Surface Water The term 'surface water' generally relates to rivers, ditches, lakes and ponds. The main surface water feature is the River Tyne, which flows from west to east across the site of the proposed immersed tube tunnel. The lower reaches of the River Don in Jarrow are tidal, and its water level is influenced mainly by water levels in the Tyne into which it flows. During unusually severe flood conditions, the Don could affect the A19 in Jarrow, but the Environment Agency has advised that this is not a major concern because it would be such a rare event (1 in 200 years). The scheme would not increase the risk of flooding in Jarrow. During construction, there would be a risk of pollution arising from the erosion of materials from exposed excavations, stockpiles and silt-laden groundwater entering the Don or the Tyne. There are also potential pollution risks associated with accidental spillages of fuel and chemicals during construction. Proven control measures are available and would be implemented during construction to mitigate these risks. The construction of new roads, junctions, toll areas and other similar areas would permanently increase the area of paved surfaces in both North Tyneside and South Tyneside. In North Tyneside, rainwater draining from the new paved areas and road surfaces would be directed to the existing local highway drainage system. There is sufficient capacity in the system to accommodate the additional flows. In South Tyneside, rainwater would be directed from the new highway surfaces to the River Don, and subsequently into the River Tyne. There would be a negligible effect on the flow of the River Don. Rainwater discharges can pick up pollutants such as oil and sediments from the surface of a road. Pollution control devices such as petrol interceptors would therefore be installed and regularly maintained to protect the River Don from highway pollutants.
Groundwater The term 'groundwater' refers to naturally occurring water found below the surface. The Environment Agency has advised that the New Tyne Crossing would not affect any environmentally important groundwater resources. Construction of the new tunnel could influence, in the short-term, the behaviour of groundwater underlying the site to the north and south of the Tyne. During construction, cut and cover excavations could require groundwater control systems to be installed. These may include a pumping system to remove any groundwater that flows into the trenches. Pumping water out of the trenches could lower groundwater levels in the vicinity. This could cause, in the absence of control measures, minor structural stresses at properties within approximately 200 metres of the excavation. There are preventative measures available to reduce such risks and these would be implemented, where appropriate. Groundwater pumped from the excavations would need to be disposed of carefully as it may be contaminated. Monitoring of water quality would therefore be required to confirm the suitability of a particular disposal route. Disposal options include discharge directly to the River Tyne (with on-site treatment to remove contaminants, if necessary), discharge to existing sewers and drains, or tankering off-site by road, if volumes are sufficiently small. The preferred discharge option would be agreed in advance with the Environment Agency, and any necessary licences or consents would be obtained. During operation of the new tunnel, the likelihood of the tunnel interfering with groundwater flows is considered to be low. |
