When logging a forest, forestry companies must build access roads to transport the logs from the forest to the mills.  On average, for every 1km of road in the forest, there are 1 or 2 stream crossings, including bridges over large streams and rivers and culverts in smaller creeks.  Building roads over streams can pose several environmental risks, so foresters choose stream crossings are designed to mitigate the environmental hazards, protect fish habitat, conserve water quality and to ensure logs from the forest can travel safely to the mills. 

Forest Companies use different designs to mitigate the environmental hazards of crossing streams in the forest.  Culverts are the most common alternative to building bridges that are used to cross small streams.  Culverts, if sized and installed properly, can allow fish to migrate upstream, control the spring floodwater, and provide a safe and cost-effective method for crossing a stream.

If sediment enters a stream through runoff, it can have negative effects on fish habitat and water quality.  Foresters employ the use of structures such as cross-drains, settling ponds, and off-takes to ensure water quality in the streams during logging operations.

Forest companies manage their road infrastructure to ensure reliability and to protect environmental values.  Regular inspections are a key part of their management system.  These inspections are used to identify priority locations for maintenance activities including run-off control and culvert replacement.  However, forest companies are not the only stream crossing owners on provincial forest land.  To manage the cumulative effects from all crossings, forest companies can use their inspection reports to work together with other stream crossing owners including energy companies and the provincial government to ensure high standards for all stream crossings in the forest.

A primary focus for forest companies is to manage their road infrastructure to ensure reliability and to protect environmental values.  Forest companies follow appropriate federal and provincial legislation related to riparian areas and watercourse crossing requirements. This includes following provincial or regional “Operating Ground Rules” as they apply to the protection of water related values.  Stream crossings are a fundamental part of the road infrastructure that is necessary to carry out operations on provincial lands.

There are a wide variety of types of stream crossing structures that are utilized by forest companies.  However, all stream crossing structures must be approved by the appropriate authorities (provincial or federal) before work is conducted at the crossing site.  Each stream crossing location is assessed on an individual basis for the appropriate structure; however, there is often more than one appropriate structure that could be used in any one given location for variety of reasons.  An example of some of these considerations is safety, soil stability, general topography, tenure, fish-bearing status, watercourse classification and crossing alignment to highlight a few.   Some examples of stream crossing structures that are most commonly in use are bridges (“timber bridges - made entirely of logs or “manufactured bridges”), arches, culverts, and “snow fills” or “log fills. 

“Manufactured” bridges are a standard stream crossing structure for crossings that require minimal ground and channel disturbance and where the channel and bank development are well defined.  They could be constructed of a combination of steel, concrete and wood and are mainly used for higher ordered watercourse classifications where meeting the watercourse crossing objectives cannot be met with any other crossing structure.  Other practical considerations for their use are that the re-location of the stream crossing is not possible or cost effective or the soil stability warrants that any construction disturbance is well out of the immediate channel area.  They can also be used for seasonal crossings on lager ordered watercourses.  “Timber bridges” are considered a less permanent stream crossing structure and used to access harvest areas for a period of a few years before the bridge is reclaimed.  Timber bridges have more limitations then manufactured bridges in the sense that the length of the span distance cannot exceed the structure capacity.  Therefore, they are used for smaller and more narrowly shaped crossing locations.

Arches are a stream crossing structures that are used when maintaining the natural stream flow or fish passage is a priority, similar to bridges. These structures are essentially and elliptical culvert (arch geometry) without a bottom section.  This allows the stream channel substrate to remain un-altered and function in a more natural state.  Historically, these structures were typically made of metal and only used for permanent crossings; however, new materials and easy install sectional designs are allowing these structures to function as very effective seasonal or temporary crossings. 

Culverts are widely used as stream crossing structures throughout Alberta.  Culverts are installed for both seasonal access or on a more permanent basis.  Culverts are used across a large spectrum of watercourse classifications and can be used to cross fish-bearing watercourses provide they are installed correctly.  Culverts that function for seasonal access (winter or summer only operations) before they are reclaimed may not take into consideration the peak flow of the watercourse since they will be removed before the spring run-off.  Adequately sizing culverts is critical to ensure that the structure will function properly for installations that are considered more permanent or remain in place for a spring freshet.  

In general, the majority of stream crossings installed by forest companies are for temporary or seasonal use.  “Log fills” or “Snow fills” are examples of these types of structures.  “Log fills” are used for lower ordered watercourses such as ephemeral draws and frozen intermittents, where run off will not directly enter a fish-bearing stream.  “Log fills’ are a bundle of logs that are limbed and placed in the watercourse to allow water to pass though.  A separation layer is used between the log layer and the dirt cap surface to prevent soil filtration down into the watercourse.  The expectation is that ‘log fills” are reclaimed after operations are finished and the watercourse will revert back to its natural condition.  “Snow fills” are used in the winter only.   They require that the appropriate watercourse is frozen solid or there is sufficient ice to allow the water to continue to flow under the ice.  They must also have sufficient snow accumulation available for construction.  Snow is used to fill in the crossing site and the compacted snow provides the medium for the stream crossing.  Water is often added to ensure the snow freezes in place and is solid enough for industrial traffic.  The “snow fill” is considered to have minimal impact or disturbance on the watercourse and the crossing will be removed prior to the spring freshet.

The goal of stream crossing installation, use and reclamation is to maintain water quality.  That goal is met by several considerations but the main objectives are to minimizing bank and channel disturbance, ensuring fish passage in fish-bearing streams and prevent the deposition of deleterious material from entering the watercourse.  Some of the common areas of concern to manage for are often related to the control of sediment from run-off that has a negative affect on the aquatic habitat.   The use of cross-drains, settling ponds in ditches and off-take channels help minimize the amount of sediment introduced into the watercourse.  Regular inspections of stream crossings are apart of forest companies monitoring systems.  These inspections determine if the structures are functioning properly and identify any priority areas that require regular maintenance or immediate corrective actions.