426
edits
Changes
Jump to navigation
Jump to search
Line 118:
Line 118:
'''Geotextile'''<br>[[File:geotextile-with-excess-and-granular.jpg|400px|thumb|right|Geotextile draped over the edges of the LID practice. Backfilling with granular material is taking place.]]
Construction Steps:*Roll out fabric on the flattened sub-grade surface*Provide a minimum overlap of 300 mm between adjacent lengths of geotextile. If the manufacturer specifies a greater overlap, follow the manufacturer’s specification*Fabric should be secured in place with stakes along the edge of the sub-grade surface and where lengths of fabric overlap*Provide 500 mm of excess at the ends of each length of fabric*Excess material should be folded on top of the infiltration medium/choker course once installed*Provide cuts for trees where appropriate
Key Inspection Points:*Geotextile is clean and free of damage*Geotextile delivered to the site matches the design specifications and is approved by the engineer prior to installation*Sufficient overlap is provided between lengths of fabric*Geotextiles have been applied as per the manufacturer’s guidelines*Structural considerations for geotextiles have been made when applied adjacent to infrastructure and the geotextile can handle expected structural loads*Class II geotextiles conform to OPSS 1860
Mistakes to Avoid:*Wrinkles in the fabric – follow the manufacturer’s procedure for installation to ensure geotextiles lie smooth on sub-grade*Unnecessary application of geotextile – mixing of media is negligible where structural loads are not expected, so geotextile does not need to be applied. Also geotextiles should not be used where root growth is encouraged to penetrate different layers of media
For more information on geotextiles, see the page on geotextiles. '''Underdrains'''<br>Underdrains are pipes that can be included to collect subsurface water. Their design is determined by the drainage requirements of the feature. Construction Steps:*Install the underdrain to grade with a consistent slope of 0.5% to 1.0%*Connect overflow risers with single-elbowed ‘y’ connections or 45° elbows*Situate maintenance risers where siltation is expected in drain lines (such as at junctions or where grade and direction changes occur)*Mark the locations of risers*Use video inspections to confirm that the interior of the underdrain remains free of debris after construction Key Inspection Points:*Size, type, and material of the underdrain conforms to the design specifications*Underdrain is perforated prior to arrival on-site*Drain material is resistant to UV radiation and any chemicals in the soil and groundwater*Clean-outs are positioned correctly and spaced appropriately for the size of the underdrain*Any manual perforations are approved by the engineer*Pipe grade matches design specifications*Tie-in locations to municipal sewers meet City specifications Mistakes to Avoid:*Incorrect overflow risers – ensure single-elbowed ‘y’ connections or 45° elbows are used for overflow risers instead of ‘T’ connections*Incorrect drain size – confirm underdrain has an internal diameter greater than or equal to 200 mm to reduce freezing and allow cleaning and camera inspections*Potential for clogging – Remove sock from underdrain prior to installation For more information on the design of under-drains, see the page on under-drains. '''Impermeable Liners'''<br>[[File:impermeable-liner-along-road.jpg|400px|thumb|right|An impermeable liner was placed along one side of the LID facility to prevent infiltrated water from contacting the nearby watermain in the road right-of-way, which runs parallel to the feature.]]Impermeable liners can be applied when LID features are not intended to infiltrate runoff into the underlying soil. Where building foundations that are adjacent to the LID feature are not waterproofed, liners can be used to protect neighbouring infrastructure. Construction Steps:*Compact 30 – 50 mm of sand over the soil onto which the membrane will be installed to protect against punctures. Alternatively, a geotextile can be used in the place of sand*Place lengths of liner on the bed of the facility as per the manufacturer’s specifications*Provide 150 mm of overlap between adjacent lengths of liner*Secure liner in-place and bond together the overlapping portions of liner as specified by the manufacturer*Where pipes provide drainage from the practice, a flange should be sealed to the pipe and liner.*Compact sand or apply cushion fabric on top of the liner to protect against punctures Key Inspection Points:*Liner is confirmed to match design specifications*Liner installation conforms to manufacturer’s specifications*Minimum overlap between lengths of liner is achieved *Need for impermeable liner is confirmed through field verification of setbacks to adjacent infrastructure*Sand and/or geotextile are applied on both sides of the liner to protect against punctures*Lengths of liner are bonded together to ensure protection against groundwater contamination For more information on impermeable liners, see the page on liners. '''Overflow or Overflow Drain'''<br>Overflows are features of inline facilities and convey larger storm events out of the LID feature. Construction Steps:*Connect the overflow drain to the under-drain *Install overflow pit to grade at the location specified in the contract documents*Fit a metal, domed grate to the overflow Key Inspection Points:*Overflow drain matches design specifications*Overflow pit is positioned at the maximum water surface elevation of the practice, as per the contract documents*Sufficient freeboard is provided between the overflow and inlet such that the inlet is not inundated by design storm flows*Overflow grate matches design specifications*Overflow grates that are located in high-traffic areas are screwed on or equipped with locks Mistakes to Avoid:*Backflows – ensure that backflows are avoided by confirming that inlet and overflow elevations match design specifications with surveys*Incorrect sequencing – install overflow drain prior to backfilling with granular material and engineered soil*Incorrect grate material – avoid using plastic overflow grates due to breakages and UV degradation For more information on overflow drains, see the page on overflows. '''Monitoring well'''<br> Construction Steps:*Anchor the perforated pipe to the bottom of the LID feature*Install a lockable cap to the top of the standpipe to protect against vandalism Key Inspection Points:*Pipe is perforated, rigid, and matches design specifications*Well is installed according to contract documents*Geotextile sock is wrapped around the perforated portion of the well Mistakes to Avoid:*Incorrect sequencing – ensure that standpipe is installed prior to backfilling with granular material For more information on monitoring wells, see the page on monitoring wells.
→Backfill Granular and Pipes (JC)
{{:Construction: final excavated grade and verification}}
{{:Construction: final excavated grade and verification}}
===Backfill Granular and Pipes (JC)===
===Backfill Granular and Pipes (JC)===
{{:Geotextiles: Installation}}
Geotextiles are filter fabrics that can be installed to separate dissimilar soils and prevent the migration of materials. As such, proper installation of geotextiles is important for ensuring the proper division of materials.
{{:Underdrains: Installation}}
{{:Impermeable liners: Installation}}
{{:Overflow: Installation}}
{{:Monitoring wells: Installation}}
Monitoring wells are important for sampling procedures and ensuring that bioretention features are performing as intended.
===Backfill Granular and Pipes (SPC)===
===Backfill Granular and Pipes (SPC)===