Chapter 13 Road Drainage and the Water Environment
Document Reference MNB Part 6.1.14
Regulation Reference 5(2)(a)
PINS Reference Number TR010010
AECOM A1-SENSLR: MNB – Environmental Impact Assessment – Volume 2: Environmental Statement 13-2
Chapter 13 Road Drainage and the Water Environment
Introduction 13.1 This Chapter presents the assessment of the proposed bypass on the water environment. This includes a consideration of the potential effects on surface water quality, hydrogeology and flood risk. It sets out the environmental baseline, describes the scope and assessment methodology, presents the findings of the assessment, of likely effects for the construction and operation phases and any mitigation measures that have been taken into account. 13.2 Part 3 of the ES contains the following supporting information: Appendix 13.1 Legislation, Planning Policy and Scoping Consultation; Appendix 13.2 Surface Runoff Assessment (Method A), Groundwater Assessment (Method C), and Spillage Risk Assessment (Method D); Appendix 13.3 Hydrological Analysis and Hydraulic Assessment (Method E and F); Appendix 13.4 Baseline Data; Appendix 13.5 Environment Agency Flood Map; Appendix 13.6 Routine Runoff and Spillage Risk – Summary of Results; and Appendix 13.7 WFD Programme of Measures.
Legislation and Planning Policy Legislation 13.3 The following lists European and National Legislation relevant to this study. More detail is provided in Appendix 13.1. European o Groundwater Directive (1980/68/EC) (to be repealed 2013)1; o Water Framework Directive (2000/60/EC); o Groundwater Daughter Directive (2006/118/EC, replacing 1980/68/EC)); o Environmental Liability Directive (2004/35/EC); o Fish (Consolidated) Directive (2006/44EC, replacing 78/659/EC)1; o Nitrates Directive (91/676/EC) o Dangerous Substances Directive (76/464/EC)1 o Dangerous Substances Directive (2006/11/EC replacing 76/464/EC)1;and o Priority Substances Directive (2008/105/EC). National o The Environmental (England and Wales) Permitting Regulations 2010; o The Flood and Water Management Act 2010; o The Planning and Compulsory Purchase Act 2004; o The Water Act 2003; o The Water Resources Act 1991; o The Land Drainage Act 1991 (as amended); o Part IIA of The Environmental Protection Act 1990; o The Town and Country Planning Acts and Regulations (various dates).
1 To be repealed by the WFD when fully implemented AECOM A1-SENSLR: MNB – Environmental Impact Assessment – Volume 2: Environmental Statement 13-3
o The Water Environment (Water Framework Directive) Regulations 2003; o The Control of Pollution (Oil Storage) (England) Regulations 2001; o The Conservation of Habitats and Species Regulations 2010; and o The Groundwater (Water Framework Directive) Direction 2006.
Planning Policy 13.4 The Government’s water strategy for England, Future Water, was published in February 2008. This strategy sets out the Government’s long-term vision for water and the framework for water management in England. 13.5 The National Planning Policy Framework (NPPF) (March 2012) replaces existing national planning policy adopted since 2004 (e.g. Planning Policy Statement (PPS) 23 and PPS25). In particular, Section 11 Conserving and Enhancing the Natural Environment paragraph 109 states that development should be prevented from contributing or put at unacceptable risk from, or being adversely affected by unacceptable levels of water pollution. Section 10 Meeting the Challenge of Climate Change, Flooding and Coastal Change paragraphs 94 and 99 emphasise the need to adopt proactive strategies to mitigate and adapt to climate change over the long term, taking into account flood risk. 13.6 Local Planning Policy is set out by NCC using the former Castle Morpeth Local Plan, adopted in February 2003 as a guide for the time being. Policy RE4 Water Quality states that the Council will resist development which may adversely affect the quality of surface, underground or coastal water. Furthermore, any initiative to improve surface or coastal water quality will be encouraged. Policy RE5 Surface Water Run-Off and Flood Defences, prevents development in flood risk areas, or where development may increase the risk of flooding somewhere else, unless it falls into an exception category. In Castle Morpeth, however, because of geological conditions the safeguarding of ground water resources is not seen as an issue requiring formal policies, though the Council subscribes to the objective of the protection and efficient use of water supplies. In particular, water quality may be affected by emissions of water which has passed through old mine workings and been contaminated. Policy RE8 dealing with Contaminated Land is considered in Chapter 14 Geology and Soils. More detail on these policies is presented in Table 13.1.2 in Appendix 13.1.
Methodology Scope of Assessment 13.7 This assessment has been carried out in accordance with guidance in Volume 11, Section 3, Part 10 of the Design Manual for Roads and Bridges (DMRB) (henceforth referred to as HD45/09). This assessment has identified the potential effects on the water environment by assessing the likely effects of the proposed scheme during construction and operation. The effects of the proposed scheme have been assessed, taking into consideration the magnitude of the effect and the importance of the receptor. 13.8 There are four assessments (HD45/09 assessment reference is denoted in brackets): Effects of routine runoff on surface waters (Methods A and B); AECOM A1-SENSLR: MNB – Environmental Impact Assessment – Volume 2: Environmental Statement 13-4
Effects of routine runoff on groundwater’s (Method C); Spillage Risk Assessment (Method D); and Flood Effects (Methods E and F). 13.9 For the purpose of the surface water (water quality and flood risk) the study area includes all features within approximately 1km of the site boundary. However, watercourse flow effects may propagate downstream, thus where relevant this study has also considered a wider study area (up to 2km downstream of the site boundary). In addition, since flood risk can affect upstream and downstream areas, this study has also considered a wider study area, where relevant. 13.10 Effects on groundwater may be local or regional in scale, depending on the size and duration of the imposed stresses and properties of the hydrogeological regime. For example, local effects may occur in permeable drift deposits by lowering of the water table, which may be temporary through construction dewatering, or permanent by land drainage. Regional effects associated with roads may include groundwater pollution as a result of diffuse pollution from surface water road drainage, discharged to soakaway, to bedrock over many kilometres of road. The area of interest for local or temporary effects is considered to be within 1km of the road, whereas regional effects may occur at the scale of the total catchment area for a public supply well or the entire aquifer. 13.11 Development parameters as defined in Table 2.3 of Chapter 2, and their relevance in this assessment, are presented in Table 13.1. AECOM A1-SENSLR: MNB – Environmental Impact Assessment – Volume 2: Environmental Statement 13-5
Table 13.1 Development Parameters Is the information important in the assessment of If so how was the information included in the assessment, and in Development Parameter ‘likely significant effects’? Why? what form? Yes, the extent of the red line boundary defines the All watercourses within the red line boundary have been identified and Red Line Boundary area in which watercourses may be affected by the assessed. The potential affect of pollution on watercourses considers a scheme. study area that extends beyond the red line. Not directly. The vertical road alignment influences Vertical Road Alignment Please refer to the footprint of earthworks below. the size of earthworks, which is relevant. Watercourses tend to flow north-south and the proposed route is aligned Horizontal Road Yes, the horizontal alignment influences the broadly east-west, thus irrespective of the horizontal alignment, the same Alignment watercourses that are crossed by the scheme. watercourses are crossed. These crossings have been assessed in this chapter. Yes, the size of the road is relevant as this influences The number of lanes is fixed. The area of carriageway and the volume of Number of carriageways the volume of runoff and amount of vehicle derived traffic it is predicted to carry are data inputs to the assessment of routine pollutants that it will contain. runoff. No, the location of roundabouts is not a relevant Location of roundabouts No further comment. consideration for this assessment. Area of development See comment for ‘red line boundary’ above. No further comment. This chapter considers a range of mitigation measures to manage earthworks to prevent significant adverse effects on the water The volume of earthworks is relevant to the environment. The main risk is where earthworks are in close proximity to Volume of earthworks assessment of construction effects on watercourses watercourses. The detail of these measures will be developed by the (i.e. from silt laden runoff). Contractor during detailed design. The assessment is precautionary and has assumed a worst case, and an appropriate range of measures has been proposed. Appropriate measures have been proposed to manage earthworks close This is relevant to the assessment where earthworks to watercourses. Site specific measures will be determined by the Footprint of earthworks are close to watercourses. Contractor during detailed design and as part of Flood Defence Consent applications. The height and angle of embankments (during Height and angle of Mitigation measures have been proposed to manage any silt laden runoff construction) can be a source of fine particulates that repose of embankments from embankments. can lead to silt laden runoff/ Landscape planting Not relevant. No further comment. Changes to construction materials used during the Arched Structure design – construction of these structures is not relevant to this No further comment. type, diameter etc. assessment. AECOM A1-SENSLR: MNB – Environmental Impact Assessment – Volume 2: Environmental Statement 13-6
Is the information important in the assessment of If so how was the information included in the assessment, and in Development Parameter ‘likely significant effects’? Why? what form? The routine runoff assessment presented in this chapter summarises the The proposed scheme has committed to SUDS, treatment required to which SUDS will need to be designed to. The which will be used to treat runoff and provide spillage assessment is based on there not being a structure within 100m that Location, type and containment. The location and time of SUDS is not would encourage deposition of sediment bound pollutants from outfalls 1 volume of SUDS relevant, as long as any future changes provide and 2. However, no additional assessment is considered to be required adequate treatment as has been defined in this should the location of the outfall be moved to within 100m upstream of chapter. such a structure because there is spare capacity in the treatment measures provided. Although the precise location of the outfall may move Location of surface water slightly, there is no intention to alter the watercourse No further comment. outfalls into which the highway runoff will be discharged. Route of replacement Not relevant. No further comments. PRoW Cut and fill balance Please refer to comments to ‘earthworks’. Please refer to comments to ‘earthworks’. Lighting – location, type, number, and height of Not relevant. No further comments. lighting columns Bridge, large structure Watercourse bridging structures has been considered No further comments. designs earlier. Changes to the provision Not relevant. No further comments. for pedestrians and cyclist Vehicle speed rating for Not relevant. No further comments. the bypass Gradient Not relevant. No further comments. Road surface Not relevant. No further comments. characteristics AECOM A1-SENSLR: MNB – Environmental Impact Assessment – Volume 2: Environmental Statement 13-7
Surface Water 13.12 The assessment has been carried out in accordance with HD45/09 and includes both qualitative and quantitative assessments. Initially a desk study was carried out to: Map the location of all major and minor watercourses and other water features within the study area; Identify areas sensitive to water pollution; and Review available information on surface water quality/resources obtained from the Environment Agency (EA) (www.environment-agency.gov.uk). 13.13 This desk study was supplemented by a walkover survey carried out on the 9th July 2008 and geomorphic surveys at the location of proposed outfalls on the 18th and 19th February 2010. 13.14 Based on the above information and experience of other road schemes, environmental constraints were identified so that they could be taken into account by the schemes design. 13.15 A routine runoff assessment and a spillage risk assessment [in accordance with HD45/09 and using the Water Risk Assessment Tool (HAWRAT)] have been carried out to quantify the effects of spillages and routine runoff on receiving watercourses. The methodology followed for both assessments is presented in detail in Appendix 13.2. 13.16 The quantitative assessments described in Appendix 13.2 take into account the overriding objectives of the WFD (i.e. no deterioration in water quality and no failure to improve). However, it is also important that the proposed bypass does not compromise other measures proposed to improve WFD designated watercourses (including the River Wansbeck, Cotting Burn and How Burn). Therefore, this assessment has identified relevant measures from the Northumberland River Basin Management Plan (RBMP) and considered the scheme’s compatibility with them.
Groundwater 13.17 The scheme drainage network has been designed so that road runoff discharges to surface watercourses, rather than groundwater via soakaway. However, runoff will be collected and conveyed by grassed swales either side of the carriageway and it is anticipated that a small amount of road runoff will infiltrate into the ground. Therefore, as a precautionary measure a Method C Groundwater Assessment as described in HD45/09 has been carried out. A full description of the method has been presented in Appendix 13.2 in Part 3 of this ES. 13.18 In addition to operation phase effects, potential significant effects from the construction phase have also been assessed, qualitatively. 13.19 Potential effects of the road on groundwater have been assessed from British Geological Survey (BGS) geological and hydrogeological maps and memoirs, the Northumberland RBMP, mining records, environmental database search, desk studies and site AECOM A1-SENSLR: MNB – Environmental Impact Assessment – Volume 2: Environmental Statement 13-8
investigation reports itemised in the Chapter 14 Geology and Soils, and enquiries to Public Authorities.
Flood Risk 13.20 The flood risk (from all sources) associated with the development has been quantitatively assessed in accordance with the requirements of NPPF, the Technical Guidance and in accordance with HD45/09 (Method E and F). The objective of this is to assess three main issues in relation to flood risk: Risk to the proposed scheme from all potential sources of flooding; Risk of increasing flooding elsewhere due to the proposed scheme; and Appropriate mitigation measures to limit the effect of flooding on the scheme and offsite flooding due to increased runoff. 13.21 The following key sources of information were reviewed as part of the assessment: Ordnance Survey (OS) Mapping; EA Flood Maps; Information provided by the EA, Northumbrian Water, and NCC; Geological information; and NCC Initial Drainage Design. 13.22 Potential sources of flood risk were identified based on the available information. A site visit was also undertaken on the 19th February 2010 to consider the potential sources of flood risk in greater detail. 13.23 A hydraulic and hydrological assessment has been undertaken in accordance with HD45/09 and NPPF, and using ISIS software to quantify the effects on river flood risk. The methodology followed for both assessments is presented in detail in Appendix 13.3.
Assessment of Significance 13.24 The assessment of significance follows the guidance set out in HD 45/09. In assessing the significance of potential effects of the proposed development, three key factors have been taken into consideration: The likelihood of that effect occurring; The sensitivity and/or importance of the receiving environment; and The potential magnitude of effect. AECOM A1-SENSLR: MNB – Environmental Impact Assessment – Volume 2: Environmental Statement 13-9
13.25 The likelihood of an effect occurring is based on a scale of certain, likely or unlikely. The importance of the receiving environment is defined in Table 13.2.
Table 13.2 Criteria to Determine the Importance of Features Importance of feature/ Criteria Example attribute Surface Water: EU Designated Salmonid/Cyprinid fishery; Site protected/designated under EU or UK habitat legislation (SAC, SPA, Attribute has a SSSI, WPZ, Ramsar site). WFD Class ‘High.’ high quality Very High and rarity on a Flood Risk: Flood plain or defence protecting more than 100 residential regional or a properties from flooding. national scale Groundwater: Principal aquifer providing a regionally important resource or supporting site protected under EC and UK habitat. SPZ1. Surface Water: Major Cyprinid Fishery species protected under EU or UK wildlife legislation. WFD Class ‘Good’. Attribute has a high quality Flood Risk: Flood plain or defence protecting between 1 and 100 High and rarity on a residential premises from flooding. local scale Groundwater: Principal aquifer providing locally important resource or supporting river flow. SPZ2. Surface Water: WFD Class ‘Moderate’. Attribute has medium Flood Risk: Flood plain or defence protecting 10 or fewer industrial Medium quality and properties from flooding. rarity on a Groundwater: Aquifer providing water for agricultural or industrial use local scale with limited connection to surface water. SPZ3. Surface Water: WFD Class ‘Poor.’ Attribute has low quality and Flood Risk: Flood plain with limited constraints and a low probability of Low rarity on a flooding of residential properties. local scale Groundwater: Unproductive aquifer. (Source: Table A4.3 from HD45/09) AECOM A1-SENSLR: MNB – Environmental Impact Assessment – Volume 2: Environmental Statement 13-10
13.26 The magnitude considers the scale of the predicted change to baseline conditions resulting from a given potential effect and takes into account the duration of an effect (i.e. temporary or permanent) and whether it is direct or indirect. The magnitude has been identified independently of importance/sensitivity using the criteria in Table 13.3.
Table 13.3 Criteria to Determine the Magnitude of Effect Magnitude of Criteria Examples Effect(1) Surface Water: Deterioration of water quality parameter resulting in a reduction in class status and preventing the water body from meeting its target (only relevant for non-temporary effects); Failure of both soluble and sediment-bound pollutants in HAWRAT (Method A, Annex I) and compliance failure with EQS values (Method B); Calculated risk of pollution from a spillage >2% annually Results in (Spillage Risk Assessment, Method D, Annex I); loss of Loss or extensive change to a fishery; and attribute Loss or extensive change to a designated Nature Conservation Major adverse and/or Site. quality and Flood Risk: integrity of Increase in peak flood level (1% annual probability) >100mm the attribute (Hydrological Assessment of Design Floods and Hydraulic Assessment, Methods E and F, Annex I). Groundwater: Loss of, or extensive change to, the status of an aquifer; Potential high risk of pollution to groundwater from routine runoff – risk score >250 (Groundwater Assessment, Method C, Annex I); and Loss of, or extensive change to, groundwater supported designated wetlands. Surface Water: Deterioration in water quality parameter potentially resulting in a reduction in class status and contributing to the failure of the water body from meeting its target (only relevant for non- temporary effects); Failure of both soluble and sediment-bound pollutants in HAWRAT (Method A, Annex I) but compliance with EQS values Results in (Method B); effect on Calculated risk of pollution from spillages >1% annually and Moderate integrity of <2% annually; and adverse attribute, or Partial loss in productivity of a fishery. loss of part Flood Risk: of attribute Increase in peak flood level (1% annual probability) >50 mm. Groundwater: Partial loss or change to the status of an aquifer; Potential medium risk of pollution to groundwater from routine runoff-risk score 150-250; Calculated risk of pollution from spillages >1%annually and <2%annually; and Partial loss of integrity of groundwater supported designated AECOM A1-SENSLR: MNB – Environmental Impact Assessment – Volume 2: Environmental Statement 13-11
Magnitude of Criteria Examples Effect(1) wetlands. Surface Water: Deterioration of water quality but insufficient to cause the class status to change or to prevent the water body meeting its target (only relevant for non-temporary effects); Failure of either soluble or sediment-bound pollutants in Results in HAWRAT; and some Calculated risk of pollution from spillages >0.5% annually and measurable <1% annually. Minor adverse change in Flood Risk: attributes Increase in peak flood level (1% annual probability) >10mm. quality or Groundwater: vulnerability Potential low risk of pollution to groundwater from routine runoff- risk score<150; Calculated risk of pollution from spillages >0.5% annually and <1% annually; and Minor effects on groundwater supported wetlands. Surface Water: Discharges to watercourse but no significant loss in quality, Results in fishery productivity or biodiversity; affect on No effect on WFD classification; attribute, No risk identified by HAWRAT (pass both soluble and sediment- but of bound pollutants); and Negligible insufficient Risk of pollution from spillages <0.5%. magnitude Flood Risk: to effect the Negligible change in peak flood level (1% annual probability) use or <+/-10 mm. integrity Groundwater: No measurable effect on an aquifer and risk of pollution from spillages <0.5%. Surface Water: Where the proposal provides an opportunity to enhance the Results in water environment; some HAWRAT assessment of either soluble or sediment-bound beneficial pollutants becomes Pass from an existing site where the effect on baseline was a Fail condition; and attribute or Minor beneficial Calculated reduction in existing spillage risk by 50% or more a reduced (when existing spillage risk is <1% annually). risk of Flood Risk: negative Reduction in peak flood level (1% annual probability) >10 mm. effect Groundwater: occurring Calculated reduction in spillage risk by 50% or more to an aquifer (when existing spillage risk <1%annually). (Source: Amended from Table A4.4 from HD 45/09) 13.27 Note (1) - Criteria for better than minor beneficial effects have not been presented as the effect assessment does not predict any such effects. 13.28 The significance of effects has been then determined using the matrix presented in Table 13.4. The significance of a given effect is based on a combination of the AECOM A1-SENSLR: MNB – Environmental Impact Assessment – Volume 2: Environmental Statement 13-12
sensitivity/importance of the receptor and the magnitude of a potential effect. Effects can be beneficial or adverse, and their significance very large, large/very large, large, moderate/large, moderate, slight/moderate, slight or neutral.
Table 13.4 Assessment of Significance Matrix Magnitude of Effect Major Moderate Minor Negligible
Importance of Very High Very large Large/very large Moderate/large Neutral Attribute High Large/very large Moderate/large Slight/moderate Neutral Medium Large Moderate Slight Neutral Low Slight/moderate Slight Neutral Neutral (Source: Taken from HD 45/09) 13.29 Effects are first determined without taking into account mitigation measures and good practice construction techniques (as indicated by the guidance documents listed in paragraph 13.159). Effects that remain following mitigation measures being taken into consideration are residual effects. Temporary effects are considered in the construction period whilst permanent effects are discussed in the operational phase, albeit that the effect may first occur during construction (e.g. morphological changes). Effects of moderate adverse or worse are considered to be significant.
Limitations and Assumptions 13.30 During the course of the effect assessment no significant difficulties were encountered. Key modelling assumptions and data limitations have been discussed in Appendix 13.2 and 13.3. Table 13.3 provides some example magnitude criteria referring to changes to spillage risk and routine runoff. Since this is a new road these examples do not apply. The design has sought to ensure treatment/containment facilities are incorporated to control any risk to the water environment.
Consultation 13.31 The EA, NCC, Northumbrian Water and the Highways Agency all provided comments with regards to the assessment of effects on the water environment. These have been detailed in Table 13.1.3 in Appendix 13.1 and include reference to the need for an assessment of discharges on surface and groundwater quality during construction and operation, including the effects on the existing A1, the need to avoid culverting watercourses to protect river biodiversity, and recommendation for the assessment of flood risk. 13.32 Further to the correspondence attached in Table 13.1.3 in Appendix 13.1, AECOM liaised with the EA following the submission of the Environmental Statement submitted to NCC in 2011 and a series of standard planning conditions were agreed with respect to unsuspected contamination, pollution prevention and flood risk (surface water management). These are summarised below: AECOM A1-SENSLR: MNB – Environmental Impact Assessment – Volume 2: Environmental Statement 13-13
A Surface Water Drainage Scheme, based on sustainable drainage principles and assessment of the hydrological and hydrogeological context of the development, will need to be submitted to and approved by the Local Planning Authority. This should include confirmation that the discharge rates to nearby watercourses will be restricted to greenfield runoff rates; details on pollution prevention measures to protect ground and surface water quality; and details of how the scheme will be maintained and managed after completion; The site lies within Zone III of a Source Protection Zone. Therefore, road runoff infiltrating into the ground should be treated (via oil interceptors or lining) prior to discharge to avoid pollution of groundwater receptors; Details should be provided on lock off valves for pond outlet(s) to provide containment in order to prevent surface water pollution, should a large spill occur; A construction sediment management plan should be submitted to and approved by the Local Planning Authority to treat and remove suspended solids from surface water runoff during construction so as to prevent pollution of Cotting, How and Benridge Burns and Fulbeck. These watercourses have currently poor habitat (in-stream and riparian) and reduced water quality (in particular detrimental nutrient and silt loading). The proposal should not contribute to any further deterioration in these watercourses, particularly with regard to the potential for increased sediment loading as a result of the construction and operation of the bypass; Whilst it is unlikely that the land on which the bypass will be built is affected by contamination, the removal of the diesel oil storage tank from domestic premises (Rose Cottage) may pose a risk of contamination. A remediation strategy detailing how this unsuspected contamination will be dealt with should be implemented; The WFD requires, as a minimum, no deterioration to the status of watercourses, but also requires the restoration and enhancement of watercourses wherever possible. Whilst consideration of enhancement measures targeted at protected species is welcomed, the EA considered that it may be more useful to target enhancement towards improving the catchment as a whole; An Environmental Permit may be required under the Environmental Permitting Regulations 2010 for engineering activities that involve the injection of grouts or other media for the purpose of sealing or ground stabilisation. The document ‘Civil engineering activities involving grouts or other media for the purpose of sealing or ground stabilisation (issues June 2011)’ should be reviewed to ensure all regulatory requirements are adhered to, or to apply for an Environmental Permit if required; and Erection of flow control structures or any culverting of a watercourse will require the prior written approval of the Environment Agency under s.23 of the Land Drainage Act 1991 or s.109 of the Water Resources Act 1991.
AECOM A1-SENSLR: MNB – Environmental Impact Assessment – Volume 2: Environmental Statement 13-14
Baseline Conditions 13.33 This Section sets out the environmental baseline conditions.
Sources of information 13.34 The following information was received from the EA: Confirmation of the status (main rivers or ordinary) for watercourses within the study area; Details of the latest River Ecosystem (RE) Class, chemical and biological General Quality Assessment (GQA) grades, and background water quality data (in particular dissolved copper, total zinc, and water hardness) for any monitored watercourses within the study area (e.g. River Wansbeck, Cotting Burn and How Burn); Locations and details of discharges and abstraction licenses (location, source and use) within the study area or within 2km downstream; The location of any nearby gauging stations where flow records may be available; Identification of any European designated or non-designated commercial fisheries within the study area or 2km downstream including details of the likely fish species that are/could be present; Details of any recorded pollution incidents (within the past five years); and Any other environmental reports, studies or information that may be relevant (e.g. relating to the hydrology of the proposed site).
Site Location 13.35 The proposed bypass is within the catchment of the River Wansbeck. The River Wansbeck is a statutory Main River and flows through the centre of Morpeth. It is the ultimate destination of runoff from the proposed road. The River Wansbeck has excellent water quality and supports healthy fish populations. 13.36 The new road will be constructed to the north of Morpeth and will cross four tributaries of the River Wansbeck (Cotting Burn, Fulbeck tributary of Cotting Burn, How Burn and How Burn tributary), each of which flow in a north to south direction (See Figure 13.1). Of these, the two main tributaries of the River Wansbeck are Cotting Burn (joining the River Wansbeck in the centre of Morpeth) and How Burn (which flows into the River Wansbeck at Whorral Bank, 1 km downstream of Morpeth).
Surface Water Baseline 13.37 A site walkover was carried out on the 9th July 2008 during fair weather (although unsettled conditions with frequent rain had occurred in the previous two weeks). All of the watercourses within the study area were visited (where possible) and a description of watercourses, as observed, is presented in Table 13.5 and illustrated on Figure 13.1 Surface Water Features. A second site visit to measure basic geomorphic characteristics of the receiving watercourses at the point of discharge from the road was carried out on the 18th/19th February 2010, in cold conditions with some snow. AECOM A1-SENSLR: MNB – Environmental Impact Assessment – Volume 2: Environmental Statement 13-15
Table 13.5 Watercourse Description Watercourse Description The River Wansbeck flows west to east through the town of Morpeth. This description has been taken just before River Wansbeck (Main River) the river enters the town at NZ 180 858. At this point the channel is approximately 20m to 30m wide. Upstream (Description taken from NZ 180 858) there is a weir that crosses the entire channel. The channel is tree lined both up and downstream. The Scotch Gill Wood Local Nature Reserve (LNR) is located immediately downstream of this point. The River Wansbeck was also observed at NZ 208 865 just downstream of Morpeth. The channel is River Wansbeck (Main River) approximately 15m wide at this point with clear fast flowing water. At this location the river is also flowing through (Description taken from NZ 208 865) a wooded area. Upstream there is a small vegetated island in the channel and little aquatic vegetation could be seen. Cotting Burn flows north to south joining the River Wansbeck in the centre of Morpeth. At the point of observation Cotting Burn (Main River) the channel is approximately 3m wide and it is culverted under the road. The channel is tree lined and the (Description taken from NZ 190 871) surrounding land use is private residential gardens. There is no evidence of aquatic vegetation. Downstream from this point there is a surface water pipe which flows into the channel from the minor road. How Burn flows northwest to southeast before joining the River Wansbeck at NZ 208 867. At the point of How Burn (Ordinary Watercourse) observation the channel is approximately 1.5m wide. Downstream the channel is sinuous with grassed banks. The surrounding land use is fields of grass, however further downstream this becomes arable farmland. There is (Description taken from NZ 201 883 little aquatic vegetation where the description was taken from and a pipe discharges to the watercourse from the (downstream) NZ 200 885 (upstream)) minor road at this location. Upstream the channel is straight with thick vegetation on both banks and aquatic vegetation in the channel and surrounded by grassed fields. How Burn (Ordinary Watercourse) At this location How Burn flows through a very steep sided ravine, and access was not possible. (Description taken from NZ 208 868) Shield Hill Burn flows north to south into Cotting Burn to the east of Northgate Hospital. The channel is Shieldhill Burn (Ordinary Watercourse) approximately 0.3m wide. Upstream the channel is sinuous and flows through pastoral farmland where the bank sides and surrounding vegetation is predominantly grass. Downstream the watercourse was overgrown by bank (Description taken from NZ 192 885) side vegetation made up of shrubs and grasses which opens out to arable fields, which could be a sign of excessive nutrients/stagnation of flow.
Unnamed watercourse 1 (Ordinary This unnamed watercourse flows from north to south before flowing into Cotting Burn to the east of Northgate Watercourse) Hospital at approximately NZ 188 878. The channel is approximately 0.5m wide, however both up and downstream the channel was overgrown with bank side vegetation made up of scrubs and grasses. To both (Description taken from NZ 185 884) sides of the channel the surrounding land use is arable farmland.
Unnamed watercourse 2 (Ordinary This watercourse flows southwest to northeast from the A192 into Cotting Burn at approximately NZ 187 871. Watercourse) The channel is approximately 0.5m wide and is sinuous. The bank side and surrounding vegetation are grassed (Description taken from NZ 186 870) fields becoming wooded further downstream. AECOM A1-SENSLR: MNB – Environmental Impact Assessment – Volume 2: Environmental Statement 13-16
Surface Water Quality 13.38 Under the WFD the UK is divided into River Basin Districts (RBD). The study area is in the Northumberland RBD. For each RBD a RBMP has been prepared and Annex B of these plans presents the result of monitoring of ecological, physico-chemical, and hydromorphological parameters. The stretch of the River Wansbeck between the River Font and the North Sea (including both Cotting Burn and How Burn) is designated under the WFD and Table 13.6 presents a summary of this information.
Table13.6 Water Framework Classifications for River Wansbeck (River Font to North Sea) Predicted Hydro - Current 2015 Overall Watercourse morphological Chemical ecological Protected areas Classification Status Quality status / potential Freshwater Fish Fail (due to Directive River Wansbeck Benzo (ghi) Heavily (Salmonid) perelyene Moderate (from Font to Modified (due Poor (due to and indeno Potential Nitrates Directive North Sea, i.e. as to flood phytobenthos) (123-cd) (good by it passes through protection and Urban Waste pyrene and 2027) Morpeth) urbanisation) Water Treatment tributyltin GB103022077060 Directive compounds (UWWTD) River Wansbeck (from Hart Burn to Freshwater Fish Moderate Good Font, i.e. Directive Not designated Status (due to Not assessed Ecological upstream of (Salmonid) fish) Status Morpeth) Nitrates Directive GB103022077060 (Source EA website 2009 www.environment-agency.gov.uk) AECOM A1-SENSLR: MNB – Environmental Impact Assessment – Volume 2: Environmental Statement 13-17
13.39 The River Wansbeck has been classified as a heavily modified water body (HMWB), thus the WFD objective is good ecological potential, not status. It has been classified as a HMWB due to urbanisation and flood protection. It is currently at poor ecological potential as a result of the phytobenthos being classified as poor. The River Wansbeck is predicted to achieve good ecological potential and chemical status by 2027, as meeting its objective by 2015 would be disproportionately expensive and technically unfeasible. 13.40 Although now superseded by the WFD monitoring, water quality monitoring up to 2008 under the RE and GQA methods for the River Wansbeck, Cotting Burn and How Burn have been presented in Table 13.7.
Table 13.7 River Ecosystem and General Quality Assessment Water Quality Data Grid Watercourse Stretch RE Class Chemical GQA Biological GQA Reference RE 1* Font Burn River (compliant A (between to Cotting NZ 195 862 A* (since 1990) Wansbeck since 2002- 1990 and 2008) Burn 2004) RE 2* since A (from 1996 to 1998/99 2008, apart Cotting River (marginal from 2003 and A (between 2002 Burn to NZ 208 867 Wansbeck between 2004 2004 when was and 2008) How Burn and 2006) classified as grade B) RE 2* A* between How Burn River (compliant 2004 and2006 ( A (between 2002 to Morpeth NZ 206 863 Wansbeck since 1998/99) B in previous and 2006) STW years)] RE 2* since Source to 2000/02 D* since 2003 (C in Cotting Burn Northgate NZ 187 877 D* (2004-2006) (significant 1995) Hospital* failure 2004/06) Northgate RE 3* (marginal D* (since Cotting Burn Hospital to NZ 195 863 since 1994) D* (since 1990) 2001/03) Wansbeck* How Burn RE 2* C* since C* since 2000 (D Hebron (significant 2004/06 (D/E How Burn NZ 201 896 between 1990 and East Farm failure since between 2000 2000) SHE 1999/01) and 2002)] Hebron RE 2* C* since 2000 (D East Farm (compliant B* (since How Burn NZ 206 864 between 1990 and to since 1998/99) 1995/97) 2000) Wansbeck* GQA Class Description: A = Very Good Quality, B = Good Quality, C = Fairly Good Quality, D = Fair Quality, E = Poor Quality, F = Bad Quality (Source EA website 2009 www.environment-agency.gov.uk) AECOM A1-SENSLR: MNB – Environmental Impact Assessment – Volume 2: Environmental Statement 13-18
(*) Obtained from the EA website 2008. This information is not currently available on the EA website (since 2009) following introduction of WFD monitoring. 13.41 This information is useful as it provides a long term measure of general water quality. The chemical water quality of the River Wansbeck along the stretch from its confluence with the River Font to Morpeth STW is classified as grade A (Very Good). In terms of biological water quality of the River Wansbeck, the stretch from Font Burn to Morpeth STW is classified as grade A (Very Good). 13.42 There are two water quality monitoring sites along Cotting Burn, from the source to its confluence with the River Wansbeck it has been classified as grade D (Fair) for both chemical and biological GQA. 13.43 How Burn mainly has been classified as grade C (Fairly Good) for both chemical and biological GQA. However the stretch between Hebron East Farm and the River Wansbeck has been classified as grade B (Good) for chemical GQA. Overall the water quality of this watercourse has improved since 2000.
Aquatic Fauna and Fisheries 13.44 The River Wansbeck and associated tributaries contain a significant population of native white clawed crayfish. In the data search of 2007 NCC provided information that the River Wansbeck has a very strong population of white-clawed crayfish, and further information to confirm this was provided by the EA (See Chapter 7 Ecology and Nature Conservation). AECOM surveys carried out in 2007 and 2009 identified White Clawed Crayfish at the confluences of Cotting Burn and How Burn with the River Wansbeck, but not further upstream of their courses. 13.45 In addition, according to the EA, the following UK Biodiversity Action Plan (UKBAP) and Local BAP species are present: Salmon (Salmo salar) are present in the River Wansbeck as far as Bothal Castle (which is just less than 4 km downstream from Morpeth.). However, there are two weirs between there and Morpeth which render the rest of the Wansbeck inaccessible to Salmon (according to the County Ecologist salmon and sea trout are present in the upper catchment following 2008 floods breaching Highford Weir, which is 2km west of Morpeth town centre); Brown trout (Salmo trutta) are present throughout the study area; Eels (Anguilla Anguilla) are present throughout the study area; and Bullhead (Cottus gobio) have been found at Stanners in the Morpeth area. AECOM A1-SENSLR: MNB – Environmental Impact Assessment – Volume 2: Environmental Statement 13-19
13.46 According to the County Ecologist the River Wansbeck also has populations of stone loach and brook lamprey. 13.47 The River Wansbeck, including its tributaries, is designated as a local Site of Nature Conservation Importance.
Water Resources and Pollution Incidents 13.48 There are 21 active discharge consents within the study area (these have been detailed in Appendix 13.4 Table 13.4.1). Only 9 of these are active discharge consents to Benridge Burn, Cotting Burn, Cotting Burn Tributary, Fulbeck and How Burn. A further 19 active discharge consents have been identified in the surrounding area along the River Wansbeck, but not within the study area. 13.49 No significant pollution incidents have been documented in the past five years.
Importance of Surface Water Features 13.50 The importance of the relevant water bodies within the study area has been assessed applying the criteria presented in Table 13.2 to the baseline information presented throughout this Section. The level of importance for each water receptor and the justification for their classification is compiled in Table 13.8:
AECOM A1-SENSLR: MNB – Environmental Impact Assessment – Volume 2: Environmental Statement 13-20
Table 13.8 Importance of Surface Water Features Level of Watercourse Justification Importance This watercourse is designated as a Salmonid river under the European Fish (Consolidated) Directive. It was marginally compliant with its RE2 target with both chemical GQA and biological GQA of grade A (Very good). There are also a number of UKBAP species present within this watercourse. Under more recent WFD classification this watercourse (where it passes Morpeth) is considered to be currently at poor ecological potential, not because of its physical River Wansbeck modifications, but due to hydrocarbons and tributyltin compounds. Very High However this stretch is over 10 km long and it is not known how many sample sites the EA operate, and thus, the WFD classification for upstream of Morpeth was also taken into account. This stretch is predicted to achieve good ecological status by 2015. The River Wansbeck also supports a population of White Clawed Crayfish, a protected species of European importance. Overall, therefore, the River Wansbeck has been assigned a very high level of importance. No water quality information is available for Benridge Burn. Benridge Burn is a tributary of the River Wansbeck. Assuming that a number of Benridge Burn UKBAP and local BAP species might be present and that this Medium watercourse ultimately discharges into River Wansbeck, it has been assessed to have a medium level of importance. Classified under the WFD as part of the River Wansbeck, into which it discharges, but was classified as having chemical and biological water quality GQA grade D (Fair). UKBAP and local BAP species are present Cotting Burn High in the area [native white clawed crayfish, brown trout, eels, bullheads at Stanners (Wansbeck)]. As a result, it has been assessed as being of high importance (precautionary). No water quality information is available for Cotting Burn tributary. Cotting Burn Based on professional judgement, this watercourse is considered of Low tributary low importance. No water quality information is available for Fulbeck. Based on Fulbeck professional judgement and site inspection, this watercourse is Low considered of low importance. Classified under the WFD as part of the River Wansbeck, into which it discharges. How Burn was classified as having GQA grades C (Fairly Good) and B (Good), although according to local County Ecologists it is suffering with organic pollution, possibly from pastoral farming and How Burn discharges from septic tanks (see reference 1 in Table 13.4.1 in High Appendix 13.4 and Figure 13.1). UKBAP and local BAP species are present in the area [native white clawed crayfish, brown trout, eels, bullheads at Stanners (Wansbeck)]. As a result, it has been assessed as being of high importance (precautionary). There is no water quality information available for the How Burn How Burn tributary. Based on professional judgement and site inspection, this Low tributary watercourse is considered of low importance. AECOM A1-SENSLR: MNB – Environmental Impact Assessment – Volume 2: Environmental Statement 13-21
13.51 The proposed road scheme does not cross the River Wansbeck; however it is the ultimate destination of road runoff.
Hydrogeology Baseline 13.52 The site is underlain by Carboniferous bedrock comprising Millstone Grit Series to the west, approximately from St. George’s roundabout), and overlying Coal Measures strata to the east. The Pegswood Moor Fault runs just north and parallel to the proposed route from How Burn House past Whorral Bank roundabout with a throw to the north of about 40m. Further details are presented in Chapter 14 Soils and Geology. The Northumberland Carboniferous Limestone and Coal Measures are classified by the EA as a Secondary A Aquifer (Waterbody ID GB40302G700200). This is the usual designation for what were formerly termed Minor Aquifers. These are permeable layers capable of supporting water supplies at a local rather than strategic scale, and in some cases forming an important source of base flow to rivers. The Northumbrian Carboniferous aquifer is a Drinking Water Protected Area under the WFD with an overall status of poor, due to poor chemical status with regard to effect on surface waters. This is interpreted to result from the effect of historical mining exacerbated by groundwater rise through abandoned mine workings subsequent to cessation of mine pumping. Although measures to mitigate these effects are actively being pursued by the regulatory authorities, the target for achieving good chemical status is not until 2027 due to the disproportionate expense. The Northumbrian Carboniferous aquifer is also designated as Nitrate sensitive due to excessive agricultural nutrients, although this is not a particular concern for the scheme. 13.53 The site is within the Total Catchment Area [Source Protection Zone (SPZ) 3] of a group of water supply wells within the Morpeth area. The Millstone Grit Series is likely to be the main source of water due to its higher productivity. The edge of the SPZ3 is demarcated by the Pegswood Moor Fault which throws the Millstone Grit with its open joints and fractures against the less permeable tight Coal Measure mudstones. The thin sandstones of the Coal Measures may provide some water as evidenced by the water well formerly used for dust suppression at the Pegswood opencast site. Groundwater monitoring within the bedrock indicates that piezometric levels reduce with depth to approximately 10m AOD (c.50 mbgl) indicating under-drainage of the Carboniferous bedrock. 13.54 The Carboniferous bedrock is overlain by a tripartite series of glacial deposits, interpreted as an over consolidated lodgement till, comprising an upper stony clay, middle sands and gravels and the lower boulder clay. The sand and gravel beds are fairly extensive within the Morpeth District and are defined by the EA website as being a Secondary A Drift aquifer. Fingers of this deposit spread out from south of the site to intercept the route at Cotting Burn, How Burn, Pegswood Moor and Whorral Bank. A separate body of sand and gravel intercepts the route from the north at St. George’s roundabout. Narrower bands of alluvial deposits also show traces within the various streams. From the disposition of the streams, it is conjectured that the sand and gravel deposits provide their baseflow. Groundwater monitoring indicates that water levels within the sand and gravel are close to the base of the deposit and similar to stream levels. The base of the sand AECOM A1-SENSLR: MNB – Environmental Impact Assessment – Volume 2: Environmental Statement 13-22
and gravel is relatively impermeable ‘boulder clay’ separating the upper drift aquifer from the lower carboniferous bedrock aquifer. 13.55 Aquifer vulnerability is controlled by the thickness and permeability of the overlying soils. The Carboniferous bedrock is protected by the drift deposits, with the possible exception of two areas of incursion of the former Pegswood Opencast Pit just east of How Burn and west of Whorral Bank roundabout. Being on the edge of the opencast, it is not certain whether these areas were excavated completely to bedrock. The former opencast has a fishing lake northeast of the site within the backfill, which appears to drain into the underlying Coal Measures. However, the coal seams northeast of the road are separated from the worked seams underlying the site by the Pegswood Moor Fault, which is conjectured to be of low permeability. Nevertheless, it is suspected that the Pegswood Opencast may intercept old mine workings, which could connect with adits driven from the vicinity of How Burn. Therefore there is a plausible linkage between water draining to the former Pegswood Opencast and How Burn, and by extension the River Wansbeck. Given the low groundwater levels measured in the Carboniferous bedrock, the significance of this flow will be limited, although it could increase due to rising mine water. Pore water seeping downwards to the bedrock water table will have a significant thickness of 10’s of metres through a sequence of seat earths, coals, sandstones and mudstones cyclothems, through which to attenuate potential pollutants through processes of absorption, cation exchange and chemical or biological breakdown. 13.56 The EA aquifer vulnerability mapping shows most of the route to be covered by drift and not to be water bearing. However, between West Lane End and Fulbeck Grange the soils are defined as L1, which defines soils of intermediate leaching potential which have a moderate ability to attenuate diffuse source pollutants, or in which it is possible that some non-absorbed diffuse source pollutants, and liquid discharges from a wide range of pollutants, could penetrate the soil layer. Fingers of sand and gravel deposits intercepting the route from the south, between Pegswood Moor and Whorral Bank, are defined as H3 having coarse textured or moderately shallow soils of high leaching potential, which readily transmit non-adsorbed pollutants and liquid discharges but which have some ability to attenuate adsorbed pollutants because of their relatively large organic matter or clay content. 13.57 Results of testing reported in Allied Exploration and Geotechnics Ltd.’s, Ground Investigation Factual Report for Morpeth Northern Bypass, Contract No 3746 (March 2010) indicate the soils along the route to be not significantly leachable for metals, metalloids and anions commonly found in mine waste and road embankment fill. 13.58 The information provided by the EA and Northumberland County Council (formerly Castle Morpeth Borough Council) suggests that there is only one active abstraction licence within 1km of the scheme. This water abstraction is noted approximately 330m south east of the centre of the site search (Licence 01/22/05/65). Water is abstracted from BH No. 3 for industrial / commercial / public service general use and is listed as being operated by V- Fuels Ltd, ACS Dobfar UK Ltd and Synpac Pharmaceuticals Ltd. AECOM A1-SENSLR: MNB – Environmental Impact Assessment – Volume 2: Environmental Statement 13-23
13.59 The importance of the relevant groundwater bodies within the study area has been assessed applying the criteria presented in Table 13.2 to the baseline information presented throughout this Section. The level of importance for each water receptor and the justification for their classification is compiled in Table 13.9:
Table 13.9 Importance of Groundwater Features Level of Aquifer Justification Importance Carboniferous Limestone Secondary A aquifer providing water for agricultural or and Coal Measures industrial use with limited connection to surface water. Medium bedrock aquifer SPZ3. Secondary A aquifer but not a significant groundwater Sand and Gravel Drift resource due to limited extent and connectivity, no Medium aquifer abstraction but locally important for baseflow to streams.
Flood Risk Baseline
Flooding from Rivers 13.60 The proposed bypass is located within the catchment area of the River Wansbeck. The proposed road will cross four tributaries of the River Wansbeck; Cotting Burn, Fulbeck (tributary of Cotting Burn), How Burn and a tributary of the How Burn. Of these four watercourses, the two main tributaries of the River Wansbeck are Cotting Burn and How Burn. 13.61 The Cotting Burn and How Burn have been modelled by the EA to produce the Flood Map (Appendix 13.5). Fulbeck and the tributary of the How Burn have not been modelled by the EA to produce the Flood Map due to their size. 13.62 The EA Flood Map shows that during a 1 in 100 year event, only small areas of land located immediately adjacent to the Cotting Burn and How Burn are at risk of flooding in the study area. Where the 1 in 100 flood outline extends beyond the channels of the Cotting Burn and How Burn, the outline is very narrow and does not extend a significant distance from the watercourses channels. 13.63 The EA has records of Morpeth flooding in 1963, 1967 and 2008. The EA has no records of flooding along the Cotting Burn and How Burn within the study area. However, NCC are aware of flooding occurring in the lower reaches of the Cotting Burn in 2009, where it is culverted.
Flooding from the Sea 13.64 The study area is located approximately 10km to the west of the North Sea, at above 50m AOD. None of the watercourses detailed under river flooding are tidally influenced as they flow through the study area and based on the EA Flood Map (Appendix 13.5) the study area is not located within a tidal floodplain. AECOM A1-SENSLR: MNB – Environmental Impact Assessment – Volume 2: Environmental Statement 13-24
13.65 The risk to the study area from sea flooding is therefore considered to be low, and the proposed Morpeth Northern Bypass should not have an effect on the risk from sea flooding. Flooding from the sea has therefore not been considered in the Identification of Effects Section.
Flooding from Land (i.e. surface water and overland flow) 13.66 The topography of an area affects flooding from land, as does drainage systems and the presence of development. 13.67 The study area is predominantly agricultural. Where land is used for agricultural purposes, land drainage systems are usually installed and were also observed during the site visit. The former Pegswood colliery site has recently had an extensive field drainage system installed. The presence of drainage systems indicates that the study area is likely to be well drained. 13.68 Based on the general topography of the area, any overland flow would be directed into the Cotting Burn and How Burn. This reduces the susceptibility of the study area to flooding from the land. 13.69 The risk to the study area from flooding from land is therefore considered to be low.
Flooding from Groundwater 13.70 Information on the hydrogeology of the area was provided in the Hydrogeology Baseline Section. As detailed in this section, the study area is underlain by carboniferous bedrock overlain by glacial deposits of clay sand and gravels. Groundwater monitoring indicates that groundwater levels are close to the base of the glacial deposits and similar to water levels in the local watercourses. During the site visit, water levels within the watercourses in the study area were observed to between 1 and 2m below surrounding ground levels. Low groundwater levels were measured in the Carboniferous bedrock. 13.71 Based on evidence that groundwater levels are not high within the study area, the risk to the study area from groundwater flooding is considered to be low. There are also no known instances of groundwater flooding occurring within the study area. 13.72 Thus since groundwater levels are low, the operation phase should not adversely affect groundwater flooding. There is however the potential for groundwater to be a risk source during construction including the potential for excavations during the construction phase to have an effect on groundwater flooding, and this is considered in the Construction Section of the Identification of Effects Section.
Flooding from Sewers and Water Mains 13.73 Asset plans were obtained from Northumbrian Water. Based on the asset plans obtained, there are a network of public sewers and water mains in the Morpeth area. The proposed bypass will cross a public rising water main that runs along the A192, a public trunk main that runs to the west of the Fulbeck Grange area and a private water main that serves the Fulbeck Grange area. AECOM A1-SENSLR: MNB – Environmental Impact Assessment – Volume 2: Environmental Statement 13-25
13.74 There are no known records of sewer or water main flooding within the study area, and there are also no known problems with local water main or sewer network that pose a flood risk. Furthermore, Northumbrian Water maintains their assets, so the probability of an asset failing is low. The risk to the study area from sewer and water main flooding is therefore considered to be low.
Flooding from Other Artificial Sources (i.e. reservoirs, canals, lakes and ponds, excluding sewers and water mains) 13.75 The proposed bypass does not cross any large artificial water bodies, and there are no reservoirs or canals located within close proximity of the study area. There are a number of ponds located within the study area, predominately in the north west of the study area. The Pegswood Community Park pond is the largest artificial water body within the study area, and is located approximately 350m to the north east of the proposed bypass route. 13.76 During the site visit, the water level in the Pegswood Community Park pond was observed to be well below the bank. The water level within the pond is managed, and there is an overflow from the pond that connects into the How Burn (via the How Burn Tributary). In the event of the capacity of the pond being exceeded, any over flow would be directed to the How Burn. Based on the level freeboard available the within the Pegswood Community Park pond, the probability of the Pegswood Community Park overflowing is considered low. 13.77 There are two small ponds to the south of Pegswood Community Park pond, which form part of the overflow route to the How Burn as shown in Figure 13.2. The contour lines within the Environment Agency’s Risk of Flooding from Rivers and Sea online map shows that the How Burn tributary traverses low points in the topography of the area. Topographical survey information confirms the existing ground level of the two small ponds is lower compared to those of the surrounding area. Based on this assessment, the overland flow route from Pegswood Community Park pond to How Burn can be considered to start from the south western outfall of the community park pond into the How Burn Tributary via the two small ponds and terminating upon connection to How Burn. 13.78 The overflow route of Pegswood Community Park pond will be maintained under the proposed scheme. The proposed bypass will cover the upstream pond, and the second downstream pond will be reduced in size as part of the construction of the bypass. The proposed scheme includes the provision of a new upstream pond with a footprint of approximately 1800 m2 with the reduced second downstream pond having a footprint of 170m2. The footprint of the new upstream pond is approximately twice that of the combined footprint of the existing two small ponds. Assuming the proposed pond mimics the side slope, depth and freeboard allowances of the existing small ponds, this new upstream pond is able to provide sufficient volume compensation for the loss of footprint in the existing upstream pond and partial footprint loss of the second downstream pond. 13.79 The orientations of the proposed ponds are to remain the same as that of the existing (i.e. along the route of the How Burn tributary). The catchment of the two small ponds AECOM A1-SENSLR: MNB – Environmental Impact Assessment – Volume 2: Environmental Statement 13-26
encompasses a large majority the area to the north east of the ponds including the area surrounding Pegswood Community Park pond. The proposed bypass would effectively divide the catchment of the two small ponds into two segments; upstream of bypass and downstream of bypass. Although divided, the new overland flow regime mimics that of the existing with the majority of the catchment draining into the Pegswood Community Park pond and a section of How Burn tributary upstream of the small ponds. The runoff from the smaller catchment downstream of the bypass would be captured by the second smaller pond in the proposed scheme. The scheme should ensure that the current flow regime and flow rates through this portion of the tributary are maintained with the intention that the flood risk of the site and offsite is not affected. 13.80 Although the proposed bypass will affect the existing two small ponds, the changes proposed should not affect the risk of flooding from these small ponds should the current flow regime be maintained. The risk to the study area from flooding from other artificial sources is therefore considered to be low.
Drainage Proposals 13.81 The proposed road scheme will require the crossings of Cotting Burn, Fulbeck, How Burn, and a tributary of How Burn (See Figure 13.1). However, detailed design for the crossings of Cotting Burn and How Burn has been carried out taking into consideration potential environmental effects. 13.82 A buried structure will support the proposed bypass as it crosses How Burn. This structure will consist of a corrugated steel buried half arch with a span of 6m. The arch will be seated on a reinforced concrete slab with reinforced concrete walls which will be supported by piles. The corrugated steel buried structure will maintain a greater level of natural light through the structure than other possible structures. It is proposed to realign a short stretch of How Burn to the north of the alignment which will shorten the length of the required structure. Habitat improvement will also be carried out along the realigned watercourse at either sides of the crossing with willow spiling and a re-graded bank profile. A natural invert will be provided within the arch structure and will have a minimum thickness of 500mm. A temporary diversion of How Burn will be also required during construction works to allow for the construction of the permanent buried structure. 13.83 The proposed crossing at How Burn has been designed to allow the creation of a natural river bed by allowing a minimum 500mm depth of natural material on top of the base slab (i.e. natural invert). Additionally, any disturbed ground along the watercourse bank at either side of the proposed crossing, will be stabilised with willow spiling for enhanced river habitat. 13.84 Where the bypass crosses Cotting Burn the road will be elevated on an embankment. A buried structure will support the proposed bypass as it crosses Cotting Burn. This buried structure consists of a corrugated steel half arch structure with a span of 4m. The arch is 58m long and will be supported by a reinforced concrete slab with reinforced concrete walls, which in turn are supported on top of piles socketed into rock head. This crossing will require excavations for the installation of the piles and base slab. AECOM A1-SENSLR: MNB – Environmental Impact Assessment – Volume 2: Environmental Statement 13-27
13.85 The corrugated steel buried structure will maintain a greater level of natural light through the structure than other possible structures. Cotting Burn will be diverted during construction works to allow for the construction of the permanent buried structure. A haul road will cross over Cotting Burn using a temporary crossing. The foundations for both structures will be piled. 13.86 Two minor watercourses will be piped, as described in Chapter 2. 13.87 In addition, a number of new outfalls will be required. These have been summarised in Table 13.10.
Table 13.10 Approximate Location of Proposed Outfall (see Figure 13.1)
National Receiving Outfall Catchment Outfall Purpose Grid Ref. Water Number Road drainage from the A1 junction. Outfall via Benridge 1 NZ 174 870 1 drainage ditch starting at St. Leonards Lane. Burn Road drainage from the section east of the A1 Cotting Burn 2 NZ 186 870 2 junction to Northgate roundabout and from the Tributary A192. Road drainage from Northgate roundabout to St. 3 NZ 187 872 3 Cotting Burn George’s roundabout. Two outfalls at Road drainage from St. George’s roundabout to 4 NZ 193 875 4 Fulbeck just east of How Burn. And NZ 194 875 Road drainage from just east of How Burn to How Burn 5 NZ 206 874 5 Whorral Bank roundabout. Tributary 13.88 The installation of any new structure along the banks, or across a watercourse, will have a permanent localised effect on the watercourses through loss of bank habitat and potential erosion, in addition to secondary effects on fauna. The detailed design will need to take into account the water environment so that new structures are appropriate and environmentally sympathetic. 13.89 The scheme proposes a SUDS based approach for the treatment and attenuation of road runoff, avoiding the use of mechanical treatment facilities where possible. Runoff from the proposed bypass will be drained predominantly into grassed swales running alongside the carriageway and only into pipes where there are restrictions on the use of swales. Swales will be 1.5m wide 400mm deep and semi-circular shape. The swales are designed to convey the flow towards outfalls to nearby watercourses, although there will be a small amount of infiltration into the ground where the swales are not on embankment. Where on an embankment infiltration will be prevented by increasing the clay content of the swale soil matrix or by providing a geotextile liner (subject to detailed design). In areas other than those with a low permeability similar measures may be required to prevent highway contaminants seeping into the Secondary Aquifer (although the majority of the site is underlain by relatively impermeable Glacial Till and Clays). This is considered to be most AECOM A1-SENSLR: MNB – Environmental Impact Assessment – Volume 2: Environmental Statement 13-28
significant between St. George’s Roundabout to the east of How Burn Embankment where Fluvial-Glacial Sands and Gravels are present in the upper superficial geology (i.e. Chainage 1850 to 2700). However in certain locations drainage will flow to larger storage/carrier ditches (Benridge Burn and St. George’s). Kerbs and gulleys will be used to collect the runoff at the roundabouts, and the slip roads will be drained over the edge into swales. Both will be piped to the necessary outfall or ditch. Chambers with sumps (catchpits) will be used on piped sections and at the end of swales (where runoff has to be drained into another ditch or piped section) to trap particulates. 13.90 The road will drain via swales to a drainage ditch and settlement (dry) ponds or wet ponds (ponds will be lined) prior to outfalls to receiving watercourses, except Catchment 3 where no pond is proposed. However, in some locations (mainly cuttings) swales may not be possible and pipes will be used to convey flows. Table 13.11 summarises the treatment to be provided for each outfall:
Table 13.11 Proposed outfall location and purpose (see Figure 13.1)
National Grid Receiving Outfall Catchment Treatment Ref. Water Number Runoff will be collected by swales adjacent to the carriageway which will discharge into a new drainage ditch to convey flows across green Benridge 1 NZ 174 870 1 fields to an outfall to Benridge Burn. An Burn overspill storage pond (grassed/dry pond) will be located close to this outfall to attenuate flows during flood events. Road runoff from the new road will be collected by swales and runoff from new Northgate roundabout and existing A192 by kerb and gullies. Flows will be carried towards the Cotting Burn 2 NZ 186 870 2 existing highway drainage. Outfall from the Tributary existing manhole into Cotting Burn tributary will be via a dry overflow basin with measures to reduce mobilisation of sediments. Road runoff will be collected by grassed swales NZ 187 872 before discharging into Cotting Burn. Sumps 3 3 Cotting Burn will be located at strategic locations to assist with the removal of particulates. Runoff from the east of St. George’s Two outfalls at Roundabout will drain into a wet pond before NZ 193 875 discharging into Fulbeck. Runoff in this 4 4 Fulbeck and catchment from south of St. George’s NZ 194 875 Roundabout will drain via the second wet pond only. Grass swales will convey road runoff to a new dry overflow basin north of the bypass which How Burn 5 NZ 206 874 5 will discharge treated flows back under the road Tributary and via the existing wet pond into the tributary of How Burn. AECOM A1-SENSLR: MNB – Environmental Impact Assessment – Volume 2: Environmental Statement 13-29
Identification of Effects 13.91 If not adequately controlled, effects from construction and operation may have a number of effects on the water quality of watercourses within the study area.
Construction Phase
Surface Water 13.92 During the construction phase, temporary effects on water quality could occur if good practice mitigation measures are not implemented on site. The potential effects of the proposed scheme on surface water quality could include: Water pollution from silt-laden runoff if, allowed to drain directly into watercourses untreated; Chemical/fuel spillages and leaks from plant and machinery, and from chemicals and other pollutants (e.g. cement, paints, etc.) used/stored on site; Localised erosion of banks and beds of watercourses when works are required in their proximity (e.g. construction of new crossings); and Inappropriate disposal of foul water from the construction site. 13.93 If not adequately controlled, effects from construction may have a number of short-term effects on the quality of watercourses within the study area. The proposed bypass will cross Cotting Burn, Cotting Burn tributary and How Burn, which ultimately flow into the River Wansbeck which has excellent water quality and contains a significant fish population (in particular supports a large salmonid population downstream of Morpeth). Without appropriate mitigation measures, silt laden runoff, erosion of beds and banks, and chemical spills could have adverse effects. These effects could propagate downstream to the River Wansbeck where the effects could be more significant. 13.94 Silt-laden runoff is generated principally by rainfall onto land where surface vegetation has been removed and the ground compacted, preventing infiltration. Other sources of silt- laden runoff come from the use of water as part of construction works (e.g. vehicle washings, runoff from stockpiles, works next to and in watercourses and pumping from excavations). High levels of suspended sediment in water can suffocate fish by blocking their gills, can remove essential oxygen from the water, and can adversely affect plants, animals and insects living in water by stopping sunlight reaching them. 13.95 The greatest risk is where works are carried out near watercourses, or on steep slopes which will encourage overland flow. There is also the risk from existing drains and other conveyors of silt laden runoff to watercourses. The proposed construction work will be carried out in accordance with good practice. The Construction Environmental Management Plan (CEMP) will make reference to mitigation measures to prevent/reduce the formation of silt-laden runoff, to protect watercourses (by using earth bunds, silt fences etc.) and to intercept and filter runoff prior to disposal, either by spraying over grassed fields or via temporary discharges (under EA consent) into watercourses. These measures are set out in more detail in the “Mitigation” section of this chapter which AECOM A1-SENSLR: MNB – Environmental Impact Assessment – Volume 2: Environmental Statement 13-30
follows. Summary of the predicted magnitude of effect from silt pollution is presented in Table 13.12:
Table 13.12 Magnitude of Effect from silt pollution without mitigation
Importance Magnitude of Effect Without Mitigation Receptor River Wansbeck Very High Minor Adverse Cotting Burn and How Burn High Moderate Adverse Benridge Burn Medium Minor Adverse All other watercourses Low Moderate Adverse
13.96 During construction, fuel, hydraulic fluids, solvents, paints and detergents and other potentially polluting substances will be stored and/or used on site. Leaks and spillages of these substances could pollute the watercourses within the study area, and the River Wansbeck downstream if they are not managed accordingly. To allow such substances to enter a watercourse would be in breach of the Water Resources Act 1991. Therefore, measures to control the storage, handling and disposal of such substances will need to be put in place prior to and during construction. 13.97 The storage of potentially hazardous substances will be in accordance with the Control of Substances Hazardous to Health Regulations 2002 and the Control of Pollution (Oil Storage) (England) Regulations 2001. Construction works will take place following good practice as set out in the various documents listed in paragraph 13.159. This will include bunded fuel storage areas (minimum 110% storage capacity), designated refuelling areas isolated from surface runoff drainage, easily accessible spill kits and oil absorbent materials, and training for construction workers. As a result, it is unlikely that the storage of these substances will lead to pollution of Cotting Burn (and tributaries), How Burn (and tributary), Benridge Burn, and ultimately the River Wansbeck. Specific measures will be required for any plant operating close to watercourses. Summary of the predicted magnitude of effect from chemical spillages is presented in Table 13.13.
Table 13.13 Magnitude of Effect from chemical spillages without mitigation Receptor Importance Magnitude of Effect Without Mitigation River Wansbeck Very High Minor Adverse Cotting Burn and How Burn High Moderate Adverse Benridge Burn Medium Minor Adverse All other watercourses Low Moderate Adverse
13.98 Where crossings are proposed work will be required within Cotting Burn, and along the banks of this watercourse and How Burn. Culverting of minor watercourses will also be required in two locations. Construction works close to and within watercourses may lead AECOM A1-SENSLR: MNB – Environmental Impact Assessment – Volume 2: Environmental Statement 13-31
to erosion of the beds and banks, increasing suspended sediment. Where plant is used there is also the risk of small spillages of oil. Other activities may include the use of wet concrete, which is highly alkaline and toxic in the water environment. As a consequence of works close to and within watercourses, there may be effects on stream hydrodynamics and secondary effects on the aquatic riparian environment. Accordingly, any works close to or within a watercourse will need to be strictly controlled to prevent and minimise adverse effects on water quality (and therefore aquatic fauna/flora) or through physical changes (long term changes are considered under operational effects). All work will be controlled by good practice guidance including the EA’s Pollution Prevention Guidelines (PPGs) as set out in paragraph 13.159. Such works will require Flood Defence Consent from the EA, and where necessary a diversion will be used. Summary of the predicted magnitude of effect from erosion of bed and banks is presented in Table 13.14:
Table 13.14 Magnitude of Effect from erosion of bed and banks of watercourses without mitigation Magnitude of Effect Without Importance Receptor Mitigation Cotting Burn and How Burn High Moderate Adverse Benridge Burn Medium Minor Adverse All other watercourses Low Moderate Adverse
13.99 Foul water drainage from the construction site will be connected to the nearest public sewer. If this is not possible, portable toilets, etc. will be used. These will be regularly emptied by an appropriate contractor and disposed of at a suitable facility off-site. Construction site foul water will not be discharged into a watercourse under any circumstances. Therefore, the magnitude of this potential effect is considered to be negligible for all watercourses within the study area. Groundwater 13.100 Section 14.47 of Chapter 14 Geology and Soils confirms that ground investigation indicates that none of the proposed structures are underlain or affected by historical mine workings at a depth that could affect the integrity of the foundations. Therefore, compensation grouting of potential mine workings is not proposed as part of the scheme. 13.101 Four drainage basin ponds are proposed for the route. The drainage basin between West Lane End Farm and East Lane End Farm is located on alluvial deposits within an old stream bed, in continuity with the current tributary of Cotting Burn. The underlying till is not considered to be water bearing on EA mapping and no effect on groundwater is anticipated. The significance of effect on the two aquifers is neutral for this drainage basin, for both construction and operational phases. Two drainage basins are planned south of the St. George’s roundabout. These are adjacent to a spring, conjectured to be draining sand and gravel deposits to the north. The underlying till is not considered to be water bearing on EA mapping and negligible effect on groundwater is anticipated. The significance of effect on the two aquifers is AECOM A1-SENSLR: MNB – Environmental Impact Assessment – Volume 2: Environmental Statement 13-32
neutral for these two drainage basins, for both construction phase and operational phase. A drainage basin is proposed at Pegswood Moor at the head of an existing pond conjectured to be receiving base flow from underlying sand and gravel deposits. The drainage basin encroaches onto the area of the former Pegswood Moor Opencast site. The groundwater vulnerability is considered on EA Mapping to be high (H3) due to the presence of coarse textured or moderately shallow soils associated with sand and gravel deposits. Opencast mining has removed till in this area, which has mitigated the risk of polluted water entering the Secondary A Drift Aquifer. Spills during construction may enter the opencast backfill and percolate down to the Coal Measures aquifer. Magnitude of effect is considered to be negligible to the sand & gravel aquifer and minor adverse to the Coal Measures aquifer during the construction phase and negligible during the operational phase. The significance of effect for this drainage basin on the Carboniferous bedrock aquifer, and for the sand and gravel aquifer, is slight adverse for the construction phase without mitigation and neutral for the operational phase. 13.102 The route crosses areas of made ground in the A1 embankment and the Pegswood Moor Opencast site. Disturbance of these soils will have a neutral significance for groundwater, due to a negligible magnitude of effect by virtue of low leachability and uncontaminated status. See Chapter 14 Geology and Soils for further details. 13.103 Groundwater levels within the drift and underlying bedrock are below the road pavement and therefore there is a neutral significance of effect on groundwater levels. During construction there will be bridge footings works which are likely to intercept the sand and gravel aquifer. Groundwater exclusion may be required in these areas, but as the water flow from the sand and gravel deposits is channelled along the watercourses above the less permeable till there is little effect anticipated on groundwater levels, and any effects will be highly localised. Control measures for bridge footings will have a neutral significance for groundwater.
Flood Risk Flooding from Rivers 13.104 As detailed under baseline conditions, the proposed bypass crosses four tributaries of the River Wansbeck; Cotting Burn, Fulbeck (tributary of Cotting Burn), How Burn and a tributary of the How Burn. 13.105 There is, therefore, the potential for the construction of the bypass to effect these watercourses and subsequently cause flood risk. For example, the construction process could cause blockages within the watercourses and/or effect upon the floodplain of these watercourses and reduce their floodwater storage capability. 13.106 Based on the size and characteristic of these four watercourses (e.g. steep channels), the baseline risk of flooding from these watercourses and the rural nature of the study area, any effect on river flooding during construction is considered to be minor adverse.
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Flooding from Land (i.e. surface water and overland flow)
13.107 The construction of the bypass could potentially affect the agricultural drainage systems within the study area and change overflow flow routing in the area. The construction of the bypass could also potentially increase the rate of surface water runoff, if impermeable areas are temporarily increased. 13.108 Based on the rural nature of the study area, any effect on flooding from the land is considered to be minor adverse during construction.
Flooding from Groundwater 13.109 Groundwater levels within the drift and underlying bedrock are below proposed road pavement level therefore there is perceived to be no risk of flooding at the operational stage. During construction there will be bridge footings works which are likely to intercept the sand & gravel aquifer. There is, therefore, the potential for localised groundwater flooding to occur at the bridge footing works as the footings will be going down to the groundwater level of 2m below the surface, if appropriate groundwater exclusion construction techniques are not implemented. 13.110 Based on the fact groundwater is only likely to be encountered at the bridge footings works during construction, the potential effect on groundwater flooding, if appropriate construction techniques are not implemented, is considered to be minor adverse.
Flooding from Sewers and Water Mains 13.111 If the construction process does not take into account the location of existing water mains and sewers, there could be a risk of flooding from water mains and sewers during construction. The effect would be a short term moderate adverse effect. 13.112 Foul water services need to be provided during construction. As previously detailed, the preferred option is to connect foul water services to the nearest public sewer. If this is not possible portable toilets etc. will be provided. The foul services should be maintained by a professional contractor and removed regularly from the site for appropriate disposal. If these services are not maintained appropriately there is the potential for foul water flooding to occur. Based on the rural nature of the study area, and the temporary nature of the risk, the potential effect on foul water flooding is considered to be minor adverse.
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Flooding from Other Artificial Sources (i.e. reservoirs, canals, lakes and ponds, excluding sewers and water mains) 13.113 Flood risk onsite and offsite may be affected if sufficient pond volume compensation is not provided during construction for the two small ponds to the south of Pegswood Community Park pond which form part of the overflow route from to the How Burn. 13.114 Based on the size and function of the two small ponds, any effect on flooding from other artificial sources is considered to be minor adverse during construction.
Operational Phase
Surface Water 13.115 During the operational phase the following effects could occur: Potential for morphological changes to the watercourses as a result of new crossings, structures etc. Water pollution from routine road runoff that will contain vehicle derived pollutants (gaseous and particulate materials, oil and petrol etc.) deposited on the highway; and Spillages of polluting substances (e.g. petrol, acid, foodstuff, etc.) from traffic related accidents.
Morphological Changes 13.116 During the operational phase of the proposed bypass there is the potential for morphological changes to How Burn, which will be diverted for a short stretch, and to other watercourses from the installation of new structures. Table 13.10 describes the five new outfalls that will need to be constructed to convey runoff to the initial receiving watercourse. In addition, there will be new corrugated buried structures across How Burn and Cotting Burn. 13.117 The new structures have taken into account “green bridge” concepts where possible to minimise morphological and secondary effects on aquatic ecology and water quality. Natural banks and beds in both How Burn and Cotting Burn will remain unaffected. Although a small section of How Burn will be diverted, the realigned watercourses will be improved with “natural” banks constructed of willow spiling and faggots, alternating along stream alignment and regraded bank profile, to promote biodiversity. Where these structures and new outfalls are located, the habitat replaced will be permanently lost and the structure will influence the immediate surroundings, potentially resulting in some long term minor erosion. The siting of new outfalls, subject to detailed design and consent from the EA, also will seek to minimise any adverse effects. Although five new outfalls are proposed, they are spread across four separate watercourses (see Table 13.10) and therefore any effects will be very localised. There are no outfalls proposed directly into the channel of How Burn. As a result, a permanent adverse effect will occur of minor adverse magnitude to How Burn, Cotting Burn, and its tributaries.
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Routine Runoff Assessment 13.118 A quantitative assessment has been carried out in accordance with HD45/09, using the HAWRAT Excel based interface, in order to predict the effects on receiving surface watercourses of dissolved and sediment-bound pollutants contained within highway runoff. The results have been summarised in Appendix 13.6.
Assessment without Mitigation 13.119 Ponds and swales are proposed prior to all the outfalls, which will provide a degree of treatment and attenuation of road runoff. However, the initial routine runoff assessment was followed without taking into account any proposed mitigation measures (Table 13.6.1 in Appendix 13.6). The results (without mitigation) are as follows: - All outfalls pass the short term effect assessment for dissolved pollutants. - The predicted annual average concentrations for dissolved copper and zinc were well below the WFD. Based on the assessments, it is concluded that the operation of the scheme is compliant with the WFD. - In terms of sediment bound pollutants the initial assessment (Tier 1) concluded that outfalls 1, 2 and 3, and the aggregated outfalls 2+3 could result in extensive sediment accumulation. 13.120 As failures were predicted on the sediment-bound assessment for outfalls 1, 2, 3 and 2+3 during Tier 1, a Tier 2 assessment was required for these outfalls. Unfortunately, no survey data was available for the tributary of Cotting Burn (Outfall 2) therefore no Tier 2 assessment was possible and the need for mitigation was determined based on the Tier 1 results. 13.121 The Tier 2 assessment predicts that sediment is unlikely to accumulate within Benridge Burn (outfall 1) and Cotting Burn (outfall 3).
Assessment with Mitigation 13.122 Table 13.6.2 in Appendix 13.6 presents a summary of the Step 3 - Tier 1 and 2 results for those outfalls where failures were predicted, The proposed drainage includes dry/wet ponds, as well as swales, prior to each of the outfalls, to regulate the flow and provide a degree of treatment and attenuation prior to discharge to the watercourses. Step 3 of the HAWRAT assessment predicts the amount of treatment necessary for those outfalls failing to achieve the required standards. Table 13.15 presents the mitigation measures proposed/required to achieve the required standards. AECOM A1-SENSLR: MNB – Environmental Impact Assessment – Volume 2: Environmental Statement 13-36
Table 13.15 Summary of the Results from the Step 3 Routine Runoff Assessment Percentage of Minimum mitigation percentage of Additional Proposed required for mitigation measures Outfall (1) measures dissolved required for required? pollutants sediment Individual Swales and dry None None None 1 Benridge Burn overflow pond
2 Cotting Burn Swales and dry None 30% None (Cotting Burn overflow pond Tributary) Swales and 3 Cotting Burn None None underground None storage
4 Cotting Burn Swales and wet None None None (Fulbeck tributary of overflow pond Cotting Burn) Swales and wet 5 How Burn None None None (How Burn Tributary) ponds Aggregated outfalls for solubles Swales and dry 2+3+4 Cotting Burn None None None overflow ponds Aggregated outfalls for sediment Swales and dry 2+3 Cotting Burn None 60% None overflow ponds (1) Location used in the assessment. In brackets, proposed location of the outfall. 13.123 Settlement for sediments is required in Cotting Burn (outfall 2 and 2+3) to meet adequate standards. Grassed swales are proposed which can provide more than 60% sediment removal (HA103/06). This treatment will be supported by other facets of the drainage system e.g. catch pits, plus a degree of natural treatment in the initial receiving minor watercourse. 13.124 At this stage (Step 3) the assessment has only been carried out on those outfalls where treatment/attenuation is required to meet the necessary standards. According to the initial assessment (assessment without mitigation) the other outfalls (outfall 1, 4 and 5) are unlikely to cause short or long term adverse water quality effects in the watercourses during the road operation. This is most likely due to a combination of factors (e.g. low traffic flows, relatively high dilution and velocities to distribute sediments). Nevertheless, the River Wansbeck and associated tributaries are salmonid rivers under the Fish (Consolidated) Directive, and thus particularly sensitive to sediment pollution. The AECOM A1-SENSLR: MNB – Environmental Impact Assessment – Volume 2: Environmental Statement 13-37
proposed drainage strategy is based on SUDS techniques and includes multiple barriers to intercept and remove sediment from routine runoff (including swales, drainage ditches, catch pits, and settlement basins/ponds). There are also components of the drainage system that utilise biological and physico-chemical processes to treat dissolved pollutants found in the runoff. 13.125 The overall significance of effects from routine runoff is negligible.
Groundwater 13.126 Runoff will initially be collected and conveyed via grass swales either side of the bypass and the A1 (through the junction with the bypass). These swales have been designed to treat runoff and convey flows rather than encourage infiltration, although it is expected that some infiltration will take place. A Method C Groundwater assessment has been undertaken for five typical strata that may be encountered throughout the study area and these are presented in Tables 13.6.4 to 13.6.8 of Appendix 13.6 in Part 3 of the ES. 13.127 The upper superficial strata from the western end of the scheme (including the A1 Junction) through to St. George’s Roundabout, and from east of How Burn (approximately CH2700) to Whorral Bank Roundabout (except a small area around the Pegswood Moor Tributary) consist mainly of three strata types: B1 (Upper Glacial Till), B2 (Laminated Clay), and D2 Made Ground – Cohesive Clay Fill). The Method C Groundwater Assessment predicts only a low risk to groundwater in these areas (due to limited infiltration potential) and therefore any seepage through the substrate of the swale will be limited and no effect is predicted to the Secondary A aquifer and the streams its supports. 13.128 Intermittently between St George’s Roundabout (approximately CH 1850), at approximately CH1575 to CH 1650 (north of Fulbeck) and to just east of How Burn (approximately CH 2700) the Secondary A aquifer (strata b3) is exposed at the surface and infiltration from the swales is likely to be greater. In these locations a medium risk to groundwater is predicted by the Method C Groundwater Assessment. For much of the section between St George’s Roundabout to How Burn the bypass is raised on embankment and it is unlikely that direct infiltration will be allowed. Subject to detailed design it is proposed that the soil matrix for the swales could include a greater clay content to reduce any infiltration, or if necessary a liner could be provided. When this is taken into account with the potential significant dilution (of residual dissolved pollutants not removed by the swale vegetation and soil matrix) of the small proportion of runoff that may infiltrate to the superficial Secondary aquifer, only a minor adverse effect is predicted. 13.129 Between approximately CH 1575 to CH 1650 the bypass is in cutting. Regardless, infiltration will be reduced in by altering the swale soil matrix or by providing a liner to prevent any adverse effect on the Secondary Aquifer. 13.130 In the same location, the distance over which any infiltration would need to travel (during which dilution will take place) is considered to be sufficient to mitigate any adverse effect on How Burn. It should be remembered that the Method A assessment of routine runoff on How Burn assumed all runoff was discharged and under these circumstances, and without mitigation, no adverse effect was predicted. AECOM A1-SENSLR: MNB – Environmental Impact Assessment – Volume 2: Environmental Statement 13-38
13.131 For a small section of the bypass where it crosses the Pegswood Moor Tributary on an embankment there is also a medium risk to groundwater (and the stream it supports) due to the presence of alluvial sand, gravel and clays. However, since the bypass will be on an embankment in this location, through which direct infiltration is unlikely to be allowed (controlled by either a liner, increased clay content of swale soil matrix etc. which is subject to detail design) runoff is likely to be conveyed to the proposed attenuation ponds before being discharged to the minor watercourse. In areas other than low permeability wet and dry ponds should be lined to prevent them drying out and to enable them to act as spillage containment if required, however unlikely a spillage is to occur. Assessment of the potential effect on the tributary has already been considered above.
Dealing with Low Flow Uncertainty 13.132 There is some uncertainty with regards to the methods that can be used to predict Q95 flows within receiving watercourses, and no method is entirely reliable. This is important because low flow is one of the more sensitive input parameters into HAWRAT. A prediction of natural Q95 using a method devised by the Institute of Hydrology (see Appendix 13.2) has been used in this assessment. In order to account for error in its prediction, the assessment for each outfall was re-run applying a 25% reduction to the predicted Q95 values. The results (again without mitigation measures being considered) for the short term dissolved pollutant assessment were unchanged. Although predicted concentrations for long term dissolved pollutants in the receiving watercourse increased, these were still well below WFD EQS’s. Finally, although the reduction in Q95 led to the accumulation of sediment in Benridge Burn and Cotting Burn, the accumulation was not significant and the treatment measures proposed would be adequate to filter the runoff before it is ultimately discharged into either watercourse.
Effect on Minor Watercourses 13.133 The assessment is focused on the potential effect on the more important watercourses (i.e. Benridge Burn, Cotting Burn and How Burn) and not on the small minor watercourses and drains that have little ecological, recreational and economic value, into which runoff initially will flow (i.e. outfall 2 into a field drain at East Lane End Farm, outfall 4 into Fulbeck tributary of Cotting Burn, and outfall 5 into the small hill side drain from the community pond near Whorral Bank Roundabout). It is inherently difficult to assess the effect on these minor watercourses due to the large errors associated with estimating low flows, as well as uncertainty over the reliability of flow. However, an attempt has been made to apply HAWRAT to provide an indication of effect. The results show that without treatment, sediment could accumulate and the runoff specific threshold for copper could be exceeded, although with the proposed treatment measures any effect should be adequately mitigated.
Spillage Risk Assessment 13.134 There is also a risk that a significant road traffic accident will lead to a major spillage that could cause a serious pollution incident should it be discharged to a local watercourse. AECOM A1-SENSLR: MNB – Environmental Impact Assessment – Volume 2: Environmental Statement 13-39
The Spillage Risk Assessment (see Appendix 13.2 for methodology) predicts return periods greatly exceeding the 100 year return period for non-sensitive sites and the 200 year return period threshold for sensitive sites without mitigation. With the proposed ponds and swales in all five catchments to provide containment in the event of a spillage, the return periods are further increased. Therefore, there is a very low risk that an accident along this stretch of road will lead to a serious pollution incident. A negligible effect is therefore predicted on all receiving watercourses.
WFD Programme of Measures 13.135 Within the Northumbria RBMP a Programme of Measures has been set out to address the key pressures in the region. The WFD identifies the key pressures for each water body and sets out a set of measures to reduce these. The proposed road scheme has been appraised against the proposed actions to achieve the WFD target, taken from Annex C of the Northumbria RBMP. Only operational effects have been considered because construction effects are temporary and will therefore not have an effect on WFD objectives. 13.136 Any relevant measures for the Northumbria River Basin District have been considered. There are measures to promote the use of SUDS and to avoid the migration of fish species, both of which have been considered in the design of the new road itself, and the structures that will cross the existing watercourses. There are also measures to promote ecological enhancement and to achieve the WFD requirements for hydromorphology. The new road will be compliant with these objectives. More details are presented in Table 13.7.1 in Appendix 13.7. 13.137 Overall, it is considered that the proposed road scheme is compatible with actions proposed in the Northumbria RBMP to improve the quality of the water environment, and will not cause deterioration or prevent watercourses within the study area from achieving its WFD target.
Flood Risk
Flooding from Rivers 13.138 The bypass crosses four watercourses; Cotting Burn, Fulbeck (tributary of Cotting Burn), How Burn and a tributary of the How Burn. There is therefore the potential for the operation of the bypass to affect these watercourses and subsequently chance/probability of flood risk. For example, the bypass could affect the floodplains of these watercourses and reduce their floodwater storage capability. 13.139 There is also the potential for the proposed watercourse crossings to cause afflux. Afflux is the rise in water level on the upstream side of a structure or obstruction, and is caused when the effective flow area at the structure or obstruction is less than the flow area of the river or stream immediately upstream. The structure or obstruction therefore impedes flow, causing the upstream water level to increase and the downstream water level to decrease. An additional problem relates to the over sizing of the new structures. If a larger AECOM A1-SENSLR: MNB – Environmental Impact Assessment – Volume 2: Environmental Statement 13-40
structure is built, than currently exists, this could pass more flow downstream and have a detrimental effect downstream. 13.140 A hydraulic assessment (Appendix 13.3) was undertaken to assess the potential effects of the bypass on the Cotting Burn and How Burn. Based on the size and characteristics of Fulbeck and the How Burn tributary, a hydraulic assessment was not undertaken of potential effects on these watercourses. 13.141 The proposed bridge crossing designs were provided by NCC. Based on the hydraulic assessment undertaken, both proposed structures cause afflux. However, in both cases the afflux is relatively small and reduces to zero within 60m upstream of the proposed structures. In addition, the flow is within the channel upstream of the proposed structure at both locations for the 1 in 100 year event. 13.142 The hydraulic assessment also determined that the loss of floodplain storage, as a result of the proposed crossing, was insignificant. This was due to the steep nature of the two watercourses, and the fact that the flow is within the channel upstream of the proposed structure at both locations for the 1 in 100 year event. 13.143 As detailed above, a hydraulic assessment of potential effects on Fulbeck and the How Burn tributary has not been undertaken. Based on the hydraulic assessment of Cotting Burn and How Burn watercourse crossings, the proposed bypass is also considered to have a minimal effect on flooding from Fulbeck and the How Burn tributary during operation. Similar watercourse crossings are proposed on the Fulbeck and the How Burn tributary, which should have a minimal effect on floodplain storage and afflux. 13.144 The potential effect of the bypass on river flooding is therefore considered to be negligible with the bridge crossing designs currently proposed. No mitigation measures are therefore considered necessary.
Flooding from Land (i.e. surface water and overland flow) 13.145 The proposed bypass will increase the proportion of impermeable areas in study area, as the bypass route runs through greenfield land. The increase in impermeable areas will increase the rate of surface water runoff in the study area, if an appropriate drainage system is not installed. The bypass could also potentially have an effect on the local agricultural drainage systems, and change overflow flow routing in the area, if an appropriate drainage system is not installed. 13.146 If an appropriate drainage strategy is not implemented for the bypass, the bypass will increase the risk of flooding from the land. Based on the rural nature and topography of the study area (which generally directs overflow into the network of local watercourses), the potential effect of the bypass on flooding from the land is considered to be minor adverse, if an appropriate drainage system is not installed.
Flooding from Sewers and Water Mains 13.147 The proposed bypass will cross a public rising water main that runs along the A192, a public trunk main that runs to the west of the Fulbeck Grange area and a private water AECOM A1-SENSLR: MNB – Environmental Impact Assessment – Volume 2: Environmental Statement 13-41
main that serves the Fulbeck Grange area. It may therefore be necessary to divert or upgrade these assets to cope with the weight of vehicular loads. If these assets are not diverted or upgraded there is the potential, during the operational phase, to increase the risk of flooding from sewers and water mains. The potential effect of flooding from sewers and water mains is considered to be moderate adverse.
Flooding from Other Artificial Sources (i.e. reservoirs, canals, lakes and ponds, excluding sewers and water mains) 13.148 The proposed scheme includes the provision of a new upstream pond with a footprint of approximately two times that of the combined footprint of the existing two small ponds. Assuming the proposed pond mimics the side slope, depth and freeboard allowances of the existing small ponds, this new upstream pond is able to provide sufficient volume compensation for the loss of footprint in the existing upstream pond and partial footprint loss of the second downstream pond. 13.149 The potential effect of the bypass on flooding from other artificial sources is therefore considered to be negligible with the pond footprint currently proposed. No mitigation measures are therefore considered necessary.
Mitigation 13.150 If not adequately controlled, effects from construction activities may have significant short term effects on the surface water environment. Appropriate measures will need to be put in place prior to, and during, the construction phase of the proposed scheme in accordance with legislative requirements and good site practice guidance.
Construction Phase
Surface and Groundwater 13.151 Procedures and mitigation measures to be adopted during the construction phase are recommended to be documented in a CEMP. Construction work will require a number of separate consents and licences from the EA, which are in part required to prevent adverse effects on the water environment. These include: The discharge of trade effluent (including treated site runoff) into a controlled water will require a Water Activity Permit under the Water Resources Act 1991 and the Environmental Permitting Regulations 2010; and Flood Defence Consents under the Land Drainage Act 1991 for works along Main Rivers where they are required in, over, under, or within 8 m of the bank top that could affect the flow. 13.152 Applications for appropriate permits as described above will be made following detailed design. All consents and licences will be in place prior to commencement of any works. The works will be carried out in accordance with any conditions imposed by these consents and licences.
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13.153 The CEMP will also make reference to the following good practice guidance documents: CIRIA Report 697 (2007) The SUDS Manual; CIRIA Report 648 (2006) Control of Water Pollution from Linear Construction Sites; CIRIA Report 532 (2001) Control of Water Pollution from Construction Sites; CIRIA Report 142 (1994) Control of Pollution from Highway Drainage Discharges; NETREGS (June 2010) Concrete and Grout http://www.netregs.gov.uk/netregs/businesses/construction/62407.aspx; WRAP/EA (undated) A technical report on the manufacture of products from pulverised fuel ash (PFA) and furnace bottom ash (FBA); and EA Pollution Prevention Guidelines (PPG), the most relevant being: o PPG 1 – General Guide to the Prevention of Pollution (no date); o PPG 2 – Above Ground Oil Storage Tanks (February 2004); o PPG 3 – Use and Design of Oil Separators in Surface Water Drainage Systems (April 2006); o PPG 5 – Works or Maintenance in, or Near Watercourses (October 2007); o PPG 6 – Working at Construction and Demolition Sites (no date); o PPG 7 – Refuelling Facilities (August 2004); o PPG 8 – Safe Storage and Disposal of Used Oils (February 2004); o PPG 13 – Vehicle Washing and Cleaning (July 2007); o PPG 18 – Managing Fire Water and Major Spillages (no date); o PPG 21 – Pollution Incidence Response Planning (February 2004); o PPG 22 – Dealing with Spillages on Highways (no date); and o PPG 23 – Maintenance of Structures Over Water (no date). 13.154 The mitigation measures that will be developed in the detailed design phase to control silt- laden runoff and spillages are described below. 13.155 A Silt Management Plan will be produced which will include: Works that are likely to generate silt-laden runoff (e.g. earthworks and excavations) will be undertaken preferentially during the drier months of the year; Site compounds and stockpiles will be located away from water bodies; The drainage system will be developed to prevent silt-laden runoff from entering surface water drains and ponds without treatment (e.g. earth bunds, silt fences, straw bales, or proprietary treatment) under any circumstances; Where possible an 8m buffer strip of existing vegetation will be maintained alongside watercourses. Where this buffer zone is necessarily breached (i.e. at crossings) the design and construction of structures will be environmental sympathetic; Any work along watercourses will be isolated to prevent silt propagating downstream; Earth stockpiles will be seeded as soon as possible, covered with geotextile mats or surrounding by a bund to minimise the risk of sediment-rich runoff; Mud will be controlled at entry and exits to the site using wheel washes and/or road sweepers; AECOM A1-SENSLR: MNB – Environmental Impact Assessment – Volume 2: Environmental Statement 13-43
Tools and plant to be washed out and cleaned in designated areas within the site compound where runoff can be isolated for treatment before discharge to watercourse/ground or sewer under appropriate consent; If required, vehicles will cross watercourses at designated crossing points only, which will include protection to minimise silt-laden runoff/mud from entering the watercourse; Debris and other material will be prevented from entering watercourses; Construction SUDS (such as settlement lagoons or other temporary attenuation) to be used during construction if necessary; Diversion of minor watercourses will be carefully managed to prevent suspension of silt (or contamination by other pollutants); and Discharges to watercourses and ponds will only be carried out under a consent from the EA.
Storage and Spillage Emergency Response Fuel and other potentially polluting chemicals will be stored in a secure impermeable and bunded storage area (minimum capacity 110%); Refuelling of plant will take place in a designated area at the site compound only; Maintenance of vehicles will take place at designated areas in the site compound; Fixed plant will be self bunded; Mobile plant will be in good working order, kept clean and fitted with drip trays where appropriate; Spillage kits and oil absorbent material will be carried by mobile plant and located at vulnerable locations (e.g. crossings of land drains and ditches); The site will be secured to prevent vandalism that could lead to a pollution incident; Designated concrete wash out areas will be constructed in accordance with good practice guidance and will be clearly identified and used; Construction workers will be trained to respond to spillages; An Emergency Response Plan will be prepared; and Construction waste/debris will to be prevented from entering any water body.
Work in and Adjacent to Watercourses 13.156 Potential adverse effects are greater where works are in and adjacent to watercourses. Such work will be minimised where possible, but where it is essential it will be carried out in accordance with the EA’s PPG 5 and Flood Defence Consent. In particular: Affected area to be kept to a minimum; It would be preferable if works were carried out during dry weather; Temporary crossings have been avoided where possible. However, the temporary haul road over Cotting Burn will be subject to the same design controls as permanent structures. Drawing HE092631/2/A197/B3/07 in Appendix 2.1 illustrates the proposed design for this crossing which will prevent vehicles travelling through the Burn directly; Works in the channel carried out in a bunded, dry working space with any waste water pumped out for treatment; A boom is to be set out across the channel downstream to collect oil/surface material; AECOM A1-SENSLR: MNB – Environmental Impact Assessment – Volume 2: Environmental Statement 13-44
Pre-fabricated structures to be used wherever possible to minimise the use of wet concrete near water; Once structures are erected, debris netting will be provided to stop material falling into the channel; No refuelling of plant or machinery is to take place near watercourses (designated sites within construction compound to be used only); All plant to be clean and self bunded; and Following completion of any in channel works, the channel will be cleared of debris/materials, the natural bed reinstated, and water allowed to flow from downstream spilling up channel to prevent remobilisation of loosened material. Flood Risk
Flooding From Rivers 13.157 The effect of the construction process on the watercourses within the study area, and their floodplains will be mitigated as far as practically possible. It is obviously not possible to prohibit construction work within the watercourse channels and floodplains, although where this does occur it will be temporary and short term. However, it is possible to monitor and limit construction work carried out within the fluvial floodplain. Furthermore, construction equipment will not be stored within the fluvial floodplain outline.
Flooding from Land (i.e. surface water and overland flow) 13.158 It is recommended that the effect of the construction phase on flooding from land is considered further during construction. If surface water runoff and overland flow are assessed to be having a significantly adverse affect then installing a temporary appropriate drainage system may be necessary. 13.159 Installing an appropriate temporary drainage system would mitigate any adverse effect, and could possibly be provided in the form of a simple ditch drainage system discharging to numerous watercourses in the area..
Flooding from Groundwater 13.160 The construction process will take the groundwater level into account. If groundwater is encountered during the bridge footing works, appropriate construction techniques will be utilised to mitigate the risk. Dewatering and ground freezing techniques are examples of appropriate construction techniques that could be utilised during construction, if required.
Flooding from Sewers and Water Mains 13.161 The construction process will take the location of existing water mains and sewers into account, and it will be ensured that the construction process does not effect on these assets. This will ensure that there is no risk of flooding from sewers or water mains during the construction phase. AECOM A1-SENSLR: MNB – Environmental Impact Assessment – Volume 2: Environmental Statement 13-45
13.162 Foul water from services provided during construction will be drained to a nearby sewer where possible. If there are no suitable nearby sewers then foul flows will be maintained by a professional contractor and removed regularly from the site for appropriate disposal. This will ensure that there is no foul discharge to surface water, either directly or indirectly via sewers, and that there is no risk of foul water flooding.
Flooding from Other Artificial Sources (i.e. reservoirs, canals, lakes and ponds, excluding sewers and water mains) 13.163 The construction process will take the existing volume of two small ponds to the south of Pegswood Community Park pond which form part of the overflow route from to the How Burn into account. Sufficient pond volume compensation will be provided during construction for the two small ponds either in a temporary storage area or as proposed in the permanent solution. This will ensure that the flood risk on site and off site is not affected. Operational Phase 13.164 The remainder of this section considers the mitigation measures that have been built into the design to prevent adverse effects from the schemes operation. Surface Water 13.165 The drainage design for the proposed bypass includes a range of SUDS techniques (including grassed swales, ponds and drainage ditches) together with conventional measures (such as catchpits/sumps) to provide treatment of road runoff. Based on the results of the effect assessment, no further mitigation measures are required. Groundwater 13.166 Where the Secondary A aquifer (strata b3) is exposed at the surface (i.e. intermittently between St. Georges Roundabout (approximately CH 1850), at approximately CH1575 to CH1650, and to just east of How Burn (approximately CH 2700)) and where the bypass crosses the Pegswood Moor Tributary on embankment, infiltration to ground will be restricted. In these areas runoff will be encouraged to drain towards the surface water treatment ponds prior to being discharged to nearby watercourses. This may be achieved by the provision of a suitable liner or by increasing the clay content of the swale soil matrix, and is subject to detailed design. Flood Risk
Flooding from Land (i.e. surface water and overland flow) 13.167 In order to mitigate any potentially adverse effects on flooding from the land, an appropriate drainage strategy will be installed for the bypass. NCC has prepared a preliminary drainage design, which consists of a network of pipes, swales, ditches, dry overflow basins and wet overflow basins. The proposed drainage scheme has been discussed with the EA, and will discharge surface water into Cotting Burn, Fulbeck, How Burn, a tributary of the How Burn and the Benbridge Burn. The Benbridge Burn is located AECOM A1-SENSLR: MNB – Environmental Impact Assessment – Volume 2: Environmental Statement 13-46
to the west of the bypass route and A1, and is not crossed by the proposed bypass. Paragraphs 13.86 to 13.95 provide details information on the proposed drainage system that will, amongst other things, dispose of surface water safely, without increasing flood risk.
Flooding from Sewers and Water Mains 13.168 Water mains and public sewers crossed by the bypass will be diverted or upgraded as appropriate to cope with the vehicular loads. This will ensure that these assets are not affected by the proposed bypass, and there are no adverse effects on sewer and water main flooding.
Residual Effects 13.169 The residual effects predicted for the construction and operation phases have been presented in Table 13.16 and Table 13.17, respectively. These have been determined following the method outlined in paragraphs 13.10 to 13.35 and present the effects predicted to occur once mitigation measures have been taken into account. AECOM A1-SENSLR: MNB – Environmental Impact Assessment – Volume 2: Environmental Statement 13-47
Table 13.16 Residual Effects - Construction Residual Classification Magnitude of the Effect Description of of Potential Receptor (importance) Effect without Proposed Mitigation Measures Significance potential Effect Effect Mitigation (with Mitigation) River Wansbeck (Very High) Minor Adverse The site will operate a temporary drainage Water Likely Cotting and How Burn (High) Moderate Adverse system using construction SUDS (e.g. silt pollution from Direct fences, sedimentation lagoons, earth bunds Benridge Burn (Medium) Minor Adverse Neutral silt laden Temporary etc.) to control and treat silt-laden runoff runoff Short term All other watercourses (Low) Moderate Adverse generated by works. Discharge consents from the EA will be in place if necessary. The storage of potentially hazardous River Wansbeck (Very High) Minor Adverse substances will be in accordance with the Control of Substances Hazardous to Health Chemical Cotting and How Burn (High) Moderate Adverse Regulations 2002 and the Control of Pollution spills from oils Unlikely (Oil Storage) (England) Regulations 2001. and other Direct Construction work will also take place following Benridge Burn (Medium) Minor Adverse Neutral potentially Temporary good practice. This will include bunded fuel
polluting Short term storage areas (minimum 110% storage substances capacity), designated refuelling areas isolated All other watercourses (Low) Moderate Adverse from surface runoff drainage, easily accessible spill kits and oil absorbent materials, and training for construction workers. Localised Any works close to or within a watercourse erosion of (Controlled Water) will need to be strictly Slight/Moderate
banks and controlled to prevent adverse effects on water Adverse Cotting and How Burn (High) Moderate Adverse beds of quality (and therefore aquatic fauna/flora) or (temporary and Likely Surface WaterQuality watercourses through physical changes (long term changes short term) Direct when works considered under operation effects). All work Temporary & Benridge Burn (Medium) Minor Adverse Neutral are required in will be controlled by good practice guidance permanent their proximity including the EA’s PPGs. Such works will Short term (e.g. require Flood Defence Consent from the EA. construction of All other watercourses (Low) Moderate Adverse With these measures the magnitude of adverse Neutral new effects can be reduced to minor adverse on all crossings) watercourses. River Wansbeck (Very High) If possible construction foul water will be Inappropriate Unlikely Cotting and How Burn (High) discharged to the nearest foul sewer. If this is disposal of Direct not possible foul water (e.g. waste from Benridge Burn (Medium) Negligible Neutral construction Temporary chemical toilets) would be collected from site by site foul water Short term All other watercourses (Low) an approved specialist contractor for appropriate disposal elsewhere. AECOM A1-SENSLR: MNB – Environmental Impact Assessment – Volume 2: Environmental Statement 13-48
Residual Classification Magnitude of the Effect Description of of Potential Receptor (importance) Effect without Proposed Mitigation Measures Significance potential Effect Effect Mitigation (with Mitigation) Pollution Unlikely during Direct Carboniferous bedrock Carry out good practice measures as for construction of Minor Adverse Neutral Temporary aquifer (north of road) working near to water courses. Pegswood Short term drainage basin Cotting Burn (Medium) Likely Monitor and limit construction work carried out Slight Adverse Flooding from Direct How Burn (Medium) within watercourse channels and their Minor Adverse Rivers Temporary Fulbeck (Low) floodplains. Construction equipment will not be Short term stored within the fluvial floodplain outline. Neutral How Burn tributary (Low) Likely If surface water runoff during construction is Flooding from Direct assessed to have a significantly adverse affect Surface Water Negligible Neutral Land Temporary then a temporary drainage system will be Short term installed. Groundwater exclusion techniques will be Likely
implemented during construction, if required. Flooding from Direct Groundwater Negligible Dewatering and ground freezing techniques are Neutral Groundwater Temporary examples of appropriate groundwater exclusion Short term techniques. Account for the location of sewers and water FloodRisk mains, and ensure construction does not effect on these assets.
Foul water from services provided during Unlikely construction will be drained to a nearby sewer Flooding from Sewers and Water Mains Direct where possible. If there are no suitable nearby Sewers and Negligible Neutral Temporary sewers then foul flows will be maintained by a Water Mains Foul Water Short term professional contractor and removed regularly from the site for appropriate disposal. This will ensure that there is no foul discharge to surface water, either directly or indirectly via sewers, and that there is no risk of foul water flooding.
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Residual Classification Magnitude of the Effect Description of of Potential Receptor (importance) Effect without Proposed Mitigation Measures Significance potential Effect Effect Mitigation (with Mitigation) Flooding from Other Artificial Sources (i.e. Likely Provide sufficient pond volume compensation reservoirs, How Burn tributary (Medium) Direct will be provided during construction for the two canals, lakes Minor Adverse Neutral Temporary small ponds either in a temporary storage area and ponds, How Burn (Low) Short term or as proposed in the permanent solution. excluding sewers and
water mains)
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Table 13.17 Residual Effects - Operation Residual Classification Magnitude of the Effect Description of of Potential Receptor (importance) Effect without Proposed Mitigation Measures Significance potential Effect Effect Mitigation (with Mitigation) River Wansbeck (Very High) Negligible The drainage design for the proposed bypass Likely Cotting Burn (High) Minor Adverse includes a range of SUDS techniques (including Water Direct grassed swales, ponds and drainage ditches) pollution from Benridge Burn (Medium) Minor Adverse Neutral Permanent Cotting Burn Tributary (Low) Minor Adverse together with conventional measures (such as highway runoff Long term catch pits/sumps) to provide treatment of road How Burn Tributary (Low) Negligible runoff. Unlikely River Wansbeck (Very High) The spillage risk from the proposed bypass is Spillage risk Direct Cotting and How Burn (High) low. Grass swales ditches and/or ponds on all from polluting Negligible Neutral Temporary Benridge Burn (Medium) outfalls provide a means to contain any spillage, substances Short term All other watercourses (Low) should one occur. Buried Corrugated steel structures are proposed Slight / Cotting Burn and How Burn for the two crossings of Cotting Burn and How Moderate Likely (High)
Surface WaterQuality Burn. These will allow for a minimum of 500 mm Morphological Direct Adverse Minor Adverse depth of natural material on top of structural changes Permanent Cotting Burn and How Burn invert. The placement of other structures (such Long Term Neutral tributaries (Low) as headwalls for outfalls) will take environmental factors into account during detailed design. Infiltration will be limited in areas where the Likely Secondary A Aquifer may be exposed at the Water surface. This may be achieved through the Direct Secondary A Aquifer Slight pollution from Minor Adverse Permanent (Medium) provision of a suitable liner or by increasing the Adverse highway runoff Long term clay content of the swale soil matrix. This will be determined during detailed design.
Likely
Groundwater Water How Burn (High) and Direct pollution from Pegswood Moor Tributary Negligible No mitigation required. Neutral Permanent highway runoff (Low) Long term AECOM A1-SENSLR: MNB – Environmental Impact Assessment – Volume 2: Environmental Statement 13-51
Residual Classification Magnitude of the Effect Description of of Potential Receptor (importance) Effect without Proposed Mitigation Measures Significance potential Effect Effect Mitigation (with Mitigation) The spillage risk across the bypass is predicted to be very low and no measures to protect Unlikely groundwater have been required. It is expected Spillage risk Direct Secondary A Aquifer that an Emergency Response Plan will be from polluting Negligible Neutral Temporary (Medium) maintained by the road authority and emergency substances Short term services so that in the unlikely event of a spillage swift and appropriate action can be undertaken to reduce any adverse effect.
Cotting Burn (Medium)
Likely How Burn (Medium) Appropriately designed bypass and watercourse Flood From Direct Negligible crossings in accordance with HD45/09 and Neutral Rivers Temporary Fulbeck (Low) NPPF guidance. Short Term
How Burn tributary (Low) Install an appropriate drainage system. Likely Northumberland County Council has prepared a Flooding from Direct preliminary drainage design, which demonstrates Surface Water Negligible Neutral FloodRisk Land Temporary that surface water from the bypass can be Short term disposed of safely, without increasing flood risk.
Unlikely Water mains and public sewers crossed by the Flooding from Direct bypass will be diverted or upgraded as Sewers and Sewers and Water Mains Negligible Neutral Temporary appropriate, so they can cope with vehicular Water Mains Short term loads. AECOM A1-SENSLR: MNB – Environmental Impact Assessment – Volume 2: Environmental Statement 13-52
Cumulative Effects 13.170 The timing of any of the proposed other developments along the bypass route corridor and potentially affecting the various local watercourses (e.g. Cotting and How Burn) is uncertain. However, it is predicted that the risk to the water environment from cumulative effects is negligible since all construction work will need to comply with the same strict regulations imposed by the Environment Agency. It is therefore reasonable to assume that all of these developments will be applying the same standard of best practice as set out by the guidance listed earlier, and will include measures to protect the water environment from pollution, which, should it occur, is an offence under Section 85 of the Water Resources Act 1991 (as amended). 13.171 One of the core reasons for development of the proposed bypass is to reduce the need for vehicle traffic, including HGVs, from travelling through the centre of Morpeth to join the A1. The centre of Morpeth currently experiences severe traffic congestion as a result. Due to the nature of the roads in Morpeth, it is unlikely that there are any treatment or spillage containment measures, and runoff from roads is likely to contain quantities of vehicle derived pollutants such as oils and heavy metals, that will ultimately end up in the various watercourses draining the town. By reducing traffic flows and congestion through the town the proposed bypass will reduce the loading on these untreated roads, and thus will reduce the contribution of highway runoff to the overall effect from urban diffuse pollution. It is difficult to determine the significance of this effect, but the effect will be beneficial. A similar beneficial effect is predicted from a reduction in spillage risk through the town centre. 13.172 Another reason for the proposed new bypass is to open up new areas of land for commercial development. Taken together, these developments will result in an urbanising effect across the northern fringe of Morpeth, and will generate surface water runoff that will contain typical diffuse urban pollutants (although the highway element has been taken into account by the assessment of routine runoff set out in this assessment). Under the Flood and Water Management Act 2010 all new development needs to demonstrate that it has considered SUDS to treat surface water runoff and attenuate flows to avoid increasing the risk of flooding, with the proposals to be approved by newly set up SUDS Approval Bodies. Where development does not demonstrate that the relevant risks have been identified and appropriate measures proposed, planning permission is likely to be rejected. Therefore, it is assumed, as part of this effect assessment, that the developments identified along the proposed bypass corridor and shown on Figure 16.1 and listed on Table 16.1 provides appropriate treatment measures to ensure that the water environment is protected during operation. Thus, no effects are predicted. 13.173 In terms of interrelated effects, it is possible that effects on water quality could combine with other effects to have cumulative effects on aquatic ecological receptors. However, the assessment of ecological effects in Chapter 7 takes water pollution into account within the AECOM A1-SENSLR: MNB – Environmental Impact Assessment – Volume 2: Environmental Statement 13-53
assessment and thus interrelated effects are inherently included in the assessment already undertaken. Summary and Conclusions 13.174 This Chapter of the ES has considered the potential effects of the proposed bypass on the water environment, including appropriate assessments of the possible effects on surface water, groundwater and flood risk. It has been carried out in accordance with the methodology presented in HD45/09. Residual effects have been presented in Table 13.16 for the construction phase and Table 13.17 for the operational phase, respectively. 13.175 The proposed bypass has the potential to adversely affect the surface water environment during both the construction and operational phases. Works to construct the new structures across Cotting Burn and How Burn (and its diversion) could lead to short term, temporary slight/moderate adverse effects. In the long term the permanent loss of habitat and secondary effects on aquatic ecology and water quality are predicted to be only slight/moderate adverse. Effects on other watercourses, assuming good practice methods are implemented during construction (as set out in this Chapter) are short term, temporary, and of only slight adverse significance. During the future operation of the bypass, adverse effects could occur from the effects of contaminated routine runoff, from spillages, and from permanent morphological changes. A quantitative assessment has been carried out into the likely effects of road runoff as a result of dissolved or sediment- bound pollutants, providing the proposed mitigation measures (including grass swales and ponds) are implemented no adverse effects have been predicted. The spillage risk is also very low and no residual adverse effect is predicted, irrespective of the containment that the drainage system will provide. Although unquantifiable, it is believed that the transfer of traffic flows from the centre of Morpeth, where it is thought there are no treatment and containment facilities as part of the existing drainage system, to the bypass with dedicated treatment/containment facilities, is likely to have a net beneficial effect on the local water environment. In the long term, the proposed development is therefore compliant with the saved policy of the former Castle Morpeth Local plan policy RE4 Water Quality; and Strategy Policy 36 The Aquatic and Marine Environment, listed in the now revoked North East Regional Spatial Strategy. 13.176 Groundwater resources are not likely to be effected significantly during normal construction activities, due to the presence of low permeability drift over most of the site and appreciable depth to the water table in the underlying bedrock aquifer. Limited groundwater resources are available within sand and gravel deposits within the drift, but with mitigation, and taking into account hydrogeological sensitivity, the effect on these is not significant. 13.177 There is the potential for slight adverse effects on the Secondary A aquifer where it is exposed at approximately CH 1575 to CH 1650 and between St. George’s Roundabout and How Burn. In this area, infiltration through the swale will be reduced and encouraged AECOM A1-SENSLR: MNB – Environmental Impact Assessment – Volume 2: Environmental Statement 13-54
to flow through the proposed ponds before being discharged into How Burn. No adverse effect to groundwater is predicted from potential spillages since the risk is very low across the entire bypass. 13.178 The proposed bypass has the potential to adversely affect flood risk during both the construction and operational phases. Appropriate mitigation measures will be implemented during both construction and operational phases, to ensure the proposed route does not have an adverse effect on flood risk within the study area. Taking into account the drainage design, the watercourse crossings and the mitigation measures that will be implemented; the effect of the proposed route on flood risk should be neutral. However, there is the potential for slight adverse effects on river flooding during construction, as construction within the watercourse channels is required.