How do the levels measured fit in with what was seen before the Cerro Grande Fire?
For several of the larger canyons draining the Laboratory there are many pre-fire sample results to compare post-fire runoff events against. Because of less than normal precipitation in the late 1990s, however, for some of the smaller streams there is limited data from before the fire. The average and maximum measured at the wetter sampling stations is indicated on the data table. These are based on data collected at each of these stations from 1995-1999. Although runoff data has been collected for much longer than that, the pre-1995 data was all collected manually. Manual samples are generally collected late in the flow event, because it takes some time for the sampling team to get to the flow when it starts raining. Therefore, manual samples do not include the first movement of water and sediments in the flow, known as the “first flush”. The first flush generally contains the highest concentration of contaminants, so the manual samples generally do not include these potentially highe