Glynn County Board of Commissioners Oak Grove Causeway Culvert Maintenance and Improvements Glynn County, Georgia


This serves as notification from the Coastal Marshlands Protection Committee and the Georgia Department of Natural Resources of a request from the Glynn County Board of Commissioners for a Coastal Marshlands Protection Act (CMPA) permit under the Official Code of Georgia (O.C.G.A.) 12-5-280 et seq., to conduct maintenance and improvements to existing culverts on Oak Grove Island Road over Cowpen Creek, Glynn County, Georgia. The proposed project is under 1/10 of an acre, and therefore may be considered a minor alteration of coastal marshlands under O.C.G.A. 12-5-280 et. seq.

The proposed project is located where Oak Grove Island Road crosses Cowpen Creek. The project sites consist of an existing two-lane asphalt road with vegetated road shoulders and coastal marshlands on each side. The east and west culvert locations each consist of two (2) 48 in. reinforced concrete pipes (RCP) with sheet pile headwalls and concrete caps at the upstream and downstream ends of the pipes. Scattered rip rap is located at the pipes below Mean Low Water (MLW) and along the adjacent shorelines.

The proposed project consists of temporary installation of sheet pile coffer dams, replacement of the existing downstream headwalls, replacement of the downstream tide gates, lining the existing pipes, and placement of supplemental rip rap for stabilization. 

Prior to commencing the proposed project, approximately 175 ft. (11 sq.ft.) of proposed temporary sheet pile coffer dams will be installed to allow for work below MLW. The existing RCP will be lined with 42 in. high-density polyethylene (HDPE) pipes and low-density cellular grout will be injected to fill the void between the RCP and HDPE pipes. New 42 in. aluminum flap gates will be installed on the downstream ends of the proposed HDPE pipes that will extend beyond the proposed downstream headwalls.

The downstream headwalls are compromised and in need of total replacement. Prior to removal of the existing downstream headwalls, new sheet pile headwalls with concrete caps will be constructed approximately 5 ft. seaward of the existing headwalls. Once constructed, the existing headwalls will be removed, and the area between the existing headwall and proposed headwall will be filled with a clay-sand mixture topped with filter fabric. Additional rip rap for erosion protection will be installed at both upstream and downstream ends of the proposed HDPE pipes at an approximate 2:1 slope. Upon completion, the temporary coffer dams will be removed. 

The proposed improvements associated with the western project site would result in 793 sq.ft. (0.018 acres) of permanent impacts to coastal marshlands. The improvements associated with the eastern project site would result in 747 sq.ft. (0.017 acres) of permanent impacts to coastal marshlands.  Temporary impacts associated with the proposed coffer dam installation and removal is 2,100 sq.ft (0.05 acres).

It is the responsibility of the applicant to demonstrate that the project is not contrary to the public interest and that no feasible alternative sites exist. Impacts to coastal marshlands must be minimal in size. In passing upon the application for permit, the Coastal Marshlands Protection Committee shall consider the public interest: (1) Whether or not unreasonably harmful obstruction to or alteration of the natural flow of navigational water within the affected area will arise as a result of the proposal; (2) Whether or not unreasonably harmful or increased erosion, shoaling of channels, or stagnant areas of water will be created; and (3) Whether or not the granting of a permit and the completion of the applicants proposal will unreasonably interfere with the conservation of fish, shrimp, oysters, crabs, clams, or other marine life, wildlife, or other resources, including but not limited to water and oxygen supply.

Please provide this office with substantive, site-specific comments as to why the proposed work should or should not proceed. Comments and questions concerning this proposed project should be submitted in writing and be submitted by the close of business on November 1, 2018 to Josh Noble, Department of Natural Resources, One Conservation Way, Brunswick, Georgia 31520.

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