Bayou d’Inde/Lower Canal Sediment Remediation
Significant Project Features
- Provide an In Situ Cap of a minimum of 12 inches of clean sediment over the impacted sediment in the Lower Section of the PPG Canal
- Dredge 113,000 cubic yards of impacted sediment from the Bayou d’Inde Channel
- Dredge 80,000 CY from the Mud Pond Onsite to be used as additional cap/fill
- Dredge 500,000 CY from the Port of Lake Charles BT-2 Terminal expansion. This material would also be used to provide cover in the fringe marshes
- Dredge 95,000 CY of new work dredging to build a new barge slip
- Installation of 31,400 SF of NZ26 steel sheeting
- 287 – 18 inch steel pipe piles to support a concrete pad
- Provide an In Situ Cover of a minimum of 6 inches over the impacted sediments in three Fringe Marshes adjacent to Bayou d’Inde (approximately 20 acres) and over a portion of Lockport Marsh to the east of Bayou d’Inde (approximately 128 acres) using dredged material in a thin layer approach
- Soft foundation marsh roadway improvements using 25,000 tons of stone to contain dredged material with open marshes
- Once complete, the marsh was restored with native wetland grasses
History & Location Details
Axiall Corporation, LLC, operates a former PPG Industries, Inc., facility located approximately 2.5 miles west of Lake Charles, Louisiana, within the north-central portion of Calcasieu Parish in southwestern Louisiana. The plant is located on the west bank of the Coon Island Reach of the Calcasieu River Ship Channel. The facility has operated since 1947 and currently manufactures a variety of chemical products including chlorine, chlorinated hydrocarbons, and caustic soda.
Approach Project 1
To contain the dredged material, Sevenson increased the roadway elevations on roads in proximity to Lockport Marsh 1 and 2, constructed temporary berms (side casted sediment total 7,267 FT), and install permanent sheet piling (875 LF). Sevenson utilized a long front excavator mounted on tracked pontoons (marsh excavator) to excavate and sidecast sediments as temporary berms to contain the dredged material.
Sevenson constructed 10 weirs (4 FT x 4 FT) to control the water elevation within, transfer between, and discharge out of the individual marsh areas.
To perform the dredging required, Sevenson utilized two hydraulic dredges. One 8 inch cutter suction dredges was utilized to dredge the Mud Pond. All other dredging was performed by a 16” hydraulic cutter suction dredge.
The cap and cover within the marshes were critical components to the project requiring both a minimum thickness (12 inch cap and 6 inch cover) over underlying sediments and target elevations for the placed surface to promote wetland development and ensure 100% coverage of minimum cap/cover thicknesses. 85% had to be within the +/- 6-inches of the specified elevation. Sevenson utilized various manifolds and inflow points coupled with rigorous hydrographic surveying and marsh fill area topographic surveys to monitor, assess, and control the placement of dredged sediments. The manifolds were capable of splitting flow to reduce flow rates as required to reduce resuspension while also enabling even distribution of cap/cover materials. The discharge lines along the perimeter and within the placement areas were managed by a tracked excavator on top of the stone roadway and a long front marsh excavator, respectively.
Approach Project 2
The purpose of this project was to construct a new barge slip along Bayou d’Inde for delivery of large equipment and modular systems that required direct access to the project site, by water. The barge slip was constructed in an existing finger marsh west of the Axiall Park on Bayou d’Inde. The slip was 360 FT x 470 FT with a water depth of 16 FT. The east and north sides of the slip were constructed using sheet pile. The west side was sloped over 82 FT from the bottom of the slip to the natural bank elevation. On the east side of the slip, Sevenson constructed a paved apron for crane off-loading. The north side of the slip also had a paved apron for direct drive off of barges brought into the slip. Due to poor soil conditions, the barge slip required an extensive system of deep driven piles to be installed to support the sheet piles and aprons. Also, approximately 95,000 cubic yards of material were hydraulically dredged to complete the slip. The dredge materials were pumped 5,000 to 8,000 feet away into a nearby marsh for wetland restoration. The materials were used to raise the existing mudline to an elevation suitable for wetland development.
Other project details:
- 40 FT x 18” Piles = 64
- 50 FT x 18” Piles = 179
- 75 FT x 18” Piles = 44
- 31,400 SF of NZ26 steel sheeting
- 50 Barge Fenders
- 1,500 tons of crushed limestone
- 1,000 tons of rip rap
- 5,000 tons of structural fill behind the wall
- 1,253 CY of Concrete
- Electrical lighting work for the slip area