SEMS-RM DOCID # 100000381
JULY 24, 2017
UPDATED SOUTHERN AREA CHARACTERIZATION REPORT AND CONCEPTUAL SITE MODEL REVISION 2.0
APACHE POWDER SUPERFUND SITE COCHISE COUNTY, ARIZONA
PREPARED BY: PREPARED FOR:
HARGIS + ASSOCIATES, INC. Apache Nitrogen 1820 East River Road #100 Products, Inc. Tucson, Arizona 85718 P.O. Box 700 Benson, Arizona 85602 1
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UPDATED SOUTHERN AREA CHARACTERIZATION REPORT AND CONCEPTUAL SITE MODEL REVISION 2.0 APACHE POWDER SUPERFUND SITE COCHISE COUNTY, ARIZONA
TABLE OF CONTENTS
Section Page ACRONYMS AND ABBREVIATIONS ...... iv 1. 0 INTRODUCTION ...... 1 1.1 SCOPE ...... 1 1.2 SITE LOCATION AND HISTORY ...... 2 1.2.1 History of the Southern Area Groundwater Remedy ...... 4 1.2.2 Status of the MNA Remedy ...... 6 1.2.3 History of Changes to CSM for Southern Area ...... 6 1.2.4 Significant New Findings Regarding CSM for Southern Area ...... 8 2. 0 REGIONAL GEOLOGY AND HYDROGEOLOGY ...... 9 3. 0 HYDROGEOLOGY OF THE SOUTHERN AREA ...... 11 3.1 GROUNDWATER LEVEL ELEVATIONS AND HYDROGRAPHY ...... 11 3.1.1 PERCHED ZONE A – WATER ELEVATION...... 12 3.1.2 PERCHED ZONE B – WATER ELEVATION...... 13 3.1.3 MW-24 AREA – WATER ELEVATION ...... 14 3.1.4 LATERALLY-CONFINING UNIT ...... 14 3.1.5 SHALLOW ALLUVIAL AQUIFER ALONG THE SAN PEDRO RIVER – WATER ELEVATION...... 15 3.1.6 WATER ELEVATION COMPARISONS ...... 15 3.2 GROUNDWATER QUALITY ...... 16 3.2.1 PERCHED ZONE A – NITRATE-N ...... 16 3.2.2 PERCHED ZONE B – NITRATE-N ...... 17 3.2.3 MW-24 AREA – NITRATE-N ...... 18 3.2.4 SHALLOW ALLUVIAL AQUIFER ALONG THE SAN PEDRO RIVER – NITRATE-N ...... 19 3.3 PERCHED ZONE A – PERCHLORATE ...... 19 3.3.1 PERCHED ZONE B – PERCHLORATE ...... 19 3.3.2 MW-24 AREA – PERCHLORATE ...... 20 3.3.3 SHALLOW ALLUVIAL AQUIFER ALONG THE SAN PEDRO RIVER – PERCHLORATE ...... 21 3.3.4 TOTAL DISSOLVED SOLIDS ...... 21 4. 0 CONCEPTUAL SITE MODEL ...... 22 4.1 CSM COMPONENTS ...... 22 4.2 FEATURES OF THE REVISED CSM ...... 22 4.3 SUPPORTING RATIONALE ...... 24 5. 0 SUMMARY ...... 28 5.1 PRIMARY FEATURES OF THE CSM ...... 28 5.2 REMEDY IMPLICATIONS ...... 33
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TABLE OF CONTENTS (continued)
6. 0 CONCLUSIONS ...... 37 7. 0 REFERENCES ...... 38
TABLES
Table
1 RAIN SEASON PRECIPITATION BENSON, ARIZONA
2 SATURATED THICKNESS OF PERCHED ZONE AREAS - AUGUST 2016
FIGURES
Figure
1 LOCATION OF APACHE POWDER SUPERFUND SITE, COCHISE COUNTY, ARIZONA
2 FACILITY BOUNDARY AND LOCATION OF SOUTHERN AREA PERCHED SYSTEM (PZ-A AND PZ-B)
3 CONCEPTUAL VIEW OF PERCHED ZONE AND SHALLOW AQUIFER IN 1994 (TIME OF ROD)
4 CONCEPTUAL VIEW OF PERCHED ZONE, MOLINOS CREEK SUB-AQUIFER (MCA), LATERALLY CONFINING UNITS AND SHALLOW AQUIFER IN EARLY 2000s
5 CONCEPTUAL VIEW OF PERCHED ZONE AND MOLINOS CREEK SUB-AQUIFER IN 2007
6 CONCEPTUAL SCROSS-SECTION (WEST-EAST) SHOWING PERCHED WATER IN ISOLATED DEPRESSIONS OR POCKETS IN PZ-A AND PZ-B
7 CHANGE IN AREAL EXTENT OF PERCHED ZONE A 1995 TO 2017
8 CONCEPTUAL VIEW OF PERCHED SYSTEM (PZ-A AND PZ-B) IN 2017
9 MONITOR WELLS AND BORINGS WITHIN SOUTHERN AREA
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TABLE OF CONTENTS (continued) 10 CONCEPTUALIZED CROSS SECTIONS A–A’ AND B–B’
11 CONCEPTUALIZED CROSS SECTIONS C-C’ AND D-D’
12 GROUNDWATER ELEVATIONS PERCHED ZONE A
13 GROUNDWATER ELEVATIONS PERCHED ZONE B
14 GROUNDWATER ELEVATIONS ISOLATED AREA AT MW-24
15 GROUNDWATER ELEVATIONS PERCHED ZONE A & B AND ALONG SAN PEDRO RIVER
16 ELEVATION OF GROUNDWATER 2016
17 NITRATE IN GROUNDWATER - MAXIMUM DETECTED CONCENTRATION
18 NITRATE IN GROUNDWATER – 2015/2016
19 PERCHLORATE IN GROUNDWATER - MAXIMUM DETECTED CONCENTRATION
20 PERCHLORATE IN GROUNDWATER – 2015/2016
21 TOTAL DISSOLVED SOLIDS IN GROUNDWATER
22 CONCEPTUALIZATION OF GROUNDWATER EXCHANGE BETWEEN PERCHED ZONE A AND B
APPENDICES
Appendix
A SUMMARY OF INVESTIGATIONS AFTER 2007
B HISTORIC GROUNDWATER ELEVATION FIGURES
C WATER LEVEL AND WATER QUALITY HYDROGRAPHS
D TRANSPIRATION AND EVAPORATRANSPIRATION CONCEPTS
E PREVIOUS SOUTHERN AREA CSM REPORTS (DIGITAL)
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ACRONYMS AND ABBREVIATIONS
ADEQ Arizona Department of Environmental Quality ADHS Arizona Department of Health Services ANPI Apache Nitrogen Products, Inc. bls below land surface COC chemical of concern CSM Conceptual Site Model EPA U.S. Environmental Protection Agency ESD Explanation of Significant Differences H+A Hargis + Associates, Inc. HBGL Health-Based Guidance Level LCU laterally confining unit MCA Molinos Creek Sub-Aquifer MCL Maximum Contaminant Level mg/l milligrams per liter MNA monitored natural attenuation msl mean sea level nitrate-N nitrate-nitrogen NPL National Priorities List PI preliminary investigation PRB perchlorate-reducing bacteria PZ-A Perched Zone A (in area of former ponds) PZ-B Perched Zone B (formerly referred to as MCA) RI remedial investigation TDS total dissolved solids the Site Apache Powder Superfund Site μg/l micrograms per liter ROD Record of Decision
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SOUTHERN AREA CHARACTERIZATION AND REVISED CONCEPTUAL SITE MODEL APACHE POWDER SUPERFUND SITE COCHISE COUNTY, ARIZONA
REVISION 2.0
1.0 INTRODUCTION
This report updates the hydrogeology and conceptual site model (CSM) of the groundwater system located in the southern portion of the Apache Powder Superfund Site (Southern Area of the Site or Southern Area). This update follows previous updates of the CSM for the Southern Area (H+A, 2003 and 2007), and was necessitated as a result of further exploration and data acquisition in the Southern Area. These previous reports are included for reference in digital format attached to this report (Appendix E).
1.1 SCOPE
The Apache Powder Superfund Site (the Site) is a National Priorities List (NPL) site in Cochise County, Arizona (Figure 1). This report is being issued as an update of the conceptual understanding and remedial status of a portion of the groundwater remedy known as the Southern Area (Figure 2). It follows in a succession of related reports prepared on the Southern Area (Hargis + Associates, Inc. [H+A], 2001, 2003a, 2003b, 2003c, 2006, 2007a, 2007b, 2013).
In particular, this report redefines areas where groundwater contamination remains in the Southern Area. From the time of the 1994 ROD through 2016, areas with groundwater contamination in the Southern Area have been referred to as the Perched Groundwater Zone(s), the Shallow Aquifer, and beginning in 2003, a new area was identified as the Molinos Creek Sub-Aquifer (MCA). The chemicals of concern (COCs) in the Southern Area have been nitrate-nitrogen (nitrate-N) and perchlorate, with perchlorate being detected only in the Perched Groundwater Zone. By the mid-2000s, nitrate contamination was no longer detected in the Shallow Aquifer in the Southern Area. In 2017, the only areas with residual nitrate and
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perchlorate contamination in the Southern Area are related to the perched groundwater. This updated CSM now identifies this area as the Southern Area Perched System comprised of two sub-areas. Specifically, these are now referred to as Perched Zone A (PZ-A) and Perched Zone B (PZ-B).
PZ-A refers to the perched groundwater present underlying the area where Apache Nitrogen Products, Inc. (ANPI) formerly discharged process wastewaters to unlined evaporation ponds. PZ-B refers to the area formerly referred to as the MCA, which lies to the east of PZ-A and where groundwater is present at a lower elevation than in PZ-A. PZ-A resulted from infiltration from the former ponds. PZ-B resulted from downward and lateral seepage eastward from PZ-A. Infiltration and lateral seepage eastward no longer occurs due to the closing and capping of the former evaporation ponds in 1995. Neither perched zone is hydraulically connected to the shallow alluvial aquifer along the San Pedro River to the further to the east.
Much of the footprint of PZ-B is present beneath the ANPI property. The extent beyond ANPI’s boundary is limited, but uncertain. However, it has been determined that there is little risk of exposure because PZ-B is not presently a suitable water supply nor would it serve as a water supply in the future due to its low yield and limited volume.
This information relates to the CSM of the groundwater system and therefore presents information relevant to the approach to remedial action for residual contamination within PZ-A and PZ-B groundwater.
1.2 SITE LOCATION AND HISTORY
The Apache Powder Superfund Site is located in Cochise County, Arizona, approximately nine miles southeast of Benson, Arizona, and west of the Town of St. David, Arizona (Figure 1). The Site incorporates the entire property of ANPI, a nitrogen products manufacturing plant, plus areas immediately adjacent to the ANPI property where the groundwater contamination was found to exist.
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The ANPI property covers approximately 1,200 acres. Presently, ANPI manufactures nitric acid, solid and liquid ammonium nitrate, aqua ammonia, and nitrogenous fertilizer products. In the past, blasting agents, detonating cord, safety fuse, nitroglycerin-based explosives, ammonia, sulfuric acid, and water-gel high explosives were also produced at the plant. From 1973 to 1979, Dye Carbonics, Inc. operated a carbon dioxide plant at the Site. Most of these historic operations, including the manufacturing of explosives, were performed at locations other than the locations of present-day operations.
Throughout its operational history, ANPI has relied on groundwater for industrial, landscape irrigation, and drinking water uses. Industrial use, landscape irrigation, and drinking water supplies are derived exclusively from wells tapping the deep, or regional, aquifer, with the exception of process waters that are treated and recycled via the Brine Concentrator. Shallow aquifer or perched groundwater is not and never has been used by ANPI for any of these purposes. With respect to wastewater, prior to 1971, the plant wastewater stream was routed via unlined ditches directly to dry wash tributaries of the San Pedro River. These washes were informally named by EPA during its preliminary investigation as Washes 1 through 6 (Figure 2). Historically, most of ANPI’s industrial wastewater was discharged to Washes 5 and 6, whose watersheds include the bulk of ANPI’s operational areas (Figure 2). No wastewater is believed to have been discharged to Washes 1 and 2. Washes 3 and 4 are reported to have received very little, if any, wastewater, but probably received stormwater runoff from some operational areas.
From 1971 to 1995, ANPI used unlined evaporation ponds throughout the site and wastewater was routed via unlined channels to several of these ponds (Figure 2). Ponds 1A, 1B, 2A, 2B, 3A, and 3B, located south of the Site Operations Area within the Wash 6 watershed, received the bulk of the wastewaters. During their active use, impounded wastewater and wastewater flowing in the unlined channels infiltrated into the underlying coarse terrace deposits. Downward percolation of the wastewater was eventually impeded upon encountering the St. David clay, the uppermost fine-grained stratum of the St. David Formation comprising dense, impermeable clay. As the volume of water infiltrating increased, a “mound’ of water formed and began to spread laterally creating what is now known as PZ-A. The accreting mound of perched groundwater underlying the former group of ponds is known to have migrated laterally to the
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east eventually discharging to what is now known as PZ-B. In April 1995, it became possible to discontinue discharge of wastewaters to Ponds 1A, 1B, 2A, 2B, 3A, and 3B due to the construction of the Brine Concentrator facility to which the wastewater stream was rerouted and which continues to receive and treat process wastewaters through the present day. The overall effect of these water management and source control operations has had the effect of allowing the previously-established mound of perched groundwater in the Southern Area to recede both in saturated thickness and areal extent. In turn, the seepage of the contaminated PZ-A into PZ-B has terminated.
1.2.1 History of the Southern Area Groundwater Remedy
Based on the hydrogeology interpreted from the Site remedial investigation and subsequent studies, groundwater remedies were addressed in two areas of the Site, referred to as the Northern and Southern Areas. As of 2017, the Southern Area includes the perched system with two sub-areas of contaminated residual perched groundwater referred to as PZ-A, PZ-B. These two areas of residual perched groundwater are considered within the overall context of the shallow alluvial aquifer located to the east along the San Pedro River in the vicinity of St. David, Arizona. A laterally confining unit isolates the contaminated residual perched groundwater in the west from the shallow aquifer to the east, and an uncontaminated MW-24 area located to the north of the perched zones (which previously was included as part of the MCA).
In 1994, the EPA issued a Record of Decision (ROD) that called for (1) extraction of perched groundwater and treatment in ANPI’s newly-constructed Brine Concentrator facility, and (2) extraction of groundwater from the shallow aquifer and treatment in a constructed wetland. The remediation standard for the cleanup was established for nitrate as nitrogen (nitrate-N) and was set at 10 milligrams per liter (mg/l), the Federal Maximum Contaminant Level (MCL) for drinking water. Later and as discussed below, it was determined based on new information that neither of these two remedies were implementable. Moreover, as discussed in this report, contamination within the shallow aquifer in the Southern Area, is limited to PZ-B, which has now been determined to be hydraulically isolated from the shallow aquifer.
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First, the treatment of PZ-A groundwater using the Brine Concentrator facility, which was designed and intended to treat process wastewater from ANPI’s manufacturing facility, was not implementable due to the high concentration of total dissolved solids (TDS) within the perched zone groundwater. Effectively, the specifications of the Brine Concentrator were not equipped to handle such high TDS concentrations. While it was determined that the Brine Concentrator had at least an excess capacity of ten percent, mixing high TDS waters into its influent stream would cause upset conditions and probably damage the facility. However, continued monitoring of the body of perched groundwater underlying the ANPI operations area over the years subsequent to the ROD issuance revealed that the footprint of the perched zone was rapidly shrinking (Figure 2). The groundwater level monitoring of PZ-A and the area to the east, then believed to be part of the shallow aquifer, revealed that the PZ-A was draining into the “shallow aquifer.”1 Hence, it was decided that, instead of treatment by the Brine Concentrator, the PZ-A would be allowed to drain into the “shallow aquifer” over time, where it could be treated in the context of the shallow aquifer remedy. This decision was documented in an Explanation of Significant Differences (ESD) issued by EPA (EPA, 1997).
But in 1998, as a result of a request by the Arizona Department of Environmental Quality (ADEQ) to investigate whether perchlorate was present in Site groundwater, perchlorate was indeed detected in the Southern Area. Further research into why perchlorate was present, considering that it was not a component of any of ANPI’s manufacturing products, revealed that it came onto the plant as an impurity within a feedstock, Chile saltpeter. This feedstock was used in a long-abandoned process for manufacture of nitric acid. In light of the discovery of perchlorate in the groundwater, EPA determined that its selected remedy involving wetland treatment was not advisable considering the potential for ecological exposures. Thus after a time and after considering additional studies performed in the early 2000s by ANPI, in 2005 EPA signed a ROD Amendment that changed its selected groundwater remedy for the Southern Area to monitored natural attenuation (MNA) with institutional controls (EPA, 2005). Additionally, EPA set the cleanup standard for perchlorate in groundwater at 14 micrograms per liter (μg/l) based on the Arizona Department of Health Service’s (ADHS) Health-Based Guidance Level (HBGL) (EPA, 2005).
1 As noted above, the drainage was not into the shallow aquifer along the San Pedro River, but rather into the alluvium comprising PZ-B, which is hydraulically isolated from the actual shallow alluvial aquifer.
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1.2.2 Status of the MNA Remedy
After several years of MNA operation, trending analyses of the status of MNA in the “shallow aquifer” indicated that the projected cleanup timeframe could be as long as 100 years. Moreover, while concentrations of the nitrate-N and perchlorate COCs were progressing toward ROD standards over most of the footprint of the contaminated area, one area in the western part of the footprint showed increasing concentrations.
Accordingly, EPA directed ANPI to consider methods to enhance MNA for the purposes of accelerating the cleanup (EPA, 2012). ANPI thereby launched a program of investigation to evaluate the feasibility of using in situ methods for denitrification/dechlorination (H+A, 2013). During the initial phases of this investigation, which included drilling, sampling, and testing of new wells sited in the highly contaminated western area, it was learned that the sediments exhibited a high degree of heterogeneity with markedly poor lateral hydraulic continuity. This finding thereby limited the ability to either extract or inject fluids as would be required for in situ or even ex situ treatment.
Additional investigations performed in 2015 have provided additional information used to update the CSM. An exploratory boring (EXB-27) was drilled next to MW-15 and a monitor well (MW-47) was installed along the east side of PZ-B
1.2.3 History of Changes to CSM for Southern Area
The CSM has changed considerably since the 1994 ROD and the 2005 ROD Amendment due to additional field studies conducted during the last decade. These changes relate to EPA’s understanding of both the nature and extent of the perched groundwater in the Southern Area (now known to be a perched system with two sub-components) and the proximity of the perched zones to the shallow aquifer.
Hence the quotation marks.
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At the time of the 1994 ROD, the Southern Area Groundwater was defined as two separate areas: (1) a single perched zone underneath unlined evaporation ponds; and (2) a shallow alluvial aquifer of the San Pedro River. The single perched zone was assumed to be hydraulically connected to the shallow aquifer and the San Pedro River (Figure 3, Conceptual View in 1994). However, this concept is no longer supported by the current data. As the CSM has evolved over time, based on a growing body of information, ANPI has completed three updated southern area characterization reports in 2003 (Hargis, 2003), 2007 (Hargis, 2007) and again in 2017 (Hargis, 2017). The 2003 report redefined the Southern Area Groundwater Area as four separate areas: (1) perched zone; (2) an area immediately east of the perched zone identified as the MCA; (3) a laterally confining unit with limited water: and (4) the shallow aquifer connected to the San Pedro River (Figure 4, Conceptual View in 2003). In 2003, these areas were still believed to be hydraulically connected (even if limited) to the shallow aquifer. The 2007 report further refined the CSM based on additional drilling conducted in the Southern Area. The investigative studies concluded that the MCA was not a continuous system, but instead greatly reduced in lateral extent. The MCA was determined to be separated into two lobes; one small uncontaminated area in the north near Monitor Well MW-24, and a larger contaminated area in the south still referred to as the MCA (Figure 5, Conceptual View in 2007).
Most recently, field studies conducted from 2012-2016 further demonstrated that the MCA was an isolated unit (part of a separate “perched system”) without hydraulic connection to the shallow aquifer along the San Pedro River, as shown in the attached cross-section (Figure 6, Conceptual Southern Area Cross-Section in 2017). As of 2017, the perched groundwater created by migration from the unlined evaporation ponds has reduced significantly in size from its original extent in 1995 to just minimal pockets of residual contaminated water (Figure 7, Areal Extent of Water in Perched Zone A). The contaminated perched system is recognized as two sub-areas, Perched Zone A (PZ-A), and Perched Zone B (PZ-B) (Figure 8, Conceptual View in 2017), formerly known as the MCA (Figure 5, Conceptual View in 2007). The isolated and shrinking Perched Zone A to the west, which was created by the prior discharges of process waste waters into unlined evaporation ponds on the ANPI property no longer has hydraulic connection to Perched Zone B, and the Perched Zone B has no hydraulic connection to the shallow aquifer along the San Pedro River. Although nitrate was detected in the shallow aquifer
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along the San Pedro River in the 1990s, nitrate has not been detected in the shallow aquifer or the river in the Southern Area since the mid-2000s. Perchlorate has never been detected in the shallow aquifer or the river. Therefore, the cleanup standards for the shallow aquifer in the Southern Area have been met.
1.2.4 Significant New Findings Regarding CSM for Southern Area
As reported above, there have been significant findings in recent years that refine and update the state of earlier knowledge regarding the Southern Area groundwater and, in particular, the CSM for the Southern Area (See Appendix E). These differences are critical to remedy decisions. In summary, key differences are listed here and are further explained in the summary section of this report.
• There are two distinct perched zones. • The two perched zones are isolated hydraulically from each other, and isolated from the shallow alluvial aquifer by a laterally-confining unit (LCU). • Groundwater occurrence in PZ-B is discontinuous. • Distribution of COCs in PZ-B varies from west to east. • Estimation of COC mass and water volume in previous CSM was incorrect. • Poor overall hydraulic conditions are present between water bodies in PZ-B. • No nitrate contamination detected in shallow aquifer after mid-2000s. • No perchlorate contamination ever detected in shallow aquifer. • Cleanup standards have been met for shallow aquifer in Southern Area.
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2.0 REGIONAL GEOLOGY AND HYDROGEOLOGY
The Site is located in the Upper San Pedro River Basin, which is situated within the Basin and Range physiographic province (Fenneman, 1931). The Basin and Range province is typified by broad, gently sloping alluvial basins separated by north-northwest trending crystalline fault block mountains (Fenneman, 1931). The tectonic movement that created the Basin and Range province began during the Miocene Epoch as part of the Miocene Basin and Range Orogeny (Melton, 1965). The basins were created by the subsidence of structural grabens along high angle normal faults. Sedimentation within the grabens coincided with the gradual subsidence, resulting in a thick sequence of fine- to coarse-grained late Cenozoic terrestrial sediments derived from the igneous, metamorphic, and sedimentary rocks of the surrounding mountain ranges (Gray, 1965; Smith, 1994). Due to the closed drainage environment during subsidence, sediments deposited gradationally, with the coarse-grained sediments near the mountains and fine-grained sediments near the basin centers (Anderson, 1995). The thickness of the alluvial sediments in the Basin is unknown, but is thought to be greater than 1,000 feet near the center of the basin, thinning to a veneer along the mountain fronts (Gray, 1965; H+A, 1991). Extensive fine-grained units overlying coarser grained sediments produced confined conditions in the center of several basins (Anderson et al, 1992). The St. David Formation in the Basin is one such extensive fine-grained unit, producing confined conditions in the center of the Basin surrounding the Site (Koniezcki, 1980). Most notably, the upper unit of the St. David Formation typically comprises a thick, red brown clay unit which effectively confines aquifers in deeper coarse-grained units, which form the regional aquifer tapped as a primary water source. A more recent treatise further describing the geology and geomorphic evolution of the San Pedro River Basin has been prepared by Pearthree and Cook (2015).
The dominant surface water drainage feature in the Basin is the San Pedro River. Its overall watershed is approximately 2,500 square miles, including 700 square miles in Mexico. The San Pedro River originates near Cananea, Sonora, Mexico, approximately 65 miles south of the Site, and flows north to join the Gila River near Winkelman, Arizona. The ancestral San Pedro River began depositing recent flood-plain sediments throughout a period of aggradation during the last 10,000 years (Gray, 1965). As the fluvial dynamics of the region changed from an
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erosional to a depositional environment, the surface water flow patterns were controlled by the paleochannels (Deane, 2000). This resulted in the deposition of coarse-grained sediments in the paleochannels and fine-grained sediments between the paleochannels through lateral and vertical accretion (Graf, 1988; Deane, 2000).
Lateral accretion occurs in a through-flowing stream channel. Lateral accretion is typified by deposition of coarse-grained sediments, such as sands and gravels, in the channel due to the winnowing effect of channel water that separates suspended sediment load (silts and clays) from the total sediment load. The bedload (sands and gravels) are then deposited in the channel, and the silts and clays are transported farther downstream until the transport energy decreases below a critical threshold. This energy loss often occurs as streams enter receiving lakes, ponds, or swamps. Vertical accretion occurs outside of the stream channel and results from deposition of fine-grained sediments, known as overbank sediments, on the adjacent land surfaces during flood events. As flood waters leave the channel and spread out over the adjoining land surface, the transport energy decreases, resulting in deposition. Typically, coarse-grained sediments (bedload) are deposited next to the channel and fine-grained sediments (suspended load) are deposited farther from the channel banks (Graf, 1988). This complex and changing depositional environment resulted in the heterogeneous hydrostratigraphy of the shallow aquifer (Graf, 1988; Deane, 2000).
The heterogeneity of the alluvial materials comprising the shallow aquifer is evident from lithologic conditions logged during the drilling of numerous wells, monitor wells, and exploratory borings across the Site. As typical, alluvial materials in the Basin have properties that vary over limited vertical and lateral dimensions. On a scale relevant to this investigation the alluvium comprises a single hydrostratigraphic unit.
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3.0 HYDROGEOLOGY OF THE SOUTHERN AREA
Characterization of the hydrogeology and groundwater quality of the Southern Area has been ongoing as a result of the remedial investigations associated with the Site since the late 1980s (Figure 9). As a result of these characterization efforts, as well as implementation of initial remedies and testing, it has been possible to gather sufficient information to further revise the Southern Area CSM and consider appropriate remedial alternatives. At this time it has been determined that, conceptually, the Southern Area should still be considered as comprising two major areas, a perched system and a shallow alluvial aquifer. However, it now includes four sub-areas; PZ-A, PZ-B, monitor well MW-24 area, and the shallow alluvial aquifer along the San Pedro River. PZ-A and PZ-B (now referred to as the Southern Area Perched System) remain contaminated with nitrate and perchlorate. The Perched System is separated by a laterally confining unit from the MW-24 area and the shallow alluvial aquifer along the San Pedro River, which are no longer contaminated by nitrate. The following sections describe the specific characteristics of the hydrogeology and groundwater quality of the overall Southern Area, in particular as they relate to potential future remedial efforts.
3.1 GROUNDWATER LEVEL ELEVATIONS AND HYDROGRAPHY
Assessment of groundwater levels in terms of both areal mapping and time-series hydrography can provide essential inferences with regard to groundwater flow and other aspects of system conceptualization. Areal groundwater-level mapping provides inferences with regard to the direction of groundwater flow, recharge, discharge, potential stresses on the aquifer system, and even to some extent variability in aquifer hydraulic properties. Hydrographic examination may also infer important information regarding aquifer stresses such as factors influencing aquifer recharge and discharge. Areal comparisons of such time-series data may indicate hydraulic similarities and dissimilarities that may tie to and corroborate various concepts.
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3.1.1 PERCHED ZONE A – WATER ELEVATION
In PZ-A groundwater occurs within course grained materials deposited on the erosional surface of the St. David clay. The erosional surface of the St. David clay in the area of PZ-A slopes from west to east from a high of 3,660 feet msl, near piezometer P-01 down, to a low of 3,615 feet near monitor well MW-30 (Figure 10). As discussed below the erosional surface of the St. David clay in the area of PZ-B is lower in elevation (Figures 10 and 11). Historically, the highest levels of groundwater occurred in the early 1990s as infiltration from the evaporation ponds was active (Figures 10 and 12). The groundwater sloped from west to east from approximately 3,675 feet msl near P-01 to 3,640 feet msl near P-10. Because groundwater heads in some of the monitor wells were up to 15 feet above the base of fine-grained units it is possible that some of the groundwater occurred in confined to semi-confined conditions in the early 1990s (Figures 10 and 11). In other words, the heads were higher than the top of the aquifer materials indicating artesian pressures. Between 1995 and 1998 water elevations dropped approximately 20 feet, with all but four monitor well locations becoming dry. Since 1998, groundwater has only been consistently observed at piezometers P-01 and P-03 (Figure 12). Between 1998 and 2014 water levels at these two piezometers declined approximately at 0.1 to 0.15 feet per year. Since late 2014, possibly in response to the high precipitation recorded in 2014, groundwater levels in P-01 and P-03 have risen approximately five feet. Precipitation records from Tombstone and combined precipitation records from Benson and Apache (Benson/Apache) are presented in Table 1. Between 1979 and 2013 the annual precipitation at Tombstone and Benson/Apache was 13.4 and 11.9 inches respectively (Table 1). In 2014, the annual precipitation at Tombstone and Benson/Apache was 26.13 and 16.37 inches respectively, or a range of 37% to 95% greater than average annual precipitation. The seasonal variations observed in PZ-B are not observed in PZ-A monitor wells, possibly indicating minimal phreatophytic influence.
At its greatest extent, in the 1990s, the footprint of PZ-A covered approximately 53 acres (Figure 2). Between 1995 and 1998, as water seeped out of the PZ-A and into PZ-B most of PZ-A became dry, leaving only a couple isolated pockets of remnant groundwater near P-01 and P-03. These isolated pockets of remnant groundwater occur in sand filled depressions in the eroded surface of the St. David clay. Use of the evaporation ponds was discontinued in 1995, and by 2003 all the seepage of perched groundwater from PZ-A to PZ-B had stopped.
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Monitor wells MW-29, -30, -31, and -32, along the edge of PZ-A, have remained dry since that time.
Again, the original waters that entered PZ-A were contaminated wastewaters. Later fresh water discharged from the brine concentrator component testing recharged PZ-A, elevating the water levels in PZ-A. So if in the future precipitation were to increase to a degree that would facilitate recharge thereby raising water levels in PZ-A, even to a degree that seepage from PZ-A into PZ-B were to resume, it would be expected that this would result in an overall improvement of water quality, especially considering this water could not migrate beyond the LCU and would mix vertically.
3.1.2 PERCHED ZONE B – WATER ELEVATION
In PZ-B groundwater occurs within course-grained materials deposited on the erosional surface of the St. David clay. The areal extent of the PZ-B extends over an area of approximately 13 acres (Figure 2). The erosional surface of the St. David clay generally slopes from west to east from an elevation of approximately 3,600 feet msl, near MW-44, to 3,570 feet msl near EXB-18 (Figure 10). However locally, the surface appears to have been deeply incised by erosional features. Elevation differences of up to 17 feet over a distance of 35 feet have been observed (Figure 10).
Groundwater-level monitoring at four PZ-B wells (MW-15, -21, -23, and -39) since their respective installations have indicated rather steady declines overall with seasonal variations of approximately 2.5 feet (Figure 13). These seasonalities are primarily believed to be the result of phreatophytic transpiration.2 In the early 1990’s, the highest elevations of groundwater, approximately 3,617 feet msl, were observed. Since 1995, around the time period when operation of the evaporation ponds ceased, groundwater elevations have declined approximately 15 feet at a rate of 0.8 feet per year (Figure 13). As a result of this decline, some locations where the surface of the St. David clay is high have become dry. In late 2012 to 2014 groundwater elevations reached a low of approximately 3,597 feet msl. Water elevations
2 See Appendix D for further explanation of transpiration and evaporation concepts.
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have risen two to three feet since 2014, potentially due to local recharge from the high precipitation events occurring in 2014 and 2015.
In the 1990s the groundwater gradient in the PZ-B was from the west to the east. This was the result of groundwater seepage from PZ-A. In the 1990’s, groundwater levels along the western edge of the PZ-B were approximately two feet higher than at other locations. After seepage of groundwater from PZ-A ceased, the elevation differences among all monitor wells across the PZ-B have decreased to the point that there are essentially no elevation differences, hence no hydraulic gradient. Thus, the groundwater level across PZ-B is essentially flat (no gradient) inferring that there is no groundwater flow.
3.1.3 MW-24 AREA – WATER ELEVATION
Within the monitor well MW-24 area groundwater occurs within silty sands located between 23 to 27 feet bls, at elevations of approximately 3,602 to 3,597 feet msl. Beneath these silty sands are 37 feet of fat clay. It is significant that monitor well MW-24 is situated along an east- west transect of monitor wells that, moving from west to east, also includes monitor well MW-14 and monitor well MW-22 (Figures 9, 11 and 14). It is then noted that there is a significant difference in groundwater level elevations, on the order of approximately eight feet, between monitor well MW-24 in comparison with the two eastern monitor wells in the transect. This suggests hydraulic isolation, probably due to intervening fine-grained sediments of the type forming the LCU. Between 2000 and 2015 groundwater elevation at monitor well MW-24 declined approximately 2.9 feet and at a rate of approximately 0.15 feet/yr (Figure 14). Additionally, groundwater elevations show a seasonal cycle of approximately three feet.
3.1.4 LATERALLY-CONFINING UNIT
In the LCU water is absorbed to silts and clays and occasionally saturates thin, interfingered coarse-grained strata. Due to the high clay and silt content and limited occurrence of saturated zones within the LCU materials, monitor wells have not been constructed across the LCU. Its
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characteristics, however, have been well-established as a result of a network of exploratory borings (Figure 9). Effectively, the LCU extends over an area of approximately 125 acres, forming a lateral barrier to groundwater movement from PZ-B into the shallow alluvial aquifer along the San Pedro River.
3.1.5 SHALLOW ALLUVIAL AQUIFER ALONG THE SAN PEDRO RIVER – WATER ELEVATION
Within the shallow alluvial aquifer along the San Pedro River groundwater occurs within coarse- grained deposits in direct contact with the San Pedro River (Figure 16). Historical data, such as wellhead surveys and topographic maps, suggest that the elevations of groundwater are relatively stable over time and generally shallow ranging from 12 to 25 feet below land surface.
3.1.6 WATER ELEVATION COMPARISONS
Groundwater elevations from selected wells within PZ-A, PZ-B, MW-24 areas, and within the shallow alluvial aquifer along the San Pedro River are presented on Figures 14 and 15. The pattern of changing groundwater elevations between the four areas indicate that hydrologic conditions vary significantly. As earlier described, the occurrence of groundwater in PZ-A formed directly as the result of seepage from the evaporation ponds. Once seepage terminated, PZ-A groundwater quickly drained into PZ-B. Much of PZ-A has since become dry with some groundwater remaining in isolated depressions on the surface of the eroded St. David clay. Within PZ-B, the occurrence of groundwater was directly related to seepage from PZ-A, although creation of the PZ-B groundwater body probably began prior to ANPI’s construction and utilization of the ponds in 1971. This would have been the result of ANPI’s having routed wastewater along unlined ditches and into dry washes crossing the area. Once seepage from PZ-A ceased, groundwater elevations began to decline. The slowing rate of decline in groundwater level elevations at present and the flatness of the groundwater surface provides evidence that groundwater is not flowing out of PZ-B or even across its footprint. The flatness of the groundwater surface indicates that there is no hydraulic gradient to drive flow. The superposition of seasonal variations upon the declining hydrograph appear to indicate
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phreatophytic transpiration losses. Within the MW-24 Area groundwater elevations may also be slowly decreasing (Figure 14). The isolation of the MW-24 Area from the shallow alluvial aquifer is suggested by the several feet difference in groundwater elevations (Figure 14).
3.2 GROUNDWATER QUALITY
Two COCs, nitrate-N and perchlorate, were designated in EPA’s ROD Amendment for the Southern Area groundwater (EPA, 2005). Nitrate-N is a chemical oxyanion present in ANPI’s wastewater stream and is associated with the production of ammonium nitrate and nitric acid. Perchlorate is a naturally occurring impurity in Chile saltpeter or sodium nitrate. Chile saltpeter was a feedstock that was brought on-site for a, now discontinued, manufacturing process. As previously discussed, discharge of nitrate-N and perchlorate-laden wastewater to the evaporation ponds created a perched zone within the underlying alluvium and resting on the St. David clay unit (Figures 10 and 11). PZ-A began to recede both in saturated thickness and in areal extent after the cessation of ANPI’s wastewater discharges to the ponds in early 1995.
3.2.1 PERCHED ZONE A – NITRATE-N
Historically nitrate concentrations at all sample locations across the PZ-A have exceeded the 10 mg/l ROD cleanup standard with maximum concentrations ranging from 220 mg/l to 15,000 mg/l (Figure 17). The highest concentration, 15,000 mg/l has been detected at P-03. Starting in the mid-1990s nitrate-N concentrations at piezometer P-03 have consistently increased until 2013 when a decreasing trend has started. Over the most recent sampling events nitrate-N was detected at piezometer P-03 at 7,200 mg/l. At P-01 the trend of nitrate-N concentrations has displayed sudden and extreme variability over short timeframes, ranging from less than 1 mg/l to 220 mg/l. Between 2011 and November 2014 nitrate-N concentrations were generally between 150 and 220 mg/l. Starting in November 2014 the concentration of nitrate-N started to decline, and since August 2015 have been below 10 mg/l. Except for P-01 and P-03 the other monitor wells and piezometers across the PZ-A have largely dried up, with
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the exception of some slightly measurable increases in 2016, at P-10, MW-03 and MW-04, in response to unseasonably higher precipitation, and therefore recharge.
At piezometer P-03, since 2014, when nitrate was detected at 15,000 mg/l, concentrations have decreased in a relatively linear trend (Appendix C, Figure C-2). Sampling results from the most recent sampling event performed in 2016, show nitrate concentrations of 7,200 mg/l at piezometer P-03, well above the 10 mg/l ROD cleanup standard. At piezometer P-01 the most recent nitrate-N concentration was 2.5 mg/l and based on its highly variable historical concentrations may exceed the 10 mg/l ROD cleanup standard in the future (Figure 18, Appendix C, Figure C-1).
3.2.2 PERCHED ZONE B – NITRATE-N
Historically nitrate concentrations at all sample locations across the PZ-B, except at monitor well MW-47, have exceeded the 10 mg/l ROD cleanup standard with maximum concentrations ranging from 23 mg/l to 7,000 mg/l (Figure 17, Appendix C, Figures C-7, C-8 and C-9). The highest concentrations have been detected at monitor well MW-21 with a maximum concentration of 7,000 mg/l in November 5, 2013 (Figure 17, Appendix C, Figure C-8). Monitor well MW-21 is located at the point just where groundwater from PZ-A seeped into PZ-B. The second highest concentration of nitrate-N were detected at MW-15 located near the center of PZ-B. Prior to becoming dry in 2010, nitrate-N in MW-15 was detected at a maximum of 550 mg/l (Figure 17, Appendix C, Figure C-7) in 2001. The maximum nitrate concentration at monitor well MW-47 was 6.7 mg/l, however, since this monitor well was installed in 2015 historical nitrate concentrations as this location could not be determined. Concentrations of nitrate-N have shown a decreasing trend at monitor wells MW-15 and MW-39 (Appendix C, Figures C-7 and C-11). There is no consistent trend of nitrate-N at monitor well MW-23 (Appendix C, Figure C-9). At monitor well MW-21 nitrate-N concentrations have increased until 2013 when a decreasing trend started (Appendix C, Figure C-8).
Sampling results from the most recent sampling event performed in 2016, show nitrate-N concentrations exceed the 10 mg/l ROD cleanup standard along the western and northern
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portions of PZ-B at monitor wells MW-21 and MW-39 (Figure 18, Appendix C, Figures C-8 and C-11). The highest nitrate-N concentrations, 4,300 mg/l are observed at monitor well MW-21, located on the western side of PZ-B. At monitor well MW-39, along the northern portion of the PZ-B nitrate-N was detected most recently at 31 mg/l. Along the eastern and southern portions nitrate-N concentrations are less than the 10 mg/l ROD cleanup standard, at MW-23 and MW-47 (Figure 18). At monitor wells MW-23 and MW-47 nitrate-N was detected at 5.3 mg/l and 6.7 mg/l respectively (Figure 18).
3.2.3 MW-24 AREA – NITRATE-N
Historically nitrate-N was only detected once above 10 mg/l. In 1999 nitrate-N was detected at monitor well MW-24 at 11 mg/l (Figure 17, Appendix C, Figure C-10). Since then concentrations of nitrate-n in MW-24 have shown a declining trend. Sampling results from the most recent sampling event performed in 2016, show nitrate in monitor well MW-24 at a concentration of 0.88 mg/l (Figure 18).
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3.2.4 SHALLOW ALLUVIAL AQUIFER ALONG THE SAN PEDRO RIVER – NITRATE-N
Along the San Pedro River, nitrate-N concentrations in the shallow alluvial aquifer have been monitored using four monitor wells: MW-01, MW-14, MW-22 and MW-33. Except for MW-14, nitrate-N has not been detected at concentrations greater than 1.0 mg/l (Figure 17, Appendix C, Figures C-12 through C-17). In the early 1990s nitrate-N was detected at monitor well MW-14 at a maximum concentration of 37 mg/l. Concentrations since have decreased rapidly and have remained below 1.0 mg/l since 1996. Sampling results from the most recent sampling events, performed in 2016, show nitrate-N has not been detected in the shallow alluvial aquifer along the San Pedro River (Figure 18).
3.3 PERCHED ZONE A – PERCHLORATE
Historically perchlorate concentrations at all sample locations across the PZ-A have exceeded the 14 μg/l ADHS health-based guidance level (HBGL), with maximum concentrations ranging from 17 μg/l to 810 μg/l (Figure 19, Appendix C). The highest concentration, 810 μg/l was detected at piezometer P-03. Perchlorate concentrations at piezometer P-03 are highly variable with an overall slight decrease in concentrations. Perchlorate concentrations at piezometer P-01 likewise are highly variable. Sampling results from the most recent sampling event performed in 2015 and 2016, show perchlorate concentrations exceeding the 14 μg/l HBGL at piezometers P-01 and P-03 with concentrations of 17.8 μg/l and 483 μg/l respectively (Figure 20, Appendix C Figures C-1 and C-2).
3.3.1 PERCHED ZONE B – PERCHLORATE
Historically perchlorate concentrations in PZ-B have been detected above 14 μg/l at all monitor well locations except for monitor well MW-47. The highest concentrations have been detected at monitor well MW-15 with a maximum concentration of 540 μg/l (Figure 19, Appendix C, Figure C-7). The highest concentrations were detected in late 2002 and decreased steadily
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until the monitor well became dry in 2010. The next highest concentrations of perchlorate were detected at monitor well MW-21 with a high of 420 μg/l (Figure C-8). At monitor well MW-21 perchlorate concentrations have increased significantly since 2004 until 2015 when a slight decreasing trend has been observed. Within monitor well MW-39 concentrations have shown a decreasing trend. The lowest concentrations of perchlorate have been observed at monitor wells MW-23 and MW-47 with maximum concentrations of 64 μg/l and 13 μg/l respectively. Monitor well MW-23 has shown a decreasing trend (Appendix C, Figure C-9). At monitor well MW-47 the time series is not long enough to determine a trend.
Sampling results from the most recent sampling event performed in 2016, show perchlorate concentrations exceed the 14 μg/l HBGL along the western and northern portions of PZ-B at MW-21 and MW-39 (Figure 20, Appendix C, Figures C-8 and C-11). The highest perchlorate concentrations, 210 μg/l were observed from monitor well MW-21, located on the western portion of PZ-B. Along the eastern and southern portions of PZ-B, perchlorate concentrations are less than the 14 μg/l HBGL, as observed at monitor wells MW-23 and MW-47 with concentrations of 3.6 μg/l and 12 μg/l respectively (Figure 20, Appendix C, Figure C-9). The perchlorate concentrations in MW-23 have been generally declining since 2010 and have been below 14 μg/L since 2012 (Appendix C, Figure C-9).
3.3.2 MW-24 AREA – PERCHLORATE
Historically perchlorate has been detected at monitor well MW-24 at concentrations up to 54 μg/l (Figure 19, Appendix C, Figure C-10). Concentrations of perchlorate in MW-24 have shown show a declining trend, and since 2003 have been less than the 14 μg/l HBGL. Sampling results from the most recent sampling event in 2014, perchlorate was detected at monitor well MW-24 at a concentration of 1.3 μg/l (Figure 20, Appendix C, Figure C-10).
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3.3.3 SHALLOW ALLUVIAL AQUIFER ALONG THE SAN PEDRO RIVER – PERCHLORATE
Within the shallow alluvial aquifer along the San Pedro River, perchlorate concentrations have been monitored using four monitor wells: MW-01, MW-14, MW-22 and MW-33 (Figures 9 and 19). Perchlorate has not been detected at concentrations greater than the 14 μg/l HBGL (Figure 19, Appendix C, Figures C-12 through C-17). Perchlorate has been detected at monitor wells MW-14 and MW-22 at maximum concentrations of 0.7 μg/l and 4.4 μg/l, respectively (Figure 19, Appendix C, Figures C-14 and C-15).
Sampling results from the recent sampling event performed in 2016, perchlorate was only detected at monitor wells MW-14 and MW-22 at concentrations of 0.7 μg/l and 0.67 μg/l, respectively (Figure 20, Appendix C, Figures C-14 and C-15).
3.3.4 TOTAL DISSOLVED SOLIDS
Total dissolved solid (TDS) concentrations have been tested at monitor wells in the PZ-A, PZ-B, MW-24 Area and the shallow alluvial aquifer along the San Pedro River (Figure 21). The highest concentrations were detected at PZ-A and PZ-B, with concentrations ranging from 1,200 mg/l to 28,000 mg/l, well above EPA’s secondary drinking water standard of 500 mg/l. At monitor well MW-24 TDS concentrations have ranged from 430 mg/l to 640 mg/l. Within the shallow alluvial aquifer along the San Pedro River, TDS detections have ranged from 280 mg/l to 830 mg/l. However, higher concentrations have been detected in the vicinity of monitor wells MW-25, MW-26, and MW-27, where TDS concentrations have ranged from 2,300 mg/l to 2,700 mg/l. At these three monitor wells, sulfate concentrations ranging from 1,500 mg/l to 2,400 mg/l have been detected, thus apparently contributing to the high TDS. Based on the configuration of the shallow aquifer boundary, it may be that low groundwater circulation may have resulted in less flushing of sulfate compounds.
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4.0 CONCEPTUAL SITE MODEL
A conceptual model of a groundwater flow and hydrologic system is an interpretation or working description of the characteristics and dynamics of the physical hydrogeologic system. The development of the conceptual model requires collection and analysis of geologic and hydrogeologic data pertinent to the aquifer system under investigation toward a purpose of consolidating such information into a set of assumptions and concepts that can be evaluated quantitatively (ASTM, 2014).
4.1 CSM COMPONENTS
The updated CSM for the Southern Area now includes two major components; a contaminated Perched System consisting of two sub-areas (PZ-A and PZ-B) with the uncontaminated shallow alluvial aquifer located to the east along the San Pedro River (Figure 9). Except for the time when PZ-A discharged to PZ-B all the areas are hydraulically isolated from each other.
The shallow alluvial aquifer along the San Pedro River is in direct communication with the San Pedro River along certain reaches. The aquifer generally receives water from the river, however, at some locations the shallow alluvial aquifer discharges into the river. In hydrologic terms, the former condition is referred to as influent and the latter as effluent, relative to the aquifer. Relative to the River, the respective terms are losing and gaining reaches. Except for a period in the early 1990s at MW-06, COCs have not been detected in the aquifer above action levels.
4.2 FEATURES OF THE REVISED CSM
An earlier CSM for the Southern Area was presented in detail in a 2003 report (H+A, 2003a), which was further refined in 2007 (H+A, 2007), based on interim investigations. An overview of the findings from these reports is summarized in Section 1.2.3 History of Changes to CSM for
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Southern Area. However, findings from recent investigations necessitate an additional revision of the previous CSM versions. Most significantly, this revision affects the CSM for PZ-B. The essential features of the revised Southern Area CSM include:
• Essentially complete cessation of recharge to both PZ-A and PZ-B as a result of ANPI’s pond closures (Figure 22). • Cessation of seepage from PZ-A to PZ-B, again as a result of ANPI’s pond closures (Figure 22). • Hydraulic isolation between PZ-B and the San Pedro River and its associated shallow alluvial aquifer. • Occurrence of residual water in PZ-A limited to depressions in the surface of the St. David clay (Figure 22). • Continuing declines of residual water in PZ-B primarily as a result of phreatophytic transpiration losses (Figure 22). • Significant contrast in COC concentrations across PZ-B from west to east. • Prevention of downward leakage of water from PZ-A and PZ-B by the low hydraulic conductivity characteristics and thickness of the St. David clay (Figure 22). • Overall poor hydraulic connectivity over short distances.
The rationale associated with the refinements are described in the following sections according to the individual components of the model.
As discussed earlier, the perched zone is now defined as existing in two components termed PZ-A and PZ-B. This is done in emphasis of the fact that, based on the years of exploration and investigation, information has supported that both zones appear to have been artificially created exclusively as a result of artificial recharge from ANPI’s historical industrial wastewater management practices (Figure 22). Neither zone has apparent hydraulic interaction with the shallow alluvial aquifer associated with the San Pedro River to the east. The underlying St. David clay unit limits downward and lateral movement of water within the saturated zone and controls its areal occurrence as a result of its variable erosional surface.
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4.3 SUPPORTING RATIONALE
Since the cessation of ANPI’s wastewater discharges to the unlined, formerly-active ponds, all monitor wells and piezometers in PZ-A have gone dry, except piezometers P-01 and P-03, and occasionally monitor wells, MW-03 and MW-04 (Appendix C, Figures C-1, C-2, C-4 and C-5). Hydrographs of both piezometers have also shown generally declining water levels. In two recent quarterly monitoring events some groundwater has been detected monitor wells MW-04 and P-10. These two piezometers are located within depressions on the surface of the St. David clay base. The groundwater present at these locations is primarily residual groundwater from the time PZ-A was receiving recharge from ANPI’s former unlined evaporation ponds. However, recent recharge events occurring as a result of high precipitation have also contributed to small volumes of water captured within these depressions. No hydraulic connection between the two locations is evident as confirmed by the differences in measured water level elevations.
Prior to 2003, it was evident that there was lateral groundwater seepage eastward from PZ-A to PZ-B. This was due to higher mounding of groundwater in PZ-A as a result of residual seepage from the formerly active ponds, particularly as a result of the release of 1.2 million gallons of fresh water used to test the surge tank constructed for ANPI’s Brine Concentrator. Deane (2000) postulated that the path of seepage from PZ-A to PZ-B was primarily along a buried former channel he identified as “Apache Wash,” which had been eroded into the St. David clay surface in the geologic past. ANPI subsequently constructed a line of piezometers along the edge of PZ-A to monitor potential seepage into PZ-B. Since about 2003, these piezometers (MW-29, -30, -31, and -32) have remained dry, thereby indicating that the seepage has ceased. During the 2014 rainy season, a measurable water level did appear on the monitor well MW-30 hydrograph. However, it was later determined that the water level was only present in the well’s tail pipe, and not within the saturated sediments.
As then would be expected, with the cessation of a recharge source into PZ-B, the groundwater levels in PZ-B monitor well began to decline across the area. Even following the cessation of this seepage, groundwater levels measured quarterly in the PZ-B monitor wells have declined significantly, indicating as much as 17 feet (See Appendix C, Figure C-8, for example). These
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declines are believed to be attributable largely to transpiration losses due to phreatophytic uptake. This is inferred as a result of seasonalities superimposed onto declining hydrographic trends. This consumptive loss may also be responsible for decreases in COC concentrations observed over the same timeframe. Additionally, one other consideration is leakage from the PZ-B sediments into sediments of adjacent areas, such as along the boundary of PZ-B and even into the underlying clay.
In light of information emerging from such recent field investigations, the former CSM for the Southern Area groundwater at the Site has been revised considerably. The concepts presented beginning with Deane (2000) in regard to the paleogeomorphic evolution of the PZ-B have been reconsidered in the context of these new findings. Essentially, Deane’s idea of the development of paleodrainages in the post-glacial timeframe appears to at least partially explain the local development of a complex topography on the surface of the St. David clay. However, his concept of the larger paleodrainage tributary to the ancestral San Pedro River, and extending to the vicinity of monitor well MW-24, which he identified as Molinos Creek, appears to be inconsistent with subsequent exploration to the south of monitor well MW-24.
Instead of one larger paleodrainage, the latest information seems to support a concept that the paleodrainage on the St. David clay surface developed a more complex pattern of smaller erosional channels that were subsequently backfilled with coarser sediments. The resulting configuration in three dimensions forms a small basin, but with deep depressions at its lowest elevations (i.e., near the contact with the St. David clay). A similar occurrence may have been responsible for the conditions observed in the vicinity of monitor well MW-24, which is situated in an apparent depression, similar to that in the vicinity of monitor well MW-21.
Deane also conceptualized the area known as the laterally-confining unit (LCU), as essentially finer-grained overbank deposits of the ancestral San Pedro River and/or Molinos Creek. Such LCU-type deposits have been found at every location where exploratory drilling has been conducted to the north and east of the PZ-B (Figure 9). It is possible that Deane’s Molinos Creek was in fact present, but buried beneath the finer sediments of the LCU.
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So owing to the boundary conditions of the area defined as the PZ-B, we have defined an isolated groundwater area, which, for purposes of considering its potential for exploitation, has been referred to as a “sub-aquifer.” The term “sub-aquifer” signifies a body of groundwater that does not exhibit typical properties of an aquifer such as transmissivity and does not readily yield water to wells. But more recently, considering the observed occurrence of groundwater in the area and its similarity to that of PZ-A, the area is now referred to as PZ-B.
The PZ-B is bounded laterally on the east by the LCU, on the west by old terrace deposits of the ancestral San Pedro River, and beneath by the St. David clay surface. Water in the PZ-B is believed to be present primarily if not solely as the result of artificial recharge from ANPI’s historical wastewater management practices. Natural recharge, if any, is minimal.
ANPI’s plant process modifications eliminated unlined evaporation ponds as its method of wastewater management in 1995. This led to the mounding of the perched zone groundwater in PZ-A, which in turn seeped into PZ-B, groundwater in the PZ-B, which has dissipated significantly in areal extent and volume. Water level declines have been monitored at least quarterly since the time of the changes in wastewater management. Presently, field testing and exploration seems to indicate that residual water in the PZ-B is very limited in distribution and discontinuous, occurring primarily in depressions in the surface of the St. David clay. These depressions are believed to be present as a result of the paleodrainages referred to earlier. Further, as a result of the isolation of residual water in such clay surface depressions, there is extremely poor, if any, hydraulic communication between the areas where water is present. Again, this situation is essentially equivalent to the situation in the adjacent PZ-A, where small bodies of residual groundwater also are present only in a few isolated areas.
It is again noted that the groundwater levels across the PZ-B were significantly higher in the past, perhaps as much as 17 feet as indicated by the well hydrograph at monitor well MW-15 (Figure 13). At such times when groundwater levels were high, hydraulic communication was present and groundwater could flow between the areas now in apparent hydraulic isolation. With the information on hand and considering the aforementioned discontinuities, it is not possible to estimate the volume of residual water in the PZ-B. Previous estimates, based on an
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assumption of a continuous body of groundwater occupying a sedimentary basin, are no longer valid.
Recent exploration and hydraulic testing in the vicinity of monitor well MW-21, particularly the drilling of monitor wells MW-43 and MW-44 has shown that the high concentrations of COCs in that area is essentially limited in areal extent and that the saturated thickness of the materials decreases rapidly moving eastward from the monitor well MW-21 location. Of course, moving westward, the boundary of PZ-B is encountered over a short distance.
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5.0 SUMMARY
Based on the information presented, this section summarized the findings in regard to the CSM.
5.1 PRIMARY FEATURES OF THE CSM
As listed earlier, the primary and relevant features of the revised CSM are that:
• Contamination in the Southern Area is limited to a Perched System, which has two distinct perched zones. • The perched zones are isolated hydraulically by a laterally-confining unit (LCU) and likewise isolated from the shallow alluvial aquifer. • Groundwater occurrence in PZ-B is discontinuous. • Distribution of COCs in PZ-B varies from west to east. • Estimation of COC mass and water volume in previous CSM was incorrect. • Poor overall hydraulic conditions are present between water bodies in PZ-B. • No Site-related contamination is present in the shallow aquifer in the Southern Area.
These are further explained and summarized below.
Perched System Consists of Two Distinct Zones
Conceptualization of the area of groundwater contamination in the Southern Area has been progressive as new information has been generated. The initial interpretation performed in the Preliminary Investigation (PI) assumed that the perched zone was part of the shallow aquifer (Black & Veatch, 1988). During the Remedial Investigation (RI), it was noted that there was a significant difference in the water level elevations between the perched zone and the “shallow aquifer” to the east of the perched zone (H+A, 1992). It was further noted that the groundwater underlying the unlined evaporation ponds in the ANPI operations area occupied sedimentary materials overlying the St. David clay, a low conductivity stratum, which is part of the St. David
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Formation, and is present underlying most of the area in the St. David area. Hence this was interpreted as perched groundwater and its presence was attributed to leakage of wastewater from the unlined ponds.
To the east, groundwater was present at a lower elevation. At the time of the RI, this was believed to be groundwater that was part of the shallow alluvial aquifer along the San Pedro River. Later, investigations performed by Deane suggested that this area east of the perched zone was largely isolated from the main part of the shallow alluvial aquifer along the San Pedro River (Deane, 2000). This conceptualization was based on Deane’s interpretation of the paleogeomorphology of an ancestral San Pedro River. Recognizing that the area was probably hydraulically isolated, it was thereafter identified as the MCA. The coined term, sub-aquifer, was intended to highlight that groundwater in that part of the Site was neither part of the shallow alluvial aquifer nor a discrete aquifer in a classical sense. Rather, it was largely created as a result of historical wastewater management practices at ANPI.
Investigations conducted between 2012 and 2016 revealed distinct similarities in the behavior of groundwater in the perched zone with that in the MCA. Most significantly, as groundwater levels declined, the occurrence of groundwater was limited to isolated depressions in the surface of the underlying St. David clay (Figures 10 and 11). This seems to further explain the relative hydraulic isolation of “puddles” of groundwater between locations where it is found. Therefore, based on its behavior similar to the perched zone, the MCA is now referred to as “Perched Zone B,” (PZ-B), and the original perched zone is now referred to as “Perched Zone A” (PZ-A) (Figure 2). Thus effectively, in the Southern Area we have only a contaminated perched system consisting of two distinct perched zones.
Lateral Hydraulic Isolation
As discussed above, in the 1990s the perched groundwater zone to the east (which was identified as the MCA in 2003 and is now identified as PZ-B) was initially thought to be a part of the San Pedro River. Based on Deane’s work, it was later characterized as being substantially isolated hydraulically from the San Pedro River by a laterally confining unit (LCU). Deane’s premise was that there was an ancestral stream (either of the San Pedro River or a tributary)
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that flowed into the area along the western margin of the present shallow aquifer boundary, and exiting to the north in the vicinity of monitor well MW-24. To the east, Deane postulated, were fine-grained overbank deposits that provided lateral hydraulic isolation from the coarser alluvial sediments along the San Pedro. This area of fine-grained sediments was thus termed the LCU. Subsequent drilling of exploratory borings verified that the area of PZ-B is indeed laterally isolated from the shallow alluvial aquifer by fine-grained sediments to the east, but that Deane’s idea that there was a possible connection between the main part of PZ-B and the area in the vicinity of monitor well MW-24 was not substantiated (Figures 9, 10 and 11). Hence, the MW-24 area represents a separate anomaly.
Presently the four areas of groundwater occurrence in the southern area (PZ-A, PZ-B, the MW-24 area and the shallow alluvial aquifer) are isolated from each other. In the past groundwater from PZ-A seeped into PZ-B, however, after the used of the evaporation ponds ceased and the groundwater elevation in PZ-A decreased, seepage into PZ-B ceased. The isolation of the four areas is observed in the different groundwater elevation patterns observed in hydrographs for the four areas. For example, the groundwater elevation in the MW-24 area is not only significantly lower than the nearby shallow alluvial aquifer (wells MW-14 and MW-22), the two foot seasonal fluctuation observed in MW-24 and not present in the shallow alluvial aquifer wells (Figure 14). Groundwater elevations in PZ-A and PZ-B have decreased significantly since 1995 while little to no significant change has been observed in the shallow alluvial aquifer and the area of MW-24 over the same time period (Figures 14 and 15). Additionally, the seasonal fluctuations observed in PZ-B are not evident in PZ-A (Figure 15). These noted differences in groundwater elevation changes over time demonstrate the hydraulic isolation between the four groundwater occurrence areas. Groundwater in the area around MW-24, PZ-B and the shallow alluvial aquifer are separated from each other by the LCU (see Section 3.1.4) (Figure 2). Groundwater in PZ-A is isolated from the other areas because it is confined depressions within the eroded surface of the St. David Clay (Figure 10).
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Groundwater Occurrence in Perched Zone B
After confirmation of the presence of the LCU in 2003, interpretation of the groundwater remaining in PZ-B was conceptualized as a bowl-shaped body of groundwater, created as a result of historical groundwater seepage from PZ-A. Groundwater levels in PZ-A have been carefully monitored from 1997 onwards to determine whether the water from PZ-A was effectively draining into PZ-B as predicted. The monitoring confirmed that in about 2003, the drainage had effectively ceased and has not since resumed. This information served as a basis for the source control prerequisite for MNA, which was selected in 2005.
However, another important bit of information that resulted from the drainage of PZ-A was how the residual “puddles” of water remained within depressions atop the St. David clay surface, such as in the vicinity of piezometer P-03 (Figures 2 and 10).
In recent years, monitoring data collected since the late 2000s indicate that groundwater levels in PZ-B have been rapidly declining (Figure 13). Considering the flat gradient across the area, it was determined that the water level declines were largely attributable to transpiration losses due to phreatophytic vegetation (mesquite) (Figure 22 and Appendix D, Figure D-1) and secondarily due to seepage into adjacent sediments (laterally and vertically). But the result of this overall water level decline was that, much like what has been observed across the footprint of PZ-A, water was becoming isolated in the “puddles” formed in the St. David clay surface depressions (Figures 9 and10). And as such, the locations of groundwater occurrence were hydraulically isolated from each other.
Distribution of COCs in Perched Zone B
As mentioned earlier, the concentrations of COCs across most of PZ-B have declined, with the exception of an area in the western part, where concentrations have increased. Normally, this would indicate input of COC mass from a continuing source. However as also discussed earlier, the source of mass inputs has been cut off since about 1995 when discharges to the unlined evaporation ponds ceased. Interpretation of this counterintuitive phenomenon requires consideration of operational history along with hydrogeologic concepts. In 1995, before the
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Brine Concentrator facility was first brought on line, one component of that facility, a 1.2 million gallon surge tank, was pressure tested by filling with fresh water derived from ANPI’s deep aquifer well #3. After successful testing of the tank, the water was released mostly to Pond 3B, one of the formerly active evaporation ponds. Water released into the unlined ponds, evaporation ponds, which did not dissipate via evaporation, leaked into the underlying sediments, thus creating a lens of fresh water (from the pressure testing) on top of the contaminated perched groundwater present in PZ-A. Considering the attitude of the underlying St. David clay which slopes to the east, perched groundwater in PZ-A eventually seeped eastward into PZ-B. As a result, a lens of fairly fresh water from the 1.2 million gallon surge tank was superimposed upon the existing, more highly contaminated water that was present in PZ-B. The effect of this influx of water resulted in a relatively stratified water column at each monitor well. This stratification persisted due to relatively little vertical mixing within the aquifer. A more recent influx of fresh water occurred starting in 2014 when greater precipitation fell over the area. Increases in groundwater elevation were noted in PZ-A monitor wells P-01 and P-03 and PZ-B monitor well MW-21. As the water elevations in these wells increased the concentration of nitrate-N decreased (Appendix C) as a result of dilution.
At the monitor well MW-21 location, which is at the westernmost edge of PZ-B and nearest the point of entry of the seepage from PZ-A, the vertical contrast through the water column was probably most evident. Additionally, the construction of monitor well MW-21 is such that the screened interval extends throughout the full saturated thickness of the sediments down to the St. David clay (Table 2). Moreover based on the drilling logs for monitor well MW-21 and adjacent logging at monitor wells MW-43 and MW-44 (Appendix A), it appears that monitor well MW-21 is located in a “deep pocket” indented into the St. David clay. Thus, there was likely a lot of highly concentrated mass stored in the lowest portions of the well. Sampling a well such as this results in an integrated water sample such that the older, more highly concentrated portion is mixed with the shallower, fresher water. But as time progressed and the water level declined, the remaining water to be sampled in the “MW-21 puddle” became predominantly biased by the older and deeper, more highly concentrated portion of the water column. In other words, the overlying fresh water lens became proportionately a lesser fraction of the overall water column. There is no known source of COCs that accounts for the increasing
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concentrations demonstrated on the time-series graphs. In contrast, other monitor wells to the south and east within PZ-B displayed decreasing concentrations of COCs with time.
Estimation of COC Mass and Water Volume
In the mid-2000s, at the outset of MNA implementation, estimates of the volume of groundwater and COC mass were attempted based on the earlier concept of a bowl-shaped groundwater body. The configuration of the PZ-B footprint, the water-level elevations, assumed average porosity, and the surface contour of the underlying St. David clay determined the volume using simple geometry.
As discussed above, the geometry no longer approximates a “bowl” shape. Rather it comprises various “puddles” of undetermined shapes. Moreover, the “puddles” are apparently unconnected hydraulically such that attempts to extract at one location would not necessarily affect an adjacent location.
Poor Overall Hydraulic Conditions
In 2013, a field effort was directed towards determining how to use in situ methods as a component remedy to MNA. Initially, an aquifer test was attempted in order to provide parameters needed for pilot test design. During testing it was learned that groundwater extraction was greatly limited as a result of the poor hydraulic conditions in the sedimentary materials. Specifically, pumping at a low rate from monitor well MW-21 failed to produce drawdown in adjacent observation wells MW-43 and MW-44 located at 25 and 32 feet from MW-21. Further, it was learned that the pumping well went dry after a short pumping period. Based on this information, it was evident that neither in situ or ex situ methods would be effective as a remedy component.
5.2 REMEDY IMPLICATIONS
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Ten years after implementation of MNA as a remedy for the Southern Area of the Apache Powder Superfund Site, field results indicate that the rate of contaminant reduction in portions of the area is insufficient to achieve cleanup standards in a reasonable timeframe. Specifically, this is the case in the western portion of PZ-B, in the vicinity of monitor well MW-21, where, instead of declining concentration trends, concentrations have been increasing with time (Appendix C, Figure C-8).
In fact, this had been noted in 2012, during EPA’s Third Five Year Review (5YR) Report, when it was proposed that:
“Remedy enhancements, such as in-situ treatment, should be considered for MNA Remedy for Southern Remedy Molinos Creek Sub-Aquifer (MCA).” (EPA, 2012)
In particular, it is apparent that one mechanism that was originally suggested in 2003 as a key for the efficacy of natural attenuation in PZ-B may be deficient and inoperative. Specifically, it is that of biodegradation of the COCs. ANPI’s report notes that:
“… MCA hydrochemistry could support bioremediation of nitrate and perchlorate, and that bioremediation may occur in part by in situ heterotrophs and autotrophs if a suitable carbon source is available.” [Emphasis added] (H+A, 2003b)
Bench scale studies performed in advance of the 2005 ROD Amendment reported that perchlorate-reducing (PRBs) bacteria were found in soils sampled during the opportunistic drilling of various monitor wells in both the vadose and saturated zone at the Site (Gearheart, et al., 2000 and 2001). However, it appears that, despite their presence, the PRBs (and nitrate- reducing bacteria) cannot perform effective bioremediation due to the low availability of a carbon source within Site soils.
Following EPA’s 2012 5YR Report proposal, in 2013, ANPI undertook a field testing program in preparation for conducting in situ pilot testing in the vicinity of monitor well MW-21. Initially, aquifer testing was performed to gain information regarding the hydraulic properties of the aquifer materials. This information would assist in the design of the necessary injection system
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as well as providing estimates of the spacing and numbers of wells that would be required for a potential full-scale operation. Unfortunately, the results of this initial testing program indicated that the strata in the vicinity of the test well were extremely tight hydraulically, such that, during pumping, a response could not be detected as near as 25 to 30 feet away. Moreover, the intervening strata were extremely heterogeneous, and the saturated thickness at one well was only two to three feet (Table 2). Obviously, such conditions are not only unsuitable for in situ treatment, they are equally unfavorable for ex situ treatment.
First, protectiveness of health must be considered. In that regard, the CSM shows that the existing groundwater in PZ-A and PZ-B are of limited extent, contained, stagnant and are not being utilized as a groundwater source for human consumption. Groundwater in PZ-A is present only within the ANPI owned property in the vicinity of P-01 and P-03. The underlying thick unit of St. David clay hydraulically isolates the deep regional aquifer from any contamination in the overlying strata. While historically groundwater seeped from the PZ-A into PZ-B, ANPI’s wastewater management practices no longer contribute to infiltration and maintenance of a groundwater body in PZ-A. PZ-A groundwater no longer seeps into PZ-B, and therefore does not act as a source of contamination to PZ-B.
PZ-B is also contained within a certain area (Figure 2). It does not have hydraulic connections with either PZ-A or with the shallow alluvial aquifer along the San Pedro River. As is the case for the PZ-A, groundwater in PZ-B is hydraulically isolated from the deep regional aquifer by virtue of the underlying St. David clay. As previously described, the situation in PZ-B is of primary concern only in the western part of the area (Figures 18, 19 and 20), where concentrations of the COCs remain high. This highly contaminated groundwater occurs only within ANPI owned property and does not appear to be migrating laterally. Additionally, based on the aforementioned field testing, the hydraulics of the aquifer materials in the vicinity of monitor well MW-21, which is where the highly contaminated groundwater occurs, are not favorable for groundwater production from wells.
As to the conditions within the eastern and southern portions of PZ-B, well drilling that would target groundwater within PZ-B on private properties is also unlikely. It is known that residences in these areas rely on deep wells tapping the regional aquifer for domestic, agricultural, and
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livestock supplies. Such wells are capable of delivering abundant quantities of water, many times greater than possible with wells drilled into PZ-B. Further, the quality of water available in PZ-B at those locations is high in TDS, exceeding secondary MCLs (Figure 21). It is further noted that, at monitor well MW-39 for example, the COC concentration trends have been downward since construction, and at monitor well MW-23, the concentrations of both COCs are now well below their respective cleanup standards. Thus, it appears that, in time, the areas to the east will attain cleanup standards without further action.
Exposure pathways with regard to groundwater contamination are essentially limited to ingestion of groundwater from wells. As is discussed above however, the likelihood of groundwater exploitation from either PZ-A or PZ-B is essentially non-existent. It is believed that there is phreatophytic uptake of groundwater from PZ-B as evident from hydrographic seasonalities. Accordingly, there would be uptake of the COCs, thereby passive bioremediation can be inferred.
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6.0 CONCLUSIONS
Based on consideration of information generated since the previous iterations of the CSM (H+A, 2003 and 2007) for the Southern Area groundwater at the Site, it can be concluded that the primary components of the CSM relevant to consideration of an appropriate remedy should be based on:
• The rapid dewatering observed in both PZ-A and PZ-B. This is a direct result of the cessation of plant wastewater discharges to the former, unlined evaporation ponds adjacent to the plant operations area. Additionally, utilization of the residual water by phreatophytes has caused further dewatering within PZ-A and PZ-B, along with the pumping and evaporation of water in the vicinity of piezometer P-03.
• The apparent role of phreatophytic transpiration in the dewatering of these perched zones. As indicated above, mesquite act as phreatophytes utilizing available water within both PZ-A and PZ-B. This is evident from the hydrographic pattern of wells and piezometers, which show distinct seasonal patterns superimposed on declining trends.
• Hydraulic containment of the perched zones such that contamination cannot migrate into the shallow or the regional aquifers. This containment is evident from the limited areal extent of water within the perched zones, the low hydraulic conductivity of the underlying St. David clay unit, and the comparatively low hydraulic conductivity of the adjacent laterally confining unit, which has been identified utilizing various borings.
• On the basis of the above-described conditions, neither PZ-A or PZ-B are suitable for groundwater resource development. Hydraulic testing has shown that yield to wells is extremely poor and that the occurrence of groundwater is spotty and limited to isolated pockets within each area.
.
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7.0 REFERENCES
Anderson, T.W., Geoffrey W. Freethey, and Patrick Tucci. 1992. Geohydrology and Water Resources of Alluvial Basins in South-Central Arizona and Parts of Adjacent States. U.S. Geological Survey Professional Paper 1406-B, 67 p.
Anderson, T.W. 1995. Summary of the Southwest Alluvial Basins, Regional Aquifer-System Analysis, South-Central Arizona and Parts of Adjacent States. U.S. Geological Survey Professional Paper 1406-A, 33 p.
Arizona Department of Environmental Quality (ADEQ), 2014. Water Quality Division: Safe Drinking Water: Perchlorate Studies Frequently Asked Questions (FAQ). Accessed January 28, 2014. http://www.azdeq.gov/environ/water/dw/perchfaq.html
Arizona Department of Health Services, 2000. Health Based Guidance Level for Perchlorate - (ClO4 ). May 2000.
ASTM, 2014. ASTM E1689-95(2014), Standard Guide for Developing Conceptual Site Models for Contaminated Sites, ASTM International, West Conshohocken, PA, 2014. www.astm.org
Black & Veatch, 1988. Preliminary Investigation Report, Apache Powder Site, Cochise County, Arizona. Prepared for the U.S. Environmental Protection Agency. June 1988.
Deane, T., 2000. Conceptualization of Groundwater Flow in the Shallow Aquifer along the Apache Reach of the San Pedro River, Cochise County, Arizona. Master’s Thesis, Department of Hydrology and Water Resources, University of Arizona. Tucson, Arizona.
Fenneman, N.M., 1931. Physiography of Western United States. New York: McGraw-Hill Book Company, Inc. 1931
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Gearheart, R.A., M.A. Ives, and W.J. Snible, 2000. Initial Studies of Perchlorate Bioremediation, Apache Powder Superfund Site, Cochise County, Arizona. November 21, 2000.
_____, 2001. Isolation of Indigenous Perchlorate Reducing Bacteria and In-Situ Simulation Studies of Perchlorate Contaminated Groundwater, Apache Powder Superfund Site, Cochise County, Arizona. June 11, 2001.
Graf, W.L., 1988. Fluvial Processes in Dryland Rivers. Springer-Verlag.
Gray, R.S., 1965. Late Cenozoic Sediments in the San Pedro Valley near St. David, Arizona. PhD Dissertation, University of Arizona, Tucson, Arizona.
Hargis + Associates, Inc. (H+A), 1991. Hydrogeologic Investigation Report, Apache Nitrogen Products, Benson, Arizona. June 21, 1991.
_____, 1992. Remedial Investigation Report, Apache Powder Superfund Site. April 2, 1992.
_____, 2001. Summary of San Pedro River Sampling and Analysis, October 2001. December 21, 2001.
_____, 2003a. Characterization of Groundwater Systems in the Southern Area, Apache Powder Superfund Site, Cochise County, Arizona. Revision 1.0. June 10, 2003.
_____, 2003b. Applicability of Monitored Natural Attenuation, Apache Powder Superfund Site, Cochise County, Arizona, Revision 2.0. July 9, 2003.
_____, 2003c. San Pedro River, Summary of Investigations, Apache Powder Superfund Site, Cochise County, Arizona. July 9, 2003.
_____, 2006. Southern Area Remedial Design Workplan, Apache Powder Superfund Site, Cochise County, Arizona. September 8, 2006.
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_____, 2007a. Southern Area Characterization Report, Apache Powder Superfund Site, Cochise County, Arizona. March 27, 2007.
_____, 2007b. Southern Area Performance Monitoring Plan, Apache Powder Superfund Site, Cochise County, Arizona, Revision 2.0. September 19, 2007.
_____, 2013. Southern Area Groundwater Remedy Acceleration Investigation, Part I. Bench Testing Workplan. January 18, 2013.
Konieczki, A.D., 1980. Maps showing ground-water conditions in the Upper San Pedro Basin Area, Pima, Santa Cruz, and Cochise Counties, Arizona-1978. USGS Water Resources Investigations. Open File Report 80-1192. Sheet 1 of 2.
Melton, M.A., 1965. “The Geomorphic and Paleoclimactic Significance of Alluvial Deposits In Southern Arizona.” Journal of Geology, v. 73, p. 1-37.
Pearthree, P.A. and J.P. Cook, 2015. Geology and Geomorphology of the San Pedro River, Southeastern, Arizona. Arizona Geological Survey, Special Paper 10.
Smith, G.A., 1994. “Climatic influences on continental deposition during late-stage filling of an extensional basin, southeastern Arizona.” Geological Society of America Bulletin, v. 106, p. 1212-1228.
U.S. Environmental Protection Agency (EPA), 1994a. Record of Decision; Apache Powder Co. September 30, 1994.
_____, 1994b. EPA Unilateral Administrative Order for Remedial Design, Remedial Action and Other Response Actions. December 29, 1994.
_____, 1997. Explanation of Significant Differences: Apache Powder Superfund Site. April 16, 1997.
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_____, 2005. Record of Decision Amendment: Apache Power Co. September 20, 2005.
_____, 2012. Five-Year Review Report: Third Five-Year Report for Apache Powder Superfund Site, Cochise County, Arizona. September 20, 2012. U.S. EPA Region IX.
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TABLES
TABLE 1
RAIN YEAR PRECIPITATION BENSON, ARIZONA
PRECIPITATION (INCHES) PRECIPITATION TOMBSTONE APACHE/BENSON (RAIN YEAR) (Station 028619) (Stations 020309 & 020683) 1979 8.07 9.64 1980 10.95 9.39 1981 10.90 9.66 1982 17.96 17.28 1983 16.79 17.94 1984 23.01 19.82 1985 13.73 14.32 1986 17.35 17.64 1987 13.50 11.31 1988 16.06 17.39 1989 9.01 11.63 1990 17.24 14.27 1991 15.31 19.45 1992 18.09 15.69 1993 7.67 13.61 1994 18.46 14.28 1995 8.79 10.09 1996 14.06 8.19 1997 14.98 14.65 1998 8.07 8.51 1999 14.22 14.47 2000 22.51 16.72 2001 9.00 11.79 2002 10.55 8.08 2003 14.92 9.91 2004 9.45 7.92 2005 5.19 5.66 2006 10.94 14.82 2007 10.83 6.23 2008 20.06 8.26 2009 12.40 4.19 2010 10.01 9.58 2011 14.00 8.17 2012 14.04 7.08 2013 10.12 9.51 Average 1979-2013 13.38 11.92
2014 26.13 16.37 2015 10.84 12.21 NOTE: Rain year from: June to May Stations: Tombstone, Arizona (028619) Period of Record: 7/1/1893 - 6/10/16 Apache Powder Company, Arizona (020309) Period of Record: 07/01/1923 to 04/30/1990 Benson 6 SE, Arizona (020683) Period of Record: 05/01/1990 to 06/10/2016
Table 1 Rain Season Precipitation 04/21/2016 TABLE 2 SATURATED THICKNESS OF PERCHED ZONE AREAS AUGUST 2016
Saturated Thickness (in feet) Above St. David Within Coarse Within Fine Well_ID Clay Grained Materials Grained Materials P-01 4.90 4.90 0.00 P-03 10.82 10.82 0.00 MW-15 Dry Dry Dry MW-21 40.00 10.00 30.00 MW-23 10.81 0.00 10.81 MW-39 23.59 21.00 2.59 MW-43 3.00 3.00 0.00 MW-44 3.00 3.00 0.00 MW-47 16.98 8.90 8.08
Table 2 Saturated Thickness 4/13/2017 HARGIS + ASSOCIATES, INC.
FIGURES
APACHE POWDER
SONORA MEXICO
JO 60
MILES
HARGIS+ ASSOCIATES, INC DATE 5/17 RPT NO . 13 0 .41 410-4609 A
FIGURE 1. LOCATION OF APACHE POWDER SUPERFUND SITE COCHISE COUNTY, ARIZONA EXPLANATION Non-Contiguous Property Former Unlined Evaporation Ponds Owned by ANPI Nitrate/Perchlorate Contamination I 0 750 1,500 Feet
SAN PEDRO RIVER
WASH 1 WASH 2
WASH 3
SHALLOW WASH 4 AQUIFER BOUNDRY
WASH 5 MW-24 AREA SOUTHERN AREA
PERCHED ZONE A
WASH 6 ANPI Facility Boundary LATERALLY CONFINING UNIT
PERCHED ZONE B
APACHE NITROGEN PRODUCTS, INC (ANPI) FACILITY BOUNDARY AND LOCATION OF SOUTHERN AREA PERCHED SYSTEM (PZ-A AND PZ-B) FIGURE 2 EXPLANATION Former Unlined Evaporation Ponds Nitrate/Perchlorate Contamination
SAN PEDRO RIVER
S. Apache Powder Rd
PERCHED ZONE
WASH 6
SHALLOW AQUIFER ALONG SAN PEDRO RIVER
ANPI SHALLOW Facility Boundary AQUIFER BOUNDRY
Rail Road I 0 500 1,000 1,500 Feet
APACHE NITROGEN PRODUCTS, INC (ANPI) CONCEPTUAL VIEW OF PERCHED ZONE AND SHALLOW AQUIFER IN 1994 (TIME OF ROD)
FIGURE 3 EXPLANATION Former Unlined Evaporation Ponds Nitrate/Perchlorate Contamination
SAN PEDRO RIVER
??
SHALLOW S. Apache Powder Rd AQUIFER ALONG MOLINOS SAN PEDRO CREEK RIVER SUB-AQUIFER PERCHED ZONE
WASH 6
ANPI SHALLOW Facility Boundary AQUIFER BOUNDRY
Rail Road I 0 500 1,000 1,500 Feet
APACHE NITROGEN PRODUCTS, INC (ANPI) CONCEPTUAL VIEW OF PERCHED ZONE, MOLINOS CREEK SUB-AQUIFER (MCA), LATERALLY CONFINING UNIT AND SHALLOW AQUIFER IN EARLY 2000s
FIGURE 4 EXPLANATION Former Unlined Evaporation Ponds Nitrate/Perchlorate Contamination
SAN PEDRO RIVER
MW-24 AREA
SHALLOW S. Apache Powder Rd AQUIFER ALONG MOLINOS SAN PEDRO CREEK RIVER SUB-AQUIFER PERCHED ZONE
WASH 6
LATERALLY CONFINING UNIT SHALLOW AQUIFER BOUNDRY ANPI Facility Boundary
Rail Road
I 0 500 1,000 1,500 Feet
APACHE NITROGEN PRODUCTS, INC (ANPI) CONCEPTUAL VIEW OF PERCHED ZONE AND MOLINOS CREEK SUB-AQUIFER IN 2007
FIGURE 5 WEST EAST
PZ-A PZ-B Laterally Confining Unit Shallow Aquifer along San Pedro River Former Pond
San Pedro River Silts & Clays Sands & Gravels Sands & Gravels Isolated Pockets of Water
0 500 feet St. David Clay
CONCEPTUAL CROSS-SECTION (WEST-EAST) SHOWING PERCHED WATER IN ISOLATED DEPRESSIONS OR POCKETS IN PZ-A AND PZ-B
FIGURE 6 EXPLANATION
Former Unlined Evaporation Ponds Nitrate/Perchlorate Contamination
S. Apache Powder Rd 1995 1996
2017 WASH 6 2000 2000
PZ-A 2017
PZ-B
ANPI Facility Boundary
I 0 320 640 Feet
APACHE NITROGEN PRODUCTS, INC (ANPI) CHANGE IN AREAL EXTENT OF PERCHED ZONE A 1995 TO 2017 FIGURE 7 EXPLANATION
Former Unlined Evaporation Ponds Nitrate/Perchlorate Contamination
SAN PEDRO RIVER
S. Apache Powder Rd
MW-24 AREA SHALLOW AQUIFER ALONG 1995 SAN PEDRO PERCHED RIVER ZONE A EXTENT
PZ-A WASH 6
PZ-B LATERALLY CONFINING UNIT SHALLOW AQUIFER ANPI BOUNDARY Facility Boundary
Rail Road
I 0 500 1,000 Feet
APACHE NITROGEN PRODUCTS, INC (ANPI) CONCEPTUAL VIEW OF PERCHED SYSTEM (PZ-A AND PZ-B) IN 2017 FIGURE 8 MW-26 EXPLANATION MW-25 MW-27 PIEZOMETER Wash 4 Dynagel MONITOR WELL Wash 3 Pond MW-33 D(18-21)08bdb EXPLORATORY BORING
OTHER WELL TYPE
SURFACE WATER SAMPLE
Wash 5 D(18-21)08bdc D(18-21)08acd D(18-21)08acd APACHE PROPERTY BOUNDARY
EXB-24 RAILROAD Pond 7 EXB-25 D(18-21)08000 MW-24 ROADS D(18-21)08cab MW-22 D(18-21)07daa EXB-03 MW-14 WASH EXB-17 ISOLATED AREA D(18-21)08ca0 FORMER POND EXB-16 AT MW-24 D(18-21)07cac EXB-14
EXB-15 EXB-11 S. Apache Powder Road EXB-10 PERCHED ZONE A D(18-21)08dac EXB-12 (PZ-A) EXB-13
Extent of PZ-A in 1995 Extent of PZ-A Wash 6 D(18-21)07ddb San Pedro River MW-04 in 2016 D(18-21)08cdb D(18-21)07cca2 P-01 (intermittent flow) MW-01 1A D(18-21)08cda MW-03 P-8 1B MW-16 2B MW-32 P-02 2A MW-28 EXB-20 SW-12 P-4 LATERALLY P-03 P-9 MW-31 MW-39 EXB-02 CONFINING UNIT EXB-19 P-10 MW-30 D(18-21)07ddc1 3A 3B P-5 MW-21 D(18-21)08cdc D(18-21)08cdd MW-02 MW-7 MW-44 MW-47 D(18-21)07ddc3 MW-29 EXB-27
P-6 P-11 Southern Pacific Rail Road P-7 D(18-21)07ddc2 SHALLOW ALLUVIAL AQUIFER EXB-26 EXB-8 EXB-9 MW-15 EXB-18 D(18-21)07cdd ALONG SAN PEDRO RIVER MW-43 MW-23 EXB-22 D(18-21)18aba D(18-21)18aba PERCHED ZONE B EXB-1 (PZ-B) D(18-21)18aab D(18-21)17ba MW-06
D(18-21)18bac Located Further 0 600 ft South SCALE
HARGIS + ASSOCIATES, INC. Hydrogeology/Engineering FIGURE 9: MONITOR WELLS AND BORINGS WITHIN SOUTHERN AREA APACHE POWDER SUPERFUND SITE A A’ (West) (East) 3700 3700 PERCHED ZONE A PERCHED ZONE B LATERALLY CONFINING UNIT P-01 MW-04 P-02 P-03 P-10 RECENTLY INSTALLED MW-30 MW-21 MW-44 1990 2000 2010 1990 2000 2010 MW-15 EXB-27 MW-47 EXB-18
3650 1990 2000 2010 3650 EXB-8
1990 2000 2010
1990 2000 2010 DRY SILT/CLAY ELEVATION
3600 1990 2000 2010 DRY 3600 1990 2000 2010
SAINT DAVID CLAY SILTY/CLAYEY SAND/ SAND / GRAVEL GRAVEL
3550 3550
B EXPLANATION B’ (South) PREDOMINANTLY EXB-1A MW-23 (North) CLAY OR SILT SEAL MW-15 EXB-27 EXB-2 MW-16 LOCATION 3650 3650 CASING UNKNOWN
FILTER SAND / GRAVEL SCREEN ≥15% FINES SILTY/CLAYEY GROUNDWATER SAND / GRAVEL ELEVATION SAND / GRAVEL <15% FINES SILT/CLAY DRY 1990 to Recent 1990 2000 2010
3600 DRY 3600 1990 2000 2010 MOST RECENT SAINT DAVID CLAY 1990 2000 2010 GROUNDWATER ELEVATION (Filled with white if dry) ELEVATION
SAND/ GRAVEL 40 ft
3550 3550 2.5 Vertical SAINT DAVID CLAY Exaggeration 20
0 0 100 200 ft
FIGURE 10: CONCEPTUALIZED CROSS SECTION A - A’ AND B - B’ APACHE POWDER SUPERFUND SITE C C’ D D’ (South) (North) (West) (East) MW-24 EXB-3 MW-14 MW-22 EXB-22 MW-47 EXB-18 EXB-19 MW-39 EXB-20 3650 3650
1990 2000 1990 2000 2010 3600 3600 SILT/CLAY 1990 2000
SILTY/CLAYEY SAND / GRAVEL SILT/CLAY 3600 3600 1990 2000
ELEVATION SAND/ ELEVATION GRAVEL 3550 3550
SILTY/CLAYEY SAND/ SAND / GRAVEL GRAVEL
3550 SAINT DAVID CLAY 3550 SAND/ 3500 GRAVEL 3500
EXPLANATION SAINT DAVID CLAY PREDOMINANTLY CLAY OR SILT 3450 3450 SEAL
CASING UNKNOWN LOCATION
FILTER SAND / GRAVEL LOCATION SCREEN ≥15% FINES
GROUNDWATER SAND / GRAVEL ELEVATION <15% FINES 1990 to Recent
1990 2000 2010
MOST RECENT SAINT DAVID CLAY GROUNDWATER ELEVATION (Filled with white if dry)
40 ft
2.5 Vertical Exaggeration 20
0 0 100 200 ft
FIGURE 11: CONCEPTUALIZED CROSS SECTION C - C’ AND D - D’ APACHE POWDER SUPERFUND SITE 3,680
MW-04 P-01 P-03 P-10
3,670
3,660
3,650 ELEVATION (ft msl)
3,640
3,630
Note: Unfilled symbols indicate well was dry when measured. 3,620 Jan-90 Jan-95 Jan-00 Jan-05 Jan-10 Jan-15 FIGIURE 12: GROUNDWATER ELEVATIONS PERCHED ZONE A 3,620
MW-15 MW-21 MW-23 MW-39
3,615
3,610
ELEVATION (ft msl) 3,605
3,600
Note: Unfilled symbols indicate well was dry when measured. 3,595 Jan-90 Jan-95 Jan-00 Jan-05 Jan-10 Jan-15 FIGIURE 13: GROUNDWATER ELEVATIONS PERCHED ZONE B 3,612 MW-14 MW-22 MW-24
3,610
3,608
3,606
3,604
3,602 ELEVATION (ft msl)
3,600
3,598
3,596
Note: Unfilled symbols indicate well was dry when measured. 3,594 Jan-90 Jan-95 Jan-00 Jan-05 Jan-10 Jan-15 FIGIURE 14: GROUNDWATER ELEVATIONS ISOLATED AREA AT MW-24 3,665
MW-01 MW-15 P-03 MW-21
3,655
3,645
PERCHED ZONE A
3,635
3,625 ELEVATION (ft msl)
ALONG RIVER 3,615
3,605
PERCHED ZONE B Note: Unfilled symbols indicate well was dry when measured. 3,595 Jan-90 Jan-95 Jan-00 Jan-05 Jan-10 Jan-15 FIGIURE 15: GROUNDWATER ELEVATIONS PERCHED ZONE A & B AND ALONG SAN PEDRO RIVER MW-25 MW-27 3599.67 3600 EXPLANATION ? MW-26 PIEZOMETER Wash 4 Dynagel MONITOR WELL Wash 3 Pond MW-33 3603.39 ELEVATION OF GROUNDWATER 3642.69 All measurements taken 5/27/16 - 6/2/16; except for MW-01 taken on 2/23/16. Dry = Well dry in 2016. 3605 DIRECTION OF GROUNDWATER FLOW Wash 5 ? LINE OF EQUAL GROUNDWATER ELEVATION Quarried where inferred. Pond 7 APACHE PROPERTY BOUNDARY
MW-24 3599.18 MW-22 RAILROAD 3608.21 3610 MW-14 3608.39 ROADS ISOLATED AREA AT MW-24 WASH NOTE: Wells not measured for water in 2016 colored grayed. FORMER POND S. Apache Powder Road ? PERCHED ZONE A (PZ-A)
Extent of PZ-A in 1995 Extent of PZ-A Wash 6 San Pedro River MW-04 in 2016 P-01 3663.44 (intermittent flow) MW-01 3667.13 3612.47 1A MW-03 P-02 3640.59 P-8 1B MW-16 2B MW-32 2A Dry P-4 MW-28 LATERALLY P-03 P-9 MW-31 3615 3640.11 Dry MW-39 CONFINING UNIT P-10 3600.16 MW-30 MW-213601.54 3A 3B P-5 Dry Dry MW-02 MW-44 MW-7 MW-29 MW-47 P-6 P-11 P-7 Dry 3600.75 Southern Pacific Rail Road SHALLOW ALLUVIAL AQUIFER MW-15 Dry ALONG SAN PEDRO RIVER MW-43
MW-23 3600.46 ? PERCHED ZONE B
(PZ-B) MW-06 3625.28 Located Further 0 600 ft South SCALE
HARGIS + ASSOCIATES, INC. Hydrogeology/Engineering FIGURE 16: ELEVATION OF GROUNDWATER 2016 APACHE POWDER SUPERFUND SITE MW-26 nd EXPLANATION MW-25 nd MW-27 nd PIEZOMETER Wash 4 Dynagel MONITOR WELL Wash 3 Pond MW-33 0.42 SURFACE WATER SAMPLE
1500 NITRATE-N IN GROUNDWATER Maximum detected concentration in mg/l
Wash 5 APACHE PROPERTY BOUNDARY
RAILROAD
Pond 7 ROADS
MW-24 11 MW-22 WASH MW-14 1 37 FORMER POND ISOLATED AREA AT MW-24 NOTE: Wells not sampled and analyzed are colored gray. mg/l = milligrams per liter.
S. Apache Powder Road PERCHED ZONE A (PZ-A)
Extent of PZ-A in 1995 Extent of PZ-A Wash 6 San Pedro River MW-04 in 2016 P-01 1100 (intermittent flow) MW-01 220 0.2 1A MW-03 P-8 1B 2,600 970 MW-16 2B MW-32 P-02 2A 950 MW-28 SW-12 P-4 LATERALLY 1.2 450 P-03 P-9 MW-31 1,020 MW-39 15,000 280 CONFINING UNIT P-10 MW-30 MW-21 3A 3B P-5 1000 7000 MW-02 1180 MW-7 MW-44 6400 MW-47 688 MW-29 MW-15 6.7 410 P-6 P-7 P-11 550 Southern Pacific Rail Road 770 520 470 SHALLOW ALLUVIAL AQUIFER ALONG SAN PEDRO RIVER MW-43 MW-23 5100 23
PERCHED ZONE B (PZ-B) MW-06 210 Located Further 0 600 ft South SCALE
HARGIS + ASSOCIATES, INC. Hydrogeology/Engineering FIGURE 17: NITRATE-N IN GROUNDWATER - MAXIMUM DETECTED CONCENTRATION APACHE POWDER SUPERFUND SITE MW-25 MW-27 EXPLANATION
MW-26 PIEZOMETER Wash 4 Dynagel MONITOR WELL Wash 3 Pond MW-33 SURFACE WATER SAMPLE <0.5 mg/l <0.5 mg/l NITRATE-N IN GROUNDWATER Most recent concentration from 2015 - 2016 sampling events.
Wash 5 APACHE PROPERTY BOUNDARY
RAILROAD Pond 7 ROADS MW-24 0.88 mg/l MW-22 <0.5 mg/l WASH MW-14 <0.5 mg/l FORMER POND ISOLATED AREA AT MW-24 NOTE: Wells not sampled and analyzed in 2015/16 colored gray. mg/l = milligrams per liter.
S. Apache Powder Road PERCHED ZONE A (PZ-A)
Extent of PZ-A in 1995 Extent of PZ-A Wash 6 San Pedro River MW-04 in 2016 P-01 (intermittent flow) MW-01 2.5 mg/l <0.5 mg/l 1A P-02 P-8 1B MW-03 2B MW-16 2A MW-32 Dry SW-12 P-4 MW-28 LATERALLY P-03 <0.5 mg/l P-9 MW-31 7,200 mg/l Dry MW-21 MW-39 CONFINING UNIT P-10 MW-30 4,300 mg/l 31 mg/l 3A 3B P-5 Dry MW-02 MW-44 MW-7 MW-29 MW-47 P-6 P-11 MW-15 P-7 Dry 6.7 mg/l Southern Pacific Rail Road SHALLOW ALLUVIAL AQUIFER ALONG SAN PEDRO RIVER MW-43
MW-23 5.3 mg/l PERCHED ZONE B
(PZ-B) MW-06 <0.5 mg/l Located Further 0 600 ft South SCALE
HARGIS + ASSOCIATES, INC. Hydrogeology/Engineering FIGURE 18: NITRATE-N IN GROUNDWATER - 2015/2016 APACHE POWDER SUPERFUND SITE MW-26 nd EXPLANATION ndMW-25 MW-27 nd PIEZOMETER Wash 4 Dynagel MONITOR WELL Wash 3 Pond MW-33 nd SURFACE WATER SAMPLE
1500 PERCHLORATE IN GROUNDWATER Maximum detected concentration in ug/l
Wash 5 APACHE PROPERTY BOUNDARY
RAILROAD
Pond 7 ROADS
MW-24 54 MW-22 WASH MW-14 4.4 0.7 FORMER POND ISOLATED AREA AT MW-24 NOTE: Wells not sampled and analyzed are colored gray. ug/l = micrograms per liter.
S. Apache Powder Road PERCHED ZONE A (PZ-A)
Extent of PZ-A in 1995 Extent of PZ-A Wash 6 San Pedro River MW-04 in 2016 P-01 (intermittent flow) MW-01 32.1 ND 1A MW-03 P-8 1B 63 MW-16 2B MW-32 P-02 2A 21 MW-28 LATERALLY SW-12 P-4 ND P-03 P-9 MW-31 MW-39 810 250 CONFINING UNIT P-10 17 MW-30 MW-21 3A 3B P-5 420 MW-7 MW-44 MW-02 404 MW-47 MW-29 13 150 MW-15 P-6 P-7 P-11 540 Southern Pacific Rail Road SHALLOW ALLUVIAL AQUIFER ALONG SAN PEDRO RIVER MW-43 MW-23 339 64
PERCHED ZONE B (PZ-B) MW-06 ND Located Further 0 600 ft South SCALE
HARGIS + ASSOCIATES, INC. Hydrogeology/Engineering FIGURE 19: PERCHLORATE IN GROUNDWATER - MAXIMUM DETECTED CONCENTRATION APACHE POWDER SUPERFUND SITE MW-25 MW-27 EXPLANATION
MW-26 PIEZOMETER Wash 4 Dynagel MONITOR WELL Wash 3 Pond MW-33 <0.65 ug/l <0.5 mg/l PERCHLORATE IN GROUNDWATER Most recent concentration from 2015 - 2016 sampling events.
Wash 5 APACHE PROPERTY BOUNDARY
RAILROAD Pond 7 ROADS MW-24 MW-22 1.3 ug/l WASH Nov 2014 0.67 ug/l MW-14 0.7 ug/l FORMER POND ISOLATED AREA AT MW-24 NOTE: Wells not sampled and analyzed in 2015/16 colored gray. ug/l = micrograms per liter.
S. Apache Powder Road PERCHED ZONE A (PZ-A)
Extent of PZ-A in 1995 Extent of PZ-A Wash 6 San Pedro River MW-04 in 2016 P-01 (intermittent flow) MW-01 17.8 ug/l <2 ug/l 1A P-02 P-8 1B MW-03 2B MW-16 2A MW-32 Dry SW-12 P-4 MW-28 LATERALLY P-03 P-9 MW-31 483 ug/l Dry MW-21 MW-39 CONFINING UNIT P-10 MW-30 210 ug/l 41 ug/l 3A 3B P-5 Dry MW-02 MW-44 MW-7 MW-29 MW-47 P-6 P-11 P-7 Dry 12 ug/l Southern Pacific Rail Road SHALLOW ALLUVIAL AQUIFER MW-15 ALONG SAN PEDRO RIVER MW-43 MW-23 3.6 ug/l
PERCHED ZONE B
(PZ-B) MW-06 <0.65 ug/l Located Further 0 600 ft South SCALE
HARGIS + ASSOCIATES, INC. Hydrogeology/Engineering FIGURE 20: PERCHLORATE IN GROUNDWATER - 2015/2016 APACHE POWDER SUPERFUND SITE MW-26 2,400 EXPLANATION MW-25 2,300 - 2,400 MW-27 2,700 PIEZOMETER Wash 4 Dynagel MW-33 MONITOR WELL Wash 3 Pond 510 - 640 SURFACE WATER SAMPLE
1,500 - 2,300 TOTAL DISSOLVED SOLIDS IN GROUNDWATER Range of detections in mg/l Wash 5 APACHE PROPERTY BOUNDARY
RAILROAD Pond 7
MW-24 430-640 ROADS MW-22 MW-14 280 290 - 830 WASH
ISOLATED AREA FORMER POND AT MW-24 NOTE: Wells not sampled and analyzed are colored gray. mg/l = milligrams per liter.
S. Apache Powder Road PERCHED ZONE A (PZ-A)
Extent of PZ-A in 1995 Extent of PZ-A Wash 6 San Pedro River MW-04 in 2016 P-01 2,055 (intermittent flow) MW-01 1,900 - 2,200 410-472 1A MW-03 2,300 - 6,490 P-8 1B 5,900 - 7,300 MW-16 2B MW-32 P-02 2A MW-28 SW-12 P-4 LATERALLY 340-430 3,400 P-03 P-9 MW-31 MW-39 1,500 - 28,000 CONFINING UNIT P-10 MW-21 2,200 - 4,800 2,400 - 6,200 MW-30 2,900 - 20,000 3A 3B P-5 5,300 MW-02 MW-7 MW-44 MW-47 5,010 - 5,900 MW-29 P-6 P-7 P-11 4,100 - 4,500 Southern Pacific Rail Road SHALLOW ALLUVIAL AQUIFER 4,200 - 4,900 MW-15 4,990 - 5,500 ALONG SAN PEDRO RIVER MW-43 MW-23 1,200 - 1,600
PERCHED ZONE B (PZ-B) MW-06 360-392 Located Further 0 600 ft South SCALE
HARGIS + ASSOCIATES, INC. Hydrogeology/Engineering FIGURE 21: TOTAL DISSOLVED SOLIDS IN GROUNDWATER APACHE POWDER SUPERFUND SITE PERCHED ZONE A PERCHED ZONE B LATERALLY Plant wastewater (PZ-A) (PZ-B) CONFINING UNIT stream. Transpiration San Pedro River Seepage from unlined ponds.
Pheatophyte Roots Sands/ Gravels Uneven eroded surface of the St. David clay. Ongoing discharge Silty or Clayey from perched zone. Sand / Gravel Silt / Clay Groundwater gradient slopes from west (near point of recharge) to the east. ST DAVID CLAY
PERIOD OF ACTIVE DISCHARGE FROM PONDS (Pre-1995)
Transpiration
San Pedro River Seepage from unlined ponds stopped. Pheatophyte Roots Sands/ Gravels As Perched Zone drys, isolated pockets of Discharge from Silty or Clayey pooled water remain Sand / Gravel at different elevations perched zone terminiated. Silt / Clay on the eroded surface After recharge stopped, of the St. David clay. groundwater gradient nearly flat. Water levels drop ST DAVID CLAY from transpiration.
PERIOD AFTER DISCHARGE FROM PONDS CEASED (Post 2003)
HARGIS + ASSOCIATES, INC. Hydrogeology/Engineering FIGURE 22: CONCEPTUALIZATION OF GROUNDWATER EXCHANGE BETWEEN PERCHED ZONE A AND B HARGIS + ASSOCIATES, INC.
APPENDIX A
SUMMARY OF INVESTIGATIONS AFTER 2007 APPENDIX A
RECENT SOUTHERN AREA INVESTIGATIONS
Appendix A describes field investigations performed in the Southern Area since March 27, 2007, when the Southern Area Characterization Report, Apache Powder Superfund Site, Cochise County, Arizona (H+A, 2007, “Characterization Report”) was issued. The 2007 Characterization Report described field investigations performed in 2006 and 2007.
2012 INVESTIGATION
At monitor well MW-21, concentrations of the chemicals of concern (COC) had been increasing in comparison with decreasing COC concentrations at other locations within PZ-B. ANPI therefore initiated a testing program directed towards determining the feasibility of remedy acceleration using an in situ method. Initially, hydraulic testing was performed to determine aquifer properties related to injection of fluids. The area in the vicinity of monitor well MW-21 was selected because it represented the location where concentrations of both nitrate-N and perchlorate in the PZ-B were the highest. On September 6, 2012, a constant rate discharge test was initiated at that location. A submersible pump was placed in monitor well MW-21 and pumped at an initial discharge rate of 6.25 gallons per minute (gpm). The water level declined quickly in the well, and the test was terminated at 6 minutes (min) with a total drawdown of 14.35 feet (ft). If pumping had continued it was projected that the well would have become dry after 11 to 12 min. After 23 min, the testing was restarted at a discharge rate of 6 gpm and again the water level declined quickly. If pumping had continued at 6 gpm, it was projected that the well would have become dry after 15 min. The discharge rate was then reduced to 3 gpm which, after 7 min, produced a drawdown of 11.37 feet. Pumping was sustained at a low rate from 7 to 240 min, during which time the discharge rate varied between 2.97 and 3.87 gpm. Due to inconsistencies, the drawdown information was erratic and not useful for aquifer analysis. In particular, it was decided that monitor well MW-21, due to its primary design as a monitor well, was not properly constructed to serve as a test well that would yield information appropriate for aquifer testing. 2013 INVESTIGATION
Based on information collected to date, it was determined that further exploration was needed in PZ-B in order to conduct meaningful tests in the vicinity of monitor well MW-21. An exploratory boring, EXB-26, was therefore drilled, and later monitor wells MW-43 and MW-44 were constructed. Monitor well MW-43 was designed with a larger diameter for the purpose of testing. Exploratory boring EXB-26 was also drilled in the vicinity of MW-21 with the intention constructing a monitor well, however, the St. David clay was encountered at a higher elevation than expected at that location, and no saturated materials were observed. The results of the investigation are summarized in the following sections. 2013 INVESTIGATION: DRILLING
In 2013 activities included the drilling of an exploratory boring, EXB-26, and construction of monitor wells MW-43 and MW-44. All of these were performed in the vicinity of MW-21 in the western area of PZ-B.
Exploratory boring EXB-26 was drilled on July 17, 2013. The eight-inch borehole was located approximately 50 ft southeast of monitor well MW-21 and was advanced to 75 feet below land surface (bls) utilizing a sonic drilling technique (Figure A-1). Initially, it was intended that a monitor well would be completed at that location, with a screen interval depth comparable to monitor well MW-21. The lithology encountered however was predominantly silts to a depth of 50 ft bls, and, between 50 and 55 ft bls, the strata were dry to moist silty sand and silty gravel. The St. David clay was encountered at 60 feet bls. Drilling was continued down to 75 ft bls, but no saturated zone was encountered. Due to the lack of water bearing materials, it was determined that the borehole would be abandoned and backfilled with borehole cuttings, and a location nearer to monitor well MW-21 was sited.
Monitor well MW-43 was drilled and constructed on July 23, 2013. It was sited approximately 25 ft south-southeast of monitor well MW-21, and again, it was anticipated that it would be completed as a monitor well with a screen interval depth comparable to monitor well MW-21 (Figure A-1). The eight-inch borehole was advanced to 75 ft bls utilizing a sonic drilling technique. From the surface to 49 ft bls the borehole lithology was predominantly clays and silts. From the 49 ft to 63 ft bls the lithology was a highly permeable layer of well-graded sand with gravel. Saturated materials were encountered at 62 ft bls. The St. David clay was encountered at 63 ft bls. Monitor well MW-43 was constructed using 6-inch diameter, schedule-40 PVC, and screened from 46 ft to 66 ft bls. A filter pack was emplaced from 42.7 ft to 69.5 ft bls. Subsequently, the well was developed by surging, bailing, and pumping. Slow recovery time from well development actions was noted. The groundwater elevation at the time of development was approximately 63.8 ft bls. Following development, a groundwater sample was collected and analyzed by Turner Laboratories, Inc. of Tucson for nitrate-N, perchlorate, and specific conductivity.
Monitor well MW-44 was drilled and constructed on July 24, 2013. It was sited approximately 32 ft east of monitor well MW-21, and again anticipating that it would be completed as a monitor well with a screen interval depth comparable to monitor wells MW-21 and MW-43 (Figure A-1). The eight-inch borehole was advanced to 100 ft bls utilizing a sonic drilling technique. From the surface to 53 feet bls the borehole lithology was predominantly clays and silts, and from 53 ft to 73 ft bls the borehole lithology was predominantly coarser sandy materials, interbedded with thin sandy gravel layers. Saturated materials were encountered at approximately 60 ft bls. The St. David clay was encountered at 73 ft bls. Monitor well MW-44 was constructed using 6-inch diameter, schedule-40 PVC, and screened from 44 ft to 64 ft bls, and capped at 67 ft bls. A filter pack was emplaced from 44 ft to 69.2 ft bls. Monitor well MW-44 was developed by surging, bailing, and pumping. Well development showed monitor well MW-44 recovered more readily than monitor well MW-43. The groundwater elevation at the time of development was approximately 64.4 feet bls. Following development, a groundwater sample was collected and analyzed by Turner Laboratories, Inc. of Tucson for nitrate-N, perchlorate, and specific conductivity. Resulting Testing Configuration for Monitor Wells MW-21, MW-43 and MW-44 and Exploratory Boring EXB-26.
2013 INVESTIGATION: HYDRAULIC TESTING
In order to better understand the hydraulic connectivity between the newly-drilled monitor wells MW-43 and MW-44, and the existing monitor well MW-21, testing was performed. The purpose of the test was to determine whether hydraulic properties of the sediments in that area favored an in situ or ex situ component capable of accelerating the existing MNA remedy for PZ-B. Observations of recovery rates during well development indicated that monitor well MW-44 was best suited for pumping while conducting an aquifer test. A submersible pump was placed in monitor well MW-44 and pumped at an average discharge rate of 1.65 gpm. Monitor wells MW- 21 and MW-43 were used as observations wells. The pumping was sustained for 240 minutes, and recovery was monitored for an additional 240 minutes after pumping was terminated. Total drawdown measured in pumping well at end of test was 2.19 ft. Drawdown within the observation wells MW-21 and MW-43 was 0.15 ft. and 0.13 ft., respectively. Analysis of drawdown and recovery data estimated a range of transmissivity of 328 to 3,960 gallons per day per foot (gpd/ft), and a hydraulic conductivity in the range of 15.5 to 176.4 ft/day.
A submersible pump was placed in monitor well MW-43 and pumped at an average discharge rate of 0.47 gpm. Monitor wells MW-21 and MW-44 were used as observations wells. The pumping test was conducted for 128 minutes, and recovery was monitored for an additional 180 minutes after pumping was terminated. The well was pumped dry with a total drawdown measured in pumping well at end of test of 5.53 ft. None to negligible drawdown within the observation wells MW-21 and MW-44 was observed. The drawdown date from testing MW-43 was not considered useful for aquifer analysis.
2012 AND 2013 HYDRAULIC TESTING RESULTS
The investigation showed that transmissive units, as represented by coarser sediments, in the PZ-B were unexpectedly thin and discontinuous. In particular, there is a significant decrease in the apparent saturated thickness of sediments extending eastward from the position of monitor well MW-21 (Table A1). This seems to indicate that monitor well MW-21 is in a “deep pocket” incised into the St. David clay, and suggesting that the high concentration of COCs have limited lateral extent and distance to move. The dry conditions encountered at exploratory boring EXB- 26 provide further evidence of this limited stratigraphy. Moreover, the limited lateral extent and low hydraulic conductivity within this area suggest that further treatment by either in situ or ex situ methods will be of marginal value as potential component remedies.
2015 DRILLING PROGRAM
In 2015 drilling and well construction was performed in the central and eastern areas of PZ-B in an effort to address data gaps relating to the extent of groundwater occurrence and groundwater quality along the ANPI property boundaries to the east and south (Figure A-2). This effort involved the drilling of exploratory boring EXB-27 and construction of monitor well MW-47.
Exploratory boring EXB-27 was drilled adjacent to monitor well MW-15 on September 23, 2015. This location was chosen based on the obsolescence of monitor well MW-15, which had a limited screened interval, designed when water levels in PZ-B were much higher. Therefore, it was decided that a new monitor well would be completed at the exploratory boring EXB-27 location with a screen interval deeper than MW-15. The eight-inch borehole was advanced to 60 ft bls using a sonic drilling technique. Overall, the borehole lithology was predominantly clays and silts to a depth of 39 ft bls. Between 39 and 50 ft bls the lithology was predominantly dry to moist silty sand. The St. David clay was encountered at 50 ft bls. Three feet into the St. David clay, at 53 feet bls, a 2-inch saturated clayey sand stringer was encountered. The boring was left open for 10 minutes, but the stringer did not produce water into the open hole. Therefore the unit was determined not to be aquifer material. Because saturated material above the St. David clay was not encountered, the clayey sand stringer in the St. David clay was thin, and the open hole did not produce water, the boring was not completed as a monitor well and was backfilled with the soil cuttings.
Monitor well MW-47 was drilled on September 24, 2016. The eight-inch borehole was advanced to 80 ft bls using a sonic drilling technique. From the surface to 32.5 ft bls the borehole lithology encountered was predominantly clays and silts. From the 32.5 ft to 66 ft bls the borehole lithology encountered was interbedded sands, silty sands, sandy silts, and clay. Saturated materials were encountered at 46.5 ft bls. The St. David clay was encountered at 66 feet bls. Monitor well MW- 47 was constructed using 4-inch diameter, schedule-40 PVC, and screened from 39.5 feet to 64.5 feet bls. A filter pack was emplaced from 37 feet to 66.5 feet bls. Monitor well MW-47 was developed be surging, bailing, and pumping. The groundwater elevation at the time of development was approximately 50 feet bls. Following development, a groundwater sample was collected and analyzed by Turner Laboratories, Inc. of Tucson for nitrate-N, perchlorate, and specific conductivity.
2015 DRILLING PROGRAM RESULTS
Borehole EXB-27 was drilled in the vicinity of the now dry monitor well MW-15 to determine if groundwater is still present at that location. When monitor well MW-15 was constructed in 1990, saturated material was observed from 40 ft below land surface (bls) down to 64 ft bls (where the St. David clay was encountered). MW-15 was constructed with a screened interval of 39 to 54 ft bls. Between 1990 and 1995 the depth to water ranged from 38 to 40.5 ft bls. Starting in 1995, coincident with the cessation of wastewater discharges to the unlined ponds overlying PZ-A, groundwater level elevations at MW-15 started to decline and the well became dry in 2010. Because the well was only screened from 39 to 54 ft bls the saturated materials from 54 to 64 ft bls could not be monitored, so whether deeper materials remained saturated could not be determined. In September 2015, exploratory boring EXB-27 was drilled in the vicinity of monitor well MW-15 to a depth of 60 ft bls. In monitor well MW-15 the St. David clay was encountered at 64 ft bls, however, in exploratory boring EXB-27, located approximately 15 ft from monitor well MW-15, the St. David clay was encountered at approximately 50 ft bls or approximately 13.8 ft higher in elevation. Additionally, no saturated materials were encountered in monitor well EXB- 27 above the St. David clay. Considering the difference in elevation over such a short lateral distance, the results from EXB-27 indicate that the upper surface of the St. David clay is very uneven. This is consistent with what was learned from the drilling and testing in the vicinity of monitor well MW-21 to the west, and offers an explanation for the poor lateral hydraulic continuity.
Monitor well MW-47 was drilled to determine the groundwater conditions in the vicinity of exploratory boring EXB-18 located on the eastern side of the PZ-B, along the eastern ANPI property boundary. When exploratory boring EXB-18 was drilled in 2007, saturated sand with gravels was encountered from 48 ft to 88.5 ft bls, where the St. David clay was encountered. When monitor well MW-47 was drilled, saturated sands and gravels were encountered at 48 ft bls, however, the St. David clay was encountered at 66 ft bls, or approximately 18 ft higher in elevation than at exploratory boring EXB-18, again indicating a significant change in the surface of the St. David clay over a relatively short lateral distance (approximately 15 feet).
Nitrate-N and perchlorate were detected in development water from monitor well MW-47 at concentrations of 3.8 milligrams per liter (mg/l) and 7.4 micrograms per liter (μg/l), respectively. Similarly, analyses of quarterly groundwater samples collected from monitor well MW-47 in December 2015, detected nitrate-N and perchlorate at 3.8 mg/l and 7.4 μg/l, respectively. Both sampling events detected nitrate-N and perchlorate less than the respective cleanup standards of 10 mg/l and 14 μg/l.
The monitoring results from monitor well MW-47 indicate that approximately 8.9 to 17 ft of saturated materials are present in the eastern portion of the PZ-B. Similar to the conditions encountered at exploratory boring EXB-27, and in the 2013 drilling program near MW-21, the upper surface of the St. David clay is very uneven, with significant elevation changes in the clay surface over short distances. REFERENCES
Hargis + Associates, Inc. (H+A), 2007. Southern Area Characterization Report, Apache Powder Superfund Site, Cochise County, Arizona. March 27, 2007. HARGIS + ASSOCIATES, INC.
TABLE TABLE A1 SATURATED THICKNESS OF PERCHED ZONE AREAS
Saturated Thickness: Well_ID Max. Min. P-01 4.9 4.9 P-03 10.8 10.8 MW-15 Dry Dry MW-21 40.0 10.0 MW-23 10.8 0.0 MW-39 23.6 21.0 MW-43 3.0 3.0 MW-44 3.0 3.0 MW-47 17.0 8.9
NOTES:
Values based on water level measurements taken August 2016. Minimum based on water level within course-grained materials. Maximum based on water level above top of St. David clay.
_Table A1 Saturated Thickness 10/24/2016 HARGIS + ASSOCIATES, INC.
FIGURE
MW-26 EXPLANATION MW-25 MW-27 PIEZOMETER Wash 4 Dynagel MONITOR WELL Wash 3 Pond MW-33 D(18-21)08bdb EXPLORATORY BORING
OTHER WELL TYPE
SURFACE WATER SAMPLE
Wash 5 D(18-21)08bdc D(18-21)08acd D(18-21)08acd APACHE PROPERTY BOUNDARY
EXB-24 RAILROAD Pond 7 EXB-25 D(18-21)08000 MW-24 ROADS D(18-21)08cab MW-22 D(18-21)07daa EXB-03 MW-14 WASH EXB-17 ISOLATED AREA D(18-21)08ca0 FORMER POND EXB-16 AT MW-24 D(18-21)07cac EXB-14
EXB-15 EXB-11 S. Apache Powder Road EXB-10 D(18-21)08dac EXB-12 EXB-13 PERCHED ZONE A
Extent of PZ-A in 1995 Wash 6 D(18-21)07ddb San Pedro River MW-04 D(18-21)08cdb D(18-21)07cca2 P-01 Extent of PZ-A in 2012 (intermittent flow) MW-01 1A D(18-21)08cda MW-03 P-8 1B MW-16 2B MW-32 P-02 2A MW-28 EXB-20 SW-12 P-4 LATERALLY P-03 P-9 MW-31 MW-39 EXB-02 CONFINING UNIT EXB-19 P-10 MW-30 D(18-21)07ddc1 3A 3B P-5 MW-21 D(18-21)08cdc D(18-21)08cdd MW-02 MW-7 MW-44 MW-47 D(18-21)07ddc3 MW-29 EXB-27
P-6 P-11 Southern Pacific Rail Road P-7 D(18-21)07ddc2 SHALLOW ALLUVIAL AQUIFER EXB-26 EXB-8 EXB-9 MW-15 EXB-18 D(18-21)07cdd OF SAN PEDRO RIVER MW-43 MW-23 EXB-22 D(18-21)18aba PERCHED ZONE B D(18-21)18aba EXB-1
D(18-21)18aab D(18-21)17ba MW-06
D(18-21)18bac 0 600 ft SCALE
HARGIS + ASSOCIATES, INC. Hydrogeology/Engineering FIGURE A2: MONITOR WELLS AND BORINGS WITHIN SOUTHERN AREA APACHE POWDER SUPERFUND SITE HARGIS + ASSOCIATES, INC.
APPENDIX A1
BORING LOGS APACHE NITROGEN PRODUCTS, INC. Lithologic Log: EXB-26
Northing (ft): 11571485 Drill Method:Sonic Easting (ft): 1877071 Diameter of Casing: NA LS Elev. (ft): 3,660 Type of Casing: NA Ref. Pnt.:NA Slot Size: NA Ref. Pnt. Elev. (Ft): Filter: NA Total Depth bls (ft): 75 Note: Depth to Water (ft): 60 ± Date:7/17/13
Lithologic Description Log (feet) USCS DEPTH SAMPLE Lithologic
0 SILTY SAND - Light Brown (7.5YR7/2); 50% fine to medium sand; 50% nonplastic fines; dry; strong reaction to HCL; abundant fine platy gypsum crystals; weak cementation; contains lighter sandy lenses
SM
10 ML SILT - Light Brown to Brown (7.5YR5/4); 80% loose, non to slightly plasticity fines; 20% fine sand; dry; strong reaction to HCL; moderate to weak cementation. SILTY SAND - Brown (7.5YR6/4); 50% fine to medium sand; 50% nonplastic fines; strong reaction to HCl; weak cementation; dry. At 27' more organized due to calcium carbonate layer.
20 SM
30 Logged by MFW; Checked by GLG HARGIS + ASSOCIATES, INC. Hydrogeology/Engineering PAGE 1 OF 3 LITHOLOGIC LOG FOR EXPLORATORY BORING EXB-26 Lithologic Log: EXB-26
Lithologic Description Log (feet) USCS DEPTH SAMPLE Lithologic
30 SILTY SAND - Continued.
40
SM
50
SILTY GRAVEL - Reddish Brown (5YR5/3); 50% gravel; 30% nonplastic fines; 20% fine GM sand; dry; strong reaction to HCl; weak cementation; poorly sorted with sub angular clasts >2. LEAN CLAY with SAND - Reddish Brown (5YR4/4); 85% slightly plastic fines; 15% sandy silt inclusions; strong reaction to HCl; moist; very hard; moderate cementation. CL
FAT CLAY - Reddish Brown (5YR4/3); 90% slightly plastic fines; 10% sandy silt 60 inclusions; strong reaction to HCl; moist; very soft; high cementation; high elasticity; CH homogeneous. At 60' saturated zone was penetrated and Upper St. David Clay encountered. At 61' St. David Clay encountered. LEAN CLAY - Reddish brown (5YR4/4); 90% slightly plastic fines; 10% sandy silt inclusions; strong reaction to HCl; moist; very hard; moderate cementation; moderate elasticity CL
At 68' borehole diameter decreased from 8" to 6".
70 Logged by MFW; Checked by GLG HARGIS + ASSOCIATES, INC. Hydrogeology/Engineering PAGE 2 OF 3 LITHOLOGIC LOG FOR EXPLORATORY BORING EXB-26 Lithologic Log: EXB-26
Lithologic Description Log (feet) USCS DEPTH SAMPLE Lithologic
70 LEAN CLAY Continued.
CL
TOTAL DEPTH OF BORING = 75 FEET BELOW LAND SURFACE
80
90
100
110 Logged by MFW; Checked by GLG HARGIS + ASSOCIATES, INC. Hydrogeology/Engineering PAGE 3 OF 3 LITHOLOGIC LOG FOR EXPLORATORY BORING EXB-26 APACHE NITROGEN PRODUCTS, INC. Lithologic Log: EXB-27
Northing (ft): 31.8763 Drill Method:Sonic Easting (ft): 110.2361 Diameter of Casing: NA LS Elev. (ft): ~3,652 Type of Casing: NA Ref. Pnt.:NA Slot Size: NA Ref. Pnt. Elev. (Ft): Filter: NA Total Depth bls (ft): 60.0 ADWR Reg. No. 55-918675 Depth to Water (ft): Note: ± Date:09/23/15
Lithologic Description Log (feet) USCS DEPTH SAMPLE Lithologic
0 Hand Augered.
SILT (0,5,95) Brown (7.5YR 4/3), dry, medium plasticity; sand: fine.
10
ML
At 15 feet: Slightly moist.
At 16.5 feet: Minor roots.
ML SILT (0,20,80) Dry, medium plasticity; rootlets; sand: fine. 20 SP-SM SAND WITH SILT (10,80,10) Brown (10YR 5/3), fine- to coarse-grained, predominantly fine, well sorted; gravel up to 1.5 inches. ML SILT (0,20,80) Brown (7.5YR 5/3) dry, low plasticity.
CLAY (0,tr,100) Brown (7.5YR 4/3) moist, very stiff, high plasticity.
CL
At 29 feet: Becomes harder. 30 Logged by CAP; Checked by LSL HARGIS + ASSOCIATES, INC. Hydrogeology/Engineering PAGE 1 OF 2 LITHOLOGIC LOG FOR EXPLORATORY BORING EXB-27 Lithologic Log: EXB-27
Lithologic Description Log (feet) USCS DEPTH SAMPLE Lithologic
30 CLAY (0,5,95) Light reddish brown (5YR 6/4), moist, high plasticity. CL
CLAY (0,0,100) Reddish brown (5YR 4/4), moist, very stiff, high plasticity.
CL
SP SAND (10,85,5) Fine- to coarse-grained, predominantly fine, sub-angular, well sorted. 40 SM SILTY SAND (5,65,30) Dry, fine- to coarse-grained, poorly sorted, rounded. SILTY SAND (0,60,40) Brown (7.5YR 5/3), moist, fine-grained, poorly sorted.
SM
SAND (0,85,15) Brown (7.5YR 5/3), dry, fine-grained, well sorted. SM 50 SAINT DAVID FORMATION. CLAY (0,10,90) Reddish brown (5YR 5/4), very moist, CL medium plasticity. At 53 feet: 3-inch saturated interbed of SAND (0,60,40) fine-grained, well sorted CLAY (0,5,95) Reddish brown (5YR 5/3), very moist, medium plasticity; sand: fine.
CL
60 TOTAL DEPTH OF BORING = 60 FEET BELOW LAND SURFACE
70 Logged by CAP; Checked by LSL HARGIS + ASSOCIATES, INC. Hydrogeology/Engineering PAGE 2 OF 2 LITHOLOGIC LOG FOR EXPLORATORY BORING EXB-27 APACHE NITROGEN PRODUCTS, INC. Lithologic and Well Construction Log: MW-43
Northing (ft): 11571505 Drill Method:Sonic Easting (ft): 1877046 Diameter of Casing: 6-inch LS Elev. (ft): 3,660 Type of Casing: Sch-40 PVC Ref. Pnt.:Top of Casing Slot Size: 0.020-inch Ref. Pnt. Elev. (Ft):3657.21 Filter: 8-12 Total Depth bls (ft): 75.0 Note: Depth to Water (ft): 61.5 feet bls ± Date:7/18/13
Lithologic Description Well Log
(feet) Construction USCS DEPTH SAMPLE Lithologic
Above Surface 0 Completion OL/OH ORGANIC SOIL WITH SAND (tr,15,85)Very dark brown (7.5YR 2.5/2), nonplastic; moderate to strong reaction to HCl. GRAVELLY SILT WITH SAND (25,20,55) Light brown ML (7.5YR 6/4), dry, very soft, nonplastic; strong reaction to HCL; gravel: fine to coarse, subrounded to subangular; sand: fine to X?, subrounded to subangular. SILT (0,5,95) Brown (7.5YR 5/4), dry, very soft, non- Neat Portland plastic; strong reaction to HCL, sand: fine, subrounded. Cement (0 to 24.5 feet)
10
6” ID Schedule 40 ML PVC Casing (-2 to 46 feet)
At 17 feet: Caliche, greater than 4 inch, subrounded. 12-inch diameter borehole (0 to 68.5 feet) 20 SILT (0,0,100) Reddish brown (5YR 4/3), Moist, soft, 55% nonplastic silt; 45% slihglty plastic clay; blocky.
ML
Bentonite Pellets (24.5 to 41.1 feet)
30 Logged by MFW; Checked by GLG HARGIS + ASSOCIATES, INC. Hydrogeology/Engineering PAGE 1 OF 3 LITHOLOGIC LOG FOR MONITOR WELL MW-43 Lithologic and Well Construction Log: MW-43
Lithologic Description Well Log
(feet) Construction USCS DEPTH SAMPLE Lithologic
30 SILT Continued.
Bentonite Pellets (24.5 to 41.1 feet)
6” ID Schedule 40 PVC Casing (-2 to 46 feet)
ML 40
#60 Sand (41.1 to 42.7 feet)
6” ID Schedule 40 PVC 0.020 inch Screen 50 SAND WITH GRAVEL (15,80,5) Brown (7.5YR 5/4), dry, (46 to 66 feet) very soft, fine- to coarse-grained, poorly sorted; strong reaction to HCL , gravel: up to 1 inch, subrounded to rounded.
12-inch diameter borehole SW (0 to 68.5 feet) At 57 feet: Increase in moisture. At 57 to 59 feet: Some clay interbeds, Reddish brown (5YR 4/3). 60
At 61.5 feet: Saturated. 8x12 Sand (42.7 to 71 feet) CLAY WITH SAND (5,10,85) Reddish brown (5YR 4/4), wet, firm, strongly cemented, slightly plastic; strong reaction to HCL; sand: rounded; gravel: subangular; with sand and gravel interbeds. CL
9-inch diameter borehole (68.5 to 71 feet) 70 Logged by MFW; Checked by GLG HARGIS + ASSOCIATES, INC. Hydrogeology/Engineering PAGE 2 OF 3 LITHOLOGIC LOG FOR MONITOR WELL MW-43 Lithologic and Well Construction Log: MW-43
Lithologic Description Well Log
(feet) Construction USCS DEPTH SAMPLE Lithologic
70 CLAY Reddish brown (5YR 4/4), high plasticity; sand 8x12 Sand and gravel interbeds absent; gypsum throughout matrix; (42.7 to 71 feet) otherwise same as above. CH 9-inch diameter borehole (68.5 to 71 feet) Slough (71 to 75 feet) TOTAL DEPTH OF BORING = 75 FEET BELOW LAND SURFACE 7-inch diameter borehole (71 to 75 feet)
80
90
100
110 Logged by MFW; Checked by GLG HARGIS + ASSOCIATES, INC. Hydrogeology/Engineering PAGE 3 OF 3 LITHOLOGIC LOG FOR MONITOR WELL MW-43 APACHE NITROGEN PRODUCTS, INC. Lithologic and Well Construction Log: MW-44
Northing (ft): 11571518 Drill Method:Sonic Easting (ft): 1877068 Diameter of Casing: 6-inch LS Elev. (ft): 3,660 Type of Casing: Sch-40 PVC Ref. Pnt.:Top of Casing Slot Size: 0.020-inch Ref. Pnt. Elev. (Ft): 3656.89 Filter: 8-12 Total Depth bls (ft): 100 Note: Depth to Water (ft): 60.5 feet bls ± Date:7/18/13
Lithologic Description Well Log
(feet) Construction USCS DEPTH SAMPLE Lithologic
Above Surface 0 Completion SILTY SAND - Brown (7.5YR4/4); 65% fine to medium sand; 25% nonplastic fines; 10% fine sub rounded gravels; dry, loose formation; strong reaction to HCl; SM abundant fine platy gypsum crystals.
SILT WITH SAND - Light brown to brown (7.5YR6/4 to Neat Portland Cement 7.5YR4/4); 80% loose, non to slightly plasticity fines; (0 to 22.6 feet) 20% fine sand; loose formation.
At 9' - formation more competent. 10
6” ID Schedule 40 ML PVC Casing (-2 to 44 feet)
12-inch diameter borehole (0 to 67 feet) 20
LEAN CLAY - Reddish brown (2.5YR4/4); 90% slightly plastic fines; 10% fine sand; strong reaction to HCl; CL contains visible tabular clay nodules; dry. SILTY CLAY - Reddish brown (5YR4/4); 90% Bentonite Pellets nonplastic to slightly plastic fines; 10% fine sand; (22.6 to 42 feet) strong reaction to HCl; abundant fine gypsum crystals CL 30 and caliche stringers. Logged by MFW; Checked by DLG HARGIS + ASSOCIATES, INC. Hydrogeology/Engineering PAGE 1 OF 3 LITHOLOGIC LOG FOR MONITOR WELL MW-44 Lithologic and Well Construction Log: MW-44
Lithologic Description Well Log
(feet) Construction USCS DEPTH SAMPLE Lithologic
30 SILTY CLAY Continued. CL Bentonite Pellets (22.6 to 42 feet) LEAN CLAY - Reddish brown (5YR4/4); 95% slightly CL plastic fines; 5% fine sand; strong reaction to HCl.
SILTY CLAY Same as above; dry, loose formation. 6” ID Schedule 40 PVC Casing (-2 to 44 feet)
CL 40 At 40 to 41' - contains small cinders
At 43' contains root fragments. #60 Sand (42 to 44 feet) CL LEAN CLAY - Reddish brown (2.5YR4/4) Same as above; contains root fragments and fine gypsum. SILT WITH SAND - Reddish brown (2.5YR4/4); 75% nonplastic fines; 25% fine subangular to subrounded 6” ID Schedule 40 sand; 40%; strong reaction to HCl. PVC 0.020 inch ML At 46' - formation contains cinders. Screen 50 (44 to 64 feet) SILTY SAND WITH GRAVEL - Reddish brown (5YR5/3); 45% fine to coarse subrounded sand; 40% fine, minor coarse subangular to subrounded gravel; 15% nonplastic fines; strong reaction to HCl. SILT WITH SAND - Dark reddish brown (2.5YR3/4); SM 80% nonplastic fines; 20% fine sand; strong reaction to HCl; contains fine gypsum crystals. 12-inch diameter ML borehole SILTY SAND- Brown (5YR5/3); 60% fine to medium (0 to 67 feet) SM sand; 40% nonplastic fines; strong reaction to HCl; contains caliche nodules to 1". At 57' - silt stringer. SW-SM WELL GRADED SAND WITH SILT; 90% fine to coarse 60 subrounded to rounded sand; 10% nonplastic fines; 8x12 Sand GP trace fine gravel. (44 to 69.2 feet) POORLY GRADED GRAVEL WITH SAND - 80% fine subangular to subrounded gravel; 20% fine to coarse sand; slight reaction to HCl. 6” ID Schedule 40 At 60' - formation wet. PVC Casing SILT - Dark reddish brown (2.5YR3/4); 90% nonplastic (64 to 67.5 feet) ML fines 10% fine sand; soft formation, becomes 9-inch diameter competent with depth; abundant gypsum and caliche borehole nodules; moisture decreases with depth; strong local (67 to 69.2 feet) reaction to HCl. 7-inch diameter Upper Saint David Clay. borehole 70 (69.2 to 71 feet) Logged by MFW; Checked by DLG HARGIS + ASSOCIATES, INC. Hydrogeology/Engineering PAGE 2 OF 3 LITHOLOGIC LOG FOR MONITOR WELL MW-44 Lithologic and Well Construction Log: MW-44
Lithologic Description Well Log
(feet) Construction USCS DEPTH SAMPLE Lithologic
70 SILT Continued. Slough ML (69.2 to 71 feet)
7-inch diameter borehole CLAY - Dark reddish brown (2.5YR3/3 to 2.5YR2.5/4); (69.2 to 71 feet) 100% slight to moderately plastic fines; trace fine sand; strong reaction to HCl throughout section, contains abundant crystalline gypsum and interbedded silts.
80 Bentonite Chips (71 to 101.1 feet)
CL
90
100
TOTAL DEPTH OF BORING = 101.1 FEET BELOW LAND SURFACE
110 Logged by MFW; Checked by DLG HARGIS + ASSOCIATES, INC. Hydrogeology/Engineering PAGE 3 OF 3 LITHOLOGIC LOG FOR MONITOR WELL MW-44 APACHE NITROGEN PRODUCTS, INC. Lithologic and Well Construction Log: MW-47
Northing (ft): 31.87635 Drill Method:Sonic Easting (ft): 110.2349372 Diameter of Casing: 4-inch LS Elev. (ft): ~3,651 Type of Casing: Sch-40 PVC Ref. Pnt.:Top of Casing Slot Size: 0.020-inch Ref. Pnt. Elev. (Ft): Filter: 8-12 Total Depth bls (ft): 80.0 ADWR Reg. No. 55-918676 Depth to Water (ft): ~48 feet bls Note: ± Date:09/23/15 - 09/24/15
Lithologic Description Well Log
(feet) Construction USCS DEPTH SAMPLE Lithologic
Above Surface 0 Completion Hand Augered.
SILT (0,5,95) Strong brown (7.5YR 5/6), dry, medium plasticity; sand: fine.
Cement 10 (0 to 20 feet)
ML
At 15 to 17 feet: Increased clay content. 4” ID Schedule 40 PVC Casing (0.5 to 39.5 feet)
20 CLAY (0,0,100) Brown (7.5YR 4/4), moist, medium CL plasticity. Bentonite Chips (20 to 34.8 feet) CLAY (0,0,100) Reddish brown (5YR 4/3), moist, medium plasticity.
8.25-inch diameter CL borehole (0 to 80 feet)
30 Logged by CAP; Checked by LSL HARGIS + ASSOCIATES, INC. Hydrogeology/Engineering PAGE 1 OF 3 LITHOLOGIC LOG FOR MONITOR WELL MW-47 Lithologic and Well Construction Log: MW-47
Lithologic Description Well Log
(feet) Construction USCS DEPTH SAMPLE Lithologic
30 CLAY (0,0,100) Reddish brown (5YR 4/4), moist, CL medium plasticity. Bentonite Chips SAND WITH SILT (10,80,10) Pink (7.5YR 7/3), moist, (20 to 34.8 feet) fine- to course grained, predominantly fine to medium, SP-SM moderately sorted, sub-angular to sub-rounded. #60 Sand (34.8 to 37.3 feet) SILTY SAND (0,70,30) Light brown (7.5YR 6/4), moist, SM fine-grained, well sorted. 4” ID Schedule 40 PVC Casing 40 GRAVELLY SAND (15,85,0) Light reddish brown (5YR (0.5 to 39.5 feet) 6/4), moist, fine- to course-grained, poorly sorted, SW subangular; gravel: up to 2 inches, sub-angular to sub- rounded.
ML SANDY SILT (0,35,65) Reddish brown (5YR 4/4) moist, medium to high plasticity. SM SILTY SAND (5,80,15) Reddish brown (5YR 4/4) fine- to course-grained, predominantly fine, well sorted, sub- rounded. 4” ID Schedule 40 PVC 0.020 inch SM SILTY SAND (0,55,45) Reddish brown (5YR 5/3), Screen saturated, fine-grained, well sorted. (39.5 to 64.5 feet) At 48 feet: Driller says there is water. 50 SILTY SAND (0,85,15) Reddish Brown (5.YR 5/3), wet, SM fine- to medium-grained, trace course, well sorted.
SANDY SILT (0,35,65) Reddish brown (5YR 4/4), wet, ML medium plasticity. 8.25-inch diameter CLAYEY SAND (10,60,30) Reddish brown (5YR 5/4), borehole (0 to 80 feet) SC fine- to course-grained, predominantly fine to medium, moderately sorted. CLAY (0,5,95) Reddish brown (5YR 5/4), moist, CL medium to high plasticity. 60 CLAY (0,5,95) Reddish brown (5YR 5/4), moist, high CL plasticity; sand: medium. 8x12 Sand (37.3 to 66.5 feet)
GRAVELLY SAND (25,70,5) Pink (5YR 7/4) wet, fine- to SW course-grained, poorly sorted, sub-angular to rounded; gravel: up to 6 inches. CLAY (0,0,100) Brown (7.5YR 5/4) high plasticity. CH Bentonite Chips (66.5 to 80 feet) ML SILT (0,5,95) Brown (5YR 5/4) moist, medium plasticity. 70 Logged by CAP; Checked by LSL HARGIS + ASSOCIATES, INC. Hydrogeology/Engineering PAGE 2 OF 3 LITHOLOGIC LOG FOR MONITOR WELL MW-47 Lithologic and Well Construction Log: MW-47
Lithologic Description Well Log
(feet) Construction USCS DEPTH SAMPLE Lithologic
70 SILT continued.
ML At 73.25 feet: Interbed of SILTY SAND (0,75,25) Reddish brown (5YR 4/3) wet, fine-grained, well sorted. SILT Brown (5YR 5/4) moist, medium plasticity. Bentonite Chips (66.5 to 80 feet)
ML
8.25-inch diameter 80 borehole TOTAL DEPTH OF BORING = (0 to 80 feet) 80 FEET BELOW LAND SURFACE
90
100
110 Logged by CAP; Checked by LSL HARGIS + ASSOCIATES, INC. Hydrogeology/Engineering PAGE 3 OF 3 LITHOLOGIC LOG FOR MONITOR WELL MW-47 HARGIS + ASSOCIATES, INC.
APPENDIX B
HISTORIC GROUNDWATER ELEVATION FIGURES 3620
' ", ...... _ __
FIGURE B-2 -, I ·~B~...r-·-:w \ I WHERE WATERTABLE CONTOUR. DASHED -3660- INTERVAL 2 0 FT. INFERRED. CONTOUR 112 I SEA LEVEL. o 1/4 DATUM IS MEAN Ml~
IN WELL I- ELEVATIONOF WATERLEVEL ~11. AQUIFER. COMPLETEDIN UNCONFINED
WELLELEVATION NOT SURVEYED.
I . FIGUJt! 7-11 YATERTABLE, DECEMBER1987, UNC0?1FINED AQUIFER I APACHEPOWDER PI REPORT
,._, FIGURE B-1 FIGURE B-2 FIGURE B-3 FIGURE B-4 FIGURE B-5 FIGURE B-6 4 !(
WASH EXPLANATION ") D(18-21)08bab 3602.80 3 5 360 MW-08 !( SHALLOW AQUIFER MON ITOR WELL !( WASH 5 MW-25 D(18-21)08cda 3600.21 ") WASH SHALLOW AQUIFER PRIVATE WELL !( MW-33 MW-04 !> 3604.57 PERCHED ZONE MONITOR WELL
D *# SAN PEDRO RIVER MONITORING STATION OA SW-12 R 3.3 cfs APPROXIMATE SURFACE WATER FLOW IN 3610 CUBIC FEET PER SECOND (cfs) MW-24 !( !( R !( MW-22 E WD 3620 APPROXIMATE LINE OF EQUAL WATER ELEVATION 3600.56PO 3608.75 MW-14 IN FEET ABOVE MEAN SEA LEVEL, DASHED
HE WHERE INFERRED AC 3608.98 AP H 6 WAS ER IF MW-01 D(18-21)08cda INFERRED WATER LEVEL
AQU UTM MW-16 ") UTM APPROXIMATE BOUNDARY OF SHALLOW AQUIFER !( 3615 !( DRY EEK PERCHED ZONE R *# EPHEMERAL STREAM S C SW-12 O !( REACH WITH FLOW !( 3.3 cfs OLIN M MW-21 !( 3604.29 LATERALLY CONFINING UNIT MW-23 0 3604.48 MW-15 362 3604.19
SAN
S PEDRO OUTHER
RIVE 0 750 1,500
N N ³
P 5 R
ACIFIC ACIFIC 362 Feet R.R. MW-06 !( APACHE NITROGEN PRODUCTS, INC. MMMM BENSON, ARIZONA MMM 3624.94
WATER LEVEL ELEVATIONS IN THE SOUTHERN AREA SHALLOW AQUIFER FEBRUARY 2005
4/05 FIGURE 2 PREP BY ____BA__S REV BY ___LSL___ RPT NO ___130___.24 ARC130242Q1 05 FIGURE B-7 (!0 EXPLANATION 3595 MW-12 MW-13 SH 2 (! MW-06 WA DRY (! 3594.22 (! SHALLOW AQUIFER MON ITOR WELL SH 4 3600 WA )" D(18-21)08bab D(18-21)08bab )" SHALLOW AQUIFER PRIVATE WELL 3601.69
SH 3 (! 00 SW-12 *# SAN PEDRO RIVER MONITORING STATION WA MW-25 36 APPROXIMATE SURFACE WATER FLOW IN SH 5 3605 3600.56 CUBIC FEET PER SECOND (cfs) WA (! MW-33 3605.01 3620 APPROXIMATE LINE OF EQUAL WATER ELEVATION
D IN FEET ABOVE MEAN SEA LEVEL, DASHED
OA R WHERE INFERRED MW-24 (! (! (! MW-22 R E 3610 3600.92WD 3609.18 PO MW-14 INFERRED WATER LEVEL HE AC 6 3608.9 AP H WAS EPHEMERAL STREAM MW-01 3612.67 (! APPROXIMATE BOUNDARY OF SHALLOW AQUIFER #* 3615 SW-12 (! 3605 (! DRY
MW-21 (! 3603.94 MW-23 3604.19 MW-15 3603.99
SA 3620
N PE SOU
D
TH RO R ER
N N IVE
P R AC
IFI 3625 0 7³50 1,500 C R C
.R (! . Feet MW-06 3625.25 APACHE NITROGEN PRODUCTS, INC.
MMMM MMM BENSON, ARIZONA
WATER LEVEL ELEVATIONS IN THE SOUTHERN AREA SHALLOW AQUIFER MAY 2006
6/06 FIGURE 2 PREP BY ___BA___S REV BY ___LSL___ RPT NO ___130___.24 ARC13024-2Q2 06 FIGURE B-8 EXPLANATION
D(18-21)0Sbab • SHALLOW AQUIFER PRIVATE WELL MW-06 • SHALLOW AQUIFER MONITOR WELL SW-12 SAN PEDRO RIVER SURFACE MONITORING STATION < 1 cfs (APPROXIMATE SURFACE WATER FLOW IN SAN PEDRO RIVER IN CUBIC FEET PER SECOND (cfs)) 3620 APPROXIMATE LINE OF EQUAL WATER ELEVATION IN FEET ABOVE MEAN SEA LEVEL
INFERRED WATER LEVEL
EPHEMERAL STREAM ~ APPROXIMATE BOUNDARY OF SHALLOW AQUIFER D REACH WITH FLOW
., .. LATERALLY .. CONFINING UNIT .. I N ..'
0 750 1,500 l ~ Feet
APACHE NITROGEN PRODUCTS, INC. BENSON, ARIZONA
WATER LEVEL ELEVATIONS IN THE SOUTHERN AREA SHALLOW AQUIFER l NOVEMBER 2007
~ii;::: HARGIS+ ASSOCIATES,INC. 1/08 -===HYDROGEOLOGY•ENGINEERIHG FIGURE 2 PREP BY ...... ae.s.....REV BY _b§.L RPT NO mzL, ARC130.24 2 04 07 FIGURE B-9 EXPLANATION
0(18-21 )08bab SHALLOW AQUIFER PRIVATE WELL li1 MW-06 SHALLOW AQUIFER MONITOR WELL
SW-12 • SAN PEDRO RIVER SURFACE MONITORING STATION 1.39 cfs A (APPROXIMATE SURFACE WATER FLOW IN SAN PEDRO RIVER IN CUBIC FEET PER SECOND (cfs)) 3620 , APPROXIMATE LINE OF EQUAL WATER ELEVATION ?,6\0 IN FEET ABOVE MEAN SEA LEVEL INFERRED WATER LEVEL
MW-01 EPHEMERAL STREAM 3613.2 APPROXIMATE BOUNDARY OF SHALLOW AQUIFER . SW-12 . LATERALLY .' REACH WITH FLOW I CONFINING UNIT LA :- LY NlfJaA&.UNIT ~ IN • OLINOS CREEK AQUIFER N
0 750 1,500 ~ Feet
APACHE NITROGEN PRODUCTS, INC. BENSON, ARIZONA
WATER LEVEL ELEVATIONS IN THE SOUTHERN AREA SHALLOW AQUIFER NOVEMBER 2008
12/08 :;!!:;=HARGIS+ASSOCIATES, INC. === HYDROGEOLOGY,ENGINEERING FIGURE 2 AR FIGURE B-10 EXPLANATION 00 4 6 H 3(! AS W MW-25 3599.52
MW-33(! D(18-21)08bab ") 3602.1 SHALLOW AQUIFER PRIVATE WELL
5 SH WA 5 ( 360 MW-06 ! SHALLOW AQUIFER MONITOR WELL
SW-12 *# SAN PEDRO RIVER SURFACE MONITORING STATION < 1cfs (APPROXIMATE SURFACE WATER FLOW IN SAN PEDRO MW-24 (! MW-22 (! 3598.24 3606.71(! RIVER IN CUBIC FEET PER SECOND (cfs)) 0 MW-14 361 3620 3607.7 APPROXIMATE LINE OF EQUAL WATER ELEVATION IN FEET ABOVE MEAN SEA LEVEL
INFERRED WATER LEVEL
EPHEMERAL STREAM P-01 5 MW-04 MW-01 3665.12 > (! DRY MW-30 3612.71 MW-03 > DRY MW-32 SW-12 APPROXIMATE BOUNDARY OF SHALLOW AQUIFER DRY > DRY *#< 1 cfs P-03 5 >MW-31 3637.56 P-10 DRY MW-39 (! 6 5 5 SH DRY > 3599.84 61 REACH WITH FLOW WA MW-29(! 3 > DRY MW-21 3599.66 (! LATERALLY MW-23 CONFINING UNIT UTM
MOLINOS CREEK SAN 20 AQUIFER 36
A
PE
P A
. DR C
R
. H R O
E C
RIVE
FI P
I
OW C
PA R ³
N D
R
E 0 750 1,500
E R
TH
R
U OA O
S Feet
D 5 362
MW-06 (! 3625.69 APACHE NITROGEN PRODUCTS, INC. BENSON, ARIZONA
WATER LEVEL ELEVATIONS IN THE SOUTHERN AREA SHALLOW AQUIFER NOVEMBER 2010
02/16/2010
FIGURE B-2 FIGURE B-11 MW-25 EXPLANATION 3598.96 !( 3600 WASH 4
!( MW-33 D(18-21)08bab ") 3603.05 SHALLOW AQUIFER PRIVATE WELL 3605 WASH 5 !( MW-06 SHALLOW AQUIFER MONITOR WELL
SW-12 *# SAN PEDRO RIVER SURFACE MONITORING STATION 1.03 cfs (APPROXIMATE SURFACE WATER FLOW IN SAN PEDRO MW-24 !( !( MW-22 3610 3597.59 !( 3608.46 RIVER IN CUBIC FEET PER SECOND (cfs)) MW-14 3620 3608.77 APPROXIMATE LINE OF EQUAL WATER ELEVATION IN FEET ABOVE MEAN SEA LEVEL
INFERRED WATER LEVEL
P-01 3664.97 EPHEMERAL STREAM 5 MW-30 >MW-04 DRY !(MW-01 DRY UTM MW-03 > MW-32 SW-12 APPROXIMATE BOUNDARY OF SHALLOW AQUIFER DRY > DRY *# DRY 5 P-03 >MW-31 3637.18 5P-10 DRY !( MW-39 WASH 6 > 3598.69 REACHWITHFLOW DRY !( MW-21 3615 > 3598.91!(MW-15 MW-29 DRY DRY !( MW-23 LATERALLY 3598.61 CONFINING UNIT
MOLINOS CREEK SAN PEDRO RIVER AQUIFER 3620 PCEPWE ROAD POWDER APACHE ³
0 1,000 2,000
SOUTHERN PACIFIC R.R. Feet 3625
!( MW-06 3625.77 APACHE NITROGEN PRODUCTS, INC. BENSON, ARIZONA
WATER LEVEL ELEVATIONS IN THE SOUTHERN AREA SHALLOW AQUIFER NOVEMBER 2011
12/16/2011 Path: 2011\Southern_Water_Level_Elevation_ANP_11_11.mxd P:\Project Storage\130 - ANP\ANP GIS\Figures\130.24\Quarterly\2011\November FIGURE 2 FIGURE B-12 EXPLANATION MW-25!( 3598.54 WASH 4 3600
!( MW-33 ") 3602.69 D(18-21)08bab SHALLOW AQUIFER PRIVATE WELL
WASH 5 !( 3605 MW-06 SHALLOW AQUIFER MONITOR WELL
SW-12 *# SAN PEDRO RIVER SURFACE MONITORING STATION DRY (APPROXIMATE SURFACE WATER FLOW IN SAN PEDRO MW-24 !( !( MW-22 3596.84 !( 3608.09 RIVER IN CUBIC FEET PER SECOND (cfs)) MW-14 3608.31 3620 3610 APPROXIMATE LINE OF EQUAL WATER ELEVATION IN FEET ABOVE MEAN SEA LEVEL
INFERRED WATER LEVEL
MW-30 EPHEMERAL STREAM P-01 5 DRY 3663.89 > MW-04 !( MW-01 3662.09 3611.86 MW-03 > MW-32 SW-12 APPROXIMATE BOUNDARY OF SHALLOW AQUIFER 3636.85 > DRY *# DRY 5 P-03 >MW-31 3637.3 5 DRY !( MW-39 WASH 6 > 3597.93 REACHWITHFLOW P-10 !( MW-21 3622.4 MW-29 > 3598.46!(MW-15 DRY DRY 3615 !( MW-23 3597.96 LATERALLY
SAN PEDRO RIVER d CONFINING UNIT
MOLINOS CREEK
AQUIFER PCEPWE ROAD POWDER APACHE 3620 ³
0 1,000 2,000
SOUTHERN PACIFIC R.R. Feet
3625 !( MW-06 3625.66 APACHE NITROGEN PRODUCTS, INC. BENSON, ARIZONA
WATER LEVEL ELEVATIONS IN THE SOUTHERN AREA SHALLOW AQUIFER NOVEMBER 2012
1/18/2013 Path: 2012\Figure P:\Project 2_Southern_Water_Level_Elevation_ANP_11_12.mx Storage\130 - ANP\ANP GIS\Figures\130.24\Quarterly\2012\Nov FIGURE 2 FIGURE B-13 EXPLANATION MW-25 3600!( 3600.41 WASH 4
MW-33 3604.79 !( 3605 D(18-21)08bab ") SHALLOW AQUIFER PRIVATE WELL
WASH 5 !( MW-06 SHALLOW AQUIFER MONITOR WELL
SW-12 *# SAN PEDRO RIVER SURFACE MONITORING STATION DRY (APPROXIMATE SURFACE WATER FLOW IN SAN PEDRO MW-24 !( !( MW-22 3610 3600.38 !( 3608.71 RIVER IN CUBIC FEET PER SECOND (cfs)) MW-14 3620 3608.85 APPROXIMATE LINE OF EQUAL WATER ELEVATION IN FEET ABOVE MEAN SEA LEVEL
INFERRED WATER LEVEL
P-01 3664.4 EPHEMERAL STREAM 5 >MW-04 !(MW-01 DRY 3612.7 MW-03 > MW-32 SW-12 APPROXIMATE BOUNDARY OF SHALLOW AQUIFER DRY > DRY *# DRY 5 P-03 >MW-31 3637.58 DRY !( MW-39 WASH 6 5 MW-30> MW-21 3601.54 3615 REACHWITHFLOW P-10 DRY > !( DRY 3601.66!(MW-15 MW-29 DRY DRY !( MW-23 LATERALLY 3601.27 CONFINING UNIT
MOLINOS CREEK SAN PEDRO RIVER AQUIFER 3620 PCEPWE ROAD POWDER APACHE ³
0 1,000 2,000
SOUTHERN PACIFIC R.R. Feet 3625
!(MW-06 3625.7 APACHE NITROGEN PRODUCTS, INC. BENSON, ARIZONA
WATER LEVEL ELEVATIONS IN THE SOUTHERN AREA SHALLOW AQUIFER MAY 2012
8/20/2012 :PoetSoae10-APAPGSFgrs102\urel\01My2011\Southern_Water_Level_Elevation_ANP_05_11.mxd P:\Project Storage\130 - ANP\ANP GIS\Figures\130.24\Quarterly\2011\May FIGURE 2 FIGURE B-14 APACHE POWDER ROAD
3595 EXPLANATION MW-13 3593.58 3600 WASH 3 (!
WASH 4 D(18-21)08bab )" D(18-21)08bab SHALLOW AQUIFER PRIVATE WELL )" 3601.39 MW-06 !( SHALLOW AQUIFER MONITOR WELL WASH 5 MW-25 3600.38 (! SW-12 *# SAN PEDRO RIVER SURFACE MONITORING STATION 3605 DRY (APPROXIMATE SURFACE WATER FLOW IN SAN PEDRO MW-33 (! RIVER IN CUBIC FEET PER SECOND (cfs)) 3604.69 3620 APPROXIMATE LINE OF EQUAL WATER ELEVATION IN FEET ABOVE MEAN SEA LEVEL
MW-22 MW-24 INFERRED WATER LEVEL 3608.55 3600.5 (! (! 3610 (! MW-14 EPHEMERAL STREAM 3608.76 APPROXIMATE BOUNDARY OF SHALLOW AQUIFER
REACH WITH FLOW P-01 5 MW-04 > DRY MW-03 3664.07 DRY MW-32 > DRY > MW-39 P-03 5 MW-31 MW-30 > DRY 3601.26 3636.76 P-10 5 DRY (! DRY > 3615 WASH 6 (! MW-15 MW-29 > DRY DRY MW-21 (! 3600.99 (! LATERALLY MW-23 CONFINING UNIT 3601.16
MOLINOS CREEK SAN PEDRO RIVER AQUIFER 3620 APACHE POWDER ROAD POWDER APACHE ³ 0 1,000 2,000
Feet
SOUTHERNPACIFIC R.R. 3625 APACHE NITROGEN PRODUCTS, INC. (! BENSON, ARIZONA MW-06 3625.86 WATER LEVEL ELEVATIONS IN THE SOUTHERN AREA SHALLOW AQUIFER MAY 2013
9/11/2013 P:\Project Storage\130- ANP\ANPGIS\Figures\130.24\Quarterly\2011\May 2011\Southern_Water_Level_Elevation_ANP_05_11.mxd FIGURE 2 FIGURE B-15 APACHE POWDER ROAD
EXPLANATION
3595
WASH 3 (! MW-13 3600 3593.79 )" WASH 4 D(18-21)08bab SHALLOW AQUIFER PRIVATE WELL D(18-21)08bab (Tenopir) )" 3600.9 MW-06 !( SHALLOW AQUIFER MONITOR WELL
WASH 5 MW-25 SW-12 3600.2 *# SAN PEDRO RIVER SURFACE MONITORING STATION DRY (! (APPROXIMATE SURFACE WATER FLOW IN SAN PEDRO 3605 MW-33 RIVER IN CUBIC FEET PER SECOND (cfs)) 3604.64 3620 (! APPROXIMATE LINE OF EQUAL WATER ELEVATION IN FEET ABOVE MEAN SEA LEVEL
INFERRED WATER LEVEL
EPHEMERAL STREAM MW-22 MW-24 3610 (! (! 3608.92 3599.98 (! APPROXIMATE BOUNDARY OF SHALLOW AQUIFER MW-14 3608.8 SAN PEDRO RIVER
P-01 3663.57 5 MW-04 > DRY MW-03 MW-32 >DRY DRY SW-12 > *# DRY MW-39 5 >MW-31 P-03 P-10 3599.89 5 MW-30> DRY (! WASH 6 3635.15 DRY DRY 3615 (! MW-15 LATERALLY > MW-21 (! MW-29 DRY CONFINING UNIT DRY 3599.56 (! MW-23 MOLINOS CREEK 3600.56 AQUIFER ³
SAN PEDRO RIVER 0 1,000 2,000
3620 APACHE POWDER ROAD POWDER APACHE Feet
APACHE NITROGEN PRODUCTS, INC. BENSON, ARIZONA
SOUTHERN PACIFIC R.R. 3625 WATER LEVEL ELEVATIONS IN THE SOUTHERN AREA SHALLOW AQUIFER MAY 2014 (! MW-06 3626.05 7/23/2014 P:\Project Storage\130- ANP\ANPGIS\Figures\130.24\Quarterly\2011\May 2011\Southern_Water_Level_Elevation_ANP_05_11.mxd FIGURE 2 FIGURE B-16 3595 EXPLANATION MW-13 3594.07 WASH 3 !( 3595 3600 ") WASH 4 D(18-21)08bab SHALLOW AQUIFER PRIVATE WELL
") D(18-21)08bab (Tenopir) MW-06 !( SHALLOW AQUIFER MONITOR WELL 3603.04
WASH 5 MW-25 SW-12 3601.6 3605 *# SAN PEDRO RIVER SURFACE MONITORING STATION DRY !( (APPROXIMATE SURFACE WATER FLOW IN SAN PEDRO RIVER IN CUBIC FEET PER SECOND (cfs)) 3620 > APPROXIMATE LINE OF EQUAL WATER ELEVATION MW-33 IN FEET ABOVE MEAN SEA LEVEL 3606 INFERRED WATER LEVEL
MW-22 EPHEMERAL STREAM MW-24 3609.07 3601.78 !( !( !( 3610 APPROXIMATE BOUNDARY OF SHALLOW AQUIFER MW-14 3609.55 SAN PEDRO RIVER
P-01 3666.57 5 MW-01 ") MW-03 MW-29, -30, -31, -32 !( DRY 3612.74 MW-04 DRY") > DRY 5 !( MW-21 MW-39 P-03 5 !( !( 3601.62 3602.06 WASH 6 3637.2 P-10 !( 3615 !( !( DRY MW-15 LATERALLY DRY CONFINING UNIT !( MOLINOS CREEK MW-23 AQUIFER 3601.79 ³ 0 1,000 2,000
3620 Feet
APACHE NITROGEN PRODUCTS, INC.
APACHE POWDER ROAD BENSON, ARIZONA
WATER LEVEL ELEVATIONS IN THE 3625 SOUTHERN AREA SHALLOW AQUIFER MAY 2015 !( MW-06 3625.67 7/25/2015 P:\ProjectStorage\130 - ANP\ANP GIS\Figures\130.24\Quarterly\2011\May2011\Southern_Water_Level_Elevation_ANP_05_11.mxd FIGURE 2 FIGURE B-17 EXPLANATION
WASH 2 3595 MW-13 WASH 3 3593.41 ? (! 3600 D(18-21)08bab )" SHALLOW AQUIFER PRIVATE WELL
WASH 4 MW-06 ( )" D(18-21)08bab (Tenopir) ! SHALLOW AQUIFER MONITOR WELL 3601.27 SW-12 WASH 5 *# SAN PEDRO RIVER SURFACE MONITORING STATION DRY (APPROXIMATE SURFACE WATER FLOW IN SAN PEDRO (! MW-25 ? RIVER IN CUBIC FEET PER SECOND (cfs)) 3601.17 3605 3620 MW-33 APPROXIMATE LINE OF EQUAL WATER ELEVATION (! 3604.84 IN FEET ABOVE MEAN SEA LEVEL
INFERRED WATER LEVEL
EPHEMERAL STREAM ? MW-24 MW-22 3610 (! (! APPROXIMATE BOUNDARY OF SHALLOW AQUIFER 3601.27 (! 3608.78 MW-14 3608.93 SAN PEDRO RIVER
P-01 MW-29, -30, -31, -32 . ? 3667 > MW-03 DRY 3642.69 MW-21 MW-04 > > 3603.23 3663.29 MW-39 . P-03 > 3602.56 . MW-44 (! 3640.27 P-10 > WASH 6 3597.59 3615 (!(! MW-47 3623.44 > (! (! MW-43 3603.13 LATERALLY 3597.71 MW-15 CONFINING UNIT ! MW-23 ( DRY 3602.43 ³ 0 1,000 2,000 ? MOLINOS CREEK Feet AQUIFER 3620
APACHE NITROGEN PRODUCTS, INC. BENSON, ARIZONA APACHE POWDERROAD
WATER LEVEL ELEVATIONS IN THE SOUTHERN AREA SHALLOW AQUIFER MW-06 3625 MAY 2016 3625.41 (! 8/1/2016 P:\Project Storage\130- ANP\ANPGIS\Figures\130.24\Quarterly\2011\May 2011\Southern_Water_Level_Elevation_ANP_05_11.mxd FIGURE 2 FIGURE B-18 HARGIS + ASSOCIATES, INC.
APPENDIX C
WATER LEVEL AND WATER QUALITY HYDROGRAPHS HARGIS + ASSOCIATES, INC.
3680
3675
3670
3665 screen bottom WATER LEVEL ELEVATION (ft msl)(ft ELEVATION LEVEL WATER
3660
3655 01/90 01/92 01/94 01/96 01/98 01/00 01/02 01/04 01/06 01/08 01/10 01/12 01/14 01/16
DATE Perched Zone Piezometer P-01
40 Nitrate-N (mg/l) MCL = 10 mg/l Perchlorate (ug/l) HBGL = 14 ug/l 35 200
30
150 25
20
100 15
NITRATE CONCENTRATION (mg/l) CONCENTRATION NITRATE 10 50 PERCHLORATE CONCENTRATION (ug/l) CONCENTRATION PERCHLORATE 5 DRY = Water level below bottom of screen; No formation water is present.
0 ft msl = feet above mean sea level 0 01/90 01/92 01/94 01/96 01/98 01/00 01/02 01/04 01/06 01/08 01/10 01/12 01/14 01/16 DATE Perched Zone Piezometer P-01
FIGURE C-1. WATER LEVEL AND WATER QUALITY HYDROGRAPHS FOR PERCHED ZONE PIEZOMETER P-01 HARGIS + ASSOCIATES, INC.
3670
3665 *22 data pts. exceed range from 2/23/91- 3660 7/5/95
3655
3650
3645
3640
3635 WATER LEVEL ELEVATION (ft msl)(ft ELEVATION LEVEL WATER
3630 screen bottom
3625 01/90 01/92 01/94 01/96 01/98 01/00 01/02 01/04 01/06 01/08 01/10 01/12 01/14 01/16
DATE Perched Zone Piezometer P-03
16000 1000 15000 Nitrate-N (mg/l) MCL = 10 mg/l 900 14000
Perchlorate (ug/l) HBGL = 14 ug/l 13000 800
12000 11000 700 10000 600 9000 8000 500 7000 400 6000
5000 300 4000 3000 200 NITRATE CONCENTRATION (mg/l) CONCENTRATION NITRATE
2000 (ug/l) CONCENTRATION PERCHLORATE 100 1000 0 0 1/90 1/92 1/94 1/96 1/98 1/00 1/02 1/04 1/06 1/08 1/10 1/12 1/14 1/16
DATE Perched Zone Piezometer P-03
FIGURE C-2. WATER LEVEL AND WATER QUALITY HYDROGRAPHS FOR PERCHED ZONE PIEZOMETER P-03 HARGIS + ASSOCIATES, INC.
3650
3645
3640
3635
3630 WATER LEVEL ELEVATION (ft msl)(ft ELEVATION LEVEL WATER
3625
DRY
3620 screen bottom 01/90 01/92 01/94 01/96 01/98 01/00 01/02 01/04 01/06 01/08 01/10 01/12 01/14 01/16 DATE Perched Zone Piezometer P-10
500 Nitrate-N (mg/l) MCL = 10mg/l
400
300
200 CONCENTRATION (mg/l) CONCENTRATION
100
MCL =10 mg/l 0 1/90 1/92 1/94 1/96 1/98 1/00 1/02 1/04 1/06 1/08 1/10 1/12 1/14 1/16 DATE Perched Zone Piezometer P-10
FIGURE C-3. WATER LEVEL AND WATER QUALITY HYDROGRAPHS FOR PERCHED ZONE PIEZOMETER P-10 HARGIS + ASSOCIATES, INC.
3665
3660
3655
3650
3645 WATER LEVEL ELEVATION (ft msl)(ft ELEVATION LEVEL WATER 3640
screen bottom DRY 3635 1/90 1/92 1/94 1/96 1/98 1/00 1/02 1/04 1/06 1/08 1/10 1/12 1/14 1/16 DATE Perched Zone Monitor Well MW-03
3000 100
Nitrate-N (mg/l) MCL = 10mg/l
Perchlorate (ug/l) HBGL = 14 ug/l 2500 g/l)
80 μ
2000
60
1500 DRY = Water level below bottom of screen; No formation water is present. ft msl = feet above mean sea level 40
1000
NITRATE CONCENTRATION (mg/l) CONCENTRATION NITRATE 20 500 PERCHLORATE CONCENTRATION ( CONCENTRATION PERCHLORATE
0 0 1/90 1/92 1/94 1/96 1/98 1/00 1/02 1/04 1/06 1/08 1/10 DRY1/12 1/14 1/16 DATE Perched Zone Monitor Well MW-03
FIGURE C-4. WATER LEVEL AND WATER QUALITY HYDROGRAPHS FOR PERCHED ZONE MONITOR WELL MW-03 HARGIS + ASSOCIATES, INC.
3675
3670 WATER LEVEL ELEVATION (ft msl)(ft ELEVATION LEVEL WATER
3665
screen bottom DRY
3660 1/90 1/92 1/94 1/96 1/98 1/00 1/02 1/04 1/06 1/08 1/10 1/12 1/14 1/16 DATE Perched Zone Monitor Well MW-04
FIGURE C-5. WATER LEVEL HYDROGRAPH FOR PERCHED ZONE MONITOR WELL MW-04 HARGIS + ASSOCIATES, INC.
3620
3615 Constructed 5/2000 Constructed
3610 screen bottom DRY WATER LEVEL ELEVATION (ft msl) msl)(ft ELEVATION LEVEL WATER 3605
3600 01/90 01/92 01/94 01/96 01/98 01/00 01/02 01/04 01/06 01/08 01/10 01/12 01/14 01/16 DATE Perched Zone Monitor Well MW-29
1000 200
Nitrate-N (mg/l) MCL = 10 mg/l 900 180 Perchlorate (ug/l) HBGL = 14 ug/l
800 160
700 140
600 120
500 100
400 80
300 60
200 40 NITRATE CONCENTRATION (mg/l) CONCENTRATION NITRATE 100 20 PERCHLORATE CONCENTRATION (ug/l) CONCENTRATION PERCHLORATE
0 0 1/90 1/92 1/94 1/96 1/98 1/00 1/02 1/04 1/06 1/08 1/10 1/12 1/14 1/16 DATE Perched Zone Monitor Well MW-29
FIGURE C-6. WATER LEVEL AND WATER QUALITY HYDROGRAPHS FOR PERCHED ZONE MONITOR WELL MW-29 HARGIS + ASSOCIATES, INC.
3620
3615
3610
WATER LEVEL ELEVATION (ft msl)(ft ELEVATION LEVEL WATER 3605
DRY 3600 screen bottom 1/90 1/92 1/94 1/96 1/98 1/00 1/02 1/04 1/06 1/08 1/10 1/12 1/14 1/16 DATE Molinos Creek Sub-Aquifer Monitor Well MW-15
1000 1000
900 Nitrate-N (mg/l) MCL = 10 mg/l 900
Perchlorate (ug/l) HBGL = 14 ug/l 800 800
700 700
600 600
500 500
400 400
300 300
NITRATE CONCENTRATION (mg/l) CONCENTRATION NITRATE 200 200 PERCHLORATE CONCENTRATION (ug/l) CONCENTRATION PERCHLORATE
100 100
0 0 1/90 1/92 1/94 1/96 1/98 1/00 1/02 1/04 1/06 1/08 1/10 1/12 1/14 1/16 DATE Molinos Creek Sub-Aquifer Monitor Well MW-15
FIGURE C-7. WATER LEVEL AND WATER QUALITY HYDROGRAPHS FOR MOLINOS CREEK MNA MANAGEMENT ZONE MONITOR WELL MW-15 HARGIS + ASSOCIATES, INC.
3620
3615
3610
3605 WATER LEVEL ELEVATION (ft msl)(ft ELEVATION LEVEL WATER 3600
3595 1/90 1/92 1/94 1/96 1/98 1/00 1/02 1/04 1/06 1/08 1/10 1/12 1/14 1/16 DATE Molinos Creek Sub-Aquifer Monitor Well MW-21
7500 500
7000 Nitrate-N (mg/l) MCL = 10mg/l
6500 g/l)
Perchlorate (ug/l) HBGL = 14 ug/l μ 6000 400
5500
5000
4500 300
4000
3500
3000 200
2500 NITRATE CONCENTRATION (mg/l) CONCENTRATION NITRATE
2000 ( CONCENTRATION PERCHLORATE
1500 100
1000
500
0 0 1/90 1/92 1/94 1/96 1/98 1/00 1/02 1/04 1/06 1/08 1/10 1/12 1/14 1/16 DATE Molinos Creek Sub-Aquifer Monitor Well MW-21
FIGURE C-8. WATER LEVEL AND WATER QUALITY HYDROGRAPHS FOR MOLINOS CREEK MNA MANAGEMENT ZONE MONITOR WELL MW-21 HARGIS + ASSOCIATES, INC.
3620
3615
3610
3605
3600 WATER LEVEL ELEVATION (ft msl)(ft ELEVATION LEVEL WATER Constructed 8/99
3595 screen bottom
3590 1/90 1/92 1/94 1/96 1/98 1/00 1/02 1/04 1/06 1/08 1/10 1/12 1/14 1/16 DATE Molinos Creek Sub-Aquifer Monitor Well MW-23
50 100
Nitrate-N (mg/l) MCL = 10mg/l
g/l)
40 Perchlorate (ug/l) HBGL = 14 ug/l 80 μ
30 60
20 40 NITRATE CONCENTRATION (mg/l) CONCENTRATION NITRATE PERCHLORATE CONCENTRATION ( CONCENTRATION PERCHLORATE
10 20 MCL =10 mg/l
0 0 1/90 1/92 1/94 1/96 1/98 1/00 1/02 1/04 1/06 1/08 1/10 1/12 1/14 1/16 DATE Molinos Creek Sub-Aquifer Monitor Well MW-23
FIGURE C-9. WATER LEVEL AND WATER QUALITY HYDROGRAPHS FOR MOLINOS CREEK MNA MANAGEMENT ZONE MONITOR WELL MW-23 HARGIS + ASSOCIATES, INC.
3615
3610
3605
3600
WATER LEVEL ELEVATION (ft msl)(ft ELEVATION LEVEL WATER
3595 Constructed 8/99
3590 1/90 1/92 1/94 1/96 1/98 1/00 1/02 1/04 1/06 1/08 1/10 1/12 1/14 1/16 DATE Molinos Creek Sub-Aquifer Monitor Well MW-24
15 50 Nitrate-N (mg/l) MCL = 10mg/l 45
Perchlorate (ug/l) HBGL = 14 ug/l g/l)
12 40 μ
MCL =10 mg/l 35
9 30
25
6 20
15
NITRATE CONCENTRATION (mg/l) CONCENTRATION NITRATE 3 10 PERCHLORATE CONCENTRATION ( CONCENTRATION PERCHLORATE
5
0 0 1/90 1/92 1/94 1/96 1/98 1/00 1/02 1/04 1/06 1/08 1/10 1/12 1/14 1/16 DATE Molinos Creek Sub-Aquifer Monitor Well MW-24
FIGURE C-10. WATER LEVEL AND WATER QUALITY HYDROGRAPHS FOR MOLINOS CREEK MNA MANAGEMENT ZONE MONITOR WELL MW-24 HARGIS + ASSOCIATES, INC.
3610
3605
3600
WATER LEVEL ELEVATION (ft msl)(ft ELEVATION LEVEL WATER 3595 Constructed6/2007
3590 1/90 1/92 1/94 1/96 1/98 1/00 1/02 1/04 1/06 1/08 1/10 1/12 1/14 1/16 DATE Molinos Creek Sub- Aquifer Monitor Well MW-39
500 500
Nitrate-N (mg/l) MCL = 10mg/l
Perchlorate (ug/l) HBGL = 14 ug/l
g/l)
400 400 μ
DRY = Water level below bottom of screen; No formation water is present. ft msl = feet above mean sea level 300 300
200 200
NITRATE CONCENTRATION (mg/l) CONCENTRATION NITRATE 100 100 PERCHLORATE CONCENTRATION ( CONCENTRATION PERCHLORATE
0 MCL =10 0 1/90 1/92 1/94 mg/l1/96 1/98 1/00 1/02 1/04 1/06 1/08 1/10 1/12 1/14 1/16 DATE Molinos Creek Sub-Aquifer Monitor Well MW-39
FIGURE C-11. WATER LEVEL AND WATER QUALITY HYDROGRAPHS FOR MOLINOS CREEK MNA MANAGEMENT ZONE MONITOR WELL MW-39 HARGIS + ASSOCIATES, INC.
3625
3620
3615
WATER LEVEL ELEVATION (ft msl)(ft ELEVATION LEVEL WATER 3610
3605 1/90 1/92 1/94 1/96 1/98 1/00 1/02 1/04 1/06 1/08 1/10 1/12 1/14 1/16
DATE Shallow Aquifer Monitor Well MW-01
20 3.5
Nitrate-N (mg/l) MCL = 10mg/l
3 g/l) Perchlorate (ug/l) HBGL = 14 ug/l 16 μ
2.5
12 2
MCL =10 mg/l 1.5 8
1 NITRATE CONCENTRATION (mg/l) CONCENTRATION NITRATE
4 ( CONCENTRATION PERCHLORATE 0.5
0 0 1/90 1/92 1/94 1/96 1/98 1/00 1/02 1/04 1/06 1/08 1/10 1/12 1/14 1/16
DATE Shallow Aquifer Monitor Well MW-01
FIGURE C-12. WATER LEVEL AND WATER QUALITY HYDROGRAPHS FOR SOUTHERN AREA MNA UPGRADIENT MONITOR WELL MW-01 HARGIS + ASSOCIATES, INC.
3645
3640
3635
3630
3625 WATER LEVEL ELEVATION (ft msl)(ft ELEVATION LEVEL WATER
3620
3615 1/90 1/92 1/94 1/96 1/98 1/00 1/02 1/04 1/06 1/08 1/10 1/12 1/14 1/16 DATE Shallow Aquifer Monitor Well MW-06
225 1
Nitrate-N (mg/l) MCL = 10mg/l 200
g/l)
Perchlorate (ug/l) HBGL = 14 ug/l 0.8 μ 175
150
0.6 125
100 0.4
75 NITRATE CONCENTRATION (mg/l) CONCENTRATION NITRATE PERCHLORATE CONCENTRATION ( CONCENTRATION PERCHLORATE 50 0.2
25
MCL =10 mg/l 0 0 1/90 1/92 1/94 1/96 1/98 1/00 1/02 1/04 1/06 1/08 1/10 1/12 1/14 1/16
DATE Shallow Aquifer Monitor Well MW-06
FIGURE C-13. WATER LEVEL AND WATER QUALITY HYDROGRAPHS FOR SOUTHERN AREA MNA UPGRADIENT MONITOR WELL MW-06 HARGIS + ASSOCIATES, INC.
3620
3615
3610
WATER LEVEL ELEVATION (ft msl)(ft ELEVATION LEVEL WATER 3605
3600 1/90 1/92 1/94 1/96 1/98 1/00 1/02 1/04 1/06 1/08 1/10 1/12 1/14 1/16 DATE Shallow Aquifer Monitor Well MW-14
50 3.5 Nitrate-N (mg/l) MCL = 10mg/l 45
Perchlorate (ug/l) HBGL = 14 ug/l 3 g/l)
40 μ
35 2.5
30 2
25
1.5 20
15 1 NITRATE CONCENTRATION (mg/l) CONCENTRATION NITRATE PERCHLORATE CONCENTRATION ( CONCENTRATION PERCHLORATE 10
MCL =10 0.5
5 mg/l
0 0 1/90 1/92 1/94 1/96 1/98 1/00 1/02 1/04 1/06 1/08 1/10 1/12 1/14 1/16 DATE Shallow Aquifer Monitor Well MW-14
FIGURE C-14. WATER LEVEL AND WATER QUALITY HYDROGRAPHS FOR SOUTHERN AREA MNA SENTINEL MONITOR WELL MW-14 HARGIS + ASSOCIATES, INC.
3620
3615
3610 Constructed 8/99
3605 WATER LEVEL ELEVATION (ft msl)(ft ELEVATION LEVEL WATER
3600 1/90 1/92 1/94 1/96 1/98 1/00 1/02 1/04 1/06 1/08 1/10 1/12 1/14 1/16 DATE Shallow Aquifer Monitor Well MW-22
20
Nitrate-N (mg/l) MCL = 10mg/l
Perchlorate (ug/l) HBGL = 14 ug/l g/l)
16 μ
12
MCL =10 mg/l
8
NITRATE CONCENTRATION (mg/l) CONCENTRATION NITRATE DRY = Water level below bottom of screen; No formation water is present.
ft msl = feet above mean sea level ( CONCENTRATION PERCHLORATE
4
0 0 1/90 1/92 1/94 1/96 1/98 1/00 1/02 1/04 1/06 1/08 1/10 1/12 1/14 1/16 DATE Shallow Aquifer Monitor Well MW-22
FIGURE C-15. WATER LEVEL AND WATER QUALITY HYDROGRAPHS FOR SOUTHERN AREA MNA SENTINEL MONITOR WELL MW-22 HARGIS + ASSOCIATES, INC.
3610
3605
3600 Constructed 5/00
WATER LEVEL ELEVATION (ft msl)(ft ELEVATION LEVEL WATER 3595
3590 1/90 1/92 1/94 1/96 1/98 1/00 1/02 1/04 1/06 1/08 1/10 1/12 1/14 1/16 DATE Shallow Aquifer Monitor Well MW-25
20 1
Nitrate-N (mg/l) MCL = 10mg/l 0.9
Perchlorate (ug/l) HBGL = 14 ug/l g/l)
16 0.8 μ
0.7
12 0.6
MCL =10 mg/l 0.5
8 0.4
0.3 NITRATE CONCENTRATION (mg/l) CONCENTRATION NITRATE
4 0.2 ( CONCENTRATION PERCHLORATE
0.1
0 0 1/90 1/92 1/94 1/96 1/98 1/00 1/02 1/04 1/06 1/08 1/10 1/12 1/14 1/16
DATE Shallow Aquifer Monitor Well MW-25
FIGURE C-16. WATER LEVEL AND WATER QUALITY HYDROGRAPHS FOR SOUTHERN AREA MNA BUFFER ZONE MONITOR WELL MW-25 HARGIS + ASSOCIATES, INC.
3615
3610
3605 Constructed 9/2002
3600 WATER LEVEL ELEVATION (ft msl)(ft ELEVATION LEVEL WATER
3595 1/90 1/92 1/94 1/96 1/98 1/00 1/02 1/04 1/06 1/08 1/10 1/12 1/14 1/16 DATE Shallow Aquifer Monitor Well MW-33
20 3.5
Nitrate-N (mg/l) MCL = 10mg/l
Perchlorate (ug/l) HBGL = 14 ug/l 3 g/l)
16 μ
2.5
12 2
MCL =10 mg/l
1.5 8 DRY = Water level below bottom of screen; No formation water is present. ft msl = feet above mean sea level
1 NITRATE CONCENTRATION (mg/l) CONCENTRATION NITRATE PERCHLORATE CONCENTRATION ( CONCENTRATION PERCHLORATE 4 0.5
0 0 1/90 1/92 1/94 1/96 1/98 1/00 1/02 1/04 1/06 1/08 1/10 1/12 1/14 1/16 DATE Shallow Aquifer Monitor Well MW-33
FIGURE C-17 WATER LEVEL AND WATER QUALITY HYDROGRAPHS FOR SOUTHERN AREA MNA BUFFER ZONE MONITOR WELL MW-33 HARGIS + ASSOCIATES, INC.
APPENDIX D
TRANSPIRATION AND EVAPOTRANSPIRATION CONCEPTS
APPENDIX D TRANSPIRATION AND EVAPOTRANSPIRATION CONCEPTS
An important concept relating to the hydrogeologic system present in Perched Zone A (PZ-A) and Perched Zone B (PZ-B) is that of transpiration by phreatophytic vegetation present at the site. Specifically, the area overlying the footprints of PZ-A and PZ-B has extensive stands of mesquite trees, which are known phreatophytes (Figure D-1). For example, Figure D-2 shows the hydrograph recorded quarterly at monitor well MW-21 over the period from 1997 through 2016. In particular, over the period from 1997 through 2014, the time series depicts water level declines with a seasonal overprint with amplitudes up to approximately two feet. This pattern is attributed to: • Minimal recharge to the system. • Transpirational effects of the mesquite phreatophytes.
The latter part of the hydrograph is believed to be the result of recharge that occurred during the exceptionally high period of precipitation in 2014, which was double the average of previous years. Thus, it is seen that under typical climatic conditions, there is little recharge occurring in the system.
The following sections provide further explanation of the effects of the transpiration phenomena.
Conceptualization
Transpiration is the process by which moisture is carried through plants from roots to small pores on the underside of leaves, where it changes to vapor and is released to the atmosphere. Transpiration is essentially evaporation of water from plant leaves (USGS, 2016a). When phreatophytes tap into the water table to access water for the process of transpiration, their utilization, if at a sufficient rate, can produce a localized depression in the water table as shown in figure D-3.
Figure D-3. Example of phreatophyte causing localized, seasonal depression in water table. (after USGS, 2016a). Note that this effect is seasonal, responding to the seasonal utilization of groundwater by the phreatophytes.
Characteristics of Mesquite Trees
In order to utilize groundwater, phreatophytes must have root systems that are capable of accessing water at whatever depths groundwater is present. If shallow water or surface water is available, they will generally utilize those sources. On the other hand, some phreatophytes, mesquites for example, can have long taproots extending to depths exceeding 50 feet up to perhaps 90 feet.
Within PZ-B, the water table recently has been typically measured at depths ranging from 50 to 60 feet bls. Considering the rate and degree of decline in the water table, nearly a foot per year and approximately 15 feet, respectively, phreatophyte root systems must potentially be capable of reaching or growing to these depths below land surface. Such characteristics have been well- documented in the technical literature (For example, Robinson1958; Ansley, et al. ND; Nielsen, et al., 1983; Stromberg, et al., 1992; Meader 2014; USGS, 2006 a, b).
Evapotranspiration
Evapotranspiration, in contrast to transpiration, is defined as the water lost to the atmosphere from the ground surface, evaporation from the capillary fringe of the groundwater table, and the transpiration of groundwater by plants whose roots tap the capillary fringe of the groundwater table (USGS, 2016b). Thus, evapotranspiration represents the sum of evaporative and transpirational effects. This is illustrated conceptually on Figure D-4, which shows soil water losses from both the effect of plant transpiration and evaporation from the soil surface.
Figure D-4. Conceptualization of evapotranspiration of soil water (after USGS, 2016b).
With regard to the hydrographic responses observed at PZ-B, it is believed that transpiration dominates over evapotranspiration, although some would prefer to refer to the inclusive term of evapotranspiration. It is also noted that in PZ-A, evaporation is utilized as a discharge measure. Perched groundwater is pumped periodically from piezometer P-03 into steel stock tanks where it is left to evaporate, thereby reducing the volume of perched groundwater in storage. References
Ansley, R.J., J.A. Huddle, and B.A. Krampk, ND. Mesquite Ecology. Texas Agricultural Experiment Station. Accessed at: http://texnat.tamu.edu/library/symposia/brush- sculptors-innovations-for-tailoring-brushy-rangelands-to-enhance-wildlife-habitat-and- recreational-value/mesquite-ecology/.
Meader, N., 2014. Riparian Mesquite: How Much Water Does It Use? Accessed at: http://cascabelconservation.org/downloads/Mesquite%20Water%20Use%20Info%20She et-9-28-14.pdf.
Nielsen, E.T., M.R. Sharifi, P.W. Rundel, W.M. Jarrell, and R.A. Virginia, 1983. Diurnal and Seasonal Water Relations of the Desert Phreatophyte Prosopis Glandulosa (Honey Mesquite) in the Sonoral Desert of California. Ecology (64)6, p. 1381-1393.
Robinson, T.W., 1958. Phreatophytes, Geological Survey Water-Supply Paper 1423.
Stromberg, J.C., J.A. Tress, S.D. Wilkins, S.D. Clark, 1992. Response of Velvet Mesquite to Groundwater Decline. Abstract accessed at: https://asu.pure.elsevier.com/en/publications/response-of-velvet-mesquite-to- groundwater-decline.
U.S. Geological Survey [USGS], 2006a. Distribution Patterns, Effects of Hydrologic Conditions, and Water Use by Riparian Vegetation. Accessed at: https://pubs.usgs.gov/fs/2006/3027/.
_____, 2006b. Hydrologic Requirements of and Evapotranspiration by Riparian Vegetation along the San Pedro River, Arizona. Accessed at: https://pubs.usgs.gov/fs/2006/3027/.
_____, 2016a. Transpiration – The Water Cycle. Accessed at: https://water.usgs.gov/edu/watercycletranspiration.html.
_____, 2016b. Evapotranspiration – The Water Cycle. Accessed at: https://water.usgs.gov/edu/watercycleevapotranspiration.html. HARGIS + ASSOCIATES, INC.
FIGURES ANPI PROPERTY LINE
MW-03 A!
PERCHED ZONE A A! P-03 P-10 MW-39 A! A! ? MW-21 MW-44 PERCHED ZONE B MW-29 A!!A! ! A MW-47 A MW-43 MW-15 ! A! A ?
? ? ? MW-23 A! ? ?
Source: Esri, DigitalGlobe, GeoEye, Earthstar Geographics, CNES/Airbus DS, USDA, USGS, AEX, Getmapping, Aerogrid, IGN, IGP, swisstopo, and the GIS User Community
FIGURE D-1 DISTRIBUTION OF MESQUITE TREES ACROSS PERCHED ZONE-A AND PERCHED ZONE-B HARGIS + ASSOCIATES, INC.
3620
3615
3610
3605 WATER LEVEL ELEVATION (ft msl) (ft ELEVATION LEVEL WATER 3600
3595 1/90 1/92 1/94 1/96 1/98 1/00 1/02 1/04 1/06 1/08 1/10 1/12 1/14 1/16 1/18 DATE Perched Zone B Monitor Well MW-21
7500 500
7000 Nitrate-N (mg/l) MCL = 10mg/l
6500 Perchlorate (ug/l) HBGL = 14 ug/l g/l) μ 6000 400
5500
5000
4500 300
4000
3500
3000 200
2500 NITRATECONCENTRATION (mg/l)
2000 ( CONCENTRATION PERCHLORATE
1500 100
1000
500 MCL = 10mg/l 0 0 1/90 1/92 1/94 1/96 1/98 1/00 1/02 1/04 1/06 1/08 1/10 1/12 1/14 1/16 1/18 DATE Perched Zone B Monitor Well MW-21
FIGURE D-2 WATER LEVEL AND WATER QUALITY HYDROGRAPHS FOR PERCHED ZONE B MONITOR WELL MW-21 HARGIS + ASSOCIATES, INC.
APPENDIX E
PREVIOUS SOUTHERN AREA CSM REPORTS-DATA CD
CHARACTERIZATION OF GROUNDWATER SYSTEMS IN THE SOUTHERN AREA REVISION 1.0 DATED JUNE 10, 2003
SOUTHERN AREA CHARACTERIZATION REPORT DATED MARCH 27, 2007