The pressure to deliver a cost effective drainage installation with minimum environmental impact has never been greater, but despite this, some pipelines are still fully surrounded in expensive imported granular bedding when a more considered approach to the design and selection of the pipe material could result in the use of a less costly, lower carbon installation.
There are various classes of bedding, providing varying degrees of support for the pipe. What is required will depend upon the material of the pipe, the surface load (traffic, weight of the ground and any overlaying fill) and the reaction from the ground below to support the pipe.
For structural design purposes pipe materials are classified – in BS 9295: Guide to the Structural Design of Buried Pipelines – as either rigid, semi-rigid or flexible. Concrete and clay pipes are defined as “rigid”; ductile iron and thick-walled steel are all classed as “semi-rigid” while thermoplastic, glass reinforced plastic and thin-walled steel pipes are all classed as “flexible”.
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The practice of carbon accounting for pipeline products and sewerage construction projects is not new, but PAS 2080 introduces something new. In this blog we identify how five carbon accounting principles in PAS 2080 will change the sector’s understanding of embodied carbon.
Many water companies, highway authorities, other drainage infrastructure asset owners and supply chain partners already employ project carbon calculators. However, there are significant differences between these tools. PAS 2080 introduces a structured approach to tackle this inconsistency problem: It also provides clear boundary rules and a framework for whole life carbon accounting based on European standard EN 15978 where carbon claims can be verified and low carbon solutions can be robustly assessed.
PAS 2080 could mark the end of unproven claims for manufacturers of pipeline products. Data sources such as the Bath University ICE database will no longer be the main source of embodied carbon data. For manufacturers, PAS 2080 introduces five main principles which will change how embodied carbon is dealt with: These are
- Consistency in methodology
- The ‘Cradle-to-Grave’ approach
- Data Quality Requirements
- Third party accreditation
- Data challenging and re-baselining
FIVE FACTS THAT MAKE PAS 2080 DIFFERENT
PAS 2080 states “Consistent methodologies and data sources for carbon management and assessment are to be used to allow comparisons of emissions over time”. Users are obliged to assess inconsistencies and continuously challenge their suppliers for more accurate and robust data. The standard doesn’t embrace a specific methodology but European standard EN 15978 indicates that the European Commission’s TC350 methodology is probably the route to be taken by any future revision of PAS 2080. This means that the Bath University ICE Database may no longer be an automatically valid option as it compiles carbon values from a wide range of studies that are not aligned to EN 15978 requirements.
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Published by the Treasury in late 2013 the Infrastructure Carbon Review documented the prospect of infrastructure value chain participants to collaborate in the expansion of low carbon infrastructure developments.
PAS 2080:2016 Carbon management in infrastructure was commissioned to facilitate this into reality. Mott McDonald and Arup developed the standards with support from the Green Construction Board (GCB). Figureheads within the infrastructure sector described the new standard as a ‘game changer’ which will pave the way for ‘consistency of methods and reporting’ across the supply chain.
It is specifically targeted to decision makers (asset owners/managers, designers, constructors and material suppliers) PAS 2080 provides a regular framework on how to manage whole life carbon when delivering infrastructure assets.
Manufacturers should take note that PAS 2080 introduces a new requirement for providing precise carbon data for their products, which ideally is 3rd party accredited. This puts emphasis on the whole life evaluation and through its adoption of boundary defined modular approach, carbon assessments now need to be more inclusive than ‘Bath University ICE database’ assumptions. In order to become a more reliable, representative and transparent format, similar to the one used in standards such as EN 15978 and ISO 21930.
You can also find PAS 2080 is available at the BSI Website for £100 HERE
THE CARBON FOOTPRINT OF CONCRETE PIPES
In 2010 we commissioned Carbon Clear consultancy to consider the performance of precast concrete pipes and manholes with their plastic counterparts. The study concluded that concrete pipes’ carbon footprint was 35% lower than the plastic alternative.
Credited to: Hafiz Elhag, Sustainability Manager, British Precast
In 2015 the planning regulations in England and Wales were amended to ‘expect’ Sustainable Urban Drainage Systems (SuDS) to be included in all new housing developments of 10 or more homes.
SuDS is about dealing with rain where it falls, this is in contrast to conventional drainage solutions which carry run-off from a development to an outfall as quickly as possible.
To deal with the surface water where it falls clients, designers and installers have the option of using hard and soft SuDS solutions. Hard SuDS include proprietary engineered products installed underground such as precast concrete soakaways, attenuation tanks and treatment chambers whereas soft SuDS are generally landscaped, vegetated features such as swales and detention ponds.
Soft SuDS are a useful starting point when considering design options because they can provide amenity to a development. The downside is that vegetated features often require larger areas of land, land that could otherwise have been used for development. By contrast, proprietary solutions such as precast concrete underground systems help ameliorate run-off without using valuable land. A balance of both hard and soft SuDS components is often the most appropriate and cost effective sustainable drainage solution.
Hard SuDS solutions can help developers manage surface water run-off without using up valuable development land explains Stuart Crisp, Business Development Director at the Concrete Pipeline Systems Association (CPSA).
To help introduce customers to sustainable drainage principles and precast concrete SuDS components, the CPSA has produced an accredited, free CPD seminar entitled Surface Water Management using Proprietary Precast Concrete SuDS systems.
The Concrete Pipe Lifter is a safer way to offload, handle and install pipes whilst simultaneously speeding up operations and reducing costs. You simply attach it to your excavator using the quick–hitch coupling. The Pipe Lifter has no slings or chains that hands could get trapped in, and requires no additional power requirements or hydraulic links. By removing people from the process, the risk of harm is eliminated. Nobody is needed on the vehicle during offloading and nobody is needed in the pipe trench during jointing. We’ve published a factsheet on the risks of manual handling in accordance with HSE’s best practices. It concludes that pipes of any material DN300 and over should be mechanically lifted.
Concrete pipeline systems have been part of the backbone to the UK’s sewerage network for over 150 years for good reason. The inherent strength of precast concrete products, their durability and their availability in a wide choice of sizes and cross-sectional shapes has made them a favourite choice. This blog adds some of the detail behind the headlines in our Heavyweight campaign.
The reasons concrete products were selected for use in drainage systems over a century ago are as valid now as they were then. But in today’s competitive drainage market the lower installed cost and whole life cost benefits resulting from their long service life coupled with excellent environmental credentials is ensuring precast concrete drainage products are still in favour with today’s engineers, contractors and asset owners.
Installed cost savings can be significant. For example, because concrete pipes are structural elements they can often be laid without the need for a full granular bedding surround. This may also save on installation time. It also means the quantity of imported granular material can be kept to a minimum while providing the opportunity to reuse excavated material, saving on disposal costs. And, once placed in the pipe trench, the inherent weight of concrete products ensures that they offer a natural resistance to flotation.
Despite the heavy weight of concrete pipes, using the award-winning pipe lifter can make unloading pipes from the delivery vehicle and the installation process up to half the time of traditional methods and, most importantly, safe as no-one is required on the vehicle or in the trench during the operation.
In addition to saving money, the inherent strength of concrete pipes makes them the preferred choice where loads from traffic running over the buried pipeline are significant. Their strength also makes them the preferred choice for deep installations where greater ground loads are imposed on a pipe.
Once installed the advantage of concrete pipeline products is immediately apparent. They do not deform or lose shape over their service life which ensures their hydraulic efficiency and structural integrity is maintained. They are also more resilient to damage from maintenance using high-pressure water jetting compared to many lightweight systems.
Concrete pipes also offer some major advantages when it comes to environmental sustainability; for example they are made from responsibly sourced local materials. In fact, a study by the CPSA and Carbon Clear demonstrated that a DN2100 concrete pipe has up to 35% lower embodied carbon on a like-for-like Class S cradle to site basis compared to the same size HDPE pipe.
Modern drainage asks for so much from its materials that it is clear that this is not a job for a lightweight. What is needed is Concrete, the Heavyweight Champion of the Drainage World.
The introduction of asset management period six, known as AMP6 by industry regulator Ofwat has seen water company costs measured on a total expenditure basis for the first time, which requires the proper consideration of the long term performance of assets in addition to capital cost efficiencies.
The five year period of AMP6 between April 2015 and March 2020 aims to increase the efficiency of asset management without increasing costs for consumers.
Under previous asset management periods, water companies have tendered contracts to construction firms to update some of the company’s assets and to keep existing infrastructure properly maintained for the five-year duration of the AMP. Ofwat, however, was concerned that under these AMPs water companies may have been using capital expenditure (capex) to build assets, such as water treatment works, to make a business more valuable for its shareholders rather than on reducing operational expenditure (opex) to deliver better value to customers.
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This blog focuses on deflection of flexible (e.g. plastic) sewer pipelines and aims to inform the reader so that appropriate decisions can be made when designing, specifying, buying, installing and operating a sewer pipeline.
It is vitally important that users understand the differences between flexible pipes such as plastic and rigid pipes such as concrete and to appreciate how these materials perform in terms of structural integrity and hydraulic efficiency.
CPSA has produced a number of publications covering this subject, all of which can be downloaded free of charge on our web site.
The latest issue of Pipelines, CPSAs eNewsletter focuses on sustainable drainage systems (SuDS). It contains an excellent case study at Susdrain.org where a residential development in Leicestershire used a combination of soft landscaped SuDS features and precast concrete SuDS components. Also featured is information on latest SuDS technical guidance and standards in England and Wales plus other useful references and case studies from the CPSA.
For more information on the use of concrete for sustainable urban drainage systems visit our website. If you would like to receive regular updates in the concrete drainage industry you can register to receive our free monthly eBulletins and quarterly eNewsletters!
Stuart Crisp, Business Development Director of the Concrete Pipelines System Association explains the advantages to be gained from working with precast concrete pipeline manufacturers to deliver the optimum drainage solution.
The more challenging a pipeline project the more important it is that contractor, distributor, manufacturer and client work effectively together to deliver the optimum drainage solution. This was the case with construction of the Chelmsford Effluent Pipeline. Here the project team had to overcome a lack of site storage, a high water table and, most challenging of all, a delivery date which was abruptly brought forward by six months and yet were still able to deliver the project on schedule.
This £9million project for Essex and Suffolk Water, part of Northumbrian Water, was constructed to almost double the capacity of the existing dual sewerage outfall from 828l/s to 1524l/s with the installation of a third pipeline.
The 1.4m diameter gravity pipeline was installed by civil engineering contractor Roadbridge along an 11km route from the Chelmsford sewerage treatment works to an existing outfall location on the River Blackwater Estuary. Buried between 3m and 5m below the surface, the pipeline connects to existing concrete pipelines both upstream and downstream. This made precast concrete the obvious material choice for the new pipeline.
Roadbridge worked with consultant RPS Group to develop the scheme’s detailed design. One of the challenges the team had to overcome with the pipeline’s route through the low-lying Essex countryside was dealing with a very high water table. To enable the pipeline to be installed in the low-lying ground, Roadbridge constructed a series of de-watering boxes 200m ahead of the pipe laying team. These temporarily lowered groundwater levels to keep the trench free of water during construction, while the self-weight of the concrete pipes helped guard against flotation during and after installation.
It was, in fact, because of the high water table and the likelihood of winter flooding that the project’s delivery date was brought forward by six months to ensure its completion by November.
Suddenly bringing forward the project’s delivery date by six months placed an increased onus on precast concrete pipe manufacturer and CPSA member Stanton Bonna Concrete to deliver. To meet the revised deadline Stanton Bonna introduced double shift working to significantly increase pipe production. Alongside increasing output the manufacturer also arranged storage for 4000m of pipe to enable the pipe supplier Keyline to meet a just-in-time delivery schedule. Keyline’s Gareth Twohey said the company did “a fantastic job” in working with Keyline to ensure it met the revised completion date.
Delivery of the precast concrete pipes was also a challenge. Access to the pipeline was predominantly from narrow, single lane country roads with limited space for delivery vehicles and storage. To ensure the operation ran smoothly, Keyline took the unusual step of pre-booking the haulage three months in advance.
This project demonstrates the benefits that can be gained from working closely with precast concrete pipe manufacturers and the advantages of pipes with high inertia (due to high self-weight) to counteract the risk of flotation in high groundwater. For the Chelmsford effluent pipeline, the efforts of the supply chain and precast concrete pipe manufacturer were essential in helping deliver this challenging project on schedule.