November 4, 2023 

It’s been 7 months since handover almost to the day and Henley have finally decided to have a good go at fixing the drainage problems they created. Yesterday morning Henley sent over 2 licensed drainers and a mini excavator to repair the mess, sadly, they only repaired part of the problem. 

The day started well enough – Henley finally sent out an electrician to finish the installation of my air conditioner. It only took 7 months. Thanks Henley. 

What does the drawing say?

Since my onsite meeting with 4 Henley representatives their construction manager has contacted their consulting engineers, DEV in Queensland, and claim that having Agi pipe and associated trenches within 250mm of my concrete slab is OK. This is despite the engineers own drawing claiming the Agi should be no closer than 1500mm. The bottom right of the drawing below. 

Note the specifications on the bottom right under the heading "Sub-Surface Drainage."Also not toward the top left where it says "It is the builders responsibility to provide adequate site drainage at the time of construction." This drawing formed part of my signed contract with Henley.

To give you some idea of why I am concerned about the latest representations of DEV, here is a link to an article from another Queensland based engineer who hold grave concerns about the use of Agi pipe near “waffle pod” slabs. Henley built my home on a waffle pod slab. 

Action at last

In any case, I was relieved that Henley was taking any action at all. As can be seen in the drawing below, the purple highlighter shows the 4 silt pits connected underground by 18m of slotted Agi pipe. On top and to each side of the Agi pipe there is a roughly 300mm layer of 20mm scoria rock which is there to allow any surface water to cascade past and safely into the Agi . From there it eventually exits into the stormwater. Or at least it should. 

On top of the scoria layer, it is normal to cover it with soil while landscaping as the water can still pass through and into the scoria and then the Agi. Under no circumstances should the scoria layer be covered in clay as this does not allow surface water to safely pass through to the scoria layer, it just sits on top. Sound familiar? 

Henley left my site with a thick layer of clay covering the scoria and this was part of the reason the front of my place looked like a lake when it rained, the drainers used the excavator to remove the clay, and the toxic layer of blue muck which Henley left for me. This took most of the day to fix. Imagine how long it would have taken if I had to do it myself, by hand. 

Does water run up hill?

During the excavation process I pointed out to the drainers that much of the Agi pipe was running the wrong way, that is, uphill. The start of the drainage system, the highest point, should be the silt pit located a few meters in front of my front door, then head downhill via the Agi to pit 2, 3 & 4 before exiting to stormwater. That’s not what’s happening. 

On the only exposed bit of Agi I put a level on it. The should flow from the left side toward the right. This means the bubble on the level should be on the left hand side - the high point.

For a start, in the only place the drainers exposed the Agi pipe on Friday, they felt it all looked pretty good. I put a level on the pipe to prove them wrong and photographed the result. If the Agi were installed correctly the bubble on the level should be on the left side. It’s on the right. 

Here's a zoomed in view with the bubble on the wrong side (the right)

After I convinced Henley’s drainers that the pipework pictured above was defective, they decided to replace the small section of Agi between pits 2 & 3. They would not be persuaded that the Agi between pit 1 & 2 was sloping the wrong way. After the clay layer was cleared, the small section of Agi replace and the new scoria added, they headed off. 

I'm a tradie and can measure too

Later on, I took some measurements using a long level and a tape measure and found pipe entering pit number 2 is 70mm higher than pipe exiting pit 1 at my front door. I would have expected that to be the other way around. Remember, there is supposed to be a 100:1 down slope from pit 1 to pit 2, 3 & 4. 

How the drain looked by the end of the day. At the bottom of the photo is pit 1, with pit 2 toward the top. Pit 1 is so low that a 2nd pit had to be inserted into the original because it is so far underground. Because my concrete path has now been installed it makes it tough to raise pit 1 and the Agi which runs under the path.

As far as I can tell there is no easy or cheap way to fix this problem. I had contacted Henley to rectify the drainage problem before I had my concrete path installed. They acted too slowly.  

If past experience is anything to go by, Henley will pretend that this problem does not exist. With that in mind I now have to decide how far I wish to pursue Henley to fix the problems their negligence created. 

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