Title 18 . Environmental Conservation

Chapter 80 . Administrative Enforcement

Section 300. Maximum contaminant levels (MCLs)

18 AAC 80.300. Maximum contaminant levels (MCLs)

(a) General requirement. Subject to a variance issued under 18 AAC 80.370, a variance issued under 18 AAC 80.371, or an exemption granted under 18 AAC 80.375, the owner or operator of a public water system may not cause or allow the use of water from that system for human consumption if the water contains, or has a significant potential for containing

(1) a contaminant in a concentration that exceeds a primary maximum contaminant level (MCL) set by (b) of this section; or

(2) a contaminant other than one described in (1) of this subsection, if the department determines that the concentration of that contaminant is high enough to make the water a hazard to human health.

(b) Primary MCLs : The primary MCLs for a public water system are as follows:

(1) inorganic chemical contaminants : for the listed inorganic chemical contaminants, the following MCLs apply

(A) to a community water system:

Contaminant Maximum Contaminant Level (mg/l) Antimony 0.006 Arsenic before January 23, 2006 0.05 Arsenic on or after January 23, 2006 0.010, with compliance to be reported as required under 18 AAC 80.305(b) (4) Asbestos 7 million fibers/liter, for fibers longer than 10 m m Barium 2 Beryllium 0.004 Cadmium 0.005 Chromium 0.1 Cyanide 0.2, as free cyanide Fluoride 4.0 Mercury 0.002 Nickel none, but monitoring requirements under this chapter apply Nitrate 10, as nitrogen Nitrite 1, as nitrogen Total nitrate and nitrite 10, as nitrogen Selenium 0.05 Thallium 0.002

(B) to a non-transient non-community water system:

Contaminant Maximum Contaminant Level (mg/l) Antimony 0.006 Arsenic before January 23, 2006 0.05 Arsenic on or after January 23, 2006 0.010, with compliance to be reported as required under 18 AAC 80.305(b) (4) Asbestos 7 million fibers/liter, for fibers longer than 10 m m Barium 2 Beryllium 0.004 Cadmium 0.005 Chromium 0.1 Cyanide 0.2, as free cyanide Mercury 0.002 Nickel none, but monitoring requirements under this chapter apply Nitrate 10, as nitrogen Nitrite 1, as nitrogen Total nitrate and nitrite 10, as nitrogen Selenium 0.05 Thallium 0.002

(C) to a transient non-community water system:

Contaminant Maximum Contaminant Level (mg/l) Nitrate 10, as nitrogen Nitrite 1, as nitrogen Total nitrate and nitrite 10, as nitrogen

(2) organic chemical contaminants : MCLs are established for the following types of organic chemical contaminants:

(A) pesticides : for listed pesticides, the following MCLs apply:

Contaminant Maximum Contaminant Level (mg/l) Alachlor 0.002 Aldicarb 0.003 Aldicarb sulfoxide 0.004 Aldicarb sulfone 0.002 Atrazine 0.003 Carbofuran 0.04 Chlordane 0.002 Dalapon 0.2 Dibromochloropropane 0.0002 Dinoseb 0.007 Diquat 0.02 Endothall 0.1 Endrin 0.002 Ethylene dibromide 0.00005 Glyphosate 0.7 Heptachlor 0.0004 Heptachlor epoxide 0.0002 Lindane 0.0002 Methoxychlor 0.04 Oxamyl (Vydate) 0.2 Pentachlorophenol 0.001 Picloram 0.5 Simazine 0.004 Toxaphene 0.003 2,4-Dichlorophenoxy acetic acid (2,4-D) 0.07 2-(2,4,5-Trichlorophenoxy)-p ropionic acid (2,4,5-TP) 0.05

(B) volatile organic chemicals (VOCs) : for listed volatile organic chemicals, the following MCLs apply:

Contaminant Maximum Contaminant Level (mg/l) 1,1-Dichloroethylene 0.007 1,1,1-Trichloroethane 0.2 1,1,2-Trichloroethane 0.005 1,2-Dichloroethane 0.005 1,2-Dichloropropane 0.005 1,2,4-Trichlorobenzene 0.07 Benzene 0.005 Carbon tetrachloride 0.005 cis-1,2-Dichloroethylene 0.07 Dichloromethane 0.005 Ethylbenzene 0.7 Monochlorobenzene 0.1 o-Dichlorobenzene 0.6 para-Dichlorobenzene 0.075 Styrene 0.1 Tetrachloroethylene 0.005 Toluene 1 trans-1,2-Dichloroethylene 0.1 Trichloroethylene 0.005 Vinyl chloride 0.002 Total xylenes 10

(C) disinfection byproducts : for the periods specified, MCLs are established for the following types of disinfection byproducts:

(i) on or before December 31, 2001, the MCL for total trialomethanes (TTHMs) is 0.10 mg/l, this MCL applies only to a Class A public water system that serves a resident population of 10,000 or more individuals and that adds a disinfectant to the water during any part of the drinking water treatment process;

(ii) for a Class A public water system that uses a surface water source or GWUDISW source, and a Class A public water system that uses a groundwater source only and that adds a disinfectant to the water during any part of the drinking water treatment process, the following MCLs apply for the following listed disinfection byproducts:

Contaminant Maximum Contaminant Level (mg/l) Bromate 0.010 Chlorite 1.0 Haloacetic acids (five) (HAA5) 0.060 Total trihalomethanes (TTHMs) 0.080

(D) other organic contaminants : for listed organic contaminants, the following MCLs apply:

Contaminant Maximum Contaminant Level (mg/l) Benzo[a]pyrene 0.0002 Di(2-ethylhexyl)adipate 0.4 Di(2-ethylhexyl)phthalate 0.006 Hexachlorobenzene 0.001 Hexachlorocyclopentadiene 0.05 Polychlorinated biphenyls (PCBs) 0.0005 2,3,7,8-TCDD (Dioxin) 3 x 10 -8

(3) Turbidity : the MCL for turbidity applies only to a Class A or Class B public water system using a surface water source in whole or in part, as described in 18 AAC 80.610; the MCL for turbidity is:

(A) one NTU, based on a monthly average as required in 18 AAC 80.610, except that the department will allow an MCL of five NTUs or less if the owner or operator demonstrates to the department that the higher turbidity does not

(i) interfere with disinfection;

(ii) prevent maintenance of a detectable residual disinfectant concentration throughout the distribution system; or

(iii) interfere with microbiological determinations; or

(B) five NTUs, based on an average for two consecutive days as required in 18 AAC 80.610;

(4) radionuclides : for radionuclides, the MCLs set out in 40 C.F.R. 141.66, adopted by reference in 18 AAC 80.010(a) , apply;

Contaminant Maximum Contaminant Level Gross alpha radioactivity, including radum-226 but excluding activity from radon and uranium 15 pCi/l Combined radium-226 and 228 5 pCi/l Strontium-90 8 pCi/l Tritium 20,000 pCi/l Gross beta radioactivity 4 mrem

(5) total coliform bacteria : the MCL for total coliform bacteria is based upon the presence or absence of total coliforms in a sample, as follows:

(A) for a system that collects 40 or more routine and repeat samples in a month, if no more than five percent of the samples collected during a month are total coliform positive, the system is in compliance with the MCL for total coliforms;

(B) for a system that collects less than 40 routine and repeat samples in a month, if no more than one sample collected during a month is total coliform positive, the system is in compliance with the MCL for total coliforms; and

(C) a fecal coliform-positive repeat sample, an Escherichia coli -positive repeat sample, a total coliform-positive repeat sample following a fecal coliform-positive routine sample, or a total coliform-positive repeat sample following an Escherichia coli -positive routine sample

(i) constitutes a violation of the MCL for total coliforms; and

(ii) is an acute risk violation of the MCL for total coliforms for the purposes of public notification requirements in 40 C.F.R. 141.201 - 141.210 and Appendices A, B, and C to 40 C.F.R. 141, Subpart Q, adopted by reference in 18 AAC 80.010.

(c) Secondary MCLs . The secondary MCLs for a public water system are as follows:

Contaminant Secondary MCL Aluminum 0.05 to 0.2 mg/l Chloride 250 mg/l Color 15 color units Copper 1.0 mg/l Corrosivity Non-corrosive Fluoride 2.0 mg/l Foaming agents 0.5 mg/l Iron 0.3 mg/l Manganese 0.05 mg/l Odor 3 threshold odor number pH 6.5 minimum - 8.5 maximum Silver 0.1 mg/l Sodium 250 mg/l Sulfate 250 mg/l Total dissolved solids 500 mg/l Zinc 5 mg/l

(d) The department will require a public water system to meet the secondary MCLs if the department determines that public health is threatened or that exceeding a secondary MCL is not in the public interest.

History: Eff. 10/1/99, Register 151; am 9/28/2001, Register 159; am 1/11/2004, Register 169; am 5/2/2004, Register 170; am 1/11/2006, Register 177

Authority: AS 46.03.020

AS 46.03.050

AS 46.03.070

AS 46.03.710

AS 46.03.720