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In-line rubber duckbill check valves from Proco Products eliminate backflow risks for military base’s mission-critical culvert system

Reliable stormwater drainage is mission critical at Djibouti’s Camp Lemonnier, the only permanent U.S. military base in Africa. Nestled along the northern Horn of Africa, Djibouti’s desert climate is exceedingly dry, typically receiving only about 6 in (15 cm) of annual precipitation. However, when storms hit, they hit hard — the region is highly sensitive to the El Niño– Southern Oscillation, which delivers the entirety of Djibouti’s annual rainfall in only a few short, intense events during the monsoon season. Camp Lemonnier, owned and operated by the U.S. Navy, occupies a strategic location between neighboring Djibouti– Ambouli International Airport and the Gulf of Aden. As a hub for aerial operations throughout Africa as well as the entire Persian Gulf region, much of the base encompasses runways and aircraft support facilities paved with impervious tarmac and concrete.

Poor drainage capabilities create high potential for standing water and stormwater flooding during monsoon season, which threatens to disrupt base operations. According to estimates from the United Nations’ International Civil Aviation Organization, inadequate stormwater drainage is the most frequent cause of runway mishaps worldwide, with films of water as thin as 0.1 in (3 mm) dramatically increasing risks for aquaplaning and loss of aircraft control during takeoffs and landings. For this reason, the reliable function of Camp Lemonnier’s culvert system — which drains runoff from the base into the Gulf of Aden — is a matter of operational security.

Setting Sights on Security, Size, and Simplicity

After experiencing issues with standing water during recent monsoon seasons, in 2023, Camp Lemonnier personnel determined that the series of concrete pipes constituting the base’s culvert system were undersized and required replacement.

SEAPAC Engineering, who contracted with the U.S. Navy to deliver the upgrade project, recognized that the newly designed culverts would need ironclad protection against saltwater backflow from the Gulf of Aden in order to maximize drainage efficiency. Backflow prevention was a top priority for the new culverts given their discharge into a marine environment where choppy waves can disrupt the outward flow of water — particularly during monsoon storms, when the culverts are most necessary.

The alignment and location of the culverts also demanded that this backflow-prevention solution fit comfortably within the new pipes, forgoing exterior pieces that would expand the installation’s physical footprint. Finally, the solution had to be low maintenance, both during installation and throughout its lifespan, to ensure base personnel could focus on their mission without worrying about troubleshooting drainage problems. This not only called for a design element that could be added without construction on existing structures, but also one that could reliably stand up to peak flows, tough debris, temperature extremes, and head-loss concerns, all while operating passively.

Understanding the Duckbill Difference

To satisfy each of the U.S. Navy’s priorities with a single product, project managers turned to in-line, rubber duckbill-style check valves.

Duckbill-style check valves are a passive backflow-prevention solution activated by water pressure, requiring no energy or manual operation. Installed at the end of a pipe, their namesake feature is a flexible, elastomeric piece that provides complete obstruction of the pipe during dry conditions when water is not flowing. When even small volumes of water travel down the pipe, the elastomeric piece cracks open to allow discharge before returning to a 100-percent-closed position as soon as incoming water stops flowing. This forbids the entry of water from the opposite direction.

Typical duckbill-style check valves feature an elastomeric piece on the outside of the pipe, responding to water pressure by cracking open progressively wider as the volume of outgoing water increases. By contrast, in-line duckbill check valves are contained completely within the pipe, taking the shape of a sleeve fitted to the pipe’s diameter. The bottom of the piece lifts in response to head pressure, allowing a full-port flow of water and rapid head dispersion while tightly constricting around any foreign media on the exterior side of the valve. This creates a unique flushing motion which, in contrast to the trickling motion of exterior duckbill check valves, provides superior blockage resistance for an in-pipe piece in cases where available space is scarce.

Both styles of duckbill check valves boast unmatched sensitivity, cracking open in response to head pressures as low as 1 to 2 in (2.5 to 5 cm) over back pressure and closing instantly and completely upon loss of pressure.

Compared to metal flap gates or other conventional, non-elastomeric approaches to backflow protection, by design, duckbill check valves carry no risk of jamming from large obstructions or binding in unwanted positions — two of the leading causes of failure in end-of-pipe devices. They also sport innate resistance against rust and corrosion, unlike metal-based solutions.

Stability in Stormy Seas

Whether above the waterline or submerged, in-line duckbill check valves are ideal for marine applications. While thoughtfully chosen elastomers provide natural resistance against the accumulation of algae, barnacles, as well as sand and sediment, the duckbill’s in pipe placement offers an extra barrier against wave action and disruptions from watercraft or floating debris. For applications in especially turbulent waters, end-of-pipe side walls or rock pilings can offer additional stabilization.

On the Frontlines: ProFlex™ Style 790 Check Valves

As with everything else at Camp Lemonnier, the U.S. Navy sought to procure only the strongest and most dependable backflow prevention units for its new culverts. Assistant Project Manager Vignesh Ashokraj, with SEAPAC Engineering, approached Proco Products, Inc. to answer the call with their industry-leading ProFlex™ Style 790 In-Line Rubber Duckbill Check Valves.

The Camp Lemonnier culvert project called for more than 30-27.5- in (700-m) -wide ProFlex™ Style 790 valves to cap its new pipes, each offering a simple, slip-in installation process. After the custom fitted valves arrived in Djibouti, bringing them into operation was effortless, requiring only expandable clamps to secure them in place.

Component quality is key to any well-functioning device, and in the case of the ProFlex™ Style 790 valves, high-performance elastomers make all the difference. Although they are available in variants including ANSI/NSF-61, EPDM, nitrile, natural rubber, chlorobutyl, and other materials, the standard choice for ProFlex™ valves is Neoprene (also known as polychloroprene). Striking a balance between sturdiness and flexibility with top-of-the-line resistance against abrasions, acidic conditions, temperature extremes, and other stressors, Neoprene-based valves have a design lifespan as long as 50 years or more without maintenance needs. Further, all components of the ProFlex™ Style 790 valves — from the elastomers to the high-tensile wires and steel rods — are autoclaved and vulcanized to enhance durability while minimizing delamination risks.

Proco’s ProFlex™ Style 790 valves are available in standard diameters of 3 in (75 mm) to 78 in (1950 mm) with larger sizes available upon request. Camp Lemonnier’s new culvert system entered service in early 2024. Base personnel describe that the valves have performed perfectly ever since, reliably keeping flooding and backflow at bay during the system’s inaugural monsoon season.

 

Other common applications for in-line rubber duckbill check valves include: • Controlling odors in commercial and office settings • Protecting residential gutters and wastewater pipes • Mitigating combined sewer or sanitary sewer overflows • Enhancing outfalls for sea walls and other coastal infrastructure

 

Learn more about ProFlex™ Style 790 In-Line Rubber Duckbill Check Valves, as well as Proco’s full line of state-of-the-art check valves and expansion joints, at procoproducts.com

Download this rubber duckbill check valves case study