This document discusses various studies and case studies related to the impacts of development on water quality. It summarizes that effective solutions require maintaining watershed hydrology through low impact development techniques like reducing impervious surfaces, incorporating bioretention areas, and maintaining wetlands and riparian buffers. A case study of the Carpenter Village development showed positive results from using clustered housing, narrow streets, integrated open space and bioretention to minimize impacts on water quality.

1. Designing to Protect Water
Quality

2. Belle Hall Study: Sprawl

3. Belle Hall Study: Cluster

4. Belle Hall Study: Results

5. Impacts are related to more
than just imperviousness . . .
We need to try and maintain
watershed hydrology

6. Surface Hydrology Basics

7. Surface Hydrology by the
Numbers
Source: Center for Watershed Protection, 1996
Parameter ParkingLot Meadow
Curve Number 98 58
Runoff Coefficient 0.95 0.06
Time of Concentration (minutes) 4.8 14.4
Peak: 2 yr, 24 hr., CFS 4.3 0.4
Volume, 1”, CFT 3450 218
Velocity, 2 yr, FT/Sec 8 1.8
Change
1.6 Times More
15 Times More
3 Times Less
10 Times Higher
15 Times More
4 Times Faster

8. Effects on Streamflow

9. Flood Plain Effects

10. Carpenter Village
Project Partners:
WW Partners
Ferrell Land Dev Co.
Town of Cary
NC Cooperative Ext.
Funding Agencies:
NC DENR - DWQ 319
NC DENR - DLQ

11. Monitoring Design
Below
Treatment Basin
Above
Control Basin
Below
Carpenter Village

12. Annual Loads at Carpenter
Annual Loads at Carpenter
0
5
10
15
20
25
30
35
40
Load(kg/ha)
Clearing Building
TP
TN
NO3
NH3

13. Annual Loads at Carpenter
Annual Loads at Carpenter
0
5000
10000
15000
20000
25000
Load(kg/ha)
Clearing Building
TSS

14. Rainfall vs. Runoff
Rainfall vs Runoff
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
Runoff/rainfall
Clearing Building Wooded
Runoff

15. Cooperators and Participants
NCSU School of Design Extension Programs
Design Research Laboratory
NCSU Water Quality Group
NC Dept of Health, Shellfish Sanitation Program
Duke Marine Laboratory
UNC Sea Grant
NCDENR Division of Water Quality 319 Program
Wetland Restoration Program
Clean Water Management Trust Fund
Carteret Craven Electric Cooperative
Jumping Run Creek Watershed Citizens
Jumping Run Creek

16. Facts:
1)Shellfish closures occurring since 1979.
2) Imperviousness less than 5%.
3) Water moving through the system to shellfish bed within hours.
4) Bacterial loading has increased steadily through the years, while
rainfall has stayed consistent.

17. J1 J2 J4 HY J1 J2 J4 HY J1 J2 J4 HY
0
50
100
150
Load(kg)
Nonstorm
Storm
Loads from 9/5/99-6/5/00
NH3 NO2+3 PO4

18. J1 J2 J4 HY
0
5
10
15
20
25
30
TSSLoad(1,000kg)
Nonstorm Storm
Loads from 9/5/99-6/5/00

19. J1 J2 J4 HY
0
5
10
15
20
25
30
FecalColiform(1,000,000,000mpn)
Nonstorm Storm
Loads for 9/5/99-6/5/2000

20. Conclusions
*Impervious area not adequate indicator
of water quality threat.
*Strategies to mitigate development
need to address hydrologic alterations.
*Bacterial source, not just
location, needs to be known to
properly manage.

21. Can Design and Planning Help?
• Competing Values, Needs, and Interests.

22. Planning where development
occurs really can matter
• Wetlands
• Headwater Streams
• Link Open Space
• Functioning Plant Communities
• High Quality Waters
• Recharge Areas
• Buffers Zones

23. Need to plan and design development
on a watershed basis
• Reliance on end-of-pipe BMP technology will not achieve the 30%
reduction standard for Nitrogen.
• Development based on imperviousness alone can encourage
sprawl.
• New urban scenarios while providing opportunities to implement
a variety of urban land use and sensitive area protection features
are high density and can be high impact.
• Source reduction approaches need to be assessed using watershed
- based planning and design techniques to get the right uses in the
right place.

24. Reduce Impervious Area:
Reduce Road Widths -- Use one way streets, pull-off zones, back
alleyways for utility infrastructure and parking, alternative
materials.
Reduce Parking Area -- Angled parking, narrower slots, lower
allocation.
Share Driveways -- Put more houses on each drive access.
Reduce Paved Sidewalk Area -- Use one side only and alternative
materials.
Contain Stormwater On-Site
Use Inverted Streets as Stormwater Collectors -- Direct to bio-filters.
Invert Parking Islands to Collect Water.
Direct Runoff from house gutters onto pervious areas.
Reduce use of street curbing -- Use grassed or vegetative swales.
Use Bioretention Areas and Rain Gardens
Use Green Building Techniques
Site Design Strategies

25. Site Design Strategies
Incorporate wetlands, bioretention areas, buffers, open space
into site plan.

26. Share Driveways -- Put more buildings / houses on each drive
access.
Direct Runoff from house gutters onto pervious areas.
Use on-site bioretention.
Minimize footprint--use taller buildings.
Collect rainwater and reuse.
Use pervious materials whenever possible.
Structures-use Green Building Techniques

27. Carpenter Village
Buffers
Clustered
Narrow / Short Streets
Integrated Open Space
Integrated Infrastructure
Alleyway Access
Varying density
Integrated land uses
Bioretention

28. Bioretention Case Study -
Carpenter Village
• Work with Developers and Town to identify
suitable locations.
– Ideal -- low area, good soils, water gathering
slope form, dispersed in the watershed, part of
city infrastructure.
– Reality -- got existing open space, high grades,
poor soils, only two locations in the watershed,
located on private property (Developers
responsibility).

29. Case Study - Carpenter Village
• Worked with site engineers and Town staff to
redesign stormwater infrastructure, streets,
sidewalks, curbs.
– Removed 17 storm drain inlets.
• Two new inlets, hooked to stormwater infrastructure, with
proper top and bottom elevation installed in location
designated for bioretention.
– Streets redesigned to direct water to swales and inyo
bioretention.
• Road Grades
• Sidewalk Contiguity
• Flat curbs

30. Case Study- Carpenter Village

31. Case Study - Carpenter Village

32. Case Study - Carpenter Village

33. Case Study - Carpenter Village

34. Case Study - Carpenter Village

35. • Rainwater Harvesting - the collection and
reuse of rainwater for non-potable
applications.
– Reduction in storm water runoff.
– Increased opportunities for re-infiltration.
– Conserve potable water.
– Save money.
Case Study- Residential
Demonstration

36. Case Study- Residential
Demonstration

37. Case Study- Residential
Demonstration

38. Case Study- Residential
Demonstration

39. Case Study- Residential
Demonstration
• If linked to city water and irrigation system
(which increases ease of use).
– Requires programmable timer.
– Labeled non-potable lines.
• If not, only normal plumbing and electrical
codes apply.

40. Case Study- Residential
Demonstration
• Rain Garden as part of the landscape
– Locate in low point of the landscape.
– Grade remainder of landscape to drain to rain
garden.
– Use simple plastic inlet system.
– Provide overflow outlet.
– Plant with facultative vegetation.

41. Case Study- Residential
Demonstration

42. Case Study- Residential
Demonstration

43. Case Study- Residential
Demonstration

44. Case Study- Residential
Demonstration

45. Case Study- Residential
Demonstration

46. Case Study- Residential
Demonstration

47. Conclusions:
•Effective solutions need a “Toolbox” approach using watershed
based planning, low impact design, and green building
implementation techniques.
•Wetlands and riparian buffers are essential for habitat and
water quality.
•Recharge rates must be addressed by capturing storm water
utilizing infiltration techniques, reapplication, and the
preservation of recharge areas, open space.
Water quality protection can happen when hydrologic functionality
of the watershed is maintained, pollutant load (including storm
hydrology) is minimized.

48. More Conclusions!
• Positive results can be achieved when there cooperation
between towns to develop management strategies on a
watershed basis.
• Within that context, the good development work can be
done if designed using multi-disciplinary teams that
include architects, landscape architects, biologists, soil
scientists, ecologists, botanists, and, yes, even engineers.