Capstone Project

1. Austin Balser, Daniel Chewning,
Kelly Creswell, Tyler DuBose

2. Introduction
 Overview
 Problem
 Goals
 Constraints
 Literature Review
 Design Methodology and Materials
 Analysis of Information
 Synthesis of Design
 Alternative Design Options
 Approach to Solution and Final Design
 Sustainability
 Budget
 Timeline
 References

3. Problem
 Recognition:
 Urban and suburban development leads to high runoff
rates and low infiltration rates which reduce the quality
of ground and surface water
 Definition:
 Rapid increase of development in Charleston, SC
leading to high volume of runoff and flooding
http://www.modelstoglobe.com/ESW/Images/Earth_Globe.png

4. Goal
 Design a stormwater management plan for Sea Aire
subdivision that:
 Meets state and local regulations by ensuring the peak
flow during a 2 and 25 year storm event doesn’t exceed
pre-development levels
 Ensures the post-development runoff volume doesn’t
exceed pre-development levels

5. Robinson Design Engineers: Site Plan

6. Robinson Design Engineers: Site Plan

7. Constraints
 Ecological: Must work with existing soil, water table,
vegetation, and waterways
 Ultimate use: Residential living and recreational
space
 Skills: Limited knowledge and experience with
stormwater design
 Cost: Budget of $1200 for design process. Must account
for travel expenses, software, and testing services

8. Questions of User, Client and Designer
 User- Residents of Sea Aire
 What is a rain garden, why are there plants in the ditch?
 What do I have to do?
 Client- New Leaf Builders through Robinson Design
Engineers
 Will this meet regulations?
 Will it cost more?
 Designer- The design team and RDE
 Will this be long lived?
 Can this be an amenity?

9. Governing Equations
 Energy Balance
 Mass Balance
 Curve Number Method
 Horton’s Equation
 Universal Soil Loss Equation

10. Stormwater Management
 Conventional Methods versus LID methods
 Conventional methods provide solutions at the bottom
of the site (ponds, basins, ect.)
 Low impact development methods encourage
infiltration from all locations on site in an effort to
mimic the more natural process

11. Comparison of Volume
1 – Pre-development
2 – Conventional Methods
3 – LID Methods
LID methods maintain pre-development
runoff volume
while conventional methods
lead to increased volume
http://water.epa.gov/polwaste/green/upload/lid_hydr.pdf

12. Conventional Methods
 Detention basins
 Drains
 Concrete ditches
 Culverts
http://precisionsetup.co http://www.stormwaterpartners.com/facilities/images/DetentionPond1.jpg m/wp-content/uploads/2013/03/v-ditch-4.jpg

13. Low Impact Development Methods
 Green roofs
 Rain water collection
 Constructed wetlands
 Bioretention cells
 Rain gardens
 Permeable pavement
https://encrypted-tbn1.gstatic.com/images?q=tbn:ANd9GcQ4Z-m20Aw00nkD4n_06eBr9JWP2j7-09BC-PVkD6LVcGVnJe6M4g
https://encrypted-tbn2.
gstatic.com/images?q=tbn:ANd9GcQE5A0MNi9kLQ7syPJpxKb0aRJ3k2h5L7U6Zzy3Fy5c
AJWabiTIF5Vo_Ds
http://www.sciotogardens.com/images/rain%20garden.jpg

14. Constructed Wetlands
 Public area of development will
need a way to catch and retain
stormwater
 Help filter and remove
containments, “Nature’s Kidney”
 Shallow depression in the ground
with a level bottom
https://www.clemson.edu/cafls/safes/faculty_staff/research/hitchcock/7_strosnider_et_al_asabe_2007.pdf

15. Design Methodology and Materials
 Analysis of Information
 Synthesis of Design
 Evaluation of Alternatives
 LID Techniques
 Stormwater Pond
 StormwaterWetland
 Selection of Final Approach

16. Analysis of Information
 Rainfall Distribution Data: Type II
 2-year storm: 4.3 inches
 25- year storm: 8.0 inches
5
4.5
4
3.5
3
2.5
2
1.5
1
0.5
0
0 5 10 15 20 25 30
Cummulative Rainfall (in)
Time (hours)

17. Determining Site Runoff
 Determined weighted curve number for site using
WebSoil Survey Data
 Calculated runoff depth using Curve Number Method
 Used HEC HMS and SWMM to compute and compare
runoff depth for the entire site
http://websoilsurvey.sc.egov.usda.gov/App/WebSoilSurvey.aspx
http://websoilsurvey.sc.egov.usda.gov/App/WebSoilSurvey.aspx

18. 2-Year Storm Hydrographs
2-Year Storm: Pre- Development
Runoff Depth: 0.62 inches
Peak Runoff Rate: 0.8 cfs
2-Year Storm: Post- Development
Runoff Depth: 2.57 inches
Peak Runoff Rate: 3.5 cfs

19. 25- Year Storm Hydrographs
25-Year Storm: Pre- Development
Runoff Depth: 2.70 inches
Peak Runoff Rate: 3.9 cfs
25-Year Storm: Post- Development
Runoff Depth: 5.82 inches
Peak Runoff Rate: 8.0 cfs

20. Change in Runoff
 Overall change for site
 2: +2.08” 25: +2.71”
 Change per lot
 2: +2.52” 25: +3.86”
 Volume retained for site
 2: 40833 ft3 (0.3 mil. gal) 25: 67892 ft3 (0.5 mil. gal)
 Volume retained per lot
 2: 1024 ft3 (7666 gal) 25: 1570 ft3 (11743 gal)

21. Design Options
 Detention Basin
 125717 ft3 (0.94 million gal)
 0.9 Acres (15%)
 Treatment Wetland
 138288 ft3 (1 million gal)
 1 Acre (17%)
 LID Techniques
 1860 ft2 lot area (50%)
 1133 ft2 roof area

22. Evaluation of Options
 Detention Basin
 Low cost
 Space
 Treatment Wetland
 Higher cost
 Space
 LID Techniques
 Lower cost
 Lower space

23. Final Approach
 LID Techniques
 Vegetative Roof
 Rain Barrel
 Rain Garden
 Porous Pavement
 Infiltration Trench
 Bioretention Cell
 Constructed Wetland

24. Average Residential Lot
 Lot Area: 4857 ft2
 Roof Area: 1133 ft2
 Driveway Area: 527 ft2
 Garage Area: 264 ft2
 40% of the residential lot is impervious
Robinson Design Engineers: Site Layout

25. Vegetative Roof
 Plants
 Sedum
 Growing Media
 Filter fabric
 Drainage Layer
 Root Protection
Layer
 Waterproof
Membrane
 Structural
Component
http://godfreyroofing.com/wp-content/uploads/2011/09/green-roofing-layers.png
http://www.optigreen.com/produkte/draenageplatten/fkd-40/

26. Design Considerations
 Initial Growth of Vegetation
 Avoiding Leaks
 Cost of Materials
 Access to Roof- Maintenance
 Pitch of Roof
 Gutter System
http://i.stack.imgur.com/tW8B8.jpg
http://www.jrsmith.com/uploads/fileLibrary/1010_rdp_lg.jpg

27. Vegetative Roof Holding Capacity
 Designed to hold 50% of the amount of water falling on the
roof during a 2-year storm
 Each layer of a vegetative roof has a certain water capacity
Component Water Holding Capacity Total
Plants - -
Media Layer 40%, 4 inches 148.7 ft3
Filter Fabric - -
Drainage Layer 8 L/m2 32.3 ft3
Root Protection Layer 4 L/m2 14.8 ft3
Waterproof Layer - -
Roof Material - -
 Total Water Storage: 195 ft3

28. Rain Barrels
 Balance between aesthetics and
storage
 1800 gallons roof runoff (2 yr.storm)
 2700 gallons roof runoff (25 yr. storm)
 Linked barrels  increased
volume without overwhelming size
 Tank Volume: 200 gallon tanks
 Dimensions: 47’’height, 36’’ diameter
 To be placed on both the house and
garage
 Total Storage Capacity: 800 gallons
(4 barrels total)
 Overflow management: Automatic
Downspout Diverter
http://gardenwatersaver.com/c
onnector-kits/
http://gardenwatersaver.com/connector-kits/

29. Automatic Downspout Diverter
http://www.gardeners.com/buy/downspout-diverter/33-991VS.html

30. Permeable Pavement
http://www.bae.ncsu.edu/stormwater/PublicationFiles/PermPave2008.pdf
• Pavement
• Surface
• Storage
• Underdrain

31. Design Considerations
 Permeable Interlocking Concrete Pavements (PICPs)
 Maintenance
 Street sweeping
 Pressure washing
 Vacuum truck
 At least once per year, or after evident damage

32. PICP Design
 3-inch pavement layer
 Surface slope = 2 to 3%
 Storage thickness = 6 to 18
inches
 Underdrain pipe = 1 to 4
inches from bottom of
layer
http://www.bae.ncsu.edu/stormwater/PublicationFil
es/ICPIreport2004.pdf

33. Infiltration Trench
 Underground water storage and infiltration feature
 Coarse gravel surrounded by filter fabric and topped
with soil
Schueler, Controlling Urban Runoff

34. Design Details
 Appropriate area and volume
 15% of the lot area
 2196 ft3
 Water storage
 40% void space
 878 ft3
 Infiltration rate
http://stormwaterbook.safl.umn.edu/sites/stormwaterbook.safl.umn.edu/files/fig9.3.jpg

35. Rain Garden
 Surface Area: 600 ft2
 Soil Media – 70% sand content
 Depth: 3 ft. (Infiltration rate x 24 hr)
 Ponding Depth: 6 in.
 Plants: Beautyberry, Palmetto Dwarf, Purple Coneflower
 Water Table Level
http://kawarthaconservation.com/images/rain-garden_diagram.jpg

36. Bioretention Cells
 Bioretention cells in public area
 The cells will overflow into vegetative swales or
underdrain pipes below the bioretention cell to leave
the site via the constructed wetland
http://www.northinlet.sc.edu/LID/FinalDocument/loRes/4.2%20Bioretention%20low%20res.pdf

37. Constructed Wetland
 Manage water flowing onto the site through existing
ditch
 Treat water for quality and quantity before it leaves the
site
 Handle excess runoff from individual lots and
common areas
http://pubs.ext.vt.edu/448/448-407/L_IMG_fig6.jpg

38. Can We Do It?
Design Storm
Pre-Development
Runoff Depth (in)
Post-Development
Runoff Depth (in)
Water Storage Capacities of LID Methods
• If all LID methods were used together the 25 year storm could
theoretically be contained on each property
• Due to spatial and budgetary constraints, not all LID controls will be
installed on a property
• Balance between space allotment, water capacity, and budget
• Therefore, management of flow into the main area from individual
plots must still be considered
Increase in Runoff
Depth After
Development (with
no LID controls) (in)
Runoff Volume (gal)
2 year 0.62 3.14 2.52 7629
25 year 2.7 6.56 3.86 11686
Units Green Roof Rain Barrels Infiltration Trench Permeable Pavement Rain Garden Total Water Storage
Gallons 1465 800 6567 1800 5520 16152
Feet3 196 107 878 241 738 2159

39. SWMM Model
http://www.hydraulicmodel.com/sites/hydraulicmodel.com/files/images/epa_logo_1_2.th
umbnail.png
EPA SWMM, Tyler Dubose

40. SWMM Cont.
EPA SWMM, Tyler Dubose

41. Sustainability Measures
 Life Cycle Assessment (LCA)
 Materials selected
 Carbon and Water costs
 Efficiency
 Societal Issues
 Overall Carbon and Water footprint

42. Life Cycle Assessment
 Vegetative Roof:
 Polypropylene, HDPE, PVC, media transportation
 Rain Garden and Bioretention Cell:
 PVC, material transportation, construction
 Porous Pavement:
 PICP, gravel
 Infiltration Trench:
 Geotex filter fabric, gravel, excavation and transportation
 Rain Barrel:
 Polyethylene
 Constructed Wetland:
 Plants, soil media, drain materials

43. LCA Cont.
 Ecological – goal of zero impact on the runoff volume
coming from the site as a means of maintaining the
existing ecosystem
 Social – ultimately serves the people living in the
development. Promotes an active lifestyle and provides
an educational opportunity.
 Economic – prevents future flooding and erosion
 Ethical– aim to balance the wishes of the clients and
the biological integrity of the site

44. Sustainability
 Efficiency
 Capture 100% of stormwater runoff on site for design
storm
 Carbon and Water footprint
 Carbon negative
 Gravity fed systems
 Plants will sequester carbon
 Potential for decreased freshwater demands due to
rainwater recycling (rain barrels)

45. Budget
 Vegetative Roof
 $5700 not including construction cost or initial roofing cost,
approximately $5/ft3
 Rain Garden:
 $2300, not including installation costs
 Porous Pavement:
 $3450, not including installation costs
 Rain Barrels:
 $1170 for all 4
 Infiltration Trench:
 $1800 gravel and geotex

46. Timeline
Event 9/8 9/10 9/17 9/24 10/1 10/7 10/8 10/15 10/22 10/29 11/5 11/12 11/19 11/26 12/3
Finish Proposal
Present Proposal
Finish majority of Literature Review
Pick Design
Start Writing Midterm Paper
3- week progress report
Develop preliminary Design
Calculations for Design
Finish Writing Midterm paper
Midterm Presentation and paper due
Cost Analysis for Design
Bring together final design
Write Final Paper
Final Presentation

47. Questions?
Robinson Design Engineers

48. References
 http://landstudy.org/Resources.html
 Fangmeier, D.D., Elliot, W.J., Huffman, R.L.,
Workman, S.R. 2013. Wetlands. Soil and Water
Conservation Engineering. Seventh Edition. 287-302.
 Best Management Practices Handbook. South
Carolina Department of Health and Environmental
Control.
www.scdhec.gov/Environment/waterquality/stormwat
er/BMPHandbook/