API Publ 4664 is a technical reference for Mixing Zone Modeling and Dilution Analysis for Water-Quality-Based NPDES Permit Limits, issued in 1998 as a 150-page API document. It is aimed at professionals who need a structured basis for understanding how mixing zone behavior and dilution analysis relate to water-quality-based permit limits. For buyers evaluating relevance, the document is useful where environmental compliance, technical review, and permit support intersect with operational planning and engineering judgment. API Publ 4664 is a practical reference for teams that must align site activities with wastewater permitting considerations.

Purpose of API Publ 4664

The purpose of API Publ 4664 is to provide technical background and reference material on mixing zone modeling and dilution analysis in the context of NPDES permit limits tied to water quality. As an API document, it serves as a recognized industry reference rather than a field manual, helping users frame permit-related evaluations with a consistent technical basis. It is most relevant when organizations need to support engineering review, environmental compliance assessment, or documentation tied to discharge limits and water-quality considerations. The document helps establish a common technical language for permit-related analysis.

Common use cases of API Publ 4664

API Publ 4664 is commonly used by environmental, engineering, operations, and compliance personnel involved in wastewater permitting and discharge analysis. It can support internal technical review when facilities need to understand dilution behavior, mixing-zone assumptions, or the basis for water-quality-based limits under NPDES requirements. Procurement and project teams may also reference it when evaluating compliance-related documentation or consultant deliverables. For companies with process facilities, terminals, or other regulated sites, the document can help align permit support work with consistent technical expectations.

Why API Publ 4664 matters

API Publ 4664 matters because permit-related decisions often depend on clear technical support, especially when discharge conditions and receiving-water impacts must be evaluated carefully. Having this document on hand can improve consistency across engineering review, environmental documentation, and compliance planning. It may also help reduce uncertainty during permit preparation, third-party review, or internal quality checks by giving teams a shared reference for mixing zone and dilution concepts. For organizations managing regulated water discharges, API Publ 4664 supports more defensible technical work and better coordination between responsible functions.

• Mixing zone modeling reference
• Dilution analysis support
• Water-quality-based permit context
• NPDES compliance documentation
• Environmental and engineering review
• Internal technical consistency