Sheet pilings

Plume Containment. WeUs can be placed at a contaminated site to prevent the contamination from spreading further or migrating offsite. In the past, containment efforts often reHed on physical methods such as bentonite slurry trenches, grout curtains, sheet pilings, weU points, and fixative injections. Containment by judiciously placed weUs generally costs less, takes less time to install, and is more flexible because pumping rates and locations can be varied. 

Very often steel sheet pilings exist in conjunction with steel-reinforced concrete structures in harbors or locks. If cathodic protection is not necessary for the reinforced concrete structure, there is no hindrance to the ingress of the protection current due to the connection with the steel surfaces to be protected. The concrete surface has to be partly considered at the design stage. An example is the base of the ferry harbor at Puttgarden, which consists of reinforced concrete and is electrically connected to the uncoated steel sheet piling. 

This group includes platinised-titanium, platinised-niobium, lead alloys and lead-platinum anodes, which are used for immersed structures, e.g. jetties, sheet piling and power stations. 

NS A, Blast Furnace Slag, Ideal Backfill Material for Steel Sheet Piling, 166.2, National Slag Association, Alexandria, VA, 1966. 

Retaining dikes and berms. Retaining dikes and berms include earthen embankments, earth-filled cellular and double-sheet pile walls, water inflated dams, and so on, which aim to minimize the transport of contaminated sediments. 

This relatively new application of subsurface dams has proved useful to focus groundwater flow to a recovery area. A typical application, referred to as a funnel-and-gate system (Figure 7.2), involves construction of a sheet pile, or slurry wall,... 

The lET barrier system is a patented, commercially available in situ technology for the diversion and collection of contaminated groundwater or the confinement of contaminated soil. The lET barrier can be constructed as a boom around a portion of the contaminated area or as a bottomless tank. Barriers consist of a high-density polyethylene (HDPE) liner or thick steel sheet pile with a patented locking mechanism. Collection reservoirs are installed adjacent to the barrier and can be used to treat contaminants in place or to pump contaminated groundwater to the surface for treatment. 

Intermittent rock layers or ledges would restrict the cost effective installation of the lET barrier. In addition, the installation of the lET barrier in caving sands or gravel is difficult and in some cases possible only to a depth that shoring will allow. Epoxy-coated and sealed joint sheet pile may be used to create the barrier in instances where sand and gravel are a problem. AU information is from the vendor and has not been independently verified. 

Table 2 presents vendor-supplied cost estimates for implementing their frozen barrier technology at brownfield redevelopment sites. Costs for RKK s system are compared with costs for a sheet pile wall barrier. The estimates are based on the cost of containment at a 3.5-acre site with contamination 50 ft below ground surface (D221647, p. 3). 

TABLE 2 Vendor-Supplied Cost Estimates for Using Frozen Barriers and Sheet Pile Wall Barriers at Brownfield Redevelopment Sites (Assumes a 3.5-Acre Site with Contamination 50 Ft Deep)... 

Technology Components Sheet Pile Wall Barrier (millions of dollars) Frozen Soil Barrier (millions of dollars)... 

Sheet piling barriers can be snccessfully used for many remediation situations ... 

The Waterloo Barrier is a low-permeability cutoff wall for groundwater containment and control. The technology uses steel sheet piling with joints that can be sealed after the sheets have been driven into the ground. This technology has also been used as a soil-gas barrier. 

The Waterloo Barrier does not remediate wastes. The contaminant plume must be small enough for enclosure to be practical. The vibration and noise associated with pile driving equipment may be a problem in densely populated areas. Funnel-and-gate system can be problematic because they alter groundwater flow. In bouldered terrain and very dense unconsolidated sediments, the use of sheet piling may not be possible. Steel sheet pile applications are generally restricted to depths of less than 30 m. At some sites it is necessary to seal the barrier system to bedrock. 

The cost of this technology is site specific and depends upon the size of the project, location, thickness of the sheet pile, depth of the installed barrier, soil conditions, and type of sealant. According to the vendor, prices generally range from 15 to 28/fF of fully installed wall. 

A Waterloo Barrier was installed to a depth of 32 ft at Canadian Forces Base Borden in Ontario, Canada. The sheet piles interlocked to form a cell that was 18 ft long and 5 ft wide. The joints were sealed with a bentonite-base sealant. The barrier was used to control groundwater flow to allow for the installation of a permeable reactive barrier (PRB). After the PRB was installed, the Waterloo Barrier was removed and treatment began. The installation costs for the PRB were 30,000. This total included the installation and removal costs for the Waterloo Barrier but excluded the costs for labor and the reactive material used in the PRB (D21297F, p. 33). 

At the Dover Air Force Base in Delaware, a Waterloo Barrier was emplaced as part of a funnel-and-gate system in 1998. The sheet piles extended to a depth of 45 ft and were keyed to a clay aquitard. The total costs for the funnel-and-gate PRB were 800,000. This figure included design, construction, materials, and the reactive media (D206097, p. 1). 

Recent variations include the use of backfilled caissons media-filled, hollow-vibrating beams and emplaced reaction vessels. The funnel typically consists of sheet pilings, slurry walls, or some other material and is preferably keyed into an impermeable layer (clay, bedrock) to prevent contaminant underflow. Particular care is required in designing and constructing the connection between the impermeable funnel section and the permeable gate section in order to avoid bypass of contaminated ground water. 

The gate shape may be controlled by construction techniques, but most commonly they have been rectangular. The more typical rectangular or box-shaped gate can be built by driving temporary sheet pilings and/or building removable subsurface walls within which the reactive materials are placed. 

Aging Conditions. Paper Samples were aged as (a) loose sheets hung vertically on a rack which permitted free air-flow around them, and (b) 100 sheet piles placed between Plexiglas sheets. Test samples were removed from the middle of the piles. 

Sheet piling in order to control groundwater migration into and out of the waste if waste... 

The tunnel invert was located 17 ft below track level, and the lower half of the tunnels was in clay. Above the clay was 2 to 4 ft of sand overlain by meadow mat about a foot thick. Mixed cinder and sand fill were above the meadow mat. Two shafts were put down by driving sheet piling. They were 270 ft apart, spanning the tracks. Concrete pipe was to be jacked into place, forming the tunnels. Figure 19.1 shows sketches of the job parameters. 

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