Drainage considerations in property development

When scoping a new development, sewerage and drainage may not be the first thing to spark everyone’s interest, but they are an essential component. Effective drainage is key to the functionality and success of any development.

This article examines the legal position and regulations around drainage, with the aim of demystifying common queries and misconceptions. 

Who owns what? 

Sewerage undertakers have a general duty to provide public sewers and to clean and maintain them to enable effective drainage.  

A key distinction is between public and private sewers and drains: anything that does not fall within public ownership will, by default, be the responsibility of the relevant land owner - be this a developer or homeowner.  

The Water Industry (Schemes for Adoption of Private Sewers) Regulations 2011 (2011 Regulations) changed the application of this distinction. 

Historically individual homeowners were responsible for drains that connected their house to the public sewerage system - often under the public highway - and this included any ‘lateral drain’ that linked sewers within their property boundary to the public sewer. 

Where this connecting piece of the drainage puzzle - between the property boundary and the public sewer - served multiple houses, each homeowner had a shared responsibility for this segment. This position was considered to be unfair for homeowners that could be landed with large and unexpected costs to repair sewers, which weren’t on their property and/or didn’t exclusively serve their home.  

The 2011 Regulations removed this considerable burden from homeowners. 

Now, a property owner will only be responsible for drainage where it is both within their property boundary and it exclusively serves their property.

The 2011 Regulations therefore transferred the following into public ownership: 

• Surface and foul water sewers that connect the public sewer to private homes, which do not serve a single building or buildings within the same curtilage.
• Lateral drains that connect the public sewer to a single building, but run outside the building’s property boundary.

New build developments 

There are many factors for a developer to consider to ensure a development will have an effective drainage system. These are likely to differ from one site to another: an industrial development will have very different requirements to a housing development, and so on. 

A developer of a housing estate or other facility will need to lay new sewers and drains to deal with sewerage and surface water, but these will not automatically fall into public ownership until formally transferred. 

The developer, therefore, needs to ensure a Section 104 agreement is in place before any construction is commenced. By contrast, a Section 102 agreement may be used where a developer wishes to have an existing sewerage network transferred into public ownership where no previous Section 104 agreement was in place. 

A Section 104 agreement is effectively an agreement between the sewerage undertaker and developer, which prescribes a standard for the drainage system to meet in order for it to be adopted as part of the public sewerage system. 

Normally, a bond will be payable by the developer to the sewerage undertaker at the outset - typically reflecting 10% of the anticipated construction cost – that the undertaker will hold for the duration of the agreement and can use if the developer fails to deliver a network up to the required standard. 

Once the sewerage network has been constructed pursuant to a Section 104 agreement, the developer will usually be obliged to maintain the network for a set time period after the development is occupied - up to a few years - to ensure that the system is working smoothly. 

Once this period has expired, and provided no significant issues have arisen, the network is formally adopted pursuant to a Section 104 agreement.  

Sustainable Drainage Systems (SuDS) 

Sustainability is a key factor for many developers and, with flood risk increasingly at issue, the development market is increasingly seeing a rise in the use of SuDS.  

A spotlight on sustainability, coupled with more developments being constructed in higher flood risk areas than was once the case means that SuDS is a common solution. 

It is a model of drainage design, which manages rainfall locally close to where it falls and as close to its source as is possible, in order to mimic natural drainage and encourage infiltration and, in turn, reduce pollution. 

SuDS are more sustainable than more traditional methods for drainage in various ways:

• Manage water flow and quantity from hard surfaces, which reduces the impact of flooding on urban areas.
• Utilise any surface water run-off for other benefits.

Protect and improve water quality, in particular avoiding water pollution; and/or enhance any local wildlife, habitats and local environmental needs. 

SuDS are, therefore, environmentally beneficial and ensure that minimal detrimental damage is caused to a relevant area. SuDs are now recommended for most new-build developments and have already been made compulsory in Wales.  

Key takeaways

All sewers and lateral drains, which connected to the public drainage system on 1 July 2011 were automatically transferred into public ownership and consequently the responsibility of sewerage undertakers on 1 October 2011.

Pursuant to the 2011 Regulations, a property owner - whether this is an individual or a business - will be responsible for the drainage, which is (a) within their property boundary and (b) exclusively serves their property.

Under Section 104 of the Water Industry Act 1991, a developer may enter a voluntary agreement - Section 104 agreement - with a sewerage undertaker for the adoption of new sewers serving a development.