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6. Regrade banks. Restore, stabilize and reclaim watercourse banks and approaches to as close to original grade as practical.
DWG. NO. 1
1. Obtain additional temporary workspace to allow instream spoil to be stored on banks.
2. Install vehicle crossing if warranted.
3. Install sediment and erosion control structures, as required.
4. Leave plugs at end of standard trench.
5. Complete construction of the instream pipe section. Weight and pretest pipe, if warranted, prior to commencement of instream activity.
6. Trench through watercourse retaining hard plugs back from each bank until just prior to pipe installation. Stockpile all instream spoil on banks. Construct berms (e.g., subsoil, saddle weights, shotrock) to prevent saturated spoil from flowing back into watercourse (see Dwg. 16). Maintain streamflow, if present, throughout crossing construction.
7. Lower-in and backfill immediately. Restore stream channel to approximate preconstruction profile and substrate. Attempt to complete all instream activity within 24 hours.
8. If necessary to control water flow and trench sloughing, install temporary soft plugs and dewater trench on to stable vegetated land, not directly to watercourse.
9. Restore, stabilize and reclaim watercourse banks and approaches to as close to original grade as practical.
Source: Adapted from TERA 1998
CONSTRUCTION TECHNIQUE – TYPICAL OPEN CUT OF SMALL WATERCOURSES
DWG. NO. 2
1. Obtain additional temporary workspace to allow as much instream spoil to be stored on the banks as is practical.
2. Leave plugs at the end of the standard trench.
3. Install sediment and erosion control structures, as required.
4. Complete construction of the instream pipe section. Pretest and weight pipe well in advance of anticipated completion of instream trenching.
5. Retain plugs back from each bank until just prior to pipe installation. Stockpile as much spoil on banks as possible. Place instream storage spoil in piles avoiding areas of highest water velocity. Instream spoil should be piled in long piles parallel to flow in order to minimize erosion. Do not windrow spoil across the channel or block more than 2/3 of the channel. Maintain streamflow, if present, throughout crossing construction. Exact trenching and spoil storage requirements will depend on local conditions and equipment used.
5. If necessary, to control water flow and trench sloughing, install temporary soft plugs and dewater trench on to stable vegetated land, not directly to watercourse.
6. Lower-in pipe and backfill immediately. Restore stream channel to approximate preconstruction profile and substrate. Attempt to complete all instream activity as quickly as practical.
7. Restore, stabilize and reclaim watercourse banks and approaches to as close to original grades as practical.
Source: Adapted from TERA 1998
CONSTRUCTION TECHNIQUE – TYPICAL OPEN CUT OF LARGE WATERCOURSES
1. Schedule instream activity for low flow periods and for the appropriate timing window, if feasible.
2. Obtain additional temporary work space to allow instream spoil to be stored on banks.
3. Complete construction of the instream pipe section. Weight and pretest the pipe, if warranted, prior to commencement of instream activity.
4. Construct berm and/or sump to prevent saturated spoil from flowing back into watercourse. Use earth moving equipment to move excavated spoil to a remote storage pile. Attempt to complete all instream activity as quickly as practical.
5. Restore stream channel to approximate preconstruction profile and substrate. Restore, stabilize and reclaim watercourse banks and approaches to as close to original grades as practical.
Source: Adapted from Express Pipeline 1995, TCPL 1994
DWG. NO. 6
1. Install vehicle crossing, if required, on the work side edge of the right-of-way to allow for a wide excavation.
2. Ensure adequate electric power supply and adequately sized pumps to handle anticipated flow. Have standby pumps and generators capable of handling 100% of anticipated flow onsite and ready to be used if the operating pumps fail.
3. Install high volume pump in pool located upstream of the excavation. Excavate temporary upstream sump in the right-of-way if no natural pool exits. Add additional pumping capacity if required. Discharge water through or into an energy dissipator into the channel sufficiently downstream of the trench to prevent water flowing back into the excavation.
4. Immediately initiate fish salvage from isolated pools. Ensure fish salvage permit(s) are acquired prior to installing pump.
5. Excavate a small sump downstream of crossing to collect silt laden waters. Install small pumps in sump and trench to discharge silt-laden water on to well vegetated soils away from watercourse.
6. Excavate trench, complete installation and backfill trench. Move hose if warranted to maintain streamflow.
7. Wash backfilled trench area into sump. Pump silt-laden water from trench onto a well vegetated area off right-of-way. Complete this step each evening prior to shutting off upstream pump, if instream work is to occur on successive days.
DWG. NO. 7
1. A crossing-specific drawing to supercede this typical should be prepared for implementation during construction.
2. Ensure sufficient working space within the coffer dam to accommodate a wide unstable ditch.
3. If there is a high velocity streamflow, install deflection barrier (e.g., median barriers) to permit construction of coffer dam outside full streamflow.
Construct coffer dam from local materials, sandbags, 1 m3 sandbags, aquadams, sheet piling, median barriers, gravel or other 4.
appropriate material to extend over halfway across the watercourse.
5. Install impermeable barrier within coffer dam.
6. Install riprap on upstream side to protect the dam from erosion if dam is constructed of loose material.
7. Install sumps to collect seepage and then pump to dewatering area.
8. Ensure discharge area can handle the volume of water and silt pumped to shore.
9. Complete trenching, lowering in, backfilling and mark end of pipe.
10. Remove coffer dam, reconstruct bank.
11. Install similar structure on opposite side of watercourse enclosing the marked pipe end.
DWG. NO. 10
1. Obtain geotechnical data prior to initiating drilling. Drilling may not be feasible in some materials such as unconsolidated gravels.
2. Ensure temporary workspace rights have been obtained to conduct monitoring and that access is available for monitoring activities.
3. Set up drilling equipment back from the edge of the watercourse; do not clear or grade within the buffer zone.
4. Employ full time inspectors to observe for an inadvertent mud release into the watercourse.
5. Ensure that only bentonite based drilling mud is used. Do not allow the use of any additives to the drilling mud without the approval of appropriate regulatory authorities.
6. Install suitable drilling mud tanks or sumps to prevent contamination of watercourse.
7. Install sumps downslope from the drill entry and anticipated exit points to contain any release of drilling mud.
8. Dispose of drilling mud in accordance with the appropriate regulatory authority requirements.
9. Prepare a drilling mud release contingency plan.
Source: Adapted from ASCE 1996, TERA 1998
DWG. NO. 11 (b)
1. Install a temporary bridge (e.g., log, pre-fabricated span) to allow vehicles to cross watercourses that are sensitive or that have unstable bed and banks. Bridges are also used where watercourses are too deep, wide or fast to permit an alternative crossing structure. This method minimizes sedimentation of the watercourse, and bank and bed restoration work. It is generally limited to watercourses less than 30 m in width.
2. Utilize approach fills rather than cuts in banks to minimize erosion potential. Do not constrict flow with approach fill or support structures. Ensure adequate free-board to handle anticipated streamflows. Use a geotextile liner to prevent fine material from entering watercourse.
3. Remove bridge immediately after use. If bridge is to remain in place through spring break-up to access final clean-up, it must be designed for spring floods and ice jams. Remove support structures and approach fills. Restore and stabilize banks.
4. Install curb stringers of logs or plywood to ensure that fill material does not spill into the watercourse, where required.
Source: TERA 1998
DWG. NO. 13
1. Install ramp and culverts to allow vehicles to cross relatively narrow watercourses where sedimentation must be minimized or fish passage allowed.
2. Design culverts to handle 150% of maximum anticipated flows or to a five year flood level and according to specific guidelines where fish passage (i.e., migration) is required. Contact government authorities for minimum water depth specifications, and maximum water velocities. Ensure dam is impermeable.
3. Place ends of culverts below the natural grade of watercourse at an angle that does not exceed normal watercourse gradient.
Depth of placement is dependent upon bed type, culvert size and expected flow conditions.
4. Remove temporary culverts and ramp materials when no longer required. Remove culvert and ramp prior to freeze-up (summer construction) and prior to spring break-up (winter construction).
5. Restore and stabilize bed and banks.
Source: Alliance 1998
DWG. NO. 14
1. Use fords to provide vehicular access across relatively shallow (less than 1 m) and narrow watercourses with granular beds and stable banks. Where water depth, streambed composition or banks slopes could pose trafficability problems for rubber tired vehicles, limit ford traffic to tracked equipment.
2. Do not use ford during fish spawning, incubation or migration periods.
3. Minimize grading in proximity to watercourse. Grade and grub only along the trenchline and an area immediately adjacent to the trenchline. Pull soil and debris away from watercourse, if banks require sloping.
4. Minimize use of ford.
5. Stabilize banks and approaches with granular blanket underlain by a geotextile, if warranted.
6. Mark boundaries of ford on both sides of crossing to confine all vehicle traffic to ford.
7. Restore and stabilize beds and banks to original contour when ford is no longer needed. Granular blanket need not be removed if it is not a barrier to fish during low flow conditions.
1. Construct sump or berms to contain excavated instream spoil so that silty runoff does not enter watercourse or flow off right-ofway.
2. Strip topsoil from area to be used as spoil storage.
3. Maintain sufficient buffer from the top of the streambank.
4. Berms which do not adequately prevent leakage, such as those made of boulders, shotrock or saddle weights may need a geotextile liner to prevent silty water from entering watercourse.
Source: Adapted from Alliance 1998
DWG. NO. 16
1. Watercourses that have moderate to high sensitivity of fish habitat and/or have steep approach slopes at the proposed crossings may need silt fences during construction, as determined by the Environmental Inspector.
2. Install silt fences at the base of approach slopes following clearing and grading using the method and materials above or other approved designs.