Water Quality
Water Quality > Hudson River Estuary Data > Rockland County & Westchester County Sites > Tappan Zee Bridge mid-channel

Tappan Zee Bridge mid-channel

Tappan Zee mid-channel
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Physical/Chemical Data

Physical, chemical and biological properties of the surface water that are measured continuously while the patrol boat is underway.

Entero Count (fecal indicator) and Rainfall

122 Samples taken

Sample Date [i] Enterococcus Count
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Entero Count

Enterococcus (“Entero”) is a fecal indicating bacterium that lives in the intestines of humans and other warm-blooded animals. It is the EPA preferred indicator for sewage contamination.

Quality Rain, day of (in) Prior Day 2 Days Prior 3 Days Prior Rain 4 Days Total Rain
Sort Sort Sort Sort Sort Sort Sort Sort
10/17/2023 <10 Acceptable 0.0 0.0 0.0 0.6 0.6
09/19/2023 <10 Acceptable 0.0 1.0 0.2 0.1 1.3
08/22/2023 <10 Acceptable 0.0 0.0 0.0 0.0 0.0
07/18/2023 10 Acceptable 0.0 0.0 1.4 0.2 1.6
06/27/2023 <10 Acceptable 1.3 1.6 0.0 0.3 3.1
05/02/2023 74 Beach Advisory 0.0 0.2 2.2 1.6 4.0
10/10/2022 <10 Acceptable 0.0 0.0 0.0 0.0 0.0
09/10/2022 <10 Acceptable 0.0 0.0 0.0 2.1 2.1
08/12/2022 <10 Acceptable 0.0 0.0 0.1 0.0 0.1
07/15/2022 <10 Acceptable 0.0 0.0 0.0 0.0 0.0
06/14/2022 20 Acceptable 0.1 0.0 0.0 0.0 0.1
05/24/2022 <10 Acceptable 0.0 0.0 0.0 0.0 0.0
10/29/2021 420 Beach Advisory 0.0 0.0 0.0 3.4 3.4
09/14/2021 10 Acceptable 0.0 0.0 0.0 0.0 0.0
08/17/2021 <10 Acceptable 0.0 0.0 0.0 0.1 0.1
07/20/2021 <10 Acceptable 0.0 0.1 0.3 0.9 1.3
06/08/2021 <10 Acceptable 0.0 0.0 0.0 0.0 0.0
05/17/2021 <10 Acceptable 0.0 0.0 0.0 0.0 0.0
10/14/2020 <10 Acceptable 0.0 0.3 0.3 0.0 0.6
09/18/2020 10 Acceptable 0.0 0.0 0.0 0.0 0.0
08/14/2020 <10 Acceptable 0.0 0.0 0.0 0.0 0.0
07/14/2020 <10 Acceptable 0.0 0.0 0.0 2.2 2.2
06/16/2020 <10 Acceptable 0.0 0.0 0.0 0.0 0.0
05/26/2020 <10 Acceptable 0.0 0.0 0.0 0.2 0.2
10/08/2019 10 Acceptable 0.1 0.2 0.0 0.0 0.3
09/10/2019 <10 Acceptable 0.0 0.0 0.0 0.0 0.0
08/06/2019 10 Acceptable 0.0 0.0 0.2 0.9 1.1
07/09/2019 <10 Acceptable 0.0 0.0 0.0 0.6 0.6
06/04/2019 <10 Acceptable 0.0 0.0 0.0 0.0 0.0
05/07/2019 <10 Acceptable 0.0 0.1 1.1 0.1 1.3
10/10/2018 10 Acceptable 0.0 0.0 0.1 0.0 0.1
09/10/2018 10 Acceptable 1.7 0.1 0.1 0.0 1.9
08/14/2018 <10 Acceptable 0.0 0.8 0.2 1.9 2.9
07/17/2018 31 Acceptable 1.6 0.1 0.3 0.5 2.5
06/13/2018 <10 Acceptable 0.0 0.0 0.0 0.0 0.0
05/06/2018 <10 Acceptable 0.2 0.0 0.0 0.3 0.5
10/16/2017 <10 Acceptable 0.1 0.0 0.0 0.0 0.1
09/11/2017 <10 Acceptable 0.0 0.0 0.0 0.0 0.0
08/14/2017 <10 Acceptable 0.0 0.0 0.4 0.3 0.7
07/10/2017 <10 Acceptable 0.0 0.0 0.0 2.2 2.2
06/12/2017 <10 Acceptable 0.0 0.0 0.0 0.0 0.0
05/15/2017 <10 Acceptable 0.0 0.1 1.7 0.0 1.8
04/04/2017 10 Acceptable 1.1 0.0 0.0 0.1 1.2
10/13/2016 <10 Acceptable 0.1 0.0 0.0 0.0 0.1
09/14/2016 <10 Acceptable 0.0 0.0 0.0 0.0 0.0
08/15/2016 <10 Acceptable 0.0 0.1 0.1 0.2 0.4
07/13/2016 <10 Acceptable 0.0 0.0 0.0 0.0 0.0
06/15/2016 <10 Acceptable 0.0 0.0 0.0 0.0 0.0
05/20/2016 <10 Acceptable 0.0 0.0 0.0 0.0 0.0
10/12/2015 <10 Acceptable 0.0 0.0 0.0 0.1 0.1
09/11/2015 <10 Acceptable 0.3 1.3 0.1 0.0 1.7
08/12/2015 <10 Acceptable 0.0 1.0 0.0 0.0 1.0
07/08/2015 <10 Acceptable 0.0 0.1 0.0 0.0 0.1
06/11/2015 <10 Acceptable 0.0 0.0 0.2 0.2 0.4
05/12/2015 <10 Acceptable 0.0 0.0 0.0 0.0 0.0
10/13/2014 <10 Acceptable 0.0 0.0 0.4 0.0 0.4
09/08/2014 <10 Acceptable 0.0 0.0 0.0 0.0 0.0
08/12/2014 <10 Acceptable 0.0 0.0 0.0 0.0 0.0
07/08/2014 <10 Acceptable 0.2 0.0 0.0 0.0 0.2
06/13/2014 <10 Acceptable 1.4 0.0 0.1 0.0 1.5
05/13/2014 <10 Acceptable 0.0 0.0 0.1 0.3 0.4
10/17/2013 <10 Acceptable 0.0 0.0 0.0 0.0 0.0
09/19/2013 10 Acceptable 0.0 0.0 0.0 0.0 0.0
08/15/2013 <10 Acceptable 0.0 0.0 0.7 0.4 1.1
07/18/2013 20 Acceptable 0.0 0.0 0.0 0.0 0.0
06/20/2013 <10 Acceptable 0.0 0.0 0.3 0.2 0.5
05/30/2013 <10 Acceptable 0.0 0.0 0.4 0.0 0.4
10/11/2012 <10 Acceptable 0.0 0.1 0.0 0.0 0.1
09/11/2012 <10 Acceptable 0.0 0.0 0.0 1.4 1.4
08/14/2012 <10 Acceptable 0.0 0.0 0.0 0.0 0.0
07/17/2012 <10 Acceptable 0.0 0.0 0.2 0.0 0.2
06/12/2012 <10 Acceptable 0.0 0.0 0.0 0.0 0.0
05/16/2012 <10 Acceptable 0.1 0.4 0.1 0.0 0.6
10/20/2011 <10 Acceptable 0.0 0.1 0.0 0.0 0.1
09/15/2011 20 Acceptable 0.0 0.0 0.0 0.0 0.0
08/17/2011 <10 Acceptable 0.0 0.0 0.0 3.4 3.4
08/15/2011 <10 Acceptable 0.0 3.4 0.0 0.0 3.4
07/25/2011 <10 Acceptable 0.0 0.0 0.0 0.0 0.0
07/22/2011 <10 Acceptable 0.0 0.0 0.0 0.0 0.0
07/21/2011 <10 Acceptable 0.0 0.0 0.0 0.1 0.1
07/18/2011 <10 Acceptable 0.0 0.0 0.0 0.0 0.0
06/28/2011 <10 Acceptable 0.0 0.0 0.0 0.0 0.0
05/17/2011 52 Acceptable 1.2 0.0 0.8 0.0 2.0
10/13/2010 10 Acceptable 0.0 0.1 0.3 0.0 0.4
09/12/2010 <10 Acceptable 0.0 0.0 0.0 0.0 0.0
08/18/2010 <10 Acceptable 0.0 0.0 0.2 0.3 0.5
07/22/2010 <10 Acceptable 0.0 0.1 0.0 1.4 1.5
06/16/2010 <10 Acceptable 0.0 0.0 0.0 0.0 0.0
05/22/2010 30 Acceptable 0.0 0.0 0.0 0.0 0.0
10/20/2009 <10 Acceptable 0.0 0.0 0.0 0.0 0.0
09/15/2009 <10 Acceptable 0.0 0.0 0.0 0.0 0.0
08/21/2009 <10 Acceptable 0.0 0.0 0.0 0.0 0.0
07/29/2009 <10 Acceptable 0.0 0.0 0.0 0.2 0.2
06/23/2009 <10 Acceptable 0.0 0.0 0.6 0.5 1.1
06/06/2009 <10 Acceptable 0.0 0.8 0.4 0.4 1.6
05/13/2009 <10 Acceptable 0.0 0.0 0.0 0.0 0.0
10/21/2008 10 Acceptable 0.0 0.0 0.0 0.0 0.0
10/20/2008 <10 Acceptable 0.0 0.0 0.0 0.0 0.0
10/19/2008 <10 Acceptable 0.0 0.0 0.0 0.0 0.0
09/23/2008 <10 Acceptable 0.0 0.0 0.0 0.0 0.0
09/07/2008 30 Acceptable 0.0 4.8 0.0 0.0 4.8
08/21/2008 <10 Acceptable 0.0 0.0 0.0 0.0 0.0
07/15/2008 <10 Acceptable 0.0 1.1 0.0 0.0 1.1
06/25/2008 142 Beach Advisory 0.0 0.0 0.0 0.1 0.1
06/16/2008 6 Acceptable 0.0 0.0 1.7 0.0 1.7
05/20/2008 16 Acceptable 0.0 0.0 0.2 0.1 0.3
05/19/2008 <10 Acceptable 0.0 0.2 0.1 0.9 1.2
05/16/2008 <10 Acceptable 0.9 0.0 0.0 0.0 0.9
09/09/2007 1 Acceptable 0.0 0.0 0.0 0.0 0.0
09/06/2007 <10 Acceptable 0.0 0.0 0.0 0.0 0.0
08/23/2007 1 Acceptable 0.0 0.0 1.3 0.1 1.4
08/16/2007 <10 Acceptable 0.0 0.0 0.0 0.0 0.0
07/16/2007 3 Acceptable 0.0 0.0 0.0 0.0 0.0
07/11/2007 2 Acceptable 0.0 0.0 0.0 0.0 0.0
06/20/2007 1 Acceptable 0.1 0.3 0.0 0.0 0.4
06/18/2007 2 Acceptable 0.0 0.0 0.0 0.0 0.0
05/21/2007 4 Acceptable 0.0 0.0 0.2 0.0 0.2
04/25/2007 86 Beach Advisory 0.0 0.0 0.0 0.0 0.0
04/18/2007 252 Beach Advisory 0.0 0.0 0.9 7.6 8.5
11/10/2006 182 Beach Advisory 0.0 0.0 3.6 0.0 3.6
10/18/2006 1 Acceptable 0.0 1.1 0.0 0.0 1.1
09/26/2006 1 Acceptable 0.0 0.0 0.0 0.1 0.1

Entero Count (fecal indicator) and Rainfall Correlation

122 Samples taken

All Water Quality Parameters

122 Samples taken

Sample Date [i] Entero Count
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Entero Count

Enterococcus (“Entero”) is a fecal indicating bacterium that lives in the intestines of humans and other warm-blooded animals. It is the EPA preferred indicator for sewage contamination.

Quality [i] Temp (f)
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Temperature

Hudson River water temperature changes seasonally. Surface water temperature can change on small scales in the river reflecting natural and human influences.

[i] Salinity
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Salinity

Estuaries like the Hudson are where freshwaters in rivers meet the sea. Salinity tells us about the relative contribution of fresh and salt water within a particular region of the estuary. 

[i] Chlorophyll
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Chlorophyll

A measure of the amount of microscopic algae present in the water. High chlorophyll counts can mean high levels of the nutrients phosphorus and nitrogen, and the threat, or presence, of algae blooms.

[i] Turbidity
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Turbidity

Turbidity is a measure of the amount of fine particles suspended in the water. As turbidity rises, light penetration, a key factor for aquatic plants and algae, diminishes.

[i] Oxygen
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Oxygen

Oxygen concentrations in the water are closely connected to biological activities. Surface waters are typically in equilibrium with the atmosphere such that the oxygen concentration near the surface is close to fully saturated (100%).

Sort Sort Sort Sort Sort Sort Sort Sort
10/17/2023 <10 Acceptable 16.58 3.37 1.08 7.2 104.9
09/19/2023 <10 Acceptable 22.18 5.53 2.31 n/a n/a
08/22/2023 <10 Acceptable 24.53 3.19 2.84 6.2 86.5
07/18/2023 10 Acceptable 26.17 0.21 5.13 17.6 86.5
06/27/2023 <10 Acceptable 71.8 6.5 15.5 5.8 102.9
05/02/2023 74 Beach Advisory 54.5 2.1 2.2 1.8 93.7
10/10/2022 <10 Acceptable 63.5 10.4 2.8 6.8 89
09/10/2022 <10 Acceptable 77.5 10.4 6.3 10.9 82.3
08/12/2022 <10 Acceptable 81.9 11.5 9.9 6.8 101.1
07/15/2022 <10 Acceptable 79.2 10.7 9 11.3 104.5
06/14/2022 20 Acceptable 70.5 6 17.4 16.3 101.1
05/24/2022 <10 Acceptable 63.1 5.6 1.9 11.3 96.4
10/29/2021 420 Beach Advisory 60.6 0.8 2.5 12 89
09/14/2021 10 Acceptable 73.6 1.4 3.4 13 88
08/17/2021 <10 Acceptable 78.0 5.6 3.5 11 87
07/20/2021 <10 Acceptable 79.4 0.3 6.5 14 91
06/08/2021 <10 Acceptable 71.0 4.1 11.6 9 110
05/17/2021 <10 Acceptable 64.7 1.6 3.4 14 107
10/14/2020 <10 Acceptable 65.4 9.1 2.2 5 91
09/18/2020 10 Acceptable 72.4 11.8 3.1 19 81
08/14/2020 <10 Acceptable 84.3 5.9 24.1 10 128
07/14/2020 <10 Acceptable 82.0 7.0 18.5 7 120
06/16/2020 <10 Acceptable 73.4 4.8 9.5 9 129
05/26/2020 <10 Acceptable 65.3 6.0 8.9 10 121
10/08/2019 10 Acceptable 68.4 7.1 5.3 4 93
09/10/2019 <10 Acceptable 76.1 6.6 6.6 4 94
08/06/2019 10 Acceptable 81.8 8.4 7.7 9 85
07/09/2019 <10 Acceptable 81.2 4.3 12.1 11 116
06/04/2019 <10 Acceptable 66.6 4.7 2.1 13 92
05/07/2019 <10 Acceptable 58.2 0.9 2.2 29 95
10/10/2018 10 Acceptable 71.8 0.4 5.2 19 93
09/10/2018 10 Acceptable 74.8 6.7 3.5 7 78
08/14/2018 <10 Acceptable 82.2 4.2 4.8 13 77
07/17/2018 31 Acceptable 80.5 10.1 14.6 13 102
06/13/2018 <10 Acceptable 70.6 6.2 51.4 11 133
05/06/2018 <10 Acceptable 55.2 0.2 2.7 27 104
10/16/2017 <10 Acceptable 70.1 9.0 2.7 19 85
09/11/2017 <10 Acceptable 71.0 8.8 3.9 16 89
08/14/2017 <10 Acceptable 79.1 5.8 9.3 10 98
07/10/2017 <10 Acceptable 78.2 3.7 3.8 13 102
06/12/2017 <10 Acceptable 71.2 1.3 3.5 18 104
05/15/2017 <10 Acceptable 58.4 0.6 3.2 23 97
04/04/2017 10 Acceptable n/a n/a n/a n/a n/a
10/13/2016 <10 Acceptable 66.0 9.7 5.4 35 98
09/14/2016 <10 Acceptable 80.9 8.8 20.4 n/a 153
08/15/2016 <10 Acceptable 86.9 5.4 32.4 30 173
07/13/2016 <10 Acceptable 80.1 6.0 14.5 9 112
06/15/2016 <10 Acceptable 73.7 4.1 6.2 19 117
05/20/2016 <10 Acceptable 64.9 2.7 7.2 n/a 120
10/12/2015 <10 Acceptable 68.0 8.8 5.2 10 96
09/11/2015 <10 Acceptable 78.7 10.5 6.3 17 90
08/12/2015 <10 Acceptable 80.0 8.4 18.0 10 127
07/08/2015 <10 Acceptable 78.7 1.4 9.5 21 102
06/11/2015 <10 Acceptable 76.3 2.7 7.7 3 117
05/12/2015 <10 Acceptable 65.9 3.9 3.2 25 103
10/13/2014 <10 Acceptable 64.7 9.6 0.1 20 90
09/08/2014 <10 Acceptable 77.8 8.0 17.0 14 106
08/12/2014 <10 Acceptable 78.5 6.6 5.9 25 85
07/08/2014 <10 Acceptable 78.6 2.2 10.5 12 105
06/13/2014 <10 Acceptable 68.5 7.2 16.4 21 96
05/13/2014 <10 Acceptable 58.5 3.8 2.0 n/a 99
10/17/2013 <10 Acceptable 66.3 10.6 2.6 21 85
09/19/2013 10 Acceptable 71.0 5.9 4.1 8 89
08/15/2013 <10 Acceptable 76.8 4.3 10.6 9 105
07/18/2013 20 Acceptable 83.0 2.9 6.2 17 93
06/20/2013 <10 Acceptable 69.7 0.6 3.6 15 96
05/30/2013 <10 Acceptable 65.1 1.0 0.7 46 91
10/11/2012 <10 Acceptable 65.9 5.5 4.5 22 86
09/11/2012 <10 Acceptable 76.1 8.1 9.4 18 93
08/14/2012 <10 Acceptable 82.1 8.8 5.8 5 105
07/17/2012 <10 Acceptable 82.4 8.7 18.8 7 126
06/12/2012 <10 Acceptable 72.3 2.0 3.8 22 91
05/16/2012 <10 Acceptable 63.9 0.5 5.0 19 108
10/20/2011 <10 Acceptable 63.6 0.8 0.5 74 91
09/15/2011 20 Acceptable 69.8 0.1 1.8 135 85
08/17/2011 <10 Acceptable 81.3 5.5 4.6 14 95
08/15/2011 <10 Acceptable n/a n/a n/a n/a n/a
07/25/2011 <10 Acceptable 82.9 3.4 16.0 7 n/a
07/22/2011 <10 Acceptable 86.0 1.8 12.9 8 n/a
07/21/2011 <10 Acceptable n/a n/a n/a n/a n/a
07/18/2011 <10 Acceptable 82.0 3.7 4.9 16 n/a
06/28/2011 <10 Acceptable 78.3 1.7 5.1 0 92
05/17/2011 52 Acceptable 59.9 2.8 2.7 140 91
10/13/2010 10 Acceptable 65.4 0.2 6.3 21 90
09/12/2010 <10 Acceptable 72.5 8.1 6.1 15 85
08/18/2010 <10 Acceptable 79.9 7.7 32.1 44 104
07/22/2010 <10 Acceptable 81.8 8.7 27.0 23 132
06/16/2010 <10 Acceptable 72.9 6.5 5.3 17 85
05/22/2010 30 Acceptable 65.1 5.0 6.0 6 102
10/20/2009 <10 Acceptable 57.5 5.1 2.6 15 90
09/15/2009 <10 Acceptable 74.6 6.3 3.7 29 94
08/21/2009 <10 Acceptable 81.1 6.5 5.7 24 86
07/29/2009 <10 Acceptable 78.9 2.3 3.2 17 91
06/23/2009 <10 Acceptable 70.7 0.4 1.3 29 93
06/06/2009 <10 Acceptable n/a n/a n/a n/a n/a
05/13/2009 <10 Acceptable 61.7 1.3 1.6 24 100
10/21/2008 10 Acceptable 59.8 8.4 3.5 6 91
10/20/2008 <10 Acceptable 61.2 10.6 2.9 10 92
10/19/2008 <10 Acceptable 62.3 12.5 2.2 16 87
09/23/2008 <10 Acceptable 71.4 6.0 2.0 6 92
09/07/2008 30 Acceptable n/a n/a n/a n/a n/a
08/21/2008 <10 Acceptable 78.0 5.0 5.3 9 95
07/15/2008 <10 Acceptable 79.6 5.8 5.7 27 104
06/25/2008 142 Beach Advisory 75.1 6.0 6.2 13 99
06/16/2008 6 Acceptable n/a n/a n/a n/a n/a
05/20/2008 16 Acceptable 58.8 3.6 1.4 34 94
05/19/2008 <10 Acceptable 60.0 3.4 1.3 29 94
05/16/2008 <10 Acceptable n/a n/a n/a n/a n/a
09/09/2007 1 Acceptable 77.7 11.4 7.1 19 99
09/06/2007 <10 Acceptable 75.7 10.0 5.7 11 95
08/23/2007 1 Acceptable 75.5 6.6 2.9 4 86
08/16/2007 <10 Acceptable 80.4 7.4 5.7 13 95
07/16/2007 3 Acceptable 78.7 8.6 2.6 17 89
07/11/2007 2 Acceptable 78.2 8.6 6.1 20 97
06/20/2007 1 Acceptable n/a n/a n/a n/a n/a
06/18/2007 2 Acceptable n/a n/a n/a n/a n/a
05/21/2007 4 Acceptable 61.8 0.8 1.3 115 93
04/25/2007 86 Beach Advisory 47.9 0.1 1.4 202 105
04/18/2007 252 Beach Advisory 41.5 0.1 1.5 125 100
11/10/2006 182 Beach Advisory 52.2 0.1 0.0 135 95
10/18/2006 1 Acceptable 62.7 5.6 n/a 14 86
09/26/2006 1 Acceptable 68.9 5.0 2.4 n/a 99

Water Quality*

Acceptable (0–60) Beach Advisory (61+)

*Single sample thresholds;
Enterococcus count per 100mL

Prior Four Day Rainfall
(in inches)

Dry Weather (0–0.25) Wet Weather (0.25+)

Enterococcus is an EPA-approved fecal contamination indicator.

Samples taken by Riverkeeper, Lamont-Doherty Earth Observatory and CUNY Queens College staff, and processed on the Riverkeeper vessel, according to the 2014 Quality Assurance Project Plan.

Rainfall data comes from wunderground.com. Wet weather is a common trigger of fecal contamination.

What do the Numbers Mean?

Water Quality scoring is based on the 2012 Recreational Water Quality Criteria from the US Environmental Protection Agency (EPA) for safe swimming. Learn More

About this location:

Tarrytown, NY
This deep water site at the Tappan Zee Bridge has boating, kayaking and fishing.

Agencies Responsible:

Westchester County Dept. of Health: 914-813-5000, Rockland County Dept. of Health: 845-364-2900 and NYSDEC Region 3: 914-428-2505

Tell Gov. Hochul to block invasive species at the Erie and Champlain canals
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