Growing On and Under Asphalt
We did a lot of experimenting.
We built a sifter out of recycled lumber from someone’s deck that was being torn down. The sifter has four legs, and stands about four feet tall. A sifting box hangs from the legs via four chains. The sifting box is built out of four 2x4s and has heavy-duty hardware cloth attached to the bottom. Below the sifting box we attached some plywood that angles together towards the center of the sifters frame. This is important because we built the sifter high enough so that we can push a wheelbarrow under it. To use the sifter you simply shovel a few scoops of the sand and gravel mixture into the sifting box. You can then rock the box back and forth, which is easy because it hangs freely from the four chains. The sand slips through the screen, made from hardware cloth, falls down and hits the plywood, which guides the sand into the middle of the wheelbarrow parked below.
The sifter makes the job of separating the sand from the gravel very easy. We then mix the sand with cement and lime to make a mortar that we use to build our asphalt retaining walls.
We experimented with multiple saws, trying to find the best way to cut blocks from the asphalt. In fact when I was writing the grant the first saw that I used was a cordless dewalt circular saw, which only cut about six inches before the battery ran out. Once we received the grant funding we upgraded to a gas powered chop saw that cut fast but was hard to work with because it was heavy and the dust that gets kicked up made it hard to work for very long. We then rented a walk behind concrete saw from a tool rental shop. This saw was actually kind of small and while it also cut well the one problem we had was that it was too light. Our parking lot has lots of dips and bulges from years of neglect, which made it hard to cut in straight lines, which is important because we are trying to save money by reusing the asphalt as bricks to build retaining walls along the perimeter of the farm. So we eventually found a large used walk-behind concrete saw for sale. This saw is self propelled and it weighs a lot so it made it easier to guide the saw along our string lines we set up.
We discovered that it takes a lot of time to cut asphalt into one-foot by two-foot blocks. When we first started it took us about an hour to cut one bed, which is five feet by twenty feet. That produces asphalt blocks. The thing that slows us up the most is having to constantly raise and lower the blade on our big cutter, we are however slowly becoming more efficient with how we lay out our cutting lines, which has helped us decrease the amount of time that it takes to finish cutting one bed.
Another thing we learned is that we had to be ready to build our asphalt walls immediately after prying up the blocks. For the first six beds we stacked the blocks onto pallets so that they could be stored until we were ready to build our walls. Unfortunately the blocks melted together in the hot summer sun. Which would have been fine if they were already set in place, but instead since they were on the pallets those blocks were unusable. We are now building the walls as we pull up the asphalt.
So far the most labor demanding task is digging out the sand and gravel once the layer of asphalt has been removed. So far we’ve found that it takes two people two hours to dig out one bed and move the gravel to the storage space. The thing that slows us down the most is that the gravel is extremely compacted. Which make it hard to shovel it right out , so we have to take pickaxes to a small section at a time first loosening the gravel thus making it easier to use our shovels. We are thinking about finding a Jackhammer to experiment with, hoping that it can loosen the layer of gravel quicker and less labor intensively than the pickaxes.
We took one soil test and discovered that like we expected our organic matter in the soil below the asphalt was very low, only 1.1 percent. Our phosphate levels were also low: 11. And our pH is high: 7.7. One issue with our first soil test is that we were only able to test one spot, since we only had one bed finished at the time. We are going to take another test this spring now that we have more beds dug out.
We hosted two volunteer workdays consisting of 16 volunteers who helped us dig gravel and double dig beds. Our first two work days were an overall success, but since we were still experimenting with our different techniques for digging and cutting we were not as efficient with our labor as we hope to be this spring and summer.
We hope to improve the efficiency of our volunteer crews this season by increasing the number of tools available. We only had three working wheelbarrows this last summer and three pickaxes. Kansas City Community Gardens will be allowing us to borrow three additional pickaxes, six shovels, and three additional wheelbarrows.
We have not gotten very far with the tire boards that we hope to use as the walls on twenty of the forty beds. We did purchase our jigsaw back in January and we experimented on ten tires by cutting out ten treads to be used as boards. This process is hard and is not something that our volunteers will be able to do. We also found that the more worn down the tires are the easier they are to cut and use for the beds. We also found two good sources of tires. But we do not intend to start producing our tire boards until this fall, since we are going to be focusing on finishing digging out our remaining beds this spring and summer. We plan to cut all the tread and then have volunteers help us assemble the boards together.
Our website is about halfway done and we have already compiled lots of media such as pictures and videos, which we will use to compile a how-to best-practices guide for converting an urban parking lot to growing space using the methods described in our grant proposal.
So far we have used the grant funds to purchase spades and forks for double digging. We purchased a grinder and jig saw for constructing the tire boards, and we spent money on renting a concrete saw and purchasing a blade.
-This is hard work
- Last summer was really hot.
- Cutting asphalt from one bed takes 45 min.
- Digging out sand and gravel from one bed takes two people two hrs.
- Double digging one bed takes two people 1.25 hrs.
- Soil pH: 7.7
- Soil Organic Matter: 1.1 percetn
- Phosphate: 11
- Potash: 161
- Total Volunteer Hours: 64 hrs
- Total Beds Complete as of 3/31/12: 8 beds; in progress 20 beds
WORK PLAN FOR 2012
-We will have three workdays in the month of April; we are expecting 48 volunteers and 352 volunteer hours devoted to the project in April.
-We will also have one big work day each month through the fall.
-We are expecting to have all the remaining beds cut and the asphalt removed by the end of April.
-In preparation for our April workdays we will lay the foundation for our walls so that we just have to move the asphalt blocks into place. We will also have the remaining twenty beds cut and ready.
-Once we get all the beds dug out, hopefully by the end of May, we will finish double digging the remaining beds.
-In the fall we will build our two demonstration beds with help from Kansas City Community gardens since it is their model that we are demonstrating.
-We will also begin construction of our tire boards with the goal of having them installed by the end of October.
-We will spend the rest of the winter compiling our data and media into our how-to guide that will be shared with Cultivate Kansas City and Kansas City Community Gardens.
-In the Spring of 2013 we will host a workshop at our farm sharing our results and demonstrating all the techniques we learned along the way.
In June this last year we were a part of the Kansas City urban farms and garden tour; around 95 residents from around Kansas City came to visit our farm. We got great feedback about our project. We setup our farm to show the different stages of converting the parking lot to growing space. So we had one sample bed for each step of the process. The first bed was marked and measured out with our string lines; the next bed had all the asphalt blocks cut but the blocks remained in place. The third bed had the asphalt blocks removed and stacked on a pallet next to the bed to show the amount of asphalt being removed from one bed. The third bed also revealed the layer of sand and gravel, where we demonstrated the compaction and showed what it took to loosen and dig out the gravel. The fourth bed was completely dug out revealing the soil below both layers of sand, gravel, and asphalt. The sand and gravel layer was also stacked next to the bed to show the amount of material that had to be removed from each bed. This is where we also shared about the conditions of the soil; we taught about the how soil compaction affects plant health as well as the importance of organic matter in the soil. We also shared about the amount of time it takes for new healthy soil to be produced with sustainable growing methods and how soil loss is a serious issue we must address in our modern agricultural practices. The fifth bed was where we demonstrated how we plan to incorporate organic matter into the soil; we also talked about other methods of improving soil health such as cover cropping. The last bed was a finished bed, showing what we hope to replicate. It was a great opportunity to share our SARE project and information on sustainable agriculture.
We have three volunteer days planned for April. There will be about 20 people helping us on the 19th and 20 more on the 20th. Then on April 28th we will have about ten volunteers helping us. We then hope to have a monthly workday throughout the summer.
We plan to continue to have volunteer workdays this coming season where we invite neighborhood members as well as supporters to come and help with the project.
In the spring of 2013 we will host a workshop at our farm sharing our results and demonstrating all the techniques we learned along the way. We also plan to distribute our how-to guide.