The missing dimension

You don’t have to search very hard in the Environmental Statement (ES) documents to find understated impacts and overstated benefits. For example, some bright spark working on one of the sections on noise felt that he/she could claim (see footnote 1):

“By avoiding many noise-sensitive locations and by keeping the proposed alignment as low in the ground as possible, the Proposed Scheme has been able to reduce its overall noise impact.”

There was much “weeping and gnashing of teeth” when I stumbled across this claim – well now I’m exaggerating; my reaction wasn’t quite of biblical proportions, but I was a trifle peeved. My dispute was not with the idea that keeping the “proposed alignment as low in the ground as possible” would reduce noise impacts; no, it was that someone might think that this had been what the HS2 Ltd designers had tried to achieve. If you have read my blog A change of heart (posted 18 Apr 2013) you will be aware that, although the aim of HS2 Ltd in its first flush of benevolence did appear to be to keep the trackbed as low as it could, once the 2011 consultation was got out of the way a new, viperish HS2 Ltd emerged, intent only on cutting costs any way that was possible, and to hang with the environmental consequences. So it is that just a few hundred metres from where I live I can point to a spot where the proposed trackbed height has risen, when I was last able to check, no less than nine metres. Whilst this is the worst increase in my community forum area, it is symptomatic of a general, and appreciable, increase throughout that area, and I understand that this pattern has been repeated elsewhere.

However, I have no quarrel with the principle that the height of the trackbed has implications for the noise impacts that will result from train operations; and it’s not only noise, but the landscape and visual consequences that also depend on the third dimension. The ES contains, in a myriad of “environmental topic reports and map books”, more data, on the complete range of environmental topics, than you might think that anyone could even need, much of it in separate sets of volumes for each community forum area, with one volume for each topic. Yet, in spite of all of this data being provided, it appears that HS2 world is defined only in two dimensions; I have only found one circumstance where maps in the ES have depicted height – the specification of fence noise barrier height that I mentioned in my blog Down in the valley, part 3 (posted 20 Feb 2014). Apart from this exception, essential information such as the trackbed vertical alignment and the height of earthworks appears to be totally absent from the ES.

This flat-earth approach by HS2 Ltd is not new; it was also a “feature” of the draft Environmental Statement. However, at least HS2 Ltd appeared to recognise this shortcoming of the draft document and published a set of “plan and profile” maps (example), alongside the draft ES, to address the omission. In addition to a plan view of the route design, similar in form to the various maps that are now presented in the ES, this earlier set of maps also includes longitudinal section drawings – the “profile” – that depicts both the natural terrain heights along the route and the trackbed alignment within that terrain, as illustrated in the sample below.

Sample profile (Source: HS2 Ltd)

Sample profile (Source: HS2 Ltd)

This profile considers intervals spaced at 100 metres along the track, which is termed, in deference to the way things were measured by our Victorian forebears “chainage” (see footnote 2). At each 100 metre interval the undisturbed ground level (“existing level”), the trackbed height (“proposed level”) and the trackbed height above or below the undisturbed ground level (“cut and fill”) have been specified. So, even if these profiles told us nothing about the height of any environmental mitigation earthworks, at least they showed where the trackbed would lie in relation to the terrain through which it would pass.

In contrast to the absence of profile information in the ES, the hybrid Bill documents include five volumes of “sections”: Volume 4 Euston-Ickenham, Volume 5.1 Colne Valley-Burton Green part 1, Volume 5.2 Colne Valley -Burton Green part 2, Volume 6.1 Balsall Common-Handsacre part 1, and Volume 6.2 Balsall Common-Handsacre part 2. However, these sections employ a very different presentation of data to the profiles published alongside the draft ES. In the first place, chainage is missing from the sections in the hybrid Bill; horizontal distances are measured for each separate railway “Work No”, starting at 0km at the southernmost end of the stretch of track that is covered by that Work No. Secondly, trackbed height is only specified at the start and end of every section of track of consistent gradient; these vary in length from 100 metres or so to more than a kilometre. This means that the spacing between adjacent trackbed height measurements is irregular, and does not generally align with the 100-metre spaced measurements in the draft ES profiles.

Whilst I am sure that it will be possible, with a certain degree of measurement and translation, to make a comparison between the trackbed heights now and at the draft ES stage, this will be a very tedious and time-consuming process. However, I do feel that it is important to do this work for my community forum area, as I am suspicious that there have been some further increases in trackbed height since the draft ES was published.

Footnotes:

1. The claim is made in ES Volume 1, paragraph 9.12.1.

2. The term refers to the metal chain used as a measuring tool by surveyors, which was 22 yards long. In the imperial system of measurements, there are ten chains in a furlong and eight furlongs in a mile; therefore a mile comprises 80 chains. An acre is also derived from this system of measurement, and is the area of land in a rectangle one chain by one furlong (4,840 square yards). Distances along a railway track used to be measured in miles and chains, and many location markers employing these units remain on the rail network. The term “chainage” has been retained for HS2, although distances are specified in metric units.

Advertisements

One response to this post.

  1. Posted by chriseaglen on February 24, 2014 at 11:47 am

    Hopefully the MPs in the Hybrid Bill and petitioning will be able to understand these surveying and civil engineering matters well enough to judge.
    Suggest if you are submitting to the Environmental Audit Committee a local input you raise this under heading two on processes and sytstems. Also under the first heading of the ES not adequately reflecting and assessing the track bed height and heights in general heading.

    Reply

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s

%d bloggers like this: