Water and clay don't mix
Well, I got my wish today and had Big Girl all to myself for the entire day. Young Parm came at about 4ish to haul away the only load for today. I was able to scrape away the rest of the north bank in preparation for the blocks, finish excavating most of the remaining site other than what was under the tractor pad at the top, install the lid assembly of the sump, and then work on managing the pit ground water.
This involved cutting in a ‘stream’ through the pit to drain water from the back side to the front side and then scraping off any of the loose clay that had become saturated and the consistency of a wet cement slurry (just cement powder and water, no aggregate). The stuff is horrible to work with and around. Once saturated it would take months to dry out and harden again. So I am going to end up with spots that I have to add a lot more gravel below the slab to fill up the over excavation we are having to do to get rid of the water. I will probably get some 3/4 crushed gravel delivered that I will spread out on the pit floor as a sacrificial work surface that Alfie can move across without chewing up more clay. The ditch was channelled to the base of the new sump where I dug a 4ft hole filled with gravel and then installed the pit pump in a buck flush with the top surface of the gravel. This will act as the pit drain until the footings and perimeter drain are in place.
I have decided to put the perimeter drain in as soon as the footings are poured instead of the typical time frame of after the complete foundation is poured. This will make it much easier to install the pipe (not working in tight quarters between the excavation and foundations walls) and will allow me to manage the storm water much earlier in the process. Per the Geotech’s comments, I may also put a couple of runs through the middle of the house footprint to expedite the movement of water away from the house footprint.
All of this ground water scares me when I consider the typical construction where minimal gravel is installed below the slab and the footings are not typically installed over gravel and in full contact with the water table. Rising damp (the process where concrete via capillary action sucks the water up) can lead to moisture issues in basement often resulting in mould growth. I will discuss more in the future, but my footings will not only be above a gravel bed, but also encased in a water proof bag called FastFoot. This will be sealed to the poly under the slab and the fulled adhered membrane I will install on the outside of the ICF to create a fully water proof below grade enclosure. This is compared to the code minimum that only requires a thin spray on coating of asphalt to ‘damp proof’ the foundation.
I will apparently have all hands on deck tomorrow morning with at least three drivers. They want to get the excavation completed except for the portion of the North wall that we will not be able to remove until the lock blocks on the rest of the wall have been installed. Lets see how the day goes.
Thanks for visiting.
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