Trades & Labor Best Posts in Thread: Rock/Boulder removal?

Since I posted here some info on Septic tanks, I have been talking to a friend who was telling me his Tank collapsed and that was due to lack of Rebar inside the CHB, this had been built some 10/12yrs ago. Having given this some thought it has made me realise that it is not good to build any tank in CHB, the problem being although they are rendered on the inside very few if any are rendered outside, so the rebar is subject to constant wet conditions from the outside as CHB is quite porous, perhaps that had added to my friends problem not only did he lack enough rebar likely what was there was rotting anyway after 10yrs?

I have seen many underground chambers built in UK, these were used to install telephone cables, the contractors had a very simple method they would dig a hole with clean cut sides slightly larger that the required size of the chamber and then line it with Polythene, throw some concrete in the bottom then lower a reinforcement cage on to that, once in place they would add more concrete to form the base, after that was set they would drop in some wooden formwork, the nice clean cut earth covered with poly would form the outside of the chamber walls and the wood form gave a clean finish to the inside, many of these had to be made on busy roads and they needed the quickest method possible to get the road open again after one week.

This can be a great method for building a septic tank, cast in place concrete the steel inside the concrete would be well protected from both water and inside waste and outside water also, it just may be slightly more expensive but it is 10 times stronger and likely to last 10 times longer, also this requires no rendering at all, so that is a saving of time.

 

I have to say that even though people will sometimes disagree with @DAVE1952 (as they will with anyone who posts on the Forum as, interestingly, we are all individuals and think differently!) I have found his information on building here very illuminating. I have had my eyes opened to the pitfalls and they are greater than I ever thought and have been pointed into certain directions I had not considered. So I am very pleased to have his input.

 

I think you were stung by SRT, sometimes if you deal with the owner direct Ronnie, you can get a far better price, I guess I was lucky with the small machine he has, the driver of that was excellent.

Whatever way you build your septic tank do not use the pure Portland use the Pozzolan blended, the pure is high in Hydro Chlorates or something of that nature? and the sulphates in a septic eat it away, much the same for any underground work even foundations in mineral soils, in fact just use the Pozzolan for everything and you cannot go wrong, I know many will try and dispute this, when I asked for the Pozzolan from the hardware stores the assistants will tell me all foreigners use the more expensive Premium Portland, you do get slightly more working time with blended before it sets, I have also been advised to slightly dish the bottom of the digestive tanks and they work better in this manner, can't say either way if this is true or not, but it does seem to work?

If you care to google Portland vs Blended, you will see that the blended are more commonly used in first world countries.

 

One other thing I forgot to mention the access covers on a septic are better sealed with some weak cement or tile grout (something that is easily broken later on) much water can pass through the covers and fill the tank, also better to have a slight run on the top to shed the rain water off.

I have heard of a few people needing regular cleanouts of their tanks due to then filling quite quickly, likely they have bad fitting covers or they have been mixed up when removed before?

 

I ended up going with Santillian, they used the medium size track hoe for 2200p an hour and 5k for delivery. The first day the guy worked fast but the next he sand bagged on me a bit so ended up 9 and half hours. So now half of my lot has buried boulders on it but its clean, I just need to figure out a good spot for the septic tank where there are no hidden rocks.

 

You might find this link of some use.

http://www.carnationconstruction.com/Techniques/10-03-Techniques-Tools-RockBreaking.html

Best of Luck!