Project Description

The project includes a biosolids plant, load out and odour control buildings, and a pipe bridge, as well as excavation and backfilling of the east half of the south ash lagoon.
The plant site is land reclaimed from Lake Ontario. Sanitary and earth fills were placed over peat and organic silt deposits underlain by sand and a thin veneer of glacial clayey silt till over grey shale bedrock with limestone interbeds of the Georgian Bay (Meaford Dundas) Formation.

Seven boreholes were advanced to a maximum depth of 24.5m (80ft) using casing and wash boring methods, and then diamond drilled to confirm bedrock levels and conditions. The borings encountered 6m (20ft) of loose to very dense ash fill; 6m (20ft) of loose to dense, wet sand; 3m (10ft) of very soft to stiff organic silt; 7m (23ft) of compact to very dense, wet sand considered to be an aquifer; a thin layer of glacial clayey silt till; and weathered, grey shale below 20 to 23m (66 to 75ft) depth. The short term groundwater level is at 3 to 4 m depth and slightly above the average level of Lake Ontario at approximate Elev. 74.7m along this northwest shoreline section.

Report recommendations include open cut and braced excavations, groundwater control measures, steel sheet piled cutoffs with deadman anchors, wellpoint dewatering, backfilling requirements using native soils and imported select aggregates, consolidation and settlement considerations for the compressible organic silt, deep end bearing steel H pile load capacities to support structures, floor slabs, subsurface drainage requirements, groundwater chemistry and protective measures for foundations and underground service trenches and pipes, subgrade preparation, heavy duty pavement thickness designs, and geoenvironmental testing and site assessment reviews.