A public-private partnership in the City of Miami is transforming a 16-km-long strip of contaminated land beneath the city’s elevated mass transit system into a multi-modal path and green infrastructure project that features bioswales, rain gardens, stormwater ponds, and micro-forests to protect a storm-prone urban area.
Known as The Underline, the projected $150-million project is a partnership between the Department of Transportation and Public Works (DTPW), the Parks, Recreation and Open Spaces (PROS) Department, Friends of the Underline, the City of Miami and the City of Coral Gables.
Set to be complete in 2026, the stretch of land was formerly host to a railroad before it became the Miami Metrorail. That history meant developers faced arsenic contamination in the soil that needed to be addressed through each stage of the multi-year project.
The Underline is expected to utilize a Japanese afforestation method called Miyawaki, which can create a diverse forest ecosystem quickly by planting some 24,000 seedlings that can grow 10 times faster than the average urban forest.
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When the project is done, the path’s various green infrastructure elements will feature more than 500,000 native plants and trees, according to project officials.
Stormwater ponds along the path will naturally guide, absorb, and allow stormwater from the Metrorail and nearby areas to percolate back into the aquifer, according to local officials.
“The rain gardens are natural flood mitigation systems, temporarily collecting stormwater in rocky shallow areas and utilizing multiple sediment layers to filter out pollutants,” states The Underline’s website. “The depressed rock gardens manage stormwater and filter it as it seeps into the aquifer. Additional features include insect hotels, bird houses, and elevated pathways to encourage the exploration of these innovative systems.”
The project has been under construction for several years and opened its first phase to the public in 2021. The Underline is being built in three phases.
