As a general rule, it’s important to avoid letting your hands remain too clean for too long. So when my friend and former GRACE colleague, Gwen Schantz, asked if I'd help her move some soil, I immediately agreed. The soil weighed 1.2 million pounds and needed to be hoisted onto a roof seven stories above a busy street in New York City.
Indeed, this was no backyard garden; Gwen and her partners were building a one-acre, commercially viable rooftop farm. The goal: repurpose a formerly unproductive urban space to grow vegetables, sell the vegetables to members of the surrounding community and local businesses, and earn a living in the process.
The Brooklyn Grange team – comprised of Gwen, Ben Flanner (of Eagle Street Rooftop Farm fame), Chris Parachini and Brandon Hoy (co-owners of Bushwick’s renowned sustainable eatery, Roberta’s), and Anastasia Plakias (whom I've never met but am sure is worthy of laudatory parenthetical description) – originally intended to construct the rooftop farm in Brooklyn. But after a long search of the borough failed to yield a suitable space, the team ultimately chose a site in Long Island City, a formerly industrial section of Queens just across the 59th Street Bridge from Manhattan. Check out high-flying and low-flying birds-eye views of the location, courtesy of everyone’s favorite mapping tool.
The construction of the farm occurred in early May, when NYC weather is generally at its best. I managed to volunteer on a rainy, windy day when the unseasonably cold temperature never rose above 50 degrees. But who needs sun when there’s soil to haul?
Here’s an overview of the rooftop farm installation process (see video slideshow above for illustration):
Step 1 : The Sweep
First, the roof was swept to ensure that it was free of rocks and any other debris that might puncture the plastic membrane. This task was completed before I arrived (if the labor doesn’t soil my hands, I don’t participate).
Step 2 : Membrane
After the big sweep, the roof was covered with an impermeable, root-proof membrane, which is a thin sheet of plastic similar to the material used during building construction (i.e., thicker than a heavy-duty garbage bag, but thinner than a tarp). This stuff comes in huge rolls, which makes it easy to spread out, but difficult to keep in place if it’s windy (think giant sail)… and seven stories above the street, it’s always windy.
Step 3 : Felt
Next, a thick layer of felt was rolled out over the plastic. On a traditional farm (i.e., the kind that’s not perched atop a roof), water is stored in the soil below crops – but rooftop farms have much less soil (partially because roofs have limited weight-bearing capacity, and partially because it’s expensive to obtain soil and move it to the top of a building). Rooftop farms compensate for the reduced water storage capacity either by irrigating constantly or by incorporating a water reservoir below the thin soil. At Brooklyn Grange, the felt serves as a giant sponge, absorbing and storing water that passes through the thin layer of topsoil; as the soil dries, water is pulled back out of the felt and sucked up by the vast web of roots.
Step 4 : Drainage Mats
After laying down the felt, we sprayed the material with a garden hose to give it some weight (i.e., wind proofing) and get a head start on building the water reserves, then covered the entire surface with semi-rigid sheets of rectangular plastic that resembled giant egg crates. These drainage mats are designed to further boost the roof’s water storage capacity by creating a layer of moisture collection pools below the soil.
Step 5 : More Felt
A second, slightly thinner layer of felt was placed over the egg crates to complete the great sandwich of water retention. More water was sprayed across the fuzzy surface.
Step 6 : Soil!
Finally, the roof was ready to be soiled – but not with any old dirt; Brooklyn Grange purchased Rooflite Intensive, an engineered soil mix (technically a "growing media") developed specifically for green roofs – it’s light, able to effectively retain moisture, and also capable of draining excess water. The stuff comes in enormous bags, each of which is about the size of a golf cart – and at roughly 2,000 pounds, nearly four times as heavy.
Thankfully, the Brooklyn Grangers hired a crane, which plucked the massive bags from the sidewalk and emptied soil into motorized buggies on the roof. (The dirt-toting roof buggy is a peculiar creature best described as a cross between segway and dump truck – the front is a bucket that holds several cubic feet of soil; the operator stands on the back to steer.) The buggies carried loads from one corner of the roof to the membrane/felted/egg-crated portion at the opposite end, where enthusiastic volunteers helped empty the buckets and spread the soil. The effort was satisfying. And sufficiently vigorous to prevent me from succumbing to hypothermia.
Steps 7, 8, 9, 10, 11:
During my day on the roof, we laid membrane, rolled out felt, positioned drainage mats and spread 50 bags of soil. The following week, the Brooklyn Grange team finished installing the roof lining, spread another 310 bags of soil, created level planting beds, dug walkways through the soil, installed drip lines for irrigation, transplanted hundreds of seedlings that had been growing offsite since March, and planted thousands of new seeds.
State of the Grange
In the time I've spent delaying completion of this post, Brooklyn Grange has produced a bounty of fresh vegetables. In addition to providing produce to local restaurants, Roberta’s and Vesta, the Grange now offers CSA shares and sells veggies onsite and at two additional markets. If you're in the area, stop in and buy some produce fresh from the roof!
What’s So Great About Rooftop Farms?
- We need all the good agriculture we can get – it’s always beneficial to produce food without harmful synthetic pesticides and fertilizers.
- Ultra-local – since cities are population dense, produce from urban rooftops can be moved from farm to fork without using tractor trailers or jumbo jets.
- Food access – urban farms can provide nutritious food to communities that otherwise lack access to fresh, high-quality produce.
- Reestablishing the connection to agriculture – city residents are able to see how food is actually produced.
- More greenspace – plants are a welcome addition to the concrete jungle.
The not so obvious:
- Building efficiency – rooftop farms improve energy efficiency by providing insulation, which keeps buildings warmer in the winter and cooler in the summer.
- Moderating the heat island effect – traditional roofs absorb the sun’s radiation during the day and release the heat at night. In cities, where the ground is covered by pavement, concrete and non-green roofs, the radiation of all this heat raises air temperatures, which increases energy used for cooling, and causes additional air pollution. Green roofs absorb much less heat, and thus decrease the heat island effect.
- Reducing runoff – since cities have so many impermeable surfaces, most precipitation ends up washing into storm sewers, carrying pollutants from roads and sidewalks. Although most cities treat storm water before releasing it into rivers, lakes, oceans or other waterways, heavy storms can overload local wastewater treatment facilities, causing polluted water to flow directly into the surrounding environment. Green roofs capture precipitation, transforming this potential pollution stream into a useful resource.