intermittent periods of drying greenish) in each soil horizon. Include (perched or seasonal watertable). a photograph to illustrate. Electrical EC test result infers the salinity of the This cheap and simple test measures soil and its potential impact on plant the amount of dissolved salts and can Conductivity growth on the LAA. Refer to Hazelton be undertaken using a hand-held (EC) & Murphy (2007) for interpretation of meter using 1:5 soil:water EC test results. Application of suspension, or in a suitable soil effluent increases salt content of testing laboratory. soils over time. Feature Explanation Assessment Process Emerson EAC results infer dispersibility (as The Emerson Aggregate Test (EAT) Aggregate ped slaking, soil dispersion or both). is used to assess soil dispersibility Class LAAs should not be installed in soils and susceptibility to erosion and with moderate or high dispersibility, degradation. Refer to Hazelton & without adequate mitigation (e.g. Murphy (2007) for test methodology. addition of gypsum, use of The EAT should be the first test of irrigation). soil structure stability; if the soil is dispersive measuring its sodicity is highly desirable and can lead to a correct gypsum dosing recommendation. Permeability The rate at which water moves Generally, assessment of soil texture and Design through the soil reflects the soil’s is adequate to determine soil Loading Rate permeability and determines the rate permeability from AS/NZS1547:2012. at which effluent is applied to land in The constant-head permeameter litres per square metre per day (mm (AS/NSZ1547:2012) can also be per day). The application rate for used, but not if are waterlogged each type of land dispersal and or shrink-swell cracks are present. recycling system is listed in Table 9 NOTE that the falling-head in the Code. Whilst the loading rate percolation test is no longer for LAA design is based on the considered acceptable by the EPA. permeability, it is less than the true permeability.
intermittent periods of drying (perched or seasonal watertable). greenish) in each soil horizon. Include a photograph to illustrate. Electrical Conductivity (EC) EC test result infers the salinity of the soil and its potential impact on plant growth on the LAA. Refer to Hazelton & Murphy (2007) for interpretation of EC test results. Application of effluent increases salt content of soils over time. This cheap and simple test measures the amount of dissolved salts and can be undertaken using a hand-held meter using 1:5 soil:water suspension, or in a suitable soil testing laboratory. Feature Explanation Assessment Process Emerson Aggregate Class EAC results infer dispersibility (as ped slaking, soil dispersion or both). LAAs should not be installed in soils with moderate or high dispersibility, without adequate mitigation (e.g. addition of gypsum, use of irrigation). The Emerson Aggregate Test (EAT) is used to assess soil dispersibility and susceptibility to erosion and degradation. Refer to Hazelton & Murphy (2007) for test methodology. The EAT should be the first test of soil structure stability; if the soil is dispersive measuring its sodicity is highly desirable and can lead to a correct gypsum dosing recommendation. Permeability and Design Loading Rate The rate at which water moves through the soil reflects the soil’s permeability and determines the rate at which effluent is applied to land in litres per square metre per day (mm per day). The application rate for each type of land dispersal and recycling system is listed in Table 9 in the Code. Whilst the loading rate for LAA design is based on the permeability, it is less than the true permeability. Generally, assessment of soil texture is adequate to determine soil permeability from AS/NZS1547:2012. The constant-head permeameter (AS/NSZ1547:2012) can also be used, but not if are waterlogged or shrink-swell cracks are present. NOTE that the falling-head percolation test is no longer considered acceptable by the EPA.