With careful planning and execution, foresters can keep local waterways pure when building roads and crossings. A look at everything from planning through to culvert selection and installation, grass seeding and de-activation.
The modern forester has a lot of responsibilities. In the early days of commercial logging, it was widely believed that our forest resource was inexhaustible. Today, we recognize not only the limitation of our timber supply, but also the multitude of values associated with our forests and rangelands: complex ecosystems, First Nations' culture and history, recreational opportunities, and the purity of local water sources.
In fact, the importance of protecting our water has been given special emphasis lately both across Canada and in B.C.
The province has become a world leader in establishing forest practices legislation that will protect the working forests for future generations. Many other provinces and countries are modeling new forestry legislation after B.C.'s recently introduced Forest Practices Code. The Code is setting high standards for forestry operations in B.C. and is establishing enforcement provisions that promote responsible forest stewardship.
The regulations specify the forest practices that apply province-wide. Standards may also be established by the chief forester to expand on the regulations. Forest Practices Code guidebooks have been developed to support the regulations.
While not mandatory, the recommendations in the guidebooks provide information to help users exercise their judgment in developing site-specific strategies to accommodate resource management objectives. When a recommendation or a passage from a guidebook is included in a plan, it then becomes enforceable under the Forest Practices Code.
British Columbia, like other provinces, has a law that specifically regulates the use and diversion of water. The intent of the B.C. Water Act is to protect the environment and the rights of other licensed users, and to minimize flood damage. A developer working on private land must obtain a water license or approval before work is done in or around a stream. (A stream is technically defined as having continuous and fixed banks and a crossing is required for all continuous and intermittent drainage flow channels, springs, seeps and moist areas.)
The Water Act clearly defines how an applicant can make certain types of changes in and around a stream.
Maintaining the purity of local water resources involves a lot of informed options. So, although it is by no means exhaustive, here's a foresters' guide to safe, environmental, efficient, and economic stream crossings. The material is drawn from Canadian governments, forestry papers, industry expertise and guidelines, as well as from measures used in good forestry practices.
First, a plan
A forest development plan, spanning five years, must be prepared for each unit within a forest company's harvesting area. Roads, stream-crossing structures, and sites should be selected, designed and constructed to ensure optimum use of roads, minimize costs of deactivation, and accommodate all resource values.
All bridge crossings, culverts, fords and ditches must be designed and constructed to maintain natural drainage patterns, allow fish passage where needed, and avoid cross-surface drainage.
Culvert and bridge crossing location and design must match individual site needs and accommodate the following flood returns:
- 50 years for a temporary structure on public lands; 100 years for a permanent structure on public lands.
- 200 years or the channel capacity on land not covered by the Code.
For minor culvert installations, a detailed site plan is usually not required. Major culverts and bridge crossings require a detailed site plan supported by geotechnical and biophysical information, such as slope and soil composition, stream characteristics, channel configuration, and riparian vegetation.
Design of a crossing must conform to current requirements of all agencies and governments. During construction, ensure that road and crossing design specifications are followed.
Clear up questions
Construction specifications and drawings are reviewed and compared against the actual work being completed as well as variations to the specifications. Often joint licensing/agency on-site visits can clear up questions.
Construction drawings and specifications are applied to all permanent or semi-permanent bridges and major culverts, according to the latest code requirements of the Canadian Standards Association Design of Highway Bridges, CAN/CSA-S6, and the latest version of the Canadian Foundation Engineering Manual. The peculiarities of unbalanced logging truck loads and eccentricities must be considered in all bridge designs.
Factors that affect a crossing include: debris passage, icing, sediment as a bedload mover, livestock damage, and human damage.
In special situations, the main flow of a stream or river may be temporarily diverted using ditches, berms, dykes, piping, high capacity pumps, or an existing alternate channel, allowing work to proceed. Diversions are challenging and require planning, forethought and timely execution. Stream diversions may not be allowed in certain locations or seasons.
During all stages of the diversion, it is imperative to avoid siltation by using hay bales, sediment socks, settling ponds, silt fences, filter cloths, and naturally vegetated areas to remove silt from water pumped or running from the work area. Use strainers to keep fish out of pump inlets.
When debris movement is anticipated at the crossing structure for non-fish-bearing streams, it is necessary to install some form of debris control. "Grizzlies" debris catchers or debris basis can be installed or constructed to catch or divert debris from the culvert entrance. All debris-control structures must be routinely inspected and maintained.
Review and renew
Wild animals, environmental degradation, construction, and harvesting practices can damage field markings. Before starting construction, all markings should be reviewed and, if necessary, renewed. Markings for winter use must be above the potential snow level.
The right of way should be of variable minimum width needed for road and crossing construction. All standing trees within the clearing width must be felled, and, as much as possible, trees must be directionally felled away from streams or wetlands. Felling and yarding techniques must be selected to prevent streambank destabilization.
Planners, construction managers, and operators should work together to develop a construction plan that supports the objectives of habitat protection. Such basic measures as avoiding storing materials, fueling and servicing equipment, undertaking equipment maintenance, and cleaning in riparian areas, go a long way toward reducing harmful effects. Excavation should be suspended during bad weather -- heavy rainfall, for example -- when the potential for damage to the environment is greatest.
Ensures natural drainage
Correct selection and installation of culverts is one step toward ensuring that natural drainage is maintained and sediment transfer kept to a minimum. There are many choices of culvert materials: wood, concrete, metal and corrugated polyethylene.
Log culverts can be efficient and durable structures that protect natural stream features and can be ideal for forest road construction where suitable logs and experienced crews are available.
Proper installation of culverts -- regardless of the material used -- is critical to ensuring that road stability will not be compromised by ineffectively installed drainage. Unstable or erodable fill at culvert inlets-outlets should be protected with erosion-resistant material to prevent scour and erosion. The foundation beneath the pipe must provide reasonably uniform resistance. Avoid installing culverts where situations may cause uneven settling or pressure points on culverts leading to blockage.
The multi-plate arch used for drainage is a semi-circular, galvanized, corrugated steel structure, which does not disturb the stream bed and provides a natural course for water flow. The arch is constructed bolting single, curved, steel plates together onto prepared footings. Properly designed and installed, the arch has an expected service life of 100+ years with minimal maintenance.
Must be fully functional
Slash and debris must be disposed of and managed in such a way that the material does not enter a watercourse or contribute to slope instability.
Temporary or permanent drainage systems must be built concurrent with subgrade construction, and must be fully functional and maintained. Excavated material must not be sidecast on steep slopes with high or very high mass-wasting potential.
To ensure long service life, culverts must be properly backfilled and compacted. Granular materials such as pitrun gravel or coarse sands are recommended. Ensure that the material does not contain large rocks that could, over time, affect the structure.
Many culvert-fill failures are caused by the lack of adequate compaction during backfilling. When cohesive-type materials are used, attention must be given to ensuring it is compacted at optimum moisture content. Thorough compaction should be done in lifts of 150 to 300 mm of material at a time, and worked by hand or with mechanical equipment, tampering rollers, or vibrating compactors.
Records must be kept
All temporary and semi-permanent bridges and major culverts must be inspected at least once every two years and permanent bridges at least once every three years, or after unusually high flows and other unexpected events that could damage structures. Records of inspection, noting the general condition of all components, must be kept. Excellent drainage control depends on follow-up actions to implement the inspection results.
Roads must be inspected and maintained to protect the structural integrity of the road prism, keep drainage systems functional, and ensure user safety requirements. An annual maintenance plan must be prepared and followed and maintenance checks must ensure that sediment production and effects on other resources are minimized. New to the industry is the use of an "inspection tracking system." Many operations have hundreds of kilometres of old and new roads; keeping track of all of these can be a formidable task.
Inspections and remedial work must be carried out as often as indicated by the risk to the road, its users, and adjacent resources. This inspection process must assess the adequacy of ditches and culverts, the requirements for improved drainage works, road surfacing or re-vegetation, and other elements of road integrity and safety.
Unique solutions
While it is recognized that there are general techniques and procedures to minimize environmental damage, site-specific conditions may require a solution unique to a location.
It is recommended that grass seed mixtures be applied to all exposed soil that will support vegetation in the first growing season after construction (ground disturbance). Areas to be revegetated include inactive borrow pits, waste areas, road cuts, fill slopes, and all other disturbed areas.
There are many species and varieties of grasses and legumes. Each mix is usually suited to an application and site. In British Columbia, where rainfall, winter and summer temperatures and elevation vary widely, site-specific formulations are the key to success.
In riparian areas and some slope situations, it is desirable to plant appropriate trees and shrubs as well as grass and legumes. Woody plants provide stronger root systems than grass and contribute to restoring the productivity of the riparian area or stream and, in all applications, provide slope stability.
The best time to place seed is immediately after the ground has been disturbed. This allows the seed to fall into openings in the soil, before the surface becomes compacted by the effects of weather. However, consideration must be given to moisture and temperature conditions. For best results, it is suggested that dry seeding be done when moist weather is anticipated for at least three weeks or on the snow in the spring.
Hydro-seeding offers engineers and erosion-control specialists a variety of options in erosion protection. With its ability to broadcast seeds over a large, inaccessible area quickly, safely, accurately, and with relatively high probability of germination, it offers unique advantages. Applying seed in a medium creates a "mat," which holds the seed in place. The added mass increases accuracy and throw distance. The liquid medium adds stability to soils in exposed, windy areas, and the mulch helps retain soil moisture, accelerating germination and enhancing the survival rate of grass seedlings.
Hydro-mulches act as carrying agents in the hydro-seeding process. The most common hydro-mulches are made of paper, paper mill sludge, wood fibre, or a combination. In additional to acting as carrying agents, hydro-mulches help to retain soil moisture, enhancing seed germination and survival.
Additives like tackifiers, soilbonding agents, moisture-retention agents, and fertilizers can all be incorporated into hydro-seeded mixtures. Depending upon the type used and the site-specific conditions, these additives may maintain their effectiveness for up to two years, decomposing over time.
There are many types of hydro-seeding delivery equipment systems available and each has its pros and cons. Sizes range from 30-gallon ATV-mounted pumpers to 30-gallon 4 x 4 pickup mounted units, 10-wheeled, 4,000-gallon behemoths to helicopter buckets.
Use pre-approved plan
Roads must be deactivated according to the pre-approved plan when they are no longer in regular use and are not being regularly maintained. At this time, the roadway prism and cleared width must be stabilized and natural drainage restored.
Integrated resource management objectives and ongoing and future vehicle access requirements as identified in the access management plan must be incorporated into deactivation planning.
The extent of deactivation as identified in the access management plan must take into consideration the period that regular use of the road is to be suspended, and the risk to other resources.
Information must be posted to advise road-users of hazards that may be expected due to deactivation.
Particular attention must be paid to stream-crossing areas to ensure water quality during and after the deactivation process.
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