Guidance for developers

CMP and SuDS method statement

Before work can start on a development site, you must have both:

  • a Construction Management Plan (CMP)
  • a Sustainable Drainage Systems (SuDS) Method Statement

You must have measures in place to manage the impact on the existing highway network. You must take reasonable steps to prevent the risk of flooding and pollution on and off site during construction.

When and how you construct SuDS features will differ from site to site. You must consider how you will manage surface water and prevent flooding to surrounding land during the construction phase. If you construct SuDS features at the beginning of the project, you must protect them for the remainder of the construction phase.

You can find further details in the CIRIA SuDS Manual.

Standard contents

  • Contact details for who is ensuring the CMP and SuDS MS is available and adhered to
  • Details of the nature of work must be complete.
  • Site plans
  • A written summary of the proposed surface water management for pre, during and post-construction. This should include:
    • the existing site use
    • soil types
    • infiltration
    • groundwater
    • outfall points (both temporary and permanent)
    • the future maintenance of drainage systems
  • Details and supporting plans for the build route, phasing plan and sequence of works. It must consider show homes, visitor parking and early occupations in this phasing.
  • Strategy and plans showing:
    • the site compound
    • parking for site operatives and visitors
    • details for the loading, unloading and storage of plant and materials
    • details for wheel washing facilities
    • details for deliveries and refuse collection
  • Temporary and permanent access to construction phasing and plans.
  • Routing for construction traffic
  • The details of utility connections. This must include the consideration of trench sharing and collaborative working between statutory undertakers
  • Details of any traffic management needed on the existing highway network. It must consider lead-in times.
  • Details of scaffolding, skips and hoarding needed on the existing highway
  • The strategy that states how you will manage surface water run-off on and from the development during construction. This needs support from plans
  • Details of any site-specific ecological issues or features that need protection
  • The strategy for sediment control and erosion control. This must include:
    • consideration of how this may impact on the final performance of the drainage system
    • any requirements for necessary protection measures at the end of construction
  • Pollution control arrangements, including any possible water quality issues
  • Measures to prevent inadvertent access across any complete or incomplete SuDS features
  • Measures to ensure the formation of vegetation in SuDS features. This must include due consideration of seasonal planting, turf etc.
  • Details of the EA Flood Warning System, if necessary

We must inspect each stage of road construction.

Temporary drainage options

There are three options available during construction:

  1. Build, use and undertake remediation on the permanent drainage system
  2. Install, use and remove a temporary drainage system
  3. Use existing drainage systems with pollution control measures. This applies to brownfield sites only

There is no one size fits all for SuDS protection or remediation during construction.

Each site has different characteristics. You must consider each site individually and thoroughly.

Careful planning and programming of SuDS construction are vital.

Potential protection and remedial measures

In the production of your CMP and SuDS Method Statement, you must consider:

  • complete soil stripping sparingly and with care
  • the exposure of areas for extended periods following earthworks
  • the use of temporary bunds
  • regular pumping or emptying of attenuation areas may be necessary
  • the use of silt curtains, blankets, wattles and fences
  • covering all materials
  • using geotextile gully guards on positive systems
  • constructing temporary drainage grips, channels and slope drains
  • physical barriers around complete SuDS features to prevent vehicular access
  • vehicle routing through the site to avoid permeable surfaces becoming polluted with dust or mud
  • temporary fencing to prevent overland flows to third party land
  • the use of straw bale barriers
  • gravel trenches upstream of areas of exposed land
  • protecting swales and filter drains by using geotextiles and erosion control fabrics
  • the use of sediment traps and basins
  • removing any unstable sediment, you can then incorporate this into the topsoil
  • installing perimeter drains with stable outfalls and place around areas of significant construction works
  • temporary seeding and mulching for stabilisation
  • installing permanent stabilisation measures after final profiling
  • methods for identifying soft spots, other than proof rolling
  • the use of reinforced grass protection
  • complete isolation from run-off, if infiltration systems are on low points of the site but not for temporary drainage
  • installing a sacrificial layer of soil before final excavation
  • rotovating or scarifying sub-base
  • using a geotextile and temporary cover over permeable sub-bases
  • a strategy to avoid utility services breaking any geotextile wrapped elements of SuDS. This may include the use of 'top hats'
  • the breaching of any encapsulated contaminated land by intrusive excavation
  • the use of temporary filter trenches, especially where there is a proposal of permeable paving

This list is not exhaustive, and you may require different solutions.