Holdfast Training Services Trial Blog

Just when I thought that I had heard the last of Acid Sulphate Soils (ASS) they rear their ugly head again.

Almost out of the basement must be time for Phase 3

Those of you that are familiar with my blog posts will be aware of the regular discussions I have with my brother comrades in the CFMEU Union.  The latest affront seems to be that our Basement level 6 stinks!  There is concern that this is a ruptured gas line.  At 22 m below the surface, this would have to be a very deep gas pipe! Personally, I cannot smell gas but I thought it might be have  a faint smell of ammonia.

We have checked the area with a gas sniffer and the air quality is fine.  The guys are not making it up though and it really does stink down there. We still have water coming through the holes made for the ground anchors and while the quality of the piles is pretty good there is a small amount of water leaking between the secant piles. I suggested that it might be due to mould that is starting to grow on the piles and areas of stagnant water (caused by blockages in the spoon drains).  This was pretty quickly shot down because if it is mould we can expect our site to be shut down.  Some bright spark has hit on the idea that it is water contaminated in Acid Sulphate Soil.

Basement 6 ‘the dungeon’ – It puts the lotion in the basket

Here comes the Science again:

ASS occurs when sulphates in the soil are exposed to air and broken down by bacteria.  On our site there is a clay layer that contains a high concentration of  sulphates.  During excavation we exposed this soil to air so it oxidised and produced Sulphuric Acid.  Now we have finished excavation and all of the ASS has been removed.  The only ASS around us what is left outside of our site.  Now it is possible that the ground water around the site seeps through this soil and flows into our site through the anchors and from under the ground bearing slabs, where it is then collected by the site drainage system.

What I think is happening behind the wall (Not a flow net!)

A less than perfect flow net. 

However, the soil outside of our site has not been excavated and therefore cannot have been oxidised.  The site is approximately 200 m from the Brisbane River to the North and the West. As you can see from my diagram the area is flushed by sea water with the tide .  Sea Water is naturally basic and so counteracts any effect of the ASS. When I last had the water tested to get approval for discharge into the stormwater drainage the water was mildly alkaline and similar to the pH of the Brisbane River. SO NO IT’S NOT MY ASS!

What are we doing about it:

I now have to hold a workshop with the blokes to explain that it is not gas or ASS in the meantime the guys are cleaning up the walls to remove any mould (although there is no mould officially there) and remove the stagnant water that is on site.  We are installing some temporary fans to move the air around the basement until the permanent fans are installed.