Best Practice of Intelligent Algorithms to Optimize and Prioritize Capital Investments and Asset Rehabilitation

Purpose The purpose of the presentation is to illustrate that for digital-water solutions to be successful we need to shift the focus from 'digital' and 'smart,' data and tools to the people and value added. It is easier and cheaper than ever to collect data, numerous tools are available for data processing/visualization, vendors offer different digital twin platforms to integrate and deliver this new information. The key component in the future success of digital-water implementations is not in the digital domain, but instead it is in a clear definition of value added / return on investment and close collaboration with the utility staff on the implementation of the solution. The Jefferson County, AL, application of intelligent algorithms to optimize and prioritize capital investments and asset rehabilitation demonstrates a collaborative approach through every stage of the project and delivers simple to understand optimal solutions based on cutting-edge technology.

Benefits This presentation will provide the following benefits to the audience and industry:

-- demonstrate how formal optimization software can be applied using best practice techniques to evaluate alternatives.

-- provide an apples-to-apples comparison of the SSO Remedial Measures Plan (RMP) developed using traditional trial-and-error modelling techniques and the optimized RMP developed using optimization software

-- illustrate how performing sensitivity analyses on the effectiveness of I/I reduction identifies basins that are cost-effective and ensures conservative conveyance capacity upgrades.

-- demonstrate how asset condition and sediment data can be incorporated into an optimization to determine whether it is more cost-effective to clean the sediment or replace and upsize based on a holistic consideration of conveyance, storage, and I/I reduction alternatives.

-- demonstrate how the optimization approach can incorporate multiple design storms in a single analysis to determine the cost-effective strategy that eliminates SSOs in both events.

-- illustrate how Optimizer can be applied to prioritize the schedule of implementation of a capital program to maximize return on investment.

Background Jefferson County owns and operates wastewater collection systems across nine treatment plant basins serving approximately 600,000 people. A total of approximately 200 reported SSOs are currently recorded by Jefferson County. In 2019, Jefferson County engaged WCS and Hazen to undertake an optimization demonstration project to evaluate conveyance, storage and I/I reduction alternatives for the Valley Creek basin which had the highest density of reported SSOs. This project successfully demonstrated life-cycle cost savings on the order of $54 M (30%) when compared to the Baseline RMP (developed using traditional trial-and-error modelling). It also demonstrated that a prioritized capital improvement schedule could achieve 40% SSO volume reduction within the first 10% of capital expenditure and 98% reduction within 70% of the total capital expenditure required to eliminate all SSOs and achieve surcharge objectives. The Jefferson County, System-Wide RMP Optimization project was undertaken and completed in 2020 based on the success of the Valley Creek demonstration project. The system-wide optimization incorporated five treatment plant basins that are all interconnected either by existing or potential future flow diversion structures.

Details The primary objective of this study was to apply intelligent algorithm optimization technology, 'Optimizer', to evaluate and prioritize remedial measure alternatives including conveyance, storage, inter-basin transfer, treatment, and inflow and infiltration (I&I) reduction alternatives to eliminate SSOs in the 2-year design storm (6-hour and 24-hour events). Secondary objectives include performing sensitivity analyses for key assumptions and to identify aspects of the planning strategy that may require further investigation. The 'Optimizer' software integrates improvement alternatives, comprehensive life-cycle costs, design criteria, and the calibrated hydraulic model of the collection system. In a single analysis, the software applies intelligent algorithms and cloud computing to evaluate tens of thousands of possible solution configurations with respect to life-cycle cost and hydraulic performance. Scenarios and sensitivity analyses are easily completed by adjusting relevant assumptions or inputs and rerunning the cloud-based optimization.

-- Improvement alternatives evaluated in the optimization include:

-- Parallel relief sewers and upsized gravity sewers
-- Sediment removal.
-- Pump station upgrades. Force mains.
-- New storage facilities.
-- Inter-basin diversion controls
-- High rate treatment facilities.

I&I reduction. Unit cost rates adopted for the optimization analysis are planning level estimates developed by Hazen based on the County's bid tab records. The unit costs include capital, O&M, and replacement estimates of all alternatives.

System-wide optimization runs were completed for the following scenarios:

Conveyance-Only
-- Optimization without storage or I&I reduction alternatives
-- Conveyance + Storage - Optimization without I&I reduction alternatives
-- All Alternatives (Ultra-Conservative I&I)
-- All Alternatives (Conservative I&I)
-- All Alternatives (Aggressive I&I)

The optimized solution costs for each scenario are compared in Figure 1. The preferred RMP strategy was the All Alternatives (Aggressive I&I) scenario illustrated in Figure 2. The optimization model used for the prioritization task was formulated to select projects from the Optimized RMP (aggressive I&I reduction scenario). The prioritization analysis used the optimization model to determine the sequence of implementation that provides the maximum return on investment with respect to reducing total overflow volume in the 2-year design storms. The preliminary prioritization results are shown in Figure 3.

Conclusion The Jefferson County, Valley Creek Optimization demonstration project and the System-Wide Optimization project demonstrate both significant savings when compared with an apples-to-apples Baseline RMP developed using traditional trial-and-error modelling and highlighted opportunities for incorporating flexibility to allow the RMP to be adapted over time. The prioritization analysis completed for each project consistently demonstrated a high return on investment whereby the vast majority of SSOs could be eliminated at a fraction of the total program cost. This outcome allows Jefferson County to provide customers with immediate and noticeable improvements in system performance during the early stages of the program while also providing an opportunity for the final stages of the program to be adapted and potentially eliminated if a diminishing return on investment can be illustrated as more data is collected. The County considered the optimization projects successful in minimizing capital expenditure required to meet consent requirements and informing decision making when selecting where to focus short-term investments to maximize value provided to customers.