Development of a risk-based tool for groundwater well rehabilitation and replacement decisions

Abstract

Groundwater wells are critical drinking water infrastructure elements that widely support basic system supply needs while also providing supply reliability, better water quality (in some cases), and comparatively lower operational costs. Well rehabilitation and replacement are thus an area where water utilities could benefit from rational decision support frameworks and quantitative tools that enable them to better navigate the complex trade-off relationship(s) that exist among a variety of environmental quality, public health, financial, regulatory, organizational, and technological dimensions. Consistent with these considerations, a business risk-based prioritization tool was developed for this study that augments/extends California Water Service (Cal Water)'s well rehabilitation and the replacement decision-making process. For this derivation, a business risk exposure methodology is combined with an analytical hierarchy process (AHP), with the AHP being utilized to determine the weights of the factors involved in the likelihood of failure and the consequence of failure calculation. It is expected that the new tool will assist in optimizing inspection and action plans and identify the wells requiring attention and/or additional work for water utilities.

Effective well management using the J100 framework and methodology

“…In this study, the first step was to establish an overall framework and determine its individual components based on data availability. In contrast to a previous study (Güngör‐Demirci et al, 2019), a unique framework patterned around the ANSI/AWWA J100‐10(R13) standard was developed for this research. As defined in the original standards document, “J100 is a process for analyzing and managing the risks associated with malevolent attacks and naturally occurring hazards against critical infrastructure.” (AWWA, 2010).…”

“…It is widely used by practitioners for determining and tracking the productivity of a well. For this study, the procedure used in a previous study was adopted (Güngör‐Demirci et al, 2019). First, the average of the five most recent SC values for each well (SC RECENT ) was calculated.…”

“…In this study, the monitoring results obtained for six specific secondary contaminants-namely total dissolved solids (TDS), and chloride (Cl À ), iron (Fe), manganese (Mn), sodium (Na), and sulfate (SO 4 ) ions-were used in the vulnerability analysis. More specifically, the Water Quality Index (WQI) method, originally developed by Brown et al (1970) for surface water, and later used by others (e.g., Sadat-Noori et al, 2014) for groundwater, formed the basis for this analysis in a manner consistent with previous writings (Güngör-Demirci et al, 2019). The most recent water quality measurements were compared with the current drinking water standards set by the U.S. Environmental Protection Agency (US EPA; USEPA, 2019) except for sodium (Na + ), where the World Health Organization's standard was used.…”

“…Well age is a useful indicator of well condition since it is reasonable to assume that an older well will be in poorer condition than a new well under similar conditions (SSWD, 2009). As in previous research in this area (Güngör-Demirci et al, 2019), a linear relationship was assumed between well age and well condition, with the age being calculated from the time of original commissioning until May 2019. The final vulnerability scores assigned based on well age, as derived within this construct, are outlined in Table 1.…”

“…The objective of this study is to develop a comprehensive risk‐based prioritization framework and tool to support well rehabilitation and replacement decisions and to test this new tool on a relatively large water system. This work builds upon previous efforts to apply business risk exposure principles to well asset management (Güngör‐Demirci et al, 2019) by incorporating key principles contained within the AWWA/ANSI J100 Risk and Resilience Management Standard. Business risk exposure, criticality, and risk‐based prioritization concepts have been used in well rehabilitation and replacement decisions for years (e.g., SEFC, 2020; SSWD, 2009).…”