Thames Tideway Tunnel: Hammersmith Pumping Station – highly constrained working

Retrofitting dense urban neighborhoods with green stormwater infrastructure (GSI) requires early and ongoing outreach to the affected public. Add in a combined sewer overflow (CSO) control project that is under a federal consent decree, giving affected neighbors little choice about the upcoming changes to their neighborhood, and a troubled history with large-scale GSI projects in the city, and public outreach takes on greater importance. The King County Wastewater Treatment Division took on its first GSI project for CSO control in two Seattle neighborhoods. Community outreach on the project design began in earnest in 2011. The project, which is nearing the completion of its first construction season, has overcome many challenges and has learned lessons about how to effectively work with the affected community on large-scale urban GSI projects. This paper focuses on the outreach tools and techniques employed during the design phase that built community acceptance of the project and enabled a smooth transition into construction and operation. Examples include taking advantage of creative educational opportunities, building relationships and trust, understanding and speaking to specific concerns about retrofit GSI projects, employing effective outreach techniques (going beyond public meetings), and building neighborhood trust in the construction team. These lessons are applicable to any agency or developer that wants to implement GSI in a dense, heavily used public space where public concerns could slow or stop the project.

Stimulated by the recent USEPA’s green stormwater infrastructure (GSI) guidance and policies, GSI systems have been widely implemented in the municipal area to control the combined sewer overflows (CSOs), also known as low impact development (LID) approaches. To quantitatively evaluate the performance of GSI systems on CSO and urban flooding control, USEPA-Stormwater Management Model (SWMM) model was adopted in this study to simulate the behaviors of GSI systems in a well-developed urban drainage area, PSW45, under different circumstances. The impact of different percentages of stormwater runoff transported from impervious surfaces to the GSI systems on CSO and urban flooding control has also been investigated. Results show that with current buildup, GSI systems in PSW45 have the best performance for low intensity and short duration events on both volume and peak flow reductions, and have the worst performance for high intensity and long duration events. Since the low intensity and short duration events are dominant from a long-term perspective, utilizing GSI systems is considered as an effective measure of CSO control to meet the long-term control strategy for PSW45 watershed. However, GSI systems are not suitable for the flooding control purpose in PSW45 due to the high occurrence possibility of urban flooding during or after high intensity events where GSI systems have relatively poor performance no matter for a short or long duration event.

The Thames Tideway Tunnel is one of the largest current infrastructure projects in the UK: upgrading London’s Victorian sewer network and extending over 25km across the city. The Tideway construction site at the Earl Pumping Station raised a number of technical, managerial, logistical and environmental challenges. At this 'postage stamp' sized site, a 52m deep drop shaft intercepting a 6.45m TBM-dug tunnel, a combined sewage overflow chamber and other ancillary structures have been constructed within heavily contaminated ground immediately adjacent to the live Thames Water pumping station serving the local South London community. Solutions developed between the joint venture of Costain, Vinci Grands Projects & Bachy Soletanche (CVBJV) and its partners, required extensive geotechnical works including: a diaphragm wall installed using a hydrofraise, Cased Continuous Flight Auger (CCFA), rotary bored and Sectional Flight Auger (SFA) piling, deep soil mixing (both panels and columns), and grouting (as jet, chemical and cementitious permeation). This paper discusses the approaches to reviewing the challenges, risks and lessons learnt on and off site, with the aim of showcasing the cohesive implementation and integration of complex schemes within the very congested site space and challenging delivery programme.

A combined-sewer overflow (CSO) is a significant contributor of contamination to surface waters. During a rain event, the flow in a combined sewer system (CSS) may exceed the capacity of the intercepting sewer leading to a wastewater treatment plant, thus releasing a mixture of storm water and raw sanitary wastewater into the receiving water. As CSOs contain untreated domestic, commercial, and industrial wastes, as well as surface runoff, many different types of contaminants can be present. Because of these contaminants and the volume of the flows, CSOs can cause a variety of adverse impacts on the physical characteristics of surface water, impair the viability of aquatic habitats, and pose a potential threat to drinking water supplies. The resulting short-term problems are poor aesthetics (floatables, turbidity, oil and grease), and beach closure due to increased harmful bacteria levels. The long term impacts include reduced dissolved oxygen in receiving waters, eutrophication and sediment contamination. Since CSO is considered to be a major source of water quality impairment for the receiving waters, much attention has been directed to reducing the quantity and quality of CSO discharged to meet the Ministry of Environment guidelines. There are several approaches to control the quantity and quality of CSO. The selection of a particular treatment technology depends on various factors such as site conditions, CSO characteristics, receiving water requirements. One of the emerging options is the vortex separator technology for High Rate Treatment (HRT) facilities at overflow location. There are many devices for CSO control in different trade names where vortex separator technology has been used (e.g. EPA Swirl Concentration, FluidSep(TM), Storm King(TM), CDS®). This study articulates the different CSO control technologies with emphasized [sic] on vortex separator technology. The City of Niagara Falls HRT pilot project for CSO control to the Niagara River is presented as a case study in this report. The performance of two HRT devices - Storm King(TM) and CDS® are evaluated in the pilot project. Analytical Probabilistic Model has been used a a tool in this study to evaluate the potential pollution reduction at the Niagara Falls CSO system.

As point sources of pollution are being eliminated others, less apparent, are becoming increasingly threatening to many water users. Non-point sources of pollution generated by combined sewer overflows have been found to be responsible for many of our water quality problems. The purpose of this paper is twofold: (a) to offer a summary of the combined sewer overflow control problem, and (b) to suggest a methodology for the anticipation or prediction of runoff flows from an urban catchment.Two types of regression models designed to predict urban runoff are presented and compared with the calibrated runoff model ILLUDAS. The simplicity of regression models and their ease of application to the real-time automatic control of combined sewer overflows make their use very promising.

In 1999, The Metropolitan Sewer District of Greater Cincinnati, Ohio (MSD) began negotiations with the United States Department of Justice, the United States Environmental Protection Agency, and the State of Ohio to create a program to address sanitary sewer overflows (SSO) and combined sewer overflows (CSO). The resulting document, the Consent Decree, formally outlined a process that MSD would follow and that government agencies could recognize and support. MSD had been addressing removal and reduction of SSOs and CSOs prior to the Consent Decree negotiations, but the Consent Decree defined a time frame as well for MSD. The Consent Decree required MSD to update the CSO Long Term Control Plan (LTCP). An important component of the CSO LTCP Update is the assessment of CSO control alternatives with respect to receiving water quality. As such, a field program was designed and implemented to support water quality modeling and CSO planning objectives. The field program would coincide with the water recreation season, starting in May and ending in October. The field program contained several components associated with dry and wet weather sampling and monitoring as outlined by the Consent Decree; Ohio River sampling, source characterization (CSO, SSO and Storm), and tributary sampling and continuous monitoring. This paper discusses the continuous monitoring component of the tributary sampling and monitoring program. Starting with the conceptual plan described by the Consent Decree, it outlines the process of converting a conceptual ideal into a workable field program including the installation, maintenance, data management and demobilization activities. Specific examples of unique site limitations are provided with the solutions tried and the resulting outcomes.

An innovative optimization‐simulation framework is applied to a case study of the Province of Quebec, Canada, to optimize the spatial distribution of green infrastructure (GI), the capacity and location of gray infrastructure, and the parameters specific to real‐time control (RTC) operating rules of a sewer system for reducing combined sewer overflows (CSOs) frequency and volume. GI, gray infrastructure, and RTC are applied either individually or in integration through eight optimization scenarios which are simulated over a nine‐year period of historical rainfall data. Among all scenarios, spatial optimization of GI with RTC leads to maximal CSO volume reduction (98%) and is the most cost‐effective option analyzed (70$/m3 of seasonal average CSO reduction compared to 140$/m3 for the scenario involving gray infrastructure alone). However, it requires a high GI implementation level and the CSO frequency under this scenario is sensitive to varying GI design parameters. The findings suggest that the best alternative for CSO control is the integration of the optimization of green and gray infrastructures with RTC as it still provides high CSO volume reduction (95%) and remains a cost‐effective solution (90$/m3 of CSO reduction), while providing robustness under cost and design uncertainties.

The idea of green infrastructure (GI) has generated great interest and creativity in addressing a range of challenging and expensive environmental problems, from coastal resilience to control of combined sewer overflows (CSOs). The appeal of GI stems from its cost savings compared to traditional “gray” infrastructure and the multiple benefits it provides, including biodiversity, aesthetics, and carbon sequestration. For example, a “green” approach to controlling CSOs in New York City saved $1.5 billion compared to a “gray” approach. Despite these advantages, GI still does not have detailed design and reliability specifications as compared to engineered gray infrastructure, potentially hindering its adoption. In this paper, we review some of the potential applications of GI in modern environmental science and discuss how reliability and associated (un)certainty in net benefits need to be addressed to realize the potential of this new approach.

City of Richmond, Virginia conducts Bacteriological Monitoring in the James River as Indicator of the Effectiveness of its Established Long Term Combined Sewer Overflow (CSO) Control Program

A case study for integrated real-time control (RTC) of an urban drainage system in the city of Wilhelmshaven (Germany) is explained. The fuzzy based RTC strategy combines control of the sewer system and inflow to the waste water treatment plant. The main objective in controlling the sewer system is to reduce the number of overflows and the volume at a combined sewer overflow (CSO), located close to a bathing beach. Based on online measurements, the operation mode of two pumping stations is modified. This approach allows the safe activation of free storage volume in the sewer system without constructive measures. To avoid critical situations in the treatment process, the inflow to the treatment plant is automatically reduced to a defined value if high inflows to the treatment plant occur in combination with unfavorable conditions on the secondary clarifiers during rainfall events. The integrated RTC system has been operational for approximately one year.

Combined sewer overflows (CSOs) have made water quality of receiving water bodies, including rivers and lakes, worse year by year. A new distributed runoff simulation model of storm water and pollutants in urban sewer pipe systems, which can be used to investigate appropriate counter measures for the CSOs and evaluate the effects of the measures, is proposed.In this model, PWRI Model, which is a lumped model and was proposed by the Public Works Research Institute, Ministry of Construction, Japan, is improved to a distributed model that can treat a back water effect.Simulated pollutographs by the proposed model are compared with simulated ones by PWRI Model as well as observed ones at a pumping station, and the adaptability of the model is investigated.

The forebay of pumping stations is an important hydraulic structure that connects the channel with the inlet channel. Actual test observations and theoretical studies have shown that poor precursors produce backflow, vortex, and water flow disturbances in the forebay water. In this paper, taking a lateral inlet pump station as an example, we study the nonmeasures and five rectification measures—“Y” type diversion pier, “T” shaped diversion pier, narrow bottom hole, high and wide bottom, and diversion wall—through adopting the method of numerical simulation and model test. For the numerical simulation, the corresponding three-dimensional model is established by UG solid modeling software, and then the computational fluid is simulated numerically with CFX. Based on the analysis and comparison of the results during the test of numerical simulation and model test, the stability of the rectification measures is considered after taking into consideration the results of the uniformity test of the velocity distribution of the surface layer, the bottom layer, and the front section of each scheme. The proposed scheme 3 (“T” diversion pier) is regarded as the pumping station flow control measures.

Control and treatment of stormwater discharges and combined sewer overflows (CSO) from urban areas are issues of increasing importance in the field of water qu…

Combined-sewer overflow (CSO) must be controlled by a storage-treatment system because storm flow in the combined sewerage system is intermittent and highly variable in both pollutant concentration and flow rate. A treatment facility operating without the benefit of upstream storage would need to be very large and costly in order to handle the relatively high volume and flowrate of a CSO. Similarly, if storage is used without treatment, the storage volume required would be very large and also expensive. This paper describes a strategy to optimize CSO control system. This optimized system maximizes the use of the existing system before new construction and sizes the storage volume in concert with the wastewater treatment plant capacity to obtain the lowest-cost storage and treatment system.

Installation of combined sewer overflow (CSO) consolidation conduits in difficult waterfront conditions would have been no easy task as originally designed and bid, using cut-and-cover methods, yet an aggressive Value Engineering (VE) proposal was accepted and the installation accomplished using pipe jacking methods. Five-hundred-and-ten (510) feet of conventional pipe jacking was successfully accomplished to install 54-inch and 30-inch consolidation conduits as part of the Narragansett Bay Commission's (NBC) CSO Control Facilities Program. This paper will present site conditions, a comparison of the original cut-and-cover design and the VE pipe jacking proposal, provide construction details and challenges. The conduits were installed in a narrow strip of land between historic waterfront structures and the Providence River with a portion of the alignment beneath high-tension towers and transmission lines. The ground conditions consisted of urban fill, a soft organic silt deposit, and abandoned power tunnels, slips and wharfs. Bid documents directed an open cut with an Owner-designed secant pile wall support of excavation and installation of reinforced concrete pipe (RCP) for the conduits, and the Contractor's proposed VE largely eliminated open cut and included pipe jacking with sheeted pits. The VE proposal was negotiated and the Contractor successfully completed the pipe jacking using an open-face shield, ground improvement using chemical grouting, Permalok steel casing and high density polyethylene (HDPE) pipe. Several large obstructions, including concrete-filled vaults, abandoned tunnels, timber piles, and steel sheet piling were encountered and excavated from within the pipe jacking shield. Challenges and risks associated with open-cut excavation in a difficult waterfront environment were significantly reduced by implementing the pipe jacking VE change, but were not entirely eliminated.