Case studies - Living Roofs in Integrated Urban Water Systems - page 155

As the world's irst urban project of its kind and scale consisting of multiple buildings
with multiple programs, it remains a leading example of how to achieve innova-
tive and environmentally conscious solutions through highly collaborative design
processes. The project initiated collaboration between all design consultants to
ind an urban-scale, integrated-systems solution to reduce both peak stormwater
runoff and high demands on the municipal water supply, irrigation and water
features. The solution was achieved by using harvested rainwater on living roofs
atop all 19 buildings in the complex. The system reduces stormwater runoff and
recycles rainwater for reuse for intensive living roof irrigation, toilet lushing, ire-
safety sprinkler supply, and supplying the at-grade, publicly accessible artiicial
lake with potable-grade, recycled water.
This project operates as a fully integrated stormwater management system.
Stormwater runoff from the roofs cannot recharge the ground at grade due to
the project's location over an underground parking garage, which spans the
entire breadth of the Potsdamer Platz. Instead, runoff is irst treated by ultravio-
let technology. Treated water is then harvested in cisterns, which are located in
the underground parkade of the Potsdamer Platz in order to avoid consump-
tion of precious usable space above-grade. After feeding the artiicial lake of
the Potsdamer Platz (a major feature of the project) and irrigating the roofs,
excess cleansed water from the cisterns is designed to overlow into the nearby
river.
5.2.4.2 Key living roof design features
1 PROCESS
The sheer scale of the Potsdamer Platz project and the large number of differ-
ent design consultants necessitated an integrated planning process that
involved all design consultants on the project. The most complex issue
addressed by all parties involved was deinition of liabilities and assignment of
individual tasks. For example, there was a great deal of discussion as to
whether the structural engineer was solely responsible for calculating the
weight of the intensive living roof courtyards in dry and wet conditions, or
whether the landscape architect was also responsible. It became clear from the
beginning that early communication was necessary and that responsibility allo-
cation required speedy resolution.
Compliance with German planning permissions policy was a primary driver in
the design and implementation of living roofs. This policy mandated the provi-
sion of social space and offsetting of potential negative environmental impacts.
In summary, the policy required that public amenity space with pervious cover be
provided somewhere within the city in order to offset disruption of the hydrologi-
cal cycle by any constructed impervious surface cover. This space could be either
at grade or off-site (e.g., a playground in a low-income and/or socially resource-
poor neighborhood) or on-site above grade (e.g., vegetated roof area). In order
to meet the city's desire to reduce demands on municipal water consumption,
the artiicial lake had to be fed with recycled rainwater. This meant that the