Backfill

Waterproofing this retaining wall is one job that I hope not to see again for a very long time! Most of my day today was spent in behind the wall, clearing the clayey, mucky spill out of the drainage trench in order to get the plastic sheet and drain pipe in place ready for the backfill. Mostly this involved scrabbling and scraping with bare hands in the freezing muck, as the trench is only about 100mm wide and I don’t have a shovel or trowel that small.

This was all well and good in the sections in which I could physically fit, but in the narrower bits there’s only about a foot between the wall and the hill and it’s near impossible to get in there to clear the trench by hand.

What I really needed was a trenching shovel, but I don’t have one and there’s nowhere within range on a Saturday afternoon to get one. So, necessity being the mother of invention and all I made one. I took an offcut of corrugated iron sheet which was lying around, hammered it flat and folded it up into a U-shape around a length of 70x35 pine, tek screwed in place. Brilliant, did the job perfectly! :)

So with the socked drainage pipe nestled in the trench below the level of the slab and the plastic sheet in place I was able to fire up the bobcat and start backfilling the void with the load of 20mm pebble I had delivered last week.

An hour or two later and approximately 13t of pebble found a new home:

This was itself a bit of an adventure - although it looked pretty solid on the surface, the hillside was incredibly soft under the weight of the bobcat and it sank up to its belly every chance it got. It was never quite bogged enough to require recovery, but it got close a couple of times where the only way out was downhill towards the retaining wall - not somewhere I wanted to be on very soft ground in a 3 tonne machine.

I’m going to have to have a think about how I will excavate this bit of hillside for the upper slab-on-ground. I think I will have to park the bobcat and use the backhoe attachment to reach in and dig, rather than my original plan of digging out level with the machine itself - it’s just too soft and wet to get in there…

So the plan for the coming weekend is to get another load of pebble delivered so I can finish filling the void, and then think about starting the excavation of the slab-on-ground site. It’s shaping up to be a dry week, so with any luck…