Environmental Engineering Reference
In-Depth Information
Fig. 1 Site plan (left) and aerial image (right) of the Star City in Seoul (Source UNEP and SEI
2009
)
infrastructure (IWA
2008
). Built on a 6.25 ha site (originally a playing
field) owned
by Konkuk University, Star City is a major real estate development project with more
than 1,300 apartment units (accommodating 4,000
5,000 people) spread between
four apartment blocks (each between 35 and 57 storeys) plus a department store. Each
apartment block has a plan area of 1,500 m
2
. The rainwater harvesting system has
been designed by the Rainwater Research Center at Seoul National University and
Professor Mooyoung Han. The catchment area consists of 6,200 square metres of
rooftop and 45,000 square metres of terrace. Rainwater is piped to the RWH base-
ment under the 35-storey block where there are three separate storage tanks each of
1,000 m
3
capacity (3,000 m
3
-
in total) (Fig.
1
). The basic design idea of the RWH
systemwas to collect up to the
first 100 mm of rainwater that falls on the complex and
to use the collected rainwater for gardening and public toilets. The
rst two tanks are
used to collect rainwater from the rooftop and the ground and mitigate
flood risk in the
area during the monsoon season. A special feature is that most of the irrigated water in
the garden is in
ltrated into the ground and returns to the tank for multiple use. The
third tank is used to store tap water in case of emergency.
The water conservation is expected to be approximately 40,000 m
3
per year,
which is about 67 % of the annual amount of rainfall over the Star City complex.
The ratios of the volume of water conserved per month to the monthly amount of
rainfall, ranged widely from 18 % in July to more than 200 % in November. More
than 200 % could be achieved by supplying stored rainwater left from the previous
month and by irrigation, which is recycled to the rainwater tank (Han and Mun
2011
). The tank volume
catchment area ratio of 5.8 m
3
/100 m
2
and 10-year design
period for this building would provide protection from a 50-year rainfall
-
ood
event. The risk of
floods is controlled pro-actively with the remote control system,
by emptying or
filling the tanks appropriately. With regard to energy saving,
approximately 8.9 MWh of electricity is expected to be saved per year by rainwater
use in the Star City project.
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