Smart Solutions

Smooth Sailing for Seattle’s Floating Bridge Thanks to Anvil Products

Anvil products played a critical role in helping Diamond B complete the wastewater removal system of the new State Route 520 Floating Bridge (right) that protects Lake Washington from the runoff. The new bridge opened in April 2016 and replaced the former bridge (left), which was completed in 1963.

Diamond B Constructors Completes Complex Rainwater Management Systems with Anvil’s American-Made Flexible Couplings and Fittings

For Seattle’s new State Route 520 Evergreen Point Floating Bridge, Diamond B Constructors, Inc. knew they could count on Anvil International for flexible couplings and fittings for the Schedule 40 pipe of the bridge’s wastewater removal system. In addition, because Anvil’s products used on this project were manufactured in its U.S. plants, they satisfied the requirements of the Federal Highway Administration for American-made construction supplies.

Replacing the World’s Largest Floating Bridge

American-made Anvil products, such as this endcap from the Gruvlok 7000 Series Fire Protection line, were the ideal choice for contractors like Diamond B and others to meet the purchasing requirements for the partially federally funded bridge.

Completed in 2016, the new bridge is the longest floating bridge in the world. Spanning Lake Washington and connecting Seattle on the western side of the lake to Medina on the eastern side, the 7,710′-long bridge replaces the previous 7,578′ bridge, which was the longest floating bridge in the world. The new bridge is designed to reduce traffic congestion and improve safety. The bridge opened to traffic on April 11, 2016.

Two important components of the construction of the bridge were the design and construction of the dry standpipe fire systems and the mechanical wastewater removal system to remove rainwater from the road surface and filter it before returning it to the lake. Contractors for these systems needed grooved pipe couplings, hangers, and other piping products that would meet or exceed the needs of this unique bridge style, and they reached out to Anvil International to supply the products.

The State of Washington Department of Transportation (WSDOT) sought to replace the existing bridge with a wider span that would reduce traffic congestion and improve overall safety for cars, cyclists, and pedestrians. The new bridge has two standard travel lanes, as well as an HOV (high-occupancy vehicle) lane, a shared 14′-wide bike/pedestrian access path, and shoulders of 4′ at the inside and 10′ on the outside. It is also designed to better resist severe storms and earthquakes than the previous one.

The new Route 520 Floating Bridge, featuring Anvil International products in critical roles in both the fire suppression dry standpipe and wastewater removal systems, opened on April 11th, 2016.

A floating bridge design was selected due to the depth of Lake Washington (over 200′ at its deepest point) and the soft condition of its lakebed. A more conventionally designed bridge would require very tall support towers to support the roadbed, which would be cost-prohibitive. Instead, the bridge’s roadbed is supported by a series of large, floating concrete pontoons. Because the bridge floats on the surface of Lake Washington, it must be designed to expand, contract, and roll with the motion of the water, whether that motion comes from wind, storms, thermal changes, or other factors.

The new bridge consists of two separate decks: an upper deck for traffic and a lower deck for maintenance and operations. The bridge features a mechanical wastewater removal system that handles the removal of rainwater from the roadway. In addition, it has remotely controlled fire protection dry standpipe systems. Approximately 1.5 miles in length, the bridge is constructed much like a viaduct, with a superstructure that rests between 14′ and 80′ above the 23 pontoons, the largest of which are 360′ in length. The design and construction of the bridge took approximately four years.

Wastewater System Keeps Roadway Clear

Diamond B found that Anvil’s 7000 Series couplings are flexible enough to handle the motion of the floating bridge.

As the contractor for the rainwater removal system, Diamond B looked to Anvil products to meet its needs. “Our company has a history of purchasing products from Anvil International, and so we were confident that their products and service would meet our needs for quality, reliability, and price,” said B. J. Winn, general foreman at Diamond B. “All told, this project went very well, and the products and support that we received from Anvil contributed to that success.”

Rainwater flows off the bridge deck into a series of 160 catch basins on the bridge, designed to trap sediment at the bottom. From there, it filters through Schedule 40 pipe ranging from 10″ down to 6″ and ends up in the 44 sump wells built into the bottom deck of the bridge. These sump wells are located in the middle of the pontoons, so that the rainwater flows back into the lake but is separated from the rest of the lake water so that oil from the roadway doesn’t contaminate the water and can be cleared off of the surface of the isolated wells periodically.

The motion of the bridge from the water was also of concern with the wastewater pipes. The Anvil Gruvlok® 7000 Series lightweight, flexible grooved couplings were selected for their ability to handle the pipes’ motion.

Anvil hot-dip zinc galvanized the couplings and then sent them to a company in Portland, OR, for an epoxy coating. This step was deemed necessary for ecological reasons by the bridge designers, who feared that the galvanization would flake when in contact with water and negatively affect lake wildlife.

In total, the rainwater removal system contains approximately 15,000′ of pipe, 3,000 pipe couplings, and 1,500 pipe fittings. It is located under the bridge’s traffic deck on both sides and spans the length of the bridge. It took approximately 14 months to install and was completed in March 2016.

Fire Suppression System Ensures Safety

Diamond B and other contractors relied on Anvil’s Gruvlok grooved couplings because they are ideal for the floating bridge’s rainwater removal system and dry standpipe fire systems.

Because the bridge is too long to rely exclusively on fire trucks for fire suppression water supply, it requires dry standpipes along the length of the bridge. Once they arrive, trucks can access one of the hose stations along the bridge, drawing up lake water for use in fighting fires.

The fire standpipe is split into two separate systems. Each system has two 180-pounds-per-square-inch, 1,250-gallons-per-minute vertical turbine fire pumps and motorized valves as primary and secondary sources of water, ensuring backup in the event of a pump failure. The systems are interconnected with a motorized valve, which is a third source of water in the extremely unlikely event that the first two sources should fail. All of these systems are remotely controlled from the WSDOT monitoring station in Shoreline, WA. Bridge and fire authorities have several other options for activating the fire systems, which are also remotely operated from the local maintenance building or at the hose stations themselves.

The fire suppression systems include approximately 8,000′ of 8″ Schedule 40 piping, all of which must be joined with appropriate pipe couplings that must be flexible so that they can withstand the bridge’s motion. Anvil’s Gruvlok grooved couplings precisely met the needs of the project.

Anvil hot-dip zinc galvanized and coated the couplings for Diamond B’s wastewater removal system with epoxy, ensuring that bridge design requirements were met and wildlife is protected.

In addition, most of the hanger assemblies consist of roller hangers attached to Anvil Strut/Channel. They serve to suspend the fire system’s dry standpipe from the underside of the bridge’s upper deck. They give it the flexibility to move independently of the bridge, which is critical to the pipe’s ability to withstand the motion of the bridge from the water. Anvil provided rollers, nuts, bolts, clamps, rods, and various channel materials for all of the hanger assemblies of various designs, working closely with contractors to ensure that the couplings and hangers met their needs exactly.

The couplings and components of the hanger assemblies were all hot-dip zinc galvanized by Anvil, a critical project requirement. Anvil also ensured that even after galvanization, all of the fittings fit together properly, saving time during construction. The Anvil team was praised for being responsive to design changes, easy to contact, and able to provide information like product documentation backup promptly.

Bridge Opens to Traffic

The bridge’s grand opening took place on April 2, 2016. Shortly afterward, the bridge was open to traffic, and its predecessor was taken out of commission. Anvil International played a critical part in the construction of this new, safer bridge, meeting the needs of both the fire and wastewater system contractors for high-quality, high-value, and American-made products, designed to the exact specifications necessary for the project.

For more information, visit MCAA thanks Anvil International for being a major sponsor of MCAA 2017 and supporting the Fun Run/Walk.