I declared dislike for concrete pavement. So what was I to do with the concrete pavement that already existed, such as the parkway path? Rip it up and replace it with something that has a better longevity and is more artistic?
That was a very tempting thought, but it came up against my practical inclinations. The best time to replace things is when they start falling apart. The existing parkway path was not at that point – yet.
That left me with the question about what to do with this monolithic gray mass.
How about the “putting lipstick on a pig” approach? I could frame the concrete path with a row of salvaged, old Chicago street pavers, transforming it from monolithic to something the eye can manage.
Unlike the parkway path with the pavers, the monolithic concrete slab did not need a structural constraint around the edges. It was both, constraint and pavement. That allowed me to place the framing pavers on a simple gravel base, instead of a concrete bed.
The pavers will get almost no traffic, and with that almost no stress. People prefer to walk along the centerline of the path, i.e. on the concrete slab. Rarely will anyone need to step on the pavers.
My last thought on this subject went toward deconstruction. At one point, I would like to replace the concrete slab. Removing the paver edge and concrete slab will be a easier with the pavers just sitting on gravel.
I had to excavate our parkway rain garden to a ponding depth of six inches. It was a very simple task, except for the treasure hunting aspect of our urban soils.
I didn’t want to start with the excavation until I had a barrier around the rain garden. Although the drop into the bottom of the rain garden wouldn’t be more than nine inches, I still was worried someone could fall into it. Now that I had a fence surrounding the parkway rain garden, with the exception of the fence panels, I was ready to start digging.
My goal was to plant my rain garden plants into a medium that resembles top soil. That was not an unrealistic goal, considering that the top layer in the parkway was a fairly good quality topsoil. But what was lurking underneath made things a lot more interesting. In a way, it was a little bit like archeological discovery that told a story corroborated by the surrounding landscape.
The parkway rain garden will stretch across two city lots. To the east is a vacant lot. It once had a building on it, but that was torn down. I am not quite sure when but it must have been sometime after the 60s. To the west is the lot on which sits our house, which was built in 1902. It think it is fair to assume to most buildings on our block were built around that time, including the house that once stood proudly on the vacant lot.
In my preparations for excavating I noticed that the parkway at the vacant lot had topsoil layer of about four inches, followed by a good six to eight inches of soil mixed with rubble. Below that was a decent layer of dark colored subsoil.
The parkway section in front of our house did not have the rubble layer. The topsoil slowly transitioned into an equally dark colored subsoil. It comes close to an uncontaminated or clean soil profile.
That may speak to the construction methods around 1900. I could assume that the crews cleaned up the site once they were done with the building, but I seriously doubt that. I think it is more likely that back in the day, builders didn’t use the equipment we have available today, and thus didn’t recklessly ruin the soils the way we do today.
The rubble layer at the vacant lot, on the other hand, most likely dates back to the tear down of the building.
Overall and given our urban environment we are blessed with decent soils, which we could maintain as long as I could find a way to address the rubble layer.
My method was as follows: I started by excavating and saving the topsoil, which is now in a stock pile in the vacant lot. Next I excavated the rubble layer and hauled it off site. Once I started excavating to the west, I relocated part of that topsoil to the east, until I had met my ponding depth of six inches.
A Tom Sawyer moment
When I started excavating, it was still summer break and the kids on the block were stifled by boredom, including four brothers who live two houses down. First they found some distraction by watching me dig. That lasted about ten minutes. Then they riddled me with questions. That lasted a little longer. Then they argued among each other who would do the best job digging. And finally they were begging me to help.
I got my spare shovel and let them have a try. To my surprise, the youngest and smallest of the four was not only the most skillful, but also the most relentless. He almost kept up with me. And once the last of his brothers had his turn, he wanted right back into the game – and I was grateful for the help!
Did I mention that I would like to convert our parkway into a rain garden? In case you haven’t read the previous posts, let me mention it again.
A rain garden is a shallow excavated and vegetated area that allows stormwater runoff to infiltrate into the ground. That begs the question: where will the stormwater for my parkway rain garden come from?
The contributing area
The adjacent concrete sidewalk will contribute some runoff, but not much, because the sidewalk surface area is actually smaller than the parkway rain garden.
The stormwater that I would really like to manage in the rain garden comes from the street and gutter. Surface drainage on our street is poor and we always end up with standing water in the gutter – sometimes for a couple of days, and sometimes for a couple of weeks. I would like to drain and infiltrate the street runoff into the parkway.
With that goal established, I could look at the appropriate rain garden depth and storage capacity. The elevation of our curb averaged around three inches above the gutter. The top of the curb roughly equaled the grade elevation in the parkway.
To manage the street runoff from the half of the street bordering the parkway (924 square feet), I should plan for a six inch ponding depth across the 470 square feet of rain garden. At a tested infiltration rate of two inches per hour, the parkway rain garden should be able to handle the 100 year design storm for the 924 square feet of contributing area.
The issue of conveyance
The next big question was, how do I get the runoff into the rain garden? I have a street curb that is in the way.
Typically one would rely on curb cuts to allow the water to flow from the street and gutter into the rain garden. But this is not my curb and I don’t want to get into trouble with the City. Whatever I do has to be easily reversible in case they end up not liking what I am doing.
I think I’ll start by drilling a number of one inch holes through the curb at the gutter low spots. Those holes can be easily filled and patched if needed. But because the holes only allow a limited amount of volume to flow through at any time, I may not be able to get all the runoff from intense downpours into the rain garden. So even though the rain garden could manage a 100 year design storm, the limited conveyance capacity may reduce that effectiveness.
I also will have the issue of maintenance. There is always a lot of debris in the gutter, which could clog the one inch holes. I will probably have to check on those holes a couple of times a month to keep them clear.
And I have two paths crossing the parkway, which leaves me with three rain garden cells. To connect these cells hydraulically, I incorporated PVC pipes under the path. This way runoff can easily flow from one rain garden cell into the other.
I get a kick out of reusing and repurposing salvaged materials, whether it is in the house, the yard, or in this case, our parkway landscape.
We have two gates to our property: the main gate leading up to the front door and the side gate leading into the side yard. It made sense to provide a path crossing through the parkway landscape at each gate.
We already had a path crossing at the main gate, although it needed some additional work. More about that later. But there was no formal path crossing at the side gate. While laying out and installing the parkway knee fence, I made sure to provide a gap for a path to connect to the street.
A material question
No, I will not use poured concrete. Boring! It can be the default pavement choice around the country all day long. That doesn’t mean I have to like it or bow to it. And on top of that, it’s not even that practical. It tends to crack over time. And repairing it always looks like – well – it has been repaired.
I had some beautiful salvaged graystone and clay pavers in my yard that were perfect to craft a path crossing through the parkway. I knew I could repurpose the graystone into a curb flanking the path left and right. The clay pavers are modular, which makes for a much higher quality pavement if installed correctly. It doesn’t crack, because it has cracks already built into it – the joints between each paver. And it is easy to repair, because – well – it’s modular.
Building it up from the base
I put a decent eight inch base down using recycled aggregate and made sure to compact it thoroughly. Integrated into the base were two two-inch PVC pipes. They will hydraulically connect the parkway rain garden to the east and west of the path.
I also had the city water vault and shut-off valve in the path of the parkway path. (Probably not perfect, perhaps even painful, to pitch this many p’s in one phrase. But once I plunge into a pattern of packing p’s I am past picky.)
I had to align the pavement elevation with the valve and vault. The elevation of the valve was set and I couldn’t change it. But I could adjust the elevation of the vault base and I did, so that it matched the path slope determined by the valve.
With the pavement elevations set, I put a concrete base down and set the curb using my salvaged graystone. Most paver installations need a structural constraint around the edges, or otherwise the pavers start migrating over time. That is particularly true if they are adjacent to a downward slope like my planned rain garden – even if it’s only a four or six inch drop. So the curb on a concrete base was a must.
After the concrete had cured for a day, I could bring the gravel base up to the right elevation and start to screed the sand bed (setting layer) for the pavers. Then I set the clay pavers right into the sand bed. There was some fitting involved along the edges and around the vault. To fill the smaller gaps I switched from clay pavers to graystone scraps.
To finish the job, I needed to fill in the paver joints with sand, make sure the pavers sat firmly in the sand bed, and assure the paver surface was even. The sand can be broomed and washed into the joints. To set the pavers firmly I used a two by four and a hammer and whacked the pavers into the sand bed. That process also allowed me to get to an even surface.
The fence posts were in place, which allowed us to install the bottom and top rails. Because the bottom rail will sit right at the pavement edge, we had to excavate a little more along the sidewalk. The curb side edge was already excavated from our paver edge installation.
We cut the top and bottom two by four rails to length and attached them with structural connectors to the posts. At the same time, we pre-drilled the two by two rails that will hold the rebar and attached them to the back of the two by four rails.
I chose to only install the fence rails around the perimeter, because I still have to excavate for the rain garden. That will be easier to do if I can move up and down the parkway and in and out at the path crossings.