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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
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
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
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
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?
Governing Equations Energy Balance
Mass Balance
Curve Number Method
Horton’s Equation
Universal Soil Loss Equation
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
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
Conventional Methods Detention basins
Drains
Concrete ditches
Culverts
http://precisionsetup.com/wp-content/uploads/2013/03/v-ditch-4.jpghttp://www.stormwaterpartners.com/facilities/images/DetentionPond1.jpg
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:ANd9GcQE5A0MNi9kLQ7syPJpxKb0aRJ3k2h5L7U6Zzy3Fy5cAJWabiTIF5Vo_Ds
http://www.sciotogardens.com/images/rain%20garden.jpg
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
Design Methodology and Materials Analysis of Information
Synthesis of Design
Evaluation of Alternatives
LID Techniques
Stormwater Pond
Stormwater Wetland
Selection of Final Approach
Analysis of Information Rainfall Distribution Data: Type II
2-year storm: 4.3 inches
25- year storm: 8.0 inches
0
0.5
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1.5
2
2.5
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3.5
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0 5 10 15 20 25 30
Cu
mm
ula
tiv
e R
ain
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)
Time (hours)
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
2-Year Storm Hydrographs2-Year Storm: Pre- DevelopmentRunoff Depth: 0.62 inchesPeak Runoff Rate: 0.8 cfs
2-Year Storm: Post- DevelopmentRunoff Depth: 2.57 inchesPeak Runoff Rate: 3.5 cfs
25- Year Storm Hydrographs
25-Year Storm: Pre- DevelopmentRunoff Depth: 2.70 inchesPeak Runoff Rate: 3.9 cfs
25-Year Storm: Post- DevelopmentRunoff Depth: 5.82 inchesPeak Runoff Rate: 8.0 cfs
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)
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
Evaluation of Options Detention Basin
Low cost
Space
Treatment Wetland
Higher cost
Space
LID Techniques
Lower cost
Lower space
Final Approach LID Techniques
Vegetative Roof
Rain Barrel
Rain Garden
Porous Pavement
Infiltration Trench
Bioretention Cell
Constructed Wetland
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
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/
Design Considerations Initial Growth of Vegetation
Avoiding Leaks
Cost of Materials
Access to Roof- Maintenance
Pitch of Roof
Gutter System
http://www.jrsmith.com/uploads/fileLibrary/1010_rdp_lg.jpg
http://i.stack.imgur.com/tW8B8.jpg
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
Total Water Storage: 195 ft3
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 - -
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/connector-kits/
http://gardenwatersaver.com/connector-kits/
Permeable Pavement
http://www.bae.ncsu.edu/stormwater/PublicationFiles/PermPave2008.pdf
• Pavement• Surface• Storage • Underdrain
Design Considerations
Permeable Interlocking Concrete Pavements (PICPs)
Maintenance
Street sweeping
Pressure washing
Vacuum truck
At least once per year, or after evident damage
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/PublicationFiles/ICPIreport2004.pdf
Infiltration Trench Underground water storage and infiltration feature
Coarse gravel surrounded by filter fabric and topped with soil
Schueler, Controlling Urban Runoff
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
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
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
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
Can We Do It?
• 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
Design StormPre-Development
Runoff Depth (in)
Post-Development
Runoff Depth (in)
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 GreenRoof RainBarrels InfiltrationTrench PermeablePavement RainGarden TotalWaterStorage
Gallons 1465 800 6567 1800 5520 16152
Feet3 196 107 878 241 738 2159
WaterStorageCapacitiesofLIDMethods
SWMM Model
http://www.hydraulicmodel.com/sites/hydraulicmodel.com/files/images/epa_logo_1_2.thumbnail.png
EPA SWMM, Tyler Dubose
Sustainability Measures Life Cycle Assessment (LCA)
Materials selected
Carbon and Water costs
Efficiency
Societal Issues
Overall Carbon and Water footprint
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
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
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)
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
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
FinishProposal
PresentProposal
FinishmajorityofLiteratureReview
PickDesign
StartWritingMidtermPaper
3-weekprogressreport
DeveloppreliminaryDesign
CalculationsforDesign
FinishWritingMidtermpaper
MidtermPresentationandpaperdue
CostAnalysisforDesign
Bringtogetherfinaldesign
WriteFinalPaper
FinalPresentation
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/stormwater/BMPHandbook/
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