Scientists say the planned completion of the Mark Clark Expressway could turn acres of wetlands into barren mud flats.
The state office of Ocean and Coastal Resource Management said Friday that 30 acres of tidal wetlands and creeks on Johns and James islands would be affected by shade from bridges.
Experts say wetlands areas with too much shade end up as mud flats and no longer provide habitat for fish and shellfish.
The OCRM office also says about 17 acres of wetlands, including three acres of salt marsh, would be permanently destroyed by the construction.
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The project is intended to relieve traffic congestion south and west of Charleston. The new parkway would connect to Interstate 526 but would have lower speed limits than the expressway.
The (Charleston) Post and Courier