## Hydrology

###### *P.D. Thorne, D.G. Horton, and G.V. Last* {#p.d.-thorne-d.g.-horton-and-g.v.-last .unnumbered}

Characterization of hydrology at the Hanford Site includes surface
water, the vadose zone, and groundwater. The vadose zone is the
unsaturated or partially saturated region between the ground surface and
the saturated zone. Water in the vadose zone is called soil moisture.
Groundwater refers to water within the saturated zone. Permeable
saturated units in the subsurface are called aquifers.

### Surface Water

Surface water at Hanford includes the Columbia River, springs, and
ponds. Intermittent surface streams, such as Cold Creek, may also
contain water after large precipitation or snowmelt events. In addition,
the Yakima River flows along a short section of the southern boundary of
the Hanford Site (Figure 4.4-1), and there is surface water associated
with irrigation east and north of the Site.

#### Columbia River

The Columbia River is the second largest river in the contiguous United
States in terms of total flow and is the dominant surface-water body on
the Hanford Site. The original selection of the Hanford Site for
plutonium production and processing was based, in part, on the abundant
water provided by the Columbia River. The existence of the Hanford Site
has precluded development of this section of the river for hydroelectric
production and barge transportation.

Originating in the Canadian Rockies of southeastern British Columbia,
Canada, the Columbia River drains a total area of approximately 680,000
km^2^ (262,480 mi^2^) en route to the Pacific Ocean. Most of the
Columbia River is impounded by 11 dams within the United States: 7
upstream and 4 downstream of the Hanford Site. Priest Rapids is the
nearest upstream dam, and McNary is the nearest downstream dam. Lake
Wallula, the impoundment created by McNary Dam, extends upstream past
Richland, Washington, to the southern part of the Hanford Site. Except
for the Columbia River estuary, the only unimpounded stretch of the
river in the United States is the Hanford Reach, which extends from
Priest Rapids Dam downstream approximately 82 km (51 mi) to Lake
Wallula, north of Richland. The Hanford Reach of the Columbia River was
recently incorporated into the land area established as the Hanford
Reach National Monument.

Flows through the Hanford Reach fluctuate significantly and are
controlled primarily by releases from three upstream storage dams: Grand
Coulee in the United States, and Mica and Keenleyside in Canada. Flows
in the Hanford Reach are directly affected by releases from Priest
Rapids Dam; however, Priest Rapids operates as a run-of-the-river dam
rather than a storage dam. Flows are controlled for purposes of power
generation and to promote salmon egg and embryo survival. ^(^[^1]^)^
Columbia River flow rates near Priest Rapids during the 83-year period
from 1917 to 2000 averaged nearly 3360 m^3^/s (120,000 ft^3^/s). Daily
average flows during this period ranged from 570 to 19,500 m^3^/s
(20,000 to 690,000 ft^3^/s). The lowest and highest flows occurred
before the construction of upstream dams. During the 10-year period from
1991 through 2000, the average flow rate was also about 3360 m^3^/s
(120,000 ft^3^/s). Daily average flows through the Hanford Reach for
1994 through April 2005 are plotted in Figure 4.4-2. Storage dams on
tributaries of the Columbia River also affect flows.

![](media/image1.jpeg){width="6.569444444444445in"
height="7.570833333333334in"}

> **Figure 4.4-1**. Surface Water Features on the Hanford Site,
> Washington, including Rivers, Ponds, Major Springs, and Ephemeral
> Streams

![](media/image2.wmf){width="6.241666666666666in"
height="3.8680555555555554in"}

> **Figure 4.4-2**. Average Daily Flow for the Hanford Reach, Columbia
> River, Washington, from January 1994 through April 2005 (data from
> USGS 2005, provisional data not yet reviewed and subject to change)
> (1 m^3^/s = 35.3 ft^3^/s)

During 1996 and 1997, exceptionally high spring runoff resulted from
larger than normal snowpacks. The highest daily average flow rate during
1997 was nearly 11,750 m^3^/s (415,000 ft^3^/s) (USGS 2005). Peak daily
average flow during 2004 was 4842 m^3^/s (171,000 ft^3^/s) (Figure
4.4-3). Columbia River flows typically peak from April through June
during spring runoff from snowmelt and are lowest from September through
October. As a result of daily discharge fluctuations from upstream dams,
the depth of the river varies over a short time period. River stage
changes of up to 3 m (10 ft) during a 24-hr period  may occur along the
Hanford Reach (Poston et al. 2003). The width of the river varies from
approximately 300 m (1000 ft) to 1000 m (3300 ft) within the Hanford
Reach. The width also varies with the flow rate, which causes repeated
wetting and drying of an area along the shoreline.

The primary uses of the Columbia River include the production of
hydroelectric power, irrigation of cropland in the Columbia Basin, and
transportation of materials by barge. The Hanford Reach is the upstream
limit of barge traffic on the mainstem Columbia River. Barges are used
to transport reactor vessels from decommissioned nuclear submarines to
Hanford for disposal. Several communities along the Columbia River rely
on the river as their source of drinking water. The Columbia River is
also used as a source of both drinking water and industrial water for
several Hanford Site facilities (Poston et al. 2003). In addition, the
Columbia River is used extensively for recreation, including fishing,
hunting, boating, sailing, water-skiing, diving, and swimming.

#### Water Quality of the Columbia River

The water quality of the Columbia River from Grand Coulee Dam to the
Washington-Oregon border, which includes the Hanford Reach, has been
designated as Class A, Excellent (WAC 173-201A) by Washington State
(Poston et al. 2003). Class A waters are suitable for essentially all
uses, including raw

![](media/image3.wmf){width="6.497916666666667in" height="4.03125in"}

**Figure 4.4-3**. Average Daily Flow for the Columbia River During
Calendar Year 2004 (data from USGS 2005, provisional data not yet
reviewed and subject to change) (1 m^3^/s = 35.3 ft^3^/s)

drinking water, recreation, and wildlife habitat. State and federal
drinking water standards apply to the Columbia River (Section 6.2.2).

During 2002, the USGS measured several water quality parameters at
Vernita Bridge, upstream of Hanford Site operations areas, and at the
Richland pumphouse, which is downstream of the Hanford Site (Figure
4.4-4). Total dissolved solids measured near the Hanford Site during
2002 ranged from 71 to 99 mg/L, and total dissolved nitrogen ranged from
0.16 to 0.37 mg/L. Dissolved oxygen ranged from 10 to 14 mg/L and pH was
7.7 to 8.2. There were no statistically significant differences between
upstream and downstream samples for these parameters (Poston et al.
2003).

PNNL measured both radiological and nonradiological constituents in
Columbia River water during 2002 as part of a continuing environmental
monitoring program (Poston et al. 2003). Cumulative water samples are
collected at Priest Rapids Dam and at the Richland pumphouse (Figure
4.4-4). Additional samples were taken at transects of the river and at
near-shore locations at the Vernita Bridge, 100-F Area, 100-N Area, the
Hanford Townsite, and the 300 Area. These water samples were collected
at frequencies varying from quarterly to annually. Results are presented
in Bisping (2003) and summarized in Poston et al. (2003). These data
show a statistical increase in tritium, nitrate, uranium, and iodine-129
along the Hanford Reach. All these constituents are known to be entering
the river from contaminated groundwater beneath the Hanford Site
(Section 4.4.3). Measurements of strontium-90 at the Richland pumphouse
were not statistically higher than those at the Vernita Bridge even
though strontium-90 is known to enter the river through groundwater
inflow at 100‑N Area. Measurements of tritium along transects showed
higher concentrations near the shoreline relative to mid-river for
samples from the 100-N Area, the Hanford Townsite, the 300 Area, and the
Richland pumphouse.

![](media/image4.jpeg){width="6.503472222222222in"
height="7.3597222222222225in"}

> **Figure 4.4-4**. Surface Water and Sediment Monitoring Locations,
> Hanford Site, Washington (Poston et al. 2003)

Other sources of pollutants entering the river are irrigation return
flows and groundwater seepage associated with irrigated agriculture. The
USGS (1995) documented nitrate groundwater contamination in Franklin
County, which also seeps into the river along the Hanford Reach.
However, in spite of pollutants introduced from both the Hanford Site
and other sources, dilution in the river results in contaminant
concentrations that are below drinking water standards (Poston et al.
2003).

#### Yakima River

The Yakima River follows a portion of the southwestern boundary of the
Hanford Site and has much lower flows than the Columbia River. The
average flow, based on 70 years of daily flow records (USGS 2005), is
about 100 m^3^/s (3530 ft^3^/s), with an average monthly maximum of
497 m^3^/s (17,550 ft^3^/s) and minimum of 4.6 m^3^/s (165 ft^3^/s).
Exceptionally high flows were observed during 1996 and 1997
(Figure 4.4-5). The highest average daily flow rate during 1996 was
nearly 1300 m^3^/s (45,900 ft^3^/s). Average daily flow during 2000 was
89.9 m^3^/s (3176 ft^3^/s). Average daily flow during 2004 was 73 m^3^/s
(2580 ft^3^/s) (USGS 2005). The Yakima River System drains surface
runoff from approximately one-third of the Hanford Site. Groundwater is
expected to flow from the Yakima River into the aquifer underlying the
Site rather than from the aquifer into the river because, based on well
water-level measurements, the elevation of the river surface is higher
than the adjacent water table (Thorne et al. 1994). Therefore,
groundwater contaminants from the Hanford Site do not reach the Yakima
River.

#### Springs and Streams

Springs are found on the slopes of the Rattlesnake Hills along the
western edge of the Hanford Site (DOE 1988). There is also an alkaline
spring at the east end of Umtanum Ridge (Hall 1998). Rattlesnake and
Snively springs form small surface streams. Water discharged from
Rattlesnake Springs flows in Dry Creek for about 3 km (1.6 mi) before
disappearing into the ground (Figure 4.4-1). Cold Creek and its
tributary, Dry Creek, are ephemeral streams within the Yakima River
drainage system in the southwestern portion of the Hanford Site. These
streams drain areas to the west of the Hanford Site and cross the
southwestern part of the Site toward the Yakima River. When surface flow
occurs, it infiltrates rapidly and disappears into the surface sediments
in the western part of the Site. The quality of water in these springs
and streams varies depending on the source. However, they are upgradient
of Hanford waste sites and groundwater contamination plumes.

#### Columbia Riverbank Springs

Riverbank springs were documented along the Hanford Reach long before
Hanford operations began (Jenkins 1922). During the early 1980s,
researchers identified 115 springs along the Benton County shoreline of
the Hanford Reach (McCormack and Carlile 1984). Seepage occurs both
below the river surface and on the exposed riverbank, particularly at
low-river stage. Riverbank springs flow intermittently, apparently
influenced primarily by changes in river level. In many areas, water
flows from the river into the aquifer at high river stage and then
returns to the river at low river stage. This "bank-storage" phenomenon
has been modeled numerically for the 100-H Area (Peterson and Connelly
2001).

In areas of contaminated groundwater, riverbank springs are also
generally contaminated. However, the concentrations in seeping water
along the riverbank may be lower than groundwater because of the
bank-storage phenomenon. Contaminants have been detected in near shore
samples downstream from riverbank springs (Poston et al. 2003).
Riverbank springs are monitored for radionuclides at the 100-N Area, the
Hanford Townsite, and the 300 Area (Figure 4.4-4). Hanford-origin
contaminants occur in some of these springs (Peterson and Johnson 1992,
Poston et al. 2003). Detected radionuclides include strontium-90,
technetium-99, iodine-129, uranium-234, -235, and -238, and tritium.
Other detected

![](media/image5.wmf){width="6.496527777777778in"
height="4.079861111111111in"}

**Figure 4.4-5**. Average Daily Flow for the Yakima River, Washington,
from 1994 through April 2005 (data from USGS 2005, provisional data not
yet reviewed and subject to change) (1 m^3^/s = 35.3 ft^3^/s)

contaminants include arsenic, chromium, chloride, fluoride, nitrate, and
sulfate. Volatile organic compounds were below detection limits. Results
for riverbank spring samples analyses are listed in Bisping (2003) and
summarized in Poston et al. (2003). For a listing of the regulatory
standards for groundwater, refer to Table 4.4-1.

The highest strontium-90 concentration detected in riverbank springs
during 2002 was 3.3 pCi/L (0.12 Bq/L) at the 100-N Area. A spring in
this area previously had a reported strontium-90 concentration higher
than 1000 pCi/L (37.34 Bq/L). However, because of decreased groundwater
elevations, no flow has been observed at this spring during the past six
years (Poston et al. 2003). Tritium concentrations in riverbank springs
varied widely with location. The highest tritium concentration detected
in riverbank springs during 2002 was 58,000 pCi/L (2,100 Bq/L) at the
Hanford Townsite. The highest iodine-129 concentration of 0.19 pCi/L
(0.007 Bq/L) was also found in a Hanford Townsite spring. Concentrations
of radionuclides including tritium, technetium-99, and iodine-129 in
riverbank springs near the Hanford Townsite have generally been
increasing since 1994. This is an area where a major groundwater plume
from the 200 East Area intercepts the river. However, tritium
concentration has declined since 1997. This decline may be due to the
effects of radioactive decay and/or less wastewater disposal, which
would cause the groundwater tritium plume to move at a slower velocity.

**Table 4.4-1**. Regulatory Drinking Water Standards for Groundwater

![](media/image6.wmf){width="6.022916666666666in"
height="3.0791666666666666in"}

#### Runoff and Net Infiltration

Total estimated precipitation over the Pasco Basin is about 9
x10^8^ m^3^ (3.2 x 10^10 ^ft^3^) annually (DOE 1988). This was
calculated by multiplying the average annual precipitation averaged over
the Pasco Basin by the 4900 km^2^ (1900 mi^2^) basin area. Precipitation
varies both spatially and temporally with higher amounts generally
falling at higher elevations. Annual precipitation measured at the HMS
has varied from 7.6 cm (3 in.) to 31.3 cm (12.3 in.) since 1945. Most
precipitation occurs during the late autumn and winter, with more than
half of the annual amount occurring from November through February. Mean
annual runoff from the Pasco Basin is estimated at 3.1 x 10^7^ m^3^/yr
(1.1 x 10^9 ^ft^3^/yr), or approximately 3 percent of the total
precipitation (DOE 1988). Most of the remaining precipitation is lost
through evapotranspiration; however, a portion of the precipitation that
infiltrates the soil is not lost to evaporation or transpiration and
eventually recharges the groundwater flow system. The amount of recharge
varies spatially based primarily on soil texture and vegetation (Gee et
al. 1992, Fayer and Walters 1995). Recharge also varies temporally with
the majority occurring in the winter and spring. There is some evidence
that the most significant recharge events are associated with rapid
melting of relatively large snowpacks, which may only occur a few times
in a decade (Fayer and Szecsody 2004).

#### Flooding

Large Columbia River floods have occurred in the past (DOE 1987), but
the likelihood of recurrence of large-scale flooding has been reduced by
the construction of several flood control/water-storage dams upstream of
the Hanford Site (Figure 4.4-6). Major floods on the Columbia River are
typically the result of rapid melting of the winter snowpack over a wide
area augmented by above-normal precipitation. The maximum historical
flood on record occurred June 7, 1894, with a peak discharge at the
Hanford Site of 21,000 m^3^/s (742,000 ft^3^/s). The floodplain
associated with the 1894 flood was modeled based on topographic
crosssections of the river channel (ERDA 1976) (Figure 4.4-7). The
largest recent flood

![](media/image7.png){width="6.415972222222222in"
height="7.374305555555556in"}

> **Figure 4.4-6**. Locations of Principal Dams within the Columbia
> Plateau, Washington and Oregon (DOE 1988)
>
> ![](media/image8.png){width="5.75in" height="8.336805555555555in"}
>
> **Figure 4.4-7**. Flood Area on the Hanford Site, Washington, during
> the 1894 Flood Based on Modeled Topographic Cross Sections (DOE 1986)

took place during 1948 with an observed peak discharge of 20,000 m^3^/s
(700,000 ft^3^/s) at the Hanford Site. The exceptionally high runoff
during the spring of 1996 resulted in a maximum discharge of nearly
11,750 m^3^/s (415,000 ft^3^/s) (USGS 2002b). There are no Federal
Emergency Management Agency (FEMA) floodplain maps for the Hanford Reach
of the Columbia River. FEMA only maps developing areas, and the Hanford
Reach has been specifically excluded because the adjacent land is
primarily under federal control.

Evaluation of flood potential is conducted in part through the concept
of the probable maximum flood, which is determined from the upper limit
of precipitation falling on a drainage area and other hydrologic factors
such as antecedent moisture conditions, snowmelt, and tributary
conditions that could result in maximum runoff. The probable maximum
flood for the Columbia River downstream of Priest Rapids Dam has been
calculated to be 40,000 m^3^/s (1.4 million ft^3^/s) and is greater than
the 500-year flood (Figure 4.4-8). This flood would inundate parts of
the 100 Area adjacent to the Columbia River, but the central portion of
the Hanford Site would remain unaffected (DOE 1986).

The U.S. Army Corps of Engineers (Corps) (1989) has derived the Standard
Project Flood with both regulated and unregulated peak discharges given
for the Columbia River downstream of Priest Rapids Dam. Frequency curves
for both unregulated and regulated peak discharges are also given for
the same portion of the Columbia River. The regulated Standard Project
Flood for this part of the river is given as 15,200 m^3^/s
(54,000 ft^3^/s) and the 100-year regulated flood as 12,400 m^3^/s
(440,000 ft^3^/s) (DOE 1998c). Impacts to the Hanford Site are
negligible and would be less than the probable maximum flood
(Figure 4.4-8).

Potential dam failures on the Columbia River have been evaluated.
Upstream failures could arise from a number of causes, with the
magnitude of the resulting flood depending on the degree of breaching at
the dam. The Corps evaluated a number of scenarios on the effects of
failures of Grand Coulee Dam, assuming flow conditions of 11,000 m^3^/s
(400,000 ft^3^/s). For emergency planning, they hypothesized that 25 and
50 percent breaches, the "instantaneous" disappearance of 25 or 50
percent of the center section of the dam, could result from the
detonation of explosives. The discharge or floodwave resulting from such
an instantaneous 50 percent breach at the outfall of the Grand Coulee
Dam was determined to be 600,000 m^3^/s (21 million ft^3^/s). In
addition to the areas inundated by the probable maximum flood (Figure
4.4-8), the remainder of the 100 Area, the 300 Area, and nearly all of
Richland would be flooded (DOE 1986, ERDA 1976). No determinations were
made for failures of dams upstream, for associated failures downstream
of Grand Coulee or for breaches greater than 50 percent of Grand Coulee
Dam. The 50 percent scenario was believed to represent the largest
realistically conceivable flow resulting from either a natural or
human-induced breach (DOE 1986). It was also assumed that a scenario
such as the 50 percent breach would occur only as the result of direct
explosive detonation, and not because of a natural event such as an
earthquake, and that even a 50 percent breach under these conditions
would indicate an emergency situation in which there might be other
overriding major concerns.

The possibility of a landslide resulting in river blockage and flooding
along the Columbia River has been examined for an area bordering the
east side of the river upstream of the city of Richland. The possible
landslide area considered was the 75-m- (250-ft-) high bluff generally
known as White Bluffs. Calculations were made for an 8 x 10^5^ m^3^ (1 x
10^6^ yd^3^) landslide volume with a concurrent flood flow of
17,000 m^3^/s (600,000 ft^3^/s) (a 200-year flood), resulting in a
floodwave crest elevation of 122 m (400 ft) above mean sea level. Areas
inundated upstream of such a landslide event would be similar to those
occurring during the probable maximum flood (DOE 1986).

![](media/image9.png){width="5.634027777777778in"
height="8.370138888888889in"}

> **Figure 4.4-8**. Flood Area for the Probable Maximum Flood on the
> Hanford Site, Washington, as Determined by the Upper Limit of
> Precipitation and Maximum Runoff (DOE 1986)

There have been fewer than 20 major floods on the Yakima River since
1862 (DOE 1986). The most severe occurred during November 1906, December
1933, May 1948, and February 1996; discharge magnitudes at Kiona,
Washington, were 1870 m^3^/s (66,000 ft^3^/s), 1900 m^3^/s
(67,000 ft^3^/s), 1050 m^3^/s (37,000 ft^3^/s), and 1300 m^3^/s
(45,900 ft^3^/s), respectively. The average flow of the Yakima River is
104 m^3^/s (165 ft^3^/s), and the average monthly maximum is 490 m^3^/s
(17,500 ft^3^/s). The recurrence intervals for the 1933 and 1948 floods
are estimated at 170 and 33 years, respectively. The development of
irrigation reservoirs within the Yakima River Basin has considerably
reduced the flood potential of the river. The southern border of the
Hanford Site could be susceptible to a 100-year flood on the Yakima
River (Figure 4.4-9).

During 1980, a flood risk analysis of Cold Creek was conducted as part
of the characterization of a basaltic geologic repository for high-level
radioactive waste. Such design work is usually done according to the
criteria of Standard Project Flood or probable maximum flood, rather
than the worst-case or 100-year flood scenario. Therefore, in lieu of
100- and 500-year floodplain studies, a probable maximum flood
evaluation was performed based on a large rainfall or combined
rainfall/snowmelt event in the Cold Creek and Dry Creek watershed
(Skaggs and Walters 1981). The probable maximum flood discharge rate for
the lower Cold Creek Valley was 2265 m^3^/s (80,000 ft^3^/s) compared to
564 m^3^/s (19,900 ft^3^/s) for the 100-year flood. Modeling indicated
that State Route (SR) 240 along the Site's southwestern and western
areas would not be usable (Figure 4.4-10).

#### Non-Riverine Surface Water

Active ponds on the Hanford Site include West Lake and the 200 Area
Treated Effluent Disposal Facility (TEDF) disposal ponds (Figure 4.4-1).
West Lake is north of the 200 East Area and is a natural feature
recharged from groundwater (Gephart et al. 1976, Poston et al. 1991).
West Lake has not received direct effluent discharges from Site
facilities; rather, its existence is caused by the intersection of the
elevated water table with the land surface in the topographically low
area. Water levels of West Lake fluctuate with water table elevation,
which is influenced by wastewater discharge in the 200 Areas. The water
level and size of the lake has been decreasing over the past several
years because of reduced wastewater discharge (Section 4.4.3.2). There
is unsubstantiated information that sewage sludge may have been dumped
in the vicinity of West Lake during the 1940s, and this has been cited
as the reason for elevated dissolved solids and nitrate in the lake
water (Emery and McShane 1978, Meinhardt and Frostenson 1979). However,
it is possible that the concentration of salts resulted from evaporation
of groundwater at the lake, which has no outlet. Total dissolved solids
are approximately 15,000 mg/L and pH is greater than 9. Nitrate and
ammonia concentrations of about 1.8 and 2.6 mg/L, respectively, have
been reported, which are greater than freshwater lakes, but lower than
other alkaline lakes in Washington such as Soap Lake and Lake Lenore.
West Lake contains relatively high levels of uranium that are thought to
be from natural sources concentrated by evaporation in the lake (Poston
et al. 1991, 2003).

TEDF is east of the 200 East Area and consists of two disposal ponds.
These ponds are each 0.02 km^2^ (0.008 mi^2^) in size and receive
industrial wastewater permitted in accordance with Ecology's State Waste
Discharge Permit Program (WAC 173-216). The wastewater evaporates into
the air or percolates into the ground from the disposal ponds.

There are several naturally occurring vernal ponds near Gable Mountain
and Gable Butte (Hall 1998). These ponds appear to occur where a
depression is present in a relatively shallow buried basalt surface.
Water collects within the depression over the winter resulting in a
shallow pond that dries during the summer months. The formation of these
ponds in any particular year depends on the amount and temporal
distribution of precipitation and snowmelt events. The vernal ponds
range in size from about 20 ft x 20 ft to 150 ft x 100 ft (6.1 m x 6.1 m
to 45.73 m x 30.5 m), and were found in three clusters.

![](media/image10.png){width="6.210416666666666in"
height="7.9631944444444445in"}

> **Figure 4.4-9**. Flood Area from a 100-Year Flood of the Yakima River
> near the Hanford Site, Washington (DOE 1986)

![](media/image11.png){width="6.043055555555555in"
height="7.936805555555556in"}

> **Figure 4.4-10**. Extent of Probable Maximum Flood in Cold Creek
> Area, Hanford Site, Washington, delineated using the U.S. Army Corps
> of Engineers' HEC-2 Water Surface Profiles model (Skaggs and Walters
> 1981)

Approximately 10 were documented at the eastern end of Umtanum Ridge, 7
were observed in the central part of Gable Butte, and 3 were found at
the eastern end of Gable Mountain (Figure 4.0-1).

Other than rivers and springs, there are no naturally occurring bodies
of surface water adjacent to the Hanford Site. There are wetlands caused
by irrigation, on the east and west sides of the Wahluke Slope, which
lies north of the Columbia River and on the White Bluffs east of the
Columbia River. Hatcheries and irrigation canals constitute the only
other surface water in the Hanford Site vicinity. The Ringold Hatchery
is located just south of the Hanford Site boundary on the east side of
the Columbia River (Figure 4.4-1).

### Hanford Site Vadose Zone 

The vadose zone is that part of the geologic media which extends from
the earth's surface to the water table. At the Hanford Site, the
thickness of the vadose zone ranges from 0 m (0 ft) near the Columbia
River to greater than 100 m (328 ft) beneath parts of the central
plateau (Hartman 2000). Unconsolidated glacio-fluvial sands and gravels
of the Hanford formation make up most of the vadose zone. In some areas,
such as most of the 200 West Area and in some of the 100 Areas, the
fluvial-lacustrine sediments of the Ringold Formation make up the lower
part of the vadose zone. The Cold Creek unit also makes up part of the
vadose zone. The integrated knowledge obtained from previous and
on-going studies provides a good conceptual understanding of the
geologic, hydraulic, and geochemical environment and its controls on the
distribution and movement of contaminants within the vadose zone (DOE
1999b; Last* *et al. 2004).

Moisture movement through the vadose zone is important because it is the
driving force for migration of most contaminants to the groundwater.
Radioactive and hazardous wastes in the soil column from liquid-waste
disposals, unplanned leaks, solid waste burial, and underground tank
storage are potential sources of continuing and future vadose zone and
groundwater contamination. Contaminants may continue to move downward
for long periods (tens to hundreds of years depending on recharge rates
and the distribution coefficient of the contaminant) after termination
of liquid waste disposal.

Except for the State Approved Land Disposal Site (SALDS), the 200 Area
TEDF ponds (Figure 4.4-1), and septic drain fields, liquid discharges to
the vadose zone ended during the mid-1990s. Currently, the major source
of moisture to the vadose zone is precipitation. Infiltration and deep
drainage of meteoric water in the vadose zone causes older preexisting
water to be displaced downward by newly infiltrated water. The amount of
deep drainage (below the root zone) at any particular site is dependent
on the total amount of water available at the time of the event, soil
type, and the presence of vegetation. Usually, vegetation reduces the
amount of deep drainage through the biological process of transpiration.

The vadose-zone stratigraphy influences the movement of liquid through
the soil column. Where conditions are favorable, lateral spreading of
liquid effluent and/or local perched water zones may develop. Lateral
spreading can occur along any strata with contrasting conductivity.
Perched water zones form where downward moving moisture accumulates on
top of less-permeable soil lenses or highly cemented horizons. Even in
relatively uniform sediments the influence of grain orientation is
important and can give rise to anisotropic hydraulic properties, causing
significant lateral movement of contaminant plumes (Ward et al. 2002a,
b; Zhang et al. 2003). Lateral spreading can delay the arrival of
contaminants at the water table but may cause mixing of the subsurface
plume at one site with that of an adjacent site. Spreading may also
require increasing the area of surface barriers to cover wider plumes.

Preferential flow may also occur along discontinuities, such as clastic
dikes and fractures. Clastic dikes are a common geologic feature in the
suprabasalt sediments at the Hanford Site. Their most important feature
is their potential to either enhance or inhibit vertical and lateral
movement of contaminants in the subsurface, depending on textural
relationships (Fecht et al. 1999).

#### Vadose Zone Contamination

The Hanford Site has more than 800 past-practice liquid-disposal
facilities. Radioactive liquid waste was discharged to the vadose zone
through reverse (injection) wells, French drains, cribs, ponds,
trenches, and ditches. From 1944 through the late 1980s, 1.5 to 1.7
billion m^3^ (396 to 449 billion gal) of effluent were disposed to the
soils (Gephart 1999). Most effluent was released in the 200 Areas. The
major groundwater contaminant plumes emanating from the 200 Areas are
those of tritium and nitrate. The major source for both was discharges
from chemical processing of irradiated nuclear fuel rods.

Also present are technetium-99 and iodine-129 which, like tritium and
nitrate, are mobile in both the vadose zone and groundwater. The major
sources of technetium-99 and iodine-129 were discharges to liquid
disposal facilities. Vadose zone sources for these contaminants remain
beneath many past-practice disposal facilities. However, other than
physical sampling and laboratory analysis, there are few direct ways to
monitor tritium, nitrate, technetium-99, and iodine-129 in the vadose
zone.

Liquid wastes generated during plutonium recovery processes at Z Plant
in the 200 West Area contained carbon tetrachloride. These wastes were
discharged to nearby subsurface liquid waste disposal facilities from
1955 to 1973 (Rohay et al. 1994, Swanson *et al*. 1999). Soil vapor
extraction is being used to remove carbon tetrachloride from the vadose
zone in the 200 West Area (Hartman et al. 2004).

Approximately 280 unplanned releases in the 200 Areas also contributed
contaminants to the vadose zone (DOE 1997b). Many of these were from
underground tanks and have contributed significant contamination to the
vadose zone. In addition, approximately 50 active and inactive septic
tanks and drain fields and numerous radioactive and non-radioactive
landfills and dumps have impacted the vadose zone (DOE 1997b). The
landfills are and were used to dispose of solid wastes, which, in most
instances, are easier to locate, retrieve, and remediate than are liquid
wastes.

One hundred and forty-nine single-shell tanks and 28 double-shell tanks
have been used to store high-level radioactive and mixed wastes in the
200 Areas. The wastes resulted from uranium and plutonium recovery
processes and, to a lesser extent, from strontium and cesium recovery
processes. Sixty-seven of the single-shell tanks are assumed to have
leaked an estimated total of 2839 to 3975 m^3^ (750,000 to
1,050,000 gal) of contaminated liquid to the vadose zone (Hanlon 2001).
The three largest tank leaks were 435,320 L (115,000 gal), 37,850 to
1,048,560 L (10,000 to 277,000 gal), and 265,980 L (70,365 gal). The
average tank leak was between 41,640 and 60,565 L (11,000 and
16,000 gal) (Hanlon 2001).

In addition to removing pumpable liquids from the single-shell tanks,
interim measures have been taken to reduce the movement of tank farm
contaminants in the vadose zone. Infiltration of water has been
identified as the primary means by which contaminants are displaced
beneath the farms. Surface water controls have been constructed to
reduce surface water run-on from major meteorological events and from
breaks in waterlines. Also, waterlines that were determined unnecessary
have been isolated, cut, and capped. Waterlines that were found to be
necessary for continued operations are being leak tested and any lines
found to be leaking will be replaced.

Cooling water from the single-pass reactors along the Columbia River was
routinely routed to retention basins in the 100 Areas prior to return to
the river. Thermal shock from the hot cooling water cracked the basins
so that much of the cooling water leaked into the vadose zone. In
addition, trenches were used for disposal of cooling water from 100-KE,
100-KW, and 100-N Reactors. The disposed cooling waters contained
fission and neutron activation products and some chemicals and
actinides. Tritium, strontium-90, nitrate, and chromium migrate through
the vadose zone to groundwater, and ultimately, to the Columbia River in
the 100 Areas. Chromium is actively being remediated at the 100-K and
100-H Areas by pump-and-treat methods and in the 100-D/DR Area by
pump-and-treat and in situ redox methods (Hartman et al. 2004).

Contaminated cooling water that had contacted broken fuel rods was
routed to trenches rather than being directly returned to the river.
These fluids contained large quantities of fission and neutron
activation products. In addition, leakage from fuel-storage basins in
the 100-K Area also contributed quantities of fission products,
transuranics, and carbon-14 to the soil column (Johnson et al. 1995).
Thus, both past-practice sites and fuel-storage basin leakage are
potential vadose zone sources of contaminants in the 100 Areas.
Groundwater monitoring data from wells near the 100-KE and 100-KW basins
do not show any indication of current leakage from either basin.

The amount of contamination remaining in the vadose zone is uncertain.
Several compilations of vadose zone contamination have been formulated
through the past years. DOE (1997b), Kincaid et al. (1998, 2001), and
Simpson et al. (2001) contain the most recent inventories of
contaminants disposed to past-practice liquid disposal facilities in the
200 Areas. Dorian and Richards (1978) list contaminant inventories
disposed to most 100 Area past-practice facilities. Agnew (1997) and
Anderson (1990) list inventories of effluents sent to single-shell tanks
and Simpson et al. (2001) list the compositions of fluids leaked from
single-shell tanks. Most recently, the Hanford Tank Farm Vadose Zone
Project has issued a series of reports that estimate the curies of
gamma-emitting radionuclides and the volumes of contaminated soil
associated with each single-shell tank farm
(<http://www.gjo.doe.gov/programs/hanf/> ).

Further information on vadose zone characterization and monitoring
activities on the Hanford Site is available online at
[http://vadose.pnl.gov](http://vadose.pnl.gov/) and
<http://www.hanford.gov/cp/gpp/> as well as in the annually updated
Hanford Site groundwater monitoring report (i.e., Hartman et al. 2004).

### Hanford Site Groundwater

Groundwater at the Hanford Site originated as either recharge from rain
and snowmelt, or from excess irrigation, canal seepage, and wastewater
disposal. Most of this groundwater will eventually discharge to the
Columbia River. Some will be brought to the surface through wells, or
excavations, or through evaporation or transpiration in shallow water
table areas.

Groundwater beneath the Hanford Site is found in both an upper
unconfined aquifer system and deeper basalt-confined aquifers. The
unconfined aquifer system is also referred to as the suprabasalt aquifer
system because it is within the sediments that overlie the basalt
bedrock. Portions of the suprabasalt aquifer system are locally
confined. However, because the entire suprabasalt aquifer system is
interconnected on a site-wide scale, it is referred to in this report as
the Hanford unconfined aquifer system.

#### Basalt-Confined Aquifer System

Relatively permeable sedimentary interbeds and the more porous tops and
bottoms of basalt flows provide the confined aquifers within the
Columbia River Basalts. The horizontal hydraulic conductivities of most
of these aquifers fall in the range of 10^-10^ to 10^-4^ m/s (3 x
10^-10^ to 3 x 10^-4^ ft/s). Saturated but relatively impermeable dense
interior sections of the basalt flows have horizontal hydraulic
conductivities ranging from 10^-15^ to 10^-9^ m/s (3 x 10^-15^ to 3 x
10^-9 ^ft/s), about five orders of magnitude lower than some of the
confined aquifers that lie between these basalt flows (DOE 1988).
Hydraulic-head information indicates that groundwater in the
basalt-confined aquifers generally flows toward the Columbia River and,
in some places, toward areas of enhanced vertical interaquifer flow with
the unconfined aquifer system (Hartman et al. 2004, DOE 1988, Spane
1987). The basalt-confined aquifer system is important because there is
a potential for significant groundwater movement between the two
systems. Head relationships presented in previous reports (DOE 1988)
demonstrate the potential for such interaquifer flow. In addition,
limited water chemistry data indicate that interaquifer flow has
occurred in an area near the Gable Mountain anticlinal structure, north
of the 200 East Area (Graham et al. 1984, Jensen 1987).

#### Unconfined Aquifer System

The unconfined aquifer system is composed primarily of the Ringold
Formation and overlying Hanford formation (Section 4.3). In some areas,
the coarse-grained multilithic facies of the Cold Creek unit
(pre-Missoula gravels) lie between these formations and below the water
table. The other subunits of the Cold Creek unit are generally above the
water table.

Water table elevations (Figure 4.4-11) show that groundwater in the
unconfined aquifer at Hanford generally flows from recharge areas in the
elevated region near the western boundary of the Hanford Site toward the
Columbia River on the eastern and northern boundaries. The Columbia
River is the primary discharge area for the unconfined aquifer. The
Yakima River borders the Hanford Site on the southwest and is generally
regarded as a source of recharge. Along the Columbia River shoreline,
daily river level fluctuations may result in water table elevation
changes of up to 3 m (10 ft). During the high river stage periods of
1996 and 1997, some wells near the Columbia River showed water level
changes of more than 3 m (10 ft). As the river stage rises, a pressure
wave is transmitted inland through the groundwater. The longer the
duration of the higher river stage, the farther inland the effect is
propagated. The pressure wave is observed farther inland than the water
actually moves. For the river water to flow inland, the river level must
be higher than the groundwater surface and must remain high long enough
for the water to flow through the sediments. Typically, this inland flow
of river water is restricted to within several hundred feet of the
shoreline (McMahon and Peterson 1992).

Gee et al. (1992) and Fayer et al. (1996) estimate that recharge rates
from precipitation across the Hanford Site range from near zero to over
100 mm/year (3.94 in./yr). Recharge is variable both spatially and
temporally. It is greatest for coarse-textured soils bare of deep-rooted
vegetation and in years with rapid snowmelt events and precipitation
during cool months. The magnitude of recharge at a particular location
is influenced by five main factors: climate, soils, vegetation,
topography, and springs and streams. Events such as the fire that burned
vegetation from a large portion of the Hanford Site during the summer of
2000 also affect recharge rates. Fayer et al. (1996) used several types
of field data and computer modeling to estimate the areal distribution
of mean recharge rates for the soil and vegetation conditions at the
Hanford Site, including any disturbance by Hanford operations.

Between 1944 and the mid-1990s, the volume of artificial recharge from
Hanford wastewater disposal was significantly greater than recharge from
precipitation. An estimated 1.68 x 10^12^ L (4.44 x 10^11^ gal) of
liquid was discharged to disposal ponds, trenches, and cribs during this
period. Wastewater discharge has decreased since 1984 and currently
contributes a volume of recharge in the same range as the estimated
natural recharge from precipitation. Because of the reduction in
discharges, groundwater levels are falling, particularly around the
operational areas (Hartman et al. 2004).

After the beginning of Hanford operations during 1943, the water table
rose about 27 m (89 ft) under the U Pond disposal area in the 200 West
Area and about 9.1 m (30 ft) under disposal ponds near the 200 East Area
(Figure 4.4-11). The volume of water that was discharged to the ground
at the 200 West Area was actually less than that discharged at the 200
East Area. However, the lower hydraulic conductivity of the aquifer near
the 200 West Area inhibited groundwater movement in this area resulting
in a higher groundwater mound. The presence of the groundwater mounds
locally affected the direction

![](media/image12.png){width="6.5in" height="8.092361111111112in"}

> **Figure 4.4-11**. Water Table Elevations in Meters (1 m = 3.28 ft)
> and Inferred Groundwater Flow Directions for the Unconfined Aquifer at
> Hanford, Washington, March 2004 (Hartman *et al*. 2005)

of groundwater movement, causing radial flow from the discharge areas.
Zimmerman et al. (1986) documented changes in water table elevations
between 1950 and 1980. Until about 1980, the edge of the mounds migrated
outward from the sources over time. Groundwater levels have declined
over most of the Hanford Site since 1984 because of decreased wastewater
discharges (Hartman et al. 2004). Although the reduction of wastewater
discharges has caused water levels to drop significantly, a residual
groundwater mound beneath the 200 West Area is still shown by the curved
water table contours near this area and small groundwater mounds exist
near the 200 Area Treated Effluent Disposal Facility (TEDF) and SALDS
wastewater disposal sites (Figure 4.4-11).

Horizontal hydraulic conductivities of sand and gravel facies within the
Ringold Formation generally range from about 1 to 100 m/d (3 to
330 ft/d), compared to 10 to 3000 m/d (33 to 10,000 ft/d) for the
Hanford formation and the coarse-grained multilithic facies of the Cold
Creek unit (pre-Missoula gravels) (DOE 1988, Cole et al. 2001, Thorne
and Newcomer 2002). Because the Ringold Formation sediments are more
consolidated and partially cemented, they are about 10 to 100 times less
permeable than the sediments of the overlying Hanford formation. Before
wastewater disposal operations at the Hanford Site, the uppermost
aquifer was mainly within the Ringold Formation, and the water table
extended into the Hanford formation at only a few locations (Newcomb et
al. 1972). However, wastewater discharges raised the water table
elevation across the Site. The general increase in groundwater elevation
caused the unconfined aquifer to extend upward into the Hanford
formation over a larger area, particularly near the 200 East Area. This
resulted in an increase in groundwater velocity because of both the
greater volume of groundwater and the higher permeability of the newly
saturated Hanford formation sediments.

#### Limitations of Hydrogeologic Information

The sedimentary architecture of the unconfined aquifer is very complex
because of repeated deposition and erosion. Although hundreds of wells
have been drilled on the Hanford Site, many penetrate only a small
percentage of the total unconfined aquifer thickness, and there are a
limited number of wells that can be used for defining the deeper
sediment facies. A number of relatively deep wells were drilled in the
early 1980s as part of a study for a proposed nuclear power plant (PSPL
1982), and these data are helpful in defining facies architecture. For
most of the thinner and less extensive sedimentary units, correlation
between wells is either not possible or uncertain. Major sand and gravel
units of the Ringold Formation (e.g., Units A, B, C, D, and E) are
separated by mud-dominated units (Figure 4.3-5). In some places the mud
units act as aquitards that locally confine groundwater in deeper
permeable sediments.

A limited amount of hydraulic property data is available from testing of
wells. Hydraulic test results from wells on the Hanford Site have been
compiled for the Hanford Groundwater Monitoring Project and for
environmental restoration efforts (Kipp and Mudd 1973; Connelly et al.
1992 (a, b); Thorne and Newcomer 1992, 2002; Spane and Thorne 1995,
2000; Spane et al. 2001(a, b); Spane et al. 2002). Most hydraulic tests
were conducted within the upper 15 m (49 ft) of the aquifer, and many
were open to more than one geologic unit. In some cases, changes in
water table elevation may have significantly changed the unconfined
aquifer transmissivity at a well since the time of the hydraulic test.
Few hydraulic tests within the Hanford Site unconfined aquifer system
have yielded accurate estimates of aquifer-specific yield.

#### Groundwater Travel Times

Tritium and carbon-14 measurements indicate that groundwater residence
time (time that ground water has been in the subsurface) is up to
thousands of years for the unconfined aquifer and more than 10,000 years
for groundwater in the shallow confined aquifer (Johnson et al. 1992).
Chlorine-36 and noble gas isotope data suggest groundwater ages of
greater than 100,000 years in the deeper confined systems (Johnson et
al. 1992). These relatively long residence times are consistent with
semiarid-site recharge conditions. However, groundwater travel time from
the 200 East Area to the Columbia River has been shown to be much
faster, in the range of 10 to 30 years (USGS 1987, Freshley and Graham
1988). This is because of large volumes of recharge from wastewater that
was disposed in the 200 Areas between 1944 and the mid-1990s and the
relatively high permeability of Hanford formation sediments, which are
below the water table between the 200 East Area and the Columbia River.
Travel time from the 200 West Area is greater because of the lower
permeability of Ringold Formation sediments. Plume monitoring indicates
that groundwater from the 200 West Area has moved about 6 km (3.7 mi)
during the past 50 years. Groundwater travel times from the 200 Areas to
the Columbia River are expected to decrease because of diminishing
wastewater recharge in the 200 Areas and the resulting reduction of the
hydraulic gradient.

#### Groundwater East and North of the Columbia River

The Hanford Site boundary extends east and north of the Columbia River.
Hanford Site activities in these areas have not impacted the
groundwater. However, the groundwater in this area is impacted by high
recharge from irrigation and canal leakage. The South Columbia Basin
Irrigation District manages surface water used to irrigate land east and
north of the Columbia River. Recharge from irrigation water has
increased water table elevations in large areas of the Pasco Basin by as
much as 92 m (300 ft) (Drost et al. 1989).

There are two general hydrologic areas that impinge upon the Hanford
Site boundaries to the east and north of the river. The eastern area
extends from north to south between the lower slope of Saddle Mountain
and the Esquatzel Diversion canal and includes the Ringold Coulee, White
Bluffs area, and Esquatzel Coulee. The water table occurs in the Pasco
gravels of the Hanford formation in both Ringold and Esquatzel Coulees.
Brown (1979) reported that runoff from spring discharge at the mouth of
Ringold Coulee is greater than 0.631 m^3^/s (22.3 ft^3^/s). Elsewhere in
this area, the unconfined aquifer is in the less-transmissive Ringold
Formation. Irrigation has also created perched aquifers and resulted in
a series of springs issuing from perched water along the White Bluffs.
The increased hydraulic pressure in these sediments has caused
subsequent slumping and landslides (Brown 1979, Newcomer et al. 1991).

The other principal irrigated area is the northern part of the Pasco
Basin on the Wahluke Slope, which lies between the Columbia River and
the Saddle Mountain anticline. Irrigation return waste-water paths off
of the Wahluke Slope have created ponds and springs in the Saddle
Mountain Wildlife Refuge. The direction of unconfined groundwater flow
is southward from the basalt ridges toward the Columbia River. Bauer et
al. (1985) reported that lateral water table gradients are essentially
equal to or slightly less than the structural gradients on the flanks of
the anticlinal fold mountains where the basalt dips steeply.

### Groundwater Quality 

The quality of groundwater at the Hanford Site, uncontaminated by
Hanford activities, varies depending on the aquifer system and depth,
which generally is related to residence time in the aquifer (DOE 1992a,
1997c; Hartman et al. 2004). DOE has conducted a study examining
historical data and new data from wells in areas not affected by Hanford
Site contaminants (DOE 1997c).

Groundwater chemistry in the basalt-confined aquifers displays a range
depending on depth and residence time (DOE 1988). The chemical type
varies from calcium- and magnesium-carbonate water to sodium- and
chloride-carbonate water. Some of the shallower basalt-confined aquifers
in the region (e.g., the Wanapum basalt aquifer) have exceptionally good
water quality characteristics: less than 300 mg/L dissolved solids; less
than 0.1 mg/L iron and magnesium; less than 20 mg/L sodium, sulfate, and
chloride; and less than 10 ppb heavy metals (Johnson et al. 1992).
However, deeper basalt-confined aquifers typically have high dissolved
solids content and some have fluoride concentrations greater than the
drinking water standard of 5 mg/L (DOE 1988).

Groundwater beneath large areas of the Hanford Site has been
contaminated by radiological and chemical constituents resulting from
past Hanford Site operations. These contaminants were primarily
introduced through wastewater discharged to cribs, ditches, injection
wells, trenches, and ponds (Kincaid et al. 1998). Additional
contaminants from spills, leaking waste tanks, and burial grounds
(landfills) have also entered groundwater in some areas. Contaminant
concentrations in the existing groundwater plumes are expected to
decline through radioactive decay, mineral adsorption, chemical
degradation, and dispersion. However, contaminants also exist within the
vadose zone beneath waste sites (Section 4.4.2) as well as in waste
storage and disposal facilities. These contaminants have a potential to
continue to move downward into the aquifer.

Some contaminants, including tritium and chloride, move at the same
velocity as groundwater. The movement of other contaminants is slower
because they react with or are sorbed on the surface of minerals within
the aquifer or the vadose zone. The factor by which the velocity of a
constituent is reduced compared to average groundwater flow velocity is
called the "retardation factor." Therefore, tritium in groundwater will
move ten times faster than a contaminant with a retardation factor of
ten. For Hanford sediments, it has been estimated that technetium and
chromium have small retardation factors and move at nearly the same
velocity as groundwater (Thorne 2004). Iodine, nitrate, uranium,
and carbon tetrachloride were estimated to have median retardation
factors between 3 and 12. Strontium, cesium, and plutonium were
estimated to have median retardation factors between 290 and 27,000.
Cantrell *et al*. (2002) and Serne and Kaplan (2000) offer additional
information on retardation of chemicals transported in groundwater.

Groundwater contamination is being actively remediated through
pump-and-treat operations at the 200-West Area, 100-F Area, and 100-K
Area. These operations are summarized in Hartman et al. (2004). At the
100-N Area, pump-and-treat remediation has been terminated and a passive
treatment barrier is being used to reduce contaminant migration.

[]{.mark}

Monitoring of radiological and chemical constituents in groundwater at
the Hanford Site is performed to characterize physical and chemical
trends in the flow system, establish groundwater quality baselines,
assess groundwater remediation, and identify new or existing groundwater
problems. Groundwater monitoring is also performed to verify compliance
with applicable environmental laws and regulations. Samples were
collected from 710 wells and 79 shoreline aquifer sampling tubes during
FY 2003 to determine the distributions of radiological and chemical
constituents in Hanford Site groundwater (Hartman et al. 2004).

[]{.mark}

To assess the quality of groundwater, concentrations measured in samples
were compared with maximum contaminant levels (MCL) or interim Drinking
Water Standards (DWS) and DOE's Derived Concentration Guides (DCG). The
MCL or DWS standards are legal limits for contaminant concentrations in
public drinking water supplies enforceable by the Washington State
Department of Health or EPA. Although these standards are only
applicable at the point of consumption of the water, they provide a
useful indicator of negative impacts to the groundwater resource. The
DCG applies only to radionuclides and is based on the concentration that
would result in a dose exposure of 1 mSv/year (100-mrem/year) effective
dose equivalent, a calculation of dose that assumes ingestion under
specified intake scenarios.

Radiological constituents including carbon-14, iodine-129, strontium-90,
technetium-99, gross alpha, gross beta, tritium, and uranium were
detected at levels greater than the DWS in one or more onsite wells.
Concentrations of strontium-90, tritium, and uranium were detected at
levels greater than DOE's DCG. Certain nonradioactive chemicals
regulated by EPA and the State of Washington (nitrate, fluoride,
chromium, cyanide, carbon tetrachloride, chloroform, trichloroethylene,
and tetrachloroethylene) were also present in Hanford Site groundwater
during fiscal year 2003 (Table 4.4-2). The extent of radiological and
non-radiological contamination in Hanford Site groundwater above the
applicable DWS is determined annually (Figures 4.4-12 and 4.4-13). The
area of contaminant plumes on the Hanford Site with concentrations
exceeding drinking water standards was estimated to be 190 km^2^
(89.2 mi^2^) during fiscal year 2004.

### 100 Area Hydrology

The hydrology of the 100 Area is affected by its location adjacent to
the Columbia River. The water table ranges in depth from near 0 m (0 ft)
at the river edge to 30 m (107 ft). The groundwater flow direction is
generally toward the river. However, during high river stage, the flow
direction may reverse immediately adjacent to the river. The unconfined
aquifer in the 100 Area is composed of either the Ringold Unit E gravels
or a combination of the Unit E gravels and the Hanford formation (Figure
4.3-5). There are two large areas where the water table is within the
Ringold Formation (Lindsey 1992), and the Hanford formation is
unsaturated (Figure 4.4-14). In the 100-H and 100-F Areas, the Ringold
Unit E gravels are missing and the Hanford formation lies directly over
the fine-grained Ringold lower-mud unit. In most of the 100 Area, the
lower Ringold mud forms an aquitard, and the Ringold gravels below the
mud are locally confined. Additional information on the hydrology of the
100 Area is available in Hartman and Peterson (1992) and Peterson et al.
(1996). A number of studies of various sites in the 100 Area present
specific hydrologic information. These include: 100-B/C Area - Lindberg
(1993a); 100-D Area - Lindsey and Jaeger (1993); 100-F Area - Lindsey
(1992), Peterson (1992); 100-H Area - Liikala et al. (1988), Lindsey and
Jaeger (1993); 100-K Area - Lindberg (1993b); and 100-N Area - Gilmore
et al. (1992), Hartman and Lindsey (1993).

### 200 Areas Hydrology

In the 200 West Area, the water table occurs almost entirely in the
Ringold Unit E gravels, while in the 200 East Area, it occurs primarily
in the Hanford formation and in the Ringold Unit A gravels (Figure
4.3-5). Along the southern edge of the 200 East Area, the water table is
in the Ringold Unit E gravels. The upper Ringold facies were eroded in
most of the 200 East Area by the ancestral Columbia River and, in some
places, by the Missoula floods that subsequently deposited Hanford
gravels and sands on what was left of the Ringold Formation (DOE 2002b).
Because the Hanford formation and possibly the Cold Creek unit sand and
gravel deposits are much more permeable than the Ringold gravels, the
water table is relatively flat in the 200 East Area, but groundwater
flow velocities are higher. On the north side of the 200 East Area,
there is evidence of erosional channels that may allow interaquifer flow
between the unconfined and uppermost basalt-confined aquifer (Graham et
al. 1984, Jensen 1987).

The hydrology of the 200 Areas has been strongly influenced by the
discharge of large quantities of wastewater to the ground during a
50-year period. The discharges caused elevated groundwater levels across
much of the Hanford Site resulting in a large groundwater mound beneath
the former U Pond (Figure 4.4-11) in the 200 West Area and a smaller
mound beneath the former B Pond, east of the 200 East Area. Water table
changes beneath the 200 West Area have been greatest because of the
lower transmissivity of the aquifer in this area (Cole et al. 2001).
Discharges of water to the ground have been greatly reduced, and
corresponding decreases in the elevation of the water table have been
observed.

**Table 4.4-2**. Maximum Concentrations of Selected Groundwater
Contaminants during Fiscal Year 2003 (modified from Hartman et al. 2004)

**100-BC-5 100-KR-4 100-NR-2 100-HR-3-D 100-HR-3-H 100-FR-3**

\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\--
\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-- \-\-\-\-\-\-\-\-\-\-\-\--
\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\--
\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\--
\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\--

**Contaminant, units DWS(a) Aquifer Aquifer Aquifer Aquifer Aquifer**

**(alphabetical order) Wells Tubes Wells Tubes Wells Wells Tubes Wells
Tubes Wells Tubes**

arsenic (filtered), µg/L 10

cadmium (filtered), µg/L 5 3.3 3.1 3.4 3.9

carbon tetrachloride, µg/L 5

carbon-14, pCi/L 2,000 **20,900** 67.2 15.4

cesium-137, pCi/L 200 ND

chloroform, µg/L 100 1 7.2 1.1

chromium (dissolved), µg/L 100 46 38 **542** 52 **168** **5,440**
**295** **154** 43 90

cis-1,2-dichloroethene, µg/L 70

cobalt-60, pCi/L 100 ND

cyanide, µg/L 200

fluoride, mg/L 4 0.51 0.49 1 0.45 0.45 0.72

gross alpha, pCi/L 15 2.99 7.14 3.07 3.94 **72.4** 10.1

gross beta, pCi/L 50 **221 3,590 16,000** **466** **183 51.1**

iodine-129, pCi/L 1

nickel (filtered), µg/L 100 28.8 17 **416** 21.6

nitrate, mg/L 45 27.9 **195** 3.6 **228** **107** **474 177**

nitrite, mg/L 3.3 0.135 0.299 **7.55**

plutonium-239/240, pCi/L NA(b)

strontium-90, pCi/L 8 **98.9 15 2,440** ND **8,000** 7.06 **23.2 27.8**

technetium-99, pCi/L 900 46.7 85.4 **986** ND

trichloroethene, µg/L 5 **11** 9.8

tritium, pCi/L 20,000 **21,900** **32,200** **1,270,000** ND **31,400**
**23,700** **29,700** 6,210 11,500

uranium, µg/L 30 3.58 **119**

Note: Location description refers to Operable Unit groundwater interest
area designation.

Table lists highest measured concentration for fiscal year 2003 in each
groundwater interest area. Concentrations in bold exceed drinking water
standards. Blank space indicates the constituent not of concern in the
given area.

\(a\) DWS = Drinking water standard or U.S. Environmental Protection
Agency maximum contaminant level (MCL) if there is no DWS

\(b\) There is no drinking water standard for plutonium-239/240. The
Department of Energy Derived Concentration Guide is 30 pCi/L (1.1 Bq/L)

Conversion: 27 pCi/L = 1 Bq/L

NA = Not applicable ND = Not detected.

**Table 4.4-2**. (cont'd)

**200-ZP-1 200-UP-1 200-BP-5 200-PO-1 300-FF-5 1100-EM-1**

**Contaminant, units DWS(a) \-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\--
\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-- \-\-\-\-\-\-\-\-\-\-\-\--
\-\-\-\-\-\-\-\-\-\-\-\-- \-\-\-\-\-\-\-\-\-\-\--
\-\-\-\-\-\-\-\-\-\-\-\-\--**

**(alphabetical order) Wells Wells Wells Wells Wells Wells**

arsenic (filtered), µg/L 10 4.1 8.7 7.6 9.2

cadmium (filtered), µg/L 5 3.2 3.1 4.6 3.3

carbon tetrachloride, µg/L 5 **6,200** **690** 0.29 0.35

carbon-14, pCi/L 2,000

cesium-137, pCi/L 200 **1,170**

chloroform, µg/L 100 31 20 0.46 3 4.4

chromium (dissolved), µg/L 100 **592** **209** 54.9 **6,250** 7.3

cis-1,2-dichloroethene, µg/L 70 0.09 **160** 48

cobalt-60, pCi/L 100 48.4

cyanide, µg/L 200 6.4 **275**

fluoride, mg/L 4 **4.3** 0.7 0.98 1.3 0.52 **4.3**

gross alpha, pCi/L 15 6.73 13.9 **324** 10.7 **43.9 77**

gross beta, pCi/L 50 **4,390** **71,200** **12,100** **79.7** **97.5**
34.7

iodine-129, pCi/L 1 **36.7** **35.3** **3.65** **11.9**

nickel (filtered), µg/L 100 **328** **120** **133** **864** 41.6

nitrate, mg/L 45 **2,160** **1,930** **735** **170** **134** **261**

nitrite, mg/L 3.3 0.361 0.46 1.12 0.233 0.069 0.043

plutonium-239/240, pCi/L NA(b) **74.8**

strontium-90, pCi/L 8 1.29 **53.6** **5,680** **21.4** 4.03

technetium-99, pCi/L 900 **11,117** **188,000** **10,600** 287 319 27

trichloroethene, µg/L 5 **18** **11** 0.88 **7.2 27**

tritium, pCi/L 20,000 **2,170,000 634,000** **27,600 5,570,000
3,670,000** 251

uranium, µg/L 30 **367** **1,190** **554** 7.19 **235** 18

Note: Location description refers to Operable Unit groundwater interest
area designation.

Table lists highest measured concentration for fiscal year 2003 in each
groundwater interest area. Concentrations in bold exceed drinking water
standards. Blank space indicates the constituent was not of concern in
the given area..

\(a\) DWS = Drinking water standard or U.S. Environmental Protection
Agency maximum contaminant level (MCL) if there is no DWS

\(b\) There is no drinking water standard for plutonium-239/240. The
Department of Energy Derived Concentration Guide is 30 pCi/L (1.1 Bq/L)

Conversion: 27 pCi/L = 1 Bq/L

NA = Not applicable ND = Not detected.

![](media/image13.jpeg){width="6.4944444444444445in"
height="8.052777777777777in"}

> **Figure 4.4-12**. Distribution of Radionuclides in Groundwater on the
> Hanford Site, Washington, at Concentrations above the Maximum
> Contaminant Level or Interim Drinking Water Standard during Fiscal
> Year 2003 (Hartman et al. 2004) (27 pCi/L = 1 Bq/L)

![](media/image14.png){width="6.5in" height="8.059722222222222in"}

> **Figure 4.4-13**. Distribution of Hazardous Chemicals in Groundwater
> on the Hanford Site, Washington, at Concentrations above the Maximum
> Contaminant Level or Interim Drinking Water Standard during Fiscal
> Year 2003 (Hartman et al. 2004)
>
> ![](media/image15.png){width="5.903472222222222in"
> height="8.979861111111111in"}

The decline in part of the 200 West Area groundwater mound has been more
than 8 m (26 ft) (Hartman et al. 2004). Water levels are expected to
continue to decrease as the unconfined groundwater system reaches
equilibrium with the new level of artificial recharge (Wurstner and
Freshley 1994).

A number of reports dealing with the hydrogeology of the 200 Areas are
available including Williams *et al*. (2000, 2002), Graham et al.
(1981), Last et al. (1989), and Connelly et al. (1992a, b).

### 300 Area Hydrology

The unconfined aquifer water table in the 300 Area (Figure 4.4-11) is
found in both the Hanford formation and the Ringold Formation. It is 0
to 19 m (0 to 62 ft) below ground surface depending on location.
Elevation of the Columbia River stage strongly affects the groundwater
levels and flow near the river in the 300 Area. Water table contours in
the vicinity of the 300 Area are somewhat concentric, showing that there
is a groundwater discharge area for the unconfined aquifer system in the
area of convergence. Groundwater flows from the northwest, west, and
even the southwest to discharge into the Columbia River near the 300
Area. Schalla et al. (1988), Swanson (1992), and Hartman *et al*. (2004)
have provided more detailed information on the hydrogeology of the 300
Area.

### Richland North Area Hydrology

The Richland North Area (Figure 4.4-13) is located in the southern part
of the Hanford Site and includes the former 1100 Area,^(^[^2]^)^ which
was transferred from the DOE to the Port of Benton on October 1, 1998.
The groundwater in this area is influenced by artificial recharge
associated with the North Richland recharge basins and nearby irrigated
farming (Liikala 1994). Water is pumped from the Columbia River to the
recharge basins and subsequently pumped from nearby wells. This system
is used by the city of Richland as a backup filtration system for city
water. Because an excess of water is pumped into the recharge basins, a
mound has been created in the water table, which helps to reduce the
potential for groundwater flow from the Hanford Site into this area
(Hartman et al. 2004). The river stage elevation of the Yakima River,
which flows just west of the area, is high enough such that the river
also acts as a recharge source for the groundwater system. However, a
study of water levels in wells adjacent to the river showed that flow
between the Yakima River and aquifer may be inhibited in some areas by
mud deposited along the riverbed (Thorne et al. 1993).

The southern portion of the tritium plume from the 200 East Area extends
to the 300 Area. However, tritium concentrations decrease from greater
than 10,000 pCi/L (373.4 Bq/L) to less than 100 pCi/L (3.734 Bq/L)
across the 300 Area and the distribution across this area has changed
little since fiscal year 1999 (Hartman et al. 2004). A few wells south
of the 300 Area, in the vicinity of Richland's recharge ponds, have
shown slightly elevated tritium levels compared to expected background
levels for the groundwater. However, the observed tritium levels are
consistent with tritium concentrations in the Columbia River water that
is pumped into the ponds (Hartman et al. 2004). Nitrate contamination is
also found in the Richland North Area. This is the result of industrial
and agricultural sources off the Hanford Site. The nitrate plume is
migrating eastward and entering the Columbia River. Concentrations above
the 45-mg/L maximum contaminant level are found over most of the
Richland North Area (Hartman et al. 2004).

##  {#section .unnumbered}

[^1]: (?) The Vernita Bar Agreement (signed June 16, 1988 by the U.S.
    Department of Energy, federal and state agencies, Tribal
    governments, and public utility districts in Grant, Chelan, and
    Douglas counties) was created to prevent redds (salmon nests) from
    being left high and dry when river flows fluctuate to meet peak
    power demands.

[^2]: (?) The 1100 Area was the location of general stores and
    transportation maintenance facilities at the Hanford Site. The 1100
    Area was declared clean by the regulatory agencies during September
    1996.