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Mechanisms in a Subsurface Infiltration Stormwater Control Measure
Citation:
Liu, J. AND Mike Borst. Mechanisms in a Subsurface Infiltration Stormwater Control Measure. Presented at International Low Impact Development Conference, Nashville, TN, August 12 - 15, 2018.
Impact/Purpose:
Shaft use and clogging were investigated by examining the changes in drawdown rate associated with different hydraulic heads through the monitoring period to understand the mechanisms in subsurface infiltration stormwater control measure. Under a Cooperative Research and Development agreement, EPA and the Louisville and Jefferson County Metropolitan Sewer District monitored exfiltration from three permeable pavement strips (10D, 14D and 17D) located in east downtown Louisville, KY. Monitoring occurred from April 2013 through December 2015 (189 storm events > 2.54 mm). Each strip has a series of 0.46-m diameter subsurface infiltration shafts along the length of control. Shaft use and clogging were investigated by examining the changes in drawdown rate associated with different hydraulic heads through the monitoring period. Although statistical analysis generally shows sequential filling, for individual events, shafts were neither always filled sequentially from upgradient to downgradient, nor filled in the same order. Overflow may not be the main reason driving the fill order. There were 5, 7, and 10 shafts installed in strips 10D, 14D and 17D, respectively. To manage 80% of the rain events, strips 10D and 14D required all the shafts, but strip 17D needed only 6 of the 10 shafts. The 5-min rainfall intensity and event rainfall depth are important factors effecting the number of shafts needed in a storm event. During the monitoring period, only the first three shafts in strip 10D and the first shaft in strip 14D showed exfiltration rate decreased (clogging). There was no obvious trend found for other shafts.
Description:
Under a Cooperative Research and Development agreement, EPA and the Louisville and Jefferson County Metropolitan Sewer District monitored exfiltration from three permeable pavement strips (10D, 14D and 17D) located in east downtown Louisville, KY. Monitoring occurred from April 2013 through December 2015 (189 storm events > 2.54 mm). Each strip has a series of 0.46-m diameter subsurface infiltration shafts along the length of control. Shaft use and clogging were investigated by examining the changes in drawdown rate associated with different hydraulic heads through the monitoring period. Although statistical analysis generally shows sequential filling, for individual events, shafts were neither always filled sequentially from upgradient to downgradient, nor filled in the same order. Overflow may not be the main reason driving the fill order. There were 5, 7, and 10 shafts installed in strips 10D, 14D and 17D, respectively. To manage 80% of the rain events, strips 10D and 14D required all the shafts, but strip 17D needed only 6 of the 10 shafts. The 5-min rainfall intensity and event rainfall depth are important factors effecting the number of shafts needed in a storm event. During the monitoring period, only the first three shafts in strip 10D and the first shaft in strip 14D showed exfiltration rate decreased (clogging). There was no obvious trend found for other shafts.