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Water Quality Restoration for Coastal Subdivision

Retention Ponds

Lorimar SerranoMarie DeLorenzo

College of Charleston, SC

Background Information• Storm water retention ponds

• Used as “Best Management Practices” (BMPs) in residential & commercial developments

• Control flooding

• Settle out contaminants

• Aesthetic and recreational uses

Why care about retention ponds?• Water quality problems in storm water ponds

– Water eutrophication• algal blooms, algal toxins, water discoloration, bad

odor – High contaminant concentrations– High fecal coliform bacteria levels

• 11 acre fresh water lake• drainage area = 107 acres (300 homes)

• Lake’s importance:• overflow into Kushiwah Creek• aesthetic value• wildlife habitat• recreational boating • fishing

• model for retention pond management

Lake Edmonds

Methodology

• Parameters Measured– Water quality (DO, temp., pH, turbidity,

salinity, conductivity)– Nutrients (NH4

+, NO2-, NO3-, PO43-) (mg/L)

– Chlorophyll a (µg/L)– HABs (cells counts)– Algal toxins (microcystin [µg/L])– Fecal coliform bacteria (CFU/100mL) &

antibiotic resistance (E. coli)– Pesticides [µg/L]

• Atrazine & 2,4-D (Herbicides)• Chlorothalonil (Fungicide)• Chlorpyrifos (Insecticide)

Fecal Coliform Bacteria

0.00

100.00

200.00

300.00

400.00

500.00

600.00

700.00

May-04 Jun-04 Jul-04 Aug-04 Sep-04 Oct-04 Nov-04 Dec-04 Jan-05 Feb-05 Mar-05 Apr-05 May-05 Jun-05

FCB (

CFU/1

00mL

)

SC DHEC Standards:

Recreational uses

FC

B c

onc.

(C

FU

/100

mL)

Nutrient Levels

0.00

0.10

0.20

0.30

0.40

0.50

0.60

0.70

0.80

0.90

1.00

5/27

/04

6/3/

04

6/10

/04

6/17

/04

6/24

/04

7/1/

04

7/8/

04

7/15

/04

7/22

/04

7/29

/04

8/5/

04

8/12

/04

Tota

l nitr

ogen

con

c. (m

g/L)

0.00

0.20

0.40

0.60

0.80

1.00

1.20

1.40

5/27

/04

6/3/

04

6/10

/04

6/17

/04

6/24

/04

7/1/

04

7/8/

04

7/15

/04

7/22

/04

7/29

/04

8/5/

04

8/12

/04

8/19

/04

8/26

/04

9/2/

04

9/9/

04

Phos

phat

e co

nc. (

mg/

L)

EPA water quality standards for lakes

Atrazine Levels

0

0.02

0.04

0.06

0.08

0.1

0.12

0.14

0.16

0.18

0.2

Jun-04 Jul-04 Aug-04 Sep-04 Oct-04 Nov-04 Dec-04 Jan-05 Feb-05 Mar-05 Apr-05 May-05 Jun-05

Atraz

ine co

nc. (u

g/L)

A

traz

ine

conc

. (u

g/L)

2,4-D Levels

0

0.5

1

1.5

2

2.5


2,4-D

conc

.(ug/L

)

2,4

-D c

onc.

(ug

/L)

Anabaena sp. Density

0

5000

10000

15000

20000

25000

30000


# c

ells

/mL

Bloom density

0

2000

4000

6000

8000

10000

12000

Jun-04 Jul-04 Aug-04 Sep-04 Oct-04 Nov-04 Dec-04 Jan-05 Feb-05 Mar-05 Apr-05 May-05

# ce

lls/m

L

Microcystis sp. Density

Bloom density

Residents Survey

• A total of 45 residences in the Lake Edmonds Homeowners Association were surveyed regarding land use practices that may influence water quality

• Including: pet waste management, pesticide applications, pond uses, and homeowner interest in the pond’s water quality.

66.7% back !!!

Survey Results

• Pet Waste Management– 75% of dogs & cats were reported as being kept either outdoor or

indoor/outdoor

– Only 9% of homeowners pick up pet waste daily

• Fertilizer Application– 29% of homeowners apply fertilizer to their lawns

– 68% apply fertilizer 2 or more times per year

• Pesticide Application– 73% of homeowners apply herbicides to their lawns

– 83% apply insecticides to their lawns

– 33% apply fungicides to their lawns

– Majority of respondents make 2 or more applications of each pesticide class per year

Survey Results (cont’d)

• Lake uses

– boating activities 73.68%

– fishing activities 63.16%

• Observed algal blooms 76.67%

• Established vegetative buffer in lawns 10.71%

• Willing to install buffer 68.96%

• Willing to change practices 94.74%

Conclusions

• Water quality problems were detected in the model retention pond, Lake Edmonds:

– high fecal coliform bacteria levels

– high phosphate concentration

– harmful algal bloom development

– persistent herbicide concentration

• Residential lawn care practices such as the use of fertilizers and pesticides are affecting the water quality of this retention pond.

• Pet waste left on lawns may increase fecal coliform bacteria levels in the lake (runoff with rainfall).

Recommendations

• Some examples of the practices we recommend are:– Lawn care product recommendations

• lower chemical and nutrient content products

• organic and biodegradable products

• use of the product as directed

– Collection of pet waste from yard and deposit in trash

– Grow plants on the edges between the yards and the retention pond (vegetative buffer installation)

– Proper disposal of lawn clippings (avoid deposition into the pond)

http://edisto.cofc.edu/~lserrano/