Ward Cove, Alaska Thin Layer Capping
and Sediment Remediation Project
Along the shores of Ward Cove in Ketchikan, Alaska, a former pulp mill operated from 1954 – 1997 processing logs into lumber, pulp, and paper materials. When pulp production began in 1954, effluent from the mill was discharged directly into the Cove. With institution of federal and state environmental regulations in 1971, the effluent began to be treated in an onshore wastewater treatment plant.
Numerous environmental studies were conducted to evaluate the potential environmental effects associated with the historical discharges of the mill operations. Ultimately the sediments in the Area of Concern (AOC) were determined by USEPA Region 10 to be toxic to benthic biota, and a Record of Decision (ROD) was issued for cleanup of the Ward Cove Marine Operable Unit under CERCLA. The objectives of the cleanup were to reduce toxicity of surface sediments in the biologically active zone (top 10 cm) of the seabed and enhance recolonization of the bottom sediments that would support ecosystem recovery.
The selected remedy included removal of sunken logs, navigation dredging of a barge access channel, capping with imported clean sand over 27 acres of impacted sediment by thin layer placement (15 cm to 30 cm thick), or, by mounding if thin layer placement was not successful, and natural recovery for other areas within the Area of Concern.
Under a work agreement with the prime contractor, a leading A/E consultancy, Lally was requested to serve concurrently as the project’s construction manager and site design engineer for planning, setup and remediation of the Ward Cove Marine Operable Unit. His responsibilities included overseeing project mobilization and startup, management of dredging/capping and offloading contractors, dive contractors, and consulting scientists on site, engineering design modifications, conducting on-site meetings, project documentation, project health and safety, and overall construction management.
To ensure the goals of the project were met, Lally led the development and implementation of advanced electronic bucket positioning methods, new thin layer capping techniques, and construction quality assurance approaches. He also coordinated extensively with the on-site Owner, USEPA Region 10 project management personnel, USACE – Seattle District technical oversight personnel, contractors, third-party consultants, local stakeholders and the media.
The Ward Cove Remediation project, executed over the winter of 2000/2001 by a uniquely qualified and dedicated multi-disciplinary project team of regulators, consultants and contractors, was successful in its mission. Over 680 tons of submerged logs were removed, 8,700 CY of material was dredged from the barge access channel, unforeseen contaminated hot spot dredging was completed, and thin layer marine capping of over 28 subtidal acres was accomplished and verified in water depths ranging from 0 ft. to 120 ft.
Despite the aggressive, one-season construction schedule and severe winter weather, the project was completed in accordance with the ROD, ahead of schedule and under budget, and with no health and safety incidents.
Post-construction monitoring since conducted by USEPA under its 5-year review program indicate the project has been successful in eliminating sediment toxicity and stimulating colonization of benthic macroinvertebrate species such that diverse communities now inhabit the remediated areas of this site.
Expertise Provided
Project Planning, Mobilization and Setup
Site Dredge and Cap Remedy Design
Oversight of Marine Contractor, Dive Contractors, and Consultant Field Personnel
Development of a New Thin Layer Capping Method
Construction Management
Location
Alaska, USA
Period
1999 – 2001
The Ward Cove Sediment Remediation Site was site of the first major thin layer capping project in the United States. To accomplish then unprecedented placement requirements, working with team subcontractors Lally applied prior precision dredging experience to develop the crane-based ‘SWATH’ thin-layer capping method. The SWATH method has since become an industry standard and applied to cost-effectively remediate numerous contaminated sediment sites in North America.