drain would have overflowed.

The entrepreneur reassures his clients by mentioning that he will drop by to see what it is all about. In the meantime, he is racking his brains to figure out what could be the cause (s) of this episode, although he had paid particular attention to the execution of the foundation drainage system.

Drainage pipes used are standard, corrugated 4″ in diameter covered with a geotextile membrane and deposited on undisturbed soil. The pipes are positioned flush with the footings and covered with 6″ of clean stone above and to each side. In addition, to facilitate normal maintenance of the drainage system, the contractor took care to equip the system with cleaning chimneys.

Iron Ocher?

When the contractor arrived on the scene, the owners informed him that they had had a camera inspection of the drain made, and that they had to have it cleaned because of the presence of a plug caused by the presence of the drain iron ocher. After only one year of service life, you will understand that the owners are not very happy with the turn of events.

Stunned by customer claims that the soil contains iron ocher, the contractor is adamant that there is no way that the soil in the area contains iron ocher. The site is not wooded, there is no ditch, no significant difference in level, the nearby retention basin shows no orange traces in the water and the soil, during excavation, also revealed no trace. In short, absolutely no visual sign suggests the presence of iron ocher.

The situation remains in suspense, believing in an isolated episode. About two months go by and the phone rings again: another blockage in the drain and more water seeping in.

Help From the APCHQ Technical Department

This time, the entrepreneur decides to investigate further to find out. He therefore calls on the Technical Department of the Quebec Association of Construction and Housing Professionals. Accompanied by a service representative, he performed a camera test, which proved inconclusive as the owners had the drain cleaned again. After visual inspection, the Technical Service representative concludes that it is indeed unlikely that iron ocher is present in the area. Only the presence of very slight orange traces in the catchment basin does not allow us to conclude that we are in the presence of such a problem.

By questioning the entrepreneur about the history of the land, however, we learn that the residential development is based on a former golf course. While there are no visual or physical signs to suggest the presence of iron ocher in the soil, the answer lies in the history of the site.

It is quite possible that the bacteria were transported from site X to this one by the machinery, during the construction of the golf course. Being latent and not having the elements conducive to its development when using the site as a golf course, it therefore remained “dormant.”

By carrying out the housing development, creating an upheaval in the soil and a considerable supply of water and oxygen, the bacteria grew. The corrugated drainage pipes allow the orange mud to slide with difficulty and cause blockages to form. In addition, the geotextile membrane that covers the pipes is a nutrient for the bacteria; it clings to it and prevents water from reaching the drainage system, clogging the backfill that can no longer do its job.

Don’t just be fooled by appearances, they could lead you on the wrong track.
Sometimes you have to dig deeper to get to the bottom of the story.

Iron Ocher


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