© Office of Water Programs — 2010

The Office of Water Programs

Christian Carleton, P.H., CPSWQ, CPESCBrian Currier, P.E.David Alderete

LID Implementation Challenges:Monitoring and Measuring Results

Select OWP Experiences

©

• Field monitoring guidance

• Results of testing at Sacramento State

Field Monitoring Guidance

• Flow Monitoring Issues– Accurate rain gauges and drainage areas– Influent flume sizing

• We know large storms bypass, so why size flumes to monitor what we already know? Size flumes up to the design storm for water quality purposes

• 0.16 in/hr is a common water quality design intensity, so 0.5 in/hr may be reasonable for a good range of storms.

– Effluent flume sizing • Smaller flumes should be used for flows from filter media or

orifice-controlled outlets

• Do not ignore small events– Monitor flow on the small events

and consider a few water quality events as bonus data

– There is far more uncertainty in the hydraulic performance than there is in the quality of filtered water, so focus on the flow!

Small storms are avoided to minimize

‘false-starts’ for water quality samples due to insufficient volume to

collect a minimum number of aliquots.

Field Monitoring Guidance

• 80/20 Sand/Compost• Initial hydraulic capacity

can be very high and depends on drying

• Maximum was nearly 500 in/hr

• Mostly-saturated hydraulic capacity ranged from 40 to 60 in/hr, though as low as 17 in/hr was observed.

Results of Testing at Sacramento State

• Dry-weather flow negatively impact LID systems

– Soil doesn’t have a chance to dry out– How does it happen:

• Raised-landscaping runoff

• Irrigation overspray

• Vehicle/street/sidewalk/driveway

washing

Results of Testing at Sacramento State

• Treatment is governed by hydraulics

• Instantaneous and short-term treatment tests are very misleading

• Filtered vs. bypass depends on:

– Media type, depth, area, and ponding depth

– Local hydrology

– Catchment size and shape

Results of Testing at Sacramento State