Growing On and Under Asphalt

Final Report for FNC10-813

Project Type: Farmer/Rancher
Funds awarded in 2010: $3,835.30
Projected End Date: 12/31/2013
Region: North Central
State: Missouri
Project Coordinator:
Robert Wright
Conception Community Farm
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Project Information


Conception Community Farm is a small urban farm in Kansas City, Missouri. We are located in an east side neighborhood that is known for crime and economic blight. Neighbors in the community are mostly African-American. Most of the older families had deep ties to farming before they moved north. Younger, transient families do not have much if any experience with growing food. The land that we have been converting into a farm for 4 years now sits on the property of a church that has been a staple in the neighborhood for close to 100 years. The church owns most of the city block, which is a little over two and a half acres. The downside of this land is that it is mostly covered in asphalt parking lots, which have sat abandoned for many years. These parking lots had trees and bushes growing through the cracks when we first moved in. The rest of the property consists of steep slopes and two city lots that have had houses demolished on them within that last 10 years. We have been experimenting with multiple ways of transforming this property into a productive farm that would serve the neighborhood. A lot of the work we have done has been rooted in the value of using local resources and using methods that are affordable and replicable, especially for our neighbors in the community. We use tires, pallets, old deck lumber, reclaimed fence pickets, and pretty much anything else that we can find in the neighborhood to build terraces, raised beds and other farm projects such as our chicken coop. We grow mostly vegetables: lots of greens, tomatoes, onions, sweet potatoes, etc. We have 23 hens and one turkey that we raise for eggs. We get about a dozen and a half eggs everyday which excites us because we can now sell some to our neighbors. On the two lots where the houses were demolished, we have 30 fruit trees planted, and 700 sq ft. of berries. Our SARE research project was written so that we could experiment with different strategies for transforming the parking lots on our property into productive growing space. We focused on one parking that has a foot print of 10,000 sq ft and so far we’ve been able to bring 4,800 sq ft into production.

No sustainable practices were conducted before this grant.


1. Convert an abandoned parking lot into productive growing beds. Compare labor and cost of four different methods for building beds. Experiment with/develop methods that are affordable for low-income communities.
2. Experiment with/develop methods for cutting out asphalt, and digging out gravel from abandoned parking lots. Experiment with ways of incorporating organic matter into heavily compacted clay sub soil below the asphalt parking lot. Experiment with /develop methods for reusing asphalt and gravel left over from digging out beds.
3. Test a method for constructing bordered raised beds out of used tires found in the neighborhood.


Clearing the Parking Lot:
We started with a parking lot. The lot was covered with grass, trash, and chunks of broken asphalt. In the cracks and along the edges there are shrubs and small trees growing. The first thing we had to do was clear the lot so that we could begin work. This involved, strangely enough, scraping an inch of soil off the top of the asphalt, so we could cut through the parking lot to get to more soil. Most of the soil and plant debris was mixed with small pieces of asphalt. We piled this up in the corner of the parking lot. It took a couple of volunteer workdays to get this work done. We used digging spades to scrape the asphalt as well as brooms and a gas-powered blower to get up the small pieces. When we were finish, it actually looked like a nice, useable parking lot. The joke at the time was the church was going to have second thoughts on letting us tear up the parking lot now that it looked so nice. We quickly moved onto the next steps.
Designing and Marking the Beds:
We designed the farm to have 32 beds that would be 90 sq ft apiece, each being 18 feet long by five feet wide. That would give us a total of 2,880 sq ft to start. Each bed would be spaced two feet apart. When it came to making out the beds, we found that screws actually screw into asphalt rather easily (we used 3-inch screws). We marked the corners and with a cordless drill, screwed in our screws. We only inserted the screw a couple of inches and left about an inch above the surface so we could tie string between each screw that would act as our marking line and guide asphalt hauled away. Our original idea was to cut out the asphalt in one-foot by two-foot blocks. This required putting a string every foot. This also took a considerable amount of time. I spent around 3.5 hours marking eight beds with screws and tying a string at tone foot spacing. Eventually we figured out how to use the guide on our concrete saw to space our cuts off the first cut. This ended up saving a lot of time on the last beds because we no longer had to run a string for each cut.
Cutting Out the Beds:
When groups come to volunteer or tour our project site I tell a funny story about our evolution in cutting asphalt. When we first had the idea of cutting up the parking lot to build our farm I took my cordless circular saw, and with a masonry blade I tried cutting through the asphalt. I got about 16 inches before my battery ran out. With 3,456 lineal feet of asphalt to cut and only 16 inches down, we knew we were going to need a much bigger saw. When we took our first soil samples from the parking lot, we used a gig handheld gas-powered concrete saw to cut two ft. squares. That saw cut really well and if someone was just doing a couple of beds it would probably be sufficient, but for the scale we were working at we needed a walk-behind saw. The difficulty with using the handheld saw was having to work bent over. Furthermore, the dust and water thrown up by the saw was thrown all over you.
When we really got into cutting we rented a smaller walk-behind concrete saw from Home Depot. The saw rented for $70. This saw was probably the same size as our handheld saw, however it was mounted on wheels so we could easily guided it along the cut lines marked out in the previous step. That saw also cut as well as our handheld saw and it had a lever to adjust blade depth, which was something the handheld saw lacked. The first issue with this saw was that it was not very heavy and was not self-propelled. Our parking lot had lots of bumps and potholes in it due to all the trees and shrubs that had grown up through the pavement. This made it difficult to keep the saw going straight, and this particular saw was hard to push because the small wheels kept getting stuck. This made the work frustrating and long. It took us five minutes to cut one 18-foot pass. Each bed required six cuts. Those five minutes did not include raising/lowering the blade and repositioning the saw after each cut. Those were just the long cuts. Cutting across the beds (five feet across) took a lot longer because we would need to raise the blade every five feet, move forward two feet, realign, lower the blade, cut five feet and repeat across eight beds per pass. We did this raising and lowering of the blades because we only wanted to cut asphalt out of the 18 foot by five foot area of the beds. Everywhere else the asphalt would remain as pathways between the beds. The first day we rented the saw, we got six beds cut out in about seven hours. Our inexperience was probably the main factor that made the work so slow, but it did get us thinking that we should maybe buy a bigger concrete saw.
Since we were worried about spending a lot of money renting a saw at least five times at the pace we were cutting, we began searching Craigslist for a used walk-behind concrete saw. It turned out that there are a lot of them, and they are fairly cheap considering that they sell new for over $4000. We came across a bunch in the $600-1000 range; however we purchased ours for $500. It is a Core Cut CC1800, with a 16 hp Briggs engine. It just needed filters changed and a carb cleaning. Our saw is self-propelled with an adjustable speed control. This allowed us to focus on guiding the saw along the marked lines rather than trying to push and keep it straight. We thought this was a wise investment for the future of our project, mainly because we do not plan on stopping at 32 beds. Eventually we would like to have all the abandoned parking lot converted into growing space. Plus we reasoned that we could probably sell the saw after we were finished and get at least what we paid for it and possibly more.
A note about water and blades: if you have never used a concrete saw before, you need to have a water source to keep the dust down and the blade cool. We hooked up a hose to a neighbor’s house. The saw should have a female water valve to attach your hose to. Depending on the saw, there should be an adjustment valve that regulates how much water comes out. You don’t need it on all the way; I turn it on, start cutting, and back it down and set it right above the point where the water coming out of the cut is muddy. As far as blades go, we purchased one 14 inch all-purpose asphalt/concrete blade. This cost around $90.00. We were not sure how long these blades would last, but now that all of our cutting is finished, at least for this phase, we still have a lot of life left in the first blade. Along with keeping water on the blade, we only lowered the blade as deep as the asphalt which was 2-3 inches. That will also help increase the life of your blade by cutting into the gravel as little as possible. Once we finally got our final saw, and we built up some cutting experience, the time I took to cut each bed was cut down significantly. Our last set of eight beds took us 4.5 hours to cut all eight; a little over 30 minutes each bed.
Removing the Asphalt Blocks:
We would usually cut eight beds at a time and then dig out those eight beds before we cut more. After we were done cutting we had all these two-foot by one-foot blocks of asphalt. The original goal was to stack these up and save them to be used for building terraces on some of the sloped portions of our farm. Pulling the asphalt out is easy once you get one piece out. All you need is a pickaxe. Drive it into one of the cracks and then pry out the first piece, and repeat for all the rest. Each cut bed produced 45 asphalt blocks. After we pried all the blocks out, we stacked them in neat piles on the pallets in a corner of the parking lot. We later learned that this was a big mistake. Our project requires a lot of labor, and we planned to experiment with building our asphalt retaining walls after the beds were completely finished. That way we could focus on building the beds, which was a main goal. What ended up happening was the hot temperatures heated up our asphalt block on the pallets. The asphalt blocks began to crack, warp, and fuse together into one giant asphalt block on a pallet. We then decided to get rid of the asphalt because it was not going to be useable. If you are trying to save the asphalt for purposes like building retaining walls, it’s best to use them right away to keep the damage from happening. We did end up making a second stack. We didn’t stack this one as high as the first. Though not perfect, it limited the damage, so those blocks were still useable. By the time we got to our last beds, we decided we did not have enough time left to continue with our method of cutting out the blocks. Not only did it take a lot more time cutting out the blocks, but our idea of using the blocks for retaining walls seemed to be too much effort. On the last eight beds we just cut the perimeters. To get the asphalt out, the same method of course produced bigger pieces, but asphalt is brittle so it was easier to break it into smaller manageable pieces for removal.
Digging Out the Sand and Gravel:
Up to that point the work was fairly easy and not too labor intensive. However, this step was more work. A majority of our volunteer groups helped out with this process. Up to that point we’d hosted 10 volunteer groups, totally 90 volunteers and 480 labor hours. While our volunteers helped us our tremendously, we did not use their rates of digging to calculate the labor it takes for constructing a bed. Each group was so different. Most of them had eight to ten people working with them, and they would work in four-hour chunks. Some groups in those four hours could get 4 beds dug out, while others would barely get two.
After the asphalt had been removed, there was six inches of compacted sand and gravel that we had to remove to get to the soil line. Because it was so compacted, we could not just dig a shovel down and pull it out. We first had to pickaxe the whole bed to loosen it up enough to dig out the sand and gravel. We tried multiple methods for doing this work. We feel the best method was to dig a trench down to the soil line. It was important for us not to dig up any soil with the sand and gravel because we were reusing that material for other farm projects such as concrete slabs, mortar for concrete blocks, and Ferro cement. We also used flat digging spades to scrape along the soil line so we weren’t digging into the soil. The trench that we started with was the width of the bed (five feet) and about two feet long. Once we dug our first trench, it was easier to dig into the wall of gravel with the pickaxe. We only wanted to pick up a couple of feet at a time, loosen up that section, then scoop out the loose sand and gravel and repeat. Average time for digging our one bed of compacted sand and gravel was one hour and 45 minutes. That was with two people. We really cleaned the beds of all the gravel by scraping the soil line with the end of our spades and by using a broom. We never dug more than two beds in a day, unless we had volunteers. This was a lot of work and the days were hot so we were exhausted after two beds.
We dug the first 24 beds using this method. For the last eight beds we brought in a mini excavator and skid-steer to see how much time we could save. With the help of the heavy equipment, we were able to dig all eight beds in a day but there were some negatives. It was not very easy to dig out the gravel without mixing in some of the clay as well. In the same way, it was hard to get along the edges without doing damage to the asphalt pathways. Once we got a majority of the sand and gravel dug out, there was still about 40 minutes of cleanup work along the edges to do. This took a majority of the time. The biggest disappointment was that the heavy equipment ended up breaking up more asphalt. Since we cut big holes in the parking lot, the asphalt was no longer stable and the weight of the equipment broke up a lot of asphalt in the pathways that we wanted to keep. This only added to our work, since we then had to patch those holes. Once we got all the gravel out, it was nice to use the excavator to loosen the soil up a couple of feet down. This only took about five minutes.
Note on heavy equipment: we had access to a skid-loader and excavator free of charge. Not everyone has this. To rent this equipment cost $240 a day for the mini excavator and $180 a day for the skid-loader. At minimum, you would need three days to get the work done. That’s $1,260 for the equipment rental and figure in a couple hundred dollars for fuel. On top of that, the benefit of digging out the sand and gravel by hand is that you can store it on-site and use it for multiple projects. The material that’s dug out by an excavator has too much clay mixed in it to be used for a lot of projects, so you will need to have it removed and taken to a clean fill site. For the whole project, we pulled out 53.44 cubic yards of sand and gravel. We got estimates to remove the waste for $1,000. Altogether, the introduction of the heavy equipment adds an additional $2,260 to the project. We do not believe that this fits into our goal of developing methods that are affordable for anyone from our neighborhood to replicate.

Loosening Up the Soil and Working in Compost and Top Soil:
We now have our beds dug out to the soil line. The holes are 18ft by 5ft holes in the ground that are eight inches deep. We needed to work in organic matter and loosen the compaction. After a hard rain, these holes would fill with water and remain full for days, so we couldn’t just add soil back into the hole. We used digging forks and worked in two inches of compost into the subsoil about 10-12 inches down. This not only improved the drainage but it also raised the soil line up four inches. This was a slow process; you only move your fork a few inches and pry back. This also was not easy. It took 45 miures to do one bed, and some beds took longer because there were more rocks and debris in them than others. We used the excavator to do this work on eight of the beds. It only took five minutes per bed. The soil line in these beds rose up six inches because we were able to dig down deeper.

Phase 2 - Building Bordered Beds:
A big goal of ours was to experiment with ways of building bordered beds that are not only affordable, but if possible we wanted to use materials that can be easily found within the neighborhood. In our grant, we outlined one method that a local organization uses to build raised beds out of rough-cut cedar and a 50/50 mixture of compost and topsoil. Their standard beds are 12 feet by 4 feet and are eight inches deep if situated on top of tilled soil. The materials for these beds average out at $120 per 48 sq. feet bed or $2.50 per sq. foot. For this project we wanted to construct 32-90sq.ft. beds for a total of 2880 sq. feet of growing space. If we were to pursue the method that is recommended by the local organization, we would spend $14,000 for the 16-inch beds and $21,600 for the 24-inch beds. The major cost of their beds is the price for rough-cut cedar, which accounts for 70 percent of the cost per bed. Another issue we have with the beds is the life span is only ten years. We pursued these methods because we really believe that we can build bordered beds a lot cheaper; these next examples are how we achieved it.

Un-Bordered Beds:
The first method we show visitors on our site is you do not really need borders on a bed. If you are building beds on a parking lot and you cut out the asphalt to dig out the gravel you’ll have an eight-inch deep hole ready to be filled. All you need to do now is break up the compacted subsoil with a fork and bring in eight inches of topsoil and you’re ready to plant. If you have access to the tools to cut the asphalt and dig the beds, your only material cost is the soil. One 90sq. foot bed costs $69, which will give you highly productive growing beds. This does not include the cost of removing the asphalt and gravel, so that cost will need to be factored in if your situation requires that material to be removed from the site.

Bordered Beds – Tire Boards:
This method is what we were most excited to experiment with. Tires are things that can be found on almost every street corner in the city. Individuals and even businesses dump them illegally because of the cost and difficulty of disposal. We started thinking about how we could use these tires on our farm we did a lot of internet searches and we came across a method pioneered by the Samuel Roberts Nobel Foundation, where the treads are cut out of the tires and screwed together to make tire boards. You can find their methods with a simple Google search. We wanted to experiment with this method because there is nobody doing this in our area and it could be a solution to tire pollution in urban neighborhoods.
We just drove up to the local tire shop, which has a mountain of tires behind it. We told them that we wanted as many tires as we could fit on our trailer. We got 70 tires on our 12-foot trailer. The tire shop workers helped us tie them in. It is important to get tires that have lots of wear, but the wire should not be exposed.
To cut out the treads, you’ll need a jig saw and metal cutting blades with 17 to 24 tpi. You’ll want to cut into the sidewall and then turn to cut parallel to the sidewalls, essentially cutting out the doughnuts on both sides of the tread. I would find a line on the tread that was just to the outside of where the steel mesh inside the tread came to on the tire. You will feel the difference in cutting. The blade slices through the rubber sidewalls with ease but there is considerable resistance when you get to the steel mesh. It’s important not to cut where the steel mush is because you will eat through your blades much faster. You want to cut right on the edge. Note the mesh for most tires stopped just before the tire starts to curve into the sidewalls. I would stand the tires up to find my line, cut a few inches, rotate the tire, then cut some more until I got all the way around the tire. When you get one sidewall cut out, do the other side. When both are done you should have a circle of tread. The last thing you need to do is cut across the tread so you can lay out the tread flat on the ground. We did this for all of our tires and lined them up by width on the ground. Each tire will have a different width, anywhere between six to eight inches. We had a pile of 8-inch treads, 7.5 inch treads, 7-inch treads, 6.5 inch treads, and 6-inch treads. We did this because we wanted the ends to match up when we screwed them together. I was able to cut out and sort nine tires in one hour. Whenever the treads are laid out, they will measure between five to eight feet in length. It takes at least three treads to make one wall for an eighteen-foot bed. Two walls plus two treads for end pieces equals eight treads per bed.
The next step is to cut a bunch of 6-inch squares of tread out of some already cut treads. You should get 12 to 16 pieces from each tread. These 6-inch squares will be screwed in every foot and a half along your tire board. They will serve as pockets that you will drive rebar through to stabilize your tire boards. Each tire board needs nine 6-inch squares, which adds up to 18 squares per bed.
Now that all the treads and squares are cut it’s time to screw the treads together to make boards. All you need to do is line up three treads in a row and overlap the ends at least six inches. Screw four screws into the four corners where the tread is overlapping six inches. The idea here is that the screws will wrap around the steel mesh as it is driven through both treads and will hold the treads together tightly. The screws that you’ll want to use are the Number 10 sheet metal screws – we used the screws that are one-inch long. For both ends of the board, you’ll loop over the tread and screw three screws through. The next step is installing the 6-inch pockets every 1.5 feet or so. I spread them out evenly across the length of the board and put just two screws though, leaving enough room for the rebar to fit between. Keep in mind that the two places where we overlapped the three pieces of tread count as pockets to insert your rebar through. This process of attaching the treads and installing the 6-inch pockets took 20 minutes for each board. Each board uses 32 screws. A complete bed requires 80 screws, 32 for each bed, and 16 to attach the end walls.
When all the screws are in, you’ll need to flip the tire board over and grind off any heads that might have poked through. We used a metal cutoff blade effectively for this task. It is also wise to switch to a grinding wheel and grind down any of the steel mesh that might have been exposed from cutting the treads. We waited to do this until after we had the entire bed installed. This whole process only took five minutes per board.
Once we were finished with our tire boards, we needed to buy rebar and cut it to length. The idea with a tire board is that you drive a stake into one end and stretch the board as tight as you can. Then you insert a piece of rebar into the pockets every foot and a half and the board becomes really solid. We used a 3/8 inch rebar for the pockets. This rebar was cut to two-foot lengths. Each of our 18ft boards required 11 2-foot pieces of 3/8 inch rebar – 22 pieces for an entire bed. The end pieces you drive in first should be much stronger than the 3/8 inch rebar. The Samuel Roberts Nobel Foundation recommends 5/8 inch rebar for this, but we found that these bend too easily when stretching the tire boards. We purchased some 1-inch EMT conduit and cut it to 3-foot lengths. When we drove this into the ground and tightened the beds, we got much better results. Each bed requires four of the 3-foot sections of conduit.
Tightening the beds is accomplished with the help of a couple of chains and a come-along wench. Drive in the first 3-foot section of conduit leaving about eight inches above the soil line. Next, loop the end of your tire board over that piece of conduit sticking out of the ground. On the other end, insert the second piece of conduit but don’t hammer it in. you’ll need a couple of chains for this. I used two locks to make loops to wrap around the conduit. You’ll need to loop one need of the chain over the conduit sticking out of the top of your tire board, and loop the other end over the conduit that’s sticking out of the bottom. I only pushed the conduit through about three inches. This should allow you to attach the wench to the chins in a way that will allow for an even pull. To set up your wench, drive in a six-foot t-post about five feet behind the point that you’ll be driving in the conduit. Attach another chain and link your com-along wench between the two chains. Make sure your t-post is driven in enough so it will not bend when you start tightening up the beds. You can hold your boards up by pushing in rebar a few inches on either side of the board. Tighten your bard with the wench. When I did this I inserted the rebar before drove in the end piece of the conduit. Once you have both boards done all you have to do is attach one tire tread on each end with four screws per corner. The end walls will be round. If you didn’t grind down the exposed steel mesh, this is the time to do it.
Filling the beds with the remaining soil and cleanup was our last step. We had lots of volunteer groups help us with this. We did not track individual labor hours for this because it would be the same for each method.

Most of our help came from individual volunteers from the neighborhood and volunteer groups. We occasionally bounced ideas and questions off Daniel Dermitzel, formerly of Cultivate Kansas City and Ben Sharda, Director of Kansas City Community Gardens.

We were able to track labor and material expenses for converting our parking lot into a productive farm.
Our cost per square food is the highest with the cedar beds, as high as $7.60 per square foot, if you were going to build right on the asphalt. Digging out the asphalt and working in compost is the cheapest method at $.076 a square foot. The tire boards are not that much more expensive to build coming in at $1.01 a square foot.
The biggest difference was the labor. You could construct a cedar bed on top of the asphalt in less than an hour but it takes 4.78 hours to dig out the asphalt and gravel and an additional 3.12 hours to construct one tire bed.

We learned that this was really hard work. We still know that it is really expensive to build beds out of cedar. Is eight hours of labor too much energy to put into these beds that we built? I guess it depends. This is the land that we have access to and these were the barriers that we faced. We don’t have $20,000 to build on top of the asphalt, so this was probably our best option. I think what was the hardest part about this grant is that we had a time line. We were really rushing to get everything done this last year. We all have part-time jobs so we only have three days a week to have available for the work. I can foresee us continuing with this method. However, we will probably only add four to five beds every year instead of 32. I for sure want to continue to experiment with the tire boards in the future. I am even interested in seeing if the tire shops will pay me to take the tires to lower the cost even further. I would love to share our story with other farmers and ranchers especially those who are working in an urban environment.

In June of 2011, 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 set up our farm to show the different stages of converting the parking lot to growing space. We had one sample bed for each stop of the process. The first bed was marked and measured pout 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 n0065t to the bed to show the amount of asphalt being removed from one bed. It also revealed the layer of sand and gravel, were 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 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 our 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 will also show the finished project in this year’s 2013 Urban Farms and Gardens Tour.
We work really closely with Cultivate Kansas City and Kansas City Community Garden. We will continue to experiment and hopefully distribute a guide through both of these organizations outlining our project.


Participation Summary
Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture or SARE.