6


Groundwater


I. BACKGROUND   §6.1

II. HYDROGEOLOGIC CHARACTERIZATION   §6.2

A. Hydrogeologic Units   §6.3

B. Groundwater Flow   §6.4

Figure 6-1: Groundwater Piezometric Map

C. Groundwater Fluctuations   §6.5

Figure 6-2: Groundwater Fluctuation in Monitoring Well MW53-93-16-69 Versus Rainfall   

D. Groundwater Quality   §6.6

Table 6-1: Long-Term Average Mineral Concentrations in Different Formations

III. GROUNDWATER MONITORING RESULTS   §6.7

Figure 6-3: Approximate Locations of Monitoring Wells Closest to Berkeley Lab Property Line

Table 6-2: Metals Detected in Groundwater Samples from Monitoring Wells

Table 6-3: VOCs Detected in Groundwater Samples from Monitoring Wells

Table 6-4: Tritium Detected in Groundwater Samples from Monitoring Wells

IV. GROUNDWATER CONTAMINATION PLUMES   §6.8

Figure 6-4: Groundwater Contamination Plumes (December 1998)

A. VOC Plumes   §6.9

Figure 6-5: Groundwater Contamination (Total Halogenated Hydrocarbons
                    in
mg/L) in Old Town Area (December 1998)

Figure 6-6: Groundwater Contamination (Total Halogenated Hydrocarbons
                    in
mg/L) at Building 51/64 VOC Plume (December 1998)

B. Freon Plume   §6.10

C. Tritium Plume   §6.11

D. Petroleum Hydrocarbon Plumes   §6.12

Figure 6-7: Approximate Locations of Monitoring Wells Associated with
                    Underground Storage Tanks

Table 6-5: Total Petroleum Hydrocarbon Concentrations at UST Sites

V. INTERIM CORRECTIVE MEASURES   §6.13

A. Source Removal or Control   §6.14

B. Preventing Discharge of Contamination to Surface Waters   §6.15

C. Preventing Further Migration of Contaminated Groundwater   §6.16

D. Treatment Systems   §6.17

Table 6-6: Treatment of Contaminated Groundwater



§6.1      I. BACKGROUND

This section reviews the groundwater monitoring program at Berkeley Lab, emphasizing the 1998 results. Additional details on the program can be obtained in the Environmental Restoration Program (ERP) quarterly progress reports, which contain all the groundwater monitoring data, site maps showing monitoring well locations and contaminant concentrations, and graphs showing changes in contaminant concentrations over time. The quarterly progress reports are available for public review at the UC Berkeley campus Doe Library.

The Berkeley Lab groundwater monitoring program was started in 1991 to:

The Groundwater Protection Management Program Plan1 established the program to accomplish these objectives by providing a framework for preventing future groundwater contamination and for remediating existing contamination at the site. The Laboratory has installed an extensive system of wells to monitor groundwater quality. Four categories of contaminants are monitored under the program: volatile organic compounds (VOCs), hydrocarbons, metals, and tritium. Selected wells are also sampled for other potential contaminants.

Under the RCRA Corrective Action Program,2 the Laboratory identifies areas of soil and groundwater contamination that may have resulted from past releases of contaminants to the environment. It then determines the sources and extent of the contamination and develops and implements remediation plans.

Activities are closely coordinated with the regulatory oversight agencies, including the Cal/EPA Department of Toxic Substances Control, San Francisco Bay Regional Water Quality Control Board, City of Berkeley, and the Department of Energy. These agencies review and comment on the work plans prepared for all activities. Berkeley Lab submits quarterly progress reports to these agencies and meets with them each quarter to review results of the previous quarter’s activities.

Results in this chapter are compared against drinking water standards. Such a comparison should be interpreted with caution because the groundwater at the Berkeley Lab site is not used for human consumption.

§6.2      II. HYDROGEOLOGIC CHARACTERIZATION

Sections 6.3, 6.4, 6.5, and 6.6 discuss the hydrogeological setting of Berkeley Lab, including a review of the hydrogeologic units, a discussion of groundwater flow, and a description of the hydrologic properties of the shallow water-bearing zones. For more detailed information on hydrogeology, see the 1994 Berkeley Lab RCRA Facility Investigation Progress Report.3

§6.3      A. Hydrogeologic Units

Moraga Formation volcanic rocks, Orinda Formation sediments, and Great Valley Group sediments constitute the major rock units at the site. The structural geology and the physical characteristics of these three units are the principal hydrogeologic factors controlling the movement of groundwater and groundwater contaminants at the Laboratory. Two additional units, the Claremont Formation and the San Pablo Group, have a limited presence in the easternmost area of the Laboratory.

§6.4      B. Groundwater Flow

Depth to water is measured monthly in all site monitoring wells. The depth to groundwater ranges from approximately 0 to 30 meters (0 to 98 feet). A groundwater piezometric map indicating the hydraulic head distribution at Berkeley Lab, based on water levels measured in wells, is given in Figure 6-1. This map indicates that the direction of groundwater flow generally follows the topography.


Figure 6-1      Groundwater Piezometric Map


In the western part of Berkeley Lab, groundwater generally flows toward the west; in the rest of the Laboratory, groundwater generally flows toward the south. In some areas, groundwater flow directions show local deviations from the general trends shown on the piezometric map because of the subsurface geometry of geologic units and the contrasting hydrogeologic properties across geologic contacts. The velocity of the groundwater varies from approximately 0.001 meters per year (0.003 feet per year) to about 10 meters per day (33 feet per day).

§6.5      C. Groundwater Fluctuations

Fluctuations in measured groundwater levels in wells generally show a good correlation with rainfall, as shown in Figure 6-2. Generally, there is a fairly rapid response (on the order of days) of water levels in most site wells after rainfall occurs. Fluctuations as great as 4.2 meters (14 feet) are common in wells in the Old Town area.


Figure 6-2      Groundwater Fluctuation in Monitoring Well MW53-93-16-69 Versus Rainfall



§6.6      D. Groundwater Quality

Groundwater samples from monitoring wells are tested for total dissolved solids (TDS), cations, and anions. The TDS concentrations measured in groundwater monitoring wells range from 105 to 4,460 mg/L. Average mineral concentrations for the three primary geologic units are listed in Table 6-1.

Table 6-1      Long-Term Average Mineral Concentrations in Different Formations

   

Average concentration (mg/L)


Parameter

Drinking water standard (mg/L)

Orinda Formation

Moraga Formation

Great Valley Formation

Total dissolved solids

500a

921

485

712

Nitrate

45

24

14

2.4

Sulfate

500

140

30

173

Chloride

250a

118

31

49

Bicarbonate

b

510

413

419

Potassium

b

4.2

2.2

4.6

Sodium

b

279

61

119

Magnesium

b

19

32

33

Calcium

b

33

69

76

pH

6.5-8.5 pH units

8.1 pH units

7.6 pH units

7.7 pH units

a Indicates secondary standard (aesthetic standard).
b No drinking water standard exists for substance.

§6.7      III. GROUNDWATER MONITORING RESULTS

In 1998, 20 new monitoring wells were installed, bringing the total in the program to 174 wells. Twenty monitoring wells are located close to the site boundary, and one well is located downgradient from the Laboratory (see Figure 6-3).



Figure 6-3      Approximate Locations of Monitoring Wells Closest to Berkeley Lab Property Line


Tables 6-2, 6-3, and 6-4 summarize groundwater monitoring results for 1998. Tables 6-2 and 6-3 summarize the metals results and VOC results, respectively. The tables show the drinking water standard (maximum contaminant level or MCL) for the analyte,4 the number of monitoring wells sampled, the number of monitoring wells in which the analyte was detected, and the ranges in concentrations detected. Table 6-4 presents tritium results.

Table 6-2      Metals Detecteda in Groundwater Samples from Monitoring Wells




Metal


Number of
wells
sampled



Number of
samples


Number of
wells analyte
detected


Range of
concentrations
(µg/L)

Drinking water
standard (µg/L)

Antimony

53

55

2

1 – 1.1

6

Arsenic

69

71

49

2.1 – 82.6

50

Barium

51

53

38

6.2 – 442

1,000

Beryllium

51

53

1

1.3

4

Chromium

53

55

27

1.2 – 32.2

50

Cobalt

51

53

9

1 – 4.5

NSb

Copper

51

53

26

1 – 28

1,000c

Lead

51

53

1

3.2 – 9.2

15d

Mercury

53

55

1

2.3

2

Molybdenum

59

61

32

1.1 – 404

NSb

Nickel

51

53

12

1.5 – 25.9

100

Selenium

51

53

19

2.6 – 160

50

Thallium

51

53

1

1.5

2

Vanadium

52

54

35

1 – 66.4

NSb

Zinc

51

53

21

5.5 – 50

5,000c

a Metals not detected in any samples include cadmium and silver.
b NS = Not specified
c Secondary MCL
d Action level


Table 6-3      VOCs Detected in Groundwater Samples from Monitoring Wellsa

Analytes detected

Number of
wells analyte detected


Range of
concentrations
(µg/L)

Drinking water
standard (µg/L)

Aromatic or nonhalogenated hydrocarbons

Benzene

2

1.5 - 43.5

1

Bis(2-ethylhexyl)phthalate

1

18

NSb

sec-Butylbenzene

1

3.2

NSb

1,2-Dichlorobenzene

1

0.59

NSb

1,4-Dichlorobenzene

2

0.6 - 0.83

NSb

p-Isopropyltoluene

2

1.1 - 2.8

NSb

Toluene

5

0.58 - 2

150

1,2,4-Trimethylbenzene

1

1.2

NSb

1,3,5-Trimethylbenzene

1

1.1

NSb

Halogenated hydrocarbons

     

Bromoform

2

0.64 - 1.3

NSb

Carbon tetrachloride

21

0.87 - 2,400

0.5

Chloroethane

1

0.97

NSb

Chloroform

42

0.51 - 256

100

1,1-Dichloroethane

30

0.52 - 9,110

5

1,2-Dichloroethane

4

1.4 - 56.3

0.5

1,1-Dichloroethene

39

0.55 - 2,780

6

cis-1,2-Dichloroethene

53

0.54 - 1,200

6

trans-1,2-Dichloroethene

12

1 - 64.7

10

Dichlorodifluoromethane (Freon-12)

1

0.64

NSb

1,2-Dichlorotrifluoroethane(Freon-123A)

5

1.1 - 3.4

NSb

Methylene chloride

1

120

5

Methyl tert-butyl ether

1

0.62

NSb

1,1,1,2-Tetrachloroethane

2

13 - 19

NSb

1,1,2,2-Tetrachloroethane

1

0.59

1

Tetrachloroethene

54

0.51 - 54,900

5

1,1,1-Trichloroethane

18

0.53 - 24,000

200

1,1,2-Trichloroethane

3

0.64 - 7.1

5

Trichloroethene

78

1 - 43,600

5

Trichlorofluoromethane (Freon-11)

2

0.97 - 3.5

150

1,1,2-Trichlorotrifluoroethane (Freon 113)

9

0.51 - 43.5

1,200

Vinyl chloride

14

0.87 - 104

0.5

a 475 samples taken from 165 wells during the year, except for Bis(2-ethylhexyl)phthalate (1 sample), Freon-123A (416 samples from 133 wells), and Methyl tert-butyl ether (427 samples from 149 wells).
b NS = Not specified


 

 

Table 6-4      Tritium Detecteda,b in Groundwater Samples from Monitoring Wells

 

Well number

January–March
(Bq/L)

April–June
(Bq/L)

July–September
(Bq/L)

October–December
(Bq/L)

MW91-4

33

NSc

27

NSc

MW91-5

252

NSc

50

NSc

MW91-6

208

NSc

68

NSc

75-92-23

142

NSc

37

NSc

75B-92-24

124

NSc

188

NSc

75-97-5

NSc

NSc

536, 455d

807, 999, 1,043d

75-97-7

46

22

22

50

69-97-8

<11

NSc

<11, <11d

17, <11

69-97-21

42, 70

20, 19

14

16, 18d

75-98-14

NSc

NSc

NSc

24

MW76-1

<11

NSc

12

NSc

76-93-6

67

NSc

58

NSc

76-93-7

<11

NSc

<11

20, <11

78-97-20

232

129

81

133

MW91-2

21

NSc

30

NSc

77-94-6

572

293

202

370, 433d

77-97-9

443

432

241

356

77-97-11

275

81

98, 102d

179, 208d

31-97-17

47

55

33

43

MWP-7

<11

<11

<11

26, <11

a Wells without detectable results in all quarters of sampling include MW90-3, 46A-92-15, 71-93-1, 71-95-1, 69A-92-22, 75-96-20, 75-97-6, 75-98-15, 76-92-25, MW91-1, MWP-9, MWP-10, 77-92-10, 61-92-12, 77-93-8, 77-94-5, 31-97-18, 31-98-17, MWP-2, OW3-225, MWP-8, 52-94-10, 52-95-2, 74-94-7, 62-92-26, 62-92-27, MWP-1, MWP-4, MWP-5, MWP-6, 37-92-6, and CD-92-28.
b For comparison, the drinking water standard determined by California Department of Health Services is 740 Bq/L (20,000 pCi/L).
c NS = Not sampled
d Duplicate sample


§6.8      IV. GROUNDWATER CONTAMINATION PLUMES

Based on groundwater monitoring results, eight principal groundwater contamination plumes have been identified on site. The plumes are listed below, and the locations are shown in Figure 6-4:

Contamination was also detected in groundwater in other areas of the site in 1998. Based on current information, however, the extent of contamination in these areas is limited.


Figure 6-4      Groundwater Contamination Plumes (December 1998)


§6.9      A. VOC Plumes

Covering the area of Buildings 7, 53, 27, and 58A and the slope west of Building 53, the Old Town VOC plume is the most extensive plume at Berkeley Lab. This plume is defined by the presence of tetrachloroethene (PCE), trichloroethene (TCE), and lower concentrations of other halogenated hydrocarbons, including 1,1-dichloroethene (1,1-DCE), cis-1,2-DCE, 1,1-dichloroethane (1,1-DCA), 1,2-DCA, 1,1,1-trichloroethane (1,1,1-TCA), 1,1,2-TCA, carbon tetrachloride, and vinyl chloride, several of which are products of PCE and TCE degradation. The maximum concentration of total halogenated hydrocarbons detected in 1998 in groundwater samples collected from wells monitoring the Old Town VOC plume was 97,800 µg/L, which primarily consisted of PCE (54,900 µg/L), TCE (39,700 µg/L), and carbon tetrachloride (2,400 µg/L). Figure 6-5 shows the areal extent of VOCs in groundwater in the Old Town area.


Figure 6-5      Groundwater Contamination (Total Halogenated Hydrocarbons
in µg/L) in Old Town Area (December 1998)


The presence of the maximum VOC concentrations north of Building 7 suggests that the primary source of the Old Town VOC plume was apparently an abandoned sump located between Buildings 7 and 7B. The sump was discovered and its contents removed in 1992. The sump was removed in 1995 after underground utility lines that crossed the sump were relocated. Other less significant source areas for groundwater contamination are indicated by relatively high concentrations of halogenated hydrocarbons detected in groundwater samples from monitoring wells west of Building 16, east of Building 52, and west of Building 25A. The sources of the contamination detected in those wells have not been identified. The contaminated groundwater from these sources flows westward, where it intermixes with the main Old Town plume.

Four interim corrective measures (ICMs) have been instituted to manage the Old Town VOC Plume (see §6.13):

A second plume of VOC-contaminated groundwater, the Building 51/64 VOC Plume, extends from the southeast corner of Building 64, under Buildings 64 and 51B. This plume is defined by the presence of 1,1,1-TCA, 1,1-DCA, 1,1-DCE, PCE, TCE, and lower concentrations of other halogenated hydrocarbons. Halogenated hydrocarbons were detected in 1998 at a maximum total concentration of 822,400 g/L in a water sample from a boring in the source area of the plume. The maximum concentration of total halogenated hydrocarbons detected in 1998 in samples collected from groundwater monitoring wells in the Building 51/64 area was 41,200 µg/L. The contaminants primarily consisted of 1,1,1-TCA (24,000 µg/L) and 1,1-DCA (9,100 µg/L). Figure 6-6 shows the areal extent of VOCs in groundwater in the Building 51/64 area.

Other VOC plumes have been identified south of Building 71 (Building 71 VOC plume) and east of Building 37 (Building 37 VOC plume). These plumes cover less area than the Old Town plume, and fewer contaminants have been detected. The sources of these contaminant plumes are not known.


Figure 6-6      Groundwater Contamination (Total Halogenated Hydrocarbons in µg/L)
at Building 51/64 VOC Plume (December 1998)


The Building 71 VOC plume is defined by the presence of halogenated hydrocarbons, predominantly PCE, TCE, cis-1,2-DCE, 1,1-DCA, 1,1,1-TCA, and vinyl chloride. The maximum concentration of total halogenated hydrocarbons detected in wells monitoring the plume, 262 µg/L, was detected in a monitoring well installed southwest of Building 71B to help locate the source of the plume. Contaminated groundwater from the plume is discharged continuously through five subhorizontal drains (hydraugers). Effluent from these hydraugers is collected and treated before being released under permit to the sanitary sewer.

The Building 37 VOC plume is defined by the presence of halogenated hydrocarbons, primarily PCE and TCE in monitoring wells MWP-7 and MW37-92-6. There has been a decreasing trend in VOC concentrations detected in these two wells since January 1994, when pumping groundwater for plume management was initiated. The maximum concentration of total halogenated hydrocarbons detected in wells monitoring the plume in 1998 was 8.9 µg/L.

§6.10      B. Freon Plume

High concentrations of freon-113 were detected in groundwater south of Building 71 in 1993 and 1994. The source of freon-113 was most likely past spills from the Linear Accelerator Cooling Unit located in Building 71. The cooling unit is no longer operational. Concentrations of freon-113 have decreased from 8,984 µg/L in 1994 to 43.5 µg/L in June 1998. The MCL for freon-113 is 1,200 µg/L. Contaminated groundwater from the plume is continuously discharged through two hydraugers. Effluent from these hydraugers is collected and treated before being released under permit to the sanitary sewer.

§6.11      C. Tritium Plume

The tritium plume covers the areas of Buildings 31, 75, 76, 77, and 78. The source of the tritium is the National Tritium Labeling Facility at Building 75. The maximum concentration of tritium detected in monitoring wells in 1998 was 1,043 Bq/L (28,200 pCi/L), which is above the drinking water standard of 740 Bq/L (20,000 pCi/L).5 Tritium has been detected above the drinking water standard in only one monitoring well.

§6.12      D. Petroleum Hydrocarbon Plumes

Monitoring wells have been installed at or downgradient from two abandoned and seven removed underground fuel storage tanks (USTs). Figure 6-7 shows the approximate locations of these wells. The maximum concentrations of total petroleum hydrocarbons (TPH) detected at these sites in 1998 are listed in Table 6-5.


Figure 6-7      Approximate Locations of Monitoring Wells Associated with Underground Storage Tanks


Table 6-5      Total Petroleum Hydrocarbon Concentrations at UST Sites


UST location


Status

Present or previous contents

Maximum
concentration (µg/L)

Building 51

Removed

Diesel

NDa

Building 70A

Removed

Diesel

NDa

Building 62

Removed

Diesel

NDa

Building 74

Removed

Diesel

TPH-Db = 840

Building 76

Removed

Diesel

TPH-Db = 440

Building 76

Removed

Gasoline

TPH-Gc = 75

Building 7E

Removed

Kerosene

TPH-Db = 63,000e

Building 88

Abandoned

Diesel

ND

Building 46A

Abandoned

Gasoline

NSd

a ND = Not detected
b TPH-D = TPH quantified as diesel range hydrocarbons
c TPH-G = TPH quantified as gasoline range hydrocarbons
d NS = Not sampled
e Sample collected during groundwater extraction for interim corrective measure


The only UST site where aromatic hydrocarbons were detected was the Building 7E former kerosene tank. The plume (Building 7 Diesel Plume) is located north of Building 6. No BTEX components (i.e., benzene, toluene, ethyl benzene, xylenes) were detected at UST sites. A dual phase (groundwater and soil vapor) extraction and treatment system was installed at the location of the Building 7E former UST as an interim corrective measure.

Methyl tertiary butyl ether (MTBE) was detected in one monitoring well at a concentration of 0.62 µg/L. The US/EPA Drinking Water Advisory for MTBE is 20 to 40 g/L.

§6.13      V. INTERIM CORRECTIVE MEASURES

Interim corrective measures are used to remediate contaminated media or prevent movement of contamination, where the presence or movement of contamination poses a threat to human health or the environment. Throughout the RCRA corrective action process, Berkeley Lab has conducted the following interim corrective measures in consultation with regulatory agencies:

§6.14      A. Source Removal or Control

The need for interim corrective measures is evaluated if (1) the contaminant concentrations pose a potential threat to human health or the environment or (2) leaching of contaminants from soil may affect groundwater. Several sources of contamination have been removed at the Laboratory, including the following in 1998:

§6.15      B. Preventing Discharge of Contamination to Surface Waters

Slope stability is a concern at Berkeley Lab because of the geology and topography of the site. Free-flowing hydraugers were installed in the past to dewater and stabilize areas of potential landslides. Effluent from these hydraugers generally enters the creeks. Some of the hydraugers intercept contaminated groundwater. To prevent the discharge of the contaminated groundwater to the creeks, Berkeley Lab installed a system to collect and treat the hydrauger effluent where the water was contaminated with VOCs.

§6.16      C. Preventing Further Migration of Contaminated Groundwater

As interim corrective measures to control groundwater plumes that could migrate off site or contaminate surface water, Berkeley Lab is capturing and treating contaminated groundwater using extraction wells and subdrains. In addition, two groundwater collection trenches were constructed to prevent further migration of the Old Town plume. The first trench was installed west of Building 53 and the second at the base of the slope west of Building 58.

§6.17      D. Treatment Systems

As described above, Berkeley Lab is using extraction wells and subdrains to control groundwater plumes that could migrate off site or contaminate surface water. Seven granular-activated carbon treatment systems have been installed. The treated water is recycled for industrial use on site, released to the sanitary sewer in accordance with Berkeley Lab’s treated groundwater discharge permit from EBMUD,6 or recirculated to flush contaminants from the subsurface. Table 6-6 lists both the volume of contaminated groundwater treated by each system in 1998 and the total volume treated since the treatment systems were first placed in operation.

Table 6-6      Treatment of Contaminated Groundwater

 



Source of contamination



Treatment system

Volume of water treated in 1998 (liters)*

Total volume treated
(liters)

  

Building 37 VOC plume

Building 37

975,247

3,284,509

  

Old Town VOC plume

Building 46

5,613,515

22,090,354

  

Building 71 VOC plume and
water collected from purging
monitoring wells

Building 51 firetrail

566,861

892,700

  

VOC-contaminated hydrauger
effluent

Building 51 hydraugers

4,002,021

32,396,875

  

Building 51 subdrain system

Building 51 sump

1,682,917

3,247,030

  

Old Town VOC plume

Building 7 trench

2,482,343

3,512,703

  

Building 6 former underground
storage tank

Building 6 bioventing

400,033

400,033

  

Total volume treated

15,722,935

65,824,204

  

*1 liter = 0.264 gallons