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is not revegetated and much of this is either encrusted with a <br />thick layer of evaporite salts, or is disturbed by frequent frost <br />heaving. Water movement through the area has become naturally <br />channelized. In places it has eroded through the eight to ten <br />inch thick layer of peat that remains, thus exposing the <br />underlying till material. A depositional delta has formed at the <br />downstream end of the excavated area just above where the stream <br />channel enters undisturbed vegetation. There is also evidence of <br />iron staining on rocks (yellowboy) in the lower reaches of the <br />disturbed area. This, in association with the presence of pH <br />measurements in the range of 3.2 to 4.3 (from pore waters; stream <br />water pH =7.2), suggests that sulfuric acid is being produced <br />through the oxidation of pyrite. The results of water quality <br />analysis indicate that sulfate concentrations increase from 2 <br />mg /l upstream of the disturbance to 569 mg /l below the <br />disturbance. <br />An interesting observation on the sensitivity of the natural <br />fen vegetation to disturbances in the hydrology was made during <br />the site visits. Vehicle tracks leading into the undisturbed <br />area just above the excavation had left depressions about five <br />inches deep in the peat surface. This provided a channel which <br />intercepted the flow of water to an area between the tracks and <br />the edge of the excavation. The resulting five inch drop in the <br />level of the water table over this area dried out the soil enough <br />to cause all the plants living there to die. This exemplifies <br />Appendix B (vii) • <br />