InfoNet for CCTV Management

Utrecht uses Wallingford Software's InfoWorks CS urban water cycle modelling solution. The city also has a sewer monitoring network and a customer complaints database.

CCTV inspection data is used in network assessments. There are many sewer data management systems available to enable such data to be stored, but because the city was already using InfoWorks for its model simulations it was considered an advantage to combine this with its sister solution InfoNet, using the latter to store the CCTV data.

Customer complaint data

The city also needed to include customer complaint data in the solution because it is very easy to visualize in InfoNet. But as sewer-related customer complaints comprise just 6% of annual municipal complaints it is difficult to ensure the front office has a robust database that can be used to analyse the causes or help the city in its related work.

Before sewer cleaning is undertaken, the city's contractors estimate the sediment height and store this information in .csv files. These are easy to import into InfoNet using configuration files. From the sediment height, the city calculates a relative sediment height that it might use as a gauge for the need to clean the sewer concerned. The relative height is simple to calculate from the pipe height and the observed sediment height.

From the city's point of view it is extremely useful to be able to create a field map of sediment depth. Data from previous years of sewer cleaning can be loaded and a quick overview obtained of areas of the network where there is a sediment build-up, and the differences between districts or locations close to CSOs or pumps - hotspots where almost completely blocked sewers have been found. Using InfoNet also allows the city modelers to bypass the GIS system, which had to be used in order to visualise the data before InfoNet was purchased.

The solution has also been a very powerful tool for storing historical data from a number of cleaning rounds in locations that suffer recurrent blockages. This data is now easily stored, whereas its other data management system was only able to store one set of measurements. This facilitates visualizing sediment build-up after cleaning.

Visualising sediment build-up

In InfoNet v9.5 it is simple to log data and visualize sediment build-up over time without the need to export data to Excel for processing. Another desirable analysis would be to discover whether there is a relationship between sediment height and pipe height. Initial observation shows that the smaller pipes are more prone to blocking than the larger ones, and the city would like to investigate the reasons for blockage - whether pipe diameter, slope and location, or other factors are significant.

The data also illustrate the need for verification of sediment height in relation to pipe height. The city uses InfoNet's powerful validation tool to check for incorrect data once it is loaded. In future the city plans to closely supervise the quality of data it receives from its contractors.

Once the data is loaded it is easy to visualize and investigate the causes of blockages. For instance, the city received complaints around three years ago about odours and blockage from the location of one blocked section, and earlier this year it was suspected that the problem had recurred. The pipe was cleaned, but it was thought that there might be a problem in the pipe itself such as a negative slope, and a CCTV survey was commissioned.

Once the data was loaded, it was possible to see that this was not the cause of the problem. There was a severe displacement that was almost completely blocking the path of the pipe and causing the upstream network to block occasionally. The pipe is now scheduled for replacement.

Cleaning program

The sewer network cleaning program entails cleaning every district completely every ten years. This work has been undertaken for around that length of time, so it was deemed to be a good point at which to assess the effectiveness of cleaning the pipe network over this time frame.

It is easy to open the InfoNet database as a guest database in InfoWorks CS, and relate the sediment data to model simulations. The city considered the calculations that indicated areas that were likely to flood even after flood prevention measures, to identify whether sediment remained a problem. Those areas are scheduled for cleaning this year, and if the data suggests significant sediment build-up it would be useful to clean at more frequent intervals.

Conversely, the city also needed to consider flood-prone areas to find the cause of flood-related customer complaints. In one instance it was necessary to ensure that the complaint was not related to hydraulic flooding, and the survey data showed the cause to be soil ingress from a faulty inlet that had, over a period of years, almost completely blocked the pipe. It is hoped to prevent that sort of situation from arising.

This article is based on a paper presented at the Wallingford Software International User Conference in September 2008 by Judith Sloot (MSc) of the city of Utrecht in The Netherlands.