§ 118.10 - Worst case discharge.

§ 118.10 Worst case discharge.

Non-transportation-related onshore facility owners or operators are required to model a worst case discharge scenario, determine appropriate endpoints using Appendix B as per § 118.3(c)(1) and (3) from a discharge into or on the navigable waters or a conveyance to navigable waters, calculate the distances to endpoints and CWA hazardous substance planning distances, and compare the distances to endpoints against the CWA hazardous substance planning distances from the non-transportation-related onshore facility. If the CWA hazardous substance planning distances determined are shorter than the distances to endpoints as per Appendix B, the worst case discharge can cause substantial harm. Owners or operators shall also use their worst case discharge scenario(s) to determine if the non-transportation-related onshore facility has the ability to adversely impact public water systems per § 118.3(c)(2) from a discharge into or on the navigable waters or a conveyance to navigable waters. The worst case discharge scenarios must represent each CWA hazardous substance onsite that meets or exceeds the threshold quantity set in § 118.3(a). Each scenario must use the largest quantity following the below parameters:

(a) Determination of worst case discharge quantity. The worst case discharge quantity shall be the greater of the following:

(1) For CWA hazardous substances in separate containers, the maximum quantity of a single container, such as a bulk storage tank, process vessel, rail car, or mobile or portable container;

(2) For CWA hazardous substances in interconnected containers, the maximum quantity of a group of interconnected containers; or

(3) For substances in pipes, the maximum quantity of a pipe or interconnected pipes, and the owner or operator must provide evidence in Appendix A that containers with common piping or piping systems are not operated as one unit.

(4) For mixtures of CWA hazardous substances, follow the procedures in § 118.9.

(b) Planning distance determinations. To determine the distance to endpoints for fish, wildlife, and sensitive environments, public water systems, and public receptors as referenced in § 118.3(c), an owner or operator shall use a methodology, model, or other technique that accounts for facility-specific conditions and accounts for the stated requirements in this paragraph. An owner or operator may use proprietary models, provided that the owner or operator allows EPA access to the model, submits documentation that demonstrates the reliability and analytical soundness of the methodology used, and describes the model's features to local emergency planners, upon request. Any models used for planning distance determinations shall be used in exercises conducted per § 118.13.

(1) Endpoints for fish, wildlife, and sensitive environments are provided in Appendix B of this part.

(2) Endpoints for public receptors are provided in Appendix B of this part.

(3) In determining CWA hazardous substance planning distance endpoints, owners or operators shall consider the following parameters:

(i) Factors affecting overland transport including:

(A) Nearest opportunity for discharge into or on the navigable waters;

(B) Ground conditions which may include topography of the surrounding area, drainage patterns, land use coverage, impervious cover, soil distribution or porosity, and soil absorption rate or soil saturation during adverse weather conditions; and

(C) Properties of the CWA hazardous substance, which may include evaporation rate based on wind speed; atmospheric stability, ambient temperature, pressure, and humidity; reactivity with rainwater and/or other substances along the overland flow path into or on the navigable water; and ignitability and explosive potential;

(ii) Factors affecting in-water transport including:

(A) Point of entry to navigable waters;

(B) Flow rate and duration of the discharge;

(C) Direction of the discharge at the point of entry;

(D) Surface versus underwater entry; and

(E) Conditions of the receiving water including the velocity of the navigable waters which may be affected by: Slope of the river; hydraulic radius; turbulence and potential for cross-channel mixing; Manning's Roughness coefficient; differentiation of still, tidal or moving waters; currents; wave height; tidal influence; and water temperature, pH, alkalinity, and salinity.

(iii) Adverse weather conditions, which shall be calculated based on adverse winds, currents, and/or river stages, over a range of seasons, weather conditions, and river stages.

(iv) Properties of the CWA hazardous substance such as solubility in water, speciation in water, density (relative to water), polarity, vapor pressure, reactivity with water and common solutes in natural waterbodies, human toxicity, mammalian toxicity, aquatic toxicity, and flammability.