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Uganda investment forum_-_natural_resources_-_keith_winning_-_cbi Uganda investment forum_-_natural_resources_-_keith_winning_-_cbi Document Transcript

  • Pipeline Design - Protecting the Environment: Application of GIS to Pipeline Route Selection Keith Winning Uganda Investment Forum - Driving Growth in Africa Kampala, Uganda 11th - 12th April 2013
  • Uganda Investment Forum – Driving Growth in Africa th th Kampala, Uganda 11 – 12 April 2013 Pipeline Design – Protecting the Environment: Application of GIS in Pipeline Route Selection Presentation by: Keith Winning CB&I Abstract The effects of soil erosion worldwide are a major concern; it impacts on the environment, food security and public health. It is estimated that 75 billion metric tons of soil worldwide are lost per annum; with Africa, Asia and South America typically experiencing average losses of 30 to 40 tons ha-1 year-1, with the accepted sustainable rate of soil loss being less than 10 tons ha-1 year-1. Soil erosion is the process of soil loss due to detachment, transportation and deposition of soil by water or wind and is dependent on a number of factors, including: rainfall energy, soil strength and cover, slope length and angle, crop and land management. The effect of soil erosion is two-fold; on-site impacts include the loss of soil functions, structure and fertility, while the off-site impacts include the increased turbidity and eutrophication in water courses. Figure 1 – Erosion types (Sheet, rills and gullies) The severity of the erosion is rated by a simple scoring system based on the identification of the visible erosion features, with the accepted sustainable rate of soil loss is less than 10 tons ha-1 year-1 (erosion risk 3) [1]. By using remote sensed data and spatial analysis within the application of a Geographical Information System (GIS), it is possible to predict the soil loss (erosion risk) at the initial route selection phase of the project. This enables the engineer to select a route which minimises the environmental impact due to soil erosion and provide better input to the capital expenditure (CAPEX) costs and the operational (OPEX) costs for the pipeline which are used to determine the optimum configuration and route selection of the pipeline. Erosion Risk Keywords Soil Erosion  Pipeline Routing  GIS  USLE  Environment Impact K. Winning () Principal Pipeline & Geomatics Engineer CB&I, 40, Eastbourne Terrace, London. W2 6LG. Tel: +44 (0)20 7053 3778 e-mail: kwinning@cbi.com 1. Introduction Soil erosion is the process of soil loss due to detachment, transportation and deposition of soil by water or wind and is dependent on a number of factors, including: rainfall energy, soil strength and cover, slope length and angle, crop and land management.[1] Erosion is broadly defined as being: • Sheet or inter-rill: where the soil is removed in uniformly thin layers and the flow is unconfined (overland flow). • Rill: Initiated at a critical distance down slope when the overland flow becomes channelled. This is temporary and can be ploughed out. • Gully: Confined, channelled and permanent. 1 2 Erosion Rate (tonnes/ha) <2 2–5 3 5 – 10 4 10 – 50 5 50 – 100 6 100 – 500 7 > 500 Visual Assessment No wash marks or scours. Shallow rills every 50 – 100m. Discontinuous rills every 20 – 50m. Continuous network of rills every 5 – 10m or gullies every 50 – 100m. Continuous network of rills every 2 – 5m or gullies every 20m. Continuous network of channels with gullies every 5 - 10m. Extensive network of large gullies every 20m Table 1 – Erosion Risk Classification [1] The effective use of erosion control in agriculture has long been established, with early work carried out in America by Hugh Bennett in the 1920s. From this work, mathematical models to predict soil loss have been developed, the Universal Soil Loss Equation (USLE) Equation (1), issued in 1965 [2] and the Revised Universal Soil Loss Equation (RUSLE) in 1978 [3]; further models have since been developed, including the Morgan-Morgan-Finney (MMF) [4]. Increasingly, it is being recognised that soil erosion due to construction has significant environmental impacts [1]. 3
  • Uganda Investment Forum – Driving Growth in Africa th th Kampala, Uganda 11 – 12 April 2013 A=R×K×L×S×C×P Where: A = Soil loss in tons ha-1 year-1 R = Rainfall factor K = Soil erodibility factor L = Slope length in metres S = Slope factor C = Crop factor P = Support practice factor to eutrophication caused by the run-off of fertiliser rich soil into the Volga River. Equation 1 – Universal Soil Loss Equation 2. The Effects of Soil Erosion Figure 3 – Caspian Sea showing eutrophication (http://visibleearth.nasa.gov/view.php?id=66761) 3. Figure 2 – Gully erosion in highly erodible soils The effects of soil erosion worldwide are a major concern; it impacts on the environment, food security and public health. It is estimated that 75 billion metric tons of soil worldwide are lost per annum [5]; with Africa, Asia and South America typically experiencing average losses of 30 to 40 tons ha-1 year-1[5]. Soil Erosion and Pipelines In addition to the impact of soil erosion already discussed, erosion control for buried pipelines is important in order to reduce the environmental impact and reduce the risk of exposing the buried pipe [1]. Exposure of buried pipelines can lead to free spanning where a length of the pipeline is unsupported, which can result in mechanical failure; in such cases the effect on the environment can be significant. On-site impacts include the loss of soil function from the breakdown of the soil structure and the reduction in organic matter. The outcome of this is reduced yields, loss of arable land, reduced food security and risk to existing infrastructure such as roads, railways and pipelines. Off-site effects, due to the transportation of sediment include the increased turbidity in water courses leading to public health issues and a risk to infrastructure (hydroelectric generation and irrigation) [6]. With increased turbidity comes eutrophication or hypertrophication, which is the response of aquatic systems to raised levels of nitrates or phosphates. This leads to hypoxia, a reduction of oxygen in the water and rapid growth in algae [7]. Figure 3, taken from the Moderate Resolution Imaging Spectroradiometer (MODIS) on the Terra satellite on June 11, 2003 shows the growth of the algae in the northern part of the Caspian Sea (shown in green), due 4 Figure 4 – Pipeline spanning due to soil erosion Once a pipeline has been installed, the right-of-way is reinstated and if possible the original ground cover reestablished. Soil erosion due to rainfall energy can cause the bio-restoration to fail due to soil detachment and washout of young seeds due to runoff.
  • Uganda Investment Forum – Driving Growth in Africa th th Kampala, Uganda 11 – 12 April 2013 Erosion at this level will necessitate post installation monitoring and remedial works, adding to the operational (OPEX) cost of the pipeline. Any construction work involving the temporary removal, storage and return of the topsoil and compaction of the subsoil by machinery increases the potential for soil erosion due to reduced porosity, as the infiltration rate on the compacted soil is reduced, resulting in greater runoff and poorer rates of bio-restoration and therefore greater erosion [8]. 4. Application of GIS to Route Selection Geographical Information Systems (GIS) integrate hardware, software and data for capturing, managing, analysing and displaying geospatial data. GIS can aid in the route selection process in a number of ways; one of these is by predicting the soil loss (erosion risk). Using public domain data enables this to be carried out during the initial route selection phase of the project. Using Landsat imagery with bands 5, 4 and 3 (infrared, near infrared and red), healthy vegetation is displayed in bright green and bare soils in mauve. This is then classified into 6 classes by the RGB colour value: water/ice, vegetation, cloud cover, rock, soil and soil/rock; from this an assessment of the soil erodibility factor (K) can be predicted. The Shuttle Radar Topography Mission (SRTM) provides a highresolution (90m) digital elevation model of 80% of the world’s land mass. This is used to determine the slope factor (SL). In order to determine the rainfall factor (R), data from the World Meteorological Organization (WMO), the annual rainfall data was plotted and a choropleth map produced. The crop factor (C) and the practice factor (P) are 1 as the pipeline right of way, initially has no vegetation immediately after reinstatement. By using GIS and remote sensed data it is possible to predict the soil loss (erosion risk) along a proposed pipeline route, early in the route selection phase. From this the post construction requirements to ensure that soil loss is less than 10 tons ha-1 year-1 (erosion risk 3) are determined, which include seeding, matting, berms and outlets [9]. This aids the engineer in minimising the erosion risk of the pipeline route at the initial route selection phase of the project. In addition it forms the basis for identifying those areas that are more susceptible (erosion risk 4 to 7), to soil erosion for field verification. 5. Conclusions As our demand for oil and gas increases, the diameter and length of the pipelines required to transport these commodities increases, with this comes the potential for greater environmental impact. By using remote sensed data and spatial analysis within the application of a Geographical Information System (GIS), it is possible to predict the soil loss (erosion risk) at the initial route selection phase of the project. This enables the engineer to select a route which minimises the environmental impact due to soil erosion and provide better input to the capital expenditure (CAPEX) costs and the operational (OPEX) costs for the pipeline which are used to determine the optimum configuration and route selection of the pipeline. In addition, it identifies those areas that require field verification. Acknowledgements The author would like to thank Professor Hann of Cranfield University for reviewing this paper. References [1] Morgan RPC. Soil erosion and conservation. Third Edition: Wiley-Blackwell; 2009. [2] Wischmeier WH, Smith DD. Predicting RainfallErosion Losses from Cropland East of the Rocky Mountains. In: Agricultural Research Service USDoA, editor. Washington D.C.1965. [3] Wischmeier WH, Smith DD. Predicting Rainfall Erosion Losses. In: Agricultural Research Service USDoA, editor. Washington D.C.1978. [4] Morgan RPC, Morgan DDV, Finney HJ. A predictive model for the assessment of soil erosion risk. Journal of Agricultural Engineering Research. 1984;30:245–53. [5] Pimentel D, Harvey C, Resosudarmo P, Sinclair K, Kurz D, McNair M, et al. Environmental and economic costs of soil erosion and conservation benefits. SCIENCE-NEW YORK THEN WASHINGTON-. 1995:1117-. [6] Holmes TP. The offsite impact of soil erosion on the water treatment industry. Land Economics. 1988:356-66. [7] Vollenweider RA. Scientific fundamentals of the eutrophication of lakes and flowing waters, with particular reference to nitrogen and phosphorus as factors in eutrophication. OECD REPORT, SEPTEMBER 1970 159 P. 1970. [8] Mohitpour M, Golshan H, Murray MA, Mohitpour M. Pipeline design & construction: a practical approach. Third Edition Edition: ASME press New York; 2000. [9] Morgan RPC, Mirtskhoulava TE, Nadirashvili V, Hann MJ, Gasca AH. Spacing of Berms for Erosion Control along Pipeline Rights-of-way. Biosystems Engineering. 2003;85:249-59. ©CB&I 2013 5
  • Uganda Investment Forum – Driving Growth in Africa th th Kampala, Uganda 11 – 12 April 2013 Appendix – Presentation Slides Slide 1 Slide 2 6
  • Uganda Investment Forum – Driving Growth in Africa th th Kampala, Uganda 11 – 12 April 2013 Slide 3 Slide 4 7
  • Uganda Investment Forum – Driving Growth in Africa th th Kampala, Uganda 11 – 12 April 2013 Slide 5 Slide 6 8
  • Uganda Investment Forum – Driving Growth in Africa th th Kampala, Uganda 11 – 12 April 2013 Slide 7 Slide 8 9
  • Uganda Investment Forum – Driving Growth in Africa th th Kampala, Uganda 11 – 12 April 2013 Slide 9 Slide 10 10
  • Uganda Investment Forum – Driving Growth in Africa th th Kampala, Uganda 11 – 12 April 2013 Slide 11 Slide 12 11
  • Keith Winning Principal Pipeline & Geomatics Engineer Project Engineering and Construction Office: +44 (0)20 7053 3778 E-Mail: kwinning@CBI.com