Changes

Excavation to the specified depths in the drawings is critical to the LID feature’s future performance. It also requires heavy machinery which, if used incorrectly, can compact soils and lower their native infiltration rates. <br/>

Excavation to the specified depths in the drawings is critical to the LID feature’s future performance. It also requires heavy machinery which, if used incorrectly, can compact soils and lower their native infiltration rates. <br/>

[[File:Excavation outside in 2.JPG|400px|thumb|Excavating from impervious surfaces adjacent to the LID practice minimizes compaction.|right (Photo Source: CVC, 2018)]]

[[File:Excavation outside in 2.JPG|400px|thumb|right|Excavating from impervious surfaces adjacent to the LID practice minimizes compaction. (Photo Source: CVC, 2018)]]

'''Construction steps'''

'''Construction steps'''

#Mark out the limit of excavation.

#Mark out the limit of excavation.

*Confirm the limit of excavation.

*Confirm the limit of excavation.

*Use of excavation equipment specified in the contract, in the required manner (from the outside in, with a mini excavator, etc.).

*Use of excavation equipment specified in the contract, in the required manner (from the outside in, with a mini excavator, etc.).

*Confirm excavated rough grade and final grade prior to backfilling using survey equipment

*Confirm excavated rough grade and final grade prior to backfilling using survey equipment.

*Use of toothed bucket and scouring the bottom of practice if applicable

*Use of toothed bucket and scouring the bottom of practice if applicable.

*If appropriate, measure compaction using a cone penetration test or a cone penetrometer  

*If appropriate, measure compaction using a cone penetration test or a cone penetrometer .

*If appropriate, field verify infiltration rates at excavated bottom of practice using Guelph permeameter or double ring infiltrometer

*If appropriate, field verify infiltration rates at excavated bottom of practice using Guelph permeameter or double ring infiltrometer.

'''Mistakes to avoid:'''

'''Mistakes to avoid:'''

*making too many passes with heavy machinery within the LID footprint.

*Making too many passes with heavy machinery within the LID footprint.

*leaving heavy machinery within the LID’s footprint (for breaks, lunch, overnight, etc.)

*Leaving heavy machinery within the LID’s footprint (for breaks, lunch, overnight, etc.).

*using the wrong equipment

*Using the wrong equipment.

*over excavating

*Over excavating.

*smearing the bottom of the practice with the bucket, which can compact native soils

*Smearing the bottom of the practice with the bucket, which can compact native soils.

==Final excavated grade and verification==

==Final excavated grade and verification==

LID designs typically have specific grading requirements. Verifying depths and slopes is critical for the optimal performance of the facility. For example, if the design calls for a channel with a 1% slope, the channel may not function as designed if it has a 2% slope instead.  

LID designs typically have specific grading requirements. Verifying depths and slopes is critical for the optimal performance of the facility. For example, if the design calls for a channel with a 1% slope, the channel may not function as designed if it has a 2% slope instead.  

[[File:trimble unit.JPG|400px|thumb|right|Always confirm elevations throughout construction. (Photo source: CVC)]]

[[File:trimble unit.JPG|400px|thumb|right|Always confirm elevations throughout construction. (Photo source: CVC, 2022)]]

Excavation to the sub-grade will differ depending on whether the design is for a [[Bioretention: Variations|full infiltration, partial infiltration, or no infiltration LID system]]. If it’s a full infiltration or partial infiltration practice, the sub-grade should be as level as possible to promote even infiltration across the facility’s footprint.  For no infiltration designs,  excavate sub-grade slopes to the design grade in the direction of the underdrain, typically 1 to 2%.  

Excavation to the sub-grade will differ depending on whether the design is for a [[Bioretention: Variations|full infiltration, partial infiltration, or no infiltration LID system]]. If it’s a full infiltration or partial infiltration practice, the sub-grade should be as level as possible to promote even infiltration across the facility’s footprint.  For no infiltration designs,  excavate sub-grade slopes to the design grade in the direction of the underdrain, typically 1 to 2%.  

*Confirm final excavated depths and slopes.

*Confirm final excavated depths and slopes.

'''Mistakes to avoid'''

'''Mistakes to avoid'''

*“eye-balling” depths and slopes

*“Eye-balling” depths and slopes