Rental costs for two vibratory hammers to drive in the foundations of the new cruise ship pier were claimed as an extra by contractor Correia Construction.

According to figures from both Government and Correia, more than $530,000 for rental of the two hammers was billed under 'dolphin mitigation' - which were measures to safeguard the health of the animals at nearby Dolphin Quest.

The equipment was needed to drive 306 steel pipes and sheet piles to form the foundations of the new dock and Ground Transportation Area.

However, it was costed under the $3.7 million overrun for "dolphin mitigation", not in the original quote for the job on which the $39 million Government contract was based.

Two ICE Model 28B Vibratory Driver/Extractor hammers were leased from US subcontractors Norwalk Marine International (NMI) to Correia between May 2007 and August 2008.

Company director Dennis Correia told The Royal Gazette in May this year they were used to minimise noise that could be damaging to the dolphins in captivity.

A vibratory hammer vibrates a pile into place whereas a diesel hammer uses a heavy weight to repeatedly pound the pile down.

"We didn't need vibro hammers to do this job but brought them in just for the dolphins and they cost us $600,000-$700,000," Mr. Correia told The Royal Gazette.

On April 18, 2007, a letter from Dolphin Quest stated: "The considerable underwater noise (mechanical energy) of driving piles is a very real threat to the balanced sensory environment of newborn dolphin calves. We strenuously and respectfully request delaying the commencement of any construction activities until no earlier than September 15, 2007."

The project was postponed until the calves were three months old and during the summer Correia explored various methods of minimising construction noise and disturbance.

The dolphin mitigation measures included pile driving tests at Morgan's Point.

Mr. Correia said he had planned to rent a vibratory hammer to install the GTA piles, but after speaking with consultants, decided to drive all the piles with vibro hammers.

"In the past I have always used diesels," he said. "But the vibratory hammer allowed you to drive a pile without causing any noise or disturbance to the dolphins. It was a collective agreement (to use vibro hammers), through the dolphin mitigation, probably around the end of June."

Correia rented one hammer from NMI from May 2007, to August 2008, and the second between August 2007, and May 2008.

A diesel hammer was also used for the final stages of the pile driving, to check each pile's weight-bearing capacity.

In March this year, Premier Dr. Ewart Brown told MPs that $3.7 million of the Dockyard project's $6 million over-run in 2008 was due to "dolphin mitigation".

In a subsequent interview with this newspaper in May, Mr. Correia said $613,000 of the costs were due to: "Vibratory rentals, vibratory hammer equipment used to help reduce the noise associated with the pile driving." The pile driving testing amounted to an additional $62,000.

The following month, the Ministry of Tourism and Transport attributed $532,312 in costs to: "Correia Construction rental of vibratory hammer" and $62,560 to "pile testing dolphin mitigation".

The figures were submitted in Parlimentary Answers to Opposition Senate Leader Michael Dunkley, who had asked for a breakdown of the $3.7 million in extra costs.

According to Correia's US subcontractor NMI however, the vibratory hammers were an essential part of the job and should not have incurred extra cost.

"The vibratory hammers were chosen because they were a more efficient and effective means of getting the job done. It had nothing to do with the dolphin mitigation," NMI owner Louis (Skip) Gardella said. "It would take two minutes to go 80 feet. If you were to do that with an impact (diesel) hammer it would take 45 minutes."

He said: "The use of a vibro was necessary for the project and would easily fit inside the cost to install the piles."

In an original estimate for the Dockyard project, the cost of labour and material for a 110 ft pile is estimated at more than $31,000.

Although some piles went down as far as 167 ft to reach the volcanic rock, Mr. Gardella claimed the equipment costs should not have cost an additional $600,000.

"Correia had the money in his estimate for equipment costs," said Mr. Gardella.

He added: "As for the dolphin mitigation testing, it was nothing. We tested one pile with the vibratory once and then drove two piles with a diesel hammer at Morgan's Point. Then they (Correia) made the plywood (for the wooden and styrofoam baffles) and tried the air bubbles (a bubble 'curtain' recommended by US consultants MACTEC) but that didn't work.

"They had four days of work there and then put that barrier (the baffles) in the tunnel (to the Dolphin Quest Keep)." According to NMI's financial records, Correia Construction paid $425,765 for renting the two hammers.

Mr. Correia also bought a 28B vibratory hammer directly from ICE in spring 2008, returning one of the hammers to NMI at this time. Such equipment would cost around $214,000 to buy in the US.

Correia Construction claimed $613,000 under 'dolphin mitigation' costs to rent two vibratory hammers, at $16,000 a month.

Had the company bought two hammers, at $214,000 each taking into account a 33.5 percent rate of duty on a purchase and $10,000 shipping costs this would have cost taxpayers $580,000.