Question to the Department for Transport:

To ask the Secretary of State for Transport, what quantity of water will be required for the Phase 1 High Speed Two tunnelling in Buckinghamshire; from what location that water will come; how that water will be (i) used, (ii) processed and (iii) disposed of; what assessment he has made of the (A) level and (B) type of contaminants in that water after use; what processes will be used to remove those contaminants; and what steps he is taking to prevent the contamination of local aquifers in that area.

The quantity of water required to operate the two Tunnel Boring Machines (TBMs) for the Chilterns Tunnels is currently calculated to be 6.5 mega-litres per day on average over a 36 month period. It is intended that the water will be supplied from Affinity Water and Thames Water sources. The water will be used to convert the chalk material to a slurry, for flushing and cooling of slurry pumps and for TBM cleaning operations. The slurry will be treated in an on-site slurry treatment plant that will recover and reuse water to reduce the demand for fresh water. There will be instances where water reuse will not be possible and, after on-site treatment, this water will be discharged. The design of the water treatment plant and attenuation ponds has taken the likely water quality into account. Any discharge will be managed and regulated under the terms of a consent from the Environment Agency, which will take into account the quality of the water being discharged. HS2 Ltd has been working closely with experts from the Environment Agency and the relevant water companies for a number of years to prevent construction work from causing contamination of the chalk aquifer and to safeguard the provision of public water supplies.