Issue Date: July 2023

Calculating the effective solubility of dissolved phase contaminants is an important step in evaluating and risk assessing groundwater concentrations on sites with NAPL sources. The aim of the Effective Solubility Tool and accompanying documents is to provide a peer reviewed spreadsheet tool and guidance on how to calculate and assess dissolved phase effective solubility limits for a range of hydrocarbon contaminants where these derive from NAPL sources.
The tool has been produced based on equations published in a variety of recognised technical guidance (e.g. CL:AIRE 2014, LNAPL handbook) and features:

  • a description of the methodologies and parameters used in the calculations;
  • a NAPL molecular weight calculator;
  • an Effective Solubility calculator based on ”TPHCWG” carbon banding;
  • an Effective Solubility calculator using the “Top 20” compounds present in a mixed NAPL;
  • an example library of published fuel compositions and real composition analysis of a range of NAPL types collated from the SoBRA contributors;
  • a library of organic compounds and their physical properties used in the calculations.

The document provides guidance on when and how to use effective solubility calculation in groundwater risk assessments and provides some worked example calculations.