CATCHMENT DEMONSTRATION INITIATIVE – PROJECT SHEET SIPHON TRIAL ON HILLSIDE SEEP (OB5) This project demonstrates the use of a siphon LOCATION technique to recover an area of saline land caused by a hillside seep. This should reduce further salinity risk of arable land below. The hillside seep is caused by a near-surface rock outcrop intercepting sub-surface water flow from deep sandy duplex soils from the north east and from the deep gradational sands to the north. A backhoe pit dug above the seep showed the water table to be near the surface and highly saline. The lower slopes of the seep have relatively fresh water. This indicates that high groundwater movement through the soils of the gradational sands is also contributing separately to this site (i.e. below the bedrock). It is expected that these soils also contribute to the seep above where groundwater is saline. Continuous discharge from the siphon will be “IF SIPHONING IS through a pipe and into the O’Brien Creek. SUCCESSFUL THEN THE NEED In February 2006 a 21 day trial of the proposed FOR EXPENSIVE POWER, groundwater siphon at the site. The flow rate over the 21 days of the trial was 0.1 litres/second using 19 mm PUMPING EQUIPMENT AND polyethylene pipe. Prior to the trial the groundwater ASSOCIATED MAINTENANCE level was 0.775 m above ground level, at the IS NOT AN ISSUE. THERE MAY completion of the trial it was 0.11 m below ground level. 25mm pipe has now been installed and flow rate EVEN BE POTENTIAL USES is 0.2litres/second. FOR THE WATER” FURTHER INFORMATION Contact: Glenice Batchelor Phone: +61 8 9045 4006 Email: firstname.lastname@example.org Website: www.kellerberrin.wa.gov.au Land owner Colin Wilkins and CDI Project Manager Glenice Batchelor monitoring siphon yield at project site OB5 during the 21 day testing phase. PROJECT SITE INFORMATION 2006 Landholders Involved • Colin and Betty Wilkins and family Location The upper slopes of the O’Brien Catchment. Threat A hill-side seep east of Mission Road affects 12.5 ha of agricultural land and threatens a further 5 ha. A 200m section of the road is also affected including a culvert requiring work. Previous Activities Previous management including WISALT banks to control surface water has not reduced the seep significantly. Salinity Risk Existing and further risk to land and Shire road. Groundwater Quality 2250mS/m Groundwater pH 5.41 Site Investigations & Partnerships 1. Paddock scale geophysical survey using contractors and interpretation was completed by CRC LEME/Curtin and Technical Advisory Group. 2. Test drilling for siphon and siphon installation supervised by Department of Agriculture and Food WA. Groundwater yield testing was undertaken. 3. Surface water management structures assessed with assistance from Department of Agriculture and Food WA. Regulatory Issues A Notice of Intent to Drain or Pump (NOI) was submitted and was not objected to. Permission to test siphon for 21 days was required. Critical Information • Slope gradient from site to discharge outlet. • Geophysics was used to locate the drilling program. • Drilling of monitoring holes confirmed that the saline area is groundwater derived (there is near-surface bedrock) and could be siphoned. • The water quality from yield testing meant a detention basin was not required. Costs Pipes, fittings, installation - $1500, Geophysics - $5000, Drilling program - $5000. No ongoing running costs. Labour not included in these costs. NB: A significant amount of Technical Advisory Group and Partnership time is not accounted for in these costs. Expected Benefits of Project • Recovery of productive land and reduction in further salinity risk. • Monitoring of bores will indicate impact of the siphoning. It is anticipated that the water quality will improve over time. This will be monitored regularly.