Sec. 861.6A. Application of criteria for toxic pollutants

(a) Delaware River estuary.

(1) In establishing wasteload allocations and other effluent requirements, exceedances of stream quality objectives for the protection of aquatic life from acute effects may be permitted in small areas near outfall structures, provided that all of the following requirements are met.

(i) As a guideline, the dimensions of the area where objectives are exceeded should be limited to the more stringent of the following restrictions:

(a) a distance of 50 times the discharge length scale in any direction from the outfall structure; or

(b) a distance of five times the local water depth in any direction from the outfall structure.

(ii) Stream quality objectives shall not be exceeded in areas designated as critical habitat for fish and benthic organisms.

(iii) Stream quality objectives shall not be exceeded where effluent flows over exposed benthic habitat prior to mixing with the receiving waters.

(iv) A zone of passage for free-swimming and drifting organisms equal to 50 percent of the surface width of the river at the location of the discharge shall be provided.

(v) The total surface area of the Delaware River estuary where stream quality objectives for the protection of aquatic life from acute effects are exceeded shall be limited to:

(a) five percent of the total surface area of zones 2, 3 and 4; and

(b) five percent of the total surface area of zone 5.

(vi) Upon the request of one or more dischargers, the executive director may consider requests for alternatives to the requirements of subparagraphs (i)-(v) of this paragraph. Such requests shall provide a demonstration that the alternative requirement requested will not adversely impact free-swimming, drifting and benthic organisms. The demonstration(s) shall provide a sound rationale, and be supported by substantial scientific data and analysis. The methodology and form of the demonstration shall be approved by the executive director. The executive director may reject any requests which are not substantive. The commission may establish alternative areas where acute stream quality objectives may be exceeded based upon the evaluation of submitted demonstrations.

(vii) The executive director may consider requests to conduct studies to confirm the mixing characteristics and the predicted dilution isopleths of a discharge. Such requests shall provide a demonstration based upon sound scientific and technical rationale, and be supported by substantial data and analysis. The methodology and form of the demonstration shall be approved by the executive director. The executive director may reject any requests which are not substantive. The commission may establish alternative dilution factors based upon the evaluation of submitted demonstrations.

(2) For those stream quality objectives whose numerical value is related to hardness, a median hardness value of 74 mg/l as CaCO₃ shall be used to represent the hardness of the receiving water for the purposes of determining the numerical value of those objectives. This median hardness value shall be used to establish the aquatic life objective for protection from chronic effects; and in conjunction with the site-specific median hardness value of the effluent and the dilution factor, the aquatic life objective for protection from acute effects.

(3) For those stream quality objectives whose numerical value is related to pH, a median pH value of 7.1 shall be used to represent the pH of the receiving water for the purposes of determining the numerical value of those objectives. This median pH value shall be used to establish the aquatic life objective for protection from chronic effects; and in conjunction with the site-specific median pH value of the effluent and the dilution factor, the aquatic life objective for protection from acute effects.

(4) Assumptions for estuarine mixing. Complete vertical and lateral mixing shall be assumed in the estuary in applying chronic aquatic life and human health stream quality objectives under design conditions. Site-specific data which does not support this assumption will be considered by the executive director in establishing allocations to discharges.

(5) Deriving total recoverable wasteload allocations for metals. Wasteload allocations developed from the dissolved stream quality objectives for seven cationic metals shall be converted into total recoverable wasteload allocations using a translator. The translator shall be determined using procedures specified by the commission. In the absence of data to develop a translator for any of the metals, the reciprocal of the conversion factor established under section 860.3(c)(2) of this Title shall be used for the translator.

(b) Definitions.

(1) Critical habitat.

Specific areas within the tidal Delaware River which are or could be occupied by a species absent the toxic effect of pollutants; and which have those physical, chemical and biological features which are essential to the conservation and maintenance of the Delaware estuary population. The commission shall identify and determine critical habitat within the tidal Delaware River. Such determination shall consider the spatial and temporal requirements of the species including critical life stages. Determinations shall be governed by the commission's rules of practice and procedure relating to review, hearing and decisions of objections thereto.

(2) Discharge length scale.

The square root of the cross-sectional area of any discharge outlet.