Mally Road, Hodgson Vale is a main connection route to the New England Highway for a rural residential area approximately 10km south of Toowoomba. Following a level 2 inspection undertaken by Toowoomba Regional Council it was determined that the existing corrugated metal culvert under Mally Road required replacement.

 

Toowoomba Regional Council commissioned HIG to carry out the detailed design of the new culvert structure and associated roadworks.

 

Following hydraulic analysis of various culvert configurations, it was determined that the new culvert size be 2/2400x2400 RCBC’s. This provided an improvement of flood immunity from the current less than 5-year immunity to be flood free for the 100-year event.

 

The project required the closure of the road during the construction period but pedestrian access was required to be maintained during construction. This required the design of a temporary path on the adjoining property.

 

To contain the new culvert and associated wingwalls within the road reserve specifically designed wingwalls were required to ensure that the culvert and associated wingwalls was contained within the road reserve. Council also required the portion of wingwall over an existing water main be removable to allow future access to the water main. Gabions were used to allow removal and replacement of the water main in the event of a failure of the water main.

 

The existing gully is defined as an amber waterway under the Queensland Fisheries Act. This required the culvert to be designed to be in accordance with the requirements of Waterway barrier works. This required that the base slab of the culvert be roughened to allow for fish to pass through the culvert.