SH 89

Zachry Construction Corporation of San Antonio is more than halfway completed building a $44.4-million State Highway 89 project around Sinton, north of Corpus Christi. SH 89 will be a bypass for US 181 traffic around the small town of approximately 6,500 people. US 181 is the more scenic route between the San Marcos/Austin area and Corpus Christi, avoiding San Antonio.

Zachry set their goal of trying to complete this three-year project in only two years, according to project manager Roger Lopez. Currently, the overall project is around 68-percent complete, with just under 47 percent of the time allotted for the project used, calculated Joe Escamilla, TxDOT project chief inspector.

"The work is progressing rapidly due to the manpower they have assigned to this project," Escamilla said. The project, scheduled for completion in 2009, is now expected to be completed by spring of 2008.

Two other aspects aid the momentum, as Gilbert Lopez of Zachry Construction explained. "The roadway is being built through undeveloped land, and because there is need for traffic control in so few places, project phases can be constructed simultaneously."

This project involves construction of a new four-lane divided roadway from US 181 south of Sinton to US 181, 3 miles north of Sinton, and overpasses at US 77, US 181, Oliver Creek, and Chiltipin Creek.

Phase 1 of the project from FM 1074 along US 181 to Oliver Creek has been completed.Phase 2 will be from SH 188 to Business 77.Phase 3 will be from BU 77 to US 77.Phase 4 will be from US 77 to US 181.

Construction operations are being monitored for the Texas Department of Transportation (TxDOT) Corpus Christi District through the office of Sinton Area Engineer Bill Reitmann, P.E.; Sinton office transportation engineer, Armando Bosquez, P.E.; and project inspector, Joe Escamilla.

GPS And The Road

Zachry's Caterpillar 140H motorgrader outfitted with GPS has also been a real help in speeding the project along, from cutting the base to grade, to contouring the flex base over the geogrid sheeting, according to Gilbert Lopez.

John Stewart Jr., Zachry's survey manager, described their GPS system, "It's a hybrid model. The GPS unit is a first-generation Trimble that is about five years old, but it has just been updated with new software and a single post receiver. Our Trimble representative, Tim Jochec of Western Data Systems, made the upgrade on the job site."

"We upgraded their Trimble GPS sight vision motorgrader system to a Trimble GCS900 single antenna with cross-slope sensor system," Jochec explained. "The MS980/MS990 Smart GPS antenna allows blade control to 0.1-foot. This system will allow Zachry to use the motorgrader with either GPS [global positioning system] or ATS [auto tracking system]."

Soil Conditions

Because the area contains pockets of soil that are either too sandy or too clay-laden in PI tests, Zachry found it necessary to excavate about 210,000 cubic yards of soil. It was replaced with select fill that was also used for embankment material, a total of 1.375 million cubic yards hauled in from the Martin Marietta Materials pit in Gregory, about 15 miles away.

Lime treatment will additionally stabilize the pavement subgrade. Over 11.5 tons were supplied by Chemical Lime.

Drainage throughout the project in this coastal area required the installation of approximately 11,300 linear feet of concrete box culverts ranging in size from 4 feet by 3 feet to 10 feet by 5 feet, installed by LA Utilities.

Bridge Construction

Large & Sons Foundation Drilling of Corpus Christi has almost completed the more than 10,000 linear feet of drill shafts for bridge piers, according to Bosquez. Varying in diameter from 18 inches to 48 inches, their depths range from 48 feet to 54 feet.

"All of the 16,663 linear feet of prestressed concrete beams supplied by Bexar Concrete Works have been placed," Bosquez added. Bexar Concrete Works is also supplying the precast panels for the MSE (mechanically stabilized earth) walls.