On Tue, 05 Nov 2013 09:56:06 +0000, Nightjar wrote:

Well, we've finally found where the 'ole in the top of the septic tank
is. Doing a bit of garden tidying yesterday, I found a paving slab in
the earth between a tree and the hedge. Lifting that, there was another
paving slab. Then a bit more. Then a brick. Then another paving slab...
I didn't lift that one, because a crack opened up between it and the
earth to one side - a bit of loose earth slid in, and landed with a
sploosh. I've not investigated any further, and have no great desire
to. The slabs are lobbed back in position at the moment.

Generally, not an ideal access setup. /understatement

So - what think you all? I've got a little stack of blocks at the back
of one of the outbuildings. The path of least resistance would appear
to be to lay those into the earth as best as possible, mortaring them
together.
Mebbe lay a rough wooden frame underneath the first layer, to ensure
they stay put. A couple of layers, laid "low but wide", should give
sufficient strength without having to worry too much about earthworks.
Then a manhole frame & lid over the top.

Various options he

http://www.pavingexpert.com/drain05.htm

Mmm. A simple plastic raising piece plus cover sounds like the ideal
solution. I'll have a chat with the guys in the local builder's merchant,
too, see what they reckon.

There's not going to be any traffic over the top - vehicle or even
foot.

You should, nevertheless, build it on the assumption that somebody,
someday, will step on it.

Oh, absolutely.

But - trust me - no matter how bad, it's GOTTA be better than what's
there already.