I.2.0 WATER RESOURCES

Baseline conditions for water resources and hydrology encompass surface water, vadose zone, and groundwater, each of which may be impacted by implementing proposed TWRS activities.

I.2.1 SURFACE HYDROLOGY, INCLUDING FLOODPLAINS

The following subsections describe surface water resources, including the occurrence and characteristics of surface water, floodplains, and runoff.

I.2.1.1 Occurrence and Characteristics of Surface Water

West Lake and two small spring-fed streams in the Fitzner Eberhardt Arid Lands Ecology (FEALE) Reserve are the only naturally occurring water bodies on the Hanford Site. West Lake is several hectares in size and is located approximately 8 km (5 mi) northeast of the 200 West Area and about 3 km (2 mi) north of the 200 East Area. It is situated in a topographically low-lying area and is sustained by groundwater inflow resulting from an intersection with the groundwater table. West Lake was considered to be an ephemeral lake before operations began at the Hanford Site, with water level fluctuations dependent on groundwater level fluctuations. However, because of recharge (primarily from B Ponds) that contains low-level waste processing and cooling water from B Plant, water levels in the lake have become more stable.

Rattlesnake Springs, located 10 km (6 mi) west of the 200 West Area, forms a small surface stream that flows for approximately 2.5 km (1.6 mi) before it disappears into the ground as a result of seepage and evapotranspiration. The stream's base flow is approximately 0.01 cubic meters per second (m³/sec) (0.4 cubic feet per second [ft³/sec]). Snively Springs is located to the west and at a higher elevation than Rattlesnake Springs. It flows to the west and off of the Hanford Site (Cushing 1994).

Two ephemeral creeks, Cold Creek and its tributary, Dry Creek, traverse the uplands of the Hanford Site south and southwest of the 200 Areas. These creeks drain southeasterly toward the horn of the Yakima River, located south of the Hanford Site. Surface runoff from the uplands in and west of the Site is minor. These ephemeral creeks are not sustained by groundwater baseflow during any part of the year because depth to groundwater is over 46 m (150 ft) near the intersection of these creeks. The Columbia River is 16 to 24 km (10 to 15 mi) downgradient from the nearest TWRS site toward the east and approximately 11 km (7 mi) toward the north. The river forms the eastern boundary of the Hanford Site and comprises the base-level and receiving water for groundwater and surface water in the region.

I.2.1.2 Floodplains and Runoff

There are no floodplains in the 200 Areas. The potential Vernita Quarry and McGee Ranch borrow sites are also not within areas of high flood risk. Although floods in Cold Creek and Dry Creek have occurred historically, there have not been any observed flood events or evidence of flooding in these creeks that has reached the 200 Areas before infiltrating into permeable sediments.

Natural runoff generated onsite or from offsite upgradient sources is not known to occur in the 200 Areas. Measurable runoff occurs during brief periods in two locations, Cold Creek Valley and Dry Creek Valley, which are west and southwest of the 200 West Area (Newcomb et al. 1972). This surface runoff either infiltrates into the valley floor or evaporates. During periods of unusually rapid snowmelt or heavy rainfall, surface runoff extends beyond Rattlesnake Springs in the upper part of Dry Creek. However, this runoff quickly infiltrates into the alluvial sediments of Cold Creek Valley. The total amount of annual recharge to the unconfined aquifer from these areas is estimated to be 555,000 square meters (m²) ( 5,970,000 square feet [ft²]). This generally occurs east of the Hanford Site (Newcomb et al. 1972).

I.2.2 GROUNDWATER

Groundwater conditions in the 200 Areas are described in the following subsections in terms of the general hydrogeologic setting, vadose zone characteristics, aquifer characteristics, and groundwater flow. Groundwater conditions in the areas of the potential Vernita Quarry and McGee Ranch borrow sites are similar to those of the 200 Areas, although limited specific information is available. Groundwater quality and supply are discussed in Section I.2.3.

I.2.2.1 Hydrogeologic Setting

A thick vadose zone (approximately 70 m [200 ft] to over 90 m [300 ft] thick) as well as both confined and unconfined aquifers are present beneath the 200 Areas (DOE 1993a and b). The vadose zone is over 90 m (300 ft) thick in the vicinity of the TWRS site in the 200 East Area (DOE 1993a). The unconfined aquifer has not formally been named. This aquifer consists variably of the Ringold Formation (where present) and the lower portion of the Hanford formation. The confined aquifers are found primarily within the Columbia River Basalts. The confined aquifers are not a major focus of this EIS because they are separated from the TWRS facilities by the vadose zone, unconfined aquifer (the focus of the groundwater modeling effort), and confining layer(s) and thus are not likely to be impacted. The conceptual hydrogeologic column for the Hanford Site is illustrated in Figure I.2.2.1. Figure I.2.2.2 is a generalized cross section through the 200 Areas showing the major geologic units and the relative position of the water table. The water table is generally at or near the interface between the Hanford and Ringold formations, as illustrated in both Figures I.2.2.1 and I.2.2.2.

The occurrence and flow of groundwater in the unconfined aquifer must be described on a conceptual basis due to the difficulty of direct measurement. Five important concepts that describe flow in this aquifer are listed below:

1. The numerous strata within the Ringold Formation, described in the previous section on stratigraphy, result in a much lower vertical hydraulic conductivity compared to the horizontal hydraulic conductivity. This results in a strong preference for groundwater to move horizontally.
2. Groundwater movement occurs mostly in the upper portion of the Ringold Formation. That is, most groundwater movement occurs in the sands and gravel that predominate in the upper portion of the Ringold Formation (Unit E Gravels).
3. The overbank deposits and the lower mud sequence near the base of the Ringold Formation act as confining layers, hydraulically separating the overlying unconfined aquifer from the confined aquifer.
4. Recharge to the unconfined aquifer is primarily from artificial sources (e.g., B Pond), groundwater inflow from the Dry Creek and Cold Creek synclines, and recharge from the Columbia River along the western reach of the horn of the Colombia River near N Reactor.
5. Discharge from the unconfined aquifer is primarily to the Columbia River from the top of the horn south of the Columbia River to the 300 Areas, and in the vicinity of the B and C Reactors. Groundwater discharge also occurs to West Lake.

Natural recharge to the unconfined aquifer on the Hanford Site is extremely low and occurs primarily in the upland areas west of the Hanford Site. Artificial recharge from retention ponds and trenches contribute approximately 10 times more recharge than natural recharge. Seasonal water table fluctuations are not large because of the low natural recharge.

I.2.2.2 Vadose Zone Characteristics

The vadose zone extends from the ground surface to the top of the saturated sediments of the unconfined aquifer. Vadose zone characteristics determine the rate, extent, and direction of liquid flow downward from the surface. This zone variably includes the Hanford formation and locally includes the Ringold Formation Unit E Gravel. In the 200 West Area, the vadose zone is approximately 72 m (240 ft) thick (DOE 1993b). In the 200 East Area, the vadose zone is over 90 m (300 ft) thick, based on the 1991 depth to water level of the unconfined aquifer (DOE 1993a).

Figure I.2.2.1 Conceptual Hydrologic Column for the Hanford Site

Figure I.2.2.2 Generalized Cross Section of the Hanford Site

The following sections describe vadose zone characteristics (infiltration, perched water, and soil moisture) and vadose zone contamination .

I.2.2.2.1 Infiltration

The thick vadose zone, combined with the general aridity of the climate in the area, result in natural infiltration ranging from near zero (below detection) to approximately 11 centimeters per year (cm/yr) (4.3 inches [in.]/yr) (Gee et al. 1992). Some episodic recharge of groundwater may occur following periods of high precipitation, especially if combined with topographic depressions, highly permeable surface deposits such as gravel, and where the land is denuded of vegetation. Also, present conditions (bare ground and coarse sand and gravel surfaces) within the tank farms are conducive to higher infiltration than would be expected on undisturbed ground within the 200 Areas. For such conditions, infiltration near the upper range of 10 cm/yr (4.0 in./yr) would not be unreasonable. However, there are relatively recent changes that occurred after 1940 and would not necessarily have altered the flow within the full thickness of the vadose zone.

The total natural recharge in the 200 West Area is estimated to be approximately 1.3E+8 liters per year (L/yr) ( 3.4E+07 gallons [gal]/yr)(DOE 1993b). This is based on an average recharge rate of 0.1 cm/yr (0.04 in./yr) through fine-textured soil with deep-rooted vegetation. This value is approximately 10 times lower than recharge volumes from artificial sources.

The current principal sources of artificial recharge in the 200 West Area are four cribs and one ditch associated with the U Plant area, located in the eastern portion of the 200 West Area (DOE 1993b). There are also four septic tanks and drain fields that actively discharge water to the soil. The combined volume discharge from these drain fields is estimated to be 12,000 L/day (3,200 gal/day). The total wastewater discharged from these facilities from 1944 to 1992, including the U Plant cribs and ditches, is estimated to have been 1.7E+11 L (4.4E+09 gal). T Plant and S Plant operations also resulted in large volumes of wastewater discharged to the soil. Liquid is no longer discharged to the soil column from U, T, or S Plants.

Natural recharge in the 200 East Area is estimated to be approximately 2E+7 L (5E+06 gal) (DOE 1993a). This is based on a similar average natural recharge rate through fine-textured soil with deep-rooted vegetation, as noted previously for the 200 West Area. Artificial recharge in the 200 East Area is associated with approximately 140 ponds, trenches, cribs, and drains that were used to dispose of approximately 1E+12 L (3E+11 gal) of wastewater. The wastewater, except for limited discharges to the B Pond, is not directly discharged to the ground. The wastewater is treated to meet the State groundwater standards and piped to a common discharge location in the 200 Areas for discharge to the soil column. The remaining discharges to the ground at B Pond will be rerouted to the common discharge location in 1997. Currently, there are 11 active waste management units and 20 active drain fields. These waste management units are associated with B Plant and the Plutonium-Uranium Extraction (PUREX) Plant and are located east and northeast of the TWRS site (DOE 1993a). The primary recipients of the wastewater from three waste management units were the ponds and trenches associated with B Plant and PUREX Plant; the 216-A-25 and B-3 Ponds received approximately 7.0E+11 L (2.1E+11 gal) . Liquid is no longer discharged to the soil column from B Plant or the PUREX Plant.

Wastewater, such as the condensate removed from tank waste by the 242-A Evaporator, which is located in the eastern portion of the 200 East Area, is transferred by pipeline to the Effluent Treatment Facility, also located in the 200 East Area. The treated effluent from the Effluent Treatment Facility is then transferred by pipeline and discharged to the ground at the State-approved land disposal site located north of the 200 West Area. The treated wastewater meets all State groundwater discharge requirements except for tritium. The water is disposed of at this location further to the west so that the tritium contamination will decay to below drinking water standards in the groundwater before it reaches the Columbia River.

I.2.2.2.2 Perched Water

Perched water may occur within the vadose zone in the 200 West Area upon the caliche layer, approximately 55 m (180 ft) beneath the ground surface (DOE 1993b). Measured hydraulic conductivities of this unit range from 0.0009 to 0.09 m/day (0.003 to 0.3 ft/day). Caliche layers have not been encountered in the 200 East Area, and perched groundwater is not as likely to occur except in localized areas (Hoffman et al. 1992). Perched water has been reported in the vicinity of B Pond within the lower part of the Hanford formation.

I.2.2.2.3 Soil Moisture

In areas where artificial recharge is occurring from ponds and trenches, soil is expected to be close to saturation and would not likely be capable of holding substantial amounts of additional liquid. In addition, groundwater mounds have developed beneath these recharge areas. Where there is no artificial recharge, soil in the 200 Areas has a large moisture-holding capacity (DOE 1992a). The potential effect of recharge from Site waste water disposal activities is discussed in Volume Five, Appendix K, Section K.4.1.

I.2.2.2.4 Vadose Zone Contamination

Contaminants in the vadose zone in the 200 Areas are believed to be associated primarily with waste disposal practices that use engineered structures such as cribs, drains, septic tanks and associated drain fields, and reverse wells (wells that do not penetrate to the groundwater); percolation from ponds, ditches, and trenches such as B Pond and U Pond; and unplanned releases such as leaks from single-shell tanks (SSTs). The vadose zone is expected to be impacted by these past (and in some cases ongoing) waste management practices in the area immediately beneath the discharging facility and in an undetermined adjacent area (due to spreading as liquid percolates downward). Emerging data regarding vadose zone contamination from past SST leaks are provided in Volume Four, Appendix F, and Volume Five, Appendix K. Most Hanford Site environmental investigations have focused on the potential impacts of contaminants to the groundwater, not the vadose zone. Vadose zone investigations have often relied on geophysical gamma logs that are semi-quantitative. The types of contaminants potentially present in the vadose zone near planned and unplanned release sites can be inferred by contaminants detected in the underlying groundwater, contaminants that are reported in waste disposal inventories, or from the Track Radioactive Component (TRAC) inventory system used for SSTs that may be leaking. Table I.2.2.1 lists these contaminants, which include both radioactive materials (transuranic isotopes, U, and fission products) and nonradioactive materials (metals, volatile organics, semivolatile organics, and inorganics).

1.2.2.3 Aquifer Characteristics

Groundwater of the unconfined aquifer is found throughout the Hanford Site in the suprabasalt sediments and locally includes the Rattlesnake Ridge Interbed in the area north of the 200 East area, where erosion has removed a portion of the basalt sequence (Trent 1992b). The relationship between the various stratigraphic units and the hydrogeologic units is shown in Figure I.2.2.1.

Table I.2.2.1 Isotopes, Metals, and Organic Chemicals of Potential Concern at the 200 Areas

I.2.2.3.1 200 West Area

In the 200 West Area, the water table begins approximately 70 m (230 ft) beneath the surface. The saturated section, considered to be the unconfined aquifer, is composed of Ringold Formation Units A, B, C, D, and E gravels and is approximately 110 m (350 ft) thick above the Elephant Mountain member of the basalt. Hydraulic conductivities measured in the 200 West Area in the Ringold Unit E aquifer range from approximately 0.02 to 60 m/day (0.06 to 200 ft/day). Hydraulic conductivities range from 0.5 to 1.2 m/day (1.6 to 4.0 ft/day) in the semiconfined to confined Ringold Unit A Gravels (DOE 1993b). A discontinuous layer of silt and sand cemented by calcium-carbonate (caliche Plio-Pleistocene Unit), with a thickness up to 9 m (30 ft), occurs locally nearly 55 m (180 ft) in depth in the 200 West Area. This unit is believed to be responsible for perched water conditions in the vicinity of the TWRS sites in the 200 West Area.

I.2.2.3.2 200 East Area

Depth to groundwater in the 200 East Area ranges from 97 m (320 ft) in the southeast to 3 6 m (120 ft) in the vicinity of the 216-B-3C Pond (B Pond mound) located approximately 5 km (3 mi) east of the TWRS sites (DOE 1993a). The unconfined aquifer occurs within the Hanford and Ringold Formations. Groundwater near the TWRS sites occurs under unconfined conditions within the Ringold formation, approximately 96 m (315 ft) deep. The saturated (groundwater) section is approximately 34 m (110 ft) thick. Erosional windows occur in the basalt several kilometers north of the 200 East Area that allow some interconnection between the regionally confined Rattlesnake Ridge Interbed of the Ellensburg Formation in the basalt and the unconfined aquifer of the Hanford and Ringold Formations. Hydraulic conductivities of the unconfined aquifer near the TWRS sites in the 200 East Area range from 150 to 300 m/day (500 to 1,000 ft/day) (DOE 1993a).

I.2.2.4 Groundwater Flow

This section describes the physical characteristics of groundwater flow in the 200 Areas.

I.2.2.4.1 200 West Area

Figure I.2.2.3 is a contour map that shows the groundwater elevations for the Hanford Site. Groundwater generally flows from west to east, with some localized exceptions. In the northwest corner of the 200 West Area, groundwater flow is to the north. Also, it appears that flow from the 200 West Area may bifurcate east of the Gable Butte subcrop, with a lesser flow component north toward the gap between Gable Butte and Gable Mountain and the remaining flow east toward the Columbia River (Kasza 1994).

These groundwater movement patterns are also indicated by the 1994 distribution of tritium and nitrate in the unconfined aquifer, as shown on Figures I.2.2.4 and I.2.2.5, respectively. A north or northwest groundwater flow direction may also be indicated by the nitrate distribution in the area north and west of the 200 West Area. Because of the contrast in hydraulic conductivity, most basalt subcrops and outcrops appear as impermeable compared to groundwater flow in the transmissive Hanford and Ringold Formations.

Figure I.2.2.3 Groundwater Elevation Map of the Hanford Site

Figure I.2.2.4 Distribution of Tritium in the Unconfined Aquifer, 1994

Figure I.2.2.5 Distribution of Nitrate in the Unconfined Aquifer, 1994

The tank farms in the 200 West Area are located above a groundwater mound caused by artificial recharge from the U Plant area, especially the 216-U-10 Pond. Groundwater elevations have declined greatly since the 216-U-10 Pond was decommissioned in the fall of 1984. Large declines in groundwater elevations have been recorded in seven wells in the U Plant area since 1984. Hydrographs of two wells (299-W19-1 and 299-W19-10) west of the tank farms indicate that groundwater elevations have declined approximately 5 m (15 ft) since the 216-U-10 Pond was decommissioned. The mound seems to have shifted slightly as it continues to dissipate beneath 216-U-10 Pond toward the northeast beneath the 216-U-14 Ditch and 216-Z-20 Crib (DOE 1993b).

I.2.2.4.2 200 East Area

Groundwater flow in much of the 200 East Area is characterized by relatively low hydraulic gradients, ranging from 0.01 to 0.02 m/day (0.3 to 0.6 ft/day) (Kasza 1994). As shown in Figure I.2.2.3, water table elevations in the uppermost aquifer generally decrease from the margins of the Yakima Ridge in the west to the Columbia River in the east. There is a strong relationship between the water table as shown in Figure I.2.2.3 and the distribution of tritium in the uppermost aquifer as shown in Figure I.2.2.4. Both figures indicate that groundwater flow in the vicinity of the TWRS sites in the 200 East Area is toward the southeast.

I-129 is an unretarded contaminant (i.e., it moves with groundwater at the average groundwater velocity), as are nitrate and tritium. The distribution of i-129 in the unconfined aquifer (Figure I.2.2.6) also shows a southeasterly groundwater flow direction. The i-129 plume is much smaller than the plumes associated with nitrate and tritium, probably because i-129 sources are not as ubiquitous in the unconfined aquifer.

The mound resulting from discharge from the 216-B-3 Pond is a notable perturbation to the easterly flow direction. B Pond is approximately 5 km (3 mi) east of the TWRS sites. Near the western portion of the mound, the groundwater gradient has been reversed in a west direction. The magnitude of this gradient direction reversal is currently diminishing as the mound decays. The groundwater gradient in the southeastern portion of the 200 East Area is expected to resume a more easterly trend as the decay continues (Kasza 1994).

I.2.2.4.3 Vertical Gradients

Vertical hydraulic gradients in the unconfined aquifer are estimated from water measurements in wells that are near to each other (sometimes referred to as well pairs) and have their sensing zones (screened intervals) completed at different elevations within the unconfined aquifer. In both the 200 East and 200 West Areas, downward hydraulic gradients have been observed (Trent 1992, and b). In general, these downward hydraulic gradients are associated with the moundings that have been created from infiltration of water discharged to the U Pond and B Pond. Away from these mounds, the vertical gradients are smaller. For instance, near the Grout Treatment Facility in the 200 East Area, which is located along the central portion of the eastern part of the 200 East Area, the vertical head differences between nearby well pairs are so slight that they are indistinguishable from measurement errors (Trent 1992b). For information on the impact of the mounds on future groundwater flow see Appendix F, Section F.2.4.1.2.

Figure I.2.2.6 Distribution of Iodine-129 in the Unconfined Aquifer, 1994

I.2.2.4.4 Aquifer Communication

Aquifer communication is a process in which groundwater from distinct hydrogeological systems intermingle and mix. Of importance to the EIS is the degree of aquifer communication that exists between the unconfined aquifer and the underlying confined aquifer (Rattlesnake Ridge aquifer [Trent 1992b]). Several methods have been used to estimate the degree of aquifer communication at the Hanford Site including: analysis of joint and fracture systems in the basalt and presence of erosional windows, hydraulic head comparisons between aquifers, analysis and comparison of contaminant concentrations in adjacent aquifers, stable isotope analysis, and analysis of contaminant concentrations in adjacent aquifers. Interconnection between the unconfined and lower confined aquifer is possible across the Central Plateau; however, except for the area near the erosional windows, which occur in the basalt several kilometers north of the 200 East Area and B Pond vicinity, there is no indication of aquifer interconnection. In the vicinity of B Pond, groundwater mounding from B Pond discharges has resulted in a downward hydraulic gradient. Several kilometers north of the 200 East Area there is an absence of confining layer(s) associated with an erosional window that has resulted in enhanced interconnection of the aquifers in this area.

I.2.3 WATER QUALITY AND SUPPLY

Water for the Hanford Site is supplied by the Columbia River via distribution systems located at the 100-B, 100-D, 200, and 300 Areas, and at the Washington Public Power Supply System reactor. Wells supply water to the 400 Area and facilities at several remote locations. The city of Richland supplies water to the 700, 1100, and 3000 Areas.

Richland, Pasco, and Kennewick draw water from the Columbia River and operate their own water supply and treatment systems. Richland derives approximately 67 percent of its water from the Columbia River, 15 to 20 percent from a well field in North Richland, and the remaining 13 to 18 percent from groundwater wells (Cushing 1995). Richlands total water use in 1994 was 2.6E+10 L (6.9E+09 gal ).

Pasco also obtains its water from the Columbia River and in 1994 consumed an estimated 8.6E+9 L ( 2.3E+09 gal ) of water (Cushing 1995). The city of Kennewick's water supply is derived from the Columbia River and two wells. The wells serve as the sole source of water between November and March. The total maximum water supply for Kennewick is approximately 2.8E+10 L (7.3E+09 gal); the wells can supply approximately 62 percent of that total. Kennewick's total water use in 1994 was 1.5E+10 L (3.9E+09gal) (Cushing 1995).

I.2.3.1 Surface Water

Surface waters considered for this EIS are onsite ponds, riverbank springs and seeps at the Columbia River, and the waters of the Columbia River. Water quality in ephemeral creeks is not known to be impacted by Hanford Site activities.

I.2.3.1.1 Columbia River

River water samples are routinely collected at the sample locations shown on Figure I.2.3.1. Additionally, river water samples have been collected at cross sections established at the Vernita Bridge upstream of the Hanford Site, and at the Richland City Pumphouse, downstream of the Hanford Site.

Radionuclides consistently detected in Columbia River water levels in 1995 were tritium, Sr-90, I-129, U-234, U-238, Pu-239, and Pu-240 (PNL 1996 ). Strontium-90 and tritium may come from worldwide fallout, as well as from releases of Hanford Site effluent. Tritium and U also occur naturally in the environment. Radionuclide concentrations at Priest Rapids Dam (upstream of the Site) generally were lower than those at the Richland Pumphouse (downstream from the Site), and were similar to levels observed in recent years.

All radiological contaminant concentrations measured in 1995 were less than the U.S. Department of Energy (DOE) Derived Concentration Guides and Washington State surface water quality standards (PNL 1996). Washington State classifies the Hanford Reach of the Columbia River as a Class A (Excellent) area. Class A waters are to be suitable for essentially all uses (e.g., raw drinking water, recreation, and wildlife habitat). Both State and Federal drinking water standards apply to the Columbia River and currently are being met (Neitzel 1996).

I.2.3.1.2 Ponds

Three ponds on the Hanford Site are routinely sampled: West Lake (located north of the 200 East Area), B Pond (located east of the 200 East Area), and the Fast Flux Test Facility Pond (located southeast of the 200 Areas) (PNL 1993a). Sampling data indicated that the ponds are impacted by Hanford Site activities, although the ponds are not used for human consumption. With the exception of U-234 and U-235 in the October 1995 sample of West Lake, all radionuclide concentrations were less than the DOE Derived Concentration Guides (PNL 1996) . Average annual total beta concentrations exceeded the ambient surface water quality criteria in West Lake. The U.S. Environmental Protection Agency (EPA) proposed Hanford Site-specific drinking water standards for U also was exceeded in West Lake. All other radionuclide concentrations were less than the applicable surface water quality criteria (PNL 1996) . West Lake surface water quality reflects the quality of the groundwater that feeds the lake (PNL 1993a).

Riverbank Springs and Seeps

Riverbank spring discharges have been documented along the Hanford Reach of the Columbia River since before the startup of Hanford Site operations. They have been observed to be of relatively small volume and to occur intermittently (PNL 1993a). Several springs in the 100 Areas, as well as the Old Hanford Townsite Springs and the 300 Area Springs, are routinely sampled. Water flows from these springs are a mechanism by which groundwater contaminated by past Site activities enter the river. All radiological contaminants measured in 1995 were less than the applicable DOE Derived Concentration Guides. However, Sr-90 in the 100-H Area and tritium in the 100- B Area and along the Old Hanford Townsite exceeded Federal and Washington State drinking water standards (PNL 1996) . Total U exceeded the proposed EPA Hanford Site-specific drinking water standards (PNL 199 6 ). The 1995 nonradiological contaminant concentrations were below Washington State ambient surface water toxicity standards with the exception of copper and zinc in the 100-K Area spring. The chronic toxicity level of cadmium and the EPA standard for trichlorethylene also were exceeded in the 100-K Area Spring (PNL 1996).

Figure I.2.3.1 Water and Sediment Sampling Locations, 1992

I.2.3.2 Groundwater

I.2.3.2.1 Supply

Groundwater is not used in the 200 Areas except for emergency purposes. Three wells for emergency cooling water are located near B Plant in the 200 East Area. Water for drinking, most emergency uses, and facilities processes is obtained from the Columbia River. There are no water supply wells downgradient of the 200 Areas. Water supply wells on the Hanford Site are located at the Yakima Barricade, 6 km (4 mi) west of the 200 West Area; in the 400 Area, 16 km (10 mi) southeast of the 200 Areas; and at the Hanford Safety Patrol Training Academy, 25 km (16 mi) southeast of the 200 Areas.

I.2.3.2.2 Water Quality

Contamination by both radionuclide and nonradionuclide contaminants has been identified in the groundwater beneath the Hanford Site. Liquid effluents have been discharged to various ponds, cribs, and other Hanford Site waste management structures. Adsorption into soil particles, chemical precipitation, and ion exchange attenuate or delay the movement of some radionuclides and nonradionuclide contaminants in the effluent as they percolate downward through the vadose zone (PNL 1993a).

Constituents such as Sr-90, Cs-137, Pu-239, and Pu-240 are attenuated to varying degrees but eventually enter the groundwater. Compounds such as nitrate and radionuclides such as tritium, technetium-99 (Tc-99), and I-129 are not readily attenuated in the soil and reach the groundwater sooner than those that are. These ions then travel downgradient at the same rate as the natural groundwater (PNL 1993a). Figure I.2.2.4 shows the distribution of tritium in the unconfined groundwater. Two other major contaminant plumes include nitrates (Figure I.2.2.5) and I-129 (Figure I.2.2.6).

Groundwater beneath the 200 Areas and in plumes leading from the 200 Areas toward the Columbia River is contaminated with hazardous chemicals and radionuclides at levels that exceed Federal drinking water standards and State groundwater criteria. Hazardous chemical contaminants present at levels exceeding drinking water standards and State groundwater criteria include nitrates, cyanide, fluoride, chromium, chloroform, carbon tetrachloride, trichloroethylene, and techrachloroethylene. Radiological contaminants include I-129, tritium, Cs-137, Pu-239, Pu- 240, and Sr-90. Generally, the groundwater contamination beneath the 200 Areas substantially exceeds drinking water standards and State groundwater criteria. For example, I-129 is present at levels that exceed standards by up to 20 times. While other groundwater plumes from the 200 Areas tend to have lower levels of contaminants than the I-129 levels, many contaminants still exceed drinking water standards and State groundwater criteria. Groundwater use is controlled at the Hanford Site to prevent use of contaminated groundwater.

I.2.3.2.3 200 East Area

Unconfined groundwater beneath the 200 East Area contains 13 different contaminants that have been mapped as plumes: arsenic, chromium, cyanide, nitrate, gross alpha, gross beta, tritium, Co-60, Sr-90, Tc-99, I-129, Cs-137, Pu-239, and Pu-240 (DOE 1993a).

I.2.3.2.4 200 West Area

Beneath the 200 West Area, 13 overlapping contaminant plumes are located within the unconfined gravels of Ringold Unit E: Tc-99, U, nitrate, carbon tetrachloride, chloroform, trichloroethylene, I-129, gross alpha, gross beta, tritium, arsenic, chromium, and fluoride (DOE 1993b). The tank farms are within the boundaries of most of these plumes. Plumes of Tc-99, U, I-129, gross alpha, and gross beta are associated with the U Plant area.