Background information

here are features of a city that are like close family; we see them often, we share our daily work with them and sometimes we complain about them. These are the city assets, which are streets, sidewalks, street light poles, traffic lights, parks and squares, bridges, tunnels, municipal buildings, hospitals and schools, vacant lots, etc.

We also use many conveniences that rarely see how they reach or leave our homes, our places of work, our commerce and factories. These are potable water, sewer, storm water, and fire water networks. Confidently we use city tunnels, bridges, underpasses, beaches, without even thinking who the owner is, if they are safe, or who maintains them.

In other words, we take their existence for granted, and only when one of them fails, we notice their absence. These, and others, are the city assets, and in large cities valued in billion of dollars. Like any other asset, municipal assets have to be maintained and replaced when have surpassed their useful life, or repaired when there is a damage or deterioration, or enlarge and upgrade when population growth make them inadequate in terms of volume of population served. We are talking here about a great deal of work, lots of responsibility, a very complex organization and hard and difficult planning.

Immense quantity of money is needed, and some authors (Vanier, 2007), estimates that in order for a city' infrastructure to be economically sustainable, 4 % (i.e. 2% for maintenance and 2 % for renewal) of the current replacement value must be available to ensure that the existing infrastructure is in good working condition and that old assets will be renewed when required.

Unfortunately problems do not end here, large amounts of water are wasted everyday because faulty water trunks, seeping into the ground. According to The Ends Report (2004) (see Bibliography), losses by the main water companies in the U.K. from leaks amount of 3,650 megaliters/day. As another example, in July 2005, leaks in potable water amounted to at least 34 percent in the Andalusia Community is Spain (ABC, July 12, 2005).

Besides, working to maintain the present day service with a reasonable reliability and providing non-contaminated water - in itself a daunting task in large cities - it is also necessary to plan for the future considering the expected natural population growth.

This explains the need for assets management.

Table 1 reproduced by Courtesy of Dana Vanier [Vanier, 2007] offers a clear view of the classes and subclasses of municipal infrastructure assets

Classes and subclasses of municipal infrastructure assets

Table 1 by courtesy of Dana Vanier

The problem has been very briefly exposed, and most probably these comments do not illustrate the reader about its actual magnitude and shear complexity. Of course, public utilities have been around for more than a century and in reality we are profiting from the wisdom of our forefathers, building and still using on what they initiated, and improving what they built without the technical means available today. Naturally, population growth, age, heavy traffic, etc. and sometimes density, imposed a heavy burden to those structures that in many cases need to be replaced.

Of course actual administration have another kind of problems that were inexistent when these structures were built, such as a much heavier demand for services, for since the WWII many people moved to cities creating a huge demand for services. Actual administration also have physical problems because there is usually no room to enlarge buried services at a low depth, because subways tunnels, underground parking lots, large building foundations, gas, telephone and cable networks, etc., and for that reason work has to be done at a great depth. Nowadays urban aqueducts are very large conduits, buried deep beneath the city streets, and marvels of engineering.

For instance, Tunnel number 3 in New York City , was excavated in the bedrock and is located at a depth of 244 meters below street level, with a length of about 21 km, and a diameter of more than 7 meters. Most large cities have a mix of old and new tunnels and pipes, some of them more than 100 years old. Of course, age, corrosion, water pressure, soil pressure, tremors, and other events take a toll in these works and produce breaks in the water mains, which can have extremely severe consequences. Imagine living without water for say two weeks!

Considering all the above, the first thing a city needs to do in order to develop its assets policy, is to have an inventory of them as well as an evaluation of their status. In other words it is necessary to build a data base with information related to age, technical characteristics, conditions, load capacity (for bridges). Table 2 suggests such a format for such an inventory.

City assets inventory

Table 2

Once this inventory has been completed it is necessary to indicate costs for repair as well as scheduling when the works will be done, and also establishing priorities for each asset class. Naturally this example is a very simple scheme for a data base; the amount of information needed for decision making is staggering, but needs to be completed.

Vanier (publication cited, Chapter 7) puts it very nicely. A city needs to have answers for these questions:

•  What does the city own?
•  What is it worth?
•  What can be deferred?
•  What is the condition?
•  What is the remaining service life?
•  What does the city fix first?

All of this information serves to the final objective which is the decision making stage.

There are some techniques to help in this function and Vanier (cited) proposes an innovative technique for dealing with the decision making process. This is called the Analytic Hierarchy Process (AHP) to determine weights. After weights are evaluated, another tool, based in mathematical programming should be used to establish a schedule of projects or activities to be executed and subject to different constraints such as available funds, asset conditions, deferral, etc.

References:

“News in Brief”. (2004), The Ends Report , Number 355, page 14, Environmental Data Services, Ltd, London , U.K.

Vanier , Dana (2007). Towards sustainable municipal infrastructure asset management, Munier (ed), ‘Handbook on Urban Sustainability', Springer, Dordrecht , The Netherlands