How do you stabilise a steep gully carved by the action of 80 years of run-off from an active and then disused commercial piggery?
Carefully and with precision
The River Is Down There In That $%^%$…
Once we had finished renovating the shed and after a very successful 50th birthday party for Richard our attention turned to the hill that runs down to the river. Since the end of the drought in 2020 with all the rain dumped by successive La Ninas the hill had gone from a dry, slippery skree slope into an unmanageable and dangerous mudslide filled with long grass, weeds, rabbits, snakes and buried old farm scrap,
After 5 successive floods the river and shore was filling with silt and driftwood. We didn’t go down there often and couldn’t let family or friends, particularly children, anywhere near the slopes or banks.
We gotten rid of a lot of the blackberries that lined the banks up to the fence, then found more old fences in amongst blackberries closer to the bank and tangled in the flood junk. Even the path that we had cut in 2020 had become too slippery for the quad. It was a dangerous mess that with more water and time would only get worse.
Something had to be done, but what?
A Plan Comes Togather
Looking down from the deck Sarah came up with the idea. “The only thing that will work is terraces. It’s too steep to clear or grade, and how do you stop the hill just eroding into the river. Has to be terraces.”
But would terraces work? Were they legal? Could they be built? What would it cost?. After careful investigation and surveying the answers were Yes, Yes, Yes and A Fair Bit. We were still waiting for yet more reports Goulburn Mulwaree Council wanted for the development application (more delays) so we had time before that was going anywhere. Better to get it sorted before we got heavily into the main build once the application was approved (or so we thought – it wasn’t approved).
The design we came up with wasn’t too radical. A series of retaining walls marching up the hill with a staircase running down along the fence linking to the path below.Each terrace would be wide enough and level to get the zero turn in and the lowest tier would be wide, level and stable enough for vehicles to access the river as needed.
A longer retaining wall would run along the road below up to the gate to create a even platform along the same line. Keep the original fence line and gates so we can maintain separate paddocks for the animals whilst still provide easy passage for humans and vehicles.
Clean and elegant fitting into the natural shape and slopes of the land.
A 10.2m drop was required. Each tier would be 1.25m higher than that
below so the retaining walls would only be 1m high with a 25cm fall for
water drainage. Each platform would get progressively narrower to cater
for the increasing steepness of the gully . By following the natural line
of the hill we would need a little bit of cutting and almost no fill,
so the extra dirt could smooth out the shape of the hill to the south
making that a lot easier to mow. Better for the soil to smooth our hill then be washed into the river with the next thunderstorm. Safer too.
Nothing major to be done as long as we were precise with our measurements and careful with any excess soil. The rock was firm underneath (we did some test drills) so there was no danger of slippage with short retaining walls as long as we provided proper drainage. Ag line will handle that possibility nicely.
“Struth”, we thought, “this will work! Chris, when can we get started?”
Start At The Bottom
There’s nothing magical or particularly tricky involved in the construction. Cut room for the retaining wall, install posts, check your levels, add the panels, pull back with anchors and wire, install drainage and mesh, then carefully fill. Rinse and repeat.
Start from the bottom path, then the central spine up the stairs. That way you can check and verify your levels and the height and width of each tier as you install tier. Fan out each tier from there ensuring you line up the curves as you go around the hill.
We used 1.5-2m 3mm angle for the posts driven straight into the ground adding concrete as needed with 50mm H4 sleepers for the panels. Very strong. Agline covered in drainage gravel for the drainage connected to 100m PVC pipe running under the staircase makes sure we don’t get a build up of water and wet dirt sagging against the panels. Finally the electrics and audio conduits buried 900mm deep running down the hill. Safe from humans, animals and water.
Standard stuff. A bit boring actually. once we got into it.
Didn’t take long to finish, even with some very wet days when you have to stop. Machinery and mud just lead to a mess and rivers of silt which we obviously could not have.
We were done by early September 2022 and over the next several months we just let everything settle and the greenery grow..
It’s hard to argue with the results. Check out The Amphitheatre page to see how it turned out and read about how we renovated The Shed.
If you are interested in hiring or staying in The Shed for a wedding or party, camping a night or two, hosting a BBQ, our crops, mulch or agistment services, or you are just passing through and want a look, just Contact Richard or Sarah. or Book Online now.
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