You may have noticed the Water Department was recently in your neighborhood, building green stormwater systems along sidewalks and intersections to soak up stormwater and beautify the community.

Once these systems are built, there is often a gap of time between infrastructure installation and planting of trees and flowers. Have you ever wondered why there is a pause after construction is completed?

Green City, Clean Waters

Philadelphia’s combined sewer system serves about 60 percent of the city. During wet weather, this older section of our system often overflows. As a result, billions of gallons of stormwater and diluted sewage flow into local waterways each year.

Green City, Clean Waters is Philadelphia’s 25-year initiative to reduce the volume of stormwater entering combined sewers by pairing green infrastructure with traditional infrastructure improvements.

A green stormwater infrastructure project installs “green tools” – known in the GSI world as “systems” – such as bumpouts, tree trenches, rain gardens, and subsurface storage trenches. Projects include GSI that is packaged together in a neighborhood.

The outreach process begins years before these tools are installed and aims to connect with residents for feedback and education. During this time, the project moves through the Water Department processes, from designing the project specifications to contractor bidding and funding.

In Comes the Construction: Systems Getting Built

Construction starts once a contractor has been awarded the project and works collaboratively with PWD Construction to develop a project schedule and submit permits. The green systems, like bumpouts and tree trenches, are constructed one at a time and typically take 4 to 6 weeks each for completion.

Once systems are installed, the Water Department schedules a final walk-through to ensure that all the work was done as planned. Only at this point is a project considered ‘substantially complete’ and is able to be passed along to the next step.

Landscaping Scheduling

Once a project is substantially complete, it’s handed off to the Water Department’s Green Stormwater Operations (GSO) Team. It will join a list of projects that need to be planted through PWD’s landscaping contract.

PWD prioritizes planting native species that are usually robust and occur naturally in the region. These plants are specifically selected to withstand the conditions in the ‘green systems’ and often have a high success rate of surviving. The vegetation is most likely to thrive if planted in the spring or fall, so we have two planting seasons each year.

Fall planting is done between mid-September and the end of November, and Spring planting runs from mid-March through the end of May. If a project is not substantially complete in time for planting during the current season, it is stabilized in preparation for planting the following season. (For example, if a system is completed in May, the planting schedule for spring may be filled up, and therefore the system would have to wait until the next planting season in Fall. If construction is completed in February, the system would added to the Spring planting schedule.)

This schedule explains the gap residents often see once work is complete. It may look like the system was built and abandoned, but the systems are just waiting for their planting when the vegetation will do their best.

PWD has signage we like to distribute to sites that are awaiting planting – if you see systems in your neighborhood that could use an educational sign, reach out to Amy Hopf at [email protected].

To learn more about both recent and upcoming planting, visit the Philadelphia Water Department website.