1. Objectives
2. Source of information
3. Expected results
4. Progress
5. Literature cited

Objectives

In this term project, a map of Texas which shows susceptibility of soil and groundwater to contaminants will be created. Both of (1)non-ionic, aqueous chemicals and (2)non-aqueous phase liquid are considered as sources of contamination. Ionic chemicals are not considered because of their complex interaction with soil mineral surface. Vapor phase chemical transport also left outside of the scope of this project.

The obtained susceptibility map will be compared with other map showing related properties, such as hydrologic properties and the groundwater vulnerability determined by DRASTIC method.

Source of information

Raw data

It is expected that STATSGO (see also its documentation [310k pdf] and meta-data for Texas) will provide data for spatial distribution of parameters which is required for this project. Estimating vertical rate of water movement requires at least following parameters.

• porosity of the bed,
• water content,
• precipitation, infiltration, run-off,
• organic carbon content of the soil,
• bulk density, and
• permeability

Susseptibility evaluation

At the beginning of the project, a little literature search is needed to identify soil properties which has significant effect on determining migration potential of non-aqueous contaminants. Using these parameters, vertical rate of chemical transport (daily, monthly or annual average) will be calculated (probably normalized for K_oc). The models for calculation will be found in literature (e.g., Charbeneau and Daniel). Other information sources for estimating susceptibility include Vrba and Zaporozec, which provides overview of groundwater vulnerability estimation/presentation method. Review of vulnerability mapping concept is prepared based on this reference.

The hydrologic data which is related with the susceptibility in this project would be found in STATGO, too. TNRCC provides a DRASTIC vulnerability map in Arc/Info format (*.e00). These will be compared and correlated with the susceptibility map created in this project above. This comparison allows how soil property is, or is not, reflected in a existing vulnerability model. Statistical tool which allow analysis of spatial correlation between two set is yet to be found.

Expected results

The main result expected is, as stated in the objective, a map showing susceptibility of soils to a contamination. In addition, spatial correlation of the susceptibility and other related properties will be analyzed.

Following sub-document contains stuff I came up with after this outline was made.

1. Concept of groundwater vulnerability mapping (3/17/1997)
2. Statistically defined vulnerability using nitrate concentration in groundwater (3/26/1997)
3. Course of progress of this project (4/19/1997)
4. Source files for Tom's statistical vulnerability analysis with documentation(4/25/97)

Literature cited

Aller et al. DRASTIC: A standardized system for evaluating ground water pollution potential using hydrogeologic settings. EPA/600/2-87/035 USEPA, Ada, 1987

Charbeneau and Daniel. "Contaminant transport in unsaturated flow". in Handbook of Hydrology. Maidment (ed.), Ch. 15, McGraw-Hill, New York, 1993.

Evans and Maidment. A spatial and statistical assessment of the vulnerability of texas groundwater to nitrate contamination. CRWR Online Report 95-2, http://www.ce.utexas.edu/prof/maidment/GISHydro/docs/reports/evans/rep95_2.htm, 1995.

Kolpin, Burkart, and Thurman. Hydrogeologic, water-quality, and land-use data for the reconnaissance of herbicides and nitrate in near surface aquifers of the Midcontinental United States, 1991. USGS Open-File report 93-114. USGS, Iowa City. 1993.

Vrba and Zaporozec (eds.). Guidebook on Mapping Groundwater Vulnerability. Intl. Assoc. Hydrol., Hannover, 1994.