Green Infrastructure

How is storm water being handled?

Storm water is being managed using best management practices, including use of infiltration trenches, which are rock-filled trenches built under curbs and boulevards along most of University Avenue. Storm water runoff is stored in the voids of the rock-filled trenches and slowly infiltrates through the bottom and into the soil, increasing groundwater recharge. Pollution is also filtered through the soil through this process.

Were recycled and durable materials used in the building of the line?

The project used materials with a high recycled content. These include copper for station roofing, ground rods and wire and steel for bridge trusses, track rail and rebar. The project specifications allowed for recycled bituminous to be used for the roadway sub-base in selected areas along the corridor.

Copper

The average recycled content from copper materials is up to 45 percent. The high cost of mining copper ore and refining it makes recycling copper attractive.

Rail

Track rail is made from at least 30 percent recycled steel. (An exact figure is difficult to come by because the project acquired the steel rail as part of the larger civil construction contracts.) More than 12,300 tons of rail were required for the project.

Rebar

Rebar is typically 95 percent recycled content from sources such as old cars and railroad track, for example. More than 4,300 tons of rebar was used.

Truss and structural steel

Specifications for the truss steel did not require a specific recycled content. But almost all new plates and shapes have a high recycled content of more than 85 percent. Nearly 2,540 tons of steel were needed to retrofit the Washington Avenue Bridge.

Are LED lights being used?

LED lighting is used throughout the 18 light rail stations. LED stands for light-emitting diode. LEDs are small light sources that become illuminated by the movement of electrons through a semiconductor material. The U.S. Department of Energy estimates the rapid adoption of LED lighting in the United States over the next 20 years can deliver savings of about $265 billion, avoid the need for 40 new power plants and reduce lighting electricity demand by 33 percent in 2027.

What green building concepts were incorporated into the Operation and Maintenance Facility?

Project designers were very proactive in pursuing sustainable building strategies. They did extensive analysis of various sustainable/ green building energy use concepts while participating in Xcel Energy’s Energy Design Assistance Program. The regional program allows designers of qualified projects to work with the Weidt Group to conduct comparative energy analysis on various design schemes. As a result of the analysis and design, the project not only addressed building responsibly, but also considered long-term operations and maintenance through implementing numerous sustainable and energy conservation measures. A variety of sustainable and energy-saving strategies were adopted. Among them:

• Occupancy sensors and dual-level occupancy sensor lighting controls that set the light level at 50 percent when occupants enter the room and requires them to manually switch to 100 percent light level.
• Mechanical strategies, such as premium efficiency motors, variable fan drives on water circulation pumps, carbon monoxide and carbon dioxide controls and sensible heat recovery, to name a few.
• Creating buffer spaces along the perimeter of the building to help minimize heat loss through the exterior walls by locating cool functions, such as the vehicle storage and train inspection areas along the perimeter of the building, and concentrating the more sensitive areas, such as offices and locker rooms, along the center spine of the building.

The building uses District Energy’s hot and cold water as its main energy source. District Energy’s primary source of fuel is “clean urban wood waste, which is a form of biomass, the sustainable, renewable energy stored in green plants and other organic matter. The overall results of the final design are:

• The building reaches savings of 41 percent of its annual energy use compared to Xcel Energy’s program baseline.
• 35 percent annual energy cost savings, which equates to $167,000 annual cost savings.
• Heating needs are 25 percent of Xcel’s program baseline; 16 kBtu/sf compared to the 64 kBtu/sf baseline.