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Engineering Constraints

Constraints Module

Engineering constraints are site-specific factors that determine which BMPs are feasible at a given location. They act as filters in the engineering reasoning chain:

Regulation -> BMP Strategy -> [Site Constraints] -> Design Workflow
Reference: [Agents/13_engineering_reasoning_layer.md](https://github.com/InfusedChooch/Opal_Rev1/blob/main/Agents/13_engineering_reasoning_layer.md)

Constraint Topics

Constraint Type Effect on BMP Selection
Soil Permeability Testing Infiltration capacity HSG C/D requires underdrain or limits infiltration BMPs
Groundwater Mounding Subsurface hydraulics Large infiltration volumes may raise water table unacceptably
Seasonal High Water Table Groundwater depth SHWT < 2 ft limits infiltration; affects media depth
Drainage Area Limits Contributing area Determines small-scale vs large-scale BMP applicability
Infiltration Feasibility Combined assessment Integrates soil, SHWT, mounding, and site conditions

Additional Site Factors

Factor Where Addressed
Karst geology Infiltration Feasibility
Contaminated soils Infiltration Feasibility
Slopes and topography Drainage Area Limits
Setbacks (buildings, utilities) Drainage Area Limits
Pollutant loading Soil Permeability Testing

How Constraints Filter BMP Selection

  1. Identify site constraints from soil report, survey, and site visit.
  2. Apply to BMP candidates from the BMP Library.
  3. Eliminate infeasible BMPs.
  4. Advance feasible BMPs into Design Workflow.

See Decision Trees for structured constraint-based BMP selection logic.

Source Alignment (Auto-Synced Draft)

Auto-synced from Outs/Phase3_Master2026_Content.md -> "4.1 The Chapter 12-13-14 Design Workflow" on 2026-03-05. Manual review required before release.

The 2026 manual's structural improvement is the explicit creation of a three-chapter subsurface and volumetric design sequence:

  1. Chapter 12 (Soil Testing): Answer the feasibility question — can this site infiltrate? At what rate? What is the verified SHWT?
  2. Chapter 13 (Groundwater Mounding): Answer the safety question — will operating the proposed BMP at design capacity cause the water table to rise and compromise the 2-foot SHWT buffer?
  3. Chapter 14 (Volumetric Reduction): Answer the compliance question — do the proposed GI BMPs collectively reduce enough volume to meet the regulatory WQV requirement?

The 2023 manual addressed Chapters 12 and 13 but had no Chapter 14 — meaning the volumetric reduction compliance accounting was left to the designer to assemble from disparate guidance sources. The 2026 structure eliminates this ambiguity and creates a checkable sequence for both applicants and reviewers.