Introduction

In the context of the HS2 programme, activities that may impact surface water or groundwater are subject to approval under Part 5 of Schedule 33 (Sch33.5) of the HS2 Phase One Act ^[1]. This includes works related to drainage, flood storage, and the conservation of water resources. Approval from the Environment Agency or the Lead Local Flood Authority is required before commencing any specified works, unless an exemption applies.

Any potential impacts on inland waterways are addressed in Part 4 of Schedule 33 which gives the Canal and River Trust the power to approve plans and specifications for works affecting waterways for which it is responsible. However, this is not included in the scope of this paper.

While this paper utilises the HS2 Phase One Act as a case study, it is essential to recognise that the regulatory consenting regime in the UK encompasses various pieces of legislation, relevant to construction projects beyond HS2. This is why it is important to have a broad understanding of consent applications and compliance verification. This document explains these requirements and covers best practice from HS2, for the benefit of the wider the industry.

Consent application and compliance process

Overview

Ensuring compliance with a consent requires a series of interrelated steps or activities as shown in Figure 1 below. This ensures a systematic approach to identifying potential environmental impacts and subsequent actions to either mitigate or better characterise a risk. Each step shown below is a vital element in the compliance process, with any issues (misunderstandings, delays, incompleteness) having a knock-on effect along the chain.

Consent application

Consent applications for temporary and permanent works requires ‘joined up’ thinking at an early collaboration stage to ensure a comprehensive approach which accounts for all stages of construction, to reduce the likelihood of design clashes and construction delays. Regular, clear communication between the contractor and regulator at every stage of the consent application process is crucial to facilitate decision making and encourage problem solving to eliminate misunderstandings and misinterpretations.

A comprehensive overview of the consenting process falls outside the scope of this paper. However, a general overview of the consent application is important as consents form the basis for compliance. In essence, as outlined in the HS2 Technical Standard ^[2], contractors are responsible for obtaining all consents, approvals, variations, and revocations from the relevant consent granting bodies (CGBs).

Key considerations at this initial stage are as follows:

Addressing all applicable legislation – ensuring construction activities are conducted in an environmentally responsible and sustainable manner.

For activities considered as part of the consent application, awareness and thorough understanding of the current legislation is required. To allow for this, important legislation to be accounted for includes (but is not limited to):

• Water Framework Directive (WFD; 2000/6/EC) ^[3]

• Groundwater (Daughter) Directive (2006/118/EC) ^[4]

• Environmental Permitting (England and Wales) ^[5]

• Regulations 2010; Environment Act 1995 ^[6]

• Water Resources Act 1991 (WRA) as amended by the Water Act 2003 ^[7]

• The Conservation of Habitats and Species Regulations 2010 ^[8]

Assessment of environmental risks – assessing construction activities which have the potential to impact the water environment.

To enable a complete assessment, associated documents for the consent application pack should include (but are not limited to):

• Groundwater risk assessment (GWRA) and water monitoring plan.

• WFD compliance documentation.

• If applicable:

• Flood Risk Assessment (FRA)

• H1 Risk Assessment (H1RA) – where a discharge to surface watercourse is required

• Land Quality Assessment (LQA) – where a historic land use or contaminant source is identified

• Remediation Strategy (RS) – as required by the above

• Remediation Implementation Plan (RIP) – as above

Environmental risks associated with construction activities/materials are given with further detail later in paper.

Further information of environmental risks associated with construction activities may be found in Appendix 1.

To fulfil the requirements of the CGB’s Sch33.5 ^[1]consents, assessments are undertaken to provide all necessary information relating to the proposed construction activities and future operations. They are needed to evaluate any potential impacts relating to groundwater, surface water and/or flooding. In addition, environmental risks are determined from a detailed understanding of contaminants of concern (e.g. concrete, bentonite etc.) and how construction activity affects source-pathway-receptor linkages at an asset.

Establishing a monitoring plan – summarising a monitoring network, parameters to collect and frequency of monitoring.

From a review of environmental risks, the need for monitoring associated with the construction activity is assessed. These monitoring requirements should be clearly outlined as part of the Sch33.5 consent and associated documents. For simplicity, typical monitoring relating to WFD objectives (ecological status), remediation-related objectives (soil and gas) and parameters other than water monitoring are not considered as part of the scope of this paper – only groundwater and affected surface watercourses are considered.

Monitoring relating to the water environment includes water quality, water levels and water volumes (relating to abstraction and discharges). For an effective water monitoring plan, the monitoring network, frequency, and parameters should  all  be determined proportional to the risk identified during the risk assessment(s). All monitoring as part of the various Sch33.5 consent risk assessments should be collated to ensure a monitoring network fit for multiple purposes (including geotechnical, environmental compliance, remediation) to ensure efficient use of resources.

The monitoring section later in the paper provides further details of best practice relating to determining an effective water monitoring plan.

Data collection

Once the Sch33.5 consent has been granted and the works have started, the contractor is responsible for demonstrating compliance with the consent conditions by following the monitoring plan. The steps required for monitoring are detailed below:

Completing monitoring – adhering to a robust monitoring process for the collection of water data. For water monitoring, this can be subdivided into monitoring for water levels, water flow and water sampling.

Water levels – measurement of the height of a water level top surface.

Surface water levels are measured with a stilling well which is used to dampen waves or surges while permitting the water level in the well to rise and fall with the major fluctuations of the main body of water (Figure 2a). Continuous measurements of water level are achieved by installing a data logger.

Groundwater levels are measured at monitoring wells (Figure 2b) using dip meters for spot readings and/or data loggers for continuous reading. A thorough analysis of the hydrogeological setting is required to determine whether the groundwater conditions are perched, unconfined and confined.

Water flow – collection of abstraction and discharge flow rates.

Abstraction and discharge flow monitoring involves using flow meters with correct accreditation and calibration to ensure sufficiently accurate and precise recordings (Figure 2c). In the absence of flow monitoring equipment, to ensure no exceedance of limits within the consents, the maximum flow may be determined based on limits imposed by maximum pumping levels or by a maximum discharge levels pipe.

Watercourse (i.e. river) flow monitoring consists of measurements of river flow discharge, with the objective to demonstrate no deterioration of WFD status. Flow measurements comprise of flow impellor measurements at set increments across a watercourse (Figure 2d). Depending on the size and sensitivity of the watercourse, different flow measuring methods can be applied.

Water samples – collecting samples that are representative of the targeted feature (e.g. groundwater of a specific strata or discharge point of a pond)

Surface water sampling of rivers, streams, ponds and lakes (Figure 2e) may require considerable planning to ensure adherence to international standard BS EN ISO 5667-6:2016 on the design of sampling programmes from rivers and streams. The method of sampling water from watercourses depends on many factors including the nature of the water body to be sampled, ground conditions, what the water is to be analysed for, the decontamination method chosen and the technical objectives of the investigation.

Appropriate instruments are used to sample groundwater quality of either abstraction points or monitoring wells (Figure 2f) and requires best practice sampling techniques based on guidance on BS EN ISO 22475-1 ^[8] or BS ISO 5667-11 ^[9]. Care needs to be taken not to change the chemistry of the sample to ensure that the sample is representative of the groundwater conditions of the targeted strata. Similar to surface water sampling, industry standard equipment with appropriate calibration is to be used with detailed records kept of sampling location, water conditions (water depth, physical appearance), time sampled, sampling method used and any settlement or filtration.

Ensuring sample packing transport and lab analysis (if applicable) – for surface water and groundwater samples, sample handling and transport protocols are to be adhered to.

If sampling was incorrectly carried out or not possible to be completed, water quality will not be able to be analysed to determine compliance. Although this may not be a significant issue in the short-term, if this continues for a prolonged period, then this lack of monitoring data poses a greater environmental risk as water environment conditions are unable to be determined.

As part of the sampling stage, there is a requirement for necessary checks, including completed Chain of Custody forms, properly packing samples, maintaining cool storage conditions during transport and ensuring acceptable holding time between sample collection and laboratory analysis (which varies significantly between different analyses).

Management of data – to allow for efficient data storage and processing

All data is to be kept in a centralised and secure database management system. Data underpins any assessment and therefore requires high levels of accuracy and reliability. A database management system can ensure data consistency through standardised formats, data validation, and error-checking routines. An example of a database management system includes MonitorPro5 by EHS Data which manages all environmental and compliance data in one centralised platform.

Compliance assessment

All sampling requirements from supporting documents should be considered and ‘tied-in’ to demonstrate whether or not there is overall environmental compliance at a given asset. The steps are as follows:

Assessing Compliance – results relating to the Sch33.5 consent (including water levels, flows and quality) are compiled, assessed by the contractor, compared against critical levels, and reported to the regulator at an agreed frequency. A summary of all construction activity should be included to ensure that monitoring relevant to the works is completed. Monitoring parameters are compared against baseline conditions to determine whether there is any impact to the environment:

Assessed as compliant – water quality measurements are comparable or indicate an improvement (particularly for contaminated sites requiring remedial works) to baseline conditions. Any limits within the consent relating to water level and/or flow are adhered to. This ensures safeguarding of the environment, and the compliance assessment process continues (until approval is granted by the regulator to conclude post-construction monitoring).

Assessed as non-compliant – water quality measurements indicate a worsened level relative to baseline conditions. Limits within the consent relating to water level and/or flow are breached. Appropriate mitigation management measures are to be implemented.

The Strategy for Compliance Limits Breaches section provides an overview of the steps required for determining compliance and subsequent actions in the event of non-compliance.

Monitoring

Justification

Monitoring is essential to demonstrate whether there is any impact to the surrounding water environment. Monitoring the water environment for levels, flows and quality enables the compliance targets to be met and ensures water resources are managed effectively.

For water level and flow monitoring, this includes providing data to confirm compliance with permitted abstraction volumes and rates from aquifers and watercourses and provides evidence that exceedances of discharge limits are not breached. In addition, potential impacts on river morphology can be assessed and assurance of downstream river flows for ecology maintenance provided. Monitoring of the water quality can also be used to assess remedial efforts by tracking improvement or deterioration from baseline conditions.

Visual inspections should also not be underestimated. These inspections are straightforward checks which give real time assessment of site conditions. Visual inspections will not ensure compliance with discharge or abstraction permits; however, they can enable a rapid response to unexpected changes or potential pollution events to complement routine sample analysis procedures.

The monitoring plan is designed to be proportionate to the risk identified during the risk assessment(s). Once the risks are identified the monitoring network, monitoring frequency and sampling parameters are adjusted accordingly. It should be refined to guarantee that both the baseline conditions and any potential impacts resulting from construction activities are effectively captured.

Endeavours should be made to balance the necessity for adequate monitoring with the costs involved. This requires regular reviews of the monitoring programme and agreement with the regulator to reduce superfluous monitoring where no environmental impacts can be demonstrated – as indicated by water conditions consistently being at or below baseline conditions.

Monitoring network

The monitoring network comprises locations positioned for the collection of water data at and surrounding construction works. The network integrates surface water and groundwater monitoring points from which water quality, water level and flow data can be measured. A conceptual understanding of the linkages (as described in Appendix 1) is key to determine the most appropriate locations. Monitoring should be carried out systematically and requires representative data of the targeted waterbody.

Re-occurring surface water monitoring is typically carried out at rivers and streams which should ideally include, as a minimum, an upstream and downstream sampling point to capture any potential impact. Any discharge points from attenuation / balancing ponds and water treatment plants should also be included in the network. Ideally, all sampling points should be made accessible long-term throughout works with a thorough assessment of the surroundings to understand whether any activity could cause change to sampling results. In addition to ongoing sampling, ad-hoc sampling points may be required for other purposes separate to the Sch33.5 (discharge to sewer network, water tankering offsite, canal monitoring etc.).

Groundwater monitoring (level, flow, and quality) is typically from boreholes and abstraction points from dewatering activities. Attention should be given to ensure that the full extent of the construction works is captured which includes targeting the appropriate strata and engineering depth where any potential contamination may flow through towards a receptor. To ensure adequate coverage, perimeter wells should also be selected with a minimum of one upgradient well and two downgradient wells to evaluate any changes caused by construction activity. If dewatering activity is present, it is best practice to also sample abstracted groundwater – a sample representative of surrounding drawn down groundwater within radius of influence.

Practical considerations should always be applied for the construction of both stilling wells and groundwater monitoring wells to ensure placement away from activity to maximise survivability for at least two years’ post-construction. As a priority, effective communication is required for anyone involved with nearby site work to ensure that the presence of wells is known and to encourage awareness for the protection of wells. A list is provided below as guidelines for both wells.

Stilling wells 

1. To maintain the well in good condition, ensure it is firmly positioned and fixed in the riverbed, vertical and upright, and clear of surrounding vegetation.           
2. Monitoring wells should be positioned away from mobile plants and construction activity.
3. Ideally, the well is to be marked up with signage to make it more clear from afar.

Groundwater monitoring wells (example shown in Figure 3) 

1. To ensure the well is in good condition, make sure the headworks cap is sealed tightly to prevent any silt or surface water from entering. If the area is prone to flooding, the cap should extend above ground level to provide adequate protection.
2. Monitoring wells should have a border and a cordoned-off perimeter to demonstrate that that area is to be protected from mobile plant and construction activity: Ideally, this should be a concrete ring if the well is used for particularly high-risk areas (due to high traffic or construction activity); Alternatively, three attachable fences should be used.
3. The well should be marked with a post and / or flag to make it more clear from afar and in uneven terrain. This reduces the risk of an incorrect borehole being monitored.

In cases where monitoring must be discontinued at a particular site (due to inaccessibility or damage to the borehole / stilling well), it is vital to promptly locate a nearby alternative point with a similar waterbody target. This enables a comparison of monitoring data and ensures that the replacement point accurately mirrors the conditions of the original site, serving as a suitable substitute.

Duration and frequency of monitoring activities

The monitoring of the water environment is a crucial process that spans pre-construction, during construction, and post-construction phases. Before any construction begins, pre-construction monitoring is essential to establish a baseline of the water environment. This phase typically involves collecting data for a minimum of 12 months to capture seasonal variations and reflect the conditions immediately before any construction activities that could pose environmental risks. These then serve as a reference point for future comparisons both during and after construction.

Monitoring should persist until construction is completed and until comparable or improved conditions relative to the baseline are achieved. The frequency and duration of monitoring is decided upon by assessing risks – more sensitive waterbodies and environmentally impactful construction activities require more frequent monitoring over an extended period, further beyond construction completion. In addition, it is advised that the construction works process is understood which will allow monitoring to be carried out in a phased manner as construction advances.

Sampling parameters

The most prevalent contaminants of concern need to be understood. A comprehensive review of risks should be outlined in the Sch33.5 consent application (as detailed in Section 3) and should include the scope of works and interactions between works and contaminants of concern. For assets with an elevated risk of contamination (i.e. contaminated brownfield sites), a more comprehensive suite of analysis will be required. Indicators are required to identify what substance or construction activity is causing a change to the surrounding surface or subsurface water environment. A breakdown of contaminants of concern is presented in Table 1.

Other contaminants of concern include organics (e.g. sewage), galvanised metals, and industrial waste. Further details of the contaminants of concern and key indictors may be found in CIRIA guidance papers ^[10][11].

Key performance indicators (KPIs)

Based on the main contaminants of concern, KPIs are strongly recommended. To ensure that the task of reviewing and reporting data remains efficient and manageable, the list of KPIs should remain short (less than ten determinants).

For example, an asset could be an embankment which has liming activity and deposition of material which has the potential to leach copper and zinc. As a minimum, to determine any deterioration of water quality, it would be prudent to include pH, alkalinity, copper, and zinc testing. Additional KPIs may be used to check for calcium, magnesium, and sodium to determine general water quality. If KPIs signal any significant exceedances from baseline conditions, then this should trigger a review with a greater range of measured determinants.

In addition to KPIs, for remedial works with elevated levels of pre-construction contamination, there may be site-specific assessment criterions (e.g. as part of a remediation strategy) which are required to demonstrate suitability for use in accordance with the authoritative CL:AIRE Definition of Waste Development Industry Code of Practice ^[12]. Various assessments should be ‘tied-in’ together to ensure a holistic approach and consideration of all risks together.

Non-compliance

A thorough understanding of all monitoring and assessment criteria is needed, as outlined in the issued consent and relevant supporting documents. This is the foundation for any review and provides a measure for whether there is any impact to the environment. Any deviations from Sch33.5 consent (e.g. missed samples, destroyed borehole, sampling suite error etc.) are to be reported, with the appropriate resolution measures implemented.

The review of the monitoring data, which should be carried out as soon as practically possible, should confirm whether the construction activities are compliant or non-compliant. Examples of breaches include sustained elevated levels of the KPIs; over-abstraction with flow rates exceeding specified limits; and site-specific assessment criterions not been maintained or reached.

In the event of a non-compliant monitoring parameter, all relevant contractors, HS2 and regulatory parties are to be informed and immediate actions are taken for the protection of the environment. This includes determining root cause(s) of the contaminant source(s) and coordinating risk-appropriate contingency measures and development of an effective environmental management strategy agreed with the regulator.

Risk mitigation

Following on from determining a non-compliance, as shown in Figure 1, any identified risks during the assessment phase are to be mitigated as far as practicably possible. Best management practices should be implemented, including silt management, flood management and spill prevention. A monitoring programme is to be designed and agreed upon with the regulators to track the effectiveness of these risk management measures, ensuring compliance through regular reporting of the findings to the relevant regulatory authorities.

The Washwood Heath site (Appendix 2) exemplifies the implementation of a comprehensive monitoring network, including groundwater and surface water sampling points, to assess and manage contamination risks in a complex industrial site undergoing significant construction activities. This case study demonstrates the importance of tailored monitoring strategies for specific site conditions, particularly in areas with historical industrial use and potential contamination issues.

Adaptive management is essential to allow for continuous improvement of the compliance assessment plan based on monitoring results and changes to design. Following this type of comprehensive water compliance assessment process, any environmental impacts are identified and minimised or eliminated.

Re-evaluation of monitoring network and collection

In the event of a non-compliance, there is to be a re-evaluation of the various components of the compliance assurance process. For the monitoring programme, this may include altering the monitoring network, frequency and sampling suite to ensure that it is sufficient for the consented activity and / or risk mitigation measures. Additional short-term monitoring may be required to enable design of mitigation measures and the assessment of the efficacy of the same (see Appendix 2). Investigations may also be required if a source of contamination is not known, or the extent of the contamination is to be determined (see Appendix 2).

In addition, quality control and quality assurance measures may need to be revisited for the various processes of each step of the process. Checks are carried out for the sampling undertaken to ensure no errors have occurred (e.g. the incorrect borehole being sampled, mixed-up sampling IDs of boreholes and / or samples, breakages of samples via transit, labs mistaking samples etc.). Any errors with data or process of data entry and use are to be corrected if identified.

Outcomes and Learning

• A systematic approach is critical for identifying potential environmental impacts and actions to mitigate or better characterise risks.
• Environmental risks associated with construction activities impacting the water environment must be thoroughly assessed for Sch33.5 Consent.
• Clear and regular communication between contractors and regulators is essential throughout the consent application process.
• Compliance involves compiling and assessing all results related to the Sch33.5 consent, comparing them against critical levels, and reporting to regulators at an agreed frequency.
• These recommendations are intended to guide practitioners in the field of construction management and environmental compliance. By implementing these best practices, we can promote risk mitigation and responsible environmental stewardship, ensuring the protection of the water environment during and after major construction projects.
• Overall, there has been successful adherence to a robust monitoring process for water data collection, – demonstrating compliance with consent conditions. Any potential consent breaches have immediate actions for water protection, including determining root causes, and coordinating risk-appropriate contingency measures.

Conclusion

Successful delivery on any project, including HS2, hinges on a proactive approach to environmental management, rigorous monitoring, and effective remediation strategies. This includes ensuring that construction activities do not adversely impact surrounding ecosystems or water environment. Key indicators of successful delivery encompass the timely identification and resolution of contamination incidents, as seen in the HS2 WOC and BTIS case studies, where immediate actions were taken to mitigate risks and prevent further environmental degradation. Moreover, successful delivery is characterised by the implementation of robust monitoring systems that provide real-time data on surface water and groundwater conditions, enabling informed decision-making throughout the project lifecycle. The consistent maintenance of water quality below intervention thresholds, as demonstrated at the WWH site, reflects a commitment to sustainable practices and compliance with regulatory standards. Successful delivery entails achieving project objectives while safeguarding the environment, ultimately contributing to the long-term viability of the HS2 initiative. This approach not only ensures the project’s sustainability but also sets a benchmark for future infrastructure endeavours

Acknowledgements

The authors gratefully acknowledge the contributions of the following members of Aecom, Enitial and Balfour Beatty Vinci for providing advice, photographs and recommendations:

Aecom: Leanne Cooney, Oli Dodds, Claire Griffiths, Lewis Jones, Simon Shepherd

Enitial: Chris Glover, Alice Stevens

BBV: Gregory Ashrat, Sima Baqa, Papa-Samba Drame, Paul Sandall, Seb Wagner

References

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2. High Speed Two (HS2) Limited, 2017. Technical Standard – Water resources and flood risk consents and approvals. Document no.: HS2-HS2-EV-STD-000-000015. 2017.

3. Water Framework Directive (WFD), Directive 2000/60/EC (Dec 2020) Available at: Directive 2000/60/EC of the European Parliament and of the Council of 23 October 2000 establishing a framework for Community action in the field of water policy. Accessed 10 December 2024.

4. Groundwater Daughter Directive, Directive 2006/118/EC. 2006 Dec 12.

5. Environmental Permitting Regulations 2010, SI 2010/675 (UK).

6. Environment Act 1995, Environmental Permitting Regulations 2010, SI 2010/675.

7. Water Resources Act 1991, as amended by the Water Act 2003.

8. The Conservation of Habitats and Species Regulations 2010, SI 2010/490 (UK).

9. International Organization for Standardization. ISO 22475-1:2021 Geotechnical investigation and testing – Sampling methods and groundwater measurements – Part 1: Technical principles for the sampling of soil, rock, and groundwater. 2021.

10. Ciria, 2001. Control of water pollution from construction sites. Guidance for consultants and contractors. Construction Industry Research and Information Association.  London: CIRIA; 2001.

11. Ciria, 2006. Control of water pollution from linear construction projects. Site guide. London: CIRIA; 2006.

12. CL:AIRE, 2011. The Definition of Waste: Development Industry Code of Practice. London: Contaminated Land: Applications in Real Environments (CL:AIRE). Version 2. London: 2011.