Innovative Treatment Solutions for Challenging Sites

Stormwater designers are often faced with challenging sites for stormwater treatment; the most common difficulties are a lack of fall or a lack of space.

This paper details three different case studies where the site conditions where prohibitive to installing traditional treatment methods. Innovative solutions were developed by adapting stormwater technology to fit within existing stormwater infrastructure, to overcome the site constraints.

The projects are as follows:

• A low drop filter with surface-level entry, pre-treating a plastic detention system at Penrose high school. The outlet from the treatment device could be no deeper than 500mm from ground level.
• A screening system for gross pollutants for a public soakage network in Epsom, Auckland. A screening device was retrofitted into an existing urban network to protect a soakage disposal system from clogging.
• An integrated filtration/ drywell for an infiltration system on a NZTA arterial upgrade-Pound Road in Christchurch. The treatment system designed integrated a filtration system with a drywell to minimize the number drainage structures required on site.

The paper reviews the design criteria including hydraulics, targeted contaminants and sizing for these three projects. The paper also details the installation of these systems and looks at how they are performing now.