Bay Bacteria Sampling

On September 10th, 2025, twenty stations were sampled for fecal coliform bacteria in the Providence and Seekonk Rivers; five of these stations were also sampled for enterococci bacteria. In the five days prior to sampling, 1.59 inches of precipitation was recorded at TF Green. Overall, bacteria counts were higher than during the previous sampling event.

Fecal coliform counts were higher in the Seekonk River, compared to the Providence River (geometric mean of 94 MPN/100 mL for the Seekonk River compared to 19 MPN/100mL for the Providence River) for sampling conducted on September 10th. The maximum count (1,500 MPN/100 mL) was measured at the Point Street Bridge sampling location.

Fecal coliform counts were higher in the Providence River, compared to the previous sampling on August 27th (geometric mean of 19 MPN/100 mL compared to 6 MPN/100 mL on 8/27). Fecal coliform counts were higher in the Seekonk River, compared to the previous sampling on August 27th (geometric mean of 94 MPN/100 mL compared to 23 MPN/100 mL on 8/27). 

Enterococci results had an overall geometric mean of 10 MPN/100 mL. Enterococci counts ranged from <10 MPN/100 mL at most sites to 20 MPN/100 mL at Point Street Bridge.

The next scheduled sampling date is September 24th.

​The table below lists the Rhode Island bacteria standards for primary contact and shellfishing established by the Rhode Island Department of Environmental Management (RIDEM). RIDEM defines primary contact as any recreational activities in which there is prolonged and intimate contact with water, involving considerable risk of ingesting water (e.g., swimming, diving, water skiing and surfing). Please note that the RIDEM bacteria standards are provided here for informational purposes only and are not intended to indicate official state compliance with primary contact or shellfishing standards.

Summary of Rhode Island Bacteria Standards for Saltwater Primary Contact and Shellfishing

​​	​Fec​al Co​li​fo​r​m	Enterococci
Primary Con​​​t​a​c​t1​​​​​	Geom​e​tric ​m​e​a​n​ ≤50​ MPN/1​​00​ mL​ <10% ​o​f​​ samples >4​00 MPN/100 ​mL	Geom​etric mean ≤35 colo​nies​/100 mL​ All sa​mples ≤104 colonies/100 ​​mL2
Shellfishing	Geometr​ic mean ≤14 MPN/100​ mL <10% of samples >49 MPN/100 mL3​	NO ENTEROCOCCI CR​ITERIA​

¹Fecal coliform primary contact criteria app​lied only when adequate enterococci data are not available; ²Single sample maximum criterion for determining beach swimming advisories at designated beaches as evaluated by the Rhode Island Department of Health; ³For a three-tube decimal dilution.

Table adapted from Rhode Island Water Quality Regulations (250-RICR-150-05-1)​; see regulations for complete details.​​​​​​​​​​

On August 27th, 2025, twenty stations were sampled for fecal coliform bacteria in the Providence and Seekonk Rivers; five of these stations were also sampled for enterococci bacteria. There was no precipitation at TF Green over the five days prior to the August 27^th, 2025 sampling event. Overall, bacteria counts remained approximately the same as the previous sampling event.

Fecal coliform counts were higher in the Seekonk River, compared to the Providence River (geometric mean of 23 MPN/100 mL for the Seekonk River compared to 6 MPN/100mL for the Providence River) for sampling conducted on August 27th. The maximum count (93 MPN/100 mL) was measured at the Point Street Bridge sampling location.

Fecal coliform counts remained approximately the same in the Providence River, compared to the previous sampling on August 15th (geometric mean of 6 MPN/100 mL compared to 7 MPN/100 mL on 8/15). Fecal coliform counts also remained approximately the same in the Seekonk River, compared to the previous sampling on August 15th (geometric mean of 23 MPN/100 mL compared to 25 MPN/100 mL on 8/15). 

Enterococci results had an overall geometric mean of 13 MPN/100 mL. Enterococci counts ranged from <10 MPN/100 mL at most sites to 52 MPN/100 mL at Point Street Bridge.

The next scheduled sampling date is September 10th.

​The table below lists the Rhode Island bacteria standards for primary contact and shellfishing established by the Rhode Island Department of Environmental Management (RIDEM). RIDEM defines primary contact as any recreational activities in which there is prolonged and intimate contact with water, involving considerable risk of ingesting water (e.g., swimming, diving, water skiing and surfing). Please note that the RIDEM bacteria standards are provided here for informational purposes only and are not intended to indicate official state compliance with primary contact or shellfishing standards.

Summary of Rhode Island Bacteria Standards for Saltwater Primary Contact and Shellfishing

​​	​Fec​al Co​li​fo​r​m	Enterococci
Primary Con​​​t​a​c​t1​​​​​	Geom​e​tric ​m​e​a​n​ ≤50​ MPN/1​​00​ mL​ <10% ​o​f​​ samples >4​00 MPN/100 ​mL	Geom​etric mean ≤35 colo​nies​/100 mL​ All sa​mples ≤104 colonies/100 ​​mL2
Shellfishing	Geometr​ic mean ≤14 MPN/100​ mL <10% of samples >49 MPN/100 mL3​	NO ENTEROCOCCI CR​ITERIA​

¹Fecal coliform primary contact criteria app​lied only when adequate enterococci data are not available; ²Single sample maximum criterion for determining beach swimming advisories at designated beaches as evaluated by the Rhode Island Department of Health; ³For a three-tube decimal dilution.

Table adapted from Rhode Island Water Quality Regulations (250-RICR-150-05-1)​; see regulations for complete details.​​​​​​​​​​

On August 13th, 2025, twenty stations were sampled for fecal coliform bacteria in the Providence and Seekonk Rivers; five of these stations were also sampled for enterococci bacteria. There was no precipitation at TF Green over the five days prior to the August 13^th, 2025 sampling event. Overall bacteria counts were lower than during the previous sampling event.

Fecal coliform counts were higher in the Seekonk River, compared to the Providence River (geometric mean of 25 MPN/100 mL for the Seekonk River compared to 7 MPN/100mL for the Providence River) for sampling conducted on August 13th. The maximum count (93 MPN/100 mL) was measured at the Division St. Dock, Bishop Point, and Collier Point Park sampling locations.

Fecal coliform counts remained approximately the same in the Providence River, compared to the previous sampling on July 30th (geometric mean of 7 MPN/100 mL compared to 9 MPN/100 mL on 7/30). Fecal coliform counts were lower in the Seekonk River, compared to the previous sampling on July 30th (geometric mean of 25 MPN/100 mL compared to 55 MPN/100 mL on 7/30). 

Enterococci results had an overall geometric mean of 11 MPN/100 mL. Enterococci counts ranged from <10 MPN/100 mL at most sites to 20 MPN/100 mL at Point Street Bridge.

The next scheduled sampling date is August 27th.

​The table below lists the Rhode Island bacteria standards for primary contact and shellfishing established by the Rhode Island Department of Environmental Management (RIDEM). RIDEM defines primary contact as any recreational activities in which there is prolonged and intimate contact with water, involving considerable risk of ingesting water (e.g., swimming, diving, water skiing and surfing). Please note that the RIDEM bacteria standards are provided here for informational purposes only and are not intended to indicate official state compliance with primary contact or shellfishing standards.

Summary of Rhode Island Bacteria Standards for Saltwater Primary Contact and Shellfishing

​​	​Fec​al Co​li​fo​r​m	Enterococci
Primary Con​​​t​a​c​t1​​​​​	Geom​e​tric ​m​e​a​n​ ≤50​ MPN/1​​00​ mL​ <10% ​o​f​​ samples >4​00 MPN/100 ​mL	Geom​etric mean ≤35 colo​nies​/100 mL​ All sa​mples ≤104 colonies/100 ​​mL2
Shellfishing	Geometr​ic mean ≤14 MPN/100​ mL <10% of samples >49 MPN/100 mL3​	NO ENTEROCOCCI CR​ITERIA​

¹Fecal coliform primary contact criteria app​lied only when adequate enterococci data are not available; ²Single sample maximum criterion for determining beach swimming advisories at designated beaches as evaluated by the Rhode Island Department of Health; ³For a three-tube decimal dilution.

Table adapted from Rhode Island Water Quality Regulations (250-RICR-150-05-1)​; see regulations for complete details.​​​​​​​​​​

Most people picture Narragansett Bay as calm, sparkling, and post card-perfect. But if you’ve ever been out there in a small boat with a cooler full of sample bottles and a mission to track down bacteria data, you should know the truth: the bay has trolls.

Every other week, we’re out on the bay collecting water samples to test for bacteria. Why? Because the health of Narragansett Bay isn’t just about how pretty it looks, its about what’s living in it, and sometimes, what’s floating in it that shouldn’t be. Bacteria levels can mean the difference between a thriving shellfish industry and a “DO Not Harvest” sign. Our data helps protect public health, the environment, and the economy.

Why would trolls be out in the bay, you ask? A few theories staff have in mind. Perhaps trolls follow the plankton blooms. Scientist track all sorts of information, why not troll movement. Trolls may have a curiosity about science and wants to see what we are doing. Water sampling is fascinating! Finally we think the trolls like a good swim in the Narragansett Bay. So, next time your out on the bay and something catches your eye, don’t be too quick to dismiss it. It just might be …a troll!

On July 30th, 2025, twenty stations were sampled for fecal coliform bacteria in the Providence and Seekonk Rivers; five of these stations were also sampled for enterococci bacteria. In the five days prior to sampling, 1.91 inches of precipitation was recorded at TF Green. Overall bacteria counts were lower than during the previous sampling event.

Fecal coliform counts were higher in the Seekonk River, compared to the Providence River (geometric mean of 55 MPN/100 mL for the Seekonk River compared to 9 MPN/100mL for the Providence River) for sampling conducted on July 30th. The maximum count (930 MPN/100 mL) was measured at the Point St. Bridge sampling location.

Fecal coliform counts were lower in the Providence River, compared to the previous sampling on July 16th (geometric mean of 9 MPN/100 mL compared to 16 MPN/100 mL on 7/16). Fecal coliform counts were lower in the Seekonk River, compared to the previous sampling on July 16th (geometric mean of 55 MPN/100 mL compared to 82 MPN/100 mL on 7/16). 

Enterococci results had an overall geometric mean of 14 MPN/100 mL. Enterococci counts ranged from <10 MPN/100 mL at most sites to 109 MPN/100 mL at Point St. Bridge.

The next scheduled sampling date is August 13th.

​The table below lists the Rhode Island bacteria standards for primary contact and shellfishing established by the Rhode Island Department of Environmental Management (RIDEM). RIDEM defines primary contact as any recreational activities in which there is prolonged and intimate contact with water, involving considerable risk of ingesting water (e.g., swimming, diving, water skiing and surfing). Please note that the RIDEM bacteria standards are provided here for informational purposes only and are not intended to indicate official state compliance with primary contact or shellfishing standards.

Summary of Rhode Island Bacteria Standards for Saltwater Primary Contact and Shellfishing

​​	​Fec​al Co​li​fo​r​m	Enterococci
Primary Con​​​t​a​c​t1​​​​​	Geom​e​tric ​m​e​a​n​ ≤50​ MPN/1​​00​ mL​ <10% ​o​f​​ samples >4​00 MPN/100 ​mL	Geom​etric mean ≤35 colo​nies​/100 mL​ All sa​mples ≤104 colonies/100 ​​mL2
Shellfishing	Geometr​ic mean ≤14 MPN/100​ mL <10% of samples >49 MPN/100 mL3​	NO ENTEROCOCCI CR​ITERIA​

¹Fecal coliform primary contact criteria app​lied only when adequate enterococci data are not available; ²Single sample maximum criterion for determining beach swimming advisories at designated beaches as evaluated by the Rhode Island Department of Health; ³For a three-tube decimal dilution.

Table adapted from Rhode Island Water Quality Regulations (250-RICR-150-05-1)​; see regulations for complete details.​​​​​​​​​​

On July 16th, 2025, seventeen stations were sampled for fecal coliform bacteria in the Providence and Seekonk Rivers; five of these stations were also sampled for enterococci bacteria. In the five days prior to sampling, 0.01 inches of precipitation was recorded at TF Green. Overall bacteria counts were lower than during the previous sampling event.

Fecal coliform counts were higher in the Seekonk River, compared to the Providence River (geometric mean of 82 MPN/100 mL for the Seekonk River compared to 16 MPN/100mL for the Providence River) for sampling conducted on July 16th. The maximum count (430 MPN/100 mL) was measured at the India Point Park sampling location.

Fecal coliform counts were lower in the Providence River, compared to the previous sampling on July 2nd (geometric mean of 16 MPN/100 mL compared to 49 MPN/100 mL on 7/2). Fecal coliform counts were lower in the Seekonk River, compared to the previous sampling on July 2nd (geometric mean of 82 MPN/100 mL compared to 4916 MPN/100 mL on 7/2). 

Enterococci results had an overall geometric mean of 11 MPN/100 mL. Enterococci counts ranged from <10 MPN/100 mL at most sites to 20 MPN/100 mL at Point St Bridge.

The next scheduled sampling date is July 30th.

​The table below lists the Rhode Island bacteria standards for primary contact and shellfishing established by the Rhode Island Department of Environmental Management (RIDEM). RIDEM defines primary contact as any recreational activities in which there is prolonged and intimate contact with water, involving considerable risk of ingesting water (e.g., swimming, diving, water skiing and surfing). Please note that the RIDEM bacteria standards are provided here for informational purposes only and are not intended to indicate official state compliance with primary contact or shellfishing standards.

Summary of Rhode Island Bacteria Standards for Saltwater Primary Contact and Shellfishing

​​	​Fec​al Co​li​fo​r​m	Enterococci
Primary Con​​​t​a​c​t1​​​​​	Geom​e​tric ​m​e​a​n​ ≤50​ MPN/1​​00​ mL​ <10% ​o​f​​ samples >4​00 MPN/100 ​mL	Geom​etric mean ≤35 colo​nies​/100 mL​ All sa​mples ≤104 colonies/100 ​​mL2
Shellfishing	Geometr​ic mean ≤14 MPN/100​ mL <10% of samples >49 MPN/100 mL3​	NO ENTEROCOCCI CR​ITERIA​

¹Fecal coliform primary contact criteria app​lied only when adequate enterococci data are not available; ²Single sample maximum criterion for determining beach swimming advisories at designated beaches as evaluated by the Rhode Island Department of Health; ³For a three-tube decimal dilution.

Table adapted from Rhode Island Water Quality Regulations (250-RICR-150-05-1)​; see regulations for complete details.​​​​​​​​​​

On July 2nd, 2025, twenty stations were sampled for fecal coliform bacteria in the Providence and Seekonk Rivers; five of these stations were also sampled for enterococci bacteria. In the five days prior to sampling, 0.03 inches of precipitation was recorded at TF Green. Overall bacteria counts were higher than during the previous sampling event.

Fecal coliform counts were higher in the Seekonk River, compared to the Providence River (geometric mean of 4916 MPN/100 mL for the Seekonk River compared to 49 MPN/100mL for the Providence River) for sampling conducted on July 2nd. The maximum count (240,000 MPN/100 mL) was measured at the Point St. Bridge sampling location.

Fecal coliform counts were higher in the Providence River, compared to the previous sampling on June 4th (geometric mean of 49 MPN/100 mL compared to 30 MPN/100 mL on 6/4). Fecal coliform counts were higher in the Seekonk River, compared to the previous sampling on June 4th (geometric mean of 4916 MPN/100 mL compared to 93 MPN/100 mL on 6/4). 

Enterococci results had an overall geometric mean of 333 MPN/100 mL. Enterococci counts ranged from <10 MPN/100 mL at Conimicut Point and Gaspee Point to 6488 MPN/100 mL at Point St Bridge.

The next scheduled sampling date is July 16th.

​The table below lists the Rhode Island bacteria standards for primary contact and shellfishing established by the Rhode Island Department of Environmental Management (RIDEM). RIDEM defines primary contact as any recreational activities in which there is prolonged and intimate contact with water, involving considerable risk of ingesting water (e.g., swimming, diving, water skiing and surfing). Please note that the RIDEM bacteria standards are provided here for informational purposes only and are not intended to indicate official state compliance with primary contact or shellfishing standards.

Summary of Rhode Island Bacteria Standards for Saltwater Primary Contact and Shellfishing

​​	​Fec​al Co​li​fo​r​m	Enterococci
Primary Con​​​t​a​c​t1​​​​​	Geom​e​tric ​m​e​a​n​ ≤50​ MPN/1​​00​ mL​ <10% ​o​f​​ samples >4​00 MPN/100 ​mL	Geom​etric mean ≤35 colo​nies​/100 mL​ All sa​mples ≤104 colonies/100 ​​mL2
Shellfishing	Geometr​ic mean ≤14 MPN/100​ mL <10% of samples >49 MPN/100 mL3​	NO ENTEROCOCCI CR​ITERIA​

¹Fecal coliform primary contact criteria app​lied only when adequate enterococci data are not available; ²Single sample maximum criterion for determining beach swimming advisories at designated beaches as evaluated by the Rhode Island Department of Health; ³For a three-tube decimal dilution.

Table adapted from Rhode Island Water Quality Regulations (250-RICR-150-05-1)​; see regulations for complete details.​​​​​​​​​​

On June 4th, 2025, twenty stations were sampled for fecal coliform bacteria in the Providence and Seekonk Rivers; five of these stations were also sampled for enterococci bacteria. In the five days prior to sampling, 0.39 inches of precipitation was recorded at TF Green. Overall bacteria counts remained approximately the same as the previous sampling event.

Fecal coliform counts were higher in the Seekonk River, compared to the Providence River (geometric mean of 93 MPN/100 mL for the Seekonk River compared to 30 MPN/100mL for the Providence River) for sampling conducted on June 4th. The maximum count (430 MPN/100 mL) was measured at the Point Street Bridge sampling location.

Fecal coliform counts were lower in the Providence River, compared to the previous sampling on May 21st (geometric mean of 30 MPN/100 mL compared to 45 MPN/100 mL on 5/21). Fecal coliform counts were higher in the Seekonk River, compared to the previous sampling on May 21st (geometric mean of 93 MPN/100 mL compared to 37 MPN/100 mL on 5/21). 

Enterococci results had an overall geometric mean of 18 MPN/100 mL. Enterococci counts ranged from <10 MPN/100 mL at most sites to 183 MPN/100 mL at Point St Bridge.

The next scheduled sampling date is June 18th.

​The table below lists the Rhode Island bacteria standards for primary contact and shellfishing established by the Rhode Island Department of Environmental Management (RIDEM). RIDEM defines primary contact as any recreational activities in which there is prolonged and intimate contact with water, involving considerable risk of ingesting water (e.g., swimming, diving, water skiing and surfing). Please note that the RIDEM bacteria standards are provided here for informational purposes only and are not intended to indicate official state compliance with primary contact or shellfishing standards.

Summary of Rhode Island Bacteria Standards for Saltwater Primary Contact and Shellfishing

​​	​Fec​al Co​li​fo​r​m	Enterococci
Primary Con​​​t​a​c​t1​​​​​	Geom​e​tric ​m​e​a​n​ ≤50​ MPN/1​​00​ mL​ <10% ​o​f​​ samples >4​00 MPN/100 ​mL	Geom​etric mean ≤35 colo​nies​/100 mL​ All sa​mples ≤104 colonies/100 ​​mL2
Shellfishing	Geometr​ic mean ≤14 MPN/100​ mL <10% of samples >49 MPN/100 mL3​	NO ENTEROCOCCI CR​ITERIA​

¹Fecal coliform primary contact criteria app​lied only when adequate enterococci data are not available; ²Single sample maximum criterion for determining beach swimming advisories at designated beaches as evaluated by the Rhode Island Department of Health; ³For a three-tube decimal dilution.

Table adapted from Rhode Island Water Quality Regulations (250-RICR-150-05-1)​; see regulations for complete details.​​​​​​​​​​

On May 21st, 2025, twenty stations were sampled for fecal coliform bacteria in the Providence and Seekonk Rivers; five of these stations were also sampled for enterococci bacteria. In the five days prior to sampling, 0.04 inches of precipitation was recorded at TF Green. Overall bacteria counts were lower than during the previous sampling event.

Fecal coliform counts were lower in the Seekonk River, compared to the Providence River (geometric mean of 37 MPN/100 mL for the Seekonk River compared to 45 MPN/100mL for the Providence River) for sampling conducted on May 21st. The maximum count (2,300 MPN/100 mL) was measured at the Point Street Bridge sampling location.

Fecal coliform counts were lower in the Providence River, compared to the previous sampling on May 7th (geometric mean of 45 MPN/100 mL compared to 369 MPN/100 mL on 5/7). Fecal coliform counts were lower in the Seekonk River, compared to the previous sampling on May 7th (geometric mean of 37 MPN/100 mL compared to 1121 MPN/100 mL on 5/7). 

Enterococci results had an overall geometric mean of 16 MPN/100 mL. Enterococci counts ranged from <10 MPN/100 mL at most sites to 74 MPN/100 mL at Point St Bridge.

The next scheduled sampling date is June 4^th.

​The table below lists the Rhode Island bacteria standards for primary contact and shellfishing established by the Rhode Island Department of Environmental Management (RIDEM). RIDEM defines primary contact as any recreational activities in which there is prolonged and intimate contact with water, involving considerable risk of ingesting water (e.g., swimming, diving, water skiing and surfing). Please note that the RIDEM bacteria standards are provided here for informational purposes only and are not intended to indicate official state compliance with primary contact or shellfishing standards.

Summary of Rhode Island Bacteria Standards for Saltwater Primary Contact and Shellfishing

​​	​Fec​al Co​li​fo​r​m	Enterococci
Primary Con​​​t​a​c​t1​​​​​	Geom​e​tric ​m​e​a​n​ ≤50​ MPN/1​​00​ mL​ <10% ​o​f​​ samples >4​00 MPN/100 ​mL	Geom​etric mean ≤35 colo​nies​/100 mL​ All sa​mples ≤104 colonies/100 ​​mL2
Shellfishing	Geometr​ic mean ≤14 MPN/100​ mL <10% of samples >49 MPN/100 mL3​	NO ENTEROCOCCI CR​ITERIA​

¹Fecal coliform primary contact criteria app​lied only when adequate enterococci data are not available; ²Single sample maximum criterion for determining beach swimming advisories at designated beaches as evaluated by the Rhode Island Department of Health; ³For a three-tube decimal dilution.

Table adapted from Rhode Island Water Quality Regulations (250-RICR-150-05-1)​; see regulations for complete details.​​​​​​​​​​

On May 7th, 2025, twenty stations were sampled for fecal coliform bacteria in the Providence and Seekonk Rivers; five of these stations were also sampled for enterococci bacteria. In the five days prior to sampling, 2.10 inches of precipitation was recorded at TF Green. Overall bacteria counts were higher than during the previous sampling event.

Fecal coliform counts were higher in the Seekonk River, compared to the Providence River (geometric mean of 1121 MPN/100 mL for the Seekonk River compared to 369 MPN/100mL for the Providence River) for sampling conducted on May 7th. The maximum count (9,300 MPN/100 mL) was measured at the Collier Point Park sampling location.

Fecal coliform counts were higher in the Providence River, compared to the previous sampling on April 23rd (geometric mean of 369 MPN/100 mL compared to 12 MPN/100 mL on 4/23). Fecal coliform counts were higher in the Seekonk River, compared to the previous sampling on April 23rd (geometric mean of 1121 MPN/100 mL compared to 72 MPN/100 mL on 4/23). 

Enterococci results had an overall geometric mean of 128 MPN/100 mL. Enterococci counts ranged from <10 MPN/100 mL at Conimicut Point to 2046 MPN/100 mL at Point St Bridge.

The next scheduled sampling date is May 21^st.

​The table below lists the Rhode Island bacteria standards for primary contact and shellfishing established by the Rhode Island Department of Environmental Management (RIDEM). RIDEM defines primary contact as any recreational activities in which there is prolonged and intimate contact with water, involving considerable risk of ingesting water (e.g., swimming, diving, water skiing and surfing). Please note that the RIDEM bacteria standards are provided here for informational purposes only and are not intended to indicate official state compliance with primary contact or shellfishing standards.

Summary of Rhode Island Bacteria Standards for Saltwater Primary Contact and Shellfishing

​​	​Fec​al Co​li​fo​r​m	Enterococci
Primary Con​​​t​a​c​t1​​​​​	Geom​e​tric ​m​e​a​n​ ≤50​ MPN/1​​00​ mL​ <10% ​o​f​​ samples >4​00 MPN/100 ​mL	Geom​etric mean ≤35 colo​nies​/100 mL​ All sa​mples ≤104 colonies/100 ​​mL2
Shellfishing	Geometr​ic mean ≤14 MPN/100​ mL <10% of samples >49 MPN/100 mL3​	NO ENTEROCOCCI CR​ITERIA​

¹Fecal coliform primary contact criteria app​lied only when adequate enterococci data are not available; ²Single sample maximum criterion for determining beach swimming advisories at designated beaches as evaluated by the Rhode Island Department of Health; ³For a three-tube decimal dilution.

Table adapted from Rhode Island Water Quality Regulations (250-RICR-150-05-1)​; see regulations for complete details.​​​​​​​​​​