Recovery of chemical and physical properties of boreal plain soils impacted by pipeline burial

Pipeline construction on the Canadian boreal plain occurs on woodland and/or agricultural fields, but soil recovery from its impact is not well documented. Therefore, we quantified changes over 3 yr (1992 to 1994) in the chemical properties of two Grey soils and the physical properties of a Grey soil that were subjected to pipeline burial and cropped to barley. The pipeline right-of-way (RoW) was divided into three zones: a road (or work) area used for vehicular traffic, a trench area for burying pipeline, and a pile (or spoil) area where soil was stockpiled during excavation. Pipeline construction resulted in mixing of subsoil material with topsoil, and the chemical properties most affected were those that varied most with depth. The pH, electrical conductivity, soluble sulphate, and exchangeable Ca and Na were increased in the surface 20 cm of soil, particularly the road and trench areas. The affected properties moderated 2 or 3 yr after pipeline construction as soluble components were dissolved or dispersed and translocated back to lower soil depths. The RoW zones had increased soil strength and compaction, and reduced water retention and infiltration rates. However, the deterioration in soil physical condition was similar across the RoW zones, indicating that it was due mainly to land clearing, a requirement to convert woodland to agricultural land. Improvement in bulk density, and water infiltration and retention in 1993 and 1994 indicated that the RoW was undergoing rehabilitation with time as a result of natural processes and annual cropping. Key words: Chemical properties, exchangeable cations, sulphate, physical properties, soil-water, pipelines