Procedures for Detection and Quantitation

Clean Water Act Program Uses Continuum

National Water Quality Criteria
- Based solely on data and scientific judgments on the effect of pollutant concentrations on human health and aquatic life. The Great Lakes Initiative (GLI) developed separate criteria applicable to the Great Lakes States, which included the first ever criteria for protection of wildlife for four chemical classes.
- Can be below D/Q limits
- Foresee no D/Q implications. Need to be as stringent as available science suggests to protect public health and aquatic life (and in the case of the GLI, wildlife).
State Water Quality Standards
- Except for five nondelegated states (and Puerto Rico), states set Water Quality Standards for individual state waterbodies. States may adopt the National Water Quality Criteria, modify it, or adopt standards based on other science.
- Can be below D/Q limits. Except for nutrients, most States base WQS on the National Water Quality Criteria.
- Foresee no D/Q implications. States need flexilbiity to establish State standards to address site-specific issues.
Water Quality Monitoring
- Ambient monitoring is used to assess the existing quality of surface waters to, among other things, determine trends over time, support development of Water Quality Based Effluent Limits (WQBELs), and to assist in decisions on reporting/listing of water bodies under sections 305(b) and 303(d). A single methodology for water quality attainment status is not specificed and likely varies from State to State.
- D/Q implications/issues
  - Can we achieve consistency in use of D/Q for assessment purposes?
  - What happens to water body assessment/status if procedures for D/Q limits change (up or down)?
Stormwater Monitoring
- Under Phase I regulations, industrial sources and large municipalities must perform monitoring. Stormwater permits contain no numerical limits for monitored parameters
  - Industrial sources - some sources must perform monitoring semi-annually (must report), others annually (keep data on site). Under the multi-sector general permit, with some exceptions, industrial sources must monitor and report discharges quarterly during years 2 and 4 of permit coverage.
  - Municipalities - monitoring results are required in the permit application.
- D/Q implications/issues
  - Should there be a consistent data reporting protocol for data that is below the D/Q limits?
National Effluent Limitations for Point Sources
- National effluent limitation guidelines for water discharges are based on data from facilities that have the "best" treatment and control technologies.
- National guidelines are generally set at or above the Quantitation Limit of the method available at the time of promulgation.
- D/Q implications/issues
  - If D/Q procedures change, will this affect already promulgated ELGs?
Permitting of Point Sources (direct and indirect dischargers)
- Point source dischargers (facilities) must have a permit issued by a state, in the case of direct dischargers, or by local government in the case of indirect dischargers (pretreatment). Nondelegated state permits are issued by EPA Regions.
- Permit limits can be a National Effluent Limit (i.e., an effluent limitation guideline or categorical pretreatment standard), a more stringent Water Quality-Based Effluent Limit (WQBEL), or a local pretreatment limit.
- D/Q implications/issues
  - Permits
    - WQBEL can be established below the D/Q limit.
    - How should monitoring data below the D/Q limit be viewed when determining what limits should be placed in the permit?
  - Compliance/Enforcement
    - Reporting of data - what if data is below the D or Q limit? How is it reported?
    - Enforcement - how should the state respond to data that is below the D or Q limit? Enforcement action? More monitoring? Nothing?
  - The Great Lakes WQ Initiative regulation requires that an imposed effluent limitation that is below the quantitation level of the most sensitive test method be accompanied in the permit with a requirement for the permittee to conduct a pollutant minimization program (PMP) that has its goal meeting the WQ based limitation even as effluent monitoring is not able to quantify levels of the pollutant.
Non-EPA Laboratory Measurement
- D/Q implications/issues
  - There is no consistent practice for reporting data below the D/Q limits. This is confusing for labs.
Methods Development/Validation/Promulgation
- Currently EPA establishes D (MDL) and Q (ML) limits through its validation process. These are incorporated in 40 CFR Part 136 through rulemaking.
- D/Q implications/issues
  - If procedures for D/Q change, how will this affect previously promulgated EPA reference methods? ATPs?
  - If procedures for D/Q change, how can we ensure the further development of more sensitive methods?
Other Uses of Detection and Quantitation
- Nonregulatory operational monitoring -- Industry often uses 40 CFR Part 136 methods in internal process optimization studies.
- Regulatory and other studies - EPA may conduct studies to characterize water quality or water pollutant effects. These studies may be used to make regulatory or other policy decisions.

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