effective stormwater management through the use of low-impact development (lid) techniques
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Effective Stormwater Management Through the Use of Low-Impact Development (LID) Techniques. Justin Gregory, PE Jones Edmunds & Associates October 3, 2012. OVERVIEW. Current Stormwater Situation. Current Stormwater Situation. Low Impact Development. - PowerPoint PPT PresentationTRANSCRIPT
Effective Stormwater Management Through the Use of Low-Impact Development (LID) Techniques
Justin Gregory, PEJones Edmunds & Associates
October 3, 2012
OVERVIEW
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Low Impact Developmen
t
Current stormwater problems
New Facilities
RetrofitSwales
Regulations
Current Stormwater Situation
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Impairments
TMDLs and BMAPs
Energy Independence and Security Act
Current Stormwater Situation
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Traditional solutions not working well enough.
How do we meet our stormwater management goals?
Low Impact Development
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LID / Green Stormwater Infrastructure
Distributed
Treatment train
Replicate natural hydrologic response
NASA Propellants North Admin & Maintenance Facility
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LEED Platinum
Designed to reach net-zero energy
Rainwater harvesting key aspect of design
NASA Propellants North Admin & Maintenance Facility
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7,500-gallon rainwater harvesting.
• Toilets.• Irrigation.• Treated water for drinking and hand washing.
Supplies:
Other LID components
Sunset Boulevard Bioretention
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Community facing large nutrient load reduction goals
Erosion problem
LID Retrofit Opportunity
Existing Conditions
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Direct discharge to Indian River Lagoon
Erosion problems at discharge to Lagoon
Limited space within the ROW
High infiltration rates
Solution
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Offline bioretention
Median Swale/Inverted Median
Solution
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Curb cuts
• Overflow - Extreme Events.
Inverted median advantages
• 30% more volume than swales.
Normal Flow.
Overflow during extreme events
Performance
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8” Rainfall 7-9 Oct 2011.
• Visual Monitoring.• No observed runoff.• Recovered overnight.
Costs
• TN < 30% conventional treatment.• No land purchase needed.
Sarasota County Swale Study
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Enhance County-wide pollutant loading model
Measure effects of conveyance swales
Account for possible load reductions
Sarasota County Swale Study
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Promote distributed infiltration
Disconnect impervious area
Common in Sarasota County
Versus
Phillippi Creek Basin
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2 curb & gutter sites
3 swale sites
Besides drainage type all else was equal
7 months/40 samples
Phillippi Creek Basin
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TSS
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78% lower
Statistically significant
Literature 61-86%
Nitrogen
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TN - 68% lower.
TKN – 72% lower.
Nox – 22% lower.
Highest removal particulate nitrogen.
Phosphorus
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TP - 25% lower.
Ortho-Phosphorus – 17% lower.
Not statistically different.
Runoff
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Rainfall vs. Percent Runoff
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
0 0.5 1 1.5 2 2.5
Rainfall, in.
Perc
ent R
unof
f
Runoff Coefficient 58% lower
3x as much rain without runoff
5x lower annual runoff volume
Observed Load Differences
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TN – 93%
TP – 81%
TSS – 95%
BOD – 93%
LID Constraints
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Technical.
Inertia.
Regulatory.
LID Manuals
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Local Design Standards.
Account for local hydrology.
Provide reasonable assurance.
Meet WMD Permitting Requirements.
Promote LID.
Local Hydrology
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Varies across the state.
Significantly effects LID performance.
How do we account for this?
-6
-5
-4
-3
-2
-1
0Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
Aver
age
Dept
h to
Wat
er (
feet
)
Average Depth to Water at USGS Well 270959082203003
Sarasota
-1.6
-1.4
-1.2
-1
-0.8
-0.6
-0.4
-0.2
01 2 3 4 5 6 7 8 9 10 11 12
Dept
h Be
low
SHW
T (F
eet)
Months
Jacksonville
Local Design Curves
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Consider local climate.
Consider local hydrology.
Simplify permitting.
Allow for BMAP credits.
Key Components
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Alter practices for local conditions.
Work with end user of the manual.
Performance based design curves.
Average annual effectiveness.
Conclusion
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LID provides additional tools to meet our stormwater requirements .
Replicate natural runoff response.
Conclusion
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Distributed stormwater treatment.
• Infiltration• Settling• Filtration• Sorption• Biogeochemical processes
Design should consider all removal mechanisms