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Most of the coastal mining in Thailand is along the wes! coast of Phang-nga Province
facing the Andamarr Sea. Weather conditions limit mining in ihese areas to the calm seas of
the northeast monsoon (November-April) each year. When in operation, the sediment plunn
from an aggregation ot small boats or from large dnedges can easily be detected by satellite.
Effects of minino
Within the last few years, the effects of mining in coastal waters have created public
concern in Thailand with respect to both the aesthetic value and the produclivily of coastal
ecosystems. Public reaction also depends upon the location of the dredging. Mast concern
arises from conflicts of interest in the utilizetion of coastal resources by various sectors. For
this reason, some informaLion is available regarding potential environmental damage lo
resources from mining off the west coast of Phuket Island, although mining on the west coast
is recent in companison to the 75 years of mining on the east coast and in Phang-nga Bay.
The main issue concerns the mining of rich deposits along ihe west coast which have become
popular resorLs because of [heir beautiful sandy beaches and clear waters. Income from
tourism has become more important locally and nationally at about the sarne time as tin
deposits m land have become depleted after more than 100 years of mining m Phuket Island.
Recently, the National EnvironmenLal Board of Thailand has completed a I year study of the
physical environment and living resources of Lhe coastal waters. The sLudy will be used for
future planning of nesource utilization to minimize zuch conflicts of inLerest and lo prepare
measufes to decrease environmental damage from mining qerations.
In brief, these studies found turbulent water movement up to 40 netres depth along Lhe
shore (Charoenlaph, 1982). Therefore any s-rspended solids brought up dredging would spread
along the coast, mly settling out at a speed determined by the current velocity. Unless
measures can be taken to limit plume distribution effectively, the water quality of several
beach resorts will be affected. Mininq close to shore could also cause beach instability.
Corel reefs
With regard to effecls on benthic communities along the west coast, coral reefs are
identified as one of the major fesources affected by mining activities. An inven[ory of reef
resources (Chansang et al., 1982) showed that fringing reefs are found along the west'coas[
within bays and along proLected shorelines. Since reefs are highly valued both their unique
attractiveness and their importance as highly productive resources, the destruction of coral
reefs has been one of the major issues, together with turbidity, in the public debate about
mining. The same reporl showed that in Bang Tao Bay on the west coast with ongoing
dredging act,ivity, the reef areas covered by dead coral arc 67.7Yo on the norlhern side and
62.wo on the southern side. All dead corals are covered by sediment. At the northern reef,
sediment may also have come from the land in the pasL, as there is sttbstantial land accreLion
at the mouth of a canal draining in[o the bay at lhe norlhern end.
In general, tJre ef f eets of sedimentation upon coral reef s ate guite well known
(Johannes, 1975; Bak, f978). Drawing on the results of various investigators, Loya (f976)
summarized the detrimental effec[s of sedimentation on corals as follows: a) causing the
deaLh of corals when they are heavily coated or buried by sediments, b) reducing coral
growth potential directly by abrasion and smothering and indirectly by blocking lighl' c)
inhibiting coral planulae settlement and development and d) modifying the growth of corals
sometimes toward lhe evolution of forms rnore resistant to sedimentation.
The damaged reefs at Bang Tao Bay are clear evidence of the effect of uncontrolled
mining operalions. In trying io accommodate dredging activity while maintaining water quality
and preserving the environnent in some localities, ari the National Env.ironmental Board
intends, one of the main challenges will be to establish water quality standards in dredging
areas on a sound scientific basis to ensure that both immediate and long lerm effects of
increasing turbidity will not occur. lt is quite likely that the mining indus[ry would object to
any high water quality standard since the technology for limiLing plume distribution has not
yeL been tried in tin dredging and since capital investment would be higher. Howeverr a
compromise in the water quality standard would mean increased long term turbidity which
would be likely to affect both coral reefs and tourism. Coral reefs along the west coast of
Phukel are already in more turbid waters than other known reefs which attract tourism;
increasing turbidity would reduce their value even further. Changes in their community
structure are also possible.