Citation:

Brown, R. AND Mike Borst. Monitoring Strategies in Permeable Pavement Systems to Optimize Maintenance Scheduling. Presented at 2015 International Low Impact Development Conference, Houston, TX, January 19 - 21, 2015.

Impact/Purpose:

There is limited guidance for scheduling maintenance on an as needed basis. Three instrument types [water content reflectometers, a passive capillary lysimeter, and pressure transducers] were selected to be installed beneath the surface of six permeable pavement systems in Louisville, KY to remotely monitor the longitudinal progression of surface clogging and predict maintenance needs. This presentation describes how each instrument was used to provide guidance for maintenance scheduling and highlight the lessons learned about how site specific factors can hinder this objective in field applications.

Description:

As the surface in a permeable pavement system clogs and performance decreases, maintenance is required to preserve the design function. Currently, guidance is limited for scheduling maintenance on an as needed basis. Previous research has shown that surface clogging in a permeable pavement system progresses from the upgradient edge. Based on this observed surface clogging pattern, three instrument types were selected to be installed beneath the surface of permeable pavement systems to remotely monitor the longitudinal progression of surface clogging. The instruments include: water content reflectometers (WCRs), a passive capillary lysimeter, and pressure transducers. The Louisville and Jefferson County Metropolitan Sewer District installed 14 permeable pavement strips in parking lanes in a 6.9-ha sewershed in Louisville, Kentucky. The strips were 2.4-m wide and ranged in length from 16.8 to 36.6 m. Based on the longitudinal street slope, six were selected to be instrumented. All were instrumented with WCRs and pressure transducers and one had a passive capillary lysimeter. The WCRs were used to measure the relative amount of infiltrating water. As surface clogging progressed to a WCR position, more runoff infiltrated over the WCR producing a significantly larger response compared to the response from direct rainfall. The magnitude of the response decreased as surface clogging advanced beyond the WCR position. The passive capillary lysimeter measured the infiltration rate through a 20.3-cm diameter divergence control tube. Unlike the relative response measured by the WCRs, the passive capillary lysimeter provided a quantifiable infiltration rate. Pressure transducers in piezometers were installed in at least three locations along the length to measure the rise and fall of water. The infiltrating water created a subsurface gradient. As surface clogging progressed along the length and approached the next downgradient piezometer, the gradient between the piezometers reversed. The results from the three instruments supported each other and that surface clogging progressed from the upgradient edge. Embedded instruments with remote monitoring capabilities reduce the need for manual surface infiltration tests or multiple site visits to understand surface condition and schedule maintenance. This presentation describes how each instrument was used to provide guidance for maintenance scheduling and highlight the lessons learned about how site specific factors can hinder this objective in field applications.

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