Trainor, Kevin

Kevin is a PE with 12 years of experience working on municipal infrastructure planning and design projects. Kevin uses a variety of hydrodynamic modeling tools to develop and evaluate flooding and combined sewer overflow mitigation projects. Kevin received his bachelor's and master's degrees in Civil Engineering from the University of Maine and works out of Woodard Curran's Portland, ME office.

Titles from this speaker

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.

SpeakerTrainor, Kevin

Presentation time

16:15:00

16:45:00

Session time

13:30:00

16:45:00

SessionLocal Case Studies

Session number23

Session locationConnecticut Convention Center, Hartford, Connecticut

TopicClimate Change Adaptation, Collection Systems, Combined Sewer Overflow, Combined Sewer System, Construction, Deep Sewer Tunnel, Design Storm, Infiltration/Inflow, Precipitation Frequency, Sewer Separation, SSO Reduction, Stormwater Case Study/Application, Surface Water, Utility Management, Water Quality

Author(s)

Trainor, Kevin

Author(s)K. Trainor1

Author affiliation(s)Woodard & Curran, Inc. 1

SourceProceedings of the Water Environment Federation

Document typeConference Paper

PublisherWater Environment Federation

Print publication date Apr 2024

DOI10.2175/193864718825159340

Volume / Issue

Content sourceCollection Systems and Stormwater Conference

Word count10

Description: Intercepting Maine's Largest Combined Sewer Overflow Volumes with 1-D and 3-D...

Intercepting Maine's Largest Combined Sewer Overflow Volumes with 1-D and 3-D Dynamic Hydraulic Modeling

Abstract

Since the 1990s, the City of Portland, Maine has made significant strides in mitigating combined sewer overflow (CSO) volumes. The City's next important step is the creation of the 3.5 million-gallon (MG), off-line Back Cove South Storage Facility (BCSSF), which broke ground in July 2020. This facility is designed to capture the first flush of CSO from approximately 1,435 acres within the City, reducing the annual CSO volume at outfalls 016, 017, and 018 from 150 MG to 18 MG. These outfalls account for about half of the City's and about one quarter of Maine's annual CSO volume. To ensure the best return on its substantial investment in the BCSSF, the City opted to advance the project under a design-build contract that facilitates a collaborative approach between the City, the City's Owner Project Manager (OPM), and design-build team. The purpose of this presentation is to share information on the hydraulic design approach successfully applied and the challenges, considerations, findings, and lessons learned along the way. Advanced modeling, pairing 1-D collection system and storage models with 3-D computational fluid dynamics (CFD) models of key structures, informed the hydraulic design of a combined sewer overflow (CSO) control facility to fulfill regulatory, owner, and design-build delivery requirements. This approach instilled confidence in all project stakeholders that the hydraulic design addresses CSO control requirements while preserving the operation and service level of the existing collection system. The BCSSF concept design for this storage project began as a box conduit under a major thoroughfare and active business district. This idea evolved into installing a single, large tank below a public soccer field, which mitigated traffic and business impact, but posed its own logistical problems. The field's proximity to a tidal mudflat and elevated interstate highway created significant geotechnical and structural concerns. To address the differential settlement concerns born from the one large tank concept, the idea of four interconnected tanks designed to fill sequentially was proposed by the design-build team and accepted by the project partners. Additionally, installing the tanks in two sequential phases ensures the stability of the site and adjacent features during construction. Each phase consists of excavating an area 500-feet long by 75-feet wide by 30-feet deep, installing two cast-in-place tanks, and backfilling. This approach reduces the risk of rotational slope failure related to the elevated highway and allows the construction crews more space on the field to work without disrupting traffic or the nearby public trails. In addition to protecting the integrity of adjacent areas, the project team also had to address the fundamental challenge of capturing inflow from three separate, tidally-influenced CSOs. With a diurnal tidal range of 10 feet (greater during king tides and storm surge events) and the existing pipe elevations four to five feet below mean sea level, the system hydraulics dictated that the bases of the storage tanks would need to be at least 30 feet below ground surface or around 20 feet below sea level. The design team used a dynamic stormwater management model (SWMM) to account for the tidal cycles, interconnecting outfalls, backflow prevention, storage tank connections, as well as the losses imparted by diversion and access structures. This modeling helped confirm that the flow diversion and storage is passive at all tidal stages and that interactions and flow redistribution resulting from hydraulic connection of three CSO outfalls will not negatively impact the upstream collection system. The impact of independent connections between the four tanks was incorporated into the hydraulic model. Connection elevations were based on a cumulative distribution function of recent CSO events and were designed to minimize tank cleaning frequency without sacrificing the overall project goal of storage. Additionally, the team used state-of-the-art 3-D modelling methods to confirm that the hydraulic design of CSO diversion structures meets the City's CSO control requirements. This included computational fluid dynamics (CFD) modeling of diversion structures using FLOW-3D to understand internal flow regimes during typical year peak and extreme precipitation flows. CFD modeling results were used to quantify head losses associated with diversion structures independent of tidal stage. These results were used in conjunction with the system wide SWMM model to assess impacts to upstream collection systems and set design elevations for the storage facility. Once a design water surface elevation within the tanks of -6.50 feet was established, system performance was simulated with dynamic routing under steady peak design inflows to confirm design flows would be fully intercepted, even as tanks approach full storage capacity. System performance was also evaluated under unsteady flow conditions to account for interactions between upstream collection system volume and tidal stage during precipitation events. By pairing 1-D and 3-D modeling for analysis, the team arrived at a comprehensive design, instilling confidence in the proposed approach and final design. The 1-D and 3-D model analysis indicates that the CSO diversion structures impart reasonably low head loss, even at high design flows with surcharged pipes, comparable to a typical access manhole. The most dramatic hydraulic impact was created by the proposed replacement of rectangular tide gates with inline, elastomeric backflow preventers, which impart an order of magnitude greater head loss. In addition, connecting the three CSO outfalls shifted the flow balance between the outfalls during heavy precipitation events. Left unaddressed, this would negatively impact the system upstream in a densely developed area. This required additional design modifications downstream of one diversion structure to accommodate the redistribution of flows. The passive capture of CSO flows means water surface elevation within the tanks is controlled by the tide during heavy precipitation events. The BCSSF is the latest phase of the City's Long-Term Control Plan (LTCP), which has required extensive planning, collaboration, and detailed analysis. The completion of this project will provide dramatic and immediate improvements to the water quality of Back Cove and Casco Bay, which are vital to the identity and economy of the area. The hydraulic analysis and design for this project are complete. Experience gained through the hydraulic design of this off-line CSO storage system is highly transferable and will benefit those designing similar projects that impact the hydraulics within a CSO system.

This paper was presented at the WEF Collection Systems Conference in Detroit, Michigan, April 19-22.

SpeakerTrainor, Kevin

Presentation time

14:00:00

14:30:00

Session time

13:30:00

16:30:00

Session number11

Session locationHuntington Place, Detroit, Michigan

TopicCombined Sewer Overflow, Stormwater Management Design And Analysis, Wet Weather

Author(s)