Soil Vapor Extraction Calculator

This calculator sizes a soil vapor extraction (SVE) system for removing volatile organic compounds from the vadose zone (the unsaturated soil above the water table) by applying vacuum to extraction wells. Air-filled porosity — the fraction of soil pore space actually available for airflow — is total porosity times (1 minus volumetric moisture content), since water-saturated pores block air movement. The radius of influence (ROI, how far a single well's vacuum effectively pulls air) is estimated from an empirical curve keyed to the log of soil air permeability, scaled to roughly match published EPA guidance ranges (about 2m for silt-like low-permeability soils up to 25-30m for coarse gravel).

Well spacing is set at 1.2× the ROI to ensure slight overlap between adjacent wells' capture zones, and the number of wells needed is the ceiling of treatment length and width each divided by that spacing, multiplied together for full-area coverage. Required total airflow targets one full exchange of the air-filled pore volume per day, a common rule-of-thumb minimum for effective vapor-phase removal, then converts that into blower horsepower using applied vacuum, a 60% blower efficiency assumption, and standard air-power relationships. The estimated daily VOC mass removal rate is the least site-specific number here: it assumes a fixed 50 mg/m³ vapor concentration regardless of what your actual contaminant is or its concentration, so treat that figure as an illustrative starting point rather than a site-calibrated removal-rate forecast — real removal rates should be based on soil-gas monitoring data once the system is operating.