DRASTIC GROUNDWATER VULNERABILITY MAP OF TENNESSEE

James Bond – Capstone ProposalGEOG 596A

Overview of Presentation

Introduction Methodology Anticipated Results & Problems References

INTRODUCTION

Introduction

My Project DRASTIC Groundwater Vulnerability Map of

Tennessee DRASTIC

What is it? Identifies areas where groundwater is

susceptible to pollution What are the applications?

Guides land development & resource protection Flexible

Used at a variety of scales Can be modified to include or exclude parameters

Example DRASTIC Map

METHODOLOGY

DRASTIC Overview

DRASTIC – methodology guided by EPA Developed by EPA & National Water Well

Assoc. 600+ page guidance document Link to Guidance:

http://nepis.epa.gov/Exe/ZyPURL.cgi?Dockey=20007KU4.txt

Purpose – Over large areas, used to identify regions where groundwater is more or less susceptible to impact from pollution.

DRASTIC Overview Cont.

Overview of DRASTIC Simplified GW vulnerability model Qualitative Produces a relative-risk scale Applicable over large areas Used as a screening tool Results guide land development & resource

protection For small, specific sites, more detailed

assessment needed

DRASTIC Method Assumptions DRASTIC Makes Four Assumptions:

1. Contamination is introduced at the ground surface

2. Contamination is flushed into the groundwater by precipitation

3. Contamination has the mobility of water4. Area being evaluated is 100-acres or larger

If these assumptions are not met, then DRASTIC is not the appropriate methodology

DRASTIC Factors

Seven hydrogeologic factors used. They form the acronym DRASTIC

D – Depth to WaterR – Net RechargeA – Aquifer MediaS – Soil MediaT – TopographyI – Impact of Vadose Zone MediaC – Hydraulic Conductivity of Aquifer

Weights & Ratings

Significance of each factor in contaminant transport varies

Relative weight is assigned to each factor Scale of 1 to 5 1 is least important factor 5 is most important factor

Each factor also has a rating applied according to a category or range of values.

Feature WeightDepth to Water 5Net Recharge 4Aquifer Media 3Soil Media 2Topography 1Impact of Vadose Zone Media 5Hydraulic Conductivity of Aquifer 3

DRASTIC – The Equation

Once ratings and weights have been applied, they are multiplied and added

DRASTIC equation:

DrDw + RrRw + ArAw + SrSw + TrTw + IrIw + CrCw = Pollution Potential

r = ratingw = weight

Results are symbolized on a map overlaying study area

Methodology - Example

Example of how ratings and weights are applied

Will use D Factor (Depth to Water) as example

D receives a weight of 5 It is very significant in potential impact to

GW Based on actual depth to groundwater, D

also receives a rating.

Range Rating0-5 105-15 9

15-30 730-50 550-75 375-100 2>100 1

DEPTH TO WATER (ft bgs)

Methodology – Example Cont. If depth to water was 10 ft then D rating

would be 9

DrDw = 9 x 5 = 45

If depth to water was 100 ft, then D rating would be 2

DrDw = 2 x 5 = 10

This process is repeated for each of the factors

Capstone Process

Data Analysis Process

Self-Imposed Project Parameters Due to time constraints, need to impose

parameters on the analysis Use unmodified version of method Use existing datasets as much as possible To fill datagaps will use the easier of two

approaches: Derive missing data from other existing data Use generalized values in EPA guidance

ANTICIPATED RESULTS & PROBLEMS

Anticipated Results

State of TN groundwater vulnerability map

Detailed report of methodology and data used

Map will be technically correct Considered FINAL within context of

capstone project Considered DRAFT by public and

professionals who may use it

Anticipated Problems

Low Resolution Data Anticipate using only small scale data

Missing data Not all inputs may be available May have to infer data or use generalized

inputs Room for improvement

Analysis can be easily re-run with better data Better data = better results Additional refinement outside the scope of

this capstone project

Summary

Summary

Project to produce groundwater vulnerability map of Tennessee

Has not been done for Tennessee Use EPA DRASTIC vulnerability

methodology Use small scale, publicly available data Result will be a first cut at groundwater

vulnerability mapping Model will have room for refinement

Outside the scope of this project

Q&A

Questions?

Thank you

REFERENCES

References

U.S. EPA DRASTIC Guidance Document United States Environmental Protection Agency (EPA), 1987, DRASTIC: A

Standardized System for Evaluating Ground Water Pollution Using Hydrogeologic Settings, EPA/600/2-87-035, Robert S. Kerr Environmental Research Laboratory, Ada, OK 74820

Examples of the Application of DRASTIC Arthur, Jonathan D., et al., 2005, Florida Aquifer Vulnerability Assessment (FAVA):

Contamination Potential of Florida’s Principal Aquifer Systems, Division of Resource Assessment and Management, Florida Geological Survey

Chowdhury, Shafiul, et al, 2003, Comprehensive approach of groundwater resource evaluation: a case study in the Chippewa Creek watershed in Ohio, The Ohio Journal of Science, December 2003

Crider, S.S., 1989, A Cursory Application of DRASTIC to the Savannah River Site, WSRC-RP-89-744, DE92 009778, Division of Engineering Fundamentals, Virginia Polytechnic Institute and State University, Blacksburgh, VA 24061-0218

 Evans, Barry, et al, 1990, A GIS-Based Approach to Evaluating Regional Groundwater Pollution Potential with DRASTIC, Journal of Soil and Water Conservation, March-April, pp. 242-245

Rupert, Michael G., 1999, Improvements to the DRASTIC Ground-Water Vulnerability Mapping Method, USGS Fact Sheet FS-066-99, Department of the Interior, US Geological Survey, Denver, CO 80225