site investigation report - abbg.com.au geotechnical report.pdf · 2017. 4. 21. · report es1662.1...

GEOTECHNICAL ASSESSMENT

SITE: 35 Wait-A –While Rd. Wyelangta, Victoria. 3237 DEVELOPER; Archier Architecture. REPORT NUMBER; ES1662.1 DATE; 18/07/16 REPORTING TO; COLAC OTWAY SHIRE Planning Scheme, Erosion Management Overlay Procedures (EMO), 2013. Amendment C68

2020Engineering Solutions

1745 Colac – Forrest Rd

Colac. Vic. 3249

Ph 0428 141441 Fx (03)5233 4608

ABN 57 215 499 312ACN 11 9460 865

www.2020es.com

REPORT ES1662.1 2020 ENGINEERING SOLUTIONS ACN 11 9460 865

www.2020es.com of 18 www.2020es.com

CONTENTS Executive Summary Succinct Recommendations Preamble 1.0 Consultant 1.1 Details of Qualifications, Experience and Expertise 1.2 Specific Expertise 1.3 Equipment 2.0 Date of Assessment 2.1 Reporting Date 3.0 Site Description 3.1 Address 3.2 Title Details 3.2.1 Property Owner 3.3 Developer 3.4 Responsible Authority 3.4.1 Planning Details 4.0 Site Assessment Plans 5.0 Surface Conditions 5.1 Subsurface Conditions 5.2 Geology 5.3 Groundwater 6.0 Regional Instability 6.1 Mapped 6.2 Unmapped 7.0 Assessment Methodology 8.0 Additional Investigation : Fig 1 Basic Model, Fig 2 Circular Model, Fig 3 Block Analysis 9.0 Risk Analysis 9.1 Probability Analysis 9.1.1 Spatial Analysis 9.2 Consequence Analysis 9.3 Vulnerability Analysis 9.4 Calculated Risk 10.0 Development Conditions 10.1 Footing structure and Foundation Materials 10.2 Cut and Fill Earthworks 10.3 Soil Retention Structures 10.4 Drainage 10.5 Building Design and Structural System 10.6 Vegetation 10.7 Wastewater Management 10.8 On-going Maintenance and Mitigation Measures 10.9 Development Timeframe 10.10 Additional Geotechnical Requirements 11.0 Landslip Risk Assessment Statement 12. Report Recommendations 13. Report Restrictions 14. Professional Compliance Statement 15. Controlling and Referenced Documents 16. Site Plan (Kris Thomas Building Design 17. Geology and Topography Map 18. Landslide Inventory Map 19.Geotechnical Declaration 20.Report Limitations



Executive Summary Gives annual risk to life of 1.0 x 0.5 x 0.3 x 10-5 = 1.5 x 10-7 This figure is below the advised Acceptable Limit. Property Risk would be Low. This figure is below the advised Acceptable Limit for existing slopes. Succinct Recommendations a) The proposal be allowed as the calculated risk is within the acceptable range. b) A Landslide Risk Assessment is not required. Preamble Note; This document reports to Schedule One to the Erosion Management Overlay as in operation at the time of commissioning. Amendment C68 to the Planning Scheme was introduced 31 Jan. 2013. The Shire contains areas of land that are susceptible to landslip..... In areas susceptible to landslips, it is necessary to assess the potential impact of buildings, works and vegetation removal on the environment, in order to minimise risk to life and property. (EMO Policy Basis) The basic proposal, as outlined in the Planning Application, is for the construction of a dwelling replacing an existing habitable structure. This report considers the geotechnical implications of the proposal with respect to the adjoining dwelling, surrounding landscape and existing site conditions.



1.0 Consultant Michael Daniel Delahunty ‘Culliamurra’ 1745 Colac – Forrest Road Colac, Victoria. Australia. 1.1 Details of Qualifications, Experience and Expertise Bachelor Degree in Mining Engineering University of Ballarat. 2001-2003 Civiltest, Geotechnical technologist 2006- to current 2020Engineering Solutions P/L Managing Director, Principal Engineer Member Institute of Engineers Australia Member # 2274072 1.2 Specific Expertise Over the past sixteen years I have personally conducted several hundred site and soil investigations across SW Victoria. This work, along with academic qualifications, has equipped me with an understanding of typical and atypical sub-soil conditions. The author has valid professional indemnity insurance at the time of inspection and reporting. As part of a commitment to on-going professional development the author is undertaking the process of accreditation and attainment of chartered status. 1.3 Equipment Kobelco 007 hydraulic mounted auger General Laser Level C60X Garmin GPS Samsung Camera 2.0 Date of Assessment 02rd Mar 2016 2.1 Reporting Date 29nd Mar 2016 18th July 2016



3.0 Site Description The general region comprises an elevated, moderately sloping hillside with a SE aspect. The proposed building envelope is located on a low angle portion of a broad spur ridge, in a grassed area upslope of an orchard. 3.1 Address 35 Wait-a-While Rd. Wyelangta, Victoria. 3.2 Title Details SPI 20A~B\PP3919 3.2.1 Property Owner Client of Archier Architecture 3.3 Developer Archier Architecture 3.4 Responsible Authority Colac Otway Shire Rae St. Colac Vic. 3250 3.4.1 Planning Details Planning Application; TBA Proposal; Construction of a dwelling 4.0 Site Assessment Plans Attached 5.0 Surface Conditions As noted in 3.0 the site adjoins an existing orchard and comprises, open, cleared, managed grazing land.



5.1 Subsurface Conditions From the site investigation the sub-surface contained a weathered in-situ Silty Sand over a Silty Clay which tended to Sandstone causing auger refusal at 3.0m. 5.2 Geology Published maps indicate the area is located in a region of Cretaceous Age sediments of the Eumeralla Formation which is part of the Otway Group. 5.3 Groundwater Groundwater and/or issues developing from pore water pressure are not anticipated to generate significant instability hazards, however storm water, roof water and waste water, (ES1661), will need careful disposal. 6.0 Regional Instability 6.1 Mapped Inventory of Landslides, Colac Otway Shire Map, does not indicate any mapped slip systems on or within impact distance of the proposed building site. 6.2 Unmapped As noted in Section 5.1, in the opinion of the author, the site contains minimal indicators of instability or ground movement. 7.0 Assessment Methodology Given the extent of the subject land under investigation the principal assessment tool was visual, with GPS derived elevations and subsurface profiling. The following computer analysis is performed using RocScience Slide V6 and field derived or typical material properties.



8.0 Additional Investigation Computer Stability Analysis

Figure 1. Basic model of slope, incorporating footing loads and seismic factor.

Figure 2. Circular analysis of modelled slope. Comment; Not surprisingly the indicated stability decreases with the steepness of the surface and underlying landform but as indicated in the model this is physically a fair distance from the proposed building envelope.

2.0182.018

50.00 kN/m2

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Figure 3. Block Analysis of slope model. Comment; Both analysis indicate the portion of the slope with the lowest factor of safety is the landform downslope of the development and proposed development. The analysed slip circles under the building envelope returned a significant Factor of Safety. 9.0 Risk Analysis Based upon the observed conditions, the foregoing analysis and with respect to the 10 failure types, the author considers there to be no plausible mode of failure to affect the proposed development, however a generic event will be used for the following analysis. 9.1 Probability Analysis Rare, 10-5, an event might occur over the design life, under very adverse circumstances. In this geology and slopes at this angle, slip events throughout the district are highly unusual but could involve movement within the underlying clay/sandstone. Such an event would remove support from foundations causing collapse. 9.1.1 Spatial Analysis As the proposal is for a dwelling spatial exposure will be taken as unity. 9.2 Consequence Analysis Life; 0.5 Injury,. Property; Major, 60%

1.9671.967

50.00 kN/m2

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9.3 Vulnerability Analysis Life; 0.3 Property; 1.0 If event occurs building cannot move away. 9.4 Calculated Risk Gives annual risk to life of 1.0 x 0.5 x 0.3 x 10-5 = 1.5 x 10-7 This figure is below the advised Acceptable Limit. Property Risk would be Low. This figure is below the advised Acceptable Limit for existing slopes. 10.0 Development Conditions From the borehole the material can be expected to display good stand-up time. 10.1 Footing structure and Foundation Materials Conventional into Clay 10.2 Cut and Fill Earthworks Earth works should only be to the minimum. 10.3 Soil Retention Structures Structures for soil retention are not recommended. Cut and fill batters should be vegetated with deep rooted perennial grass species, especially on the mounds. 10.4 Drainage Excess roof water to be directed to a suitable legal point of discharge, downslope and away from the proposed structure/s. 10.5 Building Design and Structural System Conventional as per ES1660 Site Classification.



10.6 Vegetation At the time of inspection the subject land contained a grassed grazing area with small trees in a plantation located to the south. No vegetation is scheduled for removal. 10.7 Wastewater Management As per ES1663. 10.8 On-going Maintenance and Mitigation Measures This report does not recommend specific on-going erosion mitigation measures apart from general good practice and diligence in the maintenance of plumbing fixtures. 10.9 Development Timeframe There is no geotechnical timeline for this development 10.10 Additional Geotechnical Requirements Additional geotechnical requirements will be detailed in the recommendation section. 11.0 Landslip Risk Assessment Statement In the opinion of the author a Landslip Risk Assessment is not required due to the low risk to property and low risk to life. 12. Report Recommendations a) The proposal be allowed as the calculated risk is within the acceptable range for existing slopes. 13. Report Restrictions Should the final proposal differ substantially from the assessed proposal, the testing and resultant recommendations, may not be valid. It also assumes the ‘as tested’ conditions are consistent across the site. If this is not the case, the client would be advised to contact the author, should encountered conditions vary from those reported. 2020Engineering Solutions takes no responsibility for errors or omissions contained in sourced material. This report should be read in entirety and not selectively reproduced.



14. Professional Compliance Statement The author has valid professional indemnity insurance at the time of inspection and reporting. As part of a commitment to on-going professional development the author is undertaking the process of accreditation and attainment of chartered status. 15 Controlling and Referenced Documents; AS1726-1993 (incorporating amendments to #2-1994) AS4360-2005 Risk Management Set AS4200-2000 General Conditions of Contract for Engagement of Consultants AS2870-2011 Residential Slabs and Footings Colac Otway Shire Planning Scheme, Erosion Management Overlay Procedures (EMO) Schedule 1 Geographic Information System (GIS) Data base Geological Survey of Victoria (GSV) Colac 7621-3 Zone 54 1:50,000 Map Series Tickell S.J. 1990. Report 103 (Department of Agriculture, Energy and Minerals) Australian Geomechanics Vol 42 No.1 March 2007. 2020ES JSA 01.23.02.16 www.dse.vic.gov.au



Section 16 a. Site Plan



Section 16 b. Floor Plan



Section 17. Geology & Topography Map



Section 18. Landslide Inventory Map



Section 19.Geotechnical Declaration



Section 20.Report Limitations