426
edits
Changes
Jump to navigation
Jump to search
Line 1:
Line 1:
'''Visual Inspection (Level 1)'''<br>This qualitative method is low cost and requires minimal effort to conduct. Visual inspection should be used as an initial step to determine if the LID practice is operating properly. Visual inspections can be performed during dry weather and wet weather to identify situations where water is ponding for longer than intended (24 hours).<br>
Using infiltrometers or permeameters to measure the hydraulic conductivity at several locations in the LID feature at various times of year can quantitatively verify that the practice can perform as intended.<br>
To perform the test, the practice must be filled with synthetic runoff and the change in water level must be monitored. Using clean water from a fire hydrant or water truck, synthetic runoff testing can measure the performance of an LID feature in a controlled environment. For this test to be feasible, a series of conditions must be met:*A water supply that can deliver the required discharge and volume requirements*The LID feature must be offline*No precipitation must be expected for 48 hours*Outflow paths must be temporarily plugged or measured (aside from infiltration)*The water surface elevation can be measured throughout the test<br>
Line 22:
Line 35:
Monitoring offers a comprehensive approach to assessing peak flow reduction and water volume reduction. These reductions can be quantified by completing a water budget during natural storm events, specifically through the measurement of inflow and outflow. Long-term monitoring is especially recommended if the LID feature that is the subject of the test is the first of its kind in its given jurisdiction, if geologic conditions pose a concern, or if the feature is being implemented to protect sensitive and significant natural features. It is important to recognize, however, that the unpredictability of natural storm events can lead to inaccuracies in data collection. Furthermore, long-term monitoring generally has the highest cost of the four levels of monitoring.
no edit summary
Final inspection requirements are in-place to ensure that a final site-wide inspection is performed and allow for mitigation to occur before the contractor is relieved of responsibility. Final certifications are performed by knowledgeable personnel, such as the design engineer, who are qualified to ensure that LID features are operating as intended. This stage is critically important, as it is the last opportunity for issues to be resolved before the property owner assumes responsibility of the practice. The University of Minnesota and the Minnesota Pollution Control Agency recommend four (4) levels of inspection for final inspections of LID infiltration and filtration practices. The level of inspection, or combination of tests, that is selected is dependent on the goals of the assessment and feasibility of each inspection.<br>
'''Final Certification'''
Final inspection requirements are in-place to ensure that a final site-wide inspection is performed and that mitigation can occur before the contractor is relieved of responsibility. Final certifications are performed by knowledgeable personnel, such as the design engineer, who are qualified to ensure that LID features are operating as intended. This stage is critically important, as it is the last opportunity for issues to be resolved before the property owner assumes responsibility of the practice. Four (4) levels of inspection exist for final inspections of LID infiltration and filtration practices. The level of inspection, or combination of tests, that is selected is dependent on the goals of the assessment and feasibility of each inspection.
'''Visual Inspection (Level 1)'''
This qualitative method is low cost and requires minimal effort to conduct. Visual inspection should be used as an initial step to determine if the LID practice is operating properly. Visual inspections can be performed during dry weather and wet weather to examine various aspects of LID performance, such as the following:
*draw-down time
*ponded water
*soil properties
*plant cover and plant health
*sedimentation
[[File:Double ring.JPG|300px|thumb|right|Double-ring infiltrometer.]]
[[File:Double ring.JPG|300px|thumb|right|Double-ring infiltrometer.]]
'''Surface Infiltration Capacity Testing (Level 2)'''<br>
'''Surface Infiltration Capacity Testing (Level 2)'''
Level 2 includes the employment of quantitive methods of testing and data collection. These tasks are also cost-effective and can establish if the LID feature was built in conformance with the design specifications. Some level 2 tests include the following:
*soil sampling and testing
*elevation surveys
*infiltration testing
*synthetic runoff testing
'''Synthetic Runoff Testing (Level 3)'''<br>
'''Continuous Water Level Monitoring (Level 3)'''
Site infiltration rates can be measured with greater accuracy through continuous water level monitoring. This monitoring approach evaluates seasonal infiltration performance through the monitoring of temperature and groundwater levels. The following conditions and equipment are necessary for continuous water level monitoring:
#A perforated observation well
#A water level logger
#A rain gauge within 5 km of the site
Using rainfall and water level data can provide an understanding of drawdown times after variously sized storms.
<gallery mode="packed" widths=300px heights=300px>
<gallery mode="packed" widths=300px heights=300px>
</gallery>
</gallery>
'''Long-term Monitoring (Level 4)'''<br>
'''Long-term Monitoring (Level 4)'''
High-intensity monitoring is a comprehensive but expensive approach to assessing peak flow reduction and water volume reduction during natural runoff events. These reductions can be quantified by completing a water budget during natural storm events, specifically through the measurement of inflow and outflow. Pollutant load reductions can also be quantified with the appropriate technology. Long-term monitoring is especially recommended if the LID feature that is the subject of the test is the first of its kind in its given jurisdiction, if geologic conditions pose a concern, or if the feature is being implemented to protect sensitive and significant natural features.
For greater detail on certification protocols see: [[https://cvc.ca/wp-content/uploads//2021/07/2016-04-21-web-version-CVCbioretentionCertificationProtocols.pdf | Low Impact Development Certification Protocols: Bioretention practices]]