preliminary soil salinity assessment - Mid Western Regional Council

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likely to have reduced the concentration of salts in the upper layers of soil across the site. The rateof leaching depends on a number of factors including the amount of water applied and how freelydraining soils are through the profile and determining the long term movement of leached salts isbeyond the scope of this preliminary investigation.2.4 Site InspectionOn 8 th May 2012 Minespex carried out a brief site inspection for the purpose of planning for soiltesting. Initial soil salinity testing on the northern side of Saleyards Lane was restricted by:Stockpiles of roadwork’s material being stored on this area of land creating areas that wereinaccessible to the excavator and soil sampler ;Activity of machinery on the site during soil testing associated with this roadwork material.The following week on 15 th May 2012 a field investigation was carried out onsite with visualobservations recorded including topography, existing vegetation type and density, and soilcondition. At this time Minespex also carried out top and subsoil sampling to assist with an overallpreliminary salinity assessment at four sites (Sites 1 to 4). The soil samples were forward to ALSLaboratory in Sydney for analysis to determine electrical conductivity (EC w 1:5 ), cation exchangecapacity (CEC), sodium (ESP % and sodium mg/kg), pH w , chlorides (meq/100g) and soil texture.Following receipt of these initial soil test results and improved access to the northern area of thesubject land with the council removing roadworks stockpiles and leveling the site, further top andsubsoil testing was carried out at two sites (Sites 5 and 6) immediately adjacent to the truckwashdown facility and remaining leachate pond on 3 rd July 2012. The soil samples were to ALSLaboratory in Sydney for analysis of the same parameters as for Sites 1 to 4.2.5 Landscape Description and Site Observations of Salinity IndicatorsThere are a number of factors that have been considered to provide a preliminary assessment of thesalinity hazard at the site such as regional salinity issues, topography, vegetation, site history, soiltype, soil condition and surface water movement. This information has been used as part of theoverall salinity risk assessment and to determine a suitable soil sampling protocol for the site.The previous land use has impacted dramatically on vegetation across the site with the majority ofgroundcover consisting of species that are able to establish and survive in highly disturbed, poorsoils. In particular, couch grass (Cynodon dactylon) and slender rat’s tail grass (Sporobolus spp.) aredominant on the southern side of Saleyards Lane, with kikuyu (Pennisetum clandestinum) growingprolifically on the land north of the lane and other low lying areas across the subject land.Whilst both couch and kikuyu grasses are considered salinity indicator species, they are also knownto invade disturbed, poor soils where salinity is not an issue and are found extensively within theMudgee region as lawn grasses.No bare patches, saline scalds or seepage areas were visible during the site inspection. Trees acrossthe site were in reasonable condition.The SES building had very little indication of possible salinity damage to the exterior. There were noobvious wet ‘tide’ marks on the building. White colouration was seen on three small spots on bricksPRELIMINARY SOIL SALINITY ASSESSMENT8
and mortar in the lower 30cm (approximately) of the exterior walls and one brick was found with alittle crumbling however there was no white marking around this brick.2.5.1 Topography and Surface Water MovementThe land generally slopes down from a small hill on the south western side of the subject area with anorth and north eastern aspect as shown on the topographic map of the general area contained inAppendix B: Current Site Layout, Topography and Soil Pit Locations. The upper slopes are relativelysteeply sloped with the lower slopes more gently sloping down to the virtually flat area of land northof Saleyards Lane. A small embankment runs along the north eastern boundary of Lot 2 in DP534336 the site dropping steeply by approximately 1m down to the alluvial swampy flats adjacent tothe subject land. It appears this embankment has resulted from leveling of the site.The site is dominated by the small hill on the western side of the subject land with limited surfacewater runoff entering the main area of the site from outside. However, a natural watercourse runsalong the eastern side of Lot 399 in DP 1132580 with local drainage flowing north easterly.2.5.2 Soils and Site ConditionErosion was minimal across most of the site however the upper slopes of the hill had very littletopsoil and sparse vegetation, which is typical of light, gravelly soil types after heavy grazing.No significant bare patches, saline scalds or saline seepage areas were visible during the siteinspection. Couch grass (Cynodon dactylon) and kikuyu (Pennisetum clandestinum) were observed inareas across the site. These species are considered to be salinity indicator species as they aretolerant of mildly saline conditions.Given that the site was being used for stockpiling roadworks, and on the basis of visual observationsrelating to soil salinity, for the purpose of a preliminary salinity assessment four (4) sites wereinitially selected within the subject land. These sites were believed to be representative of thedevelopment area and were determined to be areas where soil salinity may occur due totopography, previous land use and existing water movement within the landscape. Soil pits wereexcavated to approximately 120cm at each of these sites and are identified throughout this report asSites 1 – 4. Further soil testing was carried out at sites immediately adjacent to the truck washdownpad (close to the SES building) and immediately next to the remaining leachate pond, once theseareas became accessible and are identified as Site 5 (north of truckwashdown pad, west of SESbuidling) and Site 6 (west of leachate ponds). The locations of the 6 soil pit sites were recorded usinga handheld GPS device and are shown on the maps in Appendix B: Current Site Layout, Topographyand Soil Pit Locations. Observations of the soil profile were recorded for each pit and soil samplingconducted as detailed in Section 2.6 below.The soil profiles at the six soil pits excavated for use in the field investigation are shown in Plates 1to 6 below. In general, the upper layers of the soil profiles (A and B Horizons) across the site aregenerally sandy loams and loams with clay subsoils (C Horizons).Site 1 had grey brown sandy loam topsoil (A Horizon) down to approximately 15cm. Below this layer,the upper subsoil (B Horizon) was a leached, pale grey clay loam that contained dark grey to black,angular gravel less than 20mm diameter appearing in a relatively defined layer. This gravel materialdid not appear to be consistent with the soil type and is likely to have been brought in to improvePRELIMINARY SOIL SALINITY ASSESSMENT9
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,
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
Page 20 and 21: 2.6.3 Soil Sampling for Laboratory
Page 22 and 23: Table 12: ECe Values of Soil Salini
Page 24 and 25: 3 SITE INVESTIGATION RESULTS AND DI
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Page 28 and 29: As discussed previously (Section 3.
Page 30 and 31: 4. Consider drainage with adequate
Page 32 and 33: Appendix ALocation MapThe land subj
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Page 40 and 41: Appendix CLaboratory Certificate of
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