Water Quality Issues To Consider

Water Quality Standards and Effluent Limits

Water Quality Standards (WQS) are the benchmarks set by each state to maintain water quality under the Clean Water Act. In Oregon, the DEQ sets water quality standards in two steps. First, the DEQ determines the existing or potential uses for each water body. Designated uses are determined by basin and are available on the DEQ website in the Oregon Designated Uses Table. Uses may include recreation, fishing, aquatic life, public water supply, and irrigation. Then, the agency sets criteria necessary to maintain those uses by identifying the minimum chemical, physical or biological characteristics allowable. Criteria can be numeric or narrative. Oregon’s water quality standards are also on the DEQ website and are codified in the Oregon Administrative Rules.

A permit will establish effluent limits based on water quality standards to ensure that pollutants discharged will not impair designated uses. Effluent limits are set if the agency determined through a Reasonable Potential Analysis (RPA) that the discharge is likely to violate state standards and that industry-wide technology-based limits are insufficient to protect water quality.

WQS and Effluent Limits Questions:

• What are the existing uses of the receiving waterbody?
• Will the proposed permit harm existing uses?
• Will the permit violate water quality criteria?
• Did the DEQ perform a reasonable potential analysis for relevant pollutants?
• What are the specific pollutants and how do they affect existing uses?

Technology-Based Limits

Federally based technology standards are set as numeric criteria specific for each type of industry (ie: pulp and paper mills, sewage treatment plants, etc.). These limits require a minimum level of treatment of pollutants for discharges based on available technologies. It is when these standards are not sufficiently protecting water quality, that a permit must set effluent limits according to water quality standards. Water quality standards serve as a sort of backstop for technology-based limits.

For municipal facilities (publicly owned treatment works or POTWs), technology-based effluent limits are derived from National Secondary Treatment Standards. Also, Chapter 5 of the U.S. EPA NPDES Permit Writer's Manual provides an overview of the process for establishing technology-based effluent limits.

Technology-Based Questions:

• Is the facility using the Best Available Technology?
• What type of new technologies are available?
• How long has it been since this facility upgraded?
• Has there been growth in the population of the community such that the facility requires upgrading?

Mixing Zones

Although it is mentioned nowhere in the Clean Water Act, federal regulations allow states to include mixing zones in their water quality standards. (40 CFR 131.13). Mixing zones are the areas immediately surrounding a discharge, like at the end of the pipe. Dischargers are allowed to violate water quality standards in this area while the discharge is “mixing” with the water in the receiving waterbody. The area directly surrounding the pipe is the “zone of initial dilution (ZID)” where toxicity is highest. The defined area surrounding the ZID is defined as the “mixing zone.”

Mixing zones are addressed in the Oregon Water Quality Standards in the Oregon Administrative Rules (340-041-0053 – see WQS above). Among other important requirements, WQS require mixing zones to be clearly defined in the proposed permit and to:

(A) Be as small as feasible;

(B) Avoid overlap with any other mixing zones to the extent possible and be less than the total stream width as necessary to allow passage of fish and other aquatic organisms;

(C) Minimize adverse effects on the indigenous biological community, especially when species are present that warrant special protection for their economic importance, tribal significance, ecological uniqueness, or other similar reasons determined by the Department and does not block the free passage of aquatic life;

(D) Not threaten public health;

(E) Minimize adverse effects on other designated beneficial uses outside the mixing zone.

OAR 340-041-0053.

Mixing Zones Questions:

• Is the mixing zone as small as possible?
• Has the size or shape of the mixing zone changed since a previous permit?
• Are there existing uses affected by the mixing zone?
• What kind of toxicity is being discharged?

Antidegradation Policy

DEQ has an anti-degradation policy to keep waters clean and to ensure that water quality is maintained at the highest possible level. It falls under water quality standards and requires the DEQ to determine whether a proposed permit will impair existing uses or degrade water quality when the water quality is already higher than the minimum quality required. There are three tiers of waters protected under the anti-degradation policy:

Tier 1 Waters – Protect all existing uses.

Existing uses include actual uses of the waterbody and any potential uses that the current level of water quality would support, even though it might not be used for something presently. (ie: it could be used for swimming, but no one uses it for that now). In tier 1 waters, existing uses must be protected if they have been present or in existence at any time since November 28, 1975.

Tier 2 Waters – Maintain and protect “high quality” waters.

Tier 2 waters have higher water quality than the pollutant-by-pollutant criteria set to protect designated uses. Waters may be “high quality” tier 2 waters for some criteria, while violating WQS for other pollutants, thereby requiring a TMDL for that pollutant. (ie: a water may be “high quality” for turbidity, but require a TMDL for temperature). DEQ must evaluate alternatives to adding or increasing a discharge in tier 2 waters. The costs (ecological and social) must be clearly outweighed by the benefits (such as socio-econmic) of such discharge. Tier 2 waters are never allowed to go lower than tier 1 requirements – existing uses must always be protected.

Tier 3 Waters – Protect Outstanding National Resource Waters.

This is the most protective category. Unfortunately, Oregon has yet to designate any waters as “Outstanding National Resource Waters.” Waters can earn this designation because of recreational or ecological significance. New direct discharges are usually prohibited and management focuses on protecting the highest level of water quality.

Antidegradation Questions:

• Has the DEQ done an anti-degradation review of existing uses?
• Are there potential uses to consider?
• Did the DEQ adequately evaluate the social and economic costs of the proposed discharge?

Already Degraded Waters - TMDLs

Oregon is required, under the Clean Water Act, to identify waterbodies that are threatened or that don’t meet basic water quality standards. These rivers, streams, lakes and bays are listed on the state’s “303(d) list” as water quality limited for the specific parameters that exceed state standards. (ie: temperature, turbidity, bacteria, etc.). You can find your local waterbodies on the DEQ’s water quality assessment database to determine if they are water quality limited.

The 303(d) list also includes the prioritization and plan for bringing each waterbody back into compliance with water quality standards. States set a Total Maximum Daily Load (TMDL) for each waterbody for each pollutant that currently exceeds standards. Every permit that includes a discharge into a 303(d) water quality limited water is required to adhere to the TMDL, considering that the TMDL is the overall limit that applies to all the dischargers in the area. Essentially, each discharger gets “a share” of the total discharge allowed under the TMDL for each specific pollutant/parameter.

Check out DEQ’s TMDL Program for more information.

TMDL Questions:

• Is the receiving water listed on Oregon’s 303(d) list? For what pollutants?
• Does the permit include the TMDL?
• Is the TMDL consistent with water quality standards?
• Was the TMDL in the permit calculated properly?
• Does the permit adequately consider other dischargers in the area?