Good morning. Here's the progress from last week. It doesn't look like much, but it took a fair bit of time.
Pit lids and deliveries
We've ordered the Gatic lids for the sewer and stormwater tanks. In total they weigh about 200 kg. They get inverted and cast into the tank roof to form the access opening.
There isn't much storage room on site, so we've cleaned up and set aside one area as the delivery zone. The hardstand has to stay clear, and a 2 to 3 m skip will go in for waste. The ramp also has non-slip treads now, because the sand makes it slippery with people running up and down.
Council and the water
We've had a visit from the council's environmental team after complaints about the discharge water. There's no issue with the water quality. It's tested weekly, by two separate parties, and we know exactly what's in it. It just has high tannins, which make it look dark.
People don't know what we're discharging, and they're well within their rights to complain. Our job is to manage the council: give them what they need, and push back where it's warranted. This is one of those times, and we'll see it through.
Shaping the thickenings by hand
All the excavated sand has been brought back to one spot. We're trying not to use the excavator inside the dig now, because every time it tracks over the detailed excavation, it wrecks it. So everything is being dug by hand.
Most of last week went into shaping the thickenings and their batters (the sloped sides). Thickenings sit under all the structural support elements, so the levels have to be right. Sand is hard to shape, because it goes soft and slumps.
Two DCP tests by the geotechnical engineer last week confirmed we've reached the minimum design compaction. Sprinklers run overnight over the whole area, because if the sand dries out it goes fluffy and loses that compaction.
Height pins for the blinding
Height pins are going in everywhere: short lengths of reinforcing bar driven down to the exact level and capped. The concreter screeds the blinding layer off the tops of the pins, so it finishes flat and at the right height. The concreter starts on Wednesday.
The plumber and drainer start
The plumber and drainer started on Friday, with an inspection today. This is where the grids come into play: everyone measures off the same grid lines, which makes setting out much easier.
They're hand digging and laying the first 100 mm sewer pipe in the sand. It's a little different from what you'd see on a normal house. Every pipe under the slab is sheathed in closed-cell foam. The house is expected to settle 20 to 30 mm once the site is fully loaded. The foam compresses, so the slab can come down without loading and cracking the pipe. This is the double lagging from Post 43, now going in.
A 12-hour dewatering outage
We had the sewer and stormwater pit fully dug out. Then on Thursday afternoon, the dewatering stopped for 12 hours.
After troubleshooting, the dewatering company found the VSD had failed. That's the variable speed drive that runs the pump motor. The system has plenty of alarms, but the failed VSD still showed power going through it, so no alert went off. The pit filled back up with water. First job this morning is to dig the sand out and clean it again, so the concreters can get the blinding in and the pits can be done.
Planning ahead
- Backfill. We'll need some of this sand to backfill later, so we're making sure we keep enough on site rather than paying to bring material back in.
- Access and deliveries. These are the main challenge on this site.
- Permanent formwork. The purchase order is in for the permanent formwork system. The tank walls will be called up for delivery soon. They come in 3 m sections, so we need room to store them.
- Waterproofing. We've confirmed the details with Xypex, whose crystalline admixture is going into the concrete for the basement levels and probably the whole house. That includes the waterproofing at the floor-to-wall joint and the banding of the joints in the PVC formwork. The products are confirmed, and we're just waiting on final concrete prices.
And the site pigeon seems very happy.
The concreters start the blinding on Wednesday, and the plumbers will have more of the under-slab drainage in. Expect more action in the next update.
