This document discusses stormwater management and erosion mitigation techniques for an area of the Epoch apartment complex characterized by erodible soil with a 6-10% slope. The area was modeled pre-and post-development using WEPP software, showing a large increase in annual runoff and soil loss after the addition of impermeable surfaces. Proposed mitigation techniques discussed include permeable pavement, erosion control systems, bioswales with engineered soil mixes, and planting native vegetation to reduce runoff and prevent erosion. Appropriate stormwater management is important for this site given its proximity to a lake used daily for recreation.

1. Stormwater Management and Erosion Mitigation for the Epoch
Apartment Complex
Natalie Whitaker, Freddy Nocella, Allison Barrera
This project will look at a specified section of the
Epoch apartment complex property that is
characterized by erodible soil and sits at 6-10%
slope, making it severely eroded under
predevelopment conditions. Post-development,
the area has become more susceptible to erosion
and runoff with the addition of impermeable
pavement and rooftops. The area will be
modeled using WEPP software and erosion as
well as water quality improvement techniques
will be discussed.
Objectives
Site Description and Models
Based off information from the USDA Soil Survey
Data Base, most of the Epoch property is on clay
loam soil at a 6-10% slope. The WEPP models on
the right show pre and post development soil
loss and runoff values. The predevelopment is
modeled as being all forested land whereas the
post development is being modeled as 2500 ft of
pavement and 500 ft of forest that ends at the
lake.
Figure 2. This image shows the pre-development WEPP model. It gives an average
annual runoff estimate of 8.31 in and an average soil loss of 0.157 tons/acre
Figure 3. This image shows the post-development WEPP model. It gives an average
annual runoff estimate of 20.62 in and an average soil loss of 255.83 tons/acre.
There is a great amount of runoff caused due to the large asphalt
roadways and parking lots at Epoch. Permeable pavement is made up of
many layers consisting of (permeable paver layer, geotextile, sand, and
crushed stone base. all layers are porous and allow water to infiltrate
through them and absorb into the soil below. In one study a rainfall
intensity of 90.47 (mm/hr) did not reach an overflow for 2.5 hours.
Due to the large slopes caused by the construction at Epoch, it is
recommended that coir fiber rolled erosion control systems be
implemented on areas with increased slopes. These solutions can last up
to 5 years while vegetation takes greater hold in the soil. The best
performing geotextile is one made up of loose fibers stitched with
threads between two nets.
Erosion Prevention Discussion
Stormwater Quality Discussion
Bioswales can be located downhill on large slopes on site.
Bioswales that use engineered soil mixes (ESM) can reduce
sediment runoff, increase tree growth, and reduce nutrient
runoff. Bioswales with ESM were found to reduce runoff
pollutants by more than 99.5%. The bioswale should be
planted with native vegetation to increase water retention by
uptake of water through transpiration and to increase root
channels for water to infiltrate through.
Conclusion and Importance
As the student population of Clemson continues to grow, there will be
increased need to develop land for the construction of additional
apartment complexes. This project showed how drastically construction
projects such as this one can impact the amount of runoff and soil loss in
areas surrounding Clemson. It is important to consider the
implementation of some of these erosion prevention methods for new
and existing sites. Appropriate stormwater and runoff water quality
management is especially important in a complex such as Epoch due to
its proximity to the lake. It is necessary to keep the lake in good condition
since it is used by residents for recreational activities daily.
References
Figure 1. This image shows an aerial view of the Epoch
property. This project focuses on the section labeled CcC3 and
is modeled as a straight line from the dirt area (now road) to
the forest and into the lake
Figure 4. The lake area at Epoch is used extensively for recreational
activities such as swimming, boating, and fishing.