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Line 1: ===Excavation and mass grading: final excavated grade and verification===
Construction: final excavated grade and verification (view source)
Revision as of 14:58, 22 September 2022
, 1 year agono edit summary
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 very specific grading requirements. Verifying depths and slopes is critical for 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. Similarly, if the designs call for 1 metre of excavation from grade and only 90 cm are excavated, it will not have enough storage space to meet the design criteria. <br/>
[[File:trimble unit.JPG|400px|thumb|right|Always confirm elevations throughout construction. (Photo source: CVC)]]
<u>Excavation to the sub-grade</u> 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%.
As with all infiltrating LID practices, avoid compaction of sub-grade soils whenever possible. However, depending on the design and the local municipality, compaction of the sub-grade may be required for permeable pavement LIDs.
'''Construction steps'''
'''Construction steps'''
#Excavate from the rough grade to the finish grade using appropriate equipment. This is often done with hand tools.
#Excavate the final 100 mm, to the final design grade, using appropriate equipment. This is often done with hand tools.
#Confirm excavation depths and slopes using appropriate equipment (transit levels, global navigation satellite systems, etc.)
#Confirm excavation depths and slopes using appropriate equipment (transit levels, global navigation satellite systems, etc.)
'''Key inspection points'''
'''Key inspection points'''
*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