Pipeline Project N.Z.
Mangere Branch Sewer Pipeline MetaFLO Licensee, New Zealand
April 2008
Project Background: The Mangere Branch Sewer Pipeline is a 5km section of pipeline in South Auckland. Part of the mostly open cut project involved the installation of 106m of 630mmOD (25”) SDR 12 PE directionally drilled under State Highway 20. As well as 326m of 560mmOD (22”) SDR 13.6 PE at a depth of 5m. Bore logs indicated a very firm silty clay overlying Waitemata group sedimentary. Both installations were designed at near flat grades 0.3% and 0.4% respectively.
Installation: A DitchWitch JT8020 was used on this project and started with the State Highway crossing. The pilot phase was carried out using a Railhead Incredibit and Eclipse locating system. Pullback was conducted the following day over 7 hours using a 60,000 lbs TensiTrak data-logging unit. In order to prevent collapse of the borehole no pre-reaming was carried out and the pipeline was towed in during back reaming. As a precaution the pipe was installed “open ended” to allow pressure to escape should flows in the annulus be lost. The pullback was achieved in 7 hours.
Muds: All fluids were mixed for the first time using the Surface to Surface M3-G mixing unit, which kept up with the fluids demands without putting any stress on the operators. Running 15 minute rods and pumping 66 gallons per minute (2:1 fluid/solids ratio) we were able to clean the hole and produce a 10 lbs slurry.
Disposal Traditional: Usually we would dispose of our slurry using vac trucks and tipping at landfill. Currently there are very few landfills accepting drilling slurries in the Auckland region so it works out to a 3 hour round trip. Note that recycling of drilling fluids does not work out to be efficient in Auckland as the nature of the clay make physical separation very time consuming.
Disposal PDM-300E/R-T-STM: After bench testing of the slurry produced on this project it was determined that 0.5% R-T-STMTM dosing rate was sufficient to adequately solidify our returns.
By using the MetaFLO PDM-300E/R-T-STM system we were able to tip in a location closer to site with 6 wheel trucks of the same capacity as the vac trucks but at significantly lower hourly rates. In this process we used our TriFlow reclaimer with a 40 mesh screen to remove anything that was going to block the PDM filters. The reclaimer was also used to circulate the slurry to keep it in a homogeneous state.
There were no tipping fees charged as the property owner wanted to use the solidified slurry to hoe into the field, which is affected by dry conditions over the summer months.
Another benefit of the R-T-STM system was that the solidified slurry was combined with topsoil, which was then used by the head contractor to topsoil their backfilled trenches. See photos of slurry/topsoil mixture (one has been grass seeded 6 days prior to compare to growth on the rest of the site).
Target Markets for processed slurries: In order to further save costs using this technology, the solidified product would need to be marketed for its use in horticulture and home gardening. Working with farmers and growers who are using the material would be beneficial to enable them to improve the water retaining properties of their soils. Another target is ready lawn producers who have significant problems in keeping their product adequately watered after laying. Vegetation growing in the solidified material is much less prone to wilting during extended periods of no rainfall. Also tomatoes and peppers ripen and are a much better quality when grown in a combination of solidified slurry/topsoil than topsoil alone.
Markets to target with slurry to solidification:
- Industrial liquid waste transfer stations
- Drilling muds and Tailings ponds
- Horizontal Directional Drilling – highest outgoing costs are disposal related and the R-T-STMTM process helps solve this
- Stormwater detention ponds (contaminated, non-contaminated) Landfills Leachate– on-site applications
- Harbour Clean-Up and Waterway Dredging(contaminated ponds,rivers and lakes
