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City puts contingency plans in place to tackle sewer collapses in Strand <p>​The City’s Water and Sanitation Directorate has been actioning a multi-pronged approach to address and prevent sewer pipes from collapsing in Strand. </p><div><br></div><div>Over recent months sewers that have collapsed in De Villiers and De Ruyter Streets have been repaired. </div><div><br></div><div>Sewers can collapse for various reasons, including naturally ageing infrastructure, which gradually results in cracks over time, as well as the internal walls of pipe corroding gradually because of the acidity of the wastewater. </div><div><br></div><div>These are the key aspects to the multi-pronged approach:</div><div><br></div><div>Assessing Trappies Sewer</div><div>The Trappies Sewer is a bulk sewer that services a large area within the Helderberg region.</div><div><br></div><div>A condition and capacity assessment study was completed on the Trappies Sewer (900mm diameter section in De Villiers Drive) in 2015.  The study assessed the sewer’s existing and future capacity based on the City’s Sewer Masterplan. In addition to the capacity assessment, a condition assessment involving CCTV footage and pipe wall sampling (cut-outs) of the sewer was completed to comment on the pipes existing condition and to advise on the need for future rehabilitation/assessment.  </div><div><br></div><div>The report at the time concluded the following:</div><div>•<span style="white-space:pre;"> </span>The sewer did not have enough capacity for expected future flows.</div><div>•<span style="white-space:pre;"> </span>The sewer is in a good condition and it is not a high priority for rehabilitation.</div><div><br></div><div>The report recommended the following:</div><div>•<span style="white-space:pre;"> </span>The Trappies Sewer’s condition be reassessed between 2020 and 2025. This will still be done, however, due to its current condition, the focus will be to prioritise upgrading this infrastructure.</div><div>•<span style="white-space:pre;"> </span>The capacity issue is to be addressed with the construction of a new Gordons Bay Sewer Pump Station at the Gordons Bay Wastewater Treatment Works that will reduce the flow into the Trappies sewer during peak periods.</div><div><br></div><div>New Gordon’s Bay Sewer pump station</div><div>The Gordon’s Bay Sewer Pump Station is currently in the final stage of design. The planned commencement date for the construction of the Gordon’s Bay Sewer Rising Main Project is in the 2023/24 financial year. The function of the Gordon’s Bay Pump Station is to relieve capacity constraints on the Trappies Sewer pipeline.</div><div><br></div><div>‘Based on the available information and observations on site, it is clear that the sewer has corroded more rapidly than anticipated. The City is monitoring the condition of The Trappies Sewer because any internal pressure or increased external pressure can cause a collapse,’ said the City’s Action Mayoral Committee Member for Water and Sanitation, Councillor Siseko Mbandezi.</div><div><br></div><div>The Annual Sewer Replacement Programme is a City-wide programme that includes reactive replacements/rehabilitation of deteriorated sewers and pro-active replacement/rehabilitation of ageing sewers.</div><div><br></div><div>‘For the 2022/23 financial year, the 450mm diameter portion of the Trappies Sewer will be replaced via three projects at R22 million.  Preparatory work is currently under way and lining commencement is expected in January 2023 as the liner needs to be imported,’ said Councillor Mbandezi. </div><div><br></div><div>Annual sewer pipe replacement programme update in the Helderberg region:</div><div>There has been an increase in sewer pipe replacements in the Helderberg region over the past two financial years. </div><div><br></div><div>Areas in this region include Macassar, Strand, Somerset West, Gordon’s Bay, and Sir Lowry’s Pass Village.</div><div><br></div><div>For the 2021/22 financial year, 16 159 metres of newly installed sewer mains were installed and 4 089 metres of sewer mains have been replaced. </div><div><br></div><div>This was an increase in comparison to the 2020/21 financial year, when 967 metres of newly installed sewer mains were installed and 3 376.4 metres of sewer mains have been replaced.</div><div><br></div><div>It is important to identify what causes sewer collapses.</div><div>Sewer collapses occur when the crown of the pipe (top section) cannot accommodate the internal and external loads imposed on the pipe wall.  The strength of the pipe, as well as the change in internal and external loading, are factors that influence sewer collapses.</div><div><br></div><div>Damaged pipes caused by root ingress of large trees and the misuse of the sewer system such as the dumping of foreign objects including bricks and other building rubble as well as car parts also make the existing pipe more fragile and contribute to sewer collapses.</div><div><br></div><div>Increases in internal and external loading can occur due to various situations.  The following are the most common:</div><div>•<span style="white-space:pre;"> </span>Unauthorised building works on top of the sewer;</div><div>•<span style="white-space:pre;"> </span>Excessive earth filling and compaction on top of the sewer;</div><div>•<span style="white-space:pre;"> </span>Construction vehicles, heavy vehicles and excessive traffic loading on top of the sewer;</div><div>•<span style="white-space:pre;"> </span>A higher water table during winter months;</div><div>•<span style="white-space:pre;"> </span>Surcharged (full flow) conditions due to capacity constraints or unexpectedly high volumes of stormwater ingress can cause internal pressure.</div><div><br></div><div>Tips to prevent a sewer collapse</div><div>•<span style="white-space:pre;"> </span>Report sinkholes on the road immediately.</div><div>•<span style="white-space:pre;"> </span>Prevent illegal stormwater connections into the sewers.</div><div>•<span style="white-space:pre;"> </span>Prevent dumping of foreign objects, such as rubble, litter, materials, into sewers.</div><div>•<span style="white-space:pre;"> </span>Report illegal connections/dumping.</div><div><br></div><div>Log water and sanitation service requests</div><div>Residents can use the following channels to report issues such as sinkholes, illegal connection/dumping, blocked sewers (Please provide the street address, and get a reference number):</div><div>•<span style="white-space:pre;"> </span>WhatsApp 060 018 1505</div><div>•<span style="white-space:pre;"> </span>Online:</div><div>•<span style="white-space:pre;"> </span>Email</div><div>•<span style="white-space:pre;"> </span>SMS 31373 (maximum 160 characters. Standard rates apply)</div><div>•<span style="white-space:pre;"> </span>Call 0860 103 089</div><div>•<span style="white-space:pre;"> </span>Visit a City walk-in centre (see to find the one closest to you) <br></div><p><br></p>2022-10-05T22:00:00ZGP0|#1d539e44-7c8c-4646-887d-386dc1d95d70;L0|#01d539e44-7c8c-4646-887d-386dc1d95d70|City news;GTSet|#62efe227-07aa-45e7-944c-ceebacca891dGP0|#a6816b64-c5b9-4b8d-b55a-cf8b94490ab8;L0|#0a6816b64-c5b9-4b8d-b55a-cf8b94490ab8|maintenance and repairs;GTSet|#2e3de6c1-9951-4747-8f53-470629a399bb10


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