Under the Resources tab click on the Data Repository for information related to when it is believed the pipeline break occurred. Note the simulation time at the top of Map View and estimate the number of days since the pipeline break occurred and the number of days since the emergency response team removed the source of contamination. The contaminants that entered the ground-water flow system just after the pipeline break are at the leading edge of the plume. The contaminants that entered the aquifer closer to the time the emergency response team arrived on the scene are near the trailing edge of the plume closer to the pipeline break.
For example, from the information on Map View shown below, the simulation starts 42 days after discovery of the contamination when you will install your first monitoring well. The estimated date when the pipeline break occurred is 2 to 3 weeks prior to discovery. If we assume the shorter time span, the leading edge of the contamination has been in transit for a total of 56 days (42 days + 14 days). The leakage end date is assumed to be 4 days after discovery or 38 days (42 days – 4 days) prior to the start of the simulation.