Restoration of Stormwater Infiltration Basin Performance

Stormwater infiltration basins form a key part of the suite of low impact urban design devices to treat and dispose of urban stormwater runoff. These basins may suffer a reduction in performance with time, either as a result of improper construction or some step change, such as effects relating to an earthquake. In this paper several methods and tools available for remediation of stormwater infiltration basins that exhibit reduced performance are discussed, with reference to relevant case studies in the Christchurch area.

The case studies presented cover a range of remediation techniques, including surface aeration and complete replacement of topsoil and underlying drainage media. In one case a complete loss of performance was incurred following discharge of 200,000 litres of milk and beer into the infiltration basin during one of the Christchurch earthquakes. In other cases infiltration basins exhibited very low infiltration rates and poor drainage, potentially as a result of poor initial construction. The remediation techniques in these cases include the construction of drainage trenches and aeration of topsoil. The analysis and assessment techniques used for establishment of the cause of poor performance, together with validation of performance post remediation, are also discussed in this paper.