The construction of a 4.3 km railway tunnel under Long Valley and Kwu Tung helps to eliminate potential environmental impacts to this ecologically sensitive area. This avoided affecting the Long Valley habitat which supports a diverse range of flora and fauna, including a number of globally, regionally and locally threatened species of birds of conservation importance.

The selection of a scheme based on bored tunnels beneath Long Valley removes the major ecological impacts and potential impacts on the hydrology of the area Long Valley which would arise from an above ground option.

(i) Potential hydrological impacts and proposed mitigation measure(s):
The risk of a drop in the groundwater levels during construction has been minimized through the use of an Earth Pressure Balance Tunnel Boring Machine (EPB TBM). This machine constantly balanced the external pressure with an equal pressure in the cutter face to minimize the risk of collapse of the cutting face and exclude ingress of groundwater.

(ii) Potential ecological impacts and proposed mitigation measure(s):
In particular the sensitivity of Long Valley has been considered in the development of the tunnel alignment option. A hydrological impact assessment for the construction and operation of the tunnel below Long Valley has shown minimal impact on the wetland nature of Long Valley, which indicates minimal impact on ecological functions in this area.
More descriptions on the ecological impacts and proposed mitigation measures on Lok Ma Chau area could be found in Project 10 of this website.