Results

INTRODUCTION The City of Chattanooga (the City) owns and operates the 870-megaliter per day (ML/d) Moccasin Bend Wastewater Treatment Plant (MBWWTP) that discharges treated effluent to the Tennessee River. Over the last 20 years, the City has been making strategic investments in planning level studies and innovative technologies to engage in the circular economy. Recently, site constraints and a limited capital improvements budget drove the City to investigate how thermal hydrolysis (TH) pre-treatment paired with intensified anaerobic digestion could optimize the capacity of existing assets thus avoiding costly anaerobic digestion (AD) expansion work in the future with potential economic paybacks through resource recovery. A previous investigation of TH+AD versus conventional AD indicated a narrow margin in capital and annual operating costs, however conservative planning criteria resulted in a recommendation to forego TH and expand the existing digester complex. Preliminary calculations suggested more aggressive planning criteria for a TH+AD alternative could result in a more favorable 20-year life cycle cost and opportunity for long-term return on investment through resource recovery. However, limited full-scale proof of such aggressive criteria presented unacceptable risk and required application of uncertainty factors that would again render TH+AD economically unfavorable. Therefore, the City elected to make a small ($500,000) investment in a pilot-scale demonstration study to generate site-specific data and a comprehensive life cycle cost evaluation. The objective of this paper is to discuss how the City used the pilot-scale study to de-risk a conceptual level life cycle cost evaluation and avoid approximately $50,000,000 in capital and operational expenditure over a 20-year planning period. METHODS The City completed a TH+AD pilot study to inform cost-estimating efforts associated with implementation of TH+AD at the MBWWTP. The results of this pilot study were used together with analysis of historical operating data, previous planning efforts, and industry experience to conduct a comprehensive, life cycle cost-based business case evaluation (BCE). The primary components of the BCE included flow and load projections, conceptual design of alternatives, pilot-scale testing to empirically verify the potential benefits to anaerobic digestion and sludge dewaterability, detailed capacity analysis of the existing facilities, and calculation of the 20-year life cycle cost of alternatives. The evaluation proposed and compared three alternatives: Alternative 1: Conventional Anaerobic Digestion Alternative 2: Partial-Plant TH and Intensified Anaerobic Digestion Alternative 3: Full-Plant TH and Intensified Anaerobic Digestion Site-specific operating data derived through the pilot evaluation are summarized in Table 1 and were supplemented with additional vendor testing, literature, and industry experience. These data were used to develop conceptual designs for the three alternatives including major equipment size, type, quantity, configuration, and performance. Table 1: Summary of Pilot-Derived Data Cost estimators developed a Class 5 Opinion of Probable Construction Cost (OPCC) based on the conceptual designs and price information provided by equipment vendors. The Class 5 OPCC included construction costs (direct costs and general costs), taxes, bonds, insurance, and 25 percent construction contingency and is summarized in Table 2. Escalation, estimate contingency (2.5 percent), engineering, and administrative costs are not included in the OPCC but are included in the Total Project Cost Estimate (TPCE) used in the value business case evaluation. Table 2: Capital Cost Estimates Annual O&M costs were estimated assuming 2034 annual average flow conditions (Table 3). Electricity costs were based on the number of duty units in operation at 2034 annual average solids loading conditions. Chemical costs included pre-THP dewatering polymer and biosolids dewatering polymer. Operational and maintenance labor costs were based on experience at other THP facilities and the City's hourly wage rates. Biosolids hauling costs were estimated based on the projected wet tons produced annually and vendor quoted costs for handling Class A and B biosolids. Table 3: Annual Operating Cost Estimates Finally, results were incorporated into a qualitative alternatives assessment to incorporate non-monetary considerations associated with the triple bottom line into the decision-making process. The team worked collaboratively with multiple City stakeholders to evaluate and rank each alternative under 11 criteria (Table 4). Table 4: Qualitative Evaluation Matrix RESULTS 20-year life cycle costs were prepared assuming design and construction of all alternatives occur over four years, beginning in 2020. The cumulative annual life cycle cost of each alternative was calculated (Figure 1). The estimated annual expenditure was similar for each alternative, with TH-based alternatives being slightly less due to significant savings in biosolids hauling costs. Alternative 2 was shown to have the lowest life cycle cost. However, concerns with partial-plant TH were identified early in the evaluation including inability to achieve Class A biosolids. As a result, Alternative 2 was eliminated. Alternative 3 had a lower life cycle-cost than Alternative 1 and a more favorable score in the categorical comparison. Therefore, Alternative 3 was selected as the recommended alternative. Figure 1: Cumulative Life Cycle Cost CONCLUSIONS The City's small investment in a pilot-scale demonstration study resulted in meaningful, site-specific data that increased confidence in planning criteria and life cycle cost estimates that were ultimately used to make important capital planning decisions. As a result, the City anticipates approximately $50M in capital and annual operating cost avoidance over the 20-year planning period. Several additional recommendations were proposed based on findings made throughout the evaluation. Recommendations are summarized in chronological order below. 1. Further de-risk planning and budgeting efforts by conducting a solids sampling campaign confirm or revise the blended sludge assumptions made under this evaluation. 2. Review and update flow and load projections and re-evaluate facility build-out capacity. 3. Progress Alternative 3: Full-Plant TH+AD to Preliminary Design (30 percent). Conduct value engineering, a Class 3 cost estimate, and an alternative delivery method evaluation. 4. Evaluate secondary treatment capacity considering current performance, future performance under projected flows and loads, current and future nutrient regulations, and opportunities to retrofit existing infrastructure for sidestream treatment. 5. Design and construct full-plant THP and intensified anaerobic digestion incorporating findings from recommendations 1 through 4. 6. Design and construct sidestream treatment (likely in conjunction with TH project). 7. Evaluate energy management alternatives in a small study after TH and digester system commissioning. 8. Implement selected energy recovery based on results of evaluation and available funding.

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

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

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

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

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

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

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

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

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

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

-- Improvement alternatives evaluated in the optimization include:

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

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

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

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

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

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

The water sector is at a critical juncture, a moment of extraordinary opportunity for utilities and the communities they serve. Digital solutions hold the key to water systems delivering bold water, energy, and cost savings while achieving greater operational and financial resilience in the face of unpredictable economic, demographic, and environmental shifts. Regulators and policymakers, whose decisions set the pace for technology adoption in the water industry, are playing an important role in this transition, but the benefits of digital solutions go well beyond regulatory compliance. A data-driven digital strategy allows water managers to 'turn on the lights' within their systems, empowering them to make better, more informed decisions across a range of operational and financial parameters. And as digital water technologies themselves continue to advance, the game-changing outcomes they can deliver are becoming ever more accessible and affordable for utilities across the map. But if the benefits of digital transformation are well understood by the world's water utilities, the path to realizing those benefits is often less clear. Every community, every utility, and every water system is different, with different starting points and ending points based on their own unique configuration of resources, capabilities, challenges, and strategic priorities. And utility leaders and staff often feel that they lack the time, knowledge, or confidence to chart a successful path forward for their organizations in a rapidly changing digital marketplace. In this presentation, Xylem and Bluefield Research will present a practical how-to guide for 'going digital' in the water industry, based on our in-depth research into the digital transformation stories of more than a dozen pioneering utilities from nine countries across North America, Europe, and Asia. We will highlight the ways that these utility leaders have tackled four of the thorniest problems of digital transformation-how to set a realistic and appropriate pace and direction of change, how to bring staff onboard for the journey, how to turn small wins into lasting benefits, and how to articulate the value of data and digital technology for customers and stakeholders. We will focus on practical, tangible, and accessible advice and lessons learned, to help utilities of all sizes chart the next steps on their digital transformation journeys.

ABSTRACT A brewery wastewater treatment plant (WWTP) experienced high hydrogen sulfide (H2S) concentrations in and around the biosolids handling building which led to concerns around worker safety, overloading of the existing odor scrubber, and odor complaints from the surrounding neighborhoods. The Brewery WWTP dewaters a total of 250,000 300,000 gallons per day of mixed primary and waste activated sludge (biosolids). Of the total flow to the dewatering presses, 80% is from the brewery and the remaining 20% from a nearby municipal wastewater treatment plant. Historically, the brewery fed sodium permanganate ahead of the belt filter press in an effort to reduce H2S odors in and around the biosolids dewatering area. A second permanganate dosing point of was added in 2021 to address the continued odor complaints. Later in 2021, both permanganate injection points were decommissioned due to operational concerns. Permanganate was also suspected of contributing to elevated manganese levels at the effluent due to release of manganese in the filtrate. In early 2022, the brewery WWTP embarked on a 90-day field trial of Peroxide Regenerated Iron Technology (PRI-TECH ®) to address H2S odors generated in the biosolids dewatering facility and also eliminate a source of manganese in the final effluent. For H2S control, PRI-TECH ® functions in two ways: 1) Direct oxidation of H2S by hydrogen peroxide (H2O2) and 2) regeneration of bound iron (e.g, FeS) in-situ, yielding either free ferrous (Fe2+) or ferric (Fe3+) iron and colloidal sulfur. This regenerated iron is now available to bind additional H2S in the biosolids handling process, functioning the same as if fresh iron salts were being added. Pre-trial laboratory testing showed that there were already significant levels of total available iron present in the brewery biosolids (15 25 mg/L total Fe). This equates to 35 40 lbs. per day of iron that was available for regeneration. In this case, the iron needed for PRI-TECH ® was already present in the biosolids and could be used for the benefit of H2S control in the belt filter press area. For the PRI-TECH ® trial, hydrogen peroxide was fed into the combined biosolids line upstream of the belt filter presses to oxidize H2S and regenerate free iron (Fe+2, Fe+3). Baseline (untreated) H2S levels at the belt press ranged from 5 90 ppm with an average above 10 ppm. The brewery safety committee set the H2S compliance target below an average of 10 ppm during dewatering operations to ensure worker safety and to reduce complaints from surrounding neighborhoods. Trial results showed that PRI-TECH ® reduced the sulfide levels by >95% with operational vapor level averages <1ppm inside the belt filter press room. Operations noticed a substantial reduction in local and personal H2S alarms (alarm at 10 ppm) in and around the dewatering building, local odor complaints also decreased, and there were no effluent manganese violations since beginning the PRI-TECH ® program, supporting compliance with metal discharge limits. Based on the successful trial results, the brewery WWTP will continue utilizing PRI-TECH ® to maintain effective H2S control in the dewatering facility to ensure worker safety and maintain effective H2S odor. Future work is planned to further optimize PRI-TECH ® program, with additional investigation into the improvement in critical metals reduction.

Stated Purpose: The propose of this presentation is to summarize the planning approach for replacing and upgrading one of the Metropolitan Sewer District of Greater Cincinnati's (MSDGC) critical collection system assets – the Pleasant Run Force Main (FM) system. This presentation will provide an inside look at MSDGC's innovative planning approach for replacing the Pleasant Run FM system, the various alignment and coordination challenges, and the use of FLAMROC as MSDGC's planning tool for evaluation and final selection of alternatives. Benefits of Presentation: Several large cities have critical aging assets in heavily urban locations. Replacement and upgrades to these critical assets present various planning, design, and construction challenges. The Pleasant Run FM upgrades project is one such example of a planning challenge. The Pleasant Run FM's were originally constructed in the 1970's, have historically been maintenance intensive, and are considered to be among the most critical assets maintained by MSDGC due to the significant consequence of failure and large number of customers served. Sections of the force mains have been replaced and/or repaired frequently, and the lack of redundancy in the system presents one of the most significant environmental risks to MSDGC. There is currently no contingency plan to address failures which would result in large quantities of sewage overflowing into local streams or residential neighborhoods. The planning goal is to develop innovative cost feasible solutions that offer operational redundancy, 50-year asset life, and can be constructed with minimal interference to the existing system operation. Key take-aways from this presentation will include the development of alternatives through alignment challenges (such as avoiding a cemetery, crossing County boundaries, I-275 highway crossing, etc), coordination challenges of working with multiple local city governments and townships and their associated existing infrastructure (such as water main, storm sewers etc.) and the use of FLAMROC planning methodology for screening and final selection of alternatives. Project Description: This project is located in the Mill Creek sewer shed in Hamilton County, Ohio, between John Gray Road on the north, just south of Waycross Road on the south, the Pleasant Run West Pump Station (WPS) on the west, and the Pleasant Run East Pump Station (EPS) on the east. The EPS FM discharges to a 3,000-feet (ft) long, 16-inch diameter FM which runs along Hazelgrove Drive to Mill Road and discharges into the Central Pump Station (CPS). The WPS discharges into a 5,500-ft long, 24-inch diameter force main which runs under John Gray and Mill Roads to the CPS. The CPS repumps flow from the EPS and WPS into a 24-inch diameter force main which runs 7,000 feet under and along Mill Road to Gravity Sewer Manhole 30811002. Planning Approach Summary: Thirteen conveyance alternatives, and several sub-alternatives were evaluated to determine the best combination to convey wastewater from the Pleasant Run FM's to the downstream gravity sewer system. After narrowing down the alternatives into four options, the FLAMROC analysis evaluated alternatives on their Flexibility, Land Availability, Adaptability, Maintainability, Reliability, Operability, and Constructability (FLAMROC). The four alternatives listed below were found to be the most feasible and beneficial to MSDGC. 1. Alternative 1 (EPS to CPS, WPS to CPS, CPS to MH NO. 30811002) - One new FM from EPS to CPS (utilize existing force main) - Two new FM's from WPS to CPS - Two new FM's from CPS to MH - Rehab EPS, WPS and CPS - Equalization at WPS 2. Alternative 2 (EPS to WPS via force main, WPS to MH NO. 30811002) - Two new FM's from EPS to WPS - Two new FM's from WPS to MH - Rehab EPS - New WPS (demolish existing WPS) - Eliminate (demolish) CPS - Equalization at WPS 3. Alternative 3 (EPS to WPS via force main and gravity sewer, WPS to MH No. 30811002) - Two new FM's from EPS to high pt., 1 new dedicated gravity sewer from high pt. to WPS or upsize lower reach of existing downstream sewer to WPS to accommodate the added flow - Two new FM's from WPS to MH - Rehab EPS - New WPS (demolish existing WPS) - Eliminate (demolish) CPS - Equalization at WPS 4. Alternative 4 (EPS to WPS via deep gravity sewer, WPS to MH No. 30811002) - One new dedicated deep gravity sewer from the existing EPS site to WPS, including a majority of the gravity sewer installed via trenchless technology Two new FM's from WPS to MH - New WPS (and demolish existing WPS) - Eliminate (demolish) EPS - Eliminate (demolish) CPS - Eliminate (demolish) Kemper Mill Village Pump Station (KMPS) - Equalization at WPS. Based on FLAMROC scoring analysis, Alterative 2 (Figure 2) was eventually selected as the recommended alternative. This alternative includes the following components: - Rehabilitate the existing EPS - Install new dual FM from the existing EPS to the new WPS - Abandon in place the existing EPS FM - Construct new WPS - Demolish the existing WPS - Abandon in place the existing WPS FM - Construct new 300,000-gallon EQ Tank at WPS. - Install new dual FM from the new WPS to existing MH 30811002 - Demolish the existing CPS - Abandon in place the existing CPS FM The projected costs are as follows: - Total Construction Cost: $27,2,000,000 - Total Budgetary Cost: $49,308,000 - Net Present Value (NPV) / Life Cycle Cost: $39,400,000 - Equivalent Annual Life Cycle Cost: $2,500,000 Project Status of Completion: The planning phase was completed in the summer of 2021. The project is anticipated to take over five years from design through construction, with Design of Alternative 2 beginning in August 2021. Originality: This project had several creative and innovative solutions evaluated as part of alternative development. Alterative 4 proposed to build a deep gravity tunnel and install dual FM's in the same casing pipe as that of the gravity sewer. Alternative 2 proposed redundant force mains with cross over vaults to switch flows between dual force mains when needed. MSDGC's FLAMROC analysis was used to develop weighted scoring criteria for non-cost factors that were important to MSDGC. 

Orange County Sanitation District (OC San) chemically treats the wastewater in its collection system to mitigate sulfide levels, nuisance odors, and corrosion potential. Ferrous chloride, magnesium hydroxide, and calcium nitrate are the chemicals predominantly used for odor control. However, market volatility and supply chain issues have impacted the availability and cost of chemicals over the past several years. OC San has been proactively taking measures to develop strategies to address these issues, including using a combination of chemicals, optimizing chemical dose requirements, and identifying alternate chemicals or chemical formulations. The increasing market volatility in recent months has made optimization a high priority. A chemical dosing strategy was developed that involves adding an iron-based compound, increasing the pH using an alkaline material such as magnesium hydroxide, and, in some instances, adding calcium nitrate. Increasing the wastewater pH increases the solubility of sulfide (as bisulfide HS- ) and minimizes the release of odorous hydrogen sulfide (H2S) to the headspace. Further, iron salts are more effective in precipitating dissolved sulfide compounds as ferrous sulfide at higher pH than at lower pH. Finally, since wastewater microorganisms prefer nitrate over sulfate as an electron acceptor, adding calcium nitrate will lower the microbial reduction of sulfate and the formation of sulfide. Increasing the wastewater pH improves the effectiveness of calcium nitrate as the preferred electron acceptor. Hence, at elevated pH through alkaline addition, the iron and nitrate dose requirements can be significantly reduced to achieve the same level of odor reduction compared to chemical dosing at the native pH of the wastewater in the collection system. In 2019, OC San received a United States patent (US 10,435,316 B2) for this approach to reducing chemical dosing requirements and chemical costs for odor control. This patent requires adding at least one iron-based compound. The patent allows adding an alkaline compound to increase pH and also allows adding a nitrate compound to minimize the reduction of sulfate to sulfide. OC San intends to make this chemical usage approach available to other wastewater utilities. OC San has performed several field evaluations to verify and demonstrate the effectiveness of these chemical combinations. Historically, OC San used calcium nitrate compound in these efforts. Recently, in an effort to further increase its chemical supply security, OC San identified another nitrate-based compound that can potentially be used for odor control. Calcium ammonium nitrate (marketed as CAN-17) is predominantly used in the agricultural industry as a fertilizer. Since it is manufactured in a process that is very different from that used for calcium nitrate, it can provide additional chemical supply security. Table 1 provides a comparison of key characteristics of calcium nitrate and calcium ammonium nitrate. Briefly, calcium ammonium nitrate has a higher nitrate nitrogen content (17% nitrate) than calcium nitrate (9% nitrate). However, calcium ammonium nitrate has a higher ammonia content (5.4% ammonia nitrogen) than calcium nitrate (0.58% ammonia nitrogen), and that might increase the ammonia in the wastewater treatment plant influent. Currently, the cost of calcium ammonium nitrate is approximately 25% lower than calcium nitrate for equal nitrate content. Initially, OC San performed a theoretical analysis comparing the wastewater quality and cost implications of using calcium ammonium nitrate instead of calcium nitrate. The potential cost savings based on historic chemical usage and the potential increase in the treatment plant influent ammonia levels with calcium ammonium nitrate were estimated. The preliminary evaluation indicated that OC San could save approximately $250,000 annually by using calcium ammonium nitrate. The treatment plant influent ammonia levels would increase by less than 0.25 mg/L. A pilot study in the collection system was performed to verify these findings. The testing was performed at the Baker-Main trunkline using the chemical dosing approach identified in the OC San patent. The average wastewater flow during the testing was approximately 17 MGD. Initially, magnesium hydroxide and calcium ammonium nitrate or calcium nitrate were added to the sewer line near the Main Street Pump Station (Figure 1). Subsequently, ferrous chloride was added three miles further downstream of the Main Steet Pump Station and injected about midway to the treatment plant. An average of approximately 240 gallons per day (gpd) of magnesium hydroxide and 280 gpd of ferrous chloride were dosed. The nitrate dosing was 183 gpd of (8.42% N) calcium nitrate. The pilot testing with calcium ammonium nitrate used 183 gpd or 131 gpd (11.6% N). Various parameters related to collection system odor, including headspace H2S, dissolved sulfide, sulfate, ammonia, nitrate, pH, DO, and BOD, were monitored. The testing was conducted over four to five weeks for each of the nitrate formulations. Samples were collected upstream and downstream of the ferrous chloride addition. Figure 1 shows the monitoring (sample collection) locations. The goal of the testing was to maintain a headspace H2S level below 45 ppm. The results indicated that calcium ammonium nitrate at both tested concentrations maintained the headspace H2S level well below the target concentration of 45 ppm throughout the testing period (Figure 2). The average H2S level at the higher and lower calcium ammonium nitrate doses was approximately 13 ppm and 20 ppm, respectively. However, during the calcium nitrate testing, the daily average H2S exceeded the target concentration on 8 of the 28 days of testing. The average ammonia levels during the high and low calcium ammonium nitrate doses were approximately 50 mg/L and 48 mg/L, respectively. The average ammonia level during calcium nitrate dosing was approximately 46 mg/L. This difference resulted in a difference of less than 1 mg/L in the ammonia level at the plant influent. This indicated that using calcium ammonium nitrate did not significantly increase the plant-influent ammonia levels. This presentation will provide an overview of OC San's odor control pattern and benefits, present results from initial testing using calcium nitrate and ferrous chloride with and without magnesium hydroxide, review the test results using calcium nitrate or calcium ammonium nitrate as the nitrate compound, and report data with and without ferrous chloride addition during the recent tests.

PURPOSE
The presentation will provide an overview of the City of Raleigh's Public Utilities Department, Raleigh Water (Raleigh Water) complex collection system odor and corrosion challenges, current approach to treating and handling odor and corrosion, and how modeling was used to evaluate hotspots and optimize treatment. The presentation will benefit the industry by providing integrated approaches to collection system odor and corrosion control assessment, design criteria, planning, and detailed treatment solutions through advanced sewer modeling.

PROBLEM STATEMENT
Raleigh Water is grappling with a complex and rapidly growing collection system with interceptors of varying age and materials, both concrete and inert. Due to the complexity and frequent changes, the system has areas at high risk of high hydrogen sulfide, potential odor nuisance, and corrosion. Raleigh Water maintains an active odor control program with the goal of addressing elevated and consistent odors within the wastewater collection system. The odor control program includes a liquid chemical feed program in which different odor control chemicals (ferrous sulfate, hydrogen peroxide, and calcium nitrate) are added to the wastewater at different strategic points within the collection system to reduce and/or suppress the formation of hydrogen sulfide. Routine monitoring of liquid and gaseous hydrogen sulfide levels is conducted to assess performance at the different dosage locations and to identify any needed adjustment to chemical feed rates. In addition to the chemical dosage program, Raleigh Water also has vapor phase odor treatment systems at several of its regional pump stations to treat the odorous air collected at the pump station. Raleigh Water's strives to build a programmatic system approach for odor and corrosion. Although the Raleigh Water has an expansive chemical dosing system in place that has had success, there are still gaps and areas in need of improvement. Raleigh Water recognizes these gaps and has a goal to optimize their system both for treatment and cost efficiency, while also minimizing elevated and consistent odors system wide.

BACKGROUND AND METHODOLOGY
Raleigh Water operates a collection system that spans over 2,500 miles of pipe, both gravity and forcemain, and conveys wastewater to one of three resource recovery facilities. Figure 1 shows Raleigh Water's collection system, locations of pump stations, dosing stations, and resource recovery facilities. The odor control treatment program is comprised of liquid treatment at more than 20 chemical dosing stations (varying chemical usage) and several vapor phase systems throughout the collection system. The chemical dosing stations throughout the collection system treat the system with different chemicals depending on the location. Calcium nitrate, iron, and peroxide are used throughout the system. In 2017, Raleigh Water completed an odor and corrosion control master plan that evaluated the ongoing treatment program for areas of improvement and potential areas in need of treatment. This was completed through extensive sampling, both liquid and gas phase, and collection system modeling. In 2022, HDR, The WATS Guys, and Raleigh Water worked together to build upon the findings from the previous master plan and assess Raleigh Water's collection system for odor and corrosion control using the Wastewater Aerobic/Anaerobic Transformation in Sewers (Mega-WATS) model. The Mega-WATS model was used for the project because it analyzes and solves complex in-sewer transformations including microbial-induced concrete corrosion, odor formation, and potential for nuisance risk caused by hydrogen sulfide air emissions from pressurized sections of the sewer. Additionally, the model can predict anticipated effects and results of utilizing hydrogen sulfide control strategies, both liquid phase and vapor phase throughout a collection system. The model was used as a key tool in an integrated master planning effort that began in January 2022 and will be completed in December 2022, providing integrated approaches to collection system odor and corrosion control assessment, design criteria, planning, and detailed treatment solutions through advanced sewer modeling. The analysis was done using two modeling scenarios:
1. 2022 average weather and flow conditions
2. 2025 projected average weather and flow conditions

The 2022 model was calibrated using 2015 sampling data as well as updated sampling data completed in June 2022. The model input parameters incorporated existing chemical dosing and vapor phase treatment information to represent field conditions and predict the level of hydrogen sulfide control within the system. The 2022 model findings were evaluated for corrosion risk and areas with high concentrations of hydrogen sulfide in comparison with known odor complaint locations.

RESULTS AND FINDINGS
The 2022 model results were used to determine odor and corrosion hotspots throughout the entire collection system. These hotspots were detected by assessing areas with model predicted hydrogen sulfide presence, known odor complaints, and/or model predicted corrosion. Plots similar to Figure 2 were used to define the hotspot areas and prioritize them based on parameters such as: hydrogen sulfide presence, odor complaints in the area, known high risk asset, high predicted corrosion rate, and known planned monitoring or replacement. The presentation will provide a more detailed assessment of the hotspots and how they were evaluated and prioritized from the modeling results. The 2022 odor and corrosion hotspots were used to develop over ten capital improvements solutions as well as potential operational changes. The developed solutions were primarily related to adding chemical dosing sites in areas with hydrogen sulfide hotspots that were not already being treated, as well as pilot testing different chemicals and combinations of chemicals along flow paths to assess for improved and optimized treatment. One specific flow path evaluated is made up of several oversized forcemains and has an overall detention time of more than 60 hours. The flow path currently has three chemical dosing sites that treat the line with calcium nitrate upstream and iron followed by peroxide downstream. Although his treatment combination has helped mitigate some of the hydrogen sulfide formation, there is still concern for corrosion and odor along the flow path. The project team completed a desktop evaluation on the flow path and found that the addition of a pH adjustment (to a pH between 8-9), such as magnesium hydroxide, upstream of the iron dosing improved the iron's precipitation capabilities with dissolved sulfide. The combination of pH adjustment followed by iron was predicted to be an effective chemical optimization strategy on other flow paths in the system as well. The model also predicted downstream pH with these chemical combinations matched would not adversely impact the resource recovery facility. The team has recommended pilot testing in various locations in the collection system to validate the treatment combination. This presentation will provide the detailed flow path findings, results, evaluation (economic and non-economic benefits), and recommendations that evolved throughout the project. The presentation will provide insight and potential mitigation solutions for other utilities experiencing problematic hydrogen sulfide levels, odorous air, ineffective chemical treatment or corrosion throughout their collection systems.

KEYWORDS Sludge dewatering, data collection, screw press, meta-analysis BACKGROUND Performance estimation for Biosolids dewatering is of great importance for project planning and dewatering system design. Given the cost implications associated with dewatered solids hauling, polymer consumption, and capture rate efficiency, identifying accurate ranges for predicted equipment performance is advantageous to facilities that produce and process biosolids. Equipment manufacturers are able to collect data from existing installations and pilot scale testing for utilization in large scale meta-analysis. This analysis increases predictive capability as it yields insight into how upstream processes and sludge composition influence dewatering performance. Bench scale testing can also be utilized, however should be viewed with more scrutiny, as it cannot exactly replicate onsite performance. METHODS Bench, Pilot, and Full Scale installation testing data was collected from hundreds of facilities across the United States, during a period of time between 2014 and 2022. A Screw Press dewatering device was used on all tests. Figure 1 below shows the number of data points for each type of testing: Bench Scale Testing Pilot Scale Testing Full Scale Installation Testing ~360 ~200 ~100 Table 1: Number of data points for each type of testing conducted in this analysis Figure 1. Dewatered Cake Solids from Screw Press Equipment To assist in the statistical analysis of performance data, multiple descriptive 'tags' were created and assigned to various parameters of the sludge being tested. These tags allowed for the storage, categorization, and comparison of performance data between similar sludges. Each parameter used in the meta-analysis was obtained from a questionnaire filled out by the facility contact, and is one of the 23 following: Sludge Parameter Tags 1. Cake Solids (%) 2. Polymer Dose (lb active/DT) 3. Capture Rate (%) 4. Feed Solids Concentration (%) 5. Throughput (gpm) 6. Solids loading (lb/hr) 7. Machine Size 8. Facility Flow (MGD) 9. Waste Sludge Flow (GPD) 10. Sludge Age (days) 11. Sludge Type (WAS, Primary, Blend) 12. Volatile Solids Ratio (%) 13. Digestion Type (Aerobic, Anaerobic) 14. Total Dissolved Solids (mg/L) 15. Sludge pH 16. Chloride Value (mg/L) 17. Phosphate Value (mg/L) 18. Nitrate/Nitrite (mg/L) 19. Sludge Temp (F) 20. Bench Cake/Bench Polymer Dose (For comparison to field values) 21. Biological Process Type 22. Type of sludge storage (Day tank, Holding tank, Lagoon) 23. Digestion temperature range (Mesophilic, Thermophilic, TPAD, None) Table 2: Sludge Parameter Tags Recorded parameters were tabulated and analyzed using Microsoft Excel, as this provided the easiest means for exporting data collected from online forms. The programming language Visual Basic was utilized as a tool to filter and plot all of the data, allowing for comparison and determination of trends between two different sludge parameters. RESULTS The operator of this analysis tool is able to define X-axis and Y-axis parameters for comparison. Once selected, data points will be plotted along with a trend line to describe the behavior of the data set. Any additional filters applied to the data will further narrow the data set, allowing the operator to view only those data points which fall within a desired range of sludge characteristics. Figure 2. Data Analysis Main Page Further analysis employing the use of standard deviations for each data set allowed for the creation of statistically derived ranges that aid in estimating performance to a more accurate degree than sludge type alone. One such example is shown below in Figure 3, where Cake Solids (%) is compared with Volatile Solids Ratio (%). This search is further refined by only looking at Waste Activated Sludges (no primary component) with Aerobic Digestion. This returns a truncated list that provides a clear relation between Cake Solids and VSS for the sludge type specified. Figure 3. Cake Solids vs. VSS Ratio for Aerobically Digested WAS Sludges Another example of this can be found in Figure 4, which shows a trend of polymer dose compared to feed solids. This is further filtered by looking only at anaerobically digested sludges which fall within the mesophilic temperature range. Figure 4. Polymer Dose vs. Feed Solids for Anaerobically Digested Sludges in the Mesophilic Temperature Range DISCUSSION The tool shown above is useful in making performance determinations and estimations for new and existing projects by leveraging past data from multiple sources. The accuracy of this tool will continue to increase as the data set becomes more robust, meaning that the usefulness of this meta-analysis for project planning will continue to increase. Cooperation between manufacturers, consultants, municipalities, and academia in combination with tools similar to the one described herein has the potential to bridge the gap between dewatering system expectation and actual performance, as each party is able to bring unique contributions to the discussion. The intent of this project was to continue the conversation on ways to create more accurate projections for municipal sludge dewatering performance. Further, this project aimed to explore and qualify the intricacies that are inherent in the municipal wastewater treatment process, and provide a way to identify the factors that can positively or negatively affect dewatering system performance. It should be noted that while this project aimed to be as thorough as possible in terms of data collection and analysis, the study of sludge Dewaterability is ongoing, and as such some factors which influence dewaterability were not included at the time of writing. SIGNIFICANCE/IMPLICATIONS Manufacturers typically have the greatest access to large quantities of data, due to the many projects that they entertain. Through coordinated efforts between all involved parties, a qualitative approach to data analysis can allow for a better understanding of how to estimate performance, especially at new facilities where sludge is not available for testing. Statistical meta-analysis can provide a higher degree of certainty regarding performance expectations as compared to traditional estimations based on sludge type alone.

A 'cloudburst' is a sudden, heavy downpour that can overwhelm sewer systems and result in flash floods. These intense rainfalls are becoming more frequent, disruptive, and damaging in New York City (NYC); devastating residents, destroying homes, and disrupting businesses. On September 1, 2021, Hurricane Ida shattered the record for the highest single-hour rainfall in NYC, set only two weeks earlier by another extreme storm, Tropical Storm Henri. Both storms caused flooding, damaged property, disrupted critical infrastructure, and polluted New York's rivers and Harbor. NYC's Cloudburst Program will protect vulnerable communities, mitigate flood damage, and improve water quality. Historical data measuring which neighborhoods were hit hardest by Hurricane Ida were used to identify cloudburst planning areas, including flood extents with sea level rise, structural damage reports, sewer backups, and social vulnerability index. All the recommended Cloudburst projects are in flood-prone environmental justice areas. This project redefines stormwater management in the built environment by transforming streets, parks, and other open public areas into multi-functional community assets for recreational use and flood mitigation. Stormwater runoff from sidewalks and streets is absorbed by porous parking lanes, bike lanes, or medians and then transferred into redesigned public spaces that safely accommodate flood waters. After a storm has passed and sewers have regained capacity, the water drains back into sewer systems. This project is the first large-scale innovative application of interconnected green infrastructure for cloudburst management. NYC's ultra-dense built environment is congested and presents complex challenges that require meticulous coordination among multiple private and public agencies. Further, the complex drainage network requires careful consideration to maintain gravity flow. These challenges were addressed through interagency partnerships, stakeholder consensus building, sewer system modeling, and developing cost-effective integrated solutions. Cloudburst stormwater management integrates flood-protection solutions into public spaces, instilling a positive public perception of how engineering solutions can complement community goals. Integrating public amenities and open spaces with stormwater management solutions, such as sunken basketball courts, water squares, and playgrounds with subsurface storage, transforms these public spaces into multi-beneficial community assets. Based on recommendations from this project, the city announced $400 million in the construction of Cloudburst Resiliency Projects to better manage intense rainfall events in flood-prone neighborhoods. This presentation will cover: 1) NYC Cloudburst Program Goals 2) Social and Physical Vulnerability Assessment 3) Opportunity Screening and Adaptation Analysis 4) Cloudburst Adaptation Toolbox 5) Social, Economic, and Sustainable Design Considerations.

According to an October 2022 article published by the National Oceanic and Atmospheric Administration (NOAA), the year had below average precipitation, but by the end of September, the country had sustained 15 separate billion-dollar weather and climate disasters, including several significant rainfall events. In the first nine months of 2023, the National Centers for Environmental Information reported 24 such events, of which included 18 severe storms, two floods, and one tropical cyclone. As of October 10, 2023, these weather events caused 373 deaths across the country, with unprecedented economic impact in the Northeast and southern California. It is clear to weather experts that the increased occurrence and severity of rain-related events are no longer a future problem but are happening now. Significant rainfall events are more intense and occurring more frequently than before, taxing infrastructure systems in a myriad of ways. Communities across the country often designed infrastructure planned for less severe storms, if they planned at all. Capacity limitations and aging infrastructure have resulted in floods that wreak havoc on roads, buildings, and other utilities. Furthermore, many communities lack the stormwater funding resources to rebuild resilient infrastructure needed to limit further impact of future severe weather events. Moreover, National Pollutant Discharge Elimination System (NPDES) regulatory requirements continue to increase, necessitating additional investments in stormwater treatment and other clean water initiatives. It is apparent that creative approaches to funding the future of stormwater will be necessary. The Massachusetts Clean Water State Revolving Fund (SRF) has a unique grant program designed to fund asset inventory and management planning projects. Historically, these funds were used to develop conventional asset management plans for wastewater and stormwater systems, with a focus on condition assessment. Increasingly, these funds are being used for stormwater systems and include stormwater capacity analysis as a primary component of risk assessment. This is a relatively new development for the program. The state expects this grant money will help establish current conditions of stormwater systems and drive more funds in the SRF to finance stormwater infrastructure. In addition to the SRF program, Massachusetts Municipal Vulnerability Preparedness (MVP) program provides grants to fund the identification of climate hazards and infrastructure vulnerabilities, including water quality vulnerabilities, as well as the development and prioritization of action plans to improve resilience to climate change, building climate resilience, equity, and climate justice. In 2021, Senate Bill 1954 was signed into law, establishing the Resilient Florida Program for a coordinated approach to the state's coastal and inland resilience. The legislation funnels a significant investment toward protecting inland waterways, coastlines, and shores, and provides aid to communities that want to prepare for the impacts of sea level rise, intensified storms, and flooding. In February 2023, the state's governor announced more than $275 million in grants was being awarded to 75 resilience projects, which will help safeguard homes, businesses, and critical infrastructure from damages incurred by storm surge and flooding. While California has experienced significant drought conditions over the past decade, the state's Department of Water Resources (DWR) released $9.2 million in grants in 2023 to fund five projects aimed at restoring streams and creeks to more natural environmental conditions, which will help reduce flood risk in several communities. This funding is part of DWR's Riverine Stewardship and Urban Stream Restoration programs designed to protect listed fish species, while also addressing flood risk reduction and ecosystem enhancement of urban streams. State experts are anticipating 2024 will be another wet year with strong El Nino conditions. The state government has earmarked more than $430 million in its recent budget for flood response and projects designed to mitigate future flood damage. Furthermore, municipalities and county governments can leverage financial assistance under the California Disaster Assistance Act when natural disasters occur. Funds through this program can cover up to 75 percent of cost for activities, such as basic engineering for construction projects, repair, permanent restoration, and replacement of public facilities. This presentation will examine each state's unique approach to accessing regional and federal funding resources that enable projects aimed at improving infrastructure resiliency, addressing water quality, and mitigating damage caused by heavy rain and flooding events. Presenters will provide case studies from communities that have already applied for and receive funding for risk and vulnerability assessments, as well as the resulting projects prioritized during the evaluation process. Attendees will learn how this work goes hand in hand with the regulatory framework of Municipal Separate Storm Sewer System (MS4) and NPDES permitting.

Introduction After four decades of operating a cogeneration facility to produce electricity and heat, Metro Water Recovery (Metro) commissioned a Biogas Utilization Study in 2021 to consider historical and new beneficial uses of biogas at their Robert W. Hite Treatment Facility (RHWTF) that serves Colorado's Denver metropolitan area. While cogeneration has been the industry standard for biogas utilization at water resource recovery facilities (WRRFs) for decades, biogas upgrading to renewable natural gas (RNG) has become more prevalent due to federal incentives available under the Renewable Fuel Standard (RFS) program created under the Energy Policy Act of 2005. And while the RFS program has been the historic driving force behind the shift to RNG, a drive by major companies to reduce the carbon footprint of their operations are leading to further incentives for biogas, potentially mitigating the risk of relying on a single revenue stream. This study investigated two alternatives for beneficial reuse of the biogas resource at Metro's RWHTF: - Upgrade and continue to operate the Cogeneration Facility to generate electricity and heat using biogas. - Construct a new facility that converts biogas into RNG for direct injection into a natural gas pipeline owned by Xcel Energy (Xcel) and monetize the RNG. While WRRFs across the country have embarked on similar evaluations; this project was unique in that it included an in-depth evaluation of the long-term viability of financial incentive markets, sustainability impacts, future natural gas demand, and the potential impact from current and future state policies. This evaluation was then used to inform sensitivity evaluations of the two alternatives to facilitate decision making. Monetizing RNG The study evaluated four pathways for Metro to generate a revenue source from their RNG. These revenue sources included: 1. Sale of brown gas, 2. Participation in the Renewable Fuel Standard (RFS) program, 3. Participation in state-specific Low Carbon Fuel Standard (LCFS) programs, and 4. Participation in the voluntary market. The sale of brown gas is typically tied to regional natural gas indices, with revenue calculated based on the amount of gas injected into the natural gas utilities' pipeline. The sale of brown gas can be paired with renewable credits as shown in Figure 1. The study evaluated the long-term viability of the RFS program, considered the potential for an LCFS program in the State of Colorado, state legislature geared towards the reduction of the carbon footprint of building heat, and reviewed the strength of voluntary markets. The renewable volume obligations (RVO) under the RFS are set to expire at the end of 2022, and members of Congress have voiced support for the replacement of the RFS with a national LCFS program (similar to California) that provides incentives for a wider range of low carbon fuels. To date, there remains a significant gap in RNG supply to meet the originally planned renewable volume obligations. Whether the RFS program is continued or replaced by an LCFS program, it is anticipated that a system of federal renewable credits will remain in place for the foreseeable future for RNG. The viability of an electric renewable identification number (e-RIN) pathway was also considered; however, the EPA has not approved any such project, despite receiving approval requests. The Colorado Energy Office recently evaluated the viability of an LCFS program for the State of Colorado. This report (Low Carbon Fuel Standard Feasibility Study, September 2020, ICF Resources, L.L.C.) stated that, 'Experience in California, Oregon and British Columbia has shown that LCFS programs can deliver on the above policy objectives, and that LCFS programs are a cost-effective mechanism to reduce GHG emissions and increase the share of lower carbon fuels in the transportation sector, while having a smaller cost impact on retail fuel prices relative to other decarbonization policies.' No movement has been made to date by the State legislature to introduce such a program. Many corporations and utilities have established 'carbon-free' energy goals, which has created a voluntary market for RNG. Due to the higher RIN pricing, increasing RNG demands in the voluntary markets have resulted in increasing value and revenue potential. Table 1 shows the pricing variability for the voluntary markets and illustrates the increases in the market based on current conditions and drivers towards RNG sustainability goals. Long-term Natural Gas Demand As the energy sector transitions to meet renewable energy goals, there is increasing demand for natural gas that is anticipated to continue through 2050. The U.S. Energy Information Administration (EIA) projects increasing demand for compressed natural gas (CNG) over the next 30 years at 1 percent compounded annually. CNG demand is also expected to remain strong in the transportation sector, despite the focus on electrification of light-duty vehicles. CNG continues to be the major fuel source for heavy-duty vehicles. Figure 2 expands on the uses of CNG in the transportation sector and demonstrates there is a steady increase in CNG consumption through 2050. As Xcel, the local electric and natural gas utility, further develops their renewable energy portfolio to meet their 2050 carbon-free electricity goals, natural gas is anticipated to remain the backbone of reliable energy sources and backup emergency power for the next 20 years. State of Colorado Policy Impacts The State of Colorado is targeting a reduction of greenhouse gas emissions by 90 percent of the 2005 values by the year 2050. Legislation approved in 2021 requires natural gas and electric utilities (i.e. Xcel) to reduce the use of natural gas by consumers. Xcel could purchase RNG from Metro to decrease the reliance on natural gas. While a cap-and-trade program introduced this year was vetoed by the Governor, the Public Utility Council is currently reviewing a means of implementation for the legislation which could include an avenue for RNG. Alternatively, Metro could decide to pursue this type of program on a voluntary basis with other states or utilities that have existing programs. While the State has evaluated different types of RNG legislation and potentially creating their own LCFS program, nothing has materialized that would influence Metro's decision on which biogas alternative to move forward with. Variability of Utility Costs Electricity and natural gas costs are large operating expenses for Metro's annual budget. Pricing volatility for electricity and natural gas could impact either of the biogas alternatives. The EIA forecasts that increasing renewable energy capacity will result in a slight decrease of electrical rates through 2050. However, regional differences will occur based on the level of renewable energy in the regional electric utility's portfolio. According to the EIA, natural gas pricing fluctuates based on weather, economic growth, market competition, gasoline prices, and availability. Figure 3 illustrates the yearly average Henry Hub natural gas spot pricing. Sensitivity Evaluations Sensitivity analyses were developed to capture the financial viability of both alternatives based on the changing future conditions described above. Figure 4 presents the range of life cycle costs for the cogeneration alternative, with consideration of changing electricity prices and renewable electricity credit value. Figure 5 presents the range of life cycle costs for the pipeline injection alternative, with consideration of RIN pricing, voluntary market, and natural gas market volatility. Based on the sensitivity evaluations, the pipeline injection alternative in almost all cases provides a positive financial return to Metro when compared to the cogeneration alternative. The pipeline injection alternative has a simple payback of 3 to 10 years depending on the revenue model. When comparing the base case alternatives, pipeline injection has a 20-year net present value that is $205 million higher than the cogeneration alternative. Based on the recommendations of this study, Metro is planning to proceed with preliminary design and development of a biogas upgrading and pipeline injection system.

Purpose: Urban areas located near shorelines and/or tidally influenced riverbanks face a growing climate threat from the combined effects of increasing and more frequent rainfall and elevated tailwater conditions due to sea level rise and/or storm surge, restricting gravity-driven sewer performance during periods when capacity is needed the most. These tailwater conditions pose a challenge to historic sewer systems designed to drain by gravity, and this challenge is further exacerbated when rainfall rates exceed sewer design capacities. This presentation will share a case study on how to build resilience in sewer systems against these threats in a dense, urban environment, providing lessons learned to other communities facing similar challenges. Overview of Master Plan: Lower Manhattan is at the core of New York City's transportation system, economy, and civic life. Yet by the 2040's, Lower Manhattan's shoreline will begin to experience frequent tidal flooding from sea level rise, impacting streets, sidewalks, buildings, and critical infrastructure. In addition to tidal flooding, Lower Manhattan is at risk from more frequent and severe storms, like hurricanes and nor'easters, bringing storm surge and rainfall to this low-lying area. This has been exemplified by the devastating effects of Hurricane Sandy in 2012 and the record rainfall and widespread pluvial-driven flooding from Tropical Storm Henri (2021), remnants of Hurricane Ida (2021), and remnants of Tropical Storm Ophelia (2023). To reduce both acute and chronic flood risk to the neighborhood, NYC Economic Development Corporation worked with an Arcadis-led consultant team to study climate adaptation strategies and develop a Climate Resilience Master Plan. A major challenge of the master plan was how to upgrade and adapt the city's aging, gravity-driven, combined sewer system to mitigate the combined effects of rainfall, sea-level-rise, and storm surge-driven flooding in this future climate. To do so, the use of the sewer system during extreme weather events had to be re-imagined relative to its original design. This challenge was coupled with designing a coastal flood barrier system in a densely urban area, requiring an assessment of both on-land and in-water solutions (i.e., extending the shoreline of Lower Manhattan via land reclamation) to implement a comprehensive flood risk reduction strategy. To develop the Climate Resilience Master Plan, the team first built a 1D-2D hydrologic and hydraulic (H&H) model of the study area. One complexity of the model-build was the necessity to include upstream drainage areas and downstream discharge areas along the interceptor system so that operation of storm surge isolation components could be assessed across neighboring coastal flood protection system projects. After developing the model, the team identified the depth and extents of surface flooding that would occur under a variety of existing and future extreme weather events assuming a coastal flood protection barrier was implemented without upgrading the existing sewer system. The team then worked across multiple city agencies and stakeholders to develop level-of-service goals for the master plan under these future climate events and developed an alternative analysis to identify a suite of proposed drainage solutions that could meet the level-of-service goals under future sea level rise, storm surge, and rainfall conditions. The alternatives were evaluated for performance, constructability, cost, long-term and emergency-use operational requirements (e.g., operating large interceptor gates and/or pump stations during hurricane conditions), and alignment with other design components of this large, multi-disciplinary project. After evaluation, a subset of stormwater management solutions was carried forward for further development in the master plan, including an innovative approach to reverse the flow in a large-diameter existing interceptor sewer during extreme weather events, a large emergency-use combined sewage pump station, sewer conveyance improvements, and a green infrastructure corridor along the proposed extended shoreline. These solutions needed to fit within a multi-level, community-serving waterfront that maintains access for residents, park space, and active ferry terminals. Benefits of Presentation: Benefits of the presentation include the lessons-learned for many coastal and riverine communities that will face similar climate challenges in coming years, and sharing the innovative solutions employed here that may be considered on similar projects. The presentation will highlight the challenges of designing and siting new drainage infrastructure in dense, space-limited neighborhoods, and considerations for how to integrate this new infrastructure in an existing, aging sewer system. It will discuss considerations regarding coordination with stakeholders on adjacent, ongoing coastal resilience projects. Finally, it will share lessons learned and recommendations to other communities facing similar challenges. Status of Completion: The Master Plan was completed and released in December 2021 and is shared with the public at: [https://fidiseaportclimate.nyc]. The team is currently advancing the early design and engineering of the master plan, which will be completed in 2025. The presentation will cover the completed master plan and new components incorporated in the ongoing work. Conclusion: The employed methodology, proposed solutions, and lessons-learned provide an example to address similar issues in urban areas impacted by the combined effects of increasing rainfall and coastal or tidal riverine tailwater conditions throughout the United States. The presentation will explain the challenges with operating combined sewer systems to meet current level-of-service goals under a future climate and then describe the H&H modeling approach to assess flood risk and alternative analysis to identify mitigation strategies to build a more resilient Lower Manhattan.