www.inl.gov 

### A Simple Approach for Identifying

Contaminants of Most Concern to Underground Drinking Water Supplies from Hydraulic Fracturing Operations

Carl D. Palmer and Earl Mattson
EPA Hydraulic Fracturing Workshop (Fate and Transport) March 28 – 29, 2011 Idaho National Laboratory392 Chemicals in hydraulic fracturing fluids

207 Chemicals in flow back and produced waters

Spills

Natural Fractures/Abandoned Wells Casing/Grout Failures Water Supply Aquifer

Gas Reservoir

(USEPA, 2011)

## Objective: To determine which contaminants are likely to be of most 

### concern with regard to hydraulic fracturing. 

## Approach: 

# • Identify contaminants reported from laboratory tests, injection water compositions and from groundwater sampling at field hydraulic fracturing tests, 

# • Estimate the relative toxicity of the contaminants, 

# • Estimate the mobility of those contaminants.

## Estimate “Toxicity”



## • obtain maximum reported aqueous concentration ( C max), 

## • determine some “safe” contaminant concentration (C MCL) 

# • drinking water standards (EPA) 

## • secondary drinking water standards (EPA) 

## • state drinking water standards/guidelines 

## • foreign drinking water standards/guidelines (Canada, UK, EU) 

## • Identify (e.g., from ATSDR, EPA databases) an oral Maximum Risk Level (MRL) or similar criterion to estimate C MCL 

# • divide C max by C MCL

## Estimating “Mobility”



## • Estimate retardation factor 

# • Mobility = 1/R

## Neutral, hydrophobic Organics:

## Neutral, hydrophobic Organics:

## Neutral, hydrophobic Organics: Empirical and Structure based relationships between Koc and the octanol - water partition coefficient ( Kow)

## Toxicity and Mobility

## Example: 

## Application to Oil Shale Retorting

## Organic Contaminants



## • phenols (2,4 - dimethylphenol) 

## • ketones (2 - butanone) 

## • alcohols (2 - ethyl - 2 - hexanol) 

## • organic acids (benzoic acid) 

# • aromatics (benzene) 

## • nitrogen compounds (pyridine) 

## • alkanes (trimethylcyclohexane) 

## • PAHs (phenanthrene) 

## • halogenated compounds ( tribromophenol ) 79 Reported Compounds

## Organic Contaminants

## Organics of Most Concern Benzene 1 - Methylnaphthalene 2 - Butanone Aniline 2 - methylphenol 3 - and 4 - Methylphenol acetonitrile Phenol Thiophene Pyrrole 2 - Methylnaphthalene Benzidine Isophorone Chloroethane 2 - pyrrolidone vinyl chloride Bromomethane 4 - methylphenol Acetone 2 - Hexanone

## Limitations with the Approach



## • Use of maximum observed concentrations, 

# • How to include frequency of occurrence, 

## • Insufficient guidelines or MCLs, 

## • Lack of octanol/water partition data for some compounds, 

## • Partition coefficients are a function of temperature, 

## • Have not included potential biodegradation, 

## • Potential mineral precipitation, 

## • Potential for colloidal transport, 

## • Additional difficulties with fracture flow.

### Summary


## • Obtain data (field and laboratory) on concentrations associated with hydraulic fracturing, 

## • Consider the risk of these contaminants based on their relative mobility and toxicity, 

## • Create an initial prioritized list of contaminants that should be considered, 

## • Identify potential contaminants that require additional information.