Hidden Apparent Losses Becomes the Source of Significant Real Losses in the Southborough DMA.

INTRODUCTION:

The Southborough District Metered Area (DMA) encountered significant challenges regarding Non-Revenue Water (NRW), with initial assessments revealing a staggering loss of 1500 m3/day. This report chronicles our journey to identify and rectify the elusive sources of water loss, restoring efficiency within the DMA.

INITIAL NRW ASSESSMENT AND FIELD INVESTIGATION:

When the Southborough DMA was finalized and commissioned, an initial NRW assessment was made in order to establish a baseline in and plan the activities needed to reduce the losses to an acceptable level. The initial level of NRW was calculated to be 1500 m3/day, one of the highest levels of NRW within the Portmore project area. Upon discovering this substantial water loss, an urgent leak detection sweep was conducted, revealing 129 leaks, but only one was considered a major leak. These leaks were promptly repaired, albeit resulting in a marginal reduction of about one litre per second in losses (86.4 m3/day).

Recognizing the size of the DMA (24km) and the need to narrow down the area of interest, a successful step-test was conducted, and the results showed that 50% of the losses were concentrated (about 750 m3/day) in one specific area, despite this area representing only 24% of the total size of the DMA. A thorough investigation into the area of concern was conducted. The focus was on a DN50 supply to a disused sewage plant, which was identified as a potential source of losses. After prioritizing repairs on this connection, we installed a flow meter. Despite the plant's inactivity, the meter indicated a steady flow of 2 litres per second (172.8 m3/day), prompting the closure of this connection. However, even after addressing this major source of losses, the NRW levels in this specific area remained alarmingly high.

A HOLISTIC APPROACH:

A collaborative meeting involving all the project's leaders from NWC and Miya was called in order to strategize and prioritize actions to reduce the NRW in the area of interest. During the course of the conducted repairs, reports surfaced of an inaccessible swamp located just behind the sewage plant, an area residents referred to as 'swamp water' due to its extensive greenery for many years. Additionally, the metering department flagged an unusual and visible presence of water in this same area.

Utilizing satellite imagery from ArcGIS and Google Earth, we observe a notable increase in greenery surrounding the sewage plant over the years, continuing into the project's duration. This growth was significantly higher compared to other areas within the same DMA, indicating a potential issue that required further investigation and immediate action.

This prompted an immediate response from the Leak Detection department, which discovered the presence of chlorine in the supposed swamp. This finding confirmed that the increased greenery in the surrounding area was due to a continuous supply of water from an unidentified leaking connection, potentially the DN50 supply to the plant and/or a significant leak in the DN250 main pipeline, probably escaping underground to the swamp.

Accurately pinpointing the exact location of the leaking pipeline or connection proved challenging. Furthermore, the persistence of the swampy conditions despite the closure of the plant's supply added to the complexity of the situation, presenting a puzzling scenario that requires further meticulous investigations.

To address this challenge, an exhaustive investigation was conducted by the Leak Repair and Pressure Management departments. Bush clearing exercises were carried out followed by excavations in the swampy area for a few days, in search of any signs of a pipeline, but these efforts proved unsuccessful. This led to the excavation and inspection of the DN250 pipeline, spanning approximately fifty meters in and around the existing connection. Despite the difficulties, this effort led to the discovery of another supply to the sewage plant, an unknown and clandestine DN50 connection. This supply was completely ruptured and responsible for the swamp, that had been existing for many years. The presence of two connections to the plant - one known and the other previously concealed - remains an enigma.

RESOLUTION AND RECOVERY:

The unknown connection was promptly capped, leading to further recovery of nearly 483 m3/day. This successful intervention not only rectified the losses but also prompted a broader investigation into sewage plant connections to pre-empt similar incidents. the proactive approach demonstrated the importance of comprehensive assessment and swift actions in addressing non-revenue water issues, ultimately contributing to the overall efficiency and sustainability of the water network.

CONCLUSION:

The journey to mitigate NRW within the Southborough DMA exemplifies the multifaceted challenges inherent in water management. Through meticulous investigation and collaborative efforts, hidden losses were uncovered and rectified, underscoring the importance of initiative taking strategies in NRW mitigation.

RECOMMENDATIONS:

Moving forward, we advocate for continued vigilance and comprehensive assessment in NRW management. Embracing advanced technologies and fostering interdepartmental collaboration are paramount in pre-empting and addressing NRW challenges effectively.

ACKNOWLEDGEMENT:

We extend our gratitude to all stakeholders and team members whose dedication and collaboration were instrumental in the successful resolution of NRW challenges within the Southborough DMA.