How to Build a Rain Garden in Eugene: A Step-by-Step Guide for Lane County Homeowners
How to Build a Rain Garden in Eugene: A Step-by-Step Guide for Lane County Homeowners
Create a sustainable landscape that manages stormwater runoff and protects the Willamette Valley watershed by installing a functional rain garden.
What You'll Need
- Shovel and garden rake
- Wheelbarrow
- Sonde or soil test kit
- Native plants (e.g., Slough Tera, Red Osier Dogwood)
- Organic mulch
- Measuring tape and marking paint
Steps
Step 1: Site Selection
Identify a natural depression or a low point where rainwater naturally collects, ensuring it is at least 10 feet away from your home's foundation. Avoid areas directly over septic tanks, underground utility lines, or near large old-growth trees.
Step 2: Soil Percolation Test
Dig a hole about 12 inches deep and fill it with water to see how quickly it drains. In Eugene's typical clay-heavy soils, slow drainage is common, which may necessitate adding a soil amendment of compost and sand to increase infiltration.
Step 3: Marking and Excavation
Outline the garden's perimeter using marking paint or a garden hose. Dig out the area to a depth of 6 to 12 inches, creating a shallow basin with a flat bottom and gently sloping sides.
Step 4: Soil Amendment
If your soil is heavy clay, mix the excavated soil with organic compost and coarse sand. This improves the soil structure, allowing water to penetrate deeper into the ground rather than pooling on the surface.
Step 5: Establishing an Overflow Path
Designate a clear exit point for excess water during extreme Lane County rain events. Create a shallow swale or a rock-lined channel that directs overflow away from the house and toward a safe drainage area or storm drain.
Step 6: Selecting Native Plants
Choose plants native to the Pacific Northwest that can tolerate both saturated soil and periods of summer drought. Group plants by their moisture needs, placing the most water-tolerant species at the center of the basin.
Step 7: Planting and Mulching
Install your plants according to their spacing requirements and cover the entire surface with 2 to 3 inches of shredded hardwood mulch. This suppresses weeds and prevents soil erosion during heavy downpours.
Step 8: Initial Maintenance
Water new plants regularly during their first growing season to ensure root establishment. Remove invasive weeds by hand to prevent them from competing with your native species.
Expert Tips
- Use a 'rain-to-garden' diversion by directing your downspouts toward the basin using an extension pipe.
- Avoid using chemical fertilizers, as rain gardens are designed to filter pollutants before they reach the groundwater.
- Consult the Lane County soil maps to determine if your specific property has high clay content.