F.
OCEANOGRAPHY.
The causeway alternative would block wave and wind driven circulation on
the eastern reefs and lagoon and modify tidal circulation between the ocean
and lagoon. The addition of culverts and bridge openings through the causeway
could reduce but not eliminate these effects.
In the absence of an adequate
Causeway maintenance and repair program, the failure of the causeway from
storm wave damage could also disrupt water quality and circulation.
Water quality effects from aquatic disposal of excavated soil could result
in extensive turbidity and sediment plumes. The extent of these impacts can
be reduced or eliminated by confined aquatic disposal in one of the lagoon
bomb craters (such as BRAVO crater), land disposal on another island (such as
Nam), or reef flat expansion of Bikini Island by disposal of excavated soil
behind protective berms. Bagging of excavated soil prior to aquatic disposal
would be another technique to reduce the effect of turbidity and sedimentation.
Filling operations during causeway construction could also result in
excessive production of turbidity and suspended sediments. Finally,
cutterhead dredging operations to obtain sources of replacement soil could
also generate excessive turbidity and sedimentaton; this can be reduced
considerably by establishing settling basins on land to contain discharge
slurry waters from the dredging operation.
Quarrying operations on the reef
flats to obtain armor rock and other stone for revetments should not result in
major adverse effects on water quality, if done properly.
G.
MARINE BIOLOGY.
Any alternatives involving construction in the water (such as for a
causeway), aquatic disposal of soil, dredging, or other discharges could have
an adverse effect on coral reef and subsistence fishery habitat. The causeway
alternative in particular would be destructive to subsistence fishery and reef
habitat from the direct effects of heavy equipment operation on the reefs and
the discharge of fill materials and from the indirect effects of circulation
and water quality changes as mentioned earlier. In addition, causeway
construction and dredging could result in the outbreak of ciguatera fish
poisoning which would further reduce the availability of fresh protein food
resources to the islanders and increase public health risks. The latter
effect could be mitigated by a monitoring program for the toxic algae and fish
but most of the remaining adverse ecological effects would be unavoidable.
The migrations of fish, shellfish, and other invertebrates between the
lagoon and ocean side of the reef could also be inhibited by the causeway, but
this effect can be reduced considerably by adequate numbers and sized culverts
and
bridge openings.
Quarrying operations for protective structures including.
the causeway revetment can also destroy existing marine biological habitat,
but quarry sites and operations can be designed and located in a manner to
reduce adverse effects and promote recruitment and colonization by fish and
corals (based upon evidence from existing quarries at Kwajalein and Enewetak).
S00014)
E-14