A stab in the dark, part 5

(… continued from A stab in the dark, part 4, posted on 6 Jul 2017).

In this concluding part of the blog series I will consider, by way of a coda, the impacts that the Initial Preferred Route (IPR) for HS2 Phase 2a, or Route C as I have identified it, will have on Lionlodge Covert Site of Biological Importance (SBI) and the remnant of inland salt marsh that lies within the SBI.

Lionlodge Covert was first surveyed for the Staffordshire Ecological Record in 2014 (see footnote 1). It is a broadleaved, mixed and yew, plantation woodland that is growing on drained saltmarsh. The woodland is 15.4 ha in extent and is privately-owned. Consistent with its name, it is used for the raising of gamebirds.

Lionlodge Covert – drainage ditch

In 2015 a further ecological survey was carried out, and the “woodland boundary was extended” to include the area of inland saltmarsh that lies to the south of Lionlodge Covert, and which I have referred to in this blog series as the Ingestre/Tixall Salt Marsh. The current extent of this marsh is 1.5 ha and it is described in the Ecological Site Report as poor semi-improved grassland.

Ingestre/Tixall Salt Marsh

Following the second survey the site was designated as a Site of Biological Importance (SBI) and recognised as comprising two sub-sites: woodland, and inland saltmarsh (see footnote 2).

The Ecological Survey Report notes that the SBI designation has been afforded to Lionlodge Covert because of its “species-rich woodland ground flora which supports several ancient woodland indicator species” (see footnote 3). Examples of such species are noted in the report as “frequent Bluebell, Dog’s Mercury, Wood Speedwell and occasional Enchanter’s Nightshade where the ground was wetter” (see footnote 4). A good selection of other woodland plants are listed in the report as having been recorded, including four species of fern.

The report describes the Ingestre/Tixall Salt Marsh as “an area of rank, wet grassland”: the photograph reproduced above confirms that it is not much to look at, but this image problem belies its ecological importance as an example of natural inland salt marsh (see footnote 5). Although, due to drainage schemes being employed, it is now only a remnant of its historical extent, which records indicate was something in excess of 35ha (see footnote 6), what remains of the Ingestre/Tixall Salt Marsh is, like its more-illustrious cousin at Pasturefields, a rare example of a habitat type that is listed as a priority habitat in Annex 1 to Directive 92/43/EEC of the EU Council.

The Ecological Site Report records that the Ingestre/Tixall Salt Marsh “supports extensive areas of Saltmarsh Rush” which is “currently only recorded on two other sites in Staffordshire”, one of which is Pasturefields. However, the report also credits the Ingestre/Tixall Salt Marsh with an accolade that cannot be claimed by Pasturefields:

“The site also is host to Stiff Saltmarsh-grass which has not been recorded in the county since 1923 and is a significant record for the country. The species is nationally scarce and normally confined to coastal locations. At present there is only one other inland site in Britain (in Cheshire) where the species has been recorded in modern flora accounts.”

The report also notes records of breeding Northern Lapwing and of Eurasian Curlew “displaying breeding behaviour” – more recent information indicates that Eurasian Curlew is now an established breeder on the site (see footnote 7). Both of these birds are “red listed” as birds of the highest conservation concern in the UK; the Eurasian Curlew is of particular concern as it has moved from amber to red (see footnote  8), and has been authoritatively described as “[the UK’s] highest priority species from a global perspective” (see footnote 9).

The map reproduced below indicates that the HS2 IPR Route C will be bad news for Lionlodge Covert and the Ingestre/Tixall Salt Marsh (see footnote 10).

Source: HS2Ltd

HS2 Ltd advises that the construction of the Trent North embankment, shown on the map, “would result in the permanent loss of approximately 5ha (approximately 30%) of Lionlodge Covert LWS” (see footnote 11). According to the Ingestre with Tixall Parish Council, this breaks down to a loss of approximately 25% of the woodland sub-site and the whole of the saltmarsh sub-site (see footnote 12).

It is a condemnation of the way that environmental protection operates in the UK that there are two similar inland saltmarsh sites within a mile of each other, with one being strictly protected under the EC Habitats Directive and the other having nothing more than the ineffectual protection offered by Local Wildlife Site (LWS) status. Inland salt marsh is an irreplaceable habit, and the Ingestre/Tixall Salt Marsh is, surely, potentially of national importance.

Sadly, as the treatment of ancient woodland on Phase 1 of the HS2 project has demonstrated only too clearly, HS2 Ltd pays no regard to the irreplaceability of habitat and appears to treat LWS status as an open invitation to trash with impunity.

The Ingestre with Tixall Parish Council has also learnt a lesson that many respondents to the public consultations on Phase 1 would recognise; that HS2 Ltd pays little regard to intelligence fed to it by local communities. The Council notes that it has passed a “considerable quantity of information” to HS2 Ltd, but that “but none has been acted on”, and that “almost all previously supplied information had been ignored or misrepresented” in the draft Environmental Impact Assessment that was published in September 2016 (see footnote 13).

There is however one matter that HS2 Ltd would be well-advised to pay some attention to. The Ingestre with Tixall Parish Council has warned HS2 Ltd that the “brine springs that feed [the Ingestre/Tixall Salt Marsh] remain active” and that “local measurements of brine concentration and flow rate at just one of the outflow points from the drainage network of the marsh gives a daily loss of 1.34 Tonnes (0.5m³) of salt” and that this salt derives from “natural dissolution of halite that underlies the salt marsh”. The Council adds that it regards this figure as “a minimum as there are several outflow points and not all were measured” (see footnote 14).

The Council concludes that (see footnote 15):

“Apart from the corrosive nature of brine, it appears that HS2 Ltd has created for itself significant engineering challenges in maintaining track stability in the face of the loss of supporting ground amounting to several hundred cubic metres per annum.”

That this may be a much wider problem in the area is, perhaps, indicated by the following map, which shows where salt dissolution subsidence can occur (see footnote 16).

Source: British Geological Survey

This map is evidence of the “geological instability” that I referred to in part 1 of this blog series, which is a legacy of both the history of commercial salt extraction and the natural processes that have created the two inland salt marshes. Historic ground subsidence is a matter of record and Dr Anthony Cooper, at the time a geologist with the British Geological Survey, warns in a paper reviewing the “geohazards” associated with the erosion of rock salt deposits, that “further subsidence may occur” as “only about 10% of the volume of salt removed … has been accounted for by recorded subsidence” (see footnote 17).

The IPR for HS2 Phase 2a (Route C), coloured dark green, cuts across the north-eastern corner of the large area that is marked as being “prone to some salt dissolution subsidence” on the BGS map that I have reproduced above. This potentially problematic traverse is in contrast with the much safer original first choice route, Route B (coloured light green), which avoids the subsidence-prone area altogether: it is extremely unlikely that this increased risk factor, and the consequential engineering expenses of overcoming the subsidence risk, was taken into account when the additional £154million cost of Route C was calculated by HS2 Ltd.

Footnotes:

1. The site reference in the Staffordshire Ecological Record is 92/84/70. The Ecological Site Report is not currently available on the internet.
2. Site of Biological Importance is a non-statutory designation used locally by the Greater Manchester, Cheshire and Staffordshire County Councils to protect locally valued sites of biological diversity, which are described generally as Local Wildlife Sites by the UK Government.
3. Although Lionlodge Covert is not, of course, ancient woodland.
4. The report notes that the “native Bluebell is at risk from being displaced” by the Hybrid Bluebell that occurs along the main access tracks “if it continues to spread”.
5. For an explanation of the importance of this habitat type see part 1 of this blog series.
6. See bullet point 1 under Section 7 (Cultural Heritage) 7.3.7 and 7.3.8 (Non-designated Assets) in the response to Question 3 in HS2 Phase 2a: West Midlands to Crewe Environmental Impact Assessment Report Response by Ingestre with Tixall Parish Council 7.11.2016 on the Council’s HS2 webpage.
7. Breeding of Eurasian Curlew at the Ingestre/Tixall Salt Marsh is confirmed in a private email circular, dated 12^thApril 2017, transmitted by the Deputy Chairman of the West Midland Bird Club.
8. There was an overall UK decline in Eurasian Curlew population of 42 per cent between 1995 and 2008 and the UK is host to as much as 27 per cent of the world’s breeding curlews.
9. According to Dan Brown, Conservation Adviser with RSPB Scotland – see the web article Curlew should be UK’s top conservation concern says RSPB Scotland, Royal Society for the Protection of Birds, 3^rdDecember 2015.
10. The map is a section of drawing LV-11-109 in the publication High Speed Two Phase 2a: West Midlands to Crewe Working Draft Environmental Impact Assessment Report Volume 2: Map book CA2: Colwich to Yarlet, HS2 Ltd, September 2016. I have rotated the axis of the map to comply with the north upwards presentation of all the other maps that have been used to illustrate this blog series.
11. See paragraph 8.4.6 in the publication High Speed Two Phase 2a: West Midlands to Crewe Working Draft Environmental Impact Assessment Report Volume 2: Community Area report CA2: Colwich to Yarlet, HS2 Ltd, September 2016.
12. See under 8.3.9 (Environmental Baseline – Existing baseline – Lionlodge Covert LWS) in the response to Question 3 in the response to the HS2 Phase 2a EIA by Ingestre with Tixall Parish Council.
13. See Section 1 (Introduction) in HS2: Notes on costs and benefits from seeking a route change on the HS2 webpage of the Ingestre with Tixall Parish Council.
14. See bullet point 1 under Section 7 (Cultural Heritage) 7.3.7 and 7.3.8 (Non-designated Assets) and 10.3.38, 10.3.39 together with 10.4.21 (Environmental baseline – Mining/mineral resources – Halite deposits) under Section 10 (Land quality) in the response to the HS2 Phase 2a EIA by Ingestre with Tixall Parish Council.
15. See 10.3.38, 10.3.39 together with 10.4.21 (Environmental baseline – Mining/mineral resources – Halite deposits) under Section 10 (Land quality) in the response to the HS2 Phase 2a EIA by Ingestre with Tixall Parish Council.
16. This map was provided in private correspondence dated 29^thJanuary 2014 between the BGS (Dr Vanessa Banks) and Ingestre with Tixall Parish Council (Cllr Michael Woodhouse).
17. The paper is Cooper A H, Halite karst geohazards (natural and man-made) in the United Kingdom, Environmental Geology Volume 42, Issue 5, pp505-512, August 2002.

Acknowledgements:

I am very grateful to Cllr Michael Woodhouse of Ingestre with Tixall Parish Council for hosting and guiding my fact-finding visit to Ingestre, providing background information and copies of unpublished documents, checking the factual content of this blog, and for his helpful suggestions for improvements.

The Ordinance Survey mapping upon which the HS2 Ltd route design and subsidence areas have been overlaid has been reproduced in accordance with the principles of fair dealing as set out in the Copyright, Designs and Patents Act 1988.  On this basis, this mapping is:

Reproduced by permission of Ordnance Survey on behalf of HMSO.

© Crown Copyright. All rights reserved.