Potential Mitigation Measures for Environmental Issues on Infrastructure Development Projects

There are a number of potential environmental issues impacting the infrastructure development projects. The environment teams should undertake desk studies and field surveys in order to collect all relevant information.

The infrastructure designers need to incorporate the necessary measures in their design in the light of information they receive from environment specialists. The consideration of measures to eliminate or reduce the major environmental impacts should be commenced even at the conceptual design stage.

A few potential measures designers should consider are as follows:

• To reduce the impact on air quality of the area and particularly for the communities living in the vicinity of projects, road alignment should be adjusted. Reduction in the speed limits is an important potential mitigation measure in this case
• To protect the adjoining residential areas from noise, provision of noise barriers, mounding, roads in cutting and low noise surfacing should be taken into account
• To reduce the impact on existing landscaping and plantation, new planting should be included in the design
• For minimising the impacts on ecology and protected species existing in the area, refuges/safe havens for species and fencing should be proposed as a part of design
• For the protection of cultural heritage of the area, road alignment could be modified. Alternatively, all possible protection measures should be envisaged in the design stage
• In order to reduce the impact on materials and for ensuring sustainable development, the design should be based on reuse and recycling of site won materials
• For avoiding flooding and impacts on drainage system, Sustainable Drainage System (SuDS) e.g. retention ponds/delaying tanks should be proposed. Flood risk assessments should be carried out by taking global warming/climate change into account. The oil interceptors should be proposed in the design, which will protect the sub soil water from contamination due to oil spillage from the vehicles.

There is a huge responsibility on the shoulders of construction teams to eliminate or minimise the environmental impacts during the construction phase. They should undertake all measures proposed in the design documents including but not limited to design drawings, environment management plans, risk registers etc. In the following, I have tried to list out possible mitigation measures to the major environmental issues during construction phases of infrastructure development projects. ?

Noise and Vibration

Noise and vibration could be a major problem during construction of the project. It?becomes a critical issue, if the project is located or passing through?a built-up area.

Following steps could be taken to minimise the impacts of noise and vibration during construction phase:

• Undertake engagement with the local community.
• Notify owners of any properties within 50m of the construction areas prior to the commencement of construction and convey information about the length of time construction will continue.
• Provide contact details for Public Liaison Manager.
• Personnel should be instructed on best practicable means to reduce noise and vibration as part of their site induction training and in the form of toolbox talks to site staff.
• Agree any required extension of working hours with Local Authority prior to commencement of work
• Haulage routes and programming for the transportation of construction materials, equipment, fill, personnel etc. needs to be carefully considered in order to minimise the overall impact generated by these movements.
• Modern, well-maintained plant, including any which may be on hire, should be used in accordance with manufacturer’s instructions at all times. Where possible, items of plant and equipment with lower noise emissions will be used.
• Shut down vehicles and plant when not in use.
• Keep drop heights from vehicles to a minimum practicable.
• Close engine compartments when equipment is not in use and the resonance of body panels and cover plates should be reduced by the addition of suitable dampening materials. Any rattling noise should be addressed immediately by the tightening of loose parts or the addition of resilient materials.
• Semi-static equipment should be sited and orientated as far as is reasonably practicable away from noise relevant sensitive receptor.
• Machinery should be adequately lubricated in order to prevent undue screeching and squealing from moving parts.

Air Quality

Concentrations of pollutants and their associated health impacts are dependent on traffic composition and density, climatic conditions, vehicle travelling speeds and road layout.

The government need to adopt long term policies and measures to encourage use of hybrid cars and discourage pollution creating vehicles.

Appropriate dust control measures suitable for inclusion in a Construction Environment Management Plan (CEMP) may include:

• Sheeting of vehicles transporting earthworks materials to or from site.
• Wheel washing of site vehicles.
• Locating haul routes away from off-site sensitive properties, with regular watering, particularly during dry conditions (wet suppression of dust).
• Limiting site vehicle speeds on unpaved surfaces.
• Locating aggregate stocking areas away from sensitive properties.
• Minimising drop heights of material.
• Bulking of wastes to minimise transportation and handling requirements.

Measures to minimise plant exhaust emissions should also be employed during the construction phase and included in the CEMP, such as:

• Ensuring, where possible, all Non-Road Mobile Machinery (NRMM) use ultra-low sulphur diesel.
• Placing onsite operating plant far from sensitive properties as practicable.
• Ensuring vehicles and operating plant engines are note idling unnecessarily.
• Maintaining all vehicles and plant and regularly servicing according to manufacturers’ recommendations.

Landscape Impacts

Following measures should be implemented to avoid or reduce landscape impacts:

• Minimise works area to retain existing roadside vegetation that currently provides screening
• Reinstate roadside vegetation where possible using appropriate native species
• Targeted screen planting where appropriate to mitigate potentially significant effects
• Use of appropriate surfaces and finishes to structures
• Tie into existing vegetation to provide local connectivity

Ecology and Biodiversity

Generic measures that will be adopted as best practice to avoid predicted adverse impacts of degradation of terrestrial habitats, watercourses and species adjacent to work sites would include the following:

• All site works should be carried out in accordance with best environmental working practices e.g., CIRIA, UK publications.
• Necessary surveys should be carried out and appropriate mitigating measures should be planned.
• Site clearance should be avoided during nesting season.
• Alternate refuges should be provided for protected species
• Polluting materials should not be stored in works areas located within areas of significant biodiversity value, particularly within 50m of watercourses.
• Methods to minimise/prevent contamination of the watercourses during the construction works should be implemented. The EA’s Pollution Prevention Guidance (PPG) 5 should be adhered to in order to prevent damage and/or pollution to aquatic habitats.
• Retention of as many trees as possible with reference to the undertaking of any essential tree surgery to the crown or roots in accordance with British Standard (BS) 3998:2010 Tree Work Recommendations and appropriate Arboriculture Association advice notes Protection of trees.
• Any works to drainage features must include necessary mitigation to ensure the features retain their correct working function.
• The presence of significant ecological receptors would also have implications for the timing of the development work. The avoidance of periods of particular sensitivity is considered best practice for protected species such as nesting bats, birds, water voles and amphibians.
• All trenches and work excavations should be covered overnight or fenced off to prevent animals falling in, or trenches should include an earth ramp to allow animals to climb out.
• An ecological toolbox talk should be given to contractors and site staff prior to construction commencing to highlight any potential ecological issues on site. This will ensure that all personnel undertaking works on the site have been provided with a level of understanding sufficient to ensure protection of sensitive ecological features during the construction process.
• If any protected species are found during the works, work should cease until the clerk of works or ecologist has been contacted to advice on how to proceed.
• Areas of verge temporarily disturbed should be re-instated once works are completed, with a low maintenance grass seed mix for verge areas and a species diverse mix for all other areas to encourage habitats to regenerate naturally.
• Mammal crossing points, appropriate fencing and roadside signage should be incorporated into the design to mitigate for severance of habitat associated with new roads.
• The generic mitigation measures identified above should be strictly adhered to during works within or immediately adjacent to any designated sites or water courses to ensure that the integrity of ecological receptors are maintained during and after works.
• Post construction, planting should aim to restore the ecological value where affected. This could include re-instating and re-linking severed linear wildlife corridors with new planting. Consideration should be given to the inclusion of locally sourced native plant species within planting proposals and the application of sensitive management and monitoring regimes.
• A landscape planting strategy of onsite habitats will serve to ensure that the overall biodiversity value of affected habitats is regained.
• Grassland, scrub and woodland should be replaced to create a linked matrix of new habitat with increased species diversity and structure.?

Geology and Soil

• Working areas and access routes should be clearly defined
• Plans should be prepared to carefully strip, handle and separately store soils prior to construction
• All oil, chemical and hydrocarbon sources should be stored in accordance with legal requirements and best practice.
• The volume of soil disturbance should be kept to the minimum required for the construction of the proposed options.

Materials

• A Materials and Waste Management Strategy (M&WMS) should be developed for both material procurement and waste management
• As part of the M&WMS a Resource Management Plan (RMP) and Site Waste Management Plan should be produced and adhered to
• Any existing road pavement should be recycled for use
• Geotechnically and chemically suitable material from the excavations should be reused on site.
• Minimising the total material demand of the design by ensuring that material inputs match demand as closely as possible
• Minimise waste by matching material demand with material supply.?Material supply can be met from the following prioritised sources
• On site reuse / recycling of excavated materials
• Off-site reuse / recycled of excavated materials.

People and Communities

• identification of community, agricultural and commercial holdings based on landholding information
• an initial screening exercise to identify the likely level of impact on the agricultural and commercial businesses to recognise any requirements for additional information or site visits
• consultation with landowners / tenants or / and land agents who were identified as likely to be moderately or substantially affected by the proposed options or for whom there was insufficient information to complete the assessment
• evaluation of a preferred option to establish the potential impact on landowners' agricultural businesses and identify appropriate design and mitigation measures
• assessment of the significance of residual impacts on landowners' / tenants agricultural and commercial businesses and
• assessment of the significance of residual impacts on community land and facilities.

Drainage and Water Environments

• Use of Sustainable Drainage System (SuDS) features such as attenuation ponds to remove hydrocarbons, soluble metals, sediment and sediment bound pollutants from road drainage discharges where the Highways Agency Water Risk Assessment Tool (HAWRAT) and Environmental Quality Standards (EQS) assessments have identified a need for treatment. Further details on the specific routine runoff mitigation proposed will be outlined in the detailed design.
• Any SuDS features included on the networks for treatment of routine runoff will also contribute to the control of pollution from accidental spillage.
• All road drainage discharges need to be attenuated to agreed runoff rates required by the Environmental Agency (EA)
• Road drainage outfall structures should be designed flush with the watercourse bank and will discharge in the direction of flow. The structure headwalls, wing walls and erosion protection aprons should be designed to prevent erosion of the watercourse bed and banks.
• The proposed culverts should be appropriately sized to accommodate for flood flows as agreed with the EA. The culverts will also be sized to maintain the natural channel width and gradient wherever possible. The culvert inverts will be buried and backfilled with appropriate bed materials to retain natural bed and flow levels. Scour protection will also be installed upstream and downstream of the culverts where appropriate.
• Existing land drains and open field ditches should be piped/culverted under the scheme footprint or will be diverted into the earthwork’s drainage where appropriate.
• Watercourse diversions should be aligned and profiled to maintain hydraulic capacity, replicate existing channel gradients and cross-sections and reflect the existing channel geomorphology.
• Where erosion protection is required within the new diversion channels, soft engineering techniques should be used where feasible. This may include the use of geotextiles, coir rolls, pallets and log jams, where applicable.
• Road cuttings which intercept the groundwater table should be designed with appropriate drainage to deal with groundwater inflows.
• preparation of defined working zones, method statements and environmental incident response plans should be agreed prior to commencement of works with EA, with specific additional detail for storage of materials, refuelling and for all locations where working is required within 50m of existing watercourses
• the installation of construction-phase drainage as a priority before substantial earthworks commence, surface runoff should be intercepted before entering construction site and separately transferred to local surface waters to avoid site contamination
• treatment of sediment-laden construction runoff prior to discharge, typical measures, subject to location and volumes, may include silt fences, silt traps, filter bunds, settlement ponds and/or proprietary silt treatment units such as ‘silt busters’
• use of coffer dams or temporary water diversions where in-channel works are required, to provide dry working conditions. The method of isolation used would be dependent on the scale and timing of the works and the size and sensitivity of the watercourse
• Pre-cast concrete structural materials should be used, where feasible, to minimise use of wet concrete in near-channel or in-channel works
• culverts and diversions to be constructed offline, where feasible, and diversion to the new channel would be timed to allow for the establishment of vegetation within the channel.?Construction needs to proceed from the low end of the newly constructed watercourse channels, to minimise sedimentation, with ‘breakthrough’ of upper end of the channel and release of flow only when new channel is suitably prepared
• Provision of appropriate sustainable drainage design techniques to both attenuate flow and reduce pollutant loading on discharges to receiving waters from routine runoff and accidental spillage.

Cultural Heritage

Three potential areas are commonly known under the overarching aspect of cultural heritage:

• archaeological remains
• the built heritage; and
• historic landscapes.

Archaeological remains consider those materials created or modified by past human activities, which includes a wide range of visible and buried artefacts, field monuments, structures and landscape features. Built heritage considers architectural, designed or other structures with a significant historical value, such as listed buildings.

Appropriate measures to mitigate the impacts on built heritage assets include inter alia screening.