Stormwater

The typical state of stormwater drainage systems

Stormwater systems need attention

Multiple flood events and service delivery protests in recent years have brought stormwater master planning to the forefront. Bio Engineering Solutions resultantly conducted visual condition assessments (VCAs) on several municipalities’ stormwater systems, and the results are alarming.

By Danielle Petterson

The VCAs found that the general accuracy of the existing stormwater infrastructure asset registers is only 20% to 25%. This is mainly due to missing information such as dimensions of underground pipes as well as invert levels and gradients of stormwater conduits.

More concerningly, about 60% to 80% of existing stormwater systems were found to be completely blocked and/or non-functional due to a lack of maintenance.

Stormwater assessments The Bio Engineering Solutions team, led by director Matt Braune, started the study using aerial photography provided by the municipality as a basis. A team of field inspectors then walked the area to identify all stormwater infrastructure. The locality of all infrastructure was recorded along with photographic records. Another team of labourers opened all relevant structures, where they found a high degree of silting and blockages. They unblocked a portion of the infrastructure to take measurements; however, the existing pipe network could not be inspected fully due to severe blockage, which prohibited the use of CCTV.

The next phase of the study included the use of a professional surveyor to obtain both ground levels as well as invert levels of all existing stormwater infrastructure. In addition to this, the type of infrastructure, size and hydraulic capacity were also established. Based on the information, a fully integrated and complete asset register was compiled to assist the municipalities with stormwater management.

Hydrological as well as hydraulic modelling of the drainage networks was then undertaken, which enabled the compilation of a fully integrated stormwater master plan (SMP). The master plan was then used to prioritise and highlight problem areas and to establish remedial measures needed to restore the network.

Maintenance challenges Although each municipality has maintenance departments tasked with cleaning and maintaining stormwater infrastructure, Braune says standard operating procedures are needed to guide this process.

“Workers have no guidelines on how to maintain these systems and we often find that they push any surrounding debris into kerb and grid inlets. The surrounding area and the outside of the kerb inlet are now clean, but they have inadvertently blocked the underground pipe drainage system and caused further problems,” he explains.

“Local authorities are not maintaining their infrastructure, and maintenance

is not given priority in budgets. As a result, much of the existing stormwater systems needs to be replaced at an excessively high cost. The flooding resulting from blockages also causes severe damage to road infrastructure, as well as private and municipal properties, increasing the costs further.”

FIGURE 1 SMP showing required upgrading and prioritisation

Asset management register According to Braune, inaccuracies in municipalities’ asset management registers extend far beyond stormwater.

Driven by the Municipal Systems Act (No. 32 of 2000) and Municipal Finance Management Act (No. 56 of 2003), municipalities are required to keep a fixed asset register compliant with General Recognised Accounting Practice 17.

This fixed asset register should cover all municipal infrastructure, including water, sewerage, roads, stormwater and electricity. It should be updated every five years and used to inform asset management. “This is the guiding tool for setting up maintenance management systems and ensuring assets are maintained, repaired or replaced as necessary,” says Braune. Unfortunately, these asset registers are often inaccurate and/or incomplete. Braune frequently encounters insufficient details on assets and a lack of accurate and up-to-date condition assessment information. The result is often non-maintained, non-functional and broken assets.

“For municipalities, this causes losses in revenue due to leaking water supply systems, deteriorating roads that can no longer be repaired and must be replaced at an enormous cost, blocked stormwater

systems causing severe flooding, and so much more,” stresses Braune.

“It has been established that, for a typical residential area, the upgrading and replacement cost of a stormwater drainage system is 15 to 20 times higher than the average annual maintenance cost. This causes an enormous financial burden on municipalities to replace services for which there are no capital funds available.”

Braune believes there is an urgent need to obtain more accurate and detailed information on the status and condition of municipal infrastructure assets, in order to have a more complete and up-to-date asset register for infrastructure management and maintenance planning. “The asset register is the foundation for the sustainable management of all municipal infrastructure. Without it, you cannot ensure effective master planning and maintenance planning. It is essential that municipalities get this right, and I encourage them to embrace new technologies while doing it.”

For more information, contact Matt Braune on mattbraune7@gmail.com or +27 (0)82 600 5993.