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Johan Dolman’s Material Processing Equipment Has Been a Boon to Major Dredging Projects

Ron Dielhof, left, and Johan Dolman at the Miami River near where the “last scoop” of contaminated material was removed in October 2008.

Ron Dielhof, left, and Johan Dolman at the Miami River near where the “last scoop” of contaminated material was removed in October 2008.

On June 16, Johan Dolman and Ron Dielhof stood on the Miami Hyatt Regency patio near the location of the symbolic “last scoop” of the Miami River clean-up project, taken on October 15, 2008. Dolman’s company, Boskalis Dolman, part of the Boskalis group, was sub-contracted to process all 720,000 cubic yards of the material, mostly contaminated, removed from five miles of the river in that project. Ron Dielhof was a project engineer on that job, and today is Boskalis environmental process manager.

While the World Dredging Conference continued inside the hotel, Dolman reminisced on his career, which had begun in 1970 in Dordrecht in The Netherlands as manager of marine activities at a shipping company. Nine years later, he started Dolman to provide aggregate for the building industry, depositing fines in the IJsselmeer, a lake that was formed in 1932 when the Zuiderzee was closed in.  

When the Dutch government directed him to remove the fines, which had a top layer of contaminated material, he discovered that all the sand he was removing was usable, and devised a separation system to reclaim the sand and other solids, and process the contaminated fines/silts.  He began expanding his sediment processing capability, engineering each system for its specific location and purpose. He had a job to process the contaminated sediments re-moved from all the Amsterdam canals, which was a 15-year effort. The City of Hamburg contracted him to process all the material dredged from the Elbe River - approximately 1 million cubic meters per year, all contaminated with heavy metals – for six years.

The basic idea of his design was to remove the usable material – usually sand – leaving contaminated silts suspended in water, which can be processed, leaving only a small percentage of the original material to be disposed of.

By the late 1980s, the Dutch government was discovering the extent of polluted sediment in the country, and Dolman was working to expand his company to meet the demand. At that time, Boskalis asked him to become a part of its group, and Dolman was happy to relinquish the search for capital and management of the company to become Boskalis Dolman, leaving him to concentrate on the job of sediment remediation.  

“The fact that I and my staff are still with Boskalis after 20 years shows a good cultural environment in Boskalis, he told IDR in 2008.  

Dolman stepped down as managing director in June 2015 – 25 years after joining the Boskalis team. Haico Wevers, a longtime Dolman staff member, took his place as managing director.  

Dolman plans to stay involved until the end of the Fox River project in Wisconsin, which is in its eighth year – about two more years. As with all Dolman projects, one of the key objectives of the Fox River remediation is beneficial use of the sand removed from the sediment by dewatering the contaminated fines. The total estimated dredged material in the project has exceeded 3.5 million cubic yards. 

Ron Dielhof presented a paper on seven years of operational results from the Fox River sediment processing plant at WODCON XXI. 

“Our team has been able to successfully separate sand, meeting the regulatory criteria for re-use in local infrastructure projects,” he wrote. “This achievement is the first such application on a full scale sediment remediation project in the U.S.,” he said. 

By the end of 2015, approximately 90 per-cent of the total tonnage of separated sand, 315,000 short tons (286,000 metric tons), had been beneficially reused in local projects.  One whole season’s worth of sand was hauled to the U.S. Highway 41/State Highway 29 interchange project.

The Fox River project is a fitting exit line for Dolman, who has been honored by the King of The Netherlands for 40 years of benefitting the environment and contributing to the largest environmental projects in Holland and the U.S.  At his retirement ceremony at the Dordrecht Museum, he was made a Knight of the Royal Order of Oranje Nassau by the mayor of Dordrecht in recognition of his environmental services in creating a platform for beneficial use of riverbed remediation material. 

At the time the company won the Fox River job, Dolman established an office in Princeton, New Jersey for bidding on environmental projects in the U.S.  In 2012 Boskalis renamed its environmental arm Boskalis Environmental and defined two markets, one in Europe under the name Boskalis Dolman b.v., and the other in North America operating as Stuyvesant Environmental Contracting, LLC and Stuyvesant Projects Realization Inc. 

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