BMP Monitoring Sites - Urban Drainage and Flood Control District

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UDFCD BMP MONITORING SITES Pervious Concrete Pavement PERVIOUS CONCRETE PAVEMENT Description Location Typical Details Installation Photo Gallery Monitoring Data Other Examples Description General Pervious concrete pavement is a relatively new type of permanent surfacing. It is a monolithically poured pervious concrete pavement that has 15% to 21% of its volume as void. These voids within the concrete are achieved by eliminating the fine sand aggregate from the concrete mix. They provide the flow paths for rainwater from the surface of the pavement to the base course underlying it. Because the integrity of the concrete structure may be harmed by standing water during freezing weather, the use of pervious concrete pavement is not recommended for use in pervious pavement detention installations. It is critical that sufficient aggregate base course layer is provided under the pervious concrete slab to store the runoff and allow it to infiltrate slowly into the ground and drained using an underdrain pipe system. Having a sufficiently thick layer of aggregate base course is particularly critical during the months of the year when freezing of water can occur. Site Specific The pervious concrete pavement site monitored by the District is located in Lakewood. Modular block pavement was monitored in this location from 1994-2004. In 2005, the modular block was replaced with the pervious concrete pavement that is currently in place. Two separate pads of pervious concrete pavement were placed using different aggregate sizes for the base course. The east pad used
UDFCD BMP MONITORING SITES Pervious Concrete Pavement AASHTO #67 and the west pad used AASHTO #8. Below the surface, there are two lateral flow barriers in the form of concrete walls. At each barrier, the filtered water is collected in perforated pipes and carried to a manhole located adjacent to the pervious concrete pavement. Inside the manhole a riser pipe with an orifice is sized to drain the entire gravel pore volume of each cell in 6 hours or more. A riser pipe with a levelogger is located just upstream of each manhole to measure the flow coming from each cell. All flows from the pervious concrete pavement are combined and discharge east of the site through a V-notched weir where a pressure transducer measures the depth of flow and sends the data into the sampler. Adjacent to the pervious concrete pavement watershed is a control watershed of traditional asphalt pavement used to compare results of treated runoff to untreated, direct runoff. Stormwater runoff from the control watershed is collected in a sump catch basin at the northeast corner of the site. Water is conveyed a short distance to the outfall and flows through an H-flume where flow is measured by a pressure transducer. The sampling equipment is stored in a shed near the outlet works. A rain gage on top of the shed measures rainfall and signals the ISCO samplers inside the shed to begin sampling after 0.1 inches of rain falls. The samplers then draw a sample of water from both the pervious concrete pavement runoff and the control runoff after ??? cfs has passed, and then every 15 minutes until 12 hours after the storm has ended.
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BMP Monitoring Sites - Urban Drainage and Flood Control District

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