Risk management needs to be considered in all infrastructure projects. While laws and regulations must be met, it is essential to maintain our social licence to operate by being aware of the proximity of neighbours and the broader community. Even on the easiest sites, health and safety and the environment should be top priorities in earthworks management.
Risk is comprised of two components – the probability of something happening and the consequence if it does. This Manual provides engineering options to reduce both components. For example, Erosion, Sediment and Slash Control Structures (Chapter 7) gives solutions to many common forestry risks by reducing the chance of an environmental incident and the seriousness of the outcome if it did occur.
There are factors both within and outside our control. Environmental aspects that planners and forest engineers have direct control over include:
- The location of the infrastructure
- Construction design standards, including erosion and sediment control structures
- The management of earthworks construction. For example, where fill is placed, and whether earthworks meet specifications and are constructed in suitable weather conditions.
Risk must also be considered in the planning, design and construction of site factors that are outside our control. These include:
- Topography
- Soil, geology, and overall erosion susceptibility
- Climate and storm occurrence and intensity
- Protected areas such as indigenous vegetation areas, threatened species and fish habitat, historic and archaeological sites
- Sensitivity of the downstream receiving environment
- Phone lines, water pipes and other services.
1.3.1 Land ownership, boundaries and access
Always determine land and tree ownership through legal checks, before work starts.Unfortunately, sometimes harvesting, and occasionally roading, occur on a neighbouring property without knowledge or consent. Title boundaries do not always follow sensible operational boundaries so neighbours often have informal agreements. Always do a cadastral (map or survey) check in order to establish the land title and obtain an oversight on land ownership, boundaries and access. Do not just take the supposed landowner’s word that they own the land and/or trees. Access determined on a handshake a decade ago between neighbours can lead to major problems if not sorted out at the initial planning stage. Also, it is always good to let the tenant know of plans in advance if there is an absentee landowner.
Egress onto council and state highways needs to be well thought out and, where possible, should be discussed with the relevant organisation well in advance of harvest. Regulations, consents and approvals (Chapter 2) discusses in detail access onto public roads and the process to get approvals.
1.3.2 Understand site features
The following paragraphs provide some information on site features that should be considered when planning for infrastructure. It is not an exhaustive list. In some areas different factors will be significant and others irrelevant. Create checklists of factors that need to be considered in your working circle.
Site topography will influence the location/position of road and landing infrastructure, and the earthworks construction techniques employed. Obtaining suitably detailed mapping and survey data is an essential step in the planning and design process. 1:5,000 scale topographical maps with 5 m contour are often used for planning, however more detailed topographical and engineering surveys may be necessary for the design of large scale and high-risk earthworks.
Site geology and the stability of steep slopes should be assessed during the planning phase. Avoid, as far as practicable, locating infrastructure on high risk areas like gully heads, landslide scarps or slips, earthflows or near riparian margins. Terrain models produced from LiDAR survey and photography are particularly useful in identifying hazardous landforms and features such as hummocky surfaces and crescent shaped depressions.
Field inspections will identify other signs, such as trees leaning uphill or downhill, wetlands or wet ground in elevated positions, plants such as rushes or nikau palms growing on a slope, and water seeping from the ground. Soil classification and understanding the slope stability is an important factor in the design of earthworks. The Field Description for Soil and Rock – Guideline for the Field Classification and Description of Soil and Rock for Engineering Purposes is a good reference document.
Water bodies and drainage are critical elements in road and landing construction. Avoid sediment discharge to water bodies to protect aquatic ecosystems. The design process must consider the impact that the construction and ongoing use will have on water bodies. The natural drainage patterns should be identified with roads located and designed to cater for sensitive areas.
The NES-PF requires assessment of many environmental considerations but not all. For example, in many parts of New Zealand, new archaeological sites are still being regularly identified in forestry operations. Understand your obligations under Heritage New Zealand. This is discussed in Chapter 2.
Powerlines can be challenging to work with. Be careful of the distance requirements for machinery around some of the larger capacity cables like the 22 KV and larger KV lines. Work with the relevant lines company. Accidently damaging lines can have financial and social impacts to you and users.
1.3.3 Set design standards and carefully manage earthworks
These critical road components will be discussed in detail throughout the Manual. The first step in the design process is to confirm operating requirements and the design standards. Appropriate design standards will ensure fit for purpose infrastructure that is safe and efficient for road users and the harvesting operation, and which minimises the foot print (scale and extent) and environmental impact of the earthworks.
The design process should include a constructability review. This considers the timing and sequencing of work, roadline salvage operations, the safe placement or disposal of stumps and stripping, the disposal of unsuitable material and that cut to waste in end-haul earthworks. The review should be a risk assessment.
Successful and effective earthworks projects include good production planning. The contractor needs to understand the designer’s intention for the earthworks in order to plan and implement the earthworks successfully. This requires the designer to provide clear project specifications regarding the material and standard of workmanship required.