APPENDIX D 

TABLE OF QUESTIONARE RESPONSES FROM DREDGING CONTRACTORS 
QUESTIONS Great Lakes Dredge 

& dock Co 

Weeks Marine JandeNul JandeNul Blankevoort Amboy 

Aggregates 

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Respondent W. F. Pagendarm, Vice 

President 

Brion Lindholm, Vice President 

Jan den Driessche, Regional Manager 

Pierre Tison Area Manager 

Rob Boesveld Brad Simek Leo van der Graaf Ancil Taylor 

Vice President 

Mark Russell Development Manager (BMAPA) 

Dredge type Seagoing hopper dredge Hopper Hopper Hopper (TSHD) can work in 2 -3 meter waves and in 

dredge depths of 10 m to 150 meters 

Hopper Hopper Hopper Hopper (TSHD) Hopper (TSHD) 

Other types of dredges Cutterhead hydraulic 

loading barges 

Hydraulic with Spider Barge 

None due to lack of efficiency 

Stationary dredges limited to dredge depth 20-30 meters and significant wave heights of .5 to 1.0 meters. Seagoing cutter suction dredges 

Plain suction, deep suction dredges 

No Cutterhead, possibly dustpan Cutterhead possible 

loading barges 

Hopper (SH) 

Make and model of positioning equipment and accuracy 

Trimble 4000 with inhouse software. Accuracy under poor conditions +/- 5 meters, +/- 1-2 meters obtainable 

Trimble 4000 RS DGPS with accuracy of +/- 1 meter 

Trimble or Racol 

“Aquarius” by Thales and NR109 or NR203 by Sercel. Accuracy of Aquarius +/- 0.1m and Sercel about +/- 1m. Equipment check on project start and monthly. 

DGPS with PDS 1000 navigation software, Accuracy checked weekly 

Northstar DGPS with Maptech software 

PDS2000 survey system / DGPS +/- 2 to 3 meters, in shop before deployment and on site 

Bean Dredgeview II, DGPS/RTK with 2-3 centimeter accuracy in all three planes 

DGPS +/- 5 meters Dredge has on board a “Black Box” that records dredge status, time and position every 30 seconds to ensure dredge stays in permit area. 

Buffer or Exclusion Zone 

15 to 30 meters 175 meters 15 meters Buffer for pipelines and cables - 100 meters, hopper 

dredges about 20 meters, cutterhead – a few meters. Buffers should be increased if absolutely no damage to structures is allowed to account for power failures, etc. 

250 meters to 500 meters 

150 to 300 meters Fixed distance not recommended 

but 300 m is safe 

A minimum of 60 meters. Buffer should be increased if borrow are allows. 

100 meters 

Determining Factor Experience Experience 30 to 300 

meters 

Experience Experience Experience Experience Experience Experience, somewhat arbitrary but 

recently modeling to prevent erosion 

Awareness of previous damage to resources 

None Not archaeological but 

coral reefs 

No No No No No No WWII aircraft east coast. Aircraft 

and vessels lost during military service are protected 

Best system to convey buffer limits 

Not Asked Not Asked Lat/long Lat/Long or local grid with automatic warning systems 

for boundries 

Lat/Long Lat/Long Lat/Long Not Asked Lat/Long 

Future equipment upgrade 

Not Asked Not Asked May use larger 

equipment, depends on project parameters 

Bigger and faster No but is using 

30,000CM dredges now 

May use larger equipment 

May use larger Not Asked Size of dredges limited by size of 

harbors 

Mitigation of Disturbance 

Not Asked Not Asked Monitor and 

avoidance 

Bufferzones, modern positioning equipment and emergency hauling equipment, immediate action by operator if they detect a disturbance (inspection of dredged material) at an unmarked site to avoid further disturbance. 

Buffer and Exclusion zones 

Mines from Federal government channel 

 Not Asked 

Responsible Organization 

Not Asked Not Asked Not answered Usually the Employer thru the permit process. See 

FIDIC General Clause 27.1 

Government organization 

Survey Federal Channel every 6 months 

Rijkswaterstaat, dept.Noordzee Rijswijk, Holland Phone 31 70 3366600 Mr. Maarten Reinking, Mr. Marius Cox Mr. Hans Otten 

Not Asked English Nature 

Ian Oakley 

Post Dredging Hydrographic Surveys 

Not Asked Not Asked Yes Not Answered Not normally Not Asked Surveys within 6-12 months 

Emerging Technology to Reduce Adverse Environmental Impacts 

Not Asked Not Asked Using low 

turbidity and green pipe method 

Minimize turbidity by discharging overflow near bottom. 

Restricted over flow No Restricted overflow, green line, 

overflow thru hull 

Not Asked Better resource management 

Comments Recent dredging in San 

Juan, relocated shipwrecks 

 Most marine life is above 40 meters due to sunlight. 

We should check this for fact. There are some very exotic species at great depths. 

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