Baltimore Ecosystem Study Institute of Ecosystem Studies

2010 BES Annual Meeting Presentation and Poster Abstracts

Comparative Life Cycle Analysis of Two Stormwater Controls: Street Tree vs. Rain Barrel
Hopkins, Kristina
Co-Authors: Kristina Hopkins, University of Pittsburgh AND Daniel Bain, University of Pittsburgh

Abstract: Many cities have combined sewer systems (CSOs) collecting both sanitary water and stormwater. During rain events, CSOs direct untreated sewage to surface waters. Reducing CSOs requires slowing drainage during rain events. Green infrastructure can mimic natural hydrologic systems to accomplish this goal. However, green infrastructure is often implemented without post-installation evaluation. We use life cycle assessment (LCA) to compare two green stormwater controls, street trees and rain barrels, providing accounting of processes from "cradle-to-grave." Street tree Acer rubrum (Red Maple) and a RiverSafe rain barrel were evaluated based on their hydrograph delay to peak discharge (m3/sec/lifetime). These systems were selected as relatively complete data exists for Nine Mile Watershed in Pittsburgh, PA. SimaPro software was used to model environmental inputs and outputs for five life-stage categories (production, transport, installation, maintenance and disposal). Average percent canopy cover and roof footprint per parcel in the Nine Mile Run watershed were calculated using GIS and then used to model the runoff delay on a typical property. Preliminary results suggest the rain barrel will delay more peak discharge over its lifetime than the tree. Red maple’s interception potential falls drastically during the 5-6 month dormant period when leaves are absent. While rain barrels also lose functionality during freeze months, they remain operational for longer periods. Based on our LCA, we hypothesis trees may have higher installation and disposal costs than rain barrels. In contrast, the rain barrel likely has higher production/manufacturing costs. Ultimately, a tradeoff may exist between life cycle costs and hydrologic benefit.