Why concrete is 'best for 2009'
The concrete drainage industry has developed solutions that make the most appropriate answer to the challenges of 2009 and beyond, writes Andy Goring, chair of the Concrete Pipeline Systems Association (CPSA)The UK has one of the largest sewer and combined drainage networks in Europe; it collects around 10Bl of wastewater and effluent per annum, treating and returning it safely to the environment. There are about 302,000km of sewers in the UK worth an estimated asset value of £108.8B.
The current economic downturn is hitting the construction industry hard. There are new requirements for flooding mitigation following the 2007 devastating floods. And there are additional PR09 requirements to address and report on different Sustainability issues and social or environmental impacts of sewerage and drainage networks and construction operations. So, it is evident that the industry is faced with a new set of challenges. The concrete pipeline industry has developed a number of economic, durable, and robust solutions to address these challenges.
Today, members of the Concrete Pipeline Systems Association (CPSA) manufacture different products ranging from sewerage or drainage and jacking pipes to manholes, inspection chambers, soakaways, attenuation tanks and gullies. These can be used for a range of applications from storm and foul water pipeline installations to flood mitigation and attenuation systems.
All these products and systems share a number of characteristics that make them the best industry option for 2009 and beyond.
Strength and resilience
With all ranges of concrete pipeline products designed to strength class 120 (BS 5911: 2004), concrete pipes and manholes now offer the most inherently strong option in the market. Unlike other vulnerable pipe alternatives where the structure of the system will need to be built around the pipeline, the structural robustness of concrete pipe makes it less susceptible to the effects of poor bedding and installation.
This is reflected on the ability of the product to serve for long periods, with a proven and specified asset service life exceeding 100 years. This makes it a sound and sustainable financial investment. Advances in concrete mix designs, offering considerable resistance to different forms of ground thaumasite and sulphate attack, also mean that the probability of pipes failing at an early stage due to sulphate attack is now lower.
Inherent strength also means that concrete pipes can be produced and installed with larger diameters (reaching 2,400mm or even more) to meet any additional future surface drainage and flood mitigation requirements. The product can also be modified as portions of the pipe wall can be removed without loss of structural integrity and holes can be drilled into the products on site.
This can help considerably in avoiding the financial and time implications of variations and changes to system design.
Concrete pipeline systems can also resist damage from water jetting (with pressures exceeding 345 bar) and are less susceptible to damage from different solid objects being drained during flooding incidents. This will prove to be an advantage as maintenance needs for drainage systems become increasingly important.
With the current economic downturn and fluctuating oil prices, cost will continue to be a major driving factor in future infrastructure projects. Concrete pipeline systems offer a cost-effective solution. In addition to the relatively low cost of concrete pipes and manholes compared with other alternatives in the market, the cost of bedding can be significantly reduced.
Concrete pipes can be laid using Class B bedding, allowing for excavated earth material to be included and reducing the amount of imported granular material used to a minimum. This should lead to reductions in the cost of virgin granular used (including aggregate tax) and the cost of transporting excavated earth off site, along with the elimination of costs associated with recycling and landfill.
Installation costs can also be reduced as the available machinery on sites, such as cranes, can be easily employed in the handling and installation of pipes and manholes. The low probability of early product failure and reduced maintenance requirements will also lead to long-term savings.
The Thatcham flooding in July 2007 exposed the vulnerability of many urban developments in the UK to the dangers of flash floods. A variety of products and systems can enhance surface drainage and mitigate the impacts of flooding in densely populated urban areas, areas with heavy clay soils, and areas where SUDS and other ground level solutions usually fail to address the problem.
Customised solutions, comprising networks of pipes and attenuation and storage tanks, and employing a range of products (including soakaways, elliptical pipes, attenuation and storage tanks) can be used to clear large volumes of rainwater falling over relatively shorter periods of time. These systems have proved to be a success around the world - including in the Netherlands, where surface drainage is a main concern.
Inspired by the decade-old, but groundbreaking, Egan report principles, the concrete pipeline sector has managed to reduce product lead times considerably. Advances in technology, construction, and design mean that the entire process of ordering, designing, producing, transporting and installing a pipeline system can take place in a relatively short period of time. The introduction of high-frequency vibration (HFV) technology to concrete pipe manufacturing in the UK has helped considerably in this, as it now takes no more than two to three minutes to produce a concrete pipe or manhole section. Steam can be used to accelerate the concrete-curing process and provide a product ready for installation in a much-reduced time.
The sector has also developed a number of customer-focused solutions and measures to enable proper vertical integration and close engagement and coordination with different downstream supply chain partners. New product-handling techniques were introduced and, despite the heavy weight of the product installation, times are now short.
It should be noted that all members of CPSA are active partners in Concrete Targets 2010, British Precast's accident reduction scheme. This scheme and other earlier schemes have helped the precast concrete industry achieve reductions in accidents and injuries by 65% in seven years.
The sustainability agenda will have more influence on the industry in the coming period and is now at the heart of legislation and planning within the infrastructure sector. The new Ofwat PR09 Methodology places more weight on Water and Sewerage companies to report on the environmental and social impacts of their businesses.
Ofwat is also asking companies to submit estimates of the embodied carbon of their operations. Use of concrete drainage products will help considerably on this area.
Concrete is principally made of aggregates and cement produced from limestone. These are locally sourced materials with no scarcity or abiotic resource depletion concerns.
The environmental impacts associated with transporting these materials are minimal due to the short distances travelled. Concrete pipeline products are also set to be among the first generation of construction products to be declared as responsibly sourced in 2009.
This means that a number of robust social, ethical, environmental and quality measures were approved by third parties such as BRE and BSI throughout the product's chain of custody. This will put more pressure on other competitors in the market to address this important subject.
Recyclability is another key issue in the sector. Concrete drainage products can incorporate different secondary and recycled-content materials successfully.
One example is pulverised fly ash, a by-product from coal-based power stations with a very low or no carbon footprint, which has good cementitious qualities and can be used successfully to partially replace cement. In addition to the environmental advantage of using a by-product or waste from another industry, pulverised fly ash can increase concrete pipes' sulphate resistance.
Moreover, concrete waste at concrete pipe factories can be crushed and reused again in some pipeline products. But most crushed concrete is recycled and used in other applications such as infill or bedding material in roads and highways.
Concrete drainage pipeline systems have evolved considerably in the last few decades, concrete pipes and manholes are now much stronger, more resistant to damage and sulphate attack, and can live longer. The concrete drainage sector today can offer robust solutions that can help in tackling the different challenges of the 21st century.
The CPSA is confident that its members have the competitive edge on these different aspects. The sector will continue to work closely with different stakeholders and clients to build on these advantages and offer more sustainable and responsive solutions.
Andy Goring is managing director of Milton Precast and chair of the CPSA