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Six Rivers Charter School garden pathway
- 1 About the Team
- 2 Abstract & Background
- 3 Problem Statement and Criteria
- 4 Prototyping
- 5 Description of Final Design
- 6 How to build
- 7 Maintenance
- 8 Suggestions for future changes
About the Team
Environmental Resource Engineering students at Humboldt State University, Fall 2019.
Abstract & Background
Six Rivers Charter High School (abbrev. Six Rivers) 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. The team was tasked with designing a pathway that is 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 trail/pathway are safety and accessibility, and the importance of other criteria is situation specific. For this project labor intensity and cost are very important because without prioritizing these the project may not have been able to reach completion in time. Remaining criteria is valued with respect to education.
|Criteria||Weight (out of 10)|
|Safety and Accessibility||10|
|First and Second Prototypes|
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. The first problem posed was the sharp inside angle of the switchback. The fact that this would present an issue was confirmed by the second prototype which involved carving into the construction site. As a result of the prototyping process, the team chose to extend 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
The final design shown below addresses the client criteria and insight gained through the prototyping process. The full length of the pathway is approximately 90’ and the area of the landing is approximately 35 square feet. The bottom of the pathway to the landing is supported by a 66’ urbanite retaining wall that expands upon a pre-existing concrete block retaining wall. The landing is supported by a compact earth tire retaining wall measuring approximately 54” high by 13’ wide, and comprised of 24 tires arranged hexagonally. The portion of the pathway between the top and the landing does not require reinforcement. The pathway surface is composed of three layers: tamped earth as the base, a mixture of sand and gravel in the middle, and mulch on top. Outsloping of the pathway and Coweeta dips were used for drainage, and a combination of ripraps, straw, and grass seed were utilized as temporary erosion control for remaining bare slopes. All elements of the design were produced as planned to the satisfaction of the team as well as the client.
|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|
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 the wall to solid ground. 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.
|Image 1||Image 2||Step|
Step 1: Sketch potential layouts. Step 2: Layout trail with string and/or ruff digging.
|Step 3 : Formalize layout.|
|How to Do Something|
|Step 1 : Armor the trail with a hard material such as gravel.|
|Step 2 : Tamp any loose material to add strength to trail surface.|
|Step 3 : Provide an easy walking surface such as wood chips.|
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.
- Plant care: watering and fertilizing as needed.
- Remove dirt knocked onto pathway by gophers, pathway users, etc.
- 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 placed on the west side of the path running from the landing to the bottom.
- Planting 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.