St Mary Redcliffe Project 450 RIBA 2 Stage End Report

ainage
elopments. A
the existing
rmally required
here are
excavation
to drain away
this site due to
ve.
for storm
ar to green
h the green
the south
ounding trees.
dditional weight
upporting
RECOMMENDATIONS
3.3 Proposed Site Drainage
The above Current items planning should requirements be re-evaluated dictate that SuDS (Sustainable once the Urban location Drainage of the existing site drainage is
establishedSystems) 3.3 Proposed must be Site considered Drainage for surface water drainage on all new developments. A
connection to the existing public sewer is a last resort. A betterment on the existing
volume of stormwater run-off plus an allowance for climate change is normally required
Current planning requirements dictate that SuDS (Sustainable Urban Drainage
It is understood that a significant depth of relatively modern make-up exists on the north
Systems) and this level must of be betterment considered will for need surface to be water confirmed drainage by the on planners. all new developments. There are A
churchyard. connection several The methods site to the of investigations existing 3.3 providing public sustainable Proposed sewer is listed drainage; a last resort. under Site A betterment Drainage sub-section the existing 1 should be utilised to verify this and
volume of stormwater run-off plus an allowance for climate change is normally required
identify options • Swales for the or ponds- location unlikely to for be practical an attenuation this site given the tank excavation
and this level of betterment will need to be confirmed by the planners. There are
several methods required of to providing create the sustainable ponds and drainage; the limited potential for water to drain away
A confirmed drainage the clay. strategy for both surface and foul water is normally required before
• Swales Soakaways- or ponds- as above unlikely soakaways to be practical are unlikely on this to site be feasible given the on excavation this site due to
planning consent required the is clay given. indicated to create The in the the ponds suggested geotechnical and the limited information next potential provided steps for water above. should to drain away therefore be reviewed with Bristol
•
City Council at in Green the clay. or blue roofs- green roofs provide attenuation or storage for storm
commencement of RIBA 3
The main disadvantage of a green or blue roof system is the additional weight
to be needed prior to the submission of the planning application.
4.1 Flooding
of the water and soil • build Swales up which obviously or ponds- requires larger unlikely supporting to be practical A confirmed on drainage this strategy site for given both surface the and excavation
foul water is normally required
structure and foundations.
before planning consent is given, so the site investigation, set out in section 2, is likely
required to create the ponds and the to be limited needed prior potential to the submission for of water the planning to application. drain away
in the clay.
The site is generally in a low risk area of flooding as shown by the flood maps below.
• Soakaways- as above soakaways are unlikely to be feasible on this site
The
due
surface
to
water flooding map suggests that there may be a risk of surface water
the clay indicated in the geotechnical information provided above.
flooding to the south west of the site immediately to the south of the church. This is
Figure 11. Risk of flooding from rivers and the sea
• Green or blue roofs- green roofs provide attenuation or storage for storm
likely to be due to a localised low spot is not within the area of the proposed
Risk of Flooding from Rivers and the Sea
water within the soil layer of a planted roof, blue roofs are similar to green development.
Figure 11. Risk 10. of Below flooding from ground rivers and the attenuation sea tank
roofs but provide an additional cellular zone for storage beneath the green
roof finish. This may be an option on this project, particularly in the south
Figure 9. Blue roof
courtyard where the aim is to blend the building in with the surrounding trees. 3.4 Next Steps
• Below ground attenuation-
The
storage
main
tanks wrapped
disadvantage
in an impermeableof a green or blue roof system is the additional weight
Figure 9. geotextile Blue roof and buried below ground level to store storm water. A large area of
excavation is normally required of the which water may not be and desirable soil in this build case. The up which obviously requires larger supporting
A confirmed drainage strategy for both surface and foul water is normally required
• Below attenuation ground tank attenuation- would discharge storage to tanks a manhole wrapped with in a an flow impermeable control device
structure and foundations.
before planning consent is given, so the site investigation, set out in section 2, is likely
geotextile which then and releases buried water below at ground a pre-agreed level to rate store to storm the public water. drainage A large system. area of
excavation The position is of normally an attenuation required tank which also may has not impact be desirable on the landscaping
this case. The
to be needed prior to the submission of the planning application.
Figure 10. Below attenuation strategy. ground tank would attenuation discharge to a manhole tank with a flow control device
3.4 Next Steps
Current planning requirements dictate that SuDS (Sustainable Urban Drainage
Systems) must be considered for surface water drainage on all new developments. A
connection to the existing public sewer is a last resort. A betterment on the existing
Figure 10. Below ground attenuation tank
volume of stormwater run-off plus an allowance for climate change is normally required
and this level of betterment will need to be confirmed by the planners. There are
Figure
3.4
10.
Next
Below
Steps
ground attenuation tank
several methods of providing sustainable drainage;
4. Site Constraints
• Soakaways- water within the as above soil layer soakaways of a planted are roof, unlikely blue to roofs be feasible are similar on this to green site due to
the roofs clay but indicated provide an in the additional geotechnical cellular information zone storage provided beneath above. the green
• Green roof finish. or blue This roofs- may green be an option roofs provide on this attenuation project, particularly or storage in the for storm south
water courtyard within where the soil the layer aim is of to a blend planted the roof, building blue in roofs with are the similar surrounding to green trees.
roofs The main but provide disadvantage an additional of a green cellular or blue zone roof for system storage is beneath the additional the green weight
roof of the finish. water This and may soil be build an up option which on obviously this project, requires particularly larger supporting the south
courtyard structure and where foundations. the aim is to blend the building in with the surrounding trees.
which then releases water at a pre-agreed rate to the public drainage system.
The above The items position can be of an considered attenuation following tank also confirmation has impact of on the the location landscaping of the existing
site drainage. strategy.
The above items can be considered following confirmation of the location of the existing
site drainage.
A confirmed drainage strategy for both surface and foul water is normally required
before 3.4 planning Next Steps consent is given, so the site investigation, set out in section 2, is likely
A confirmed drainage strategy for both surface and foul water is normally required
before planning consent is given, so the site investigation, set out in section 2, is likely
to be needed prior to the submission of the planning application.
3. Site Constraints
4. Site Constraints
4.1 3.1 Flooding
4. Site Constraints
The site is generally in a low risk area of flooding as shown by the flood maps below.
The 4.1 surface Flooding site water is generally flooding map suggests in a low that there risk may area be a risk of surface flooding water as shown by the flood maps below. The surface
flooding to the south west of the site immediately to the south of the church. This is
The likely water site to be is generally flooding due to a localised a low map risk low area spot suggests of and flooding is not within that as shown the there area by of flood the may proposed maps be below. a risk of surface water flooding to the south west
The development.
of
surface
the site
water
immediately
flooding map suggests
to
that there
south
may be a
of
risk
the
of surface
church.
water
This is likely to be due to a localised low spot
flooding to the south west of the site immediately to the south of the church. This is
likely and to is be not due to within a localised the low spot area and is of not the within proposed the area of the proposed development
development.
Figure 12. Risk of flooding from reservoirs
Figure 12. Risk of flooding from reservoirs
Risk of Flooding from Reservoirs
4. Site
4.1 F
The site
The surfa
flooding t
likely to b
developm
Figure 11
Above: A Typical Below-Ground
Attenuation Tank
Right: An Illustrative Blue-Roof
Build-Up
Figure 9. Blue roof
Figure 11. Risk of flooding from rivers and the sea
Figure 13. Risk of flooding from surface water
Risk of Flooding from Surface Water
4.2 Trees Figure 14. South courtyard trees