In August 2018, Water UK published the pre-implementation version of Sewers for Adoption 8 (SfA8) as part of Ofwat’s Code on Adoption Agreements that will come into effect in April 2020. The draft version of Sewers for Adoption 8 was prepared by the Water Companies, developers, and other stakeholders, and was approved by Ofwat in October 2019.

It was created primarily to give guidance, for the first time, on the design and construction of SuDS (Sustainable Drainage Systems) that could then be adopted to the water and sewerage infrastructure. The intention is that it provides a unified code supported by all of the Water Companies.

The Ofwat Code on Adoption Agreement was created for Developers and Self-Lay Providers when they want an appointed water or sewerage company to take the responsibility for infrastructure that they have created, as opposed to a private maintenance company. Basically, they’re the minimum requirements new developments need to adhere to in order to connect to local water and sewerage infrastructure and have those companies take over once they’ve finished the build.

However, if it is implemented it will be the only guide to the standards that sewers must meet if they’re to be adoptable by water and sewerage companies in England. This standard would be supported by the Guidance documents, such as the non-statutory technical guidance for SuDS, as well as the CIRIA SuDS Manual.

As the first sewer adoption guidance in England that includes SuDS, this is a huge change in the industry.

In this article, we wanted to clear up some confusion around SfA8 and let people know what the changes mean to the industry.

It’s generally recognised that water and sewerage companies are the most suitable owners and operators of the sewerage network. Whenever a new development is built, most of the sewer assets are transferred to the local water and sewerage companies.

Although traditional piped drainage systems provided a means of conveying water from buildings, roads, and other hard-standing areas, these systems do not effectively treat the water discharged from these surfaces. Consequently, the receiving watercourses from the surface water network would often suffer from water quality degradation as the pollution from the hard surfaces was washed into the drainage network.  Furthermore, the traditional approach of surface water drainage networks was to discharge the water as quickly as possible to the watercourse.  As more areas became hard-standing areas, the total volume of the water discharged to the watercourses would often overwhelm the capacity of the watercourse.

This realisation spurred the implementation of SuDS (Sustainable Drainage Systems) which mimic the ‘natural’ processes by which surface water runoff is absorbed into the land or into natural water courses, slowing down the rate of discharge and enabling pollutants to be remediated through natural processes before entering the river network.

Not only does this reduce the risk of overflow when it rains heavily, but it would also provide some additional space within the system to incorporate further housing developments.

Previously within England, only guidance documents were available for SuDS with no legislative or regulatory framework.  Many Local Authorities have developed their own SuDS Supplementary Planning Documents (SPD).  However, these SPDs vary considerably in the level of detail required and oftentimes were not updated to reflect the latest Planning Policy or climate change allowances.

SfA8 details the minimum requirements for the design and construction of SuDS for water and sewerage companies to take over responsibility at the end of the development. That way, both developers and sewerage companies know what standards need to be met.

It’s important to note that not all SuDS are adoptable. The ones that are must fulfil a sewerage function. We’ll get into that in more detail later in this article.

When Sewers for Adoption 8 comes into effect (expected April 2020), it’s likely that large-scale developers and housing developers will be affected in some way. In short, anyone who is building more than one property and wants the drainage to be adopted by the water and sewerage companies will be affected.

It’s considered to be a big change in the industry, so it’s also likely to affect the level of performance required for any SuDS system. This could potentially bring with it more costs, or land take, to accommodate a compliant SuDS scheme, so that’s an important thing to consider at the design stage.

Note: if a scheme was unable to implement suitable SuDS, then the masterplan may well need to be adjusted to accommodate the requirements. This could result in delays in the Planning process if SuDS are not worked into the masterplan.

As SuDS is now a required consideration for pretty much all developments under the National Planning Policy Framework (NPPF), it is likely that consideration of the location of SuDS features and securing a surface water discharge point will become a due diligence consideration at the site acquisition stage.

Water UK have created a list of basic criteria that need to be met for a sewer to be ‘adoptable’, whether that’s traditional drainage or SuDS.

You can see the list in full on the Water UK website in their non-technical guide here.

Here are some of the key points -

The sewer system must adhere to one of these criteria:

• Be constructed for the drainage of buildings and yards appurtenant to buildings;
• Have a channel;
• Convey and return flows to a sewer or to a surface body or to groundwater;
• Have an effective point of discharge, which must have lawful authority to discharge into a watercourse or other water body or onto or into land; or,
• Allow for some infiltration into the system – provided that is not the designed purpose of the system.

Here are some examples of adoptable assets.

• Detention basins
• Swales
• Rills
• Under-drained swales
• Ponds
• Wetlands
• Infiltration basins and soakaways

Some assets that are considered non-adoptable are:

• Highway drainage (if it is the main purpose of the system. Some drainage from highway sources are fine);
• Private drainage features (such as; permeable paving, rainwater harvesting systems, rain save planters, and green/blue roofs).

There is a potential for an increase in cost with the new guidelines. However, research has shown that properties overlooking open water features can attract a premium value of up to 20% higher than similar properties not overlooking water.

Now that there will be specific standards that need to be followed, we would expect the sewer authority to take a more active role in overseeing the implementation of SuDS systems. However, until it comes into effect, we can’t say either way.

Many developers already use great quality SuDS, so it’s unlikely they’ll have to adapt their process much and therefore the costs are unlikely to change. However, with the adoption process being formalised, the design of the onsite SuDS systems will need to consider which elements to use within the adoptable areas and those to be used within private areas.

Hopefully this article has given you a bit more of an insight into what the latest Sewers Adoption guidelines are and how they’ll affect you and your future developments.

As always, if you have any questions please don’t hesitate to contact myself or the Ambiental Environmental Assessment team on [email protected] and we’ll get back to you as soon as we can.