Is
there risk of oil contaminating the drainage
from the site?
Risk
of infrequent light contamination and potential
for small spills only, e.g. car park
Risk
of regular contamination of surface water
run off with oil and/or risk of larger spills,
e.g. vehicle maintenance area, goods vehicle
parking or vehicle manoevering5
Drainage
will also contain dissolved oils, detergents
or degreasers such as vehicle wash water
and trade effluents, e.g. industrial sites
Fuel
oils are delivered to and dispensed on site,
e.g. retail forecourts
Very
low risk of oil contamination, e.g. roof
water
Source
control SUDS must be considered and incorporated
where suitable
If
not suitable
Separator
not required
Bypass Separator with alarm required
Class I if discharge
to surface water2,3
Class II if discharge
to foul sewer1
Full Retention Separator with alarm required
Class I if discharge
to surface water2
Class II if discharge
to foul sewer1
Trade
effluents must be directed to the foul sewer1
It may need to pass through a separator
before discharge to sewer for removal of
free oils
Full
Retention ‘Forecourt’ Separator with alarm
required
Class I if discharge
to surface water2
Class II if discharge
to foul sewer1,4
Clean
water should not be passed through the separator
unless the size of the unit is increased
accordingly
The use of SUDS should be considered at
all sites and they should be incorporated
where suitable. SUDS can be used to polish
the effluent from these separators before
it enters the environment6
Source
control SUDS should be considered where
possible
1 You must seek prior permission from your local sewer provider before you decide which separator to install and before you make any discharge.
2 You must seek prior permission from the relevant environmental body before you decide which separator to install.
3 In this case, if it is considered that there is a low risk of pollution a source control SUDS scheme may be appropriate.
4 In certain circumstances, the sewer provider may require a Class 1 separator for discharges to sewer to prevent explosive atmospheres from being generated.
5 Drainage from higher risk areas such as vehicle maintenance yards and goods vehicle parking areas should be connected to foul sewer in preference to surface water.
6 In certain circumstances, a separator may be one of the devices used in the SUDS scheme. Ask us for advice.
