BMP Monitoring Sites - Urban Drainage and Flood Control District

UDFCD BMP MONITORING SITES
Porous Asphalt Pavement
gravel, #3 gravel and C-33 sand. In a trench beneath the sand, a perforated pipe
collects the filtered water and conveys it to a catch basin. There is an orifice
plate at the end of the pipe where a pressure transducer measures the flow into
the catch basin from the porous asphalt pavement. There is
also a weir plate at the outlet of the catch basin with a
levelogger that measures the flow leaving the catch basin.
The difference between the flow passing the orifice plate and
the flow passing the weir plate is equal to the runoff that
bypassed the porous asphalt pavement and entered the catch
basin through the grate.
The sampling equipment is stored in a metal box in the island
adjacent to the porous asphalt pavement. A rain gage on a post
near the storage box measures rainfall and signals the ISCO
sampler inside the box to begin sampling after 0.1 inches of rain
falls. The sampler then draws a sample of water from the porous
asphalt pavement runoff after a designated flow has passed, and
then every 15 minutes until 12 hours after the storm has ended.
There is also a control watershed located a few hundred feet northeast of the
porous asphalt pavement watershed. The control watershed consists primarily of
traditional asphalt pavement and is used to compare results of treated runoff to
untreated, direct runoff. Stormwater runoff from the control watershed is collected
in a grated catch basin located in the northeast corner of the parking lot. The
water leaves the catch basin by passing through a weir
plate where a pressure transducer measures the flow.
The sampling equipment is stored in a metal box
adjacent to the parking lot in a manner similar to the
porous asphalt pavement sampling configuration.