CONSTRUCTED STORMWATER WETLANDS:

A SUSTAINABLE GREEN INFRASTRUCTURE SOLUTION

Ashley Neptune1, Bridget Wadzuk1

1Civil and Environmental Engineering, Villanova University

ABSTRACT METHODSMETHODS RESULTSRESULTS

BACKGROUNDBACKGROUND

ACKNOWLEDGEMENTSACKNOWLEDGEMENTS

LITERATURE CITEDLITERATURE CITED

Constructed wetlands may be construed as a place of muck and

mosquito infestation. However, in the context of Green Infrastructure

(GI), a Constructed Stormwater Wetland (CSW) provides multiple

functions and sustainable solutions. From peak flow reduction and

groundwater recharge to nutrient removal and wildlife habitat, CSWs

offer numerous benefits that can exceed most other GIs. Due to

CSWs requiring more land, as well as complexity in their design,

there are few presently being constructed for treatment purposes.

To demonstrate that CSWs are a viable and sustainable GI to be

included in current stormwater management plans, the present

research will highlight Villanova University’s CSW and its

development and benefits, including peak flow and volume control,

water quality improvement, educational value, habitat establishment,

and ecosystem services. The research objective is to provide

greater knowledge on CSWs and why they should continue to be

considered and implemented as part of communities’ management

plans.

Stormwater runoff is a persisting problem due to its capability to

pick up debris, chemicals, and other pollutants and carry them to

nearby water bodies. These stormwater runoff pollutants have many

severe effects including but not limited to sediments, excess

nutrients, pathogens, thermal pollution, and debris. In order to

protect our environment, the best option is to minimize the adverse

effects on the hydrologic cycle by managing stormwater runoff.

From rain gardens and wetlands to permeable pavement, the

options for treating stormwater runoff are enormous. However, the

most effective treatment choice will strongly depend on the

objectives regarding stormwater management. These most common

objectives consist of peak rate control, volume control, and water

quality control.

The Villanova University Stormwater Research and

Demonstration Park manages several stormwater control measures

(SCM) to monitor the treatment systems for water quality and peak

flow reduction. The CSW at Villanova University is an excellent

example that demonstrates the importance and success of their

stormwater control sites. The SCM was constructed in 2000 when

the first CSW (CSW 1.0) was retrofit from a detention basin up until

July 2010 when it was redesigned (CSW 2.0). The CSW lays on

approximately 1 acre of land and receives runoff from 42.6 acres

through the campus. The 42.6 acres drainage area consists of more

than 50% being impervious area. This SCM has provided valuable

information on the efforts to create an effective stormwater

management site.

WRITE

WRITE.

Figure 4: Percent exceedance concentration values for total

nitrogen with reference to PA Code Limit of 4.91 mg/L. Only 1

out of 17 storm events exceeded the TN limit.

DISCUSSIONDISCUSSIONThe methodology used in this research involves a vast collection

of water quality and quantity data in addition to visual observations,

communication with the community, as well as photographs. There

are numerous values that the CSW provides, however, within the

scope of this research only certain assets will be analyzed in detail;

these consist of the following:

• Flood Control

• Hydrologic monitoring at two inlet pipes (IW and IM) and outlet

pipe using Greyline Instruments Inc. Area Velocity Flow Meters

• Storm event peak flow and volume reduction

• Monitoring from March 2013 to October 2014

• Groundwater Recharge

• Baseflow volume reduction

• Water Quality Treatment

• Monthly storm and baseflow event sampling

• Duplicate sampling at each location (Figure 1)

• Testing follows standard protocol from Environmental Protection

Agency Methods

• Monitoring period from 2011 to December 2014

• Wildlife and Aquatic Habitat

• Education and Recreation

• Natural Biodiversity

Outlet water temperatures at the CSW remained unaffected by the

inlet temperature spikes from heated stormwater runoff.

Groundwater recharge is beneficial by providing drinking water,

irrigation, and healthy stream levels. Maintaining stream flow,

groundwater, and lake water levels makes a CSW essential in

sustaining the hydrologic cycle.

In regards to flood control, the CSW is capable of handling intense

storm events. Natural and constructed wetlands are able to hold

large amounts of water through their soil, similar to a sponge. High

peak flow reduction is indication that the CSW reduces nearby and

downstream flooding.

In addition to volume reduction and flood control, the CSW

performs well in water quality treatment (Table 2). Also, the CSW

functions exceptionally well in reducing most outlet pollutant

concentrations that rarely exceed Pennsylvania Code water quality

standards (Figure 4). These standards are important in the context

of preventing nutrient overload, which can contribute to algae

growth and eutrophication in surface waters.

Despite that the CSW lies within a suburban setting there is visual

evidence of aquatic and wildlife habitat. Animal species such as a

Snowy Egret, Common Gallinule, and mallard ducks have been

sited. Besides fauna, a healthy and sustainable ecosystem is also

defined by plant diversity. So far, the CSW has sustained

numerous types of plants such as swamp milkweed, rough leaf

goldenrod, cattails, Canadian rush, and pickerelweed.

Since the CSW is located on Villanova University’s campus,

numerous students and professors utilize the site for its scientific

importance in ecosystem services. Also, a walking path adjacent to

the CSW is frequently used by students, professors and the

community. Recreation and education benefits of the CSW are

clear indicators of sustainability in the cultural aspect.

Table 2: Water quality data for storm/S (top #) and baseflow/BF

(bottom #) events, given as average

RESULTSRESULTS

0.0

0.1

0.2

0.3

0.4

0.50

2

4

6

8

10

12

14

0 300 600 900 1200 1500 1800 2100

Rain

fall

(in

ches

)

Flo

w R

ate

(cf

s)

Time Elapsed (minutes)

Rain Inflow

Outflow

0

2

4

6

8

10

12

14

0.00.10.20.30.40.50.60.70.80.91.0

TN

(m

g/L

)

Percent Exceedance

PA Code

BF In

BF Out

Storm In

Storm Out

0

0.05

0.1

0.15

0.2

0.2516

18

20

22

24

26

28

30

32

34

0 150 300 450 600 750 900 1050 1200

Rain

fall

(in

ches

)

Tem

per

atu

re (°C

)

Time Elapsed (minutes)

RAIN

Air Temp

Temp2IN

Temp4Out

Inlet

(mg/L)

Outlet

(mg/L)

Percent

Removal

TNS

BF

2.77

2.71

1.75

1.21

37%

55.5%

TKNS

BF

1.13

1.11

1.04

0.88

7.7%

20.3%

TPS

BF

0.27

0.24

0.21

0.13

23%

45%

TSSS

BF

16.4

17.7

13

16.9

21%

4%

TDSS

BF

533

636

362

683

32%

-7%

ChlorideS

BF

362

374

207

413

43%

-10.4%

Figure 3: October 11, 2013 storm (1.99in of rain), the CSW

performed exceptionally well with a 70% peak flow and 33%

volume reduction

Flow In

(cfs)

Flow Out

(cfs)

Volume

Reduction

Peak Flow

Reduction

Storm 0.76 0.59 33% 72%

Baseflow 0.20 0.13 37%

Table 1: Average flow analysis for storm and baseflow events

IN

M1

M2

M3

OUT

Figure 1: Google aerial image (2011) of the CSW

Inlet sediment forebay

Aerial view of the meanders

Outlet structure

Snowy Egret spotted at inlet forebay Plant biodiversity at the outlet

1Kadlec, R. H. and Wallace, S. D. (2009). Treatment Wetlands, 2nd Ed. CRC Press,

Boca Raton, FL.2Michaud, J. P. (2001). “At Home with Wetlands: A Landowner’s Guide.” Washington

State Department of Ecology. Olympia, WA. 3Pennsylvania Code (PA Code). 2005. Title 25-Environmental Protection. Chapter 93-

Water Quality Standards. 4Knight, R. L. (1997). “Wildlife Habitat and Public Use Benefits of Treatment

Wetlands.” Wat. Sci. Tech. 35(5): 35-43.

Figure 2: July 14, 2014 storm (0.97in) hydrograph with reference

to CSW inlet and outlet water temperature. By observation, there is

an increase in temperature from inlet to outlet during a warm

summer day.