Small-Scale Infiltration Basins¶
Small-scale infiltration basins are governed by BMP Manual Chapter 9.8 in the live source corpus. This page now stays with the source-backed center of gravity: a surface BMP that stores runoff temporarily and infiltrates it into the native subsoil when the site evidence supports that use.
Structured citation evidence for this page lives in the sibling claim manifest.
Overview¶
In the enrolled source set, a small-scale infiltration basin is a surface storage BMP that relies on infiltration into the underlying subsoil rather than on an underdrain or media-only treatment train. That makes the chapter highly dependent on the site-investigation record and on hydraulic-impact review.
Source Mapping¶
The live citations layer resolves this route directly to the following canonical source bundles.
- Route type:
canonical - 2023 source bundle: Chapter 9.8 (
2023_BMP_9_8) - Small-Scale Infiltration Basins - 2026 source bundle: Chapter 9.8 (
2026_BMP_9_8) - Small-Scale Infiltration Basins
Key verified claims already tied to this page manifest: - Chapter 9.8 uses the infiltration-basin chapter for surface storage with infiltration into native subsoil. - Infiltration basins keep the 0.5 in/hr design permeability and 2-foot SHWT separation rules. - Infiltration-basin design permeability still follows the Chapter 12 credited design-rate framework. - Infiltration-basin viability remains tied to Chapter 12, Chapter 13, and protection of the infiltration surface.
Design Criteria¶
The reconciled design criteria below come from the live crosswalk and page-level claim set, not from the older narrative snapshot.
| Parameter | 2023 source value | 2026 source value | Change |
|---|---|---|---|
| Minimum Ksat | 0.5 in/hr design rate (minimum tested rate: 1.0 in/hr) | 0.5 in/hr design rate | unknown |
| SHWT separation | 2 ft - measured from static SHWT | 2 ft - measured from static SHWT | unchanged |
| K_design calculation | K_design = K_field / 2.0 (factor of safety = 2.0) | K_design = K_field / 2.0 (factor of safety = 2.0) | unchanged |
Source-backed criteria that still control this route: - Chapter 9.8 uses the infiltration-basin chapter for surface storage with infiltration into native subsoil. - Infiltration basins keep the 0.5 in/hr design permeability and 2-foot SHWT separation rules. - Infiltration-basin design permeability still follows the Chapter 12 credited design-rate framework. - Infiltration-basin viability remains tied to Chapter 12, Chapter 13, and protection of the infiltration surface.
Siting Constraints¶
The live source set keeps the siting review focused on:
- whether the site investigation supports infiltration into native subsoil
- whether SHWT separation is adequate at the actual basin-bottom elevation
- whether Chapter 13 hydraulic-impact review is needed
- whether pretreatment and construction protection are strong enough to keep the basin floor functional
If those conditions are weak, the basin may no longer be the right BMP for the site.
Maintenance¶
Maintenance is centered on preserving the infiltration surface:
- keep pretreatment features functioning so fine sediment does not seal the basin floor
- inspect ponding and drawdown behavior after storm events
- repair erosion and remove accumulated sediment before it migrates into the infiltration surface
- avoid treating compaction or sediment sealing as minor cosmetic issues
Related Pages¶
- Groundwater Recharge Rules
- Soil Permeability Testing
- Seasonal High Water Table
- Groundwater Mounding
- BMP Selection
Source Bundles¶
Use these source bundles when checking the live extracted text or paired OCR evidence:
- 2023 bundle: Chapter 9.8 (
2023_BMP_9_8) - Small-Scale Infiltration Basins - 2026 bundle: Chapter 9.8 (
2026_BMP_9_8) - Small-Scale Infiltration Basins