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Remediation/Mitigation


Gainesville, FL: Old Landfill - Slope And Creek Stabilization

wetlands-remediation-mitigation-gainsville-fl

Geo-Con was contracted to restore and stabilize a heavily eroded section of the Sweetwater Branch Creek in Gainesville, Florida. This section was immediately adjacent to an existing landfill and the city's wastewater treatment plant. The stream was primarily fed by groundwater seepage and storm water runoff from the City of Gainesville, and was subject to rapid flooding during rain events.

The work included channel and side slope grading, fill placement, creek channel improvements, and stabilization of a 575-foot long section of the creek. Stabilization included approximately 1,600 Cubic Yards of Gabion Mattresses and Gabion Baskets installed in the bottom and banks of the creek to prevent future erosion. Turf Reinforcement Matting was used to stabilize all disturbed areas not receiving gabion treatments.

Geo-Con faced several distinct challenges during construction:

Creek Water Control - Due to stringent turbidity restrictions, and to make construction possible, a creek water by-pass pump system had to be maintained throughout the project. The system consisted of a sheet pile cofferdam style sump area and a series of 12 and 14-inch pumps conveying water through a 24-inch pipe discharging downstream of the work area.

Weather Events - The creek received the majority of the runoff from the City of Gainesville. Even during an isolated rain event the volume and velocity of water would increase rapidly and sometimes exceeded the capacity of the bypass system resulting in flooding of the work areas. Geo-Con developed a construction approach to minimize exposed or unstabilized work areas.

Changing Conditions - Due to the erosion sensitive soils and periodic extreme flow conditions the profile and shape of the stream channel changed significantly from the time the pre-design survey was performed and the beginning of construction. Many modifications of the channel design were necessary to suit the changed conditions. Geo-Con worked closely with the City's onsite representative and Golder Associates to assess, adjust the design, and install the appropriate configuration of gabions to assure the intent of project was met in each section of the creek while maintaining production.

Limited Access - Disturbance to un-stabilized creek bottom, wooded areas, and landfill areas had to be kept to a minimum. In addition, access for the equipment and delivery of materials necessary to complete the work was extremely limited by the difficult terrain and proximity of the landfill and wastewater treatment plant. Geo-Con developed a plan to access the work areas utilizing completed or stabilized sections of the channel as a roadway. The channel reconstruction was completed (the grading and placement of gabions) in a linear progression working downstream from the bypass pump system. Wooden mats were placed on top of newly completed gabions to protect the gabion mattressed stream bottom and utilize the completed stream channel as an access road for equipment and the delivery of materials to the work point.

Safety - Due to the nature of the work, Geo-Con employees were faced with constant hazards including sharp edges, slippery surfaces, pinch points, close working quarters with heavy equipment, suspended loads, and potential contact with insects and snakes. Geo-Con implemented a safety program with an emphasis on hand protection, and equipment operator/worker communication/eye contact and was able to complete this labor-intensive project with no incidents.

Other work included sediment and erosion control, erosion repairs, topsoil placement, seeding, and general site restoration. The project was obtained after termination of a previous contractor who deemed the project impossible or at a minimum, commercially impractical. The successful completion of this project is a testament to Geo-Con's expertise and leadership in this field.



 

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