Results 1 – 10 of 10 matches
Description: 15 Years of CMOMs - A Successful and Sustainable New England Model
Abstract
15 Years of CMOMs — A Successful and Sustainable New England Model Background The City of Manchester, NH with a population of 110,00 is the largest city in northern New England. Manchester has a 'combined' wastewater collection system that consists of almost 400 miles of sewer, 12 pump stations, and a 42 mgd wastewater treatment plant. The sewer system is aging and often failing with over 100 miles of pipe over 100 years old. In addition, it was not designed for today' urban landscape, population, environmental regulations, or climate change induced weather events. To address this aging and failing sewer infrastructure in a proactive and pragmatic manner the City instituted a formal Capacity, Management, Operations, and Maintenance (CMOMs) program in 2009. This presentation will review fifteen years of Manchester's CMOMs program starting at its infancy in 2009 and tracing its development and growth into a successful and sustainable program. Overview EPA published their initial CMOM Guideline Booklet in January 2005. Although it was never formally adopted, regulators began to incorporate CMOM requirements in NPDES Permits, Consent Decrees, and as state regulations. Manchester's 2008 NPDES Permit contained the beginnings of our CMOMs program with requirements to map our collection systems, prepare an Operations and Maintenance Manual and instituted annual reporting. The City used this permit requirement to lay the foundation for a long-term sustainable CMOM program. The City's CMOMs program has developed in three general phases over the past decade and a half. The first phase focused on asset inventory, mapping, SOPs, and training. The second phase consisted of the design and construction of two multi-million-dollar sewer rehabilitation construction contracts that focused on replacement of failed systems. During this period sewer repairs were standardized into replacement, spot repair, lining, and short liners. The third phase of CMOMs consists of three more multi-million-dollar sewer rehabilitation construction contracts that were developed to address a wide array of system repairs and rehabilitation. During this time a formalized PACP certified CCTV inspection program was implemented that inspects over 120,00 linear feet of sewer and over 400 manholes annually. Over the past decade the CMOMs program also grew into a supporting program for the City's paving program and a vehicle for emergency sewer repairs throughout the city. It also became a complementary program to a large scale CSO mitigation program and newly implemented MS4 stormwater compliance initiative. To sustain this program, the City has committed $3.25 million annually for 2 years to CMOMs. Conclusions A successful and sustainable CMOM program is critical to sewer system's successful operation. It promotes system longevity in a cost effective and proactive manner. An effective CMOM program supports a collaborative approach that complements other ongoing infrastructure programs such as paving, CSO mitigation, MS4 stormwater initiatives, other utilities, and partner with local development. It is also providing the City with an extensive tool box to deal with an aging and failing sewer system, it's increased regulatory compliance requirements, and its impacts from climate change weather events. This all results in a cost effective and sustainable program to address the City of Manchester's aging and failing environmental infrastructure.
This paper was presented at the WEF Collection Systems and Stormwater Conference, April 9-12, 2024.
Author(s)F. McNeill1, B. Lundsted1
Author affiliation(s)City of Manchester 1
SourceProceedings of the Water Environment Federation
Document typeConference Paper
Print publication date Apr 2024
DOI10.2175/193864718825159403
Volume / Issue
Content sourceCollection Systems and Stormwater Conference
Word count13
Description: Adapting Collection System Infrastructure to Changing Flood Vulnerabilities - New...
Abstract
Collection systems and treatment facilities serve as an important environmental line of defense against wastewater contamination of groundwater and coastal embayments. With more intense and frequent storm events and rising sea levels, many communities are facing an increased risk to critical wastewater infrastructure from flooding and storm damage affecting critical wastewater infrastructure (Figure 1). This presentation will use case studies for collection system infrastructure along multiple types of waterbodies to discuss flood resilience measures being evaluated and implemented in Southeastern Massachusetts. The case studies discuss collection system infrastructure along: -Complex coastal estuarine shorelines -Open ocean -Tidally influenced coastal ponds -Inland river flood plains The presentation will also focus on how these communities are incorporating accommodations for projected changes in storm intensity and frequency into flood resilience evaluation, design and construction. A brief description of each case study is summarized below. Town of Wareham, MA (complex coastal estuarine shorelines) - The Town of Wareham is a coastal community with over 54 miles of coastline. Hydraulic constrictions caused by the complex coastal estuarine system results in high anticipated flood levels, up to 21 feet above mean sea level. The Town recently completed a 'Risk and Vulnerability Assessment', which provided them with a valuable tool to quantify the anticipated costs borne to the Town and its citizens if any vulnerable pump station failed during a 100-year storm event. The assessment provided the Town with a road map and prioritization strategy on which of its many competing coastal resilience wastewater infrastructure needs to address first. Building on the findings of the Assessment, the Town has proceeded with the design of coastal resilience mitigation measures for three pump stations which were among the highest priority stations because they serve critical infrastructure (a hospital, fire department and police department). Coastal resilience measures incorporated into the design include the use of flood planks, structural reinforcement of existing structures (Figure 2), sealing potential water entry points and installation of emergency bypass connections (Figure 3). The construction of pump station bypass connections has been completed and relocation and elevation of emergency generators is in progress. Additionally, following multiple Nor'easter storms in 2018 that exceeded the regional 40-year flood stage record, the Town conducted an evaluation of the impact of anticipated increased rainfall from more frequent and intense storms on the infiltration/inflow entering its collection system. The repetitive, consecutive nature of the 2018 storms elevated the groundwater table, producing more head pressure in the gravity collection system which dramatically increased infiltration rates entering the collection system and being conveyed to the Wareham Water Pollution Control Facility. The Town has successfully constructed the retrofit measures recommended by the I/I projections evaluation (Figure 4). Town of Oak Bluffs, MA (infrastructure exposed to the open ocean) -The Town of Oak Bluffs is a coastal community on the island of Martha's Vineyard. Its three vulnerable stations serve over 90% of the Town's sewered population, including many residences and the Town's primary commercial district (Figure 5). The Town recently completed the construction of mitigation measures to increase the coastal resilience of the stations through installation of a new emergency generator on a raised platform (Figure 6) and relocation of critical pump station equipment outside of the flood zone. The Town is currently in final design of an elevated electrical building superstructure designed to withstand anticipated flood conditions, with accommodations for the impacts of climate change through its design life. Town of Chatham, MA (tidally influenced coastal pond) - The Town of Chatham is a coastal community on Cape Cod. One of the Town's wet pit/dry pit pumping stations (Mill Pond) is located at the base of a tidally influenced coastal pond; updated FEMA flood maps show that the location is vulnerable to storm surges and flood events. During the Mill Pond Pumping Station Upgrade design, multiple flood protection measures were incorporated to increase the coastal resilience of the station. These measures include the establishment of a design flood elevation for the project which incorporates anticipated effects of sea level rise, installation of hydrophilic water stops and a flood proof entry door with stop blocks to provide flood mitigation measures (Figure 7). Town of Uxbridge, MA (inland river flood plain) — The Town of Uxbridge is an inland community in Central Massachusetts. Since construction of its centralized collection system the Blackstone River flood plain maps been revised and recent storm events have indicated that the Town's largest pump station is now vulnerable to the 100 year flood storm. During one storm event water was observed entering the station's wet well through conduits and rising within a couple inches of the top of the entrance tube (Figure 8). Additionally, the existing generator room was flooded, rendering equipment in the room inoperable during the storm event. The Town has finished construction mitigation measures to increase the flood resilience of this critical infrastructure, including raising vulnerable infrastructure above flood levels (Figure 9).
This paper was presented at the WEF Collection Systems and Stormwater Conference, April 9-12, 2024.
Author(s)A. Rudenko1, M. Drainville1
Author affiliation(s)GHD 1
SourceProceedings of the Water Environment Federation
Document typeConference Paper
Print publication date Apr 2024
DOI10.2175/193864718825159378
Volume / Issue
Content sourceCollection Systems and Stormwater Conference
Word count14
Description: Taking Action to Improve Sassaquin Pond with a Watershed-Based Plan
Abstract
This is the cleanest I've seen the pond in years!' remarked a passing jogger to the field crew preparing the boat for sample collection. This was one of many such statements received by CDM Smith staff during routine sampling of Sassaquin Pond in New Bedford, MA during the 2022 and 2023 field seasons following the implementation of water quality improvements by the City of New Bedford. This 38-acre 'kettlehole' pond is typical of those left throughout New England by an ice age during a former millennium. The groundwater- and surface runoff-fed pond now sits in a residential neighborhood, providing the surrounding area with aesthetic benefits but also periodic water quality concerns as a result of point and nonpoint source pollution from the residential area around the pond. This presentation will highlight the multi-pronged approach used to address water quality issues in Sassaquin Pond, from planning to implementation. This work presents a valuable case study in pond water quality planning and implementation, which will be useful for pond managers and the public alike. Background: The City of New Bedford has been working to improve the water quality in Sassaquin Pond since the 1970s. Actions taken include the installation of a sanitary sewer system in 1974 and 1975 to reduce nutrient and bacteria loads from septic systems, and the installation of structural stormwater best management practices (BMPs) to address total suspended solids and phosphorous loading in stormwater. Despite previous efforts, Sassaquin Pond remains on the 2022 303(d) Massachusetts Integrated List of Waters with impairments for Curly-leaf Pondweed, algae, fecal coliform, harmful algal blooms, and odor. Cyanobacteria blooms, such as those that occurred in 2012 and 2020, have been a particular cause for public concern. Previous studies of Sassaquin Pond have identified excess phosphorus from internal (pond sediments) and external (stormwater runoff) sources as the cause of these periodic algal blooms. Planning: CDM Smith worked closely with the City of New Bedford's Department of Public Infrastructure and the Sassaquin Pond Betterment Alliance to develop a Watershed-based Plan. This plan uses the latest field data in conjunction with information from previously completed studies to provide the City and the Sassaquin Pond Betterment Alliance with a roadmap of projects that can be implemented in a prioritized approach to improve water quality in Sassaquin Pond. The plan includes 30 recommendations for short- and long-term actions to reduce nutrient and bacteria loads to the pond. These include both structural and non-structural solutions with varying costs of implementation. As projects are implemented, progress toward water quality goals is evaluated via the monthly pond sampling program. Implementation: In the first two years since the completion of the work plan, the City of New Bedford has taken action to implement several of the plan's recommendations. These include: -Monthly pond sampling during the growing season (April to November) for 2022 and 2023, -Addition of a chemical coagulant (alum) to strip phosphorus from the water column and bind phosphorus in sediments to reduce internal loading, -Curb and sidewalk construction to reduce erosion in the watershed, -Prioritized catch basin inspections and cleaning, -Robust street sweeping, -Treatment of invasive species (Phragmites), and -The installation of green infrastructure along the pond's banks. These actions have resulted in improved water clarity, quality, and habitat. Additional structural improvements have been proposed, including re-routing some stormwater away from the pond's watershed to reduce total bacteria and nutrient loading, construction of additional shoreline green infrastructure to intercept and treat stormwater before it enters the pond, installation of more trash receptacles and pet waste collection areas, and the installation of new catch basin hoods for control of floatable debris. These projects are currently in the design phase, with construction planned in 2024. Additional field programs are also planned for 2024 including a bathymetric survey, an investigation of underwater springs, and a program to inspect and remove directly connected impervious area (DCIA) within the watershed. Results and Next Steps: This presentation will present creative and multi-faceted approaches to improving the quality of an urban pond, the lessons of which may be applied broadly to other surface water systems. The results of the routine pond monitoring provide quantitative evidence of the program's success so far. Overall, data collected from April to November of 2022 show pond water quality was significantly improved relative to historical conditions. The alum treatment helped improve water clarity. Massachusetts water quality criterion for dissolved oxygen was met in the pond, as were the guidance levels for Aquatic Life Use based on low levels of nutrients and chlorophyll. Wet weather monitoring at the three largest outfalls showed high levels of phosphorus and bacteria were discharged to the pond. Several of the actions planned for coming years are anticipated to reduce these levels.
This paper was presented at the WEF Collection Systems and Stormwater Conference, April 9-12, 2024.
Author(s)
Author(s)Z. Schmitt1, Z. Eichenwald1, B. Kolb1, S. Syde2, J. Ponte2, J. Chicca2
Author affiliation(s)CDM Smith, 1; City of New Bedford 2
SourceProceedings of the Water Environment Federation
Document typeConference Paper
Print publication date Apr 2024
DOI10.2175/193864718825159351
Volume / Issue
Content sourceCollection Systems and Stormwater Conference
Word count11
Description: Advanced Analysis Guides CSO Work along the Connecticut River
Abstract
The City of Holyoke, Massachusetts sits on the western bank of the Connecticut River, just north of Springfield. Incorporated as a city in 1873, Holyoke was once the world's leading writing paper production center, relying on the abundance of water and hydroelectric power provided by the Connecticut River. As is common in historically industrial New England cities, Holyoke relies on a patchwork system of infrastructure spanning many eras to provide wastewater collection and drainage. Currently, approximately 70% of their collection system remains combined. Under regulatory pressure from the United States Environmental Protection Agency (USEPA), Holyoke is working on implementing a Long Term Control Plan (LTCP) to address combined sewer overflows (CSOs), and next on the list is separation of the 150-acre River Terrace Drainage Area, which stretches from the bank of the Connecticut River on the east to the I-91 Corridor to the west; and from Riverview Terrace at the north end to Hillview Road to the south. Having drafted an LTCP in 2000, Holyoke has made some progress on CSO abatement goals over the past 20 years. However, significant challenges persisted, and the USEPA issued a partial consent decree in 2019, prompting the first update to the LTCP since 2000. In the 2019 update of the LCTP, a sewer separation project was recommended in the River Terrace neighborhood of the City. This recommended project was estimated to reduce annual CSO volume by 58 MG, roughly 35% of Holyoke's average annual discharge volume (2011-2018). Separation of the River Terrace neighborhood was not a new idea — it had been identified in the 1988 Lower Connecticut River Phase II Combined Sewer Overflow Study as an integral part of Holyoke reaching 90% CSO volume abatement. The project had slipped in priority in the intervening years, falling to the late 2030s in the 2019 LTCP Implementation Schedule. A new Consent Decree issued in the Spring of 2023 has caused the River Terrace Separation Project to jump the line, requiring project completion by 2027. Design had begun in 2021 but faltered. The City decided to change consultants during design, hiring Woodard & Curran to reevaluate the project approach and design. The project area is residential, developed in the late 1800's, and consists of tightly nestled residences on narrow, curving streets. Due to uncertainties around the capacity, location, and condition of the existing combined sewers, as well as a spiderweb of existing utilities, the team determined that the problem demanded a more thorough investigation and analysis. Differences between the documentation obtained by W&C as well as observed conditions, and in some cases the lack of documentation led the design team to conduct extensive field investigations, consisting of multiple rounds of field survey, CCTV investigations, flow metering, and field investigation by design engineers. The information collected was then used to develop a coupled 1D/2D combined sewer model on the InfoWorks ICM platform. Surveyed topography and publicly available land use and soils data were used to assemble the 2D domain, while existing and proposed pipe networks, including inlet locations, were used to assemble the 1D domains for existing and proposed conditions. This model provides a more sophisticated and robust tool for analysis of the hydraulic capacity of the combined sewers and therefore a more complete understanding of what is required to maintain or improve the level of service. Using the model, the design team was able to clearly identify the required capacity of the separated system and account for differences between documented and field-validated conditions. In conjunction with the investigation data, the model was also used to identify how much of the existing infrastructure could be kept intact to reduce project costs. In 2019, when the project was identified, the total cost was estimated at $16 million. With the first phase, constituting about half of the total separation, currently estimated at $12 million, any opportunities for savings must be explored. In one location, results of detailed analysis obviated the need to replace 1,200 feet of 30-inch pipe, saving over a million dollars. As a community looking at significant wastewater infrastructure investments in the coming years and a projected high burden on ratepayers, it is crucial to leverage attention to detail with the right analysis tools. This project is an example of the challenges that arise throughout a combined sewer separation project, beginning with planning and continuing through final design. The presentation will discuss specific design issues encountered throughout the project and how they were addressed. In particular, it is important to not underestimate sewer separation costs by assuming more infrastructure can be reused than can in reality. Attendees will see a pattern that helps anticipate the challenges and the tools that can be applied to navigate them, and they will take away the importance of using the right assessment tools for making decisions about significant investments.
This paper was presented at the WEF Collection Systems and Stormwater Conference, April 9-12, 2024.
Author(s)K. Trainor1
Author affiliation(s)Woodard & Curran, Inc. 1
SourceProceedings of the Water Environment Federation
Document typeConference Paper
Print publication date Apr 2024
DOI10.2175/193864718825159340
Volume / Issue
Content sourceCollection Systems and Stormwater Conference
Word count10
Description: Modernizing CSO Notification and Forecasting with Digital Tools
Abstract
The prevention, mitigation, and management of combined sewer overflows (CSO) continues to be a focal point for municipal wastewater utilities throughout the country. Regulatory requirements are constantly evolving and continue to increase emphasis on public alerting. Modern digital solutions can be used to improve the way that utilities notify the public about the occurrence and effect of CSOs in their communities. This presentation will provide examples of enhanced CSO prediction and notification tools that leverage predictive analytics and machine learning to improve transparency in CSO management. In the first example, an alert system was developed to inform community members of the risk of high bacteria levels downstream from CSOs. The alert tool uses publicly available information that is fed into an algorithm developed with historic data and relationships, including time of travel and decay constants, specific to the river. The tool has been validated against several overflow events and predicts downstream bacteria concentrations within a reasonable and useful accuracy. The results of the predictive tool are available on a public website hosted by the regional planning agency. Innovative tools that leverage existing engineering information are effective at informing the public about the real-time contamination risks of combined sewer overflows. The second example demonstrates how surrogate modeling using machine learning can predict collection system flows, and associated CSOs, in real time. This example also maximizes the use of existing available data and information to create a modern prediction tool. A calibrated hydraulic model of a combined collection system was used to train a machine learning model to produce predictive flows based on real-time weather forecasts. The knowledge of when, where, and how much combined sewage is predicted to be released into local waterways can be used to alert the public of impending closures and advisories. This type of tool can also be used by utility managers and operators to plan for upcoming overflows and increased inflow to wastewater treatment facilities.
This paper was presented at the WEF Collection Systems and Stormwater Conference, April 9-12, 2024.
Author(s)J. Lefkowitz1, A. Goldberg
Author affiliation(s)Brown and Caldwell 1
SourceProceedings of the Water Environment Federation
Document typeConference Paper
Print publication date Apr 2024
DOI10.2175/193864718825159347
Volume / Issue
Content sourceCollection Systems and Stormwater Conference
Word count9
Description: Innovative Design-Build Implementation of CSO Storage in Lewiston, Maine
Abstract
The Lewiston Auburn Water Pollution Control Authority (LAWPCA) is required to construct a combined sewer overflow (CSO) storage tank to reduce the frequency and volume of CSO discharges into the Androscoggin River from Structure B and Outfall 002 located at the Wastewater Treatment Plant (WWTP). This project will be implemented using a conventional design build (DB) approach. The WWTP is designed to handle an average daily flow of 14.2 million gallons per day (MGD) but currently treats an average daily flow of about 8 MGD. During wet weather the collection systems from Auburn and Lewiston can deliver flows approaching 50 MGD to the WWTP. Excess wet weather flow, above the peak flow capable of being treated through the full WWTP treatment process, overflows from Structure B to the Androscoggin River via a 48-inch outfall leading to Outfall 002. Control of overflows from Structure B is the OBJECTIVE of this DB project. The WWTP currently has sufficient influent pumping capacity to pump and treat a peak flow of 32 MGD. LAWPCA is currently advancing plans to increase the firm WWTP peak flow pumping and treatment capacity to 38 MGD and the 2.1-million-gallon (MG) CSO Storage Facility capacity is based on a 38 MGD WWTP capacity. Purpose of Paper and Presentation: The purpose of this paper and presentation is to convey how LAWPCA structured their conventional DB RFP to provide proposers with considerable latitude to develop and offer LAWPCA a best value solution to their needs while requiring CSO storage site utilization that will preserve options for expanding CSO storage if required in the future. Project Scope: The services in this DB project include engineering, design, permitting, and procurement of materials and equipment, construction, testing, start-up, and commissioning of the LAWPCA CSO Storage Facility. Overflow from downstream of Structure B and upstream of the Outfall 002 discharge location will be intercepted at a Diversion Structure and conveyed to a CSO Storage Pump Station with a firm capacity of 30 MGD. The CSO Storage Pump Station will pump to the Storage Tank(s). Following each storm event, the Storage Tank(s) will be dewatered by gravity to the WWTP for full treatment. The Diversion Structure, CSO Storage Pump Station, and Storage Tank(s) are required to be located within limits shown on an indicative drawing included in the DB procurement document (see attached figure). Major facilities, components, and functions that make up the CSO Storage Facility include the Diversion Structure, CSO Storage Pump Station, Storage Tank(s), ancillary piping (e.g., Diversion Structure to CSO Pump Station, CSO Pump Station to Storage Tank, Storage Tank drain, process water, etc.), Support Building including a garage bay and an Electrical and Control Room, and replacement of an existing stand-by generator. Examples of how the project technical requirements for selected facilities, components, and functions that make up the CSO Storage Facility provide proposers with flexibility while preserving LAWPCA with operational and future flexibility are presented in Table 1. Status of Completion: The design-build RFP, which is the subject of this abstract submittal, was completed in August 2023. Selection of a design builder will be completed by early 2024 with design and construction of the LAWPCA CSO Storage Facility underway by the time this conference takes place in April 2024. Benefits of Presentation: The primary benefit to those attending this presentation will be the opportunity to learn how LAWPCA was innovative in developing their conventional DB RFP to both provide latitude to proposers while preserving their options for future CSO storage expansion. The paper and presentation will expand on the examples in Table 1, above. Additional benefits will include learning how DB can be used to implement time-sensitive wet weather projects and how excess wet weather flow storage can be cost-effectively integrated into an active wastewater treatment plant process and site. Conclusion: The LAWPCA CSO Storage Facility is an important project in attaining regulatory compliance in accordance with long-term CSO control plan requirements and for improving the water quality of the Androscoggin River. Project financing and affordability are important to LAWPCA and citizens of Auburn and Lewiston. ARPA funds, which must be expended by the end of calendar year 2026, will be used to reduce the local cost burden. Selection of conventional DB for implementation of this CSO Storage Facility project will enable LAWPCA to meet that date and take advantage of a best value solution while preserving options for potential future CSO storage needs.
This paper was presented at the WEF Collection Systems and Stormwater Conference, April 9-12, 2024.
Author(s)
Author(s)K. Mignone1, G. Heath1, T. Peaslee2, O. McCullough3
Author affiliation(s)AECOM 1; Lewiston Auburn Water Poll Ctl, 2; Sebago Technics, Inc. 3
SourceProceedings of the Water Environment Federation
Document typeConference Paper
Print publication date Apr 2024
DOI10.2175/193864718825159357
Volume / Issue
Content sourceCollection Systems and Stormwater Conference
Word count10
Description: A City with a Plan is a City with a Vision. Developing the City-Wide Sewer...
Abstract
The City of Chelsea, MA is strategically located as a gateway between downtown Boston and North Shore communities and is home to a vibrant, diverse population and industry that contribute significantly to the overall wealth of the region. Chelsea is served by the Massachusetts Water Resources Authority (MWRA) for water supply and wastewater collection. Many MWRA interceptors and a major regional headworks and pumping station are located in Chelsea. Like many other coastal communities in New England, Chelsea is serviced by a mix of combined and separated sewer systems that were built more than a century ago and are at the end of their service life. This outdated infrastructure hinders new development and growth, especially in the context of increased precipitation and coastal-induced inundation risk due to climate change. As a response to this concern, Chelsea has embarked on a city-wide master plan for sewer separation and infrastructure upgrades to systematically work towards attainment of the following three main goals: 1. Allow for future growth by progressively upgrading drainage infrastructure able to accommodate future population and increased stresses from climate change; 2. Eliminate CSOs by separating existing combined sewer areas and; 3. Reduce inflows to sanitary pipes from public and private properties that currently decrease available system capacity and increase operating costs to the City. In order to create this ambitious program, a significant modeling effort was carried out following a multi-step process. The first step consisted of building and calibrating a city-wide drainage model to help understand points with weak level of service and estimate peak flow and volumes reaching the MWRA interceptors and combined sewer overflows during dry and wet weather events. The City-wide model was built in Infoworks ICM using pipe network data from multiple sources such as record drawings, GIS, field inspections, and recently collected ground-level LiDAR information captured city-wide. The second step of the process consisted of developing conceptual level pipe layouts with the goal to achieve sewer separation city-wide and improve level of service. The conceptual level plans were developed using a 'best case scenario' approach (i.e. assuming an ideal drainage network can be built without necessarily accounting for other factors such as utility conflicts or permitting issues for new outfalls). The reasoning behind this approach was the desire to delineate a network able to attain optimum hydraulic performance based on natural topography and street layout and then work backwards, if needed, when conflicts identified during later phases of the process require this layout to be modified. The conceptual storm and sanitary systems were then incorporated into an Infoworks ICM model, which was used to fine tune the conceptual network (e.g. pipe slopes, pipe sizes necessary to provide the desired level of service or flow velocities for a given event). The third step was a planning level engineering effort where a street-by-street evaluation at each sewershed was performed. The feasibility and actions needed to go from the current condition to the proposed condition in the conceptual model were evaluated and alternative actions proposed when identified conflicts could not be resolved. The fourth and final step consisted of packaging and phasing the execution of the sewer separation and inflow reduction projects based on feasibility, City's priorities and constraints, as well as interim system conditions. This product is the City's new Master Plan for Sewer Separation and Drainage Infrastructure Upgrades, which will provide a systematic approach to drainage infrastructure improvements over the next few decades.
This paper was presented at the WEF Collection Systems and Stormwater Conference, April 9-12, 2024.
Author(s)L. Mammolette1, D. Bedoya
Author affiliation(s)Dewberry Engineers Inc. 1
SourceProceedings of the Water Environment Federation
Document typeConference Paper
Print publication date Apr 2024
DOI10.2175/193864718825159402
Volume / Issue
Content sourceCollection Systems and Stormwater Conference
Word count22
Description: 30 Years in the Making - The Final Phase of the Largest Public-Works Project in...
Abstract
The Narragansett Bay Commission (NBC) owns and operates Rhode Island's two largest wastewater treatment plants along with extensive infrastructure of interceptors, pump stations, and combined sewer overflow (CSO) structures. In 1992, NBC entered into a Consent Agreement with Rhode Island Department of Environmental Management (RIDEM) that established a three-phase CSO control plan with the goal of reducing annual CSO volumes (98%) and shellfish bed closures (80%). Phases I and II of the CSO Control Program were completed in 2008 and 2015, respectively. Phase III, the final phase of the program, commenced with a re-evaluation of the original plan in 2015, including a financial capability assessment to incorporate NBC's affordability goals into the Phase III implementation schedule. Phase III final design phase started in 2018 for 12 projects, and the first projects started construction in 2021. The largest of these projects is the 2-mile long, 30-ft finished diameter, 150-ft deep rock Pawtucket CSO storage Tunnel, which is being delivered as a design-build project. The tunnel construction is scheduled to be completed in early 2024, and construction of the tunnel dewatering pump station and screening facility will start in early 2024. This presentation will provide a program progress update, diving into construction challenges and lessons learned including the following: -Sequencing of design of tunnel with follow-on work: design development of tunnel elements at interfaces with surface projects; -Regulatory coordination: multiple approvals and permits in a dynamic project delivery environment; -Management of excavated tunnel material: what do you do with one million tons of 'muck'? -Material and labor cost escalation: balancing schedule vs. cost impacts to labor and materials; -Groundwater dewatering and treatment: approach to managing and pre-treating groundwater from large excavations prior to discharge; -Inspection and repair of existing Providence Tunnel: taking a look at condition of the existing tunnel in operation since 2008. The presentation will conclude with a look ahead to the schedule for completion of the remaining near surface projects and anticipated commissioning and start-up of the Phase IIIA system in 2027.
This paper was presented at the WEF Collection Systems and Stormwater Conference, April 9-12, 2024.
Author(s)M. Carter1, K. Kelly2
Author affiliation(s)Stantec 1; Narragansett Bay Commission 2
SourceProceedings of the Water Environment Federation
Document typeConference Paper
Print publication date Apr 2024
DOI10.2175/193864718825159399
Volume / Issue
Content sourceCollection Systems and Stormwater Conference
Word count22
Description: Combined Efforts for Combined Sewers: Benefits and Challenges of Combining the...
Abstract
The Massachusetts Water Resources Authority (MWRA) and two of their member communities, City of Cambridge, MA and City of Somerville, MA, are required to submit Updated CSO Control plans for their permitted CSO outfalls that discharge to the Charles River, Upper Mystic River, and Alewife Brook. Each entity will need to submit its own individual plan, but the plans need to be coordinated as the Cambridge, Somerville, and MWRA systems are hydraulically interconnected. MWRA had originally developed a system-wide collection system model in support of its 1997 CSO Control Plan, which covered its four member communities with CSOs (Cambridge, Somerville, Chelsea and Boston). Since then, MWRA has maintained and updated its model over the years, while Cambridge and Somerville have also developed and maintained their own collection system models in parallel. The Cambridge and Somerville models were developed to a higher level of detail in their respective systems compared to the MWRA version. Not surprisingly, the three models produce somewhat different results at certain CSO locations. In order to provide coordinated Updated CSO Control Plans with consistent modeled performance, MWRA, Cambridge and Somerville decided as a group that the best path forward was to combine the individual models into one Unified Model. With this approach, one model would be used to develop baseline conditions and evaluate alternatives for all three Updated CSO Control Plans, providing consistency in the assessment of performance and upstream or downstream hydraulic impacts. The purpose of this presentation is to walk through the steps taken to combine these three collection system models and document lessons learned throughout the process. The approach and lessons learned would benefit other agencies/communities where hydraulic connectivity across municipal boundaries can complicate the hydraulic evaluation of alternatives to improve system performance. This effort required very close coordination between MWRA, Cambridge, and Somerville as well as each of their consultants that maintain their models. Bi-weekly meetings, sometimes supplemented with additional meetings, were held throughout this two-year process to discuss each step that would need to be taken to combine the models and to define the run parameters so that each entity could run the model and get consistent results. As each entity and its consultants had their own preferences for running their models, compromises were required to establish consistent modeling parameters such as model time steps, the number of run threads during a simulation, rainfall smoothing, and ground water. Similarly, agreement was also needed for post processing procedures including interevent times, volume thresholds, and statistical templates. The meetings also served as a time to identify the roles and responsibilities and to discuss methods for troubleshooting model run issues such as run time, model instabilities, reconciling differences in model results or file size. Following the combining of the model networks and agreement on the parameters described above, it became apparent that a model naming convention would be necessary to organize the different versions of the model. To address this need a model naming convention was developed and a model log was posted to a shared drive where those working on the model could make updates as needed. The basic steps for combining the model networks included the following: 1.Identify the locations where the models would be connected. 2.Prepare the models by checking for duplicate names for model nodes, conduits, and subcatchments, as well as unique names for land use, runoff surfaces, and wastewater profiles. 3.Combine the model networks. 4.Develop Design Conditions (future rainfall, sea level, and evaporation) 5.Have each team run the model independently to check that all three entities are producing similar results and check that the results are consistent with previous results for each entity's CSOs. 6.Each team added planned projects to create a version of the model representing Future Baseline Conditions (FBC) With the efforts of the entire team the MWRA, Cambridge and Somerville models were successfully integrated into one Unified Model. Each team was able to run the Unified Model independently and produce similar results. The Unified model was compared with previous model results and the differences were investigated and explained. Each team then added projects that were planned to be constructed to create an FBC version of the model. The FBC version of the model is now ready to be used for the next steps of the project. It is anticipated that the Unified Model will continue to be updated as work on this project progresses.
This paper was presented at the WEF Collection Systems and Stormwater Conference, April 9-12, 2024.
Author(s)E. Casarano1, D. Walker1, T. Brinson1, J. Hall2, W. Kilbride2, C. Woodbury3, M. DuPont4L. Hiller5D.Bedoya6
Author affiliation(s)AECOM 1; MWRA 2; Cambridge DPW 3; Stantec 4; City of Sommerville5; Dewberry6;
SourceProceedings of the Water Environment Federation
Document typeConference Paper
Print publication date Apr 2024
DOI10.2175/193864718825159395
Volume / Issue
Content sourceCollection Systems and Stormwater Conference
Word count38
Description: Bar Harbor Systemwide Conveyance Assessment: How Smart Controls Helped the Town...
Abstract
Introduction: The Town of Bar Harbor, ME (the Town), a popular tourist destination due to its proximity to Acadia National Park, operates four CSOs that discharge to Frenchman's Bay where water recreation is highly valued. The Town has two wastewater treatment facilities (WWTF); included in NPDES permits for the WWTFs are requirements for development, and periodic updates, of a CSO Master Plan to abate CSOs from the Town's four CSO outfalls. Bar Harbor prepared its first CSO Master Plan in 2006, the most recent update to the plan was approved by the Maine Department of the Environment (MEDEP) in 2021. The purpose of the CSO Master Plan is to identify abatement projects and intended implementation schedule to better control and reduce CSOs and to report on progress towards achieving those results. Project Overview: A systemwide conveyance assessment was conducted to evaluate the potential hydraulic performance for infrastructure improvements and infiltration/inflow (I&I) reduction projects identified in the CSO Master Plan and to develop a plan for other pump station, force main, storage and interceptor improvements needed to increase the system's hydraulic capacity, eliminate SSOs, and reduce CSOs to the levels of control identified in the plan. The CSO Master Plan's minimum level of control is a 1€year, 24€hour storm event producing 2.4 inches of rainfall as 'the benchmark by which alternatives are evaluated and cost€effective solutions identified.' Subsequent discussions with MEDEP in 2021 related to the West Street Pump Station (PS) CSO outfall (Outfall #007) and a feasibility study prepared in 2019, identified a 5€year, 24€hour rain event as the design storm for the solution(s). Out of the four remaining CSOs in the sewer collection system, the West Street PS CSO discharging to Eddie Brook is the highest priority for the Town's CSO reduction efforts based on potential impacts to public use and benefit of the receiving waters. A collection system hydraulic model was needed to characterize existing conditions, operations, and performance, and to evaluate cost-effective solutions to mitigate CSO's in the Town to the CSO Master Plan's level of control. The model was developed and calibrated with data from pump stations, the WWTFs, and flow meters installed in the collection system. A Jacobs 'autocalibration' tool enabled a cost-efficient and expedited calibration to the nine flow meters and other data points. Once calibrated, the model was used to evaluate proposed improvements to the collection system needed to eliminate SSOs and sewer backups, and reduce CSO overflows to the CSO Master Plan's level of control. The following goals were established for the analysis: 1.Eliminate CSOs at the West Street PS CSO outfall (Outfall #007) for the 5-year, 24-hour design storm. 2.Elimination of CSOs at the Rodick Street PS outfall (Outfall #006) and Main Pump Station (or Lower Main) outfall (Outfall #004) for the 1-year, 24-hour design storm. 3.Eliminate SSOs at known problem areas in the collection system for up to the 5-year, 24-hour design storm. Results/Benefits: A list of pump station, force main, storage and interceptor improvement projects were conceptualized to increase the collection system's hydraulic capacity and meet the stated assessment goals. The Town had several planned Capital Improvement Projects (CIP) that were included in the alternatives developed; however, prior to the model development, the Town had no way to quantify the potential improvement from these projects. The alternatives were combined in several different combinations to determine the most effective scenarios to achieve the assessment goals. The five most effective scenarios with respect to feasibility and performance were identified and modeled. Each scenario was evaluated with implementing three levels of I&I reduction (i.e., 0%, 25%, and 50%). Conceptual cost estimates for each scenario were developed to further assess the cost-effectiveness of each alternative and its performance towards achieving the assessment goals. This scenario evaluation identified that by optimizing the operation of the West Street PS and CSO Storage Tank project (a $9M project already in design), combined with an upgrade to the Town's Main Street Pump Station (with a combined cost of $4.7M), assessment goals were nearly achieved. The West Street PS project's original design goal was to provide storage for the 5-year, 24-hour event to mitigate CSOs from CSO Outfall #007; the tank was not originally utilized for lower volume storm events and thus the project not maximizing the benefits from the Town's infrastructure investment. By modeling the system using smart, real-time controls, the evaluation showed that the storage tank should be utilized for storage during smaller events, without compromising its goal eliminate CSOs from the West Street CSO Outfall during the 5-year event. The evaluation showed that with these two infrastructure improvement projects, combined with implementation of a 25% I&I reduction program, the Town would not need to complete other CIP projects originally thought to be necessary to meet assessment goals — saving the Town millions of dollars in unnecessary infrastructure improvements. Conclusion: The systemwide conveyance assessment of the collection system is complete and the Town has a plan to achieve CSO mitigation regulatory requirements, as stated in their CSO Master Plan. The West Street PS and CSO Storage Tank Project design is nearing completion and is planned to go out to bid in spring 2024 with construction starting in early summer 2024. With this assessment complete, the Town has the data and information necessary to justify to their ratepayers the benefits and necessity of the ongoing system improvements and planned capital investments into the collection system. The Town also has the data and information necessary to justify the effectiveness of the planned capital improvements to the MEDEP and the information to support completion of the next CSO Master Plan Update which is required to be submitted to ME DEP by March 28, 2027. With the collection system upgrades planned, once constructed, the Town will also have the real-time data needed to verify system improvements are meeting their CSO mitigation goals and the ability to adapt system logic, if necessary, to improve system performance. A truly adaptive solution.
This paper was presented at the WEF Collection Systems and Stormwater Conference, April 9-12, 2024.
Author(s)
Author(s)A. Braga1, M. Dever1, B. Leavitt
Author affiliation(s)Jacobs 1
SourceProceedings of the Water Environment Federation
Document typeConference Paper
Print publication date Apr 2024
DOI10.2175/193864718825159383
Volume / Issue
Content sourceCollection Systems and Stormwater Conference
Word count21

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