Delaware Administrative Code
Title 7 - Natural Resources and Environmental Control
5000 - Division of Watershed Stewardship
7400 - Watershed Assessment Section
7401 - Surface Water Quality Standards
Section 7401-4.0 - Criteria To Protect Designated Uses
Current through Register Vol. 28, No. 3, September 1, 2024
4.1 All surface waters of the State (except as detailed in Sections 7.0 and 8.0) shall meet the following minimum criteria:
4.2 Narrative Criteria for Waters With the Public Water Supply Designated Use
4.3 Certain waters of the State are subject to natural variations in salinity such that those waters meet the definition of fresh at some times and marine at other times. For such waters, the more stringent of fresh or marine water quality criteria or standards as detailed throughout this document shall apply at all times unless otherwise specified by the Department.
4.4 Coordination with Delaware River Basin Commission:
For waters of the Delaware River and Delaware Bay, duly adopted Delaware River Basin Commission (DRBC) Water Quality Regulations shall be the applicable criteria. If the DRBC has not developed an applicable regulatory standard or criteria for these waters, and Delaware has, Delaware's criteria shall be applicable.
4.5 The following criteria shall apply outside approved regulatory mixing zones unless otherwise specified:
At water temperatures greater than 84 degrees Fahrenheit, instantaneous minimum shall not be less than 4.3 mg/L
During the period of April 1 to October 31 the minimum seasonal averaged secchi depth shall be 1.0 m.
Concentrations of chlorophyll-a in free-floating microscopic aquatic plants (algae) shall not exceed levels that result in ecologically undesirable consequences - such as reduced water clarity, low dissolved oxygen, food supply imbalances, proliferation of species deemed potentially harmful to aquatic life or humans or aesthetically objectionable conditions or otherwise render tidal waters unsuitable for designated uses.
The following criteria shall apply:
The purpose of these criteria is to provide the Department with a basis to assess water quality trends and pollution control needs with regard to primary and secondary contact recreation in waters of the State and to meet Federal Beaches Environmental Assessment and Coastal Health (BEACH) Act Requirements. The criteria apply to enterococcus bacteria determined by the Department to be of non-wildlife origin based on best scientific judgment using available information. Swimming in waters affected by runoff during runoff periods may present an elevated risk of gastrointestinal illness and is not recommended.
The total coliform median MPN of the water shall not exceed 70/100 mL, nor shall more than 10% of the samples have an MPN in excess of 330/100 mL for a 3 decimal dilution test (or 230/100 mL where the 5 tube decimal test is used). These criteria shall be verified through sampling of those portions of the shellfish area most probably exposed to fecal contamination for those tidal and climatic conditions most likely to result in contamination of the shellfish area.
Nutrient overenrichment is recognized as a significant problem in some surface waters of the State.
TABLE 1
WATER QUALITY CRITERIA FOR PROTECTION OF AQUATIC LIFE
(All Values Are Listed or Calculated in Micrograms Per Liter)
Parameter |
Fresh Acute Criterion |
Fresh Chronic Criterion |
Marine Acute Criterion |
Marine Chronic Criterion |
Aldrin |
3.0 |
-- |
1.3 |
-- |
Acrolein |
3.0 |
3.0 |
||
Aluminum pH6.5-9.0 |
750. |
87. |
-- |
-- |
Ammonia |
Temperature and pH dependent, see formula after this table |
Temperature and pH dependent, see formula after this table |
||
Arsenic (III)* |
340. |
150 |
69. |
36. |
Cadmium* |
EXP^(0.9789*LN(hardness)-3.866)*(1.136672-((LN(hardness)*(0.041838)))) |
EXP^(0.7977*LN(hardness)-3.909)*(1.101672-((LN(hardness)*(0.041838)))) |
33 |
7.9 |
Carbaryl |
2.1 |
2.1 |
1.6 | |
Chlordane |
2.4 |
0.0043 |
0.09 |
0.004 |
Chlorine |
19 |
11. |
13 |
7.5 |
Chlorpyrifos (Dursban) |
0.083 |
0.041 |
0.011 |
0.0056 |
Chromium (III)* |
0.316*EXP(0.819*LN(hardness)+3.7256) |
0.86*EXP(0.819*LN(hardness)+0.6848) |
C |
-- |
Chromium (VI)* |
16. |
11. |
1,100. |
50. |
Copper* |
Freshwater criteria calculated using the EPA Biotic Ligand Model |
Freshwater criteria calculated using the EPA Biotic Ligand Model |
4.8 |
3.1 |
Cyanide1 |
22. |
5.2 |
1.0 |
-- |
DDT and Metabolites (DDD and DDE) |
1.1 |
0.0010 |
0.13 |
0.0010 |
Demeton |
-- |
0.10 |
-- |
0.10 |
Diazanon |
0.17 |
0.17 |
0.82 |
0.82 |
Dieldrin |
0.24 |
.056 |
0.71 |
0.0019 |
Endosulfan |
0.22 |
0.056 |
0.034 |
0.0087 |
Endrin |
.086 |
.036 |
0.037 |
0.0023 |
Guthion |
-- |
0.01 |
-- |
0.01 |
Heptachlor |
0.52 |
0.0038 |
0.053 |
0.0036 |
Hexachloro-cylclohexane |
.095 |
0.08 |
0.16 |
-- |
Iron |
-- |
1000. |
-- |
-- |
Lead* |
(1.46203-LN(hardness)*0.145712)* EXP(1.273*LN(hardness)-1.460) |
(1.46203-LN(hardness)*0.145712)* EXP(1.273*LN(hardness)-4.705) |
210. |
8.1 |
Malathion |
-- |
0.1 |
-- |
0.1 |
Mercury (II)* |
1.4 |
.77 |
1.8 |
0.94 |
Methoxychlor |
-- |
0.03 |
-- |
0.03 |
Mirex |
-- |
0.001 |
C |
0.001 |
Nickel* |
0.998*EXP(0.8460*LN(hardness)+2.255) |
0.997*EXP(0.8460*LN(hardness)+0.0584) |
74. |
8.2 |
Nonylphenol |
28 |
6.6 |
7 |
1.7 |
Total PCBs |
0.014 |
0.03 |
||
Parathion |
0.065 |
0.013 |
-- |
-- |
Pentachlorophenol |
EXP(1.005*pH-4.869) |
EXP(1.005*pH-5.134) |
13. |
7.9 |
Selenium |
20 |
5.0 |
290 |
71. |
Silver* |
0.85*EXP(1.72*LN(hardness)-6.59) |
-- |
1.9 |
-- |
Toxaphene |
0.73 |
0.0002 |
0.21 |
0.0002 |
Tributyltin (TBT) |
0.46 |
0.072 |
0.42 |
0.0074 |
Zinc* |
0.978*EXP(0.8473*LN(hardness)+0.884) |
0.986*EXP(0.8473*LN(hardness)+0.884) |
90 |
81 |
Notes:
1Cyanide measured as free cyanide at the lowest pH occurring in the receiving water, or cyanide amenable to chlorination.
Formulas in the table have been formatted so that they can be copied directly into spreadsheets to calculate criteria. Criteria are calculated to two significant figures.
LN = natural log base e
EXP = e = 2.71828
Hardness is expressed as mg/L as CaCO3
pH is expressed as Standard Units
* Criteria is for total dissolved form
Calculation of Freshwater Acute Ammonia Criterion:
The one-hour average concentration of total ammonia nitrogen (in mg TAN/L) is not to exceed, more than once every three years on the average, the CMC (acute criterion magnitude) calculated using the following equation:
Where:
pH=pH of interest
t= temperature degrees Celsius
Calculation of Freshwater Chronic Ammonia Criterion:
The thirty-day rolling average concentration of total ammonia nitrogen (in mg TAN/L) is not to exceed, more than once every three years on the average, the chronic criterion magnitude (CCC) calculated using the following equation:
Where:
pH=pH of interest
t= temperature degrees Celsius
In addition, the highest four-day average within the 30-day averaging period should not be more than 2.5 times the CCC more than once in three years on average.
TABLE 2
WATER QUALITY CRITERIA FOR PROTECTION OF HUMAN HEALTH
(All Values Are Listed in Micrograms per Liter)
Pollutant |
Human Health for the consumption of Organism Only (ug/l) |
Human Health for the consumption of Water + Organism (ug/l) |
Acenaphthene |
90 |
70 |
Acrolein |
400 |
3 |
Acrylonitrile |
7 |
0.061 |
Aldrin |
0.00000077 |
0.00000077 |
alpha-Hexachlorocyclohexane (HCH) |
0.00039 |
0.00036 |
alpha-Endosulfan |
30 |
20 |
Anthracene |
400 |
300 |
Antimony |
640 |
5.6 |
Arsenic |
10 (mcl) |
|
Asbestos |
7 million fibers/L |
|
Barium |
1,000 |
|
Benzene |
16 |
0.58 |
Benzidine |
0.011 |
0.00014 |
Benzo(a)anthracene |
0.18 |
0.038 |
Benzo(a)pyrene |
0.018 |
0.0038 |
Benzo(b)fluoranthene |
0.18 |
0.038 |
Beryllium |
4 (MCL) |
|
beta-Hexachlorocyclohexane (HCH) |
0.014 |
0.008 |
beta-Endosulfan |
40 |
20 |
Bis(2-Chloro-1-methylethyl) Ether |
4000 |
200 |
Bis(2-Chloroethyl) Ether |
2.2 |
0.03 |
Bis(2-Ethylhexyl) Phthalate |
0.37 |
0.32 |
Bis(Chloromethyl) Ether |
0.017 |
0.00015 |
Bromoform |
120 |
7 |
Butylbenzyl Phthalate |
0.1 |
0.1 |
Cadmium |
5 (MCL) |
|
Carbon Tetrachloride |
5 |
0.4 |
Chlordane |
0.00032 |
0.00031 |
Chlorobenzene |
800 |
100 |
Chlorodibromomethane |
21 |
0.8 |
Chloroform |
2,000 |
60 |
Chlorophenoxy Herbicide (2,4-D) |
70 (MCL) |
|
Chlorophenoxy Herbicide (2,4,5-TP) [Silvex] |
50 (MCL) |
|
Chromium (III) |
100 (MCL) |
|
Chromium (VI) |
100 (MCL) |
|
Chrysene |
0.13 |
0.12 |
Copper |
1300 (MCL) |
|
Cyanide |
400 |
4 |
Dibenzo(a,h)anthracene |
0.018 |
0.0038 |
Dichlorobromomethane |
27 |
0.95 |
Dieldrin |
0.0000012 |
0.0000012 |
Diethyl Phthalate |
600 |
600 |
Dimethyl Phthalate |
2,000 |
2,000 |
Di-n-Butyl Phthalate |
30 |
20 |
Dinitrophenols |
1,000 |
10 |
Endosulfan Sulfate |
40 |
20 |
Endrin |
0.03 |
0.03 |
Endrin Aldehyde |
1 |
1 |
Ethylbenzene |
130 |
68 |
Fluoranthene |
20 |
20 |
Fluorene |
70 |
50 |
gamma-Hexachlorocyclohexane (HCH) [Lindane] |
4.4 |
0.2 (MCL) |
Heptachlor |
0.0000059 |
0.0000059 |
Heptachlor Epoxide |
0.000032 |
0.000032 |
Hexachlorobenzene |
0.000079 |
0.000079 |
Hexachlorobutadiene |
0.01 |
0.01 |
Hexachlorocyclohexane (HCH) -Technical |
0.01 |
0.0066 |
Hexachlorocyclopentadiene |
4 |
4 |
Hexachloroethane |
0.1 |
0.1 |
Indeno(1,2,3-cd)pyrene |
0.0013 |
0.0012 |
Isophorone |
1,800 |
34 |
Methylmercury |
0.3 mg/kg |
- |
Methoxychlor |
0.02 |
0.02 |
Methyl Bromide |
10000 |
100 |
Methylene Chloride |
1,000 |
5 (MCL) |
Nickel |
4,600 |
610 |
Nitrates |
10,000 (MCL) |
|
Nitrobenzene |
600 |
10 |
Nitrosodibutylamine |
0.22 |
0.0063 |
Nitrosodiethylamine |
1.24 |
0.0008 |
Nitrosopyrrolidine |
34 |
0.016 |
N-Nitrosodimethylamine |
3 |
0.00069 |
N-Nitrosodi-n-Propylamine |
0.51 |
0.005 |
N-Nitrosodiphenylamine |
6 |
3.3 |
Pentachlorobenzene |
0.1 |
0.1 |
Pentachlorophenol |
0.04 |
0.03 |
Phenol |
300,000 |
4,000 |
Polychlorinated Biphenyls (PCBs) |
0.000064 |
0.000064 |
Pyrene |
30 |
20 |
Selenium |
4200 |
50 (MCL) |
Tetrachloroethylene |
29 |
5 (MCL) |
Thallium |
0.47 |
0.24 |
Toluene |
520 |
57 |
Toxaphene |
0.00071 |
0.0007 |
Trichloroethylene |
7 |
0.6 |
Vinyl Chloride |
1.6 |
0.022 |
Zinc |
26,000 |
7,400 |
1,1,1-Trichloroethane |
200,000 |
200 (MCL) |
1,1,2,2-Tetrachloroethane |
3 |
0.2 |
1,1,2-Trichloroethane |
8.9 |
0.55 |
1,1-Dichloroethylene |
20,000 |
7 (MCL) |
1,2,4,5-Tetrachlorobenzene |
0.03 |
0.03 |
1,2,4-Trichlorobenzene |
0.076 |
0.071 |
1,2-Dichlorobenzene |
3,000 |
600(MCL) |
1,2-Dichloroethane |
650 |
5 (MCL) |
1,2-Dichloropropane |
31 |
0.9 |
1,2-Diphenylhydrazine |
0.2 |
0.03 |
Trans-1,2-Dichloroethylene |
4,000 |
100 |
1,3-Dichlorobenzene |
10 |
7 |
1,3-Dichloropropene |
12 |
0.27 |
1,4-Dichlorobenzene |
900 |
75 (MCL) |
2,3,7,8-TCDD (Dioxin) (as TEQ1) |
5.10E-09 |
5.00E-09 |
2,4,5-Trichlorophenol |
600 |
300 |
2,4,6-Trichlorophenol |
2.8 |
1.5 |
2,4-Dichlorophenol |
60 |
10 |
2,4-Dimethylphenol |
3,000 |
100 |
2,4-Dinitrophenol |
300 |
10 |
2,4-Dinitrotoluene |
1.7 |
0.049 |
2-Chloronaphthalene |
1000 |
800 |
2-Chlorophenol |
800 |
30 |
2-Methyl-4,6-Dinitrophenol |
30 |
2 |
3,3'-Dichlorobenzidine |
0.15 |
0.049 |
3-Methyl-4-Chlorophenol |
2,000 |
500 |
p,p'-Dichlorodiphenyldichloroethane (DDD) |
0.00012 |
0.00012 |
p,p'-Dichlorodiphenyldichloroethylene (DDE) |
0.000018 |
0.000018 |
p,p'-Dichlorodiphenyltrichloroethane (DDT) |
0.00003 |
0.00003 |
The columns labeled "Fish and Water Ingestion" shall apply only to waters of the State designated Public Water Supply sources in these standards.
The column labeled "Fish Ingestion Only" shall apply to all waters of the State not designated Public Water Supply sources in this document.
Values shown with "(MCL)" under header "Fish and Water Ingestion" are Primary Maximum Contaminant Levels (MCLs) as given in the State of Delaware Regulations Governing Public Drinking Water Systems that became effective September 10, 2001
Criteria is for the "total toxic equivalence (TEQ) to 2, 3, 7, 8 - TCDD". The toxic equivalence for a sample is the sum of the concentration for each congener multiplied by its associated Toxicity Equivalence Factor (TEF) listed in table below.
TEQ = ((Concentration of Congener in sample) x (TEF))
where the TEF is unitless and the concentration is in ug/l.
Congener |
TEF value |
Congener |
TEF value |
Dibenzo-p-dioxins |
Non-ortho PCBs |
||
2,3,7,8-TCDD |
1 |
PCB 77 |
0.0001 |
1,2,3,7,8-PnCDD |
1 |
PCB 81 |
0.0003 |
1,2,3,4,7,8-HxCDD |
0.1 |
PCB 126 |
0.1 |
1,2,3,6,7,8-HxCDD |
0.1 |
PCB 169 |
0.03 |
1,2,3,7,8,9-HxCDD |
0.1 |
||
1,2,3,4,6,7,8-HpCDD |
0.01 |
Mono-ortho PCBs |
|
OCDD |
0.0003 |
PCB 105 |
0.00003 |
PCB 114 |
0.00003 |
||
Dibenzofurans |
PCB 118 |
0.00003 |
|
2,3,7,8-TCDF |
0.1 |
PCB 123 |
0.00003 |
1,2,3,7,8-PnCDF |
0.03 |
PCB 156 |
0.00003 |
2,3,4,7,8-PnCDF |
0.3 |
PCB 157 |
0.00003 |
1,2,3,4,7,8-HxCDF |
0.1 |
PCB 167 |
0.00003 |
1,2,3,6,7,8-HxCDF |
0.1 |
PCB 189 |
0.00003 |
1,2,3,7,8,9-HxCDF |
0.1 |
||
2,3,4,6,7,8-HxCDF |
0.1 |
||
1,2,3,4,6,7,8-HpCDF |
0.01 |
||
1,2,3,4,7,8,9-HpCDF |
0.01 |
||
OCDF |
0.0003 |