Freeman Marine Equipment Inc., a company known for providing security at sea by keeping water out of blue water vessels of all kinds around the world, has leveraged their expertise to lead the way in the development of closures that keep large concrete pontoon structures afloat in a variety of severe marine and climate exposures. The protection and maintenance of watertight integrity for these ultra large concrete flotation platforms is critical.
These pontoon closures are for unique, sometimes extraordinary and unusual purpose-built applications, meeting criteria for strength, corrosion resistance, interchangeability, and service life for the exacting specifications of industrial designers, civil engineers, and contractors.
The concrete pontoons are usually built on shore like a ship or boat, and upon completion are floated or launched into the water and towed to a permanent site. The overall dimensions of the concrete pontoons are typically rectangular shaped, up to 60’ wide X 360’ long X 20’ high, with walls and decks of steel strengthened concrete that are 2 feet or more thick at the thinnest sections. The pontoons are designed to carry automobiles, fully loaded trucks, support equipment, and for vessels to moor alongside.
Access to the inside of the pontoons where pump stations and other mechanical equipment are located is critical, demanding performance that requires unquestioned reliability. Entry and exit needs to be quick, safe, and with relative ease, at the same time the access route needs to maintain full watertight integrity in the closed position.
State of Washington
The State of Washington owns and operates three floating bridges, all of which are constructed primarily of large concrete pontoons. These bridges are part of a sophisticated roadway system, with video cameras continually posting real time images and updated still photographs of traffic directly to the internet where travelers can look ahead but more importantly bridge support personnel can see what’s going on at any time. Wind speed and direction is also available on line. The three State of Washington bridges collectively see more than 60,000 vehicles travel across these spans on a daily basis. As these bridges near the end of their original projected service life they are being replaced with newer designs that provide safer, less congested, and more reliable roadways.
Seattle promotes itself as the land of floating bridges, one of which is the longest in the world. Two bridges float on top of Lake Washington connecting Seattle with Bellevue (520 bridge) and the Eastside (I-90 bridge).
To the west of Seattle the Hood Canal Bridge serves as a vital economic and social link between the greater Puget Sound area and the Olympic Peninsula. Tacoma, Seattle, Everett, Bellevue, Olympia, and Bremerton lie to the west side of the canal, Port Townsend, Port Angeles, and the Olympic Peninsula lie to the east side of the canal. The highway crosses the Hood Canal at it’s northern entrance near the narrowest point which is a distance of nearly 8000 feet. The depth of the water below the Hood Canal Bridge varies from 80 feet up to 340 feet. It is one of the world’s few floating bridges over a salt-water tidal basin, with a tide range of 16.5 feet between high and low tides.
Impressive structures, these pontoons must be strong enough to withstand 120 mile per hour winds and high waves, like the storm that destroyed the west half of the Hood Canal Bridge in 1979. After the storm, the west half was replaced and reopened in 1982. 23 years later, the east half of the bridge replacement started all new as it approached the end of its service life. Freeman Marine provided all of the hatches for the east half replacement. Some of these closures are required to be watertight to nearly 22 psi, providing a seal to depths of 50 feet below the surface of the water in the event of an emergency. One of these hatches was dome shaped, had a 30” clear opening, is over ¾” thick for additional strength, and constructed primarily of Almag 35.
Over the past thirty years, Freeman Marine’s efforts to develop high quality products that will exhibit superior performance in salt water applications have resulted in Almag 35 becoming a specialty for the company. Freeman Marine is one of the largest producers of Almag 35 castings in the Western U.S. The alloy is difficult to pour but it’s characteristics for high strength and corrosion resistance make it ideal for pontoon closure applications. The Hood Canal hatch project consumed more than 40,000 pounds of Almag 35 castings, and the combination of customer need with Freeman expertise resulted in an ideal match.
In Kentucky, the Corps of Engineers operates the Olmsted Lock and Dam system on the Ohio River at River Mile 964.4. The original locks and dams in this area were built in 1929 with temporary structures put in place during the 1970’s, the locks are used primarily by barge traffic carrying heavy loads. Tonnage that passes through the locks on an annual basis totals about 90 million tons of commerce worth almost $20 billion of which about 23% is coal, other major commodities include aggregates, petroleum, grains such as corn and soybeans, chemicals, ore/minerals, as well as iron and steel. Projections are that this will increase to 121 million tons by 2010 and to 141 million tons by 2030. Most of the tonnage is traveling to or from the states of Louisiana, West Virginia, Kentucky, Ohio, Illinois, Indiana, and Tennessee. Transloading for imports and exports takes place near Baton Rouge which is downriver from where the Ohio River enters the Mississippi River.When originally built, the Olmsted Locks had no steel reinforcement, under normal operating conditions were stressed 50-100%, and temporary replacements were rapidly deteriorating to the point that the locks were often closed. The locks were replaced in 2001, with the entire project to upgrade the Olmsted Locks to be complete by 2010.
For normal travel along the river barges are rafted together with cable and winch systems. Many times one push boat/tug boat will have as many as 30 barges or more rafted together in a single tow. Traversing the lock system requires that the raft of barges be disassembled on one side of the lock and taken through the lock in smaller groups that are narrow enough and short enough to fit through the locks. On both sides of the lock is a large floating dock area where the barges can be moored while the rafts are taken apart or put back together. The size of the barges combined with the weight of their cargo is tremendous, so the construction of these docks that serve as staging areas is massive and the logical design dictates that these docks are made of concrete pontoons.
Freeman Marine provided all of the hatches for the Olmsted Lock project. In addition to using Almag 35 cover panels, the coaming/frames were fabricated of stainless steel and galvanized steel in a manner that they could be imbedded directly into the concrete without having to construct or strip forms for a labor savings and the strongest of installations possible. As with other projects of this type, all closures were 100% tested and qualified for their intended applications prior to shipment.
According to Freeman Marine’s general manager, Bo Shindler, “These civil engineering and purpose-built closure projects are truly impressive and unique efforts to develop world-class, reliable solutions for difficult situations. The same can be said for how Freeman Marine focuses its efforts at customer requirements, company growth and customer satisfaction.”
Freeman Marine notes that purpose-built closures and projects like these floating pontoons can have extremely long planning, design, approval, and delivery schedules. Many companies would find this business model to be unattractive; not Freeman Marine. According to Shindler, “Long time line requirements are similar to what we encounter in other important market niches served by Freeman so we’re used to dealing with lengthy or protracted projects. We like to be in on the ground floor and it matches up perfectly with our relationship driven company. We’ve structured the organization so that we can handle big and small at the same time, no problem.”
According to David Green, production manager, “The company focuses its resources on production design, fabrication and casting capabilities, and value added features that provide specialty sealing solutions and unique closures.” Activities are undertaken in an ISO 9001 managed environment that is systematically managed by Freeman Marine as well as regularly audited and certified for compliance by TUV Rheinland of North America. “Working within this structure, we’ve built an excellent framework for team management and put in place efforts that constantly strive to improve product and process development as well as product and customer satisfaction,” said Green.