13th April 2013, 04:09 PM
That's depressing news. We've found on many sites around here that it often pays to leave trenches for a few days/weeks - sometimes 'invisible' features appear-themselves (same is happening on my current project). I've heard of jobs where 'blank' trenches are immediately backfilled which obviously negates that approach. I did a (open-area) cemetery a few years back where the odd phenomenon was going on of graves appearing-themselves at different rates, when first stripped you couldn't see a thing, but first one and then lots more graves became visible over the next few days/weeks so that we didn't know where to turn next. I'd love to know what the soil chemistry is that causes this, presumably some form of oxidation of the slightly increased organic content in the feature fills?