Hydrogeological Impact Assessment in support of a Planning ... · PDF fileTable PP/HIA/T2...

Hydrogeological Impact Assessment in support of a Planning Application for the

restoration of Pitsford Pond, Northamptonshire

Report ref: PP/HIA

Final December 2012

Report prepared for:

GP Planning Ltd The Stables Long Lane

EAST HADDON Northamptonshire

NN6 8DU

B A R K E R S C H A M B E R S • B A R K E R S T R E E T • S H R E W S B U R Y • U N I T E D K I N G D O M • S Y 1 1 S B

T E L : 0 1 7 4 3 3 5 5 7 7 0 F A X : 0 1 7 4 3 3 5 7 7 7 1 E M A I L : i n f o @ h a f r e n w a t e r . c o m

Hydrogeological Impact Assessment in support of a Planning Application for the

restoration of Pitsford Pond, Northamptonshire

Report ref: PP/HIA

Final December 2012

Prepared by: Checked by:

L Brown MSc FGS CGeol C C Leake BSc MSc FGS

GPP Planning Hydrogeological Impact Assessment: Pitsford Pond, Northamptonshire Final

Page i December 2012

P:\Projects\Pitsford Ponds\Report\HIA Pitsford Ponds Final (Dec 12).doc

CONTENTS

1 INTRODUCTION 1

1.1 Background 1 1.2 Objectives 1 1.3 Data sources 1 1.4 Methodology of investigation 2

2 SITE SETTING 3

2.1 Location 3 2.2 Landform 3

3 BASELINE CONDITIONS 4

3.1 Background 4 3.2 Hydrology 4 3.2.1 Rainfall 4 3.2.2 Watercourses 4 3.2.3 Springs and wells 4 3.2.4 Ponds and waterbodies 5 3.2.5 Landfill sites 5 3.2.6 Protected sites and areas of ecological interest 5 3.2.7 Surface water abstraction 6 3.2.8 Discharge consents 6 3.2.9 Surface water quality 7 3.3 Geology 7 3.3.1 Regional 7 3.3.2 Local geology 8 3.3.3 Quarry workings 8 3.4 Hydrogeology 8 3.4.1 Aquifer status and regional context 8 3.4.2 Aquifer characteristics 8 3.4.3 Hydraulic conductivity 9 3.4.4 Source protection zones 9 3.4.5 Groundwater abstractions 9 3.4.6 Groundwater levels and distribution 10 3.4.7 Groundwater quality 10 3.4.8 Conceptual hydrogeology 10

4 PROPOSED DEVELOPMENT 11

4.1 Restoration 11 4.2 Compliance with landfill guidance 11 4.3 Water management during restoration 11 4.3.1 Background 11 4.3.2 Discharge requirements 11 4.4 Water management post restoration 12

5 ASSESSMENT OF IMPACTS 13

5.1 Methodology 13 5.2 Catchment sensitivity 13 5.3 Potential impacts during restoration 13 5.3.1 Groundwater levels 13 5.3.2 Groundwater abstractions 14


Page ii December 2012


5.3.3 Groundwater quality 14 5.3.4 Surface water flows 14 5.3.5 Surface water quality 14 5.4 Potential impacts after restoration 14

6 MITIGATION MEASURES AND RESIDUAL IMPACTS 15

6.1 Post-restoration 15 6.2 Cumulative impacts 15

7 SUMMARY AND CONCLUSIONS 16

TABLES

Table PP/HIA/T1 Long-term average monthly rainfall at Pitsford Reservoir raingauge (mm) 4 Table PP/HIA/T2 Details of landfill sites within 2 km 5 Table PP/HIA/T3 Discharge consents 6 Table PP/HIA/T4 Summary of solid geology 7 Table PP/HIA/T5 Public water supplies within a 2 km radius of the site 10

FIGURES Figure PP/HIA/01 Site location Figure PP/HIA/02 Site details Figure PP/HIA/03 Landform and water features Figure PP/HIA/04 Location of landfills and discharge consents Figure PP/HIA/05 Geology Figure PP/HIA/06 Location of quarried areas and groundwater monitoring boreholes

APPENDICES Appendix PP/HIA/A1 Assessment methodology Appendix PP/HIA/A2 Drawings supplied by Abington Consulting Engineers Appendix PP/HIA/A3 Groundwater inflow calculations


Page 1 December 2012


1 INTRODUCTION

1.1 Background

Pitsford Pond is part of a former mineral working located south of the village of Pitsford, Northamptonshire. The former mineral workings in which the pond is located lie within the Northampton Sand Formation, which was last worked in the early 1980s. Since then the workings were partially restored to agricultural use and partly to a shallow lake, which has been in use as a fishery. Part of the area is recorded as an inert landfill. Pitsford Pond lies adjacent to Pitsford Quarry, owned by Peter Bennie Ltd. The quarry is currently closed due to uneconomic market conditions. Peter Bennie Ltd proposes to start an inert waste recycling operation at Pitsford Quarry to recover aggregate from imported inert waste. Material from this process that is unsuitable for aggregate production will be used to infill Pitsford Pond under a Waste Recovery Permit in order to restore the site for agricultural use. Hafren Water has been requested to prepare an assessment of potential impacts on the water environment arising from the proposed development and to support a Planning Application for this development. 1.2 Objectives

The principal objectives of this study are to: � Determine baseline conditions in relation to the water environment at Pitsford Pond and its

surroundings � Identify any potential impacts of the proposed development � Assess the magnitude and significance of potential impacts � Derivation of appropriate mitigation measures for any identified potential impacts 1.3 Data sources

The following sources of data were used in this study: British Geological Survey (BGS) 1:50,000 scale geological map, Sheet 185 Northampton Geological logs of nearby boreholes Ordnance Survey (OS) Explorer 1:25,000 scale map, Sheet 223, Northampton & Market Harborough The Environment Agency (EA)

Licensed abstractions Licensed discharges Active and historical landfills

Rainfall data Surface water quality Natural England Sites of Special Scientific Interest Local Authorities (Daventry District Council) Private water abstractions




1.4 Methodology of investigation

Baseline conditions of the water environment have been defined by the collation and analysis of existing data and field observations. The potential effects of the proposed development upon the extant water environment have been assessed by reference to the baseline data and a series of matrices (Appendix PP/HIA/A1), developed to ensure a rigorous and consistent approach to the assessment of potential impacts. Mitigation measures have been proposed where appropriate.




2 SITE SETTING

2.1 Location

The Application Area is located approximately 1 km south of the village of Pitsford, Northamptonshire (Figure PP/HIA/01) and is centred on National Grid Reference (NGR) SP 760 669. The Application Area, which covers 4.8 hectares (ha), includes the access track from Harborough Road (A508), the existing weighbridge, wheelwash and offices, part of Pitsford Quarry and Pitsford Pond. Details of the Application Area are shown on Figure PP/HIA/02. Pitsford Pond (‘the site’) is bounded to the north by Moulton Road and agricultural land to the south, east and west. The nearest residential properties are located 100 m south of the site. Access to the site is currently from Moulton Road. However, during the development access will be from the A508, Harborough Road located to the west of the former quarry area. 2.2 Landform

The site lies on the southern side of an interfluve between two unnamed tributaries of the Brampton Branch at an elevation of approximately 105 metres Above Ordnance Datum (mAOD). South and west of the site, the ground slopes down at a gradient of 1:14 towards an unnamed stream, which flows to the west. North of the site, the ground rises gradually to reach 120 mAOD to the east of Pitsford village.




3 BASELINE CONDITIONS

3.1 Background

Baseline (ie existing) conditions at the site are set out below and include information relating to the environmental setting as well as current activities at the site. Knowledge of baseline conditions has been developed based on published literature, site-derived data and from experience of similar sites in similar settings. A conceptual model which sets out the current understanding of the geology and hydrogeology has been developed on the basis of the baseline data and this has been used to identify potential sources of impact. 3.2 Hydrology

The hydrology of the site and its environs has been derived from Ordnance Survey maps, a water features survey and data provided by the Environment Agency. The locations of the water features discussed in this section are shown on Figure PP/HIA/03. 3.2.1 Rainfall The nearest Environment Agency raingauge (Station No 159426) is located at Pitsford Reservoir at NGR SP 7589 6864, approximately 1.7 km north of the site. The long-term average (LTA) rainfall is 633 mm/annum. Monthly LTA rainfall is shown on Table PP/HIA/T1.

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

53 41 50 48 53 58 54 63 48 50 55 60

Table PP/HIA/T1: Long-term average monthly rainfall at Pitsford Reservoir raingauge (mm) 3.2.2 Watercourses The largest watercourse in the vicinity of the site is the Brampton Branch, located 2.5 km west of the site. The river flows from north to south, to its confluence with the River Nene at Northampton, 7 km to the south. The site lies between two unnamed tributaries of the Brampton Branch, both flowing from east to west: � The nearest tributary is located 500 m south of the site. It rises 4 km east of the site, to the

northeast of the village of Moulton, and joins the Brampton Branch 2.4 km to its west.

� The second tributary lies 1.6 km north of the site and joins the Brampton Branch 2.3 km to the northwest. The tributary was dammed in 1956, just north of Pitsford village, to form a large artificial lake, Pitsford Water.

3.2.3 Springs and wells According to the 1:25,000-scale Ordnance Survey map, historical maps and information from Daventry District Council, there are a number of springs located within 2 km of the site. Their locations are presented on Figure PP/HIA/03. � There are 11 springs to the south of the site, marked S1 to S10, all discharging into

watercourses draining into the southern unnamed tributary of the Brampton Branch. The nearest of these springs, S3, is located 400 m south of the site and a further two, S2 and




S4, within 500 m. Three springs, S9, S10 and S11, are located south of the unnamed Brampton Branch tributary.

� There are 6 springs to the north of the site, S12 to S17. All drain into the northern tributary

of Brampton Branch. The closest of these springs to the site is S13, located 1.1 km away and just to the east of Pitsford Village.

� Two springs, S18 and S19, are located to the west of the Brampton Branch. A number of wells are shown on the Ordnance Survey map and the geological map (BGS Sheet 185), as indicated on Figure PP/HIA/03. The closest, W5, is located approximately 1 km to the southwest. 3.2.4 Ponds and waterbodies Three waterbodies are located within 2 km of the site: � One waterbody lies within the site itself. This waterbody lies within an area of restored

ironstone workings and was used in the past as a fishery. The waterbody has an area of approximately 0.3 Ha.

� A waterbody is located within the valley of the Brampton Branch tributary at Boughton Park,

700 m southwest of the site. The waterbody covers an area of approximately 1 Ha. � Pitsford Reservoir is located some 1.7 km north of the site and covers an area of 400 Ha.

The reservoir is a designated Site of Special Scientific Interest (SSSI). There are several small ponds located to the north of Pitsford, 1.3 km north of the site. Note that the lake shown to the west of Pitsford Pond on the 1:25,000-scale Ordnance Survey map does not exist and there is no evidence for it on historical maps. 3.2.5 Landfill sites

Locations of historic and operational landfills are shown on Figure PP/HIA/04 and summarised in Table PP/HIA/T2. Name NGR Distance &

direction Waste Status

Pitsford/Moulton Lane Stone Quarry SP 760 669 0 km Inert Historic (Dec 1940 –

Dec 1987)

Pitsford SP 753 674 0.55 km NW Inert Historic (Dec 1985 - ?)

Boughton Grange Quarry SP 746 658 1.35 km SW Inert Historic (Jan 1982 – Dec 1986)

Boughton SP 746 658 1.35 km SW Inert Historic (Dec 1986 – Dec 1991)

Boughton Quarry SP 747 655 1.75 km SW Null Operational

Table PP/HIA/T2: Details of landfill sites within 2 km 3.2.6 Protected sites and areas of ecological interest Sites of ecological interest within a 2 km radius of the site were obtained using the Multi Agency Geographic Information for the Countryside website (MAGIC).




Pitsford Reservoir is located 1.7 km to the north and is a designated Site of Special Scientific Interest (SSSI) covering 409 Ha. It is a major site for passage and wintering waterfowl. The site supports a significant number and variety of breeding birds including great crested grebe and reed warbler. Grassland bordering the reservoir provides additional habitats valuable to a wide range of flora and fauna. There is a small colony of the locally uncommon Essex Skipper butterfly. The location of Pitsford Reservoir SSSI is presented on Figure PP/HIA/03. There are three Scheduled Monuments within 2 km of the site: Longmans Hill Long Barrow (NGR SP 75079 67745), Boughton Bowl Barrow (NGR SP 74708 65890) and Old St John’s Church (NGR SP 76477 65645). 3.2.7 Surface water abstraction Only one licensed surface water abstraction occurs within 2 km of the site. Licence No 5/32/03/*S/0022 permits Anglian Water Services Ltd to abstract 19,900 Ml/a from Pitsford Reservoir. 3.2.8 Discharge consents

There are 11 discharge consents within 2 km of the site. Their locations are shown on Figure PP/HIA/04 and summarised on Table PP/HIA/T3. Map ID

Consent No Receiving water Type NGR Location

A AWNNF13358 Moulton Brook SC SB

SP 77131 66400 Moulton A Pumping Station

B PRNNF01651 Trib of Moulton

Stream UA SP 75350 66880 Fox Covert Farm

C GWNLF40086 Groundwater AA SP 74535 67356 Covey Farm Nurseries

D PRNNF18698 Trib of Faxton Brook UA

SP 75010 68038

Spring Hill Farm

E PRNNF04380 Trib Brampton Branch River UA SP 74950 68570

Old Brickworks Site

F AWNNF13329 Faxton Brook TA SP 75280 68690 Pitsford WTW Sludge Lagoon A

G AWNNF2016 Trib of Brampton Branch River TA SP 75330 68780

Pitsford A

H AWNNF13328 Pitsford Reservoir TA SP 75760 68770 Pitsford WTW (ASG Filter Backwash WR)

I AWNNF13159

Trib of Faxton Brook TA SP 75550 68450 Pitsford WTW

J AWNNF13563 Trib of Faxton Brook

SB DA SP 75518 68415

Pitsford SPS

K PR5NF5280 Trib of Pitsford Water

UA SP 76520 68770 Moulton Grange

L EPRLP3720XG Stream to Pitsford Creek YZ SP 77069 68358

Moulton College

Table PP/HIA/T3: Discharge consents




3.2.9 Surface water quality There are no surface water quality data for the unnamed stream to the south of the site that receives spring discharges from the Northampton Sand Formation. The Environment Agency monitors water quality in the Brampton Branch at Northampton (NGR SP 75300 59700), which is taken to represent quality over a 6 km reach. In 2009, the biological grading was reported to be Grade B, while the grading for Ammonia was ‘A’ and for dissolved oxygen ‘B’. In terms of biological classification, the river water quality is close to that expected for an unpolluted river, although high concentrations of nitrate are reported. 3.3 Geology

3.3.1 Regional Regional bedrock geology comprises mainly mudstones, ironstones, sandstones and limestones of Jurassic age. Strata broadly dip southeastwards with younger rock outcropping in the southeast (Figure PP/HIA/05). Regional superficial geology comprises Alluvium and River Gravels, Boulder Clay (Till) and Glacial sand & gravels. The alluvium and river gravels are confined to the main river valleys, while the deposits of Boulder Clay are found on the higher ground on the interfluves, as shown on Figure PP/HIA/05. The regional solid geology is summarised in Table PP/HIA/T4.

Group Formation Obsolete Name Description Thickness (m)

Great Oolite

Blisworth Limestone

Great Oolite limestone Limestone 2 – 7

Rutland Formation

Upper Estuarine Series

Variegated clays and silty mudstones, limestone and marls Mudstone

5 - 9

Inferior Oolite

Lower Lincolnshire Limestone

Limestone 0 - 3

Grantham Formation

Lower Estuarine Series

Pale sand and sandstone with darker silts in places 2- 5

Northampton Sand

Formation

Northampton Sand

Ironstone ferruginous and sandy limestones 4 - 23

Upper Lias Whitby

Mudstone Formation

Upper Lias Mainly mudstone with thin limestones and shales at base

47 - 60

Middle Lias

Marlstone Rock

Formation

Marlstone Rock Bed

Ironstone and ferruginous limestone 1 -3

Dyrham Formation Silts, mudstones and thin

silty limestones 16 - 30

Table PP/HIA/T4: Summary of solid geology




3.3.2 Local geology Local bedrock geology at the site consists of Northampton Sand Formation underlain by Whitby Mudstone Formation. The younger Stamford Member outcrops to the north and immediately east of the site and the Whitby Mudstone outcrops in the valley to the south. Superficial deposits are sparse; with alluvium confined to the tributary valley to the south and an area of till deposits to the northeast of the site. A number of borehole records are held by the British Geological Survey for the vicinity of the site. However, most of these only penetrate a short distance into the Northampton Sand Formation (NSF) and do not record the base of the Formation. Six piezometers were installed by Peter Bennie Ltd, the owner of Pitsford Quarry, between the A508 and Pitsford Pond for the purpose of monitoring groundwater levels (locations are shown on Figure PP/HIA/06). No geological logs are available, but the depth to the base of the NSF is available. Piezometer EP1 was located on the western boundary of Pitsford Pond and recorded the base of the NSF as 6.5 m below ground level (mbgl) (98.43 mAOD). One borehole, drilled in August 2008 (SP76NE/137), proved the base of the ironstone at a depth of 17 mbgl with a stiff grey clay beneath. The coordinates of this borehole given in the BGS records is considered to be suspect as it does not correlate with records available from piezometers installed by Peter Bennie Ltd. 3.3.3 Quarry workings The Northampton Sand Formation has been widely quarried on a regional basis for iron, building stone and aggregate. The underlying ‘Lias clay’ (Whitby Mudstone) has also been worked in places. The areas of quarrying are shown on Figure PP/HIA/06 and described below. � Pitsford Quarry. Worked since the early 1970s and now largely restored. In some areas the

whole of the Northampton Sand Formation was removed, whilst in others only the basal ironstone was removed and the limestone returned as restoration fill. The current working area has been mothballed due to the lack of demand for the product.

� Moulton Lane Stone Quarry. Pitsford Pond lies in an area of partly restored workings. The

fields to the east of the pond appear to have been restored to the original ground surface and are now rough grassland. The western part of the quarry was used as a landfill (see Section 3.2.5). Evidence suggests that the quarry also worked the underlying mudstone, possibly for brickmaking.

3.4 Hydrogeology

3.4.1 Aquifer status and regional context The Northampton Sand Formation and overlying Grantham Formation are classified as ‘Secondary A’ and ‘Secondary B’ aquifers respectively by the Environment Agency. The underlying Whitby Mudstone Formation has no designated aquifer status. Designated productive strata in the area are confined to the outcrops of Lower Lincolnshire Limestone and Blisworth Limestone Formation, which are classified as Principal aquifers. 3.4.2 Aquifer characteristics According to Jones et al (The physical properties of minor aquifers in England and Wales, BGS 2000), groundwater flow in the Northampton Sand Ironstone is a combination of matrix and fracture flow. In the upper weathered zone, where the intergranular cement has been removed, flow is both intergranular and via fractures. The lower, unweathered, section often remains




cemented and flow is via the fracture system. It is unclear if this division occurs in the formation in the vicinity of the site. As noted in Section 3.3, the Northampton Sand Formation has been worked over a significant area to the west of the site, as well as at the site itself and immediately to the east. Some of these former quarries have been restored to agricultural use. The groundwater system in these areas will have been changed from that prevalent in the undisturbed aquifers. It is understood that in some of the quarries, only the Ironstone was removed and the limestone overburden was used to backfill the quarry void. This may result in a more permeable aquifer. 3.4.3 Hydraulic conductivity Jones et al (2000) do not record any data for the Northampton Sand Formation. A review of nearby borehole records has enabled some data to be collated: � A borehole (SP76NE/137) drilled in the vicinity of the site, but the exact location of which is

uncertain, recorded no drawdown after pumping for 2 hrs at 2 m3/hr. This suggests a very high permeability. However, there are no detailed records of the test, so the measurements of drawdown may not be reliable.

� A borehole at White Lodge Farm (SP87SW/38, NGR SP 81800 74200) recorded a

discharge of 39 m3/day from 4 m of Northampton Sand. Drawdown was not recorded, but the difference between the rest water level and the pump setting depth was 4 m. Using this as the maximum drawdown and substituting the values into the Logan Approximation equation a transmissivity of 11.9 m2/d can be estimated:

T = 1.22 Q/s

Where: T = transmissivity Q = discharge s = steady state drawdown

This gives an estimated hydraulic conductivity of 2.9 m/d for a 4 m thick aquifer. It is noted

that in this borehole the Northampton Sand aquifer is under confined conditions and may not be representative of the unconfined, weathered aquifer.

3.4.4 Source protection zones The nearest groundwater source protection zone (SPZ) is located approximately 7 km southeast of the site. 3.4.5 Groundwater abstractions Licensed abstractions: There are no licensed groundwater abstractions within a 2 km radius of the site. Private water supplies: According to Daventry District Council four private water supplies exist within 2 km of the site. Their details are shown on Table PP/HIA/T5 and locations on Figure PP/HIA/03.




Location NGR Map ID Type Comment

Spring Meadow Farm SP 768 664 S5 Spring Coordinates of farm given, may not be location of spring

Spectacle Lodge SP 768 661 S9 Spring Spring not shown at this location on maps

Holly Lodge SP 768 657 W6 Well

Fox Covert Farm SP 754 669 S1 Spring

Table PP/HIA/T5: Private water supplies within a 2 km radius of the site The springs at S1 and S5 (see section 3.2.3) are closest to the site at distances of 750 m and 800 m respectively. 3.4.6 Groundwater levels and distribution There is no information available on current groundwater levels, except for one measurement taken in borehole SP76NE/137 in August 2008. This recorded a groundwater level at 11.8 mbgl. However, records of water levels recorded in a series of monitoring boreholes are available for the period 1996 to 2004. The locations of the monitoring boreholes are shown on Figure PP/HIA/06. The closest monitoring borehole was EP1, which was located immediately to the west of Pitsford Pond. This borehole, which could not be located on a site visit on 22nd November 2012, recorded groundwater levels varying between 6.5 and 7.2 m mbgl, or 98.83 to 98.20 mAOD, a fluctuation of up to 0.62 m. The maximum saturated thickness of Northampton Sand appears to have been only 0.4 m. 3.4.7 Groundwater quality There are no data available on groundwater quality. 3.4.8 Conceptual hydrogeology Pitsford Pond is located in a partially reclaimed area of former ironstone workings. The original workings are thought to have been excavated about 1 m into the underlying Whitby Mudstone. Recent measurements of the depth of the pond indicate a maximum depth of 1.15 m (Abington Consulting Engineers, 2012). On completion of quarrying, the part of the workings now occupied by Pitsford Pond was partially restored by landfilling with inert material. Landfilling ceased in 1987 when it appears that planning permission for further filling was refused. The void remaining then filled with water from rainfall and local run-off, as well as inflow from groundwater. According to the current site owner, the water level in the pond has remained relatively constant. To the south, west and north, the site is surrounded by unworked Northampton Sand Formation. To the east lie restored workings, but the nature of the fill in this area is not known. Groundwater flow is from northeast to southwest. The edge of the Northampton Sand aquifer is approximately 300 m to the west and 580 m to the south, at which point groundwater discharges to the surface water system. The Ordnance Survey map shows only one discrete spring discharge (S3 on Figure PP/HIA/03) located down-gradient of the site. Other discharge from the aquifer is probably general seepage into the drainage system. There are no groundwater abstractions down-gradient of the site.




4 PROPOSED DEVELOPMENT

4.1 Restoration

It is proposed to restore the site to agricultural use using inert materials to infill the pond. The inert material will be derived from a temporary aggregate recycling activity at the adjacent Pitsford Quarry which will sort and screen imported inert material. Up to 85,000 tonnes per annum of inert material are expected to be imported to Pitsford Quarry where it will be screened and segregated. Suitable material will be separated and recycled to produce secondary aggregate. It is estimated that approximately 60,000 tonnes per annum of clean inert material will be available for the restoration at Pitsford Pond. It is intended that the restoration of Pitsford Pond will be undertaken under a Waste Recovery Permit, for which an application will be made to the Environment Agency. The minimum amount of material required to complete the restoration is approximately 170,000 tonnes and the restoration should take place over 3 years. Final restoration contours are shown on Drawing 12043/101 reproduced in Appendix PP/HIA/A2. 4.2 Compliance with landfill guidance

Although it is intended that the site will be restored with inert soils under a Waste Recovery Permit, the site has been assessed against the Environment Agency’s Guidance for the location of landfills in respect of their Policy and Practice for the Protection of Groundwater. The Environment Agency will object to sites where: � The location is with a Source Protection Zone I. Pitsford Pond is located outside any

source protection zone. � Where active long-term site management is essential to prevent long-term

groundwater pollution the Agency will object to sites located on (a) Major Aquifers, (b) within Source Protection Zones II and III; and (c) sites below the watertable. No active long-term management will be required at Pitsford Pond.

As the site meets these criteria, the location complies with the Agency’s Policy and Practice for the Protection of Groundwater. 4.3 Water management during restoration

4.3.1 Background Prior to the start of restoration, the pond will be dewatered to allow material to be placed in dry conditions. Water will be pumped to an infiltration lagoon located on the southwestern corner of the site, from where it will discharge to both ground and/or to a drainage ditch running along the west side of Pitsford Pond (Drawing 12043/101) and ultimately into the existing watercourse that flows to the south and into the tributary of the Brampton Branch. 4.3.2 Discharge requirements Discharge will be maintained at the greenfield run-off rate for the site of 6.4 l/s. Details of the derivation of this value are given in the Flood Risk Assessment Report (Abington Consulting Engineers, 2012). Dewatering will require removal of the water currently in the pond, plus any inflow that occurs from the Northampton Sand Formation. The volume of water in the pond has been estimated to be approximately 36,850 m3 (Abington Consulting Engineers, 2012).




Inflows from the aquifer will reach a maximum once the water level in the pond falls below the base of the Northampton Sand Formation. Inflows have been estimated using the Theim equation: Where:

Q = groundwater ingress rate (m3/d)

k = hydraulic conductivity (m/d)

h0 = saturated thickness before drawdown (m)

hs = nominal value for height of seepage face in workings (m)

hw = saturated aquifer thickness after drawdown + hs (m)

rw = radius of working area (m)

r0 = rw + radius of influence (m) Details of the calculations are given in Appendix PP/HIA/A3. Due to the lack of site-specific values for hydraulic conductivity, inflows were calculated over a range of values based on an estimate from a nearby borehole (Section 3.4.3). Based on a central value estimate of 2.9 m/d, lower and upper estimates were taken as 0.29 m/d and 29 m/d. This results in estimated inflows of 0.1 l/s (6.7 m3/d), 0.4 1 l/s (21.5 m3/d) and 1.4 l/s (71.6 m3/d). It is estimated that pumping at 6.4 l/s it will take 85 days to drain the pond, including additional inflows from groundwater. This assumes the maximum inflow rate of 1.4 l/s. The actual inflow rate is difficult to estimate due to the presence of fill material around Pitsford Pond and in the area to the east. Once the pond has been drained, the discharge volume will reduce to that required to pump out groundwater inflow. Pumping will no longer be required once the infill has risen above the groundwater level. 4.4 Water management post restoration

The lagoon used during the restoration works will be retained to control the run-off from the site so it does not exceed greenfield run-off rates (Abington Consulting Engineers, 2012). No active management will be required after restoration.

( ) ( )[ ]wowo rrhhkQ /ln/22 −= π




5 ASSESSMENT OF IMPACTS

5.1 Methodology

An assessment of the potential effects of the restoration of Pitsford Pond on its environs has been undertaken. Potential impacts were assessed with consideration of the following factors: � Magnitude of the impact � Spatial extent of the impact � Cumulative impacts � Sensitivity of the receiving environment Mitigation measures and residual impacts have been considered as part of the assessment. The method of assessment is detailed in Appendix PP/HIA/A1 together with the matrices used to provide a robust and repeatable method of assessment. 5.2 Catchment sensitivity

The characteristics of the baseline water environment are used to form a basis from which the impact assessment can be undertaken. Details of how the baseline catchment sensitivity is assessed are provided in Table A.1 of Appendix PP/HIA/A1. Pitsford Pond is located within an area previously worked to extract ironstone, part of the Northampton Sand Formation, which is classified by the Environment Agency as a Principal Aquifer. The site is not located within an SPZ and there are no groundwater abstractions, or private water supplies, down-gradient of the site. In addition, the extent of the aquifer down-gradient of the site is limited and the underlying impermeable base of the unit crops out south and west of the site. There are no surface water abstractions within 2 km of the site. Groundwater discharges to surface to the southwest of the site into an unnamed watercourse that flows into the Brampton Branch. There are no sensitive sites located within 2 km downstream of the discharge. Based on the above hydrological and hydrogeological factors, the catchment is considered to have a ‘low’ sensitivity. 5.3 Potential impacts during restoration

5.3.1 Groundwater levels During restoration, groundwater entering the site will be pumped out to maintain dry conditions while fill is being placed in the void. Groundwater levels around the site will be lowered as a result of this pumping. However, it is likely that this impact will be restricted to a distance of about 30 m from the edge of the site. The potential for impact on abstractions is considered to be ‘negligible’ with a significance of impact of ‘none’.




5.3.2 Groundwater abstractions There are no groundwater abstractions within 2 km of the site. The potential for impact on abstractions is considered to be ‘negligible’ with a significance of impact of ‘none’. 5.3.3 Groundwater quality During the initial stages of restoration groundwater will be pumped out of the pond and into an infiltration basin. There will, therefore, be no impact on groundwater quality. During the later stages of restoration, the fill in the base of the site will be in contact with groundwater. Only clean inert materials from the aggregate recycling will be used for the restoration and this will be ensured by adherence to strict waste acceptance criteria for materials arriving at the recycling facility. The potential for impact on groundwater is considered to be ‘negligible’ with a significance of impact of ‘none’. 5.3.4 Surface water flows Groundwater pumped from the site will be discharged into an infiltration basin at the southwestern end of the site. If the basin overflows, water will be discharged into the ditch to the west of the pond at a greenfield run-off rate. The potential for impact on surface water is considered to be ‘low’ with a significance of impact of ‘minor’. 5.3.5 Surface water quality As discharge from the site will be directed to the infiltration lagoon, there will be no impacts on surface water quality from the development. 5.4 Potential impacts after restoration

The site will be restored using clean soils derived from an aggregate recycling plant located on the adjacent Pitsford Quarry. Due to the nature of these materials, it is considered that impacts on groundwater quality due to the site restoration will be ‘negligible’ with a significance of ‘none’. The replacement of the open water in the pond by relatively low permeability material is likely to reduce the flow of groundwater through the site. This may result in a slight rise in groundwater level up-gradient (to the northeast) of the site and a fall down-gradient. As groundwater levels are over 6 mbgl and there are no sensitive sites in the vicinity, the impact of any rise is considered to be ‘negligible’ with a significance of ‘none’. In the event that the restoration materials have a lower permeability than the natural soils, there is a possibility that run-off from the restored site might be higher than the greenfield situation resulting in higher flows in the local stream. To mitigate against this, the infiltration pond will be retained and run-off from the site directed to the pond via a ditch on the western side of the site. Potential impacts on surface water flow due to the site restoration are considered to be ‘negligible’ with a significance of ‘none’.




6 MITIGATION MEASURES AND RESIDUAL IMPACTS

6.1 Post-restoration

Surface water In order to ensure that run-off remains at the greenfield run-off rates, run-off will be managed using an infiltration basin (shown on Drawing 12043/101). Details of this are given in the Flood Risk Assessment (Abington Consulting Engineers, 2012). Using this design, potential impacts from the restored site on surface water flows are considered to be ‘negligible’ with a significance of ‘none’. 6.2 Cumulative impacts

Cumulative impacts have been assessed with respect to groundwater levels, groundwater quality, surface water quality and the restoration proposals. Cumulative impacts are those which result from changes caused by past, present or future foreseeable actions and can be defined under two categories: Incremental impact – when one impact occurs at the same time as another from a separate development Combined impact – relates to kinds of impact caused by the development on a particular location As part of the proposed restoration of Pitsford Pond, Pitsford Quarry will be re-opened in part to accommodate the aggregate recycling plant and in part to extract the remaining reserves of Northampton Sand Ironstone. There are no proposals to change the surface of the quarry floor in the vicinity of the materials recycling facility and, therefore, no change in run-off rates is expected (Flood Risk Assessment, Abington Consulting Engineers, 2012).




7 SUMMARY AND CONCLUSIONS

� Pitsford Pond is located in a former ironstone and clay working that was partially restored using inert fill in the 1980s. The restoration allowed a shallow pond to form that was subsequently used as a fishery.

� It is now intended to restore the area to agricultural use by infilling the pond and raising

ground levels. Restoration will be undertaken using the importation of inert materials from an aggregate recycling facility to be established on the nearby Pitsford Quarry. The importation of restoration material will be undertaken under a Waste Recovery Permit.

� It is expected that up to 170,000 tonnes of inert material will be used for the restoration over

a period of 3 years. � Pitsford Pond lies in the catchment of the Brampton Branch, a tributary of the River Nene. A

small watercourse flows from west to east to the south of the site, joining the Brampton Branch 2.4 km to the west of the site.

� Pitsford Pond is located on the Northampton Sand Formation, classified by the Environment

Agency as a Secondary A aquifer. Groundwater levels recorded between 1996 and 2004 show groundwater flow to the south and southwest.

� There are no groundwater abstractions within 2 km of the site. Private water supplies are

recorded from springs to the southwest and southeast of the site, the closest being at Fox Covert Farm to the west and Spring Meadow farm to the east. Neither spring is down-gradient of the site.

� Groundwater passing through the site discharges to the surface water system to the south

and southwest of the site where the base of the Northampton Sand Formation crops out against the underlying Whitby Mudstone Formation.

� There are no surface water abstractions within 2 km of the site.

� Prior to restoration, the pond will be drained by pumping the water out to an infiltration pond.

Pumping from the pond will be limited to the greenfield run-off rate calculated for the site. It is estimated that pumping will be required for approximately 3 months to account for the volume of water stored in the pond and any groundwater inflow.

� Short-term impacts to groundwater levels will be restricted to the immediate vicinity of the

site. As the water discharged from the site will be discharged to ground, there will be no impact to natural discharges from the aquifer downstream of the site.

� The waste recycling facility will only accept inert materials that pass strict acceptance

procedures and ensuring that the material used for the pond restoration will comply with the requirement of the Waste Recovery Permit. Residual impacts to groundwater quality or surface water quality from spring discharges are considered to be negligible.


December 2012


FIGURES

Project Pitsford PondFigure No.

PP/HIA/01 Date

Dec 12

Client Title

Scale1:50,000

Barkers Chambers, Barker Street, Shrewsbury, SY1 1SB UKTel. +44 (0)1743 355770 Fax. +44 (0)1743 357771

GP Planning LtdThe Stables, Long LaneEAST HADDONNorthamptonshire, NN6 8DU

Reproduced from the OS Landranger maps 141 and 152 1:50,000scale by permission of Ordnance Survey on behalf of the ControllerOf Her Majesty's Stationary Service. © Crown copyright. All rightsreserved. Licence number WL9705.

2700

0026

9000

2680

0026

7000

2660

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5000

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471000 472000 473000 474000 475000 476000 477000 478000 479000 480000 481000 482000

Site location

Application boundary

Pitsford Pond


PP/HIA/02 Date

Dec 12

Client Title

Scalents



N

Site details

Reproduced from Plan GPP-PB-PP-12-02 Site PlanRev 3, 30 August 2012

Compound(Wheelwash, Offices, etc.)

Pitsford Pond‘the site’

Pitsford Quarry

Access


PP/HIA/03 Date

Dec12

Client Title

Scale1:25,000



2650

00

476000

Landform and water features

475000474000 477000 478000

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0026

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00

Brampton Branch

Reproduced from the OS Explorer map 223 1:25,000scale by permission of Ordnance Survey on behalf of the ControllerOf Her Majesty's Stationary Service. © Crown copyright. All rightsreserved. Licence number WL9705.

Application boundary

SpringWellSSSI

S1

S2S4 S7

S8

S11

S10

S12

S13S15

S14

S16S17

S18

S19

W1

W2

W3

W4

W5

W7

W6

S3 S6

S9

S5


PP/HIA/04 Date

Dec 12

Client Title

Scale1:25,000



2650

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476000

Location of landfills and Discharge Consents

475000474000 477000 478000

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0026

7000

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Pitsford

Pitsford/Moulton LaneStone Quarry

Boughton GrangeQuarry Boughton

Boughton Quarry

A

B

C

D

E

F H

IG

J LApplication boundary

Historic landfill

Authorised landfill

Authorised landfill

K


PP/HIA/05Date

Dec 12

Client Title

Scale1:50,00



Geology

BGS Map 185. C12/12-CSL British GeologicalSurvey © NERC. All rights reserved

Application boundary26

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476000473000 474000 475000 477000 478000 479000472000

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Project Pitsford Pond

Figure No.PP/HIA/06

DateDec 12

Client Title

Scalents

Barkers Chambers, Barker Street,

Shrewsbury, SY1 1SB

UK

Tel. +44 (0)1743 355770

Fax. +44 (0)1743 357771


Location of quarried areas and groundwater monitoring boreholes

474000 476000

2670

00


EP5

EP4

EP6

EP2EP1

EP3

95

100

NOTE: Groundwater levels are for 2004.No data has been collected since then

Areas quarried and restored

Current quarry (mothballed)

Restored workings (Pitsford Pond)

Monitoring borehole (defunct)

Groundwater contour (mAOD)

Pitsford Quarry


December 2012


APPENDIX PP/HIA/A1

Assessment Methodology


December 2012


Method of assessment The method of assessment of hydrological and aquatic effects has involved: � Characterisation of the baseline environment � Determination of the sensitivity of key catchments and watercourses � Evaluation of the significance of predicted effects taking account of the magnitude of effects

(before and after mitigation) � Evaluation of the sensitivity of the baseline environment affected A rigorous and consistent approach to the assessment has been adopted using matrices to help classify sensitivity of the resource, and determine the scale and significance of effects. Baseline sensitivity The characterisation of the baseline water environment has involved the review of data and identification of sensitivities. The characterisation of catchment sensitivities has been guided by the matrix presented in Table PP/HIA/A1.1 which lists indicative criteria. The criteria for sensitivity are based approximately on hierarchy of factors relating to the quality of the aquatic environment. The criteria have been used to guide the analysis of the sensitivity of the baseline hydrological, hydrogeological and water quality environment. Sensitivity category Sensitivity criteria

Adjacent to Application Area Downstream/in catchment

High sensitivity SSSI or Aquatic Natura 2000 site

Wetland/watercourse habitat of particular ecological importance

Highly vulnerable groundwater

Significant peat deposits on sloping ground

Aquatic Natura 2000 site or SSSI immediately downstream/ adjacent to site

Medium sensitivity Wetland watercourse habitat of particular ecological importance

Moderately vulnerable groundwater

Significant peat deposits

Aquatic Natura 2000 site or SSSI further downstream of the catchment.

Sensitive locally designated site of ecological interest

Low sensitivity Low vulnerability groundwater

Superficial peat deposits

Not sensitive No aquatic habitats or watercourses present

No significant groundwater present

Table PP/HIA/A1.1: Catchment sensitivity classification


December 2012


Impact prediction and evaluation The prediction and assessment of effects on hydrology, hydrogeology and other aquatic resources has been undertaken using a series of tables to document the various potential impacts from aspects of the proposed project. Impacts have been predicted for the proposed development based on the guideline criteria for impact magnitudes set out in Table PP/HIA/A1.2.

Impact magnitude

Guideline criteria

High Total loss of, or alteration to, key features of the baseline resource such that post-development characteristics or quality would be fundamentally and irreversibly changed, eg watercourse realignment

Medium Total loss of, or alteration to, key features of the baseline resource such that post-development characteristics or quality would be partially changed, eg in-stream permanent bridge works

Low Small changes to the baseline resource which are detectable but the underlying characteristics or quality of the baseline situation would be similar to pre-development conditions, eg culverting of very small watercourses

Negligible A very slight change from baseline conditions, which is barely distinguishable and approximates to the ‘no change’ situation, eg short-term compaction from plant movements

Table PP/HIA/A1.2: Impact magnitude Using these criteria a series of generic impacts have been predicted for the proposed development. Residual effects have been predicted taking into account site-specific mitigation. The significance of the predicted effects has been assessed in relation to the sensitivities of the baseline resource. A matrix of significance was developed to provide a consistent framework for evaluation and is presented in Table PP/HIA/A1.3. Guideline criteria for the various categories of effect are included in Table PP/HIA/A1.4.

Magnitude Sensitivity

High Medium Low Negligible

High Major Major Moderate Minor

Medium Major Moderate Minor Minor

Low Moderate Minor Minor None

Negligible Minor Minor None None

Table PP/HIA/A1.3: Significance matrix Significance Definition Guideline criteria

None No detectable change to the environment

No effects on drainage patterns, surface and groundwater quality or aquatic habitat

Minor A small but detectable change to the environment

Localised changes in drainage patterns or groundwater flows, or changes resulting in minor and reversible effects on surface and groundwater quality or aquatic habitats


December 2012


Significance Definition Guideline criteria

Moderate A larger, but non-fundamental change to the environment

Changes in water quality or quantity affecting part of a catchment or groundwaters of moderate vulnerability, or changes resulting in loss of conservation value to aquatic habitats or designated areas

Major A fundamental change to the environment

Changes in water quality or quantity affecting widespread catchments or groundwater reserves of strategic significance, or changes resulting in substantial loss of conservation value to aquatic habitats and designations

Table PP/HIA/A1.4: Significance of effects categories In the above classification, fundamental changes are those which are permanent, detrimental and would result in widespread change to the baseline environment. The matrices used to guide the assessment have been applied with a degree of flexibility since the evaluation of effects would always be subject to particular location-specific characteristics which need to be taken into account. For this reason, the evaluation of impact significance, in particular, would not always correlate exactly with the cells in the relevant matrix where professional judgement and knowledge of local conditions may result in a slightly different interpretation of the impact concerned. Cumulative effects have been taken into account through prediction and evaluation of effects at a catchment-wide level.


December 2012


APPENDIX PP/HIA/A2

Drawings supplied by Abington Consulting Engineers


December 2012


APPENDIX PP/HIA/A3

Inflow calculations


December 2012


Estimates of the inflow to the drained pond from groundwater were estimated using the Theim equation: Where:

Q = groundwater ingress rate (m3/d)

k = hydraulic conductivity (m/d)

h0 = saturated thickness before drawdown (m)

hs = nominal value for height of seepage face in workings (m)


rw = radius of working area (m)

r0 = rw + radius of influence (m) Input Values

k = min 0.29 m/d, median 2.9 m/d, max 29 m/d (estimated)

h0 = 0.40 m (Measured in piezometer EP1)

hs = 0.10 m (assumed)


rw = 178 m (√Area of pond (32,040 m2))

( ) ( )[ ]wowo rrhhkQ /ln/22 −= π

GPP Planning Hydrogeological Impact Assessment: Pitsford Pond, Northamptonshire DRAFT: 1

December 2012


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