Issue link: http://read.dmtmag.com/i/33025
terrain and validate pipeline alternatives in 3-D. For smaller projects, Mylar overlays were used to visualize thematic layers, where one translucent sheet overlain on another revealed a composite view of planning con- straints and opportunities. Today, these pipeline routing methods, albeit valid for their time, are irrelevant as digital computing and GIS continue to outpace their manual cousins. As a trio of powerful hardware, spatial-aware databases and software, GIS enables engineers and other project stakeholders to model quickly and comprehensively a universe of “what-if” route-planning scenarios. Most relevant to infrastructure planning and linear engineering (e.g., pipelines, power lines, railways, road- ways, etc.) is a spatial modeling technique called least- cost path (LCP). Based on principles of graph-theory, LCP uses a route-finding algorithm that determines the lowest accumulative cost from a begin node to a desti- nation node; or in the case of pipeline infrastructure, a supply node to a demand node. As a raster analysis, cost accumulates by travers- ing a pixel-based friction surface enforced by prede- termined routing business rules. The final output is a string of adjacent pixels revealing the lowest-cost option between nodes (see Figure 1). Generally, the cost in LCP is a qualitative value, usu- ally an integer, which indicates the hierarchical order of individual map layers and their attribute ranges (i.e., rank of slope ranges). This qualitative approach reveals its usefulness when valuing a route’s complete cost while considering the hard costs of construction, but also mitigating or avoiding sensitive impacts. For instance, a straight-line route traversing barren and gentle sloping terrain is economically cheaper when considering constructability alone, but such analyses often underestimate the cost of social and environmental impacts. As a result, some analyses provide evidence in support of longer, more-expensive alternatives over shorter routes that cross sensitive habitats or a vulnerable population. Solidifying this notion are the financiers of large inter- national pipeline projects. The World Bank Group, for example, dictates lending terms requiring biodiversity impact offsets and the economic analysis of multiple alternatives (Goodland, 2005). As punitive measures for crossing sensitive habitats, these offsets include the creation of national green space conceivably 10 times the original right-of-way impact (Goodland, 2005). Costly impacts and subsequent offsets are easily avoidable or planned for during early project phases. By leveraging existing GIS data and well-defined busi- ness rules of pipeline route planning, engineers can confidently select a route by evaluating the multiple paths of obvious (and not-so-obvious) alternatives. Seismic Zone Cost Surface ( 3 6 9 9 Start 6 9 9 1 6 6 9 9 1 3 9 End 9 9 1 1 9 9 1 1 Least Cost Path Analysis Terrain Steepness Cost Surface * 0.75 ( ( + Data Figure 2. GISPRO outputs provide engineers and other pipeline stakeholders with the appropriate level of summary detail to establish a monetary cost estimate. 1 3 3 6 Start 1 3 6 9 9 1 3 9 9 9 1 End 6 9 9 9 1 9 9 9 * 0.25 ( Data Cost Weights Rules Cost Weights Rules Global GeoDatabase Global GeoDatabase Cost Feedback Cost Feedback Route Feedback Route Feedback Cost Breakdown Summary Profile Cost Breakdown Summary Profile Materials Time Labor Materials Time Profile Labor 8 Final Report Output 8 Final Report Output M AY 2O11 / WWW . GEOPLA CE . COM 23 Profile Accumulative Cost Surface & LCP 2.5 5.25 = 7.5 8.25 Start (Cost1 * Weight1) + (Cost2 + Weight2) + … + (Costn * Weightn) CPL Routing and Cost Esimation Process CPL Routing and Cost Esimation Process Stakeholder/Expert Input Stakeholder/Expert Input Chevron LCP Routing Engine Chevron LCP Routing Engine Detailed Report 120 150 30 60 90 0 Detailed Report Executive Summary Project: Reroute XYZ Project Description: Identify plausible route alternatives for the Products system’s Lateral. The routes shall avoid constraints and end at the existing Terminal. 120 150 Key constraints: national forest, national grass lands, urban areas, excessive river and road crossings. Scenarios Conducted: 3 Scenario 1 Description: Alternative 1 (A1) Beginning with the westernmost start location along the Lateral, Alternative 1 (A1) is the “least-cost path” that avoids or minimizes crossing all key constraints listed. This route requires the construction of a booster pump station. Length: 74 miles Estimated Costs: $69,800,000 30 60 90 0 Executive Summary Scenario 2 Description: Alternative 2 (A2) Beginning with the westernmost start location along the Lateral, Alternative 2 (A2) is the “least-cost path” that avoids or minimizes crossing most of the key constraints listed above. This path assumes that an easement or permit would be granted to construct the pipeline on the edge of the route requires the construction of a booster pump station. Length: 50 miles Estimated Costs: $53,400,000 Scenarios Conducted: 3 Project Data Scenario 3 Description: Alternative 3 (A3) Beginning with the westernmost start location along the Products Mainline, Alternative 3 (A3) is the “least-cost path” that avoids or minimizes crossing most key constraints but permits grasslands crossings. This route does require the construction of a pump station. Length: 97 miles Estimated Costs: $81,300,000 Scenario 1 Description: Alternative 1 (A1) Beginning with the westernmost start location along the Lateral, Alternative 1 (A1) is the “least-cost path” that avoids or minimizes crossing all key constraints listed. This route requires the construction of a booster pump station. Length: 74 miles Estimated Costs: $69,800,000 Scenario 2 Description: Alternative 2 (A2) Beginning with the westernmost start location along the Lateral, Alternative 2 (A2) is the “least-cost path” that avoids or minimizes crossing most of the key constraints listed above. This path assumes that an easement or permit would be granted to construct the pipeline on the edge of the National Forest. This route requires the construction of a booster pump station. Length: 50 miles Estimated Costs: $53,400,000 Project Data Scenario 3 Description: Alternative 3 (A3) Beginning with the westernmost start location along the Products Mainline, Alternative 3 (A3) is the “least-cost path” that avoids or minimizes crossing most key constraints but permits grasslands crossings. This route does require the construction of a pump station. Length: 97 miles Estimated Costs: $81,300,000 LCP Corridor Key constraints: national forest, national grass lands, urban areas, excessive river and road crossings. National Forest. This LCP Corridor Project: Reroute XYZ Project Description: Identify plausible route alternatives for the Products system’s Lateral. The routes shall avoid constraints and end at the existing Terminal. Profile GISPRO Outputs GISPRO Outputs Profile 3000 6000 9000 12000 15000 0 Hydraulic & Costing Inputs 3000 6000 9000 12000 15000 0 Cost Engine Chevron $ Chevron Cost Engine $ $ 4.75 7.5 8.25 3 6.75 4.75 7.5 9 3 4.5 7 8.25 9 3 3 End 7 9 3 3 Figure 1. An example illustrates the basic concept of a least-cost path (LCP) scenario using two spatially coincident variables: seismic zones and terrain steepness. Seismic zones have a greater influence (75 percent) than terrain steepness (25 percent), and the single-path LCP is shown and highlighted in green. Hydraulic & Costing Inputs $