To ask Her Majesty's Government whether the Environment Agency has given full approval for the construction works of the HS2 Chiltern Tunnel and, if so, when; what risk assessments have been made in connection with this approval in respect of the Chiltern Aquifer regarding, (1) the risk of pollution to the water supply for (a) local residents, and (b) residents of London, and (2) the loss or diversion of the River Misbourne; and whether they will place copies of any such assessments in the Library of the House.

Approval for the construction of the Chilterns Tunnel has not yet been granted, pending the finalisation of the necessary risk assessments and monitoring plans, which are in an advance stage of production and review.

The following assessments have been produced in respect of tunnelling through the Chalk aquifer:

- Groundwater Assessment for Construction Tasks: Tunnel and Cross Passages

- Chiltern Tunnel Construction Water Environment Assessment (currently in draft)

- Construction of Chiltern Tunnel Site Specific Groundwater Monitoring (currently in draft)

This work provides a full assessment of the risks to groundwater quality, groundwater flow, public water supplies and the River Misbourne. Such assessments are not routinely placed in the House Library as the work is ongoing, and they are updated as and when necessary. Individual assessments may be released upon request, subject to any required redactions.

HS2 Ltd manages all risks associated with the delivery of the railway through their Corporate Risk registers. As we [the Govt.] has made clear, they must demonstrate compliance with the requisite technical, safety and environmental standards at all times.