After the Toowoomba and the Lockyer Valley experienced devastating floods, one of the many road rebuilding projects involved a section of the Warrego Highway between Withcott and Helidon. Withcott is a small village at the western end of the fertile Lockey Valley and at the foot of the Great Dividing Range, just a few minutes frorm Toowoomba and theDarling Downs. Helidon, just to the east, is another valley village made famous by its natural spas and spring water.
This section of the Warrego Highway caters for 22,000 vehicle movements per day. Approximately 3,300 of those movements are by heavy vehicle, 30 of which are by wide loads each month. The highway is also a major route for the coal seam gas (CSG) industry. Predictions are that heavy vehicle and wide-load traffic will increase along the motorway with the energy sector’s needs.
The Fulton Hogan Group was the successful contractor for the Warrego work. Drainage specifications were derived from Queensland Transport and Main Roads specification MRTS38, which stipulated a flexible or rigid drain with a no-fines concrete backfill.
The geosynthetic solution Megaflo®, a rigid, high-flow velocity panel drain, was selected for the work. The product, designed for roads and sports fields, requires only a narrow trench and provides long-term performance for high-flow drainage and protection against siltation. The internal core of the drain provides strong crush resistance, making it an optimal drainage support solution for the roadways increasing heavy vehicle traffic.
The narrow trenching for the panel drain helped save on project cost, as did delivery from the nearby Geofabrics’ panel drain manufacturing facility in Albury, NSW.
Initially, 33,000m of Megaflo® 300 was required for the four-lane roadway; but, during the course of construction, an additional section of road rebuild was added. This extended the total supply agreement to 37,000m and 1200+ side outlet fittings.
Many of the trenches were dug with a traditional ditch witch, but rock cutters were also used. The cutters were capable of trenching 250m per hour, cutting through hard substrate.
The Megaflo® installed quickly and the Warrego Highway was soon restored—and strengthened.
Learn more about Geofabrics Australasia’s materials and engineering expertise, including its large portfolio of work in roadway and subsurface drainage design, at www.geofabrics.co.