A mysterious low-frequency hum reported by residents across Table View, Bloubergstrand, Milnerton and surrounding areas has resurfaced, prompting the City of Cape Town to investigate whether some of its sewer maintenance operations could be contributing to the noise.

The City issued a noise alert today (Wednesday 9 September), acknowledging concerns about a persistent humming or mechanical noise reported by residents in the Milnerton, Table View and Bloubergstrand areas.

According to the City its Water and Sanitation Directorate regularly carries essential wet-well cleaning out at sewer pump stations.

Wet wells are underground chambers where sewage collects before being pumped onwards through the sewer network.

The City said the specialised vacuum and jetting trucks used during cleaning operations can generate significant mechanical noise while operating.

The work is generally scheduled between 00:00 and 04:00, when sewer flows into pump stations are at their lowest.

City to investigate possible link

The City said it would investigate whether the reported noise is linked to any current Water and Sanitation operations in the area.

It said efforts would also continue to minimise the impact of essential maintenance work on surrounding communities.

“The City will investigate whether the reported noise is linked to any current Water and Sanitation operations in the area and will continue to make every effort to minimise the impact of essential maintenance work on surrounding communities.”

Ward councillor Sue van der Linde has meanwhile started a WhatsApp group to help residents document when and where they hear the sound.

She said she had asked the City to monitor pump stations in and around the area for wet-well pumping and cleaning operations.

Residents help track the noise

“I have requested the City to monitor pump stations in and around the area for wet well pumping that occurs when the pumps are at risk of ceasing due to wet wipes and foreign objects including sand that clog up sewage pipes,” Van der Linde said.

She said the City would provide the scheduled wet-well cleaning roster and report any emergency operations over the next week.

“I will be checking this against noise reports on this group. So far I have not found a correlation but this is a deeper dive over a longer period.”

Residents have been encouraged to report the sound on the group, including their location, the time they heard it and any recordings they may have.

Van der Linde has also created a poll asking residents when and where they hear the noise in an attempt to identify patterns.

Residents offer different theories

Residents have reported hearing the sound at different times and from different locations, with some suggesting there could be more than one source.

One resident suggested the community could be dealing with two separate low-frequency sounds, possibly one affecting the Edgemead side and another around Parklands or Table View.

The resident said the sounds could overlap in some areas, making the combined hum more noticeable and potentially explaining why it appears to vary depending on where and when it is heard.

Another resident said the noise was not new and had been heard for many years, particularly at night and during the early hours.

The resident recalled that a family dog would react strongly to the sound and said a family member had driven around the area on numerous nights in an attempt to locate its source.

The resident said they believed the sound could be linked to a tarring company carrying out work during the night to avoid disrupting daytime traffic. This remains a resident’s theory and has not been confirmed.

‘Like a low-level diesel engine’

A Woodbridge Island resident also reported hearing the sound during the early hours.

“I heard this same sound. Almost like low level diesel engine running at 1.30.”

The resident said they initially assumed the noise could have been coming from a ship or activity at the docks across the foreshore.

The sound reportedly woke the resident and affected their child’s sleep.

Community search continues

For Van der Lind, the focus is now on collecting enough information to establish whether the reports correspond with specific activities or locations.

Residents are being encouraged to record the exact time they hear the noise, where they are located and, where possible, capture recordings.

The City has confirmed that it will examine whether its sewer operations could be responsible, but there is currently no confirmation that wet-well cleaning or pumping is the source of the mysterious sound.

For residents who have heard the hum repeatedly over the years the latest investigation could provide an opportunity to finally establish whether the different reports are connected, or whether several separate sources are being mistaken for one mysterious noise.

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