{
  "$schema": "https://json-schema.org/draft/2020-12/schema",
  "name": "PondLock sodium bentonite application rates by soil type",
  "description": "Minimum sodium bentonite application rates per 6-inch compacted lift for pond, lake, and dam sealing, based on USDA NRCS Conservation Practice Standard 520 guidance. Rates must be multiplied where total liner thickness exceeds 6 inches.",
  "url": "https://pond-lock.com/engineering-resources#application-rates",
  "standard": "USDA NRCS Conservation Practice Standard 520 — Pond Sealing or Lining (Compacted Soil Treatment)",
  "lift_thickness_in": 6,
  "lift_thickness_note": "NRCS CPS 520 limits compacted lift thickness to a maximum of 6 inches.",
  "rate_unit": "lb/ft2 per 6-inch compacted lift",
  "publisher": "Natural Waterscapes",
  "last_updated": "2026-09-05",
  "license": "https://pond-lock.com/",
  "rates": [
    {
      "soil_classification": "Silts and clayey silts",
      "rate_min": 2,
      "rate_max": 3,
      "notes": "Lowest rate — native soil provides some sealing"
    },
    {
      "soil_classification": "Silty sands",
      "rate_min": 3,
      "rate_max": 5,
      "notes": "Moderate permeability — common in many pond sites"
    },
    {
      "soil_classification": "Clean sands and gravelly soils",
      "rate_min": 5,
      "rate_max": 6,
      "rate_max_open_ended": true,
      "notes": "Highest rate — large pore structure requires more bentonite"
    }
  ],
  "design_constraints": {
    "max_interior_side_slope": "3H:1V",
    "min_compaction": "95% Standard Proctor density",
    "max_loose_lift_thickness_in": 6,
    "confinement_required": true,
    "confinement_note": "Bentonite achieves low permeability only when fully confined. Loss of confinement is the most common cause of liner failure and is not a material defect."
  }
}