When the F.J. Torras Causeway connecting St. Simons Island to the mainland near Brunswick, Georgia, required widening from a two-lane to a four-lane highway, it was realized that the construction would require some filling of the adjacent salt marsh. Part of the impact mitigation package for the project involved restoration of several unvegetated spoil sites paralleling the causeway to a smooth cordgrass marsh. These spoil sites were remnants of fill material from the original construction undertaken in 1950. An amphibious rotary ditcher was used to construct approximately 3,000 feet of channels at one of the spoil sites and an unchannelized comparison site was set up to determine the degree of restoration achieved. Study results show no permanent damage from the sidecast material and indicate it may have enhanced the smooth cordgrass on either side of the channel. The channelized site not only increased tidal frequency and duration, but also reduced standing water and improved soil drainage after tidal cycles. Aerial photography revealed a 58% increase in the vegetated area on the channelized site after only two years. The technique has now been approved to restore 9.5 acres. Expansion of the causeway is scheduled to begin in early 1990. Substantial savings are expected as the rotary ditching technique is estimated to cost only $25,000 compared to the estimated cost of $350,000 for the usual method of excavating the soil, removing it from the site, and sprigging smooth cordgrass.

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  • Publication Date: 1990-1

Media Info

  • Features: Photos;
  • Pagination: p. 10-11
  • Serial:
    • TR News
    • Issue Number: 146
    • Publisher: Transportation Research Board
    • ISSN: 0738-6826

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Filing Info

  • Accession Number: 00491928
  • Record Type: Publication
  • Files: TRIS, TRB
  • Created Date: Mar 31 1990 12:00AM