Final Report on the Archaeological Intensive Survey for the Thompson Island Salt Marsh Restoration Project, Boston Harbor Islands, Massachusetts

A salt marsh restoration plan for Thompson Island in Boston Harbor calls for the removal
of a stone berm that prevents tidal flushing of an existing salt marsh/pond on the central
east side of the island. Lack of daily tidal exchange has resulted in a stagnant water body
with severe algae blooms and encroachment by the invasive plant species, common reed
(Phragmites australis). The restoration plan includes archaeological investigation of the
proposed construction/demolition area as well as the inter-tidal zone and marsh/pond
bottom that may be subject to erosion once the blocked outlet is reopened. The
construction area was tested with a series of ten, 10 m-interval shovel tests arranged in
four transects. Sand and gravel predominated with a low density of late nineteenth and
twentieth century waterworn ceramics, glass, brick and coal. The south and west marsh
perimter was previously tested with 20 m-interval shovel tests by Barbara Luedtke in
1993 with only late nineteenth and twentieth century artifacts found. The remaining east
and north tidal zone, therefore, was tested with nineteen, 20 m-interval shovel tests.
These revealed sandy clay loam soils and a low density scatter of mostly waterworn late
nineteenth and twentieth century artifacts. Two gray siltstone flakes and some shatter
were identified in one test in [REDACTED]. Array tests
revealed an additional gray-green chert flake. The marsh bottom was remotely imaged
using a StrataBox subbottom profiler to search for potential submerged anomalies.
Shallow conditions and gas-charged sediments obscurred some readings, but a paleo
drainage channel was identified approximately 2 m below the marsh bottom. Although
one small Native American activity locus was identified, it was
recommended that the project proceed as planned.