DATE December 10, 201 PROJECT No. 10-1121-0260- TO Mary Jarvis Urbandale/Riverside South Development Corporation CC Justin Robitaille, Urbandale Jonathan Párraga, J.L. Richards & Associates Limited FROM Mike Cunningham, P.Eng. EMAIL Mike_Cunningham@golder.com ADDENDUM TO GEOTECHNICAL REPORT (10-1121-0260 REV 1) ADDITIONAL GEOTECHNICAL INVESTIGATION PROPOSED TOWNHOUSE BLOCKS RIVERSIDE SOUTH COMMUNITY DEVELOPMENT PHASE 9-4 PART OF 46 SPRATT ROAD OTTAWA, ONTARIO This memo presents the results of an additional geotechnical investigation carried out for the proposed townhouse blocks (Phase 9-4) to be located in the southern part of Phase 9 of the Riverside South Community in Ottawa, Ontario. It is understood that the proposed development of these blocks will include on-street townhomes, as well as access roads and services within the subdivision. The results of the geotechnical investigation relating to Phase 9 of the development were provided in a report to the Riverside South Development Corporation titled Geotechnical Investigation, Proposed Residential Development, Riverside South Community (Phase 9), Ottawa, Ontario (report number 10-1121-0260 Rev 1) dated November 2012. This memo should be considered as an addendum to that previous report. General The subject area is located southwest of the intersection of Borbridge Avenue and Brian Good Avenue, is rectangular in shape, and measures approximately 200 metres long by 100 metres wide (see attached Site Plan, Figure 1). The site has a relatively flat topography. Based on the geotechnical investigation carried out for the adjacent portion of Phase 9, the subsurface conditions within this part of the site are expected to consist of silty clay overlying glacial till at a depth of about 7 metres or more below the ground surface. Golder Associates Ltd. 2 Steacie Drive, Kanata, Ontario, Canada K2K 2A9 Tel: +1 (61) 592 9600 Fax: +1 (61) 592 9601 www.golder.com Golder Associates: Operations in Africa, Asia, Australasia, Europe, North America and South America Golder, Golder Associates and the GA globe design are trademarks of Golder Associates Corporation.
Mary Jarvis 10-1121-0260- Urbandale/Riverside South Development Corporation December 10, 201 Procedure The field work for this current investigation was carried out on November 1, 201. At that time, two boreholes (numbered 1-101 and 1-102) were put down at the approximate locations shown on the attached Site Plan. Both boreholes were advanced using a track-mounted continuous flight hollow-stem auger drill rig, supplied and operated by Marathon Drilling Company Ltd. of Ottawa, Ontario. Standard Penetration Tests (SPTs) were carried out in the boreholes at regular intervals of depth and samples of the soils encountered were recovered using split spoon sampling equipment. In situ vane testing was carried out where possible in the cohesive deposits to determine the undrained shear strength of these soils. The field work was supervised by an experienced technician from our staff who located the boreholes, directed the drilling operations and in situ testing, logged the boreholes and samples, and took custody of the soil samples retrieved. Upon completion of the drilling operations, samples of the soils encountered in the boreholes were transported to our laboratory for further examination by the project engineer. The borehole locations were selected by Golder Associates. The locations were then established and picketed in the field by Annis, O Sullivan, Vollebekk Ltd. (AOV), who also determined the ground surface elevations relative to Geodetic datum. Subsurface Conditions The subsurface conditions encountered in the boreholes put down for the current investigation are shown on the Record of Borehole sheets in Attachment A. The records from relevant boreholes (boreholes 10-1 and 10-15) put down just north and northeast of this proposed development for the previous investigation by Golder Associates are provided in Attachment B. Based on the results of the current investigation and the results of boreholes 10-1 and 10-15 from the previous investigation, the subsurface conditions on this site generally consist of topsoil overlying layered silty clay, clayey silt, sandy silt and silty sand, over glacial till. Topsoil Topsoil exists at ground surface in all four boreholes and varies from about 20 to 10 millimetres in thickness. Layered Silty Clay, Clayey Silt, Sandy Silt, and Silty Sand Layered deposits of silty clay, clayey silt, sandy silt, and silty sand were encountered in all four boreholes beneath the topsoil. The layered deposits were fully penetrated in two of the boreholes where they extend to depths of about 5.6 and 7.1 metres below the ground surface. In the remaining two boreholes, the deposits were proven to extend to at least about 7. and 8.5 metres below the ground surface. In general, the silty clay and clayey silt layers within the upper 2 to 4 metres of these deposits have been weathered to a grey brown crust with a very stiff to stiff consistency. The silty clay or clayey silt below the depth of weathering is typically grey in colour. The results of in situ vane testing in these deposits gave undrained shear strength typically in the range of 0 to kilopascals, indicating a firm to stiff consistency. The lowest undrained shear strength of about 27 kilopascals was recorded at borehole 10-15, located just northeast of this site. 2
Mary Jarvis 10-1121-0260- Urbandale/Riverside South Development Corporation December 10, 201 The thin deposits of sandy silt and/or silty sand encountered within this site are interlayered within the silty clay and clayey silt and have a very loose to loose state of packing. Glacial Till Glacial till was encountered below the layered deposits at boreholes 10-15 and 1-102 at depths of about 7.1 and 5.6 metres, respectively, below the ground surface. The glacial till generally consists of a heterogeneous mixture of gravel, cobbles, and boulders in a matrix of silty sand to sand, with a trace of clay. DISCUSSION This section of the memo provides engineering guidelines on the grading and foundation for Phase 9-4 based on our interpretation of the borehole information as well as the project requirements. For guidelines on all other geotechnical issues associated with the design, reference should be made to Golder report (10-1121-0260 Rev 1), to which this memo forms an addendum. The guidelines in this memo area also subject to the limitations in the Important Information and Limitations of This Report which follows the text of this memo. Site Grading The subsurface conditions on this site generally consist of layered silty clay, clayey silt, sandy silt, and silty sand overlying glacial till. The softer layered grey silty clay and clayey silt deposits at depth have limited capacity to accept additional load from the weight of grade raise fill and from the foundations of houses without undergoing consolidation settlements. This condition is particularly true for the northeast portion of the site where these deposits are more compressible (near borehole 10-15). Therefore, to leave sufficient remaining capacity for the silty clay and clayey silt to support house foundations, with reasonable footing sizes, the thicknesses of grade raise fill will need to be limited. The following table provides the maximum grade raises which are permitted for the assessment areas within this portion of the site, as indicated on Figure 1. These grade raise limitations have been assessed based on leaving sufficient remaining capacity in the silty clay and clayey silt deposits such that footings up to 0.6 metres in size can be designed using a maximum allowable bearing pressure of at least 75 kilopascals, consistent with design in accordance with Part 9 of the Ontario Building Code. Zone Maximum Permissible Grade Raise (m) C 1.8 D 1.0 It should be noted that these maximum allowable grade raises were calculated assuming that any fill required for site grading (above the original grade) and the backfill within the garages would have a unit weight of no more than 19.5 kilonewtons per cubic metre. Silty clay, clayey silt, sandy silt and silty sand (such as those present on this site), as well as crushed clear stone and uniform fine sand may be suitable for this purpose. Sand and gravel, glacial till, and crushed stone typically have a higher unit weight and, if these materials are to be used, the maximum permissible grade raises would be reduced and would need to be re-evaluated.
Mary Jarvis 10-1121-0260- Urbandale/Riverside South Development Corporation December 10, 201 It should also be noted that for any portions of the site where the structures will need to be designed in accordance with Part 4 of the Ontario Building Code, additional geotechnical investigation and guidelines may need to be provided. As a general guideline regarding the site grading, the preparation for filling of the site should include stripping the topsoil for predictable performance of structures and services. The topsoil is not suitable as engineered fill and should be stockpiled separately for re-use in landscaping applications only. In areas with no proposed structures, services, or roadways, the topsoil may be left in-place provided some settlement of the ground surface following filling can be tolerated. Foundations It is considered that the proposed residences may be supported on spread footings founded on or within the layered deposits of weathered silty clay, clayey silt, sandy silt and silty sand. As discussed in the preceding section, the layered deposits have limited capacity to accept the combined load from site grading fill and foundation loads. The allowable bearing pressures for strip footing foundations are therefore based on limiting the stress increases on the firm and compressible grey silty clay and clayey silt at depth to an acceptable level so that foundation settlements do not become excessive. Four important parameters in calculating the stress increase on the grey silty clay and clayey silt are: The thickness of soil below the underside of the footings and above the firm silty clay and clayey silt; The size (dimensions) of the footings; The amount of surcharge in the vicinity of the foundations due to landscape fill, underslab fill, floor loads, etc.; and, The effects of groundwater lowering caused by this or other construction. Provided that the grade raises are restricted to those indicated above, strip footing foundations up to 0.6 metre in width can be designed using a maximum allowable bearing pressure of 75 kilopascals. As such, the house footings may be sized in accordance with Part 9 of the Ontario Building Code. The post-construction total and differential settlements of footings sized using the above maximum allowable bearing pressure should be less than about 25 and 15 millimetres, respectively, provided that the subgrade at or below founding level is not disturbed during construction. Where the proposed grading approaches, but does not exceed, the permissible grade raise values specified in the preceding section, there is greater potential for settlement. The tolerance of the house foundations to accept those settlements could be increased by providing nominal levels of reinforcing steel in the top and bottom of the foundation walls. Further, the provided maximum allowable bearing pressure for footings founded within the silty clay and clayey silt corresponds to settlement resulting from consolidation of these deposits. Consolidation of the silty clay and clayey silt is a process which takes months or longer and, as such, results from sustained loading. Therefore, the foundation loads to be used in conjunction with the allowable bearing pressure should be the full dead load plus sustained live load. 4
Mary Jarvis 10-1121-0260- Urbandale/Riverside South Development Corporation December 10, 201 ATTACHMENT A Record of Boreholes from Current Investigation 6/7
PROJECT: 10-1121-0260 LOCATION: See Site Plan SAMPLER HAMMER, 64kg; DROP, 760mm RECORD OF BOREHOLE: 1-101 BORING DATE: Nov. 1, 201 SHEET 1 OF 1 DATUM: Geodetic PENETRATION TEST HAMMER, 64kg; DROP, 760mm DEPTH SCALE METRES 0 BORING METHOD GROUND SURFACE SOIL PROFILE DESCRIPTION Black sandy silt with organic matter (TOPSOIL) Very loose grey brown SILTY fine SAND to SANDY SILT STRATA PLOT ELEV. DEPTH (m) 90.05 0.00 89.82 0.2 SAMPLES NUMBER TYPE BLOWS/0.0m DYNAMIC PENETRATION RESISTANCE, BLOWS/0.m 20 40 60 80 SHEAR STRENGTH Cu, kpa nat V. rem V. 20 40 60 80 Q - U - HYDRAULIC CONDUCTIVITY, k, cm/s 10-6 10-5 10-4 10 - WATER CONTENT PERCENT Wp W Wl 20 40 60 80 ADDITIONAL LAB. TESTING PIEZOMETER OR STANDPIPE INSTALLATION 1 Very stiff to stiff grey brown SILTY CLAY (Weathered Crust) 88.98 1 1.07 2 2 1 4 5 Power Auger 200mm Diam (Hollow Stem) Firm grey SILTY CLAY 86.9.66 4 WH 6 5 WH 7 MIS-BHS 001 1011210260.GPJ GAL-MIS.GDT 12/10/1 A.B.D. 8 End of Borehole 9 10 DEPTH SCALE 1 : 81.52 8.5 LOGGED: CHECKED: H.E.C. CK
PROJECT: 10-1121-0260 LOCATION: See Site Plan SAMPLER HAMMER, 64kg; DROP, 760mm RECORD OF BOREHOLE: 1-102 BORING DATE: Nov. 1, 201 SHEET 1 OF 1 DATUM: Geodetic PENETRATION TEST HAMMER, 64kg; DROP, 760mm DEPTH SCALE METRES 0 BORING METHOD GROUND SURFACE SOIL PROFILE DESCRIPTION Black sandy silt, with organic matter (TOPSOIL) Very stiff red brown to grey brown SILTY CLAY (Weathered Crust) STRATA PLOT ELEV. DEPTH (m) 90.58 0.00 90.5 0.2 SAMPLES NUMBER TYPE BLOWS/0.0m DYNAMIC PENETRATION RESISTANCE, BLOWS/0.m 20 40 60 80 SHEAR STRENGTH Cu, kpa nat V. rem V. 20 40 60 80 Q - U - HYDRAULIC CONDUCTIVITY, k, cm/s 10-6 10-5 10-4 10 - WATER CONTENT PERCENT Wp W Wl 20 40 60 80 ADDITIONAL LAB. TESTING PIEZOMETER OR STANDPIPE INSTALLATION 1 Very loose grey brown SILTY fine SAND, trace to some clay 89.28 1.0 1 9 2 Very stiff to stiff grey brown SILTY CLAY (Weathered Crust) 88.45 2.1 2 2 4 Power Auger 200mm Diam (Hollow Stem) Firm to stiff grey SILTY CLAY 86.92.66 >96 5 4 WH 6 Compact grey SILTY SAND, some gravel, trace clay, with cobbles and boulders (GLACIAL TILL) 85.02 5.56 5 11 7 6 26 End of Borehole 8.11 7.47 MIS-BHS 001 1011210260.GPJ GAL-MIS.GDT 12/10/1 A.B.D. 8 9 10 DEPTH SCALE 1 : LOGGED: H.E.C. CHECKED: CK
Mary Jarvis 10-1121-0260- Urbandale/Riverside South Development Corporation December 10, 201 ATTACHMENT B Record of Boreholes from Previous Investigation 7/7