GISdevelopment.net --> Application --> Utility



Introduction
Pipelines are the most efficient, cost effective and environmentally friendly means of fluid transport. Transmission or trunk pipelines are examples of engineering marvel requiring high project cost and long gestation periods and operating life. Careful planning of their route can save on cost, time and operating expenses, ensure longer operational life and help prevent environmental fallouts.

Throughout the world, a large network of pipes transports oil, gas, water and different products. Pipeline transport is most prevalent in USA where nearly two-thirds of the ton-miles of oil get transported annually through a network of more than two million kilometers of pipelines, in some of the toughest terrains. Pipelines are by far the most economical, practical and safe option of fluid transport. They save enormously due to their tenfold efficiency over trucking / railroad operations and accrue important environmental and safety benefits by reducing the highway congestion, pollution and spill. This inexpensive, reliable and high capacity transport is critical to national economy and security.

In India the trend towards pipeline transport is increasing – and is likely to accentuate with privatization of petroleum sector and growth of cities. The pipeline network will see an exponential growth from the current installed network of nearly one lakh kilometer. Petroleum and petroleum products being basic raw material for many industries, the use of pipelines shall increase for sectors like fertilizers, power, petrochemicals, pharmaceuticals, plastics, industrial chemicals, transport etc., Growth of cities will likewise increase the demand for water pipelines. The method as such is general enough to apply to all linear infrastructure like transport network etc and can be applied to road, rail and conveyor transport and to transmission and distribution of power and data.

The pipelines are used for transmission, distribution and gathering. The most sophisticated and large pipelines fall in the transmission category. These are often large diameter (>100 cm dia.) pipelines incorporating automated monitoring and control of flow, pressure and fluctuations. These pipelines are highly capital-intensive installations with long lead and long life. Typical installation costs range from Rs. 6 million / km for water pipeline to Rs. 20 millions/km for gas pipelines with oil pipelines at intermediate range of 10 million. Material and laying components account for 70-90 per cent of cost. The construction of pipeline is facilitated by proper analysis of route location for access to right of way, terrain for obstructions and weather for movement of equipment.

Assessment on pipeline alignment
Pipeline operation entails a comprehensive strategy for routine operations and maintenance, damage prevention, safety, security, environmental protection and emergency response. Many of these factors fall within the regulatory framework and require compliance. Routes passing through unusually sensitive areas like water supply reservoirs, populated areas and ecologically sensitive areas need extra precautions against accidental spillage. Mapping of pipelines for administering a sound operations program is now considered essential.

Scientific planning of pipeline route can reduce cost and time of project execution and hence the operating expenses. Pipeline alignment is basically an optimization between costs of the material and the construction. Natural and man-made terrain obstructions cause spatial variation in construction cost due to changing thematic features like types of soils, intervals of slope, etc. Manual pipeline route planning uses available maps, surveys and experience and is seriously constrained due to lack of updated data and quantitative approach. This is accentuated for complex terrains and long routes. Remote sensing (RS) and GIS method on the contrary uses updated maps from latest RS data, integrates thematic cost layers in GIS environment and computes all possible routes with associated costs. Apart from saving 5-15 % route length, the method has potential benefits like cadastral overlays on route for gadget notification, precise location data on installations and organization of O&M (Operations and Maintenance data).

Background
In response to industry demand, SAC has developed a methodology for pipeline alignment using remote sensing and GIS techniques. A small study on pipeline routing using remote sensing derived land use formed the basis for this development. This study, completed in 1999 for a survey company under training project, saved 1 km pipeline length over existing 35-km alignment. Realizing the potential, SAC initiated in-depth evaluation of potential of RS/GIS techniques for pipeline alignment in 2000.

Development of pipeline alignment technique
A methodology for semi-automated pipeline alignment was developed using sample data of 15x12 km area. Objective of the study was to develop a comprehensive package for semi-automated pipeline alignment on an image processing and GIS software backbone.

The available algorithms of GIS software like path analysis and drainage analysis on accumulated cost surface, conducted by NASA under Commercial Remote Sensing Program in 1997, have limitations of local optimization, boundary constraints and high computational load, and lack flexibility in assigning start, intermediate and end points for route optimization.

The cornerstones of the SAC methodology are the cost surface and the route analysis on this surface. The cost surface is generated by combining all the thematic costs of laying the pipeline on a given terrain by a system of ranks and weights. This is consistent with the basic problem as the pipeline routing is a compromise between the minimum (straight line) distance from source to destination and the physical conditions existing above and below ground. The themes relevant for cost surface represent the physical conditions of terrain and their choice may vary by locale and project requirements. In development phase a fairly general set of themes like slope, soil, land use, geology, road/rail networks and streams are considered for generating cost surface. The cost ranking for features within the themes and weights for each theme are assigned by general recommendations, subject knowledge and expert opinion.

The route of least cost between source and destination points is searched iteratively over corridors of narrowing width using network analysis approach. The cost is computed as weighted sum of material cost of pipeline, the construction cost of laying the pipeline and the access cost of approaching the route. Thus the first rough route is obtained over entire rectangular area encompassing start and end points. The subsequent route search is limited to a broad buffer zone around the previous route. Generally third iteration with narrow corridor of buffer zone ends this global search option. Path analysis is then used to locally optimize the route, which yields final alignment.

Dry run showed clearly that routing between start and end points passed through minimum cost areas. The final route was 51 % longer than the straight-line path and has cost implications of just a fraction of percent of the straight-line cost, because the straight line passed over a hilly terrain.

1.Validation of pipeline alignment technique
A 42-km water pipeline in south of Udaipur (India) was manually aligned by a private company ( M/s MultiMantech, Ahmedabad) for carrying water from a reservoir at 800 MSL to Hindustan Zinc Ltd plant at 500 MSL under gravity flow ( i.e. without pumping). The terrain is hilly and the manual alignment mostly followed highways and roads. This problem was repeated using SAC technique as validation exercise, which was completed in two-month time.

Twelve cost layers (topography, slope, geology, soil, land use, road, distance from road, rail, forest, water bodies and streams) are selected and created using satellite data and other maps and ranked for cost contributions by features distribution. Variable weights are assigned to each of layers to reflect the project requirements and general routing criteria. The Combined Weighted Cost Surface (CWCS) is generated and semi-automated route search with three narrowing corridors is executed with cost ratio of 60:40 for material and construction costs (access cost were not considered).

The route obtained by RS/GIS method shows 5.7 km saving (13.4%) over the original 42 km alignment obtained by existing survey method. This route after reconciliation has now been accepted as final alignment after ground visits confirmed the feasibility.

Route Source	Actual Length (m)	Mean cost / unit (Relative)	Total cost (Relative)	Difference (%) (Route length)	Difference (%) (relative cost)
Reference route(Survey basedby MMIL, Ahd)	42572	1339.6 (1.00)	57046480	0.00	0.00
SAC Route	36868	1334.65 (0.996)	49205876	-13.40	-13.50

2. Route plan for Chennai-Bangalore gas pipeline
Projects and Development India Ltd (PDIL) Noida had expressed interest in optimum routing of Chennai-Bangalore pipeline, which was entrusted to them on behalf of Gas Authority of India Ltd (GAIL), New Delhi.

The cost surface search methodology was applied on this important section to further demonstrate the utility of the technique. Twelve cost layers were derived from thematic maps on soil, geology, water bodies, drainage, transport network, elevation model, slope, road distance, land use, forest maps etc on 1:250 000 scale. CWCS was generated using suitable ranks and weightages and route analysis was performed for two points west and east of Chennai and Bangalore respectively using varying material, construction and access cost ratios. Costs were optimized with mean values having relative significant only. Six different routes based on combination of material, construction and access criteria and having up to 12 per cent saving as compared to a straight-line route have been generated.

Benefits : summing up
The method for semi-automated alignment of pipelines using RS and GIS tools has unique advantages like

• Updated and integrated information on terrain,
• Shortest route by automated and computation based search techniques,
• Spatial and numerical data organization of layout,
• Cadastral overlays for route ROU/ROW measures,
• Cost well compensated by high benefits and speedy implementation and
• Downstream options for O&M support.

The method is general enough to be applicable for other sectors related to linear infrastructure planning like alignment of electric transmission lines, network plans for roads and rail etc.

Concluding remarks: Costs
Two different methods of semi-automated alignment of pipelines using RS and GIS tools have been developed and tested. The cost in terms of budget and time for implementing RS/GIS method seems unnecessary at first glance, but the experiments carries out so far indicate its high benefits compared to cost. In fact various studies point towards almost guaranteed saving of 5-15 per cent. As the cost of implementing the method is merely one-thousandth part of the project cost, cost benefit ratio of over 50 is expected in worst case scenario.