appendix 7.b private water supply risk assessment/media/pdfs/generation/wind/onshore/ke… ·...

© Entec UK Limited

Appendix 7.B Private Water Supply Risk Assessment

E.on Climate and Renewables (EC&R)

Kelmarsh Wind Farm

Risk Assessment of Private Water Supplies

21 January 2010

Entec UK Limited

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Third Party Disclaimer Any disclosure of this report to a third party is subject to this disclaimer. The report was prepared by Entec at the instruction of, and for use by, our client named on the front of the report. It does not in any way constitute advice to any third party who is able to access it by any means. Entec excludes to the fullest extent lawfully permitted all liability whatsoever for any loss or damage howsoever arising from reliance on the contents of this report. We do not however exclude our liability (if any) for personal injury or death resulting from our negligence, for fraud or any other matter in relation to which we cannot legally exclude liability.

Document Revisions

No. Details Date

i1 Draft June 2009

Final January 2010

i

h:\projects\project subfiles\23125 kelmarsh wind farm\pws risk assessment\kelmarsh pws_final.doc © Entec UK Limited 21 January 2010

Contents

1. Introduction 1

2. Site Hydrology and Hydrogeology 3

2.1 Hydrology & Topography 3

2.2 Groundwater 3

3. Identification of Water Supplies 5

3.1 Introduction 5

3.2 Cromwell Farm 5

3.3 Haselbech Hill House B&B 5

3.4 Wilderness House 6

3.5 New House Farm 6

4. Risk Assessment Methodology 7

4.1 Introduction 7

4.2 Risk Assessment Methodology 7

4.3 Risk Evaluation of Water Supplies from Wind Farm Activities 7

5. Risk Assessment of Water Supplies 11

5.1 Introduction 11

5.2 Wilderness House (and Keepers Cottage) 11

6. Summary 13

Table 3.1 PWSs Selected for Risk Assessment 5 Table 4.1 Risk Evaluation of Wind Farm Activities 8 Table 6.1 Summary 13

Figure 3.1 PWS Locations and Indicative Catchments Figure 3.2 Wilderness House PWS Infrastructure Within the Site

Appendix A Photos of Wilderness House PWS Infrastructure

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1. Introduction

The Environmental Statement hydrological assessment for Kelmarsh Wind Farm, undertaken by Entec UK Ltd for Eon, identified four private water supply (PWS) sources to be supplying four properties within a 3 km search radius of the proposed wind farm site. Information was provided through consultation with Daventry District Council (DDC) Environmental Health Department. Given the proximity of these PWSs to the proposed development, a separate risk assessment is required.

PWSs are defined as any water supply that is not provided by a statutory water undertaker and in which the responsibility for maintenance lies with the owner or person who uses the supply. These supplies may be drawn from a variety of surface and groundwater sources and are recognised as key potential sensitive water receptors.

This report assesses the potential risks to the four PWSs on a source-by-source basis. This has been done by estimating the probable catchment for each supply using the available information from DDC, from consultation with the owner/occupant of each PWS, and the findings of an additional site visit. The final scheme design layout provided in Chapter 3 has been used to determine if wind farm activities are likely to affect each source and its infrastructure. Where necessary, mitigation measures are proposed to protect water supplies that could be at risk from the construction and/or operation of the wind farm.

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2. Site Hydrology and Hydrogeology

2.1 Hydrology & Topography

The site comprises open, undulating arable fields with a small wooded area towards the centre (Tallyho Covert, SP 781 786). A farm track traverses the site in a north south direction just east of Tallyho Covert. Topography within the site is determined by the presence of the River Ise, which is sourced to the west of the site and flows eastwards through its centre, creating a shallow valley. Elevations fall from approximately 180 mAOD in the south and west, to approximately 135 mAOD as the River Ise exits the site in the northeast. Mapped within the site, there are six small ponds and two tributary drains which issue through natural springs into the River Ise (Figure 7.1, ES). However, only one of these springs (in the north west of the site) was visible during the site visit. Perimeter field drains on the site flow into the River Ise. Underlying the agricultural fields are shallow buried drainage pipes that help to encourage drainage of the arable fields. These pipes are not visible from the surface, but their discharge points into the River Ise and were noted during the site visit for the ES (undertaken in February, 2009).

2.2 Groundwater

The Groundwater Vulnerability Map of the site indicates that the Glacial Till and Clay unconsolidated material beneath the majority of the site are classified as a Non-Aquifer of negligible permeability. The Whitby Mudstone Formation predominantly underlies these low permeability deposits and is also classified as Non Aquifer, but exposed areas of Northampton Sandstone are present in small drift free areas in the west and south of the site. Where the Sandstone outcrops at the surface it is classed as a Minor Aquifer, which relates to formations with variable permeability. They seldom produce large quantities of groundwater for abstraction, but are important for both local supplies and in supplying baseflow to rivers. Soils overlying the Minor Aquifer are classed as having an intermediate leaching potential, where these soils have a moderate ability to attenuate diffuse pollutants.


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3. Identification of Water Supplies

3.1 Introduction

Four properties with PWSs have been identified within a 3 km search radius through consultation with DDC (Figure 7.1, ES). These supplies are the subject of this risk assessment, based on their proximity to the site. In order to confirm the locations of the PWS sources, a site visit was undertaken on May 27th, 2009. The site visit allowed for observations of the topography surrounding each source, and provided an opportunity to find out further information from landowners and farmers, in order to fully assess the potential impacts from the proposed wind farm activities. Table 3.1 summarises the information provided by DCC.

Table 3.1 PWSs Selected for Risk Assessment

PWS Location Property Name PWS Type

Use PWS Current Status Following Site Visit

1 469200, 277700 Cromwell Farm Spring Domestic Supply in operation for ornamental pond only. Domestic water supplied by mains water.

2 471700, 276500 Haselbech Hill House B&B

Spring Domestic Replaced by mains water supply.

3 473700, 279500 Wilderness House Spring Domestic Supply in operation.

4 470200, 279200 New House Farm Borehole Domestic Replaced by mains water supply.

Further details regarding the nature of each source and current usage of each PWS, based on the findings of the site visit and consultation with the landowners and farmers, are provided in the sections below.

3.2 Cromwell Farm

The spring source is located within a field, downgradient of the farm (Figure 3.1). A water-driven pump pipes the water supply in a buried pipe uphill to the farm where it now supplies an ornamental pond behind the farmhouse. Mains water now supplies the remainder of the farm.

3.3 Haselbech Hill House B&B

There was a private water supply until the mid-1960s when the whole area went to mains water supply.


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3.4 Wilderness House

Wilderness House is situated east of the River Ise to the northeast of the site and is supplied by a spring source which also supplies the adjacent Keepers Cottage and cattle troughs at the farm. In the past the supply also served Kelmarsh Hall and Rectory Farm, although these properties are now fed by mains water supply.

The spring source for this property is thought to lie in the field south of Bassetts Lodge Farm to the south of the proposed wind farm site. The exact location of the spring source itself is unknown (pending a search by Des Brack at Kelmarsh in the archive records) (Figure 3.1). It is carried by gravity-fed pipe to a sub-surface tank (not visible; of concrete construction with an air tight cast iron cover; has a capacity of 1000 gallons1) which lies within a field northeast of Bassetts Farm (Figure 3.2). At this location, there are also two man-made ponds, whose function is uncertain, and a small brick building which houses a gate inlet cast iron valve on the pipe, and serves to shut off water into the tank when required. The building appeared to be poorly maintained and little used on inspection (Appendix A). From here, the water supply is piped (50 mm, gravity fed) across the proposed wind farm site, beneath the A14 and toward the property. It is understood that there are two pipes, and their approximate route to the properties is known (Figure 3.1). The larger of the pipes is 75mm diameter and thought to be the live pipe, the previous being the original and no longer used. The pipework is understood to be at 450 mm below ground surface. Four or five air bleed valves to ground surface are understood to exist along the pipeline route, which were not visible during the site visit. The condition of the pipeline is not known. It is thought to have been originally installed in the 1930s, updated to the 75mm pipe in the 1960’s and some sections excavated and replaced during the construction of the A14 in 1994.

3.5 New House Farm

The spring supply was disrupted by construction of the A14, and property was put onto mains supply. A manhole just south of the A14 and adjacent to the C-road farm access marks the upper extent of a buried pipe which takes the local groundwater discharge southeast towards the site where it emerges within the field close the site boundary and flows into a surface drain (Figure 3.1). The groundwater source is no longer used for supply.

1 From consultation with Des Brack during the site visit in May, 2009 and via email June, 2009.

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4. Risk Assessment Methodology

4.1 Introduction

A risk assessment for each of the PWSs identified in Table 3.1 is presented below.

Following the review of information and the assessment of risks, an appraisal of the need and type of mitigation is then made. This mitigation is based on measures described in the Water Quality and Hydrology chapter of the proposed Kelmarsh Wind Farm ES.

4.2 Risk Assessment Methodology

The risk assessment has adopted a qualitative approach. In order to classify the risks a simple scale has been adopted based on criteria that incorporate probability of occurrence and level of effect. This has been applied to both the potential risks, based on our understanding of the hydrological environment, and the actual risks, taking into account the incorporation of the mitigation measures that have been proposed. The scale defines five levels of risks to water quantity and water quality (together termed ‘water supply’), as described below:

• None – No risk predicted, and no impact on water supply is anticipated;

• Very Low – Risks are unlikely, and no measurable change in water supply is predicted;

• Low – Risks are unlikely, with a slight change in water supply predicted over very short timescales and within the bounds of normal water supply variation;

• Medium – Risks are probable, and some impact on water supply is likely; and

• High – Risks are very probable and very likely to cause a significant impact on water supply.

4.3 Risk Evaluation of Water Supplies from Wind Farm Activities

The potential risks to water supplies from the construction and operation of the proposed win farm principally relate to effects on water quality, and have been described within Chapter 7 of the ES. However, other risks to water supplies may include issues of water quantity where supply infrastructure is potentially affected by the development.

The wind farm activities that are considered to have a significant potential effect on water quality and quantity are summarised in Table 4.1. Table 4.1 also examines the risk these effects pose to PWSs, based on the mitigation measures presented within the ES.


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Table 4.1 Risk Evaluation of Wind Farm Activities

Wind Farm Activities

Hazard Proposed Mitigation Residual Significance Level

Risk Evaluation to Water Supplies

Construction

Access tracks, turbine foundations, temporary and permanent working compounds

Erosion of exposed ground and track surfaces producing silt-laden runoff which enters local watercourse

Drainage control measures (e.g. silt traps, diversion channels, and settlement ponds) in place will prevent contamination entering watercourses. Working only small sections of cable trenches at a time and using clay bunds at interval will minimise ground disturbance.

Not Significant None

Turbine foundation and control building construction

Concrete spillages reaching the water environment

Safe working procedures change over on hardstanding bunded areas. Mitigation in place will prevent contamination entering watercourses.


Disruption of natural flow paths/Increased volumes of runoff and reduced infiltration from access tracks, cable laying, watercourse crossing and turbine foundations

Surface runoff rerouted, increased surface flow may increase soil erosion and reduce recharge

Drainage control provided. Limited land take for turbine foundations and permanent structures

Minor to Not Significant

Very Low

Access tracks, turbine foundations and crane pads

Disruption or damage to agricultural or PWS pipework leading to cessation of water supply

Detailed survey of water supply pipelines and below ground surface drainage. Potential mitigation will include re-routing agricultural pipes and PWS supply pipe around wind farm infrastructure and/or pipe upgrade, but mitigation measures still need to be agreed and discussed with landowner. Temporary interruption of supply likely during rerouting.

Minor Low

Site working practices such as refuelling and maintenance

Chemical spillages reaching watercourses or groundwater

Any spillages will be small, away from watercourses and quickly controlled



Leaks from chemical stores reaching watercourses or groundwater

Any leaks will be small, away from watercourses and quickly controlled


Operation

Access tracks used for maintenance

Erosion of track surfaces producing silt-laden runoff

Track design and other mitigation will continue to function.


Access tracks used for maintenance

Damage to existing on-site infrastructure (agricultural and PWS pipes)

Upgrade of infrastructure as required prior to construction, so that no impact likely during operation. Exact detail and preferred mitigation still open to discussion

Not Significant Very Low


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Table 4.1 (continued) Risk Evaluation of Wind Farm Activities

Wind Farm Activities

Hazard Proposed Mitigation Residual Significance Level

Risk Evaluation to Water Supplies

Watercourse crossing Disturbance of watercourse at crossing point

The upgraded River Ise culvert will remain during operation but water quality will be monitored and remedial action undertaken if necessary



Chemical spillages during maintenance operations or from on-site storage

Limited on site activity. Any spillages/leaks will be small, away from watercourses and quickly controlled


Decommissioning

Removal of wind turbines, access tracks and watercourse crossings

Potential impacts arising from various decommissioning activities. Impacts similar to, but on a smaller scale, than construction impacts.

Similar mitigation measures used in construction phase will be implemented. Where possible below ground structures left in situ.


Table 4.1 illustrates that the wind farm activities and the incorporation of mitigation measures outlined within the Environmental Statement Hydrology Chapter relating to water quality will only result in potential risks rated as ‘None’ to ‘Low’. For more detail the reader should refer to the Hydrology Chapter of the ES. However, wind farm construction activities which result in potential risks to water quantity are rated ‘Low’.

The next section outlines which of the identified water supplies would be subject to these risks (i.e. where proposed activities lie within PWS catchment or near to PWS infrastructure), and further describes potential mitigation measures to control these risks.


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5. Risk Assessment of Water Supplies

5.1 Introduction

This section outlines which of the identified water supplies would be subject to these potential risks (i.e. where proposed activities lie within PWS catchments or PWS infrastructure) and outlines additional mitigation measures to counter these risks.

To facilitate this risk assessment, indicative catchment areas for the operational spring-fed PWSs have first been defined on the basis of topography. This is because the groundwater catchment to these springs is likely to reflect the up-gradient topography. In addition, where there is known infrastructure associated with a supply this is identified. Those PWSs which are no longer in operation can be considered not to be at risk from the proposed wind farm development i.e. Haselbech Hill House B&B and New House Farm.

The estimated catchments for the currently operating PWSs are shown on Figure 3.1. Based on these indicative catchment areas, and the methodology set out in Section 4.2, the risks posed to both sources for Cromwell Farm and Wilderness House (which also supplies Keepers Cottage) are classed as ‘none’ because their catchments are removed from the areas of development. However, the infrastructure relating to the Wildnerness House supply coincides with areas of the site where wind farm activities are proposed. Specific risk assessments and further mitigation are presented below for this potentially affected water supply.

5.2 Wilderness House (and Keepers Cottage)

5.2.1 Catchment Activities

There are no proposed wind farm activities within the area of the ponds/building or upgradient (to the south) from these towards the spring source itself. However, the access track and cable trenches will be required to cross the pipeline route at two locations, and the pipeline lies within 50 m of proposed turbine 6 (Figure 3.2).

5.2.2 Potential Impacts

Potential impacts to the water supply infrastructure include:

1. Damage to the pipeline caused by ground excavations during access track construction;

2. Damage to the pipeline caused by heavy traffic during the operation of the access tracks; and

3. During the construction and operation periods the potential could exist for the spillage of materials such as lubricants being transported across the site tracks. Derogation of water supply quality by infiltration of contaminants from such spillages could occur if the pipe condition is poor.


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5.2.3 Mitigation

The exact location and depth of the pipeline needs to be confirmed by further survey prior to construction, and an assessment made of its capacity to withstand the loading of construction traffic. In order to prevent the water supply being disrupted, it is recommended that the piping is ducted with concrete prior to commencement of the wind farm construction at the location of access track crossings to prevent the integrity of the pipe from being damaged. At the location of Turbine 6, careful excavation techniques such as hand digging should be employed to locate the pipe and determine if the foundations will intersect with the pipeline. Local re routing of the pipe around the foundation area should be undertaken if required. The existing pipeline itself may require some sections to be upgraded if it is deemed that it is inadequate to withstand the weight of construction and maintenance traffic. Confirmation of the proposed mitigation is still ongoing at the time of writing and will require further negotiation between the landowner and the developer to reach an agreement.

Where cable trenches are required alongside the tracks, only small sections of trench should be worked at a time, with clay bunds used at intervals. This will ensure that the impacts on the pipeline will be minimised.

Controls will be put in place to ensure that, should spillages occur, these are contained as quickly as possible and removed in a suitable manner. Vehicles will be well maintained, and fuels and lubricants will be stored outside the indicative catchments on impermeable hardstanding with a bunded capacity of 110% of the fuel or lubricant. Drainage control measures will be applied to access track construction and cable laying, which will involve sediment traps or settlement areas to ensure that during construction turbid or contaminated water is not released towards the pipeline. Only minor volumes of sediment eroded from access tracks are anticipated following implementation of mitigation measures.

The wind farm layout has been carefully designed to avoid PWS catchments where possible, such that only small sections of access tracks will be constructed within the areas of infrastructure.

5.2.4 Risk Evaluation

Mitigation is required to prevent damage to the pipe during construction and use of the site access tracks and turbines, particularly Turbine 6 which is located within approximately 50 m of the pipeline. One option, recommended above, is for the protection of the pipe through concrete ducting at the track crossings and re routing around the turbine foundations if required. If this option was to proceed, depending on further survey work and negotiations, the resultant impact on the supply is anticipated to be only of Minor Significance for a temporary period: a temporary interruption of supply would potentially occur during the local rerouting around Turbine 6 if undertaken. Once diverted, it is anticipated that the diverted supply would no longer be affected, so that the risk of any effect would be Low during rerouting. Based on the assumption that concrete ducting is undertaken according to industry best practice, the potential risk to the infrastructure could be Very Low. However, this is based on the assumption that the crossing point of the pipe by the existing track requires no upgrade to withstand construction and maintenance traffic, and is therefore dependent on the outcome of further survey work.

The drainage and spillage control measures described in the ES will result in only minor volumes of sediment erosion and a Very Low risk of detrimental impacts from spills: it is considered unlikely that significant volumes of sediment or contaminant could infiltrate into the pipeline.


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6. Summary

This report assesses the risks to local PWSs that will be presented during the construction and subsequent operation of the proposed Kelmarsh Wind Farm. The risk assessment is based on the evaluation of post-mitigation effects presented in the Environmental Statement Hydrology Chapter (Chapter 7), though taking into account the acquired information concerning supplies in the area.

The wind farm layout has sensibly considered the locations of PWS sources and indicative catchments in the design process so that, where possible, construction activities within PWS indicative catchments or areas of infrastructure have been avoided. Based on a review of indicative catchment areas, none of the four water supply spring source areas have been identified as being potentially affected by the proposed wind farm activities. However, the infrastructure for the Wilderness House (and Keepers Cottage) supply, in particular the pipeline from the source to the properties, is likely to be affected by the proposals, during both construction and operation of the wind farm if no mitigation is implemented. Table 6.1 summarises the pertinent wind farm activities in the catchment, the key mitigation measures proposed and the resulting risk rating determined in this assessment.

Table 6.1 Summary

Water Supply Wind Farm Activities Risk Evaluation

Cromwell Farm None None

Haselbech Hill House B&B None None

Wilderness House Three crossing points of the access track over the pipeline. Turbine 6 within 50 m of the pipeline

Low (construction) Very Low (operation)

New House Farm None None

Mitigation measures recommended for Wilderness House PWS location:

- Further survey of pipeline location; - Avoidance and cordoning off of supply infrastructure to prevent damage; - Construction of concrete duct over pipe at locations where new and existing access track will cross it; - Careful excavation techniques at turbine 6 and if required local rerouting of pipe; and - Upgrade of pipeline sections if required.

Environmental Measures proposed for the site at all locations

- Access track drainage with sediment control; - Emergency spill response measures in place; - Careful design of wind farm layout;

In addition to the measures described in the ES and summarised in Table 4.1, an inspection of the individual water supply could be undertaken prior to construction to identify if simple measures could be incorporated to further safeguard this supply. Alternative mitigation may include connecting the two properties to a different natural supply, or to mains water supply.


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In conclusion, this assessment outlines that the risks to the PWS potentially affected by the proposed wind farm are rated ‘Low’ during construction, and if permanent diversion takes place, the risks during operation are likely to be reduced to ‘Very Low. Therefore, it is anticipated in the worst case that there would be a slight change in water flow or quality over short timescales. However, any changes as a result of the proposed development will lie within the bounds of normal water quality variation. However, it is concluded that, in the long term, the PWS will be safeguarded throughout the construction and operation of the wind farm.


A1

Photograph 1: Building over gate inlet valve, located onsite

Photograph 2: One of 2 ponds located adjacent to building. This one is manmade.

© Entec UK Limited

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