About the Team
Zachary Alva, Dustin Helliwell, Abdul Kamaal, and Connor White
Environmental Resource Engineering students at Humboldt State University, Fall 2019.
Abstract & Background
Six Rivers Charter High School has a garden and outdoor learning space located at the bottom of a hill below the main classrooms. The staircase originally connecting the space to the rest of the school had fallen deep into disrepair and sorely needed to be replaced. The team spent a few weeks researching pathway and stair design, slope stabilization, retaining walls, pathway construction, erosion control, and native plants before meeting with Six Rivers' Principal Ron Perry to establish their personal criteria for the design. We were tasked with designing a pathway that was safe, wheelbarrow accessible, widely plantable, cost effective, ecologically sound and aesthetically pleasing. The primary objective of our design was on functionality and durability.
Problem Statement and Criteria
The top priorities for any trial or pathway are safety and accessibility. After this choices and importance of criteria are situation specific. In our case labor intensity and and cost were very important since without prioritizing these we could not have finish the project. Our remaining criteria are ordered in relation to our specific use case of facilitating education.
Criteria | Weight (out of 10) |
---|---|
Safety and Accessibility | 10 |
Labor Intensity | 9 |
Cost | 7 |
Plantability | 7 |
Ecology | 6 |
Maintenance | 5 |
Educational Value | 4 |
Aesthetic | 4 |
Prototyping
The first prototype was constructed out of drywall compound, chicken wire, and magazines on a plywood frame. The clam-shell cement blocks are represented by the colorful foam blocks, the recycled concrete wall is represented by the black foam blocks, and the compacted earth tire wall is represented by the pieces of cork. What came to mind immediately was the sharpness of the angle of the inside of the switchback. The fact that this would present an issue was confirmed by the second prototype, which actually involved carving into the hill. As a result of the prototyping process, AZDC chose to dig the landing section of the trail farther back into the hillside, to allow for a larger inside angle on the switchback in the final design.
Description of Final Design
Final Design
The final design shown below reflects the client criteria as well as what was learned through the prototyping process. As can be seen from the photos, straw was thrown onto the hillside to prevent erosion of exposed soil until plants grow on the bare surfaces, after which their root systems will provide stabilization. All elements of the design were produced as planned to the satisfaction of the team as well as the client.
Costs
Quantity | Material or Service | Source | Cost ($) | Total ($) |
---|---|---|---|---|
As needed | Materials Transportation | Father of Dustin | 46.91 | 46.91 |
1 | Hay Bale | Three G's Hay and Grain | 8.62 | 55.53 |
1 bag | Grass Seed | Mad River Gardens | 3.76 | 59.29 |
As needed | Recycled Concrete | Donated by: Figas Construction | 0 | 59.29 |
As needed | Tires | Donated by: Anonymous | 0 | 59.29 |
1 cubic meter | Wood Chips | Free pile located at the Indianola Cuttoff | 0 | 59.29 |
Total Cost | 59.29 |
How to build
Compact Earth Tire Retaining Wall
Urbanite Retaining Wall
The urbanite retaining wall described below is constructed from recycled concrete. Pieces of concrete with one flat side such as those sourced from old sidewalk are ideal, but not critical. This type of retaining wall is known as a gravity wall because it does not have anything anchoring to solid ground the wall itself or the earth being retained. The strength and stability of this design is rooted in it's sheer weight, so it is important to remember that the sum mass of urbanite used is proportionate to the overall strength of the wall.
Trail Placement
Path Surface
Maintenance
This section details the known and anticipated maintenance that this design will require to remain functional and cosmetically intact. It is designed with the intent of being maintained by the students alone.
Schedule
This is an estimate of how often each component is anticipated to need maintenance.
- Daily
- Plant care: watering and fertilizing as needed.
- Weekly
- Remove dirt knocked onto pathway by gophers, pathway users, etc.
- Yearly
- Analyze retaining walls for points of soil erosion that could affect the long term stability of the supporting structure.
- As necessary
- Add mulch or gravel to the top layer of the pathway at points where it has become muddy or uneven.
Suggestions for future changes
Team AZDC recommends the following as future changes to the project:
- A handrail following the path on the downhill side of the pathway downhill of the switchback.
- An assortment of edible fruiting plants that would also serve as additional slope stabilization such as:
-Snow Berries -Goumi Berries -Huckleberries -Elderberries -Chilean Guava
- A cob bench embedded into the uphill side of the landing to provide additional slope stabilization as well as an aesthetic and practical feature.
Other Resources
See Help:Footnotes for more. Template:Reflist