August 1, 2013 Reference No S048 Page 1 of 5

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1 August 1, 2013 Reference No S048 Page 1 of 5 Caledon Villas Corp. 55 Blue Willow Drive Woodbridge, Ontario L4L 9E8 Attention: Mr. John Spina Re: Addendum to Soil Investigation for Proposed Residential Subdivision Northeast corner of Old Church Road and Innis Lake Road Town of Caledon Dear Sir: Further to your dated July 16, 2013, attached to which were comments from the Town of Caledon, we have reviewed the Town s comments together with our geotechnical report, Reference No S048, dated March 2012, and provide herewith our response. An updated draft plan, dated July 28, 2013, prepared by Paul A. King Planning Consultant was provided and the Borehole and Monitoring Well Location Plan, enclosed, has been revised to include the updated drawing. This letter/report/certification was prepared by Soil Engineers Ltd. for the account of the captioned clients and may be relied upon by regulatory agencies. The material in it reflects the writer s best judgement in light of the information available to it at the time of preparation. Any use which a third party makes of this letter/report/certification, or any reliance on or decisions to be made based upon it, are the responsibility of such third parties. Soil Engineers Ltd. accepts no responsibility for damages, if any, suffered by any third party as a result of decisions made or actions based on this letter/report/certification.

2 Caledon Villas Corp. Reference No S048 August 1, 2013 Page 2 of 5 Pavement Design The recommended pavement design is given in the following table: Pavement Design Course Residential Driveway Thickness (mm) Local Minor Collector OPS Specifications Asphalt Surface HL-3 HL-3F for driveway Asphalt Binder HL-8 Granular Base mm Crusher-Run Limestone or equivalent Granular Sub-base mm Crusher-Run Limestone or equivalent Stormwater Management Pond It is understood that a stormwater management pond is to be constructed at the location of Borehole 6. Details with regards to the design of the stormwater management pond were not available at the time of the letter preparation. Based on the borehole findings, the subsoils at the proposed pond location generally consist of a layer of topsoil at the surface underlain by strata of loose to dense silty fine sand and compact to dense sandy silt. Cave-in occurred at a depth of 4.0 m in Borehole 6 upon completion of the field work. Therefore, the groundwater appears to lie at a depth of 4.0± m from the prevailing ground surface and will fluctuate with the seasons.

3 Caledon Villas Corp. Reference No S048 August 1, 2013 Page 3 of 5 Due to the relatively pervious to pervious nature of the underlying soils, the water lost and gained from precipitation may have an impact on the effective storage capacity of the pond. In order to minimize this impact, an impermeable geosynthetic membrane, or clay liner, 1.0 m thick, compacted to achieve at least 95% of its maximum Standard Proctor dry density, can be placed at the bottom and sides of the pond above the sand and silt strata. Although a small localized deposit of silty clay was encountered in Borehole 12, this material is unsuitable for clay liner construction due to its high silt content. Due to the lack of suitable material on site for clay liner construction, a geosynthetic clay liner or imported clayey soils will be required. The suitability of the imported soil for clay liner construction should be assessed by a geotechnical engineer and the imported clay must meet acceptable Provincial and Town standards. The extent of the clay liner and the implementation of these measures should be confirmed during construction. The estimated percolation time for the sands and silt is 5 to 30 min/cm. The sides of the pond should be sloped at a minimum of 1 vertical:3 or + horizontal above the water level and flattened to a minimum of 1 vertical:4 or + horizontal below the wet perimeter for stability. The pond should be designed by a Municipal Engineer and the side slopes should be graded to the above recommended gradients for stability and should be designed to meet the Ministry of the Environment (MOE) and Town standards. All the proposed slopes must be vegetated and/or sodded to prevent runoff erosion. Rip-rap should be placed along the wet perimeter to protect against erosion during rapid drawdowns and ripple erosion. Infiltration Trenches It is understood that infiltration trenches will be installed within the proposed subdivision on various lots. A detailed design of the infiltration trenches and a plan

4 Caledon Villas Corp. Reference No S048 August 1, 2013 Page 4 of 5 showing the locations of the trenches were not available at the time of the letter preparation. The borehole findings show that the subsoils throughout the site consist of silty fine sand, sandy silt, fine sand, fine to medium sand and silt with localized deposits of silty sand till and silty clay found at various locations and depths. The silty fine sand, sandy silt, fine sand, fine to medium sand and silty sand till are suitable for infiltration practice, with the estimated coefficient of permeability, K, being 10-2 to 10-4 cm/sec, and the corresponding estimated percolation time, T, being 5 to 20 min/cm. The silt and silty clay are fine-grained soils and are not ideal for infiltration practice; these soils have an estimated coefficient of permeability of 10-4 to 10-6 cm/sec and corresponding estimated percolation time of 20 to over 80 min/cm. An infiltration trench built into these soils will require a larger capacity and should be designed using a percolation time of 80+ min/cm. This should be confirmed by an in situ percolation test to assess the required size of the infiltration trench. Backfill consisting of lumpy excavated silty clay is difficult to compact; therefore, pit-run sand should be used for this purpose. The coefficient of permeability and corresponding estimated percolation time of the subsoils are presented in the following table: Soil Coefficient of Permeability (cm/sec) Percolation Time (min/cm) Silty Fine Sand and Sandy Silt 10-3 to to 20 Fine Sand and Fine to Medium Sand 10-2 to to 12 Silt 10-4 to to 30 Silty Sand Till to 20 Silty Clay

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