Asheville, North Carolina Field Trip – Student Notes and Observations

3 Jun

Site

The main objective of the North Carolina Arboretum is achieving pre-development hydrology and to capture and infiltrate at least 50% of the rain water in 1.2 inch rainfall events.

Discussion

Strategies for slowing down, treating and cooling storm water before it gets to the local area water system include:

    • Oversized water cisterns for capturing rain water
    • A bottom-up approach on the formal lawn area which has two large perforated culverts and is covered with
    • A bottom-up approach on the formal lawn area which has two large perforated culverts and covered with Staylite aggregate mixed with loam, sand and silt. The lawn then sucks up the water passing through the pipes.   Pretty cool.
    • A big rain garden at the main entry roundabout. John pointed out that a rain garden needs to be at least 1/10th the size of the catchment area.  The rain garden also needs to provoke and  interact with people by having some form of art or a shape that draws attention.  The rain garden had an visible concave shape that makes it obvious and allows observation of collected rainwater and how fast it infiltrates into the ground.
    • Rain gardens need to be planted with diverse species with the main criteria for their selection being the ability to withstand wet conditions.  Woody plants should be avoided in wetlands as they provide cover for mosquito larvae and should be around 9” deep.
    • Wetlands need to be located away from the formal buildings.
    • There should be an extruded filter sock for sediment control downhill.

 Opportunities for improvement include:

    • Having lawn grass grow all the way to the slope, probably to the first foot of the rain garden floor, in order to prevent erosion.
    • The planting design of the large rain garden could be improved with a less formal and more organic plant massing.

– Written by Antony Wambui

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