What the Numbers Mean

With the defaults (C₀=100 mg/L, K=1 m/d, gradient 0.01, porosity 0.3, λ=0.001/day), groundwater moves at 0.033 m/d, so a monitoring well 10 m downgradient sees contamination after about 300 days at a concentration near 74.1 mg/L — still well above the 5 mg/L cleanup limit.

The Decay Model

This screening-level estimate uses C = C₀·exp(−λ·x/v) with v = K·i/n. The plume length to a 5 mg/L limit works out to about 100 m here. Real sites need dispersion, transient flow, and site-specific reactive-transport modeling, but this gives a fast first-order check.