Supporting Elan at Uptown

Repurposing land is one of the leading movements in modern urban development. The opportunity to renovate and rehabilitate existing sites, rather than gobble up free space in outlying areas, is important not only from an environmental standpoint but also from a community pride perspective.

However, the challenges to creating developments on these sites can be daunting.

In many cases, the available land is surrounded by infrastructure such as roads and utilities that were built to support the original use, but which now limit options for new development. When faced with these hurdles, developers need new tools to be successful.

A case in point is the current Elan at Uptown project in Minneapolis, MN. Developers wanted to construct a modern, multilevel apartment complex on the grounds of a longtime lumberyard. To make the proposed construction possible, a robust underground stormwater management system was needed to protect municipal water supplies and the surrounding area. The chosen system also had to be strong.

Because of the project schedule, the stormwater system was to be in place before construction of the building was complete. This meant that a construction crane and counterweights totaling more than 135,000 pounds would either need to be located directly over the chambers, or the contractor would have to face the expense of closing off a busy street to accommodate the crane.

Where does one turn to find an underground system that can store over 14,000 cubic feet of stormwater in a limited footprint, offer convenient porting for sediment removal and maintenance–and support 66 tons of crane apparatus under just 30 inches of backfill?

Developers turned to Triton Stormwater Solutions. Since its launch in 2007, the Brighton, MI-based company has been a leader in innovative stormwater management. Founder Joe Miskovich came up with the idea of the Triton chambers after the home he bought suffered rainwater damage during a storm. Using his engineering insights from years of experience in the automotive engineering industry, he set out to solve the problem of the stormwater runoff that was leaving sediment and debris on his and his neighbor’s property. Miskovich used his knowledge about state-of-the-art processes that are used to produce today’s automotive and aerospace parts. He also used a structural grade material to ensure unsurpassed strength and performance verses using a common, inexpensive material from which children’s toys, coat hangers, and some other chamber products are typically made.

Miskovich’s underground storage and management system would temporarily hold the water safely during a large rainstorm until such time as it could leach through the subsoil naturally, taking out any impurities as it passed through the soil. The Triton system can be easily inspected and maintained at a fraction of the cost associated with other underground systems.

His initial home-brewed solution worked so well that he immediately saw the potential for the concept to be broadened. While the initial application was for a residential use, he also recognized the opportunity represented by commercial development.

The ability to efficiently and inexpensively store water underground freed up surface areas where an unsightly retention pond might be located for more valuable uses, such as retail shops or parking lots to support retail traffic. Miskovich’s instincts were correct. His system’s advantages over the existing underground systems caught on quickly. Lighter, stronger, more cost effective, and flexible in design, the Triton chambers can create surprising amounts of stormwater storage in tight footprints. Their mix of features, ability to double stack the systems, as well as being constructed from reinforced composite materials that are widely used in structural application in the auto and aerospace industries, helps engineers find solutions to the inevitable challenges that bubble up during a complex project.

In the case of the Elan at Uptown project, developers worked with the Triton engineering staff to create two separate straight-line systems on the east and west sides of the building. Each of the systems incorporated Triton’s proprietary Main Header Row, along with special sediment flooring and inspection and maintenance ports.

To prepare for the chamber installation, narrow trenches 84 inches deep were excavated and lined with a Class 2 nonwoven geotextile. A base layer of 12 inches of washed, crushed angular stone was laid down in preparation for placement of the chambers. A four-person team then installed the chambers in a few hours, using Triton’s click-in-place design that ensures quick, correct alignment. After the chambers were set in place, the installation continued with a backfilling of crushed stone to a height of between 24 to 30 inches above the crown of the chambers.

With most projects, this would be the end of the story; but with the Elan at Uptown development, getting the system installed was only the beginning. The timing of various phases of the project dictated that construction on the building itself, involving the crane and supporting apparatus, would have to come after the stormwater management system was in place.

While Triton’s chamber strength allows for shallow cover layers (just 16 inches in most cases) to support vehicular traffic of H30 loading (48,000 pounds single-axle loading), the idea of housing nearly 137,000 pounds required a deeper dive into the system’s ultimate limits.

Triton contracted with an independent structural research and development engineering firm in Michigan to conduct a fine element analysis. After the firm looked at static and reactive loads, various backfill materials, and other site dynamics, it determined that the Triton system could bear the load with a large enough safety factor to take into account any contingencies that might be present. This allowed the developers to move the project ahead on the original timetable–and, equally important, within the specified budget.

“The fact that they could locate the crane onsite, rather than on the adjacent roadway, was a huge advantage to the overall project’s timing and cost. We were confident from the extensive original testing we had done at the University of Ohio and at other renowned third-party testing facilities that the chambers would be strong enough–but we needed the verification of a site-specific test to ensure it,” says Miskovich.

With the go-ahead provided, the construction moved forward without any problems. The Elan at Uptown Apartments and retail sites are planned to be open by fall 2013.