DLANDstudio invented the Highway Overpass Landscape
Detention System, or HOLD System, to collect and filter storm water from highway downspouts. The HOLD System includes planted, modular bio-swales that absorb, retain, and filter pollutants such as oil, heavy metals, and grease from contaminated outfalls. The green infrastructure system renders runoff much cleaner as it is released into drains and surrounding waterways.
There are more than 7000 miles of bridges and elevated highways running through US cities. There are also almost 800 cities with combined sewer systems. HOLD Systems can remediate the impact that our highway infrastructure makes on the hydrologic cycle of neighboring areas. The combined effects of cleaning overflow water from highway downspouts would have a dramatic impact on the ecological health of local, regional, and national hydrology systems.
Designed for easy transport and deployment, HOLD units can be quickly and easily installed in hard to reach, hard to drain areas along interstate highways. The two modular systems, one in-ground and one above ground, adapt to water-table height, permeability, and the availability of sun. Plant palettes selected for each site will help to break down or absorb copper, lead, cadmium, hydrocarbons, zinc and iron commonly found in runoff. Specially calibrated soils maximize plant productivity and create the ideal level of drainage for citywide storm water management needs.
HOLD systems are currently deployed in three locations in New York City. The project has received funding and support from the New York City Department of Environmental Protection, the Long Island Futures Fund, and the National Oceanic and Atmospheric Administration.