Multiple cropmark enclosure at Ardee, Co. Louth
Multiple cropmark enclosure at Ardee, Co. Louth (Photo VJK Ltd)

Archaeology & History:

A guide to NRA Archaelogy

This guide outlines the four stages the NRA undertakes to ensure best practice in archaeology.


Stage 1 - Planning
When developing the route of a new road, archaeology is an integral part of the planning process. The NRA employs Project Archaeologists to oversee the archaeological implications of all aspects of road schemes. The planning process is divided into 3 stages:

(i) Constraints
A proposed road scheme may cover a vast geographical area. Archaeologists highlight all known sites of archaeological importance so that where possible they can be avoided.

(ii) Route Selection
Following the Constraints Stage, a number of corridors emerge in the landscape within which more specific route options develop. At this stage archaeologists carry out further work such as site visits, aerial photography and historical study including more refined cartographic searches. At the end of this stage, what is called the Emerging Preferred
Route is established.

(iii) Environmental Impact Statement (EIS)
An EIS is a description of the likely effects on the environment of the proposed road development. At EIS stage archaeologists carry out more in-depth research of the area of the proposed road scheme. This work will include a field-walking survey of all archaeological sites (known and newly identified), more detailed aerial survey, geophysical survey and refined historical searches. According to law, every large scale road planning application must include an EIS.
Archaeological test trenching on the N4.
Archaeological test trenching on the N4 Sligo Inner Relief Road

 


Stage 2 - Testing
Once An Bord Pleanala has approved the EIS and the land to build the road has been purchased, the archaeologists conduct a comprehensive and extensive testing regime. Archaeological sites that are known or have been previously identified during the EIS are targeted for specific testing strategies.

This can include geophysical techniques, hand excavated test trenches and machine excavated test trenches. In advance to work being carried out all testing techniques must be agreed with the National Monuments Section of the DoEHLG in consultation with the National Museum of Ireland.

(i) Archaeological geophysics
has been defined as “The examination of the Earth's physical properties using noninvasive ground survey techniques to reveal buried archaeological features, sites and landscapes” (Gaffney and Gater 1993, 12). There are different types of geophysical technique such as Electrical Resistivity, Magnetometry and Magnetic Susceptibility.

(ii) Test trenching known areas
Where archaeological sites have been identified the site will be investigated by hand digging one or several test trenches across the site and in the vicinity of the site. This involves the hand removal of the topsoil and exposing the archaeological features beneath the soil. The object of this exercise is to establish the nature and extent of the archaeological deposits underneath.Where an archaeological site exists outside the land take for the new road but is close by the area within the land take adjacent to the site will also be test trenched in this way. Areas of archaeological potential are also identified and tested even though there may be no surface expression of sites.

(iii) Blanket testing unknown areas
Across the remainder of the proposed route which may stretch for many miles, the whole area is archaeologically test trenched. A machine digs a trench along the centre line of the entire route with a number of offsets, perhaps every 15-20m. The objective of this exercise is to try and identify large previously unknown sites that will involve extensive excavation. Once all the testing has been completed reports must be written with all the results.
Recording an Early Medieval stone lined grave.
Recording an Early Medieval stone lined grave at Balriggan, M1 Dundalk Western Bypass

 


Stage 3 - Excavation
Archaeological Excavation is a two pronged technique: on one side there is Excavation, on the other Recording. To excavate / record a site, we must:

• Understand how sites become lost and buried.

• Be able to recognise archaeological and cultural remains in order to approach
excavation in an informed manner.

• Have a flexible recording system through which sites can be untangled and interpreted.


(i) Excavating
Sites such as settlements tend to bury themselves by dynamically demolishing, levelling and rebuilding themselves continuously through time. Settlement sites can thus create a heap of stratified deposits, with the earliest material at the bottom and the latest at the top.Un-peeling stratified sites is an acquired skill since much is usually missing (removed or rotted to nothing). When clean, archaeological features can actually be seen. Each deposit or feature may contain artefacts (pottery, jewellery, weapons, tools etc) or preserved environmental remains (human or animal bone, seeds) by which a date and function can be given.

(ii) Recording
It is vital that the detailed variety within every site is preserved by record through the excavation process. If the record is jumbled, the site cannot be dated or interpreted with accuracy. To preserve site integrity, the Single Context Recording System is used. With Single Context Recording, every archaeological action, is given a unique context number. Discovered artefacts and environmental remains are bagged and labelled according to their context number. The stratigraphic relationship of all contexts is then drawn up, from the earliest to the latest, as the site matrix. The records thus ensure every archaeological object or feature can be traced back to its original stratigraphic location.

Archaeologist at work at the Conservation lab.
Conservation Lab at the Museum (Photo National Museum of Ireland)

 


Stage 4 - Post-Excavation
Archaeology is the study of past peoples, but these people often leave little behind to tell the story of their everyday lives. It is through Fact, Interpretation and Reporting that Post-Excavation breathes life into dry remains.

(i) Facts
Specialist analysis of pottery, flint, jewellery, human and /or animal bone, seeds etc can give amazing detail to many activities – bolstering the factual evidence considerably and providing a tangible link to the past.

(ii) Interpretation
Interpreting the facts is often more difficult. For example, the various features have usually had their tops cut off by modern, agricultural ploughing; and organic things can rot away to nothing – leaving no evidence. It is thus often difficult to give a function to some parts of the site: does this ditch mean there was an animal pen, a domestic house or a vegetable plot?

(iii) Reporting
In order to clarify how a site is interpreted, archaeologists use a simple technique of comparing it with similar sites that may be better preserved, better known and fully published. The overall aim of post-excavation isto circulate the results to other archaeologists and the general public.