Environmental Engineering Reference
In-Depth Information
fertilization of the cover should not be permitted, unless plants exhibit signs of
nutrient stress (then a low-strength organic fertilizer could be applied annually).
Experience indicates that it may take 5 or more years for a water-quality vegetated
cover to attain its maximum pollutant removal efficiency.
In Combination with Infiltration Measures Vegetated roof covers are fre-
quently combined with ground infiltration measures. Vegetated roofs improve the
efficiency of infiltration devices by:
• Reducing the peak runoff rate
• Prolonging the runoff
• Filtering runoff to produce a cleaner effluent
Roofs that are designed to achieve water quality improvements will also reduce
pollutant inputs to infiltration devices.
Construction of a Vegetated Roof
Inspect the completed waterproofing visually to identify any apparent flaws, irreg-
ularities, or conditions that will interfere with the security or functionality of the
vegetated cover system. The waterproofing should be tested for watertightness
by the roofing applicator.
1. Institute a program to safely install the vegetated roof system.
2. Introduce measures to protect the finished waterproofing from physical
damage.
3. Install slope-stabilization measures (pitched roofs with pitches in excess of
2 : 12).
4. If the waterproofing materials are not root-fast, install a root-barrier layer.
5. Lay out key drainage and irrigation components, including drain access
chambers, internal drainage conduit, confinement border units, and isolation
frames (for rooftop utilities, hatches, and penetrations).
6. Install walkways and paths (for maintenance or projects with public access).
7. Test irrigation systems (as relevant for roof gardens).
8. Install the drainage layer. Depending on the variation type, this could be a
geocomposite drain, mat, or drainage medium.
9. Provide protection (e.g., ultraviolet-degradable erosion control netting)
from wind disruptions as warranted by the project conditions and plant
establishment method.
Note: In some installations, slope-stabilizing measures can be introduced as
part of the roof structure and will be already be in place at the start of the
construction sequence.
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