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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 urbanite retaining wall is represented by the black foam blocks, and the compact earth tire wall is represented by the slices of wine 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 involved carving into the actual 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 gentler inside angle on the switchback. The prototype was tested by showing it to Humboldt State University engineering students who gave their opinions of what could be improved on and what could be potentially problematic or unsafe.

Description of Final Design

Final Design

The final design shown below addresses the client criteria and insight gained 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 regrow, 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

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Caption
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Caption
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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.

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Caption
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CLICK HERE FOR BACK-FILL DEMONSTRATION
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Caption BACKFILL GIF HERE

Trail Placement

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Path Surface

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How to Do Something

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

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