How to Build Swales (Part 1 Surveying & Planning)
One thing I learned as a landscaper is that a successful landscape construction job depends on proper planning. In planning a swale project in particular, or many projects in general, these are a few things that you should consider.
Design- I designed the swales by finding my contour lines, mapping them, and determining how many linear feet of swales I wanted to install, and at what depth and width. I determined that I wanted to install about 2000 linear feet of swale, with a 16 inch depth and a 2 foot width. I marked my swales with white turf marking paint. This was incidentally a requirement of the utility marking company, so they would know where I was digging. They specifically requested I mark with white paint.
Materials- I decided I was going to fill my ditches with a rough wood mulch as that would be cheap and easy to move with my tractor. I was going to fill the trenches with 6 inches of mulch. It is not necessary to fill them completely. My thought is that over time organic material will get caught in the trenches, and feed the berms downslope. Based on the volume of mulch I needed, I ordered around 100 yards of mulch if my memory serves me correct. I also needed a seed for my berms that could germinate late in the fall to hold the berms, but not take over, as I was planning to seed in a nice polyculture in the spring. I decided on annual ryegrass. One bag was all I needed as my berms totaled about 8000 square feet and one 50 pound bag of ryegrass will cover 10,000 square feet. I already had some dutch white clover, which I was going to mix with the ryegrass seed and some lime. I am not expecting the clover to germinate until spring.
Underground Utilities- I called Miss Utility for Pennsylvania to mark my utility lines. It turns out that my cable and electric go through three of my swales. I will have to hand-dig those areas. Be careful, because not all utilities are marked through this service. I had a crew hit a propane line once with a trencher, because I didn’t know it wasn’t marked. Thankfully, nobody blew up. The fire department was not amused.
Tools and Equipment- I figured out what tools and equipment I would need for the job. I settled on renting a mini-excavator for a week. It had a 21” bucket, so I figured with the teeth it would give me the 2 foot wide trenches I was looking for. I had the hand tools, and the tractor that I needed. (tractor with a front loader, 2 metal rakes, wheelbarrow, various shovels, A-frame, level, tamper, bucket, digging bar, turf marking paint and gun, flags, and a pick axe)
Labor- At first I thought that I could just do all the work myself, but I started to think about how long it would take me. Even with the excavator and the tractor, I figured the job would take 160 man hours, with a lot of hand work. That meant that if I really worked hard it would still take me at least three weeks. That would put me even deeper into the fall, and if I got bad weather it could really be a disaster. I decided to hire three temporary laborers to do the hand work for the week. I could run the machines. If all goes well, we will be done in 5 days.