These notes have been researched and prepared by Drew James

HS2  – Environmental Statement  – accompanying the High Speed (Crewe – Manchester) Bill for the Phase 2b Western Leg


Hs2’s Environmental Statement (the “ES”) for phase 2b (Crewe to Manchester) is not fit for purpose

On 6th September 2017 the Under Secretary of State for Transport (Paul Maynard) advised the House of Commons that light detection and ranging surveys had been completed by HS2 Ltd for phase 2b. He promised the Commons that “there is more work to be done to further assess geological risks and to provide suitable mitigations for them. HS2 Ltd plans to carry out early geotechnical investigation work in the mid-Cheshire area to gather more advanced survey information”

A rail track, not least a high speed rail track, cannot be constructed unless there is ground stability. The tolerance for movement is low. This is obvious. It beggars belief that after four years of waiting the ES does not address this, the most important pre-condition for the project to proceed.

In September 2021 HS2 announced it was to start searching for a team of specialist ground investigation contractors for phase 2b. The £300 million contract will include the appointment of a lead ground investigation partner, supported by up to ten specialist ground investigation contractors. This is the work that Mr Maynard promised four years earlier in 2017. This geotechnical investigation work was supposed to be done “early”, i.e. before the Hybrid Bill was debated in Parliament. To pass the Phase 2b Hybrid Bill now will place the cart before the horse.

The planned route for HS2 north of Crewe passes through 22.5 km of geologically unstable land known as the Cheshire Brinefields. It is an area prone to subsidence, with a history of salt mining and brine extraction dating back to Roman times. Parliament has patiently waited for the outcome of the geotechnical investigation work promised by Mr Maynard. It cannot now sanction the eye-watering expense of construction north of Crewe because there is a total absence of reliable independently sourced geophysical data within the ES.

HS2 Ltd is unable to present Parliament with a cost/risk analysis. Without hard data on ground stability Parliament cannot determine the true cost of construction or make a judgment on whether or not HS2 will operate free of track subsidence and expensive service interruptions.

The ES makes cursory mention of subsidence and proposes mitigation by way of raising the track onto embankments. This high-cost solution has been promoted in the hope that it’ll do. Mr Maynard’s “advanced survey information” is absent from the ES. Now, in 2022 Parliament is being asked to write HS2 a blank cheque to cover whatever subsidence hazard is encountered in the construction phase.

Given the tight squeeze on budgets, the changing geo-political situation and the looming cost of climate change transition to green energy Parliament must exercise its fiduciary duty and place a hold on Phase 2b until HS2 has done its homework and costings properly.

This briefing Note has 8 Parts:

1 – Introduction – The Parliamentary Debate of 6th September 2017                                        PAGE 2 & 3

2 – The Wardell Armstrong Report                                                                                                  PAGE 4

3 – HS2 Ltd advice to Government of July 2017                                                                             PAGE 4

4 –  HS2 announces geotechnical investigation will not commence until late in 2022           PAGE 5 – 7

5 – Are any specific salt dissolution risks considered in the ES?                                                 PAGE 8

6 – What does the Environment Statement say with reference to salt mining?                     PAGE 9 – 11

7 – Background Note : The Holford Brinefield                                                                                  PAGE 12 – 15

8 – Background Note : Three Viaducts over River Dane and Trent & Mersey Canal               PAGE 16 –  22


1 – Introduction – The Parliamentary Debate of 6th September 2017 – HS2 Phase 2b

Antionette Sandbach M.P. (Eddisbury . Con) opened the Commons debate with these words:

“The proposed route of HS2 through my constituency of Eddisbury will not only cause significant environmental damage and noise disruption to many areas, but come at a particularly high cost to the taxpayer because of the unique geotechnical challenges of routing HS2 through an area of current and historical salt mining and across land with a long history of significant subsidence risk.” and said later:

“TerraConsult Ltd produced an independent geotechnical report on the proposed (2016) change of route and concluded that there would be an increase of 11% in the route length over wet rockhead. HS2’s lead ground engineer has called the ground conditions in the Cheshire salt area “spicy”, referring to the engineering challenges of building a high-speed railway line in that area, and HS2’s own consultant, Wardell Armstrong, recognises the risks of building HS2 through Eddisbury in its report on salt-related ground instability”

Alarmingly, before making route choice proposals, HS2 had not done any detailed ground surveys for use as a baseline to track ground movement. As far as I am aware, those surveys have still not been carried out.”


A deep worry is that HS2 does not seem to be disclosing the appropriate level of technical reports to experts who are meant to be giving expert opinion highlighting proper concerns which are right to express at this stage in advance of a serious engineering project. One such expert is one of the most eminent professors in the field of salt subsidence, who wrote to the Secretary of State more than 18 months ago to emphasise that ground-level surveys ought to be started now, so that HS2 can identify subsidence and problem areas.”

Esther McVey M.P.  (Tatton. Con) said:

“My constituency, too, is full of brine fields and wells where salt has dissolved and been pumped out, which creates craters underground. Ros Todhunter, a geologist who lives in Lostock Green in my constituency, has also discussed land movement. Railway engineers talk about permitted movement of 5 mm, but we could be looking at 0.5 metres. As my hon. Friend has said, there should be discussions with people who know the land well—their families have farmed this land for hundreds of years and they know about problems under the earth that, I am afraid, the Government have so far not looked into.”

The (then) Under-Secretary of State for Transport Paul Maynard M.P. replied:

As someone born and bred in Northwich I have been brought up on photos of houses that have collapsed because of subsidence, and have suddenly disappeared into the Bull Ring in the town centre. I am more than aware of those issues; but I reassure hon. Members that we are seeking to manage them actively”

“HS2 has commissioned a specialist mining engineer, in consultation with the Cheshire Brine Subsidence Compensation Board, to undertake a study on the consultation route using available data such as those from the British Geological Survey, the salt industry and local authorities. Those light detection and ranging surveys have been completed by HS2 Ltd, identifying the wet rockhead features to which my Hon. Friend referred near to the route, and will be considered with other LIDAR surveys”

I recognise that this is a sensitive and complex section of the route. There is more work to be done to further assess geological risks and to provide suitable mitigations for them. HS2 Ltd plans to carry out early geotechnical investigation work in the mid-Cheshire area to gather more advanced survey information.”

Note: Mr Maynard was no doubt relying on misleading statements in the HS2 report published two months earlier – see Part 3 below



2 – The Wardell Armstrong Report

Wardell Armstrong are HS2’s mineral and engineering consultants. The Sunday Times newspaper saw a copy of their report concerning “salt-related ground stability” and noted in an article of 29th January 2017 that it says HS2 will be at “high risk” of ground collapse. This is the report referred to by Mr Maynard in the Commons debate of September 2017 (above)


The report noted the line will cross Britain’s biggest active salt mine, at Winsford, where digging is planned to extend its workings, and warns of “the potential for the rapid development of significant movement” in this area under the weight and vibration of trains, “with a consequent risk rating as high”. It identifies five more salt-mining or brine extraction sites near the town.



3 –HS2 Ltd’s advice to Government :  July 2017

HS2 Ltd advised the Government of proposed route changes in July 2017 in the document “High Speed Two Phase 2b Crewe to Manchester West Midlands to Leeds Route refinements”. Below are extracts concerning the salt mining area north of Crewe:


9.3.9 ……”A raised route is considered less likely to result in drainage path changes in the area and thus reduce risk. However, it may be possible to mitigate some of the drainage concerns by other means that would emerge during further design work undertaken as part of hybrid Bill preparation. We will therefore undertake more detailed consideration of the specific salt dissolution risks and the possible range of alternative risk mitigation measures, with a view to developing a design solution where the HS2 route can be lowered in the vicinity of local communities.”


“9.3.11 We do, however, recognise that this is a sensitive and complex section of the route and that there is more work to be done before the hybrid Bill is deposited to further understand the geological risks and provide suitable mitigation solutions. We are looking into carrying out early geotechnical investigation work in the mid-Cheshire area and gathering more advanced survey information (for example, by using Interferometric Synthetic Aperture Radar (InSAR) technology and analysis tools).”








4 – HS2 announces geotechnical investigation will not commence until late in 2022    

This online article needs no explanation. It is the smoking gun. Hs2 ltd have not yet done the work promised in July 2017


5 – Are any specific salt dissolution risks considered in the ES?

The short answer is No.

The ES makes reference to salt mining but only cursory reference is made to salt mining as a subsidence hazard . HS2 Ltd have produced no evidence that they have made site specific surveys for subsidence, or monitored movement. Construction on ground that is susceptible to salt dissolution requires the avoidance of actively subsiding areas and mitigation measures similar to those adopted for coal mining regions. Large structures may be particularly susceptible to unwanted movement and it is important to understand the local geology, faulting and collapse mechanisms. Below are examples of what HS2 Ltd could and should have done within the ES and before bringing the Hybrid Bill to Parliament. (Source – “Geological hazards from salt mining, brine extraction and natural salt dissolution in the UK” by Anthony H Cooper published in 2020 by the Geological Society of London)

Microgravity geophysics is a useful tool for monitoring cavity growth and subsidence owing to salt dissolution. This has been used to image a subsiding area to the east of Penny’s Lane Mine in Northwich and showed that it was not related to undermining. Subsidence was linked to salt dissolution at shallow depths owing to wild brine extraction that was being undertaken from a factory located to the east. This was drawing in brine from a considerable distance away. The microgravity signature indicated less density over time and the development of brecciated rock associated with brine dissolution and subsidence.

Long-term monitoring of the Trent–Mersey Canal where it crosses former salt workings has showed microgravity and topographical changes related to upward migrating cavities and subsiding areas.

Other geophysics such as ground-probing radar and electrical resistivity tomography also have the potential to image cavities and collapsing ground in similar circumstances.

The historical salt mines in the Northwich area have continued to cause problems for development of the town and have threatened some modern constructions. Instability of the old mine workings was aggravated by wild brine pumping, but even after this ceased in 2005 there was still concern about the stability of the mines. In 2002, £32 million was pledged by the government agency of English Partnerships to stabilize the salt mines of Barons Quay, Witton Bank, Neumanns and Penny’s Lane. Where possible these mines were ultrasonically scanned to establish their condition and dimensions. They were modelled using this information and historical mine plans. The mines were stabilized using a grout of saturated brine, pulverized fuel ash and cement. A large void volume of at depths of 90 m was successfully filled and 32 ha of ground stabilized. The exercise was a logistical challenge, bringing in cement and about 1 million tonnes of pulverized fuel ash by rail to Winnington and pumping it down a pipeline that included a 470 m horizontally bored section beneath a river and Site of Biological Interest to the grouting.




6 – What does the Environment Statement (“ES”) say with reference to salt mining?

Volume 1  – This is the Introduction to the ES and Methodology

Paragraph 5.2.11 says:

“Ground stability and the potential for managing subsidence as a result of mine workings, for example for the extraction of salt, brine, coal and limestone has been considered in the development of the design”.

In other words, Hs2 are aware that ground stability and subsidence are potential hazards, and their response has been to raise the track onto embankments They have not carried out the geotechnical investigation work promised in 2017. This leaves them ignorant of the impact that construction and train operations will have on the underlying geology

Paragraph 8.10.5 says:

“The route of the Proposed Scheme will intercept mining and mineral resources, including salt extraction, sand and gravel extraction, coal mining and aggregate production from quarries, and the exploitation of other identified resources (e.g. hydrocarbons and coal bed methane). Where these resources will be impacted by the Proposed Scheme, they have been dealt with in the context of their value as an asset

In other words, the ES does not address salt mining as a hazard that may cause subsidence to HS2 track or viaducts. It focuses instead on the impact HS2 may have on commercial mining and storage operations.

Table 6 says:

“Middlewich to Pickmere (routes through salt mining areas) …The route would avoid direct interfaces with brining and gas storage infrastructure and would be raised to allow for management of drainage and geological risk. There would also be more flexibility for ground stability mitigation options.

The reference to “infrastructure” is an obfuscation. The proposed route narrowly avoids brine well-heads and surface installations, but in the absence of a comprehensive study of underground caverns, watercourses and brine runs, the impact of HS2 on those geological features is completely unknown. Raising the track on an embankment and the driving of piles for viaducts will alter and/or create new underground watercourses/brine runs, with an unknown impact on salt dissolution leading to subsidence. Hs2’s reference to “flexibility for ground stability mitigation options” is a coded admission that HS2 Ltd are stepping into the dark and seeking Parliamentary consent to proceed without having completed their geology homework.




Volume 2 – This comprises “Community Area Reports”, each with a prefix of “MA”

They acknowledge “geological complexities relating to the crossing of brinefield and areas associated with gas storage” but go no further.


MA01 (Hough to Whalleys Green) acknowledges the potential for subsidence but there is no analysis of whether or not HS2 rail operations will be impacted by subsidence, or whether construction will be causative of subsidence in future:

“10.3.46 Areas of natural dissolution of the salt rockhead may be present in the study area as soluble rocks are present.

10.3.47 The study area is located in a brine compensation area which indicates there is the potential for subsidence resulting from the historical pumping of brine.”

This Community Area Report considers Hs2’s potential for causing land contamination and its impact on commercial mining, but there is no evidence of any site-specific investigation to consider the impact of construction and train operations on the local geology

MA02 (Wimboldsley to Lostock Gralam) acknowledges there is the potential for subsidence resulting from the historical pumping of brine, but then focusses on risks of land contamination and impacts on commercial mining. There is no analysis of whether or not Hs2 rail operations will be impacted by subsidence, or whether construction will be causative of subsidence in the future.

Damage to gas storage facilities is considered, but is then dismissed without acknowledging that deep gas storage cavities are only stable so long as pressure is maintained within. UK reliance on natural gas for heating will diminish in the next decade, and so will the need for strategic gas storage:  

10.3.31 The Holford Brinefield site is registered as a Control of Major Accident Hazards (COMAH) site in relation to gas storage, although it is understood that the wellheads associated with the site are not located within in the study area”

No reference is made to what exactly is a safe “minimum vertical distance” above a cavity, and relies upon an assumption that cavities are permanently stable structures. Some brine cavities can be as little as 60 metres below the surface.

“10.4.31 The Winsford Rock Salt Mine and Holford Brinefield, are very high value receptors. However, the Proposed Scheme would be required to maintain a minimum vertical distance from these resources in order for their continued extraction and a lateral offset from existing caverns. The effects on the Winsford Rock Salt Mine and Holford Brinefield would be negligible and therefore not significant.”

MA03 – Pickmere to Agden and Hulseheath

The omissions in MA01 and MA02 are repeated in MA03.


Volume 3This concerns Route-wide effects of the construction and operation of HS2 on the environment.

It deals with these under the following headings: :

  • Agriculture, forestry and soils (Section 2);
  • Air quality (Section 3);
  • Climate change (Section 4);
  • Community (Section 5);
  • Ecology and biodiversity (Section 6);
  • Health (Section 7);
  • Historic environment (Section 8);
  • Land quality (Section 9);
  • Landscape and visual (Section 10);
  • Major accidents and disasters (Section 11);
  • Socio-economics (Section 12);
  • Sound, noise and vibration (Section 13);
  • Traffic and transport (Section 14);
  • Waste and material resources (Section 15);
  • Water resources and flood risk (Section 16)


There is no section dedicated to Subsidence and no evidence of the “more work to be done to further assess geological risks and to provide suitable mitigations for them” promised by the Under Secretary of State for Transport in 2017. The “Land Quality” section deals primarily with contamination. Paragraph 9.5.4 says (with my emphasis in bold): “It should be noted that the Holford Brinefield landfill site and Winsford Rock Salt Mine Waste Disposal Facility are of national importance, but as the facilities are located at depth and the Proposed Scheme is at surface level at these locations the impact on these ‘landfills’ is expected to be negligible.”

Background information on Land Quality is within Hs2’s document BID LQ-002-0MA02. With regard to salt mining the focus of this document is the impact of HS2 on commercial activity





7 – Background Note :  The Holford Brinefield

The Keuper Gas Storage Project map on page 13 marks the location of brine cavities on the Holford Brinefield, south east of Lostock Gralam.  The route currently proposed for HS2 enters from the south and then swings north-north east on a route immediately adjacent to the A556 Shurlach Road.  Hs2 will be on the south east side of that road. The locations marked in red depict the site of pumping equipment for each cavity. Those numbered H213, H140, H143A, and H143B are approximately 100 metres from where HS2 track will run

The extent of cavities below ground is not shown anywhere on the maps produced by HS2 Ltd. It is however obvious that the proximity of cavities to HS2 construction works and track will be much closer than the points marked on the Keuper Gas Storage Project map

In a Geological Society article of 2018 “Geology and HS2” Chris Eccles and Simon Ferley state this:  Cavities may be up to 170m across and are as little as 30m (or less!) apart, the shallowest being only 60m below surface (in the north of the brinefield).  Some cavities at Holford are being used to store solvent waste. In a number of locations at Holford there has been break-through between adjacent cavities.  In Cheshire, no solution-mined cavities have collapsed; but near Preesall in Lancashire similar solution mining was carried out in the Northwich Halite to shallower depth, resulting in a series of collapses that created lakes. It is the nature of rock salt to creep over time, and the ground above the Holford Brinefield is slowly settling by three or four millimetres a year.  The settlement bowl extends to a wider area than the actual plan extent of the cavities. The Geological Society (

This is the northerly part of the Keuper Gas Storage Project map of 2014 found at Annex 1 in :   IEL_F_J_0001_KGSP_subsurface_safety_assessment.pdf

This is Hs2’s Land Quality map (with compass point North to the right side). It shows brinefields shaded brown, the HS2 track, and the Shurlach Road in its current position. Construction works will entail moving that road to the western side of the HS2 track



8 – Background Note :  Three Viaducts over River Dane and Trent & Mersey Canal

The maps and images (below) on pages 20 – 22 appear on HS2’s Map References LQ-01-307 & LQ-01-306 and on page 147 of Volume 2 : MA02. They show where Hs2 viaducts will cross the River Dane and Trent and Mersey Canal.

Salt mining/brinefields are marked on pages 20 and 21 with green dots for proposed mining, and with brown dots for active extraction. They illustrate the extent of the underground salt levels.  The ES makes no risk assessment for the driving of piles to support viaducts in these locations. Piles to depths of 100 or 120 metres have been mooted.  This is an area where sunken glacial till overlies salt levels that have collapsed following brine extraction. The subsided landscape is sprinkled with bodies of water known as meres or flashes. Hs2 have produced no assessment of how the driving of such piles will disrupt the migration of water underground, and accelerate salt dissolution by the introduction of unsalinated water to saline saturated cavities. The graphic below is taken from “Geological hazards from salt mining, brine extraction and natural salt dissolution in the UK” by Anthony H Cooper published in 2020 by the Geological Society of London