Typical Annual and Snowmelt Urban Stormwater Quality Characteristics Typical Annual and Snowmelt Urban Stormwater Quality Characteristics

Typical concentrations of pollutants in stormwater runoff and snowmelt runoff for select cities
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Constituent (concentrations reported in mg/L)	Annual			Twin Cities Snowmelt4
	Twin Cities1	Marquette MI2	Madison WI	Storm Sewers	Open Channels	Creeks	NURP5
Cadmium		0.0006	0.0004
Copper		0.022	0.016
Lead	0.060	0.049	0.032	0.16	0.2	0.08	0.18
Zinc		0.111	0.203
Biological Oxygen Demand		15
Chemical Oxygen Demand	169	66		169	82	84	91
Total Kjeldahl Nitrogen	2.62	1.50		3.52	2.36	3.99	2.35
Nitrate + Nitrite	0.53	0.37		1.04	0.89	0.65	0.96
Ammonia		0.2
Total Phosphorus	0.58	0.29	0.66	0.7	0.56	0.54	0.46
Dissolved Phosphorus	0.20	0.04	0.27	0.25	0.18		0.16
Chloride3				230	49	116
Total Suspended Solids	184	159	262	148	88	64
Volatile Suspended Solids	66			46	15

¹ Event mean concentrations; Reference: Brezonik and Stadelmann 2002
² Geometric mean concentrations; Reference: Steuer et al. 1997
³ Geometric mean concentrations; Reference: Waschbusch et al. 1999
⁴ Reference: Oberts, G. (Met Council). 2000. Influence of Snowmelt Dynamics on Stormwater Runoff Quality.
⁵ Reference: Median concentrations from more than 2,300 rainfall events monitored across the nation; EPA, 1983