Management

SuDS components should be visible and their function should be easily understood by those undertaking the maintenance. If the SuDS components are on the surface when problems occur, they are generally obvious and can often be remedied by using standard landscaping practice. If schemes are properly monitored, inspected and maintained, any deterioration in performance can often be managed out.

Management and maintenance is an important consideration of SuDS design. In particular these key aspects should be considered.

1. Maintenance access – ensuring appropriate and long term access to components where future maintenance may be required, this may include areas that can support heavy plant and machinery.

2. Appropriate pre-treatment (and forebays) – to allow sediment management.

3. Bypass system – or appropriate temporary drainage infrastructure for use if required during sediment management and other maintenance activities.

4. Disposal areas – should be available for organic arisings (green waste) and sediments.

5. Choice of materials – the materials used during the design and construction of the components and scheme should be easy to source and procure.

Owner’s manual

Good communication and supervision between designers, contractors and clients is important for ensuring SuDS perform as designed. As SuDS differ from traditional drainage systems and require different maintenance regimes, those that adopt SuDS or owners of developments that incorporate them should be provided with an owner’s manual.

This should include the following:

location of all SuDS component in a site
brief summary of how the components work, their purpose and how they can be damaged
maintenance requirements (a maintenance plan) and a maintenance record
explanation of the consequences of not carrying out the maintenance that is specified
identification of areas where certain activities are prohibited (for example, stockpiling materials on pervious surfaces)
an action plan for dealing with accidental spillages
advice on what to do if alterations are to be made to a development, if service companies undertake excavations or other similar works are carried out that could affect the SuDS.

The owner’s manual should also include brief details of the design concepts for the SuDS scheme and how the owner or operator should ensure that any works undertaken on a development do not compromise this.

Operation and management

There are many factors which will influence the type and intensity of maintenance required for a SuDS component or scheme at any particular site, including:

Type of SuDS component
Land use associated with contributing catchment
Level of construction ongoing within the contributing catchment
Planting types
Habitat types that have been created
Amenity requirements of the area.

The demands on the SuDS to perform a particular aesthetic function will be a key driver, with high frequencies of grass cutting and vegetation management often being required for appearance and amenity value rather than for functional reasons.

Maintenance

Maintenance is likely to be broken down into regular, occasional and remedial maintenance. Table 1 provides a breakdown of these typical requirements. Further information on adoption and maintenance can be found here.

Table 1 Typical inspection and maintenance requirements

Activity	Indicative frequency	Typical tasks
Routine/regular maintenance	Monthly (for normal care of SuDS)	litter picking grass cutting inspection of inlets, outlets and control structures.
Occasional maintenance	Annually (dependent on the design)	silt control around components vegetation management around components suction sweeping of permeable paving silt removal from catchpits, soakways and cellular storage
Remedial maintenance	As required (tasks to repair problems due to damage or vandalism)	inlet/outlet repair erosion repairs reinstatement of edgings reinstatement following pollution removal of silt build up

Inspections

As part of the on-going management of most SuDS components there is a need for regular inspections to ensure that blockages, silt and excess litter are not adversely affecting the component or scheme. It is important that this is carried out and time is allowed for corrective action to be taken.

The pre-handover inspection is discussed in the section on construction. Its objective is to provide the client or adopting organisation with a durable SuDS scheme that is unlikely to suffer premature failure due to construction defects or clogging caused by heavy silt loads in construction runoff.

Routine inspection

Routine inspections should be carried out once a month for most components, although some, such as infiltration devices, require less frequent visits (the Lamb Drove site in Cambridge performed adequately with less maintenance). Site managers and/or landscape contractors should be used to inspect the SuDS. The advantage being that they have intimate knowledge of the development and visit the site on a frequent basis.

This recurring attendance ensures monitoring of the drainage system, a rapid response to problems and “ownership” of the SuDS components. The inspections should be recorded on the maintenance record.

Waste management

SuDS generate waste - they are designed to intercept silt and allow the natural breakdown of organic pollutants. Regular maintenance of SuDS, including occasional removal of silt and vegetation that gathers in SuDS, is required to ensure long term performance. Good SuDS design and the use of source control and the SuDS management train should help to reduce and manage the accumulation of silt.

Removal of silt from surface water runoff is important because a large proportion of pollutants are attached to silt particles. If the silt is removed then most of the pollution will be dealt with. Thus retention of silt in the SuDS is one of the prime objectives and should not be seen as a problem. If siltation is occurring the SuDS is doing its job correctly, whether it is a swale, a pond, a permeable pavement or a geocellular tank system.

Organic waste should be used around the SuDS components or schemes to form wildlife piles. If this is not practical it should be composted or, as a last resort, removed to a licensed landfill site. The Environment Agency has adopted a risk based approach in relation to removal of silt from SuDS (Environment Agency 2011). However some evaluation of the silt is required to determine whether it might be a “hazardous waste”. If this is likely (industrial or heavy vehicle management areas, or end of pipe ponds) the silt will require chemical analysis and compliance with appropriate waste management legislation. Where there is a low risk of pollution (residential, schools, commercial sites, schemes with source control) a sustainable approach to waste management should be taken.

Details of the Environment Agency Regulatory Position Statement can be found here

Green waste from SuDS components and schemes is much the same as waste from normal landscape maintenance and can be managed by:
Shredded for surface spreading like a mulch
The development of wildlife piles to provide habitat, refuges, shelter etc. When they biodegrade they can compost.
On or offsite (eg Council Green Waste) composting which can provide useful mulching
Disposal to landfill often as a last resort.

Reliability

The reliability of SuDS is critically dependent on the quality of the design and construction, in particular the management of silt. If good guidance is followed, there is no reason why SuDS cannot provide a durable and reliable drainage approach.

SuDS have a design envelope within which they are intended to operate, in terms of water quality, flow rates and volumes. Events that exceed the design criteria may cause flooding or increased levels of pollution in the outflow and the consequences of this must be carefully assessed. If necessary, the design envelope should be enlarged so that the risks associated with a SuDS scheme are acceptable (this is no different to a conventional scheme). In many respects the reliability of SuDS schemes is likely to be less problematic than with some conventional techniques, since if failure does occur the results are likely to be above ground and visible and it is easier to adapt components and schemes on the surface.

Health and safety

With careful thought and consideration during the SuDS design process health and safety risks can be designed out. Generally speaking good SuDS schemes tend have water features like ponds that are small, and shallow with gentle side slopes which should also minimise health and safety risks. CIRIA’s SuDS Manual provides detailed guidance on the safe design of SuDS components. However, all proposals should be in line with the Construction, Design and Management Regulations 2007. This requires hazards to be removed by good design wherever possible rather than providing mitigation to manage risk.

Those responsible for the maintenance and management of SuDS should take appropriate health and safety precautions for activities and risk assessments should be undertaken.