INGENIEUR a
Figure 3.2 : ( a ) Typical Section of Dry Pond ( b ) Constructed Dry Pond at Site A ( picture below )
b
conveyed by swales and the reduced stormwater velocities enable more effective sedimentation , infiltration and evaporative water treatment . The maximum storage depth for dry ponds , using landscape areas , shall be at least 300mm and shall not exceed 600mm under design conditions .
Other design considerations for BIOECODS include the most suitable location for the detention pond / OSD , as this may lead to a deeper invert level compared to the discharge point invert level . The criteria considered for selecting the site for storage facility should include the site ’ s ability to support the pond environment , the discharge point and receiving water body and the costeffectiveness of locating a pond at that specific site .
The materials used in the BIOECODS are mostly environment friendly and readily available in the market . Some of the construction materials are made from recycled materials and if used responsibly may have a vital role in promoting sustainable construction . As the construction materials do not degrade , they will not require as much maintenance or replacement and thus have a longer lifespan . The natural resources used in the system such as cow grass provides greenery to the constructed area . The materials used in this BIOECODS construction ( Figure 3.3 ) include :
● Drainage module for sub-surface swale ;
● Drainage cell for sub-surface dry pond ;
● Geotextile Filter Fabric – permeability capacity of 9.30mm / s ;
● Clean / washed river sand which passed sieving test of BS 1377 ( 0.5mm-0.2mm );
● Topsoil of thickness between 25mm to 100mm ; and
● Cow grass ( Axonophus compressus ).
62 VOL 88 OCTOBER-DECEMBER 2021