Antidegradation One

The antidegradation policy is the third major required component of state water quality standards. Designated uses and water quality criteria provide minimum goals for a water body. The antidegradation policy provides both a framework for protecting water quality once goals are reached and a system for protecting the good quality of water bodies that have always met or exceeded their standards.

Federal antidegradation policy requirements

The federal policy provides an approach to water quality protection based on three key principles called tiers. See the graphic to the right.

Each state must develop and adopt an antidegradation policy that is consistent with the federal policy. It can be identical to the federal policy, or it can be more specific and more protective. It must not be any less specific or protective.

Each state must also develop a system for implementing its antidegradation policy (40CFR131.12(a)). This system should ensure that the state’s major programs, permits, decisions and day-to-day activities affecting water quality and aquatic ecosystem health will be consistent with its antidegradation policy.

Antidegradation review

According to the EPA, antidegradation implementation should be “based on a set of procedures to be followed when evaluating activities that may impact the quality of the waters of the United States” (Water Quality Standards Handbook, Chapter 4). For simplicity, the steps below focus only on proposed new or increased NPDES permitted discharges, even though the antidegradation policy applies more broadly.

It is easiest to review a permit or activity by following the three tiers of antidegradation in this order: protect outstanding waters, minimize impacts to high water quality and protect existing uses.

• Protect outstanding waters (Tier 3)
  The state should first determine whether the waters are outstanding (Tier 3). If so, then no new or increased discharges to outstanding waters or their tributaries should be allowed.

• Minimize impacts to high water quality (Tier 2)
  If the water body is not outstanding, yet it has higher water quality than what is required by water quality standards, any proposed activity that might degrade water quality must undergo an evaluation of alternatives to determine whether the activity is “necessary to accommodate important economic or social development” (40CFR131.12(a)(2)).

• Protect existing uses (Tier 1)
  If the receiving water is neither outstanding nor “high quality,” then it must be determined whether the proposed activity will cause harm to existing uses or to the water quality they require. Tier 1 requires that a proposed activity be disallowed if any existing uses will be harmed.

Many states have a "Tier 2.5"

Many states, concerned about the economic or political impact of designating ONRWs, have developed a so-called Tier 2.5 designation. It may be described as an Outstanding Resource Water or Outstanding State Water (e.g., Outstanding Florida Water) in the regulations. These hybrid designations come in many shapes and sizes, generally with the purpose of avoiding an outright prohibition of new or increased discharges, dredging, fills or impacts. In a state that is unwilling to designate ONRWs, this option can provide more specific and greater protection than Tier 2. On the other hand, the Tier 2.5 designation can deprive a water body of the Tier 3 protection it needs and deserves. If your state has a Tier 2.5 classification you should examine the criteria for it very carefully. In some states, Tier 2.5 designation offers less protection than a proper Tier 2.