Working on larger-scale projects (e.g., commercial offices, education and healthcare buildings, campus data center environments, etc.) can present unique challenges, among them the crucial need to ensure that spaces are resilient and able to seamlessly accommodate future growth capacity and other changes.
When designing agile, future-proofed spaces, it’s necessary to consider the fact that more complex, larger schemes also need more extensive duct bank systems to hold all the communication cables they require. Duct banks—the groups of conduits that safeguard cables and keep them together when running underground—are a critical component of a development’s infrastructure, allowing the flow of information that facilitates often mission-critical services and functions; especially so in a public-facing building or a data center campus responsible for holding huge volumes of important data without interruption.
As technologies continue to evolve at a rapid pace, it’s difficult to predict the evolving requirements in advance; therefore, it’s essential to introduce from the start a fiber pathway system that’s flexible enough to handle any eventuality. That means looking beyond the most common methodology and embracing fresh, alternative approaches.
Concrete-Encased vs. Trench-Duct
Traditionally, concrete-encased duct banks have been used as the go-to solution for outdoor plant fiber pathways. There are multiple design options: one of the most popular involves incorporating numerous smaller innerducts inside a larger conduit, while other methods may utilize multiple smaller conduits. Certainly, the best approach depends on the overall layout and size of the space. For longer conduit paths or paths with multiple bends, manholes can serve as a junction between duct banks while also providing a location for service loops.
Concrete-encased duct banks have been popular for good reason, offering a system that’s proven and reliable. Nevertheless, they have drawbacks, as they’re expensive and have limited capacity for future growth. After fiber has been installed in the innerducts or conduits, they’re considered “filled” and are no longer usable unless the fiber is removed. There are also increased construction costs, higher installation times and more earth displacement. Additionally, the manholes tend to fill with water and need to be pumped prior to fiber installation.
For greater flexibility, we can look to an alternative method for outdoor plant fiber, the “trench-duct,” which isn’t yet a common construction practice but offers a strong solution to typical challenges. This is a precast concrete structure with a lid—available in multiple sizes and traffic ratings—that’s also a particularly good option for use in roadways that experience high traffic or heavy loads. Trench-ducts are installed with the top of the cover flush with the grade, while the bottom has slotted openings for drainage. Covers can be equipped with locking mechanisms for increased security.
When using trench-ducts, several factors must be taken into consideration during the design stages. This includes the approach to building entrances, whereby it’s possible to transition from trench-duct to a covered cable tray. Similarly, additional details must be added for road crossings and curbs, and the fiber-bending radius for intersections also is key. In fact, trench-duct manufacturers can provide pre-cast intersections for elbows, tees and crosses.
Effective drainage is another significant element and can be supported by introducing sub-drains, specifying locking lids, properly sizing the storm drainage system and linking the sub-drain to it. Some manufacturers have floating lids, so during heavy rain where the storm system gets backed up, it’s possible for the lids to float away if the trench-ducts fill with water.
Compelling Time, Budget and Flexibility Benefits
Traditional concrete duct banks currently represent the more common construction practice. However, cost and installation time are obvious design considerations, and that’s where the benefits of trench-duct really come to light. The cost of installing trench-duct is approximately half of installing concrete duct bank, especially when it comes to large quantities of fiber cables (more than 100). The time required to install trench-duct, compared to a similar-capacity duct-bank, also is much less. What’s more, trench-duct has a far higher fiber capacity for future growth, and it enables easier fiber installation, reduces earth displacement and eliminates the need for manholes.
While cast-in-place trench-duct or large steel plates may need to be installed over road crossings for heavy loads (i.e., cranes), arguably the main perceived barrier to adoption is that this isn’t yet a mainstream construction practice, thereby carrying a steeper learning curve for contractors. Although additional time may be spent on projects to guide a contractor through the process, when construction is complete, the owner will have a fiber conveyance system that’s easy to use and better prepares them for future growth.
To overcome the roadblocks and embrace a methodology that’s not yet widely used, the industry first needs a mindset shift as well as being prepared to invest time into understanding and application. It’s a worthwhile pursuit as, on balance, the advantages of using trench-duct for outdoor plant fiber installation often outweigh those of traditional methods. 
The post Smarter Solutions: Embrace an Alternative Duct Bank Pathway for Future-Ready Developments first appeared on Informed Infrastructure.