IV. GROUNDWATER CONTAMINATION PLUMES   §6.6

§6.1      I. BACKGROUND

This chapter reviews the groundwater monitoring program at Berkeley Lab, emphasizing the 1999 results. Additional details on the program can be obtained in the Environmental Restoration Program 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. These reports are available for public review at the UC Berkeley Doe Library.

Berkeley Lab’s groundwater monitoring program was started in 1991 to:

• Characterize the magnitude and extent of groundwater contamination;
• Evaluate the potential for future contaminant migration;
  
• Monitor groundwater quality near the site perimeter; and
  
• Monitor groundwater quality near existing and removed hazardous materials or hazardous waste storage units, including underground storage tanks.

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 Resource Conservation and Recovery Act of 1976 (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 DOE. 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 quarterly 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.

              II. HYDROGEOLOGIC CHARACTERIZATION

§6.2       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 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.

§6.3      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).

§6.4      C. 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.

§6.5      III. GROUNDWATER MONITORING RESULTS

In 1999, eight new monitoring wells were installed, bringing the total in the program to 182 wells. Twenty monitoring wells are located close to the site boundary, and one well is located downgradient from the Laboratory (see Figure 6-2).

Figure 6-2      Approximate Locations of Monitoring Wells Closest to
Berkeley Lab Property Line

Table 6-1, Table 6-2, and Table 6-3 summarize groundwater monitoring results for 1999. Table 6-1 and Table 6-2 summarize the metals results and VOC results, respectively. The tables show the drinking water standard (maximum contaminant level or MCL) for the analyte,³ the number of monitoring wells sampled, the number of monitoring wells in which the analyte was detected, and the ranges in concentrations detected. Table 6-3 presents tritium results.

Table 6-1      Metals Detecteda in Groundwater Samples from Monitoring Wells
Metal	Number of wells sampled	Number of samples			Number of wells analyte detected	Range of concentrations (mg/L)		Drinking water standard (mg/L)
Antimony	69		91	9			1–2.5	6
Arsenic	84		106	70			1.6–60.5	50
Barium	67		89	67			5.7–927	1000
Beryllium	67		89	0				4
Cadmium	67		89	0				5
Chromium	70		92	53			1–35.5	50
Hexavalent Chromium	1		1	0
Cobalt	67		89	24			1–31.3	NSb
Copper	67		89	49			1–26	1000c
Lead	67		89	6			1.2–2.1	15d
Mercury	69		91	1			0.27	2
Molybdenum	75		97	68			1–430	NSb
Nickel	68		90	56			1–18.2	100
Selenium	68		90	17			2.1–93	50
Silver	67		89	0				100c
Thallium	67		89	0				2
Vanadium	68		90	57			1–65.4	NSb
Zinc	67		89	33			5.1–60.3	5000c
a Metals not detected in any samples are beryllium, cadmium, hexavalent chromium, silver, and thallium. b NS = Not specified c Secondary MCL d Action level

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Table 6-2      VOCs Detected in Groundwater Samples from Monitoring Wellsa
Analytes detected			Number of wells analyte detected	Range of concentrations (mg/L)	Drinking water standard (mg/L)
Aromatic or nonhalogenated hydrocarbons
Benzene			2	0.83–36.2	1
Methyl tert-butyl ether			1	1.3	NSb
sec-Butylbenzene			1	3.7	NSb
p-Isopropyltoluene			2	0.93–5	NSb
1,4-Dichlorobenzene			1	0.51–0.89	NSb
Toluene			5	0.54–4.9	150
Xylenes, total			1	2.4	1,750
Halogenated hydrocarbons
Bromoform			1	2	NSb
Carbon tetrachloride			20	0.79–1,800	0.5
Chloroform			49	0.78–149	100
Dibromochloromethane			1	0.58	NSb
Dichlorodifluoromethane (freon 12)			1	0.6	NSb
Dichlorotrifluoroethane (freon 123)			2	1.9–3.5	NSb
1,2-Dichlorotrifluoroethane (freon-123A)			7	1.1–3.2	NSb
1,1-Dichloroethane			33	0.5–16,900	5
1,2-Dichloroethane			3	0.5–45	0.5
1,1-Dichloroethene			44	0.55–8,680	6
cis-1,2-Dichloroethene			59	0.52–1,200	6
trans-1,2-Dichloroethene			13	0.57–36.9	10
Methylene chloride			5	1.6–210	5
1,1,1,2-Tetrachloroethane			2	18–85	NSb
Tetrachloroethene			56	0.65–38,300	5
1,1,1-Trichloroethane			18	0.54–86,400	200
1,1,2-Trichloroethane			4	0.61–8.2	5
Trichloroethene			80	1–45,000	5
Trichlorofluoromethane (freon 11)			1	2.4	150
1,1,2-Trichlorotrifluoroethane (freon 113)			3	1.1–20.7	1,200
Vinyl chloride			12	1.3–58.1	0.5
a 451 samples taken from 180 wells during the year b NS = Not specified

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Table 6-3      Tritium Detecteda,b in Groundwater Samples from Monitoring Wells
Well number	January–March (Bq/L)c		April–June (Bq/L)	July–September (Bq/L)		October–December (Bq/L)
MW91-4		31	NSd		34	NS
MW91-5		94	NS		82	162
MW91-6		138	NS		118	NS
75-92-23		202	NS		141	NS
75B-92-24		135	NS		188	NS
75-97-5		1166, 982e	925		914, 970f	989, 907e
75-97-7		52	29		NS	NS
69-97-21		24	30		NS	NS
75-98-14		NS	166		162, 152e	113
75-99-7		NS	NS		NS	198, 160e
MW76-1		<11	NS		20	NS
76-93-6		180	NS		163	NS
78-97-20		109	134		NS	NS
76-98-22		<11, 5e	<11		<11	<11
MW91-2		18	NS		24	29
77-94-6		441	394		NS	NS
77-97-9		432	448		NS	NS
77-97-11		229	228		NS	NS
31-97-17		64	45		NS	NS
a Wells without detectable results in all quarters of sampling include 46A-92-15, 71-93-1, MW91-3, 69A-92-22,    75-96-20, 75-97-6, 69-97-8, 75-98-15, 75-99-4, 76-92-25, 76-93-7, 76-98-21, MW91-1, MWP-9, MWP-10, 77-92-10,    61-92-12, 77-93-8, 77-94-5, 31-97-18, 31-98-17, 88-93-11A, MWP-2, OW3-225, MWP-8, 52-94-10, 52-95-2B,    74-94-7, 74-94-8, 62-92-26, 62-92-27, MWP-4, MWP-5, MWP-6, MWP-7, 37-92-6, 37-92-18, 37-92-18A, 37-93-5,    37-94-9, MWP-1, 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 1 Bq = 27 pCi d NS = Not sampled e Duplicate sample f  Split sample

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§6.6      IV. GROUNDWATER CONTAMINATION PLUMES

Based on groundwater monitoring results, nine principal groundwater contamination plumes have been identified on-site. The plumes are listed below, and the locations are shown in Figure 6-3:

• VOC plumes: Old Town and Buildings 37, 51/64, 71, and 76.
  
• Freon plume: Building 71.
  
• Tritium plume: Building 75/77.
  
• Petroleum hydrocarbon plumes: Buildings 7 and 74.

Contamination was also detected in groundwater in other areas of the site in 1999. Based on current information, however, the extent of contamination in these areas is limited.

Figure 6-3      Groundwater Contamination Plumes (September 1999)

§6.7      A. VOC Plumes

Covering the area of Buildings 4–7, 14, 16, 25, 27, 52–53, 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 1999 in groundwater samples collected from wells monitoring the Old Town VOC plume was 85,590 mg/L, which primarily consisted of PCE (38,000 mg/L), TCE (45,000 mg/L), and carbon tetrachloride (1,800 mg/L). Figure 6-4 shows the areal extent of VOCs in groundwater in the Old Town area.

Figure 6-4      Groundwater Contamination (Total Halogenated Hydrocarbons
in µg/L) in Old Town Area (September 1999)

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 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 groundwater collection trench was installed immediately downgradient from the former Building 7 sump to control the source of the groundwater contamination;
  
• A subdrain located east of Building 46 intercepts the northern lobe of the plume and prevents the discharge of contaminated groundwater to the stormdrain;
  
• A groundwater collection trench was installed west of Building 58 to intercept the southern lobe of the plume and prevent its further migration; and
  
• A groundwater collection trench was installed on the slope east of Building 58, in an area where high VOC concentrations had been detected in soil gas and groundwater.

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 1999 at a maximum total concentration of 349,890 mg/L in a water sample from a temporary sampling point in the source area of the plume. The maximum concentration of total halogenated hydrocarbons detected in 1999 in samples collected from groundwater monitoring wells in the Building 51/64 area was 110,652 mg/L. The contaminants primarily consisted of 1,1,1-TCA (86,400 mg/L) and 1,1-DCA (8,720 mg/L). Figure 6-5 shows the areal extent of VOCs in groundwater in the Building 51/64 area.

Figure 6-5      Groundwater Contamination (Total Halogenated Hydrocarbons in mg/L)
at Building 51/64 VOC Plume (September 1999)

Other VOC plumes have been identified south of Building 71 (Building 71 VOC plume), east of Building 37 (Building 37 VOC plume), and south of Building 76 (Building 76 VOC plume). These plumes cover less area than the Old Town plume, and fewer contaminants have been detected.

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 in 1999, 536 mg/L, was detected in a monitoring well installed south of Building 71B close to 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 1999 was 8.8 mg/L.

The Building 76 VOC plume is defined by the presence of TCE and cis-1,2-DCE. The maximum concentration of total halogenated hydrocarbons detected in wells monitoring the plume in 1999 was 16 mg/L.

§6.8      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 mg/L in 1994 to approximately 20 mg/L in 1999. The MCL for freon-113 is 1,200 mg/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.

§6.9      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 1999 was 1,166 Bq/L (31,503 pCi/L), which is above the drinking water standard of 740 Bq/L (20,000 pCi/L).⁴ Tritium has been detected above the drinking water standard in only one monitoring well.

§6.10      D. Petroleum Hydrocarbon Plumes

Monitoring wells have been installed at or downgradient from two abandoned and seven removed underground fuel storage tanks (USTs). Figure 6-6 shows the approximate locations of these wells. The maximum concentrations of total petroleum hydrocarbons (TPH) detected at these sites in 1999 are listed in Table 6-4.

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

Petroleum hydrocarbon plumes are located north of Building 6, near Building 74, and south of Building 76. No BTEX components (i.e., benzene, toluene, ethyl benzene, xylenes) were detected at UST sites in 1999. A dual phase (groundwater and soil vapor) extraction and treatment system has been 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 in 1999 at a concentration of 1.3 mg/L. The US/EPA Drinking Water Advisory for MTBE is 20 to 40 mg/L.

§6.11      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:

• Removing or controlling sources of contamination;
  
• Sbottomping discharge of contaminated water to surface waters;
  
• Eliminating potential pathways that could contaminate groundwater; and
  
• Preventing further migration of contaminated groundwater.

§6.12      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 1999:

• Approximately 30 cubic meters (40 cubic yards) of PCB-contaminated soil were excavated from the basement of the Building 51 Motor Generator Room.
  
• Highly contaminated soil and groundwater near the source location (the former Building 7 sump) are a continuing source of contamination for the Old Town plume. To control the source of contamination, the Laboratory constructed a groundwater collection trench immediately downgradient from the former sump location in 1996. Contaminated groundwater is extracted from the collection trench and treated. The treatment system removed approximately 9 kg of VOCs (consisting primarily of PCE, TCE, and carbon tetrachloride) from the groundwater in 1999.
  
• A dual phase (groundwater and soil vapor) extraction and treatment system was installed at the location of the Building 7E former UST to remove contaminants from the soil and groundwater. Approximately 54 kg of contaminant mass was removed by the vapor extraction system in 1999.

§6.13      B. Preventing Discharge of Contamination to Surface Waters

Slope stability is a concern at Berkeley Lab because of the geology and bottomography 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 contaminated groundwater to the creeks, Berkeley Lab installed a system to collect and treat the hydrauger effluent when the water is contaminated with VOCs.

§6.14      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.

§6.15      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,⁵ or recirculated to flush contaminants from the subsurface.

Table 6-5 lists both the volume of contaminated groundwater treated by each system in 1999 and the total volume treated since the treatment systems were first placed in operation.