Swan M.,AECOM Technology Corporation |
Green W.,Regional Municipality of York |
Whittard J.,AECOM Technology Corporation
Pipelines 2012: Innovations in Design, Construction, Operations, and Maintenance - Doing More with Less - Proceedings of the Pipelines 2012 Conference | Year: 2012
The York-Durham Sewage System (YDSS) is a large regional sewer system carrying approximately 80 percent of the wastewater flows from York Region as well as the communities of Ajax and Pickering in Durham Region. The Southeast Collector (SeC) trunk sewer is the primary outlet sewer to Duffin Creek Water Pollution Control Plant and as such is a critical component of the YDSS. The system will convey the wastewater flows from 1.5 million people by design year 2036. York and Durham Regions completed an Individual Environmental Assessment (IEA) in support of a major trunk sewer capacity upgrade of the SeC trunk sewer. The IEA was the first of its kind required by Ontario's Ministry of the Environment (MOE) for a major wastewater project. The IEA addressed key environmental and public concerns including groundwater impacts from construction/tunneling and public and agency opposition related to pipe construction. To address these concerns, baseline conditions were established and a three-stage methodology was implemented to identify and subsequently evaluate the alternative trunk sewer routes and alternative design methods (e.g., earth pressure balance tunnel technology versus open cut, use of sealed shaft construction, provision of dedicated haul roads and spoil sites, etc.). The IEA recommended the construction of a 15 kilometre, 3000-millimetre diameter sewer by tunnelling (using earth pressure balancing machine (EPBM) and sealed shaft construction). The project involves significant tunneling (five to 40+ metres below grade) under sensitive watercourses (cold water fishery) and associated tributaries and the protection of major groundwater aquifers serving local wells. The IEA document was approved by the MOE in August 2010 and the new sewer is currently under construction. This paper will focus on the political/regulation challenges the team faced and how approvals for this project were obtained. Specifically, a well-documented process was implemented to develop the alternative sewer routes, screen and select a shortlist of alternative routes and finally, select the preferred route. This process contributed to the various political and regulatory agencies approving this significant project. © 2012 American Society of Civil Engineering.
Macey C.,AECOM Technology Corporation |
Murphy J.,Regional Municipality of York |
Thomas D.G.,105 Commerce Valley Drive West
Pipelines 2014: From Underground to the Forefront of Innovation and Sustainability - Proceedings of the Pipelines 2014 Conference | Year: 2014
The primary trunk (PT) sewer was designed to convey wastewater from the Regional Municipality of York and to collect and transport flows from Pickering and Ajax to the Duffin Creek Pollution Control Centre (PCC) in Ontario, Canada. The total collection system area encompasses an area of 47,350 ha (117,004 acre) and a total residential population of more than 1 million people and a daily influx of more than half a million people due to employment in the area. The PT sewer was constructed in multiple contracts in the late 1970s as a low head pressure pipe. While upper reaches of the sewer have been subjected to varying levels of condition assessment, the lower 5 km of pipe (3 miles) has never had its condition formally assessed. The diameter in this area ranges from 2,550 mm (102 in.) to 3,000 mm (120 in.), and the flow regime ranges from open channel flow to surcharged flow with more than 8 m of head. Aside from combined loading, which was practiced in the 1970s, the most significant evolution in structural design of RCP from the late 1970s to present day was the recognition that larger diameter pipes needed to be designed for shear (diagonal and radial) and for flexure and service load crack control. While this concept was introduced by Frank Heger as early as 1963 it was not introduced in any standard practice until the 1993 ASCE standard practice and is still not covered by the present-day ASTM C76 standard. The initial condition assessment consisted of assessing more than 48 unique load cases with finite element analysis (FEA) techniques and additional load cases through parameter sensitivity assessment. Investigations were also carried out to identify all potential deterioration mechanisms for the installed pipe relative to its internal and external exposure environment and prioritize the nature and type of advanced condition assessment tools to be deployed in ongoing assessments. The initial assessment provided a unique overview of the original design of the sewer versus present-day design standards and a summary of the exposure conditions that could affect the rate of degradation of the pipe material utilized in the original construction and established an initial "desktop"condition assessment model to facilitate structural assessment of sewer once more advanced inspections were undertaken. The output of this assessment not only provided the basis for input into an assessment of the surcharge pressures the pipe could reasonably tolerate during long-term operations but also, through examining the vulnerabilities in the present operating condition, established the types of advanced inspection tools that are most advantageous to deploy as the next stage of a condition assessment program. © 2014 American Society of Civil Engineers.
Ko J.,University of Waterloo |
Parker W.,University of Waterloo |
Liu J.,Regional Municipality of York
Water Environment Research | Year: 2016
The use of dechlorinating chemicals for removal of chlorine from spent membrane cleaning solutions was investigated. Addition of calcium thiosulfate resulted in a decrease in pH at low dosages of calcium thiosulfate, but when higher dosages were used, the pH was not affected. Other dechlorinating agents (sodium bisulfite, sodium sulfite, and ascorbic acid) generated smaller pH declines than calcium thiosulfate. The declines in pH were observed after the dechlorination reaction was effectively complete and pH did not appear to influence the rate of dechlorination. The rate of dechlorination in spent cleaning solution was slower than that observed in clean water. Dechlorination with calcium thiosulfate resulted in the lowest half-life and reaction time. At lower doses (less than 565 mg/L), it was not possible to discriminate between the different dechlorinating agents. The times required for dechlorination were more sensitive to increases in dechlorination chemical dose at lower doses.
Hrkac T.,Regional Municipality of York |
Urschitz G.J.,STRABAG AG
Underground - The Way to the Future: Proceedings of the World Tunnel Congress, WTC 2013 | Year: 2013
The Southeast Collector Project consists of the construction of 15-km of gravity trunk sewer, 16 shafts and six related facilities within the Greater Toronto Area (GTA), Canada. The total project cost is estimated at $550 million (CAD). The tunnel will be constructed using four owner supplied 3.62 metre diameter EPB TBMs. The project design and local geology have introduced several unique challenges. This paper provides an overview of the project and explores some of those challenges. Read how a Segment Handling Device helped mitigate the schedule impacts associated with a requirement to have the two longest tunnel drives mine in orthogonal directions from a 51 metre deep shaft. Discover a unique approach to rotating an EPB TBM within a 14 metre diameter shaft. Learn how a combination of soil replacement and vertical ground freezing helped resolve challenges related to constructing a critical maintenance shaft. And find out how the logistical challenge of managing 16 pre-determined access compounds spread over 15-km, was overcome. Such innovative approaches were necessary to maintain the critical completion schedule and to avoid extensive delays to the project. © 2013 Taylor & Francis Group.
Hunter C.,Conestoga Rovers Ltd |
Berringer D.,Conestoga Rovers Ltd |
Weir B.,Regional Municipality of York
Water Quality Technology Conference and Exposition 2012 | Year: 2012
The Regional Municipality of York (Region) is a two-tiered confederation of nine local municipalities: the Town of Markham, the City of Vaughan, the Town of Richmond Hill, the Town of Newmarket, the Town of Aurora, the Town of Whitchurch-Stouffville, the Town of East Gwillimbury, the Town of Georgina, and the Township of King. Within the nine local municipalities, the Region has more than 30 steel water storage structures that provide the critical storage requirements for these communities. Over the last three years, the Region has installed more than 10 passive mixing systems to improve water quality (decreasing water age and stagnant zones) within the Region's water storage systems. During the implementation of the passive mixing systems, there was a concern that the systems were not meeting performance expectations. At the time, it was suspected that the mixing systems installed in the storage tanks were not functioning as intended as chlorine residual levels measured at the storage facilities were showing a rapid drop in residuals during drain cycles. This created concerns with respect to the water quality within the distribution system. During the investigation into the performance of the passive mixing systems, a predictive residual model was developed for the storage facilities that calculated estimated chlorine residuals in the water tanks at various fill and drain stages. Subsequent field monitoring, testing, and trials of the chlorine residual measurements indicated that the actual mixed residual levels in the water tanks were in accordance with the estimated chlorine residual levels calculated by the predictive model. Upon further investigation, it was determined that the sampling location of the instruments was responsible for the significant drops of the chlorine residuals in the samples, and the real issue with respect to chlorine deterioration was related to the water age and water reservoir turnover. This is a real case history of system water quality operational concerns, the utilization of engineering principles in the development of a predictive water storage residual model, and the steps utilized to make positive improvements to the water quality within the distribution system. The paper will focus on the evaluation of the performance of passive mixing systems in water storage tanks and the improved effects on water storage mixing and water quality. The paper will also discuss low cost strategies and operational enhancements utilized by the Region to reduce water age within the water system. © 2012 American Water Works Association AWWA WQTC Conference Proceedings.