Our Journey Continues! – Designing a Turtle Tunnel

Turtles like to feel safe. They feel safe in warm and wet conditions. They also like to cross roads in the same general area they used the year before- most often these areas are between two wetlands or aquatic habitats. Sometimes the wetlands that border roadways need free-flowing drainage between them in order that roads do not flood, therefore, culverts are installed between them. These are the sites- where culverts exist between two wetlands- that we may be able to direct turtles safely under roads and through the culverts! This solution is called an underpass, or as we like to call it; a turtle tunnel.

How to direct a turtle under a tunnel?

Directing turtles is not easy, because they are intimidated by tunnels, and because they will resist moving off course at any significant distance. However, we can point to a few key design features to explain how turtle tunnels are chosen and structured. A successful design will has these basic requirements: First, the culvert has to be quite large; at least 1 metre in diameter. Also, the culvert cannot be blocked or completely flooded or too long either. This is because turtles need to see enough light at the other end to feel safe enough to go through the tunnel. Secondly, the wetland needs to be free from interruptions such as driveways or small hills and upland areas that meet the roads- this is because the wetlands need to be fenced off entirely and completely. Turtles will look for alternatives before going through an underground tunnel, and will look to areas that they can "jump out". Therefore, a driveway or island in the middle of a wetland or the edge of the aquatic habitat are tempting and easy alternatives for them to choose rather than going through a relatively dark tunnel. Finally, and as a precaution, fencing should be set back far enough from the road, or should be designed in such a way that it will not restrict turtles or other wildlife that find their way onto the road, from getting off the road! This simply ensures that any design failures will not result in further harm to wildlife- especially to our slow moving friends.

Choosing Wisely

This safety measure is one of the many reasons we have chosen an arch shape fence that can be installed below grade (below the level of the road), and can be backfilled so that it is flush with the area above it, or entirely invisible and permeable to wildlife that are on the roads. Even snakes should be able to escape the pavement with these designs! The other reason we have chosen an arched or concave shape solution is because this shape is extremely strong and durable, resisting heavy loads. Finally, the arch shape at 1m diameter/width prevents even large snapping turtles from successfully climbing the barrier- and turtles are amazing climbers!
We are also experimenting with new materials! Traditional arched turtle fencing is made from a large pvc pipe and is all one long piece that requires installation. The pipe itself is expensive, and the installation requires heavy equipment and levels to set it just right, increasing the cost to at least $20/metre. This means turtle underpasses of this sort in The Land Between bioregion, with smaller wetlands, can cost at anywhere from $10,000.00 for each site alone. With over 970 potential tunnel (culvert crossing) sites on county roads in the region, the cost would be extremely high!

Our Pilot Solution in Progress

Therefore, we are innovating! We have sourced food-grade steel drums. These are durable, weldable, less expensive, and they can be put in one by one, by hand or with smaller equipment. We are going to test this design this winter to see how it fairs in snow conditions and if it stays in place with frost heave. This solution is not only less expensive for materials and installation at only $8.00/metre after painting and welding, but the design is more easy to maintain and manage, and it is a form of recycling! The difference in cost is in labour however; there is a lot of preparation that is required to get the drums/barrels ready for installation- but with great staff and volunteers, the work load is lighter and the cost can be reduced.

This fall we have been busy preparing for our pilot testing! We have assessed potential tunnel sites; designed the solution (and with engineering review); sourced materials; cut, grinded, and painted the cut drums, and recently we have been welding different parts together to make sure that the structure will be stable when installed.

Near the end of this last September, Garry Mercer Trucking generously delivered over 143, 55 Gallon steel drums from So Soya in Toronto to our work area at Highlanders Auto Body in Minden. Throughout the following weeks afterwards, our staff worked tirelessly to remove the tops and bottoms (creating a sort of steel tube), and then halved the steel "tube" vertically, creating two steel "half-pipes". These "C" shaped drums were then transported to our office in Haliburton, where we grounded the edges smooth and painted the bare metal parts to prevent rusting. The hard labor was finally done! Or so we thought...

In comes Taylor, a Turtle Hero in the form of a welder. Taylor is welding the tops and bottoms of the steel drums to the base of the "C" drums to provide a footing, and then welding a piece of rebar to the back to provide stability (see the picture above of a completed drum).

Once all of the welding has been complete, the turtle tunnels are ready to install! We hope that within the next three weeks, if the ground has not frozen, we will install them. If the design is stable and effective, it will be a new way forward for cost effective turtle passage solutions in Ontario. Stay tuned as we move this project forward.