Week 10: Post-Construction Maintenance and Assessment Flashcards
Why do we need to maintain?
Hint: 3 A’s
- Asset functionality
- Asset longevity
- Aesthetics
What are the main issues underpinning maintenance needs?
- Dynamic systems
- Climate change
- Poor consideration and maintenance requirements at design stage
- Significant capital investment
- SW systems are in public, shared spaces
What are the maintenance fundamentals of bioretention?
Surface
- Clogging
- Erosion
- Surface Cover
Vegetation
- Density
- Plant Health
- Presence of Weeds
Infrastructure
- Blockage
- Damage
- Inspection of all openings
What are the maintenance fundamentals of swales?
Channel
- Sediment build-up
- Erosion
Vegetation
- Density
- Plant health
- Presence of weeds
What are the maintenance fundamentals of permeable pavement?
Paver, asphalt and chip material
- Vehicle damage
- Sub-base stability
- Clogging of pores
What are the maintenance fundamentals of constructed wetlands?
Hydrology
- Water levels
- Hydraulic retention time
- Flow paths
Sediment
- No erosion
- Sediment build-up in zones
Vegetation
- Density
- Plant health
- Presence of weeds
- plants in right zones
Safety and amenity
- Unsafe access
- Odour
- Litter and aesthetics
- Structures condition
Wetlands require regular maintenance of:
- Unblocking structures
- Vegetation management
- Erosion management
- Litter removal
(as well as less frequent repairs and desilting)
Wet ponds require major sediment removal every __ to __ years.
20 to 30 years.
What are the maintenance fundamentals of wet ponds?
Hydrology
- Water levels
- Hydraulic retention time
- Flow paths
Vegetation
- Grass trimming
- Presence of weeds
Sediment
- No erosion
- Sediment build-up in forebay
- Sediment build-up in main pond
Safety and amenity
- Unsafe access
- Odour
- Litter and aesthetics
- Structures condition
What does post-construction monitoring check for?
- Treatment media
- Water level
- Infiltration rate
- Hydraulic retention time
- Drawdown time
- Pollutant removal rates
What are the objectives of post-construction monitoring?
- Compare current performance to design
- Inform maintenance
- Inform remedial and retrofit work
What is the aim of infiltration testing?
Quantify saturated hydraulic conductivity of the media. Mimic the natural process of saturation.
Why use a double ring infiltrometer rather than a single ring?
Single ring: water starts to spread out, overestimates infiltration rate
Double ring: Collar of water holds central column of water, more realistic infiltration rate
How would test location within a stormwater system affect infiltration rates?
Consider inlet vs. outlet.
Inlet: Blinding (fines) around inlet –> lower infiltration rate compared to outlet.
What assumptions are you making in infiltrometer testing?
Collar effect.
Also, constant driving head. (Can solve by kepeing constant water level but measuring values of water required to top up)
