Contractor Implementation - Mike Crystal, Sevenson Environmental Services

ERDC TN-DOER-T4

December 2001

removal. Fort James retained Hart Crowser, Inc., to help negotiate the technical terms of a

new agreement with USEPA and WIDNR and to reengineer the dredging and disposal plan.

Because capacity at the only existing local disposal site was limited, the project relied on

selecting a dredge prism that would achieve cleanup goals while limiting the removal to

50,000 cu yd [38,000 cu m]. Cleanup levels were set at 1 part per million (ppm) as the level

for no further action, and 10 ppm would trigger a requirement for 6 in. [152 mm] of clean

sand cover. The following important factors were learned from the demonstration project:

Need to use experienced operators to assure accurate positioning and maximize solids

production.

Requirements for refinement of the dewatering system.

Need for adequate redundancy of equipment to limit downtime.

Hart Crowser, Inc., also was responsible for the quality assurance of the confirmatory sampling

program after completion of dredging. Test results show that the proposed dredging plan was

viable. PCB concentrations in surface sediments were below 10 ppm after dredging. The

success of this project, owed in part to cooperative efforts of WIDNR, USEPA, and Fort James

Corporation, working with the contractor, showed that environmental dredging could be an

important component of future solutions to PCB contamination in the Fox River.

Contractor Implementation - Mike Crystal, Sevenson Environmental Services: Seven-

son Environmental was selected as the dredging contractor to implement the approved

restoration and remediation plan. Sevenson brought a project site team with experienced

operators from recent, relevant PCB removal projects on the St. Lawrence River, River Raisin,

Niagara River, and Lake Champlain in New York. Sevenson Environmental Services

proposed several refinements to the project:

Mechanical dewatering train that avoided the downtime associated with rehandling out

of the passive lagoons.

Wastewater treatment plant sized to handle low dredged solids (if necessary).

Use of multiple dredges to maintain schedule and conduct debris removal ahead of and

in conjunction with the dredging operation.

Improved dredge slurry pipeline management plan to accommodate the local shipping

schedule. These factors combined to facilitate successful implementation of the dredging

plan.

PANEL B: LESSONS LEARNED: At the conclusion of the Panel A presentations, the technical

review panel was convened as Panel B of the session to identify lessons learned and to ask questions

about how to choose an environmental dredging technology. The Co-Chair, Norman Francingues,

made a short presentation (Appendix II) on environmental dredging components, site survey and

characterization, dredging, transport, placement and disposal, and management.

If a decision is made to dredge, one needs to recognize that risk does not go away. It changes from

one type of risk to another. Each step in an environmental dredging process has a risk component.

Hopefully, when the project is completed, the total risk will be reduced to an acceptable level. There

is a cost associated with each of the components, and there is also a risk associated with each one

of these parts. So, when we define environmental dredging, the lesson that has been learned is that

we should not overlook any of these components.