Below Ground Drainage Engineering Design

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What we do

Below Ground Drainage Design

MP Consulting offer a wide range of drainage design services for the management and discharge of surface water, foul and combined water drainage.

Working closely with clients, stakeholders, contractors and approval bodies, MP provide services from desk top review and collation of survey information through design and simulation of networks to completion of construction information for implementation on site.

Although the design process is standardized, the route to approval is inherently bespoke and requires an understanding of the regional standards to achieve

Below Ground Drainage

Sustainable Urban Drainage Systems SUDS

An integral component of any construction project now relates to how the development will manage rainwater to a suitable outfall location by not adversely affecting the surrounding environment by causing or exacerbating flooding.

This design process is enshrined at both local and national levels with the National Planning Policy Framework NPPF.

Legislation has embedded within the drainage design process a forward looking parameter of climate change allowance which with ongoing adoption will begin to build resilience to drainage infrastructure on a per development basis.

Drainage design process is commenced on a hierarchical assessment of where the surface water generated by rainfall on the site can best be discharged.

The principles of Sustainable Urban Drainage Systems may then inform design decisions taken by not only how building roofs, parking, access roads and pavements are arranged, but also how landscaping areas may be utilized within a coordinated drainage strategy.

MP complete SUDS schemes for retail, commercial and residential projects, with the drainage networks being design for local authority adoption or maintenance by the owner. We have experience of multiple forms of Sustainable Urban Drainage Systems, from ponds, swales, infiltration, raingarden and porous pavement systems which can be used in combination to provide ‘SUDS train’ where enhanced restriction is dictated by site and planning parameters.

Below Ground Drainage

Drainage Design & Simulation

MP utilize the Micro-drainage design software suite to complete gravity pre-sizing of below ground drainage followed by simulation of the network to look at the resilience of the system to network flooding.

Simulation is able to look at rainfall intensity parameters based on geography and annual risk on the drainage system as a whole, including the gravity network of pipes and manholes together with structures and controls such as infiltration into the ground, open ponds & swales, flow regulation, attenuation tank structures and outfalls.

Below Ground Drainage | Drainage Design and Simulation
Micro drainage simulation allows accurate design of SUDS structures ensuring optimum size of above and below ground features. Results of the simulation are provided within a report format which is readily utilized for discharge of planning related conditions.
Below Ground Drainage

Planning Conditions, Drainage Adoption,

Typical consent for drainage is gained via the planning approval process.

There are however other stakeholders involved with the approval of drainage, in particular where the proposed development connects to the existing public sewer network which is managed regionally by multiple companies in England and nationally by Welsh and Scottish Water.

Below Ground Drainage | Planning Conditions and Drainage Adoption
Drainage adoption comprises the connection and vesting of new drainage to the public sewer network in accordance with Water Industries Act 1991. Regional bodies are consulted at pre app and full app stages in accordance with individual requirements. MP assist in the agreement of scheme parameters, compilation of application forms and provision of technical information in accordance with the requirements of Sewers for Adoption. Refer following sections for further details.
Below Ground Drainage

Environment Agency/SEPA, SAB, CRT, IDB

Environment agency approval is required for the connection of drainage to named watercourses, river and estuary bodies of water. Approval is gained via standardized EA permitting, which MP have extensive experience of completion and negotiation within England and Scotland.

Surface water drainage within Wales is defined by a process referred to as SAB. SAB comprises a detailed assessment within multiple areas to provide a robust review of SUDS, Flood risk reduction, Ecology, Bio diversity and long term maintenance strategy.

Environment Agency
The application process is two staged, with a pre-application phase allowing negotiation and agreement of strategy, in advance of full application whereby the project receives full permission. The SAB is run in parallel with the planning process for development in Wales and must be commenced with suitable lead in due to timescales to complete.

Waterways in England are controlled by the Canals and Rivers Trust CRT. The body arranges agreement to discharge surface water under license to engineered waterways. Discharge of surface water to waterways is possible by agreement and long term payment.

Numerous regions within England have strategic local drainage authorities referred to as Internal Drainage Boards IDB who manage secondary water features which fall below the remit of the Environment Agency. Discharge to watercourse bodies offers opportunities for multiple SUDS structures, which can be integrated into the project landscape strategy to provide amenity and biodiversity as part of the overall design.

Below Ground Drainage

Section 104 Agreement – WIA

The Water Industry Act outlines a legal agreement between developer and Sewerage Undertaker which allows the sewer to be constructed by the developer and then maintained in future by the Sewerage Authority.

The agreement allows private drainage within a development to connect to the public network, subject to the system complying with the requirements for public sewer laid out in the Sewers for Adoption information.

Section 104
Below Ground Drainage

Section 106 Agreement – WIA

Legal agreement between developer and Sewerage Undertaker which relates to the connection only of private drainage to the public sewer network.

Limited agreement which typically requires only confirmation of connection type and flow rate for completion.

Below Ground Drainage | Section 106

Structural Engineering Projects