Section 620

Section 620.420 Groundwater Quality Standards for Class II: General Resource Groundwater

a) Inorganic Chemical Constituents

1) Except due to natural causes or as provided in Section 620.450 or subsection (a)(3) or (e) of this Section, concentrations of the following chemical constituents must not be exceeded in Class II groundwater:

CASRN	Constituent	Standard (mg/L)^a
7440-36-0	Antimony	0.024^b
7440-38-2	Arsenic^b	0.2^d
7440-39-3	Barium	2.0^e
7440-41-7	Beryllium	0.5^f
7440-43-9	Cadmium	0.05^g
7440-47-3	Chromium (total)	1.0^g
7440-48-4	Cobalt	1^d
143-33-9	Cyanide	0.6^d
7681-49-4	Fluoride	4^e
7439-92-1	Lead	1.0^d
7439-93-2	Lithium	2.5^f
7487-94-7	Mercury (mercuric chloride)	0.01^d
7439-98-7	Molybdenum	0.308^e
14797-55-8	Nitrate as N	100^d
14797-73-0	Perchlorate	0.0081^e
7440-28-0	Thallium	0.02^h
7440-62-2	Vanadium	0.1^d

Constituent Name and Groundwater Quality Standard Notations

^aThe inorganic groundwater quality standards are based on total metal analyses for the evaluation of human health effects.

^bA treatment factor of 4 is applied to the Class I groundwater quality standard. The constituent's treatment efficiency is based on the effectiveness to treat the constituent in the groundwater at an 75% removal efficiency rate for the constituent.

^cThe constituent meets the definition of a "carcinogen" in Section 620.110.

^dThe standard is based on beneficial use for watering livestock, per "Water Quality Criteria", by National Academy of Sciences, incorporated by reference in Section 620.125.

^eThe Class II standard is equal to the Class I groundwater quality standard.

^fThe standard is based on beneficial use for irrigation of crops, per "Water Quality Criteria", by National Academy of Sciences, incorporated by reference in Section 620.125.

^gThe standard is based on beneficial use for watering livestock and irrigation of crops, per "Water Quality Criteria", by National Academy of Sciences, incorporated by reference in Section 620.125.

^hA treatment factor of 10 is applied to the Class I groundwater quality standard. The constituent's treatment efficiency is based on the effectiveness to treat the constituent in the groundwater at an 90% removal efficiency rate for the constituent.

2) Except as provided in Section 620.450 or subsection (a)(3) or (e) of this Section, concentrations of the following chemical constituents must not be exceeded in Class II groundwater:

CASRN	Constituent	Standard (mg/L)^a,b
7429-90-5	Aluminum	5^c
7440-42-8	Boron	2^d
16887-00-6	Chloride	200^e
7440-50-8	Copper	0.5^c
7439-89-6	Iron	5^e
7439-96-5	Manganese	10^d
7440-02-0	Nickel	2^d
7440-14-4	Radium (combined 226+228)	5^f
7782-49-2	Selenium	0.02^d
7440-22-4	Silver	0.058^f
14808-79-8	Sulfate	400^e
	TDS (total dissolved solids)	1,200^e
7440-66-6	Zinc	10^d

Constituent Name and Groundwater Quality Standard Notations

^aThe standard units for radium (combined 226+228) is picocuries per liter (pCi/L).

^bThe inorganic groundwater quality standards are based on total metal analyses for the evaluation of human health effects.

^cThe standard is based on beneficial use for watering livestock and irrigation of crops, per "Water Quality Criteria", by National Academy of Sciences, incorporated by reference in Section 620.125.

^dThe standard is based on beneficial use for irrigation of crops, per "Water Quality Criteria", by National Academy of Sciences, incorporated by reference in Section 620.125.

^eThe standard is the 95% confidence concentration stated in the Agency's "Integrated Water Quality Report and Section 303(d) List", incorporated by reference in Section 620.125.

^fThe Class II standard is equal to the Class I groundwater quality standard.

3) The standard for any inorganic chemical constituent specified in subsection (a)(2) and barium specified in subsection (a)(1) does not apply within fill material or within the upper 10 feet of parent material under fill material on a site not within the rural property class for which the conditions of subsection (a)(3)(A) or (a)(3)(B) are met. For pH, the standard specified in subsection (d) does not apply to groundwater within fill material below 5 feet of land surface or within the upper 10 feet of parent material under fill material on a site not within the rural property class for which the conditions of subsection (a)(3)(A) or (a)(3)(B) are met.

A) Before November 25, 1991, surficial characteristics have been altered by placing the fill material so as to impact the concentration of any parameter (constituent or pH) specified in this subsection (a)(3), and any on-site groundwater monitoring of the parameter is available for review by the Agency.

B) On November 25, 1991, surficial characteristics are in the process of being altered by placing the fill material, in a reasonably continuous manner to completion, so as to impact the concentration of any parameter (constituent or pH) specified in this subsection (a)(3), and any on-site groundwater monitoring of the parameter is available for review by the Agency.

4) For subsection (a)(3), the term "fill material" means clean earthen materials, slag, ash, clean demolition debris, or similar materials.

b) Organic Chemical Constituents

1) Except due to natural causes or as provided in Section 620.450 or subsection (b)(2) or (e) of this Section, concentrations of the following organic chemical constituents must not be exceeded in Class II groundwater:

CASRN	Constituent	Standard (mg/L)
83-32-9	Acenaphthene	1.2^a
67-64-1	Acetone	3.5^b
15972-60-8	Alachlor^c	0.01^a
116-06-3	Aldicarb	0.015^a
120-12-7	Anthracene	6^a
319-84-6	alpha-BHC (alpha-benzenehexachloride)^c	0.00006^a
71-43-2	Benzene^c	0.025^a
56-55-3	Benzo(a)anthracene^d	0.0012^a
205-99-2	Benzo(b)fluoranthene^d	0.0012^a
207-08-9	Benzo(k)fluoranthene^d	0.012^a
50-32-8	Benzo(a)pyrene^d	0.002^e
65-85-0	Benzoic acid	15^b
78-93-3	2-Butanone (methyl ethyl ketone)	2.3^b
1563-66-2	Carbofuran	0.2^a
75-15-0	Carbon disulfide	1.9^a
56-23-5	Carbon tetrachloride^c	0.025^a
12789-03-6	Chlordane^c	0.01^a
108-90-7	Chlorobenzene	0.5^a
67-66-3	Chloroform^c	0.35^a
218-01-9	Chrysene^d	0.12^a
94-75-7	2,4-D (2,4-dichloroohenoxy acetic acid)	0.35^a
75-99-0	Dalapon	2.0^e
53-70-3	Dibenzo(a,h)anthracene^d	0.0005^a
96-12-8	1,2-Dibromo-3-chloropropane^d	0.002^e
1918-00-9	Dicamba	0.12^b
95-50-1	o-Dichlorobenzene (1,2-dichlorobenzene)	1.5^f
106-46-7	p-Dichlorobenzene (1,4-dichlorobenzene)^c	0.375^a
75-71-8	Dichlorodifluoromethane	3.9^a
75-34-3	1,1-Dichloroethane	3.9^a
107-06-2	1,2-Dichloroethane^c	0.025^a
75-35-4	1,1-Dichloroethylene	0.035^a
156-59-2	cis-1,2-Dichloroethylene	0.2^g
156-60-5	trans-1,2-Dichloroethylene	0.5^a
75-09-2	Dichloromethane (methylene chloride)^d	0.025^a
78-87-5	1,2-Dichloropropane^b	0.025^a
117-81-7	Di(2-ethylhexyl)phthalate^b	0.06^e
84-66-2	Diethyl phthalate	3.1^b
84-74-2	Di-n-butyl phthalate	1.9^a
99-65-0	1,3-Dinitrobenzene	0.001^b
121-14-2	2,4-Dinitrotoluene^c	0.005^a
606-20-2	2,6-Dinitrotoluene^c	0.005^a
88-85-7	Dinoseb	0.07^e
123-91-1	1,4-Dioxane (p-dioxane)^c	0.00078^b
145-73-3	Endothall	0.1^b
72-20-8	Endrin	0.01^a
100-41-4	Ethylbenzene^c	1.0^h
106-93-4	Ethylene dibromide (1,2-dibromoethane)^c	0.0005^e
206-44-0	Fluoranthene	0.75^a
86-73-7	Fluorene	0.75^a
58-89-9	gamma-HCH (gamma- hexachlorocyclohexane, lindane)^c	0.001^a
13252-13-6	HFPO-DA (hexafluoropropylene oxide dimer acid GenX)	0.000010^b
2691-41-0	HMX (octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine)	3.9^a
76-44-8	Heptachlor^c	0.002^a
1024-57-3	Heptachlor epoxide^c	0.001^a
77-47-4	Hexachlorocyclopentadiene	0.5^e
193-39-5	Indeno(1,2,3-c,d)pyrene^d	0.0012^a
98-82-8	Isopropylbenzene (cumene)^c	1.9^a
93-65-2	MCPP (mecoprop)	0.1^b
1634-04-4	MTBE (methyl tertiary-butyl ether)	0.5^e
72-43-5	Methoxychlor	0.2^a
90-12-0	1-Methylnaphthalene	1.35^a
91-57-6	2-Methylnaphthalene	0.075^a
95-48-7	2-Methylphenol (o-cresol)	0.19^b
91-20-3	Naphthalene	0.39^a
98-95-3	Nitrobenzene	0.0077^b
1336-36-3	PCBs (polychlorinated biphenyls as decachloro- biphenyl)^c	0.0025^a
375-73-5	PFBS (perfluorobutanesulfonic acid)	0.002^b
355-46-4	PFHxS (perfluorohexanesulfonic acid)	0.000010^b
375-95-1	PFNA (perfluorononanoic acid)	0.000010^b
335-67-1	PFOA (perfluorooctanoic acid)^c	0.000004^b
1763-23-1	PFOS (perfluorooctanesulfonic acid)^c	0.000004^b
87-86-5	Pentachlorophenol	0.005^a
108-95-2	Phenol	0.1ⁱⁱ
1918-02-1	Picloram	5.0^e
129-00-0	Pyrene	0.6^a
121-82-4	RDX (hexahydro-l,3,5-trinitro-l,3,5-trianzine)	0.062^b
122-34-9	Simazine	0.04^e
100-42-5	Styrene	0.5^a
118-96-7	TNT (2,4,6-trinitrotoluene)	0.039^a
93-72-1	2,4,5-TP (silvex)	0.25^a
127-18-4	Tetrachloroethylene^c	0.025^a
108-88-3	Toluene	2.5^f
8001-35-2	Toxaphene^c	0.015^a
120-82-1	1,2,4-Trichlorobenzene	0.7^e
71-55-6	1,1,1-Trichloroethane	1^a
79-00-5	1,1,2-Trichloroethane	0.05^e
79-01-6	Trichloroethylene^d	0.025^a
75-69-4	Trichlorofluoromethane	6^a
99-35-4	1,3,5-Trinitrobenzene	2.3^a
75-01-4	Vinyl chloride^d	0.01^a
1330-20-7	Xylenes	10^b

Constituent Name and Groundwater Quality Standard Notations

^aA treatment factor of 5 is applied to the Class I groundwater quality standard. The constituent's treatment efficiency is based on the effectiveness to treat the constituent in the groundwater at an 80% removal efficiency rate for the constituent.

^bThe Agency's treatment efficiency determination demonstrates a treatment factor is not applicable for the constituent. The standard is equal to the Class I groundwater quality standard.

^cThe constituent meets the definition of a "carcinogen" in Section 620.110.

^dThe constituent meets the definition of a "mutagen" in Section 620.110.

^eA treatment factor of 10 is applied to the Class I groundwater quality standard. The constituent's treatment efficiency is based on the effectiveness to treat the constituent in the groundwater at a 90% removal efficiency rate for the constituent.

^fA treatment factor of 2.5 is applied to the Class I groundwater quality standard. The constituent's treatment efficiency is based on the effectiveness to treat the constituent in the groundwater at a 60% removal efficiency rate for the constituent.

^gA treatment factor of 3 is applied to the Class I groundwater quality standard. The constituent's treatment efficiency is based on the effectiveness to treat the constituent in the groundwater at a 65% removal efficiency rate for the constituent.

^hA treatment factor of 1.5 is applied to the Class I groundwater quality standard. The constituent's treatment efficiency is based on the effectiveness to treat the constituent in the groundwater at a 30% removal efficiency rate for the constituent.

ⁱThe standard is based on 35 Ill. Adm. Code 302.208.

2) The standards for pesticide chemical constituents specified in subsection (b)(1) do not apply to groundwater within 10 feet of the land surface if the concentrations of the constituents result from applying pesticides in a manner consistent with the Federal Insecticide, Fungicide, and Rodenticide Act (7 U.S.C. 136 et seq.) and the Illinois Pesticide Act [415 ILCS 60].

c) Complex Organic Chemical Mixtures

1) Concentrations of the following organic chemical constituents must not be exceeded in Class II groundwater:

CASRN	Constituent	Standard (mg/L)
71-43-2	Benzene^a	0.025^b
	Total BETX	13.525^c

Constituent Name and Groundwater Quality Standard Notations

^aThe constituent meets the definition of a "carcinogen" in Section 620.110.

^bA treatment factor of 5 is applied to the Class I groundwater quality standard. The constituent's treatment efficiency is based on the effectiveness to treat the constituent in the groundwater at an 80% removal efficiency rate for the constituent.

^cThe standard is the total combined Class II standard of benzene, ethylbenzene, toluene, and xylenes.

2) Atrazine and Metabolites

Concentration of the following chemical constituents must not be exceeded in Class II groundwater.

CASRN	Constituent	Standard (mg/L)
1912-24-9	Atrazine	0.015^a
	Total Atrazine and Metabolites	0.015
6190-65-4	DEA (desethyl-atrazine)
1007-28-9	DIA (desisopropyl-atrazine)
3397-62-4	DACT (diaminochlorotriazine)

Constituent Name and Groundwater Quality Standard Notations:

d) pH

Except due to natural causes, a pH range of 6.5 - 9.0 units must not be exceeded in Class II groundwater.

e) No facility that is subject to 35 Ill. Adm. Code 811 or 814 must comply with any requirement or standard of those rules to the extent it incorporates or is otherwise based on any of the following constituents or their standards under this Section:

CASRN	Constituent
13252-13-6	HFPO-DA (hexafluoropropylene oxide dimer acid GenX)
375-73-5	PFBS (perfluorobutanesulfonic acid)
355-46-4	PFHxS (perfluorohexanesulfonic acid)
375-95-1	PFNA (perfluorononanoic acid)
335-67-1	PFOA (perfluorooctanoic acid)
1763-23-1	PFOS (perfluorooctanesulfonic acid)

(Source: Amended at 49 Ill. Reg. 4488, effective March 28, 2025)