Take a Virtual Field Trip Through DC Water’s Stormwater Infrastructure

January 22, 2015

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The Lady Bird Tunnel Boring Machine is  lowered into a hole at the Blue Plains Advanced Wastewater Treatment Plant. Photo courtesy of the District of Columbia Water and Sewer Authority (Washington, D.C.).

The Lady Bird Tunnel Boring Machine is lowered into a hole at the Blue Plains Advanced Wastewater Treatment Plant. Photo courtesy of the District of Columbia Water and Sewer Authority (Washington, D.C.).

Go online to get an up close and personal view of a giant tunnel and expansive green roof. These two components of DC Water’s (Washington, D.C.) Clean Rivers Project were the subject of a Nov. 19 virtual field trip. EarthEcho (Washington, D.C.) conducted “Virtual Field Trip: Managing Stormwater with DC Water.” Classrooms logged on and students participated in the 55-minute virtual field trip.

During the event, two project engineers showcase the tunnel created by the Lady Bird Tunnel Boring Machine and green infrastructure that will capture stormwater during heavy rainfall and help reduce combined sewer overflows in Washington, D.C. From the bottom of a 43-m (140-ft) hole at the Blue Plains Advanced Wastewater Treatment Plant, engineer James Wonneberg discusses the construction of the new stormwater tunnel system. And on top of the enclosed Fort Reno Reservoir, engineer Bethany Bezak describes the reservoir’s green roof and discusses how green infrastructure helps capture rainfall and reduce stormwater.

The $2.5 billion combined sewer overflow-reduction project will require 15 to 20 years of construction, Wonneberg said in the video. When complete the tunnel system will stretch more than 21 km (13 mi) and will hold 594,245 m3 (157 million gal) of combined sewer overflow until it can be treated.

DC Water chose to combine a deep tunnel system, green infrastructure, and updates to existing infrastructure for the project after examining many alternatives. “All of these [other] options were ultimately dismissed because they were all very invasive and highly disruptive to all the people that live and work and commute through D.C.,” Wonneberg said.

To construct the tunnels, the project uses the Lady Bird Tunnel Boring Machine. After digging 1.8-m (6-ft), concrete rings are placed to form the tunnel. By Nov. 19, the machine had gone 4 km (2.5 mi), filling 40,000 dump trucks, Wonneberg said. The machine is equipped with software to operate the machine and a programmable logic controller that allows engineers to monitor it in real time. The public also can track the machine’s progress online.

“We move a whole lot of earth to dig this hole in the ground,” Wonneberg said. “Our deep tunnel system here is mostly out of sight, out of mind. Most of the D.C. residents don’t know we’re digging this tunnel,” he added.

The Fort Reno drinking water reservoir holds 21,953 m3 (5.8 million gal). The 3938 m2 (42,390 ft2) green roof was installed on top of the reservoir and features bioretention, pervious pavement, and cisterns and rain barrels that capture 90% of the stormwater onsite, Bezak says in the video, The project will help the city manage stormwater and prevent overflows from the 1016 mm (40 in.) of rain that falls each year.

View the entire virtual field trip at http://earthecho.org/news/HOA-111914.

Jennifer Fulcher, WEF Highlights

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