So what C4SLs do we actually need ?
There does seem to be a common perception that residential GAC numbers = too low = not workable.
I think that many of the existing 1% SOM GACs we currently use reflect the sort of threshold numbers I would be happy to have in my back garden (and under my house). In fact, there are a good number of 1% SOM GACs that I think are too high! (e.g. TEX compounds)
The key issue here for me are the current 1% SOM GACs that routinely fail on sites that are clearly in C4 (does anybody actually use 6% SOM for GAC without site robust SOM data?).
As it is Friday and to stimulate some healthy discussion & banter - here is a list based on my experience of using GACs on real sites. I've left out chlorinated solvents and exotics for now.
For me, the headline residential C4SLs (from inorganics, TPH, BTEX & PAH) that are urgently needed (i.e. the ones that currently fail GACs on sites that are clearly in C4) are:
- Lighter end aliphatic/aromatic TPH
- maybe a few other PAH
My view is, sort these out and live with the existing GACs for C4. Job done, move on. Leave the rest to DQRA if needed.
The initial SP101 list is:
- chromium VI
Well, that's 4 off my list. With the existing GACs, I just don't see a widespread need for cadmium and chromium VI C4SLs: the lighter TPH fractions are more important for sites we work on and zinc can be problematic.
The allotment 1% SOM GACs also need a good look at as well, but low priority. The majority of commercial 1% SOM GAC numbers seem about right or way too high (lead needs sorting of course).
Peak Environmental Solutions Limited
Unit 10, Aston Ind Estate, Parsons Lane, Hope, Hope Valley, Derbyshire, S33 6RB