Reducing the Effects of Heavy Equipment Compaction through in Situ Archaeological Site Preservation
Ardito, Anthony J., Antiquity
Salvage archaeology in anticipation of destruction is an accepted response to a site in the way of a pipe-line or other development. But is it right in principle? -- a 'full and fair' record is not quite the same as survival of the actual site. And if techniques to protect a site during construction work are well designed, may they not also be cheaper?
The protection of non-renewable cultural resources has become important in the regulatory review process of many US government agencies. Alternatives to the traditional method of recovery by salvage excavation are increasingly being used.
The recent construction of the Iroquois Gas Transmission System Pipeline (Iroquois) used a new technique for short-term preservation of archaeological deposits -- burial under protective overburden intended to preserve materials from damage caused by heavy equipment during pipeline construction.
The Iroquois pipeline extends from Ontario, Canada approximately 370 miles through northern and eastern New York State, western Connecticut, across Long Island Sound and on to Long Island, New York. Iroquois was required, under Section 106,(1) to conduct archaeological field surveys so as to identify, evaluate and protect cultural resources in one of the largest programmes of its kind ever conducted in the north-eastern United States. The field surveys identified over 500 sites in New York and Connecticut; for 40 that were potentially eligible for the National Register of Historic Places,(2) mitigation plans were developed for their protection.
To allow heavy construction equipment to operate within the area of an archaeological site while preserving its integrity, the site was given a protective overburden consisting of a geo-synthetic filter fabric and a crushed stone fill.
Although the two test sites were buried for a relatively short time, approximately 3-4 months, many factors were addressed that would arise in long-term burial/preservation: chemical and biological processes within the test area may alter the decay of buried artefacts; an overburden should minimize inadvertent mixing between the fill and existing soil while dissipating the impact of heavy equipment; various classes of artefacts need to be defined that are to be preserved; weather changes may cause variations in soil conditions; and different types of heavy equipment may have different effects.
Sites and methods
Two prehistoric Native American sites with assemblages from distinct cultural periods were chosen for test. Site 199-6-1 is a multi-component site dating from the Late Archaic (c. 3500-2500 BC) and Terminal Archaic (c. 2400-1500 BC). Site 211-1-1 is a large multi-component site dating to the Terminal Archaic (c. 2400-700 BC) and the Middle- to Late-Woodland periods (AD 300-1550).
Before construction started, extensive cultural material was recovered and used as a control. Before installation of the protective overburden, soil samples were collected and a series of tests, including particle-size count and pH level, conducted.
A US Army Corps of Engineers cone penetrometer was used to record the shear strength of the soil, expressed in pounds per square inch (p.s.i.) It reads shear strength on a scale of 0-300 p.s.i. at 1-, 3-, 6-, 12-, 18- and 24-inch depths. Readings pre- and post-construction determined whether the soils had been compressed.
A geo-synthetic woven textile filter fabric was used as the base covering. The fabric, a tightly woven material akin to polyester, is very porous, allowing air and water to pass through to the soil beneath. This material is sufficiently pliable for it to conform to the irregular surface contours of the land-form without a great deal of surface preparation and possible damage to cultural resources. Its light weight increases its manoeuvrability during installation and removal. As the fabric is synthetic, it is chemically inert, and has great resistance to damage from water erosion. …