February 7, 2014

Urban Edible Paradise: Backyard Renovation

With the planning mostly done, and a contract signed with a landscaping company, we were ready to renovate the back yard.

On an early November day, Tom's crew of 7 showed up and ripped into the backyard. It was amazing to watch. The fence came down, the trees were cut,

 asphalt broken up,

 Bobcat wreaking havoc.

A place we had gotten to know over more than a decade and seemed so static was dramatically changed in just one day.

Over the next couple weeks, these guys built a bunch of retaining wall, moved tons of soil, trimmed trees, made beds, spread mulch, put in some irrigation pipes, window wells, brick walkway, the back section of fence, a large number of fence posts, and a bunch of other stuff as well. Child 1 loved watching them drive the Bobcat and the dump truck around the yard.

Becky was busy fiddling around with plan after plan while the crew worked outside, and we often didn't have final measurements or directions for them until they were poised to put something in the ground or make irreversible choices. Once it was committed to reality, sometimes literally in stone, it also became fixed in the plan.

The back section fence was to be installed by Tom with some particular details I specified, and they would also put in the fence posts for all the other fencing. The back fence turned into a pretty big headache for everyone, but more on that later.

The plan is for me to build the side fences and gates, which will do with wood ordered from lowpricedcedar.com, along the lines of the small section of fence I made last summer. Having nearly 500 fence pickets to do though, I need to figure out how to make production of them less time consuming. Current idea is to build a robot to do most of the picket top shaping, with a little final chisel work and sanding by hand. I'm also going to change the support rail and picket attachment design.

The big wood order came by LTL freight from the pacific northwest. Shipping was pretty expensive, but even still it was far cheaper to go this way than buying the same material locally (I got numerous quotes on it). Estes, the carrier, called the morning it was due for delivery and said they would not be able to get it off the truck with a liftgate for curbside residential service like I had paid for. They refused to deliver the parcel, basically unless I had a loading dock to put it on or a forklift to take it off. So I rented a truck and picked it up at their terminal, then unloaded it by hand the next day.

It was 2.4m long, one pallet wide. I'm pretty sure they could have got it on a lift gate. Child 2 and Child 1 played in the truck and helped me by moving in the small pieces. They also hung out at the workbench using hand tools on scrap wood.

I stacked and partially stickered it in the basement.

 There it awaits my attentions.

Originally I yearned for drystone walls all around the house. Drystone is great because it drains well, can shift a bit with temperature and soil movement without cracking, can be re-built in a straightforward manner when necessary, and I think it looks sublimely good. I read a bunch of books on drystone walls, and even took a really cool class at Hancock Shaker Village in western mass while Becky was pregnant with our first child.

Wow. I look so young and full of vim in that picture! I am now too fat to fit in those overalls, and otherwise feel a lot older and more tired. 

There were about 10 people in the class, and we took down and rebuilt a section of dry stone retaining wall about 6 meters long and 1.5m high. This took 2 days, or 20 person days. I was eager to build the retaining walls in the backyard like this, but the sad reality is that the amount of time I seem to be able to scrape together for such projects is not large. It could easily take me decades to build those walls.

On the downside, drystone is a lot of work to build, and there are not that many people who have the experience, knowledge, and patience to do a good job. If you can find someone who can do it, it is going to be really expensive. It's also not the best thing for durability where kids are going to be climbing up on it and running around on top of it, unless its built from big pieces which takes a crew of skilled workers, hydraulics or a lot of manpower and windlasses and booms to maneuver. Here is a big foundation stone being moved at my class.

Another option we considered was reclaimed granite blocks. To get to a height for the two retaining walls in back of 60cm (2'), reclaimed curb was not going to do it, unless stacked flatwise several courses high. We didn't favor the look of flat stacked curb.

We looked at reclaimed foundation block, but it would have cost about $10K in materials alone to run the two walls. Plus the Bobcat was the extent of machinery readily available to Yardworks, and it was not really up to slinging the big granite blocks.

The option Tom proposed was a blasted ledge wall, built so that the exposure of mortar on the outside was minimal. Using aged or reclaimed stone would have looked nice, but the material was going to be too costly. So we used newly blasted stone, which Tom says comes from construction sites where they need to take out rock during building.

The crew is clearly experienced with this construction method and did a excellent job of it.

They sort of fit the stones together to make a front and a back face, with more attention paid to making the front look good. Then some concrete is poured in between to hold everything in place. This makes the fitting and form factor requirements of the stone stacking much less strict than with drystone work. At the top of the wall, small stones are fit in to make it more level, and the mortar is dressed in between the top stones.

They built the walls on a gravel base, but not below frost line. Tom says he's been building this type of wall for a long time and it should have good longevity. Its not totally reliant on mortar to hold it together. No special measures were taken in relation to drainage from behind the wall. The walls are short, the area behind them is not that large, and the concrete put in the center of the walls doesn't form a continuous barrier. So hopefully they will be ok.

The walls ended up being much more work than I had imagined. They built both walls together, then backfilled them with soil, so the back one ended up being quite a bit more stone than one might have expected. Tom said they brought in over 50 tons of stone for the walls, and they probably mixed 50-100 bags of concrete one sack at a time in a wheelbarrow while putting the wall together.

Granite Blocks
I did really like how the antique granite looked, and while we had to scale back to using new granite for the little center steps in the lower terrace and ditched the idea of granite for the walls, I felt that a couple of strategically placed antique blocks would make the landscape design more interesting. I worked with oldenewenglandgranite.com to scope out some pieces I had in mind. They sent pictures once they had identified some candidates, and Tom picked them up in his dump truck. One large stone, about 90x45x40cm (36x18x15") was used in the center of the rear retaining wall. This was tough to get into place since it was too heavy for the Bobcat. Tom ended up dumping it right off the truck in nearly the right spot and with some levering it was put in place.

In retrospect I should have had them set the big stone proud of the wall by a few cm since as it turned out it kind of blends into the wall too much. Still, I like having it there and I think it looks good.

Two smaller blocks were put as sort of seats positioned out in the future grass/bed area. These look cool sitting out in the space.

What if we want to move them around? Maybe we could elevate the rocks a bit in the fall, freeze a layer of ice on the ground in the winter, then push them around to their new places. Curling with 250kg rocks!

Josh, the guy I worked with at the stone yard, said these blocks were bought from the city of Boston and had been taken out of a sea wall or foundation in Chelsea during the Big Dig. They have a lot of character and look classy in the yard.

Side Path
The new walkway is brick, laid from the Boston City Hall paver product purchased from Landscape Express in Woburn.

The guys made a compacted base of gravel and crushed stone, then laid the bricks in and trimmed all the ones that needed it.

It looks great! You can also see that I am almost done with the trim on the little back porch. Just need to make some brackets, plug a few more screwhead holes, and finish up the painting. The door does need a storm, which I am slowly working on in the basement.

Before we first planted a small garden, we sent some of our soil to Umass for testing. It came back "medium" on the lead screen. The recommendation was that eating fruits was ok, but we should not plant greens or roots. We grew a few tomato plants, and eventually our housemates made us two raised beds in front where we didn't need to worry about the soil so much.

Knowing that urban soil in general is often contaminated and poor in nutrients, and also that our specific lot had some issues in that regard, we sent soil samples representative of five zones to Umass for analysis after the renovation.

We got the usual nutrient tests, lead screen, and for most of them the additional organic matter test. The worst result on lead is from right next to the house. This came up as 68ppm extracted, which is midway in the "medium" range of 22-126ppm. The side bed came in at 25ppm, at the very low end of the medium range. The new soil brought in, the front garden box, and the existing soil in back that had been scraped down during grading all were in the low range.

Reading the recommendations at Umass, It is recommended not to let pregnant women or children come in contact with soil in in the medium test range, and not to grow leafy vegetables in it. All the unmodified soil in our yard is probably in the medium range. This is typical for our area and is a legacy of 100 years of leaded gasoline and lead house paint.

It is not really practical to not let the kids come in contact with the soil anywhere on our lot, but we do try to keep it to a minimum by keeping the dirt covered with mulch or plants. Per Massachusetts law, our kids have lead tests done on their blood every year, and they have all been low. So our setup is ok as is, we just have to take care not to increase exposure.

As we talked to landscape contractors, we looked into the idea of scraping off the top 30cm of soil from the whole lot and taking it away, then bringing in new soil. No one thought this was a good idea and said it was going to be impractical, a huge amount of work, and very expensive. So we let that one go.

Further reading indicates that much of the problem with gardening in leaded soil involves ways for the soil to get ingested, rather than uptake of lead in the plant tissue itself. A potato is going to have more soil on it than an apple, and will involve more soil disturbance in planting and harvesting. Planting perennials which won't require constant working of the dirt and keeping the surface mulched seems like it should keep the level of soil exposure down. In addition, I am planning on sending out plant tissue from things grown in these areas for lead analysis before we eat much from it. There are only a few things that would be right next to the house and in the worst lead area.

Zone 1
These are the new terraces behind the retaining walls. They were filled partly with soil scraped up during grading from the side yard and zone 3, then topped with 30-50 cm of new topsoil from Landscape Express; their "Superloam" product. The soil sent for test is the new stuff on top. Probably the fill underneath has lead, but being buried under the new soil will help contain the leaded soil.

The new soil is 6.7pH, very low in lead, in the Optimal range for nutrients (other than being too high in Calcium), and has 5.1% organic matter. So this seems just about perfect.

Zone 2
The front garden box. This was originally filled with straight compost that Alexi and LeeAnn laboriously hauled in a Zipcar truck from Ipswitch. Much of our compost in the intervening years has also gotten dumped on here. But the last year or two many things have been growing very poorly in there. Lets see what the soil test says.

Wow, the meters are pegged in several areas. The level of K is 27 times the high limit of the optimal range. Ca and Mg are also extremely high, and organic matter is almost 11%. The organic matter is not surprising since it is basically aged compost, but how did the other levels get so ridiculously high? Not sure what to do to fix it, other than diluting it with other soil?

Zone 3
This will be planted in clover/grass lawn mix for the time being, and may in future turn into more gardening beds. Much of it was scraped down during the grading of the back.

It is low lead, which is interesting since it is not offsite material like zones 1 and 2. I have to think the grading took off the top layer of soil, where the lead was more concentrated. The nutrient levels are quite low. Maybe this is from the fact that it was scraped down and the lower layers don't have much nutrients. Or the fact that it was scraggly lawn over the top of it for decades. In any case it is clear this soil needs some help if we expect much to happen in it. Maybe some aerating with a broadfork followed by thick sheet mulching for a year. Or a few years of cover crops, including daikon to do some bio-drilling. But its nice to have low lead there in any case!

Zone 4
This was the worst area for lead, which makes sense since it is right next to the house and has been polluted with decades of lead paint runoff. Other levels look ok, though it is rather high in Zinc. Also high on Ca, like Zones 1 and 2.

Zone 5
This area is slightly above the low lead cutoff, so we won't worry excessively on that account but will of course keep it in mind.

In contrast to other areas, it is a little low in Ca (but way high on K..?). How do these nutrient levels get so out of whack? Organic matter is pretty good, surprisingly, micronutrients are ok. Biggest problem with this area is that we'd like to plant blueberries there. This would involve dropping the pH at least 1.5 points. I've read that dropping pH of soil more than a point is difficult and expensive to do and requires continuous application of amendments. Maybe we should look at something that won't take as much soil modification, like Haskap.

Next Steps
As spring rolls around, we will plant a bunch of the bushes, trees, and perennials that we've scoped out. Plus some annuals for this year. We may hook up some irrigation, if we should tire of dragging a big hose around for watering. I'll start working on the side fences and gates. I need to build the trellis for the apple trees in back.

I saw this book in the back of the Fedco catalog, and got it from the library:

Its pretty fun to read. I'm excited to plant me some oats and broomcorn!