Sustainable Drainage Design

Overview

SBS has partnered with Geo Environmental Sciences Limited (GESL) to offer a Sustainable Drainage Design. This comprises of a range of options for planners, architects, installers or homeowners and dependent upon requirements can include Desk Study, Site Visit, Ground Investigations or Designs for Soakaways, Swales and Basins.

Sustainable Drainage is an environmentally friendly way of dealing with surface water runoff which avoids the problems associated with conventional drainage practice. Conventional drainage is designed to move rainwater as rapidly as possible from the point at which it has fallen to a discharge point, either a watercourse or soakaway.

According to the Environment Agency this approach has a number of harmful effects:

• Run-off from hard paving and roofing can increase the risk of flooding downstream, as well as causing sudden rises in water levels and flow rates in watercourses.

• Surface water run-off can contain contaminants such as oil, organic matter and toxic metals. Although often at low levels, cumulatively they can result in poor water quality in rivers and groundwater, affecting biodiversity, amenity value and potential water abstraction. After heavy rain, the first flush is often highly polluting.

• By diverting rainfall to piped systems, water is stopped from soaking into the ground, depleting ground water and reducing flows in watercourses in dry weather.

Sustainable drainage systems can mitigate these problems.

Sign up

For more details:

Telephone: 01273 6999406
Email: geosciences@travisperkinsplc.co.uk

Or go to website for further details: www.geo-sciences.net

How to buy:

Desk Study

Desk Study: £595 includes full ecological records search; full Envirocheck Search, full Coal Authority records search, Consultation with EHO / Building Regulations Dept. / Archaeology Department, Flood Plain details, and constraints analysis

Site Visit: £495 includes a site walkover

Ground Investigation

In-situ permeability testing to derive design data e.g trial pits, auger holes, window sampling etc.

Scenario 1: Low Intrusive

Engineer: £495/day

Window Sampler: £880/day

Scenario 2: High Intrusive

Engineer: £495/day

Tanker: £550/day

JCB: £390/day

Soakaway Design

Using BRESOAK software and our knowledge of impermeable runoff areas, we can design appropriate soakaway sizes and types.

Preliminary Design: £80

Full Design: £700/day

Design of Swales and Basins

We can provide access to expert consultants for all of your design needs.

Full Design: £700/day

Note: All figures are indicative and as no ground conditions are the same and will be subject to variation on a job by job basis

Benefits

Top

Sustainable Drainage schemes are beneficial because:

• They do not contribute to flooding

• They encourage wildlife

• Create new wetland habitat, which is threatened in the UK

• Provide visually attractive, and educational amenities

Hints & Tips

We look at a range of techniques to meet your sustainable drainage needs. According to the NHBC Sustainable Drainage systems or SUDS “are a sequence of management practices, control structures and strategies designed to efficiently and sustainably drain surface water, while minimising pollution and managing the impact on water quality of local water bodies.”

There are a number of SUDS techniques and the particular combination of techniques employed on any one development depends on the local conditions at any site. A summary of the techniques that could be employed include:

• Green roofing or rain/grey water harvesting techniques

• Swales grassed depressions which lead surface water overland from the drained surface to a storage or discharge system, typically using the green space of a roadside margin

• Basins designed to hold back storm runoff for a few hours and to allow the settlement of solids

• Infiltration trenches shallow, excavated trenches, filled with stone to create an underground reservoir

• Permeable pavements permeable concrete blocks, crushed stone or porous asphalt

• Filter drains is a trench covered with gravel or rock that redirects surface and groundwater away from an area. They have perforated hollow pipes along the bottom to quickly vent water that seeps down through the upper gravel or rock

• Ponds or wetlands which can be designed to cope with variations in water levels during storms, or prolonged periods of wet weather thereby enhancing flood-storage capacity.

In line with NHBC best practice, the adoption and success of SUDS will depend on the local ground conditions (primarily type of soil) and depth to groundwater in the area. A survey of the ground conditions will be necessary before deciding on a specific SUDS technique. The assessment should also include a study of the ecological status and sediment releases of the area, the possible impacts caused by flooding, and current drainage patterns in the area.