Transcript Document

Green Infrastructure at the Campus
and Watershed Scale at the
University of North Carolina at
Chapel Hill
Carolyn Elfland, UNC Chapel Hill
Sharon Myers, UNC Chapel Hill
Ted Brown, Biohabitats, Inc.
Sally Hoyt, Biohabitats, Inc.
Carolina North
Main Campus
Mason Farm
Overview
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Background
Regulatory Framework
Central Campus BMP Implementation
Lessons Learned
Carolina North Opportunities
Background
Central Campus
• 740 acres
• 13.4 million square feet in 2000
• 7.5 million square feet to be added by 2010
• Stormwater Issues
• Flooding and pipe surcharging increasing in
frequency and severity
• Need to improve water quality leaving the
campus
Background
Satellite Campus – Carolina North
• 1000 acres
• Undeveloped except for small general aviation
airport
• Plan to develop 250 acres in 50 years
• Aggressive sustainability goals, including
stormwater
Regulatory Framework
Town of Chapel Hill Zoning
• 85% TSS removal for first 1 inch of
preciptation
• Volume leaving site post-development shall not
exceed volume pre-development for the 2 year
24 hour storm event (3.60 inches)
• Rate leaving site post-development shall not
exceed rate pre-development for the
• 1 year storm – 3.0 inches
• 2 year – 3.60 inches
• 25 year – 6.41 inches
• 50 year – 7.21 inches
Regulatory Framework
Jordan Lake TMDL
• Existing development or redevelopment
• 35% total nitrogen reduction
• 5% total phosphorus reduction
• New development
• 2.2 lbs/acre/year unit loading rate target for
total nitrogen
• 0.82 lbs/acre/year unit loading rate target for
total phosphorus
Watersheds
Bolin (lavender)
Battle (gray)
Chapel (blue)
Meeting of the Waters (pink)
Morgan (beige)
Campus Best Management Practices
Type of BMP
Green Roofs
Permeable Pavement
Bioretention
Vegetated Conveyance
Ponds and Wetlands
Underground Water Quality Devices
Underground Storage (including cisterns)
Land Cover Conversions
Number
3
7
9
2
9
7
19
15
Best Management Practices
Phillips
Hall/
Memorial
Hall
Best Management Practices
Estes
Storage
Lot
Best Management Practices
Friday
Center
Lot
Best Management Practices
Carrington
Hall
Best Management Practices
Hooker
Fields
Best Management Practices
Rams
Head
Center
Best Management Practices
cisterns
Rams
Head
Center
plastic storage modules
Best Management Practices
Rams
Head
Center
Best Management Practices
Rams
Head
Center
Best Management Practices
Rams
Head
Center
Best Management Practices
Fed-Ex
Global
Education
Land Cover
PreConstruction
Change
Without BMPs
Pervious
Acreage
442.2 acres
-10.4 acres
Impervious
Acreage
297.7 acres
+10.4 acres
Change
With BMPs
Total Nitrogen
+224 lbs/yr
-556 lbs/yr
Total
Phosphorus
+14 lbs/yr
-57 lbs/yr
Central Campus Lessons Learned
• Don’t put cisterns on roofs
• Cistern water is not free
• Make careful plant selections for green
roofs
• Porous paving design makes a
difference
• High quality fill material is important
• Education is critical
Carolina North
Applying Central Campus Lessons in an Integrated,
Sustainable and Holistic Manner
Carolina North
• Up to 250 acres of a 1,000 acre parcel
to be developed sustainably (energy,
landscape, water, transportation,
buildings) over next 50 years.
• Currently small regional airstrip
surrounded by mixed hardwood and
pine forest.
• Site also contains an inactive
municipal landfill, a chemical waste
site currently undergoing remediation
and old municipal public works and
bus depot yards
Phase 1 – First 15 Years
Phase 1 Principles
• Respect the ecology of the site
• Focus on transit-oriented
development
• Create a sense of identity and place
• Provide appropriate local connections
for bike, pedestrian, transit &
roadways
• Design for efficient land use with
appropriate density
Stormwater Strategies
• Develop a water budget for the site that
mimics the natural, undisturbed
infiltration capacity of the land using
practices and techniques that
emphasize vegetative filtering and
uptake and/or infiltration.
• Provide water quality treatment for all
impervious areas using practices that
emphasize vegetative filtering and
uptake and/or infiltration.
• Provide treatment as close to the
generating source as possible.
Horace Williams Carolina North
Existing Land Cover for Phase 1
at Carolina North
Land Cover
Forested Area:
Impervious Area:
Turf Grass Area:
Total:
Acres
34
32
43
110
% of Total
31
29
39
100
Proposed Land Cover for Phase 1
at Carolina North
Area Totals Summary
Parking Lots
Playing Fields
Buildings
Main Roads
Secondary Roads
Paved Surface
"C" Road" (Entry Road)
Forested
Other Open Space
Total
Acres
20.8
5.5
16.4
7.3
13.6
2.3
7.1
8.1
28.7
109.7
% of Total
19
5
15
7
12
2
6
7
26
100
Summary of Existing and Proposed
Conditions Peak Discharge and
Runoff Volume
Rainfall
Depth
Return
Frequency
1-yr
2-yr
25-yr
(Inches)
3.00
3.60
6.41
Peak Q (CFS)
Existing
79.7
108.2
250.0
Proposed
129.6
166.8
342.2
Change
in Q
49.9
58.6
92.2
Peak Runoff Volume (Ac-Ft)
Change
in
Volume
Existing
Proposed
13.3
17.4
4.2
17.8
22.5
4.7
41.0
47.1
6.1
• Assumes no water quality or water quantity controls in place.
Summary of Peak Discharge and
Runoff Volume with Application of
Green Infrastructure
Peak Q (CFS)
Return
Frequency
1-yr
2-yr
25-yr
Existing
79.7
108.2
250.0
Proposed
86.0
118.9
286.0
Change in
Q
6.3
10.7
36.0
Peak Runoff Volume (Ac-Ft)
Proposed
outflow from
pond
58.8
91.6
237.4
Existing
13.3
17.8
41.0
Proposed
12.0
16.4
39.0
Change in
Volume
-1.2
-1.4
-2.0
• Assumes half of impervious surface (~34 acres) is converted to either
green roofs or porous pavement.
• Still requires ~8 acre-feet of storage to provide peak flow attenuation.
New Development Nutrient Loading
Pre- and Post-development
Pre-development:
Fraction Impervious
(I) =
0.10
Total Area of
Development =
20.00
TN
Loading
(lb/yr) =
TN Exp.
Coeff.
(lb/ac/yr) =
31.40
1.57
TP
Loading
(lb/yr) =
TP Exp.
Coeff.
(lb/ac/yr) =
4.98
0.25
Post-development
without BMPs:
Fraction Impervious
(I) =
0.66
Total Area of
Development =
20.00
TN
Loading
(lb/yr) =
TN Exp.
Coeff.
(lb/ac/yr) =
231.73
11.59
TP
Loading
(lb/yr) =
TP Exp.
Coeff.
(lb/ac/yr) =
21.84
1.09
• Jordan lake unit loading criteria (2.2 lbs/ac/yr and 0.82 lbs/ac/yr for TN
and TP, respectively) are required for 20 acres of new development.
• Computations based on Tar Pamlico unit loading spreadsheet.
Nutrient Export with Application of
Green Infrastructure Components
Fraction Impervious
(I) =
0.20
Total Area of
Development =
16.70
Pre-BMP
TN
Load
(lb/yr) =
Pre-BMP
TN
Export
(lb/ac/yr) =
Post-BMP
TN Load
(lb/yr) =
Post-BMP
TN Export
(lb/ac/yr) =
56.86
3.40
36.96
2.21
Pre-BMP
TP
Load
(lb/yr) =
Pre-BMP
TP
Export
(lb/ac/yr) =
Post-BMP
TP Load
(lb/yr) =
Post-BMP
TP
Export
(lb/ac/yr) =
7.02
0.42
3.86
0.23
• Half the rooftops to be green roofs, the other half served by cisterns.
• Half of the transportation area porous, and half of the managed turf area converted to forest.
• Green roofs behave like managed pervious areas. Area draining to cisterns removed from the
total area (total area is reduced from 20 acres to 16.7 acres).
• Area consumed by porous pavement has same loading as managed pervious area.
• BMPs removal as 35% and 45% for total nitrogen and total phosphorus, respectively.
Conclusion
• UNC has committed to wide-scale implementation of green infrastructure
elements across its campus, using an adaptive management approach.
• Campus is evolving towards a whole systems approach that considers the
benefits and treatment capabilities of soils, vegetation, and topography as
well as the beneficial uses achieved through rainwater harvesting and water
conservation.
• Carolina North will be an example of UNC holistically applying green
infrastructure principles in a fully integrated and multi-functional manner.
• The intended outcome of UNC’s green infrastructure efforts is to maintain
the sense of place that defines the campus community by creating and
enhancing connections and linkages between human and natural systems in
a manner that promotes education, stewardship, and participation.
Questions?