York Region mining project’s geotechnical and hydrogeological challenges overcome through the project design

ABSTRACT: The existing regional 900 mm sewage forcemain was built about 30 years ago. Through the Environmental Assessment (EA) completed in 2013 the new forcemain will twin the existing sewer and to minimize an overall impact to the community and environment will be placed within the previously disturbed corridor parallel to the existing forcemain. The EA selected alignment has identified a number of constraints, such as: numerous crossings and proximity to the East Holland River, to railways with their bridges, to existing forcemain and to heritage buildings, construction through the public parks and areas of high public use. Most of these constraints were eliminated during Detailed Design, where the micro-tunneling construction method to minimize any disturbance to the surface has being selected. This selection was possible due to the lower the project’s vertical alignment (10-12 mbgs vs 3-5 m for an open cut and HDD at the EA design) which, in turn, has reduced potential frac-outs to the surface and into the streams. The Project was issued for Tender in January, 2019 and awarded in April, 2019. Construction will commence in June with anticipated substantial completion by the end of 2021. Region has to implement an extent construction monitoring and reporting to the Ontario Ministry of Environment, Conservation and Parks (MECP) through the entire construction.