rates, and economic return objectives would also benefit from a list of acceptable BMPs that include space-efficient LID practices.
STORMWATER ECONOMICS Government officials, site design and engineering professionals, developers, and property owners considering the LID approach should understand how the economics of LID compare to conventional development and stormwater management approaches. The costs and benefits of the LID approach should be considered over its entire lifecycle, from planning through design, installation, operation and maintenance, and decommissioning. An extensive body of research that investigates the economics of implementing LID across watershed, community, and site scales relative to conventional hard engineering practices has been developed and continues to grow. With few exceptions, this research reveals that LID generally costs less than conventional stormwater management practices when life-cycle costs are taken into account. Links to a selection of these studies are included in the References section of Part IV.
ECONOMICS AT THE WATERSHED SCALE In existing communities, stormwater management infrastructure undergoes routine maintenance and periodically need to be
expanded to handle additional runoff from new development. To maintain infrastructure concurrency and meet NPDES requirements, communities may continue to spend capital resources on extending the reach and increasing the capacity of existing conventional infrastructure, or to invest in the LID approach. An increasing number of major municipalities, including Nashville and Chattanooga, TN, and Philadelphia, PA, 80 have made green infrastructure and other LID impact avoidance, minimization, and management practices a significant component of their growth management plan and NPDES compliance strategy. In Philadelphia, 81 both conventional and LID approaches were estimated to cost in the billions of dollars, but the green infrastructure approach also afforded public recreational amenities, potential increases to property values, and enhanced air quality: value-added benefits that buried pipes and tunnels could not offer. 82 This redirection of public improvement funds away from buried pipes and culverts towards multifunctional civic amenities and widespread implementation of LID BMPs was recently adopted at the scale of multiple watersheds by the City of Philadelphia as part of its “Green City, Clean Waters” initiative. This plan is also part of the city’s strategy to satisfy NPDES permit requirements (see p176). 155