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HEALTH CONSULTATION

Past Exposure to Drinking Water From On-Base Wells 313 and 314

KELLY AIR FORCE BASE
SAN ANTONIO, BEXAR COUNTY, TEXAS


TABLES

Table 1. Production/Drinking Water Well Information, Kelly Air Force Base.

New Well Number (Same as Building Number) Old Base Well Number "I" Series Well Number USGS Well Number Year Drilled Date Plugged Total Depth (feet) Max* (gpm) Production for 7/88
(1000 gallons)
Comment
81 - - - 1994 na 1,500 2,200 0

Replacement for wells 141 and 313.

141 3 96 810 1906 6/20/91 1,400 900 0

Out of service since 1984.

313 2 124 808 1910 6/26/91 1,590 1,050 36,535

7/7/88: 5.5 µg/L PCE detected.
9/23/88: No VOCs detected.
1/31/89: Well 313 is taken out of service.
6/23/89: Horizontal pipe found with 52 µg/L PCE.
7/17/89: Gap in well at 590 feet.
3/26/91: Determined pipe comes from shallow aquifer.
6/26/91: Plug placed in pipe over horizontal pipe.
6/16/91: Well 313 is cemented and permanently sealed.

314 4 97 809 1940 6/21/98 1,608 1,500 28,289

7/7/88, 8/11/88, 9/23/88, 7/14/89, 9/6/89, 10/12/89: No contaminants detected.
2/1/90: Detected very low levels of chlorinated solvents.
3/6/90: Horizontal pipe found.
4/11/90: A patch is placed over the horizontal pipe as a precaution.
6/21/98: Well is cemented and sealed.

1040 - - - 1996 na 1,560 800 0

Replacement for well 1044.

1044 7 66 713 1924 12/19/96 1,677 550 13,627

Well plugged and replaced by well 1040.

1536 8 77 - 1943 na 1,042 650 13,338

--

1556 6 78 806 1943 1/23/97 1,030 700 15,024

Well plugged and replaced by well 2047.

1638 5 123 805 1940 na 1,632 1,600 12,864

--

1761 - - - not known na 1,460 1,500 0

Under design. Replacement for well 314.

2047 - - - - na 505 2,200 0

Replacement for wells 314 and 1556.

3010 - - - 1919 na 1,120 1,300 6,327

--

gpm = gallons per minute; na = not applicable; µg/L = micrograms per liter
*Max = Maximum potential production in gallons per minute

Note: The production wells draw water from the Edwards aquifer. All production wells feed into a closed loop distribution system. The water is used exclusively for the base--both military and civilian personnel. Since 1983, the base's population ranged from a low of 19,021 in 1995 to a high of 24,830 persons in 1999, with 21,961 persons in 1988. Information compiled by Air Force personnel suggests that the average stay on base is approximately 2 years for officers and 3 years for enlisted personnel.


Table 2. Irrigation Wells at Kelly Air Force Base.

"I" Series Well Number Year Drilled Date Plugged Comment
65 1912 See Comment

Inactive and abandoned. Kelly AFB could not locate this well and records do not exist. May be covered by Taxiway 3B.

69 1924 1996

No comments.

72 Possibly in the 1930s 1997

No comments.

73 1933 1997

No comments.

74 Unknown 1998

No comments.

75 Early 1930s Unknown

Abandonment confirmed by Kelly AFB in 1996

76 1913 Unknown

Abandonment confirmed by Kelly AFB in 1996.

80 <1934 Unknown

Abandonment confirmed by Kelly AFB in 1996.

99 1912 1996

No comments.



Table 3. Production/drinking Water Well Monitoring data (1983 -1998)1, Volatile Organic Compound Concentration by Production Well, Kelly Air Force Base.

Chemical Well 141 Well 313 Well 314 Well
1044
Well 1536 Well 1556 Well 3010 Well 1638 EPA MCL or LTHA (µg/L) EPA RBCs
(6 Years of
Exposure at
1/100,000)
(µg/L)
1,2-Dichloroethane 0.3 - 4.2
(2/6)
3 - 43
(3/9; 1/1)
nd
(0/10)
2.3 - 36
(2/12; 1/2)
nd
(0/11)
3.5 - 4
(2/8)
4.5
(1/12)
nd
(0/11)
5 6 c
17 nc
1,3-Dichlorobenzene nd
(0/6)
nd
(0/9)
nd
(0/9)
305
(1/12; 1/1)
nd
(0/11)
nd
(0/8)
nd
(0/12)
nd
(0/11)
600 LTHA 17 nc
1,4-Dichlorobenzene nd
(0/6)
nd
(0/9)
nd
(0/9)
149
(1/12;1/1)
nd
(0/11)
nd
(0/8)
nd
(0/12)
nd
(0/11)
75 24 c
1400
Benzene nd
(0/6)
3.87
(1/9)
3.37
(1/11)
0.5 - 3.58
(2/12)
4.22
(1/11)
3.43
(1/8)
3.72
(1/12)
5.74
(1/11)
100 21 c
11 nc
Chlorobenzene nd
(0/6)
nd
(0/9)
nd
(0/11)
435
(1/12; 1/1)
nd
(0/11)
nd
(0/8)
nd
(0/12)
nd
(0/11)
no value 39 nc
2-Chloroethylvinyl ether nd
(0/6)
nd
(0/7)
nd
(0/7)
0.3
(1/7)
nd
(0/6)
nd
(0/6)
nd
(0/7)
nd
(0/5)
3540* no value
Chloroform 0.4 - 3.8
(3/6)
1 - 12
(2/9; 1/1)
nd
(0/11)
1 - 6.7
(2/13)
0.3 - 4.5
(2/12)
1.4 - 21
(1/9)
1.7-10
(3/12, 1/3)
2.7 - 16
(3/11; 1/3)
700 8 c
61 nc
Ethylbenzene nd
(0/6)
nd
(0/9)
nd
(0/11)
39
(1/12)
nd
(0/11)
nd
(0/8)
nd
(0/12)
nd
(0/11)
5 1300 nc
Methylene chloride 0.5 - 1.6
(2/6)
0.5 - 5
(2/9)
2.1
(1/9)
1.1 - 3.8
(2/11)
1.7 - 2.3
(2/10)
1.3 - 1.4
(2/8)
1.3
(1/11)
2.4
(1/11)
5 215 c
1600 nc
1,1,1,2-Tetrachloroethane 0.08
(1/6)
nd
(0/9)
4.7
(0/9)
nd
(0/12)
nd
(0/11)
nd
(0/8)
nd
(0/11)
nd
(0/11)
no value 21.5 c
180 nc
Tetrachloroethene nd
(0/6)
0.12 -5.5
(4/9)
nd
(0/10)
0.2
(1/13)
nd
(0/7)
nd
(0/7)
nd
(0/8)
nd
(0/6)
5 55 c
250 nc
1,1,1-Trichloroethane 1.8
(1/6)
1.2
(1/9)
2.7
(1/11)
nd
(0/12)
2.5-2.6
(2/11)
1-1.8
(3/8)
2
(1/11)
2.5
(1/11)
200 790 nc
1,1,2-Trichloroethane nd
(0/6)
nd
(0/9)
0.6
(1/9)
nd
(0/12)
nd
(0/11)
nd
(0/8)
nd
(0/11)
nd
(0/11)
5 10 c
24 nc
Trichloroethene nd
(0/6)
nd - 2.8
(2/9)
nd
(0/10)
2.2
(1/13)
nd
(0/7)
nd
(0/6)
nd
(0/8)
nd
(0/5)
5 80 c
35 nc
Notes:
(1) Data collected by OEHL (11/23/83, 4/15/85, 1/22/86, 3/11/86, 5/15/86); Radian (1/22/86, 4/16/86); TDH (7/7/88, 12/01/93, 3/24/94, 7/8/94, 12/03/96, 11/0-3/97); and LCRA (8/14/94, 11/30/95 ); TWC (12/01/93); TNRCC (2/12/98).
Key:
c Cancer
nc noncancer
EPA RBCs EPA Region 6 Risk Based Concentrations based on 30 years of exposure 24 hours a day, 350 days per year.
LCRA Lower Colorado River Authority
LTHA Lifetime Health Advisory for drinking water
MCL EPA's maximum contaminant level
nd not detected
OEHL= Occupational Environmental Health Laboratory
µg/L= Micrograms per liter
TDH= Texas Department of Health
TNRCC= (Texas Natural Resources and Conservation Commission)
TWC= Texas Water Commission
(x/x)= (number of detects/number of samples collected)
(x/x)= (number of detects above EPA Risk Based Concentration at 6 years of exposure at 1/100,000 risk/number of detects)
* = No human health based screening levels were available for 2-chloroethylvinyl ether. This value is the surface water screening values derived by U.S. EPA Region 4 Water Management Division. These values were obtained from Water Quality Criteria documents and represent the chronic ambient water quality criteria values for the protection of aquatic life.


Table 4. Production/drinking Water Well Monitoring Data (1983 -1988), Volatile Organic Compound Concentration for Well 313, Kelly Air Force Base

Chemical Organization Collecting and Analyzing Sample with Month and Year of Sample  
Sampling as part of the SDWA Sampling as part of the IRP program Sampling as part of the SDWA
OEHL
11/83
OEHL
4/85
Radian
1/86
OEHL
1/86
OEHL
3/86
OEHL
3/86
(split)
OEHL
4/86
OEHL
5/86
TDH 7/88 TDH
9/88
EPA MCL or LTHA
(µg/L)
EPA RBCs
(6 Years of Exposure at 1/100,000)
(µg/L)
1,2-Dichloroethane ND NS ND 43 3 2.1 ND ND <1.0 <1.0 5 6 c
17 nc
1,3-Dichlorobenzene ND NS ND ND ND ND ND ND <1.0 <1.0 600 LTHA 17 nc
1,4-Dichlorobenzene ND NS ND ND ND ND ND ND ND <1.0 75 24 c
1400
Benzene ND NS 3.87 ND ND ND ND ND <0.1 <0.1 100 21 c
11 nc
Chlorobenzene ND NS ND ND ND ND ND ND <0.1 <0.1 no value 39 nc
Chloroform ND NS ND 12 1 ND ND ND <0.1 <0.1 700 8 c
61 nc
Ethylbenzene ND NS ND ND ND ND ND ND <2.0 <.2.0 5 1300 nc
Methylene chloride ND NS ND 5 0.5 ND ND ND <0.1 <0.1 5 215 c
1600 nc
Tetrachloroethene ND NS 0.34 0.6 ND ND 0.12 ND 5.5 <0.1 5 55 c
250 nc
1,1,1-Trichloroethane ND NS ND ND 2.1 ND ND ND <1.0 <1.0 200 790 nc
Trichloroethene ND NS ND 2.8 ND ND ND ND <0.1 <0.1 5 80 c
35 nc
Key:
Source: Kelly AFB.
ND= not detected
NS = not sampled
µg/L = micrograms per liter
RBC= risk based concentration
SDWA = Safe Drinking Water Act
TDH= Texas Department of Health
OEHL= Occupational Environmental Health Laboratory, U.S. Air Force
LTHA = U.S. EPA lifetime health advisory for drinking water
IRP = Installation Restoration Program


Table 5. Production/drinking Water Well Monitoring Data (1983-1998), Volatile Organic Compound Concentration for Well 314, Kelly Air Force Base.

Chemical Organization Collecting and Analyzing Sample with Month and Year of Sample  
Sampling as part of the SDWA Sampling as part of the IRP program Sampling as part of the SDWA
OEHL
11/83
OEHL
4/85
Radian
1/86
OEHL
1/86
OEHL
3/86
OEHL
3/86
(split)
OEHL
4/86
OEHL
5/86
TDH 7/88 TDH
9/88
2/90* TWC
/93
TDH
3/94
TDH 12/96 TNRCC 2/12/98 EPA MCL or LTHA
(µg/L)
EPA RBCs
(6 Years of Exposure at 1/100,000)
(µg/L)
1,2-Dichloroethane <.0.3 NS ND ND ND ND ND ND <0.001 <0.001 ND NS <0.5 NS <0.5 5 6 c
17 nc
1,3-Dichlorobenzene ND NS ND ND ND ND ND ND NS NS ND NS <1.0 NS <0.5 600 LTHA 17 nc
1,4-Dichlorobenzene 75 NS ND ND ND ND ND ND ND NS ND NS <0.5 NS <0.5 75 24 c
1400
Benzene ND NS 3.37 ND ND ND ND ND <0.001 <0.001 ND NS <0.5 NS <0.5 100 21 c
11 nc
Chlorobenzene ND NS ND ND ND ND ND ND <0.001 <0.001 ND NS <0.5 NS <0.5 no value 39 nc
Chloroform ND ND ND 17 ND ND ND ND NS <0.001 ND NS <0.5 NS <0.5 700 8 c
61 nc
Ethylbenzene ND NS ND ND ND ND ND ND <0.002 <0.002 ND NS <0.5 NS <0.5 5 1300 nc
Methylene chloride ND NS ND ND 2.1 ND ND ND NS NS ND NS <0.5 NS <0.5 5 215 c
1600 nc
1,1,1,2-Tetrachloroethane ND NS ND ND ND ND ND ND NS NS 4.7 NS NS NS <0.5 no value 21.5 c
180 nc
Tetrachloroethene <0.2 NS ND ND ND ND ND ND <0.001 <0.001 ND NS NS NS <0.5 5 55 c
250 nc
1,1,1-Trichloroethane ND NS ND ND 2.1 ND ND ND <0.001 <0.001 ND NS <0.5 NS <0.5 200 790 nc
1,1,2-Trichloroethane ND NS ND ND ND ND ND ND NS NS 0.6 NS NS NS <0.5 5 10 c
24 nc
Trichloroethene ND NS ND ND ND ND ND ND <0.001 <0.001 ND NS NS NS <0.5 5 80 c
35 nc
Key:
Source: Kelly AFB no date.
ND= not detected
NS = not sampled
OEHL= Occupational Environmental Health Laboratory U.S. Air Force
µg/L = Micrograms per liter
LTHA = U.S. EPA lifetime health advisory for drinking water
RBC= risk based concentration
TDH= Texas Department of Health
TNRCC = (Texas Natural Resources and Conservation Commission)
TWC = Texas Water Commission
* = Organization collecting and analyzing sample not reported (Gargiulo 1998).
IRP = Installation Restoration Program
SDWA = Safe Drinking Water Act


Table 6. Production/drinking Water Well Monitoring Data (1983 -1995), Volatile Organic Compound Concentration (µg/L) for Well 1044, Kelly Air Force Base.

Chemical Organization Collecting and Analyzing Sample with Month and Year of Sample  
Sampling as part of the SDWA Sampling as part of the IRP program Sampling as part of the SDWA
OEHL
11/83
Radian
1/86
OEHL
1/86
OEHL
3/86
OEHL
3/86
(split)
OEHL
4/86
OEHL
5/86
TDH 7/88 TDH
12/93
TDH
3/94
TDH 7/94 LCRA
8/95
LCRA
11/95
EPA MCL or LTHA
(µg/L)
EPA RBCs
(6 Years of Exposure at 1/100,000)
(µg/L)
1,2-Dichloroethane <0.3 ND 36 2.3 ND ND ND <1.0 NS <0.5 <0.5 <0.5 <0.5 5 6 c
17 nc
1,3-Dichlorobenzene ND ND 305 ND ND ND ND <1.0 NS <1.0 <1.0 <0/5 <0.5 600 LTHA 17 nc
1,4-Dichlorobenzene ND ND 149 ND ND ND ND <1.0 NS <0.5 <0.5 <0.5 <0.5 75 24 c
1400
Chlorobenzene ND ND 435 ND ND ND ND <0.1 NS <0.5 <0.5 <0.5 <0.5 100 21 c
11 nc
2-Chloroethylvinyl ether 0.3 ND ND ND ND ND ND NS NS NS NS NS NS 3540* no value
Chloroform ND ND 6.7 1 trace ND ND <0.1 NS 0.5 <0.5 <0.5 <0.5 700 8 c
61 nc
Ethylbenzene ND ND 39 ND ND ND ND <2.0 NS <0.5 <0.5 <0.5 <0.5 5 1300 nc
Methylene chloride ND ND 3.8 1.1 ND ND ND NS NS <0.5 <0.5 <0.5 <0.5 5 215 c
1600 nc
Tetrachloroethene ND ND 0.2 ND ND ND ND <0.1 <0.1 <0.5 <0.5 <0.5 <0.5 5 55 c
250 nc
1,1,1-Trichloroethane ND NS ND ND 2.1 ND ND <1.0 NS <0.5 <0.5 <0.5 <0.5 200 790 nc
Trichloroethene ND ND 2.2 ND ND ND ND <0.1 <0.1 <0.5 <0.5 <0.5 <0.5 5 80 c
35 nc
Key:
Source: Kelly AFB no date.
ND= not detected
NS = not sampled
OEHL= Occupational Environmental Health Laboratory
µg/L = micrograms per liter
SDWA = Safe Drinking Water Act
TDH= Texas Department of Health
TNRCC = (Texas Natural Resources and Conservation Commission)
TWC = Texas Water Commission
IRP = Installation Restoration Program
* = No human health based screening levels were available for 2-chloroethylvinyl ether. This value is the surface water screening values derived by U.S. EPA Region 4 Water Management Division. These values were obtained from Water Quality Criteria documents and represent the chronic ambient water quality criteria values for the protection of aquatic life.


Table 7. Selected history of Wells 313 and 314, Kelly Air Force Base.

Date Well Event
11/83 313 and 314 Kelly Air Force Base (KAFB) sampled Wells 313 and 314 and analyze them for VOCs for the first time. No contaminants were measured above detection limits.
4/85 313 and 314 KAFB sampled Wells 313 and 314 for selected compounds; no contaminants were measured above detection limits.
1/22/86 313 and 314 KAFB sampled Wells 313 and 314. Samples are analyzed by the Air Force's Occupational Environmental Health Laboratory and Radian Corporation under contract to the Air Force. Several compounds are detected but are not above MCLs.
3/11/86 313 and 314 KAFB sampled Wells 313 and 314. Samples are split and both samples are analyzed by the Air Force's Occupational Environmental Health Laboratory. Several compounds are detected but are not above MCLs.
4/16/86 313 and 314 KAFB conducted routine sampling in accordance with the EPA Safe Drinking Water Act (SDWA); no contaminants were detected above detection levels except for tetrachloroethene in Well 313 at at 0.12µg/L.
5/15/86 313 and 314 KAFB sampled Wells 313 and 314; no contaminants were detected above detection levels.
07/07/88 313 and 314 TDH conducted sampling. In the sample from Well 314, no contaminants are measured above detection limits. In the sample from Well 313, 5.5 µg/L of tetrachloroethene (PCE) is detected, which exceeds the MCL. During the month of July, this well contributes less than 30 percent of the total water distributed by the base water distribution system.
08/11/88 313 and 314 KAFB sampled the two wells. PCE was not measured above the detection limit (<0.1 µg/L).
09/23/88 313 and 314 TDH conducted confirmation sampling of the two wells, and no contaminants were measured above detection limits. No corrective action was required under the SDWA.
01/31/89 313 KAFB took Well 313 out of service to repair the pump; use of the well was never resumed.
06/23/89 313 In response to the sound of running water in the well casing on 6/22/89, a TV study was conducted and revealed a 12" diameter horizontal pipe about 30 feet deep running into the well's casing at 31 feet below ground level. The pipe was formerly used to convey water under artesian pressure from the well to a distribution system located between Wells 313 and 314; during the 1970s, pumps were installed in the two wells, and the distribution system was shut down and associated pipes reportedly capped.

A sample of the water running from this pipe was collected; results revealed that it contains 52 µg/L of PCE. However, this concentration is not considered precise because of the way the instruments used were calibrated. Levels of other chlorinated solvents were not measured in the sample. Metal levels were below detection limits. No information about how long the pipe has been present or how it was used is available.

06/26/89 313 KAFB has a three-foot plug placed in front of the horizontal pipe to prevent water in the pipe from entering the production well.
07/14/89 314 KAFB sampled Well 314 for parameters that include VOCs, and no contaminants were measured above detection limits.
07/17/89 313 An additional TV study shows a one-foot gap in the well at a depth of 590 feet.
09/01/89 313 A letter from "MFR" raises questions about the source of contamination in Well 313 and whether contamination might be a problem elsewhere in the base's water supply system.
09/06/89 314 KAFB samples Well 314 for metals and related parameters; no constituents were detected at levels of concern.
10/12/89 314 KAFB samples Well 314 for parameters that include VOCs, and no contaminants are measured above detection limits.
10/13/89 313 Fuel contamination was reported in an IRP monitoring well near Well 313.
02/01/90 314 Samples collected from Well 314 do not contain detectable concentrations of any regulated analytes, but certain chlorinated solvents were detected at low levels, below or slightly exceeding ATSDR's most conservative comparison values.
03/06/90 314 a horizontal pipe similar to the one discovered entering Well 313 was reported present in this well. Although no water is observed entering the well from the pipe, it is not known whether this may have occurred in the past.
04/11/90 314 Installation of a patch to prevent water in the horizontal pipe from entering this production well was completed.
03/26/91 313 KAFB concluded that the water in the horizontal pipe was coming from the shallow alluvial aquifer.
06/16/91 313 Well 313 is cemented and permanently sealed.
06/21/98 314 This well is permanently sealed.

Key: KAFB = Kelly Air Force Base; MCL = EPA's maximum contaminant level; SDWA = Safe Drinking Water Act; TDH = Texas Department of Health;


Table 8. Well Production for 1983 and 1984 in 1000 gallons.1

  Well Production in 1983 per 1000 gallons
Well Number 313 141 314 1638 1556 1044 3010 1536
January 3210 27108 42405 0 1272 9055 15639 0
February 1446 28836 38742 0 10776 6600 2952 0
March 692 31455 36969 0 23472 8183 4056 0
April 819 32395 32091 0 22560 12845 14340 0
May 2172 33939 35132 0 16464 12206 22269 0
June 28126 24408 22454 0 22704 11513 17316 0
July 32975 30159 15103 0 23520 12659 18681 0
August 30677 33696 24259 0 27024 13541 16731 0
September 34551 10470 27521 0 23376 12735 24258 0
October 38177 5130 29132 0 16824 13834 20358 0
November 28440 20898 17696 0 16272 4176 19656 0
December 29021 19431 18288 0 17634 264 19278 0

Annual total 230306 297925 339792 0 221898 117611 195534 0
Average per month 19192 24827 28316 0 18492 9801 16294 0
Average gallons per minute 437 565 645 0 421 223 371 0
Ratio 313/314

0.68

             


Well Production in 1984 per 1000 gallons

313
141
314
1638
1556
1044
3010
1536
January 33741 20637 10911 0 16828 1574 7227 11104
February 29452 16838 10068 0 10549 5185 5432 11961
March 34412 27290 17658 0 8120 11570 5685 7478
April 33967 28133 25401 0 8515 13135 9459 8726
May 38015 34398 28465 0 8841 11014 11108 15792
June 38019 36805 32150 0 17003 11551 14908 5696
July 39808 37044 32992 0 11426 14797 33933 0
August 36057 36045 30060 0 13696 14951 18262 17016
September 37247 25723 17527 11760 6660 12482 11054 15875
October 37053 10071 19805 22419 7638 4639 1595 12734
November 33719 0 16343 16416 14072 8333 14615 2613
December 33125 0 25643 11090 11716 3378 8089 15913

Total 424615 272984 267023 61685 135064 112609 141367 124908
Average per month 35385 22749 22252 5140 11255 9384 11781 10409
Average gallons per minute 806 518 507 117 256 214 268 237
Ratio 313/314

1.59

1 ATSDR obtained and reviewed the production well data for years 1983 through 1988. 1983 was the year Kelly AFB began sampling the wells and 1988 is the year that Well 313 was discontinued. The production volumes change from year to year so the calculated concentrations would also change depending on the relative production from Wells 313 and 314. For the calculated concentrations, ATSDR used the values that produced the highest concentrations to be more protective of public health in this evaluation. In these cases, 1983 produced the highest concentrations in the calculations in Appendix C-1 and 1984 produced the highest concentrations in the calculation in Appendix C-2.


Table 9. Pathway Table; Summary of Exposure Pathway Elements.

Situation Name Contaminants Exposure Pathways Elements Dates and Duration of Exposure Comments
Source Environmental Media Point of Exposure Route of Exposure Exposed Population
Exposure to Water from Wells 313 and 314 1,2-dichloroethane,
benzene,
chloroform,
ethylbenzene,
methylene chloride,
1,1,1,2-tetrachloroethane, tetrachloroethene,
1,1,2-trichloroethane, and trichloroethene
Shallow groundwater Water Water taps, faucets, and spigots throughout the base. Ingestion, inhalation, dermal contact A subgroup of civilian and military personnel and families on-base. Population estimates from 1983 to 1990 vary from 23,000 to 29,000 per year. Potential exposed population is estimated at 14,000. Past, maximum estimates are about six years, from late 1983 to early 1990. No Apparent Public Health Hazard


FIGURES

Wells in Bexar County, based on the well inventory from the Texas Water Development Board
Figure 2. Wells in Bexar County, based on the well inventory from the Texas Water Development Board

Drinking water/production wells 313 and 314, monitoring wells, and shallow groundwater information
Figure 3. Drinking water/production wells 313 and 314, monitoring wells, and shallow groundwater information

Simplified schematic of Wells 313 and 314 with horizontal pipe when pumps were located out of the wells
Figure 4. Simplified schematic of Wells 313 and 314 with horizontal pipe when pumps were located out of the wells

Simplified schematic of Wells 313 and 314 with horizontal pipe after pumps were moved to the wells with no leak in the horizontal pipe
Figure 5. Simplified schematic of Wells 313 and 314 with horizontal pipe after pumps were moved to the wells with no leak in the horizontal pipe

Simplified schematic of Wells 313 and 314 with a leak in the horizontal pipe and relative low water level in the Edwards aquifer
Figure 6. Simplified schematic of Wells 313 and 314 with a leak in the horizontal pipe and relative low water level in the Edwards aquifer

Simplified schematic of Wells 313 and 314 with a relative high water level in the Edwards aquifer
Figure 7. Simplified schematic of Wells 313 and 314 with a relative high water level in the Edwards aquifer

Water level readings from the San Antonio Water System Edwards aquifer monitoring well (J17) and private well number 6844214 in relation to the shallow aquifer water levels and the depth of the horizontal pipe
Figure 8. Water level readings from the San Antonio Water System Edwards aquifer monitoring well (J17) and private well number 6844214 in relation to the shallow aquifer water levels and the depth of the horizontal pipe


APPENDIX A: SCREENING VALUES

Screening values were obtained from U.S. EPA Region 6 (http://www.epa.gov/region06/6pd/rcra_c/pd-n/screen.htm) and modified to site-specific exposure conditions and risk levels. Only cancer screening values were modified. EPA Region 6 cancer screening values are based on 30 years exposure as an adult and a target risk of 1/1,000,000. ATSDR modified the cancer screening values to 6 years and target risk of 1/100,000 by multiplying the screening values by 50; 5 for the conversion from 30 to 6 years and 10 for the conversion from 1/1,000,000 to 1/100,000. The 6 years is based on the 6 years of exposure discussed in the Data Evaluation and Interpretation Section of this consultation. Because the U.S. EPA Region 6 cancer screening values were based on 6 years as a child and 24 years as an adult, the conversion includes child and adult exposures. The conversion from 1/1,000,000 to 1/100,000 is based on the following ATSDR cancer risk categories in which 1/100,000 is considered no apparent increased risk of cancer as shown below.

Category Definitions of Cancer Risk

Category Fraction Decimal Exponential
No Increased Risk <1/100,000 <0.00001 <1E-05
No Apparent Increased Risk 1/100,000 0.00001 1E-05
Low Increased Risk 1/10,000 0.0001 1E-04
Moderate Increased Risk 1/1,000 0.001 1E-03
High Increased Risk 1/100 0.01 1E-02
Very High Increased Risk >1/100 >0.01 >1E-02
Note: Category definitions used by ATSDR are intended to define categories of estimated risk to convey the degree of hazard from the defined exposure relative to other exposures. Categories are derived from ATSDR Decision Statement TOX.14. Draft QAA-27. Revised October 21, 1991.


APPENDIX B: WELL 1044

Well 1044 exceeded MCLs one time in January 1986. A second sample collected in January 1986 and subsequent samples collected in March and April of 1986 from this well did not exceed the MCL. In five subsequent samples from the well, collected July 1988 through November 1995, volatile organic compounds were not detected (See Table 6).

Kelly AFB investigated the inconsistency of the sampling results from Well 1044 and other wells sampled in 1986. They concluded that the following errors occurred in the sampling protocol:

  • The same sampling collection equipment was used for IRP monitoring well samples and drinking water well samples.
  • Cleaning of sample collection equipment between IRP monitoring wells and drinking water well samples identified was inadequate.
  • Samples collected from the IRP monitoring wells were switched with drinking water samples (Gargiulo 1998).

Because the levels exceeding the MCLs only occurred once and may have been erroneous, ATSDR considered the January 1986 samples not to be representative of the water in the well and not a health hazard.


APPENDIX C: CALCULATIONS

Appendix C-1. Calculation of concentration in water combined from Wells 313 and 314 using 1984 production data because it provides the highest concentrations for this calculation.

Chloroform

806 gpm (12 µg/L) + 507 gpm (1* µg/L) = 7.8 µg/L
    806 gpm + 507 gpm

1,2-Dichloroethane

806 gpm (43 µg/L) + 507 gpm (1* µg/L) = 26.8 µg/L
    806 gpm + 507 gpm

Tetrachloroethene

806 gpm (5.5 µg/L) + 507 gpm (1* µg/L) = 3.8 µg/L
    806 gpm + 507 gpm

* When not reported, 1 µg/L is assumed to be the detection limit.

Appendix C-2. Calculation of concentration of well water with shallow aquifer water at 100 µg/L and 10 µg/L flowing into the well at 10 gpm and 50 gpm, using 1983 production data because it provides the highest concentrations for this calculation.

• Water from Well 313 combining with water from the shallow aquifer at 10 gpm

(1 µg/L x (437 gpm-10 gpm)) + (100 µg/L x 10 gpm) = 3.26 µg/L tetrachloroethene
            437 gpm

(1 µg/L x (437 gpm-10 gpm)) + (10 µg/L x 10 gpm) = 1.21 µg/L trichloroethene
            437 gpm

• Combining with Well 314

437 gpm (3.26 µg/L) + 645 gpm (1 µg/L) = 1.92 µg/L tetrachloroethene
       437 gpm + 645 gpm

437 gpm (1.21 µg/L) + 645 gpm (1 µg/L) = 1.19 µg/L trichloroethene
       437 gpm + 645 gpm

• Water from Well 313 combining with water from the shallow aquifer at 50 gpm

(1 µg/L * (437 gpm-50 gpm)) + (100 µg/L * 50 gpm) = 12.3 µg/L

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