Seasonal High Water Table¶
The Seasonal High Water Table is one of the core site constraints in the live source corpus. The current evidence layer grounds SHWT work in BMP Manual Chapter 12, with related design consequences across the infiltration BMP chapters and the groundwater-mounding framework.
Structured citation evidence for this page lives in the sibling claim manifest.
Concept Explanation¶
SHWT is the controlling seasonal groundwater elevation used in infiltration-BMP design review. In the live source set, the important point is not a generic glossary definition. It is how the design team establishes the SHWT and then measures available separation to the proposed infiltration practice.
How the Live Source Set Determines SHWT¶
BMP Manual Chapter 12 provides the key rules:
- where redoximorphic features are observed, the SHWT is taken as the highest level at which the mottling is observed, unless a higher observed water table controls
- where redoximorphic features are not observed, SHWT is determined by the direct-observation methods allowed in the chapter
That is why the evidence chain for SHWT depends on real field work and logging, not just a planning-level desktop assumption.
Design Significance¶
The live citations layer also preserves the source-backed 2 foot separation standard used for infiltration practice review. In authored guidance, that means SHWT should be treated as one of the first go/no-go checks for infiltration-based designs and one of the key inputs to groundwater-mounding review.
Engineering Interpretation¶
For authored content, the safest summary is:
- establish SHWT using the Chapter 12 methods
- compare that elevation to the proposed infiltration-practice bottom
- carry the result into the recharge and hydraulic-impact workflow
That avoids the older habit of turning SHWT into a page full of unsupported universal thresholds by BMP type.