Detailed Gradiometer Survey Report - Rochford District · Detailed Gradiometer Survey Report Airport Business Park Southend, Essex ... * I= Internal Draft; E= External Draft; F= Final

Ref: 110130.02 October 2015

Detailed Gradiometer Survey Report

Airport Business ParkSouthend, Essex

making sense of heritage

© Wessex Archaeology Ltd 2015, all rights reserved Wessex Archaeology Ltd is a Registered Charity No. 287786 (England & Wales) and SC042630 (Scotland)

Airport Business Park Southend, Essex


Prepared for: GL Hearn Limited 280 High Holborn

London WC1V 7EE

On Behalf of: Henry Boot Ltd

Prepared by: Wessex Archaeology

Portway House Old Sarum Park

Salisbury Wiltshire SP4 6EB

www.wessexarch.co.uk

October 2015

Report Ref. 110130.02

http://www.wessexarch.co.uk/

Airport Business Park, Southend, Essex


DISCLAIMER

THE MATERIAL CONTAINED IN THIS REPORT WAS DESIGNED AS AN INTEGRAL PART OF A REPORT TO AN INDIVIDUAL CLIENT AND WAS PREPARED SOLELY FOR THE BENEFIT OF THAT CLIENT. THE MATERIAL CONTAINED IN THIS REPORT DOES NOT NECESSARILY STAND ON ITS OWN AND IS NOT INTENDED TO NOR SHOULD IT BE RELIED UPON BY ANY THIRD PARTY. TO THE FULLEST EXTENT PERMITTED BY LAW WESSEX ARCHAEOLOGY WILL NOT BE LIABLE BY REASON OF BREACH OF CONTRACT NEGLIGENCE OR OTHERWISE FOR ANY LOSS OR DAMAGE (WHETHER DIRECT INDIRECT OR CONSEQUENTIAL) OCCASIONED TO ANY PERSON ACTING OR OMITTING TO ACT OR REFRAINING FROM ACTING IN RELIANCE UPON THE MATERIAL CONTAINED IN THIS REPORT ARISING FROM OR CONNECTED WITH ANY ERROR OR OMISSION IN THE MATERIAL CONTAINED IN THE REPORT. LOSS OR DAMAGE AS REFERRED TO ABOVE SHALL BE DEEMED TO INCLUDE, BUT IS NOT LIMITED TO, ANY LOSS OF PROFITS OR ANTICIPATED PROFITS DAMAGE TO REPUTATION OR GOODWILL LOSS OF BUSINESS OR ANTICIPATED BUSINESS DAMAGES COSTS EXPENSES INCURRED OR PAYABLE TO ANY THIRD PARTY (IN ALL CASES WHETHER DIRECT INDIRECT OR CONSEQUENTIAL) OR ANY OTHER DIRECT INDIRECT OR CONSEQUENTIAL LOSS OR DAMAGE.

Quality Assurance Project Code 110130 Accession

Code Client

Ref.

Planning Application Ref.

Ordnance Survey (OS) national grid reference (NGR)

586473, 189766

Version Status

* Prepared by Checked and

Approved By Approver’s Signature Date

v01 I GJD ECR

28/08/2015

File: \\projectserver\wessex\Projects\110130\_Reports\110130_SouthendGEO_GJD_QC_ECR.docx

v02 E ECR LJL

06/10/2015

File: \\projectserver\wessex\Projects\110130\_Reports\110130_SouthendGEO_QC_PAB.docx

v03 E LJL C Budd

07/10/2015

File: \\projectserver\wessex\Projects\110130\_Reports\Submitted\Geo Report\110130_SouthendGEO_QC_PAB_CB_20151007.docx

v04 F LJL C Budd

14/10/2015

File: \\projectserver\wessex\PROJECTS\110130\_Reports\Submitted\Geo Report\110130_SouthendGEO_v4.0_20151014.docx

* I= Internal Draft; E= External Draft; F= Final



i

WA Doc Ref. 110130.02



Contents Summary ......................................................................................................................................... ii Acknowledgements ......................................................................................................................... iii

1 INTRODUCTION ............................................................................................................... 1 1.1 Project background ........................................................................................................... 1 1.2 Site location and topography ............................................................................................. 1 1.3 Soils and geology .............................................................................................................. 1 1.4 Archaeological background ............................................................................................... 2

2 METHODOLOGY .............................................................................................................. 3 2.1 Introduction ....................................................................................................................... 3 2.2 Method .............................................................................................................................. 3

3 GEOPHYSICAL SURVEY RESULTS AND INTERPRETATION ....................................... 3 3.1 Introduction ....................................................................................................................... 3 3.2 Gradiometer survey results and interpretation ................................................................... 4

4 CONCLUSION .................................................................................................................. 6

5 RECOMMENDATIONS ..................................................................................................... 7

6 REFERENCES .................................................................................................................. 9 6.1 Bibliography ...................................................................................................................... 9 6.2 Cartographic and documentary sources ............................................................................ 9

APPENDIX 1: SURVEY EQUIPMENT AND DATA PROCESSING ......................................... 10 Survey methods and equipment .................................................................................................... 10

APPENDIX 2: GEOPHYSICAL INTERPRETATION ................................................................ 12

APPENDIX 3: GAZETTEER OF 1997 TRIAL TRENCHING RESULTS CORRELATED TO GEOPHYSICAL ANOMALIES ...................................................................................................... 13 Figures Figure 1 Site location and survey extents Figure 2 Greyscale plot Figure 3 XY trace plot Figure 4 Archaeological interpretation



ii

WA Doc Ref. 110130.02



Summary A detailed gradiometer survey was conducted over land associated with the proposed Airport Business Park, Southend, Essex (centred on NGR 586473, 189766). The project was commissioned by GL Hearn Limited, on behalf of their client Henry Boot Ltd, with the aim of establishing the presence, or otherwise, and nature of detectable archaeological features to inform a planning application for the development of the site. The site comprised an area within arable fields located immediately to the northeast of Westcliff Rugby Club, covering an area of approximately 10 ha. This area is proposed for the relocation of the current Rugby Club and associated pitches. The geophysical survey was undertaken on 17th-21st August 2015. The detailed gradiometer survey, in conjunction with the results of previous trial trench evaluation work undertaken on a sample of the area, has demonstrated the presence of a number of anomalies of archaeological interest throughout the area. The anomalies identified as being of archaeological interest are primarily ditch-like features with some evidence for associated pit features also evident. At least four enclosure systems have been identified, and finds recovered from the previous trial trenching evaluation in 1997 provide dating evidence to suggest occupation from the Late Bronze Age through to the Romano-British period. To the north-east of the Site, complex areas of anomalies of archaeological interest are identified, including an Early Iron Age rectilinear enclosure comprised of ditch features. Surrounding this enclosure is evidence for an Iron Age/Romano-British field enclosure system. Centrally, a Late Iron Age/Early Romano-British banjo enclosure has been identified encircled by a potential double-ditch enclosure or trackway. To the south-west of the site a Late Bronze Age field enclosure system has also been identified. Additionally, numerous discrete pits and ditches have been interpreted, along with a possible round house. Throughout the site other potential anomalies have been identified and defined as trends, areas of increased magnetic response and isolated ferrous responses, all of which have not been attributed with a clear archaeological potential. Given the very high archaeological potential, further archaeological remains than those which have been detected are considered likely to be present on the site. This theory is supported by the presence of additional features, largely discrete pits and postholes, which were recorded in the 1997 evaluation but are not visible within the geophysical data.



iii

WA Doc Ref. 110130.02



Acknowledgements Wessex Archaeology would like to thank GL Hearn Limited for commissioning the geophysical survey on behalf of their client Henry Boot Ltd. The assistance of Luke Davenport, Adrian Schofield and Chris Brake is gratefully acknowledged in this regard.

The fieldwork was undertaken by Alistair Salisbury and Becky Hall. Garreth Davey processed and interpreted the geophysical data whilst the report was written by Lucy Learmonth and Garreth Davey. The report was proof-read by Naomi Brennen. The geophysical work was quality controlled by Lizzie Richley and Dr Paul Baggaley. Illustrations were prepared by Kitty Foster. The project was managed on behalf of Wessex Archaeology by Caroline Budd.



1

WA Doc Ref. 110130.02



1 INTRODUCTION

1.1 Project background 1.1.1 Wessex Archaeology was commissioned by GL Hearn Limited on behalf of Henry Boot

Ltd (hereafter ‘the Client’) on behalf of their client Henry Boot Developments Limited to carry out a geophysical survey over land associated with the proposed Airport Business Park, Southend, Essex (Figure 1), hereafter ’the Site‘ (centred on National Grid Reference (NGR) 586473, 189766). This survey was designed to inform a planning application for the development of the Site.

1.1.2 The aim of the geophysical survey was to establish the presence/absence, extent and character of detectable archaeological remains within the survey area following fieldwalking and evaluation works in 1997.

1.1.3 This report presents a brief description of the methodology followed, the detailed survey results and the archaeological interpretation of the geophysical data.

1.2 Site location and topography 1.2.1 The Site was located immediately to the northeast of Westcliff Rugby Club, approximately

1.4 km to the southeast of Rochford and approximately 3.7 km to the north of Southend-on-Sea.

1.2.2 The Site occupies an area of 10 ha of agricultural land, currently utilised for silage, which is proposed for the relocation of the Rugby Club and associated pitches in order to facilitate the proposed business park development. The Site is bounded by further agricultural land to the north, east and south whilst to the west is an area of open land and former buildings.

1.2.3 The Site is relatively flat, situated at an elevation of approximately 12 m above Ordnance Datum (aOD).

1.3 Soils and geology 1.3.1 The underlying geology of the Site is mapped as Eocene clay, silt, sand and gravel of the

Thames Group Formation with superficial Quaternary sand and gravel river terrace deposits (British Geological Survey 2015).

1.3.2 The soils underlying the Site are likely to consist of typical argillic brown soils of the 571z (Hamble 2) association (SSEW 1983). Soils derived from such geological parent material have been shown to produce magnetic contrasts acceptable for the detection of archaeological remains through magnetometer survey.



2

WA Doc Ref. 110130.02

1.4 Archaeological background 1.4.1 The archaeological background was assessed in detail within the Historic Environment

Assessment and proposed development framework for Westbarrow Hall Farm, Rochford (Place Services 2012) and furthermore in the Historic Environment Settings Assessment undertaken by Wessex Archaeology (2015a). The results from these reports and the relevant Essex Historic Environment Record (EHER) entries are summarised below.

1.4.2 Neolithic artefacts were uncovered during quarrying around Cherry Orchard Farmhouse to the south-west of the Site during the 1970s (EHER 9746) and evidence for a Bronze and Iron Age enclosure has also been recorded in the vicinity within the Western Approaches (EHER 9113-4).

1.4.3 A field walking survey was undertaken over the wider development area in 1996 prior to brick-earth extraction. This work found an extensive spread of struck flint and burnt flint as well as concentrations of prehistoric pottery particularly within the area of the Site. A concentration of Roman pottery and tile was also found and thought to indicate a possible farmstead overlooking the river just to the north of the Site.

1.4.4 A trial trenching programme was then undertaken in 1997 (Essex County Council 2001). This comprised 31 trenches within the northern field, containing the survey area that this report is concerned with, and a further 30 trenches immediately to the south in the adjacent field. The results from the evaluation indicated considerable activity in the survey area dating from the Middle Bronze Age onwards. A small quantity of Saxon pottery recovered during the evaluation suggests activity from this time within or to the north of the Site and a number ditches on the north-eastern edge of the Site may be associated with the known medieval settlement of Partricheswyk.

1.4.5 The southern area of trenching, beyond the confines of the current survey area, revealed a much lower concentration of features, with little to no conclusive dating evidence. However, an additional area of possible prehistoric settlement was located adjacent to the Lancaster Business Park.

1.4.6 Excavations in the area of Cherry Orchard Farm in the 1950s located the remains of a Roman cemetery including an early 2nd century rich burial. A medieval or post-medieval kiln (EHER 9744) is also recorded to the east of the farmhouse which may be a precursor of the later brickworks which were situated to the west of the Site.

1.4.7 To the south-east of the Site was the location of Westbarrow Hall Farm which is documented from the 13th century and can be seen on late 19th century and early 20th century Ordnance Survey (OS) maps. Medieval occupation is also recorded to the north of the Site on a site later occupied by two 17th century cottages (EHER 13416). Cherry Orchard Farmhouse is itself a Grade II Listed Building and dates from the 17th century (list entry 1322397).

1.4.8 Given the proximity of the Site to London Southend Airport, a number of World War II structures were constructed in the region as perimeter defences (EHER 20712). These include an Anti-Aircraft gun emplacement (no longer existing), associated ammunition shelter, and three pillboxes. The ammunition shelter and one of the pillboxes lies within the southern part of the Site.



3

WA Doc Ref. 110130.02

2 METHODOLOGY

2.1 Introduction 2.1.1 The geophysical survey was undertaken by Wessex Archaeology’s in-house geophysics

team between the 17th-21st August 2015.

2.1.2 Field conditions at the time of the survey were good, with mostly dry conditions during the survey. An overall coverage of 9.7 ha was achieved, the minimal reduction was due to the tree line encroaching from the field boundaries and the extant WWII feature in the southeast of the Site (WA 39, Wessex Archaeology 2015a).

2.1.3 The detailed gradiometer survey was conducted in accordance with Historic England guidelines (English Heritage 2008) and the Written Scheme of Investigation (WSI) (Wessex Archaeology 2015b).

2.2 Method 2.2.1 Individual survey grid nodes were established at 30 m x 30 m intervals using a Leica Viva

RTK GNSS instrument, which is precise to approximately 0.02 m and therefore exceeds Historic England recommendations (2008).

2.2.2 The detailed gradiometer survey was conducted using a Bartington Grad601-2 fluxgate gradiometer instrument, which has a vertical separation of 1 m between sensors. Data were collected at 0.25 m intervals along transects spaced 1 m apart with an effective sensitivity of 0.03 nT, in accordance with Historic England guidelines (English Heritage 2008). Data were collected in the zigzag method.

2.2.3 Data from the survey was subject to minimal data correction processes. These comprise a zero mean traverse function (±5 nT thresholds) applied to correct for any variation between the two Bartington sensors used, and a de-step function to account for variations in traverse position due to varying ground cover and topography. These two steps were applied throughout the survey area, with no interpolation applied.

2.2.4 Further details of the geophysical and survey equipment, methods and processing are described in Appendix 1.

3 GEOPHYSICAL SURVEY RESULTS AND INTERPRETATION

3.1 Introduction 3.1.1 The detailed gradiometer survey has identified magnetic anomalies of archaeological

interest across the Site, along with areas of increased magnetic response and ferrous responses. Results are presented as a series of greyscale plots, XY plots and archaeological interpretations at a scale of 1:1500 (Figures 2 to 4). The data are displayed at -2 nT (white) to +3nT (black) for the greyscale image and ±25 nT at 25 nT per cm for the XY trace plots.

3.1.2 The interpretation of the datasets highlights the presence of potential archaeological anomalies, ferrous/burnt or fired objects, and magnetic trends (Figure 4). Full definitions of the interpretation terms used in this report are provided in Appendix 2. Where possible, the archaeological interpretation has been informed by evidence from the trial trenching undertaken in 1997 (Essex County Archaeology 2001). A correlation table which relates the results of the geophysical survey (by WA number) to the associated features and dating recorded by the trial trenching (by trench and context number) is provided in



4

WA Doc Ref. 110130.02

Appendix 3 for ease of reference. Due to the complexity of the enclosures encountered, these have been phased by their probable periods and are illustrated in Figure 5. This figure also illustrates the locations of the previous trial trenches with their corresponding number. The location of the trial trenches is also shown on Figure 4.

3.1.3 Numerous ferrous anomalies are visible throughout the dataset. These are presumed to be modern in provenance and are not referred to unless considered relevant to the archaeological interpretation.

3.1.4 It should be noted that small, weakly magnetised features may produce responses that are below the detection threshold of magnetometers. It may therefore be the case that more archaeological features may be present than have been identified through geophysical survey.

3.1.5 Although no modern services have been identified within this dataset, gradiometer survey may not detect all services present on Site. This report and accompanying illustrations should not be used as the sole source for service locations and appropriate equipment (e.g. CAT and Genny) should be used to confirm the location of buried services before any trenches are opened on Site.

3.2 Gradiometer survey results and interpretation 3.2.1 The clearest archaeological feature is evident at 4000 as a series of linear positive

anomalies, characteristic of cut ditch-like features. These ditches are approximately 2-2.5 m wide and appear to form a rectilinear enclosure approximately 35 m by 45 m with an average magnitude of 2-3 nT. A possible break in the eastern ditch may denote an entrance. Evidence recovered during the trial trenching suggests that this enclosure dates to the Early Iron Age period.

3.2.2 Positive linear anomalies at 4001 appear to form a further later enclosure which, although on the same northeast/southwest alignment and also measuring approximately 2-2.5 m, appears to cut the enclosure identified at 4000. The magnitude for this feature ranges from 0.5-2 nT. A wider range of dating evidence suggests that this feature may have been in use for an extended period, with numerous Early Iron Age, Middle Iron Age, Late Iron Age and Roman finds recovered, in conjunction with a residual medieval tile and a possible Late Bronze Age spindle whorl.

3.2.3 Due to their similar form, alignment and response, the ditches identified at 4002 and 4003 are likely to be related to 4001. These have been identified by their own ID numbers due to their physical distance from 4001 (35 to 55 m). They have average magnetic responses of approximately 1.5 nT and 1.9 nT respectively. The dating evidence available from the trial trenching also dates 4003 to the Late Iron Age/early Romano-British period, however there were no finds recovered from 4002. The extent of the overall enclosure (4001, 4002, and 4003) is approximately 75 m by 80 m.

3.2.4 There is a further ditch within the area of increased magnetic response associated with 4004 that may be related to the enclosure at 4000, due to its form and alignment.

3.2.5 A group of positive anomalies also at 4004 have been interpreted as Probable Archaeology. Their magnitude range from 0.5-4 nT and their form suggests these are pit-like features within an enclosure ditch. Given the pattern and context, these anomalies at 4004 could potentially represent a gully denoting a possible roundhouse with a diameter of approximately 20 m but unfortunately there is no trenching evidence over these anomalies. However, Trench 19 approximately 20 m to the west is in an area where



5

WA Doc Ref. 110130.02

a high concentration of pits and postholes was recorded. These features contained dating evidence ranging from Late Bronze to Late Iron Age.

3.2.6 Negative anomalies at 4005 have been identified as a pair of parallel ditch-like features some 7-8 m apart, orientated northwest-southwest and each approximately 2-3 m wide. At the north-western extent these ditches open up to form a circular shape approximately 32 m in diameter. The elongated trackway extending from this circular shape measures approximately 95 m. A possible break to the west is noted but this may simply be due to a much weaker response in this location. Given the scale and form of the feature, it is probable that this represents a banjo enclosure. These were originated around the middle of the 1st millennium BC but were most intensively used during the period from the Late Iron Age to the Roman invasion (100 BC to 43 AD) (English Heritage 2011), a date which is supported by Late Iron Age and Roman pottery which was recovered during the trial trenching.

3.2.7 A possible ditch identified as Probable Archaeology appears to be cut by the enclosure identified at 4005. It is however not possible to identify full stratigraphic/context relationships between responses from gradiometer data alone. A number of smaller potential pits have also been identified in its vicinity

3.2.8 A series of negative linear features at 4006 appear to form a pair of fragmented parallel linear ditch-like features. These are aligned roughly east-west, and may turn gently to the north at the eastern extent. Whilst they appear to be quite fragmented and of irregular width, these anomalies do maintain a uniform separation and extend for over 200 m. They may represent a double-ditched enclosure or possibly delineate a trackway, which may be related to the banjo enclosure at 4005. Late Iron Age and Early Roman pottery recovered from the trial trenching in 1997 supports the hypothesis that 4006 is contemporary with the 4005.

3.2.9 Another pair of parallel weakly negative linear features has been identified at 4007. These are more uniform in width, extending for just under 200 m, but are also fragmented within the dataset. These may form another segment of the possible double-ditched enclosure or trackway previously suggested to surround 4005. These ditches respect the same orientation, scale and form as those found to the south at 4006 and are likely to be related. The only dating evidence available gives a Romano-British date which would place the ditches as roughly contemporary or later than 4006.

3.2.10 A collection of north-east–south-west and southeast-northwest linear features are clear at 4008. These ditches are relatively uniform and are all approximately 1.5-3 m wide. These meet at perpendicular angles and form an almost gridded area measuring approximately 130 m by 50 m.This feature appears toextend beyond the southern boundary of the survey area suggesting a continuation into the area to the south. These ditches appear to form a coaxial field enclosure system, of Late Bronze Age or earlier date based on the dating evidence available from the trial trenching.

3.2.11 A number of short lengths of positive anomalies at 4009, to the north of the banjo enclosure, appear to represent further ditch-like features. These are approximately 2 m-2.5 m wide, each measuring approximately 15-20 m, and are aligned north-east–south-west or south-east–north-west. Given the form and the surrounding archaeological remains, it is possible that these anomalies may represent partial segments of an enclosure system.



6

WA Doc Ref. 110130.02

3.2.12 Weak positive responses forming a linear feature at 4010 towards the eastern extent of the survey area may represent a possible isolated ditch-like feature. This feature is on a north-east–south-west alignment and measures approximately 50 m. This potential ditch does not have any obvious relationship with any previously discussed features as it lies on a slightly differing alignment and at a distance of over 50 m from any other identified feature. Despite the location of one of the trial trenches being situated over this feature there is no evidence recorded for a linear feature. This may be as a result of the very ephemeral nature of the feature or could suggest that the feature is natural in origin. However, the extremely regular nature of the features would indicate the former.

3.2.13 A number of magnetic anomalies identified at 4011 between 4000 and 4005 suggest an area of possible cut features which has been investigated by Trench 13. A number of these have been recorded as tree throws whilst others were recorded as pit and posthole features containing Early or Middle Iron Age pottery. Therefore, as the archaeological potential within the survey area is high, these have all been interpreted as Archaeology despite the potential for a proportion of them to be natural in origin.

3.2.14 Short positive linear anomalies measuring 15-20 m at 4012 in the north-east corner of the Site form isolated ditch-like features. These may be related to the enclosure activity surrounding 4000 and 4001, however, they are more fragmented and weaker in magnetic response. The finds recovered in the vicinity were inconclusive and were simply recorded as Prehistoric pottery. These are located within a large area of increased magnetic response measuring 105 m by 45 m at its greatest extents, which may represent areas of occupational activity.

3.2.15 A number of oval shaped positive anomalies at 4013 have been interpreted as possible pit features given their grouping and proximity to further archaeological features. However, they may also be the result of natural variations in the superficial geology.

3.2.16 Positive magnetic responses at 4014 form an “L” shaped ditch-like feature. These are more difficult to interpret than other anomalies within this dataset as the response borders on that characteristic of ferrous. There is no evidence available from the 1997 investigations for this area; therefore, due to the very high archaeological potential of the Site, this anomaly has been interpreted as Possible Archaeology.

3.2.17 There are a number of weakly contrasting and indistinct linear and curvilinear trends present throughout the Site. These have been interpreted as trends of uncertain origin as their form or magnetic response is not defined clearly enough for accurate interpretation.

4 CONCLUSION

4.1.1 This is a complex, multi-period archaeological site, with features denoting separate periods of occupation apparent throughout the survey area. The detailed gradiometer survey has been successful in detecting anomalies of archaeological interest throughout the Site, and has provided additional context to the features excavated during the trial trenching investigations undertaken in 1997.

4.1.2 In addition to these features, anomalies interpreted as trends, areas of increased magnetic response and ferrous have also been identified. Previous experience gained from other sites of similar complexity would suggest that the geophysical survey will have identified a proportion of the actual number of archaeological features present. It is therefore considered likely that there will be additional present features on the Site. This theory is supported by the presence of additional features, largely discrete pits and



7

WA Doc Ref. 110130.02

postholes, which were recorded in the 1997 evaluation but are not visible within the geophysical data.

4.1.3 The anomalies identified as being of archaeological interest are primarily ditch-type features forming a variety of enclosures dating to different periods. The most complex areas of archaeological interest are located in the north-east of the Site, where ditches form a rectilinear enclosure (4000), which appears to be cut by a later enclosure (4001). Located centrally is a further enclosure interpreted as a banjo enclosure (4005). In the south-west of the Site evidence for a probable field enclosure system (4008) has been identified.

4.1.4 It is clear from the dating evidence recovered during the trial trenching in 1997 that the Site was occupied over an extended period of time comprising a period from the Late Bronze Age through to the Romano-British period.

4.1.5 There are three main phases of archaeological occupation which are easily identifiable within this Site and likelihood that these would be further refined or added to should the Site be investigated further. The dating evidence available for 4001 and 4005 suggests that these enclosures were both in use during the Late Iron Age/Early Romano-British period. Similarly, the broad dating evidence for 4001 overlaps with 4000. This evidence does not however conclusively prove that these enclosures were in use concurrently as the dating evidence spans hundreds of years. The remaining enclosure identified at 4008 is separated by clear dating evidence and has been dated to the Early Iron Age.

4.1.6 The earliest known activity on the Site is recorded at 4008, thought to be a coaxial field system. During the previous trial trenching investigation, some of these features were recorded as Late Bronze Age due to dateable pottery recovered. The report states that some ditches within this probable field enclosure system may have been of an earlier date, although no material evidence was recovered to support this supposition.

4.1.7 The central enclosure (4005), interpreted as a banjo enclosure, has been dated to the Late Iron Age/Romano-British period. This places its occupation within the most intensive usage period for this style of enclosure. The Site however is beyond the geographical extents within which banjo enclosures are most common. Banjo enclosures have been interpreted as symbols of high status (English Heritage 2011) and it is therefore conceivable that this feature may have marked a higher status area or period in the occupation of the Site as a whole. This may indicate a connection with the Roman building suspected to be present to the north (Place Services 2012).

4.1.8 The enclosure identified as 4001 was dated to the Middle/Late Iron Age pottery although some Roman finds were also recovered which may signify its continued occupation.

4.1.9 Areas of increased magnetic response are located close to the areas of archaeological interest. Responses such as these are common in areas of occupation and are typically as a result of burnt materials or other debris and as such may be further evidence for occupation on the Site.

5 RECOMMENDATIONS

5.1.1 Following the results of the geophysical survey it is considered that, should the proposals for the relocation of the Rugby Club and pitches result in any below ground impacts to the Site further archaeological investigations will be required by the Senior Historic



8

WA Doc Ref. 110130.02

Environment Officer for Essex County Council acting as archaeological advisor to Rochford District Council .

5.1.2 Given the complexity of the archaeological remains on the Site and of the development proposals for the Airport Business Park and Rugby Club in its entirety it is proposed that appropriate strategies are discussed and agreed with the Senior Historic Environment Officer for Essex County Council. This could, for example, comprise areas of strip, map and sample along with detailed excavation areas targeted on regions of archaeological potential where construction impacts are anticipated.

5.1.3 Once agreed these will be formalised via a Mitigation Strategy document which would provide clarity on the strategies to be applied to the development site as a whole. This would provide an appropriate means of mitigation in respect of the negative impacts to the archaeology by the proposed development. This document would inform the preparation of appropriate Written Schemes of Investigation for the different elements of the construction programme.



9

WA Doc Ref. 110130.02

6 REFERENCES

6.1 Bibliography English Heritage, 2008.Geophysical Survey in Archaeological Field Evaluation. Research and Professional Service Guideline No 1, 2nd edition.

English Heritage, 2011. Introductions to Heritage Assets, Banjo Enclosures. Guidelines/Standards.

Essex County Council Planning – Field Archaeology Unit, 2001 Westbarrow Hall Farm, Rochford, Essex – Archaeological Evaluation.

Place Services, 2012, Historic Environment Assessment and proposed development framework for Westbarrow Hall Farm, Rochford

Wessex Archaeology, 2015a, Airport Business Park, Southend, Essex. Historic Environment Settings Assessment.

Wessex Archaeology, 2015b, Airport Business Park, Southend. Written Scheme of Investigation for Archaeological Geophysical Survey.

6.2 Cartographic and documentary sources Soil Survey of England and Wales, 1983. Sheet 4, Soils of Eastern England. Ordnance Survey: Southampton.



10

WA Doc Ref. 110130.02

APPENDIX 1: SURVEY EQUIPMENT AND DATA PROCESSING

Survey methods and equipment The magnetic data for this project was acquired using a Bartington 601-2 dual magnetic gradiometer system. This instrument has two sensor assemblies fixed horizontally 1m apart allowing two traverses to be recorded simultaneously. Each sensor contains two fluxgate magnetometers arranged vertically with a 1m separation, and measures the difference between the vertical components of the total magnetic field within each sensor array. This arrangement of magnetometers suppresses any diurnal or low frequency effects. The gradiometers have an effective resolution of 0.03nT over a ±100nT range, and measurements from each sensor are logged at intervals of 0.25m. All of the data are stored on an integrated data logger for subsequent post-processing and analysis. Wessex Archaeology undertakes two types of magnetic surveys: scanning and detail. Both types depend upon the establishment of an accurate 20m or 30m site grid, which is achieved using a Leica Viva RTK GNSS instrument and then extended using tapes. The Leica Viva system receives corrections from a network of reference stations operated by the Ordnance Survey and Leica Geosystems, allowing positions to be determined with a precision of 0.02m in real-time and therefore exceed the level of accuracy recommended by Historic England (English Heritage 2008) for geophysical surveys. Scanning surveys consist of recording data at 0.25m intervals along transects spaced 10m apart, acquiring a minimum of 80 data points per transect. Due to the relatively coarse transect interval, scanning surveys should only be expected to detect extended regions of archaeological anomalies, when there is a greater likelihood of distinguishing such responses from the background magnetic field. The detailed surveys consist of 20m x 20m or 30m x 30m grids, and data are collected at 0.25m intervals along traverses spaced 1m apart. These strategies give 1600 or 3600 measurements per 20m or 30m grid respectively, and are the recommended methodologies for archaeological surveys of this type (EH, 2008). Data may be collected with a higher sample density where complex archaeological anomalies are encountered, to aid the detection and characterisation of small and ephemeral features. Data may be collected at up to 0.125m intervals along traverses spaced up to 0.25m apart, resulting in a maximum of 28800 readings per 30m grid, exceeding that recommended by Historic England (English Heritage 2008) for characterisation surveys. Post-processing

The magnetic data collected during the detail survey are downloaded from the Bartington system for processing and analysis using both commercial and in-house software. This software allows for both the data and the images to be processed in order to enhance the results for analysis; however, it should be noted that minimal data processing is conducted so as not to distort the anomalies. As the scanning data are not as closely distributed as with detailed survey, they are georeferenced using the GPS information and interpolated to highlight similar anomalies in adjacent transects. Directional trends may be removed before interpolation to produce more easily understood images. Typical data and image processing steps may include:



11

WA Doc Ref. 110130.02

• Destripe – Applying a zero mean traverse in order to remove differences caused by directional effects inherent in the magnetometer;

• Destagger – Shifting each traverse longitudinally by a number of readings. This corrects for operator errors and is used to enhance linear features;

• Despike – Filtering isolated data points that exceed the mean by a specified amount to reduce the appearance of dominant anomalous readings (generally only used for earth resistance data)

Typical displays of the data used during processing and analysis:

• XY Plot – Presents the data as a trace or graph line for each traverse. Each traverse is displaced down the image to produce a stacked profile effect. This type of image is useful as it shows the full range of individual anomalies.

• Greyscale – Presents the data in plan view using a greyscale to indicate the relative strength of the signal at each measurement point. These plots can be produced in colour to highlight certain features but generally greyscale plots are used during analysis of the data.



12

WA Doc Ref. 110130.02

APPENDIX 2: GEOPHYSICAL INTERPRETATION The interpretation methodology used by Wessex Archaeology separates the anomalies into four main categories: archaeological, modern, agricultural and uncertain origin/geological. The archaeological category is used for features when the form, nature and pattern of the anomaly are indicative of archaeological material. Further sources of information such as aerial photographs may also have been incorporated in providing the final interpretation. This category is further sub-divided into three groups, implying a decreasing level of confidence:

• Archaeology – used when there is a clear geophysical response and anthropogenic pattern. • Probable archaeology – used for features which give a clear response but which form

incomplete patterns. • Possible archaeology – used for features which give a response but which form no

discernible pattern or trend. The modern category is used for anomalies that are presumed to be relatively modern in date:

• Ferrous – used for responses caused by ferrous material. These anomalies are likely to be of modern origin.

• Modern service – used for responses considered relating to cables and pipes; most are composed of ferrous/ceramic material although services made from non-magnetic material can sometimes be observed.

The agricultural category is used for the following:

• Former field boundaries – used for ditch sections that correspond to the position of boundaries marked on earlier mapping.

• Agricultural ditches – used for ditch sections that are aligned parallel to existing boundaries and former field boundaries that are not considered to be of archaeological significance.

• Ridge and furrow – used for broad and diffuse linear anomalies that are considered to indicate areas of former ridge and furrow.

• Ploughing – used for well-defined narrow linear responses, usually aligned parallel to existing field boundaries.

• Drainage – used to define the course of ceramic field drains that are visible in the data as a series of repeating bipolar (black and white) responses.

The uncertain origin/geological category is used for features when the form, nature and pattern of the anomaly are not sufficient to warrant a classification as an archaeological feature. This category is further sub-divided into:

• Increased magnetic response – used for areas dominated by indistinct anomalies which may have some archaeological potential.

• Trend – used for low amplitude or indistinct linear anomalies. • Superficial geology – used for diffuse edged spreads considered to relate to shallow

geological deposits. They can be distinguished as areas of positive, negative or broad bipolar (positive and negative) anomalies.



13

WA Doc Ref. 110130.02

APPENDIX 3: GAZETTEER OF 1997 TRIAL TRENCHING RESULTS CORRELATED TO GEOPHYSICAL ANOMALIES

WA ID WA Interp Trench ECC Context Eval Feature Fill Description Dating evidence

318 Linear aligned E-W, sloping sides, flat base, 0.88m wide

Dark brown orange clay silt, occasional charcoal flecks and burnt flints.Dark brown black clay silt containing occasional charcoal flecks and burnt flints. Mid orange brown clay silt containing occasional flecks of daub and burnt flints (Primary).

Early Iron Age and undiagnostic prehistoric pottery

1174 Linear aligned E-W, sloping sides, flat base, 1.32m wide - recut of [318]. Mid brown orange silty clay, bioturbation. None provided/available.

25 496 Unexcavated linear aligned NW-SE, 1.83m wide. None provided/available. Prehistoric pottery385 Unexcavated linear aligned NW to SE, 0.35m wide. None provided/available. None provided/available.

398 Unexcavated linear aligned E-W, 2.2m wide. None provided/available. Early-Middle Iron Age and Roman pottery

18 281 Linear aligned NE -SW, 3m wide, sloping sides, flat base. Black sandy clayey silt containing charcoal, burnt clay and small stones.

Middle Iron Age pottery and a fragment of a triangular loomweight of Early or Middle Iron Age date.

1233Linear aligned NW-SE, excavated in two segments. Extended beyond trench to NW and terminated to the SE within it. Sloping sides, flat base, 1m wide.

Dark grey brown silt containing frequent charcoal flecks and occasional daub, chalk and burnt flints.Grey brown silty clay containing common charcoal and rare chalk and small stones.

Early Iron Age pottery and a fragment of residual post-medieval tile.

443 Linear feature, aligned NW-SE, extending beyond trench. Convex sides, greater than 2m wide, not fully excavated.

Mid yellow brown silt containing occasional charcoal and daub flecks, and small flints.Mid yellow brown silt containing occasional chalk and charcoal fleck.

Early Iron Age pottery in lowest excavated fill, late Iron Age pottery upper fill. An unusual reel-shaped object, possibly a spindle whorl, of late Bronze Age to early Iron Age date.

4002 Enclosure Ditch 22 1186 Unexcavated, possible linear, 8m wide. None provided/available. None provided/available.

4003 Enclosure Ditch 25 520 Linear feature, 3.15m wide, aligned E-W, sloping sides, not

fully excavated,

Filled by a succession of mid to dark brown silty clays containing varying quantities of charcoal. The lowest excavated fill comprised a green brown silt containing frequent shell fragments and had a high organic content. This fill was partially water-logged.

Undiagnostic prehistoric and Late Iron Age or early Roman pottery (upper fill).

4004 Potential Roundhouse

7 60 Linear aligned E-W extending beyond trench. Concave sides, concave base, 3.35m wide.

Light orange brown sandy silt that contained occasion charcoal and manganese flecks. Late Iron Age pottery (possibly residual).

76 Linear aligned N-S and extending beyond the edges of the trench. V-shaped profile, 1.15m wide. Light orange brown silt containing occasional charcoal flecks. Prehistoric pottery.

78 Linear terminating to N and extending beyond trench. Sloping sides with flat base, 1.05m wide.

Light grey brown silt containing occasional charcoal and manganese flecks. Prehistoric pottery.

80 Linear feature, terminating to S and extending beyond trench. Steeply sloping sides, flat base, 0.53m wide.

Light grey brown silt containing frequent charcoal and manganese flecks and rare small stones Roman pottery.

8 128 Linear aligned E-W and extending beyond trench, 1.61m wide. Light yellow red silty clay with rare chalk flecks and small stones. Prehistoric pottery

9 68 Linear aligned NW-SE, 2.05m wide. Light yellow brown clay silt containing rare charcoal flecks. Primary was dark red brown silt with rare charcoal flecks.

Late Iron Age pottery (primary fill).Late Bronze Age, early Roman and medieval pottery (secondary fill).

14 265 Linear aligned NE to SW extending beyond trench. Steeply sloping sides, 2m wide, not fully excavated.

Filled by a series of grey brown silts containing charcoal flecks and manganese stains. Late Iron Age pottery (secondary fill).

Not trenched.

4005 Probable Banjo Enclosure 10

4006

Possible double ditch enclosure or trackway

23

24

4000 Enclosure

Enclosure4001

19

WA ID WA Interp Trench ECC Context Eval Feature Fill Description Dating evidence

5 100 Linear aligned E-W. Steeply sloping sides, flat base, 1m wide.Primary was mid reddish brown sandy clay with common iron panning and occasional small stones. Secondary was mid red brown silty sand with no inclusions.

A spindle whorl made from a Roman potsherd.

4 24 Linear aligned NE-SW. Convex sides to W, steeply sloping to E, flat base, 0.98m wide.

Dark grey brown silty clay, which contained common charcoal flecks and rare small flints. Abraded residual prehistoric pottery.

38Linear feature that terminated to the south-west and extended beyond the edge of the trench to the north-east. Concave sides, flat base, 1.17m wide.

Light yellow brown clayey silt with occasional flecks of charcoal and daub, and rare burnt flint. Late Bronze Age pottery.

56 Linear feature aligned north-east to south-west. V-shaped profile, 0.72m wide. Light yellow brown clayey silt with occasional flecks of charcoal. Late Bronze Age or earlier as cut by [38]

65 Linear feature aligned north to south. V-shaped profile, 0.98m wide.

Light yellow brown silt with occasional flecks of charcoal and daub. None provided/available.

106Linear feature aligned east to west, which extended beyond the edges of the trench. Steeply sloping sides, concave base, 0.92m wide.

Light yellow brown silt with occasional flecks of charcoal. None provided/available.

4009Possible Enclosure System

4010 Possible Ditch 29

121Irregular cut aligned E-W extending beyond the trench. Irregular sides and base, 1.8m wide. Interpreted as tree-throw disturbing earlier features.

A series of yellow brown silty clays containing varying quantities of charcoal and flints. Early to Middle Iron Age potsherds.

283 Irregular feature 0.9m by 0.6m. Steeply sloping sides, not fully excavated. Likely tree-throw. Sterile mid yellow brown sandy silt. None provided/available.

381 Sub-rectangular aligned N-S and extending beyond the trench. Steeply sloping sides, base not excavated, 0.74m by 0.31m.

A series of orange brown silty fills containing rare to occasional burnt flints. Early to Middle Iron Age pottery.

1196Irregular feature aligned E-W, extending beyond the trench. 1.25m long by 0.90m wide. interpreted as tree-throw disturbing earlier features.

Dark orange brown silty clay, over mid yellow brown sandy silt. Early Iron Age pottery.

32 654 Linear aligned W-E. 3.60m wide, concave sides, not fully excavated.

Mid grey brown clay silt over mid grey brown silty clay containing occasional small stones. The lowest excavated fill was mid orange grey clay silt containing occasional manganese stains and iron panning.

None conclusive.

31 1190 Unexcavated linear feature, 6.50m wide, aligned east to west, which extended beyond the edges of the trench. None provided/available. Prehistoric pottery.

31 612 Linear 1.42m wide, aligned SE-NE extending beyond trench. Steeply sloping sides, irregular base..

Dark grey brown silty clay containing occasional small stones and shell fragments. Late Iron Age/Early Roman pottery.

4013 Pits

4014 Possible Ditch

4007

Possible double ditch enclosure or trackway

1

Not evident in trench.

Not trenched.

4008 Enclosure

Not trenched.

Not targeted by trenching.

134011 Pits

4012 Probable ditches

586000

586500

587000

189500

190000

190500

Site location Figure 1

0 500 m

Site Boundary

Detail Survey Extents

04/09/2015

1:25000 & 1:10,000 at A4

X:\PROJECTS\110130\GIS\FigsMXD\Geophys\2015_09_04

0

KJF

Date:

Scale:

Path:

Revision Number:

Illustrator:

Contains Ordnance Survey data © Crown copyright and database right 2015.

This material is for client report only © Wessex Archaeology. No unauthorised reproduction.

586100

586200

586300

586400

586500

586600

189800

189900

190000

Date:

Scale:

Path:

Revision Number:

Illustrator:

Greyscale plot Figure 2

04/09/2015

1:1500 at A3


0

KJF

0 50 mSite Boundary



+3nT

-2nT

586100

586200

586300

586400

586500

586600

189800

189900

190000

Date:

Scale:

Path:

Revision Number:

Illustrator:

XY trace Figure 3

04/09/2015

1:1500 at A3


0

KJF

0 50 mSite Boundary



-25nT

+25nT

4012

4013

4011

4008

4014

4010

4007

4009

4006

4005

4004

4003

4002

4001

4000

586100

586200

586300

586400

586500

586600

189800

189900

190000

Date:

Scale:

Path:

Revision Number:

Illustrator:

Interpretation Figure 4

02/10/2015

1:1500 at A3


1

GJD

0 50 m


Archaeology

Probable archaeology

Possible archaeology

Ferrous

Increased Magnetic Response

Trend

Agricultural

Essex County Archaeology 1997 Trial Trenches


4012

4013

4011

4008

4014

4010

4007

4009

4006

4005

4004

4003

4002

4001

4000

586100

586200

586300

586400

586500

586600

189800

189900

190000

Date:

Scale:

Path:

Revision Number:

Illustrator:

Interpretation Figure 4

02/10/2015

1:1500 at A3


1

GJD

0 50 m


Archaeology

Probable archaeology

Possible archaeology

Ferrous

Increased Magnetic Response

Trend

Agricultural

Essex County Archaeology 1997 Trial Trenches


4

3 6

5 12

11

2

13

20

21

30

29

28

31

32

17

16

7 10

18

19

24

25

26

27

1 8 22

23

9 14

586100

586200

586300

586400

586500

586600

189800

189900

190000

Date:

Scale:

Path:

Revision Number:

Illustrator:

Proposed phasing Figure 5

02/10/2015

1:1500 at A3


0

RAM

0 50 m


Late Bronze Age

Early Iron Age

Late Iron Age/Early Romano-British

Essex County Archaeology 1997 Trial TrenchesThis material is for client report only © Wessex Archaeology. No unauthorised reproduction.

+3nT

-2nT

Wessex Archaeology Ltd registered office Portway House, Old Sarum Park, Salisbury, Wiltshire SP4 6EBTel: 01722 326867 Fax: 01722 337562 [email protected] www.wessexarch.co.uk

Wessex Archaeology Ltd is a company limited by guarantee registered in England, company number 1712772. It is also a Charity registered in England and Wales, number 287786; and in Scotland, Scottish Charity number SC042630. Our registered office is at Portway House, Old Sarum Park, Salisbury, Wiltshire SP4 6EB.

© Wessex Archaeology Ltd 2015, all rights reserved Wessex Archaeology Ltd is a Registered Charity No. 287786 (England & Wales) and SC042630 (Scotland)


Written Scheme of Investigation for Archaeological Geophysical Survey

Prepared for: GL Hearn Limited 280 High Holborn

London WC1V 7EE

Prepared by: Wessex Archaeology

Portway House Old Sarum Park

SALISBURY Wiltshire SP4 6EB

www.wessexarch.co.uk

August 2015

Report Ref. T20427.02

Airport Business Park, Southend Written Scheme of Investigation for Geophysical Survey

DISCLAIMER

THE MATERIAL CONTAINED IN THIS REPORT WAS DESIGNED AS AN INTEGRAL PART OF A REPORT TO AN INDIVIDUAL CLIENT AND WAS PREPARED SOLELY FOR THE BENEFIT OF THAT CLIENT. THE MATERIAL CONTAINED IN THIS REPORT DOES NOT NECESSARILY STAND ON ITS OWN AND IS NOT INTENDED TO NOR SHOULD IT BE RELIED UPON BY ANY THIRD PARTY. TO THE FULLEST EXTENT PERMITTED BY LAW WESSEX ARCHAEOLOGY WILL NOT BE LIABLE BY REASON OF BREACH OF CONTRACT NEGLIGENCE OR OTHERWISE FOR ANY LOSS OR DAMAGE (WHETHER DIRECT INDIRECT OR CONSEQUENTIAL) OCCASIONED TO ANY PERSON ACTING OR OMITTING TO ACT OR REFRAINING FROM ACTING IN RELIANCE UPON THE MATERIAL CONTAINED IN THIS REPORT ARISING FROM OR CONNECTED WITH ANY ERROR OR OMISSION IN THE MATERIAL CONTAINED IN THE REPORT. LOSS OR DAMAGE AS REFERRED TO ABOVE SHALL BE DEEMED TO INCLUDE, BUT IS NOT LIMITED TO, ANY LOSS OF PROFITS OR ANTICIPATED PROFITS DAMAGE TO REPUTATION OR GOODWILL LOSS OF BUSINESS OR ANTICIPATED BUSINESS DAMAGES COSTS EXPENSES INCURRED OR PAYABLE TO ANY THIRD PARTY (IN ALL CASES WHETHER DIRECT INDIRECT OR CONSEQUENTIAL) OR ANY OTHER DIRECT INDIRECT OR CONSEQUENTIAL LOSS OR DAMAGE.

Quality Assurance

Project Code T20427 Accession Code

Client Ref.

Planning Application Ref.

Ordnance Survey (OS) national grid reference (NGR)

586473, 189766

Version Status* Prepared by Checked and Approved By

Approver’s Signature Date

v01 I GJD LJL

14/08/15

File: X:\TENDERS\T20427\WSI\T20427_SouthendGEO_WSI_QC_LJL.docx

v02

File

* I = Internal Draft; E = External Draft; F = Final


i




Contents

1 INTRODUCTION ............................................................................................................... 1

1.1 Project Background ........................................................................................................... 1

1.2 Project Aim ........................................................................................................................ 1

1.3 Scope of Document ........................................................................................................... 1

1.4 Wessex Archaeology capabilities ...................................................................................... 1

1.5 Project Team ..................................................................................................................... 2

2 SITE DETAILS .................................................................................................................. 2

2.1 Site Location and Topography ........................................................................................... 2

2.2 Soils and Geology ............................................................................................................. 2

2.3 Archaeological and Historical Background ........................................................................ 3

3 METHODOLOGY .............................................................................................................. 3

3.1 Survey Area ...................................................................................................................... 3

3.2 Instrument specification ..................................................................................................... 4

3.3 Survey specification .......................................................................................................... 4

4 REPORTING ..................................................................................................................... 4

5 ARCHIVING ...................................................................................................................... 5

6 HEALTH AND SAFETY .................................................................................................... 5

7 STANDARDS .................................................................................................................... 6

7.1 Quality and Code of Practice ............................................................................................. 6

8 REFERENCES .................................................................................................................. 6

8.1 Bibliography ...................................................................................................................... 6

8.2 Cartographic Sources ........................................................................................................ 7

APPENDIX 1: SURVEY EQUIPMENT AND DATA PROCESSING ........................................... 8

Survey Methods and Equipment ..................................................................................................... 8

Post-Processing .............................................................................................................................. 9

APPENDIX 2: GEOPHYSICAL INTERPRETATION ................................................................ 10

Figures Figure 1: Site location and proposed survey extents


1




1 INTRODUCTION

1.1 Project Background

1.1.1 Wessex Archaeology has been commissioned by GL Hearn Limited (hereafter “the Client) to carry out a geophysical survey of land associated with the proposed Airport Business Park, Southend, Essex (Figure 1), hereafter “the Site” (centred on National Grid Reference (NGR) 586473, 189766).

1.1.2 The geophysical survey will be within Area B of the development, the proposed location for the relocation of the Westcliff Rugby Football Club which will entail the construction of new pitches and associated drainage.

1.1.3 The proposed development area has previously been assessed as part of the Historic Environment Assessment and proposed development framework for Westbarrow Hall Farm, Rochford (Place Services 2012). This has highlighted areas of high, medium and negligible archaeological potential within the Site.

1.2 Project Aim

1.2.1 The general aim of the geophysical survey is to establish the presence/absence, extent and character of detectable archaeological remains within the survey area.

1.2.2 This document presents a brief description of the methodology to be followed and the form that the archaeological interpretation and reporting of the geophysical survey.

1.3 Scope of Document

1.3.1 This document sets out the strategy and methodology by which Wessex Archaeology will implement the geophysical survey. In format and content it conforms with current best practice and to the guidance outlined in Management of Research Projects in the Historic Environment (‘MoRPHE’) (English Heritage 2008), the Chartered Institute for Archaeologists’ Standards and Guidance for archaeological geophysical survey (CIfA 2014) and Historic England’s Guidelines Geophysical Survey in Archaeological Field Evaluation (English Heritage 2008) and Thesauri (2013).

1.4 Wessex Archaeology capabilities

1.4.1 Wessex Archaeology has a unique track record in undertaking archaeological geophysics investigations in land, coastal and marine environments. Both in the UK and abroad, Wessex Archaeology delivers professional archaeological geophysical services. A practical and pragmatic approach to carrying out investigations is matched by a proven ability to place the results within their proper archaeological context.

1.4.2 Wessex Archaeology’s expertise in geophysical surveys is fully integrated with its archaeological services, ensuring a seamless, professional approach with direct access to


2


in-house computing, illustration, finds and environmental analysis, and scholarly and popular publication.

1.4.3 Wessex Archaeology employs a geophysics team comprising 14 specialist staff at all grades from Director to Project Assistant. This team is supplemented by archaeologists with geomatics and geoarchaeological experience from Wessex Archaeology’s wider staff and further experienced staff can be brought in on contract to meet project requirements.

1.4.4 In addition to its in-house expertise, Wessex Archaeology routinely employs the services of a range of eminent geoarchaeological, palaeo-environmental and finds specialists. The contribution of these specialists to specific projects is managed through a relevant technical manager. Further details of external specialists employed by Wessex Archaeology can be provided on request.

1.5 Project Team

1.5.1 The work will be undertaken by Wessex Archaeology’s in-house geophysics team. Dr Paul Baggaley as Director of GeoServices at Wessex will be responsible for the work and Paul is, in turn, responsible to the Chief Executive. The Chief Executive has ultimate responsibility for the maintenance of quality standards for all work within Wessex Archaeology.

1.5.2 Lucy Learmonth as Terrestrial Geophysics Manager will be responsible for the day to day running of the geophysical survey work from fieldwork through data processing, interpretation and reporting. The project will be managed overall by Caroline Budd for Wessex Archaeology.

1.5.3 Fieldwork will be undertaken by experienced members of the geophysics team and will likely comprise geophysicists from our Salisbury Office.

1.5.4 All nominated Wessex Archaeology staff are appropriately qualified and experienced for their project role. Wessex Archaeology reserves the right to vary project staff according to the operational demands of its overall programme. Career profiles can be provided on request.

2 SITE DETAILS

2.1 Site Location and Topography

2.1.1 The survey area is located approximately c1.4 km to the south-east of Rochford and approximately 3.7 km to the north of Southend-on-Sea. Area B comprises an arable field and lies immediately to the north-east of Westcliff Rugby Club, covering an area of approximately 10.2 ha (see Figure 1).

2.1.2 The Site is relatively flat situated at an elevation of approximately 12 m above Ordnance Datum (aOD).

2.2 Soils and Geology

2.2.1 The underlying geology of the Site is mapped as Eocene Clay, Silt, Sand and Gravel of the Thames Group Formation with superficial Quaternary sand and gravel river terrace deposits (British Geological Survey).

2.2.2 The soils underlying the Site are recorded as typical argillic brown soils of the 571z (Hamble 2) association (SSEW 1983). Soils derived from such geological parent material


3


have been shown to produce magnetic contrasts acceptable for the detection of archaeological remains through magnetometer survey.

2.3 Archaeological and Historical Background

2.3.1 The archaeological and historical background was assessed in detail within Historic Environment Assessment and proposed development framework for Westbarrow Hall Farm, Rochford (Place Services 2012) the results from this and relevant Essex Historic Environment Record (EHER) entries are summarised below.

2.3.2 Cherry Orchard Farmhouse which lies adjacent to the western edge of Area A is a Grade II Listed Building and dates from the 17th century (list entry 1322397).

2.3.3 The earliest evidence recorded in the vicinity relates to the fields either side of Cherry Orchard Farmhouse where Neolithic artefacts were found during quarrying activity in the 1970’s (EHER 9746).

2.3.4 Within the development area, field walking undertaken in 1996 found extensive spreads of prehistoric struck flint and burnt flint as well as concentrations of prehistoric pottery, Roman pottery and tile in Area B (EHER 17440-17443). The Romano-British material is thought to indicate a possible farmstead overlooking the river just to the north of Area B.

2.3.5 Trial trenching over parts of the Site in 1997 located the remains of a large prehistoric settlement including an additional area of settlement within the southern edge of the Site (Area A) adjacent to the Lancaster Business Park. A small quantity of Saxon pottery recovered during the evaluation suggests activity from this time within or to the north of Area B.

2.3.6 Excavations in the area of Cherry Orchard Farm in the 1950s located the remains of a Roman cemetery including an early 2nd century rich burial. A medieval or post-medieval kiln (EHER 9744) is also recorded to the east of the farmhouse which may be a precursor of the later brickworks which were situated in Area C.

2.3.7 Just to the southeast of Area A was the location of Westbarrow Hall Farm which is document from the 13th century and can be seen on late 19th century and early 20th century Ordnance Survey maps. Medieval occupation is also recorded to the north of Area B on a site later occupied by two 17th century cottages (EHER 13416).

2.3.8 During the Second World War several structures were constructed relating to the defence of the adjacent airport (EHER 20712) and several pillboxes which are still extant around the eastern perimeter of Area A and the southern perimeter of Area B.

3 METHODOLOGY

3.1 Survey Area

3.1.1 The total size of the proposed survey area is 10.2ha. It is proposed that the entire survey area is subject to detailed gradiometer survey. As much as possible of the survey area will be surveyed but artificial obstructions, such as overgrown vegetation, trees, crops, pylons, hedgerows, drains, road, farming equipment, potentially unsafe terrain etc. may prevent the total area being surveyed.

3.1.2 Stakeout data will be prepared in British National Grid coordinates prior to survey using AutoCAD, and survey data will be georeferenced accordingly. Individual survey grid nodes will be established at 30m x 30m intervals using a Leica Viva RTK GNSS instrument,


4


which is precise to approximately 0.02m and therefore exceeds Historic England recommendations (English Heritage 2008).

3.1.3 The surveyed area will be tied into the National Grid using GPS survey equipment to enable the surveyed area to be independently relocated by a third party.

3.1.4 Digital mapping and archaeological information gathered during previous work conducted by Wessex Archaeology on the Site will be used to support the interpretation of the geophysical data.

3.2 Instrument specification

3.2.1 The detailed gradiometer survey will be conducted using a Bartington Grad601-2 dual fluxgate gradiometer system, which has a vertical separation of 1m between sensors and with an effective sensitivity of 0.03nT.

3.3 Survey specification

3.3.1 Data will be collected at 0.25m intervals along transects spaced 1m apart, in accordance with Historic England guidelines (English Heritage 2008). Data will be collected in the zigzag method.

3.3.2 Data from the survey will be subject to minimal data correction processes. These would typically comprise a zero mean traverse function (±5nT thresholds) to correct for variations in the calibration between the two Bartington sensors used, and a de-step function to account for variations in traverse position due to varying ground cover and topography. These two steps are generally applied to all survey areas, with no further filtering or interpolation.

3.3.3 The data will be processed using commercially available and in-house software which allows greyscale and trace plots to be produced. Minimal processing will be applied to the data and typically includes bounded zero mean traverse and destagger functions.

3.3.4 An interpretation of the geophysical anomalies will also be presented identifying likely, probable and possible archaeological features along with linear trends and areas of increased magnetic response.

3.3.5 Further details of the geophysical and survey equipment, methods and processing are described in Appendix 1.

4 REPORTING

4.1.1 Upon completion of the fieldwork results of the detailed geophysical surveys will be compiled into an illustrated report in Wessex Archaeology’s house style describing the survey results and interpretation only.

4.1.2 The report will include the following elements:

• The name(s) of the investigators/contractors, title, date, report reference number and client details;

• A non-technical summary including the basis for the survey, its aims and results;

• Introduction including site location plan, planning reference numbers & SMR/HER casework number, Site history, National Grid Reference, Site description;


5


• An account of the background to the project and circumstances of work;

• The aims and objectives of the survey; and

• The methodology used.

4.1.3 The results of the survey will include:

• Plans at appropriate scales to include, raw data, greyscale plot, XY trace plot, interpretative plot. Each illustration will contain a scale bar and north arrow;

• A figure and text to demonstrate that the survey has been accurately geo-located;

• Detailed survey results and interpretation;

• Recommendations regarding further archaeological work necessary on site in advance of, or during, development;

• References to all primary and secondary sources consulted; and

• An appendices to include details of the geophysical and survey equipment, methods and processing undertaken and full definitions of the interpretation terms used in the report.

4.1.4 The report will be prepared within three weeks of completion of all fieldwork, and submitted to the Client for approval. If required an interim reporting can be completed following fieldwork.

4.1.5 Once approved, a digital report will be issued to the Client and to Essex County Council HER (if required) in their preferred format. Additionally hard copies of the report can be supplied to the Client on request.

4.1.6 Wessex Archaeology shall retain full copyright of the client report under the Copyright, Designs and Patents Act 1988 with all rights reserved; excepting that it hereby provides an exclusive licence to the Client for the use of the report by the Client in all matters directly relating to the project as described in the specification.

5 ARCHIVING

5.1.1 An accession number, if required, will be sought prior to work commencing.

5.1.2 Material archived will include the raw data in Geoplot usable format.

5.1.3 If the requirements of this project change, a variation can be requested for the complete project archive will be prepared in accordance with Schmidt et al. (2001) Geophysical Data in Archaeology: A Guide to Good Practice (ADS) and those required by ESHER.

6 HEALTH AND SAFETY

6.1.1 Health and safety considerations will be of paramount importance in conducting all fieldwork. Safe working practises will override archaeological considerations at all times.


6


6.1.2 All work will be carried out in accordance with the Health and Safety at Work etc. Act 1974 and the Management of Health and Safety Regulations 1992, and all other relevant Health and Safety legislation, regulations and codes of practice in force at the time.

6.1.3 Wessex Archaeology will supply a copy of their Health and Safety Policy and a Risk Assessment to the Client before the commencement of any fieldwork. The Risk Assessment will have been read and understood by all staff attending the Site before any groundwork commences.

6.1.4 Wessex Archaeology has both public liability (£10,000,000) and professional indemnity insurance (£5,000,000).

6.1.5 The geophysical survey team will be aware of safe working practices, safety equipment, emergency procedures and specific information relating to environmental conditions likely during fieldwork. Members of the survey teams will remain in visual contact at all times.

7 STANDARDS

7.1 Quality and Code of Practice

7.1.1 Wessex Archaeology is an archaeological organisation registered with the Chartered Institute for Archaeologists.

7.1.2 Wessex Archaeology endorses the Code of Practice and the Code of Approved Practice for the Regulation of Contractual Arrangements in Field Archaeology of the Chartered Institute for Archaeologists.

7.1.3 All core staff would be of a standard approved by Wessex Archaeology, be employed in line with The Chartered Institute for Archaeologists Codes of Practice and be members of the Chartered Institute for Archaeologists or be appropriately qualified.

7.1.4 Wessex Archaeology operates a Project Management System and is ISO 9001 accredited. Projects are managed in accordance with Historic England’s guidelines outlined in the document Management of Research Projects in the Historic Environment (Historic England 2015). All projects are undertaken under the direction of the Project Manager who is responsible to a Section Head, who ensures the maintenance of quality standards within the organisation. The Chief Executive has ultimate responsibility for all of the Company’s work.

8 REFERENCES

8.1 Bibliography

Chartered Institute for Archaeologists, 2014. Standard and Guidance for archaeological geophysical survey.

English Heritage, 2013. English Heritage Thesauri, [Online], Available: http://thesaurus.english-heritage.org.uk/frequentuser.htm [7th April 2015].

English Heritage, 2008. Geophysical Survey in Archaeological Field Evaluation. Research and Professional Service Guideline No 1, 2nd edition. Swindon: English Heritage.

Historic England 2015. Management of Research Projects in the Historic Environment: The MoRPHE Project Manager’s Guide. Version 1.0. Swindon: English Heritage.


7


Place Services, 2012, Historic Environment Assessment and proposed development framework for Westbarrow Hall Farm, Rochford

8.2 Cartographic Sources

British Geological Survey http://www.bgs.ac.uk/discoveringgeology/geologyofbritain/viewer.html [accessed 11/8/12]

Soil Survey of England and Wales, 1983. Sheet 4, Soils of Eastern England. Ordnance Survey, Southampton.


8


APPENDIX 1: SURVEY EQUIPMENT AND DATA PROCESSING

Survey Methods and Equipment

The magnetic data for this project was acquired using a Bartington 601-2 dual magnetic gradiometer system. This instrument has two sensor assemblies fixed horizontally 1m apart allowing two traverses to be recorded simultaneously. Each sensor contains two fluxgate magnetometers arranged vertically with a 1m separation, and measures the difference between the vertical components of the total magnetic field within each sensor array. This arrangement of magnetometers suppresses any diurnal or low frequency effects. The gradiometers have an effective resolution of 0.03nT over a ±100nT range, and measurements from each sensor are logged at intervals of 0.25m. All of the data are stored on an integrated data logger for subsequent post-processing and analysis. Wessex Archaeology undertakes two types of magnetic surveys: scanning and detail. Both types depend upon the establishment of an accurate 20m or 30m site grid, which is achieved using a Leica Viva RTK GNSS instrument and then extended using tapes. The Leica Viva system receives corrections from a network of reference stations operated by the Ordnance Survey and Leica Geosystems, allowing positions to be determined with a precision of 0.02m in real-time and therefore exceed the level of accuracy recommended by Historic England (English Heritage 2008) for geophysical surveys. Scanning surveys consist of recording data at 0.25m intervals along transects spaced 10m apart, acquiring a minimum of 80 data points per transect. Due to the relatively coarse transect interval, scanning surveys should only be expected to detect extended regions of archaeological anomalies, when there is a greater likelihood of distinguishing such responses from the background magnetic field. The detailed surveys consist of 20m x 20m or 30m x 30m grids, and data are collected at 0.25m intervals along traverses spaced 1m apart. These strategies give 1600 or 3600 measurements per 20m or 30m grid respectively, and are the recommended methodologies for archaeological surveys of this type (EH, 2008). Data may be collected with a higher sample density where complex archaeological anomalies are encountered, to aid the detection and characterisation of small and ephemeral features. Data may be collected at up to 0.125m intervals along traverses spaced up to 0.25m apart, resulting in a maximum of 28800 readings per 30m grid, exceeding that recommended by Historic England (English Heritage 2008) for characterisation surveys.


9


Post-Processing

The magnetic data collected during the detail survey are downloaded from the Bartington system for processing and analysis using both commercial and in-house software. This software allows for both the data and the images to be processed in order to enhance the results for analysis; however, it should be noted that minimal data processing is conducted so as not to distort the anomalies. As the scanning data are not as closely distributed as with detailed survey, they are georeferenced using the GPS information and interpolated to highlight similar anomalies in adjacent transects. Directional trends may be removed before interpolation to produce more easily understood images. Typical data and image processing steps may include:

• Destripe – Applying a zero mean traverse in order to remove differences caused by directional effects inherent in the magnetometer;

• Destagger – Shifting each traverse longitudinally by a number of readings. This corrects for operator errors and is used to enhance linear features;

• Despike – Filtering isolated data points that exceed the mean by a specified amount to reduce the appearance of dominant anomalous readings (generally only used for earth resistance data)

Typical displays of the data used during processing and analysis:

• XY Plot – Presents the data as a trace or graph line for each traverse. Each traverse is displaced down the image to produce a stacked profile effect. This type of image is useful as it shows the full range of individual anomalies.

• Greyscale – Presents the data in plan view using a greyscale to indicate the relative strength of the signal at each measurement point. These plots can be produced in colour to highlight certain features but generally greyscale plots are used during analysis of the data.


10


APPENDIX 2: GEOPHYSICAL INTERPRETATION

The interpretation methodology used by Wessex Archaeology separates the anomalies into four main categories: archaeological, modern, agricultural and uncertain origin/geological. The archaeological category is used for features when the form, nature and pattern of the anomaly are indicative of archaeological material. Further sources of information such as aerial photographs may also have been incorporated in providing the final interpretation. This category is further sub-divided into three groups, implying a decreasing level of confidence:

• Archaeology – used when there is a clear geophysical response and anthropogenic pattern.

• Probable archaeology – used for features which give a clear response but which form incomplete patterns.

• Possible archaeology – used for features which give a response but which form no discernible pattern or trend.

The modern category is used for anomalies that are presumed to be relatively modern in date:

• Ferrous – used for responses caused by ferrous material. These anomalies are likely to be of modern origin.

• Modern service – used for responses considered relating to cables and pipes; most are composed of ferrous/ceramic material although services made from non-magnetic material can sometimes be observed.

The agricultural category is used for the following:

• Former field boundaries – used for ditch sections that correspond to the position of boundaries marked on earlier mapping.

• Agricultural ditches – used for ditch sections that are aligned parallel to existing boundaries and former field boundaries that are not considered to be of archaeological significance.

• Ridge and furrow – used for broad and diffuse linear anomalies that are considered to indicate areas of former ridge and furrow.

• Ploughing – used for well-defined narrow linear responses, usually aligned parallel to existing field boundaries.

• Drainage – used to define the course of ceramic field drains that are visible in the data as a series of repeating bipolar (black and white) responses.

The uncertain origin/geological category is used for features when the form, nature and pattern of the anomaly are not sufficient to warrant a classification as an archaeological feature. This category is further sub-divided into:

• Increased magnetic response – used for areas dominated by indistinct anomalies which may have some archaeological potential.

• Trend – used for low amplitude or indistinct linear anomalies.

• Superficial geology – used for diffuse edged spreads considered to relate to shallow geological deposits. They can be distinguished as areas of positive, negative or broad bipolar (positive and negative) anomalies.


Site location Figure 1

Path: X:\PROJECTS\110130\Graphics_Office\Rep figs\wsi

Scale: 1:25,000

Date: 11/08/2015 Revision Number: 0

Illustrator: KMN

Contains Ordnance Survey data © Crown Copyright and database right 2012.

Site

188000

189000

190000

191000

192000

585000 586000 587000 588000

1 km0

Site boundary

Documents

Detailed Gradiometer Survey Report - Rochford District · Detailed Gradiometer Survey Report Airport Business Park Southend, Essex ... * I= Internal Draft; E= External Draft; F= Final