To meet standards for wastewater treatment plant effluent, Madison Metropolitan Sewerage District in southern Wisconsin has been implementing a wide variety of chloride source reduction actions for nearly 10 years. As part of that work, the district partnered with service-area communities to undertake a pilot project to test the efficacy of an incentive on voluntary home water softener efficiency upgrades. The district offered rebates, administered through municipalities, to incentivize softener evaluations, optimizations, and replacements. In the approximately 2 year pilot, the district demonstrated a feasible method for a municipally administered rebate system, developed cost estimates for such a program, and estimated its impact on chloride levels. While the pilot did have positive outcomes, such as raising community awareness and municipal involvement, development of a standardized softener evaluation method, participation by over 200 customers, and acquisition of other useful data, it did not demonstrate an impact pronounced enough to warrant a recommendation to scale or repeat the incentive. This pilot program both demonstrated limitations of an incentive for reducing softener discharge through voluntary household actions and raised important concerns about cost and sustainability of an efficiency-only–focused household chloride reduction strategy.

For people living in cold-weather climates, road salt is likely the most visible form of environmental salt pollution, being nearly ubiquitous throughout the winter. However, in areas with mineral-rich, calcium- and magnesium-containing “hard” water, such as southern Wisconsin, ion-exchange water softeners also contribute a significant yet often hidden source of environmental salt pollution. In the Madison, WI, area alone, an estimated 100,000 pounds (∼45,000 kg) of salt are discharged daily by water softeners; see Lake et al. (2015). Although this salt seems to disappear as it dissolves and flows down drains, its ultimate fate is similar to that of winter de-icing salt—it ends up in the environment (often after passing through wastewater treatment systems), where it can harm freshwater ecosystems.

Like most wastewater treatment plants, the Madison Metropolitan Sewerage District’s Nine Springs Wastewater Treatment Plant in Dane County, WI, is required to meet clean water standards; see Wisconsin State Legislature (2005), Environmental Protection Agency Office of Water Regulations and Standards (1986), Environmental Protection Agency (2014), and Benoit (1988). However, it cannot remove dissolved solids like chloride from salt during the treatment process, making compliance a challenge. The district has invested significant time and resources into evaluating compliance options. Treatment methods like desalination or membrane filtration are prohibitively expensive and energy-intensive, and they would therefore overall contribute to rather than ameliorate environmental harm (AECOM, 2015). As a result, the district has prioritized source reduction strategies by developing a comprehensive and multi-faceted source reduction initiative with actions to address each influent chloride source, including water softeners (Madison Metropolitan Sewerage District, 2023).

Ion-exchange water softeners, which use and discharge salt as part of their regeneration cycle, are ubiquitous in all building-type sectors across the district’s service area. Cumulatively, softeners are the largest direct source of chloride influent to the plant; they are estimated to contribute around 80,500 pounds (36,500 kg) of chloride (over 100,000 pounds [45,360 kg] of salt) per day to wastewater influent to the Nine Springs Wastewater Treatment Plant (AECOM, 2015). When it comes to source reduction, water softeners generally cannot be treated as a homogeneous group, however. The different types of softeners (commercial, industrial, institutional, residential) necessitate individualized and unique approaches, due to the scale/size of softeners, differences in use patterns, water-quality needs, ownership type, related decision-making hierarchies, barriers to action, risk tolerance, motivations, and financial planning timelines. Among all softener types, single-family home water softeners are estimated to be the largest cumulative source, contributing nearly 50,000 pounds (∼22,000 kg) of chloride per day to plant influent, as determined by interpolating chloride discharge based off of public water system meter classification type data. In addition to being the largest source, single-family home softeners as a group have been the most challenging source to develop strategies for because of the diffuse nature of the contributions and related attitudes underlying home softener maintenance and operation. For example, these appliances are relatively expensive, typically costing between $500 and $2,000 for purchase and installation. There are few intrinsic motivations for homeowners to upgrade, as the return on investment—whether in terms of water or salt savings—is minimal with efficiency gains. Moreover, water softeners often have long lifespans, frequently exceeding 20 years, leading homeowners to overlook the need for upgrades unless the appliances break down or explicitly require maintenance. Because softeners are often placed in a discreet location (essentially hidden in basements and/or utility closets), they can easily be forgotten. The underlying technologies of water softeners have remained largely unchanged for decades, providing little incentive for homeowners to pursue the latest models. Furthermore, the mechanics of how these devices function can be complex and opaque, even to many licensed plumbers. Consequently, as long as the softener seems to be working—primarily by using salt—homeowners tend to adopt an “if it ain’t broke, don’t fix it” mentality, resulting in a low turnover rate for appliance upgrades. As such, early research into the existing stock of area home softeners showed an overall low level of efficiency within this sector and therefore high opportunity for impact. Methods for increasing softener efficiency are known (developed locally through a previous pilot program; Lake et al., 2015) and are typically referred to as either optimization (softener settings adjustments) or replacement (upgrading softener by installing a newer softener model). Despite knowing that efficiency increases are possible, and opportunities are abundant, few examples of feasible and cost-effective ways for utilities to implement widespread voluntary home softener efficiency upgrades exist. To date, known existing water softener rebate programs mainly focus on removal of time clock regeneration–type softeners (Pflugerville, TX; Waterloo, ON), outright softener removal (Santa Clarita, CA; Waukesha, WI), or installation of softeners with an off-site regeneration service (Solvig, CA; San Benito, CA). In the absence of examples of successful utility programs that have stimulated widespread softener efficiency improvement measures, the district initiated its own pilot program to test methods of motivating residents to improve their home water softeners.

The Salt Savers Pilot Program was launched by the Madison Metropolitan Sewerage District in March 2020 to help fill this gap. The purpose was to encourage voluntary softener efficiency improvements, determine the feasibility of running a municipally administered water softener optimization and replacement incentive program, and measure associated costs. Behavioral science best practices suggest using incentives to change behavior when the primary barrier to action is cost alone (Mckenzie-Mohr and Schultz, 2014); however, as was previously established, many barriers underlie the home softener status quo (not price alone). Testing an incentive was nonetheless important and chosen as the intervention to use because of both community and district leadership interest, as well as requirements spelled out by regulations in Wisconsin Administrative Rules Code § NR 106.90, to both “evaluate the potential for a rebate program to install high efficiency water softeners” and “recommend residential softener tune-ups on a voluntary basis” (Wisconsin State Legislature, 2024).

The Salt Savers Pilot Program took place in a fixed geographic area, representing a mostly residential part of the district’s service area within the Village of McFarland, Town of Dunn, and Pleasant Springs Sanitary Districts (see Figure 1). In addition to being a mostly residential area, allowing focus on the target population, this area was selected for the pilot program because of its potential for wastewater monitoring. The discrete, fixed sewer-shed boundary and closed system, in which everything goes through one pumping station (with monitoring feasibility), allowed for quantitative evaluation of the pilot program intervention.

The program offered a $200 rebate for the replacement of a “clunker” (defined as older than 15 years old, a time-clock regenerating softener, or one on a specified list of outdated models not capable of improved efficiencies) and $75 for a settings optimization. Different incentive reimbursement models were used in each participating community based on community administrators’ preferences. In one community, participants received a discount on the services, and in the other community, participants received a retroactive rebate reimbursement check.

Implementation of the pilot required many prerequisites: partnership from the communities in which the pilot program was taking place; development of criteria for water softener evaluation (Madison Metropolitan Sewerage District, 2015); training of providers (mostly plumbers) to standardize water softener inspection and optimization procedures (Madison Metropolitan Sewerage District, 2024); administrative infrastructure for providers to document services provided (ESRI, n.d.); a robust advertisement/outreach strategy; an eligibility screening tool for residents (softener “self-screen”; Madison Metropolitan Sewerage District, n.d.); and mechanism(s) for collecting data and issuing the incentives (ESRI, n.d.). Table 1 outlines the final program workflow. The program workflow ultimately had to fit within existing resources/staff time constraints and tools available. In addition to meeting the goals for the pilot program, it was also designed to lay the foundation for longer-term change (such as changing norms around softener maintenance, increasing awareness of local salt pollution and consequences, expanding local provider knowledge base and services offered, as well as provision of transparent pricing) where possible.

Methods used to evaluate the pilot included the following:

  • Analysis of wastewater monitoring data to compare pre- and post-intervention chloride concentrations of pilot area wastewater.

  • The numbers of participants in each type of incentive were monitored.

  • A mid-pilot email poll was sent to rebate-eligible self-screen takers (in McFarland) who had not yet taken any recommended action on their softener by participating in the rebate program (n = 48). The poll went out by email and contained a single question ‘Do you still plan on following the recommendations?’ and two possible buttons to click (yes and no). Depending on which button was clicked, the respondent was taken to a separate screen to identify why they had not or would not take the recommended action.

  • In-person intercept interviews were conducted after the conclusion of the program (August 2022) by two district staff who asked questions to random passersby in public places in McFarland. The goal was to find out if they had heard of the program, and if so, what their opinion of it was, and if they had seen advertisements. By talking to a random sample of residents, interviewers were also able to hear from area residents if there was something major that had not been anticipated or learned about otherwise (as far as reasons for not participating or messaging missteps, for example).

  • Structured, formal exit interviews were conducted with municipal partners and providers.

  • An eight-question, post-pilot participant survey was mailed (cover letter and paper questionnaire with online return option and return addressed envelope) to 210 participants. Two additional follow-up reminders to complete the survey were sent out to non-respondents.

  • Content of building permits was analyzed before, during, and after the pilot period.

Wastewater monitoring was conducted for the pilot program in two ways: (1) through the district’s user charge (billing) program, in which the concentration of daily 24 hour flow-proportionate composite samples was measured at the district’s laboratory, per Environmental Protection Agency 600/R-93-100 Method 300.0 (Pfaff, 1993), for five consecutive days, and (2) through the novel use of a freshwater conductivity logger.

The pilot succeeded in providing key insights per the core purpose of the study (determining costs and feasibility). The Salt Savers Pilot Program wrapped up in June 2022, for a total pilot period of over 2 years. In total, 229 home water softener interventions were completed as part of this pilot program by 12 providers from five different companies at 210 different addresses. Table 2 summarizes participation by intervention across the three participating communities. As a percentage of total residential addresses, participation in the pilot is estimated around 5 percent in McFarland, 9 percent in Town of Dunn, and 2 percent in Pleasant Springs Sanitary Districts. Lower participation in Pleasant Springs Sanitary Districts could be due to the shorter amount of time the rebate was available there (less than a year), compared to the other areas.

In total, 334 self-screen reports were submitted (March 27, 2021 to July 2022), of which about half elected to determine their eligibility for the pilot program. Reviewing the self-screen submitted reports, we were able to determine that the tool was successful in providing a recommendation to three out of four self-screen takers. Of those, 37 of the self-screen takers participated in the pilot program, indicating the self-screen information did somewhat help with getting people to participate in the pilot program.

Between the two concurrently used rebate structures, there wasn’t one that was obviously better than the other. In exit interviews, providers felt overall that it was confusing to have two different types of programs running at the same time, but they didn’t have a strong preference for one over the other. Throughout the program, no feedback was received from residents in terms of comments or complaints about either model or about wanting the other community’s rebate system. In the rebate participant follow-up survey, people who participated in the rebate program overwhelmingly said that the program was easy (only 2/100 respondents said the program was difficult). Participants were generally appreciative that they did not have to send anything in, and that it was all handled automatically by the providers and the municipality. Administrators felt that the different models were about equal in amount of work overall; however, they had a slight preference for the McFarland model (reimbursement as a rebate) because of concerns about transparency in the Dunn (discount) model. That is, they were uncertain whether the discount was applied to a standard fixed softener price or an increased softener price that with the discount evened out to the standard fixed price. The higher overall participation rate in one community compared to another may have been influenced by various factors. However, there is no direct evidence linking this difference to the incentive administration model. That said, the higher percentage of optimized jobs in Dunn (60 percent) compared to McFarland (14 percent), as shown in Table 2, suggests that advertising the “free” service may have attracted more participants to that particular service.

During the pilot period, chloride concentration was measured in all user charge samples from PS09, representing a total of about 60 samples. The conductivity logger took over 100,000 measurements over 2 years, tracking conductivity every 5 minutes. Data analysis of wastewater samples (daily composite samples collected quarterly for billing, before, during, and after the program), using a change-point model with and without assuming autocorrelation, indicated there was no statistically significant decrease in the measured chloride concentration found resulting from this intervention. The probability of change large enough to observe in actual wastewater samples was not large enough to report a significant change during the pilot. The regular variability of chloride concentrations in wastewater was more than the change that may have been observed because of this program.

Although specific estimates of pounds of chloride reduced were not possible using monitoring data, estimates could be made for average daily discharge per household water softener and expected reductions resulting from optimizing and replacing outdated softeners, as developed by Lake et al. (2015). Using this method, assuming daily discharge of about a half pound per softener per day, and 27 percent expected reduction as a result of optimization and 47 percent reduction from upgrades, on average, it can be estimated that this pilot achieved an estimated daily salt reduction of 75.5 pounds (34 kg), leading to a corresponding daily chloride reduction of 45 pounds (20 kg).

The total cost of the project was about $334,000, with the major expenses being direct incentives (around $44,000) and labor for administration, sampling, promotion, etc. (around $290,000). This project took up 30 percent of time for two full-time staff positions for 2 years. The average cost per pound of chloride reduced per day through this program was $7,420.

Significant staff time went into advertising the program within the pilot communities (see Table 3), including special promotions such as raffles, drawings for local business gift cards, and referral bonuses for pilot participants, not detailed in the table included. Even so, staff time and logistical limitations left several outreach and advertisement ideas developed but not pursued, such as: targeted neighborhood outreach (door hangers, signage, event days), signage at houses that participated (peer pressure), targeted online ads (Google ads), general public signage/billboard in community, McFarland TV channel spots, realtor partnerships, and public meetings. Intercept interviews with random passersby in public places in McFarland conducted as part of the pilot program evaluation indicated that despite these efforts, awareness of the program was still not widespread; three out of four of random passersby interviewed said they had not heard about the program. Although awareness of the pilot may not have been widespread, interestingly, intercept survey respondents reported overall greater awareness of salt issues generally than had been observed previously in prior community surveys.

Although offering a municipally administered water softener efficiency improvement incentive was determined to be technically feasible through this pilot project, the incentive was costly and yielded low overall chloride savings. From 2015 to 2019, the district offered a variety of incentives to industrial and commercial facilities and pass-through grants to softener companies. Cost per pound of chloride reduced across these various incentive programs came out to around $63/pound/day. Of these past incentive programs, one in the high range of cost per pound (and likely also the most comparable to that in the current study due to its similar focus on single-family residential home water softeners) was the pilot detailed in The Reduction of Influent Chloride to Wastewater Treatment Plants by the Optimization of Residential Water Softeners (Lake et al., 2015), in which softener optimization and upgrades were fully subsidized, for which the cost per pound was estimated to be much lower than the cost per pound reduction estimated from the Salt Savers Pilot Program ($1,188 per pound chloride reduced for optimization and $5,231 per pound reduced by replacement vs. $7,420 per pound per day as a result of the Salt Savers program).

The pilot program provided a chance to evaluate the efficacy of monetary incentives to accelerate water softener efficiency improvements and related reductions in the chloride input to the sewer. The evidence of the pilot promoting these outcomes is tenuous. In a post-pilot survey of participants, many respondents cited good timing, “to take advantage of the rebate while it was available since my softener was old and had to be replaced anyway,” as a motivation for participating in the program (see Figure 2). When asked directly, “Would you have optimized or replaced your softener within the last 2 years if there had not been a rebate program?” in the same post-program follow-up survey, about half of respondents (53 percent) indicated that they would have optimized/replaced their softener within the last 2 years even had there not been a rebate program. A review of building and plumbing-specific permits issued in the Village of McFarland before, during, and after the pilot neither supports nor refutes this survey finding; the number of plumbing-specific permits pulled during the pilot program duration may have showed a slight overall positive trend (Q4 2020 to Q1 2022); however, this fact may be confounded by an overall positive trend in permits overall. Based on permits, there is not strong evidence that this incentive program provided “additionality” as defined by Bennear et al. (2013).

The timing of this pilot must be noted because it likely had some impact on participation; however, what the impact was is somewhat unclear. The pilot kickoff timing in McFarland coincided with an election, perhaps competing with a heightened news cycle for attention. A couple months into the program, just as the first major advertising push was going out, a National Emergency was declared mid-March 2020. By March 17, 2020, the State of Wisconsin and Public Health Dane County/Madison issued Emergency Order #12, “Safer at Home,” which limited Wisconsin residents from leaving their homes except for essential activities, government functions, and business operations (State of Wisconsin Department of Health Services, 2020). All “non-essential” businesses were ordered to close (Radcliffe, 2021). Although guidelines spelled out what was considered essential, including a provision for “Critical trades. Building and Construction Tradesmen and Tradeswomen,” it was not always clear whether voluntary appliance check-ups for non-emergency situations were allowed. Regardless of whether service calls would have technically been allowed or not, some community members may have been hesitant to have a service provider in their home given social distancing recommendations. The district decided to briefly put the program on pause April–June 2020. It is hard to estimate the overall impact that the coronavirus 2019 (COVID-19) pandemic had on participation, because on one hand, there was major job loss/loss of income, supply chain issues, increases in cost of building materials, and labor shortages, but on the other hand, there was also a dramatic change in how homes were/are used, and unprecedented numbers of home improvement projects were initiated (Joint Center for Housing Studies of Harvard University, 2021). In multiple providers’ exit interviews, they cited the impact of labor shortages on their ability to maximize the amount of softener check-ups and replacements. One company said they ultimately did not end up advertising the Salt Savers program because they already had too much work and couldn’t keep up with it as it was.

Interestingly, the results of this pilot program challenged two previously held ideas. First, previous research indicated that there was broad community willingness to participate in water softener optimization, especially when equipment was subsidized or offered at low/no-cost. When asked about willingness to optimize their softener, 70 percent of respondents to the district’s 2019 Community Values Survey said they would be willing to do so (with 30 percent of respondents overall saying they’d even be willing to pay up to $50 for that service; Patras et al., 2019). However, when offered a subsidized/free optimization as part of the pilot, homeowners did not participate at the same level indicated in the Community Values Survey, as seen in the percentage of eligible homes that participated, and in the summary provided in Table 2. Second, data emerged as part of this pilot that support a pivot away from focusing only on improving water softener efficiency toward tactics that promote reductions in the volume of water softened. Softener inspection reports in the town of Dunn showed a larger opportunity for soft water reduction interventions than the district had previously thought. In Dunn, 95 percent of homes inspected had all water throughout the house (often less the kitchen sink) running through the softener, and this number was 82 percent in McFarland. Softening hot water is more crucial than softening cold water due to scale formation at higher temperatures, and one potential salt reduction strategy is softening only the hot water in a home and leaving the cold water hard. The high percentage of houses in the pilot area with hot and cold softened water represents ample opportunity to reduce salt use through a reduction in total volume of softened water, an intervention that would likely reduce more chloride than softener optimizations (see Figure 3 for example). Results from the self screen also support this finding: 52 percent of takers claimed to have both hot and cold water softened, while almost 30 percent actively stated that they had only hot water softened. Whether these self-reported numbers are accurate is not certain, but it might perhaps speak to homeowners’ willingness to have only the hot water be softened by showing their perceived thoughts about how their plumbing is configured.

When considering replicating this water softener rebate program, several key factors should be addressed:

  • Scale of reductions needed. A voluntary incentive at this scale was not able to make an observable impact on chloride levels at the pumping station, let alone overall to treatment plant influent. If the highest area participation rate observed from this program (9 percent) was scaled throughout the entire Madison Metropolitan Sewerage District service area, it would yield a reduction of about 2,000 pounds (900 kg) of salt per day, which is not enough of an impact to reliably meet water-quality goals, based on calculations in AECOM (2015). Scaling, given the cost per pound reduction observed as a result of this intervention, would also not be cost-effective for rate payers. That being said, scaling would likely not even be possible in the district’s service area and should be approached cautiously overall. Elements like municipal capacity, budget, and provider willingness/ability to increase service capacity were all challenges in this pilot program and would likely be substantial barriers to scalability. Furthermore, this pilot may have presented false positives, and as such, even the results achieved might not be transferable to other communities.

  • Partnership commitment. Clear commitment from partners should be sought from all parties for a municipally administered incentive. Clear parameters and expectations around who is doing what and alignment across the organizations are necessary. In this pilot program, confusion arose in some cases with both municipal and service provider partners due to the lack of thorough written agreements and/or robust enough shared understandings. For example, while the public works department was administering the McFarland rebate program, the municipal building permits department was not waiving fees for the permits to install a new softener. So, while residents did get a rebate from their municipality, they also incurred extra fees from them in the process of pulling a permit to upgrade the softener. Lack of formal agreement from service providers led to gaps in messaging clarity, communication, and availability of providers, which were unknown to program administrators during the program, but emerged as issues during the exit interviews. For example, (1) some providers felt the work was not worth the effort and showed little interest in expanding their operations, creating a bottleneck in which the demand for services may have been left unmet, and (2) misunderstanding about prices led to an awkward situation in the Dunn model, where municipalities were advertising a “free” optimization with the understanding that this service cost $75, even though the service cost more. Service providers retrospectively told program administrators their fee was higher but reluctantly agreed to do the service for the advertised amount.

  • Community interpretation of incentives. Programs should consider if the program is making any “implicit endorsement[s] or recommendation[s]” by offering an incentive program (Krijnen et al., 2017), and what the incentive might be signaling to residents. In this pilot, an incentive was tested because state statutes required its evaluation; however, where there is not guidance suggesting issuing of incentives, program managers should consider guidance from behavioral science research. Such research suggests a municipally sponsored, voluntary program may be unintentionally signaling that that this action is not urgent, and that it is a sort of “above-and-beyond,” versus being an essential urgent action required of all to protect water quality. They may also perceive that because the government is paying for an action to happen, there is some undesirable outcome of the action that necessitates compensation.

  • What is supported through incentives. Future programs might consider expanding the incentive to include related equipment, such as iron filters and/or measures that encourage soft water reduction. In this pilot, some of the wells in the area had high iron to the point where providers were recommending installation of an iron filter ahead of the softener to keep the softener efficient longer. Theoretically, challenges with iron can be solved by running a softener at inefficient settings, but the better option, as far as minimizing salt use, is to install an additional device to specifically handle the iron. Iron filters were not covered by any incentive/program funding for this pilot. In a few instances, homeowners indicated that when given the choice about purchasing a $1,700–$1,800 iron filter to preserve softener efficiency or just continuing to run the softener at a lower efficiency, the choice was clear; softener efficiency just did not make financial sense for them. Subsidizing the cost of iron filters as well as softener improvements would further affect the cost-effectiveness of offering incentives, so incentives may not be a feasible salt reduction strategy in areas with iron-rich drinking water.

  • Durability of reductions. An efficiency-encouraging incentive may be best suited for short-term, temporary chloride reduction needs. Relying on an intervention that only encourages one-time water softener efficiency improvement is not likely to change norms underlying water softener maintenance habits in the long-term. Water softener resin is known to degrade over time, where estimates indicate as much as 2 percent per year, so efficiency programs should consider what happens in 10–20 years after the incentive program ends. For example, will the incentives be offered again or at regular intervals?

Overall, the development of a municipally administered rebate incentive was found to be feasible with successful estimates for approximate costs and expected salt reduction outcomes developed. Results indicate that this approach is unlikely to be successfully scaled and yield significant long-term chloride reductions, particularly for large metropolitan areas like the Madison Metropolitan Sewerage District service area. The pilot program showed limited evidence of program effectiveness in reducing overall chloride concentrations in wastewater and had limited evidence of accelerating the rate of naturally occurring softener upgrades. Concerns about overall cost and effort compared to outcomes, scalability, and perception issues with voluntary-only programs suggest that repeating this intervention elsewhere should be approached with caution.

A municipally administered rebate program to upgrade water softener efficiency may be useful in areas where only small, short-term water-quality improvements are needed or where opportunities for chloride reduction from other softening sectors are limited; however, for regions requiring more substantial, long-term reductions, such as large metropolitan areas, the results suggest that reliance on rebates alone is unlikely to provide a sustainable solution to impact influent chloride levels substantially.

While the pilot program did not result in large-scale chloride reductions, it catalyzed important partnerships, tools, and capacity that will continue to be valuable moving forward. Additionally, the pilot program provided insights into possible future strategies for reducing salt use from home water softeners more sustainably, i.e., via soft water volume reduction strategies. These strategies, which aim to decrease the overall demand for softened water, require further research to fully understand their viability and effectiveness. If these strategies can be successfully incentivized and scaled, they may prove to be more impactful and sustainable than continuing voluntary household softener optimization/reduction programs.

We would like to acknowledge the support of all project partners, without whom this project would not have been possible. Special thanks go to: participating service providers, cooperating household participants, the Wisconsin Salt Wise Partnership (Allison Madison, coordinator), municipal partners (Village of McFarland, Aimee Irwin, assistant to the public works director, and Jim Hessling, public works director; Town of Dunn, Cathy Hasslinger, clerk-treasurer/business manager, and Kelsey Shepperd, administrative coordinator), the myriad data scientists who touched this project in some way (Steve Corsi, U.S. Geological Survey research hydrologist; Ruoran Laura Huang, University of Wisconsin [UW] Wisconsin Science and Computing Emerging Research Stars [WISCERS] Program; Steven Moen and Nathan Aviles, UW statistics Ph.D./teaching assistants), Fall 2024 Madison Metropolitan Sewerage District Pollution Prevention Intern Ivan Castaner-Cividanes for assistance in preparation of the manuscript, and to the many employees across the Madison Metropolitan Sewerage District, in nearly every department, for all the support they provided throughout the project. From leadership, monitoring, and sample collection to information technology support, geographic information system (GIS) services, sample analysis, and advertisements, this project exemplifies that when our diverse skills come together for a common goal, we truly are #StrongerTogether. Thanks also go to Connie Fortin and the team at Bolton and Menk for organizing the Salt Symposium Conference and creating the opportunity to share this project for this special edition of Environmental & Engineering Geoscience.