Chapter 7. Topography, geology, soils and groundwater. Chapter 7

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1 Chapter 7 Topography, geology, soils and groundwater Chapter 7

2 7.0 Topography, geology, soils and groundwater 7.1 Introduction and approach A detailed assessment of the existing topographic, geological, soil and groundwater values of the study area and the project s potential impacts on these values is provided in Technical Paper 1 in Volume 2 of the revised assessment report. A summary of the major findings of Technical Paper 1 is provided below Topography, geology, soils and contaminated land The impact assessment review for topography, geology, soils and contaminated land has been undertaken as a desktop study of available information. The assessment aims to identify existing environmental conditions, potential impacts from the construction and operation of a railway along the preferred alignment and to provide suitable mitigation measures. The methodology included: review of published geological maps and memoirs, to establish the geological setting of the project detailed aerial photograph interpretation (API), and study of the digital terrain model to establish the extent and nature of the geomorphological regimes for the study corridor, as well as to identify potential preexisting contaminating activities review and collation of relevant geotechnical data from previous studies of the area review of current land uses within the proposed rail corridor for potential contaminating activities search of registered service station location databases review of the Department of Defence (Defence) Unexploded Ordnance (UXO) mapping review of the Department of Environment and Resource Management (DERM) Area Management Advice (AMA) review of the DERM Environmental Management Register (EMR) and Contaminated Land Register (CLR) creation of detailed engineering-geological maps of the study corridor Applicable Standards included: AS : Geotechnical Site Investigations AS : Method of testing soils for engineering purposes Draft Guidelines for the Assessment & Management of Contaminated Land in Queensland May 1998 AS : Minimum design loads on structures (known as the SAA Loading Code) - Earthquake loads AS : Structural design actions - Earthquake actions in Australia Queensland Acid Sulfate Soil Technical Manual, Soil Management Guidelines Environmental Protection Act 1994 (Part 8 Contaminated Land) Industry Standard Contaminated Construction Sites (2005). EPA Victoria Standards Australia (2004) Australian Standard. The Storage and Handling of Flammable and Combustible Liquids. AS Standards Australia (1994) Australian Standard. The Storage and Handling of Corrosive Substances. AS Transport and Main Roads, March

3 7.1.2 Groundwater The impact assessment review for groundwater has been undertaken as a desktop study of available information. The assessment aims to identify existing environmental conditions, potential impacts from the construction and operation of a railway along the preferred alignment and to provide suitable mitigation measures. Information required for the assessment of groundwater hydrology within the study area was acquired from DERM and included: groundwater vulnerability data existing borehole locations and associated historical groundwater data stratigraphy and aquifer details local geological and topographical mapping acid sulfate soils (ASS) data Assessment of this information has revealed a current lack of groundwater data representative of the area extending eastwards from Warrill Creek to the end of the study area. As such, there is a need for further groundwater investigation within the study area prior to the commencement of construction. Consequently, discussion of the existing groundwater environment, potential impacts and mitigation measures herein is based solely on currently available information. 7.2 Description of environmental values Topography The topography of the major landscape features of the study area reflects the underlying geology. This consists of a central anticline; the South Moreton anticline, in which the Triassic-Jurassic Bundamba and Marburg Group sandstones are exposed. The South Moreton anticline is flanked by complementary synclines containing the Jurassic Walloon Coal Measures and Tertiary sedimentary and igneous rocks. The rocks of the anticline form rugged hills, while the flanking synclines give rise to gently undulating lowlands (see Map 1.1, Figure 38). Transport and Main Roads, March

4 Figure 38 View east from the lowlands near Purga to the mountain range, including Flinders Peak and Ivory s Rock Geology The study area is a typical sub-coastal area of southern Queensland. The landscape of the corridor can be divided into three main areas; the Beaudesert Basin to the east, the central ranges and the western lowlands (see Map 1.2). The topography of these major landscape features are a reflection of the underlying geology, which consists of a central anticline, forming rugged sandstone hills, while the flanking synclines containing coal, sedimentary and igneous rocks, give rise to gently undulating lowlands. Soil distribution and physical properties indicate that parent material strongly influences soil development in the area Soils Soil mapping indicates that parent material strongly influences soil development in the area (Map 1.3). Podzolics and solodics are confined to areas of coarse-grained quartzose sediments, acid igneous rocks and areas of sandy alluvium. Prairie soils, black earths, and grey clays have developed on the finer-grained sediments, the more basic igneous rocks, and the main development of valley alluvium. Lithosols are dependent on topography and are found only on the steepest slopes; however parent material differences are evident in the texture of the soil. Along the western boundary of the Logan valley deep quartz-rich sands occur where the stream gradients have suddenly decreased, depositing thick layers of coarse sediments. Such soils are too immature to reflect soil-forming processes. Section identifies that preliminary field observations highlighted evidence of erosion on some riparian banks throughout the study area, primarily due to stock movement and access Contaminated land Of the 514 identified lots searched on the EMR/CLR database, twenty-four (24) were recorded on the EMR, while none were listed on the CLR (see Map 1.5). Of these 24 lots listed on the EMR, 15 were listed for Transport and Main Roads, March

5 operating a livestock dip or spray race facility, while other notifiable activities included hazardous contaminants (five lots), fertiliser manufacture (two lots), petroleum product or oil storage (one lot), and Area Management Advice for UXO (one lot). A review of Defence UXO mapping shows that a 1km buffer area either side of the revised alignment incorporates seventy-one (71) Lots on which Defence have identified the UXO potential as Slight (see Map 1.4). Defence recommends that all land usage and development within these areas may continue without any further UXO investigation or remediation. In addition, sixty-nine (69) Lots within the study area are currently subject to Area Management Advice (AMA) under the Sustainable Planning Act 2009 (SP Act) Groundwater The main groundwater resource within the study area is within alluvial deposits associated with the waterways network. This has been mapped as moderate-moderate to high vulnerability by DERM. Based on limited historical water quality data, the general quality of this groundwater is poor, with levels of Cl, Zn and/or Mg exceeding groundwater quality criteria levels for drinking in all registered monitoring wells. Information from landowners in the study area indicates that there is a strong reliance on groundwater in the study area, and that the quality of this groundwater is often of a standard much higher than that which is indicated by the monitoring wells of registered bores. Consequently, any potential impacts on groundwater quality and groundwater bores are highly significant to these landowners. Densely vegetated areas consume shallow groundwater resources. Such areas are situated throughout the study area and may become stressed should further degradation to groundwater quality occur. 7.3 Potential impacts and mitigation measures Topography, geology and soils Potential risks to geology and soils that should be considered and mitigated through the detailed design phase include: 1) Water courses: The preferred alignment passes over several water courses exposing the project to fluvial processes including erosion and deposition. Design standards will need to address the potential impact of stream scour and fill on bridge piers, abutments and embankments at larger water courses in the western lowlands and at the eastern connection. Smaller streams are likely to carry very little sediment load, but could carry large cobbles and boulders during flood events. The impact of these boulders on bridge infrastructure will need to be considered. 2) Earthquake: The earthquake hazard within the study area is relatively low, however the detailed design should consider earthquake action in the structural design as per Australian Standards. 3) Erosion: Loamy soils developed on alluvial plains and terraces will be more prone to erosion. The design will need to incorporate stable embankments/cuts with associated catch drains to minimise longer term erosion. 4) Mass wasting/instability: A complete geological profile of the slope (with geological/geotechnical investigations as required), along with a slope stability report, will need to be conducted prior to the commencement of earthworks. Aerial Photography Interpretation (API) has identified several areas with potential instability issues, particularly through the very steep hill slopes through the central range areas. The exposure of steep rock surfaces will increase the chance of landslides, slump features and mass wasting. Detailed design should mitigate the potential for mass wasting, incorporating rock bolting, retaining walls, and stable cuts with associated catch drains and easements where applicable. 5) Exposure of acid producing material: The potential to expose material containing pyrite within the sedimentary and igneous rocks should be identified by geological/geotechnical site investigation, and appropriate management designed (e.g. neutralisation). 3 Lots subject to AMA do not necessarily correlate with Lots classified by Defence as having slight UXO potential. Further, these lots are not necessarily identified on the EMR. Transport and Main Roads, March

6 Potential geological/soil risks that should be considered and mitigated through the construction phase and Construction Environmental Management Plan (CEMP) include: 1) Blasting: The mapped dolerite intrusive body near Peak Crossing will require blasting to cut during construction. Other small isolated outcrops of volcanic and igneous rocks may also be identified during field geological surveys. 2) Soil stabilisation: Compressive/swelling clays in alluvial soils associated with water courses may require stabilisation (e.g. preloading). 3) Erosion: Critical areas for protection include highly-erodible soils, steep slopes, haul roads, and bare areas. Shallow soils dominated by lithosols throughout, and flanking the central range area are most at risk of erosion. Mitigation includes standard erosion control measures detailed in the Environmental Management Plan (Section 19.3), and Technical Paper 1 (Volume 2). 4) Mass wasting/instability: Construction of stable batter slopes will depend on geological and geotechnical investigations during the detailed design phase. Mitigation measures will depend on slope angle and stability, depth and angle of cut, and geological profile Contaminated land Potential contaminated land risks that should be considered and mitigated through the detailed design phase include: 1) Unknown contamination status: None of the twenty-four (24) Lots listed on the EMR within the study area are subject to a Site Management Plan. Whilst basic information is known about the type of contamination on sites listed on the EMR, the exact extent of any site contamination remains unknown. Further investigation is required to establish this. If any contamination is detected, suitable management/remediation plans as per the 1998 Guidelines should be produced. 2) Unlisted potentially contaminated sites: Two sites of interest not listed on the EMR have been identified from aerial photography, and an additional site was identified by a stakeholder. A site inspection is required to determine if further site investigation is necessary along the preferred alignment. Potential contaminated land risks that should be considered and mitigated through the construction phase include: 1) Unexpected disturbance of potentially contaminated soils: If suspected contaminated soils are encountered during construction, or if EMR listed land is to be disturbed through construction plan variance, further contaminated land investigation should be conducted prior to the commencement of work. Contamination can be identified on a visual and/or olfactory basis. 2) UXO: Seventy-one (71) Lots have been identified as having slight UXO potential according to Defence mapping. If any UXO are encountered emergency authorities (Police) and the Department of Defence should be informed and the UXO removed by specialist personnel. 3) Avoid causing land contamination: Standard construction measures for machinery, hazardous materials, spillages and fill are detailed in Section 19.3, and Technical Paper 1 (Volume 2). Operation of the railway may also contaminate land (e.g. spills, herbicides, general waste and debris). Mitigation of these will mainly be an expansion of approaches used during construction Groundwater The water supply requirements for the SFRC are not known at this stage. However, detailed design should investigate the potential for groundwater in the study area to be used as a possible source of water during construction activities. Potential groundwater risks that should be considered and mitigated during the detailed design phase include: 1) Unknown human and environmental receptors: Further assessment will be needed in areas identified as moderate to high vulnerability to determine potential receptors, including: Transport and Main Roads, March

7 - Conducting a census for unregistered groundwater wells located within an approximate 250m radius of the preferred alignment - Identifying any nearby ecological environments that would be severely impacted by temporary drawdown from potential dewatering sites or potential surface chemical spills that may contaminate groundwater Potential groundwater risks that should be considered and mitigated through out the construction and operation phase include: 1) Avoid causing groundwater contamination: Standard construction measures for minimising land contamination will also protect groundwater. Mitigation measures proposed for surface waters will also protect groundwater. 7.4 Conclusion Topography, geology and soils Following the implementation of recommended mitigation measures, it is anticipated that the risk of topographical, geological and/or soil-based potential impacts occurring will be managed within acceptable (at least to statutory) standards Groundwater Given the implementation of adequate management strategies, minimal long term impacts on local groundwater quality and quantity can be expected. This is largely due to the nature of the proposed works despite the vulnerability rating assigned to alluvial deposits within the flood plains of local waterways. Transport and Main Roads, March