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Line 8: − The benefits of 'high organic' media are:+ − #Increased water holding capacity, which benefits both vegetation health and stormwater retention,+ − #Often lighter weight, even when saturated.+ − The disadvantages of a 'high organic' planting medium are:+ − #Increased [[phosphorus]] concentration in runoff water, however this may be mitigated by the reduced runoff volume resulting in a lower loading overall,+ − #The lightweight material is more prone to wind erosion, and this should be accounted for in the initial design, alternatives include erosion control blankets, soil tackifiers, or Sedum mats. + + + + +
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In many proprietary systems the default option for planting medium will be a granular material with very low organic matter content. However, many companies can arrange for a high organic content alternative to be substituted if requested.
In many proprietary systems the default option for planting medium will be a granular material with very low organic matter content. However, many companies can arrange for a high organic content alternative to be substituted if requested.
{|class="wikitable"
|+ Considerations for using a 'high organic' planting medium
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!style="background: darkcyan; color: white"|Benefits
!style="background: darkcyan; color: white"|Disadvantages
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|Increased water holding capacity, which benefits both vegetation health and stormwater retention <br>Often lighter weight, even when saturated||Increased [[phosphorus]] concentration in runoff water, however this may be mitigated by the reduced runoff volume resulting in a lower loading overall,<br>The lightweight material is more prone to wind erosion, and this should be accounted for in the initial design, alternatives include erosion control blankets, soil tackifiers, or Sedum mats.
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Increasing the depth of planting medium from 10 cm to 15 cm has been shown to benefit the vegetation<ref>MacIvor JS, Margolis L, Puncher CL, Carver Matthews BJ. Decoupling factors affecting plant diversity and cover on extensive green roofs. J Environ Manage. 2013;130:297-305. doi:10.1016/j.jenvman.2013.09.014.</ref>; stormwater retention was not improved with this increase in depth <ref>Hill J, Drake J, Sleep B, Margolis L. Influences of Four Extensive Green Roof Design Variables on Stormwater Hydrology. J Hydrol Eng. 2017;22(8):4017019. doi:10.1061/(ASCE)HE.1943-5584.0001534.</ref>.
Increasing the depth of planting medium from 10 cm to 15 cm has been shown to benefit the vegetation<ref>MacIvor JS, Margolis L, Puncher CL, Carver Matthews BJ. Decoupling factors affecting plant diversity and cover on extensive green roofs. J Environ Manage. 2013;130:297-305. doi:10.1016/j.jenvman.2013.09.014.</ref>; stormwater retention was not improved with this increase in depth <ref>Hill J, Drake J, Sleep B, Margolis L. Influences of Four Extensive Green Roof Design Variables on Stormwater Hydrology. J Hydrol Eng. 2017;22(8):4017019. doi:10.1061/(ASCE)HE.1943-5584.0001534.</ref>.