preliminary soil salinity assessment - Mid Western Regional Council

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Source: NSW Department of Primary Industries, Primefact 938 ‘Urban Salinity – Causes and Impacts’Salinity can develop in urban environments if salt contained in layers deep within the soil profile aremobilised by rising groundwater. In particular, when groundwater levels rise to within 2 m of thesurface and water containing salts is pulled to the surface through capillary action. The salt can bedetrimental to urban development in a number of ways including:Corrosive to iron/steel materials;Decreases the lifespan of road pavements;Corrodes the properties of bitumen, concrete and brick structures; andPrevents establishment of many garden vegetation species at moderate to high levels andimpacts on growth of many plant species at low to moderate salinity levels.However, without increased addition of water to the water table, salts remain attached to the soilparticles and are unable to be drawn to the surface and concentrated through evapouration(Nicholson and Wheeler, 1999).Salinity is a significant consideration for planning urban land use and investigation of salinity risks arean important prelude to further development assessments.1.3 Preliminary Salinity Investigation ScopeMinespex was engaged to carry out a preliminary salinity assessment of Lot 2 in DP 534336, Lot 399in DP 1132580, and Lot 532 in DP 1132581, Saleyards Lane, Mudgee as shown on the map inAppendix A: Location Map. This report has been prepared in the context of aiming to provideguidance regarding any site salinity issues which may restrict the suitability of the land for futureresidential uses. This preliminary assessment seeks to consider the interactions particular to this sitecombined with the likely impacts of the proposed development.The preliminary salinity assessment included a desktop review, site inspections, soil sampling andlaboratory analysis of soil samples.PRELIMINARY SOIL SALINITY ASSESSMENT2
2 SITE INVESTIGATION2.1 Desktop ReviewSoil and salinity information related to the site was reviewed including:Local Government Salinity Initiative Program information and guidelines;Mid-Western Regional Council Comprehensive Land Use Strategy – Salinity ConstraintsInvestigation for Mudgee and Gulgong, NSW 2007 (Environmental and Earth Sciences); andSoil Landscapes of the Dubbo 1:250 000 Sheet Map and report, B.W Murphy and J.W. Lawrie,1998;Proposed Development on Common Road Mudgee Salinity Inspection – Preliminary Report,A. Nicholson and H. Wheeler, 1999;NSW Natural Resource Atlas – http://www.nratlas.nsw.gov.au and discussions with NSWOffice of Water regarding groundwater data.The local rural and urban areas of Mudgee have a significant number of salinity site expressions(Nicholson and Wheeler, 1999). These are areas of land where the effects of salinity are evident anddiagnosed. Nicholson and Wheeler (1999) reported that salinity affects are visible in establishedareas of Mudgee. Public buildings and parks, commercial premises, roads and homes are affected.In the context of known salinity in the wider locality, saline soils have been identified at variousdepths in the soil profile in the Gulgong and Mudgee areas as discussed in the Mid Western RegionalCouncil Comprehensive Land Use Strategy – Salinity Constraints Investigation for Mudgee andGulgong, New South Wales (Environmental and Earth Sciences, 2007). According to theEnvironmental and Earth Sciences (2007) report, there are a limited number of expressions ofsalinity identified in the area investigated. The report states that ‘the development and/or severityof salinity in the study areas will be dependent on how groundwater levels respond to changes inland use, and in particular, impacts to natural drainage from infrastructure such as roads,stormwater and sewerage pipes, and buildings slabs.’ An area of land covering 75ha, identified in theEnvironmental and Earth Sciences (2007) report as Mudgee Area 2, is located approximately 1000mto the south of the land that is the subject of this report.An electromagnetic survey (EM-31) of Mudgee Area 2 was carried out as part of the detailedinvestigation followed by deep boring to collect soil samples for analysis to ground truth the EM-31results. Soil samples were collected over 0.50m intervals for the first 5.0m of each bore, and at 1.0mintervals thereafter to a depth of 20m. Saline soil was found at varying depths across the areahowever electrical conductivity (EC 1:5 ) was generally more elevated at depths ranging from 3.5 to 7meters below ground level with salinity at these depths rated as non-saline (NS) to moderatelysaline (MS) according to the salinity criteria applied.An actively discharging saline site was also found during the Environmental and Earth Sciences(2007) investigation within Mudgee Area 2. Indicators of salinity including couch grass, erosion andsoil structure decline were observed at the site. It was reported that “the proximity of theinvestigation area to the Mudgee Fault, the break of slope and presence of springs indicates alikelihood of this area being an active discharge point for groundwater driven by both local andPRELIMINARY SOIL SALINITY ASSESSMENT3
Page 2 and 3: This report has been prepared byCon
Page 4 and 5: Table of TablesTable 1: Summary of
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Page 10 and 11: TABLE 2: MONTHLY RAINFALL RECORDS,
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Page 16 and 17: Plate 5: Soil profile at Site 5 soi
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