Frost induced water mains failures come as no surprise
I guess that much will be written about the state of the water supply network in Northern Ireland. I should like to take the opportunity to revisit correspondence published in NCE in early 2009 where ground source heating systems were being designed based on frost penetration depths of only 450mm and to ask how are they coping this winter?
Here in South West Scotland the winter frosts have also been very damaging and the water supply network for the village of Leadhills has been replumbed.
According to the BBC: “Scottish Water said that workers removed cylinders of ice from pipes and put in a new network of pipes at a depth even lower than the normal 750mm to minimise the risk of future deep frost.”
Frost heave, where ice forms into lenses, is well documented and unless any readers think this is a new phenomenon they should perhaps look at the old Transport and Road Laboratory/HMSO publication, Soil Mechanics for Road Engineers, which details the problem quite nicely.
As regards the fitness for purpose of buried cast iron utility pipes, reference should be made to research carried out in the 1970s and 1980s by the British Gas Corporation at its Engineering Research Station. This work demonstrated that ground movement was a major factor in the failure of cast iron mains, analysis indicating two main causes: mechanical disturbance and environmental effects.
The latter were investigated using large scale testing, some of which involved forced freezing of the ground, the results being published at the International Gas Research Conference in Canada in 1986.
- Ray Owen, Longsheds, Kelton, Castle Douglas, DG7 1SF
I read with interest the article in the NCE Infrastructure 2011 supplement, which appeared with NCE 16-23 December, about sustainable flood risk management initiatives in Wales.
Many sewerage undertakers will be understandably keen to rid their systems of unnecessary surface water by the increased use of sustainable urban drainage systems (SUDS).
Highway drainage is a target for exclusion from sewers but this brings its own problems.
With severe winters becoming more common and the use of grit salt escalating, the effect on watercourses and aquifers needs to be studied to ensure our compliance with the Water Framework and Floods Directives with regard to water quality. Highway effluents inherently have high concentrations of chlorides, hydro-carbons and heavy metals.
The way English and Welsh law is currently framed, only domestic sewage water discharge has the ultimate right of outfall to sewer. Highway drainage does not enjoy that privilege.
In other words the combined effect of our law is in direct conflict with the requirements of European legislation.
Would it not make more sense to ensure that highway drainage receives proper treatment and roof water was obliged by law to be taken to natural receptors wherever possible?
When the Flood & Water Management Act 2010 is fully implemented it will present a golden opportunity for the water companies to reduce transmission and treatment and pass the water quality risks to the local authority who will be the new SUDS Approving Body (SAB).
Heaven forbid that the SAB will be forced to develop a parallel system of transmission and treatment for surface water. Time for some of that “joined up thinking” we hear so much about?
- Howard Glenn (M), email@example.com
Road to ruin
In Tom Moss’ letter (NCE 16-23 December) he states that on top of an average of £38 per each Band D household, the £200 for car tax should be more than sufficient for local authorities to deliver high quality road network maintenance.
As we all know, not all the money collected by car tax is put back into the roads themselves. At a liberal estimate this would only be around one-fifth of revenue actually raised.
The extra funds given by former chancellor Alistair Darling earlier this year to repair damage from last winter were also short of truly helping out. The conditions of last year’s and this current winter exacerbate problems for authorities as they carry out their regular maintenance duties.
No local authority intentionally neglects its road network but we must be realistic. Local authority budgets were poor before, but with the cutbacks imminent we now find ourselves at a time when more work is required.
Contractors must be paid and if sufficient funds are not available then how exactly does Moss propose the works are undertaken? A quick look at local authority highway finances would quite clearly distinguish the differences between ideals and realities.
- Greg Tasker, Greg.Tasker@newport.gov.uk
Double deck clearance
After viewing the new Arup layout design for the proposed High Speed 2 railway, I only hope that the opportunity is now taken to have sufficient height clearance to run future double deck trains.
It would terrible to leave future generations without this choice. It has always seemed to me that this country has in the past taken the short-term view in a lot of projects.
- John Hancock (F ret), firstname.lastname@example.org
Timing water spending reviews right
I read with interest British Water’s lobbying of Ofwat to separate and stagger the regulation of water and wastewater services to flatten out peaks and troughs in capital spending (NCE 16 December).
That such a move is being given serious consideration is unfortunately a reflection of them being seen as entirely separate and independent items of capital expenditure.
But more integration should be the name of the game rather than separation.
For example, water demand management activity not only reduces water resources revenue and capital costs but can also reduce wastewater (capital and revenue) expenditure by reducing the volume of sewage.
The 10-year water metering programme in New York City between 1988 and 1998 was driven not by a need to cut water resources expenditure, but by the need to reduce expenditure on wastewater infrastructure particularly as there was no land in the city to build bigger sewage treatment works.
As reducing the volume of sewage also reduces pollutant load there are potentially environmental benefits too.
Where we need rivers to achieve good ecological status as required by the Water Framework Directive, potential solutions could be more flow in the river and/or more treatment of effluent.
What we don’t want is one scheme being identified through the Water Resources National Environment Programme (NEP) and then two to three years later another identified through the Water Quality NEP, when a single integrated solution is what is required.
Piecemeal solutions are more costly for the bill payer. The Water Framework Directive, that requires integrated catchment management, is the overarching piece of legislation here and it is essential that the periodic review falls in line with it and not vice-versa.
- David Howarth (M), 2 Pepperscoombe Lane, Upper Beeding, Steyning, West Sussex, BN44 3HS
Caring and sharing
Staring at an overflowing paper recycling bin in the officeI decided to do something a little differently this year when wrapping my Christmas presents.
With one eye on trying to reduce the amount of wrapping paper that gets thrown away on Boxing Day, I also realised that old CAD drawings and superseded reports make for interesting wrapping paper!
It was nice to show my family some excerpts from my daily working life and give them an insight into some of the designs I’ve worked on over the past few months.
ICE president Peter Hansford wants to raise awareness of the civil engineering profession through his Create Sport Challenge; I’ve started with my family’s wrapping paper!
- Richard Jackson, structural engineer, Amey, Richard.email@example.com
Models help engineers avoid using unnecessary plant
Your Minature Movers plant feature (NCE 16-23 December 2010) showcased some very classy items that come at a cost, but rarely find a practical use.
I once made a rather more earthy model of a specifically rigged Liebherr 912 excavator.
Run up in the garage one evening, the aim was to demonstrate that my chosen machine could cover all the digging and lifting duties on a difficult site at Teddington Weir, where access was a significant problem.
There was some joshing when I produced the mock-up, I recall. But having a functional model enabled the right choice to be made, proving the maxim that time spent planning is rarely wasted.
It would be good if manufacturers’ models could be part of this process.
- Humphrey Thompson, firstname.lastname@example.org