A long-haul pipeline is a linear construction problem where one slow spread or a permit hold-up ripples through the whole schedule. The board wants one thing from the analysis: an in-service date it can commit to. This case study runs a Tamara schedule-risk model of a 12-activity, 540 km cross-jurisdiction pipeline - survey and permitting through trenching, welding, HDD crossings, hydrotest and commissioning - and turns that question into a confidence curve.
The S-curve is the headline: read the commitment date off it at any confidence level. P10 lands at 1,026 days, P50 at 1,153, P80 at 1,243 and P90 at 1,293. The deterministic plan completes in 970 days but is beaten in only 3% of runs - a near-certain overrun if it is treated as the promise date.
Twelve activities with three-point PERT durations, chained on a critical path, plus six discrete risk events - permits, weather, contractor disputes, ground conditions, HDD failures and logistics. One Monte-Carlo of 60,000 iterations drives every chart.
Reaching an 80% confidence date needs 273 days of contingency - nine months - on top of the 970-day plan, a direct consequence of stacking a dozen weather- and permit-exposed activities in series.
The contingency ladder converts the curve into a decision table. Each rung is the buffer beyond plan for a given service level: P50 needs +183 days, P70 +239, P80 +273, P90 +323 and P95 +363 days. Pick the rung that matches the consequence of missing the date.
The tornado ranks activities by how strongly their duration correlates with the completion date. Multi-jurisdiction permitting leads at a cruciality of 0.58, with welding and NDT second at 0.50 and trenching and excavation third at 0.41 - the front-end approvals and the linear weld spread are where management attention pays off.
Cost is schedule-linked: every day beyond plan adds about $0.18M of spread stand-by and overhead, so cost and schedule overrun together. The joint density shows 37% of runs finishing both late and over the $322M budget; at P80 the project reaches 1,243 days and $336M, already $14M past budget. Buying schedule certainty on permitting and the weld spread is the most direct way to cap cost.
The Pareto ranks the discrete risk events by expected schedule impact. Permit/regulatory delay leads at 5.0 expected weeks with extreme-weather shutdown close behind at 4.7 weeks; the top five of six events carry ~80% of the expected discrete-risk delay.