BSP supplies "heavy weights" for New Orleans' surge barrier

BSP International Foundations has supplied two of its heavy-duty hydraulic piling hammers, a CG240 and a CG300, for use in the construction of the world's largest surge barrier, which is designed to protect the coastal city of New Orleans in Louisiana, US.

The two BSP hammers, a CG240 and a CG300, were supplied last June to Traylor-Massman-Weeks (TMW), appointed by main contractor Shaw Infrastructure and Environmental, to carry out the piling works on the Inner Harbour Navigation Canal (IHNC) project.

Both hammers were supplied by Jinnings Equipment, based in Fort Wayne, Indiana and the Midwest distributor for BSP International Foundations in the USA.

TMW is using the BSP hammers to drive the 600 steel batter piles, 61 m long and 914 mm in diameter, at a 45° angle on the inland side of the barrier to support lateral loads. When completed in 2011 the surge barrier will be 3.21 km long and 7.9 m high.

Each batter pile is driven in two pieces with one welded join. The original production budget for the batter piles was three piles completed over two, 12-hour shifts.

TMW has been able to obtain the three completed piles, within a single shift, thereby doubling the production originally anticipated.

The crane-suspended CG240 with a 16 tonne ram weight is driving the piles on a day-to-day basis while the larger CG300, equipped with a 20 tonne ram weight, is on standby and used when driving is difficult as it has the extra power needed to drive a pile to the required depth.

Both hammers have been designed by BSP to operate either from pilling rig leaders or crane-suspended and are suitable to drive a wide variety of load bearing piles. They also include hinged type back guides to allow quicker installation onto the leader.

Fitted with a BSP remote control panel, the CG range is capable of delivering an infinitely variable stroke and blow rate enabling precise delivery of energy to the pile. This, said the company, allows the contractor to maximize production, avoid pile damage and problems of pile runaway.

A major feature of the CG hammers is the design of the hydraulic actuator which, for a given blow rate and energy transference, results in less fuel consumption and reduced exhaust emissions

Piling helmets are also available to efficiently transfer the hammer's impact to the pile. Using a BSP manifold control valve the CG range can be connected into existing power supply from a hydraulic piling rig or crawler crane base.

Key element

The surge barrier is a key element in a 100-year plan to protect New Orleans and the surrounding areas. It will have to resist the tremendous impact of a water surge that originates in the Gulf of Mexico during a hurricane and then enters the Inner Harbour Navigation Canal.

The barrier extends across the IHNC from the north of Louisiana's Gulf Intracoastal Waterway to the south of the Mississippi River-Gulf Outlet.

In addition to the two BSP units TMW has assembled an impressive array of equipment and as the barrier is being built from the water, all the cranes and pile drivers are mounted on barges.

There are around 50 barges and other items of equipment floating at any one time and moving around the project.

Several phases of the wall are being built simultaneously so round the clock, seven days a week working is going on.

Although a four-hour window has been set aside each day for routine maintenance to be carried out.

The central section of the barrier, approximately 2.28 km long, is being built using 43.9 m-long, 1.67 m diameter reinforced concrete spun-cast piles that are vertically driven to a depth of 39.62 m at an average rate of 10 blows per 300 mm into the soft marsh soil.

They are spaced 150 mm apart and each weigh 92 tonnes.

The space between the concrete piles is being closed using 2600, 18.28 m-long, 480 mm square concrete piles to seal the seam. A precast concrete cap, weighing around 96 tonnes, is placed on the pile and post-tensioned in place.

Sections of the cap between the precast sections will be filled with caste-in-place concrete. The final elevation with pile, concrete cap and parapet wall will be approximately 7.92 m high.

Milestone

On October 21st a major construction milestone was reached when Shaw Environmental and Infrastructure announced the final 1271st concrete pile of the project's first phase had been driven, just 10 months since the ground breaking ceremony.

Although pile driving has been fairly straight forward, the biggest problems facing the contractors are wind and rain, made worse by frequent thunderstorms.

Safety procedures are given top priority on the project. This is particularly important when wind speeds exceed 40km/hour and, with so many cranes on the site, operations are suspended.

Three gates will be incorporated in the barrier wall. A small centre gate 17 m-wide and 2.4 m-deep has been designed especially for commercial shippers and recreational boat owners travelling to and from Lake Borgne.

The two other gates, comprising a swing barge gate and a sector gate, to regulate the water level, have the same dimensions - 45.72 m-wide, 4.87 m-deep.

In addition to the IHNC flood barrier, the US Corps of Engineers, who have overall responsibility for the project, have also started work on the world's largest pumping station, which is estimated to be costing US $ 500 million and is expected to be completed in 2011.

The station will be over 180 m-long and house 13 diesel engines driving 13 pumps which are capable of pumping 570000 litres per second. In the event of a storm surge operators will shut the 9.7 m-high, 68.5 m-wide metal gates to block a 4.9 m high surge and then start pumping water back into the sea.