Planning Horizontal Directional Drilling for Pipeline Construction

7 ENVIRONMENTAL CONSIDERATIONS
HDD crossings are often undertaken to minimize the adverse environmental
effects at watercourse crossings. Nevertheless, an HDD does not guarantee that all
adverse environmental effects will be prevented. Common adverse effects are the
result of:
• inadvertent returns of drilling fluids into the aquatic, terrestrial or
social/cultural environments; and, to a lesser extent,
• disturbance of soils, vegetation, wildlife and social/cultural elements arising
from either construction of drill sites, exit areas, access roads and temporary
vehicle crossings, or the HDD activity.
Further details on the environmental effects of inadvertent releases can be found
in many documents, including:
• Horizontal Directional Drilling Best Management Practices Manual, Topical
Report. Gas Research Institute. May, 2002; and
• Quantifying the Effects of Sediment Release on Fish and Fish Habitats,
Anderson, P.G., B.R. Taylor and G. Balch. 1995. Prepared for the Department
of Fisheries and Oceans.
7.1 Aquatic Issues
A fish and fish habitat assessment of the water body to be crossed may be
warranted to assess potential effects on these resources. Information from this
assessment would be useful in prioritizing of containment / clean-up efforts in the
event of an inadvertent release into a watercourse or in the preparation of
appropriate mitigation / compensation plans if the HDD was not successful and
another crossing method was necessary.
Adverse effects on the aquatic environment can result from the following:
• introduction of drilling fluids and mud into a watercourse, and any subsequent
clean-up;
• poor surface runoff control from the drill site resulting in erosion and material
entering a watercourse;
• disruption of aquifers that feed instream upwelling;
• improper water withdrawal;
• introduction of foreign or undesirable organisms from contaminated
equipment; and
• spills of fuel or other hazardous material.
Potential effects on aquatic habitat and fish populations could include:
• HADD including instream, bank and riparian habitat at the crossing;
• elevated turbidity and increased deposition of sediment downstream;
September 2004 Planning Horizontal Directional Drilling for Pipeline Construction Page 7-1