Stormwater Management for Commercial Developments

SEL Environmental Ltd     Tel: 01254 589987     Email:

Sustainable Drainage, but better...

SEL SuDS solutions enable the principles set out in the CIRIA SuDS Manual to be applied within the environment of the commercial development. All solutions take account of regional drainage strategies and allow interface with green solutions to manage surface water which have benefits to ecology, local habitat and biodiversity and will allow integration of:

  • Permeable paving,
  • Green infrastructure (tree pits),
  • Swales and wetlands
  • Detention ponds

All solutions will incorporate a series of treatment phases specifically developed to meet the robust requirements of LLFA's, current guidelines and legislation relating to SUDS. The main design principle we use is 'Source Control' the cornerstone of good Sustainable Design

Source Control is the treatment and controlled release of surface water runoff at or very near its source. Source Control is the preferred technique for the implementation of SUDS. 

Site discharge should be according to the following hierarchy:

  1. Discharge into the ground (infiltration);
  2. Controlled discharge to a surface water body/watercourse or the sea;
  3. Controlled discharge to a surface water sewer.
Value Engineered

SEL can review your current drainage layout and where possible develop a value engineered drainage proposal. We provide full technical assistance during the design process and installation period for your development whether it be Office, Retail, Warehousing, Industrial, Leisure or a School.

permac hannel

Permachannel weir and baffle arrangement carefully designed to retain oils and allow silts to fall from suspension before passing forward.

Treatment at Source

3 phases of treatment are provided in the SEL SuDS solution for collection from hard surfaces.

Phase 1 is within the Permachannel where oils are retained by a weir and baffle arrangement. This arrangement retains a small volume of water within the main body of the Permachannel. Less dense oils will float on the surface and due to the low velocities within the system, silts can fall from suspension for later removal.

Phase 2 is provided by a Permavoid Biomat. This is a secondary treatment phase for potential residual hydrocarbons which are trapped by a pollutant-intercepting floating mat. One Permavoid Biomat cell is capable of retaining 56g of oil. The floating medium is maintained at air-water interface allowing optimum conditions for aerobic degradation of any trapped oils. The mat is self maintaining and degrades residual oils by absorption and aerobic digestion.

Phase 3 is a final polishing by a voided sub-base aggregate with is used to provide temporary attenuation within the car park construction. SEL recommend SudsAgg by Aggregate Industries which is the only GUARANTEED 30% VOIDED aggregate available on the market. Unlike other available voided aggregates, SudsAgg behave like a Type 1 Sub-base which makes installation very easy with no need for plastic grids or other pavement stabilising membranes.

Design, Supply & Install?

SEL offer all levels of support, so if you just require some technical advice we can help or if you like our support through the whole process from conception to installation we can help.

  • Identify the drivers and design criteria of the project
  • Review concept design layout options and assess which best meets the requirements of the customer and end users
  • Pursue the best balance between user requirements and cost
  • Project management through the installation cycle
  • Specialist installation saves time and manpower on site
  • Commitment to CIRIA best practice
  • Full installation ISO9001 QA and Onsite technical support
  • Post installation maintenance packages available

Permachannel connecting to a Biomat prior to diffusing into SudsAgg Sub-base

SEL SuDS solutions can help if you need to:
Overcome a high water table

High water tables and even perched water at shallow depth require specific design and construction measures to avoid issues such as flotation of attenuation structures and often prevents the use of soakaways. Anti-flotation and temporary dewatering measures are invariably very expensive, but our solution can provide the attenuation or infiltration by avoiding groundwater issues.

Avoid pumping stations

SEL recommend shallow attenuation systems which can often avoid the need for pumping, that might otherwise be required with conventional drainage or deep attention tank solutions. Pumped solutions can be costly to install and maintain and considered to be environmentally unsustainable.

Excavate in contaminated soil

Redevelopment of brownfield sites often have issues with ground contamination. The use of shallow attenuation or soakaway structures can very often avoid the need to excavate into contaminated soils that will incur significant abnormal costs in either on-site remediation or off-site disposal, plus the numerous associated environmental and CDM issues. Shallow attenuation can avoid substantial costs and reduce overall construction time.

Excavate in hard rock

Excavation of hard rock is usually expensive and slow. However, our car park suds solution is ideal for use on sites that are underlain by hard rock at shallow depth, as the system can be incorporated into the pavement construction invariably avoiding any expensive additional excavation for the drainage system.

Excavate in unstable soils

If you development is underlain with unstable soils, then a shallow drainage solution is ideal to  avoid expensive shoring and stabilisation works which would be required.

Deal with a difficult site access

In narrow, restricted or otherwise limited access sites, SEL SuDS can be easily manhandled into place without any heavy lifting or off-loading gear. With void ratios up to 95% for maximum water retention, lightweight cells can be carried and installed by a single construction worker. 

3D Virtual Tour - click on image and use mouse to zoom in/out and scroll around. Takes a few seconds to load.

Permachannel Sections.pdf Permachannel Sections.pdf
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