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4.2.1 Aquatic Assessment The primary objective of the aquatic assessment is to identify the level of sensitivity of the watercourse and aquatic resources, and to gather information for routing and crossing method selection, and development of mitigation measures.
In most cases, routine pipeline crossings of watercourses with known sensitivity do not require aquatic assessments since standardized mitigation as outlined in Section 5.0 designed to protect the aquatic resources is implemented during construction. In other situations, where little information is known relative to the sensitivity, further investigations are required.
The level of detail for these investigations will vary according to the watercourse and the construction techniques considered. Where crossing construction will not generally result in HADD of fish habitat (i.e., reaches with limited habitat potential), field data collection should be limited to basic fish habitat information including: type of fish habitat (warmwater or coldwater), common fish species;
and a general description of any fish habitat at the proposed crossing and within the zone of influence.
Where little information is available on a specific watercourse, yet regional information and initial routing investigations indicate that the watercourse may support sensitive or critical habitat, a more detailed aquatic assessment may be warranted. Table 4.2 presents a comprehensive list of parameters that could be evaluated. Generally, most watercourse assessments would include some, but not all those listed. Nevertheless, the greater the detail the more likely that the regulatory authorities will review and approve the crossing without delays caused by further field visits or additional meetings. Prior to conducting any assessments, proponents should discuss the level of detail required with regulatory agencies, at which time they may suggest the type of information and assessment requirements.
Sources: Adapted from RIC (1999) and Alberta Transportation (2001).
Note: These parameters should be considered as a very comprehensive list and not those that should be used in all assessments. Aquatic assessments should be tailored to the size and sensitivity of the watercourse. This list should be used as a guideline from which to select those parameters that are appropriate for the size and sensitivity of the watercourse.
Page 4-12 October 2005 Pipeline Associated Watercourse Crossings 3rd Edition 4.2.2 Geotechnical and Hydraulic Assessment The objective of a geotechnical and hydraulic assessment is to identify long- and short-term processes that could affect habitat and water quality as well as the presence of potential hazards that may threaten the integrity of a pipeline and, to a lesser extent, vehicle crossing. In addition, a detailed geotechnical evaluation of subsurface conditions may be required for trenchless techniques (e.g., horizontal directional drill).
River hydrology should be evaluated to identify the discharges that could be encountered during the period of construction and the potential discharges that could be encountered during a flood. Other streamflow information indicating which periods would not be suitable for construction should also be included.
A geotechnical engineer should design detailed drainage and sediment control for approach slopes. Examination of the approach slopes and textural classes of soils in the valley aids in the positioning of subdrains, trench breakers, silt fences, netting, cross ditches and diversion berms.
Before planning trenchless techniques, surficial and fluvial materials within the drill or bore path should be evaluated to determine whether they are appropriate for this method. Common techniques include ground penetrating radar (GPR) and drilling of bore holes.
Watercourse crossings often contribute to cumulative effects on fish and fish habitat, wildlife and wildlife habitat and land and resource use. Planners and engineers should be aware of the issues, timing restrictions, mitigation measures, and possible regulatory requirements for assessing and managing cumulative effects.
Cumulative effects evaluations consider the combined effects now known to take place over larger study areas and longer time frames. Cumulative effects must be specifically considered for all individual watercourse crossings where HADD authorizations are required and for all NEB-regulated projects (see Section 2.1.4 of this report). Unlike aquatic assessments that focus on sensitivity and risk during the construction period, the primary objective of cumulative effects analysis is to identify and mitigate long-term effects on fish and wildlife mortality, movements, and maintenance of habitat availability and quality. This recognizes that watercourse crossings and rights-of-way have an ‘indirect footprint’ that extends well beyond the physical footprint until native vegetation on and immediately adjacent to the right-of-way returns to pre-disturbance conditions. This generally requires decades to achieve.
In recent watercourse crossing applications, some projects have been required to assess the wildlife and vegetation resources of valleys associated with the watercourse. In particular, some jurisdictions pay special attention to overwintering ungulates (i.e., moose, deer, elk), species with special conservation status (e.g., Species At Risk Act or the Committee on the Status of Endangered Wildlife in Canada (COSEWIC) listed species, provincially listed species or migratory birds) or special status vascular plants (e.g., Species At Risk Act or COSEWIC listed species or provincially listed species).
Cumulative effect assessment is an evolving practice and no standard accepted method exists for watercourse crossings. The level of effort should be appropriate to the number of crossings being considered, other existing watershed disturbances, and the combined long-term risk to fish and fish habitat. One of the key deficiencies of current approaches is that they typically overlook the longterm cumulative effects risk from: increased harvest; movement barriers (e.g., culverts); and non-point sediment, nutrient, and contaminant input.
A detailed discussion of analysis tools is beyond the scope of this document, however proponents and technical specialists should choose the most appropriate approach from the suite of tools described in Table 4.4. Additional information is provided in the Filing Manual (NEB 2004) and Hegmann et al. (1999).
Selection and approval of watercourse crossings by the proponent and regulators, respectively, requires a thorough knowledge of the advantages and disadvantages of various crossing methods and techniques. Unfortunately, except for a few senior field personnel, most engineers, planners and regulatory staff do not attain sufficient experience to understand the various techniques to be able to sufficiently evaluate the risks of each. Tables 3.1 and 3.2 summarize the engineering and environmental advantages and disadvantages of the various techniques discussed in this document.
TERA Environmental Consultants (1996) and P.A. Harder and Associates Ltd.
(1995) summarized a total of 326 pipeline associated watercourse crossing case histories as background documents to this document (Appendix B). These studies, although largely anecdotal, do portray a good cross section of both successful and poorly constructed crossings.
4.3.1 Regulatory Risk Risks associated with not fulfilling the regulatory requirements during a crossing may be twofold. Firstly, the project may be delayed or rejected if no or insufficient information is submitted. In the event that an application is approved, insufficient information may cause the regulatory agency to invoke restrictive conditions to ensure protection of the resources. Secondly, if a project proceeds without the appropriate approvals, shut downs, charges and potentially convictions may result.
4.3.2 Construction Risk Each technique has its own risks, some for which it is very difficult to plan and others for which there is little that can be done once a problem has arisen.
Selecting and approving crossing techniques must be done with a full knowledge of the risks and proponents and regulators should recognize the adverse effects that can occur. The risks associated with each technique will vary according to many factors. This includes but is not limited to: project scope; contractor’s ability, experience and commitment; pipe size; and season of construction.
Table 4.5 summarizes some of the more common problems associated with various techniques and identifies the environmental risks associated with each.
In addition, it gives an indication of the scale of the identified risks as well as general mitigation measures and contingency plans that should be considered in advance of construction during the planning phase.
Notes: 1 Sources: Harder (1995), TERA (1996), authors’ experience 2 Scale of risk incorporates probability of occurrence and severity of effect.
In selecting a watercourse crossing technique, proponents and regulatory agencies must evaluate the economic considerations at each particular site. Ideally, the cost of protective measures should be related to the social or environmental "value" of the resource potentially at risk. For this reason, the economic costs associated with various construction techniques must be balanced against the potential adverse environmental effects.
4.4.2 Indirect Costs In evaluating the economics of a crossing, possible reductions in indirect costs are often overlooked. For instance, directionally drilling a watercourse may lead to considerable savings since no bank reclamation or ongoing maintenance will be necessary in that location and mitigation requirements for other resources (e.g., wildlife habitat) may be reduced or avoided. Conversely, horizontal directional drilling may be disproportionately expensive if contractors are unavailable, extensive geotechnical evaluation is needed prior to construction or large volumes of drilling fluids require disposal. Table 4.7 identifies relative costs associated with various activities and requirements of each watercourse crossing method.
4.5.1 Pipeline Crossings The selection of a watercourse crossing method often causes the greatest conflict between industry and regulatory agencies. In recent years, the expectations of the regulatory agencies have evolved to the point that in some jurisdictions, proponents are informed that no instream activity is permitted in flowing waters that have the potential to support any fish. In other jurisdictions, industry has become accustomed to a regulatory environment that permits instream activity as long as it is not within restricted activity periods. In either situation, it is prudent to select a crossing method in a logical and reproducible manner based on sensitivity and mitigation potential.
Recent projects have related crossing methods to established sensitivity criteria for each watercourse. This leads to a reproducible selection of crossing methods.
A more detailed matrix included in the application may allow some regulatory agencies to follow the logic behind the selection process and approve in principle other crossings as long as the proposed methods are used.
Table 4.8 summarizes considerations that can be used in selecting a watercourse crossing technique.
The table is based on generic crossings and, where several techniques are suggested, the decision as to which will be selected will depend on detailed evaluation of specific concerns.
Table 4.8 provides guidance for the selection of a crossing technique.