Tiered Retaining Wall System

The Problem

The Johnsons’ property in Nelson featured a steep slope that was experiencing erosion issues after heavy rainfall events. They needed a solution that would:

• Stabilize the slope and prevent further erosion
• Create usable garden space on the steeply sloping section
• Provide safe access to different areas of the property
• Look attractive and enhance the property’s value
• Stand the test of time with minimal maintenance

Our Engineering Solution

After consulting with a structural engineer, we developed a tiered retaining wall system that would distribute the load across multiple walls rather than one large structure. This approach offered several advantages:

1. Improved safety factor with each wall managing less height
2. Enhanced aesthetics by breaking up the visual mass
3. Better plant integration opportunities between tiers
4. More usable space created on each level
5. Comprehensive drainage to manage water effectively

The Construction Process

Phase 1: Site Preparation and Excavation

We began with careful site preparation:

• Protecting existing structures and vegetation to be retained
• Establishing proper erosion control measures during construction
• Excavating in stages to maintain site stability
• Creating appropriate foundations for each retaining wall tier

Phase 2: Lower Wall Construction

The lowest tier was built first:

• Engineered concrete block wall system with geogrid reinforcement
• Comprehensive drainage layer behind the wall
• Compacted backfill to proper specifications
• Installation of drainage collection and diversion systems

Phase 3: Middle and Upper Wall Construction

We then proceeded with the higher tiers:

• Maintaining proper setback distances between each wall
• Installing additional drainage systems at each level
• Creating access steps between tiers where needed
• Preparing planting areas for later landscaping

Phase 4: Finishing and Landscaping

The final phase brought the project together:

• Application of quality topsoil to planting areas
• Installation of native ground covers to prevent erosion
• Construction of natural stone steps for access
• Strategic planting to soften the walls’ appearance
• Final drainage connections and testing

Technical Features

This project incorporated several technical innovations:

• Engineered geogrid reinforcement extending into the soil mass
• Integrated drainage system with multiple collection points
• Flexible connections allowing for minor ground movement
• Proper compaction testing at each critical stage
• Specialized block system designed for Nelson’s seismic considerations

The Result

The completed tiered wall system has transformed a problematic slope into a functional, attractive part of the Johnsons’ property:

• Three distinct flat areas for different garden uses
• Complete elimination of erosion issues even during heavy rainfall
• Attractive visual appearance that enhances the property
• Safe access to all areas of the garden
• A durable solution engineered to last for decades