Delivering a complex project in adverse conditions – crocodiles and more crocodiles

By Michael Wanrooy, Director of Engineering, Carpentaria Shire Council

Kowanyama Aboriginal Shire Council website states that the local indigenous Yir Yoront language word for Kowanyama means “place of many waters” - where roads and water crossings become impassable during the wet season. Creek crossings rise rapidly, often without warning, from upstream rain events creating dangerous situations that catch unwary road users by surprise whilst crossing low level floodways.

This was a conversation we had while undertaking the Cultural Heritage Clearance on the Scrutton River floodway upgrade:

“We are so pleased that you are raising this causeway! Last year my family tried to get back to Kowanyama. We drove across this floodway and the floodwaters pushed our car to the edge where it got hung up on the paperbark regrowth. We climbed out of the windows and swam to safety”.

The next day, another vehicle encountered the same situation with the floodwaters claiming their car while they swam to safety.

The Scrutton River floodway upgrade was the first Aboriginal and Torres Strait Islander (ATSI) Transport Infrastructure Development Scheme (TIDS) funding used to raise and widen the existing crossing. Keeping up with the Northern Territory newspapers I wish to add that on a few occasions our construction crew observed a large 15-foot crocodile crossing the floodway during the build. In case you are wondering, the new design allows passage for fish and crocodiles to travel under the carriageway via multicell box culverts. The following year we followed up using ATSI TIDS funding with another raised floodway using 10 multicell box culverts at Dunbar Creek. And yes, I have observed a small crocodile at Dunbar Creek during construction.

This article will attempt to briefly describe the difficulties and complexity of delivering our latest ATSI TIDS project (Magnificent Creek Overflow) on an isolated road whilst enduring adverse conditions such as transport and communication failures, machinery breakdowns, heat, flies snakes, crocodiles and cranky concreters.

All the ATSI TIDS funding has been allocated to the Dunbar Kowanyama Road for the raising of existing low-level floodways. The start of the road is approximately 505 km west of Cairns or 265km north of Normanton (205km gravel and 60km bitumen surface) and a further 100km of gravel road to reach Kowanyama. The road is unpassable for 3 to 6 months of the year mainly due to narrow low-level floodways caused by annual flooding of the mighty Mitchell River which runs parallel to Dunbar Kowanyama Road for its entire length. The Mitchell River has an annual runoff of 22.4 million ML and is the second largest catchment in Australia, only marginally behind the Murray-Darling Basin with an annual runoff of 24 million ML.

Kowanyama has a population of approximately 1,000 people and this road is the only affordable freight and vehicle access to service the community from Normanton or Cairns. The pavement is comprised mostly of local silty gravel materials and in sections, good quality imported gravel as funding becomes available. The other route is via Pormpuraaw which is located further north and only open to 4X4 vehicles for a few months each year. A section of the road between Kowanyama and Pormpuraaw also falls within Carpentaria Shire. This is the area where the Mitchell River disgorges into the Gulf of Carpentaria.

On 19 April 2021 Council received approved funding for $989,212 under the 2021-22 ATSI TIDS Program.

This funding was for the upgrade of the Magnificent Creek overflow crossing to incorporate reinforced concrete box culverts and a widened, two-way raised concrete running surface to improve flood immunity and provide better access. The Magnificent Creek overflow crossing is located 12km from Kowanyama and is locally known as ‘Topsy Creek’.

This area is well known for the presence of large crocodiles with Magnificent Creek, which is a tributary of the Mitchell River, only 20 - 30m downstream of the site and running parallel to the road.

Erscon Consulting Engineers were engaged to undertake the survey, design and contract inspections. By early July 2021, after many coffee sessions and revisions, we had the right design to successfully build the causeway in an isolated area, meet Department (Agriculture and Fisheries) ‘purple stream’ approvals requirements and funding timeframes.  Our plan was to have Council order the culverts and deliver them to site in parallel with the tender process, and have construction completed by the end of November to beat the start of the monsoon season. It was predicted (due to La Nina) that we were likely to have a very long wet season with roads opened by May, leaving very little room to complete the build by end of June 2022. We were pleased with the outcome of the design and had the sizing of the 10 rows of the multi-cell box culverts, or so we thought.  

Magnificent Creek Causeway with 10 multi cell box Culverts

The first signs of disaster struck when we found out that there was an 8 to 12 month lead time to deliver the design culverts to site.  At this rate, we would not meet the funding timeframe and there was a risk of having an extension of time refused, community disappointment and reputational damage.

I had a difficult decision to make and took a risky approach by considering a cast-in-situ culvert construction at an isolated site where the probability of everything going wrong would increase. Cost increases worried me greatly. However, having taken a calculated punt, we redesigned the causeway to incorporate the cast-in-situ idea. Erscon successfully delivered the new design and by mid-August 2021, the Tender was released via Vendor Panel. The Tenders closed in early September with all pricing received over the funding budget except one ‘unusually low price’.  The lowest tender was 50% less than the estimated budget and experience that claimed - “I am an experienced plant operator and am willing to give concreting a go”.

There was no time to modify the scope and retender to meet the rescheduled December time frame, which was now pushed out from November. Recommendations were made to negotiate without reducing the scope with the second lowest tenderer who was marginally above our budget figures, as the third lowest was approximately $250,000 above the available funding.

Kowanyama Magnificent Creek overflow

I was able to fast track the Cultural Heritage clearance following an invitation to chair a meeting that included Traditional Owners and Kowanyama Shire Council representatives in Kowanyama. This included a site visit between Kowanyama and Pormpuraaw which was within Carpentaria’s Shire boundary. On the site visit we pulled up at a picnic spot 50m upstream of the Mitchell River crossing and admired the views. We were shown a photo of a crocodile swimming leisurely in the shallow water taken at this spot a few days ago. We then crossed the Mitchell River and came to a dip in the river with water reaching the top of the bonnet for about 20m. As I looked to my left, I observed half a dozen children happily swimming 20m further downstream from the crossing.

Crocodile in water at Kowanyama Mitchell River

My thoughts brought me back to the conversations I had at the Scrutton River.

“We have crocodile whisperers over here. Before we jump in the water our elders will undertake a ceremony to whisper to crocodiles to keep us safe”.

I was a bit late and unfortunately missed the whisperer’s ceremony, so I did not swim that day.

Later that day, we completed the Cultural Heritage clearance at the Magnificent Creek Overflow site. The contract negotiations were finalised and executed by the end of October and construction started on the same day. It was a gamble to start this close to the wet season as the roads could be closed anytime due to flooding, however, the project required a strong resolve if we were to meet the funding deadlines. By November there will be threats of rain around the area with weekly grey clouds forming with a bit of drizzle here or there.

Despite the logistical nightmares of isolation, camp setup requirements, the tyranny of distance, high tropical humidity, reported sightings of large crocodiles within 30m of the site (in Magnificent Creek), rough roads and onsite concrete batching, the project was delivered successfully by mid-December.

Carpentaria Shire Council, in partnership with TMR through the North West Queensland Regional Roads and Transport Group (NWQRRTG), will continue to deliver important funding opportunities to promote road safety to improve access to Kowanyama.