Highways Agency

Non-Technical Summary of the Environmental Statement, October 2004

Introduction

The South West Area Multi-Modal Study (SWARMMS), which reported in May 2002, made recommendations for a long-term strategy to address passenger and freight transport on the main road and rail corridors between London and the South West / South Wales.

SWARMMS recommended improvements to the M4 Junction 18 by construction of a climbing lane and extended diverge (slip road). The scheme was entered into the Targeted Programme of Improvements (now known as the Programme of Major Schemes) by the Secretary of State on 10 December 2002, in his response to the SWARMMS recommendations.

The Highways Agency’s proposals take the form of an Environmental Statement. The Environmental Statement has been published in accordance with EC Directives, as applied by Section 105A of the Highways Act, 1980.

This side of the leaflet describes the proposed scheme and summarises the Environmental Statement in nontechnical language. Information on the reverse provides details about the public exhibition and what happens next.

Why the Improvement is Needed

The M4 eastbound approach to Junction 18 is on a steep incline, causing heavy goods vehicles (HGVs) and towing vehicles to slow. The incline passes through Junction 18, resulting in conflicts between fast moving vehicles exiting at the junction, and slower vehicles negotiating the incline.

Congestion and delay on this section of the motorway increases the potential risk for accidents and lowers road safety for all users.

The Proposed Scheme

The proposals are all within land owned by the Highways Agency, to avoid affecting adjacent land, make best use of the Highways Agency’s estate and allow the improvements to be provided soon.

The scheme will include addition of a climbing lane and an extended off-slip lane to the existing motorway. It will improve traffic flows and relieve congestion, thereby leading to improved safety. It will not lead to the generation of any additional traffic.

The climbing lane will be constructed on the line of the existing hard shoulder. It will start at the bottom of the incline, and end just before the second Junction 18 overbridge. The layout of the eastbound exit to Junction 18 will be improved, so that traffic can leave the motorway earlier (extended off-slip lane). This longer length will help reduce the likelihood of last minute manoeuvres.

Motorway drainage will be improved to provide treatment and attenuation. Three new gantries over the motorway will provide direction signs for drivers.

Environmental Effects

Measures to Reduce Environmental Effects

The scheme has been designed to minimise, as far as possible, damage to the environment, whilst still taking account of safety, engineering design, and cost. A number of features of the scheme design are aimed at minimising adverse environmental impacts. These are:

• low noise surfacing on the new climbing lane and new hard shoulder;
• use of grass faced retaining slopes for new embankments to fit in with the existing landscape and minimise land take;
• native tree and shrub planting to help tie the road back into the landscape;

chalk grasslands to be partially reinstated on re-profiled slopes through re-use of salvaged calcareous soils; and installation of pollution control measures and treatment and attenuation ponds for carriageway drainage.

Scheme Context

Landscape Effects

The scheme is located partly within the Cotswolds Area of Outstanding Natural Beauty and lies within the Bristol and Bath Green Belt.

Landscape and visual impacts will be confined locally to the existing route corridor. Three new gantries, required for signing and safety, will be the most noticeable change within the rural landscape. The signs will be lit at night.

Planting of native tree and hedgerow species will add to existing vegetation and compensate for that lost initially to the scheme. Where appropriate, Cotswold stone, or similar, will be used to clad low retaining walls.

Ecology and Nature Conservation

There will be some loss of habitat, including valuable grassland. Slow worms and grass snakes using the grassland will be safely relocated before the works commence.

Water Quality and Drainage

Surface water run-off discharges to the River Boyd. The existing filter drains will be replaced with a solid pipe, road run-off will be treated, and provision made for containing spills. The quality of water discharged from the motorway to the River Boyd will be improved. Two new treatment and attenuation ponds will provide a secondary role as wetland habitats.

Air Quality

The scheme will not cause a deterioration in air quality. Over time, air quality will improve from advances in vehicle emissions.

Traffic Noise and Vibration

Changes in noise levels would be so small, as to not be perceptible to the human ear. Even after allowing for traffic growth not directly related to the scheme 15 years after opening, the increase will be less than three decibels and therefore imperceptible.

Geology and Soils

Excavation of the existing cutting at Junction 18 will take place. Approximately 15,000m³ of excavated material will be recycled, with approximately 14,000m³ being removed from site. It will be necessary to import approximately 18,000m³ of material.

Cultural Heritage

The scheme avoids designated historic and archaeological features. Most of the improvements will take place on land already disturbed when the motorway was originally built. A programme of archaeological mitigation, including possible evaluation, will be implemented where appropriate.

Vehicle Travellers

Benefits will be gained through reduced driver stress. This will be achieved by:

• a new climbing lane and extended off slip lane; and
• new signage, including new gantries, providing improved directional information.

Construction Effects

Construction is expected to take approximately seven months. A Construction Environmental Management Plan will be implemented to minimise environmental effects, including noise, vibration, dust and water pollution, and to protect wildlife habitats.

Disruption to road users will be minimised through the introduction of a Traffic Management System. There will be a need for contra-flow and reduced speed limits during the works, but three lanes will be generally maintained in each direction of the motorway.

Policies and Plans

The scheme would have no significant effect on National, Regional or Local Plans or Policies, and would not compromise the integrity of planning policy relating to the Cotswolds AONB or the Bristol and Bath Green Belt.

Alternatives Considered

A number of options have been considered during the development of the scheme, including narrow lanes, use of the central reserve and reducing the highway verge. The proposed solution takes account of safety, environment and economic impacts of all the alternatives considered.