preliminary soil salinity assessment - Mid Western Regional Council

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2.6.3 Soil Sampling for Laboratory Analysis2.6.3.1 Quality Assurance / Quality ControlIn summary, quality controls that Minespex employed forming the field quality assurance were: Duplicate samples collected for each of the sample sites for the sampling event;Sampling personnel were consistent throughout field sampling;Logs were kept and sampling locations were recorded using a handheld GPS mapping deviceat the time of sample collection. The GPS points were overlayed onto a topographic map ofthe subject site as contained within Appendix B: Current Site Layout, Topography and SoilPit Locations;Sample holding times were acceptable, with the samples being delivered to the laboratorywithin 24 hours of collection and transported in an esky.The duplicate has been held by Minespex in case re-sampling is required. Identical methods ofpreservation, storage and transportation were used and the duplicate is stored in cool, dryconditions.All samples were forwarded to ALS Sydney for analysis via the Mudgee ALS laboratory. ALS has NATAaccreditation for all analyses performed, ALS NATA Accreditation Number 825 – Work order no.:ES1212263 (Sites 1 – 4) and ES1216497 (Sites 5 & 6). ALS also performed tests under a qualitysystem complying with AS17025.2.6.3.2 AnalytesWith reference to ‘Site Investigations for Urban Salinity’ (DLWC, 2002), the analytes tested toprovide preliminary information on salinity at the sites sampled include:Salinity - This is a measure of the total soluble salts in a soil. A saline soil is one with anaccumulation of free salts at the soil surface and/or within the profile affecting plant growthand/or land use. It is generally attributed to changes in land use or natural changes indrainage or climate, which affects the movement of water through the landscape. Salinitylevels of soil were tested by determining the electrical conductivity (EC) of a mixture of soiland water at 1:5 ratio (Electrical Conductivity, 1:5 soil in water expressed as µS/cm –EC 1:5 ).The higher the salt content the more electrical current that the mixture conducts. The ECreading is then converted to an approximate value of EC e by using a conversion factor of soiltexture. The soil texture at each of the sample sites was analysed by ALS Laboratory andconversion factors applied for each sample as detailed in ‘Site Investigations for UrbanSalinity’ (DLWC, 2002) and summarised in Section 2.6.3.3 below.Cation Exchange Capacity (CEC) - indicates the soil’s capacity to store the available positivelycharged cations such as sodium (Na), calcium (Ca), magnesium (Mg) and potassium (K). It isdependent on the amount and type of clay and organic matter present in the soil. Thereason for the inclusion of CEC is that it is required for assessing sodicity. Sodicity is the levelof exchangeable sodium in the soil.Exchangeable Sodium (meq/100g) and Exchangeable Sodium Percentage (ESP%) – Sodicsoils are generally dispersive on wetting and impact on the soil’s drainage and erosivity.PRELIMINARY SOIL SALINITY ASSESSMENT16
Sodium is also often the main cation contributing to saline soils. Sodicity or exchangeablesodium percentage (ESP) is the amount of exchangeable sodium as a percentage of the CEC.ESP = [Exchangeable sodium / CEC] x 100.Soil pH - Measures acidity or alkalinity of a soil and is important in determining thecorrosivity of the soil to building materials.Chlorides (mg/kg) - These are negatively charged anions which are corrosive to buildingmaterial, such as steels and can damage other building structures. Soluble chloride ions (inwater) gradually penetrate into concrete and cause corrosion of the reinforcement. Sodiumchloride is a type of salt commonly found in saline soils.2.6.3.3 Selected Assessment CriteriaThere is no one prescriptive list of tests to determine the impact of salinity prior to development.Soil tests for sodicity are used to provide information on water movement through the soil andpossible impediments to drainage. Tests to assist in determining if a soil may be corrosive are usedincluding pH, EC and chlorides. Information obtained from the range of tests assists in assessing thepossible impact of water movement through the landscape and interactions with salts through theprofile.Salinity is determined in soil tests by measuring the electrical conductivity (EC) of a mixture of 1 partsoil to 5 parts distilled water (EC 1:5 ). The results can be expressed in µS/cm or converted to dS/m bydividing by 1000.The effects of salinity levels expressed as EC 1:5 at 25 o (uS/cm), on plants are:0 to 1,000 very low salinity, effects on plants mostly negligible.1,000 to 2,000 low salinity, only yields of very sensitive crops are restricted.> 2,000 saline soils, yields of many crops restricted.The impact of EC 1:5 at 25 o is then considered taking into account the inherent electrical conductivityof the soil minerals which can be described as the soil texture. Relatively impermeable soils such asheavy clays do not allow as rapid flow of electrical current as more permeable soils such as sands. Toallow for such an assessment, the EC 1:5 result may then be converted to EC e using a multiplier factorbased on the texture of the soil as shown in Table 11: Factors for Converting EC1 :5 to ECe.TABLE 11: FACTORS FOR CONVERTING EC 1:5 TO EC ESoil texture groupMultiplication factorsSands 17Sandy loams 14Loams 10Clay loams 9Light clays 8.5Light medium clays 8Medium clays 7Heavy clays 6Source: ‘Site Investigations for Urban Salinity’, Department of Land and Water Conservation (2002)17PRELIMINARY SOIL SALINITY ASSESSMENT
Page 2 and 3: This report has been prepared byCon
Page 4 and 5: Table of TablesTable 1: Summary of
Page 6 and 7: Source: NSW Department of Primary I
Page 8 and 9: egional processes”. Existing and
Page 10 and 11: TABLE 2: MONTHLY RAINFALL RECORDS,
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Page 14 and 15: drainage in the floor of the livest
Page 16 and 17: Plate 5: Soil profile at Site 5 soi
Page 18 and 19: TABLE 3: DOMINANT GROUND COVER SPEC
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Page 24 and 25: 3 SITE INVESTIGATION RESULTS AND DI
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Page 28 and 29: As discussed previously (Section 3.
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Page 32 and 33: Appendix ALocation MapThe land subj
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