Compressed high-intensity radiated pulse (CHIRP) acoustic reflection data acquired in lakes and other shallow water bodies can provide detailed imaging that is valuable for environmental and engineering geology applications well below the sub-bottom floors. However, it is often unclear to non-specialists which acquisition settings should be considered to achieve optimal imaging quality when beginning a new survey, particularly in an unfamiliar environment. We review fundamental concepts for optimizing signal design using coincident CHIRP lines from two extant glacial lakes in the eastern Sierra Nevada of California: Convict Lake and June Lake. As part of the optimization process, seismic data were recorded with different source acquisition parameters, including sweep bandwidth and length, in pre-production testing to determine the most effective acquisition parameters for satisfying survey depth and resolution objectives. We offer recommendations for best practices based on these results.
Persistent seepage from an earthfill dam and associated structures has been observed for decades at Lake Capote, a small, spring-fed, off-stream, manmade lake in southwestern Colorado. Extensive engineering measures in 2006 did not fully remediate seepage. Therefore, we employed electrical resistivity tomography (ERT), induced polarization (IP), and self-potential (SP) methods to determine the location of seepage and its relationships with local geologic conditions. ERT revealed an approximately north-south striking horizontal, high-resistivity feature extending underneath both the northern part of the dam and the adjacent south dike. IP results indicated that this interpretive feature exhibits low chargeability (i.e., a low ability to store electrical charges), and SP results identified localized high positive magnitudes in it. In the context of borehole data and published literature, ERT and IP results suggest that this feature is a rare sandstone bed in the local shale-dominated bedrock (Lewis Shale) and also that it is the location of persistent seepage. Seepage appears to be occurring under the dam along faults in the interpretive sandstone (similar faults are observable in a nearby outcrop) and also within highly fractured shale under the south dike. In contrast, the middle part of the dam shows evidence, in both ERT and IP results, for seepage through its embankment rather than in its foundation. Our results demonstrate the value added to forensic investigations of dams by the integration of different geophysical methods, and they also portend the crucial importance and cost-saving potential of preconstruction geophysical site characterization of damsites.
Degradation of urban surface water quality has increased the importance of understanding the spatial and temporal distribution of pollutants within aquatic systems. Poor water quality damages aquatic habitats and poses a human health risk. The purpose of this study was to investigate environmental and anthropogenic factors that impact water quality in the Rock Creek Watershed in Maryland and the District of Columbia by monitoring microbiological (E. coli and total coliforms), chemical, and physical water quality parameters. Sampling weekly and following >13 mm rain events during a four-month period obtained 295 total water samples. The geometric mean E. coli concentration for each month exceeded the permissible standard. Spatial and temporal data analysis using Geographic Information Systems software and statistical analysis determined that water quality is not uniform along Rock Creek. Areas with more than 50 percent agricultural and low-density land use had higher mean nitrate concentrations but lower electrical conductivity and phosphate concentrations compared with urbanized areas with a high density of older, potentially leaking sewers. Impervious surface coverage was positively correlated with mean electrical conductivity and negatively correlated with mean nitrate concentration. Precipitation and creek discharge rate were positively correlated with mean enteric bacteria concentration. Temporal (distribution of rainfall) as well as spatial (pet waste from dog walking) influences may impact the dynamics of microbial contamination in the watershed. These data may assist decision makers in understanding the relationship between water quality of Rock Creek, the factors studied, and the potential health hazards resulting from precipitation events.
This study aimed to predict the soil erodibility factor (K factor) using visible and near-infrared (VNIR) spectroscopy coupled with a partial least-squares regression (PLSR) model and to integrate the predicted K factor into the RUSLE model for improved soil erosion assessment. The K factor was calculated based on the Universal Soil Loss Equation (USLE) model and also predicted using VNIR spectroscopy coupled with the PLSR model. The combination of these factors generated a GIS map illustrating soil loss. Our results revealed a significant negative correlation between soil permeability and the USLE K factor (r =-0.75, p < 0.05). Conversely, percent silt showed the strongest positive correlation with the K factor (r = 0.55, p < 0.05). Results also showed that the K factor had significant correlations with several spectral bands, including 450 nm(r=0.36, p<0.05), 641 nm(r=-0.21, p<0.05), 990 nm (r = 0.26, p < 0.05), and 1,910 nm (r = 0.22, p < 0.05). Notably, the mean VNIR-PLSR K factor (0.28 t hr MJ(-1) mm(-1)) was twice that of the USLE K factor (0.13 t hr-1 MJ(-1) mm(-1)). The average soil loss predicted by the RUSLE model using the VNIR-PLSR K factor was 39.2 t hr(-1) yr(-1), i.e., more than double the average soil loss estimated using the USLE K factor (18.6 t hr(-1) yr(-1)). Soil loss ranged from negligible in flat areas to over 60 t ha-1 yr-1 in mountainous regions. Approximately 20 percent of the study area experienced very low to low soil loss, while another 20 percent faced very severe soil erosion.
The Southern High Plains are bounded on the west through the southern half of eastern New Mexico by the roughly linear Mescalero Ridge, an erosional, westward-facing near vertical escarpment, up to 150 ft (45.7 m) in height, capped by the 10 to 40 ft (3 to 12.2 m) thick caprock caliche. As it approaches the Texas state line, it loses linearity and topographic definition, developing numerous re-entrants and significant erosional cuts and gullying. Over this section, it is underlain or immediately adjacent to a corresponding ridge on the buried Triassic erosional surface termed the red bed ridge, a drainage divide throughout the Cenozoic. The red bed ridge and the Mescalero Ridge continue eastward into Andrews County with the Mescalero Ridge as the topographic drainage divide between the Colorado and Pecos Rivers, turning south and blending into the Cretaceous rocks of the Edwards Plateau. The buried red bed ridge is on the Triassic erosional surface of the upper part of the Dockum Group mud-stones, the Cooper Canyon Formation. The red bed ridge is at least partially of structural origin in the vicinity of the Waste Control Specialists facility just east of the New Mexico/Texas state line. A similar anticlinal structure occurs in underlying Permian units over a thickness of several thousand feet. Several commercial facilities have been developed in the state line area with the near-surface proximity of the low permeability Triassic mudstones providing isolation from potable groundwater and reliable waste containment characteristics for hazardous and radioactive wastes.
Artificial recharge is increasingly important for groundwater management in arid regions, yet its effectiveness depends on how recharge water interacts with existing aquifer salinity. In the southwestern San Fernando Valley Groundwater Basin of Los Angeles, CA, elevated sulfate and total dissolved solids (TDS) have long prevented artificial recharge west of the "bad-water line." This study evaluated whether modern salinity results mainly from conservative mixing with sulfate-rich groundwater derived from Miocene marine formations or from in situ dissolution of lithic fragments containing gypsum and pyrite in Quaternary basin-fill sediments. Groundwater discharging into the upper Los Angeles River, the only accessible source of modern southwestern basin groundwater, was sampled and analyzed for major ions, stable water isotopes, and tritium, and results were compared with imported water sources and native bedrock groundwater. Stable water isotopes show Los Angeles River groundwater plotting between imported water and bedrock-derived native groundwater, with measurable tritium indicating imported water recharge within roughly 10 to 25 years. Major anion mixing calculations yielded native water fractions of 24 to 29 percent across chloride, sulfate, TDS, and stable water isotopes, demonstrating that observed salinity is reproduced by two end-member conservative mixing. Native groundwater contains far higher dissolved solids than imported water, and mixing trajectories match observed compositions. These results show that salinity in the southwestern basin reflects non-reactive mixing rather than mineral dissolution. Managed recharge using low-TDS water can dilute saline zones and improve groundwater quality when monitoring accounts for bedrock-derived saline inflows.
Miami-Dade County, FL, has complex hydrological and water management conditions, creating challenges for predicting groundwater levels. Due to the potential impacts of increasing sea level and changes in rain patterns on flooding and saltwater intrusion, it is essential to be able to accurately predict groundwater levels and to understand the drivers of groundwater levels. The method traditionally used to predict groundwater levels in south Florida and elsewhere is through the implementation of a numerical model. This research looks at machine learning techniques as an alternative method to provide improved predictions of groundwater levels. Extreme gradient boosting is one of the machine learning techniques that uses algorithms to train a model by identifying hidden patterns and relationships between groundwater level drivers and groundwater levels. The accuracies of the extreme gradient boosting model and a numerical model were compared by computing the root mean square error as a model performance measure. Comparing these two methods showed that the extreme gradient boosting model had better accuracy in predicting groundwater levels at the majority of groundwater monitoring sites. Furthermore, comparison of these two models helped us to identify problematic areas where both models performed poorly and narrow down the factors that could cause this poor model performance. Finally, the extreme gradient boosting method gave the importance of each feature included among the potential groundwater level drivers, including the ranked importance of a particular factor and its lag time, at each of the considered groundwater level monitoring sites.
Soil erodibility parameters are quantitative indicators used to describe soil susceptibility to erosion by raindrop impact and surface runoff. Soil erodibility is a key factor in understanding and predicting soil loss under varying environmental conditions. The present study aimed to estimate soil erodibility parameters such as inter-rill erodibility (K-ib), rill erodibility (K-rb), critical shear stress (tau(cb)), and the K-factor. In this way, remote sensing data extracted from Sentinel-2 imagery and topographic data extracted from digital elevation models (DEMs) were applied as input variables in the Lake Urmia region of northwestern Iran. A total of 96 soil samples were collected and analyzed for key soil properties. Soil erodibility parameters were calculated using WEPP (Water Erosion Prediction Project) sub-models and RUSLE (Revised Universal Soil Loss Equation) equations. Three modeling scenarios were evaluated: Scenario I) topography, Scenario II) remote sensing, and Scenario III) a combination of both. Results showed that the integrated model (Scenario III) provided the most accurate predictions (R-2 values of 0.618 for K-ib, 0.337 for K-rb, 0.629 for tau(cb), and 0.503 for the K-factor). It was concluded that combining spectral and terrain data significantly improves the estimation of soil erodibility and offers a reliable and scalable approach for erosion risk assessment in semi-arid landscapes. The findings provide practical applications for land managers and policymakers to target erosion control strategies, improve watershed planning, and improve the identification of vulnerable zones in the deteriorating Lake Urmia ecosystem. WEPP (Water Erosion Prediction Project) sub-models and RUSLE (Revised Universal Soil Loss Equation) equations. Three modeling scenarios were evaluated: Scenario I) topography, Scenario II) remote sensing, and Scenario III) a combination of both. Results showed that the integrated model (Scenario III) provided the most accurate predictions (R-2 values of 0.618 for Kib, 0.337 for K-rb, 0.629 for tau(cb), and 0.503 for the K-factor). It was concluded that combining spectral and terrain data significantly improves the estimation of soil erodibility and offers a reliable and scalable approach for erosion risk assessment in semi-arid landscapes. The findings provide practical applications for land managers and policymakers to target erosion control strategies, improve watershed planning, and improve the identification of vulnerable zones in the deteriorating Lake Urmia ecosystem.
The Lutak Spur (LS) is a prominent deltaic land-form near Haines, Alaska, formed during the retreat of the Cordilleran Ice Sheet from the Last Glacial Maximum. This study evaluates its geologic evolution, soil development, and slope stability response to a December 2020 atmospheric river (AR) event that triggered multiple landslides. We posit that LS formed as an ice-contact kame delta at the margin of a retreating valley glacier. Post-glacial isostatic rebound exposed the LS surface, allowing Spodosols with iron-cemented (Fe-cemented) horizons to develop beneath forest vegetation. We used field observations, laboratory testing, surface drainage mapping, and modeling to evaluate tree throw as a possible landslide trigger. Direct shear testing indicated that Fe-cemented layers contribute cohesion to near-surface soils. On the basis of measured precipitation over a 2-day period and NOAA Atlas 14 precipitation frequency estimates, the December 2020 AR event approached the intensity of a 1,000-year storm. Hydrologic modeling indicated that peak discharges were approximately three times greater than those of a modeled 100-year storm. The SEEP/W modeling demonstrated elevated groundwater levels and pore water pressures (PWP) from infiltration. The SLOPE/W modeling indicated dry slopes were stable, but removal of the Fe-cemented layer reduced the factor of safety (FS); under saturated conditions, the FS dropped below 1.0. Field evidence, resident observations, and modeling support the hypothesis that tree throw along the slope crest disrupted the Fe-cemented layer, triggering failures. These results suggest that extreme precipitation, combined with vegetation disturbance, reduced slope stability through transient PWP increases and the loss of near-surface strength.
High-altitude regions are subjected to extreme environmental changes with climate change, significantly modifying the land-use and snow-cover dynamics. The present study analyses the spatiotemporal changes in land use and land cover (LULC) and snow cover in Lahaul and Spiti, Western Himalaya, from 1994 to 2023 through remote sensing and geospatial techniques. The findings reveal a staggering decline in snow cover from 19.34 percent in 1994 to 7.43 percent in 2023, predominantly attributed to glacial retreat and the altered snowfall pattern. In the meantime, barren lands have expanded from 77.69 percent to 87.27 percent, signifying increased land degradation. Fluctuations in vegetation cover have been recorded; however, increases in the lower elevations, in contrast to vegetation degradation in the higher altitude zones, indicate changes in ecological stability. Gradual increases in built-up areas indicate human response to environmental changes. The relation between snow-cover loss and LULC changes amplifies the call for decreasing glacial resources in water availability, agriculture, and biodiversity. These findings presage the urgency of sustainable land management and climate adaptation strategies geared toward mitigation against environmental decay in this fragile Himalayan ecosystem. Future studies must incorporate advanced geospatial modeling with climate change projections in formulating long-term conservation policies for high-altitude landscapes.
Investigating rock mass mechanical characteristics in dry-wet cycle conditions is crucial for uncovering deformation and failure mechanisms in reservoir slope subsidence zones resulting from manual excavation. Wet-dry cycling and triaxial reloading tests were performed on unloaded rock masses exposed to various excavation disturbances. The findings indicate that the order of unloading directly influences deformation patterns and rock sample failure strength during wet-dry cycles. Additionally, increasing dry-wet cycles leads to a reduction in peak strength during rock sample reloading, corresponding to increased deformation, and the elastic modulus, cohesion, and friction angle also decrease. Moreover, as unloading magnitude and the number of dry-wet cycles increase, the occurrence of cracks during rock sample failure rises significantly, demonstrating notable distinctions between the two unloading magnitudes.
Pseudokarst development in sandstones arises from the interplay of chemical dissolution, mechanical piping, structural discontinuities, and sedimentological controls. This study evaluates the mechanical-piping component of sandstone-siltstone pseudokarst formation. Although dissolution is often cited as the primary driver of preferential pathway enlargement, many sandstones lack sufficient soluble material, so mechanical piping instead dominates pathway development. Long-term piping persistence then depends on either durable cementation (e.g., silica, iron oxide, or carbonate cements) or cohesive fines to bind the grain framework. Sandstones without durable cements must rely on cohesive fines to form and stabilize field-scale piping pathways. At the Lightning Lake Research Facility field site in Oklahoma, a hillslope claypan perched above an open siltstone bedding plane induced subsurface mass removal in adjacent sandstones, producing surface-expressed pseudokarst landforms. By combining electrical resistivity imaging with hydrologic measurements, we delineate the claypan's spatial extent, demonstrate its role in confining flow and generating high hydraulic gradients, and quantify the bedding plane as the principal pathway for piping during storm events. This work demonstrates the role of cohesive fines in stabilizing field-scale mechanical-piping conduits, complements models that emphasize fine-grained sediments in piping processes, and confirms findings from soil-piping studies.
In response to the pressing need to combat rising atmospheric CO2 levels, carbon capture, utilization, and storage (CCUS) technologies have gained prominence, with particular relevance to enhanced shale gas recovery (ESGR). This study delved into the geochemical intricacies of the Raniganj shales of the Lower Gondwana Group, investigating their response to supercritical CO2 (ScCO2) exposure through an array of advanced analytical techniques, including Xray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), Brunauer-Emmett-Teller (BET) surface area analysis, Raman spectroscopy, and scanning electron microscopy with energy-dispersive X-ray analysis (SEM-EDX). The outcomes of this comprehensive analysis unveiled notable transformations within the shale matrix. Notably, there was evidence of Si-O and C-H bond degradation in the shale's framework and phyllosilicate minerals. Moreover, the precipitation of secondary minerals was observed, suggesting a complex geochemical response to ScCO2. Furthermore, the study highlights a significant increase in shale porosity following ScCO2 exposure, which has promising implications for enhanced CO2 storage. Additionally, a depth-dependent trend in thermal maturity (R0) was evident, underscoring the role of depth in shaping the geochemical response to ScCO2. A significant observation was the reduced impact of ScCO2 on greater-depth shale samples compared to their shallower counterparts. While increased porosity was observed post-ScCO2 exposure, the findings suggest that permeability enhancement may be restricted due to secondary mineral precipitation, pore throat narrowing, and depth-dependent thermal maturity effects. This study highlights how geological factors, especially depth, affect geochemical dynamics in CO2-ESGR, helping to optimize CCUS for carbon storage and shale gas recovery.
Anthropogenic reshaping of landscapes can increase landslide activity. One example of heavily modified, landslide-prone landscapes is the Appalachian region, which hosts weak geologic strata, steep slopes, a humid climate, geologically recent river incision, and large-scale landscape modifications resulting from surface mining. Surface mining conducted before the Surface Mine Control and Reclamation Act (SMCRA) of 1977 did not require reclamation to approximate original contour, so remnant highwalls and mine benches are common throughout Appalachia. This study investigated the occurrence of slope instability and failure beneath pre-law mine benches in the northern coalfields of West Virginia. Mine bench features were manually digitized based on interpretation of high-spatial-resolution digital terrain data and aerial orthophotography, and ancillary geospatial data (i.e., mine permit boundary and disturbance extent data sets). A subset of mine bench features, stratified by coal seam, was randomly selected for slope stability analysis. The lower margins of the randomly selected mine benches were differentiated into segments with and without evidence of slope failure or instability. Results suggest that local topographic slope and aspect were not strong determinants of slope instability beneath mine benches. However, the coal seam or unit that was mined was an important determining factor. The Pittsburgh seam, and to a lesser extent the Redstone seam, had a larger proportion of their lower margins showing evidence of slope failure than did other seams. This study highlights that local-scale geology controls the geomorphic response to human landscape modifications and suggests that proactive reclamation of surface coal mines might reduce slope-failure geohazards.
Wetlands are complex ecosystems that are dependent on hydrologic processes and affected by water chemistry. The Fish Lake Environmental Education Center near Lapeer, MI, is glacially influenced and contains a large bog and multiple kettles that contain ephemeral wetlands in the spring. Previous studies indicated that groundwater flow direction at the southern end of the site is towards Fish Lake, but the extent to which groundwater and surface water are interacting with the wetlands north of the lake is unclear. The goal of this project was to understand the relative contributions of precipitation and groundwater in the bog and kettle wetlands north of Fish Lake. Groundwater and surface water samples were collected monthly in the fall and winter and biweekly in the spring and summer between May 2022 and September 2023. Values of pH, electrical conductivity, water levels, nitrate, nitrite, phosphorus, and iron were analyzed and used to determine water source. Sites with low pH and low electrical conductivity were determined to be precipitation influenced. Conceptual site models based on project data suggest that the wetlands to the north are more precipitation sourced and become more heavily groundwater influenced to the south towards the lake. Glaciated regions of the Upper Midwest with similar topography can apply these methods to determine relative sources of water in different wetlands.
A landslide susceptibility map delineates the potential zones for landslide occurrence, which is critical in landslide management. The aim of this study is to produce a landslide susceptibility model of part of the Fairbanks North Star Borough, Alaska, using the analytical hierarchy process (AHP) and the frequency ratio (FR) methods in a geographical information systems (GIS) environment. To produce the susceptibility map, seven landslide-influencing factors-geology, slope angle, slope aspect, plan curvature, profile curvature, distance to the nearest road, and average annual precipitation-were selected. Spatial databases and thematic layers of all the aforementioned factors were created in a GIS environment. The AHP was applied to derive factor weights that indicated their relative importance in causing landslides. The FR method was used to derive class ranks that indicated the relative importance of individual classes for each factor. All the weighted raster maps of the factors were integrated using a weighted linear combination method to generate a landslide susceptibility map, which classified the study area into five different landslide susceptible zones, i.e., very low, low, moderate, high, and very high. The susceptibility map was validated using the area under curve (AUC) and landslide density index (LDI) methods. The AUC value of the prediction rate curve was calculated, and a 76.8 percent validation accuracy was achieved. The LDI result also indicated a successful landslide susceptibility model. The results of this study can be used to identify slopes prone to sliding on a relative basis.
The objective of this research was to explore a costeffective and non-invasive methodology to characterize the spatial variability of hydraulic conductivity using airborne electromagnetic (AEM) signatures as an alternative to traditional techniques such as borehole sampling. The relationship between AEM measured apparent resistivity and magnetic field strength was explored using a small data set that included 180 natural moisture (NM) content data points and a total data set of 546 grain size distributions that excluded the NM data. The grain size distributions were used to develop a soil indicator (SI) parameter and to estimate the hydraulic conductivity (K*) using pedotransfer functions. Predictive models were developed using three techniques: artificial neural network regression (ANNR), support vector regression (SVR), and artificial neural network classification (ANNC). The sole use of non-invasive parameters to characterize K* proved insufficient. The inclusion of supplemental invasively collected parameters showed ANNR to best characterize the relationship (R-2 = 0.64) with the smaller data set, while the SVR model performed best with the total data set (R-2 = 0.57). ANNC was shown to be a viable alternative (overall accuracy = 88 percent) when a broad characterization of K* was sufficient. This study lays out a methodology that could be used for future K* characterization using improved data sets.
Elevated chloride levels in lakes, rivers, streams, and groundwater are a concern in many snowbelt states, particularly in urban areas where deicing and anti-icing salt are major sources of chloride pollution. In agricultural and mixed land use watersheds, other chloride sources such as fertilizer, water softening, manure, wastewater discharge, and industry may be more substantial sources of chloride pollution. A chloride budget was conducted for Sand Creek watershed, a chloride-impaired, agricultural watershed in southern Minnesota, with the purpose of developing a model for watersheds with limited data and characterizing important chloride sources in less urban settings. Annual chloride mass contributions were estimated for major point and nonpoint sources from June 2013 to May 2019, including wastewater treatment plants, industry, deicing salt, potash fertilizer, livestock, and septic systems using various permitting data, monitoring data, land use data, census data, and other records. The estimated annual chloride budget was used in conjunction with a water balance model to estimate monthly and annual loads and flow-weighted mean monthly concentrations. Results from the chloride balance model show good agreement with more detailed models for the watershed. Road salt, fertilizer use, wastewater treatment plant discharge, and manure application were estimated to be the largest chloride sources that impacted a number of creeks in the Sand Creek watershed. Results from the chloride balance model for the watershed suggest significant chloride retention in the watershed across seasons and that chloride loading in the stream is more sensitive to major runoff events than timing of application from individual sources.
Monitoring groundwater quality and quantity is increasingly important as growing usage stresses many regional aquifers. Manual sampling provides high-quality data but is not scalable to the monitoring needs of multi-aquifer systems with large numbers of wells. This is the case in the Twin Cities Metropolitan Area of Minnesota. As a result, it is difficult to capture short-term, sub-annual variations in water quality in metropolitan areas using conventional manual sampling. Such short-term variations can help establish links between anthropogenic activities at the surface and their time-delayed expression in water quality at depth. We recommend an automated network of sensors be established in the region to monitor groundwater quality in real time. Here, we demonstrate the diagnostic ability of a pilot network of instrumented wells on the University of Minnesota campus that are within 1 km2 and screened in two different aquifers. In situ sensors have gathered more than 2 years of sub-hourly data on temperature, water elevation, and specific conductance. High-frequency measurements of these simple physical parameters from 2021 to 2023 resolved episodic fluctuations in chloride concentrations that range from less than 300 mg/L to more than 500 mg/L, the effects of transient pumping related to local construction de-watering on groundwater flow, and steadily increasing groundwater temperatures inside a major urban area ranging from 0.07 to 0.14 degrees C/yr. This pilot demonstration of real-time groundwater monitoring is scalable in Minnesota by state agencies with statutory responsibility for groundwater quality.
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.
