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| Stream Bank Restoration |
| Project: | City of Atlanta - Department of Aviation
Hartsfield-Jackson Atlanta International Airport |
| Owner: | Southern Conservation Trust |
| Location: | Fayetteville, Georgia |
| Designer/Engineer: | Register-Nelson Environmental Consultants |
| Contractor: | C.S. Britton, Inc - Environmental Contractors |
| Begun: | March 2008 |
Project Details: |
This project consists of a 56-acre tract of land which contains four wetland areas that receive runoff from three independent streams. The objective for the restoration was to reconfigure a previous design which failed to accomplish the desired habitat and storm water runoff effect for the conservancy. The original design called for a series of low-profile dams to check water and create small ponding areas for storm water runoff storage and habitat. Due to the inability of the dam to handle heavy rainfall events and subsequent high runoff rates, the entire area over time became a series of murky and visually unattractive swamps.
The restoration called for a complete reworking of the three gravel dams, incorporating natural stream channel restoration techniques. Prior to excavating of the dams, composite sheet piles were driven on the upstream sides of the dams to full resistance in order to eliminate scour to the new structures. The piles were then cut to the predetermined elevation in order to check the desired amount of water for the restored wetland areas. The original dams were then excavated and internally armored with large granite boulders nested together throughout. Multiple layerings of gradiated stones were then installed around the larger boulders in order to fill all cavities with structural materials. In place of the single low-level dam, the new structures include a primary channel for more consistent and predictable flow, and a flood plain area to accommodate significant rainfall events. The new structures were then covered with organic material in preparation for vegetation. When vegetated, the new structures will have the appearance of naturally-occurring dams. View this project's site map. |
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| Upstream, at the boundary with the adjacent wetland, the crew is preparing to contruct the dam's armor. |
A line of interlocking sheet piles, carefully cut to maintain a specific depth in the wetland, work together with massive granite boulders on either side, form the major defense against erosion at the dam's leading edge. |
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| The sheet piles are already working to regulate the wetland's depth, even though the structure is still under construction. This particular dam spans almost 400 feet, many boulders are required. |
At one end of the dam, an armored curved structure will direct water spilling out of the flood plain in times of flooding. Once this part of the design is completed, soil fills the voids around the boulders. |
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| The armor takes advantage of every angle. Here, one of the indents of the sheet pile locks around a protrusion on the boulder, further stabilizing the structure. |
The rest of the dam is excavated in preparation for building its internal structure. More massive granite boulders await. |
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| The restored dam is nearing completion. Layers of massive granite boulders and smaller rocks form its internal structure. |
The durable rock armor underlying the stream bed will help it maintain its channel for many years. As time passes water flow will resposition soil, revealing a very natural-looking stream feature. |
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| In normal flow, the restored stream will placidly cross the dam. In times of high flow, the flood plain in the foreground is ready to collect and direct the excess. |
By using natural stream channel restoration techniques, a beautiful and functioning stream results. |
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