I. BACKGROUND   §6.1

This section reviews the groundwater monitoring program at Berkeley Lab, emphasizing the 1997 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:

• 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. Berkeley Lab 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, the San Francisco Bay Regional Water Quality Control Board, and the City of Berkeley. These agencies review and provide 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, like those reported in chapter 5, 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 nor is the program held to these standards for compliance purposes.

This section discusses the hydrogeological setting of Berkeley Lab and includes 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

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. For further discussion of the hydrogeological characteristics of the three main units, see §§2.8–2.9.

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. The map indicates that the direction of groundwater flow generally follows the topography. In the western part of Berkeley Lab, groundwater flow directions are generally to the west; over the rest of the Laboratory, flow is generally 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 1 meter per day (3.3 feet per day).

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 6-1 [Above] Groundwater Piezometric Map

 

Figure 6-2 [Above] Groundwater Fluctuation in Monitoring Well MW7-92-19 Versus Rainfall

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 4460 mg/L. Water in the Orinda formation typically has a high TDS concentration, indicating a long residence time. Average mineral concentrations for the three primary geologic units are listed in Table 6-1.

In 1997, 23 new monitoring wells were installed, bringing the total in the program to 152 wells. Of the total number of wells, four are considered multilevel in that they allow groundwater sampling of more than one interval. Twenty monitoring wells are located close to the site boundary, and one well is located downgradient from the Laboratory (see Figure 6-3).

Tables 6-2, 6-3, and 6-4 summarize groundwater monitoring results for 1997. 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 wells in which the analyte was detected, and the ranges in concentrations detected. Table 6-4 presents tritium results. Periods in which either multiple samples or quality assurance samples were gathered from a location are included in this table.

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

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:

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

Contamination was also detected in groundwater in other areas of the site in 1997. Based on the present information, however, the extent of contamination in these areas is limited.

Figure 6-4 Groundwater Contamination Plumes (December 1997)

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 1997 in groundwater samples collected from wells monitoring the Old Town VOC plume was 92,800 µg/L, which primarily consisted of PCE (73,000 µg/L), TCE (18,000 µg/L) and carbon tetrachloride (940 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 mg/L)
in Old Town Area (December 1997)

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 these wells have not been identified. The contaminated groundwater from these sources flows westward, where it intermixes with the main Old Town plume.

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

• A groundwater collection trench was installed downgradient from the former Building 7 sump.
• A subdrain located east of Building 46 intercepts the northern lobe of the plume.
• Groundwater is extracted from MW58-95-18 at the southern lobe of the plume and treated.

Other VOC plumes have been identified south of Building 71 (Building 71 VOC plume), near Buildings 51 and 64 (Building 51/64 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.

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 1997 in wells monitoring the plume was 71 µg/L. 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 TCE and PCE 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 1997 was 8.9 µg/L.

The Building 51/64 VOC plume is defined by the presence of halogenated hydrocarbons, including 1,1-DCA, TCE, vinyl chloride, PCE, trans-1,2-DCE, and 1,1,1-TCA. Although the source of the contamination is not known, multiple sources appear to exist, based on the suite of chemicals detected in each of the wells in the area. The maximum concentration of total halogenated hydrocarbons detected in 1997 in wells monitoring the plume was 5,328 µg/L, which primarily consisted of 1,1-DCA (3,100 µg/L).

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 34 µg/L in December 1997. The MCL for freon-113 is 1200 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.

The tritium plume appears to be limited to 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 1997 was about 505 Bq/L (13,640 pCi/L), which is well below the drinking water standard of 740 Bq/L (20,000 pCi/L).⁵

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 1997 are listed in Table 6-5.

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

The only UST site where aromatic hydrocarbons were detected in 1997 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, xylene) were detected at UST sites in 1997.

Methyl tertiary butyl ether (MTBE) was detected in one monitoring well in 1997 at a concentration of 5.5 µg/L. The USEPA Drinking Water Advisory for MTBE is 20 to 40 m g/L. The source of the MTBE is not known. MTBE is the controversial new additive in gasoline sold in California.

Interim corrective measures are used to remediate contaminated media or prevent movement of contamination, especially where the presence or movement of contamination poses an immediate risk to human health or the environment. Throughout the RCRA corrective actions process, Berkeley Lab has conducted interim corrective measures in consultation with regulatory agencies. These measures include:

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

Berkeley Lab has undertaken these measures even though there are no immediate risks to health posed by the contaminations. In addition, Berkeley Lab conducts pilot testing to evaluate potential methods for remediating contaminated soil and groundwater.

Berkeley Lab has attempted to identify potential sources of contamination by reviewing site records; conducting visual site inspections; and sampling soil, soil gas, and groundwater.

If the contaminant concentrations pose a threat to human health or leaching of contaminants from the soils can affect groundwater, the need for interim corrective measures is evaluated. Several sources of contamination have been removed at the Laboratory, including the following sources removed in 1997:

• The Building 52B abandoned liquid waste aboveground storage tank was removed on September 6, 1997. Approximately 120 cubic yards of contaminated soil were also excavated. Soil at the abandoned tank site was contaminated with polychlorinated biphenyls (PCBs), polycyclic aromatic hydrocarbons (PAHs), fuel hydrocarbons (primarily diesel fuel), and crude/waste oil. The abandoned tank site was a potential source of groundwater contamination.
• 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, a groundwater collection trench was constructed immediately downgradient from the former sump location in 1996. Contaminated groundwater is extracted from the collection trench and treated. The treatment system removed approximately 14 kg of VOCs (consisting primarily of PCE, TCE, and carbon tetrachloride) from the groundwater in 1997. The treated water is either released under permit to the sanitary sewer or reinjected with the approval of the RWQCB to continuously flush subsurface contaminants to the trench for collection and treatment.

Slope stability is a concern at Berkeley Lab because of the geology and topography of its 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.

To reduce the risk of landslides, Berkeley Lab has installed numerous large-diameter slope-stability wells. The well casings are slotted and the exterior of the casings backfilled with gravel to allow the maximum volume of groundwater to be extracted. Because of the lack of a surface seal, the backfill is a potential conduit for the migration of contaminated water from the surface to groundwater. Three approaches have been selected as interim corrective measures to prevent these wells from acting as potential contaminant pathways to groundwater:

• If a slope-stability well is needed for slope-stability purposes, its construction is modified by redrilling the well and installing at least 6.1 meters (20 feet) of an impermeable cement seal in the annular space from the ground surface to the screened interval. To date, nine slope-stability wells have been modified.
• If a slope-stability well is not needed, it is abandoned in accordance with regulatory requirements. Five slope-stability wells were abandoned in 1997, bringing the total number of wells abandoned to ten.
• If a slope-stability well is needed to monitor groundwater contamination, the well is reconstructed into a monitoring well. To date, five slope-stability wells have been reconstructed into monitoring wells.

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.

As described above, Berkeley Lab is using extraction wells and subdrains to control groundwater plumes that could migrate off site or contaminate surface water. Six 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 the 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 1997 and the total volume treated since the treatment systems were first placed in operation.