Results

Advanced anaerobic digestion processes offer unique opportunities for process intensification, biosolids product production and resource recovery. Thermal hydrolysis is the current state of the art for digestion enhancement, commercially available, typically doubling the capacity over conventional systems. Co-digestion in conventional digesters has demonstrated that doubling biogas production is possible with the right mix and quantity. Combining THP with co-digestion has the potential to maximize the bioenergy yield from a fixed volume of digesters. Hampton Road Sanitation District (HRSD) as part of its recent upgrades to its 54 MGD Atlantic Treatment Plant added thermal hydrolysis (CAMBI) and FOG receiving to enhance energy generation and provide a much-needed outlet in the region for resource recovery from fats, oils and grease. HRSD installed two B-6-4 CambiTM thermal hydrolysis units at the plant which discharges thermally hydrolyzed sludge to its 6 mesophilic anaerobic digesters. HRSD had the option of FOG addition pre or post THP, but to preserve the Class A biosolids status the sludge pre-THP was selected as the process configuration. The introduction of FOG to THP requires that it achieve the same level of pre-treatment that the sludge entering it, screened to less the 5 mm and largely devoid of grit. Combining these technical requirements and lessons learned from site investigations of operating co-digestion programs a first of its kind FOG receiving station feeding THP was designed and commissioned. Figure 1, shows the general process flow of the FOG system. It was designed around the using the Envirocare Beast and a pair of heated storage tanks to raise the temperature of the FOG to 131°F prior to introduction to THP. Based on prior experience with FOG receiving station design and operations a coned bottom to the FOG storage tanks was incorporated to allow for the deposition of grit, removing it from the material fed to the THP units. The cone based design also allows for decanting and concentrating of FOG if needed; otherwise the storage tanks are completely mixed. The heated FOG is then introduced to the pulper of the THP system, in place of dilution water. An extensive characterization study by HRSD (see Table 1) of its FOG found that at an average of approximately 6% solids FOG would serve as good source of dilution water, while enhancing the energy value of the feedstock to the digesters. Since commissioning in the summer of 2021, the FOG station as operated reliably; however unanticipated repairs to FOG receiving facilities at other HRSD plants resulted in higher-than-planned FOG loading to AT throughout 2021 (Figure 2). As a result, the FOG facility at AT operated close to its peak week design basis (Table 1) nearly continuously through its startup and early operation period without undue mechanical or operational difficulties. Some early lessons learned during early operation include: - Rheological properties vary widely in high strength wastes. Screens and systems designed to process 6% FOG were able to manage 20% humus production waste - Introducing FOG to the pulper has proven reliable and viable means of maximizing the energy yield of the system. - Additional FOG water storage (or decanting, in some applications) may be a useful feature to allow additional capture of FOG through the dedicated receiving system in lieu of processing through the headworks are peak loading conditions. Storage, rather than material processing and biological processing, have proved to limit the capacity of the AT system at unanticipated high loading. Operations the THP and digesters has proven to be stable even with the high FOG loadings, demonstrating the viability of the unique microbial population attributed to THP pretreatment. This is critical in demonstrating the overall efficacy of THP to be integrated into a larger resource recovery and bioenergy program. Early biogas production numbers were hindered by system leakage but since correction, has been in line with the anticipated loadings. As part of the discussion of operations the acclimation of the digester to FOG and other high strength wastes will be discussed, as introducing FOG to a THP digester is not the same as a conventional digestion system which is inherently influenced by the feed sludge active biomass. Further at the time of presentation the THP system will have been shut down and restarted as part of it annual inspection and maintenance providing further information on the impacts of FOG and high strength waste loadings on the THP process. But also provide information on the recovery of the biological process and a return to full loading under a co-digestion scenario. Overall this information is important as the adoption of THP increases across North America and little information is currently available surrounding the integration of co-digestion with THP. At the time of presentation nearly a year's worth of data and lessons learned will have been collected and presented.

The Washington Suburban Sanitary Commission (WSSC) is in the process of implementing a Bio-Energy project to thermally hydrolyze and anaerobically digest all biosolids from their five Water Resource Recovery Facilities (WRRFs) to produce a Class A biosolids product. This presentation will discuss four key design considerations and lessons learned in laying out this facility: - Increasing reliability and availability of the Thermal Hydrolysis Plant (THP), - Design considerations for cake and sludge piping around the THP, - Challenges of an evolving market for combined head and Power (CHP) boilers on a THP project, - Squeezing the value out of biosolids. Consideration 1 Characteristics of the THP process make it potentially damaging to equipment. The inherent risks of piping and equipment failure create a need for periodic preventive and corrective maintenance shutdown for inspections and repairs, which will lead to annual periods of unavailability of the THP. Unavailability of the THP creates logistic issues with biosolids management and potential upsets downstream biological processes (digesters, sidestream), both of which the design must consider. Solution 1 A standard way to increase availability and reliability of a process is to provide this process with redundant units. When this option became available, WSSC chose to implement it through installation of add-on modules to the THP system and minor piping modifications. Consideration 2 Cake and sludge conveyance is energy intensive, and energy use is proportional to the length of the pipe. There are limits on pumps and pipe fittings that determine the maximum pressures a system can be designed for. In an ideal situation, cake reception (if using imported cake), storage, THP and digesters should be co-located, but when retrofitting an existing facility, this becomes a mighty challenge. Dual phase piping from the THP to the digesters requires a continuously ascending slope. Flow interruption on hydrolyzed sludge can create a big sticky mess. Solution 2 Most common methods to limit the headloss include use of long turning radius elbows, use of boundary layer injection (water or polymer), and other methods have been introduced in the market, such as air assisted cake pumping. When laying out a THP project, giving these elements the proper priority and importance can save big capital and operation costs. Consideration 3 Boilers in CHP systems for THP projects often have the ability to use engine generator exhaust gas and biogas along with other fuels (normally natural gas), for reliability and optimization of the energy use. They additionally need to be responsive to the steam demands which are inherently variable because THP is a semi-batch process. In Europe, composite boilers are the standard for THP projects, but the US market has not yet evolved to a point where these units are available. Instead, the standard approach for stream production from engines for CHP units is the use of heat recovery steam generators (HRSG). Bringing standard composite boilers to the US is not only extremely expensive, but also a total nightmare from the point of view of code compliance. The biogas boilers market in the US has mostly evolved from the landfill industry and there are limited options when it comes to using both engine exhaust gases and biogas. Solution 3 Available options in the US use co-firing of exhaust gas and biogas and provide limited windows of operation when it comes to limiting flame-out of the burners, due to the presence of the CO2 that comes along with the biogas. Innovative approaches using gas recirculation and multi-variable controls provide a feasible solution. Consideration 4 There are many paths to squeeze value out of the biosolids, which many times are focused on the use of THP to increase volatile solids destruction in the downstream anaerobic digestion, producing a higher value Class A biosolids, reducing hauling costs and increasing biogas production, but there are additional approaches to capture more value from THP process. Some examples of additional value include the use of biogas to generate power on engine generators, which can be coupled with a boiler than can use engine exhaust gases to improve the CHP unit overall efficiency. At Piscataway we set out to install CHP units that would serve the dual purpose of providing steam to the THP and electricity for the plant, as well as improving the energy independence from the grid. The WSSC bioenergy project is aimed at capturing the maximum value of the process without compromising the very real capital investment constraints. Solution 4 To achieve this optimization, we set out to design a CHP unit that would allow the project to apply for an energy grant offered by the State of Maryland, to CHP units that would achieve a minimum 60% energy efficiency. To reach this challenging goal, the CHP unit was designed in a way that not only included electrically efficient engines, and a boiler that uses the engine exhaust gases, but the overall system efficiency was supplemented with energy recovery from the engine secondary cooling system, through integration of this system with the Sidestream treatment process and pre-heating of the boiler feed water. Later in the project, a new more challenging energy efficiency goal was set, to achieve a 65% efficiency, to access additional grant funds from the local electrical utility company. Multiple options where analyzed, some of which were immediately discarded, some of which were later tossed out due to the complexity of their implementation and/or cost, and two were selected for implementation. The first one associated with additional energy recovery via additional preheating of the boiler feed water on economizers, and the second one, uses the heat from the engine cooling system to preheat the dilution water used to adjust the solids content in the THP feed.

ABSTRACT
City of Los Angeles Sanitation and Environment (LASAN) owns and maintains 10,800 kilometers (6,700 miles) of sewer and operates three Air Treatment Facilities (ATF) and ten Carbon Odor adsorbers located along the sewer system for removing odor and other related constituents from the collection system. The ATFs utilize Bio-trickling Filters (BTFs) technology followed by carbon adsorbers as polishing units while the Carbon scrubber sites utilize carbon adsorbers as the only treatment for foul air. In order to improve carbon life and reduce the footprint required for carbon vessels, LASAN started conducting a series of pilot tests to evaluate alternate carbon odor adsorbers with suspended media for all-around air flow compared with traditional flow carbon design. The results of this test were published in Water Environment Federation (WEF) Odor Conference in 2018 (Haddad-Zadegan/Gilani, WEF Odor Conference 2018 and UCLA Odor Conference 2017). The purpose of this test was to evaluate the performance of the new carbon vessel design with Suspended Media Chamber (SMC) and all-around air flow which provides larger media surface area, smaller footprint, and capability to separate moisture from the inlet air stream. This testing project conducted a side-by-side comparison between a deep bed traditional vertical upward air flow and the new all-around air flow design. LASAN procured and installed the new vessel design at eight (8) City carbon scrubber sites and this paper will share the result of the new scrubbers in term of their capability on removal of Hydrogen Sulfide (H2S) and other odorous compounds Volatile Organic Compounds (VOCs) from the inlet air stream. The new vessel design has the capability to separate the water voper from the inlet air stream contributing to a longer carbon life expectancy which results in significant cost savings for LASAN.

The Allegheny County Sanitary Authority (ALCOSAN) serves an area that spans approximately 310 square miles across 83 municipalities, including the City of Pittsburgh, Pennsylvania. ALCOSAN recently adopted a Clean Water Plan (CWP) to improve and protect the water quality of the region's streams and rivers by controlling combined sewer overflows (CSOs) and eliminating sanitary sewer overflows (SSOs). The CWP is part of a Federal Consent Decree (CD) to comply with the United States Environmental Protection Agency's CSO Control Policy. The CWP is made up of several components including preventing excess water from entering the sewer systems. As part of its green stormwater infrastructure (GSI) and source control (SC) program, ALCOSAN released Controlling the Source that lays out a consistent framework for evaluating GSI/SC in the Pittsburgh region. A key component involves identifying cost€effective and impactful GSI/SC projects capable of reducing sewer overflows to improve water quality. Overflow reduction efficiencies (OREs) were developed throughout the service area using automated modeling techniques to represent different GSI/SC techniques, varying implementation levels, and different system conditions. OREs provide a hydraulically-informed estimate of the relative overflow impacts of projects in different areas, so that effort and attention can be focused in those areas with the greatest potential overflow benefits. To complement the OREs, a GIS-based constraints analysis was performed to provide a geospatially-informed estimate of areas where GSI potential may be limited and/or costlier based on mapped physical and environmental constraints. Individual constraints such as shallow bedrock and slopes were assigned a range of constraint scores based the relative impact to GSI and then overlaid and summed. By targeting areas/sites with high OREs and lower levels of constraints, practitioners have powerful planning-level tools to identify projects most likely to be feasible, cost-effective, and impactful. Using these tools, ALCOSAN identified and evaluated almost 200 potential GSI opportunities. The opportunities were ranked and prioritized based on capture potential and implementation feasibility. Detailed concept plans for 60 of the higher ranked sites were developed and incorporated in discussions with municipalities as a tool to incentivize GSI project implementation in response to public comments received during the development of the CWP. This presentation will describe the development and application of the ORE modeling and the constraint scores as well as the results of the opportunity analysis and will discuss lessons learned for applicability in helping to address wet weather issues in other communities.

The City of Los Angeles is home to the most innovative infrastructure solutions in the world. Sustainability and environmental stewardship are at the core of actions taken daily to service the diverse community. Diversity in the city of Los Angeles gives the City (entity) access to a rich range of talent, representing different experiences, perspectives, and styles. These differences foster a collaborative and innovative work environment that makes industry stronger and a better organization on every level. DEI goals are both internal to the City as an organization and external with workforce development and business relationships. In order to meet the DEI goals set forth by the Mayor and LA City Council leadership, the City initiated various programs. This paper explores three programs in which public agencies partner with private industry to further advance DEI goals within the external workforce industry. In order to achieve the desired diversity our industry seeks; it is important to develop thoughtful outreach events that provide the opportunity to engage with local Minority/Women-Owned Business Enterprises (MWBE) where they are at. Equally challenging is staying connected with industry during COVID virtual environment. To stay connected and increase the participation and business opportunities with the Los Angeles MWBE community, City of Los Angeles has created specific programs. - Accessing LA is the flagship contracting and business networking event of the City of Los Angeles hosted virtually to share information and resources on how to do business with the City. The event aimed to offer MWBEs an opportunity to learn about business opportunities in the Greater Los Angeles area. Specifically, the partnership aimed to provide MWBEs with information on upcoming business opportunities in the Los Angeles Area, information on Tetra Tech and their disadvantaged business partnering programs and provide the strengthened message that Los Angeles leadership is committed to growing diverse business partners in the area. - Small Business Advisory Council hosted by Bureau of Public Works Commissioners' Aura Garcia and Mike Davis. The council consist of MWBE representatives, large prime contractor representatives, and public agency representatives. The council is focused on meeting regularly to address key issues that present challenges to growing the diverse industry base in the area. The council aims to share key procurement initiatives, make connections for business partnerships, and develop working solutions to industry challenges. Tetra Tech is an active participant in the council and provides input on growing MWBEs. - Small Business Academy hosted by the Department of Public Works Bureau of Public Administration. The L.A. Small Business Academy is a 7-session course that is made possible by the collaboration of the Department of Water & Power (DWP), the Port of Los Angeles (POLA), the Los Angeles World Airports (LAWA) and the Department of Public Works (DPW). The Academy was initiated to engender the growth, sustainability, and success of small business enterprises through the provision of courses that provide direct information and insight about marketing, financing, insuring, and working on design-build, and other future projects. The completion of an extensive program focusing on empowering and preparing small, women, minority, and military veteran-owned firms. Tetra Tech partnered with the academy to host an outreach event. These initiatives are proving successful at efforts to grow a diverse business base in Los Angeles.

The Venice Dual Force Main: Ensuring Resiliency through Redundancy in a Historically Large Scale Microtunneling Project This paper presents resiliency through redundancy construction management considerations and techniques that were used in the Venice Dual Force Main project. The project's intent is to construct a second force main sewer to operate in tandem with the existing force main sewer for the purpose of fulfilling the three key objectives, (1) The new force main will operate as a parallel system in conjunction with the existing 48' force main to meet the existing Peak wet weather Flow demands experienced at Venice Pumping Plant. (2) Add operational flexibility and reliability. (3) Allow isolation of either force main during low flow conditions to perform necessary cleaning and maintenance. During the heavy storms in 1995, Venice Pumping Plant VPP experienced tremendous amount of peak wet weather flow (PWWF) that was contributed by stormwater infiltration in the sewershed. At times, the PWWF exceeded the maximum capacity. As a result, sewage rose in the plant's equalization wet well, reaching critical level. With this potential serious public health and environmental risk, the City of Los Angeles recognized the need to increase the output capacity in order to be resilient to the existing infrastructure. With this Project the current and proposed capacity concluded that the addition of this 54' force main sewer will increase the current capacity from 44,000 gpm to 57,000 gpm, with 4 pumps operating and 1 pump in stand-by mode. With the current PWWF of 45,000 gpm, the combined 54-inch/48- inch dual force mains can safely handle, in tandem, this capacity with 3 pumps in service and 2 pumps in stand-by mode. The project is in the City of Los Angeles in the communities of Venice and Playa Del Rey which constructs approximately 10,800 feet of a new 54-inch-diameter force main sewer in the City of Los Angeles, California. The construction is being performed under a major 4 lane road in the neighboring city of Marina del rey, adjacent to multi-million dollar residences and below the water table and a dense layer of existing utilities and then crosses under the Marina Entrance Channel and Ballona Creek. From there, the alignment continues south along Pacific Avenue and Vista del Mar and connects to the junction structure of the Coastal Interceptor Sewer Venice Dual Force Main (CIS) and North Outfall Sewer (NOS) next to high visibility beach areas. To manage this complex microtunneling project in both politically and environmentally sensitive area, a team of Project, Engineering, Construction and Public Outreach management were organized to plan the tasks of design, constructability review, geotechnical investigations, environmental assessment, right of way assessment, permitting evaluations, multiple solicitation/bid and award stages, and through construction and close out. The trenchless construction method, which utilizes hydraulic jacks to push pipes through the ground behind a remotely operated Micro-tunnel boring machine (MTBM). Drive lengths are generally limited to about 1,000 feet, depending upon ground conditions and pipe size; but intermediate jacking stations can be used to extend the drive length. Unlike conventional trenching techniques that require excavation for the entire length of pipeline, excavation for tunneling is limited to the endpoints of each drive at designated launching (jacking) and receiving pits. The launching pit contains the hydraulic jacks used to push the pipes, and the receiving pit is used to recover the TBM at the end of each drive. Tunneling can proceed intermittently; although, it is often necessary to proceed continuously, particularly on long drives through sticky soils, to prevent the pipe from getting stuck short of the receiving pit. Tunnel advance rates are typically between 30 and 50 feet per 8-hour work shift, depending on soil conditions and pipe size. The tunnel face is supported by a thick liquid ('slurry'), which is a mixture of the excavated soil ('muck') and bentonite (a natural clay mineral). Keeping the slurry pressurized in a closed chamber behind the cutter-head of the TBM prevents groundwater and excess soil material from entering the TBM. During construction, the Construction Management Team implemented processes to monitor and report on a daily basis any potential problems including soil related issues (i.e. heave, settlement, slurry consistency) and tunneling machine issues (i.e. misalignment, steering or stoppage). Other than the normal construction management factors, additional processes were implemented along with a comprehensive public outreach program to mitigate public nuisances and complaints (i.e. noise and vibration problems and traffic flow). Conclusion: This paper will provide guidance and lessons learned for planners, engineers, designers, construction managers on planning, designing, and construction management of large scale microtunneling projects to ensure sustainability and redundancy to their existing infrastructure.

Charlotte Water (CLTWater) has 123 MGD of capacity between five major wastewater treatment plants (WWTPs) and is interested in sustainable and cost-effective technologies that may be selected for future WWTP expansions or for replacement of existing treatment infrastructure. Aerobic granular sludge (AGS) is an innovative secondary wastewater treatment technology that can achieve biological nutrient removal (BNR). Aqua-Aerobic Systems, Inc (AASI) is the vendor for AquaNereda, the patented AGS system that utilizes specific biological and hydraulic selection pressures to produce and maintain the AGS in a sequencing batch reactor (SBR). CLTWater elected to pilot AquaNereda to understand how it might be used to expand the capacity of our overall system, either at an existing plant or in place of another BNR technology at our new plant under design, the Stowe Regional Water Resource Recovery Facility (SRWRRF). An AGS pilot was performed at McDowell Creek WWTP from June 2019 to February 2020 to determine its viability as a treatment for CLTWater. Before starting the AquaNereda pilot, CLTWater developed a list of objectives to achieve during the piloting process with actionable and achievable goals defined for each objective. These objectives included 1. Evaluating simulated performance representing treatment with and without primary clarifiers 2. Observing development of granules from flocculant sludge 3. Evaluating solids characteristics 4. Evaluating process control and operability 5.Involving State regulatory agencies to facilitate potential future permitting processes To address the objective of evaluating solids characteristics, a separate solids study was conducted at Bucknell University to provide insight on solids handling and treatment impacts for potential full-scale Nereda implantation. CLTWater wanted to assess impacts to digestion performance, dewatering, and recycle streams when aerobic granular sludge (AGS) and conventional activated sludge (CAS) are treated concurrently. During the study, Bucknell operated four lab-scale digesters that were fed several solids blends (Table 1) including two 100% thickened waste activated sludge (WAS) digesters to demonstrate differences between AGS and CAS WAS and two 60% primary sludge (PS)/40% WAS digesters to simulate McDowell's current digestion process and the expected maximum contribution of AGS to any digestion process at CLTWater. Waste solids from the Nereda pilot reactor treating primary effluent were thickened to ‰¥5% using gravity belt thickening and shipped to Bucknell with thickened PS and CAS-WAS from McDowell's full scale processes. Bench-scale 20-day HRT mesophilic anaerobic digesters were fed daily. Biogas production was monitored throughout the trial, but other analyses were performed after 71 days (~3.5 SRTs) to ensure results were representative of steady-state conditions. Results include quantified metrics and other observations related to 1) digester performance VS destruction, biogas production; 2) solids handling sludge viscosity, polymer demand, cake solids, cake metals content and odor production; and 3) recycle streams digestate nutrient concentrations. For digester performance, results showed that volatile solids reduction (VSR) for AGS-WAS was comparable to CAS-WAS with slightly different methane yields between Digesters 3 and 4 (60% PS/40% WAS). Minor differences in solids handling parameters were observed including marginally higher viscosity and polymer demand for digested solids that included AGS, but these differences were more pronounced in the digestate from Digesters 1 and 2 (100% WAS). Recycle stream soluble TKN concentrations were similar regardless of WAS source; however, recycle streams from reactors including AGS-WAS were characterized by markedly lower soluble TP concentration. The finding of much lower soluble TP concentration for AGS-WAS was surprising given that the Nereda process includes enhanced biological phosphorus removal (EBPR) and the pilot reactor performed comparable EBPR as the full-scale mainstream conventional BNR process. Unfortunately, the pilot timeline did not allow for additional investigation into the cause of this observation, but further research may be warranted in this area. This presentation will discuss high-level results from each of the objectives targeted during the AquaNereda pilot but will focus mainly on the solids-related findings. We will present overall conclusions from the pilot as well as lessons learned related to implementing a pilot for a process that has broad reaching implications across a wastewater treatment plant. Finally, the future of AGS implementation at CLTWater will be discussed.

Speakers: Karen Counes Program and Construction Management Practice Leader CDM SMITH Jenn Harrison Regional Team Leader, Program and Construction Management CDM SMITH Julie Lucas Senior Manager of Talent Acquisition Programs CDM SMITH Sara Varvarigos, Transportation Planner and Reboot/Re-entry Graduate CDM SMITH Category: Diversity & Inclusion - Presentation title: Reboot Re-entry: Returning to a Technical Profession After a Career Detour - Description: Two steps forward, two steps back. Sometimes detours happen in our well-planned lives. If you have had a break in your science, technology, engineering, and mathematics (STEM) career and are now ready to get back in the game, let CDM Smith help you restart your career by participating in our career re-entry program. In partnership with the Society of Women Engineers and iRelaunch, we offer a 16-week program each January through April for those who left their STEM career for 2+ years and now want to return. This is a paid, full-time temporary opportunity to help you train and rejoin peers in your field. Abstract/Content In 2018, CDM Smith joined a task force with the Society of Women Engineers (SWE) and iRelaunch, a pioneering organization on career return-to-workspace and essentially 'returnships' intended to re-integrate technical professionals into the workplace after career detours. SWE's STEM Reentry Task Force and iRelaunch's research and training programs were the basis for CDM Smith's Reboot/Re-entry Program, a 16-week, 40 hrs/week paid 'returnship' geared toward those employees trained in technical professions such as engineering and construction, but had taken a hiatus in their professional career. CDM Smith's formal Reboot/Re-entry program began in 2019, and can now claim 6 full-time hires as a result of the program.

INTRODUCTION The Metropolitan St. Louis Sewer District (MSD) is undertaking a long-term program called 'MSD Project Clear' to improve water quality for the St. Louis region by reducing the occurrence of basement backups and overflows caused by excessive wet weather sanitary and combined sewage flows. One of the approaches MSD is taking to meet this goal is constructing new infrastructure to increase the capacity of their existing sewer collection system, including new relief sewers, wet weather storage facilities, and tunnels to store and transport wet weather sanitary and combined sewer flows. This presentation will describe how wet weather storage technology was applied to attenuate excess flows and eliminate wet weather sanitary sewer overflows (SSOs) and backups in a portion of MSD's collection system. This approach has been used elsewhere in MSD's system and has potential application to other similar wastewater systems through the United States. PROJECT BACKGROUND In 2014, MSD, in association with engineering consultants Burns & McDonnell Engineering Company, Inc. and Wade Trim, Inc. began planning the Gravois Trunk Sanitary Storage Facility in Crestwood, Missouri. This facility is located along the 54-inch diameter Gravois Trunk Sewer, within the Gravois Creek watershed and the sanitary sewer service area of MSD's Lemay Wastewater Treatment Facility. Multiple sites were reviewed for location of the storage tank(s) based on a series of criteria, including operational flexibility, land needed and availability, location within the watershed and ability to meet hydraulic and flow reduction requirements, maintainability, reliability, operability, constructability, and environmental considerations. All sites evaluated were required to accommodate the preliminary storage requirement of 9.25 million gallons (MG). The site of an existing City of Crestwood public works maintenance facility was selected, which is located on Pardee Lane adjacent to the Gravois Trunk Sewer and Gravois Creek. HYDRAULIC MODELING Hydraulic modeling evaluations were performed to assess the capability of the facility to achieve two (2) goals: 1) the removal of two (2) Constructed Sanitary Sewer Overflow (SSO) Outfalls; and 2) limiting the hydraulic grade line (HGL) within the Gravois Trunk Sewer to a minimum of 8 feet below grade for a 10-year return period, except in areas where the sewer is less than 8 feet deep or in areas where basements will not be impacted. Meeting these goals will provide a 10-year Level of Service (LOS) for the Gravois Trunk Sewer. A calibrated XPSWMM model of the Gravois Creek watershed was used to verify that the required 10-year LOS is being provided for three different conditions, including for the 10-year 24-hour synoptic and 10-year 3-hour cloudburst design storms, as well as for a continuous simulation using 64 years of historical rainfall data to evaluate the long-term performance using real rainfall events. The 3-hour cloudburst event represents a high-intensity lower volume rainfall event, in comparison to the lower intensity, higher volume 24-hour synoptic rainfall event. The required storage volume to provide the 10-year LOS was determined using two methods: 1) Log Person method to determine probability of recurrence of exceeding required volume, and 2) meeting HGL limitation criteria for the downstream trunk sewer. The model was also run for the full rainfall data for the years 2000 and 2008 ('Typical' and 'Wettest' years, respectively) to evaluate the expected frequency that the storage facility would be in operation. Final design sizing concluded that the following minimum storage volumes would be required to provide a 10-year LOS: Synoptic: 7.97-MG; Cloudburst: 4-MG, and Continuous Simulations: 7.85-MG. Based on these results, a total storage volume of 8.0-MG was used for design. Modeling efforts also included development of a HEC RAS model to evaluate hydraulic conditions in the sewer downstream of the diversion structure for the purpose of optimally locating level measurement instrumentation to be used in process control of the facility. DESIGN CONFIGURATION Due to the site configuration, two (2) sanitary storage tanks with a storage volume of 4.0-MG each were planned rather than a single 8-0-MG storage tank. Above-ground storage tanks were designed using the AWWA D-110 Type III standard for Wire- and Strand-Wound, Circular, Prestressed Concrete Water Tanks. Tanks are 150-feet in interior diameter, with a maximum height above ground of 45-feet, in compliance with local ordinance. Tank floors are sloped to the center at a depth of approximately 8 feet below grade, and drained by gravity back to the trunk sewer. An aesthetics committee comprised of representatives of MSD, the design team, and public stakeholders was convened during design for the purpose of soliciting feedback on such features as tank façade, landscaping, and fencing. Other facility features included: - Non-staffed and fully automated - Diversion structure - Consolidation sewers - 54-MGD influent submersible pumping station - Granular activated carbon odor control system - Vertical turbine pumping system and rainwater harvesting system - Tank and wet well cleaning systems - Gravity dewatering sewers and control valves - Site paving, lighting, and landscaping including stormwater BMPs - Instrumentation and controls - SCADA system for centralized remote control - Control Building - Electrical Primary and Secondary Power - Miscellaneous Improvements POST-DESIGN ASSESSMENT Design was completed in 2018, and a construction contract in the amount of approximately $24 Million was awarded, after competitive bidding with four responsive bids received, to Plocher Construction Co. Inc. of Highland, Illinois. Construction began in 2019 and was completed in 2021. The Gravois Trunk Sanitary Storage Facility has been in successful operation by MSD since January 2021. CONCLUSIONS - AWWA D-110 tanks provide cost-effective above-ground storage - Above-ground wet weather sanitary storage requires extensive public outreach - Hydraulic analysis needs to consider future pipe lining, as well as potential for rapidly varied flow and/or backwater conditions in locations used for flow or level measurement - Need to build flexibility and operational feedback into facility design and process flow control strategies Refer to Picture 1 below for an aerial photo taken of the completed facility.

Variations in Green Infrastructure (GI) Low Impact Development (LID) Best Management Practices (BMPs) within the right-of-way have resulted in problems with construction, maintenance, and durability. GI implementation guidance documents, standard details and specifications provide uniformity in planning, design, construction, and maintenance. By standardizing how LID is placed in the Right-of-Way agencies can reclaim valuable space for people to enjoy, turn a burden into a resource, reduce irrigation demand and stormwater runoff, and provide for a sustainable and resilient transportation corridor. When green stormwater infrastructure is integrated with complete street concepts numerous co-benefits strengthen the three pillars of sustainability; the environment, social equity, and the economy. San Diego County is one agency that implemented GI guidelines and standards. Green Infrastructure Guidelines are an outreach tool and are also intended to serve as a companion to the rest of the Green Infrastructure publications. They include an introduction, strategies, procedures and design examples for implementing Green Infrastructure projects. The strategies include tree wells, rain gardens, rock gardens, and permeable pavement. Green Infrastructure Design Criteria lay out general definitions, general policy, and landscape design criteria for Green Infrastructure strategies. Green Infrastructure Design Standard Drawings includes construction details which may be referenced in improvement plans. Green Streets Maintenance Schedules include a list with maintenance tasks, frequency, and time of year for initial, routine, and as-needed maintenance of each strategy. Green Streets Specifications include detailed construction material and installation requirements for strategies including aggregates, geosynthetics, underdrains, permeable pavement, engineered soil media, mulch, overflow risers, check dams, and tree grates. Building on the GI guidelines and standards developed within the Southern California region, these concepts were integrated into a Climate Resilient Infrastructure Guidebook for Riverside and San Bernardino Counties in southern California including climate resiliency strategies related to stormwater. The Guidebook complements city-level, climate-related transportation hazards and evacuation maps and other products developed as part of a larger resilient infrastructure initiative. The Guidebook serves as a guide to help educate local practitioners in making the transportation system more resilient to these changes. It is intended as a practical resource for jurisdictions and includes strategies, best practices, and methods for overcoming challenges and using climate resiliency tools to address changing patterns of extreme temperatures, heavy precipitation and flooding events, and drought. It was tailored to address the diverse climate, terrain, and needs of the region to ensure the long-term viability of the transportation system. Stakeholder groups and agency staff are instrumental in identifying implementation priorities and correcting procedural barriers to implementation. There is typically limited surface and underground area available within the right-of-way to accommodate often competing needs for travel lanes, parking, bike lanes, pedestrian sidewalks/paths, and utilities. In constrained right-of-way areas, this often leads to limited availability for implementation of green/climate resilient infrastructure strategies. Another challenge to implementing strategies within the public right-of-way includes often conflicting jurisdiction regulations, codes, ordinances, and standards from various levels (local through Federal) due to differing priorities of various project elements. Standardizing the implementation, design, construction, and maintenance of green stormwater infrastructure provide multiple benefits for the public and stakeholders. Integration of green stormwater infrastructure elements into transportation planning, resiliency studies and guidelines provides effective tools for planners and engineers to address changing patterns of extreme temperatures, heavy precipitation and flooding events, and drought.

Faced with increasing costs for controlling hydrogen sulfide in its wastewater collection system, the City of Bakersfield, California commissioned an evaluation of its odor control program in 2019. Among the consultant recommendations was to consider using a more efficient treatment (ferrous chloride) in place of certain of the existing Calcium Nitrate dosing stations where costs were constrained. A particular priority were those stations along the higher flow interceptor segment where chemical demands and community sensitivities were highest. An expected benefit of iron dosing is its durational control capability, which should translate into fewer dosing stations. Consequently, field testing was suggested to assess the cost-benefit. As siting dosing stations for ferrous chloride solutions can be limited (due to the corrosivity of the product), a low-hazard form of ferrous chloride, SulFeLox®, was used. The study was conducted from April to June, 2021, and consisted of 12 days monitoring of the baseline Calcium Nitrate scenario, followed by 60 days of SulFeLox dosing at different feed rates, and concluding with 14 days of no chemical dosing (i.e., the true baseline scenario). The interceptor selected for the test was a 10-mile (5-6 hour retention), 12 mgd trunkline leading to the City's Plant No. 3 (Figure 1). The particular segment of focus begins where the discharge from the Romero PS (S1) enters the interceptor and ends at the Buena Vista PS (S2) approximately 3 miles (2 hours) downstream. Controlling vapor-H2S levels at the Buena Vista PS was the primary measure of success. To assess the durational control aspects of each chemical, sampling was also performed another 3-4 miles downstream at the McCutcheon PS (S3) - just ahead of the treatment plant (S4). In this study, the SulFeLox dosing station replaced two Calcium Nitrate stations: 1) at the Romero site (S1), and 2) at the Buena Vista site (S2). With Calcium Nitrate dosing (310 gpd, combined, from the two sites), the peak vapor-H2S levels recorded at the four sampling sites averaged 3, 94, 595, and 100 ppm (Figure 2a). The liquid-phase sulfide levels were 0.0, 2.9, 6.6, and 3.5 mg/L, respectively. With SulFeLox dosing (120-210 gpd), the peak vapor-H2S levels recorded at the four sampling sites averaged 0, 30, 652, and 31 ppm (Figure 2b). The liquid-phase sulfide levels were 0.0, 1.4, 4.7, and 2.3 mg/L, respectively. Comparing the Calcium Nitrate and SulFeLox results shows 66-83% lower vapor-H2S peaks at the Buena Vista (S2) and treatment plant (S4) sites, with less benefit at the McCutcheon site (S3) where vapors are impacted by H2S by other flows into the station. (Figure 2c). Site 2 (Buena Vista PS) is located in a particularly sensitive area, and prior tests suggested upstream Calcium Nitrate feed rates would need to be 500 gpd (or more) to maintain vapor-H2S levels below 25 ppm. Figure 3 shows the vapor-H2S results in this test, where SulFeLox feed rates of 120-210 gpd achieved the compliance targets and provided H2S reductions of 84-95% (relative to 146 gpd Calcium Nitrate). On a performance basis, the field results confirmed the consultant recommendation that (for system-wide H2S control) iron dosing from one site could provide improved results relative to Calcium Nitrate dosing from two sites. SulFeLox feed rates were determined that provide interceptor-wide H2S control to 25 ppm and 10 ppm. However, a direct cost comparison between the two treatment chemistries is complicated given that system-wide H2S control could not be demonstrated with Calcium Nitrate (per the 500 gpd test in a prior study). This present study did show, however, that the cost to control to target H2S levels using SulFeLox was $600-1000 per day, where the recurring cost for Calcium Nitrate was $850-950 per day (to control to the higher level of 100-140 ppm H2S). Subsequent to this field test, the City continued to feed SulFeLox at S1 (Romero PS) and has since replaced seven other Calcium Nitrate sites with three SulFeLox sites, reducing the total number of chemical feed sites from nine to four. As a result of this work, the City is now spending approximately $660 k/yr for SulFeLox to meet its system-wide performance targets, where it was previously spending $990 k/yr (for Calcium Nitrate). Further, with now a year's experience with dosing iron into the collection system, the treatment plant has observed operational benefits, including the elimination of need for ferric chloride feed to the plant digesters. Early in 2022, the City entered into a five-year supply agreement for providing SulFeLox iron product and related services and equipment. Future work is planned to evaluate iron regeneration ahead of the treatment plant (at McCutcheon PS, S3), recognizing that this trunkline comprises 70% of total plant flow but 100% of influent iron. Oxidizing the spent iron (as FeS) to hydrous ferric oxide (using hydrogen peroxide) is expected to provide additional benefit to treatment plant operations. Figures 1. Schematic of interceptor segment tested 2. Summary of field test results: Calcium Nitrate and SulFeLox rate performance 3. Buena Vista PS: Response of vapor-H2S levels to chemical feed rates (at the upstream Romero PS). 4. Buena Vista PS: Dose-Response summary comparison of SulFeLox to Calcium Nitrate.

As the City of Somerville navigates aging infrastructure, regulatory pressures, climate change and redevelopment opportunities, innovative and cost-effective approaches for urban flood relief are being implemented under its Union Square Stormwater Mitigation Program (Program). The City is in its 10th year of program implementation. This project demonstrates how stormwater authorities and consultants can adapt their integrated planning over the course of a project life-cycle. It also features how municipal urban flooding can be creatively solved by engaging in inter-agency cooperation during major public transit projects. Flood mapping and construction photographs of the various projects construction will be featured. BACKGROUND The Union Square area is a commercial district with dense adjacent residential development that lies at the bottom of a large, combined sewer catchment. Presently, stormwater is conveyed by municipal sewers to the Massachusetts Water Resource Authority (MWRA) regional combined sewer system. The MWRA system is capacity-limited downstream of this connection. Flooding is experienced during wet weather equivalent to an existing 2-year / 24-hour design storm or greater. The flooding originates from a historical filling of the Millers River in 1879 and impacts many minority-owned small businesses, the City's Public Safety Building and multiple neighborhoods designated as Environmental Justice Neighborhoods for Minority and Income. INTEGRATED PLANNING Planning originated with an Evaluation of Flood Reduction Alternatives in Union Square (2013). This hydraulic modeling and project prioritization study evaluated the different surface runoff management and storage options throughout the watershed to mitigate or eliminate flooding in the Union Square area. To avoid maintenance-intensive combined sewage facilities, the preferred scheme was to separate sewers and overflow excess stormwater to detention facilities of various sizes. The first project planned was the Nunziato Field Stormwater Storage Tank ($13.6 Million, 2017) being a 1.6 MG storage facility located below a park with rain garden. The project was designed with sewer separation of adjacent streets on a hillside. It functions to capture peak flows and is pumped out post-storm event. The park's design also includes a interactive rain garden for stormwater quality and public education. During design of the Nunziato Tank project, an opportunity arose during expansion of the MBTA public transit system. Upon seeing that the project included stormwater conveyance for 50-year design storm events, City planners quickly recognized that the infrastructure would be underutilized when Union Square flooded. By making a connection to it, the City could regain a stormwater outfall in the Millers River watershed. To validate this plan, the City integrated MBTA's hydraulic models into its own citywide hydraulic model (InfoWorks ICM). The raised railway bed meant that stormwater would be pumped to it, which risked exceeding the available capacity of the MBTA system. Different combinations of pump capacity and storage volumes were evaluated with different degrees of sewer separation tributary to Union Square. The modeling performed convinced all parties that a maximum pumping capacity of 50 MGD could be allowed. An agreement was then negotiated for the City to discharge into the MBTA drainage system. Upon conceiving this stormwater pump station, the City began to modify its Program: -Climate change design storms for the Year 2030 time horizon were established, enabling resiliency planning for intense precipitation. A future 5-year design storm was established comparable to an existing 10-year event. -Design and construction of the Spring Hill Sewer Separation ($23.4 Million, 2021), a 71-acre project involving complete streets and green infrastructure improvements, became the new priority to unlock more stormwater to be conveyed by the future pump station. -Construction of the Nunziato Tank project was re-sequenced to occur after the pump station to allow further optimization and phasing. POPLAR STREET PUMP STATION Now, four years after developing the concept, the Poplar Street Pump Station ($80 Million, 2023) is beginning construction on a 2-acre brownfield site. The project includes a 6,100 SF building that centralizes stormwater operations across the City, a 4 MG underground storage tank, and high-visibility green infrastructure consisting of rain gardens, infiltrating bio-basins and three blocks of infiltrating tree ways to emphasize stormwater management and public education of the facility. The site is also being co-developed as a public park themed around art and urban agriculture, with adjacent complete street improvements. The pump station site lies in the center of the Brickbottom district, where its own microcosm of integrated planning required a non-traditional approach to wet weather engineering. Over the course of three years, an inter-discipline team of planners and engineers successfully resolved the facility's design with a host of complex interfaces: 1.Historic Arts Community — local citizenry passionate about maximizing the park site 2.Brickbottom Vision Plan — prioritizing alternate modes of transit next to the site (pedestrians, biking, buses and rail) 3.GLX Community Path Connection — incorporating ADA pedestrian ramps, bike lanes and a public plaza above the force main discharge 4.McGrath Boulevard — an ambitious DOT plan to eliminate an elevated highway next to the site 5.MBTA Bus Network Redesign — incorporating a prominent bus stop into the site 6.Utility Renewal — upgrade of aged water and gas mains along the force main alignment Wet Weather Management & Control During pump station start-up in late 2025, its operation will be unmanned and rely on telemetry shared between City and MBTA facilities. Level sensors monitoring storm drains along the railway will signal when the MBTA drainage system has reduced capacity, generally coinciding with the existing 5-year design storm event. Variable-speed drives are controlled to slow pumping and match the reduced capacity. For larger storms approaching an existing 10-year design event, no capacity may be available during the peak of the storm. It is these situations when the 4 MG underground storage tank activates as a peak shaving facility and is later pumped out post-event. This combination of pumping and storage eliminates stormwater flooding along the Somerville Avenue corridor for the existing 10-year design storm, providing a stimulus for large scale redevelopment. Recently enacted City stormwater regulations further require large developers to reduce their stormwater runoff into the public right of way (piped and/or overland) such that the 10-yr proposed peak flow is less than the existing 2-yr peak flow. Privately operated storm water storage tanks are being constructed in this area, enhancing the flood resiliency of Union Square. Another aspect of the pump station is how it fits into the National Pollutant Discharge Elimination System (NPDES) permitting framework. The City is studying whether the pump station discharge should be listed as a co-permittee under the MBTA's NPDES General (agency) permit or for it to be part of the City's NPDES MS4 (municipal) permit. Stormwater quality will factor into this decision.