Table 2. Comparison of observed and predicted pyrethroid concentrations.

Monitoring Date	Measured Concentration (ng/L)		Model Predicted Concentration (ng/L)
	Bif	Perm	Bif	Cyf	Cyhal	Cyper	Delta	Fenv	Perm
2/18/2009	5.6	5.0	6.7	0.9	0.4	1.3	0.6	0	0.7
2/23/2009	ND	ND	5.3	0.7	0.4	1.1	0.5	0	0.8
3/3/2009	ND	ND	4.6	0.6	0.6	1.1	0.5	0	0.9
10/13/2009	ND	ND	4.8	2.9	0.3	1.1	0.6	0	0.9
10/14/2009	ND	ND	5.1	3.0	0.3	0.9	0.6	0	0.4
1/18/2010	ND	ND	1.4	1.1	0.1	0.5	0.3	0	0.2
1/19/2010	1.8	ND	1.3	1.0	0.1	0.5	0.3	0	0.1
1/20/2010	2.1	ND	1.1	0.9	0.1	0.5	0.3	0	0.2
1/22/2010	ND	ND	1.2	1.0	0.1	0.4	0.3	0	0.1
12/18/2010	1.1	ND	0.2	0.1	0	0	0.3	0	0
12/19/2010	1.6	7.0	0.2	0.1	0	0	0.3	0	0

Bif – bifenthrin, Cyf – cyfluthrin/beta cyfluthrin, Cyhal – cyhalothrin/lambda cyhalothrin, Cyper – cypermethrin, Delta – deltamethrin, Fenv – fenvalerate/esfenvalerate, Perm - permethrin

ND – not detected at or above 1 ng/L; predicted concentrations less than 1 ng/L can be considered non-detections

Measured concentration data from [2]