U.S. DEPARTMENT OF THE INTERIOR
U.S. GEOLOGICAL SURVEY

INTRODUCTION

The “2,000-foot” sand is a major source of water in the Baton Rouge area and

surrounding parishes. In 2002, about 25.8 Mgal/d! was pumped from the “2,000-foot” sand
in the five-parish study area (East and West Baton Rouge, Pointe Coupee, and East and
West Feliciana Parishes). Nearly 88 percent of withdrawals from the “2,000-foot” sand
(22.7 Mgal/d in 2002) were in East Baton Rouge Parish, mostly in the industrial district
(fig. 1). Most withdrawals from the “2,000-foot” sand in 2002 were in the study area for
industry (40 percent), power generation (26 percent), and public supply (33 percent).

Withdrawals from the “2,000-foot” sand in the study area (particularly from East
Baton Rouge Parish) have caused declines in water levels as far away as Livingston and
Tangipahoa Parishes (Nyman and Fayard, 1978, p. 47). Concerns about declining water

levels in the “2,000-foot” sand include (1) the rate of decline, (2) the effect on saltwater”
encroachment in the Baton Rouge area, and (3) the effect on land-surface subsidence in the
Baton Rouge area.

Additional knowledge about ground-water flow and effects of withdrawals on the
“2,000-foot” sand of the Baton Rouge area is needed to assess ground-water development
potential and to protect the resource. To meet this need, the U.S. Geological Survey
(USGS), in cooperation with the Capital Area Ground Water Conservation Commission,
began a study in 2001 to measure and document the current (2002) water levels in wells
screened in the “2,000-foot” sand in the Baton Rouge area, to construct a potentiometric-
surface (water-level) map, and to evaluate changes in the potentiometric surface. This
report documents the results and findings of this study. Water-level data collected in May
2002, maps showing the 2002 potentiometric surface, and generalized location of major
withdrawals (2002) are presented. Hydrographs for four wells show water-level trends in
the “2,000-foot” sand.

lWater-use data 2002 are modified from records provided by the Capital Area Ground Water Conserva-
tion Commission to the USGS.

2saltwater in this report is defined as water that contains chloride at concentrations of more than
250 mg/L. Concentrations of chloride greater than 250 mg/L exceed the Secondary Maximum Contaminant
Level (SMCL) for drinking water (U.S. Environmental Protection Agency, 1977, 1992). SMCL’s are estab-
lished for contaminants that can adversely affect the aesthetic quality of drinking water. At high concentra-
tions or values, health implications as well as aesthetic degradation also may exist. SMCL’s are not federally
enforceable, but are intended as guidelines for the states.

Prepared in cooperation with the
CAPITAL AREA GROUND WATER CONSERVATION COMMISSION

During this study, hydrogeologic data were used to refine water withdrawal esti-
mates for the “2,000-foot” sand. Approximately 10 Mgal/d were subtracted from the
reported total withdrawal (2002) and distributed into overlying aquifers. For this report,
historical withdrawal data (data prior to 2002) also were modified. Withdrawal data
shown in figure 3 supersede earlier reports.

The authors gratefully acknowledge the assistance and cooperation of numerous
public water suppliers, industrial facilities, and private well owners that allowed site
access and collection of water-level data. Don C. Dial, Director, Capital Area Ground
Water Conservation Commission, assisted with technical support and provided
withdrawal data for the study.

GENERAL HYDROGEOLOGY

The “2,000-foot” sand and other aquifers in the Baton Rouge area (fig. 2) extend
throughout the study area, adjacent parishes, and into southwestern Mississippi. Most of
the aquifers, which are named according to their approximate depth below land surface in
the industrial district, are composed of very fine to coarse sand and may contain gravel.
The correlation between aquifers in the Baton Rouge area and regional stratigraphy is
shown in figure 2.

The Baton Rouge fault, which has been described as a leaky barrier to ground-
water flow (Whiteman, 1979, p. 10), historically has impeded freshwater flushing of
saltwater south of the fault and presently impedes saltwater encroachment northward into
freshwater areas. Along the Baton Rouge fault, vertical displacement has caused limited
hydraulic connection of the “2,000-foot” sand north of the fault with the “1,500-foot” and
“1,700-foot” sands south of the fault (Torak and Whiteman, 1982, p. 15). In the Baton
Rouge area, the “2,000-foot” sand mostly contains freshwater north of the Baton Rouge
fault. South of the fault, the “2,000-foot” sand and overlying and underlying aquifers
contain mostly saltwater.

Precipitation enters the aquifer as recharge in the outcrop area, located in
southwestern Mississippi, and moves downdip toward coastal areas in Louisiana
(Morgan, 1963, plate 1). Prior to large withdrawals (in the early 1900’s), ground-water
flow was from north to south in the study area (Rollo, 1969, p. 8). The southward flow of
freshwater was impeded at the fault, and ground water moved upward through overlying
clays and sands to discharge at land surface as seeps and springs (Rollo, 1969, p. 9).
Some freshwater from the “2,000-foot” sand leaked southward across the fault creating
localized freshwater areas south of the fault in the downthrown “1,500-foot” and
“1,700-foot” sands. Also, small amounts of freshwater from the “2,400-foot” sand (north
of the fault) leaked across the fault to create local freshwater areas in the “2,000-foot”
sand south of the fault.

System Series Stratigraphic unit Aquifer or confining unit!
Holocene Mississippi River and other sata cs q F
2 alluvialldepostts Mississippi River alluvial aquifer
Shallow sands
Pleistocene Unnamed Pleistocene deposits Upland t. a ‘400-foot” sand
auld *600-foot” sand
“800-foot” sand
Pliocene “1,000-foot” sand.
2 Blounts Creek Member “1,200-foot” sand
§
4 “1,500-foot” sand
S “1,700-foot” sand
20
f 4 Castor Creek Member Unnamed confining unit
= = | Williamson Creek Member “2,000-foot” sand
z Dough Hills Member “2,400-foot” sand
Miocene
Carnahan Bayou Member “2,800-foot” sand
Lena Member Unnamed confining unit
a
(fen ed Catahoula Formation Catahoula aquifer
Oligocene

1Clay units separating aquifers in the Baton Rouge area are discontinuous and unnamed.

Figure 2. Hydrogeologic units in the Baton Rouge area, Louisiana (modified from Stuart
and others, 1994, fig. 5; Lovelace and Lovelace, 1995, fig. 1).

SCIENTIFIC INVESTIGATIONS MAP 2872 (Sheet 1 of 2)

Tomaszewski, D.J., and Accardo, Darren, 2004, Louisiana Ground-Water Map No. 20:
Potentiometric surface of the “2,000-foot” sand of the Baton Rouge area, Louisiana, May 2002

Large ground-water withdrawals from the “2,000-foot” sand (fig. 1) upgradient (north) of
the fault have altered the distribution of hydraulic head such that water no longer discharges at land
surface near the fault. Ground water moving southward from the recharge area may now be
intercepted by withdrawal sites (fig.1), Large withdrawals from the “2,000-foot” sand north of the
fault have reduced hydraulic head in the aquifer and induced vertical leakage of water into the sand
from overlying and underlying clays and aquifers. This vertical leakage probably contributes a
large portion of present-day recharge to the aquifer (Torak and Whiteman, 1982, p. 45-46).
Withdrawals from the “2,000-foot” sand also have induced leakage of saltwater from south of the
fault into freshwater areas north of the fault (Torak and Whiteman, 1982, p. 16; Tomaszewski,
1996, p. 22).

WATER-LEVEL DATA

As withdrawals have increased in the “2,000-foot” sand, water levels in wells have
declined, Water levels in the “2,000-foot” sand were about 100 ft above land surface in the indus-
trial district in 1916 (Meyer and Turcan, 1955, p. 58). Water levels are currently (2002) more than
300 ft below land surface in the industrial district.

Water levels in the “2,000-foot” sand at wells EB-90 and PC-66 (fig. 3), show the effects
of long-term withdrawals in the Baton Rouge area. Well PC-66 is located in an area where with-
drawals are minor. As withdrawals increased in the “2,000-foot” sand and adjacent sands, water
levels in wells EB-90 and PC-66 have declined (fig. 3). Water levels were near land surface at well
EB-90 in the city of Baton Rouge about 1940. Water-levels declined about 260 ft at well EB-90
from 1942 to 2002.

The hydrograph for well EB-90 shows water levels in the “2,000-foot” sand fluctuate in
response to variations in withdrawals (fig. 3). Water levels declined about 9.1 ft/yr in well EB-90
from 1943 to about 1974, as withdrawals from the “2,000-foot” sand increased from 10 to 38
Mgal/d in the study area, Water levels began to recover slightly in about 1982 as withdrawals
decreased. Since 1990, two trends are shown. From 1990-96, water levels generally were stable
(a slight increase can be noted), and during 1997-2001, water levels declined about 16.6 ft/yr.
The same general trends can be noted at well PC-66; however, the declines and recoveries are
less in magnitude.

Water-level declines in the “2,000-foot” sand south of the fault were about 1.3 ft/yr at
well EB-778 and about 1.1 ft/yr at well WBR-111 for the period of record (fig. 4). Declines
south of the fault are minor when compared to water-level declines north of the fault. Declines
are small because withdrawals south of the fault are insignificant (no withdrawals have been
reported), and movement of water from south (the “2,000-foot” sand) to north (into the
“2,400-foot” sand), across the fault, is relatively minor (Tomaszewski, 1996, p. 38).

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; T WATER-WITHDRAWAL SITE -- Shows
WEST EAST 0.5 withdrawals, in million gallons per day, at site
; e withdrawing 0.1 million gallons per day or
more. Some sites include multiple wells i: l 7
i ieaaaal (D.C. Dial, Capital Area Ground Water | | _|
r ELICIAI A Conservation Commission, written commun., w | WELL: PC-66
2002) ye r ALTITUDE OF LAND SURFACE: 33 feet above NGVD 29 =
pm? prey FAULT — Dashed and queried where probable. Ze -100 | ES Teg OF VWEL LIE a oes Cera ind Soe to
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ie) 3 STUDY AREA BOUNDARY - Shows limits of 73 _
es study area, us L | | | al
0.5 gs -200 |— | | | ye
A cm I |
Ul oe WELL: EB-90
<O | ALTITUDE OF LAND SURFACE: 59.05 féet above NGVD 29 | | 4
= DEPTH OF WELL: 2,120 feet below land surface |
: [ | | | 4
300 Lititisiiilits cot
1940 1950 1960 1970 1980 1990 2000
0 a €.1 0.3 \f WITHDRAWAL DATA
: 0.2¢ e.¥ YEAR(S) AND SOURCE
e
; we 4 1953, Meyer and Turcan, 1955, pg. 54 1966, Rollo, 1969, p. 32
0 BATON 1954-1958, Morgan, 1961, fig. 23 1976-2002, D.C. Dial, Capital Area Gound Water
F ao ) Frdustrlal ARKANSAS 1960-1964, Kazman, 1970, fig. 9 Conservation Commission, written commun., 2003
8 | bee : ,
2 . | —: District _ Figure 3. Water withdrawals from the “2,000-foot” sand in the five-parish study area, and water levels in the “2,000-foot”
8 0 P y area, ;
sand at wells EB-90 and PC-66 in the Baton Rouge area, Louisiana.
a os i,
ad e ROUGE ib
e@ =
2 6 6, wok,
a 80 +t a
L WELL: WBR-111
5 Oe ' rr ALTITUDE OF LAND SURFACE: 25 feet above NGVD 29
\ us z im DEPTH: 2,650 feet below ground surface
is) 40
Zac ‘\ Sr
0 10 KILOMETERS oO
\ wo
‘ BoB
ses \ INDEX MAP a wo
ie} =
/ Ww
\ Eig 3 WELL: EB-778
\ = ALTITUDE OF LAND SURFACE: 28 feet above NGVD 29
| ii DEPTH OF WELL: 2,586 feet below ground surface
Base map modified from Louisiana Oil Spill Coordinator, Office of the Governor, Louisiana, Louisiana GIS CD: A Digital Map of the State, Version 2.0 go Leet | bet
1940 1950 1960 1970 1980 1990 2000

Figure 1. Location of the study area and withdrawal sites in the “2,000-foot” sand of the Baton Rouge area, Louisiana, 2002.

aZUSGS

science for a changing world

Potentiometric Surface of the “2,000-foot” Sand of the

Louisiana Ground-Water Map No. 20:

Figure 4. Water levels in the “2,000-foot” sand at wells EB-778 and WBR-111, located south of the fault in the Baton

Rouge area, Louisiana.

Baton Rouge Area, Louisiana, May 2002

By

D.J. Tomaszewski and Darren Accardo

2004

For additional information, contact:

District Chief

U.S. Geological Survey

3535 S. Sherwood Forest Blvd., Suite 120
Baton Rouge, Louisiana 70816

E-mail: de Ja@usgs gov

Fax: Coe 5490.

Telephone: (225) 298-5481

Home Page: http://la.water.usgs.gov

Copies of this report can be purchased from:

US. Gorey Survey

Branch of Information Services

Box 25286

Denver, CO 80225

E-mail: infoservices@usgs.gov

Fax: (303) 202-4188

Telephone (toll free): 1-888-ASK-USGS

Z:\groundwatermap.20\2000map.sheet1.fm