020-17 Wyo. Code R. § 17-39

Current through April 27, 2019

Section 17-39 - Water Quality Standards

(a) Surface Water. Storage tank program remediation actions shall protect surface water quality to the standards contained in Chapter 1, Wyoming Water Quality Rules and Regulations, Quality Standards for Wyoming Surface Waters.

(b) Groundwater. Storage tank program remediation actions shall protect:

• (i) All Class I, II, III, IV(a), IV(b) or Special A groundwater quality to the most stringent of the:
  • (A) federal primary MCL contained in 40 CFR 136 as of the date of this chapter,
  • (B) water quality standards contained in this section when there is no federal MCL for a substance; or
  • (C) groundwater quality standards found in Chapter 8, Wyoming Water Quality Rules and Regulations, Quality Standards for Wyoming Groundwaters.
  • (D) cleanup of groundwater which is Class I groundwater by use, shall address contaminants in the groundwater which originated from the storage tanks system. Cleanup of parameters which are naturally occurring, or are from sources other than the storage tank system, which do not meet the standards for Class I groundwater shall not be accomplished.

• (ii) All class VI groundwater to the groundwater quality standards found in Chapter 8, Wyoming Water Quality Rules and Regulations, "Quality Standards for Wyoming Groundwaters."

(c) Free Product. Whenever any free phase liquid layer of a regulated substance is encountered in groundwater or floating on the groundwater surface with a thickness in excess of 0.05 inches, restoration shall begin as soon as possible to remove the regulated substance(s) and prevent contaminant migration into previously uncontaminated areas.

(d) Drinking Water Equivalent Levels. For those chemical substances where a MCL does not exist and where there is no standard in either Chapter 1 or 8, Wyoming Water Quality Rules and Regulations, the following procedures will be used to calculate a state Drinking Water Equivalent Level (DWEL). Because storage tank remediation actions may require several years to complete and since groundwater quality in Wyoming shall be protected as a potential drinking water source(s), these calculations will be based on chronic exposure.

• (i) Non-carcinogenic substances:

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• (ii) Carcinogenic substances:

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  where;

  DWEL = Drinking water equivalent level, mg/L.

  RISK = Cancer risk for drinking water, (1 x 10^-6).

  ABW = Average adult body weight over exposure period

  (70 kg).

  CPF_o = Oral cancer potency factor (mg/kg-day)^-1; chemical specific.

  RfD_o = Oral reference dose (mg/kg-day); chemical specific.

  DWI = Adult drinking water intake, 2 L/day.

  AB = Gastrointestinal absorption rate (1.0).

  LIFE = Lifetime (70 years).

  DUR = Duration of exposure (30 years).

  FOE = Frequency of exposure, (350 days/365 days = 0.96).

  HQ = Hazard quotient (1).

  Values for oral toxicological reference doses (RfD_o) and/or cancer potency factors (CPF_o) will be obtained from current data in the U.S. Environmental Protection Agency's Integrated Risk Information System (IRIS), the EPA Health Effects Assessment Summary Tables (HEAST) toxicity data sources, or the EPA Region IX Preliminary Remediation Goals Data Base. If an oral reference dose or cancer potency factor is not listed in the above data base sources, the administrator will determine a state DWEL using the latest available toxicological data.

(e) When more than one standard exists in the above sections for any parameter, the most stringent standard shall be used.

020-17 Wyo. Code R. § 17-39