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Field Report: Fieldwork Procedure

2.0 Fieldwork Procedure

The archaeological mitigation programmes required two open area excavations, more restricted interventions in the footprint of pile caps, and in some cases ground beams. Borehole surveys and several watching briefs were imposed on concomitant service infrastructure construction (Table 1). Accordingly, appropriate fieldwork procedures, dependant on the level of recording required and the nature of excavation or monitoring, were implemented.

Table 1 Index of interventions at Blue Bridge Lane
Int	Activity	Description
1	evaluation trench	5m x 2m evaluation trench adjacent to Blue Bridge Lane
2	evaluation trench	2m x2m evaluation trench to the west of Mecca Bingo
3	evaluation trench	2m x 2m evaluation trench adjacent to Fishergate (south)
4	evaluation trench	2m x 2m evaluation trench adjacent to Fishergate (north)
5	evaluation trench	8m x 2m evaluation trench
6	evaluation trench	2m x 2m evaluation trench in car park of Mecca Bingo
7	evaluation trench	2m x 2m evaluation trench in car park of Mecca Bingo
8	evaluation trench	2m x 2m evaluation trench in car park of Mecca Bingo
9	evaluation trench	2m x 2m evaluation trench in car park of Mecca Bingo
10	evaluation trench	2m x 2m evaluation trench in car park of Mecca Bingo (west)
11	evaluation trench	1m x 1m evaluation trench in northern passageway of Mecca Bingo
12	evaluation trench	1m x 1m evaluation trench in northern passageway of Mecca Bingo
13	evaluation trench	1m x 1m evaluation trench in northern passageway of Mecca Bingo
14	evaluation trench	1m x 1m evaluation trench inside Mecca Bingo building
15	excavation	60m x 15m excavation of footprint of proposed new Bingo Hall between beam gridlines E and G
16	excavation	2m x 2m excavation of footprint of pile cap
17	excavation	2m x 2m excavation of footprint of pile cap
18	excavation	2m x 2m excavation of footprint of pile cap
19	excavation	2m x 2m excavation of footprint of pile cap
20	excavation	1m x 1m excavation of engineering testpit
21	excavation	2m x 1m excavation of engineering testpit
22	excavation	22m x 6.5m excavation of footprint of proposed new Bingo Hall between beam gridlines B7 and B11
23	excavation	12m x 3m excavation of footprint and cable trench of new electricity substation
24	excavation	6m x 2m excavation of footprint of beam gridline A (between A1 and A2)
25	excavation	23m x 2m excavation of footprint of beam gridline A (between A7 and A11)
26	watching brief	watching brief of geotechnical borehole investigation of 14 boreholes across western part of site
27	evaluation	five 1m x 1m evaluation trenches excavated along proposed access road to evaluate archaeological deposits
28	watching brief	4m x 4m limited archaeological excavation of southern end of proposed access road
29	watching brief	watching brief on construction of new drainage along Fishergate frontage and northern passageway
30	borehole survey	borehole investigation in location of proposed manholes

Table 2 Index of interventions at Fishergate House
Int	Activity	Description
1	excavation	8m x 7m excavation of footprint of proposed road access with extensions for full skeletons as appropriate
2	excavation	13.7m x 1.6m-3.4m excavation of footprint on new stair access with extensions for full skeletons as appropriate
3	building recording	photographic recording of pre-fabricated buildings adjacent to Fishergate
4	watching brief	watching brief on construction of new service network throughout grounds of Fishergate House, with extensions for full skeletons as appropriate. Included monitoring of new retaining wall along Blue Bridge Lane

Open area excavation

Where appropriate, interventions were marked out on the ground, tarmac and concrete surfaces were cut and then broken out using a 360 E mechanical excavator fitted with a breaker. Modern overburden was excavated using a wheeled mechanical excavator fitted with a 1.20m wide toothless ditching bucket, under strict archaeological supervision, and reinforced concrete and brick wall footings were removed with a pneumatic breaker. Towards the western end of the Blue Bridge Lane open area excavation (Intervention 15), a thick overburden was encountered and tested with a series of four hand-excavated 1m x 1m pits in order to determine the depth and nature of the deposit. Once the latest archaeological horizon had been reached, excavation areas were entirely hand-cleaned, modern deposits covering concrete stanchions and girders were removed to avoid finds contamination, and where possible, the concrete and brick-built features were removed. Where appropriate, areas were divided into quadrants and allocated a letter. Quadrants were then hand-cleaned, photographed and mapped, and excavation was continued by hand to the bottom of the archaeological sequence.

Small area excavation

The preparatory procedure for open area excavation was followed for smaller interventions. The nature of the archaeological deposits in these smaller excavation areas required that shoring be inserted when the depth of the trench exceeded 1.20m. Where this was necessary, the sections were recorded accumulatively and were amalgamated during post-excavation processing.

Borehole survey

A single borehole survey was undertaken in the northern area of Blue Bridge Lane adjacent to the river confluence in order to evaluate the impact of a proposed drainage scheme on underlying archaeological deposits. The positions of the proposed manholes were set out. Each core was drilled using a tracked percussion rig and one metre samples were recovered in sleeved plastic tubes. Material in each sleeve was recorded in stratigraphic order and examined for dateable material.

Watching brief

A total of four watching briefs were maintained, three at Blue Bridge Lane and one at Fishergate House. Those at Blue Bridge Lane were a response to the construction of new services and access into the sites, with the exception of Intervention 26, which was designed to monitor geotechnical investigation. Intervention 4 at Fishergate House comprised a watching brief on all new service construction associated with the residential development.

All excavation was undertaken using a wheeled mechanical excavator fitted with a 1.20m wide toothless ditching bucket, under strict archaeological supervision. Where archaeological deposits were encountered, they were subject to written, photographic and drawn records. Finds were hand-collected.

Building recording

A photographic record of the temporary 'Nissen' huts within the grounds of Fishergate house was undertaken prior to their demolition (Intervention 3). The survey was carried out using 35mm and medium format monochrome photography, using silver-based film. The photographic archive forms part of the site archive.

2.1 Excavation Procedure

The excavation and recording system employed during fieldwork is based on a set of principles known as Field Research Procedure(Carver 1999). This recording system structures excavation data in a hierarchical system. Each stratigraphic unit defined during excavation which is considered to have been formed by a single deposition is called a 'context'. Where appropriate, contexts are grouped during excavation as 'features', and similarly, features into groups called 'structures'. Separate indices are maintained for contexts, features and structures and each unit has a structured pro-forma recording sheet to be completed using a system of keywords. Indices of photographic recording, samples and drawings are compiled and cross-referenced with the context and feature indices. For Blue Bridge Lane and Fishergate House, separate context and features indices were maintained, and for Blue Bridge Lane, allocation of numbers continued from the sequence begun during evaluation. Since this resulted in duplicate feature and context numbers between sites, those from Fishergate House are suffixed with an 'F' and likewise, those from Blue Bridge Lane with a 'B' (in the few instances where it was necessary, those from Marlborough Grove have been suffixed with an 'M'). All structure numbers were allocated post-excavation and consequently, both sites share this index.

In addition to the hierarchical recording system, predetermined recovery levels were employed ranging from Recovery Level A to E, representing increasing levels of investment and intensity of investigation. For the purposes of feature excavation, Recovery Level C was predetermined and applied during fieldwork. This recovery level consists of coarse trowel definition, finds recovery by context and optional sampling - in this case, in accordance with the predetermined environmental sampling strategy. Contexts required an outline plan and full description, while features required an outline plan, full description, half-section drawing and photography and post-excavation plan and photography; structures were not identifiable until completion of the post-excavation programme. With limited exceptions (i.e. features and deposits of secure modern date), this strategy was employed and maintained during excavation, producing broadly comparable data sets.

The Ordnance Survey National Grid and Ordnance Survey Datum were used for recording purposes. All coordinates and alignments expressed in this report refer to the Ordnance Survey grid. All plans and sections were either hand-drawn to a scale of 1:10 or surveyed using a Total Station Theodolite and drawn digitally with a pen-computer. A full photographic record was compiled consisting of 35mm colour and monochrome photography.

2.2 Environmental Sampling Strategy

A systematic regime of environmental sampling was designed and implemented prior to excavation at Blue Bridge Lane. At Fishergate House, non-burial features, which were rich in animal bone, were 100% coarse-sieved and primary deposits were sampled for flotation. The on-site identification of secondary and primary deposits is integral to the hierarchical recording system employed by FAS and was key to the implementation of the following methodology.

2.2.1 Environmental recovery

The following regime was applied to primary or primary refuse deposits only. A 100 litre sample of each primary or primary refuse deposit was subject to fine-mesh sieving on a 2 millimetre mesh processed with hosed water. In addition to this, a 30 litre sample was recovered for flotation using a Siraf tank. Of these, 20 litres were processed by FAS on-site (using 500 micron mesh to capture the dense fraction and 250 micron mesh for the light fraction). If, after processing, the deposit was considered to have good environmental potential, i.e. visible uncharred organic remains and invertebrates, 10 litres were retained for paraffination. The remainder of each deposit was subject to 100% coarse-sieving on a 1cm mesh processed with hosed water, with the exception of deposits where fish bone was noted, in which cases the assemblage was retrieved by flotation.

2.2.2 Enhanced finds recovery

It was recognised that the above sampling regime would enhance the recovery of fragmentary or small artefacts, notably early medieval coins, glass vessel fragments or objects and craft-working residues. In some cases, a sieving regime was implemented for deposits of insecure status to enhance the recovery of dateable material, since vertical stratigraphy was virtually absent and many features were simply cut into subsoil. This regime was implemented at the Fieldwork Supervisor's discretion.

The environmental regime produced massive quantities of dense fraction residues, which were hand-sorted. Dry residues were sieved through a stack consisting of 5mm and 2mm mesh, producing three further fractions (>5mm, <5mm and <2mm). Each fraction was then weighed. The coarse fraction was rapidly sorted for large bulk finds and small finds. The two smaller fractions were sorted exhaustively for identifiable remains of small vertebrates, and then scanned with a magnet to recover micro-slags.

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