In my blog Moving the earth (posted 31 Jan 2014) I introduced a spreadsheet that calculates the dimensions of a simplified false cutting and compares the land take with that required for a simple embankment. For the input assumptions that I made in Moving the earth this comparison reveals that the land take is increased by around 150% if a false cutting is employed in preference to a simple embankment.
In Moving the earth I didn’t make any comment about the last three lines of the spreadsheet calculation, and I will address that omission now. What I have done in those three lines is calculate the cross-sectional area of both the false cutting and the simple embankment, because this is directly proportional to the volume of material that will be required to build the structure. This part of the calculation reveals that, for the same input assumptions, the false cutting consumes over three hundred percent more material than the simple embankment.
I mentioned in Moving the earth that HS2 Ltd was planning to ease the external slope of false cuttings to about 1:8, when it was intended that these slopes be used for arable farming. Since the example that I have used so far assumes that the external slope is 1:2.5, as steep as was reasonably possible, I have changed the slope factor on the spreadsheet to see what effect this has.
The short answer to that is, “quite a lot”. The footprint of this farming-friendly false cutting has now increased by a massive 460% on the simple embankment and the cross-sectional area, and thus the material required for construction, is 850% up.
I think that the first lesson that we may draw from this is, that in view of their large footprint, landowners may not be too enthusiastic about false cuttings, and this was precisely the reaction that I got from our local farmers when they first saw the HS2 Ltd plans for my area. The initial loss of farmland to the construction of a false cutting will hardly be fairly compensated for by the promise of the future ability to farm the slopes of the cutting, after all the quality of such restored land may be very questionable.
My contacts with local landowners indicate that HS2 Ltd has not seen the need to discuss with them these proposals for false cuttings to be built; if this is generally the case, then I can only reflect that it is, unfortunately, symptomatic of the standard of engagement that we have come to expect. Neither has HS2 Ltd made any attempt to sell the advantages of these proposed mitigation earthworks to the communities that they are designed to benefit, at least if my experience of attending the local community forum is anything to go by.
The second thing that is glaringly obvious from the spreadsheet calculation is that a false cutting consumes significantly more material in its construction than a simple embankment; just how much additional material will depend on the geometry of the false cutting, but the spreadsheet indicates that is could be as much as nine or ten times more. This fact is key to a policy of HS2 Ltd that is described Volume 1 of the Environmental Statement as an “integrated earthworks design approach”. Paragraph 5.2.4 therein explains:
“Priority will be given to reusing material excavated from the Proposed Scheme in the engineering earthworks to form embankments, and environmental mitigation earthworks along the route. This will assist in reducing the need for the off-site disposal of surplus excavated material, and its associated environmental effects. This approach will also reduce the impact of the Proposed Scheme by making best use of the excavated material to significantly reduce the need to import material.”
So there, expressed clearly in the Company’s own words, lies the prime motivation for “environmental mitigation earthworks”. HS2 Ltd wants to dispose of the huge quantities of spoil that construction work would generate as close to the point that it is excavated as possible, and what could be better than a material-greedy false cutting to provide a way of doing this?
In domestic terms, what HS2 Ltd wants to do is to throw its garden rubbish over the fence into its neighbour’s garden, rather than having the bother of taking it to the local tip.
HS2 and the environment 
Posted by chriseaglen on February 6, 2014 at 8:26 pm
The presumption of the fill being local is very questionable. That would result in the centre of the embankment being inported to the area material. Italy has rock based foundations as seen in Switzerland and parts of Autstria. The central rural area will be sigificant clays and mudstones with gravel and sand beds also. In France the Channel tunnel excavations of drier limestone on the English side were used for fill. On the French side the clayier material was mixed with water and piped to large settling pools.
Using words such a integrated to mean joined together and now being used to represent cumulative should raise the caution as spinning the issue.
By the time the balancing ponds and natural ponding are in place the impact width degradng the land will be even wider.