020-1 Wyo. Code R. § 1-39

Current through April 27, 2019

Section 1-39 - Water Quality Standards

If background concentrations of a constituent are higher than the protection standards presented in this Section, cleanup shall be completed to the background level. Cleanup shall only be completed for constituents from an eligible storage tank system.

(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:

• (i) Protect 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 141, as referenced in Section 2;
  • (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.

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

(c) Eligible Sources. Groundwater remediation shall address contaminants that originated from an eligible storage tank system. Remediation of constituents that are naturally occurring or are from sources other than an eligible storage tank system shall not be completed, except as incidental and necessary to the remediation of the eligible contaminants.

(d) 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.

(e) Drinking Water Equivalent Levels. If an MCL does not exist and there is no standard for a constituent in either Chapter 1 or 8, Wyoming Water Quality Rules and Regulations, the following procedures shall be used to calculate a state Drinking Water Equivalent Level (DWEL). Calculations shall be based on chronic exposure.

• (i) Non-carcinogenic substances:

  Equation 1:

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• (ii) Carcinogenic substances:

  Equation 2:

  Image Not Available

  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).
  CPFo =	Oral cancer potency factor (mg/kg-day)-1; chemical specific.
  RfDo =	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) shall be obtained from current data in the U.S. Environmental Protection Agency's (EPA) 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 database sources, the administrator shall determine a state DWEL using the latest available toxicological data.

(f) Multiple Standards. When more than one standard exists in Section 39 for any constituent, the most stringent standard shall be used.

020-1 Wyo. Code R. § 1-39

Adopted, Eff. 6/29/2018.