Conference Papers

Presently, digital solution adoption in the water space is accelerating, driven by the desire to extract greater value from data for operational and planning decision making. While digital technology for water management is rapidly maturing and demonstrating value, a commonly overlooked aspect is the change management process needed to successfully deploy and maintain a digital solution. Early adopter utilities of digital solutions have learned that good technological solutions are only a fraction of the ingredients needed for a digital solution to sustainably deliver value. Common questions are: -How do we go from successful demonstration project to full deployment? -Do we need a demonstration project and when is it applicable? -Who needs to be involved in the pilot and who needs to be involved in full deployment? Will there need to be an organizational change to manage the system? -Who will own the system and data? -How will the system and data owners interact with other departments? -How do we ensure we are still getting value from the system? -Who is in charge of the system maintenance? (hardware, software, IT and cybersecurity) -How will disaster response be handled? (e.g. cyber security attack, natural disaster, etc.) -Who makes decisions on changes to the system and what is the process to make changes? -How will we train people to operate and maintain the system? This presentation will explore the change management frameworks that have been used by up to 6 midsized utilities in the United States with successful digital solution implementations spanning 5 years or more. The Gestalt Cycle of Experience, a well understood model that is used by a number of corporate and public entities to drive change, will be used to explore the change process undertook by each utility. Each utility adopted a different organizational framework to drive change and adoption. Examples of these frameworks are the 'digital transformation stewards' framework, the 'digital special ops' framework, and the 'water professional of the future development' framework. Lessons learned and common denominators for success such as early stakeholder engagement and co-design workshops will be presented as conclusions along with how these utilities evaluate and track system performance. This work is complete and ready for sharing with the broader technical community.

The City of Des Moines, Iowa (the City) awarded a contract to CDM Smith for development of a comprehensive city-wide stormwater master plan (SMP). This session will communicate the value of applying a risk-based asset management framework to the City's SMP development. Municipalities will benefit from this discussion by learning about risk-based asset management principles for stormwater systems. This framework is adaptable, eases prioritization efforts, and enhances communication with stakeholders. The SMP was developed to provide a systematic, prioritized, and proactive framework for addressing the City's stormwater management challenges. To date, the SMP has consisted of two phases with the first focusing on a needs assessment and programmatic framework, and the second phase began implementation of the city-wide risk analysis and the more detailed application in the initially selected watersheds. The needs assessment and programmatic framework phase (Phase 1) was conducted by completion of a program audit, review of best practices, and identification of new practices to enhance the City's stormwater management program, including the initial development of a risk-based asset management framework. During the subsequent implementation phase (Phase 2), processes identified during the initial needs assessment were applied to characterize the existing stormwater system and provided insight for short- and long-term financial planning. Overall, the SMP informs future strategies by providing actionable recommendations and processes to manage assets more efficiently. Continued evaluation of level of service objectives, public engagement, and process refinement bring life to the SMP, allowing for future application and adaptation by the City. During Phase 1, a risk-based asset management framework was developed to prioritize stormwater asset inspections, maintenance, renewal, and capital projects. Under this structure, the Likelihood of Failure (LoF) and Consequence of Failure (CoF) are used to calculate the Risk associated with each asset. Each of these parameters ' LoF, CoF, and Risk ' range in value from 1 to 5, with 5 being the worst. LoF is based on the assessment of an asset's condition and performance, while CoF is based on an asset's significance to the stormwater system and the impact severity of failure. Condition may be evaluated through field investigations or estimated using a surrogate parameter easily obtained through analysis of asset properties, such as age and material. The preliminary LoF based on surrogate parameters may be used in conjunction with CoF to determine an initial Risk score and inform inspection priorities. This assessment allows itself to be conducted with limited field investigations to provide an initial estimate of system risk and needs. Initial estimates of system risk may then be used to identify priority catchments for detailed investigation and recommended capital improvement projects (CIPs). Specific processes for this purpose were developed as part of Phase 1. Phase 2 of the SMP applied the processes identified during Phase 1 to the City's stormwater system. A desktop analysis was performed to determine the LoF, CoF, and resulting Risk score of each asset. Surrogate parameters were used to determine LoF, because inspection data was not widely available. GIS-based algorithms were developed to calculate these LoF, CoF, and Risk scores for each asset. From this, three priority catchments were identified in the City. Upon review of priority catchments with City stakeholders, the project team deployed for field investigations to fill data gaps and determine a more accurate LoF condition score. Investigations included pole camera and CCTV of pipes and adjoining structures and visual inspections of stormwater basins. Parallel to field investigations, SWMM models were created for the priority catchments. Inspection-based LoF condition scores and LoF performance scores from the SWMM models were used to identify assets that should be included in a capital improvement project (CIP) due to the need for renewal, either by rehabilitation (lining) or replacement. Conveyance improvements and opportunities for additional storage were modeled to provide a preliminary CIP approach. Results of the desktop analysis used to inform priority catchment selection were also used to identify potential CIPs in non-priority areas. These projects were identified by focusing in areas with the highest LoF and Risk scores. Although these CIPs require additional design, the preliminary analyses results in short-term financial planning data. The necessity and reach of these identified CIP locations will be confirmed through final field investigation and detailed design. In additional to the risk-based asset management framework and identification of potential CIPs, other key outcomes of the SMP included: - Development of level of service (LOS) objectives - Development of a public outreach plan - Development of white papers regarding policy development to support the asset management framework - A summary of recommended operation and maintenance activities per asset type - Creation of Lucity-based asset management dashboards, improved asset inventory, inspection forms, and other tracking resources, as well as staff education on use of Lucity resources - Development of an Excel-based tool to estimate asset inspection and renewal needs based on surrogate parameters of age and material for use in long-term planning - A strategy for implementing SMP recommendations and processes, including identification of staffing needs - Short- and long-term financial planning recommendations Final deliverables of the Phase 2 Des Moines SMP are currently under review and will be finalized in early 2023. As the City implements SMP recommendations, the assessment methodology, data collection approach, and other processes may be refined to better support the City's system. Efforts should focus on ramping up proactive inspections to help shift asset management from reactive to proactive, further developing the asset inventory and understanding of the system's current condition. Moving forward, the developed risk-based asset management framework provides a clear path for asset evaluation and CIP prioritization, while providing flexibility for future iterations.

Following an EPA 308 Letter of Violation in 2014 citing high rates of SSOs within the collection system, Winston-Salem/Forsyth County (WSFC) Utilities identified system condition as a key driver of gravity sewer failures. A rehabilitation plan was quickly developed and implemented to assess and rehabilitate poor condition assets within the system. Five years later the plan has underwent significant changes. By understanding the basis of this program and using the results to date to improve the initial plan, a sustainable long-term collection system has been developed to achieve WSFC Utilities level of service goals. Initial rehabilitation needs were projected using a Statistically Significant Sample Survey (4S) which sampled the variety of pipes in the system to determine which features correlated with the poorest condition. Based on these findings, rehabilitation yield rates were developed for the system. Areas with assets most likely to yield high volume of rehabilitation work were prioritized for assessment and rehabilitation measures were developed based on these asset-specific inspections. This allowed WSFC Utilities to prioritize the inspection of assets most likely to be in poor condition, maximize the number of asset failures identified, and efficiently address these failures to improve overall system condition as quickly as possible. Five years later findings indicated changes from those initial assumptions. Pipes were yielding nearly double the rehabilitation requirements. Additionally, the cost of rehabilitation had begun to escalate quickly. Initial plans were no longer appropriate and needed to be modified to be sustainable over the long-term. Figure 1 shows where data has and has not been collected to date. Using the much larger data set that now included five years' worth of condition assessment data in addition to initial 4S findings, a variety of statistical and machine learning approached were used to update rehabilitation yield rates. The types of rehabilitation required for poor condition assets could now be projected as well. These improvements, combined with updated unit prices, were used to develop a update cost of bringing the system up to target service levels. Updated failure rate projections of initial asset classes can be seen below in Figure 2. Understanding the high levels of investment required to fully improve the condition of the collection system to target levels of service, WSFC Utilities elected to focus their rehabilitation program on the worst performing asset classes. By targeting condition assessment and rehabilitation activities on these poorest condition assets, overall system can be improved most efficiently. Challenges exist in collection of data on these assets only. Throughout the collection system these in-program assets are intermixed with non-critical assets. To assess condition and rehabilitate these in-program assets only would be inefficient. Even for sub-basins with the highest concentration of in-program asset classes non-critical asset data is captured. When accounting for this factor the total cost of condition assessment and rehabilitation for all in-program asset classes is approximately $158M in present value, as illustrated with Figure 3. This cost must be spread over multiple years. Resource constraints, including funding and workforce limitations, prevent the rapid deployment of these rehabilitation activities. However, as the timeline for this investment is extended the system continues to deteriorate. A sustainable long-term rehabilitation plan must invest enough resources to offset normal condition deterioration and improve conditions to target levels of service. By modeling condition deterioration and existing rehabilitation needs, WSFC Utilities can test funding scenarios to develop a plan that balances long-term service needs with financial limitations, as illustrated in Figure 4.

The SARS-CoV-2 virus can be shed in the feces of persons infected with COVID-19. As a result, sewer surveillance can be used to identify the presence of COVID-19 infections in a particular sewershed. This study involved monitoring SARS-CoV-2 at strategic locations within a sewershed serving about 600,000 customers in Washington County, Oregon. Sampling was conducted at the four wastewater treatment plants (WWTPs) and at 25 manhole locations within this sewershed from spring 2020 to fall 2021. Samples were concentrated using electronegative filtration and analyzed using a ddPCR system. The 25 manholes were chosen to represent a range of characteristics in their micro-sewersheds including varying numbers of medical centers, industrial sectors, and residential demographics. The reported cases of COVID-19 from the Oregon Health Authority (by zip codes and outbreaks) were correlated with the wastewater virus concentrations. The virus concentrations in the influent to each of the four treatment plants correlated well with the reported COVID-19 cases in Washington County. All four treatment plants showed similar trends of a moderate peak of virus concentrations in summer 2020, followed by dramatic peaks over the holiday season and late summer and fall of 2021. SARS-CoV-2 concentrations at WWTPs appeared to be a leading indicator, with increases in wastewater observed two to three weeks before cases rose (Figure 1). At the manhole sites monitored during summer 2020, the frequency of high positive measurements was highest for several food-processing industrial sites where known outbreaks occurred. During the outbreaks, the virus concentrations in wastewater closely correlated with reported COVID-19 cases at the facilities. Sites with the highest virus concentrations also tended to occur in the zip codes with the highest prevalence of COVID-19. The demographics of residential areas have been shown to affect COVID-19 case prevalence, and a similar trend was also observed in virus concentrations in wastewater. Specifically, neighborhoods with high LatinX and high poverty populations also had higher SARS-CoV-2 concentrations. There was a surprising lack of detectable SARS-CoV-2 in the effluents of hospitals and health centers, even with a known presence of COVID-19 patients. The number of COVID-19 cases relative to the total number of patients in the hospital should have produced a clear signal, given previous positive signals detected from whole neighborhoods and industries with only a few documented cases. Quarternary ammonium compounds (QAC) disinfectants are commonly used to inactivate SARS-CoV-2 on surfaces in hospitals, and they are known to destroy DNA and RNA. These disinfectants may be entering the hospital wastewater via routine disinfection procedures and degrading the SARS-CoV-2 signal, leading to concentrations below the detection limit. Experiments conducted with a QAC disinfectant used in the hospitals in this study showed that there was nearly total decay in the RNA targets at 0.1% concentration, equivalent to 0.128 ounces of disinfectant per gallon of wastewater. It is feasible that disinfectants in the hospital environments are entering the wastewater at concentrations at or above this level and damaging the RNA, thus making it undetectable with the current analytical method. This surprising finding has serious implications for WBE monitoring at and downstream of hospitals and health centers. WWTP influent samples with at least 10,000 N gene copies per liter were also sequenced to determine the SARS-CoV-2 variants present in the samples. Each surge in reported cases corresponded to the dominance of a new variant, and several region-specific sub-variants were identified. The most recent surge in cases during summer and early fall 2021 was associated with the near-total dominance of the Delta variant and its sub-variants. Interestingly, wastewater concentrations during the Delta surge were much higher per reported case than during previous surges, which corresponds to the known increase in viral load in patients infected with the Delta variant. This study has demonstrated that SARS-CoV-2 can be successfully quantified at the micro-sewershed level by selection of appropriate key manholes and used as a surrogate or supplement to swab testing. Such a micro-sewershed approach can be used to identify hot spots of high infections such as industrial facilities and can correlate wastewater concentrations of the virus with community characteristics such as income levels. Such data may prove to be useful to the health care community to determine areas for increased testing or outreach and can be used to optimize data collection and reduce costs.

Background The Los Angeles County Sanitation Districts (LACSD) own and operate Tulare Lake Compost (TLC), a biosolids composting facility in the San Joaquin Valley of California (Figure 1). TLC was permitted to process up to 500,000 wet tons of biosolids per year, sufficient for all biosolids generated by LACSD wastewater treatment plants. During the composting process, volatile organic compounds (VOCs) and ammonia (NH3) are generated and may be emitted to the atmosphere. Emissions must be controlled to meet the requirements of TLC's air quality permit issued by the San Joaquin Valley Air Pollution Control District (SJVAPCD), which caps emissions of both VOCs and NH3 on a mass basis. Since the SJVAPCD is in non-attainment for ozone and PM 2.5, extremely stringent emissions limits are placed on their precursors, specifically VOCs and NH3, respectively. The original design of windrow composting piles with fabric cover emissions control technology for TLC did not perform adequately during the summer season. Through a series of test piles, LACSD has evaluated an alternative composting technology with the extended aerated static pile (eASP) configuration. Its emissions control device is a biofilter cover layer, composed of previously finished compost, which treats VOC and NH3 emissions from the active compost below it. To satisfy permit requirements at TLC's design capacity, lifecycle emissions from eASPs must be kept below emission factor targets of 0.20 lbs-VOC and 1.79 lbs-NH3 per ton of active compost mix. TLC produces Class A exceptional quality compost, with requirements to meet the Process to Further Reduce Pathogens (PFRP) and Vector Attraction Reduction (VAR). PFRP requires maintaining a core temperature of 131 °F for 3 days for pathogen removal, while VAR requires a core temperature of 104 °F for 14 days to reduce vector (e.g. rats, flies, mosquitos) attraction. Methodology and Implementation Baseline eASP Configuration eASP design was generally based on literature, experience from emissions testing consultants, and site visits to an existing facility utilizing the process. The active compost portion of the baseline eASP consisted of multiple adjoining rows with overall dimensions of 150' long, 140' wide, and 7' high (Figure 2). The active compost was topped with 2.5' of finished compost to form the biofilter cover layer. That 2.5' layer consisted of 1' of screened finished compost above of 1.5' of unscreened finished compost. The coarser unscreened material was intended to distribute emissions laterally across the pile, while the finer screened material above would be more effective at VOC and NH3 removal. Each row within the baseline eASP was aerated through an air header; block walls were placed on two sides of the eASP to limit uncontrolled air intrusion and retain heat (Figures 2 and 3). Sprinklers on top of the eASP irrigated the biofilter cover layer to maintain adequate moisture content in the biofilter cover for emissions control (Figure 4). Aeration Testing Adjustments to aeration timing and spacing parameters were tested. The intended purpose was to (a) improve the reliability of meeting PFRP/VAR temperature compliance, and (b) reduce capital expenditures (CapEx). More air was provided early in the composting process lifecycle in comparison to the baseline eASP (Table 1). The additional aeration was intended to increase biological activity to promote faster heating of the pile and meeting PFRP and VAR temperature requirements sooner in the eASP lifetime, thereby reducing the risk of non-compliance. The spacing between air headers was increased, only providing air beneath every other row as shown in Figure 5, while using the increased early aeration schedule from part a. This was to simplify construction and operation of the eASP by eliminating the need to reroute air headers. Irrigation Testing Decreased irrigation was tested to determine the relationship between irrigation applied to the eASP versus the amount of leachate produced and VOC emissions. Irrigation is critical to maintaining moisture to support the biology in the biofilter cover on top of the eASP, but too much irrigation leads to excessive leachate production. Leachate treatment or disposal is expensive so it's important to minimize the amount of leachate produced during the composting process while providing enough irrigation to not exceed the emissions limits for the facility. Temperature Monitoring eASP core temperatures were monitored continuously with online temperature probes (ReoTemp EcoProbes). Core temperatures were measured at 38' and 40' depths for PFRP and VAR compliance. Emissions Monitoring VOC emissions were monitored with SCAQMD Method 25.3 for total non-methane non-ethane organic carbon (TNMNEOC) and helium was used as a tracer gas for air flow measurement. Ammonia emissions were monitored by both manual GASTEC tube readings and SCAQMD Method 207.1. Results Baseline eASP Configuration VOC and NH3 emission factors were 0.05 and 0.04 lbs per ton of compost mix, respectively, well below the targets previously discussed. The eASP biofilter cover technology was able to control emissions during the composting process well below levels required for full capacity use of the facility. With respect to core temperature requirements, all zones in the baseline eASP passed the PFRP and VAR criteria, but one zone significantly lagged others. The average time for all zones to meet PFRP for the pile was 7.5 days with a minimum of 4 days and a maximum of 23 days. VAR was met at an average of 18.5 days. Such a cold zone increases the risk of non-compliance, which would require re-composting that zone. In response, aeration adjustments were implemented in the subsequent eASP to promote faster heating through increased biological activity. Aeration Optimization to Reduce PFRP/VAR Compliance Risk Four piles were tested with increased early aeration. The VOC emission factors ranged from 0.12 to 0.20 lbs per ton of compost mix, either below or just meeting the emission factor target. NH3 emissions were negligible for the two test piles that relied on solely Gastec tube measurements and 0.03 lbs per ton of compost mix for the test piles utilizing Method 207.1, well below the target threshold. With respect to core temperature requirements, all zones passed the PFRP and VAR criteria. The average time for all monitored zones to meet PFRP was 3.5 days with a minimum of 3 and a maximum of 4 days. VAR was met at an average of 14.5 days. There were no lagging zones and the faster heating is apparent in Figure 6, in which the four eASPs with increased early aeration shown as the gray lines have higher core temperatures early (days 1-10) in the composting process relative to the baseline aeration schedule shown as the blue line. Providing more air early in the eASP lifecycle can yield consistent temperature compliance throughout the eASP, but also yields higher VOC emissions. Aeration Optimization to Reduce CapEx for Implementation With wider air header spacing (aeration 'b'), the VOC emission factor was 0.08 lbs per ton of compost mix; NH3 emissions measured with Gastec tubes came back with minimal readings. All zones passed PFRP and VAR requirements. The average time for all monitored zones to meet PFRP was 3.2 days with a minimum of 3 and a maximum of 4 days. VAR was met at an average of 14.2 days. As shown in Figure 7, temperatures are similar between the four eASPs with air headers under every row (aeration 'a') shown as the gray lines and the eASP with wider air header spacing (aeration 'b') shown as the green line. Thus, the wider air header spacing did not appear to adversely affect VOC emissions control or compost temperatures, so an eASP can operate with fewer blowers and twice the distance between air headers as reported in literature. This is a major benefit for TLC as it allows for simplified eASP construction without the need to reroute air headers and avoids the expense of a future capital improvement project to install permanent air headers in-between the existing air headers. Irrigation Optimization to Minimize Leachate Production The relationship between irrigation rate versus leachate production and VOC emissions is shown in Figure 8. More leachate is produced with increased irrigation rate. Lower VOC emissions correlate with increased irrigation. Establishing these relationships is significant as it provides a valuable tool to balance leachate production and emissions for the facility. Conclusion eASP with biofilter cover is a viable technology for controlling composting emissions at TLC. Changes to the aeration schedule improved temperature to meet PFRP/VAR requirements and the operation with wider air header spacing was successful. Establishing the relationship between irrigation/emissions/leachate production helps with striking a balance for operati

Regional flooding has been controlled within the Coachella Valley in Southern California since 1915, with existing facilities built or improved in the 1970s following severe floods. The Coachella Valley Water District provides stormwater protection for a 590 square mile area within the valley by using approximately 135 miles of channels along with a number of dikes and retention basins that can convey approximately 80,000 cubic feet per second of flow from the surrounding mountains into the Whitewater River. In 2017, the District partnered with Black & Veatch to launch an extensive asset inventory and support implementation of their asset management system. This presentation will show how the rapid growth of CVWD's asset management system has benefited their stormwater management program by: 1) Showing the importance of data structuring and establishing a data collection protocol for a successful asset management program. 2) Engaging stakeholders across their business to create an expansive and robust registry which supports current and future programs. 3) Providing data to justify capital improvements and preventative maintenance decisions; shifting away from reactive maintenance and developing defendable investment prioritization. The Project has completed a field-based inventory, baseline full-system condition assessment, development of risk-based prioritization criteria, and mapping business processes. The stormwater assets were collected over a 4-week field effort with zero injuries. To execute these efforts, Black & Veatch leveraged an off-the-shelf ESRI product tailored so the final asset inventory seamlessly integrated with the District's CMMS software. CVWD staff were involved in each step of the project, helping structure data hierarchies and dictionaries, collecting field data, and incorporating institutional knowledge into business process mapping and prioritization criteria development. Data management was key as the final inventory contained over 80,000 data points including sub-meter accuracy GPS coordinates, field documented asset specifications, over 1,500 photographs, opinions of replacement costs, and baseline likelihood of failure and consequence of failure criteria. Post collection, the District's forces now have verified asset locations and attributes that provide reliability to day to day efforts. Scalability was built into the implementation to support on-going and future development of the asset management system.

Stormwater systems are increasingly stressed due to the growing number of high precipitation events and the pressure on aging stormwater system capacity. Now, more than ever, efficient stormwater asset management is crucial to public safety and regulatory compliance. Unfortunately, the cost and effort of conducting field inspections and collecting accurate and comprehensive data is an ongoing challenge for municipalities. Radio frequency Identification (RFID) technology has been widely used in many industries for its unique ability to track items without needing direct visual confirmation. Passive RFID tags don't require power and can be affixed to nearly anything. Today, RFID is rapidly becoming the solution to bridging the gaps in field data collection workflows for stormwater management. This session will explore on-going deployments using RFID-enabled asset marking for stormwater assets in combination with mobile data collection and GIS-based asset management systems. Initial pilots indicate that RFID-enabled asset marking reduces the time, cost and errors in field data inspections. Several deployments will be reviewed, including how the approach performed when used with Esri's ArcGIS Online to manage water sampling stations; and when a range of assets are tagged, including catch basins, hydrants and manholes. The system consists of: RFID-enabled tags placed on assets RFID readers tied to mobile devices via Bluetooth Software apps (web or software) that run on the mobile device The workflow is as follows: 1. RFID tags are placed on the asset 2. The RFID tag is accessed through the reader and specific information is written to the RFID tag, including asset owner, date/time, lat/long 3. Then the tag data is connected to its specific asset record in ArcGIS through web apps or a widget on the mobile device which then launch inspection/maintenance forms for completion in the field. This data can be accessed and managed in the office or in the field, creating a direct link between physical assets and data. Additionally, accurate geolocation and asset performance data removes the guess-work from future location and maintenance. At the conclusion of this session, participants will be better able to: Understand the use of using RFID-enabled technology to enhance stormwater infrastructure asset locating maintenance, monitoring and management.

Introduction:
GM BluePlan Engineering Limited (GMBP) was retained by the Town of Niagara-on-the-Lake to complete an investigation in two urban watersheds containing seven storm sewer outfalls with elevated levels of Escherichia Coli (E. coli). The results from the 3-year storm sewer water quality monitoring program are applicable to all municipalities' management of wastewater assets by incorporating condition information and risk management for water protection initiatives. Successful water quality improvement was demonstrated with yearly reduction in E. coli levels ranging from 85-100% at various locations. Project Locations: 1.Site #1 ' Queens Royal Beach storm outfall was flagged by the Niagara River Remedial Action Plan as an Area of Concern (AOC) due to elevated levels of E. coli. GMBP's objective was to reduce the E. coli loading to the catchment through investigation of infrastructure condition on municipal and private property and remedial actions to eliminate and reduce sewage contamination to four storm sewer outlets. The success of this project led to removal of the AOC designation. 2.Site #2 ' Water quality near Garrison Village was monitored from 2010 to 2015 by the Niagara Peninsula Conservation Authority which flagged three stormwater outfalls with high E. coli concentrations. The investigation and rehabilitation process reduced E.coli from 500,000 Human DNA copies/100mL to Below Detection amounts. Project Stakeholders & Objective: Stakeholders included the Ministry of the Environment Conservation and Parks (MECP), Niagara Peninsula Conservation Authority, Environment and Climate Change Canada (ECCC), Public Health, Region of Niagara, and Town of Niagara-on-the-Lake.

GMBP completed the following activities:
1.Developed and implemented a water quality sampling program to understand the existing and post-rehabilitation state of the storm sewer watershed area.
2.Investigated and collected wastewater asset condition information through unique field investigations and existing digital data.
3.Developed a prioritized list of rehabilitation recommendations for infrastructure improvements to reduce E. coli loading to the catchment area.
4.Implemented infrastructure improvements for 'Quick Wins' and short-term recommendations for E. coli reduction and monitored resulting water quality improvement.
5.Developed and implemented prioritized recommendations requiring greater capital budget and implementation time. 6.Provided bi-monthly meetings to convey project progress to all stakeholders. Unique Solutions Implemented: GMBP developed a systematic study approach to identify sources of contamination, sub-catchment areas for improvement, and monitor the subsequent effect of rehabilitation action items.

The following unique solutions were implemented for each project site:
1.Water Quality Sampling using DNA Analysis ' GMBP utilized an innovative water quality grab sample analysis for the storm sewer catchment area. Monitoring was completed bi-weekly for both dry and wet weather conditions. Grab samples underwent a digital PCR analysis which categorized the E. coli to be Gull DNA (Seagulls), Human DNA (sanitary sewer contributions), or Other Animal Source (e.g., horses, racoons, rats, dogs, geese).
2.Prioritizing Assets for Rehabilitation ' GMBP developed an in-house tool (DARRT) to provide a prioritized list of recommended rehabilitation options (open cut, CIPP Liner, Spot Repair, etc.) with estimated costs for each pipe. The DARRT tool uses NASSCO standard PACP or LACP databases to examine every defect to determine each asset's overall condition. This analysis reviews defect type, severity, and proximity across the sanitary and storm systems to assist in identifying high risk areas for water quality degradation in the storm sewers.
3.Unique Field Investigations ' Work included smoke testing, dye testing, investigation during subzero temperatures to identify storm sewer locations with enough heat to emit steam, dry weather flow analysis of the storm sewer network to identify sanitary influence (diurnal flow pattern), and lateral condition assessment from both the mainline and private property. All field inspection results were digitized in GIS and overlaid with CCTV condition inspection data and water quality monitoring results to make data driven decisions for rehabilitation locations and budget prioritization.
4.Improper Connections ' Located and removed improper connections to the storm sewer system which included a wading pool, sanitary lateral and mainline connections.
5.Sanitary and Storm Mainline Rehabilitation ' Work included trenchless technology for sanitary lateral lining completed from the mainline, with open cut for defects which were too large, Ultra-Violet (UV) lining of mainline storm sewers to avoid styrene byproduct to natural watercourses, and manhole structural lining.
6.Fauna Protection ' Inlet and outlet protection of the storm system was implemented using WaStop Check Valves to prevent racoon inundation.
7.Low Impact Development ' GMBP designed and installed a Biofiltration Facility along with Smart Sponge catchbasin inserts which were effective in a 95% reduction in remaining fauna E. coli loading due to runoff from a tourist horse carriage route.

Impact and Future Initiatives:
The success of the project has led to encouragement from MECP to share GMBP's investigation method and findings with other municipalities. Through this process, GMBP has identified: -No regulation for stormwater outfall discharge currently exists in Canada. -No monitoring or sampling required of stormwater outfalls (retroactive approach). -Storm sewer system is typically the first to receive budget cuts. -Storm sewer digital records are typically lacking or incorrect. -Storm sewers are the least likely to have CCTV condition inspection data. -Historical infrastructure practices affecting storm sewer water quality: use of clay material, sanitary assets installed at an elevation above storm assets (risk increase leaking defects), improper connections and no-fill abandoned of historic mainlines which contribute to cross-connection flow between assets.

Closing:
Sewer systems are critical infrastructure and asset management through regular inspection and maintenance will detect issues, improve operational efficiencies, and enable planned improvements before defects result in system failure. Essential to this process is establishing and maintaining accurate records which provide the basis for making data driven decisions and support timely allocation of adequate funding. Storm sewers have a greater risk to discharge human waste directly to natural watercourses if upstream assets are not properly maintained. As the climate changes, with increased likelihood of more frequent and intense rain events, it is imperative that infrastructure is managed effectively to avoid the social, environmental, and economic costs related to water quality degradation. These suggested practices are an investment in system resiliency through inherent improvement of system knowledge, operation, and condition.

The Chagrin River-Lake Erie Direct Tributaries (CHALET) Stormwater Master Plan (SWMP) Study advanced the Northeast Ohio Regional Sewer District's efforts to protect Lake Erie, critical infrastructure, and over one million residents by addressing flooding, erosion, and water quality problems associated with stormwater runoff in the Cleveland Metropolitan area. Regional assets that receive and convey stormwater were evaluated throughout the 86-square-mile drainage area using a combination of field inspections and hydrologic and hydraulic (H&H) models. Field geomorphic inspections of waterways and stormwater basins were conducted through streamlined technology. Fifteen subwatershed models of the study area were also developed to identify flooding problems. Condition ratings for assets within the regional stormwater system (RSS) were then developed using standardized GIS data processing that integrated field inspection and modeled flooding results. Areas with poor ratings were grouped to define problem areas, and cloud-based GIS access facilitated the development and evaluation of alternative improvement projects. The resulting CHALET SWMP delivered a prioritized list of construction projects and operation and maintenance activities to reduce flooding and erosion risks and enhance stream health throughout the region. This presentation will focus on how inspection data and modeled flooding results were classified following the District's standards, integrated, and shared among the project consultant team to systematically compare risks across the study area and develop improvement plans. This process will be illustrated by focusing on one of the resulting 47 problem areas. This case study demonstrates how structural, hydraulic, and sedimentation and debris risks were flagged throughout the RSS and holistically considered when developing improvement projects. Key technologies that facilitated data collection, asset performance evaluation, and alternative development will also be highlighted. During the data collection process, culverted streams were inspected using closed circuit television, while stormwater basins and open channel streams were inspected through the ArcGIS Survey123 platform. These inspections produced numerous videos and photographs that were shared back with the District and hosted on their ArcGIS Online (AGO) platform. These inspections resulted in condition assessments with ratings for structural integrity and sedimentation and debris. These ratings for basins and streams were added into the GIS dataset used in the subsequent performance evaluation. In addition to the inspection data, open channel spherical imagery was collected throughout the study area. These 360-degree views of the streams were linked to a GIS dataset so that the consultant team could easily verify inspection results and develop improvement projects. This Google Street View-like tool proved invaluable for increasing the efficiency of desktop-based analysis, thus minimizing the need for return trips to the field. The CHALET SWMP team developed 15 H&H stormwater models using PCSWMM. These models drew on field inspections, flow monitoring, and spherical imagery. The PCSWMM models were used to predict flooding with the planning focus being, when feasible, to develop solutions that would avert flooding at the 100-year design storm event. Hydraulic condition ratings for RSS assets (culverted stream, basins, crossings, and streams) were based on the flooding depths of nearby buildings, roads, driveways, and other transportation assets. Using the District's standards, a condition rating related to flooding depth and a criticality rating related to asset importance were assigned to each building and transportation asset. More important buildings and roads, such as hospitals and highways, had higher criticalities than less important assets, such as residential garages or local streets. Condition ratings and criticalities of the RSS and associated buildings and transportation assets were combined to develop business risk exposure (BRE) scores in a comprehensive GIS dataset. Assets with high criticalities and poor condition ratings for structural integrity, hydraulic performance, and/or sediment and debris resulted in the highest BRE scores. Problem areas were delineated where multiple assets in close proximity had high BRE scores. Improvement alternatives were then developed for each area. Standardizing GIS data management of inspection results, generation of condition ratings, assignments of criticalities, and calculation of BRE scores supported data-driven performance evaluations and solution development. One problem area in the Euclid Creek East subwatershed serves as a case study for how comprehensive data management facilitated evaluating asset performance and improving regional stormwater management. Along this portion of Euclid Creek East Branch, inspections identified debris accumulation at a basin inlet, a failed crossing, and high criticality buildings near an eroding stream bank. Modeling predicted flooding of local roads. When considered together through the GIS database operational performance evaluation, this portion of the East Branch was flagged for problems stemming from hydraulic performance, structural integrity, and debris accumulation, and a problem area was defined. A set of baseline recommendations and two alternatives addressing flooding were created. The alternative that reduced the risk most effectively and efficiently was then recommended to the District in the SWMP. With standardized GIS data delivery, recommendations from this SWMP, in addition to the District's three previous SWMPs, can now be integrated and shared with internal District stakeholders, enabling the District to comprehensively present problem areas and recommendations across their entire service area. ArcGIS Online and the Enterprise Portal offer a dynamic and interactive method for effectively sharing SWMP recommendations. Results from this data-driven planning process now serve to prioritize nomination of improvement projects to the District's design and construction plan or for advanced stormwater planning.

Introduction: In December of 2008, the City of Buffalo, MN began to beneficially use their biosolids as a fuel source at the Buffalo Wastewater Treatment Facility (WWTF). The biosolids treatment system at Buffalo consists of both thermal drying and thermal oxidation processes to reduce the amount of material leaving the site while minimizing overall fossil fuel consumption. The objective of this paper is to discuss the process, project background and to provide an update after more than a decade of operation. The Buffalo system is one of the only North American WWTFs that uses dried biosolids onsite for energy recovery and has a long successful operational track record. With ever increasing interest in reducing fossil fuel energy consumption and concerns related to emerging contaminants, particularly perflorinated compounds such as PFAS, there is a renewed interest in thermal destruction processes such as the one operated by the City of Buffalo. Project Background: Buffalo, MN is located about 30 miles west of Minneapolis and the City of Buffalo's WWTF consists of a conventional extended aeration activated sludge process designed for hydraulic capacity of 4.3 MGD. Prior to the biosolids system upgrade, the City had a combination of biosolids treatment processes using reed beds and liquid Class B land application. The municipality was receiving complaints associated with hauling biosolids out of the facility and it was increasingly difficult to locate farmers willing to accept the biosolids. Because of the difficulties with the Class B land application program, the city became interested in thermal drying to reduce volume of product and odors at the facility. However, the City was very sensitive to conserving energy, so the typical dryer system energy demand was considered unacceptable. After a review of available technologies including systems in operation in Europe, it was found that belt drying systems were being operated in combination with furnaces at similar capacities required by the City of Buffalo. Biosolids Process Description: The City of Buffalo produces only secondary sludge. The plant contains a large aerated sludge holding tank that provide enough capacity for several weeks of sludge storage. From the aerated sludge storage tanks, biosolids are dewatered to approximately 18-20% total solids (TS) via two belt filter presses. After dewatering, the biosolids are dried to greater than 90% TS in a BioCon belt dryer and then combusted in a reciprocating grate furnace where the fuel value of the dried biosolids is utilized to fuel the drying process by recovering energy from the hot flue gas exiting the furnace. The process is known as the BioCon® energy recovery system (ERS). This process combines a medium temperature belt dryer with a biomass furnace, which uses the dry biosolids as a fuel. The intent is to completely combust all organic material and recover process heat for the belt dryer. This integrated dryer and ERS is depicted in Figure 1. The thermal treatment process consists of several steps which are depicted in Figure 2. Dewatered biosolids are pumped from a storage silo, into the dryer cabinet through oscillating depositors, and onto a slowly moving belt located inside the dryer. Heat is transferred to the biosolids by circulating air between an air to air heat exchanger that recovers energy from the furnace flue gas and the dryer cabinet. Moisture is removed from the drying air by continuously extracting a portion of the air from the dryer, transferring it through a condenser and returning it back to the dryer. A portion of the air from the condenser is removed from the system to maintain a negative pressure on the drying system. The foul air is blended with fresh air and used as combustion air in the burners and furnace eliminating the need for separate odor control systems. Screw conveyers transport dried product from the dryer to a buffer silo that feeds a reciprocating grate furnace. The flue gas from the furnace passes through an air to air heat exchanger, where the energy is recovered for the drying process. From the air to air heat exchanger, the flue gas passes through a dry flue gas treatment system that consists of activated carbon and lime injection and a bag filter before being discharged out the stack. The ash from the furnace is transported via conveyors to a storage hopper. The residuals from the bag filter are transported via conveyors to a two bag packing station. Start-up and Performance Testing: During system start-up several issues were observed. The largest two issues were related to molten ash or clinker formation in the furnace and fouling of the air to air heat exchanger. Optimization of the furnace feed, cycling and temperature control were required to mitigate the clinker issue. The air to air heat exchanger initially had sonic horns meant to prevent ash fouling but this was found to be ineffective and heat transfer efficiency would drop after just a few days of operation. Ultimately, the sonic horns were replaced with pneumatic firetube soot blasters which prevented heat exchanger fouling allowing for long term reliable operation. Other issues that were noted during start-up included modifying the level sensor in the dried biosolids feed bin and replacing the packing on the progressing cavity pumps to a mechanical seal to reduce leakage. The performance testing was conducted in two parts. The first was related to energy consumption and natural gas savings by using the ERS system. The guarantee was based on dewatered total solids and that the natural gas consumption would be 574 British thermal unit per pound water evaporated (Btu/lb H2O evap) at 18% TS feed and 164 Btu/lb H2O evap at 22% TS feed. The energy consumption is compared to 1,400 to 1,600 Btu/lb H2O evap which is expected for a typical dryer system. The performance test which was conducted with 18% TS feed showed approximately 200 to 300 Btu/lb H2O evap was required during steady state operation as depicted in Figure 3. The second part of the performance test was the emission testing. The permit limits, summarized in Table 2, were based on volatile organic compounds (VOC's), particulate matter, and mercury. The performance during the stack testing exceeded minimum requirements and it should be noted that the mercury limits were lower than the limits required for new fluid bed incinerators as shown in Table 2. Operation and Lessons Learned: Since completing start-up, the system has now been in operation for more than a decade. Because of the large volume of storage available onsite and equipment capacity, the plant currently runs the system four to six times per year for extended periods of time which is desired for this process due to the high temperature in the furnace as numerous start and stops would reduce life off the equipment. During start-up, the furnace temperature increases at a rate of 80 degrees per hour up to 1,500 F to limit wear on the refractory. Operation temperatures higher than 1,600 F creates clinkers at the bottom of furnace, resulting in bottom conveyors having difficulties with both the size and hardness of ash chunks that need to be removed. The dryer starts on natural gas but at steady state operation it is supported by heat recovered from the furnace exhaust. Improvements to the system dewatering ultimately reduced fuel requirements as initially determined during system performance testing. The operational experience has shown the system is reliable, but several improvements have been made over the years. Some modifications to the system include: - Replacing mild steel conveyors and aluminum duct with stainless steel, - Replacing ERS grates that had worn air holes that allowed too much short circuiting. Additional modifications were made to have all grates moving in synchronization for better fuel agitation, - Adding a shredder after the rotary valve to improve uniformity of dry product from dryer which improved fuel use in the furnace, - Replaced sprinkler system inside the dryer with stainless steel and replaced solenoid valve with ball valve, - Added mixers to the sludge storage tanks to homogenize liquid sludge prior to dewatering, - Modified polymer system to improve dewatering performance. These improvements and lessons learned from the decade of operation will be discussed in the detail in this paper. Conclusion: The Buffalo ERS system is an example where dried biosolids have been successfully used as a fuel source for energy recovery for over a decade. The process provides many benefits and reduces future risks associated with fuel price volatility and biosolids beneficial use reliability. As the industry continues to focus on reduced fossil fuel consumption and concerns associated with emerging contaminants, particularly PFAS, interest in these types of thermal process is anticipated to increase.

Rising chemical and sludge disposal costs, an uncertain future for biosolids disposal, and operator shortages; are some issues shared by many wastewater utilities today. The Kalamazoo Water Reclamation Plant (KWRP) dewatering upgrade case study presents a road map for other utilities on how to address the pressing issues many utilities face today by incorporating pilot testing, and utilizing operations and maintenance staff input in the equipment selection and design process, selecting the equipment to produce the driest cake, configuring equipment in a way to minimize odor and maximize the potential for future expansions, and by visualizing data to fast track the operator training process. This presentation presents a history of the plant, its past and present concerns related to biosolids, and an overview of its dewatering facility commissioned in 2022. KWRP, located in western Michigan, serves approximately 190,000 people. KWRP previously used sludge incineration, but the incinerator was abandoned in 1999 due to the implementation Title V EPA, a stringent air quality regulation for flue gas from incinerators. Until the most recent upgrade discussed here, the gravity-thickened primary sludge and waste-activated sludge from the biological nutrient removal (BNR) process were combined and dewatered together using four belt filter presses. Because a sizable pharmaceutical production plant is in the service area, activated carbon is added to the BNR process to absorb micropollutants. In 2001, because of the closure of the incinerator, KWRP started to produce Class A biosolids using the RDP lime addition and pasteurization process. This class A sludge production process did not last long. The plant experienced too many difficulties with operating and controlling the installed RDP process for the required sludge production throughput. Michigan's rising costs for land application fees were another factor for discontinuing that process. In 2008, the utility moved to 100% landfilling sludge, taking advantage of relatively low disposal cost: $17.5/wet ton. From 2008 to the present, the plant has faced a steady rise in disposal costs, on average 13.0% /year; cake dryness requirements (%TS) have also tightened. Maximizing the dryness of the dewatered cake and reduction of disposal volume became a priority for the Dewatering Facility Upgrade. Additional objectives for the upgrade included minimizing the odor source and improving the operational environment in the sludge dewatering facility, designing a flexible set up to adapt future changes in post-dewatering solids-handling, and to ensure the selected equipment is intuitive for operators to dial-in and maintain. KWRP believes pilot testing provides the most accurate data for decision-making and solidifying the facility design. The city opened an invitation for paid pilot testing to all interested manufacturers in 2014. Eleven manufacturers and six technology alternatives participated. After testing was completed, centrifuges were selected as the equipment of choice, for being the lowest annualized cost option in present-worth with the possibility for simple future expansion. (Figure 1). Figure 1: Annualized Total Cost for Kalamazoo Sludge Dewatering Options After receiving proposals from vendors, the city organized operators' visits to other water reclamation facilities and equipment manufacturing and equipment service facilities to gather KWRP staff input during the selection process. Among the equipment evaluated, Centrisys was selected for several reasons: The central location for repairs was fundamental for the centrifuge manufacturer choice, along with access to their top technical and optimization leaders in the company. Simple operation and maintenance of the hydraulic scroll drive, in comparison to a gearbox drive, was also a critical factor for the equipment selection. The hydraulic scroll drive was also preferred for its ability to generates higher torque than gear box to maximize the cake dryness. Three Centrisys CS26-4 units were installed in 2021 and successfully started up in 2022 (Figure 2). The project design includes the necessary infrastructure to support the current installation along with the possibility of an additional fourth Centrisys CS26-4 if needed. The upgrade resulted in the immediate improvement in sludge dewaterability: before the upgrade a 2-meter Andritz belt filter press was generating 16-17% cake; after the upgrade, the centrifuges now generate cake in the range of 21-24%, which translates to a disposal sludge volume reduction of 20-30%. The timing was just right: When pilot testing began, disposal costs were $30.90 per ton. In 2022, it was raised by 44% over the previous year to $92.71/wet ton, making it one of the highest in the region. Figure 2: Centrisys CS26-4 Installation at Kalamazoo Water Reclamation Plant Working through the volatility of disposal costs and uncertainties in the regulatory climate, KWRP has selected ancillary equipment to accommodate future changes better. Instead of open-top conveyors, cake piston cake pumps are now used to move the dewatered biosolids. The piston pumps can generate operating pressures up to 1,500 psi. In the case of either future regulations of emerging contaminants like PFAS, or increasing disposal costs, where further processing of the dewatered cake by means of sludge drying are required, facility additions can be accommodated by a simple reconfiguring of the pipes. The selection of the cake pumps over open conveyors minimizes the source of odor. The small amount of odorous gas generated from the decanter centrifuges and the cake pumps is now treated through activated carbon filters to improve the operator environment. Another design consideration for ease of operation is the addition of Valmet total solid meters to the centrifuge feed lines (Figure 3). The centrifuges have forward control of the polymer dosing systems: taking the measurements from the TS meter and the flow meter and pacing the polymer rate by specifying the polymer dose in lb/dry ton, rather than just a pump speed, in the control panel. This setup makes training new operators easier by giving real-time trends for the operators to learn about the plant and specifically dewatering operations. Additionally, having the polymer dose input (lb./ton) at the centrifuge which resembles what the operators learned for the operator training exam aids staff in being able to visualize the data. This in turns helps KWRP to shorten the initial training period for dewatering operations and more quickly move operators to the next level of training: tuning the centrifuges and to take on tasks such as selecting better polymers to get more out of their new equipment. Figure 3: Installed Valmet Meter KWRP addressed these challenges via a data-driven, and operator-centric approach for their biosolids dewatering facility upgrade. The primary pieces of the KWRP story are: the support from the community in funding the pilot testing piece of the dewatering equipment evaluation, the operator site visits to learn about the equipment, and the inclusion of innovative technologies such as real time solids measurement and visualization. In close collaboration with the equipment suppliers, KWRP found the winning ticket for navigating uncertain regulatory market conditions and preparing the plant for the future.

With the advent of powerful sewer process modelling tools, the range of physical, chemical, and biological processes occurring within sewers can reliably be tracked across large sewer networks and over changing conditions. These processes include:
Heterotrophic Growth,
Particulate COD hydrolysis,
Fermentation,
Sulfate conversion to sulfide,
Carbonate cycle chemistry,
Sulfur cycle chemistry/biochemistry,
Denitrification, Sulfide precipitation by metals, Natural ventilation,
Air emissions, and
Sulfide corrosion of concrete.

Heretofore, sewer process modelling has focused on sulfide generation and fate for the purpose of mitigating problems related to odor and concrete corrosion. Recently, the development of powerful and complete sewer process modelling tools has expanded to include additional capabilities such as tracing wastewater plant upset conditions upstream to identify industrial discharge release events attributable to the plant upset and anticipating the fate, transport, emissions, and exposure to the public of chemical warfare agents within a sewer network. These modelling capabilities represent a new field of inquiry designated 'forensic process modelling'. Forensic process modelling implements sewer process modelling in combination with treatment plant process modelling and atmospheric dispersion modelling to address such challenges as busting industrial pre-treatment permit violators and averting terrorist attacks. This paper illuminates the topic of forensic process modelling by demonstrating its application in two case studies. Tracing an Acid Spill to its Source The Albuquerque Bernalillo County Water Utility Authority's main water reclamation facility faces challenges related to their lower effluent pH limit. In general, the problem is kept well in hand through careful dosing of magnesium hydroxide to the collection system which, in addition to improving plant effluent pH, augments sulfide control in the collection system. Recently, a sudden pH drop at the plant was detected and the drop appeared unrelated to any process or chemical in the control of the water authority. It was suspected that an industrial discharger caused the event. To test this hypothesis and identify the culprit, the Water Authority's WATS model (Wastewater Aerobic/anaerobic Transformations in Sewers), which was developed as part of their recent sewer odor and corrosion control master plan, was adapted to represent influent conditions corresponding to the measured pH upset. Then, each industry discharger was screened to identify those which deal with acidic waste streams. WATS model scenarios were then run to represent an acid spill from each of the short-listed industry dischargers. These scenarios allowed quantitative comparison of an acid spill which could cause the plant upset to the acid waste streams of potential culprits. WATS modelling scenarios resulted in identification of the industry discharger which could be attributed to the pH upset. This forensic inquiry culminated in actionable evidence toward enforcement of the violator causing the pH upset. Anticipating a Phosgene Attack Owners of civil infrastructure have long been charged with protection of public health and safety. Unfortunately, owner responsibilities have of late expanded to include anticipating and mitigating against terrorist attacks. In the case of water treatment plants, nuclear facilities, or other facilities enclosed within a defendable fence line, attack preparation may include target hardening and increased site security. But what of sewer networks for which there is no fence line and little separation between the public and the facility? Every household has anonymous access to the sewer system through its lateral connection. Also, the sewer headspace ventilates to the ambient atmosphere with serious implications for exposure to the public. The situation represents a uniquely intractable security problem in the face of a terrorist attack seeking to use the sewer network as delivery mechanism for a chemical weapon attack. DC Water in particular, due to its symbolically important location, must anticipate terrorism. Also, they own a number of odor control systems which force ventilate air from the sewer headspace to the ambient environment. For these reasons the trajectory of a chemical attack on their sewer network is of particular interest. In this case study, a phosgene attack was simulated using the WATS model. Phosgene is a chemical warfare agent which also has wide application in the plastics industry meaning that it is potentially obtainable by individuals (as opposed to foreign governments). Phosgene degrades the pulmonary tissues and victims may not be aware of receiving a lethal dose before it is too late. The DC Water WATS model, which was developed as part of their corrosion control and asset management program, was adapted to represent the chemical and physical properties of phosgene which determine fate and transport within a two phase (liquid stream and gas headspace) sewer network. The scenario tracks a 200-gallon release into a lateral clean-out connection upstream of one of the interceptor odor control stations. Dispersion modelling was used to estimate public exposure at a neighboring facility based on WATS model predicted concentrations from the odor control stack. The case study culminates on an assessment of the possibility of lethal exposure to the public based on this relatively small poison gas attack.