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Johnson &
Johnson’s objective for the Spring House corporate campus was to mitigate the stormwater impacts in connection with the
construction of future facilities. A 150,000 sq. feet clinical
development, laboratory, and office space addition was announced in May
2007 and will finish construction in 2009. Full build-out of the
site will not be completed until 2014. The incorporation of Best
Management Practices (BMPs) reduces non-point site pollution and flash
flooding in this prone area. These sustainable development practices
will reduce the expansion project’s runoff levels by 15% compared to
pre-development runoff rates. The porous pavement parking lot has been completed,
but the wetlands are not yet under
construction.
Integrated
into Johnson & Johnson’s site expansion are the following stormwater
Best Management Practices (BMPs): 1) Porous pavement and underground
infiltration gallery; 2) Bioretention swales; 3) Constructed stormwater
wetlands.
1)
Porous Pavement and Underground Infiltration Gallery
Testing was conducted concluding that the site was suitable for the
installation of both porous pavement and an underground infiltration
gallery. Percolation testing determined that the infiltration rate would
be 1.04 inches per hour and that the two elements would capture about
42% of stormwater volumes. For a diagram of a typical porous pavement
section with underground infiltration gallery, please click here. The
subsequent project phases to incorporate other BMPs like bioretention
swales, wetlands, and other non-structural methods are meant to retain
or filter the remaining runoff.
The
construction of the porous pavement included the digging of divided
subsurface water storage cells, measuring 60 feet by 60 feet by an
average of 3 feet deep. These cells were lined with geotextile fabric.
Before AASHTO No. 1 gravel was put in place, perforated pipes connected
to the main storm sewer pipes were set at different grades to provide
conveyance and diffusion of stormwater into the storage cells. Only one
building under construction is presently hooked up to the system; per
the master plan, the storage capacity of this reservoir anticipates all
future runoff volume from buildings at subsequent stages of site
development.
2)
Bioretention Swales
When the underground infiltration gallery reaches its maximum storage
capacity excess stormwater flows through a custom “upwell” pipe relieve
system. The stormwater is filtered through graded vegetated swales
before flowing into stormwater drains. Native shrubs, trees and
ornamental grasses, all salt and moisture tolerant, were planted in the
parking lot islands to both absorb stormwater volume and dissolve common
pollutants from vehicular traffic. The swales were covered with
decorative gravel (river stone) for maintenance purposes. The porous
asphalt works so well that these swales do not encounter much runoff.
For a list of native plants used on the islands in between the parking
lot bays, please click
here.
3)
Constructed Stormwater Wetlands
This is a future project, expected to be completed after 2014. Details will be added as they become
available.
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