Subsurface Conditions

Details of the materials contacted in the boreholes are given on the Log Sheets for Boreholes 18-1 through Boreholes 18-29; included in Appendix D of this report. Reference is also made to the logs of boreholes advanced at the site during the 2011 and 2013 investigation. Reference has also been made to Terrapex’s test pit logs to assist with the classification of the various fill materials found on site. Copies of Test Pit Logs 101 through 118 and the logs of the previous borehole are included in Appendix ‘C’ of this report.

The following paragraphs present a description of the engineering characteristics of the various soil materials which were contacted in the course of the test pit and borehole explorations.

5.2.1 Asphaltic Concrete and Granular Materials

Boreholes 18-6, 18-9, 18-10 and Boreholes 101, 104 and 201 were advance from the surface of the paved areas of the former incinerator facility property while Boreholes 106 through 110 were advanced from the surface of the pavement on Algoma Street. The surface cover at these borehole locations consists of an asphaltic concrete layer ranging in thickness from 80 to 250 mm. The thickness of the asphaltic concrete layer along Algoma Street ranges from 100 to 190 mm.

The asphaltic concrete rests on granular material consisting of sand and angular gravel fill, sandy gravel fill and silty sand and gravel fill. The granular fill occasionally contains clay pockets and concrete pieces. The thickness of the granular materials range from 200 to 600 mm.

Standard penetration tests carried out on the granular fill layer measured N-values ranging from 13 to more than 50 blows/300 mm which indicate that the granular materials underlying paved surfaces have been moderately to well compacted.

The results of water contents tests carried out on samples of the granular materials provided water content values ranging from 2 % to 26%.

A 160 mm thick concrete layer was found to underlie the granular material at Borehole 104.

5.2.2 Topsoil

In general, borehole explorations were advanced from grass covered area of the site. A layer of topsoil which ranges in thickness from 25 to 350 mm covers the ground surface. A partly organic sub-unit layer underlies the topsoil at Boreholes 18-15, 18-16, 18-28 and 18-29; this sub-unit ranges from 100 to 150 mm thick.

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5.2.3 Fill Materials

Underlying the topsoil, asphaltic concrete and granular materials is a variable fill material consisting of brown, grey, dark brown and black silty clay and silty sand soils with a varying sand fraction (some sand to sandy), and trace to some gravel, trace brick, glass, asphalt, metal, cinders and shale fragments. Topsoil pockets and partly organic soils are present in Boreholes 18-11, 18-15, 18-19, 18-20, 18-24, 18-25 and 18-29 within the depth range between 1.4 and 3.0 mbgs. Occasional topsoil pockets were also contacted in Boreholes 5 and 10.

Black and dark brown variable fill materials containing deleterious, construction and waste debris was encountered in Boreholes 18-4, 18-5, 18-6, 18-17, 18-18, 18-19, 18-20, 18-22 and 18-29 in the depth range from 1.5 to 4.7 mbgs. Concrete slabs were contacted in the bases of Boreholes 18-16 and 18-22; refusal to auger advancement occurred at depths of 6.6 and 6.9 mbgs respectively at these boreholes. Concrete slabs were also contacted in Boreholes 5 and 11 at depths of 1.75 and 0.25 mbgs respectively.

The fill materials encountered in the boreholes advanced during the current investigation extended to depths ranging from 0.5 (Borehole 18-5) to 6.9 m (Borehole 18-22) below ground surface.

The fill materials present on site vary greatly. Due to the limited recovery of the material by the split spoon sampler the description of the fill materials are complimented by information presented on Terrapex’s Test Pit logs along with a review of selected samples, collected during the advancement of the Test Pit excavations carried out during their 2013 study. Detailed description is provided in the following paragraphs.

For the purpose of this geotechnical report the fill materials have been grouped into three categories:

- soils with traces of construction debris and deleterious materials;

- soils containing some to mostly construction debris and deleterious materials, and;

- materials predominately consisting of construction debris and deleterious materials with traces of soil.

The deleterious materials contacted on site consist of cinders, glass, metals, plastics, organic material and similar materials unsuitable from a geotechnical standpoint.

5.2.3.1 Fill soils with trace construction debris

This group of materials consisted of layers of:

- a pale brown to brown, damp to moist, silt and fine sand to silt with some fine sand fill material, which included a varying clay fraction ranging from trace clay to some clay and;

- a brown trace grey and black silty clay soil with a sand fraction ranging from some sand to sandy.

The clay fraction within the silt and fine sand fill occasionally imparts a weakly plastic character to the soil.

The silt and fine sand and silty clay soils where found to include traces of glass, brick, cinders and slag. The fill was found near the surface and below the granular materials at Boreholes 18-2, 18-4, 18-5, 18-6, 201, 202 and 204 and at Test Pits 102, 103, 106, 107, 108, 110, 113, 115, 116, 117 and 118 and underlying the variable fills (See Section 5.2.3.2 and 5.2.3.3) at Test Pits 101 and 105 and at Borehole 101, 103, 104 and 204.

At Borehole 202, the fill material is partly organic near the surface.

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At the test pit locations, the fill extended to depths ranging from 0.6 m (TP107) to 4.4 m (TP 105); from 1.5 m (BH 104) to 4 m (BH 103) below the ground surface at the borehole locations.

5.2.3.2 Fill soils with some to mostly construction debris and deleterious material

Layers and pockets of a:

- dark brown, black and grey, moist to wet, coarse sand and gravel fill;

- silty clay to sandy silty clay fill.

Both sand and clay fill materials contained slag, organics, pieces of glass, brick, metal, ceramic, plastic, asphaltic concrete, concrete and wood. Debris pieces ranged from gravel to cobble sizes. This fill material was found near the surface of Test Pits 101 and 105, and underlying the granular materials at Test Pits 104, 109, 111, 112,114, underlying the generally clean fill (section 5.2.3.1) at Test Pits 103, 106, 108, 117 and 118 and at Boreholes 101 and 108, and underlying the mostly deleterious fill (section 5.2.3.3) at Boreholes 202 and 204.

The variable fill materials appear to be buried below and within the relatively clean fill materials in the southwest corner of the property at depths below 0.6 m from the existing ground surface. Similar materials are also present in the eastern half of the site.

The variable granular and silty clay fill materials were found to extend from 0.8 m (TP 114) to 3.5 m (TP 110) and to depths ranging from 1.5 to 5.3 m at the Borehole locations.

5.2.3.3 Construction debris and deleterious Materials

Generally, the materials consisting predominately of glass, metal, cinders, plastic, slag with some gravel and sand are found to underlie the above noted fill materials at Test Pits 101, 102, 103, 104, 109 and 111 and at BH18-4 and BH18-5. At Boreholes 202 and 204, the deleterious materials are sandwiched between the generally clean fill and the above noted fill (fill soil with some construction debris).

Debris pieces are typically cobble sized. These materials are deposited in the center and most eastern portion of the former waste incineration facility site.

This material was found to extend to depths ranging from 2.2 m at Borehole 101 to beyond the termination depths of 5.3, 5.8 and 5.3 m at TP101, 102 and 104, respectively. The material was found to extend to depths ranging from 3.2 m at Borehole 18-4 to beyond the termination depth of 2.0 m at Borehole 18-5.

Standard penetration tests carried out in the fill measured N-values ranging from nil to more than 50 blows/300 mm, the higher values are likely the result of the sampling spoon striking buried obstructions. Mostly, the N-values range from nil to 33 blows/300mm to indicate a range of poorly to moderately well compacted materials. In Boreholes 18-4, 18-16, 18-17, 18-18, 18-19 and 18-22, the poorly compacted sub-unit of the fill was found to lie about 1.5 to 3.6 mbgs. In Boreholes 7, 8, 9, 10 and 11, the poorly compacted sub-unit of the fill layer was found to lie about 1.5 to 2 m below ground surface. In Boreholes 101, 103, 104, 108, 110, the poorly compacted fill layer was found to lie about 0.5 to 4.0 mbgs. It is inferred by the SPT results that these fill soils were loosely placed and lightly compacted.

Fill with some deleterious material to mostly deleterious material and debris is correlated to N-values ranging from 1 to 6 blows/ 300mm which indicate a range of condition from very loose to loose.

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Field vane shear tests carried out in the clayey fill materials measured undrained shear strength values ranging from 19 to more than 117 kPa.

Water content tests carried out on samples of the fill measured values which range between 6% and 52 %;

more typically the water content of the fill ranges between 11% and 28%.

Atterberg limit tests carried out on the clayey soils measured liquid limits between 29 and 31, and plastic limits between 19 and 21; these test results indicate that the materials are of low to intermediate plasticity (CL to CI designation).

5.2.4 Peat

Underlying the fill material at Borehole 7, the exploration contacted a thin layer (about 300 mm thick) of dark brown amorphous peat soil with some fibres. Examination of a sample of this soil showed that the soil has been invaded by overlying heavy concrete or other hard pieces.

5.2.5 Native SILT

Underlying the topsoil layer at Borehole 105, underlying the fill material at Boreholes 103, 104, 106, 18-6, 18-9, 18-11, 18-12, 18-14, 18-21 and 18-28, underlying the silty clay soil (Section 5.2.6) at Borehole 18-10 is a native faintly layered to layered silt with trace to some sand, some clay, trace gravel soil. The silt soil is parted by occasional to frequent clays seams.

Standard penetration tests carried out in the silt soil measured N-values ranging from 4 to 42 blows/300 mm indicating a range of conditions from loose to dense. Loose soils are contacted in Borehole 18-11 in the depth range from 2.8 to 3.4 mbgs and in Borehole 107 in the depth range from 0.8 and 1.5 mbgs; the balance of the N-values indicate a compact to dense soil. The native silt soil was found to extend from a depth of 0.8 mbgs at Borehole 18-09 to the termination depth of 6.7 mbgs at Borehole 103.

Results of water contents tests carried out on samples of the silt soils provided water content values ranging from 12 % to 23 %.

Grain size analyses were carried out on six (6) representative samples; the test results are enclosed in Appendix E as Figure 1 and 2, and summarized in the table below.

Borehole

No. Sample

No. Sample

Description (by gradation)

Gravel

%

Sand

%

Silt

%

Clay

%

103 8 SILT, some sand, trace clay - 18 73 9

105 3 SILT, some clay, trace to some sand - 10 77 13

106 3 SILT, some clay, some sand - 11 76 12

18-6 3 SILT, some clay, trace sand - 7 78 15

18-11 4A SILT, some clay, some sand - 12 73 15

18-14 5 SILT, some clay, trace sand - 1 81 18

Based on the grain size distribution test result, the coefficient of permeability (k value of the silt soil is estimated

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to be about 10^-7 cm/sec; to indicate very low permeability soil.

Atterberg limit tests were carried out on representative soil samples; the results of these tests show that the liquid limit is approximately 23, and the plastic limit is approximately 16, which indicates that the soil can be classified as a silt of low plasticity to clay of low plasticity (ML-CL designation). The clay content is sufficient to impart a weakly plastic behaviour to silt soil. The Atterberg limits are presented on Figure 6 enclosed in Appendix E.

5.2.6 Native SILTY CLAY

Underlying the topsoil at Borehole 105, underlying the fill materials at Boreholes 4, 5, 9, 10, 11, 12, 103, 104, 106, 18-4, 18-17, 18-18, 18-19, 18-21, 18-23, 18-24, 18-25, 18-26, 18-27, 18-29 and underlying the native silt soil at Boreholes 104, 105, 106, 107, 18-6, 18-9, 18-11, 18-12, 18-13, and 18-13 is a native brown and grey silty clay deposit with varying sand and gravel fractions ranging from trace sand to sandy and trace to some gravel.

The silty clay soil is occasionally parted by fissures. The faces of the fissures are observed to be oxidized.

Occasionally, thin silt and fine sand seams are found to part the clays soil. Near surface silty clay soils at Borehole 203 appear to be remoulded, likely the result of construction activity previously carried out at the site. Increasing shale fractions are present in the silty clay soil samples collected near the surface of the underlying shale bedrock. This clay soil has the engineering properties of a hard, stony clay soil.

Standard penetration tests carried out in the silty clay soil measured N-values ranging from 4 to more than 30 blows/300 mm which indicate a range of consistencies from firm to hard. The upper zone of the clay soil deposit at Boreholes 102, 105, 107, 110 and 203 is found to have a firm consistency; below a depth of 2 m the silty clay is stiff to hard. The upper zone of the clay soil deposit at Boreholes 18-04, 18-17 and 18-19 is found to have a stiff consistency; below a depth of 0.8 m the silty clay is very stiff to hard.

The silty clay soil deposit extends to depths ranging from 3.0 m in Borehole 18-27 to the termination depth of 6.3 m in Borehole 18-18.

Water content tests carried out on samples of the silty clay soil from this study range from 10 to 27%. Water content tests carried out on samples of the silty clay soil from previous studies range from 8 to 25%.

Grain size analyses were carried out on four (4) representative samples; the test results are enclosed in Appendix E as Figure 3 and 4, and summarized in the table below.

Borehole

No. Sample

No. Sample

Description (by gradation)

Gravel

%

Sand

%

Silt

%

Clay

%

105 7 SANDY SILTY CLAY some gravel 16 31 33 20

106 5 SANDY SILT CLAY some gravel 19 24 36 21

18-6 4 SILTY CLAY some sand some gravel 14 15 46 25

18-26 4 SILTY CLAY trace sand - 3 63 24

Based on the grain size distribution test result, the k value of the silt soil is estimated to be less than 10^-7 cm/sec;

to indicate very low permeability soil.

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Atterberg limits determined on samples of the silty clay soil; measured liquid limits ranging from 24.5 to 38.1 and plastic limits ranging from 12.0 to 20.7 which indicates a soil character ranging from low to intermediate plasticity (CL and CI designation). The results of these test are presented on Figures 5 and 6.

5.2.7 Weathered Shale, Shaly Clay

Underlying the fill materials and silty clay soils, the boreholes contacted a stratum of grey shaly clay soil to weathered shale bedrock. This represents the upper highly weathered to weathered zone of the bedrock stratum. Included in the upper horizons of the bedrock are occasional clay seams and thin limestone beds.

The shaly clay has the engineering properties of a hard stony clay soil.

Standard penetration tests carried out in the bedrock stratum recorded standard penetration tests N-values of more than 50 blows/300 mm.

The results of water content tests carried out on samples of the shaly clay to shale materials from this study range from 6 to 18%. The results of water content tests carried out on samples of the shaly clay to shale materials from previous studies range from 4 to 11%.

5.3 Groundwater

Summary of the groundwater conditions and cave-in of the sidewalls observed during the advancement of the boreholes from the current investigation are presented in the table below.

Borehole Location(s) Groundwater Depth (mbsg) Groundwater Elevation (mASD) Cave-in of Sidewalls (mbgs)

18-2 Dry - 1.5 18-4 2.8 84.9 5.8 18-6 1.9 85.7 Borehole Open

18-9 3.0 84.4 4.3 18-10 4.4 82.9 Borehole Open

18-17 3.7 84.9 7.0 18-18 3.0 85.0 5.8 18-19 2.3 84.6 Borehole Open

18-21 Dry - 7.3 18-22 3.0 86.8 Borehole Open

18-24 3.3 86.2 5.8 18-25 2.7 86.6 Borehole Open

The balance of the boreholes advanced for this study remained dry and open upon completion of drilling.

In general, groundwater was found to lie at approximate depths between 2.0 and 4.5 mbgs.

Groundwater was contacted in each of the borehole explorations advanced during the 2011 study and the

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rest water level at the time of the study was found to lie at depths ranging from about 3 to 5 m below the existing ground surface.

As part of the 2013 study, monitoring wells were installed in Boreholes 101 through 108. On 22 April 2013, a field technician form Terrapex measured the water levels in the wells. Water levels ranged from 1.5 to 3 m below the existing ground surface in Boreholes 101 to 108. The monitoring well installed in Borehole 107 was found to be dry.

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