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Infiltration Feasibility

In the live source corpus, infiltration feasibility is not a single rule citation. It is the combined design determination produced by the soil-testing, recharge, and hydraulic-impact framework across BMP Manual Chapters 12 and 13 together with N.J.A.C. 7:8.

Structured citation evidence for this page lives in the sibling claim manifest.

Concept Explanation

The source-backed feasibility question is whether stormwater can be infiltrated into subsoil at the proposed location without violating the technical limits in the live source set.

That requires more than one check:

  • soil and permeability testing under Chapter 12
  • SHWT determination under Chapter 12
  • hydraulic-impact review where stormwater infiltrates into subsoil
  • recharge prohibitions such as high pollutant loading

What Counts as an Infiltration BMP

BMP Manual Chapter 12 explicitly distinguishes infiltration BMPs from non-infiltration BMPs. In the live source set, the infiltration category includes examples such as:

  • bioretention without an underdrain
  • dry wells
  • infiltration basins
  • pervious paving without an underdrain
  • GI MTDs that infiltrate runoff into subsoil

That distinction matters because those BMPs trigger the soil-testing and hydraulic-impact workflow in a way that non-infiltration systems do not.

Chapter 12 also makes the testing consequence explicit: infiltration BMPs are required to test saturated soil hydraulic conductivity and identify the depth to the SHWT at the proposed BMP location. Certain non-infiltration BMPs may still need SHWT information, but they do not enter the same infiltration-feasibility lane.

Source-Backed Feasibility Screen

The authored page should treat feasibility as a combined screen:

  1. confirm soil and permeability conditions with Chapter 12 testing
  2. confirm SHWT conditions with Chapter 12 methods
  3. check whether the recharge rule prohibits infiltration for the stormwater source area
  4. if infiltration is proposed, evaluate hydraulic impact on the groundwater table

Engineering Interpretation

In practice, the live source set supports three broad outcomes:

  • infiltration is supportable
  • infiltration is only partly supportable and the design must change
  • infiltration is not supportable at that location or for that runoff source

That is a safer and more source-backed framing than older shorthand decision trees built around unsupported numeric shortcuts.

When retention by infiltration is technically impracticable

BMP Manual Chapter 14 gives a more concrete 2026 screen for cases where infiltration-based retention cannot carry the full load. The examples in the live source set include subsoil with a tested saturated hydraulic conductivity rate below 1 inch per hour, a site with a very high SHWT that cannot maintain the required separation, and runoff sources that are barred from infiltration by N.J.A.C. 7:8-5.4(b)3 or exposed industrial material.

When that happens, the site does not automatically leave the compliance framework. Chapter 14 explains that the volumetric-reduction standard can instead be met with BMPs that attenuate the post-construction WQDS peak flow rate and extend runoff hydrograph duration to match an undisturbed wooded area on HSG D soil. The examples listed in the live source set include grass swales, underdrained bioretention systems, underdrained pervious paving systems, underdrained sand filters, vegetative filter strips, and standard constructed wetlands.

Cross References