While many worry about the potential for greater expenses due to on-site landscaping material, experience has shown that LID still saves money over conventional approaches by reducing infrastructure need and site preparation work. Certain research (conducted through case studies etc) have shown as much as a 25 to 30% reduction in costs associated with site development, water fees and maintenance. The cost savings result from reductions in clearing, grading, pipes, ponds, inlets, curbs and paving. Even better still, the cost savings available through reducing the infrastructure need also enables people to add value-enhancing features to the property and to recover more developable space by removing the need for including waste land for stormwater collection and/or treatment.
As with any project, the cost is site specific and will depend on what methods you are looking to implement and to what scale. The benefit of LID is that there is a method for every budget – all that is required is some innovative thinking and some ‘Kiwi ingenuity’.
Some commonly seen cost benefits include:
- Multifunctionality - In many projects, the LID practice may originally have been designed as a landscaped feature, before its functionality as a stormwater control was introduced. In these situations, the landscaping and construction costs for stormwater are essentially free. Additionally, the cost of maintaining the landscaped areas would always be expected for a project, so one of the only major additional costs for stormwater maintenance is to ensure that drainage areas are kept clear.
- Lower lifetime costs - In any cost analysis, be sure to take into account not just the initial capital costs but also those over the structure's lifetime, which can include operation, repair, maintenance, and decommissioning. Many LID techniques are self-perpetuating, easily repairable, or can be left as natural areas at the end of their functional lifetime, while conventional facilities may require high costs to take out of commission and leave the area safe.
- Additional environmental and social benefits - At the heart of LID are the multiple benefits it provides, all of which are not readily measurable in terms of cash. Not only do the techniques provide stormwater benefits, such as groundwater recharge and cleaner streams, but they also increase urban greenery, improve air quality, reduce water pollution, enhance the appearance of a community, provide a stronger sense of place, etc.
- Reduced off-site costs - Since LID addresses stormwater at its source, it is unlikely to incur major off-site costs in the form of sewers or outfalls. Most conventional techniques will require an off-site sewer to collect the stormwater from the on-site system, resulting in additional project costs for the enhancement of downstream sewers as urban areas expand.
- Functional use of open space land - LID practices such as rain gardens can usually be designed as part of the development's open space, without any loss of developable area. Unlike large detention ponds, if these multifunctional LID practices are distributed throughout open space or previously landscaped land, they can contribute to a more park-like and community-friendly setting without incurring costs for land allocation to the drainage system.
- Costs are relative - Cost considerations vary based on the user and the project. For example, if a yard is retrofitted to replace 1/2 of its area with an LID infiltration practice such as a raingarden, do you perceive this as a loss of the use of the yard or a benefit in the fact that there is now less lawn to maintain?