As described above, the remains of the Emeryville
Shellmound were "rediscovered" after a construction inspector noted archaeological material in the soil during
industrial demolition. Archaeologists hired by the City of Emeryville Redevelopment Agency
assessed the discovery and provided recommendations for conducting archaeological
excavations and analyses to preserve important archaeological information from the
portions of the site that would be destroyed by hazardous waste remediation and
new construction.
"Data recovery" is the process of excavation and recording
that archaeologists use to obtain a sample of the materials present in the site, and of the information they represent.
A plan for excavating at the site and processing the excavated material (a "data recovery
plan") is developed before excavation starts, based on what is known about the
deposit
and the kinds of information--artifacts, strata and features-- it might be expected to
contain. Based on the kinds of materials known to be present and knowledge
of similar sites, archaeologists develop research questions about the site before excavations
begin. The research questions, data
expectations and data recovery plan form a research design to guide archaeological investigations. The
research design for the Emeryville Shellmound/Bay Street Project was
peer-reviewed by three noted archaeologists, as well as by three Ohlone individuals who had
expressed an interest in the site.
The data recovery plan for the Emeryville
Shellmound/Bay Street Project included both hand and mechanical excavation.
Archaeological fieldwork was carried out over a period
of 3 1/2 months between August and November of 1999. Archaeologists
excavated over 100 cubic meters (about 300 cubic feet) by hand with
shovels and trowels. In addition, in
order to learn more about the stratigraphy--or layers of the site
archaeologist also directed backhoe excavation of 28 trenches
totaling over 520
linear meters in length (over 3/10 of a linear mile) at various locations around the
site to depths of up to 3 meters (10 feet). These excavations provided information about site deposits over an area of more than two city blocks.
Data recovery at the Emeryville Shellmound posed some
logistical problems. Because arsenic, lead and other potentially hazardous materials were present in the soil,
archaeologists and Native American monitors received hazardous waste training and had
to wear protective gear
during excavation. The efforts of the
archaeological team had to be coordinated with the ongoing efforts of environmental
engineers and contractors to remediate the hazardous materials. Much of the major
excavation required for the remediation took place during night hours. Ground water,
which rose and fell with the tides in nearby San Francisco Bay, had to
be pumped to permit excavation near the base of the
deposit, which was partially submerged. Because the archaeological soils were so wet,
water screening was required to allow sample sorting and
runoff
had to
be controlled so that it would not pollute Temescal Creek and San Francisco Bay. In
order to permit close inspection of layers in the trenches, trenches had
to be shored. Additional mechanical excavation
also was
required to enable archaeologists to reach the bases of hand excavation units
while still complying with required safety standards. The large size of the site presented logistical
problems, which included the necessity of hauling material
from distant units to wet screening stations. These challenges required hard work by a
dedicated crew of 20 archaeologists and two Native American observers, as well
as a full time backhoe operator.
A construction trailer provided a
field laboratory
during the excavation period. Here, over 2500 artifacts and samples were washed, labeled and
catalogued. Partially processed samples, including many thousands of fragments of
animal bones, hundreds of pounds of shells, and many seed, carbon and soil
samples, were bagged and labeled for subsequent analyses by specialists at four
universities and six additional laboratories. After the field period, in a second temporary
laboratory near the site additional processing and analyses were conducted over a
further six-month period, again with Native American monitoring.
Secondary analytic processes included soil sample
flotation (separation of light materials like burnt seeds through use of very fine
mesh screen in a water tank); shell sorting; artifact drawing, and photography and description.
Because many of the artifact would be reintered with human remains from the site,
many molds of artifacts also were prepared so that replicas could be produced for analysis and
curation. Samples and nonburial artifacts then were taken to URS's facility in Oakland for
distribution to specialist labs and for additional analyses.
In the following 18 months, archaeologists, geologists and
geoengineers at the URS Oakland facility described artifacts in detail, assessed the stratigraphy (or layers)
discerned during excavation to understand the history of the site's deposition, investigated
the underlying geology of the site location, analyzed dietary shell, and described historic
bottles recovered from a Shellmound Park trash pit at the site. Beta Analytic in Florida, a
radiocarbon laboratory, dated almost 100 carbon samples from the site. UCLA's Zooarchaeology
Laboratory and other specialists identified the species of thousands of mammal, fish and
bird bones. UCLA's Paleobotany Lab microscopically examined dozens of samples of
carbonized seeds and plant material from the deposit. A microstratigraphy laboratory in
Oregon prepared slides of microscopic thin sections of columns of soil preserved from
the mound, for future analysis. At UC Berkeley, a specialist performed chemical
isotope analyses of shell specimens, to obtain data on changes over time in
temperature and salinity in the bay. Geologists at Humboldt State performed detailed assessments of
soil samples, to determine how soils and rock materials had been deposited
on the site. Chemical and microscopic analyses were performed on hundreds of samples of obsidian
(a volcanic glass used in the manufacture of chipped stone tools at the site), to provide
information on the source of the material and the time period of tool manufacture. Bone
and chipped stone tools were examined by other specialists to determine manufacturing
techniques and changes in tool styles. U.C. Berkeley's forest
products lab identified species of wood preserved in the deposit. At Sonoma State, a geomorphologist analyzed soil
profiles to provide more information about how the site's deposition and underlying
landforms. The results of these and other analyses are described and synthesized in the
lengthy technical report for the project, Emeryville Shellmound,
1999, which is available electronically on this web site. You will find links to synopses
of these results below.
