In-Situ Treatment Calculator

This calculator sizes an in-situ chemical treatment system — ISCO (oxidation, using reagents like permanganate or persulfate) or ISCR (reduction, using zero-valent iron or dithionite) — for a defined subsurface treatment zone. It starts from the treatment zone's length, width, and depth to get a total volume, then multiplies by effective porosity to isolate the pore volume, the actual groundwater that carries and reacts with the reagent. Contaminant mass is derived from that pore volume and the measured dissolved concentration, then scaled up by two factors: the stoichiometric ratio (kg of reagent needed per kg of contaminant, which varies by chemistry — persulfate typically needs roughly twice what permanganate does for the same target compound) and the natural oxidant demand (NOD) multiplier, which accounts for the reagent also being consumed by background soil organic matter and reduced minerals rather than just the contaminant itself. Well count and spacing come from the radius of influence (ROI): wells are placed on a grid spaced at ROI times the square root of two so that circular delivery zones overlap along the diagonal, guaranteeing full coverage with no untreated gaps between wells.

The reagent total is then divided evenly across wells and converted to an injection volume assuming a 3% solution by mass, a reasonable field mixing concentration for most oxidants. The biggest source of estimation error is the NOD multiplier — real soils with high organic content or reactive iron minerals can consume far more reagent than the contaminant alone would suggest, so treat the default of 5x as a starting point that should be refined with a site-specific NOD bench test. The reported cost covers reagent material only, not wells, mobilization, or labor.