Proposal

1. Clemson University Stormwater Management
Carolyn Coffey
Brendan Luther
Karris Roland
Chelsea Walker
Biosystems Engineering Senior Design
September 12, 2014
Abstract:
Stormwater management in Clemson, South Carolina is currently inefficient and costly because of an area of university property, known as the bottoms, that has an elevation below the lake level. Even during small storm events, large diesel pumps are required to move water from this low basin, which used to be part of the Seneca riverbed, into Lake Hartwell. We are proposing that bioretention cells be used to increase infiltration of runoff back into the ground. This will reduce the volume of runoff flowing to the bottoms as well as the peak flowrate of runoff across campus. There are several environmental, economic and aesthetic benefits to installing bioretention cells on Clemson University’s campus.

2. Introduction, Objectives and Constraints
The environmental impacts erosion, flooding, and interruption of ground infiltration are all potentially devastating for an ecosystem, yet simultaneously preventable with proper, low impact management. Stormwater runoff is generally caused by an increase in impervious surfaces with urban development, and is responsible for pollution of natural ecosystems and riparian zones as well as erosion and soil loss.
Here at Clemson University, stormwater runoff has become a serious issue, with problems rooted the early 20th century. As agricultural techniques changed, streams channels were straightened and the quantity of native and diverse plant species began to alter the workings of the watershed. Damage to Hunnicutt Creek has been detrimental to the natural riparian zones, which provide a habitat for fish and wildlife and a storage area for flood waters. The riparian zones are also effective at filtering sediment from runoff before being infiltrated into the groundwater.
The campus now has many impervious surfaces and continuous construction that contributes to higher runoff rates. During a precipitation event stormwater runoff is generated at those sites and collects at the lowest elevation on campus otherwise known as the “Bottoms” as well as Hunnicutt Creek. This area is home to the university aquaculture facility, student athletic facilities, and organic farm. The army corps of engineers (ACOE) were responsible for damming Lake Hartwell, and rerouting water from the Seneca river bed. This area on campus was once part of that river, and as a result, the elevation of the bottoms is lower than the lake level, causing extreme flooding during wet summers. The soil in upstate South Carolina is a sandy clay loam, which has a very low infiltration rate and also contributes to the high volumes of stormwater runoff.

3. The water from the low elevation area needs to be pumped out into the lake using large, diesel powered pumps that are capable of moving around 2,000 gal/min. The operation and costs associated with these pumps are the responsibility of the ACOE. We are hoping to be able to manage the amount of water reaching the bottoms, and reduce the operational costs of running the pumps.
This project will design a low impact design that will reduce peak flow rates of runoff during high volume storm events in Clemson, South Carolina. In doing so, the hydrograph will be flattened and the total volume of surface runoff will be reduced. The need for the ACOE pumps will be reduced or even eliminated. This will lower flood management costs for the university and the decrease reliance on running of diesel pumps. The ideal ideal payback period of this stormwater management design is 10 years or less. We also hope to integrate water quality management with quantity control.
Potential setbacks or obstacles to achieve these goals include, but may not be limited to the level of experience that the design team has, budgetary restrictions, size of the necessary design, existing soil composition and infiltration properties, permitting, and historically and environmentally sensitive areas. The location of the design must not alter pre-existing structures on campus, and will have to be integrated based on the necessary size of bioretention cell to impact the volume of water needing to be managed. Heavy machinery may be necessary for construction of a bioretention cell. Permits for stormwater runoff quality and runoff management have to be taken into consideration as well. The design also will have to be able to sustain large storm events. Though it may be unrealistic to eliminate the need for pumps during large events, the volume of water being managed at the bottoms can be dramatically reduced by encouraging infiltration of rainwater upstream of the problem. Because we will be working on university

4. property, Clemson’s historical significance will need to be considered to ensure approval of the proposed design. Environmentally sensitive areas to consider may include Hunnicutt creek, as the biodiversity provided by a healthy riparian zone can be very environmentally beneficial to the area and natural watershed characteristics.
Proposed Questions:
User - Clemson University
1. Will the sedimentation be controlled around campus during storms?
2. Will the runoff affect the daily campus use?
3. What will the design look like?
Client - Clemson University
1. How long will the design take to be implemented?
2. How much will the design cost?
3. What quantity of water be retained and will not flow down to the “Bottoms”?
Designer - The Storm
1. Which path should we focus on retaining water?
2. What do the hydrographs look for 5, 10, 25, 50, and 100 year storms and how do I model it in WINTR55?
3. How do we quantify the amount of water that flows to the “Bottoms”?
4. Which design method would be best to reduce the amount of water?
5. How can we control the quality of water?

5. Literature Review
Since ancient times, urban developers have seen the need to manage water runoff during storm events. As early as 3500 BC, in Mesopotamia, humans were building drainage systems. Until recent years the preferred management practice was to get the water off site as quickly as possible during a rain event. This however creates water quality and quantity issues downstream from the urban sites.
The objective behind a Low Impact Development (LID) approach to stormwater management is to reduce the level of stormwater that leaves the site (Che et. al 201s). To do so, restoration of the sites pre-construction depression storage and infiltration capabilities is paramount (Prince Georges County, 1999). It is a transition from the former centralized management approach where rainwater is joined with waste-water (Martin et. al 2006) to a decentralized approach, where the site is managed to trap water where it falls.
One of the most profound changes to the hydrology of a site post- development is found with impervious surfaces. Impervious surfaces, such as parking lots or rooftops do not allow for natural ground infiltration, which leads to greater amounts of surface runoff. Since Clemson’s paved infrastructure is already in place, the focus of this design will be on the implementation of structural solutions that can be integrated with these impervious surfaces to reduce discharge volume.
LID common methods of runoff retention and purification include bioretention, dry wells, buffer strips, swales, rain barrels, cisterns and infiltration trenches (Prince Georges County, 1999). As the main focus of this project is to address the water quantity issues on Clemson’s Campus, our focus will be on bioretention cells, due to the low maintenance required (Prince Georges County, 1999), and their aesthetically pleasing nature. Bioretention cells

6. promote infiltration of surface runoff thus decreasing the total volume of surface flow during and after a storm event.
To accurately predict the levels of runoff and the success of a bioretention cell in retaining surface flows, both hand calculations and software modeling programs will be used. The relevant programs and equations are listed below.
Modeling Programs
· HEC- HMS: for modeling predicted hydrographs and general watershed modeling
· SWMM: for LID runoff reduction modeling and infiltration in urban hydrology
Relevant Equations
· Horton’s Infiltration Equation: to determine infiltration capacity of soil at a time t
· Curve Number Method: to determine runoff volumes from a site location
· Water Balance Equation: to determine the allocation of water during a hydrologic event
*See Appendix A for equation details
Design considerations that will determine the effectiveness of a bioretention cell include: soil composition and characteristics, depth, plant materials and a pretreatment area. If the in-situ soil drains at a rate below .5 inches per hour, a perforated under-drain pipe will be required (Prince Georges County, 1999) to keep ponding to a minimum. While the depth of the cell underground will be 4 feet as recommended by the EPA Low-Impact Development Design Strategies handbook, the surface area will be based on the predicted runoff volume from the impervious surface and available space. Should debris from the impervious surface such as trash be present, a grass buffer strip may need to be implemented to pre-treat the water before

7. it enters the basin. In addition to reducing the total amount of surface runoff, the plants in the bioretention cell will filter pollutants out of the water (Che et. al 2013) thus releasing cleaner water to the downstream areas.
Should Clemson adopt a rainwater reuse initiative, another useful LID tool that could be implemented would be a cistern. A cistern is a rainwater catchment container that’s stores a certain volume of water, usually underground. They have been used successfully in a LID development site in China as a water source for lawn irrigation during periods of little rain (Che et. al 2013). Rainwater cisterns also reduce the total runoff volume that leaves the site by the volume of the cistern. Design considerations for cisterns include storage volume desired and location where maintenance and water removal can be handled easily (Prince Georges County, 1999).
Low Impact Design structures such as bioretention basins and cisterns have the potential to greatly reduce the stormwater volume that reaches the pumps located at the Clemson Bottoms. With accurate soil data and hydrologic event modelling, the LID structures should be cost effective and perform their desired functions.
Sustainability Measures
Reducing the amount water that enters the bottom will not only reduce flooding but will also decrease the use of pumps. Reducing the need for the pump station will lessen the amount of diesel used for operation. Ecological and historical locations will be taken into consideration in this design. If changes to a natural habitat need to be made, the effects of the alteration will be taken into consideration. Only native plants and vegetation will be

8. used for our bioretention cell design. We would like to avoid the introduction and spread of foreign pathogens and invasive species.
This design will have a social impact on the professors, students and workers of Clemson’s campus. Lessening the amount of flooding that occurs at the bottoms will make it easier for people to access the student organic farm and the aquaculture facility after a storm event. Labs will still be able to be held there, the crops want become over watered and research can still be conducted. The implementation of a bioretention cell on campus will also improve the aesthetic value of Clemson.
One aspect of our design will be to prevent water from entering the bottoms. We will ensure this is done by using the best sustainable materials we can find. By getting our material locally we can cut down on the carbon footprint that transporting the material may cause.
Time-line

9. References/Patents
Appendix A
Horton’s Infiltration Equation:
Where:
= the infiltration capacity at time t
= equilibrium capacity
k= constant rate of decrease in f capacity
= initial infiltration capacity
Water Balance:
R= Runoff
P= Precipitation
ET= Evapotranspiration
IG= Deep Groundwater
DS= Change in Soil Storage
Curve Number Method:
CN= Curve number based on ground cover and slope
Q= Runoff Volume
P= Precipitation in Inches
References
1. Barbosa, A. E., J. N. Fernandes, and L. M. David. "Key Issues for Sustainable Urban Stormwater Management." Water Research (n.d.): n. pag. Science Direct. Web.
2. Che, Wu, Yang Zhao, Zheng Yang, Junqi Li, and Man Shi. "Integral Stormwater Management Master Plan and Design in an Ecological Community." Journal of Environmental Sciences (2014): n. pag.Science Direct. Web.
3. Martin, C., Y. Ruperd, and M. Legret. "Urban Stormwater Drainage Management: The Development of a Multicriteria Decision Aid Approach for Best Management Practices." European Journal of Operational Research 181.1 (2007): 338-49. Web.
4. "Low Impact Development (LID)." Home. Prince Georges County, MD Department of Environmental Resources, n.d. Web. 12 Sept. 2014.
5. "Hartwell Dam & Lake." Savannah District. US Army Corps of Engineers, n.d. Web. http://www.sas.usace.army.mil/About/DivisionsandOffices/OperationsDivision/HartwellDamandLake/History.aspx