by Caitlin Glagola, Associate ASLA; Tim Linehan, Associate ASLA; and Rachel Streit
The Philadelphia Water Department (PWD) has one of the most progressive stormwater management plans in the country to address the city’s combined sewer infrastructure. PWD’s Green City, Clean Waters program, which begins its 7th year this July, has constructed more than 600 stormwater management practices (SMPs) in the city, including rain gardens, tree trenches, stormwater planters, and stormwater bumpouts. These stormwater landscapes, collectively known as green stormwater infrastructure (GSI), slow, filter, and infiltrate rainfall to help prevent polluted runoff from entering the city’s sewers and waterways. GSI is versatile and fits into the urban fabric of Philadelphia to not only manage stormwater but also to mitigate urban heat, improve air quality, provide habitat, improve human health, increase land value, and improve quality of life for city residents.
In February 2018, PWD published the GSI Landscape Design Guidebook (version 3.0), which shares important lessons learned and success factors for designing and implementing stormwater landscapes. Informed by PWD’s field-based observations, plant survivorship monitoring studies, and feedback from maintenance crews, the guidebook is a wealth of knowledge for anyone looking to design GSI, especially in the public realm. The guidebook includes criteria for site assessment and plant selection, guidance on addressing different hydrologic zones, consideration of site conditions such as sunlight and available space, as well as design recommendations and guidelines. Also included is PWD’s recommended plant list for GSI, along with important plant characteristics to consider when designing (i.e. seasonal interest and tree canopy form and density). Case studies are presented with their planting plans and before and after photographs to showcase successful PWD projects.
PWD’s Green City, Clean Waters program has plans to build over 9,564 greened acres of GSI throughout the city of Philadelphia by 2036. A greened acre refers to an acre of impervious cover that is retrofitted to utilize GSI to manage stormwater. In October 2017, PWD celebrated the 1,000th greened acre created by Green City, Clean Waters.
To view PWD’s GSI Landscape Design Guidebook, visit: http://documents.philadelphiawater.org/gsi/GSI_Landscape_Guidebook.pdf
by Caitlin Glagola, Associate ASLA, Ground Reconsidered (Consultant to PWD) Caitlin.Glagola@phila.gov;
Tim Linehan, Associate ASLA, Philadelphia Water Department (PWD), Timothy.Linehan@phila.gov;
Rachel Streit, CHPlanning Ltd. (Consultant to PWD), Rachel.Streit@chplanning.com