A Summary of Hydrochemical Evidence for Groundwater …cbgwma.org/groundwater modeling/HydroChemicalEvidence... · 2014-12-12 · Anchor QEA 6650 SW Redwood Lane Suite 333 Portland,

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A Summary of Hydrochemical Evidence for Groundwater Compartmentalization and Modern

Recharge within the Columbia Basin Ground Water Management Area (GWMA) of Adams, Franklin,

Grant, and Lincoln Counties, Washington

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A Summary of Hydrochemical Evidence for Groundwater Compartmentalization and Modern Recharge within the Columbia Basin Ground Water Management Area (GWMA) of Adams, Franklin, Grant, and Lincoln Counties, Washington February 2011 Prepared by: The Columbia Basin Ground Water Management Area of Adams, Franklin, Grant, and Lincoln Counties 170 N. Broadway Othello, WA 99344 509-488-3409 www.cbgwma.org

Authors: Kevin Lindsey, LHG; Travis Hammond; John Porcello, LHG GSI Water Solutions, Inc. 1020 N. Center Parkway, Suite F Kennewick, WA 99336 Dimitri Vlassopoulos Anchor QEA 6650 SW Redwood Lane Suite 333 Portland, OR 97224 And Patrick Royer GWMA 10121 W. Clearwater, Suite 100 Kennewick, WA 99336

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Contents Introduction ..................................................................................................................................... 5 Case Studies .................................................................................................................................. 13 Case Study 1. ................................................................................................................................ 15 Case Study 2. ................................................................................................................................ 22 Case Study 3. ................................................................................................................................ 33 Case Study 4. ................................................................................................................................ 37 Case Study 5. ................................................................................................................................ 42 Case Study 6. ................................................................................................................................ 47 Case Study 7. ................................................................................................................................ 55 Case Study 8. ................................................................................................................................ 61 Summary ....................................................................................................................................... 81 References ..................................................................................................................................... 82 Tables

1 Case Study Aquifer System Physical Attributes. 2 Well Construction Summary for Sampled Wells in and near the City of Odessa. 3 Well Construction Summary for Sampled Wells in the City of Moses Lake. 4 Moses Lake City Wells Affected by Regional-Scale Vertical Leakage in Uncased Wells. 5 Well Construction Summary for Sampled Wells in the Ritzville Area. 6 Well Construction Summary for Sampled Wells in the Vicinity of the East Low Canal. 7 Well Construction Summary for Sampled Wells in the Upper Quincy Basin. 8 Well Construction Summary for Sampled Wells in the Black Sands. 9 Well Construction Summary for Sampled Wells in the Royal Valley. 10 Well Construction Summary for Sampled Wells in the South Central GWMA.

Figures

1 Diagram showing the basic intraflow structures found in typical CRBG sheet flows. 2 Variation of cation ratio (Na + K)/(Na + K + Ca + Mg) as a function of carbon-14

activity (percent modern carbon) of CRBG groundwater. 3 GWMA Case Study Locations. 4 Location map of wells sampled in the Odessa case study area. 5 Cross-section through City of Odessa Well #3 and Crab Creek. 6 Plot of percent modern carbon (pmc) versus tritium. 7 Location map of wells sampled in the Moses Lake case study area. 8 Fence diagram illustrating the open intervals for Moses Lake Wells #17 and #18. 9 Moses Lake City Wells #17 (ML17) and #18 (ML18) stable isotope plot. 10 Percent modern carbon versus tritium (Moses Lake Wells). 11 Cross-section through Moses Lake Well #29. 12 Location map of wells sampled in the Ritzville case study area. 13 Tritium versus casing depth plot. 14 Location map of wells sampled in the East Low Canal case study area. 15 Percent modern carbon (pmc) versus tritium (East Low Canal Vicinity). 16 D versus casing depth. 17 Percent modern carbon (pmc) versus casing depth (East Low Canal Vicinity). 18 Location map of wells sampled in the Upper Quincy Basin case study area.

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19 Stable isotope plot of wells GR3225 and GR3226. 20 Cross-section through two wells cased into the upper Wanapum Basalt near a leaky canal. 21 Relative age plot of Black Sands groundwater. 22 Location map of wells sampled in the Black Sands case study area. 23 East to west cross-section through the Black Sands area. 24 North to south cross-section through the Black Sands area. 25 Location map of wells sampled in the Royal Valley case study area. 26 Structure contour map of the top of the Tfg unit. 27 Structure contour map of the top of the Tgsb unit. 28 Percent modern carbon (pmc) versus tritium (Royal Valley). 29 δD versus distance from the Columbia River. 30 Location map of wells sampled in the southern and central GWMA (Connell sub-area). 31 Tritium in wells open to the Wanapum Basalt. 32 Tritium in wells open to the Grande Ronde Basalt. 33 Tritium in wells open to the Wanapum/Grande Ronde Basalt. 34 Age plot of Connell sub-area wells. 35 Wanapum Basalt Piper plot. 36 Grande Ronde Basalt Piper plot. 37 Wanapum/Grande Ronde Basalts Piper plot. 38 Mixing study Piper plot. 39 Wanapum Basalt well hydrograph. 40 Grande Ronde Basalt well hydrograph. 41 Wanapum/Grande Ronde Basalts well hydrograph. 42 Residual SWL deviation. 43 Plot of percent modern carbon (pmc) versus depth to top of basalt (TOB). 44 Location of wells with respect to structure.

Appendices

A. Geologic Unit Abbreviations Definitions B. Explanation of Hydrochemical Parameters C. Groundwater Geochemical Data Used in this Report

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Introduction Underlying the geographical area of the Columbia Basin Ground Water Management Area of Adams, Franklin, Grant, and Lincoln Counties (GWMA) is a regional aquifer system hosted by layered basalt lava flows known as the Columbia River Basalt Group (CRBG). The CRBG consists of more than 300 separate basalt lava flows ranging in age from 17.5 million years to 6 million years old. The geologic designations of these basalt flows and interbedded and overlying sedimentary deposits are summarized in Appendix A. The regional CRBG basalt aquifer system is the primary water supply for most municipalities, many industries, a large number of rural homes, and a significant portion of irrigated farming in GWMA in particular, and in southeastern Washington and north-central Oregon. Within GWMA, as is the case across the region, evidence indicates that large portions of the CRBG aquifer system are at risk from over pumping that exceeds the rate at which the CRBG aquifers are recharged by natural processes. In some areas, groundwater levels have declined by tens to hundreds of feet, and some well owners have deepened wells or drilled new wells to depths exceeding 2,000 feet. As a result, it is likely that continued groundwater pumping at current rates will result in groundwater depletion in some portions of the CRBG aquifer system during our lifetimes. Since 2006, GWMA has been conducting studies to characterize the hydrogeology of the CRBG aquifer system and the availability of groundwater within the CRBG aquifer system beneath the four GWMA counties, at both a GWMA-wide scale and in more localized areas. GWMA’s initial findings are described in a series of reports released in 2009 (GWMA, 2009a, 2009b, 2009c, 2009d). These reports describe: (1) the basic physical geologic controls that influence groundwater recharge, movement, and discharge in the CRBG aquifer system, (2) evidence for limited modern water recharge (within the last 60 years) suggested by historical and newly collected groundwater geochemical data, and (3) water level data indicative of a compartmentalized CRBG aquifer system. Based on the findings presented in these reports, GWMA proposed a conceptual groundwater flow model for the CRBG aquifer system beneath the four-county GWMA area (GWMA, 2009d). This conceptual model utilizes the following key observations regarding the CRBG aquifer system:

1. The vast majority of the CRBG groundwater currently being pumped from the deeper Wanapum Basalt and even deeper Grande Ronde Basalt portions of the aquifer system is more than 10,000 to 25,000 years old.

2. Significant modern recharge to the CRBG aquifer system occurs in localized areas as a result of (a) natural rainfall and runoff processes in certain coulees (primarily Crab Creek and its tributaries), and (b) infiltration from irrigation canals and delivery systems. However, these processes primarily recharge only the uppermost parts of the CRBG aquifer system.

3. The CRBG aquifer system is layered, and groundwater continuity (movement) between deeper and shallower layers is very restricted. The vertical compartmentalization of the multiple discrete water-bearing zones that exist in the CRBG aquifer system arises from the presence of impermeable dense basalt layers that lie between each water-bearing

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zone. Sedimentary interbeds do not appear to have a significant role in restricting vertical groundwater flow beneath much of GWMA.

4. Folds, faults, and feeder dikes form lateral discontinuities in the CRBG aquifer system, subdividing GWMA into several groundwater, or aquifer, sub-systems.

Building on this conceptual CRBG aquifer system model, GWMA is preparing a digital groundwater flow model for this CRBG aquifer system. Model development is being supported by field data collection activities, including additional geologic mapping of the aquifer framework and collection of groundwater geochemical data. The geochemical data are being collected and analyzed to better understand: (1) the distribution of older (e.g. recharged >10,000 years ago) and younger groundwater (e.g. recharged ≤60 years ago) in the aquifer system, (2) the locations of areas of active modern water recharge and stream influence on both the shallow and deep portions of the CRBG aquifer system, (3) the locations and extent of mixing of younger and older groundwater, (4) the locations of lateral discontinuities in the CRBG aquifer system and their influence (e.g., more or less leaky), (5) the effects of vertical stratification on groundwater recharge and movement, and (6) the locations where different portions of the CRBG aquifer system discharge.

Objectives The primary purpose and objective of this study is to analyze and explain hydrochemical evidence showing differences in CRBG groundwater chemistry that could be the result of CRBG aquifer system compartmentalization caused by stratigraphic (layered), dike, fold, and fault boundaries. A secondary objective is to develop a more detailed understanding of the influence, or lack thereof, of modern recharge on the CRBG aquifer system in various localized areas inside GWMA. Additionally, this report has been prepared to (1) provide well owners and other local interested entities with further data and scientific analysis of the mechanisms governing groundwater occurrence and movement on local and regional scales and (2) to support the development of a detailed numerical CRBG groundwater flow model that GWMA will use to quantify the water budgets of, and evaluate the principal natural and human controls on, the CRBG aquifer system. Of particular importance to these two latter objectives is an understanding of the locations and rates of modern recharge to groundwater, the depths to which modern recharge waters are moving, and the rate of movement. Hydrochemical and age dating analyses of groundwater samples provide information that, when coupled with well construction information and geologic mapping, can indicate the degree to which a well is receiving modern recharge. The evaluation described in this report focuses primarily on age-based parameters, based on laboratory analyses of water samples for their carbon-14 (percent modern carbon [pmc]) and tritium content. In addition, concentrations of chlorofluorocarbons (CFC), and inorganic cations and anions in each water sample are used to further support the evaluations of groundwater age, mixing, and recharge sources. A brief explanation of these parameters and their interpretation is provided in Appendix B for readers who are interested in gaining an in-depth understanding of the geochemical processes and analytical methods. This study and its findings are organized as a series of case studies of eight specific areas that illustrate location-specific attributes about the CRBG aquifer system. The case studies are:

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1. Source of modern water recharge in Wanapum Basalt aquifers in the Odessa area.

2. Significant differences in the City of Moses Lake’s multiple municipal water supply wells.

3. Migration depth of modern water recharge in the Ritzville area.

4. Hydrochemical distinctions between groundwater samples collected proximal to, and distally from, the East Low Canal.

5. The influence of canal leakage recharge on shallow basalt wells in the upper Quincy Basin.

6. Discontinuity between sediment and CRBG aquifers in the Black Sands/Quincy Basin.

7. Surface water/groundwater connection of the CRBG aquifer system with the Columbia River along the western margin of GWMA.

8. The effects of structure on groundwater flow, recharge and compartmentalization in the CRBG aquifer system in the central GWMA.

A brief introduction to CRBG hydrogeology is provided in the next section. Readers who are interested in additional information about CRBG geology and hydrogeology should refer to the several reports prepared by GWMA on these topics in 2009, as well as other numerous reports and papers referenced by the 2009 GWMA reports.

Columbia River Basalt Group (CRBG) Hydrogeology The CRBG is a thick sequence of more than 300 continental flood basalt lava flows that cover an area of more than 59,000 square miles (mi2) (164,000 square kilometers [km2]) in Washington, Oregon, and western Idaho (Tolan et al., 1989) with a maximum thickness of more than 10,000 feet. Numerous reports have been written about a variety of CRBG topics, ranging from petrology, stratigraphy, and emplacement, to tectonics and hydrology. Several of the more recent compilations of CRBG geology and hydrogeology are found in PNNL (2002), GWMA (2009a, 2009b, 2009d), and Tolan et al. (2009). The CRBG has been divided into a host of regionally mappable units based on variations in physical, chemical, and paleomagnetic properties, and the stratigraphic position between flows and packets of flows (Swanson et al., 1979a; Beeson et al., 1985; Bailey, 1989). The CRBG in the Columbia Basin region is subdivided into four formations. These formations are, from youngest to oldest, the Saddle Mountains Basalt, Wanapum Basalt, Grande Ronde Basalt, and Imnaha Basalt (Swanson et al., 1979a, 1979b). These formations have been further subdivided into members that, like the formations, are defined on the basis of a combination of unique physical, geochemical, and paleomagnetic characteristics. These members can be, and often are, further subdivided into flow units (e.g., Beeson et al., 1985). Vertical exposures through CRBG lava flows reveal that they generally exhibit the same basic three-part internal arrangement of layered intraflow structures. These features, which originated either during the emplacement of the lava flow or during the cooling and solidification of the lava after it ceased flowing, are referred to as the flow top, flow interior, and flow bottom (Figure

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1). Interflow zones are the intervals between successive lava flows that can contain various combinations of flow top features (from the underlying flow) and flow bottom features (from the overlying flow). Interflow zones are hydrogeologically important in that they host aquifers and, where they outcrop, can serve as CRBG aquifer recharge and/or discharge sites. If a sediment interbed is present between the two flows, it also would be part of the interflow zone. The physical characteristics of basalt lava flow structures are important because they exert fundamental controls on groundwater occurrence and movement within the CRBG. The layered nature of the CRBG beneath GWMA results in a layered (or stratified) regional aquifer system where groundwater is found in interflow zones (Figure 1) at the tops and bottoms of many of the layers. Individual CRBG formations, members, and flows are listed in Appendix A. The CRBG aquifer system within GWMA is compartmentalized, or subdivided. The laterally extensive basalt lava flows create the layering seen in the CRBG which separates the aquifer system into a sequence of stacked, isolated water-bearing systems. Lateral boundaries are created by CRBG feeder dikes, folds, and faults. The degree of hydrologic separation across these dike, fold, and fault features varies across the region, but is pronounced enough to create observable changes in the CRBG aquifer system across the region. A large portion of the groundwater found within the CRBG aquifer system is Pleistocene in age, being more than 10,000 years old (GWMA, 2009c). Since the recharge processes of glacial melt and regional catastrophic flooding are now nonexistent, the Pleistocene-age groundwater is referred to in this report as fossil CRBG groundwater. Recent studies have found that modern recharge of many of the deeper basalt aquifers within GWMA is extremely limited to nonexistent (GWMA, 2009 b, 2009c). However, the same studies also have shown that sedimentary and shallower CRBG aquifers in limited areas within GWMA are recharged by modern surface water sources; nevertheless, in some areas this recharge occurs at rates that are insufficient for providing sustainable well production at current pumping rates (GWMA, 2009b, 2009c, 2009d).

Hydrochemical Sampling and Analysis Methodology In 2008 and 2010, 460 well and 14 surface water samples were collected for analysis of several hydrochemical parameters. All samples were sent to specialty laboratories for analysis. Based on the hydrochemical analyses used here, the differentiation of a group of groundwater samples is based on the concept that groundwater age is a descriptor of the duration of time that the sampled groundwater has resided in the CRBG aquifer system (i.e., the aquifer residence time). For example, if hydrochemical data indicate that a sample is 10,000 years old, then it is considered to be fossil CRBG groundwater that entered the saturated zone more than 10,000 years ago. In contrast, if hydrochemical data indicate that a sample is less than 60 years old, then it is considered to be modern recharge. A sample of intermediate age (slightly more than 60 years old to less than 10,000 years old) is considered to be a mixture of fossil CRBG groundwater and modern recharge groundwater; where such samples are identified, we further evaluate the local conditions to determine whether (1) a physical pathway exists that could facilitate mixing, or (2) conversely whether no such pathway exists and the water instead is truly as old as the measured age.

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The following parameters were used to estimate groundwater age or, more appropriately, the time of travel from the point where the water entered the aquifer system (at the recharge area) to the point where the sample was collected (at the well).

1. Carbon-14/Percent Modern Carbon – Used to give an absolute age date to groundwater and to assess recharge by identifying the presence of fossil CRBG groundwater. Carbon-14 is useful in constraining the proportion of young water that comprises a mixed groundwater sample (i.e., the fraction that may be considered to be renewable). Carbon-14 is used for age dating water as old as approximately 50,000 years.

2. Tritium – Used to identify the presence of modern recharge (less than or equal to (≤) 60 years old). Tritium, or 3H, is useful as a groundwater age tracer because the tritium atom, being an isotope of hydrogen, is part of the water molecule. This is the only age tracer for which this is true. Given this molecular chemistry, tritium will be present in water entering the groundwater system as recharge. The majority of tritium found in the modern environment results from the manufacture of nuclear materials. This tritium, commonly referred to as bomb-peak tritium, is a robust indicator of a young groundwater age. If tritium is not detected in a sample (<0.1 tritium units [TU]), it can be concluded that the groundwater was recharged before 1950; if tritium is detected, then the water sample contains at least a fraction that was recharged since the 1950s.

3. Atmospheric Chlorofluorocarbons (CFC-11, CFC-12, and CFC-113) – Especially useful as an indicator of recharge since 1945. CFCs are useful in simple mixing models of the ratio between modern recharge and fossil CRBG groundwater. CFCs are artificially produced by human activities.

4. Cation Ratio – Used as a proxy indicator of relative groundwater age based on hydrochemical evolution, and is a useful complement and surrogate for age information. Older groundwater generally is more chemically evolved, resulting in higher cation ratios than younger groundwater that is less chemically evolved (Figure 2). The chemical evolution of groundwater is driven simply by the geochemical reactions involving the water and the rock hosting the groundwater. With longer contact time between groundwater and the aquifer hosting rock, the groundwater chemistry will evolve or change.

Because the water samples collected in each well reflect the composite properties of all water-bearing intervals being pumped by the well, it is important to know how a sampled well is constructed. Specifically, we need to know the depth of the seal(s), casing and liner depths, and depth of the open interval(s). Comparing this information to GWMA’s subsurface geologic model we then are able to identify the primary geologic interval(s) from which that well likely is pumping water. The source of well construction information we used for this effort was compiled from Washington Department of Ecology well records for the sampled well and/or from well owner/operator information. Throughout this report we refer to wells as open to either the Wanapum Basalt, the Grande Ronde Basalt, a combination of the Wanapum and Grande Ronde, or multiple units. Wells designated as multiple unit wells are interpreted to be open to suprabasalt sediments as well as one or more basalt unit.

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Additional information on the concept of groundwater age and the above four parameters are discussed in detail in Appendix B. Appendix C tabulates the analysis results for all wells used in this report.

Figure 1. Diagram showing the basic intraflow structures found in typical CRBG sheet flows.

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Figure 2. Variation of cation ratio (Na + K)/(Na + K + Ca + Mg) as a function of carbon-14 activity (percent modern carbon) of CRBG groundwater. The arrow indicates a trend with increasing groundwater residence time. SW = wells producing from Saddle Mountains and

Wanapum Basalts, W = wells producing from Wanapum Basalts, WG = wells producing from the Wanapum and Grande Ronde Basalts, and G = wells producing from the Grande Ronde

Basalt (from GWMA, 2009c).

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Case Studies The following case studies illustrate how hydrochemical data collected by GWMA were used to define distinct groundwater bodies that could be segregated by physical barriers (i.e., stratigraphic layering, faults, folds, and dikes). The most common and laterally extensive feature representing physical groundwater separation within GWMA is the layered (stratified) nature of the regional CRBG aquifer system. For example, in Case Studies 1 though 7, CRBG groundwater segregation appears to be primarily the result of isolation of water-bearing basalt interflow zones from one another by dense flow interiors. This is mostly demonstrated by the presence of tritium-containing young water in shallower CRBG water-bearing zones and the absence of such young water in deeper CRBG water-bearing zones in the same areas. Well construction also was considered in the case studies to investigate the effect of casing depth on the groundwater hydrochemistry, and in particular the presence of tritiated water in deeper wells. Figure 3 is an area map displaying the locations of the various case study areas within GWMA. Each of the eight case studies is listed in Table 1, with its respective unique aquifer system physical attributes.

Table 1. Case Study Aquifer System Physical Attributes. Case Study

Unique Aquifer System Physical Attributes

1 Odessa Area: Source of young water recharge in Wanapum Basalt aquifers in the Odessa area.

2 City of Moses Lake: Significant differences in the City of Moses Lake’s multiple municipal water supply wells.

3 Ritzville Area: Migration depth of water in the Ritzville area.

4 East Low Canal: Hydrochemical distinctions between groundwater samples collected proximal to, and distally from, the East Low Canal.

5 Upper Quincy Basin: Influence of canal leakage recharge on shallow basalt wells in the upper Quincy Basin.

6 Black Sands Area: Discontinuity between sediment and CRBG aquifer system in the Black Sands/Quincy Basin.

7 Royal Valley: Surface water/groundwater connection of CRBG aquifers with the Columbia River along the western margin of GWMA.

8 Southern and Central GWMA (Connell Sub-area): Effects of stratigraphy, structural barriers, geographic setting, and well construction on CRBG groundwater flow, recharge, and compartmentalization from the Saddle Mountains Anticline.

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Figure 3. GWMA Case Study Locations. Case study areas are numbered (in green) according to

their appearance in the text and are as follows: (1) Odessa Area, (2) City of Moses Lake, (3) Ritzville Area, (4) East Low Canal, (5) Upper Quincy Basin, (6) Black Sands Area, (7) Royal

Valley, and (8) Southern and Central GWMA. Locations of cross-sections used in case discussions are indicated as yellow lines.

D

D′

E

E′

A′ A C′

C

1

2 3

4

5

6

7 8

B B'

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Case Study 1. Odessa Area: Source of Young Water Recharge in Wanapum Basalt Aquifers in the Odessa Area Summary Percent modern carbon, tritium, hydrogen stable isotopes, and well construction information was used to assess CRBG groundwater age and recharge near Odessa, Washington. GWMA’s findings show the presence of recently recharged CRBG groundwater in a City of Odessa well, while almost all wells around the City contain little to no modern water. The recharge pathway for this well’s modern water is interpreted to be westward down-dip flow of groundwater from Crab Creek to the open portion of the water supply well.

Discussion CRBG groundwater level declines in the area surrounding the City of Odessa, Washington, have been occurring steadily for the last few decades. For this case study, sampling results from 30 wells (listed in Table 2) near Odessa reveals that all but 3 of the wells are pumping CRBG groundwater that receives little to no modern recharge. Of the three wells that receive recharge, one is of particular interest to this case study: City of Odessa Well #3 (L1455) (Well #3), which contains a significant amount of tritium and CFCs, and has a relatively high amount (76 percent) of pmc. In Well #3, the presence of young groundwater is interpreted to be the result of a high degree of hydrologic continuity with nearby Crab Creek. This is based on the following observations:

Well #3 is cased and sealed through much of the Wanapum Basalt. The well is open to the deepest (Sand Hollow) basalt flow in the Wanapum Basalt and the underlying Sentinel Bluffs Member of the Grande Ronde Basalt.

East of Odessa, Crab Creek is incised into multiple Wanapum Basalt flows, including

those of the Frenchman Springs Member (Figures 4 and 5). In addition, the Crab Creek canyon is deep enough that it is eroded down to within less than 100 feet of the top of the Sentinel Bluffs Member of the Grande Ronde Basalt in the area east of Odessa. This area of deep erosion, essentially the Sylvan Lake area, is one where anecdotal reports by local residents and water users, commonly report losing channel reaches on Crab Creek. To the east of Sylvan Lake, Crab Creek flows most of the year; west of the lake, the creek commonly goes dry in the summer months. Hence, this reach of Crab Creek where it is deeply incised into the Frenchman Springs Member and nearly to the top of the Sentinel Bluffs Member likely provides a pathway for surface water to move into the shallow CRBG aquifer system, than move down-gradient to Well #3.

The pmc, tritium, and CFC data indicate that the CRBG groundwater pumped from Well

#3 is a mixture of modern and fossil groundwater, as shown in Figure 6. Comparing tritium to pmc yields a preliminary mixing ratio in Well #3 of approximately 73 percent

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young water and 27 percent fossil groundwater. However, these hydrochemical indicators do not tell us the source of the young water. In contrast, the stable isotope data provide evidence that complements the geologic data in pointing to Crab Creek as the likely source of the modern water at Well #3. Specifically, the hydrogen isotope (δD) value for water produced from Well #3 (δD = -125.4) lies between the values for Crab Creek and fossil CRBG groundwater (δD = -116.3 and -144.6, respectively) hinting at the possibility of Crab Creek as a source for young water in the well.

Together, these findings indicate that recharge water less than 60 years old is a significant component of the groundwater produced by Well #3. Crab Creek is the likely source of this water based on (1) the identified geologic pathway for water movement from Crab Creek toward the well; (2) the consistent indication of a nearby surface water source provided by each of the hydrochemical analyses; and (3) the absence of any other significant surface water recharge source in the immediate vicinity of the City of Odessa. In summary, the erosional thinning of CRBG layers in the Crab Creek coulee in, and around, Sylvan Lake provides an opportunity for surface water to move vertically through the erosionally thinned upper few CRBG layers and recharge CRBG interflow zones a short distance below the bedrock floor of the coulee. This recharged water then moves down-dip, generally in a westerly direction, and some of this recharged water is intercepted by, and pumped from, Well #3. Given this geometry and the observed CRBG groundwater chemistry data, the CRBG interflow zones between the Roza Member and the Sentinel Gap flow, Roza Member and Sand Hollow flow, and at the top of the Sentinel Bluffs Member of the Grande Ronde Basalt all potentially could be receiving some modern recharge from Crab Creek (and the alluvial valley fill in the coulee) just east of Odessa. A shallowly cased and sealed well, such as Well #3 (and the other two wells in this case study area with modern water in them), potentially could be pumping such water, which is a mix of relatively young (modern recharge) water and older pre-modern groundwater (including fossil CRBG groundwater). Because the other 29 deeper wells receive none of this recharge, this argues for little to no vertical leakage from the Crab Creek system into deeper wells.

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Figure 4. Location Map of wells sampled in the Odessa case study area. The approximate

location of the cross-section displayed in Figure 4 is shown.

Crab Creek

A A'

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Table 2. Well Construction Summary for Sampled Wells in and near the City of Odessa. GWMA Well ID

Total Depth

(feet bgs)

Seal Depth

(feet bgs)

Casing Depth

(feet bgs)

Open Interval Units*

GR1980 1,335 0 705 Tgsb,Tgu,Tgo GR1984 2,190 800 800 Tgsb,Tgu,Tgo,Tgg,Tgwr GR3210 2,580 800 800 Tgsb,Tgu,Tgo,Tgg GR1250 2,195 705 705 Tgsb,Tgu,Tgo,Tgg A2860 790 0 762 Tgsb L1202 1,615 621 620 Tgsb,Tgu,Tgo,Tgg

GR1972 2,075 800 800 Tgsb,Tgu,Tgo,Tgg L1246 2,245 800 800 Tgsb,Tgu,Tgo,Tgg,Tgwr L1234 2,469 807 807 Tgsb,Tgu,Tgo,Tgg L0007 2,117 800 800 Tgsb,Tgu,Tgo,Tgg,Tgwr

GR1981 1,588 0 1,281 Tgo L1258 700 10 10 Sediment,Tr,Tfsg,Tfsh,Tgsb

GR1985 470 0 21 Tr,Tfsg,Tfsh L0017 385 32 32 Tr,Tfsg,Tfsh L1455 595 250 250 Tfsh, Tgsb

GR1982 656 0 34 Tpr,Tr,Tfsg,Tfsh,Tfg,Tgsb GR1987 2,700 682 38 Tpr,Tr,Tfsg,Tfsh,Tfg,Tgsb,Tgu,Tgo,Tgg,Tgwr GR0997 890 18 18 Tpr,Tr,Tfsg,Tfsh,Tfg,Tev,Tgsb L1247 1,100 43 43 Tr,Tfsg,Tfsh,Tfg,Tgsb,Tgu L0002 716 60 59 Tpr,Tr,Tfsg,Tfsh,Tgsb L0036 1,358 33 33 Tr,Tfsg,Tfsh,Tfg,Tgsb,Tgu,Tgo L0005 700 100 100 Tr,Tfsg,Tfsh,Tgsb L0006 547 0 0 Tr,Tfsg,Tfsh,Tfg,Tgsb L0014 1,402 56 282 Tpr,Tfsg,Tfsh,Tfg,Tgsb,Tgu,Tgo

GR1983 2,265 760 20 Tpr,Tr,Tesc,Tfsg,Tfsh,Tfg,Tgsb,Tgu,Tgo,Tgg,Tgwr GR1986 1,180 42 42 Tr,Tfsg,Tfsh,Tfg,Tgsb,Tgu L0053 660 160 160 Tfsh,Tgsb L1259 505 30 30 Tr,Tfsg,Tfsh,Tgsb L0040 680 37 37 Tr,Tfsg,Tfsh,Tfg,Tgsb L1248 1,070 43 43 Tr,Tfsg,Tfsh,Tfg,Tgsb,Tgu L1420 653 0 35 Tr,Tfsg,Tfsh,Tfg,Tgsb L1235 2,430 790 20 Tr,Tfsg,Tfsh,Tgsb,Tgu,Tgo,Tgg,Tgwr,Basement

*Abbreviation definitions are in Appendix A.

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Legend

Tr Wanapum

Tesc Interbed

Tfsg Wanapum

Tfsh Wanapum

Tev Interbed

Tgsb Grande Ronde

Tgo Grande Ronde

Tgu Grande Ronde

Tgg Grande Ronde

Tgwr Grande Ronde

Basement

Odessa Well #3 Crab Creek

Ele

vati

on (

feet

AM

SL

)

Horizontal Distance (feet)

Figure 5. Cross-section through City of Odessa Well #3 and Crab Creek. The black portion of the well bore indicates the cased and sealed interval. The blue horizontal lines indicate CRBG interflow zones that host aquifers. The lowest CRBG interflow zone is tapped by the well. See

Figures 3 and 4 for the location of this cross-section.

A A′

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Figure 6. Plot of percent modern carbon (pmc) versus tritium. Displayed are relative age data for wells cased to various CRBG units within Odessa and the surrounding area. The City of Odessa Well #3 lies well within the zone of mixing outlined by the triangle.

Wells identified as “multiple” are open to sediment and the CRBG.

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Case Study 2. City of Moses Lake: Significant Differences in the City of Moses Lake’s Multiple Municipal Water Supply Wells

Summary Percent modern carbon, tritium, hydrogen stable isotopes, oxygen stable isotopes, and well construction information was used to assess groundwater conditions at the City of Moses Lake.

GWMA’s findings show the presence of modern water in many City wells, although in a wide range of concentrations. Some wells have minor amounts of modern water, while others contain exclusively modern water.

The source of modern water in the City’s wells varies. In some cases modern water reaches the well by moving several miles down-dip from a surface recharge source to the open interval of the well. In other wells, leaking casing allows small quantities of modern water to move vertically deeper into the aquifer system. In shallow wells, the pumped groundwater likely is in hydraulic continuity with nearby surface water bodies

Discussion Groundwater samples were collected for geochemical analysis from 17 of the 21 City of Moses Lake’s (City) municipal water supply wells (Table 3) by GWMA in 2008 and 2010 (Figure 7). These samples were collected for geochemical analysis. Based on these analyses, most all of the wells sampled have hydrochemical signatures indicative of a greater to lesser degree of mixing of older Pleistocene aged fossil CRBG groundwater (>10,000 years old) and modern water. Recent studies (GWMA, 2009c), anecdotal information from the City, and a recent GWMA review of static and pumping water levels in City wells (GWMA, 2009c, 2009d, 2010) have shown that modern water recharge rates are not sufficiently high to sustain current pumping rates indefinitely.

When looking at the geochemical data collected from the City’s wells, a wide range of geochemical signatures is apparent: wells that pump predominantly modern groundwater, wells that pump predominantly fossil CRBG groundwater, and wells that pump water that likely is a mix of modern water and fossil CRBG groundwater. There are three surface water bodies in the immediate vicinity of Moses Lake that potentially could contribute modern recharge water to the aquifer system underlying the City and the sampled wells. These potential surface water sources are Crab Creek, Moses Lake, and the East Low Canal. Water from these sources could potentially reach the sampled wells via:

1. Vertical leakage in boreholes having no seals or compromised seals. This could include the sampled well and/or nearby wells.

2. Down-dip groundwater movement in CRBG interflow zones that come into contact with surface water bodies up-dip.

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3. Vertical migration through erosionally thinned CRBG units.

In addition, well construction summaries show that City wells are completed in a variety of ways. Some wells are open to only one major CRBG unit and some are open to several CRBG units. In addition, the City has wells that range from deep Grande Ronde wells to wells that are shallow sediment wells. In an effort to better understand the range of aquifer conditions City wells are operating under, three specific wells were selected. The following are summaries of the selected City wells:

Well #18. An example interpreted to show that the pumped groundwater from this well is predominantly modern water that entered the CRBG aquifer system up-dip of the sampled well and then moving down-dip in the CRBG aquifer system to Well #18 via flow paths connected to surface water.

Well #17. An example of vertical leakage in cased/sealed wells.

Well #29. An example of a shallow well in direct hydrologic connection with surface water.

Moses Lake Well #18 – Recharge from East Low Canal into the Wanapum Basalt

Well #18 is completed in (open to) the lower part of the Roza Member and the upper to middle parts of the Frenchman Springs Member of the Wanapum Basalt. The carbon-14, tritium, and CFC data indicate that most, if not all, of the groundwater pumped from this well is less than 60 years old. Such an age is interpreted to indicate a direct connection to modern surface water and recharge.

GWMA’s existing geologic interpretations of the Moses Lake area indicate that the CRBG units in Well #18 are exposed just a few miles to the east of the well. In this up-dip area, the East Low Canal is trenched into the Roza Member (the dark pink zone shown in Figure 8). In addition, this up-dip area has a history of intensive irrigated farming during the past several decades. The presence of these units at, or near, the ground surface near the East Low Canal and beneath these irrigated farmed lands is interpreted to result in a high likelihood for potential modern recharge to the Wanapum Basalt. Comparison of stable isotopes of oxygen and hydrogen in samples collected from Well #18 and the East Low Canal demonstrates that the two samples have similar isotopic compositions (Figure 9). Given these physical and hydrochemical relationships, the East Low Canal and, to a lesser extent, irrigated farming in the area up-dip of Well #18, are interpreted to be the primary recharge sources for the very young CRBG groundwater being pumped from this well.

Moses Lake Well #17 – Limited Recharge to Lower Wanapum and/or Upper Grande Ronde Aquifers

Well #17 (GR1692) is a deep well that is cased into the lower Wanapum Basalt (Gingko flow-Frenchman Springs Member) and the upper Grande Ronde Basalt (Sentinel Bluffs Member) (Table 3). Static water level in this well is declining (GWMA, 2010). The apparent carbon-14 age of a groundwater sample from this well is approximately 6,000 years. However, this sample

Page 24

also contains detectable tritium, indicating a mixture of modern recharge and fossil CRBG groundwater. Based on measured radiocarbon and tritium, the water pumped from Well #17 is estimated to consist of approximately 20 percent modern water and 80 percent fossil CRBG groundwater. In addition, stable isotope data illustrate that Well #17 is not isotopically similar to nearby surface water, but closer to CRBG groundwater as described in GWMA (2009c; Figure 9).

Unlike Well #18, the CRBG layers that Well #17 are interpreted to be open to (the lower Wanapum - Gingko flow, and upper Grande Ronde Basalt - Sentinel Bluffs Member) do not come to, or near, the surface beneath the surface water irrigated grounds lying just to the east of Moses Lake. Instead, these layers approach the surface several miles east of the East Low Canal, where irrigation water sources are almost exclusively derived from deep basalt groundwater pumping. Given this, the source of the young water fraction in Well #17 is interpreted to not be surface water supplied irrigation (in the form of canals or associated irrigated agriculture).

GWMA’s 2008 sampling (GWMA, 2009b, 2009c) suggests that mixed-age groundwater samples are more common in wells located, in and near, towns, as compared to samples collected from areas dominated by deep CRBG groundwater irrigation. Given the extremely low likelihood that other towns in the Columbia Basin have been preferentially built on leaky portions of the aquifer system, the predominance of mixed-age groundwater in municipal wells suggests the presence of an artificial pathway for vertical leakage. We interpret the modern recharge component to result from vertical leakage through uncased wells that are a part of the approximately 3,850 wells known to be in the vicinity of the City of Moses Lake. In the case of Well #17, a pathway from a potential surface water source to the well is not present (in stark contrast to the situation for Well #18). Several other Moses Lake municipal wells also produce water with mixing characteristics similar to Well #17 and have no known pathway to a surface water source. In the absence of hydrogeologic connections to surface water, it is assumed that these wells having hydrochemical characteristics similar to Well #17 also are affected by limited vertical leakage through uncased wells near the sampled well (Table 4).

Moses Lake Well #29 – Recharge of Young Water to Sedimentary Aquifers

Well #29 is drilled into the upper Wanapum Basalt (Priest Rapids Member), but has an open interval that includes the overlying suprabasalt sediments, thus its designation as open to multiple units. Carbon-14 (pmc) and tritium data from groundwater samples collected from this well suggest that it contains primarily young water from modern recharge (Figure 10). Crab Creek lies approximately 1.5 miles east and up-dip of Well #29 (Figure 11). This orientation could allow for recharge water from Crab Creek to move down-dip to Well #29. However, the δD value for Well #29 is –126.0 ‰, lying between the δD values for Crab Creek (–116.0 ‰) and East Low Canal (–131.0 ‰). Given these data, the water being extracted from Well #29 is interpreted to be from a combination of flow along CRBG interflow zones in connection with Crab Creek, leaking irrigation supply canals (i.e., East Low Canal), and possibly direct irrigation infiltration and/or groundwater flow though the sediments.

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Table 3. Well Construction Summary for Sampled Wells in the City of Moses Lake.

GWMA Well ID

Total Depth

(feet bgs)

Seal Depth

(feet bgs)

Casing Depth(feet bgs)


GR6101 730 410 725 Tgsb

GR6186 1,045 0 702 Tgsb

GR0617 950 685 950 Tgsb

GR6092 1,025 20 746 Tgsb

GR0837 1,000 0 711 Tgsb

GR0615 806 155 723 Tgsb

GR6183 994 681 681 Tgsb

GR1379 568 107 N/A Tpr,Teqc,Tr,Tesc,Tfsh,Tfg

GR6141 692 236 269 Tr,Tesc,Tfsg,Tfsh,Tfg,Tev,Tgsb

GR6088 825 1,099 376 Tfsh,Tfg,Tev,Tgsb

GR1804 791 N/A 222 Tr,Tfsg,Tfsh,Tfg,Tev,Tgsb

GR1692 1,250 44 686 Tfg,Tev,Tgsb

GR6094 909 N/A 132 Tr,Tesc,Tfsg,Tfsh,Tfg,Tev,Tgsb

GR6091 740 259 259 Tr,Tesc,Tfsg,Tfsh,Tfg,Tev,Tgsb

GR1802 712 N/A 214 Tr,Tesc,Tfsg,Tfsh,Tfg,Tgsb

GR8244 134 1,152 84 Sediment,Tpr

GR7123 585 897 280 Tfsh,Tfg *Abbreviation definitions are in Appendix A.

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Table 4.Moses Lake City Wells Affected by Regional-Scale Vertical Leakage in Uncased Wells. In areas lacking structural controls on groundwater mixing, the non-uniform distribution of

tritium versus percent modern carbon in wells suggests that modern recharge to these wells is probably from groundwater mixing in situ, as a result of a compounded vertical leakage effect

from many uncased wells in the area.

GWMA Well ID

Well Name

Easting Northing Primary

Unit* Carbon-14

(pmc**) Tritium

(TU) GR0837 ML #4 325070 5219535 GR 44.25 1.18 GR0617 ML #7 327589 5222205 GR 37.21 0.62 GR6186 ML #8 327112 5220218 GR 11.23 0.74 GR6101 ML #24 325111 5225698 GR 41.46 1.57 GR6141 ML #10 326108 5220561 W/GR 18.82 0.61 GR1692 ML #17 333668 5221301 W/GR 19.97 3.23 GR6088 ML #9 326024 5223528 W/GR 7.18 0.38

* GR = Grande Ronde, W = Wanapum, W/GR = Wanapum and Grande Ronde. ** pmc = percent modern carbon TU = tritium units

Page 27

Figure 7. Location Map of wells sampled in the Moses Lake Case study area. The approximate

location of the cross-section displayed in Figure 11 is shown.

B

B'

R6

GR6091

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Figure 8. Fence diagram illustrating the open intervals for Moses Lake Wells #17 and #18. The horizontal red lines through the well bores indicate casing depth. Surface connection with the

East Low Canal can be traced to Wanapum Basalt units that come in contact with the canal at the ground surface.

Page 29

Figure 9. Moses Lake City Wells #17 (ML17) and #18 (ML18) stable isotope plot. The plot illustrates that ML 18 is isotopically similar to its most likely recharge source (East Low Canal).

ML 18 plots along the local meteoric water line (LMWL; gray dashed line) and therefore is similar to local precipitation isotopic trends. ML 17 plots below the LMWL and is more similar

in composition to fossil CRBG groundwater, indicating less mixing and hence no direct connection with a surface water source.

Moses Lake Wells

-1.00

0.00

1.00

2.00

3.00

4.00

5.00

6.00

7.00

8.00

0.00 20.00 40.00 60.00 80.00 100.00

Carbon-14 (pmc)

Tri

tiu

m (

TU

)

Grande Ronde

Wanapum

Wanapum andGrande Ronde

Multiple

#29

#18

#17

>10,000 yrs old

Modern Recharge

(<60 yrs old)

Figure 10. Percent modern carbon (pmc) versus tritium. Moses Lake Wells #18 and #29 lie in the

plot region indicative of modern (young) water recharge. Moses Lake Well #17 lies in a plot region of mixed old and young water.

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Page 31

Elevation (feet) am

sl)

Moses Lake well 29 Crab Creek Moses Lake B


Figure 11. Cross-section through Moses Lake Well #29. The closest possible surface water recharge source is Crab Creek (~1. 5 miles to the east), which appears to be in contact with a flow zone that Well #29 (GR8244) is open to down-dip. Another potential source for surface water recharge is Moses Lake (~2.4 miles to the west).

See Figure 3 for the location of this cross section.

B B'

2000 4000 6000 8000 10000 12000 14000 16000 18000 20000 22000 24000 26000 28000

200

400

600

800

1000

1200

1400Legend

Well Depth

Well Casing

Geologic Layers

ppl

Qf Sediment

Trf Sediment

Tem Saddle Mountain

Tpr Wanapum

Teqc Interbed

Tr Wanapum

Tesc Interbed

Tfsg Wanapum

Tfsh Wanapum

Tfg Wanapum

Tev Interbed

Tgsb Grande Ronde

Tgo Grande Ronde

Tgu Grande Ronde

Tgg Grande Ronde

Tgwr Grande Ronde

Basement

GR8244

Crab Creek

East Low Canal

Moses Lake

Page 32


Page 33

Case Study 3. Ritzville Area: Migration Depth of Young Water in the Ritzville Area

Summary Near Ritzville, Washington, GWMA looked at tritium and well construction to assess the depth that modern water has reached in the CRBG aquifer system. GWMA’s findings show the presence of modern water appears to be restricted to shallow portions of the CRBG aquifer system, although not all shallow CRBG aquifer wells contain modern groundwater. In the absence of deep, uncased wells, infiltration of modern water deep into the CRBG aquifer system is extremely limited.

Discussion In the Ritzville, Washington, area well depths vary from less than 200 feet deep to more than 2,000 feet deep. The wells in this area produce water from both sedimentary and CRBG units. However, casing depths reported for the majority of these wells are relatively shallow, ranging from uncased to approximately 310 feet (one exception is a well cased into the Grande Ronde Basalt at 737 feet). For this evaluation, water samples were collected from 14 wells (see Table 5 and Figure 12) to evaluate the presence or absence of modern water. Nine of the 14 sampled wells have detectable tritium (Figure 13), indicating that the pumped groundwater includes, in part, a component of modern water. Eight of these nine wells have shallow casing depths and the presence of tritium is interpreted to result from recharge from nearby reaches of Crab Creek, Sprague Lake, and Cow Creek, which are the only significant surface waters in the area. The one well with deeper casing, A0607, has a seal reported to 20 feet. The young water found in this well could be reaching depth via the unsealed casing, other leaking wells in the area, and/or natural migration through the uppermost part of the CRBG aquifer system. Because many wells shallower than A0607 are positive for tritium, it can be assumed that the young water present at 309 feet below ground surface (bgs) is from a source that could be connected to the surface. Four of the five wells with little or no tritium are as shallowly cased as those with higher tritium. It is possible that these wells, while shallow, do not have a hydraulic connection with the modern stream system or other sources of modern water. Such wells easily could occur in elevated areas where the well does not reach depths equivalent to the elevations of perennial or ephemeral streams residing in canyons and coulees. In this semi-arid climate, without a hydraulic connection to surface water, there is no other source of significant surface water recharge. Alternatively, these wells simply may have better seals preventing the downward migration of snow melt and rain water along the casing. In either case, modern water cannot reach the CRBG production interval.

Page 34

The one truly deep well in this sample set (A0560) has a casing that is set at 737 feet deep, and the well contains essentially no tritium. This well, when compared to A0607, suggests vertical leakage into the deeper portion of the CRBG aquifer system is limited to absent in this area, except where wells with shallow casings (such as well A0607) allow vertical migration to occur via the well bore. Being that the well with the deepest set casing (A0560, cased to 737 feet) contains no tritium, there is subsequently no evidence of naturally occurring modern water recharge to deep aquifer zones in this area.

Table 5. Well Construction Summary for Sampled Wells in the Ritzville Area.

GWMA Well ID

Total Depth

(feet bgs)

Seal Depth

(feet bgs)

Casing Depth

(feet bgs) Open Interval Units*

A0588 425 0 15 Tpr,Tr,Tfsg,Tfsh A2842 180 19 19 Tr,Tfsg A0617 329 0 68 Tr,Tfsg,Tfsh A0508 280 18 60 Tr,Tfsg,Tfsh A0510 156 18 18 Tr,Tfsg A0210 809 0 33 Tpr,Tr,Tfsg,Tfsh,Tfg,Tgsb A0607 675 20 309 Tr,Tfsg,Tfsh,Tfg,Tgsb A0560 737 64 737 Tgsb A0220 194 0 0 Sediment,Tpr,Tr A2890 2,020 0 20 Sediment,Tr,Tfsg,Tfsh,Tfg,Tgsb,Tgu,Tgo,Tgg,TgwrA2284 139 20 139 Sediment A0596 1,244 0 56 Sediment,Tpr,Tr,Tfsg,Tfsh,Tfg,Tgsb,Tgu,Tgo A0511 294 0 15 Sediment,Tr,Tfsg A2605 1,295 0 0 Sediment,Tr,Tfsg,Tfsh,Tfg,Tgsb,Tgu,Tgo


Page 35

Figure 12. Location map of wells sampled in the Ritzville case study area.

Cow Creek

Page 36

Ritzville Area

0

100

200

300

400

500

600

700

800

‐0.50 0.00 0.50 1.00 1.50 2.00 2.50 3.00 3.50 4.00 4.50

Tritium (Tu)

Casing Depth (feet) Grande Ronde

Wanapum


Multiple

Old Water

Figure 13. Tritium versus casing depth plot. From the plot it is apparent that most wells in the Ritzville area contain some component of modern water. From the available data, it is clear that young water has recharged to a depth of at least 309 feet below the ground surface into the upper

Grande Ronde Basalts.

A0607

Little or No Detectable Tritium

A0560

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Case Study 4. East Low Canal: Hydrochemical Distinctions Between Groundwater Samples Collected Proximal to, and Distally from, the East Low Canal

Summary Percent modern carbon, tritium, hydrogen stable isotopes, and well construction information was used to assess if leakage from the East Low Canal is a source of modern water recharge to the CRBG aquifer system. GWMA’s findings show the presence of modern water in wells with shallow casing near the East Low Canal. However, wells more than a few miles from the East Low Canal and wells with deep casing near the canal, contain little or no modern water. Impacts of East Low Canal leakage are limited to wells with shallow casing within only a few miles of the canal.

Discussion GWMA was able to collect water samples from 17 wells (Table 6) located various distances from the East Low Canal to assess the size of the area influenced by young water leaking from the canal (Figure 14). The potential for groundwater recharge from the East Low Canal was evaluated using previously specified hydrochemical parameters from wells located proximally (within ~1.8 miles) and distally (>1.8 to ~3.75 miles) to the canal in multiple locations. Relative age dating (tritium and pmc) and hydrogen stable isotope data demonstrate stark differences between the influence on shallow cased wells near the canal, deep wells near the canal, and deep and shallow wells distal from the canal. A plot of pmc versus tritium demonstrates a distinct segregation between wells proximal to and distal from, the East Low Canal (Figure 15). In Figure 15, distal wells are grouped in an area with lower pmc and tritium, indicating that these wells have a larger component of older fossil CRBG groundwater than young water originating from canal leakage. Likewise, proximal wells are grouped in an area of higher pmc and tritium suggesting a larger canal young water component from leakage and a smaller fossil CRBG groundwater component. A plot of hydrogen stable isotope (D) versus casing depth (Figure 16) displays similar trends as the modern carbon versus tritium plot (Figure 15), in terms of the hydrochemical segregation between the proximal and distal wells. Distal wells have varying casing depths and have D values very close to that of fossil CRBG groundwater (D = –144.5‰; vertical orange dashed line) with one exception (Figure 16). This exception is a well with a shallow casing. That shallow casing makes this well more susceptible to receiving recharge from the surface. Proximal wells are shallower and have D values reminiscent of the East Low Canal (D = -130.6‰; vertical green dashed line). There is also an exceptional proximal well (see Figure 16) with a value closer to that of fossil CRBG groundwater; this well has a deep casing that prohibits young water from entering the well.

Page 38

Similar trends are present on a plot of pmc versus casing depth (Figure 17). Some of the distal and proximal wells are open to the same intervals, but have very different chemistry. This suggests that the radius of influence of recharge from the canal is somewhat diminished at a distance of ~3.75 miles. The geochemical trends summarized here have an interesting corollary when compared to well drilling and deepening histories in the area. Anecdotal accounts indicate that most wells distal from the East Low Canal have been deepened as a result of falling static water levels. As these wells have been deepened, they have intersected and produced older, deeper water with less of a modern water signature. Conversely, wells more proximal to the canal generally have not been deepened. Anecdotal reports of well owners suggest that deepening of proximal wells has not been necessary because static water levels in these wells recover reliably during the non-pumping season.

Table 6. Well Construction Summary for Sampled Wells in the Vicinity of the East Low Canal.

GWMA Well ID

Total Depth (feet bgs)

Seal Depth (feet bgs)

Casing Depth (feet bgs)

Open Interval Units* Location**

GR9505 565 0 0 Sed, Tr, Tfsh, Tfg, Tev, Tgsb P

GR1099 308 0 35 Sed, Tr, Tfsh, Tfg, Tev P

GR1991 1,225 20 20 Sed, Tr, Tfsh, Tfg, Tgsb, Tgu P

GR1678 620 117 117 Sediment,Tpr,Tr,Tfsg,Tfsh,Tfg P

A2292 858 78 78 Sediment, Temb, Tpr, Tr, Tfg, Tfpf, Tgsb P

A0396 620 0 117 Tpr,Tr,Tfsg,Tfg,Tfpf,Tev,Tgsb P

A0403 625 0 0 Sediment,Tpr,Tr,Tfsg,Tfg P

A1531 960 760 767 Tgsb P

A0395 625 0 0 Sediment,Tpr,Tr P

A0394 667 145 145 Tr,Tfsg,Tfg P

GR3220 538 20 20 Sed, Tpr, Tr, Tesc, Tfsh, Tfg, Tev, Tgsb D

GR1989 1,035 0 550 Tgsb, Tgu D

GR1692 1,250 44 686 Tfg,Tev,Tgsb D

A2293 1,280 0 0 Sediment,Tpr,Tr,Tfsg,Tfg,Tfpf,Tgsb D

A0389 1,280 0 0 Sediment,Tpr,Tr,Tfsg,Tfg,Tfpf,Tgsb,Tgu D

A0390 1,060 0 0 Tgsb,Tgu D

A2321 1,455 34 34 Tgsb,Tgu,Tgo,Tgg D *Abbreviation definitions are in Appendix A. **P = Proximal (within ~1.8 miles) and D = Distal (>1.8 to ~ 3.75 miles)

Page 39

Figure 14. Location Map of wells sampled in the East

Low Canal case study area. The long rectangle oriented

northwest to southeast contains the wells that used

for analysis in this case study.

Moses Lake

Page 40

East Low Canal Vicinity

-1.00

0.00

1.00

2.00

3.00

4.00

5.00

6.00

7.00

8.00

0.00 10.00 20.00 30.00 40.00 50.00 60.00 70.00 80.00 90.00 100.00

Carbon-14 (pmc)

Tri

tiu

m (

TU

)

Proximal

Distal

Modern Recharge(<60 yrs)

>10,000 yrs old

Figure 15. Percent modern carbon (pmc) versus tritium. Two distinct groundwater populations

are apparent, based on differences in the degree of mixing between young canal leakage recharge. The two groups are (1) distal wells (>1.8 to ~3.75 miles from the East Low Canal) and

proximal wells (within ~1.8 miles of East Low Canal). Note that the lack of any wells falling within the modern recharge block indicates that each of the wells receives only part of its water

from canal leakage recharge.


0

100

200

300

400

500

600

700

800

-155 -150 -145 -140 -135 -130 -125 -120 -115 -110

Delta D

Cas

ing

Dep

th (

feet

bg

s)

proximal

distalE. Low Canal δD = -130.6‰

Fossil GWδD = -144.5‰

Figure 16. D versus casing depth. The orange dashed line represents the average D value of fossil CRBG groundwater, and the green dashed line represents the D value of East Low Canal

water. The exceptions mentioned in the text are circled.

Page 41


0

100

200

300

400

500

600

700

800

0.0 10.0 20.0 30.0 40.0 50.0 60.0 70.0 80.0 90.0

Carbon-14 (pmc)

Ca

sin

g D

ep

th (

fee

t b

gs

)

Proximal

Distal

Figure 17. Percent modern carbon (pmc) versus casing depth. This plot is further evidence of hydrochemical segregation in proximal versus distal wells, as a result of the limited radius of

influence of canal leakage recharge.

Page 42

Case Study 5. Upper Quincy Basin: Influence of Canal Leakage Recharge on Shallow Basalt Wells in the Upper Quincy Basin

Summary Hydrogen and oxygen stable isotopes were used to assess groundwater recharge sources near Quincy, Washington (Figure 19). Groundwater in the shallow Wanapum Basalt was found to be very similar to East Low Canal water. In this case, canal leakage moved directly down-dip into wells with shallow casing, providing the primary recharge source for these wells.

Discussion In portions of GWMA, some shallow CRBG wells show a high degree of hydraulic continuity with nearby surface waters. An excellent example of this is found near Quincy, Washington, where two shallow wells located within 1,000 feet of the West Canal were sampled (Figure 18). Both wells have shallow casing and seals (Table 7), and the geologic units they are open to thin and shallow to the north, beneath the nearby West Canal (Figure 20). Carbon-14 and tritium data demonstrate that these two wells produce groundwater almost exclusively sourced from modern recharge. Oxygen and hydrogen stable isotope data also show that the pumped groundwater is young (Figure 19). Geologic mapping and the wells’ operating history together suggest that the source of modern water is the West Canal, which is ~1,000 feet north of well GR3266 and ~1,700 feet north of well GR3225 (Figures 18 and 20). The operator of these wells has indicated that high pumping rates are easily maintained throughout the year, although water levels tends to be higher in the summer when the nearby West Canal is operating at maximum capacity. In this case, it is clear that upper Wanapum Basalt aquifers are being recharged with modern water, and that the canal is the source of that water (given the absence of any other appreciable surface water body in the area).

Table 7. Well Construction Summary for Sampled Wells in the Upper Quincy Basin. GWMA Well

ID Total Depth

(feet bgs) Seal Depth (feet bgs)



GR3226 360 21 105 Sediment,Tpr,Tr,Tesc,Tfsh

GR3225 251 33 33 Tpr,Teqc,Tr,Tesc,Tfsh *Abbreviation definitions are in Appendix A.

Page 43

Figure 18. Location map of wells sampled in the Upper Quincy Basin case study area. The

approximate location of the cross-section displayed in Figure 20 is shown.

C

C'

Page 44

Figure 19. Stable isotope plot of wells GR3225 and GR3226. Stable isotope data for wells GR3225 and GR3226 group with values from East Low Canal. Because all irrigation canals in this part of GWMA carry water from the same reservoir source, it is assumed that West Canal

would have isotope values very similar to those of East Low Canal. Thus, this plot can be considered as evidence of recharge to the upper Wanapum Basalt from leakage from West Canal.

GMWL is the global meteoric water line (delineates what water precipitation looks like globally). LMWL is the local meteoric water line, which delineates what precipitation looks like

in the Columbia Basin.

Page 45

C C'

GR3225

GR3226

GR1294

West Canal

Frenchman Hills WastewayTesc continues in this space but is not shown due model boundary.


Legend

Well Depth

Well Casing

Geologic Layers

ppl

Qf Sediment

Trf Sediment

Tem Saddle Mountain

Tpr Wanapum

Teqc Interbed

Tr Wanapum

Tesc Interbed

Tfsg Wanapum

Tfsh Wanapum

Tfg Wanapum

Tev Interbed

Tgsb Grande Ronde

Tgo Grande Ronde

Tgu Grande Ronde

Tgg Grande Ronde

Tgwr Grande Ronde

Basement

Figure 20. Cross-section through two wells cased into the upper Wanapum Basalt near a leaky canal. The red line portions of the well bores indicate open intervals to formations and aquifers. Well GR1294 was not sampled for analysis. See Figure 3 for the location of this cross

Ele

vati

on (

feet

AM

SL

)

Page 46


Page 47

Case Study 6. Black Sands Area: Discontinuity Between Sediment and Basalt Aquifers in the Black Sands/Quincy Basin

Summary In the Quincy Basin, the potential hydrologic connection between sediment wells and shallow CRBG wells is examined using percent modern carbon, tritium, and well construction. GWMA’s findings show that sediment aquifer water is different than much older CRBG aquifer system water. The source of most sediment aquifer water is modern, while the CRBG aquifer system contains water that is thousands of years old. Movement of modern water from the sediment aquifer downward into the CRBG aquifer system is extremely limited.

Discussion An important factor relevant to groundwater resource management in GWMA is an understanding of the vertical connectivity (or lack thereof) between the different layers comprising the stratified CRBG aquifer system. In the Quincy Basin, both the unconfined alluvial aquifer and the confined CRBG aquifer systems were sampled to better understand the nature and extent of vertical connectivity between water-bearing intervals and to assess possible recharge sources. This task was approached by analyzing pmc and tritium, and comparing these parameters to the geologic model of the area. Across large portions of GWMA, the CRBG aquifer system is overlain by sediments deposited by Pleistocene cataclysmic floods, and even older Mio-Pliocene continental alluvial systems. The area north of the Frenchman Hills, referred to as the Black Sands, or Quincy Basin, is one of these areas. In the Quincy Basin:

1. The CRBG is overlain by up to 200 feet of uncemented sandy to gravelly Pleistocene cataclysmic flood deposits (Qf), a laterally discontinuous sequence of older (Mio-Pliocene) sands and weakly cemented siltstone and claystone (the Ringold Formation; Trf), and a thin caliche layer that commonly separates these two sequences.

2. The flood deposits (Qf) can be a few feet-thick to many tens of feet-thick (GWMA,

2007). Where these strata contain groundwater, they can be quite productive, producing hundreds to more than 1,000 gallons per minute (gpm).

3. The older strata (Trf) can be absent or can be as much as 100 feet-thick, depending on

location (GWMA, 2007). Although locally sandy intervals in the Trf can produce significant water, generally this unit is a low yield water producer because it is dominated by siltstone and claystone.

Page 48

The flood deposits and the Ringold Formation together host an aquifer system that is collectively referred to as the sedimentary, or suprabasalt, aquifer. Tritium, pmc, and carbon-14 data analyzed to date from the Quincy Basin well water samples suggest that groundwater produced from sedimentary aquifer wells is predominantly modern, and that groundwater produced from CRBG wells is primarily old, except where shallow well casings facilitate downward movement of water from shallow to deep CRBG zones (Figure 21). With respect to the older CRBG groundwater, it is clear from the data collected to date that a significant portion of the CRBG aquifer system underlying the Quincy Basin contains groundwater that was recharged into the system more than 10,000 years ago.

Black Sands/Quincy Basin

‐1.00

0.00

1.00

2.00

3.00

4.00

5.00

6.00

0.00 10.00 20.00 30.00 40.00 50.00 60.00 70.00 80.00 90.00 100.00

Carbon‐14 (pmc)

Tritium (TU

)

Wanapum

Sediment

(>10,000 yrs o ld) (5,000 ‐ 10,000 yrs old) (60 ‐ 5,000 yrs old)

Modern

Recharge

(<60 yrs old)Mixed

GR4745

GR4761

GR0313

GR5597

GR4763

GR5584GR5424

GR4557

GR4802

Figure 21. Relative age plot of Black Sands groundwater. Wanapum Basalt aquifer groundwater appears to be exclusively old water while sedimentary aquifer groundwater is either exclusively

modern recharge or some mixture of young and old water. The source of the modern water is tied largely to irrigation activity, and likely includes canal and wasteway leakage, infiltration from irrigated fields, and potentially some precipitation. Some of the sampled sedimentary aquifer wells show a mix of modern recharge sources. For example, the stable hydrogen isotope level in well GR4745 (δD = –124.1‰) lies between the isotopic compositions of area surface waters (East Low Canal δD = –130.6‰, and Crab Creek δD = –116.2‰), suggesting that there are multiple modern recharge sources.

Page 49

Given these data though, not all sedimentary aquifer system water is exclusively young. A review of well construction information (see Table 8) for sedimentary aquifer wells with both young and old water suggests these wells typically are open to both young flood sands and the older Ringold Formation. The groundwater produced from these wells most likely would be a mixture of modern water from irrigation recharge (residing in the flood deposits) and older groundwater from semi-confined sand layers in the Ringold Formation. The older Ringold Formation water is interpreted to not be derived from the upward leakage from the CRBG aquifer system into the sedimentary aquifer system. Geologic interpretations of the Quincy Basin (see Figures 23 and 24) do not show the presence of (1) erosional windows through the uppermost basalt underlying these sediments, (2) significant structural deformation, or (3) other features that disrupt dense basalt flow interiors and thereby providing vertical pathways for the upward movement of CRBG groundwater.

Table 8. Well Construction Summary for Sampled Wells in the Black Sands.

GWMA Well ID Total Depth

(feet bgs) Seal Depth(feet bgs)

Casing Depth(feet bgs)


GR0313 503 20 303 Tpr, Tr

GR5597 524 34 250 Tpr, Tr, Tesc, Tfsg

GR4763 604 20 293 Tpr, Teqc, Tr

GR5424 430 255 255 Tpr, Teqc, Tr

GR5584 465 18 265 Tpr, Teqc, Tr

GR4745 171 N/A 171** Sediment

GR4761 136 20 42 Sediment

GR4557 57 18 55 Sediment

GR4802 169 20 169† Sediment *Abbreviation definitions are in Appendix A. **Perforated at 36 to 46 feet and 120 to 171 feet. †Perforated at 117 to 123 feet and 143 to 159 feet.

Page 50

Figure 22. Location map of wells sampled in the Black Sands case study area. The approximate location of the cross-sections displayed in Figures 23 and 24 is shown.

D

D'

E

E'

Page 51


Page 52

Legend

Well Depth

Well Casing

Geologic Layers

ppl

Qf Sediment

Trf Sediment

Tem Saddle Mountain

Tpr Wanapum

Teqc Interbed

Tr Wanapum

Tesc Interbed

Tfsg Wanapum

Tfsh Wanapum

Tfg Wanapum

Tev Interbed

Tgsb Grande Ronde

Tgo Grande Ronde

Tgu Grande Ronde

Tgg Grande Ronde

Tgwr Grande Ronde

Basement

D D'

GR4745

GR5424 GR5584

Winchester Wasteway


Figure 23. East to west cross-section through the Black Sands area. Open intervals are indicated by the red line portion of the boreholes. See Figure 3 for the location of this cross-section.

Ele

vati

on (

feet

AM

SL

)

Page 53

Legend

Well Depth

Well Casing

Geologic Layers

ppl

Qf Sediment

Trf Sediment

Tem Saddle Mountain

Tpr Wanapum

Teqc Interbed

Tr Wanapum

Tesc Interbed

Tfsg Wanapum

Tfsh Wanapum

Tfg Wanapum

Tev Interbed

Tgsb Grande Ronde

Tgo Grande Ronde

Tgu Grande Ronde

Tgg Grande Ronde

Tgwr Grande Ronde

Basement

E E′

GR5597 G0313 GR4761 GR44763

Winchester Wasteway

Horizontal Distance (feet) Figure 24. North to south cross-section through the Black Sands area. Open intervals are indicated by the red line

portion of the boreholes. See Figure 3 for the location of this cross-section.

Ele

vati

on (

feet

AM

SL

)

54


55

Case Study 7. Royal Valley: Surface Water/Groundwater Connection of Basalt Aquifers with the Columbia River along the Western Margin of GWMA

Summary Percent modern carbon, tritium, hydrogen stable isotopes, and well construction information was used to assess the degree of hydrologic connection between the Columbia River and the CRBG aquifer system near Wanapum Dam, in the Royal Valley, which lies in the west-central portion of Grant County. Specific portions of the CRBG aquifer system that have a direct physical connection to the river contain a very high proportion of young river water, indicating that the Columbia River can be a local source of CRBG aquifer system recharge in this area. Movement of this modern recharge is interpreted to be down-dip away from the Columbia River.

Discussion The structural characteristics of CRBG units where they contact major surface water bodies may prohibit or facilitate recharge. Mapped exposures of CRBG interflow zones along the Columbia River in western Grant County are potential recharge areas for the basalt aquifer system under certain conditions. Where an interflow zone dips (or slopes) downward toward a surface water body, water in these interflow zones generally would flow down-dip, toward the water body. However, where an interflow zone in contact with a surface water body slopes away from that water body, the body could be recharging groundwater in the interflow zone as it flows down-dip, away from the surface water source. An example of this latter scenario was investigated in the western end of the Royal Basin (located between the Frenchman Hills and Saddle Mountains) near Wanapum Dam. On the east side of the Columbia River, CRBG layers generally dip eastward and away from the river. GWMA’s subsurface geologic mapping indicates that the Gingko flow of the Frenchman Springs Member of the Wanapum Basalts (Tfg), and the upper part of the Sentinel Gap Member of the Grande Ronde Basalt (Tgsb) crop out in the Columbia River along areas of the western edge of the Royal Basin (Figures 26 and 27). Hydrochemical data (hydrogen stable isotopes, pmc, and tritium) from several wells sampled in the western Royal Basin were examined to investigate a possible connection between basalt groundwater and the Columbia River. The sampled wells are listed in Table 9. A plot of pmc versus tritium (Figure 28) indicates that several wells sampled in the Royal Basin contain a mixture of young water from modern recharge (≤60 years old) and fossil CRBG groundwater. Figure 28 illustrates that none of the wells sampled produces

56

exclusively young water. Therefore, the influence of old CRBG groundwater is present in all the wells sampled. Given this, it is the δD values in these samples that provide indications of localized recharge into certain CRBG aquifers from the Columbia River. A plot of δD versus distance from the Columbia River (Figure 29) demonstrates that some wells cased to units that come into contact with the river have δD values very similar to Columbia River water. Of particular note are wells GR1584 and GR1602, which have open intervals only in the Gingko flow. These wells have δD values almost identical to Columbia River water and contain significant amounts of tritium. Positive tritium values indicating a modern recharge component (Figure 28) coupled with δD values from wells cased to the Gingko flow is evidence that recharge into the Gingko flow via the Columbia River could be occurring. Figures 26 and 27 show the inferred aerial extent of this recharge effect, which, based on our analysis of hydrochemical data collected to date, appears to be limited to within ~6 miles of the river (Figures 26 and 27). This could be the result of a change in dip in the CRBG units that produces an uphill gradient prohibiting recharge from reaching more than ~6 miles from the river. Table 9. Well Construction Summary for Sampled Wells in the Royal Valley.

GWMA Well ID

Surface Elevation

Total Depth (feet bgs)

Seal Depth (feet bgs)



GR1593 1,010 750 25 602 Tev,Tgsb GR3199 1,116 1,109 234 1,054 Tgsb GR3202 1,228 1,472 1,055 1,055 Tgsb GR3202 1,228 1,472 1,055 1,055 Tgsb GR1294 1,308 674 0 674 Tgsb GR1599 1,003 580 131 131 Sediment,Tem,Temb,Tpr,Tr,Tesc,Tfsg,Tfsh GR1592 996 600 0 111 Tem,Tr,Tesc,Tfsg,Tfsh GR1521 1,054 657 234 234 Tem,Tr,Tesc,Tfsg,Tfsh G1543 1,261 1,065 40 40 Tem,Temb,Tpr,Tr,Tesc,Tfsg,Tfsh,Tfg,Tev,Tgsb

GR1557 939 534 232 534 Tr GR1588 549 173 160 160 Tfsh GR1590 566 355 121 121 Tfsg,Tfsh,Tfg GR1602 906 592 0 592 Tfg GR1584 522 422 90 292 Tfg GR1584 522 422 90 292 Tfg GR1532 613 390 36 36 Teqc,Tr,Tesc,Tfsg GR3198 1,154 N/A N/A 755 Tfg,Tev,Tgsb,Tgu,Tgo GR1604 1,234 1,025 20 823 Tfg,Tev,Tgsb GR3208 1,138 924 250 250 Tpr,Teqc,Tr,Tesc,Tfsg,Tfsh,Tfg,Tev,Tgsb


57

Figure 25. Location Map of wells sampled in the Royal Valley.

Royal Valley

58

Figure 26. Structure-contour map of the top of the Tfg unit. River surface

elevations above and below Wanapum Dam (WD on the map) are 573 and 489 feet, respectively. The two blue dashed lines delineate the 573-foot contour,

showing where the Wanapum Pool elevation is relative to the top of the Tfg unit. In this area, it could be physically possible for recharge water from the Columbia River to flow downgradient (to the east). However, current hydrochemical data

show that Columbia River recharge could be limited to an area extending ~6 miles eastward from the river and constrained to the area west of the orange

dashed line.

59

Figure 27. Structure-contour map of the top of the Tgsb unit. River surface

elevations above and below Wanapum Dam (WD on the map) are 573 and 489 feet, respectively. The two blue dashed lines delineate the 573 foot contour,

showing where the Wanapum Pool elevation is relative to the top of the Tgsb unit. In this area it could be physically possible for recharge water from the Columbia River to flow downgradient (to the east). However, current hydrochemical data

show that Columbia River recharge could be limited to an area extending ~6 miles eastward from the river and constrained to the area west of the orange

dashed line.

60

Royal Valley

-2.00

0.00

2.00

4.00

6.00

8.00

10.00

0.00 20.00 40.00 60.00 80.00 100.00

Carbon-14 (pmc)

Tri

tiu

m (

TU

)Grande Ronde

Wanapum


Multiple

Modern Recharge

(<60 yrs old)

(>10,000 yrs old)

Mixed

Figure 28. Percent modern carbon (pmc) versus tritium. Well GR1584, which possibly could be producing mixed groundwater with a modern component recharged from the

Columbia River, is indicated.

Royal Valley

-155.0

-150.0

-145.0

-140.0

-135.0

-130.0

-125.0

0.00 2.00 4.00 6.00 8.00 10.00 12.00 14.00 16.00 18.00

Distance from Columbia R. (miles)

Del

ta D

(p

er m

il)

Grande Ronde

Wanapum


Multiple

Figure 29. δD versus distance from the Columbia River. The orange dashed line indicates

the δD value of the East Low Canal, which has the Columbia River as its source (data from samples collected in June 2008). Wells GR1584 and GR1602, which possibly could

be producing mixed groundwater with a modern component recharged from the Columbia River, are indicated.

GR1584 GR1602

GR1584

61

Case Study 8. Southern and Central GWMA (Connell Sub-area): Effects of Stratigraphy, Structural Barriers, Geographic Setting, and Well Construction on Groundwater Flow, Recharge, and Compartmentalization with the Saddle Mountains Anticline

Summary Percent modern carbon, tritium, major ion chemistry, and static water level information was used to assess groundwater conditions that could be influenced by stratigraphy, structural barriers, geographic setting, and well construction in the central and southern GWMA, referred to here as the Connell sub-area. GWMA’s findings show that water on either side of the Saddle Mountains anticline and in the western and eastern halves of the Connell sub-area has significantly different geochemical signatures from varying degrees of mixing between fossil CRBG groundwater and modern recharge. The Saddle Mountains anticline and fold system creates a groundwater flow discontinuity in the CRBG aquifer system and appears to be a major influence of groundwater flow and compartmentalization in the Connell sub-area.

Introduction Hydrochemical and static water level (SWL) data were evaluated to identify groundwater trends and/or differentiation caused by various influences including stratigraphy, structural barriers, geographic setting, and well construction. The Connell sub-area is located in the south central GWMA and is approximately 672 square miles. Major geologic structures for the study area include the Saddle Mountains and Frenchman Hills anticlines and their associated faults, the Palouse Slope and the dike system of the Ginkgo unit of the Frenchman Springs Member of the Wanapum Basalt. CRBG aquifers are the main focus of this case study and suprabasalt sediment wells were not considered. This case study is organized follows: Hydrochemical data results and trends are discussed followed by a discussion of SWL data results and trends. Then the possible roles of stratigraphy, structural barriers, geographic setting, and well construction in producing observed hydrochemical and SWL trends are discussed. Finally, a general summary of the analyses and conclusions from this investigation of the observed hydrochemical and SWL trends is presented.

Hydrochemical Data Two age-dating parameters, pmc and tritium, were examined to identify the presence of mixing of fossil CRBG groundwater (old water) with modern recharge (young water).

62

Major ion chemistry was examined in an attempt to identify distinct hydrochemical facies (distinct bodies of groundwater identified on the basis of similar hydrochemistry) within the CRBG aquifer system that may be present in groundwater produced from wells open to multiple strata and/or are positive for tritium. Major ion data also were used to investigate possible end members for mixed groundwaters containing young water from modern recharge and fossil CRBG groundwater. Figure 30 is a location map that indicates the locations of wells sampled in the Connell sub-area. PMC and Tritium A noticeable trend in the plot of pmc versus tritium was that all but one of the wells sampled to the south of the Saddle Mountains anticline contained some component of young water from modern recharge (>0.1 TU) and that about half of the wells sampled to the north of the anticline contained exclusively fossil CRBG groundwater (Figure 31 32, 34, and 35). There is an east-west separation of Wanapum/Grande Ronde wells containing young water versus those containing no young water (Figure 33). This east-west separation is also present in Grande Ronde wells north of the Saddle Mountains anticline (Figure 32). Among the samples that were positive for tritium, only four contained exclusively young water and those were all south of the Saddle Mountains anticline (Figure 34). Also all of the wells sampled in the immediate vicinity of Connell grouped closely for tritium and pmc (Figure 34). Many wells open to both the Wanapum and Grande Ronde Formations exhibited pmc and tritium trends showing mixed fossil CRBG groundwater and young water from modern recharge. Possible reasons for mixing identified in this analysis include open or non-sealed wells, shallow depth to the top of basalt (TOB), and proximity to surface water recharge sources. Major Ion Chemistry Piper plots of major ions (K, Ca, Na, Mg, Cl, F, SO4, and HCO3) were created on the basis of well open interval (Grande Ronde only, Wanapum only, and Wanapum/Grande Ronde; Figures 35 through 38). The plots show that wells open to a single formation (either Wanapum or Grande Ronde) and containing exclusively old water were of the Na/HCO3 type, and tritium-positive wells open to a single formation had no dominant type. Wells open to multiple formations (Wanapum and Grande Ronde) containing young water had no dominant cation type or were of the Na/HCO3 type. Wells open to multiple formations that contained no young water were of the Na/HCO3 type. Surface water samples from Lake Roosevelt and East Low Canal were of the Ca/HCO3 type (Figures 37 and 38). Wells that were geographically close also were clustered on the Piper plot indicating these wells could be producing water from common hydrochemical facies. For example, in Figure 37, wells F4109 and F4107 cluster together with well F4113 in Figure 35. Wells A1584, A2339, A0321, and A0332 form a separate cluster on Piper plots (Figure 37). These two clusters contain wells that are geographically close to each other and represent two different sets of wells producing water from two different hydrochemical facies within the same CRBG aquifer system. Static Water Level SWL data from Eastern Regional Office (ERO) of the Washington Department of Ecology, dating back to the 1970s were examined for trends unique to specific areas

63

within the greater Connell sub-area. ERO hydrographs indicated that CRBG SWLs north of the Saddle Mountains anticline had greater declines than CRBG SWLs south of the anticline (Figures 39 through 41). Data from GWMA for additional non-ERO wells were examined to compare/confirm trends seen in the ERO data. In Figure 42, which is a residual SWL deviation map, it is apparent that wells in the western portion of the study area have demonstrated increasing SWL while wells in the eastern portion of the study area have decreasing SWL. It is noteworthy that wells with increasing SWLs are in areas where surface water irrigation is more prevalent while those with decreasing SWLs are in areas with less surface water irrigation. Discussion Stratigraphy North of the anticline, it is apparent that about half of the wells sealed and cased into the Wanapum, Grande Ronde, and Wanapum/Grande Ronde Formations are predominately fossil CRBG groundwater. South of the anticline, nearly all of the wells, regardless of open interval, contain young water from modern recharge. However, there are no apparent trends indicating more occurrences of young water in wells in the north or south resulting from shallow (≤75 feet) depth to TOB (Figure 43). From the age dating and major ion data, it appears that Wanapum and Grande Ronde fossil CRBG groundwaters are hydrochemically similar. However, water produced from some wells that are open to both Wanapum and Grande Ronde Formations and are tritium negative, is hydrochemically similar to Wanapum and Grande Ronde fossil CRBG groundwater (Figure 37). Water produced from some wells that are open to both Wanapum and Grande Ronde Formations and are tritium positive, plot somewhat linearly between surface water (Lake Roosevelt and East Low Canal) and fossil CRBG groundwater. This suggests that irrigation water and fossil CRBG groundwater are the primary end members in mixed Wanapum/Grande Ronde wells (Figure 38). Structural Barriers The main structural influence on CRBG groundwater chemistry in the Connell sub-area is the Saddle Mountains anticline. From the age-dating data, it is clear that there is a greater percentage of wells south of the Saddle Mountains anticline containing some component of young water from modern recharge than wells north of the anticline. The Saddle Mountains anticline also could be a flow-limiting (leaky) barrier. For example, five geographically close wells, two north and three south of the Saddle Mountains anticline, produce hydrochemically different groundwater despite being open to common geologic units. All of the five wells are located in the western Connell sub-area and thus contain a young water (tritium-positive) component (Figure 44). However, wells north of the Saddle Mountains anticline have a greater fossil basalt groundwater component and wells south of this structural feature have a greater young water component as seen in tritium and pmc data (Figure 34). One of the wells south of the Saddle Mountains anticline (F4254) has no seal, while wells near it are sealed to considerable depths (≥140 feet bgs). A portion of the young water introduced to the CRBG aquifer system resulting from the

64

construction issues of F4254 could not be reaching the nearby wells north of the Saddle Mountains anticline because this feature is a groundwater barrier. In addition, a Ginkgo dike could be present and separate these two sets of wells, accounting for some or all of the hydrochemical differences. SWL data indicate that wells south of the Saddle Mountains anticline in general are experiencing less SWL decline than wells north of this structure. Well Construction Wells with shallow casing and seal depths tend to have a young water component. This trend is more pronounced south of the Saddle Mountains anticline. For example, wells F4107, F4113, and F4109 are spatially close and open to common Grande Ronde and Wanapum Basalt units, and each is mixed and part of the same hydrochemical facies with respect to major ion chemistry (see Figures 30 and 37). Well F4107 is cased and sealed to 19 feet bgs with the TOB at 3 feet bgs. Wells F4113 and F4109 are cased and sealed to considerably deeper depths. It appears that the introduction of young water to the CRBG aquifer system is via shallow seals. This could happen from just a single well with a shallow seal where the effects of pumping from nearby wells could draw the young water out into the formation away from the culprit well. This could be the case for wells F4107, F4113, and F4109. Localized recharge to Wanapum Basalt units also appears to be occurring in the immediate vicinity of the East Low Canal as evidenced by the presence of young water form modern recharge (e.g., wells A0394 and A0395). Surface water (i.e., downward percolation from irrigation canals) also could be responsible for some shallow CRBG aquifer recharge in the western Connell sub-area, hence the increasing SWLs in that area. Because the general groundwater flow direction is to the southwest, young water from irrigation is traveling downgradient toward non-irrigated areas in the eastern Connell sub-area. Many wells open to multiple formations (Wanapum and Grande Ronde Basalts), and deeper CRBG aquifer systems (Grande Ronde Basalt) could be receiving indirect recharge from irrigation/surface water in the west via shallow CRBG aquifer systems (Wanapum Basalt).

Summary/Conclusions In general, CRBG groundwater being pumped to the north and east of the Saddle Mountains anticline is old fossil CRBG groundwater and groundwater being pumped in the western Connell sub-area and south of the Saddle Mountains anticline contains components of young water from modern recharge. It is likely that the young water in the west and south is from surface water and irrigation sources. Lesser declines in SWLs in the west and south indicate that there could be a significant amount of recharge to the CRBG aquifers in these areas that is not present north of the Saddle Mountains anticline. Tritium-positive Grande Ronde and Wanapum groundwaters from co-mingling wells appear to be mixtures of two end members: surface water used for irrigation and old fossil CRBG groundwater. It appears from this analysis that:

The Saddle Mountains anticline is serving as a groundwater barrier in the Connell sub-area.

65

Age-dating, major ion chemistry and SWL data from the CRBG aquifer systems

in the western Connell sub-area and south of the Saddle Mountains anticline indicate that the CRBG aquifer systems are receiving some significant recharge while those aquifer systems north of the Saddle Mountains anticline are not.

Localized areas of mixed young and old groundwater exist south of the Saddle

Mountains anticline may be the result of the introduction of young water to the CRBG aquifer through well construction flaws. This young water then is disseminated farther in the aquifer by pumping effects of nearby wells.

66

Figure 30. Location map of wells sampled in the southern and central GWMA (Connell

Sub-area).

Saddle Mountains Anticline

Frenchman Hills Anticline

67

Figure 31. Tritium in wells open to the Wanapum Basalt. Wells open only to the Wanapum Basalt are shown. Wells are labeled with GWMA IDs. The possible location of the Gingko dike lies between the two parallel pink lines as indicated by the arrows. Pink lines indicate barriers with moderate to some leakage. Bright green lines indicate barriers with little to no leakage. Green lines indicate barriers with a lot of leakage.

↑ N

Gingko Dike Area

68

Figure 32. Tritium in wells open to the Grande Ronde Basalt. Wells open only to the Grande Ronde Basalt are shown. Wells are labeled with GWMA IDs. The possible location of the Gingko dike lies between the two parallel pink lines as indicated by the arrows. Pink lines indicate barriers with moderate to some leakage. Bright green lines indicate barriers with little to no leakage. Green lines indicate barriers with a lot of leakage.

↑ N

Gingko Dike Area

69

Figure 33. Tritium in wells open to the Wanapum/Grande Ronde Basalt. Wells open to both the Wanapum and Grande Ronde Basalt are shown. Wells are labeled with GWMA IDs. The possible location of the Gingko dike lies between the two parallel pink lines as indicated by the arrows. Pink lines indicate barriers with moderate to some leakage. Bright green lines indicate barriers with little to no leakage. Green lines indicate barriers with a lot of leakage. .

↑ N

Gingko Dike Area

70

Age Plot

0.0

1.0

2.0

3.0

4.0

5.0

6.0

7.0

8.0

9.0

0.0 10.0 20.0 30.0 40.0 50.0 60.0 70.0 80.0 90.0 100.0

PMC

Tri

tiu

m (

TU

)

GR N

W N

W/GR N

GR S

W S

W/GR SOld

Young

Mixed

Figure 34. Age plot of Connell sub-area wells. “Old” refers to water ≥10,000 years old. “Young” refers to water ≤60 years old. The red circle contains wells in the immediate vicinity of Connell. The green oval contains wells that are geographically close while

being on different sides of the Saddle Mountains anticline.

F4257

F4258

F4255

F0470

North of Saddle Mountains anticline

South of Saddle Mountains anticline

Anticline (hypothetical; orange dashed line)

71

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100806040200

0

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0

020406080100

Bic

arbo

nate

(HC

O3)

+ C

arbo

nate

(CO

3)

Calcium

(Ca) + M

agnesium(M

g)C

hlor

ide(

Cl)

+ Fl

uorid

e(F

) + S

ulfa

te(S

O4)

Sodium

(Na) + P

otassium(K

)

Chloride(Cl) + Fluoride(F)

Sulfate(S

O4)

Calcium(Ca)

Mag

nesi

um(M

g)

CATIONSCa = 37. mg/lMg = 32. mg/lNa = 52. mg/lK = 6.7 mg/l

ANIONSHCO3 = 140. mg/lCO3 = 0. mg/lCl = 56. mg/lSO4 = 89. mg/lF = 0.4 mg/l

Symbol Key: Green symbols - wells in located in the southern Connell sub-area. Red symbols - wells located in the northern Connell sub-area.

Figure 35. Wanapum Basalt Piper plot. The red circle contains well F4113, which is geographically close to wells F4109 and F4107 in Figure 30.

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020406080100

Bic

arbo

nate

(HC

O3)

+ C

arbo

nate

(CO

3)

Calcium

(Ca) + M

agnesium(M

g)

Chl

orid

e(C

l) +

Fluo

ride(

F) +

Sul

fate

(SO

4)

Sodium

(Na) + P

otassium(K

)


Sulfate(S

O4)

Calcium(Ca)

Mag

nesi

um(M

g)



Symbol Key: Green symbols - wells in located in the southern Connell sub-area. Red symbols - wells located in the northern Connell sub-area.

Figure 36. Grande Ronde Basalt Piper plot.

73

Mag

nesi

um(M

g)

Calcium(Ca)

Sulfate(S

O4)


Sod

ium(N

a) + Potassiu

m(K

)

Chl

orid

e(C

l) +

Fluo

ride(

F) +

Sul

fate

(SO

4)C

alcium(C

a) + Magnesium

(Mg)

Bic

arbo

nate

(HC

O3)

+ C

arbo

nate

(CO

3)

100 80 60 40 20 0

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20

80



Symbol Key: Green symbols - wells in located in the southern Connell sub-area. Red symbols - wells located in the northern Connell sub-area. Brown triangle - surface water from Lake Roosevelt. Black triangle - surface water from East Low Canal. Red oval - wells F4109 and F4107 that cluster together with well F4113 in Figure 28. Blue circle - wells A1584, A2339, A0321, and A0332.

Figure 37. Wanapum/Grande Ronde Basalt Piper plot. Notice that many of the wells plot in a linear fashion between the surface waters and some wells from north of the anticline

that contain exclusively old water. This suggests that wells plotted along the line are a mixture of just the two previously mentioned end members of surface water and old fossil

CRBG groundwater.

74

80

20

60

40

40

60

20

80

20

80

40

60

60

40

80

20

100

80

60

40

20

0

0

20

40

60

80

100

100806040200

0

20

40

60

80

100

100

80

60

40

20

0

020406080100

Bic

arbo

nate

(HC

O3)

+ C

arbo

nate

(CO

3)

Calcium

(Ca) + M

agnesium(M

g)

Chl

orid

e(C

l) +

Fluo

ride(

F) +

Sul

fate

(SO

4)

Sod

ium(N

a) + Potassiu

m(K

)


Sulfate(S

O4)

Calcium(Ca)

Mag

nesi

um(M

g)



Symbol Key: Pink = Wanapum/Grande Ronde wells containing young water. Blue = Wanapum/Grande Ronde wells containing no young water. Red = Grande Ronde wells containing no young water. Green = Wanapum wells containing no young water. Brown = Lake Roosevelt surface water. Black = East Low Canal surface water.

Figure 38. Mixing study Piper plot. This plot displays the positions of mixed wells with respect to end members.

75

WB Hydrograph

500.0

550.0

600.0

650.0

700.0

750.0

800.0

850.0

900.0

950.0

1000.0

1978 1980 1982 1984 1986 1988 1990 1992

SW

L (

el.

feet

AM

SL

)

A0019

A1810

F0496

F4109

Figure 39. Wanapum Basalt well hydrograph. In the legend, wells preceded by the letter “A” are in Adams County north of the Saddle Mountains anticline and wells preceded by

the letter “F” are in Franklin County south of the Saddle Mountains anticline.

76

GRB Hydrograph

600.0

700.0

800.0

900.0

1000.0

1100.0

1200.0

1978 1980 1982 1984 1986 1988 1990 1992

SW

L (

el.

feet

AM

SL

)

A2321

A1806

Figure 40. Grande Ronde Basalt well hydrograph. In the legend, wells preceded by the letter “A” are in Adams County north of the Saddle Mountains anticline and wells preceded by the letter “F” are in Franklin County south of the Saddle Mountains

anticline.

77

WB/GRB Hydrograph

500.0

600.0

700.0

800.0

900.0

1000.0

1100.0

1978 1980 1982 1984 1986 1988 1990 1992

SW

L (

el. f

eet

AM

SL

)

A0424

A0426

A0428

A0431

A0432

A2007

A2297

F0464

F4255

F4257

Figure 41. Wanapum/Grande Ronde Basalt well hydrograph. In the legend, wells

preceded by the letter “A” are in Adams County north of the Saddle Mountains anticline and wells preceded by the letter “F” are in Franklin County south of the Saddle

Mountains anticline.

78

↑ N

Figure 42. Residual SWL deviation. This map is a surface interpolation of SWLs (residuals) observed on the Connell sub-area. Any color other than the yellow background is at least 1 standard deviation from the mean residual. Darker colors indicate greater deviation from the mean residual. Blue areas are regions of positive deviation indicating some degree of SWL increase. Red areas are regions of negative deviation indicating regions of SWL decrease. It is apparent from this figure that the western portion of the Connell sub-area has experienced some increased SWLs and that the eastern portion of the Connell sub-area has experienced some decreased SWLs.

79

TOB Depth Vs. PMC

0

50

100

150

200

250

0.0 10.0 20.0 30.0 40.0 50.0 60.0 70.0 80.0 90.0 100.0

PMC

TO

B (

feet

bg

s)

GR N

W N

W/GR N

GR S

W S

W/GR S

Old Mixed Young

Figure 43. Plot of percent modern carbon (pmc) versus depth to top of basalt (TOB). No apparent trend is present to indicate that young water may be present because of TOB depth. However, it is noticeable that most Wanapum/Grande Ronde wells in the north

(W/GR N) contain exclusively old water.

80

Figure 44. Location of wells with respect to structure. The Saddle Mountains anticline discussed in the text is the black line intersected by the double arrow. The coral-colored parallel lines indicate the estimated extent of the Gingko Dike system.

Wells north of fault Wells South of fault

81

Summary

The hydrochemical data summarized here point to major influences on groundwater occurrence and recharge that can be related to known and suspected geologic features. These geologic features include the layered nature of the CRBG aquifer system and the resulting inhibitions to vertical groundwater movement through undisturbed, laterally extensive, dense basalt flow interiors. As a result, the predominant groundwater movement pattern in GWMA is lateral, along gently dipping CRBG interflow zones. This is evident in the data presented in this report, such as (1) the vertical separation of shallow young water and deeper older water, (2) down-dip migration of young water away from surface water sources, and (3) the presence of deep old water beneath modern surface water bodies. In addition to the vertical compartmentalization of the CRBG aquifer system, the hydrochemical data summarized here also point to major geologic features that disrupt the lateral movement of groundwater at certain locations in the aquifer systems underlying GWMA. Folds, faults, and feeder dikes have the potential to disrupt the lateral flow system simply by breaking up the continuity of water-bearing interflow zones. The hydrogeochemical data collected by GWMA to date suggest that several major structures and feeder dike systems separate distinctly different bodies of groundwater. Throughout GWMA, these features exert a noticeable influence on modern water recharge and the mixing (or lack thereof) of modern water with fossil CRBG groundwater. In Case Studies 1 through 7, groundwater segregation is most likely the result of CRBG aquifer system stratigraphy. Case Study 8 demonstrates that the possibility exists for major structures within GWMA to affect groundwater segregation within individual basalt layers or groups of layers. Surface water/groundwater interaction involving the Columbia River is a possibility in the western GWMA, as was demonstrated in Case Study 7. Finally, as shown by Case Studies 1, 4, and 7, lateral, down-dip movement of groundwater away from recharge areas is occurring at least over distances of several miles. Given typical regional dip of 1 to 2 degrees in the layered aquifer system that characterizes GWMA, and the Columbia Basin in general, the potential for down-dip, downgradient movement of groundwater away from shallow sources and deep into the CRBG aquifer is great.

82

References

Bailey, M.M. 1989. Revisions to stratigraphic nomenclature of the Picture Gorge Basalt Subgroup, Columbia River Basalt Group, in, Reidel, S.P., and Hooper, P.R., eds., Volcanism and tectonism in the Columbia River flood-basalt province: Geological Society of America Special Paper 239, p. 67-84.

Beeson, M.H., Fecht, K.R., Reidel, S.P., and Tolan, T.L. 1985. Regional correlations

within the Frenchman Springs Member of the Columbia River Basalt Group - new insights into middle Miocene tectonics of northwestern Oregon: Oregon Geology, v. 47, no. 8, p. 87-96.

GWMA. 2007. Geologic framework of selected suprabasalt sediment and Columbia

River basalt units in the Columbia Basin Ground Water Management Area of Adams, Franklin, Grant, and Lincoln Counties, Washington, Ed. 2: Consultants report prepared for Columbia Basin GWMA by GSI Water Solutions, Inc. and Franklin Conservation District, August 2007.

GWMA. 2009a. A summary of Columbia River Basalt Group geology and its influence

on the hydrogeology of the Columbia River basalt aquifer system - Columbia Basin Groundwater Management Area of Adams, Franklin, Grant, and Lincoln Counties: Consultant report prepared for GWMA, prepared by GSI Water Solutions, Inc., June 2009.

GWMA. 2009b. Groundwater geochemistry of the Columbia River Basalt Group aquifer

system - Columbia Basin Groundwater Management Area of Adams, Franklin, Grant, and Lincoln Counties: Consultant report prepared for GWMA, prepared by GSI Water Solutions, Inc. and SSPA, June 2009.

GWMA. 2009c. Multiple tracer study of recharge mechanisms and the age of

groundwater in the Columbia River Basalt Group aquifer system - Columbia Basin Groundwater Management Area of Adams, Franklin, Grant, and Lincoln Counties: Consultant report prepared for GWMA, prepared by GSI Water Solutions, Inc. and SSPA, July 2009.

GWMA. 2009d. Groundwater level declines in the Columbia River Basalt Group and

their relationship to mechanisms for groundwater recharge - A conceptual groundwater system model, Columbia Basin Groundwater Management Area of Adams, Franklin, Grant, and Lincoln Counties: Consultant report prepared for GWMA, prepared by GSI Water Solutions, Inc., June 2009.

GWMA. 2010. Unpublished data analysis of City of Moses Lake Wells: Consultant

report prepared for GWMA, prepared by GSI Water Solutions, Inc.

83

PNNL (Batelle-Pacific Northwest National Laboratory). 2002. Natural gas storage in basalt aquifers of the Columbia Basin, Pacific Northwest USA – a guide to site characterization: Pacific Northwest Laboratory, Richland, Washington, Report PNNL-13962.

Swanson, D.A., Wright, T.L., Hooper, P.R., and Bentley, R.D. 1979a. Revision in the

stratigraphic nomenclature of the Columbia River Basalt Group: U.S. Geological Survey Bulletin 1457-G, 59 p.

Swanson, D.A., Anderson, J.L., Bentley, R.D., Camp, V.E., Gardner, J.N., and Wright,

T.L. 1979b. Reconnaissance geologic map of the Columbia River Basalt Group in Washington and adjacent Idaho: U.S. Geological Survey Open-File Report 79-1363, scale 1:250,000.

Tolan, T.L., and Reidel, S.P., compilers. 1989. Structure map of a portion of the

Columbia River flood-basalt province, in, Reidel, S.P., and Hooper, P.R., eds., Volcanism and tectonism in the Columbia River flood-basalt province: Geological Society of America Special Paper 239, Plate 1, scale 1:576,000.

Tolan, T.L., Martin, B.S., Reidel, S.P., Anderson, J.L., Lindsey, K.A., and Burt, W. 2009.

An introduction to the stratigraphy, structural geology, and hydrogeology of the Columbia River Flood Basalt Province - A primer for the GSA Columbia River Basalt Group field trips, in O’Conner, J.E., Dorsey, R.J., and Madin, I.P., eds., Volcanoes to Vineyards - Geologic Field Trips through the Dynamic Landscape of the Pacific Northwest: Geological Society of America Field Trip Guide 15, p. 599-643.

Page A-1

Appendix A

2

Geologic Unit Abbreviations Definitions

Sediment and CRBG Units Sediments Units - Code Name

Qf Coarse Quaternary Deposits Ql Quaternary Loess PPl Plio-Pleistocene caliche Trf Ringold Formation fines

Trwie Ringold Formation conglomerate

Basalt Units - Code Name Formation TOB Top of Basalt Tih Ice Harbor Member Saddle Mountain Basalt Tel Levey Member Sedimentary interbed Tem Elephant Mountain Member Terr Rattlesnake Ridge Member Sedimentary interbed Tp Pomona Member Tes Selah Member Sedimentary interbed Teq Esquatzel Member Ta Asotin Member

Twc Wilbur Creek Member Tu Umatilla Member

Temb Mabton Member Sedimentary interbed Tpr Priest Rapids Member Wanapum Basalt

Teqc Quincy Member Sedimentary interbed Tr Roza Member

Tesc Squaw Creek Member Sedimentary interbed Tf Frenchman Springs Member

Tev Vantage Member Sedimentary interbed Tgsb Sentinel Bluffs Grande Ronde Basalt Tgu Umtanum Tgo Ortley Tgg Grouse Creek

Tgwr Wapshilla Ridge Tgud Undifferentialted Grande Ronde

Basement Pre-Basalt Basement Rock

Appendix B

Page B‐1

Explanation of Hydrochemical Parameters

This appendix provides some basic explanations of why and how hydrochemical parameters were used to assess groundwater conditions explained herein. The following explanations of groundwater age, age tracers, and analytical parameters are excerpted from GWMA (2009). Groundwater Age The age of groundwater can be defined by the amount of time a particular water molecule has spent below the ground surface. Groundwater age is thus an absolute value (e.g., 25 years or 1,500 ± 110 years). Groundwater age also can be discussed in terms of residence time, which refers to the amount of time it takes for a water molecule to travel from its entry into the subsurface to its point of exit from the groundwater system, either through a well, spring, or other discharge to the surface. Groundwater age is numerically equivalent to groundwater residence time at the point of discharge (Kazemi et al., 2006). Because a groundwater system can have numerous recharge points, as well as temporally and spatially variable flow rates, the individual water molecules in a water sample drawn from a well may have entered the system at different times and therefore are of different ages. To reduce the amount of uncertainty in groundwater age determinations, it is important in practice to integrate results from more than one age dating technique. Individual age dating techniques generally are applicable to specific age ranges (described in more detail below). In designing site-specific investigations, it is critical to select methods that are applicable for the expected span of groundwater ages (Figure B1). For example, if residence times in the part of the aquifer system being studied are certainly less than 60 years, a combination of age dating techniques for dating young waters (e.g., tritium-helium and chlorofluorocarbons [CFC]) may be sufficient. If the water sampled is likely to be a mixture of young and older groundwater (modern to thousands of years old), it is necessary to use at least one of the younger age dating techniques in combination with at least one of the older age dating techniques (e.g., CFCs and carbon-14). In general, employing multiple age tracers for a particular study provides for a more accurate characterization of groundwater age (e.g., Plummer et al., 2001). Age Tracers Groundwater samples collected from pumping wells or springs often represent a composite mixture of water from different flow paths and therefore a mixture of water of different ages (Manning et al., 2005; Weissmann et al., 2002). The measurement and calculation of groundwater ages is further complicated by variable geologic and geochemical conditions relating to the recharge source, recharge rate, and groundwater flow paths and flow rates (the direction and spatial distribution of groundwater flow). In addition, and particularly for aquifer systems such as the CRBG, which consist of multiple water-bearing zones, groundwater samples collected from a well represent a flow-weighted composite of the water from the multiple water-bearing zones to which the

Page B‐2

well is open. A well with a relatively short open interval is more likely to yield a groundwater age that is representative of the actual residence time of groundwater at that location than can be obtained from a well with a relatively long open interval. Despite these potential complications in interpretation, groundwater ages have been widely measured, calculated, and applied in a variety of useful and critical areas of groundwater science (Kazemi et al., 2006). This is largely the result of the increasing availability of a number of analytical methods, including tritium (3H), tritium-helium (3H/3He), CFCs, sulfur hexafluoride (SF6), and carbon-14 (14C). Carbon –14 Carbon-14 (14C), also referred to as radiocarbon, is a radioactive isotope of carbon with a half-life of 5,730 years. Carbon occurs naturally in all organic life forms and in rocks and minerals (e.g., limestone and calcite, respectively). 14C is produced by cosmic radiation in the atmosphere after which it quickly forms 14CO2 and enters the biosphere through photosynthesis. Human industry and transportation that burn fossil fuels, creating CO2, actually decrease the concentration of 14C in the atmosphere as 14C is not produced by these processes. 14CO2 dissolves into atmospheric moisture and surface waters, which eventually recharge to groundwater. Once in the subsurface and with no further input of carbon (which is uncommon in most natural systems), the decay rate of 14C can be used to calculate the time elapsed since the water entered the subsurface. However, because of all of the external inputs of 14C that are possible, derivation of age dates by this method often requires carefully considered corrections. Most notably, corrections are usually required in groundwater systems where (1) carbonate minerals, such as calcite, dissolve, (2) organic matter is oxidized, or (3) sulfate reduction, methanogenesis, or geothermal processes are involved. Most of these processes generally result in addition of nonradioactive carbon to the groundwater, thereby diluting the 14C content, making the apparent groundwater ages older. Analyses of 14C typically are carried out by accelerator mass spectrometry (AMS) and reported in units of percent modern carbon (pmc) referenced to 1950 (=100 pmc). Similar to tritium, atmospheric 14C levels increased during the 1950s because of nuclear testing, but have been decreasing since the early 1960s after atmospheric testing was banned, with current levels at approximately 110 pmc (Kazemi et al., 2006). 14C contents in groundwater equal to or greater than 100 pmc are indicative of post-1950s recharge. The 14C content of water that recharged an aquifer before atmospheric nuclear testing is assumed to be 100 pmc, or less if chemical reactions diluted the dissolved carbon pool with nonradioactive 12C. The 14C age is calculated from:

2ln

ln 2/1t

Aq

At

o

Page B‐3

where t is age, ln is the natural logarithm, A is the measured 14C content of the sample, Ao is the initial 14C content in equilibrium with the atmosphere, q is the dilution factor, and t1/2 is the half-life of 14C (5,730 years).

For radioactive decay to reduce the 14C content in groundwater from 100 to 50 pmc requires one half-life, or about 5,700 years. About 11,000 years are required to reduce 14C content to 25 pmc, about 17,000 years to reduce it to 12 pmc, and so on. As alluded to earlier, these uncorrected 14C ages represent the maximum possible groundwater age and generally need to be corrected for addition of nonradioactive carbon by applying an appropriate model. It can be difficult to accurately estimate the initial 14C content in water before entering the groundwater system (e.g., after passing through the soil zone where addition of soil CO2 dilutes the 14C content), although a value of 85 pmc often is used (Vogel, 1970; Clark and Fritz, 1997). More complex correction procedures based on isotope mass balances also have been used. The robustness of a groundwater age determination can be assessed by evaluating the sensitivity of calculated ages to different correction procedures. Arguably the most useful aspect of radiocarbon dating in regards to assessment of aquifer recharge is in identifying the presence of old water and in constraining the proportion of young water in mixed groundwaters (i.e., the fraction that may be considered to be renewable). In some cases, such age distributions can be determined through application of relatively simple mixing models, although in practice these are better evaluated through application of age transport models (Kazemi et al., 2006). Tritium Tritium (3H) is the unstable, radioactive isotope of hydrogen, with a half-life of 12.43 years. This short half-life makes it a useful isotope for age dating young (<60 years) groundwater. Of all the tracers used for groundwater age dating, tritium is the only one that is part of the water molecule itself. For example, most water molecules contain the stable hydrogen isotope 1H while a very small percent of water molecules contain 3H. The tritium content of water is measured radiometrically and reported in tritium units (TU). One TU is equal to one 3H1HO molecule in 1018 water (H2O) molecules. Tritium is produced naturally in the atmosphere and by human activity. Anthropogenic sources include nuclear reactors (and their by-products), luminous watch incineration facilities, and thermonuclear explosions. Before the 1950s, naturally produced tritium resulted in levels in atmospheric moisture in the range of 5 TU. Beginning in the 1950s, there was a rapid increase of tritium in the atmosphere because of atmospheric testing of nuclear weapons; testing was banned in 1962. The increase and subsequent decline in atmospheric tritium levels produced a spike, also called the bomb-peak or bomb-pulse, which has been quantified (Figure B2), and tritium is now monitored routinely at specific laboratories around the world. Figure B2 shows how the age of a groundwater sample can be estimated from its tritium content using the atmospheric history curve (atmospheric content of tritium over time).

Page B‐4

The tritium content of the sample (e.g., 10 TU, collected in 2009) is projected backward in time (i.e., doubling every 12.32 years) and the intersection with the history curve represents the recharge age for the groundwater sample. Because of the shape of the bomb pulse, however, tritium age dating often results in more than one possible age for a single sample. For the example, in Figure B2, the best we can say is that the groundwater mostly likely was recharged sometime between 1959 and 1972. This problem often can be resolved by applying several different age dating methods and assessing the best estimate. Improved accuracy of tritium-based age estimates can sometimes be obtained by determining the concentration of helium-3, the product of the radioactive decay of tritium. Although this method has been shown to be useful in many studies of shallow sedimentary aquifers, high helium-3 concentrations associated with volcanic rocks derived from the earth’s mantle (such as the CRBG) make groundwater age interpretations in such settings problematic, if not impossible. Tritium is nevertheless useful in two main ways as a groundwater age tracer. First, the tritium atom is part of the water molecule and enters into the groundwater system along with the water, and is the only age tracer of which this is true. Second, bomb-peak tritium is a robust indicator of a young groundwater age. If tritium is not detected in a sample (<0.1 TU), it can be concluded that the groundwater was recharged before 1950, whereas if tritium is detected, then the water sampled contains at least a fraction that was recharged since the 1950s. However, because of the uncertainties in deriving the recharge age from tritium concentration data alone, it is most often best used as a qualitative indicator of recently recharged groundwater, and in conjunction with other age tracers. Atmospheric Chlorofluorocarbons (CFC-11, CFC-12, and CFC-113) Chlorofluorocarbons (CFC) are a group of synthetic organic chemicals used in a wide variety of industrial and household products (i.e., aerosol sprays). CFCs were developed to have the specific thermodynamic properties of stability, low toxicity, and inertness. Because of these properties, CFCs have a long atmospheric lifetime. Since the 1940s, atmospheric concentrations increased monotonically as a result of increasing production and industrial use, but leveled off in the mid-1990s and have been declining since then because of the ban on their use (Figure B3). Three CFC compounds are routinely analyzed for groundwater dating applications (CFC-11, CFC-12, and CFC-113) by gas chromatography-electron capture detection (GC-ECD). Water samples must be collected without contacting the atmosphere. CFC concentrations are very low and reported in units of pictograms per kilogram (pg/kg), which equals 10-6 micrograms per kilogram (μg/kg) of water. Recharge ages are obtained by converting the concentration of individual CFCs in the groundwater to the equivalent concentration of the same CFC species in the atmosphere at the time of recharge, using known solubility relationships and estimated recharge temperatures. The atmospheric concentration thus derived is compared to the atmospheric history curve to produce an estimate of the recharge date (the year in which the water was recharged to the ground;

Page B‐5

see Figure B3). The atmospheric history curves for these chemicals are well defined, as there are several stations around the world that make regular atmospheric measurements of CFCs, and the variability of these concentrations worldwide is low enough to not be a serious limitation to application of the method. There are several issues to consider in using CFCs as a groundwater age dating method. Potential sources of error include (1) error in recharge temperature estimation, (2) error resulting from exposure of the sample to air (contamination), (3) error derived from microbial degradation of CFCs in the aquifer, (4) error resulting from solute transport effects (e.g., sorption/desorption of CFCs on the aquifer matrix), (5) error from samples representing mixed age groundwater, and (6) error from lack of the method’s account of a large (>5 meter) unsaturated zone (which is present in some areas within GWMA). Kazemi et al. (2006) emphasize the sensitivity of the samples used for CFC age dating to excess air contamination. Special techniques and equipment are needed to properly collect samples. Concentrations of dissolved atmospheric gases (argon, nitrogen) typically are used to estimate recharge temperatures and the amount of excess air (air in excess of solubility) that was entrained as bubbles and dissolved into the groundwater during the recharge process. The advantages of using CFCs to age date groundwater include (1) the presence of CFCs is a strong indicator of post-1945 water, (2) one analysis provides three independent age estimates, (3) recharge dates can be derived from either the individual CFCs or from ratios of two CFCs compared with atmospheric values, and (4) the analysis is relatively inexpensive compared to other methods. Cation Ratio Cation ratio is based on the concentrations of cationic species commonly found dissolved in surface water and groundwater. The specific cations that are used to calculate the cation ratio include Na++, K++, Mg++, and Ca++ by the following configuration:

(Na+K)/(Na+K+Ca+Mg)

Infiltration of precipitation and other surface waters into the CRBG initially results in dilute, less evolved, Ca-Mg-HCO3 type water. As groundwater moves downgradient along available and accessible flow paths, progressive silicate hydrolysis and dissolution results in a more evolved groundwater, showing an increase in silica and pH (from approximately 7 to 10), while fluoride and chloride are leached from the basalt matrix. Precipitation and ion-exchange reactions further modify the water by removing calcium and magnesium in exchange for sodium, resulting in more evolved Na-HCO3 type water. Long groundwater residence times cause secondary minerals (iron-rich smectite clays, zeolites, calcite, and silica) to precipitate and also result in removal of calcium, magnesium, potassium, iron, carbonate, and silica from basalt groundwaters. This greater chemical evolution results in Na-Cl dominated water in the deepest parts of the CRBG aquifer system sampled in the central basin (Reidel et al., 2002). Older more chemically evolved groundwaters have higher cation ratios than younger less chemically evolved groundwaters.

Page B‐6

References Cited Clark, I., and P. Fritz. 1997. Environmental Isotopes in Hydrology: CRC Press, Boca

Raton.

GWMA. 2009. Multiple tracer study of recharge mechanisms and the age of groundwater in the Columbia River Basalt Group aquifer system - Columbia Basin Groundwater Management Area of Adams, Franklin, Grant, and Lincoln Counties: Consultant report prepared for GWMA, prepared by GSI Water Solutions, Inc. and SSPA, July 2009.

Kazemi, G.A., Lehr, J.H., and Perrochet, P. 2006. Groundwater Age: John Wiley & Sons, Inc.

Manning, A.H., Solomon D.K., and Thiros, S.A. 2005. 3H/3He age data in assessing the susceptibility of wells to contamination: Ground Water, v. 43, p. 353-367.

Plummer, L.N., Busenberg, E., Bohlke, J.K., Nelms, D.L., Michel, R.L., and Schlosser, P. 2001. Groundwater residence times in Shenandoah National Park, Blue Ridge Mountains, Virginia, USA: A multi-tracer approach: Chemical Geology, v. 179, p. 93-111.

Reidel, S.P., Johnson, V.G., and Spane, F.A. 2002. Natural gas storage in basalt aquifers of the Columbia Basin, Pacific Northwest USA – a guide to site characterization: Pacific Northwest Laboratory, Richland, Washington, Report PNNL-13962.

Vogel J. C. 1970. Carbon-14 dating of groundwater, in, Isotope Hydrology, p. 225-239. IAEA Symposium 129.

Weissmann, G.S., Zhang, Y., LaBolle, E.M., and Fogg, G.E. 2002. Dispersion of groundwater age in an alluvial aquifer system: Water Resources Research, v. 38, p. 16.

Page B‐7

Figure B1. Groundwater age dating methods and their useful age ranges. After Kazemi et al. (2006).

Figure B2. Estimation of possible groundwater ages from atmospheric tritium history.

Figure B3. Atmospheric concentration histories of selected tracers used for age dating young groundwaters.

Appendix C

Case Study Number Sample GWMA_Well_IDdelta18O_ deltaD_ delta13C_Carbon_14pmcC_14Age_ Tritium_ Cation_Ratio1 GB052610-04 GR1980 -16.3 -138.9 -12.6 28.14 10180 0.10 0.621 GB052610-10 GR1984 -17.7 -142.9 -15.9 1.31 34790 -0.06 0.971 GB052710-09 GR3210 -17.8 -144.6 -12.6 8.02 20270 -0.07 0.891 GB060810-05 GR1250 -17.9 -146.4 -12.7 2.09 31060 -0.08 0.911 GB071910-03L A2860 -17.9 -153.2 -14.1 7.68 20620 -0.10 0.831 GB071910-08L L1202 -17.7 -141.9 -13.2 8.65 19660 -0.06 0.871 GB06190803 GR1972 -18.1 -145.8 -10.9 7.49 20820 -0.01 0.961 GB06230802 L1246 -17.9 -143.1 -21.8 9.41 18989 0.16 0.871 GB06240804 L1234 -18.4 -146.1 -10.6 18.39 13600 0.08 0.481 GB071910-02L L0007 -17.9 -153.3 -15 3.10 27900 -0.02 0.991 GB052610-01 GR1981 -17.7 -145.1 -12.3 2.11 30980 -0.04 0.881 GB061010-02 L1258 -14.3 -121.0 -12.1 58.07 4370 0.44 0.371 GB052610-09 GR1985 -16.5 -139.4 -12.8 30.01 0.09 0.491 GB06190804 L0017 -18.4 -146.1 -10.4 8.52 19780 0.09 0.901 GB060210-01 L1455 -12.4 75.10 2300 2.06 0.431 GB082610-02 L1455 -125.4 -11.6 71.03 2750 0.451 GB052610-02 GR1982 -17.6 -143.5 -12.3 10.24 18300 0.06 0.771 GB052610-11 GR1987 -18.1 -147.2 -12.4 1.84 32110 -0.05 0.961 GB052710-08 GR0997 -18.1 -147.6 -12 13.34 16180 0.06 0.571 GB052710-08b GR0997 -17.8 -147.9 -11.6 13.08 16340 -0.04 0.561 GB071910-04L L1247 -18.0 -146.6 -13.6 12.52 16660 -0.02 0.811 GB07281007L L0002 -139.5 -12.5 23.32 11700 0.09 0.481 GB083010-01L L0036 -145.0 -12.2 1.57 33360 -0.07 0.981 GB083010-03L L0005 -145.0 -15.6 1.77 32420 0.09 0.991 GB083010-04L L0005 -144.7 -15.6 1.91 31770 0.09 1.001 GB06240802 L0006 -18.3 -145.6 -10.6 11.92 17080 0.24 0.771 GB06250803 L0014 -15.2 -124.7 -9.7 67.87 2110 3.85 0.221 GB052610-06 GR1983 -15.9 -146.3 -16.1 1.06 36490 -0.01 0.961 GB060110-01 GR1986 -17.8 -143.9 -23.1 3.62 26650 -0.07 0.951 GB060210-02 L0053 -12.8 3.81 26250 0.03 0.971 GB061010-01 L1259 -15.1 -125.3 -12.8 57.84 4400 -0.04 0.381 GB071910-06L L0040 -17.3 -138.4 -13.9 36.53 8090 0.36 0.441 GB071910-07L L1248 -18.4 -147.6 -12.9 5.82 22840 -0.03 0.491 GB083010-02L L1420 -147.0 -12 17.94 13800 0.23 0.441 GB06250802 L1235 -17.6 -141.0 -14.1 12.01 17020 0.20 0.982 GB050410-10 GR0617 -142.0 0.892 GB050410-11 GR6092 -143.9 0.872 GB050510-01 GR0837 -138.8 -11.3 44.25 6550 1.18 0.702 GB050510-02 GR0615 -138.1 0.532 GB050510-04 GR6183 -145.8 0.912 GB082410-03 GR0617 -13.2 37.21 7940 0.622 GB082410-04 GR6186 -13.9 11.23 17570 0.742 GB082410-06 GR6101 -12.3 41.46 7070 1.572 GB082410-07B GR6183 -12.6 5.20 23740 0.032 GB050410-05 GR8244 -126.0 -13.7 98.14 150 5.81 0.252 GB050410-01 GR1379 -125.9 0.172 GB050410-08 GR7123 -130.7 0.362 GB082410-08 GR7123 -128.4 -11.8 89.11 930 6.37 0.352 GB050410-02 GR6141 -141.5 -12.4 18.82 13420 0.61 0.932 GB050410-03 GR6088 -143.2 0.972 GB050410-06 GR1804 -136.1 0.542 GB050410-07 GR1692 -139.2 0.912 GB050510-03 GR6094 -147.5 0.922 GB050510-05 GR6091 -133.4 0.592 GB050510-06 GR1802 -137.6 0.562 GB082410-07 GR6088 -12.8 7.12 21220 0.383 GB042810-05 A0560 -142.2 -12.8 14.48 15520 0.07 0.843 GB072110-04 A0220 -15.6 -132.4 -13.2 72.00 2640 0.97 0.123 GB072110-05 A2890 -17.0 -140.9 -14.8 2.53 29550 -0.02 0.993 GB072110-03 A2284 -16.4 -132.0 -12.6 62.87 3730 0.40 0.163 GB071510-02 A0596 -16.1 -131.5 -13.3 32.70 8980 0.14 0.543 GB072110-01 A0511 -12.8 -111.3 -13.7 89.38 900 1.41 0.183 GB071510-05 A2605 -15.8 -128.6 -12.4 23.29 11700 0.08 0.923 GB072110-02 A0588 -15.2 -123.3 -15.2 60.56 4030 0.86 0.213 GB071510-01 A2842 -16.6 -134.3 -12.5 17.22 14130 0.02 0.773 GB071510-03 A0617 -8.6 -88.3 -10.5 102.71 3.96 0.173 GB070110-04 A0508 -15.6 -125.4 -13.1 64.69 3500 0.61 0.203 GB070110-06 A0510 -13.1 -112.0 -13.7 78.43 1950 2.413 GB072110-07 A0210 -16.8 -134.4 -13.8 50.23 5530 0.40 0.223 GB071510-06 A0607 -13.6 -113.8 -12 82.43 1550 2.13 0.154 GB081110-07 GR9505 -11.5 63.93 3590 1.584 GB072710-01 GR1099 -118.3 -11.6 60.37 4050 0.90 0.464 GB072010-01 GR1991 -16.5 -133.0 -12.5 52.21 5220 2.77 0.404 GB082610-03 GR1678 -135.6 -10.2 62.40 3790 7.33 0.534 GB081110-05 A2292 -125.8 -10.8 71.61 2680 5.41 0.444 GB062910-01 A0396 -16.1 -127.6 -9.2 74.04 2410 5.13 0.394 GB062410-02 A0403 -16.3 -128.9 -9 80.71 1720 5.85 0.364 GB042910-01 A1531 -149.0 0.914 GB062410-01 A0395 -16.3 -128.5 -9 73.02 2530 5.45 0.434 GB081710-04 A0394 -130.7 -9.5 60.72 4010 2.95 0.354 GB061510-02 GR3220 -121.7 -11.9 49.95 5570 0.15 0.404 GB060110-04 GR1989 -17.9 -144.6 -11.9 7.85 20440 -0.16 0.734 GB06240806 GR1692 -18.0 -143.8 -12.3 24.48 11300 3.97 0.944 GB062210-01 A2293 -17.8 -145.2 -12.9 13.59 16030 1.46 0.904 GB062410-03 A2274 -18.2 -144.5 0.984 GB062410-04 A0389 -18.2 -144.6 0.824 GB062410-05 A0390 -18.2 -144.3 0.974 GB062410-09 A2321 0.0 -142.5 -12.9 13.65 15990 0.02 0.945 GB10130902 GR3226 -16.0 -129.4 -12.9 90.43 810 5.44 0.005 GB10130901 GR3225 -16.5 -127.8 -14.2 98.02 160 5.76 0.386 GB080310-02 GR4557 -16.3 -137.8 -11.7 21.61 12310 1.39 0.226 GB080310-05 GR4802 -14.1 -120.7 -9.8 27.31 10430 0.10 0.176 GB080510-05 GR4761 -128.1 -13.3 65.77 3370 1.49 0.186 GB081010-03 GR4745 -124.1 -14 88.03 1020 5.12 0.196 GB080510-06 GR4763 -150.5 -13.3 5.57 23200 -0.02 0.336 GB081210-04 GR5597 -149.7 -11.3 6.00 22590 0.02 0.586 GB081210-06 G0313 -146.3 -11.8 6.59 21840 -0.07 0.566 GB081010-02 GR5424 -10.8 20.72 12640 0.09 0.386 GB081010-01 GR5584 -132.3 -12.1 25.73 10910 0.87 0.377 GB042610-05 GR1593 -137.8 -13 43.79 6630 1.76 0.447 GB071310-02 GR3199 -138.6 -14.6 21.50 12350 -0.05 0.487 GB071410-01 GR3202 -134.4 -11.8 43.47 6690 0.42 0.337 GB072810-02 GR3202 -141.5 -11.8 30.29 9590 0.31 0.297 GB081810-05 GR1294 -152.1 -12.4 6.21 22320 0.06 0.717 GB052510-02 GR1599 -137.3 -13.5 44.65 6480 5.91 0.237 GB062310-05 GR1592 -128.5 -12.9 71.04 2750 9.70 0.227 GB071310-03 GR1521 -137.3 -14.6 55.03 4800 7.32 0.217 GB080510-03 G1543 -137.5 -13.1 44.03 6590 5.37 0.367 GB050610-01 GR1557 -148.8 0.707 GB052510-03 GR1588 -141.8 0.347 GB052510-04 GR1590 -145.6 0.347 GB052510-05 GR1602 -131.1 0.267 GB071310-01 GR1584 -130.4 -14.3 50.05 5560 2.76 0.207 GB071310-01B GR1584 -130.9 -14.2 48.94 5740 2.61 0.207 GB071410-02 GR1532 -140.0 -13.9 50.27 5520 4.46 0.437 GB042610-04 GR3198 -133.3 -12.7 66.18 3320 6.29 0.237 GB062310-04 GR1604 -145.4 -13.7 12.04 17000 0.27 0.617 GB071310-04 GR3208 -148.3 -14 18.96 13360 4.05 0.328 GB080410-02 F4255 -140.5 -11.9 35.61 8290 3.74 0.578 GB080410-02b F4255 -141.8 -11.5 35.77 8260 3.64 0.588 GB080410-03 F4254 -139.6 -11 40.35 7290 4.22 0.258 GB081810-03 F4257 -141.9 -11.9 22.45 12000 2.63 0.728 GB082410-10 F4258 -141.1 -11.6 21.67 12280 1.95 0.588 GB082610-01 F0470 -143.0 -11 44.95 6420 4.62 0.15

Surface Water Cr.C Irby -116.5 -14.4Surface Water Cr.C Odessa -115.9 -14.5Surface Water E. Low Canal Hatton Rd -130.0 -16.6Surface Water E. Low Canal Moses Lake -131.2 -16.7Surface Water R.C. Canal Crab Lat -126.6 -16.2Surface Water Sprague Lake -80.5 -7.8

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