1

Location identification (id) 

Classification 

Northing 

Easting 

Land-surface elevation 

Agency database 

Aquifer completed 

Well status 

Dedicated pump

Location layer

Location id 

Classification 

Installation date

Well type

Measuring point

 elevation 

Total well depth 

Remarks

Well construction

Lo

A

D

S

S

M

C

R

 

Location id

Agency

Logging date

Lithology top

Lithology bottom

Stratigraphic unit 

Logging company

Visual description

Lithology

Location id

Depth top screen

Depth bottom

 screen

Screen diameter

Screen slot size

Percent open 

Screen material

Screened interval(s)

 Trichloroethene Dichloroethene

Location id

Agency

Contaminant

Date measured

Matrix

Concentration 

Unit

Detection limit

Data source

Location id

Agency

Contaminant

Date measured

Matrix

Concentration 

Unit

Detection limit

Data source

Location id

Agency

Contaminant

Date measured

Matrix

Concentration 

Unit

Detection limit

Data source

Vinyl chloride T

Volatile organic compounds

Location id

Agency

Contaminant

Date measured

Matrix

Concentration 

Unit

Detection limit

Data source

Benzene

Location id

Agency

Contaminant

Date measured

Matrix

Concentration 

Unit

Detection limit

Data source

Toluene

Location id

Agency

Contaminant

Date measured

Matrix

Concentration 

Unit

Detection limit

Data source

Ethylbenzene

Location data

Well-construction,

lithology, water-level

data

Water-quality data

EXPLANATION

Figure 1. Relational tables within location layer of geodatabase. 

Fort Worth

TEXAS

(NAS–JRB) at Fort Worth, Tex., constitute a 

contractor-owned, government-operated 

facility that has been in operation since 1942. 

Contaminants from the 3,600-acre facility, primarily volatile organic compounds (VOCs) and 

metals, have entered the ground-water-flow 

system through leakage from waste-disposal sites and from 

manufacturing processes. 

Environmental data collected at AFP4 and NAS–JRB 

during 1993–2002 created the need for consolidation of the 

data into a comprehensive temporal and spatial geodatabase. 

The U.S. Geological Survey (USGS), in cooperation with the 

U.S. Air Force Aeronautical Systems Center Environmental 

Management Directorate, developed a comprehensive geodatabase of temporal and spatial environmental data associated with the hydrogeologic units beneath the facility. A 

three-dimensional conceptual model of the hydrogeologic 

units integrally linked to the geodatabase was designed 

concurrently.

Three hydrogeologic units—from land surface 

downward, the alluvial aquifer, the GoodlandWalnut confining unit, and the Paluxy aquifer—compose the subsurface of interest at 

AFP4 and NAS–JRB. The alluvial aquifer consists primarily of clay and silt with sand and 

gravel channel deposits that might be interconnected or interfingered. The Goodland-Walnut 

confining unit directly underlies the alluvial 

aquifer and consists of limestone, marl, shale, 

and clay. The Paluxy aquifer is composed of 

dense mudstone and fine- to coarse-grained 

sandstone. 

Geodatabase

The geodatabase design uses a thematic 

layer approach to create layers of feature data 

using a geographic information system (GIS). 

on the basis of how they interact and 

to one another. These relational table

a collection of features and the relatio

them. A base layer contains all static 

which comprise buildings, roads, sur

bodies, and other entities that depict 

features. A location layer contains all sampling p

torical and active) at the facility. Within this lay

relational tables that encompass well-construction

water-level, and water-quality data (fig. 1). The 

provide accurate representations of the locations 

extent of the AFP4 and NAS–JRB environmental 

with a means for conducting complex spatial an

U.S. Department of the Interior

U.S. Geological Survey

USGS Fact S
2

Alluvial aquifer

Goodland-Walnut 

confining unit

Paluxy aquifer

The geodatabase is accessed using a GIS that integrates 

the spatial framework of the geodatabase and manages the 

environmental data. The GIS provides information to users 

through interactive sessions with maps and symbols on a personal computer. Thus, the geodatabase coupled with the GIS 

accepts queries for and retrieves specific geologic, hydrologic, and water-quality information. 

Conceptual Model

The conceptual model for AFP4 and NAS–JRB 

comprises computer-generated three-dimensional (oblique 

view) block diagrams of the hydrogeologic units (fig. 2). 

The model provides a platform for visualization of hydrogeologic-unit sections and surfaces and for analyses involving, for example, spatial distribution of contaminants and 

evaluation of remediation alternatives. The model also provides a framework for future conceptualization of groundwater-flow or contamination-transport modeling. 

The conceptual model is based on three structural 

surfaces and two thickness configurations at AFP4 and 

NAS–JRB. The three structural surfaces depict the altitudes 

of the tops of the three hydrogeologic units. The two thickness configurations are those of the alluvial aquifer and the 

Goodland-Walnut confining unit.

From a conceptual standpoint, identifying the hydrogeologic units and structural surfaces of the hydrogeologic units 

as they relate to all static and dynamic features is essential. 

The data used in the three-dimensional model consist of both 

spatial and physical information. The modeling process, in 

most cases, involved associating the altitude (elevation) of 

rocks of a given lithologic description with a particular point 

in three-dimensional space identified by northing, easting, 

and elevation coordinates. 

The surface of the alluvial aquifer (top diagram at right) 

was created using a USGS 10-meter digital elevation model. 

The top of the Goodland-Walnut confining unit (middle 

diagram at right) was compiled from lithologic logs from 

existing wells, available soil-boring logs, and previous 

studies. The top of the Paluxy aquifer (bottom diagram 

above) was the most challenging to depict because of a lack 

of altitude data for that unit throughout the study area. Data 

from 120 wells were obtained primarily from existing reports 

and used to create a map of the approximate altitude of the 

top of the Paluxy aquifer.

— Sachin D. Shah

This fact sheet is based on the report

Shah, S.D., 2004, Development of a geodatabase and conceptual 

model of the hydrogeologic units beneath Air Force Plant 4 

and Naval Air Station-Joint Reserve Base Carswell Field, 

Fort Worth, Texas: U.S. Geological Survey Scientific 

Investigations Report 2004–5062, 77 p.

For additional information, please contact

District Chief

U.S. Geological Survey

8027 Exchange Dr. 

Austin, TX 78754–4733

E-mail: dc_tx@usgs.gov

Phone: (512) 927–3500

FAX: (512) 927–3590

World Wide Web: http://tx.usgs.gov/

Figure 2. Block-diagram composite of hydrogeologic units 

(three-dimensional conceptual model), AFP4 and NAS–JRB.