Terraprobe Consulting Geotechnical & Environmental Engineering Construction Materials Engineering, Inspection & Testing

Transcription

1 Terraprobe Consulting Geotechnical & Environmental Engineering Construction Materials Engineering, Inspection & Testing PRELIMINARY SUBSURFACE INVESTIGATION TTC LFLRV MAINTENANCE & STORAGE FACILITIES LAKESHORE BLVD. E. & LESLIE STREET TORONTO, ONTARIO Prepared For: AECOM 300 Water Street Whitby, ON L1N 9J2 Attention: Mr. Joe Peristy File No October 1, 2009 Terraprobe Limited Distribution of Report: 2 copies - AECOM 1 copy - Terraprobe Limited Terraprobe Limited 10 Bram Court 220 Bayview Drive, Unit Kelly Lake Rd., Unit Barton Street, Unit 22 Brampton, Ontario L6W 3R6 Barrie, Ontario L4N 4Y8 Sudbury, Ontario P3E 5P4 Stoney Creek, Ontario L8E 5P5 (905) Fax: (705) Fax: (705) Fax: (905) Fax:

2

3 AECOM October 1, 2009 TTC LFLRV Maintenance & Storage Facilities, Toronto, ON File No TABLE OF CONTENTS 1.0 PROJECT DESCRIPTION AND SCOPE OF WORK SUBSURFACE CONDITIONS Stratigraphy Surface Materials Earth Fill Organic Silt Sand and Sand and Gravel Silty Clay Glacial Till Bedrock DISCUSSION Excavation Fill and Soil Quality Ground Water Quality Summary LIMITATIONS AND USE OF REPORT Procedures Use of Report Appendices: Appendix A - Borehole Logs 1 to 3 and A to H, and Test Trench Logs 1 to 4 Appendix B - Certificate of Chemical Analysis Tabulation to Table No. 1 Appendix C - Certificate of Chemical Analysis Tabulation to Table No. 3 (Soil) Appendix D - Certificate of Chemical Analysis Tabulation to Table No. 1 & 3 (Water) Appendix E - Summary of Field Investigation Protocol Figures: Figure 1 - Site Location Plan Figure 2 - Borehole and Test Trench Location Plan Figures 3 to 6 - Test Trench Plans and Profiles Photographs Terraprobe Oct TD-10_12-Prelim SUB Invest.wpd Page No. i

4 AECOM October 1, 2009 TTC LFLRV Maintenance & Storage Facilities, Toronto, ON File No PROJECT DESCRIPTION AND SCOPE OF WORK Terraprobe Limited was retained by TTC through AECOM to carry out a preliminary subsurface investigation at the potential site for a TTC LFLRV Maintenance and Storage Facility, 9 Leslie Street in Toronto, Ontario. The site is vacant land on the northwest corner of the Ashbridges Bay Waste Water Treatment Plant. A site location plan is provided on Figures 1 and 2. Most of the property is currently occupied by a fill mound of approximately 15 m height. The site is generally covered with grasses. The development of the site requires the removal of the large mound of fill from the property. The volume of fill requiring removal is estimated as 455,000 m 3. The purpose of the investigation was to characterize the stratigraphy of the fill mound and the soil below. The investigative effort comprised 11 boreholes and 4 test trenches used to sample and visually assess the fill. The investigative work was carried out from August 6 to 14, 2009; and on September 18, The test trenches are denoted as T1 through T4. The boreholes are denoted as A through H, and 1 through 3. Monitoring wells were installed in three selected boreholes (D, H and 3) to permit sampling of ground water quality. Generally, Boreholes A through H were drilled through the fill mound. Boreholes 1, 2 and 3 were drilled at the northwest corner of the property, away from the fill mound. This document presents the findings of the subsurface investigation. This document contains preliminary information which is intended for initial planning and feasibility purposes. Further, more detailed studies and engineering consultation will be required as the project proceeds. Terraprobe Oct TD-10_12-Prelim SUB Invest.wpd Page No. 1

5 AECOM October 1, 2009 TTC LFLRV Maintenance & Storage Facilities, Toronto, ON File No SUBSURFACE CONDITIONS The procedures used for the investigation, collection and handling of samples are documented in Appendix E. The borehole and test trench locations are shown on Figure 2. The detailed results of the individual boreholes and test trenches are recorded on the Borehole and Test Trench Logs in Appendix A. The ground surface elevations at the borehole locations have been referenced to a geodetic datum. 2.1 Stratigraphy Surface Materials Topsoil was penetrated at the ground surface in all borehole locations except Borehole C. The thickness of the topsoil layer varied from about 130 mm to 180 mm. The topsoil is dark brown to black in colour with a sandy silt matrix Earth Fill Beneath the topsoil layer, earth fill was penetrated to depths of 7.6 to 19.8 m below existing grade at the locations of Boreholes A through H (i.e., on the fill mound). At the locations of Boreholes 1 through 3 (away from the fill mound), the thickness of fill ranged from approximately 2.3 to 6.1 m. The earth fill comprises loose to dense sand, silty sand and sandy silt with clayey silt layers/pockets. The earth fill contains varying amounts of wood, glass, paper, cardboard, plastic, rubber, brick and concrete debris/rubble mixed with dark grey/black organic matter. The test trench excavation revealed large pieces of concrete, block, timber, clay pipe, rebar and tires. Evidence of ash, coal, and peat were found in the lower parts of the mound. The fill is generally dark grey to black and within certain horizons there are hydrocarbon odours. Based on the results of the borehole and test pit investigation, it appears that the fill consists mostly of a matrix of common earth (silty sand to clayey silt) mixed with varying amounts of building rubble and debris. The material is extremely variable in both physical composition and consistency. The fill depths are tabulated as follows: Borehole Existing Ground Surface Elev. (m) Depth of Fill (m) Approx. Base of Fill Elev. (m) A B C Terraprobe Oct TD-10_12-Prelim SUB Invest.wpd Page No. 2

6 AECOM October 1, 2009 TTC LFLRV Maintenance & Storage Facilities, Toronto, ON File No Borehole Existing Ground Surface Elev. (m) Depth of Fill (m) Approx. Base of Fill Elev. (m) D E F G H Figures 3 to 6 inclusive provide the results of the test trench works. Selected photographs illustrate the nature of the earth fill and inclusions as revealed by the test trenches Organic Silt Beneath the earth fill layer, organic silt was penetrated at depths of 7.6 to 19.8 m below existing grade in all boreholes except Borehole A. Borehole A reached auger refusal in the earth fill material at a depth of 13.4 m below grade and did not reach the silt layer. The organic silt was greyish brown, generally loose or soft, and high in moisture content which is indicative of material of organic content Sand and Sand and Gravel The organic silt was underlain by a layer of sand and sand and gravel at a depth of 21.3 m below grade in the Borehole B location. This cohesionless soil deposit was greyish brown, dense to very dense and wet Silty Clay Glacial Till The sand layer in Borehole B was underlain by silty clay glacial till. This deposit has a predominantly silty clay matrix with embedded sand, gravel, cobbles and boulders. The till had a hard/dense consistency Bedrock The glacial till is underlain by bedrock of the Georgian Bay Formation. The bedrock of the Georgian Bay Formation is a deposit predominantly comprised of thin to medium bedded grey shale. Terraprobe Oct TD-10_12-Prelim SUB Invest.wpd Page No. 3

7 AECOM October 1, 2009 TTC LFLRV Maintenance & Storage Facilities, Toronto, ON File No Ground Water Observations pertaining to the depth of water level were made in the open boreholes immediately after completion of drilling. Observation wells were installed in Boreholes D, H and 3. The water level measurements taken in the open boreholes and observation wells are summarized as follows: Borehole No. Existing Ground Surface Elev. (m) Depth of Borehole (m) Upon Completion of Drilling Depth to Cave (m) Depth to Water (m) Water Level in Monitoring Well Depth to Water (m) Elev. to Water (m) A NW NW B n/a n/a NW NW C Wet cave at 12.5 n/a NW NW D E NW NW F NW NW G NW NW H NW NW NW NW Open Terraprobe Oct TD-10_12-Prelim SUB Invest.wpd Page No. 4

8 AECOM October 1, 2009 TTC LFLRV Maintenance & Storage Facilities, Toronto, ON File No DISCUSSION The following discussion is provided for preliminary planning and feasibility purposes. This discussion is provided based on our current understanding of the project. We understand the project will generally involve removal of the existing fill mound at site, and construction of the facility. The facility will consist of a large, flat yard area for access and maintenance of light rail vehicles. A large, slab-on-grade maintenance building will also be constructed. It is anticipated that the existing fill mound will be removed, and the site grades will be similar to the existing street grades on adjacent Lakeshore Boulevard and Leslie Street. Excavations will generally not extend more than 3 m below the adjacent street grades. Excavations will generally be limited to the installation of underground utilities and services. A fill berm or mound of several metres height will be left in place along Lakeshore Boulevard as a buffer. 3.1 Excavation Excavations must be carried out in accordance with the Occupational Health and Safety Act and Regulations for construction projects. These regulations designate four broad classifications of soils to stipulate appropriate measures for excavation safety. For practical purposes all of the material found on the site is a Type 3 soil where it is above the ground water, and it is a Type 4 soil where it is below the ground water. Where workmen must enter a trench or excavation deeper than 1.2 m, the trench or excavation must be suitably sloped and/or braced in accordance with the regulation requirements. The regulation stipulates maximum slopes of excavation by soil type as follows. Soil Type Base of Slope Maximum Slope Inclination 3 from bottom of trench 1 horizontal to 1 vertical 4 from bottom of trench 3 horizontal to 1 vertical Minimum support system requirements for steeper excavations are stipulated in Sections 235 through 238, and 231 of the Act and Regulations, and include provisions for timbering, shoring and moveable trench boxes, where sloped excavation slopes cannot be used. It is noted the above recommendations apply to relatively shallow excavations (typically less than 3 m below the surrounding grade). As a result of the soft/loose nature of the fill and organic materials at the site, special considerations will apply to deeper excavations. In addition, excavations conducted directly adjacent to the fill mound will require special consideration to ensure their stability. Terraprobe Oct TD-10_12-Prelim SUB Invest.wpd Page No. 5

9 AECOM October 1, 2009 TTC LFLRV Maintenance & Storage Facilities, Toronto, ON File No Fill and Soil Quality Thirty-six samples of soil were analysed to assess soil quality. The samples were analysed for a range of parameters which may be indicative of impact found in fill materials in the Toronto area. These include: Petroleum hydrocarbons Metal and inorganic parameters Volatile organic compounds Polyaromatic hydrocarbons PCB The laboratory results were compared to the Soil and Sediment Standards found in Ontario Regulation 153/04. The results were compared to the following Standards: Table 1 Standard. This generally represents the most strict Standard for soil quality in the regulation. Soil meeting Table 1 is chemically suitable for use as fill material under almost all circumstances and for all sites. Table 3 (Residential) Standards. Soil meeting the Table 3 Standards is chemically suitable for use as fill on most properties within the GTA. Soil which exceeds the Table 3 Standards is generally not suitable for fill in the GTA. Typically, soil which exceeds the Table 3 Standards must be treated as a waste material and disposed of at an approved fill management or waste disposal site. The results of the analysis are presented as follows: Appendix B. Results are tabulated relative to Table 1 Standards. Appendix C. Results are tabulated relative to Table 3 (Residential) Standards. The results indicate that the fill materials at the site consistently exhibit exceedances of the Tables 1 and 3 Standards. These exceedances are most frequently for metals, polyaromatic hydrocarbons, and occasionally for petroleum hydrocarbons. There were a few exceedances for volatile organic compounds. It is noted that some of the samples assessed for VOC were retained longer than the stipulated holding time before analysis because of a delay in the site drilling and sorting of the samples. The results for these samples are for discussion purposes only and are not definitive. The most frequent exceedances for metals included lead and zinc, while the most frequent exceedance for polyaromatic hydrocarbons was benzo(a)pyrene. PCB compounds were not detected. Eleven of the soil samples submitted to the laboratory and found to contain elevated concentrations of metals were assessed by the TCLP method in accordance with the requirements of O.Reg.558. The results are Terraprobe Oct TD-10_12-Prelim SUB Invest.wpd Page No. 6

10 AECOM October 1, 2009 TTC LFLRV Maintenance & Storage Facilities, Toronto, ON File No presented on Page 6 of 27 of the Certificate of Analysis, Appendix C. None of the samples assessed was characterized as hazardous waste on the basis of this testing. The investigation did not include significant characterization of the quality of the underlying native soil. Further investigation is required to determine potential impact to the underlying soil. However, it is noted that fill materials will likely be found below the finished grade elevation of the site. It is likely that removal of all the fill material, down to the non-impacted native soil, will be a costly exercise. It is expected that impacted fill materials will remain on the site, and that a Risk Assessment will be required to demonstrate that the site can be safely developed for the intended purpose. For preliminary planning purposes, it should be assumed that a clean soil layer not less than 1.5 m thick will have to be made at the surface of the site, and that a thicker replacement may be desirable in buried utility corridors so that any future work on the utilities does not expose workers to the impacted soil. 3.3 Ground Water Quality Samples of ground water were obtained from the monitoring wells installed in Boreholes D, H and 3. The samples were analysed for metals and other inorganic parameters, petroleum hydrocarbons F1 to F4, volatile organic compounds, PAH and PCB. There were no significant exceedances of the Table 3 Standards for the parameters measured. It is noted that the ground water characterization is preliminary and that further sampling must be conducted to provide stabilized ground water chemistry. Based on the current information, it appears that ground water quality will not be a significant constraint with respect to the occupancy of the site. However, additional ground water quality characterization must be conducted to determine potential requirements for disposal of ground water which may enter excavations during construction, and/or for long-term drainage of ground water from the site through backfill or subsurface utilities. 3.4 Summary In summary, the results of the preliminary investigation indicate the following: There is a large mound of fill found on the property. The fill appears to extend below the elevation of the surrounding street grades at Leslie Street and Lakeshore Boulevard. The fill consists of a mixture of common earth with significant amounts of building debris and rubble. Terraprobe Oct TD-10_12-Prelim SUB Invest.wpd Page No. 7

11 AECOM October 1, 2009 TTC LFLRV Maintenance & Storage Facilities, Toronto, ON File No The fill generally exceeds the Table 3 Standards for a range of parameters including various heavy metals, PAH compounds, and hydrocarbons. Testing conducted to date indicates the fill is a non-hazardous waste material. The native soils underlying the fill consist of soft/loose organic silt. Competent soils and bedrock are found at depths of approximately 15 m or more below the proposed finished site grades. Based on the limited testing conducted to date, there appears to be no significant impact to the ground water quality at the site. The site conditions will pose significant constraints and expense to site development. The following issues must be addressed as part of site development: The fill materials at the site must be removed from the property. The fill must be removed as a waste material. Further characterization is required to assess the fill material. There is a significant potential that at least portions of the fill material may be categorized as a hazardous waste. This would likely require the material be stabilized before off-site disposal. Fill material will remain at the site below the elevation of the proposed site grades. Complete removal of the fill material is likely expensive and prohibitive. In lieu, consideration should be given to conducting a Risk Assessment for the property. A Risk Management Measure will be required to isolate the fill. Typically the Risk Management Measure will consist of a cap of clean soil over the property. Underground utilities would also be buried within a clean soil fill zone. The consistency of the fill, and the soft, loose organic silt materials will pose geotechnical constraints to site development. However, the presence of the fill mound has resulted in considerable pre-loading of the fill and native soils. On this basis, the subgrade conditions at the site will likely be suitable for pavement and rail systems, with some special considerations. Buildings or other large or heavy structures will likely require support on deep foundations carried down to the dense, native soils or bedrock. A significant portion of the cost of development will be for the off-site removal and disposal of the fill materials at the site. Additional studies are required to characterize the fill materials and determine the most appropriate and cost-effective methods for off-site disposal. Terraprobe Oct TD-10_12-Prelim SUB Invest.wpd Page No. 8

12 AECOM October 1, 2009 TTC LFLRV Maintenance & Storage Facilities, Toronto, ON File No LIMITATIONS AND USE OF REPORT 4.1 Procedures This investigation has been carried out using investigation techniques and engineering analysis methods consistent with those ordinarily exercised by Terraprobe and other engineering practitioners, working under similar conditions and subject to the time, financial and physical constraints applicable to this project. The drilling work and trenching were carried out by a drilling and an excavating contractor under the fulltime supervision of a Terraprobe technician. The borings were made by a continuous flight power auger machine using solid and hollow stem augers as appropriate to secure samples. The supervising technician logged the borings and test trenches and examined the samples as they were obtained. The samples obtained were sealed in clean, air-tight containers and transferred to the Terraprobe laboratory where they were reviewed for consistency of description by a geotechnical engineer. Ground water observations were made in the boreholes as drilling proceeded. Water levels were also assessed in the monitoring wells installed as part of these works. The samples of the strata penetrated were obtained using the technique Split-Barrel Method, ASTM D1586. The samples were taken at intervals. The conventional interval sampling procedure used for this investigation does not recover continuous samples of soil at any borehole locations. Consequently, there is some interpolation of the borehole layering between samples and indications of changes in stratigraphy, as shown on the borehole logs, are approximate. A comprehensive sampling and testing program implemented in accordance with the most stringent level of care may fail to detect certain conditions. Terraprobe has assumed, for the purposes of providing design parameters and advice, that the conditions that exist between sampling points are similar to those found at the sample locations. It may not be possible to drill a sufficient number of boreholes or sample and report them in a way that would provide all the subsurface information that could affect construction costs, techniques, equipment and scheduling. Contractors bidding on or undertaking work on the project should be directed to draw their own conclusions as to how the subsurface conditions may affect them, based on their own investigations and their own interpretations of the factual investigation results, cognizant of the risks implicit in the subsurface investigation activities. Terraprobe Oct TD-10_12-Prelim SUB Invest.wpd Page No. 9

13

14

15 APPENDIX A TERRAPROBE LIMITED

16

17

18

19

20

21

22

23

24

25

26

27

28

29

30

31

32

33

34

35

36

37

38

39

40

41

42

43

44

45

46

47

48

49

50

51

52

53 APPENDIX B TERRAPROBE LIMITED

54

55

56

57

58

59

60

61

62

63

64

65

66

67

68

69

70

71

72

73

74

75

76

77

78

79

80

81

82

83

84

85

86

87

88

89

90

91

92

93

94

95

96

97

98

99 APPENDIX C TERRAPROBE LIMITED

100

101

102

103

104

105

106

107

108

109

110

111

112

113

114

115

116

117

118

119

120

121

122

123

124

125

126

127

128

129 APPENDIX D TERRAPROBE LIMITED

130

131

132

133

134

135

136

137

138

139

140

141

142

143

144

145

146