Digital mapping and data collection prolong lifespan of wastewater infrastructure by 15-years

Recently, the District secured grant funding for planning and design improvements to their 50-year-old water and wastewater systems. Despite ongoing maintenance, many components were nearing the end of their lifespan, posing a significant failure risk as maintaining such a robust system is labour-intensive to operate and sustain. 

Specifically, due to the rise of groundwater during the wet months, they experienced significant groundwater infiltration into the wastewater collection system due to the condition of the piping and joints. Combined with poor drainage along local country roads, their systems were also inundated with stormwater runoff, which posed a significant flooding risk to residences and businesses if left untreated. This required an evaluation of the collection system as a whole and the development of targeted improvement projects to replace sections subject to high maintenance, significantly contributing to inflow/infiltration (I/I). 

At the time, the District’s infrastructure did not have automated processes with controls and alarms, which is common for smaller, older service districts. Additionally, the facility had a permitted dry weather design flow of 186,000 gallons per day (gpd) and a peak wet weather design flow of 580,000 gpd. At this rate, the client determined their facility was not operating at peak performance. Instead, it functioned at approximately 75 percent of its design capacity and would take just one torrential downpour to overwhelm the system.

To mitigate these issues, our client required a thorough wastewater treatment facility (WWTF) evaluation, a sanitary sewer evaluation survey (SSES), a comprehensive plan, and infrastructure updates that could meet future systems more effectively and improve system reliability and redundancy. 

Our Digital Intelligence (DI) team, in conjunction with university GIS students, mapped approximately 160 manhole locations, and collected asset information for sewer shed analysis and hydraulic modelling. The DI team developed a Survey 123 form to streamline data collection and catalogue sanitary sewer manhole locations, using a high-accuracy, centimetre grade, GPS antenna, where inverted depths for the sump, outflow pipe, and all incoming pipes were collected. By using location intelligence, the underground sewer pipe junctions and elevations were collected with a high degree of accuracy.

Next, the sewer system was mapped in a geographic information system (GIS) using the field data collected in Survey123, then the pipeline data were attributed using the pictures and pipe connectivity diagrams collected in the form. Using Survey123, we streamlined the data collection process and significantly reduced costs for our client, as the process is repeatable and offers electronic data gathering instead of the manual process of writing information down on paper and converting it to digital formats later. A custom geoprocessing script was developed and used to reassign each manhole ID and elevate them based on their spatial location. In a dataset, each pipeline was attributed with important information (i.e., from and to manhole ID, elevation, pipe size, material, and slope). Inverted elevations were also used to define the slope of the pipe used in sewer shed hydraulic modelling, which uncovered several areas for further investigation and recommendations for improvement.

The SSES and WWTF evaluation determined the existing plant had remaining capacity through 2030 and identified improvements to extend the plant's useful life well into 2045, including enhancements to headworks, aeration basin, clarifier, digester, chlorine contact basin, effluent pump station, and sludge handlines. In addition to upgrading the existing plant, an alternative plant design was identified. 

Flow monitoring was also used to identify the highest priority areas to investigate I/I within the municipality’s sewer sheds. Lift station improvements were identified through discussions with the District’s staff, including the implementation of supervisory control and data acquisition and ease of maintenance improvements. Flow monitoring was performed at the municipalities five lift stations and the results were used to quantify the flows expected under the 10-year, 24-hour design storm protocol.

Through spatial data, location intelligence and digital mapping, we identified the required lift station improvements, such as implementing supervisory control and data acquisition to reduce the amount of maintenance. A targeted approach was defined to prolong the system's life and reduce future maintenance costs for the District.

And, by conducting the SSES and WWTF evaluations, we prepared a costing and construction schedule and identified permitting requirements and challenges the District faced. With the field data collection and digital mapping complete, an Esri ArcGIS Online Project Delivery subscription (PDS) was launched to give our client direct access to their GIS data. The PDS is administered by GHD and provides the client’s employees with direct access to visualize, query, and update their mapped sanitary sewer assets as needed, thus enabling the client to better direct field efforts, answer crucial questions, and make more data-driven decisions.

Overall, each of the improvements identified (i.e., headworks, aeration basin, clarifier, digester, chlorine contact basin, effluent pump station, and sludge handline) will extend the plant's lifespan by 15-years. 

Due to the positive experience with the evaluation, plan, and sanitary sewer GIS tool, the District has requested their domestic water system be delivered to the online tool as well.