Streaming Along

Particularly prominent is the preservation and enhancement of water quality in the corridor’s multiple streams. State-of-the-art solar-powered monitoring equipment provides environmental managers with real-time information on turbidity and flow speeds. In cases of excessive silt or other problems, the information is relayed directly to environmental managers via e-mail and cell-phone alerts.

The design-build teams have completed nearly 74,000 linear ft of stream restoration work and constructed 1,500 linear ft of fish passages to eliminate obstructions to upstream spawning areas. In three highly sensitive watersheds, caisson foundations for bridges have reduced both the footprints and the amount of excavation and water handling typically associated with continuous foundations.

For a 525-ft structure over Little Paint Branch tributary, ICC Constructors used 84-in.-dia drilled caissons, instead of 25 x 25-ft spread footers, and carefully aligned and spaced piers to avoid water impacts and minimize tree clearing. A 323-ft crane positioned alongside the stream was used to set the bridge’s precast girders. “The bigger crane allowed bigger picks with a greater radius, requiring a smaller access footprint,” says ICC Constructors project controls manager Chuck Martin.

Little Paint Branch is home to the rare brown trout. “The last state environmental survey found only one brown trout in the stream,” Martin says. “We don’t want to be the ones who kill it.”

To build an elegant 420-ft-long bridge that rises 65 ft above Rock Creek, the team built 12 x12 x 6-ft thrust blocks embedded into the hillside to prevent erosion and support the four cast-in-place arches. The 210-cu-yd arch ribs then were installed in pours of 13 hours each. As with other ICC structures, the Arch Bridge offers an ample bank width to serve as a passageway for the corridor’s deer and other wildlife.

Nature itself has posed challenges to the work, with last winter’s rains and thawing snow often turning portions of the route into a quagmire. “We’ve had to halt earthwork several times until things dried out,” Peters says. Conditions have been so trying that MD200 Constructors resorted to using the 450º C exhaust from a jet engine to speed the drying of the moisture-rich, loamy soils.

However, design-build allowed the teams to make money-saving changes. ICC Constructors’ reconfiguration of the I-95 interchange eliminated an estimated 330,000 sq ft of bridge structures, and it redesigned the interchange at U.S. Route 29 to three from four levels.

Sound walls—often among the last components of a highway project—were put in place early in several neighborhoods to minimize noise. Sculpted soil berms have been installed alongside the road in several subdivisions to provide natural visual and sound buffers.

Rather than using space-consuming traditional stormwater management ponds, stone- and sand-filled underground storage filters are being installed beneath the ICC’s travel lanes to collect and cool runoff to 68º F and below. “Returning cooler water to the streams is much better for the native fish and further reduces tree loss,” says Carla Julian, InterCounty Constructors’ community outreach manager.