5 - Revised Risk Assessment / Forest Road Drainage Installation Practices in the Pacific Northwest

Forest Road Drainage Installation Practices
in the Pacific Northwest

5 - Revised Risk Assessment	Alternative Measures, Risk Management

If the initial risk assessment resulted in a moderate, high, or very high rating, the layout engineer and the construction supervisors should discuss possible alternative measures (below) to reduce the overall risk of sediment introduction to the stream.

Alternative Measures for Risk Reduction of Sedimentation

avoid crossing watercourses with machinery if it is unnecessary
put in place skid bridges or temporary bridge spans to gain access to the other side, in order to maintain bank and channel stability
use clean blasting mats as a temporary stream crossing
pump around, dewater or divert streams, and have a backup dam in place downstream of the work site
minimize overburden stripping and excavations near stream edges
adhere to shutdown guidelines for heavy rainfall
minimize exposure of erodible soil to the elements
control road surface runoff near streams by crowning roads, stabilizing ditches, or installing cattleguards in road approach
use rock ballast or blacktop on bridge approaches
drain surface runoff away from streams with +2% to +3% grades onto the bridge from both sides for a minimum of 10m
avoid large road cuts in favour of constructing fill retention on the down-slope side of the road where this is possible. Protect exposed erodible soils in cut and fill slopes with rock or gravel blankets
avoid bridge designs which contain components too heavy for one machine to handle if access to the far side is difficult
plan construction for the low flow / low rainfall time of year, or within the fisheries windows
find a more suitable site with a reduced sediment source potential.

Risk Management

The construction supervisor should review the risk rating and the nature of the consequence with the construction crew, e.g., proximity of the worksite to fish habitat. The construction crew should develop a strategy to ensure that a low risk of sediment delivery is maintained at all times. It is important to identify and discuss viable options beforehand to avoid uncontrollable situations during construction. If at any time during the construction an operator or supervisor feels that the risk is higher than originally determined, a revised risk assessment should take place and measures implemented to reduce the risk further. It is important to have a well-stocked sediment control kit on site to be able to deal with unexpected emergencies.

If for some reason you are uncertain about fish presence in the stream, or whether the watercourse is legally diverted downstream from your work site for domestic water use, the consequence rating should default to a "high".

Remember that you can only reduce the risk by reducing the hazard, i.e., you can not manage the consequence.

Documentation

It is recommended to document key points of agreements and discussions with affected water users, industry and agency representatives pertaining to the installation of drainage structures. Photographs of preventative measures and construction details may become useful not only for future structure inspections but also as a record that due diligence was exhibited during the installation work.

5 - Revised Risk Assessment