Over the last 20 years the Missouri Department of Transportation (MoDOT) has directed the reconstruction of Route 21 southwest of the St. Louis metropolitan area.

The Route 21 corridor starts to the north at the junction of Route 141 and ends to the south at Highway B just southwest of Hillsboro, Mo., in Jefferson County. Route 21 currently has an average daily traffic count of 14,545 with a projected count of 32,700 by the year 2025.

The final phase project was a contract awarded to Fred Weber Inc. in Maryland Heights, Mo.

“When completed the current two-lane highway will be replaced by a relocated four-lane highway,” said John Grana, resident engineer of MoDOT. “The current project will be completed under two contracts. One project includes paving, striping and highway signage, guardrail and lighting installation. The other project includes grading house demolition, construction of four bridges, the installation of four large retaining walls and utility relocation.”

Utilities being affected by these relocations were Ameren U.E., AT&T and Charter Communications.

The 3.5 mi. (5.6 km) project started on July 7, 2007 and is scheduled to be completed on Aug. 15, 2009. Grana said that MoDOT is providing a $2,000 per day incentive for early project completion up to a maximum of $500,000, based on a value engineering agreement between MoDOT and Weber.

“Two bridges, north and south bound will take the new Route 21 over Hayden Road,” Grana said. “They are both single span bridges built with pre-cast concrete I-girders and pre-cast concrete deck panels. Another bridge takes Glade Chapel Road over the new Route 21. This bridge is two spans and is also built with pre-cast concrete, I-girders and pre-cast concrete deck panels. A fourth bridge will take existing Route 21 over the new Route 21. This bridge will be a single span bridge using steel girders with pre-cast concrete deck panels. Fred Weber Inc. will build all four bridges with the reinforcing steel being placed by MTC Construction of Chesterfield, Mo.”

The excavation portion of the project has 1.7 million cu. yd. (1.3 million cu m) of unclassified material. Grana said that 51 percent of this excavated material was projected to be rock.

To handle this excavation task, Fred Weber Inc. brought in a wide arsenal of equipment. Don McGraw, senior engineer of Fred Weber Inc., stated that crawlers included two Caterpillar D6s, two D8s and one D10.

“Both the D6s and D8s are equipped with Trimble GPS systems to assist in grade and fill management.”

The excavator fleet included Komatsu PC 1250 and PC 300 with a breaker attachment along with a Caterpillar 963 crawler loader. Rock excavation was detonated using a trio of Tamrock drills.

Excavated material was hauled by Cat 773 65-ton (59 t) dump trucks, along with a fleet of Terex, Volvo and Caterpillar articulated trucks.

From this excavated material, 1.6 million cu. yd. (1.2 million cu m) was used for embankment with the remaining to be used for 18-in. (45.7 cm.) rock fill base and rock ditches.

McGraw said it worked double shifts during the heaviest excavation periods to meet deadlines.

MoDOT specified that the project have 8 in. (20.3 cm) of non-reinforced concrete pavement with 15 ft. (4.6 m) transverse joint spacing. Weber is using a model CMI 450 four-track slipform paver.

This paver used a “bobsled” to form the longitudinal joints. This eliminated the need for a longitudinal saw cut. The new pavement will have a 75-year life span. CEG

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