COSTnz
A new web application to compare the ‘whole-of-life’ costs of alternative low impact stormwater treatment devices could lead to increased use of more environmentally friendly stormwater management in your neighbourhood.
COSTnz (Cost of Stormwater Treatment in New Zealand) was developed by Landcare Research as part of the LIUDD programme. It was clear that for local authorities to determine the most appropriate stormwater treatment they needed to understand both the short- and long-term costs incurred as a result of construction and maintenance. ‘COSTnz allows users to identify and combine acquisition, routine and corrective maintenance, and decommissioning costs to determine the full life cycle cost,’ says Landcare Research environmental economist Eva Vesely.
Modules are available for ponds, rain gardens, wetlands, swales, filter strips, rain tanks, sand filters and infiltration trenches, plus a generic module enables the same analysis for various proprietary devices. In each case, users can select from a range of default values for each cost element, or input data from their own suppliers or historical information.
COSTnz uses a unit costing approach based on locally collected data, supplemented with statistical relationships for the total acquisition costs. It includes the option for discounting so that the present value of future costs can be estimated at the base year.
The set-up of the modules allows sensitivity analysis for a range of assumptions, such as lifespan of the device, different maintenance regimes, unit costs and a range of real discount rates.
Dr Vesely says COSTnz will improve understanding of long-term investment requirements and assist local authorities in their budgeting, reporting and auditing processes.
‘It will also help low impact urban design and development decision-makers make more cost-effective choices at the project scoping phase and provide a platform for negotiations between councils and developers regarding financial contributions,’ she says.
Now commercially available, COSTnz is targeted at asset managers, consultants, developers, designers and regulators. The Web application (www.costnz.co.nz) follows a logical approach with consistent layout, and is designed to be flexible and easy to use. Results are delivered in a PDF report format or as an Excel spreadsheet that enables users to develop the costing of a full treatment-train or input data into other systems.