International Dredging Review

International Dredging Review

In 2014 Marine Industrial Construction LLC (MIC) of Wilsonville Oregon performed maintenance dredging at Port Orford in Oregon. This spring the project dredged approximately 7000 cubic yards in a short time period and involved critical coordination between many parties to ensure as much of the small port could be used as possible during dredging.

The project dredged along the dock face at Port Orford (a dredging prism of 350 feet in length by 30 feet wide) to a depth of -17 feet. After the first time-window the material was expected to slough into the prism during the season and require re-dredging.

On the Port Orford dock prior to set up the Grove rough terrain crane (boom down) awaits pipe on the truck in background.

The disposal site was located on the other side of the breakwater about 600 feet away. The project was completed using a dredging pump from a shore-side crane.

Along the Oregon coast sediment deposits from upstream and/or near shore coastal processes are constantly impacting port berths and docks. This typically creates shoaling that requires maintenance for sustained use.

The U.S. Army Corps of Engineers Portland District has worked with small ports along the Oregon coast for decades dredging federal navigation channels clearing the way for commercial fishermen and recreational mariners traveling between their harbors and the Pacific Ocean. Several difficult budget years had left many Corps navigation projects including Oregon’s coastal ports without federal funding.

Port Orford Then and Now

Since 1850 the dock at Port Orford has been important to the economy of the Southern Oregon coast. It is unique in that it is the only open harbor on the Oregon coast. It is home to a large crab fleet and one of the largest live fisheries on the West Coast. It supports charters fish buyers and offshore fishers as well as recreation and tourism related activities.

This discharge pipe at the disposal site off the jetty into the Pacific Ocean is discharging about 30 percent solids here. The percentage of solids ranged from 20 to more than 40 percent during project.
Historically the harbor has had nominal shoaling. A concrete dock replaced the wood dock in 1990 and the jetty was constructed in 1969 to protect the docks from winter storms. Maintenance dredging was required in 1970 and shortly after that the sediment began to accumulate and cause significant shoaling.

Due to the lack of federal funds the area had not been dredged since 2010 and fishing and other vessels were only able to access the dock face at higher tide conditions. The shoaling also contributed to dangerous sea conditions at the dock. One of the primary reasons for the dredging is to have deeper water on the dock face in order to dissipate wave action. Deeper depths near the dock face allow improved access to the dock and the hoist crane during low water. At low tides breakers were forming against the dock face due to the shallow water. This made it difficult to unload boats and dangerous to use the hoist to lift boats from the water.

Port Orford had particular issues with sand transport along the jetty and the dock. The engineering textbook Coastal Processes with Engineering Applications by Dean and Dalrymple (2002) uses the engineering designs applied at Port Orford as an example of the sand transport mechanism. The text argues that the construction of the jetty does not allow the flushing of sand and that several other basic principles of costal engineering have increased the sedimentation on the dock.

From 2010 to 2013 the Portland District only had limited funds to support hopper dredging on the south coast of Oregon. This meant that local ports or even marinas that required dredging due to recent sedimentation had not been dredged. Since the federal funds have been limited due to shrinking national budgets in the last several years local ports have started working with local stakeholders and the state for funds to support maintenance dredging projects. The state of Oregon under the direction of Governor John Kitzhaber was able to allocate funds for dredging on the Oregon Coast.

On Sept. 17 2013 Portland District Deputy Commander Lt. Col. Glenn Pratt Oregon Gov. John Kitzhaber and Oregon Sen. Jeff Kruse signed a Declaration of Cooperation publicly committing to work together to maintain safe reliable navigation channels along Oregon’s coast. The historic Memorandum of Agreement allowed the Corps to accept state money to maintain Oregon’s coastal navigation channels. The Corps’ fiscal year 2014 Operation and Maintenance Plan includes nearly $15 million for maintenance dredging of the federal navigation channels used by Oregon’s small coastal ports.

Port Orford was a high priority project for the state and had a strong stakeholder support and training components were incorporated into the project design to make the limited resources (financial equipment labor etc.) go as far as possible.

Equipment and Safety

MIC has been performing marine work in Oregon for more than 150 years and dredging for 56 years using various dredging equipment including clamshells draglines suction dredges excavators and hydraulic pumps.

The project team at Port Orford also included the U.S. Army Corps of Engineers the Port of Port Orford and other local stakeholders including fishermen and local residents. MIC’s bid for the Port Orford project was at 60 percent below the federal engineering cost estimate and was close to 20 percent below other bids. MIC controlled costs by using techniques learned from other jobs and a skilled and experienced crew. In 2013 MIC has used:

• Conventional clamshell dredging for projects at the Port of Vancouver Washington;
• Environmental closed lipped mechanical dredges for Port of Portland Oregon with hydraulic pumping to a disposal site and placement of sand cap;
• A horizontal auger (MudCat) suction dredge at Portland Yacht Club Willow Bar for marina dredging with in-water disposal;
• Wet excavators and dragline crane excavation more than 100000 cubic yards for near-shore aggregate mining in St. Paul Oregon and Salem Oregon.

For the Port Orford hoist dredging project MIC used:

• A Toyo 150 submersible hydraulic pump with flow rated at 3200 gallons per minute with a 72-foot head and maximum solid size of slightly under five inches;
• Grove 50-ton Rough Terrain Crane with110-foot boom;
• Ten-inch HDPE pipe 1500 linear feet with custom crane saddles and flex pipe;
• Cummins 350 kW generator mounted on trailer;
• Forklift for transporting and setting up pipe (and related equipment).

All of this equipment was transported to the site using standard trucks and trailers and were configured on-site in roughly two days. At the end of each day the equipment was configured so that continued access to the dock was available for fisherman to launch boats and fish buyers to continue operations. MIC has used this configuration previously to unload bin barges and to pump dredged material to upland sites for beneficial uses (IDR March/April 2012 MIC Accomplishes Maintenance at Port of Portland without Exceeding Turbidity Requirements pg. 6 – 8).

Safety was critical on this dredging project and storms were of particular concern at Port Orford. In the winter it can be very dangerous. In fact the first day after mobilization to the site winds up to 60 mph and sea swells of 25 feet with breakers of 35 feet occurred at Port Orford. For this reason the dredging was designed to be performed from the dock and no floating equipment was used (except a surveying skiff).

The MIC crew had three on-site operators all certified as National Commission for the Certification of Crane Operators (NCCCO) signalman riggers and operators as well as a U.S. Coast Guard Master 100-ton Mate. The entire crew was trained as Occupational Safety & Health Administration (OSHA) safety supervisors (OSHA-30) and was first aid/CPR trained. MIC also had a safety officer (and quality control

supervisor) on-site during the entire project. The Corps had a quality assurance engineer on-site to review equipment and the safety of the project on an ongoing basis. The Port Orford port manger and the hoist operators were also critical members of the team providing local knowledge and assisting in communicating with local fisherman during the busy crab fishing window. In addition detailed environmental monitoring for turbidity was completed every two hours at the dredging and disposal site.

Dredging Operations

During the first dredge window in January 2014 the team was able to dredge to a depth of -12 feet in less than two weeks including mobilization and demobilization. The project occurred during the height of the crabbing season and the contractor was working in conjunction with the local fisherman the port and the Corps to minimize conflicts and maintain safety during the dredging.

The dredging material was as expected primarily
fine sands that had accumulated against dock. The pump easily moved the materials to the disposal site roughly 600 feet away at roughly 30 percent solids. A significant amount of sloughing added volume into the dredging prism. The pump was able to move up to 160 cubic yards per hour in a slurry through 10-inch high-density polyethylene (HPDE) pipes. The crane operator was able to position the pump and dredge to the specified depth and the total removal volume for the first event was 3000 cubic yards.

As expected a significant amount of material sloughed back into the dredged area due to the shoaling and wave action present. An additional 3836 cubic yards was dredged again in May 2014 to a depth of -12 feet. The dredging took six days and minimized impacts to the working dock.

Overall the production rate for the project ranged from 55 to up to 187 cubic yards per hour when running the pump and averaged more than 100 cubic yards per hour using the Toyo 150. A mobile crane from shore provided a safer and less expensive alternative to conventional marine based dredging. A submersible hydraulic pump moved large quantities of sand and required no expensive or specialized marine equipment for support.

During the project the port staff worked with the contractor to develop in-house expertise to complete this type of project in the future. The Port of Port Orford also purchased a submersible pump of its own. The port purchased a Toyo 75 which can pump up to 1600 gallons a minute with a 95-foot head and a maximum solid size of 2.4 inches. The port’s pump has a slower production rate when compared to the Toyo 150 but offered advantages in lower initial investments and significantly less weight (the Toyo 150 weighs more than 8000 pounds where as the Toyo 75 was less than 2500 pounds). This dramatically impacted the size of the crane required and how far the boom could be safely extended. One limitation of the Toyo 75 is the maximum solid size of material but this does not impact dredging at Port Orford since it is primarily fine sands.

MIC also developed a host of training materials and documentation for the port for future reference. Whereas large ports can support larger industrial facilities the majority of smaller ports have disparate users including fisheries recreation and small industrial facilities that support the transport of aggregate agricultural commodities wood products fuel and other varied interests. While many small ports do not support international trade they are critical for regional transport and inter-modality.

Engineers at Coast & Harbor Engineering are developing long-term plans for sustainable dredging in the Port Orford Harbor. With additional funds for major clamshell dredging and maintenance with the port’s Toyo submersible pump it is expected that the harbor will have good access well into the future.

About the authors: Joe Bernert is project manager at Marine Industrial Construction LLC. Gary Anderson is port manger for the Port of Port Orford.