From Rooftop to Runoff: What the High Line teaches us about green roofs

With the Grey to Green Conference coming up (June 1-2, 2015 in Montreal), all eyes will be on green infrastructure.

High Line - unique green roof with walking paths on either sideIn early April we took a cruise down the High Line in Manhattan. It’s a unique experience: it’s an abandoned elevated rail platform that’s been renovated into a narrow walking park. You get to experience the Big Apple two stories up from the streets, noise, traffic, and hustle and bustle.

Some people get drawn into the unique architecture (for example, they revived the train aesthetic and the park has glimpses of whimsical industrial-chic old rail ties, with lounge chairs overlooking the Hudson, and angular benches) and cool concrete forms. We were drawn in by the vegetation: The High Line is basically a gigantic green roof.

A Quick Green Roof 101 Tutorial

Growth media for green roof projects require a well-balanced blend to support vegetation. There are two flavors of green roofs:

  • High Line - green roof infrastructureExtensive: Extensive green roof systems have shallow profiles, with typically 3-4 inches of growth media. It’s primarily mineral and organics (no soil involved) made up of expanded shale and compost.
  • Intensive: Intensive green roof systems have a deeper profile (6”) and can support a much broader plant palette including perennials, shrubs and trees.

Learn more about green roofs.

High Line - purple crocuses in bloomA few crocuses were blooming (we loved the purple!) and a few trees were beginning to bud.

Beyond the Beauty: Why Soil Infrastructure Impacts Water Quality

A few states south, the Cheseapeake Bay Foundation has been fighting for years to curb pollution. Greenwire reporter Tiffany Stecker submitted on April 7, “Under a 2010 legal settlement between the nonprofit Chesapeake Bay Foundation and EPA, watershed states must adhere to a “pollution diet” and implement plans to meet individual nutrient-reduction goals by 2025. The states – Maryland, Virginia, Delaware, Pennsylvania, New York and West Virginia – and D.C. are required to submit reports on these efforts to EPA. The analysis released yesterday says the states collectively have reached 21 percent of the nitrogen reductions, 71 percent of the phosphorus reductions and 25 percent of the sediment reductions toward the 2025 goals.”

High Line - green roof - from rooftop to waterwayWhat does this mean? In laymen’s terms: In the past, we screwed up our waterways. Currently, we’re taking steps to reduce pollution by A) modifying our land applications and B) re-designing our built infrastructure via bioswales and green roofs (and innovative parks like the High Line) to absorb rain water during storm events. Looking ahead, we still have work to do from rooftop to runoff.

We checked in with our specialty soils guru, Dave L on how progress in the Chesapeake Bay intersects our work on land. He says,

“Bioretention facilities as well as green roof applications contribute to the amount of water introduced into the stormwater system and improve the quality of water output into this system. Overall these combined facilities improve the quality of outflow through filtration with properly blended soils and reduce the quantity of outflow by retaining water in their respective systems for plant uptake.”

Harvest Power has a lot of momentum in our specialty soils department that mixes up soils to specification – for green roofs, stormwater management, bioretention (including specs that meet Montgomery County Blends and MDE Table B.4.1 requirement), and beyond.

Want to learn more? Drop us a line.