250 R.I. Code R. 250-RICR-150-05-1.10

Current through November 7, 2024

Section 250-RICR-150-05-1.10 - Water Quality Criteria

A. The following physical, chemical and biological criteria are parameters of the minimum water quality necessary to support the surface water use classifications of §§ 1.9(B), 1.9(C), and 1.9(D) of this Part and shall be applicable to all waters of the State.

B. General Criteria - The following minimum criteria are applicable to all waters of the State, unless criteria specified for individual classes are more stringent:

1. At a minimum, all waters shall be free of pollutants in concentrations or combinations or from anthropogenic activities subject to these regulations that:

a. Adversely affect the composition of fish and wildlife;

b. Adversely affect the physical, chemical, or biological integrity of the habitat;

c. Interfere with the propagation of fish and wildlife;

d. Adversely alter the life cycle functions, uses, processes and activities of fish and wildlife; or

e. Adversely affect human health.

2. Aesthetics - all waters shall be free from pollutants in concentrations or combinations that:

a. Settle to form deposits that are unsightly, putrescent, or odorous to such a degree as to create a nuisance, or interfere with the existing or designated uses;

b. Float as debris, oil, grease, scum or other floating material attributable to wastes in amounts to such a degree as to create a nuisance or interfere with the existing or designated uses;

c. Produce odor or taste or change the color or physical, chemical or biological conditions to such a degree as to create a nuisance or interfere with the existing or designated uses; or,

d. Result in the dominance of species of fish and wildlife to such a degree as to create a nuisance or interfere with the existing or designated uses.

3. Radioactive substances - The level of radioactive materials in all waters shall not be in concentrations or combinations which will likely be harmful to humans, fish and wildlife, or result in concentrations in organisms producing undesirable conditions.

4. Nutrients - Nutrients shall not exceed the limitations specified in §§ 1.10(D)(1) and 1.10(E)(1) of this Part and/or more stringent site-specific limits necessary to prevent or minimize accelerated or cultural eutrophication.

5. Thermal Mixing Zones - In the case of thermal discharges into tidal rivers, fresh water streams or estuaries, where thermal mixing zones are allowed by the Director, the mixing zone will be limited to no more than one quarter (1/4) of the cross sectional area and/or volume of river flow, stream or estuary, leaving at least three quarters (3/4) free as a zone of passage. In wide estuaries and oceans, the limits of mixing zones will be established by the Director.

6. Non-thermal Mixing Zones - In the case of non- thermal discharges, in applying these standards the Director may recognize, where appropriate, a limited acute and/or chronic mixing zone(s) on a case-by-case basis. The locations, size and shape of these zones shall provide for the maximum protection of fish and wildlife.

7. At a minimum, all mixing zones must:

a. Meet the criteria for aesthetics, in accordance with § 1.10(B)(2) of this Part;

b. Be limited to an area or volume that will prevent interference with the existing and designated uses in the associated waterbody segment and beyond;

c. Allow an appropriate zone of passage for migrating fish and other organisms, prohibit lethality to organisms passing through the mixing zone, and protect for spawning and nursery habitat; and

d. Not allow substances to accumulate in sediments, fish and wildlife or food chains such that known or predicted safe exposure levels for the health of humans or fish and wildlife will be exceeded.

8. For activities that will likely cause or contribute to flow alterations, streamflow conditions must be adequate to support existing and designated uses.

C. Applicable Conditions - The water quality standards apply under the most adverse conditions, as determined by the Director according to sound engineering and scientific practices on a case-by-case basis unless defined below. The ambient water quality criteria are applicable at or in excess of the following flow conditions:

1. Aquatic Life Criteria - The acute and chronic aquatic life criteria for freshwaters shall not be exceeded at or above the lowest average 7 consecutive day low flow with an average recurrence frequency of once in 10 years (7Q10). The acute and chronic aquatic life criteria for seawater shall not be exceeded beyond the boundary of the mixing zone(s), as defined and determined by §§ 1.10(B)(5) and (6) of this Part, and thence throughout the waterbody. If a mixing zone has not been established, these criteria shall not be exceeded in any portion of the receiving water.

2. Human Health Criteria - The freshwater human health criteria for non-carcinogens and carcinogens are applicable at or in excess of the harmonic mean flow, which is a long-term mean flow value calculated by dividing the number of daily flows analyzed by the sum of the reciprocals of those daily flows. For seawaters, the ambient human health water quality criteria for carcinogens and non-carcinogens are applicable when the most adverse hydrographic and pollution conditions occur at the particular point of evaluation.

D. Class Specific Criteria-Freshwaters

1. The table below presents the class-specific criteria for freshwaters, classifications AA, A, B, B1, and C and any partial use designation freshwaters.

CRITERION	CLASS AA1	CLASS A	CLASS B, B1, B{a}, B1{a}	CLASS C
Dissolved Oxygen	Cold Water Fish Habitat - Dissolved oxygen content of not less than 75% saturation, based on a daily average, and an instantaneous minimum dissolved oxygen concentration of at least 5 mg/l, except as naturally occurs. For the period from October 1st to May 14th, where in areas identified by the RI Division of Fish and Wildlife as cold water fish spawning areas the following criteria apply: For species whose early life stages are not directly exposed to the water column (ie, early life stages are intergravel), the 7 day mean water column dissolved oxygen concentration shall not be less than 9.5 mg/l and the instantaneous minimum dissolved oxygen concentration shall not be less than 8 mg/l. For species that have early life stages exposed directly to the water column, the 7 day mean water column dissolved oxygen concentration shall not be less than 6.5 mg/l and the instantaneous minimum dissolved oxygen concentration shall not be less than 5.0 mg/l. (See § 1.25 of this Part for coldwater designated waters) Warm Water Fish Habitat - Dissolved oxygen content of not less than 60% saturation, based on a daily average, and an instantaneous minimum dissolved oxygen concentration of at least 5.0 mg/l, except as naturally occurs. The 7 day mean water column dissolved oxygen concentration shall not be less than 6 mg/l. (See § 1.25 of this Part for warmwater designated waters)
Sludge deposits, solid refuse, floating solids, oil, grease, scum	None allowable.			None in such amoutns that would impair any usages specifically assigned to this class.
Color and turbidity	None in such concentrations that would impair any usages specifically assigned to this class. Turbidity not to exceed 5 NTU over background.		None in such concentrations that would impair any usages specifically assigned to this class. Turbidity not to exceed 10 NTU over natural background.
Fecal Coliform Bacteria (MPN/100ml)	Drinking Water Supply Criteria: - applied at the terminal reservoir of the system - Not to exceed a geometric mean value of 20 MPN/100 ml and not more than 10% of the samples shall exceed a value of 200.			None in such concentrations that would impair any usages specifically assigned to this class.
	Primary Contact Recreational/Swimming Criteria - Not to exceed a geometric mean value of 200 MPN/100 ml and not more than 10% of the total samples taken shall exceed 400 MPN/100 ml, applied only when adequate enterococci data are not available
Enterococci	Primary Contact Recreational/Swimming Criteria Non-Designated Bathing Beach Waters Geometric Mean Density: 54 colonies/100 ml Designated Bathing Beach Waters Geometric Mean Density: 33 colonies/100 ml Single Sample Maximum*: 61 colonies/100 ml * Criteria for determining beach swimming advisories at designated beaches as evaluated by Health.			None in such concentrations that would impair any usages specifically assigned to this class.
Taste and odor	None other than of natural origin and none associated with nuisance algal species.		None in such concentrations that would impair any usages specifically assigned to this class nor cause taste or odor in edible portions of fish.
pH (Standard Units)	6.5 - 9.0 or as naturally occurs.
Temperature/Temperature increase	No activity shall raise the temperature of the receiving waters above the recommended limit on the most sensitive receiving water use nor cause the growth of undesirable or nuisance species of biota. In no cases shall an activity cause the temperature to exceed 83 degrees F. Heated discharges into designated coldwater habitats (See § 1.25 of this Part for coldwater designated waters) shall not raise the temperature above 68 degrees F outside an established thermal mixing zone. In no case shall the temperature of the receiving water be raised more than 4 degrees F.
Chemical constituents	None in concentrations or combinations that could be harmful to humans or fish and wildlife for the most sensitive and governing water class use, or unfavorably alter the biota, or which would make the waters unsafe or unsuitable for fish and wildlife or their propagation, impair the palatability of same, or impair waters for any other existing or designated use. None in such concentrations that would exceed the Water Quality Criteria and Guidelines as found in § 1.26 of this Part. The ambient concentration of a pollutant in a water body shall not exceed the Ambient Water Quality Criteria and Guidelines, (§ 1.26 of this Part) for the protection of aquatic organisms from acute or chronic effects, unless the criteria or guidelines are modified by the Director based on results of bioassay tests conducted in accordance with the terms and conditions provided in § 1.29 of this Part.
Nutrients	Average Total Phosphorus shall not exceed 0.025 mg/l in any lake, pond, kettlehole or reservoir, and average Total P in tributaries at the point where they enter such bodies of water shall not cause exceedance of this phosphorus criteria, except as naturally occurs, unless the Director determines, on a site-specific basis, that a different value for phosphorus is necessary to prevent cultural eutrophication. None in such concentration that would impair any usages specifically assigned to said Class, or cause undesirable or nuisance aquatic species associated with cultural eutrophication, nor cause exceedance of the criterion above in a downstream lake, pond, or reservoir. New discharges of wastes containing phosphates will not be permitted into or immediately upstream of lakes or ponds. Phosphates shall be removed from existing discharges to the extent that such removal is or may become technically and reasonably feasible.
1 Class AA waters used for public drinking water supply may be subject to restricted recreational use by State and local authorities.

E. Class Specific Criteria-Saltwaters

1. The table below presents the class-specific criteria for saltwaters, classifications SA, SB, SB1, and SC and any partial use designation saltwaters.

CRITERION	CLASS SA, SA{b}	CLASS SB, SB1, SB{a}, SB1{a}	CLASS SC
Sludge deposits, solid refuse, floating solids, oil, grease, scum	None allowable.		None in such amounts that would impair any usages specifically assigned to this class.
Color and turbidity	None in such concentrations that would impair any usages specifically assigned to this class. Turbidity not to exceed 5 NTU over background.	None in such concentrations that would impair any usages specifically assigned to this class. Turbidity not to exceed 10 NTU over background.
Fecal Coliform Bacteria	Shellfishing Criteria: - Not to exceed a geometric mean value of 14 cfu per 100ml (MF mTEC method) and not more than 10% of the samples or the estimated 90th percentile of the samples shall exceed 31 cfu per 100ml (MF mTEC method).		None in such concentrations that would impair any usages specifically assigned to this class.
	Primary Contact Recreational/Swimming Criteria - Not to exceed a geometric mean value of 50 MPN/100 ml and not more than 10% of the total samples taken shall exceed 400 MPN/100 ml, applied only when adequate enterococci data are not available.
Enterococci	Primary Contact Recreational/Swimming Criteria Geometric Mean Density: 35 colonies/100 ml Single Sample Maximum*: 104 colonies/100 ml * Criteria for determining beach swimming advisories at designated beaches as evaluated by the Rhode Island Department of Health.		None in such concentrations that would impair any usages specifically assigned to this class.
Taste and odor	None allowable except as naturally occurs.	None in such concentrations that would impair any usages specifically assigned to this class nor cause taste or odor in edible portions of fish or shellfish.
pH	6.5 - 8.5 but not more than 0.2 units outside of the normally occurring range.
Dissolved Oxygen	See § 1.10(F) of this Part
Chemical constituents	None in concentrations or combinations that could be harmful to humans or fish and wildlife for the most sensitive and governing water class use, or unfavorably alter the biota, or which would make the waters unsafe or unsuitable for fish and wildlife or their propagation, impair the palatability of same, or impair the waters for any other existing or designated use. None in such concentrations that would exceed the Water Quality Criteria and Guidelines as found in § 1.26 of this Part. The ambient concentration of a pollutant in a water body shall not exceed the RI DEM Ambient Water Quality Criteria & Guidelines (§ 1.26 of this Part) for the protection of aquatic organisms from acute or chronic effects, unless the criteria or guideline is modified by the Director based on results of bioassay tests conducted in accordance with the terms and conditions provided in § 1.29 of this Part.
Nutrients	None in such concentration that would impair any usages specifically assigned to said Class, or cause undesirable or nuisance aquatic species associated with cultural eutrophication. Shall not exceed sitespecific limits if deemed necessary by the Director to prevent or minimize accelerated or cultural eutrophication. Total phosphorus, nitrates and ammonia may be assigned site-specific permit limits based on reasonable Best Available Technologies. Where waters have low tidal flushing rates, applicable treatment to prevent or minimize accelerated or cultural eutrophication may be required for regulated nonpoint source activities.
Temperature/Temperature Increase	Activities shall not increase the temperature except where the increase will not exceed the recommended limit on the most sensitive receiving water use and in no case shall an activity cause the temperature to exceed 83 degrees F nor raise the normal temperature more than 1.6 degrees F, 16 June through September and not more than 4 degrees F from October through 16 June. All measurements shall be made at the boundary of such mixing zones as is found to be reasonable by the Director.

F. Saltwater Dissolved Oxygen Criteria - The following information details the use of continuous dissolved oxygen data in estuarine waters.

1. For surface waters above a seasonal pycnocline, not less than an instantaneous value of 4.8 mg/l more than once every three years, except as naturally occurs.

2. For waters below the seasonal pycnocline, Aquatic Life Uses are considered to be protected if conditions do not fail to meet protective thresholds, as described below, more than once every three years. DO criteria presented here shall be protective of the most sensitive life stage - survival effects on larvae which affects larval recruitment - for both persistent and cyclic conditions. This criteria evaluates effects of exposure to low DO over time on larval recruitment. Because larval recruitment occurs over the whole season, the low DO exposure effects are cumulative. Exposures are evaluated on a daily basis to determine the total seasonal exposure. The criteria to protect larval survival is established to limit the number of exposure days over the range of low DO conditions such that the cumulative percentage of larvae affected shall not exceed a 5% reduction in larval recruitment over the season. If the Director determines that a smaller percent impairment on larval recruitment is necessary on a site specific basis, a criteria modification will be process in accordance with § 1.21(F) of this Part. Protection of larval survival will also afford adequate protection of juvenile and adult life stages. The critical recruitment season for evaluation of DO exposure is defined as May 1 through October 31. While recruitment may occur at other periods of the year, this timeframe reflects periods when hypoxia are most prevalent. Waters with a DO concentration above an instantaneous value of 4.8 mg/l shall be considered protective of Aquatic Life Uses. When instantaneous DO values fall below 4.8 mg/l, the waters shall not be:

a. Less than 2.9 mg/l for more than 24 consecutive hours during recruitment season; nor

b. Less than 1.4 mg/l for more than 1 hour more than twice during the recruitment season; nor

c. Shall they exceed the cumulative exposure presented in § 1.10(F)(3) of this Part.

d. The method for calculating cumulative low DO exposure throughout the recruitment season is as follows:

(1) For persistent low DO conditions (low DO conditions that vary little within a day, e.g., <0.5 mg/l), the limit represents allowable DO conditions below 4.8 mg/l provided the exposure duration (number of days observed) does not exceed the corresponding allowable number of days (as presented in § 1.10(F)(2)(d)(1)(AA) of this Part) that ensure adequate larval recruitment over the course of the season. The cumulative seasonal low DO effects are evaluated by totaling the fractions of the observed (or projected) exposure duration (in days) divided by the allowable number of days for each DO concentration. The sum of the decimal fractions shall not exceed 1.0. The minimum daily DO measurement is used to represent the daily DO value. The criteria for 24 hour DO concentration and allowable number of days as presented in § 1.10(F)(2)(d)(1)(AA) of this Part are calculated using the following equations:

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(AA) Saltwater DO Criteria for Waters Below the Seasonal Pycnocline

24 Hour (Daily) DO Exposure Concentration (mg/L)	Daily Percent Larval Mortality (%)	Allowable Number of Days Without Exceeding a 5% Reduction in Seasonal Larval Recruitment
4.6	4.96	42
4.5	6.05	30
4.4	7.36	24
4.3	8.93	20
4.2	10.79	18
4.1	12.98	16
4	15.55	14
3.9	18.51	12
3.8	21.88	10
3.7	25.69	9
3.6	29.89	8
3.5	34.47	7
3.4	39.36	6
3.3	44.46	5
3.2	49.69	4
3.1	54.92	3
3	60.05	2
2.9	64.97	1

(2) For cyclic low DO conditions (DO conditions that fluctuate broadly within a day, e.g.>0.5 mg/l), the limit represents the allowable number of days as a given daily larval percent mortality that protects against great than 5% cumulative impairment of larval recruitment over a recruitment season. The maximum daily percent larval mortality is a function of DO minimum for any exposure interval/range (mg/l) and the duration of the interval (hours) and is determined using the Time-to-death (TTD) curves presented in § 1.10(F)(2)(d)(2)(AA) of this Part The maximum daily percent larval mortality from cyclic exposures is determined from the observed data point falling closest to a TTD curve of greatest effect (ie., highest percent mortality). The calculated maximum daily percent larval mortality shall not exceed the allowable number of days as presented in §§ 1.10(F)(2)(d)(1)(AA) and 1.10(F)(2)(d)(2)(BB) of this Part. Cumulative cyclic low DO effects observed over the course of the season are evaluated by tallying the number of days at each percent mortality observed for the season. The observed number of days at each percent mortality are divided by the allowable number of days for each percent mortality. The sum of the decimal fraction shall not exceed 1.0.

(AA) Time To Death (TTD) Curves for 5-60 % Mortality

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(BB) Cyclic Translator for Waters Below the Seasonal Pycnocline

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(3) For seasons with both cyclic and persistent cycles of low DO, all data will be treated as cyclic exposure patterns with the persistent data set at the 24 hour/1-day exposure duration. Daily percent mortalities will be determined from § 1.10(F)(2)(d)(2)(AA) and § 1.10(F)(2)(d)(1)(AA) of this Part will be used to determine the acceptable number of days the low DO pattern can occur over the course of the season.

3. For waters without a seasonal pycnocline, DO concentrations above 4.8 mg/l shall be considered protective of Aquatic Life Uses. When instantaneous DO values fall below 4.8 mg/l, the water shall not be:

a. Less than 3.0 mg/l for more than 24 consecutive hours during the recruitment season; nor

b. Less than 1.4 mg/l for more than 1 hour more than twice during the recruitment season; nor

c. Shall they exceed the cumulative DO exposure presented in § 1.10(F)(2)(d)(1)(AA) of this Part.

d. Cumulative low DO exposures in the 2.95 - 4.8 mg/l range shall be evaluated as described above in § 1.10(F)(2) of this Part but shall not exceed the information presented in § 1.10(F)(3)(e)(1)(AA) of this Part.

e. The method for calculating cumulative low DO exposure is as follows:

(1) For persistent low DO conditions in water without a seasonal pycnocline, the criteria for 24 hours DO concentration and allowable number of days as presented in § 1.10(F)(3)(e)(1)(AA) of this Part are calculated using the following equation:

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(AA) Saltwater DO Criteria for Waters without a Seasonal Pycnocline

24 Hour (Daily) DO Exposure Concentration (mg/L)	Daily Percent Larval Mortality (%)	Allowable Number of Days Without Exceeding a 5% Reduction in Seasonal Larval Recruitment
4.6	4.96	16
4.5	6.05	14
4.4	7.36	12
4.3	8.93	11
4.2	10.79	10
4.1	12.98	8
4.0	15.55	7
3.9	18.51	6
3.8	21.88	5
3.7	25.69	4
3.6	29.89	3
3.5	34.47	2
3.4	39.36	1

(2) For cyclic low DO conditions in waters without a seasonal pycnocline, the daily percent mortalities for observed data are determined from § 1.10(F)(2)(d)(2)(AA) of this Part and shall not exceed the allowable number of days presented in §§ 1.10(F)(3)(e)(1)(AA) and 1.10(F)(3)(e)(2)(AA) of this Part.

(AA) Cyclic Translator for Waters Without a Seasonal Pycnocline

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(3) For seasons with both cyclic and persistent cycles of low DO, all data will be treated as cyclic exposure patterns with the persistent data set at the 24 hours/1-day exposure duration. Daily percent mortalities will be determined from §§ 1.10(F)(2)(d)(2)(AA) and 1.10(F)(3)(e)(1)(AA) of this Part will be used to determine the acceptable number of days the low DO pattern can occur over the course of the season.

250 R.I. Code R. 250-RICR-150-05-1.10

Amended effective 12/28/2023