No. 237 Maritime Archaeology in the People's Republic of China ...

Figure 102. Bai Jiao. The wreck site is located at the base of the reef
in the foreground (CHI/95/144).
The site was visited each day from the expedition base at
Xiao Chen using a local fishing boat that acted as the dive
platform. It was a 30 to 40 minute journey each way.
Site description
we at h e r a n d S e a C o n d i t i o n S
The Dinghai area is usually affected by the typhoon in summer,
that is July and August. The monsoon from the north-east comes
in winter and spring, and the wind and waves are weakest
at this time. The southerly wind usually comes in summer
bringing with it often violent waves.
The direction and velocity of the current is changeable
and affected by the tide. Generally, the speed is 1 metre per
second. The average temperature of the surface water is
approximately 20°C. The lowest is in February, between 8˚C
and 9˚C, and highest is in summer (August) generally between
27˚C and 28˚C. The visibility is generally better in summer
and worst in spring.
Winds on the site were predominantly from the south or
north-east during the season of excavation. Occasionally the
southerly would bring rain and conditions that made diving
difficult. Northerlies were generally warmer. The weather was
very variable, ranging from warm and humid through to wet
and cool. Quite strong winds developed from the mid to the
latter part of June. These winds created sloppy sea conditions
which sometimes prevented work on the wreck site.
Tidal change often affected the visibility and it was
particularly difficult to work just before slack water. A large
tidal range (7 metres) created a reasonably strong current along
the site. The current could be used to advantage to carry away
sediment during hand fanning and excavation. Turbulence was
created when water came over the reef to the north of the site
as the tide approached its highest level, periodically affecting
visibility. Visibility ranged from 0.5 metres to 3 metres. Neap
and spring tides were also influential in working on the site,
further increasing the tidal range. Low tide tended to give
the best visibility, probably aided by increased light from the
surface. Visibility was also affected by sand dredging in the
area. On occasion the excavation team arrived at Bai Jiao 1
to discover dredger slurry had flowed right across the site in
a cloud, reducing visibility to zero. A mooring buoy for the
work boat was attached to the large concretion in grid square
OG4 (refer to Figure 9).
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Se a-b e d C o m P o S i t i o n
The wreck site is situated at the base of a steeply sloping reef
of jagged igneous rock. At the interface with the sea-bed the
rock is fractured into regular shapes. The sea-bed comprises
sand, shell grit and easily disturbed fine sediments. This
composition of materials overlies a substrate of viscous grey/
green clay-like mud. The viscous and clay-like condition of
the mud suggests the subsurface environment is anaerobic. An
exception to this is likely to occur where the passages of marine
worms carry oxygenated water and this may effect artefact
materials encountered during burrowing. The overlying sand
is likely to be an aerobic environment.
Ge n e r a l o b S e rvat i o n S
The work site for 1995 extended along the base of a steeply
sloping block reef wall which runs along the north part of
the site. The site covers a 30 metre by 6 metre area (if the
1990 survey and excavation is taken into account), although
there is a concentration of remains toward the middle of the
artefact spread.
The site itself is located in a depth of water that varies
between 6 and 13 metres depending on the tide. Initial
inspection of the site discovered a large concentration of
artefact material was located east of the concretion identified
in the work undertaken in 1990.
The wreck remains are dominated by these two iron
concretions (approximately 1.5 metres square by 1 metre high).
They lie some 2 metres apart and are joined by a single baulk of
timber. A number of ceramic bowls are partly encapsulated in
the concretions. Separate small concretions also engulf ceramic
bowls. The remainder of the site comprised concentrations
of bowls many of which remain stacked together. There are
isolated scattered bowls among the rocks and down the sand
slope which forms the boundary of the site.
Initial survey and methodology
The initial location of the site in 1995 was hampered by the
lack of transits photographs or the availability of accurate
GPS location. Low visibility also complicated the circular
survey conducted in the approximate site vicinity. However,
after several attempts the large identifying concretion (2x2x1
metres) from 1990 was located. Surface survey showed that
the 1990 area of work was relatively sterile. The general area
of survey extended in an easterly direction 18 metres and in
a north-south direction over 6 metres.
Figure 8 shows the previous 1990 site work and grid
system, together with the intended area of excavation, drawn
after initial inspection in 1995. The decision was made to
continue using a 2x2 metre grid system started in 1990 and
extend this along to the eastern part of the site. The large
concretion with a timber extending from it which had been
used as the zero datum in the 1990 work was again used for
the 1995 excavation work.
A 2x2 metre grid frame was constructed and a baseline laid
that continued the 245˚ east-west orientation of the previous
baseline from 1990. A second baseline was then laid 2 metres to
the north of this to aid the accurate placement of the moveable
grid frame. The recording method followed a simple numbering
system identifying parallel and perpendicular reference to the
primary baseline. The letter ‘G’ was imposed as representing