DryStoneGarden

Pack Mules on Duck Pass Trail

The topic for this month’s design workshop at Gardening Gone Wild is dealing with slopes. The description mentions “tips for building steps and paths to make slopes easier to navigate,” so I thought I’d cite the source I learned from, the forest service Trail Construction and Maintenance Notebook, which is online and in the public domain (Who owns this government document? We do!). The text might have a few elements geared towards public trails rather than residential gardens, but the diagrams are good and the principles are solid.

Step Construction

‘Build stairways from the bottom up, at a break in the grade. The most common mistake is to start part way up a grade. If you do so, the trail will wash out below the stairs. The bottom stair should be constructed on a solid, excavated footing. If it is constructed on top of exposed rock, it should be well pinned to the footing. Each successive stair is placed atop [or against] the previous stair. Dry masonry rock stairs usually rely on the contact with the stair below and with the footing to provide stability.

‘Hikers, especially backpackers, generally don’t like steps and will walk alongside them if there is any opportunity. The steps need to be comfortable to climb or they won’t be used. This means keeping the rise a reasonable 6 to 8 in (150 to 200 mm) and the run long enough to hold a hiker’s entire foot rather than just their toe. It’s helpful to armor the sides of steps with rocks to encourage users to stay on the steps.’

Stepping Rock and Riser Stairways

‘The most important area of the step is usually in the run. This is where most traffic steps as it climbs. If the step is composed of something like a board on edge with fill behind it, then the traffic will step onto the landing. Almost all foot traffic descending the step will walk off the edge of the step. The top of the step (and landing) should be stable and provide secure footing. The edge of the step should be solid and durable. The face of each step should not contain a batter that creates a “face run” of over 2 in (50 mm) from top to bottom. This is particularly important as the rise of the step increases.

‘Steps with landings are a bit harder to secure in place because the stairs do not overlap. Each step can either be placed in an excavated footing and the material below the rise removed to form the landing of the next lower step. This is usually the most stable arrangement. Or the step can be secured on the surface and fill used to form a landing behind it. The material used to provide the rise does double duty as a retaining structure when the landing consists of tamped fill. These steps must be seated well to prevent them from being dislodged by traffic. For stock use, landings should be long enough to hold all four of the animal’s feet.’

Riprap Stairway

‘In more primitive settings, you don’t need a uniform flight of steps as long as the route is obvious and there is solid tread at each stepping point. In the Sierra, a cross between cobblestones and stairs, locally called riprap, is commonly used for this purpose.

‘If the stairway climbs straight up the hill, each step should be slightly crowned to drain water to the edges or slightly sloped to one side. When the trail traverses a slope, each step and landing should be slightly outsloped. Water should not be allowed to descend long lengths of a set of steps or to collect on or behind a step on the landing. A drain dip where the trail approaches the top of the steps is a good idea.

‘In all steps, the key is to use the largest material possible and to seat it as deeply as possible. Rocks should be massive and rectangular. On steps that traverse a slope, it helps to seat the upper end of the step material in footings excavated into the slope.’

Rock Staircase

Best practice for building a stairway these days, if the rocks are big enough, is to butt them against each other instead of on top of each other. That way it is possible to repair one of the steps without redoing the whole staircase.

Rock Staircase

It doesn’t say in the notebook, but I was taught to kick test every step. If the stone moves when you kick it, it isn’t solid enough. A bit of a shock, sometimes, to see someone kick the structure you just labored on, but the step is definitely going to get kicked when people use it, so you might as well find out if it is going to last. You want to feel confident that your stairs are safe. It’s scary enough the first time you see a mule train crank through a set of steps that you’ve built even when you know the steps are solid. There aren’t mules in residential backyards, but the foot of a 150 lb. person can easily impact with 300 lbs. of force, so the basic principle is the same. Steps should be strong.

Steps also need to be regular. The test is to walk up and down the stairway without looking down at your feet. If the rise and run are even, you shouldn’t trip or stumble.

Old Town Wall Steps

In the front country I usually don’t get to work with stones that are “massive and rectangular,” but I still kick test every step and walk the staircase with my eyes closed. This set of steps, built with a local sandstone called Old Town Wall, was a lot of work, getting the risers to all match and the stones all interlocked enough to stay in place. I was working for a designer who is a serious dry stone purist, so mortar was out of the question. I think the steps and cheekwall took me longer than the entire rest of the wall.

Mortared Arizona Flagstone Steps

When it’s up to me — though I’m a dry stacker at heart — I usually build steps with mortar, usually by stacking flagstone with a recessed mortar joint. I don’t think that method holds up in areas with heavy freezes and probably not if the steps are going to be used by mules, but it does well in Bay Area gardens. A before photo of these steps and another mule photo are below. (more…)

Rock Step 'Clancy'

Instead of a bridge, my crew spent most of our time building rock steps, primarily on Duck Pass Trail in the Mammoth Lakes basin.

Arrowhead Lake

The trail to Duck Pass is one of the area’s quickest routes up into the high country, so it gets a ton of usage. The first section is a series of steep dusty switchbacks through lodgepole pine forest, but then you’re up in granite country the rest of the way to the pass. Arrowhead Lake is only a mile and a half in, with a fifteen foot high rock to jump from (unbelievably refreshing after a day of moving rock, jump at your own discretion), and then Skelton Lake’s another mile and Barney Lake’s another mile after that.

For some reason, this trail somehow became THE TRAIL for cross-country running teams from Los Angeles. Every day, we would have entire high school and college teams run through our work site, forty or fifty runners at a time, once on their way up and then again on their way back down an hour or two later. I’d never worked on such a popular trail. It was frustrating to have people constantly walking through our work site, but then, on the other hand, I’ve never had so many people thank me for anything I was doing. Literally hundreds of people thanked us. A much used and much loved trail.

High Timber Step

The trail is slowly evolving into a giant staircase. Because it’s a steep trail, gullies form and then steps are installed to try and control the gullies. The steps hold the tread in place on their uphill side, but then the downhill side of each step slowly erodes and it becomes necessary to add another step in front of it, which inevitably needs another step in front it, and so on. My crew spent the bulk of our time building new steps in front of the steps that past crews had built, and future crews will no doubt build more steps in front of ours. At times it felt a bit sisyphean.

Rock Step 'Bigeasy'

The steps we built are western trail steps, designed for horses and mules. Each step is supposed to be 4-6 feet long so that a horse can have its front and back legs on each step before stepping onto the next one. This step, Bigeasy, we actually sited even further in front of the timber step above it because that step is overly close to the next step above it. When that timber step inevitably rots out and needs to be replaced, it can be relocated a couple of feet forward and then all three steps will have proper spacing.

'Bigeasy' in transit

Finding the rock, aka rock-shopping, is probably the most enjoyable part. Moving it to the work site is often the biggest chore. Did I mention Sisyphus?

Rockbar Power Activate!

You do develop a good sense for the shape and size of each rock as you roll or skid it through the landscape, though. We gave names to most of the big ones. Basically, if you found the rock and spent enough time wrestling with it, if it was big enough and gravity-enfused enough, then it became ‘your’ rock and you got to choose a name for it. Names were usually descriptive, but sometimes random. For instance, Clancy (a big one fit snugly between Elton and John) was named after a forest service guy who had his macho turned up to eleven. Mammoth was an early 500 pounder. Bigeasy was surprisingly painless and easy to move. P.I.T.A. (Pain-in-the-Ass) was the opposite. Melon was low-hanging-fruit. Quickie was finished quickly. The macho, male names of our early rocks led to a series of less macho names, Howard and Jeffrey, then Fabio (very handsome), then Buttercup, Jewel, and Pearl. Showtime, the Three Musketeers, Mastodon, Alligator, and Shitzy round out the list, the last of the names I remember. A few of those steps and the view from near the top of Duck Pass are below. (more…)