Page build
External
Surface Water
To minimise the risk of downstream flooding in times of high rainfall, design is necessary to delay the rain water entering watercourses and forming a peak flow overloading the downstream network and causing flooding. Water can be temporarily stored in the underlying soil strata with delay resulting from the natural rate of water percolation. Current Building regulations require the use of permeable surfaces to allow this to happen for surfaces such as paths, driveways and hard standing areas. Hard concrete and paved areas are no longer allowed. Direct discharge into watercourses is no longer allowed for new structures. The technique of soak-aways has been used for many years in house building, where a hole was dug in the garden and filled with general rubble. The outflow from the gutters was fed into this soak-away pit. Design has become more refined and the ability of the soil absorb the rainwater from sudden downpours is now tested to ensure that a localised flooding problem is not introduced. This is defined as the “BRE365” test. This requires a hole of known dimensions to be dug on site and then filled with water. The time taken for the water to soak away between the 75% and 25% points is measured. The result determines if the soil strata meets the permeability requirements for on site soak-away or if the rate of drainage is so long that additional on site storage is needed to ensure localised flooding is avoided.
The local association is that the area is a sandy free draining soil, but a solid sub strata exists below that result sin poor drainage properties. A buried attenuation tank formed of plastic crates to form a temporary storage of peak rainfall is used. The tank size is determined by simulation the likely quantity of rain collected in a 1 in 100 year event.
However, the process could cause over drainage of the site compared to its current state, resulting in stress to the surrounding trees on the site. Attention has therefore been paid to make sure that water can be returned to the site in a controlled constant discharge rate to ensure that the balance between peak and mean flow can be balanced.
Internal
The building has been designed to allow isolation of individual facilities components to ensure operation continuity. Wherever feasible, potential individual single points of failure have been avoided.
- Position all services and stairs access outside of the working envelope to secure maximum space flexibility.
- Access requirements for services to minimise security checks and safe working requirements from external contractors
- Ducting included in the external wall and ceiling to enable services such as electrical, data networking and security services to be maintained with minimum intrusion
- Heating and Ventilation to avoid hot surfaces with quick response to changing environmental conditions.