chapter 10 hydrogeology and soils · 2019-11-13 · chapter 10 cross tay link road hydrogeology and...

CHAPTER 10 HYDROGEOLOGY AND SOILS

Cross Tay Link Road

Revision Number

Date Status Author Technical Reviewer

Checker Approver

P01.1 15.04.19 WORK IN PROGRESS

K. LEGGATT

R. HARRISON

R. McLEAN D. RITCHIE

P01 15.11.19 S4 FOR STAGE APPROVAL

K. LEGGATT

R. HARRISON

R. McLEAN D. RITCHIE

BIM Reference: 119046-SWECO-EGT-000-RP-EN-20011

This document has been prepared on behalf of Perth and Kinross Council by Sweco for the proposed Cross Tay Link Road Project. It is issued for the party which commissioned it and for specific purposes connected with the above-captioned project only. It should not be relied upon by any other party or used for any other purpose. Sweco accepts no responsibility for the consequences of this document being relied upon by any other party, or being used for any other purpose, or containing any error or omission which is due to an error or omission in data supplied to us by other parties. Prepared for: Prepared by: Perth and Kinross Council Sweco Pullar House Suite 4.2, City Park 35 Kinnoull Street 368 Alexandra Parade Perth Glasgow PH1 5GD G31 3AU

pw://CSPWInt.grontmij.net:PW_UK%20Production/Documents/Projects/Transportation/119046%20-%20CTLR/Environment/Geology%20and%20Soils/Docs%20-%20Report/119046-SWECO-EGT-000-RP-EN-20011

CONTENTS 10 HYDROGEOLOGY & SOILS .............................................................................................. 1

10.1 Executive Summary .................................................................................................................. 1 10.2 Introduction ............................................................................................................................... 2 10.3 Scope of Assessment ............................................................................................................... 2 10.4 Methodology ............................................................................................................................. 2 10.5 Baseline Conditions .................................................................................................................. 5 10.6 Potential Effects ........................................................................................................................ 9 10.7 Mitigation and Enhancement ..................................................................................................10 10.8 Residual Effects ......................................................................................................................11 10.9 Cumulative Effects ..................................................................................................................11 10.10 Statement of Significance ...................................................................................................12

FIGURES

Figure 10.1: Solid Geology Figure 10.2: Superficial Deposits Figure 10.3: Aquifer Productivity - Superficial Deposits Figure 10.4: Aquifer Productivity - Bedrock Figure 10.5: Groundwater Vulnerability TABLES

Table 10.1: Sensitivity Criteria .................................................................................................................... 4 Table 10.2: Impact Magnitude Criteria ....................................................................................................... 5 Table 10.3: Significance of Effects ............................................................................................................. 5 APPENDIX

Appendix 10.1 – Impact Assessment Tables

CHAPTER 10 CROSS TAY LINK ROAD

HYDROGEOLOGY AND SOILS EIA REPORT (VOLUME 2)

November 2019 PAGE 1 OF CHAPTER 10

10 HYDROGEOLOGY & SOILS

10.1 EXECUTIVE SUMMARY This assessment of potential effects arising from the proposed Cross Tay Link Road (CTLR) Project on hydrogeology and soils has been undertaken in accordance with the DMRB Volume 11, Section 3, Part 11: Geology and Soils, 1 and relevant associated guidance. The environmental baseline has been established from a detailed desk study review of the proposed CTLR Project area, including available existing site investigation information. Mitigation measures for the construction phase will comprise standard good construction practices covered by a Construction Environmental Management Plan (CEMP) produced by the appointed Contractor, which will include the following:

• Provision of emergency spill kits to protect against potential pollution;

• Regular checks and maintenance of construction plant;

• Control and management of site drainage measures and concrete and cement mixing areas; and

• Limiting of construction traffic to certain areas of the development to avoid unnecessary soil compaction or erosion.

Mitigation measures for the operational phase will be subject to detailed design, but are likely to comprise standard engineering design mitigations, which may include the following:

• The reuse of topsoil, including its stripping and proper storage will follow BS 3882:2015 (Specification for Topsoil) to minimise loss of the resource;

• Stripping of topsoil on dedicated haul routes, followed by the ripping of subsoil prior to re-topsoiling on completion of the works;

• Site drainage measures to collect and treat increased surface run-off where necessary;

• Appropriate risk assessment of imported or reused fill materials to confirm their suitability for use; and

• Appropriate design of drainage (including SuDS and pipe routes), and other granular material filled utility tracks to minimise risks to the water environment.

The recommended mitigation measures are considered sufficient to minimise the identified potentially significant effects on sensitive receptors to a non-significant level. Similarly, significant cumulative effects are not predicted. In summary, based on the currently available information no adverse residual or cumulative effects have been predicted which are considered significant in the context of the EIA Regulations.

1 The Highways Agency (1993): Design Manual for Roads and Bridges (DMRB), Volume 11, Section 3, Part 11, Geology and Soils, 1993. The Highways Agency, Scottish Executive Developmental Department, The National Assembly for Wales and The Department of Regional Development Northern Ireland.




10.2 INTRODUCTION This chapter provides an assessment of the effects of the proposed CTLR Project on Hydrogeology and Soils. The chapter should be read in conjunction with the table in Appendix 10.1. Aspects of the proposed CTLR Project that are considered within the assessment are associated with the construction of roads (including cuttings and embankments), junctions and associated structures, as outlined in Figure 2.3 and described in Chapter 2: Project Description.

10.3 SCOPE OF ASSESSMENT The EIA Scoping Report, submitted in September 2018, concluded that likely impacts to geology and contamination are considered to be low and therefore should be scoped out of further EIA assessment (please refer to Chapter 5: Consultation and Scoping). This proposed approach was agreed with the Council’s Planning Authority in October 2018 and these topics have therefore been scoped out of the assessment. Further details of potential effects on surface water and drainage, including flood risk, are considered separately in the section on Chapter 15: Road Drainage and the Water Environment. Further details of potential effects on soils with respect to loss of agricultural potential are considered separately in Chapter 14: Agriculture, Forestry and Sporting Interests, and potential effects on groundwater dependent terrestrial ecosystems (GWDTE) are considered in Chapter 9: Biodiversity.

10.4 METHODOLOGY

10.4.1 Legislation and Guidance The assessment of potential effects arising from the construction and operation stages of the project, on hydrogeology and soils, has been undertaken in accordance with the DMRB Volume 11, Section 3, Part 11: Geology and Soils2 and following guidance by Scottish Natural Heritage (SNH), which is presented in its EIA Handbook3. The assessment was carried out in accordance with the following legislation, published guidance and other relevant sources:

• Scottish Environment Protection Agency (SEPA) Position Statement (WAT-PS-10-01);

• SEPA Supporting Guidance (WAT-SG-53) Environmental Quality Standards and Standards for Discharges to Surface Waters (Feb 2018);

• The Water Environment (Controlled Activities) (Scotland) Regulations 2011 (as amended) (CAR);

• CIRIA C552: Contaminated Land Risk Assessment – A guide to good practice;

• Land Use Planning System SEPA Guidance Note 31, Version 3, 11/09/2017: Guidance on Assessing the Impacts of Development Proposals on Groundwater Abstractions;

• BS 5930:2015 Code of practice for ground investigations and BS 10175: 2011+A1:2013 Investigation of potentially contaminated sites: code of practice;

• CAR Practical Guide v8.2 (SEPA, 2018);

• DMRB Volume 11, Section 3, Part 10 (HD45/09): Road Drainage and the Water Environment (Highways Agency et al., 2009) 1;

• British Geological Society (BGS) website – Historical boreholes, geology, hydrogeology and land use information from the GeoIndex Onshore Online Maps: http://www.bgs.ac.uk/;

• BGS GIS digital mapping – Groundwater Vulnerability map 1:50,000 (Sourced from the Council);

• BGS GIS digital mapping – Aquifer Productivity map 1:50,000 (Sourced from the Council);

• BGS GIS Digital mapping – Solid Geology and Superficial Deposits;

3 Scottish Natural Heritage (2018): A Handbook on Environmental Impact Assessment, Guidance for Competent Authorities,

Consultees and others involved in the Environmental Impact Assessment Process in Scotland. Scottish Natural Heritage (5th Edition, 2018).

http://www.bgs.ac.uk/




• Scotland’s Environment Website – Interactive Map: https://www.environment.gov.scot/maps/scotlands-environment-map/;

• The Drinking Water Quality Regulator (DWQR) for Scotland Interactive Map of Private Water Supply Locations https://dwqr.scot/private-supply/pws-location-map/;

• BGS Hydrogeological Maps of Scotland (1988, 1:625,000 scale);

• James Hutton Institute and Soil Survey of Scotland data https://www.hutton.ac.uk/learning/natural-resource-datasets/soilshutton/soils-maps-scotland/download#soilmapdata; and

• Scotland’s Soils – Interactive online mapping http://soils.environment.gov.scot/.

10.4.2 Study Area The proposed CTLR Project, consists of a road linking the A9 over the River Tay to the A93 and A94 north of Scone. It includes the realignment of a section of the A9, provision of an overbridge over the A9, provision of a grade separated junction on the A9 north of Inveralmond Roundabout, a bridge over the River Tay (River Tay Crossing Bridge) and Highland Mainline Railway, roundabouts at Stormontfield Road, the A93, Highfield Lane and the A94, and a green bridge at Highfield Plantation. The study area is the red line boundary of the proposed CTLR Project.

10.4.3 Limitations to the Assessment The assessment is limited to desk based hydrogeological information and records provided by consultees, and there is potential for unrecorded private water supplies (PWS) within the study area. Although both desk-based assessments of the proposed CTLR Project area and the intrusive site investigation have been used to inform the assessment, there is the potential for ground conditions to vary within the proposed CTLR Project area.

10.4.4 Baseline Data Gathering In addition to the above information sources, baseline information relating to soils and hydrogeology has been collated as part of previous and recent assessments as listed below. This includes desk study information, intrusive site investigation, consultation with SEPA and the Council’s Contaminated Land Officer (CLO) and geo-environmental assessments to identify potential contamination risks that could affect the proposed CTLR Project.

• Preliminary Sources Study Report (PSSR), Sweco, 119046-SWECO-HGT-000-RP-GE-003 Rev P04, February 2018. This report summarises all available desk-based information and walk over survey data and provides a preliminary assessment of potential geotechnical and geo-environmental constraints. Consultation was undertaken with the Council’s CLO to determine a baseline for the PSSR; and

• Ground Investigation Report (GIR), Sweco, 119046-SWECO-VGT-000-RP-GE-00001 Rev P01, January 2019. This report summarises ground investigation data across the proposed project to inform the design and construction of the scheme and presents interpretation and a risk assessment of the potential impact on receptors from encountered contamination, following intrusive investigation across the proposed CTLR Project.

The baseline information gathered from these reports is included in Section 10.5 and was used to determine potential effects on the identified soil and hydrogeology receptors.

10.4.5 Assessment of Significance and Mitigation Potential effects have been identified by predicting the changes (impacts) that would be caused by the construction and operation of the proposed CTLR Project in relation to the baseline situation. The significance of the effect has been defined by considering the sensitivity of the receiving environment, the potential likelihood or probability of the impact occurring, and magnitude of the change. Professional judgement is used to inform the assessment. Full details of the assessment undertaken to determine the significance of each potential effect is included in Appendix 10.1.

https://www.environment.gov.scot/maps/scotlands-environment-map/

https://dwqr.scot/private-supply/pws-location-map/

https://www.hutton.ac.uk/learning/natural-resource-datasets/soilshutton/soils-maps-scotland/download#soilmapdata

https://www.hutton.ac.uk/learning/natural-resource-datasets/soilshutton/soils-maps-scotland/download#soilmapdata

http://soils.environment.gov.scot/




The sensitivity of a receptor to change, includes its capacity to accommodate the type of changes that may occur as a result of the proposed CTLR Project. Table 10.1 provides examples of the characteristics that have been used to define the sensitivity of each receptor (soils and hydrogeology).

Table 10.1: Sensitivity Criteria

Importance (Sensitivity) Definition & Examples

Very High Receptors with a high quality and/or rarity, regional or national scale and limited potential for substitution/ replacement

Soils: Soils are of high value and importance, e.g. peat, very highly productive agricultural soils, superficial soils of high value or geological importance.

Hydrogeology: Hydrogeological catchment area is of very high value and importance i.e. provides river baseflow and is used extensively for private and public water supplies, e.g. groundwater abstractions for public or private drinking within 0-250m of the proposed project (greater than 1m depth excavations) or 0-100m (excavations less than 1m depth), Groundwater typically also has a vulnerability classification of 4 or 5.

High Receptors with a high quality and/or rarity, local scale and limited potential for substitution/replacement or receptor with a medium quality and rarity, regional or national scale and limited potential for substitution / replacement

Soils: Soils are of medium value and importance, e.g. carbon rich soils, highly productive agricultural soils.

Hydrogeology: Hydrogeological catchment area is of high value and importance i.e. provides baseflow and used for local private water supplies, e.g. groundwater abstractions for private supply within 250m of the proposed project (greater than 1m depth excavations) or 0-100m (excavations less than 1m depth). Groundwater typically also has a vulnerability classification of 3.

Medium Receptors with a medium quality and/or rarity, local scale and limited potential for substitution/replacement or receptor with a low quality and rarity, regional or national scale and limited potential for substitution / replacement

Soils: Soils are of medium value, e.g. productive agricultural soils.

Hydrogeology: Hydrogeological catchment area is of medium value and importance and is not generally used for public or private water supplies. Groundwater typically also has a vulnerability classification of 2.

Low Receptors with a low quality and/or rarity, local scale and potential for substitution/replacement. Environmental equilibrium is stable and is resilient to changes that are greater than natural fluctuations, without detriment to its present character

Soils: Soils are of low value and importance, e.g. general superficial soils of low value or geological importance.

Hydrogeology: Hydrogeological catchment area is of low value and importance and is not used for public or private water supplies. Groundwater typically also has a vulnerability classification of 1.

The magnitude of a potential impact includes consideration of its timing, scale, size and duration, which for the purposes of this assessment are defined in Table 10.2.




Table 10.2: Impact Magnitude Criteria

Magnitude Criteria

High Results in loss of attribute, i.e. long term, permanent change to receptors resulting from activities associated with the proposed CTLR Project, e.g. major changes to the hydrogeological regime or complete loss of soil / carbon resource.

Medium

Impacts integrity of attribute or results in loss of part of attribute, i.e. short to medium term change to receptors resulting from activities associated with the proposed CTLR Project, e.g. non-significant alteration to the hydrogeological regime or substantial loss of soil / carbon resource.

Low Results in minor impact on attribute, i.e. detectable but non-material and transitory changes to receptors resulting from activities associated with the proposed CTLR Project, e.g. minor alteration to the hydrogeological regime or minor loss of soil / carbon resource.

Negligible Results in an impact on attribute but of insufficient magnitude to affect the use/integrity, i.e. no perceptible changes to receptors resulting from activities associated with the proposed CTLR Project.

The sensitivity of the receiving environment, the magnitude of the potential impact and consideration of its likelihood of occurring, helps to evaluate the significance of the effect predicted prior to and after application of mitigation measures. The significance of effect has been defined using professional judgement, guided by the criteria outlined in Table 10.3: Significance of Effects. Effects of moderate significance and above (adverse and beneficial) are considered ‘significant’ and mitigation measures would be considered to avoid, reduce or offset any predicted significant effects. A minor or negligible level of effect is not considered to be significant and therefore no mitigation measures are generally required.

Table 10.3: Significance of Effects

Sensitivity

Magnitude Very High High Medium Low

High Major Major Moderate Minor

Medium Moderate Moderate Moderate Minor

Low Minor Minor Minor Negligible

Negligible Negligible Negligible Negligible Negligible

10.5 BASELINE CONDITIONS To maintain consistency with the PSSR and GIR, the baseline conditions presented in the following section will be separated by the headings “Trunk Road” (A9 realignment) and “Non-Trunk Road” (CTLR Mainline), where relevant.

10.5.1 Topography

Trunk Road The topography, as shown on Figures 10.1 to 10.5, is generally flat along the far northern section of the Trunk Road with elevations of 30-35m AOD becoming more undulated around the area of the A9 overbridge ranging between 13m and 36m AOD. A topographic high rises to 44m AOD across the eastern section of the Trunk Road, and falls to flat lying ground at approximately 10m AOD.




Non-Trunk Road A relatively flat floodplain (approximately 10m AOD to 20m AOD) characterises the topography along the non-trunk road immediately to the east of the River Tay, as shown on Figures 10.1 to 10.5. Ground levels undulate eastwards gradually increasing to a topographic high of 113m AOD, north of Scone.

10.5.2 Topsoil Trunk Road Alluvial soils are recorded to be present locally along the banks of the River Tay and River Almond. These soils typically comprise mineral alluvial soils with peaty alluvial soils derived from recent riverine alluvial deposits. Associated landforms include floodplains and river terraces. Alluvial soils within the Trunk Road study area are typically poorly or very poorly drained soils, and capable of producing high yields of a wide range of crops. Humus-iron podzols with some gleys of the Corby Group are recorded to be present in the northern section of the Trunk Road study area, surrounding Denmarkfield Farm and Redgorton. Parent material comprises glaciofluvial and raised beach sands and gravels derived from acid rocks, and associated landforms include undulating lowlands, mounds and terraces with gentle slopes. Humus-iron podzols of the Corby Group within the Trunk Road study area are typically free-draining, cultivated podzols capable of supporting arable crops. Within the westernmost section of the Trunk Road study area, west of Broxy Kennels, brown earths of the Balrownie Group are recorded. These soils typically comprise imperfectly drained brown forest soils with gleying, with some freely drained brown forest soils and some poorly drained non-calcareous gleys. Associated landforms include non-rocky, undulating lowlands and foothills. Arable land use within the area typically exhibits high to moderate yields.

Further details and figures of the soil distribution can be found in Chapter 14: Agriculture, Forestry and Sporting Interests and Figure 14.2.

Non-Trunk Road

Non-calcareous gleys of the Stirling Group cover much of the western section of the Non-Trunk Road study area, across the River Tay floodplain. In addition, these soils are recorded between Old Scone and Scone, in the southern section of the Non-Trunk Road study area, and within Highfield Plantation and Muirward Wood in the north eastern section of the study area. These soils typically comprise non-calcareous gleys with silty clay texture, derived from estuarine raised beach deposits. Associated landforms include level and gently sloping, raised beach terraces only. Land use often comprises cultivated, arable and permanent pastures capable of producing a moderate range of crops with moderate yields. Humus-iron podzols with some gleys of the Corby Group are recorded to be present surrounding Stormontfield Road, Sherifftown, Old Coney Bank and Old Scone. Parent material comprises glaciofluvial and raised beach sands and gravels derived from acid rocks, and associated landforms include undulating lowlands, mounds and terraces with gentle slopes. Humus-iron podzols of the Corby Group within the Non-Trunk Road study area are typically free-draining, cultivated podzols capable of supporting arable crops. The majority of the Non-Trunk Road study area is underlain by brown earths of the Balrownie Group. This unit is recorded to extend from the Stormontfield Road junction with the A93, north to Blairhall Plantation and east to the A94, excluding the area surrounding Highfield Plantation and Muirward Wood (as previously stated, this area is underlain by soils of the Stirling Group). Soils of the Balrownie Group typically comprise imperfectly drained brown forest soils with gleying, with some freely drained brown forest soils and some poorly drained non-calcareous gleys. Associated landforms include non-rocky, undulating lowlands and foothills. Arable land use within the area typically exhibits high to moderate yields.




Further details and figures of the soil distribution can be found in Chapter 14: Agriculture, Forestry and Sporting Interests and Figure 14.2.

10.5.3 Geological Setting Superficial Deposits Trunk Road Superficial deposits along the Trunk Road vary with topography, and comprise Glacial Till deposits, Raised Marine Deposits, Glaciofluvial Deposits and Alluvium. Topographically high areas north and south of the A9 overbridge comprise thick deposits of Glacial Till (greater than 70m south of the A9 overbridge) and Glaciofluvial Deposits with lower lying areas comprising Raised Marine deposits, Glaciofluvial Deposits and Alluvium overlying Glacial Till. The superficial geology is presented on Figure 10.2. The mapped ground conditions were generally confirmed by the intrusive investigation. Peat, organic matter and plant remains were recorded as inclusions within the raised marine deposits in three locations. Non-Trunk Road Superficial deposits vary with topography along the Non-Trunk Road and comprise Glacial Till deposits, Raised Marine Deposits, Raised Tidal Flat Deposits, Glaciofluvial Deposits and Alluvium. Generally flat lying Alluvium Deposits extend east of the River Tay to Coney Bank, overlying Glacial Till. Topography rises eastwards along the remainder of the route comprising generally thin Glacial Till deposits, up to 20m overlying bedrock. The mapped ground conditions were generally confirmed by the intrusive investigation. Localised deposits of fibrous peat were recorded within the raised tidal flat deposits, although these comprised thin discontinuous layers with a maximum thickness of 0.7m. The superficial geology is presented on Figure 10.2.

Solid Geology The Trunk Road and Non-Trunk Road sections are underlain by sedimentary strata of the Lower Devonian Scone Sandstone Formation, part of the Garvock Group (Lower Old Red Sandstone Supergroup) and bedding generally dips towards the northwest. The Formation has been displaced along the south-eastern most section of the Non-Trunk Road by three faults. The solid geology is presented on Figure 10.1.

10.5.4 Hydrology The following summarises the hydrology relevant to the assessment in this chapter. Further information, drawings and consideration of potential impacts is given in the section on Chapter 15: Road Drainage and the Water Environment.

Trunk Road A number of watercourses flow throughout the study area (as shown in Figure 15.1):

• East of the existing A9, the River Tay flows south towards Perth and the Firth of Tay;

• Immediately south of the realigned A9 trunk road, the River Almond flows east and meets the River Tay at a confluence approximately 500m east of the southern extent of the realigned A9 trunk road;

• Several small unnamed issues and field drains flow east from Bertha Loch (located approximately 800m west of the proposed grade separated junction and the surrounding area, into an unnamed stream, which flows east later meeting the River Tay at a confluence. This unnamed stream flows through culverts under the existing A9 and the Highland Mainline Railway; and




• A small pond is located immediately west of the existing A9 at Four mile house. An issue flows southeast from the pond, through a culvert under the A9 and the Highland Mainline Railway into the River Tay.

In addition, several field drains of various orientations and unnamed ponds are scattered across the study area, typically located within close proximity to those watercourses detailed above.

Non-Trunk Road A number of watercourses flow through the Non-Trunk Road area (as shown in Figure 15.1):

• Local to the westernmost extent of the proposed Non-Trunk Road, the River Tay flows south towards Perth and the Firth of Tay;

• Whiggle Burn flows west from Muirward Wood, later becoming Gelly Burn. The burn is located north of the proposed Non-Trunk Road and flows towards the River Tay. Gelly Burn meets the River Tay at a confluence at the north western corner of Drumshogle Wood;

• Cramock Burn flows southwest from Balboughty towards the River Tay. The burn is located south of the proposed Non-Trunk Road and flows approximately parallel to the proposed road alignment. Cramock Burn meets the River Tay at a confluence approximately 800m south of the River Tay Crossing Bridge;

• Within the Highfield Plantation, unnamed field drains flow beneath the proposed Non-Trunk Road route, northwest of Spoutwells; and,

• Northeast of the proposed Non-Trunk Road roundabout junction with the A94, Annaty Burn flows south parallel to the A94 before changing direction flowing west to the south of Scone and into the River Tay.

In addition, several field drains and springs of various orientations, and unnamed ponds are scattered across the study area, typically located within close proximity to those watercourses detailed above.

10.5.5 Hydrogeology The following information relevant to the Trunk Road and Non-Trunk Road was obtained from the BGS Aquifer Productivity and Aquifer Vulnerability digital GIS datasets supplied by the Council, and from intrusive site investigation data. The data is presented on Figures 10.3, 10.4 and 10.5.

Trunk Road Groundwater Vulnerability (Figure 10.5) classification varies beneath the Trunk Road ranging from 1 to 4a (low to high vulnerability). Low (1) is defined as ‘only vulnerable to conservative pollutants in the long term when continuously and widely discharged/leached’ and high (4a) is defined as ‘vulnerable to those pollutants not readily adsorbed or transformed. Aquifer productivity classes range from Low-Medium intergranular flow to High intergranular flow along the Trunk Road with areas to the south, including the topographic high, defined as ‘not a significant aquifer’. Intrusive site investigation of the Trunk Road encountered groundwater within the lower lying glacial alluvium deposits in the south and the raised marine deposits and glacial fluvial deposits in the central and northern areas (Figure 10.3). Groundwater was generally absent within the glacial till deposits south of the A9 overbridge, or present as perched water within granular layers or lenses. A number of historical wells are noted, between approximately 50m and 1km from the Trunk Road, however information provided by the Council did not identify any existing private water supplies within 1km of the Trunk Road. Regional groundwater flow direction beneath the Trunk Road is east towards the River Tay.




Non-Trunk Road Groundwater Vulnerability classification varies beneath the Non-Trunk Road ranging from 1 to 4a (low to high vulnerability) (Figure 10.5). Low (1) is defined as ‘only vulnerable to conservative pollutants in the long term when continuously and widely discharged/leached’ and high (4a) is defined as ‘vulnerable to those pollutants not readily adsorbed or transformed. Areas of lower groundwater vulnerability lie within 2km east of the River Tay and areas further east are classified as higher vulnerability. Aquifer productivity classes range from Low-Medium intergranular flow to High intergranular flow along the western portion of the Non-Trunk Road with large areas along the route classed as ‘not a significant aquifer’. Intrusive site investigation of the Non-Trunk Road route encountered groundwater within raised tidal flat deposits, glacial alluvium, glacial fluvial and glacial till deposits, although in the latter generally present as perched water within granular layers or lenses. A number of historical wells have been identified between approximately 100m and 900m from the Non-Trunk Road, however, information provided by the Council did not identify any existing private water supplies within 1km of the Non-Trunk Road. Regional groundwater flow direction beneath the Non-Trunk Road is west towards the River Tay.

10.6 POTENTIAL EFFECTS A construction effect is short term and will only result from impacts occurring during the construction of the proposed CTLR Project (e.g. effects due to pumping groundwater from excavations, spillage of oils or chemicals). An operational effect is one that could potentially occur due to impacts during construction but will have a longer lasting effect e.g. permanent alteration of the groundwater regime. A number of potential effects on the identified baseline soil and hydrogeology receptors associated with the proposed CTLR Project have been identified and are detailed in the Construction and Operation subsections below. The full detail of the assessment to determine the significance of these effects is detailed in Appendix 10.1.

10.6.1 Construction The assessment of potential construction effects takes into account the site conditions, baseline sensitivities and construction activities anticipated. The following potentially significant construction effects have been identified:

• Accidental release, leakage or spillages of hydrocarbons, chemicals, fuel or oils from storage tanks or construction plant during construction causing contamination of groundwater;

• Localised increase in alkalinity from spillages of concrete or unset cement causing pollution of groundwater, the severity of which may be increased during times of heavy or prolonged rainfall; and

• Potential contamination of the water environment due to the disturbance of contamination associated with construction works and in particular deep excavations (e.g. bridge foundations, deep utility excavations), or the mobilisation of contaminants due to groundwater pumping.

10.6.2 Operation Potential operational effects on soils and hydrogeology are expected to occur (or continue to occur) once the proposed CTLR Project is in operation. The following subsections detail the identified potential effects associated with the operational stage.




10.6.3 Soils The following potential effects on soils have been identified:

• Stripping of topsoil from construction areas on site having an adverse effect on the top soil resource – potential to cause deterioration of topsoil even if reused;

• Soil compaction associated with construction traffic may reduce soil permeability and increase surface runoff;

• Potential for increased erosion effects on topsoil (and consequently the water environment) associated with tree and vegetation removal; and

• Potential adverse effects on the superficial deposit geological resource from excavations or road/structure construction.

10.6.4 Hydrogeology The following potential effects on hydrogeology have been identified (note that risks to surface water associated with similar effects are considered further in Chapter 15: Road Drainage and the Water Environment, Section 15.6):

• Dewatering and alteration of the groundwater regime (drift aquifer) including potential disruption to private water supplies caused by the proposed CTLR Project, especially from excavations and the construction of deep foundations (e.g. large cuttings and piled foundations for the River Tay Crossing Bridge);

• Potential contamination of water environment by leachable contamination from imported fill materials or SuDS drainage;

• Surface runoff from the new road, causing pollution of groundwater; and

• Reduction in infiltration caused by increased hardstanding cover or compaction of soils, resulting in impacts on groundwater.

10.7 MITIGATION AND ENHANCEMENT The following mitigation measures have been proposed to avoid, reduce or offset any significant predicted effects identified in Section 10.6. These are split into mitigation during construction and operational phases of the proposed CTLR Project. Further details of the mitigation measures for each of the effects are set out in the assessment in Appendix 10.1, and a summary of the proposed mitigations follows.

10.7.1 Construction Measures to mitigate potentially significant effects arising from the construction of the proposed CTLR Project are based on standard best practice on site. These will be detailed within the CEMP to be produced by the Contractor, examples of which are presented below:

• Emergency spill kits available on site to protect against accidental release, leakage or spillage of potentially contaminative substances and materials;

• Construction plant will be checked regularly for leakages and will undergo maintenance on a regular basis;

• Construction traffic will be limited to allocated areas of the proposed CTLR Project area;

• Concrete and cement mixing and washing areas will be sited at appropriate distances from any surface watercourses to limit potential pollution of the water environment; and

• Site drainage measures, including drainage ditches and silt traps will be provided to collect and treat increased surface run-off.




10.7.2 Operation Measures to mitigate potentially significant effects arising from operation of the proposed CTLR Project are presented below.

Soils Measures to mitigate against the potential Moderate effects on the topsoil resource during operation include:

• The reuse of topsoil, including its stripping and proper storage will follow BS 3882:2015 (Specification for Topsoil) to minimise loss of the resource; and

• Dedicated plant routes, ripping of subsoil prior to topsoil placement, and site drainage measures to collect and treat increased surface run-off where necessary will be detailed in the CEMP.

No mitigation measures are considered necessary for the effects on the superficial geological resource from excavations or road / structure construction as the effects are considered to have Minor significance.

Hydrogeology Considering the medium sensitivity of the groundwater body underlying the study area and the potential long term change, a Moderate Significance is considered appropriate. The specific requirement for the application of mitigation measures will be subject to detailed design, but will comprise standard engineering design, such as suitable design of temporary dewatering methods, appropriate foundation design, chemical analysis and assessment of imported fill materials or site-won materials intended for reuse, lining of SuDS within areas of made ground, and suitable treatment of road runoff prior to discharge. No mitigation measures are considered necessary for effects from dewatering or reduction in infiltration as the effects are considered to have a Minor significance.

10.8 RESIDUAL EFFECTS All of the identified potentially significant effects on identified soil and hydrogeology receptors during the construction and operational stages are considered to be mitigated to a non-significant level (Minor significance) following implementation of the identified mitigation measures. Therefore, no significant residual effects are predicted.

10.9 CUMULATIVE EFFECTS The cumulative effect of the proposed CTLR Project combined with the development of other proposed developments within the proposed CTLR Project area have been considered. These developments are described in Volume 3. There may be minor cumulative effects on the groundwater flow regime due to excavations and hardstanding cover associated with future developments, although these are localised and not considered to be significant considering the size and scale of the catchment. Also, the closest development will begin construction after completion of the proposed CTLR Project, which will minimise cumulative construction effects. Considering the proposed mitigations for effects on topsoil, and the generally low sensitivity of the superficial geology resource, it is not predicted that there would be any significant construction or operational cumulative contamination effects from identified future developments.




10.10 STATEMENT OF SIGNIFICANCE The committed mitigation measures outlined in this chapter and detailed in Appendix 10.1 are considered sufficient to avoid or reduce the identified potentially significant effects on sensitive receptors to a non-significant level (minor or negligible level of effect). No significant residual effects (those potentially significant effects remaining following adoption of mitigation measures) are predicted to remain. In summary, based on the currently available information, no adverse effects have been predicted from the proposed CTLR Project which are considered significant in the context of the EIA Regulations.




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CSTD-MCQGB

CXF-MDSI

SCN-SDST

This drawing should not be relied on or used in circumstances other than those for which it was originally prepared and for which Sweco UK Limited was commissioned. Sweco UK Limited accepts no responsibility for this drawing to any party other than the person by whom it was commissioned. Any party which breaches the provisions of this disclaimer shall indemnify Sweco UK Limited for all loss or damage arising therefrom.

Sweco, Suite 4/2, City Park, 368 Alexandra ParadeGlasgow, G31 3AU, Tel: +44 (0)141 414 1700

Scale @ A3Project No. 119046

Drawn Appr'dDrawing StatusRev. Rev. DateJMFor InformationP01

Figure 10.1 Solid GeologyPage 1 of 3

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LegendProposed CTLR ProjectPSSR Study Area - 1km buffer fromProposed CTLR ProjectInferred Fault

Solid Geology - Bedrock *CSTD-MCQGB, Central Scotland LateCarboniferous Tholeiitic Dyke SwarmCXF-MDSI, Cromlix Mudstone FormationSCN-SDST, Scone Sandstone Formation

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BIM No. 119046-SWECO-EGN-000-DR-GS-20046

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Contains OS data © CrownCopyright and database right2019

Reproduced by permission of Ordnance Survey on behalf of HMSO. © Crown copyright and database rights 2019 OS 100016971. © and database right Crown copyright and Landmark Information Group Ltd (All rights reserved 2019). Based upon data from 50K scale BGS Digital Data under Licence 2015/031F Comp1 British Geological Survey. @NERC.

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Note:* Landmark BGS Superficial Deposits Dataset is limited to a 500m buffer extent surrounding the proposed infrastructure, for additional 500m extent refer to GIS data for BGS WMS.

CSTD-MCQGB

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ALV-XCZSV

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RTFDF-XZCRMDV-XCZSV

GFSD-XVSZ

GFSD-XVSZ

GFSD-XVSZGFIC-XVSZ

TILLD-DMTN

TILLD-DMTNTILLD-DMTN

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Figure 10.2 Superficial DepositsPage 1 of 3

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LegendProposed CTLR ProjectPSSR Study Area - 1km buffer fromProposed CTLR Project

Superficial Geology **ALV-XCZSV, Alluvium, Clay Silt Sand andGravelGFIC-XVSZ, Glaciofluvial Ice ContactDeposits, Gravel Sand and SiltGFSD-XVSZ, Glaciofluvial Sheet Deposits,Gravel Sand and SiltRMDV-XCZSV, Raised Marine Deposits -Devensian, Clay Silt Sand and GravelRTFDF-XZC, Raised Tidal Flat Deposits OfFlandrian Age, Silt and ClayTILLD-DMTN, Till - Devensian, Diamicton

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Cross Tay Link Road

Note:Landmark BGS Superficial Deposits Dataset is limited to a 500m buffer extent surrounding the proposed infrastructure, for additional 500m extent refer to GIS data for BGS WMS.

ALV-XCZSV

ALV-XCZSVALV-XCZSV

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T his d rawing should not b e re lie d on or use d in circum stanc e s othe r than those for whic h it was originally p re p are d and for whic h S we c o U K Lim ite d was com m issione d . S we c o U K Lim ite d ac c e p ts no re sp onsib ility for this d rawing to any p arty othe r than the p e rson b y whom it was com m issione d . Any p arty whic h b re ac he s the p rovisions of this d isclaim e r shall ind e m nify S we c o U K Lim ite d for all loss or d am age arising the re from .

S we c o, S uite 4/2, City Park, 368 Ale xand ra Parad eGlasgow, G31 3AU , T e l: +44 (0)141 414 1700

S c ale @ A3Proje c t No. 119046

Drawn Ap p r'dDrawing S tatusRe v.Re v. DateJMFor Inform ationP01

Figure 10.3 Aquife r Prod uctivity – S up e rfic ial De p osits

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LegendProp ose d CT LR Proje ctPS S R S tud y Are a - 1km b uffe r fromProp ose d CT LR Proje ct

Aquifer Productivity – SuperficialDeposits, Intergranular Flow

High Prod uctivityMod e rate to High Prod uctivityLow to Mod e rate Prod uctivityNot a signific ant aquife r

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Contains OS d ata © CrownCop yright and d atab ase right2019

Clie nt

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Re p rod uc e d b y p e rm ission of Ord nanc e S urve y on b e half of HMS O. © Crown cop yright and d atab ase rights 2019 OS 100016971. De rive d from 50K scale BGS DigitalData und e r Lic e nc e 2015/031F Com p 1 British Ge ologic al S urve y @NERC.






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This dra win g should n ot b e relied on or used in circum sta n ces other tha n those for which it wa s origin a lly prepa red a n d for which S weco UK Lim ited wa s com m ission ed. S weco UK Lim ited a ccepts n o respon sib ility for this dra win g to a n y pa rty other tha n the person b y whom it wa s com m ission ed. An y pa rty which b rea ches the provision s of this discla im er sha ll in dem n ify S weco UK Lim ited for a ll loss or da m a ge a risin g therefrom .

S weco, S uite 4/2, City P a rk, 368 Alexa n dra P a ra deGla sgow, G31 3AU, Tel: +44 (0)141 414 1700

S ca le @ A3P roject No. 119046

Dra wn Appr'dDra win g S ta tusR ev.R ev. Da teJMFor In form a tionP 01

Figure 10.4Aquifer P roductivity – Bedrock

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LegendP roposed CTLR P rojectP S S R S tudy Area - 1km b uffer fromP roposed CTLR P roject

Aquifer Productivity – BedrockIn tergra n ula r & Fra cture Flow; HighP roductivityIn tergra n ula r & Fra cture Flow; Modera teP roductivityFra cture Flow; Low P roductivityFra cture Flow; V ery Low P roductivity

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BIM No. 119046-S W ECO-EGN-000-DR -GS -20073

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Con ta in s OS da ta © CrownCopyright a n d da ta b a se right2019

R eproduced b y perm ission of Ordn a n ce S urvey on b eha lf of HMS O. © Crown copyright a n d da ta b a se rights 2019 OS 100016971. Use of this da ta is sub ject to term s a n d con dition s. Derived from 50K sca le BGS Digita l Da ta un der Licen ce 2015/031F Com p1 British Geologica l S urvey. @NER C.

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Figure 10.5 Groundwater VulnerabilityPage 1 of 3

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Groundwater Vulnerability Classifications5 - Vulnerable to most pollutants, with rapidimpact in many scenarios.4a - Vulnerable to those pollutants not readilyadsorbed or transformed. Less likely to haveclay present in superficial deposits (thereforegenerally higher vulnerability than 4b).4b - Vulnerable to those pollutants not readilyadsorbed or transformed. More likely to haveclay present in superficial deposits (thereforegenerally lower vulnerability than 4a).3 - Vulnerable to some pollutants; many otherssignificantly attenuated.2 - Vulnerable to some pollutants, but onlywhen they are continuouslydischarged/leached.1 - Only vulnerable to conservative pollutantsin the long term when continuously and widelydischarged/leached.0 - Not sufficient data to classify vulnerability.

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HYDROGEOLOGY & SOILS EIA REPORT (VOLUME 2)


CHAPTER 10 HYDROGEOLOGY AND SOILS APPENDIX 10.1: Impact Assessment Table



November 2019 PAGE 2 OF APPENDIX 10.1

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HYDROGEOLOGY & SOILS EIA REPORT (VOLUME 2)


Appendix 10.1: Impact Assessment Table

PHASE POTENTAIL EFFECTS

(WITHOUT MITIGATION)

SIGNIFICANCE OF POTENTIAL EFFECT (PRE-MITIGATION)

JUSTIFICATION MITIGATION MEASURES

SIGNIFICANCE OF POTENTIAL EFFECT (POST MITIGATION)

SENSITIVITIY MAGNITUDE SIGNIFICANCE SENSITIVITY MAGNITUDE

CO

NS

TR

UC

TIO

N

Accidental release, leakage or spillage of hydrocarbons, chemicals, fuel or oils from storage tanks/construction plant during construction causing contamination of groundwater

Medium Medium MODERATE

Due to the limited use of the hydrogeological resource as a public or private water supply and the scale of the catchment area, the water environment within the proposed project area is considered to be of Medium sensitivity.

If these effects were to occur, it is considered likely that they would result in a short to medium term change to the quality of the groundwater body underlying the study area.

Considering the medium sensitivity of the groundwater body underlying the study area and the potential short to medium term change likely to occur, the identified potential effect is considered to be of Moderate Significance. A number of measures to mitigate against this potential effect will be detailed in the CEMP and implemented during construction stage, including: emergency spill kits available on site to protect against accidental release, leakage or spillage of potentially contaminative substances and materials; construction plant will be checked regularly for leakages and will undergo maintenance on a regular basis; construction traffic will be limited to allocated areas of the proposed project area; concrete and cement mixing and washing areas will be sited at appropriate distances from any surface watercourses to limit potential pollution of the water environment; site drainage measures, including drainage ditches and silt traps to collect and treat increased surface run-off, will be implemented where required.

MINOR

Localised increase in alkalinity from spillages of concrete or unset cement causing pollution of groundwater, severity may be increased during heavy or prolonged rainfall

Medium Medium MODERATE MINOR

Potential contamination of the water environment due to the disturbance of contamination associated with construction works and in particular deep excavations (e.g. bridge foundations, deep utility excavations), or the mobilisation of contaminants due to groundwater pumping

Medium Medium MODERATE MINOR

OP

ER

AT

ION

SO

ILS

Stripping of topsoil from construction areas on site having an adverse effect on the topsoil resource – potential to cause deterioration of topsoil even if reused

High Medium MODERATE

Topsoil resource present across the study area comprises variable soils, including some capable of producing high agricultural yields, and some less productive (moderate and below). Consequently topsoil has been conservatively assigned a High Sensitivity.

Although the effect will only apply to a small proportion of the overall regional topsoil and agricultural resource, considering the scale of the development a Medium magnitude has been conservatively applied, representing 'substantial loss of soil resource'.

Some of the topsoil materials will be suitable for reuse, which will be used within the development where possible, and if this is not possible may be reused on other developments. The reuse of topsoil, including its stripping and proper storage will follow BS 3882:2015 (Specification for Topsoil) to minimise loss of the resource.

MINOR

Soil compaction associated with construction traffic may reduce soil permeability and increase surface run-off

High Medium MODERATE

A number of measures to mitigate against the potential effects of soil erosion and compaction will be detailed in the CEMP and implemented during construction stage, which may include stripping of topsoil on dedicated haul routes, followed by the ripping of subsoil prior to re-topsoiling on completion of the works, and site drainage measures, such as drainage ditches and silt traps to collect and treat increased surface run-off where necessary.

MINOR

Potential for increased erosion effects on topsoil (and consequently the water environment) associated with tree and vegetation removal

High Medium MODERATE MINOR

Potential adverse effects on the superficial deposit geological

High Low MINOR Occasional peat and carbon rich superficial soils were recorded during site investigation to

Considering the localised nature of the carbon rich soils,

Considering the Minor significance, mitigation measures are not considered necessary for this potential effect.

MINOR










resource from excavations or road / structure construction

underlie the study area, within the raised tidal flat deposits in the vicinity of the River Tay (non-trunk road section). No designated geological sites (SSSI or RIGS) have been recorded, and the superficial soils generally have a low economic value. Considering the presence of carbon rich soils within the scheme (although localised), the superficial geology has been conservatively classified as High Sensitivity.

and that the majority of the route is on embankment at this location, the effect will only apply to a small proportion of the overall regional superficial geological resource, and so a Low magnitude has been applied, representing 'minor loss of soil resource'.

HY

DR

OG

EO

LO

GY

Dewatering and alteration of the groundwater regime (drift aquifer) including potential disruption to private water supplies caused by the proposed project, especially from excavations and the construction of deep foundations (e.g. large cuttings and piled foundations for the River Tay crossing)

Medium Low MINOR

Due to the limited use of the hydrogeological resources as public or private water supplies and the scale of the hydrogeological catchment area, the groundwater body underlying the proposed development is considered to be of Medium sensitivity.

If these effects were to occur, considering the scale of the catchment relative to the likely alteration to the groundwater flow regime, it is considered likely that piled foundations would result in a detectable but localised and non-material change and so a Low magnitude is considered appropriate. Although there are substantial cuttings proposed as part of the trunk road, an assessment of the volumes of groundwater likely to be generated indicates a Low magnitude of impact is likely.


MINOR

Potential contamination of water environment by leachable contamination from imported fill materials or SuDS drainage

Medium Major MODERATE

If these effects were to occur, it is considered possible that they would result in a long term change to the quality of the groundwater body underlying the study area.

Considering the medium sensitivity of the groundwater body underlying the study area and the potential long term change a Moderate Significance is considered appropriate. The specific requirement for the application of mitigation measures will be subject to detailed design, but will comprise standard engineering design, such as suitable design of temporary dewatering methods, appropriate foundation design, chemical analysis and assessment of imported fill materials or site-won materials intended for reuse, lining of SUDS within areas of made ground, and suitable treatment of road runoff prior to discharge.

MINOR

Surface run-off from the new road causing pollution of groundwater

Medium Major MODERATE MINOR










Reduction in infiltration caused by increased hardstanding cover or compaction of soils, resulting in impacts on groundwater

Medium Low MINOR

Considering the limited hardstanding cover and small footprint of the works relative to the catchment size, if this effect were to occur it is considered likely that it would result in a detectable but localised and non-material change and so a Low magnitude is considered appropriate.


MINOR




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