Page 169 - The Green Building Bottom Line The Real Cost of Sustainable Building

148 CHAPTER 5

As is usual with all new technologies, the rainwater collection cistern comes with an
array of maintenance considerations. Algae growth in water is a huge issue in the south,
especially during warmer months, and controlling it has proved more challenging than we
anticipated. To combat algae proliferation, we specified freshwater plants to be installed
in the large water fountain. In the cistern, we installed two pumps that move the water and
discourage algae growth. However, we underestimated the aggressiveness of algae.
Because a conventional chemical solution would damage and most likely kill plant
life in the fountains and our landscaping, we knew had to attack the algae problem
from a slightly different angle. First we installed additional pumps in the cistern, but
this time we used de-stratifying pumps that move the water from the bottom to the
top instead of the kind of pumps that move the water around in circles. Second, we
installed a relatively new technology in the war against algae from Grander Tech-
nologies—a metal tubular structure that actually alters the chemical makeup of algae
as it passes through the structure’s rings. This process kills the algae, and it works with-
out the use of harmful chemicals or electricity. So far, it’s doing the job.

STORMWATER MANAGEMENT

At Abercorn Common, we made a great effort to design the site so that stormwater
runoff did not negatively impact our neighbors. In early studies of the site and the sur-
rounding area, we learned that during severe rains, street flooding occurred down gra-
dient from the existing shopping center. This concerned us greatly; any part of our
design that didn’t take people into consideration was deemed unsustainable and
revised. Since Abercorn Common is less than one mile from marshlands, we were also
concerned about where our stormwater was going and what contaminants it might
carry with it to waterways, such as fertilizers, oils, and gasoline. We designed our
shopping center to collect and hold rainwater on site and allow it to percolate into the
soil, as it would on unpaved land.
To help prevent flooding and contamination of our local waterways, we first used
grade inlets and porous concrete to help absorb and hold rainwater. To do this, we lim-
ited the number of grade inlets normally seen in a development of this size, forcing
the storm water to sheet flow across the parking lot for longer distances and to flow
over porous concrete before arriving at a storm grade inlet.
Additionally, we increased the size of our cistern so it would hold more water, which
lessened the stormwater impact on our two very small detention ponds. Where we could,
we used porous sidewalks made of soft limestone (formed largely from crushed coquina
shells) in the parking lot islands. As our out-parcel building, Shops 600, is not connected
to the rainwater collection system that feeds the cistern and two detention ponds, we de-
signed and built an infiltration trench (more about this later) to allow water to flow through
to the ground, where it is filtered by sands and soils as it is returned to the water table.
Collectively, our efforts have reduced stormwater runoff at Abercorn Common by
30 percent. This is in comparison to years past, when houses in the surrounding
neighborhood in the area known as the Fairmont Basin would flood in heavy rains.