How do I best explain to a d4 dozer operator how to efficiently dig swales? What is the best way to dig the swale and the back cut on 15 to 20 degree slope without packing down the loose soil on the lower side of the swale? I would love for the swale to be the width of the dozer blade but I am not sure that is possible on this slope.
He has seen the property. He understands I want ditches dug on the contour of the land.
(I have tried for 4 months now to get a trackhoe operator to come to the property and he has not made the time. I called a dozer operator and he showed up an hour after I called him.)
What type of soil do you have? How compacted is it? Does the d4 have rippers?
My knee jerk reaction is that this is not the best tool for the job. If you have compacted soil and the dozer doesn't have rippers he'll have a tough time digging in. He'll also be compacting everything as he goes. I just used a d3 for an earthworks project. It didn't have rippers on it and I can definitely say I would not be able to make swales I would be happy with, with that machine alone.
Road graters are pretty ideal for making swales, have you called anyone with one of them?
If the dozer has rippers you might be able to make terraces with a humus ditch in the back. My gut feeling is that you would have a tough time doing more good than harm though if the dozer is your only tool.
depending on the operator, they are more than likely more than capable of figuring it out, provided they have something to go by... I would suggest finding a good youtube video on the purpose and design of swales and quite a few pictures to show them. Someone who runs a dozer for a living can do things with it that don't seem possible and do it in a time frame that is quite quick compared to a novice. I've worked with heavy equipment most of my life, but when it comes time to do a big project I have found that it saves me money to hire someone who can do it faster even if the hourly rate costs more than rental since they'll easily get twice the work done.
The compaction is a valid point though. A dozer will compact the HECK out of the ground but that can be mitigated by growing a deep rooted cover crop that will till the soil and break it up for you, might take a few seasons, but it'll eventually fix itself with the right cover crops. A good mix would be something that is successfully used in no till farming since their goals are nearly identical in that they want to mitigate compaction caused by driving tractors over the same area over an over.
anyhow, my answer to your question is that if the operator is good at what they do, a few pics and a little video discussing the design and purpose of the swales should be plenty. From what I understand, it is similar (not the same, but similar) to constructing silt ponds to catch construction run-off.
Ajila Ama Farm Western North Carolina
Just throwing this into the mix. 15-20% is a steep grade. From Geoff Lawton's earthworks class, he does NOT put in swales if the grade is 17% or over due to stability issues. Instead he plants those steeper slopes to Zone 5 forest that will act as the top level soil hydrology mechanism on the property. The issue is the stability of the back cut - too steep and you run the risk of destabilizing the hillside over time. However, if you make a very gradual back cut, you may not end up with much of a swale. Planting in nativetrees will help stabilize the soil and still be a productive part of the site's hydrology system.
You'll also want a machine with a bucket capable of being angled to create the correct angle of back cut for the slope, shape the swale and appropriately mound the berm of earth. Angled buckets can be very, very accurate with this process and save loads of time an money making up for poor (or even destabilizing) back cut issues and berm shaping.
Subtropical desert (Köppen: BWh)
Elevation: 1090 ft Annual rainfall: 7"
I am in the same boat in that I would like to hire the work done, but I don't have any confidence in my ability to explain the concept. Here is a video that might be helpful - it's what I was thinking of using as an explanation.