The importance of Aquifer Data to Size and Locate Stormwater Infiltration Basins

Stormwater infiltration basins have become an important method of treating runoff from developed land in the Canterbury area. Infiltration basins provide a method of maintaining rainfall recharge to the underlying aquifer and hydraulic neutrality for any stormwater runoff. In most situations, infiltration basins are located above unconfined aquifers. To determine the invert level of the basin requires an assessment of the highest groundwater level along with the amount of mounding that occurs when stormwater discharges through the basin. This requires knowledge of aquifer parameters such as transmissivity and storativity.

The author’s describe their experiences with the investigations required to locate and design infiltration basins so that the risk of groundwater entering the basins or compromising their operation and performance is minimised. They will describe the importance of obtaining sufficient information such as long-term groundwater records and localised measurements to ensure that the maximum groundwater levels at the location of the infiltration basin can be predicted. They will show how the data is used to size components of the infiltration basins.

The paper will also explain the impacts of not carrying out these investigations fully, particularly in relation to the operation and maintenance of the infiltration basins.