Austin Balser, Daniel Chewning,

Kelly Creswell, Tyler DuBose

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

Robinson Design Engineers: Site Plan

Robinson Design Engineers: Site Plan

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

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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/

Automatic Downspout Diverter

http://www.gardeners.com/buy/downspout-diverter/33-991VS.html

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

SWMM Cont.

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

Questions?

Robinson Design Engineers

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/