Existing Salt Deposit Study TM & EPA Review Comments

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From: Wangerud, Ken To: "David Abranovic" Cc: Catherine D. LeCours ([email protected]); Justin Burning; Kevin Lundmark; Aaron Baird Subject: RE: Existing Salt Deposit Study TM - EPA review/comments Date: Tuesday, May 23, 2017 2:33:00 PM Attachments: image001.png image002.png EPA comments on Existing Salt Deposit Study_Final5Dec2016.pdf

David:

I apologize for the tardiness of these comments; I appreciate Catherine LeCours reminding me that this remained outstanding. Our PM’s conversation yesterday about the status of the SCTS brine/leach-testing reminded me this was also something needing catch-up.

Please incorporate these comments into the SCTS work as consideration of salt-cap possibilities continues towards the FS work for the site.

Cheers, Ken

Ken Wangerud Remedial Project Manager Superfund Remedial Program Ecosystem Protection & Remediation U.S. EPA – Region 8 1595 Wyncoop Street Denver, CO 80202-1129 Ofc. Tel. 303-312-6703

From: David Abranovic [mailto:[email protected]] Sent: Thursday, September 29, 2016 1:13 PM To: Wangerud, Ken Cc: R. David Gibby ([email protected]) ; Catherine D. LeCours ([email protected]) ; Justin Burning ; Kevin Lundmark Subject: RE: Existing Salt Deposit Study TM

Ken,

Please find attached the US Mag Existing Salt Deposit Study Technical Memorandum for your review. This study was completed according to the methodology in the Tier 1 Salt Cap Treatability Study Work Plan (April 2016) and addresses the first objective of the Tier 1 SCTS to evaluate the weathering of existing salt caps (salt deposits) in order to provide qualitative information on the short-term and/or long-term behavior of salt deposits.

Please feel free to call me if you have any questions regarding this submittal.

David Abranovic Partner

ERM 7272 E Indian School Road, Suite 108 | Scottsdale, AZ | 85251 T +1 480 455 6070 | M +1 602 284 4917 E [email protected] | W www.erm.com

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Please visit ERM's web site: http://www.erm.com From: Wangerud, Ken To: "David Abranovic" Cc: Catherine D. LeCours ([email protected]); Justin Burning; Kevin Lundmark; Aaron Baird Subject: RE: Existing Salt Deposit Study TM - EPA review/comments Date: Tuesday, May 23, 2017 2:33:00 PM Attachments: image001.png image002.png EPA comments on Existing Salt Deposit Study_Final5Dec2016.pdf

David:

Please incorporate these comments into the SCTS work as consideration of salt-cap possibilities continues towards the FS work for the site.

Cheers, Ken

Ken Wangerud Remedial Project Manager Superfund Remedial Program Ecosystem Protection & Remediation U.S. EPA – Region 8 1595 Wyncoop Street Denver, CO 80202-1129 Ofc. Tel. 303-312-6703

Ken,

Please feel free to call me if you have any questions regarding this submittal.

David Abranovic Partner

ERM 7272 E Indian School Road, Suite 108 | Scottsdale, AZ | 85251 T +1 480 455 6070 | M +1 602 284 4917 E [email protected] | W www.erm.com

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Please visit ERM's web site: http://www.erm.com EPA’s Technical Comments on ERM’s Existing Salt Deposit Study Technical Memorandum (29 September 2016) U.S. MAGNESIUM NPL SITE, TOOELE COUNTY, UTAH 5 December 2016

The U.S. Environmental Protection Agency (EPA) is providing the following comments on the Existing Salt Deposit Study Technical Memorandum (Tech Memo) dated 29 September 2016. The Tech Memo was prepared by US Magnesium’s contractor, Environmental Resources Management (ERM), and summarizes the observations from the field reconnaissance activities conducted on 6 June 2016 at three existing salt caps/deposits: the former Knolls Solar Ponds 0 and 1, Cargill Salt Ponds 2 and 3 East, and US Magnesium Solar Evaporation Pond 1 South. Mr. Aaron Baird of PWT was onsite to provide EPA oversight of the salt cap reconnaissance activities. Reconnaissance activities were performed in accordance with Sections 4.1 and 8.1 of the Tier 1 Salt Cap Treatability Study Work Plan dated April 2016. EPA generally agrees with the ERM observations documented in the Tech Memo; however, PWT noted additional observations that were not mentioned in the Tech Memo.

GENERAL COMMENTS

1. Topography appears to play an important role in salt accumulation and erosion. In the former Knolls solar ponds, west of the sand dunes, the ponds are relatively flat but have a very gradual slope to the west/northwest. The thickness of the salt deposit was significantly greater in the west/northwest portion of the ponds and there was much less erosion. ERM shall revise the Tech Memo to include discussion regarding topagraphical impact on salt accumulation and erosion.

2. In the Weathering Characteristics and Behaviors discussion for the former Knolls solar ponds (second bullet, page 4 of the Tech Memo) it is noted that where external drainage of surface water runoff occurs, erosional features in the salt deposit were observed, including cracks up to 6 inches wide, rills up to 5 feet wide, and channels up to 20 feet wide and 6 feet deep. ERM shall revise the Tech Memo to include photographs of these features if available. Examples of these features are shown in the following photographs taken in Knolls Pond 1 during a site visit in May 2013.

3. Flowing groundwater seeps were present in lower elevation areas along the western portion of the former Knolls solar ponds. Examples of these features are shown in Photograph 17 of the Tech Memo and in the following photograph of Pond 0. ERM shall revise the Tech Memo to include this discussion and additional photographs as necessary.

4. The Tech Memo reports weathering characteristics and behaviors of salt deposits at US Magnesium’s Solar Pond 1S were not observed due to the inundation of brine. The assessment of Pond 1S is incomplete and the pond shall be re-visited during a more optimal time (possibly Fall?) when the weathering characteristics and behaviors can be observed. ERM shall prepare an addendum to the Existing Salt Deposit Study Technical Memorandum to report the observations of Pond 1S. Ken Wangerud, EPA, captured the following photo during a site visit in May 2013. This photograph was taken from the north berm separating US Magnesium Solar Pond 1N and 1S. The view is looking south over brine waters with an approximate 10 to 20 foot diameter dissolution-cavity visible approximately 50 feet south of the berm. The cavity purportedly forms from water moving through the berm from the higher head-elevation water of Pond 1N and upwelling into Pond 1S (per Tom Tripp, US Magnesium). There were numerous such features in Pond 1S along the length of the berm/levee. These are features that warrant attention, particularly as related to ERM’s note that there was also such a feature in the Cargill salt flat (second bullet, page 7 of the Tech Memo).

Environmental Technical Memorandum Resources Management

To: Ken Wangerud, USEPA 7272 E. Indian School Road Suite 108 From: Lonnie Mercer P.G., ERM Scottsdale, AZ 85251 Kevin Lundmark, ERM (480) 998-2401 (480) 424-1818 (fax) David Abranovic P.E., ERM

Date: 29 September 2016 Subject: Existing Salt Deposit Study II ------ERM®

INTRODUCTION

This Existing Salt Deposit Study Technical Memorandum (Tech Memo) has been prepared to describe observations from field reconnaissance activities performed on 6 June 2016 for three salt deposits. Reconnaissance activities were performed in accordance with Sections 4.1 and 8.1 of the Tier 1 Salt Cap Treatability Study Work Plan (SCTS Work Plan) dated April 2016 (ERM-West, Inc. [ERM] 2016). The SCTS Work Plan was prepared by ERM to define the scope of work for a treatability study that will provide basic information about a salt cap barrier remedial alternative that will be evaluated in the feasibility study for the US Magnesium National Priority List (NPL) site in Rowley, Tooele County, Utah. The Tier 1 SCTS Work Plan is the first step in the evaluation process for a salt cap barrier and is designed to provide basic high level information about how a salt cap barrier remedy would perform at the US Magnesium NPL site.

An objective of the Tier 1 SCTS is to evaluate the weathering characteristics of existing salt caps (salt deposits) to provide qualitative information on the short-term and/or long-term performance of salt deposits as a barrier to underlying soil and sediment. The questions to be answered by the existing salt deposit study are: 1. How do salt caps weather? 2. What are the short-term and long-term behaviors of salt caps?

These questions were answered by performing a qualitative field reconnaissance of existing salt caps (salt deposits) in the Great Salt Lake (GSL) basin to document weathering characteristics and behaviors. In addition, the salt deposit reconnaissance evaluated salt deposits to ascertain, where possible, the comparability of evaporite types and

substrate materials with US Magnesium-specific materials and substrate

PAGE 2 conditions. The weathering of salt deposits was evaluated by observing the deposits for indications of erosion by wind or water runoff, dissolution by precipitation or underlying groundwater, the formation/sealing of desiccation cracks, and variations in surface competence. The short-term and long-term behaviors were evaluated by comparing properties of salt deposits of varying ages.

Three existing salt deposits were observed during the reconnaissance: the former Knolls solar ponds, Cargill Salt, and US Magnesium Solar Evaporation Pond 1 South (Figure 1). The salt deposit reconnaissance was performed by Mr. Lonnie Mercer (ERM), who was accompanied by Mr. Don Silva (US Magnesium) to facilitate access and to provide information regarding Solar Pond 1 South and historical operations at the former Knolls solar ponds. Mr. Aaron Baird (Pacific Western Technologies) provided United States Environmental Protection Agency oversight of reconnaissance activities. Mr. Bill Ratcliff (Cargill) accompanied the reconnaissance team at the Cargill Salt facility.

Observations and photographs were collected at 13 locations during the reconnaissance. Each location was recorded using a GPS instrument, and key observations for each location are summarized in Table 1. Photographs are provided in Attachment A, and observation locations are illustrated on Figures 2 and 3. Core sampling was performed at two locations at the former Knolls solar ponds (observation locations 3 and 10) and is described in Table 1.

FORMER KNOLLS SOLAR PONDS

The former Knolls solar ponds are located just north of the Knolls exit on Interstate 80 (Exit No 41), approximately 27 miles west-southwest from the US Magnesium plant (Figures 1 and 2). The Knolls solar ponds were constructed in 1987 by AMAX, the operator of the Rowley magnesium plant at the time. The Knolls solar ponds provided an alternate source of brine feedstock after the rising water levels in the GSL inundated AMAX’s Stansbury Basin solar ponding complex in June 1986.

The Knolls solar ponds were constructed at the southeast corner of Newfoundland Basin, which received brine inflow from GSL between April 1987 and June 1989 as part of the West Desert Pumping Project. The

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West Desert Pumping Project was initiated to remove brine from GSL in an effort to help mitigate flooding in the GSL Basin caused by elevated lake levels of GSL. Brine from GSL was pumped to Newfoundland Basin to form a brine pond that was referred to as “West Pond.”

To obtain brine feedstock for magnesium production, brine from West Pond was first conveyed by a 6-mile canal to the Knolls solar ponds, where the brine was evapo-concentrated through a series of solar ponds. Brine transmitted by the inlet canal entered the Knolls solar ponds in the southwestern corner of the pond complex. Brine flowed initially into Pond 0 or Pond 1 and then sequentially through ponds 3, 5, and 7 (Figure 2; note that Ponds 4 and 6 are not identified on available drawings). According to US Magnesium, Pond 0 was used for brine concentration operations from approximately 1987 to 1998. Between 1998 and 2001, brine form West Pond was conveyed directly to Pond 7, and AMAX/MagCorp operations at the Knolls solar ponds ceased in 2001.

The Knolls solar ponds reconnaissance focused on observations at Ponds 0 and 1 because the composition of salt deposits (principally halite) in Ponds 0 and 1 is most similar to the salt cap barrier that would be constructed at the US Magnesium NPL site. Ponds 0 and 1 received the initial brine flow into the Knolls solar ponds complex. By contrast, salt deposits in the Pond 7 complex are relatively enriched in magnesium, potassium, and sulfate (including kainite, epsomite, and hexahydrite along with halite) because they precipitated later in the evapo- concentration process.

Mud flats are present throughout the Knolls solar ponds area and are divided by lineaments of sand dunes. A prominent set of dunes extends in a northeast-southwest trend across the pond complex (Figure 2). The Knolls solar ponds were constructed with perimeter berms and utilizing natural slopes. For example, Pond 0 has extensive perimeter berms on the north and west sides (totaling approximately 10 miles) and uses a relatively short berm (approximately 0.5 miles) on the south side that connects to the sand dunes, which function as a berm on the east side of Pond 0. Ponds 0 and 1 encompass approximately 9,500 and 3,500 acres, respectively.

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Weathering Characteristics and Behaviors

Reconnaissance activities at the Knolls solar ponds noted the following observations of salt deposit weathering at Ponds 0 and 1: • Thin layers (less than 1/8 inch) of windblown dust were observed as a cover over limited portions of the salt surface and interbedded with salt deposits, as observed in exposed vertical sections of salt deposits. The observed surficial deposits of dust covered relatively small areas (10s but not 100s of acres) of the approximately 10,000-acre Pond 0 area. • Where external drainage of surface water runoff occurs, erosional features in the salt deposit were observed, including cracks up to 6 inches wide, rills up to 5 feet wide, and channels up to 20 feet wide and 6 feet deep. Significant erosion of salt deposits was observed in the northwestern corner of Pond 1 where the berm between Ponds 0 and 1 was intentionally breached during the final phase of operations, allowing surface water to flow into the inlet canal. Where external drainage of surface water runoff is not present (i.e., in the northwestern corner of Pond 0), evidence of erosion of salt deposits was not observed. • Internal containment of surface water in the northwestern portion of Pond 0 allows the salt surface to remain flat, smooth, and very hard. In addition, the salt retained a bright white color, indicating a relatively low amount of impurities. It should be emphasized that a uniform, competent salt cap covering a large area (more than 1,000 acres) in the northwest corner of Pond 0 has persisted for over 20 years without any salt or berm maintenance activities (e.g., addition of brine, earthwork activities on berms, etc.). • Significant dissolution of salt deposits by precipitation (as evidenced by a pocked and rough salt surface) was apparent only where external drainage of surface water runoff has occurred. Evidence of dissolution of salt deposits caused by underlying groundwater was not observed at the Knolls solar ponds. • Self-healing of erosional features (cracks, rills, and channels) was observed where runoff of precipitation is entirely or partially retained on the salt deposit, which allows for dissolution, redistribution and precipitation of salts as the surface water accumulates in low areas and evaporates.

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• While salt deposits were generally competent throughout Ponds 0 and 1, the salt surface was observed to be hardest in the northwestern corner of Pond 0 where external drainage of surface water is prevented by the pond berms.

Comparability to US Magnesium Materials and Conditions

Site conditions at Ponds 0 and 1 were observed to be similar to the proposed salt cap barrier remedial alternative for the US Magnesium site, as follows: • Ponds 0 and 1 were constructed on lakebed playa and adjacent mudflat areas using a combination of man-made berms and existing topography (i.e., sand dunes), which is similar to the current wastewater pond and Old Waste Pond (OWP) at US Magnesium. • The salt deposits are halite-dominated, laterally extensive, and up to 4 feet thick. Salts deposited from GSL brine at US Magnesium are also dominated by halite. • Where external drainage of surface water is prevented, the salt deposits have hard, flat, smooth salt surfaces and are not subject to significant weathering and erosion. • Surface lithology in the pond bottoms is dominated by clay and silty clay soils. These soils are comparable to soils observed within the OWP and portions of the current wastewater pond at US Magnesium. • Sandy soils are present along some margins of Ponds 0 and 1 (i.e., sand dunes on east margin of Pond 0 and north margin of Pond 1). Natural and man-made berms surrounding the current wastewater pond and the OWP at US Magnesium are also composed of sandy soils. • Salt deposits in the northwest portion of Pond 0 cover an area comparable in size to the OWP at the US Magnesium facility.

CARGILL SALT

The Cargill Salt operation is located adjacent to the Timpie Springs Waterfowl Management Area approximately 12 miles south of the US Magnesium plant (Figures 1 and 3). Access to the Cargill operation is from Interstate 80 Exit 77. The facilities at Cargill were constructed by AKZO

PAGE 6 salt from 1991 to 1994. The operation was purchased by Cargill Salt in 1997. Cargill receives brine for its operations from US Magnesium, who contractually delivers brine via a canal from US Magnesium Solar Pond 1 North. Operations at the Cargill facility include a series of evaporation ponds, a salt washing facility, and infrastructure for transporting salt by truck and rail.

The Cargill reconnaissance was conducted at Pond 2 East and Pond 3 East because they have remained fallow for approximately 8 years. According to Mr. Ratcliff, salt deposits in these two ponds have not been fully harvested due to a relatively high amount of impurities in the salt. Limited harvesting (to an approximately depth of 4 inches) was apparent around the perimeter of Pond 2 East based on site observations and may have been performed in the past at Pond 3 East based on a review of historical aerial photographs. At the time of the reconnaissance, evidence of harvesting at Pond 3 East was not apparent.

The Cargill ponds were constructed with perimeter berms on each side, and Cargill maintains an 18-inch floor/foundation of salt deposits in each of their ponds as a structural support for operations. Pond 2 East and Pond 3 East have an additional 16 inches of salt crop/product on top of the 18-inch floor, totaling approximately 34 inches of salt in these ponds. Pond 2 East and Pond 3 East cover approximately 165 and 120 acres, respectively.

Weathering Characteristics and Behaviors

Reconnaissance activities noted the following observations of salt deposit weathering at Pond 2 East and Pond 3 East of the Cargill facility: • Cargill indicated that these ponds have not been extensively harvested because the salt is off-specification, due to the relatively high amount of impurities (e.g., potassium salts) in the salt deposit. • Limited harvesting has created salt surface elevation differences that enable surface water flow across portions the pond. The runoff has created erosional features in salt deposits, including cracks typically 0.25 to 2 inches wide and 4 inches deep and rills up to 1 foot wide and 4 inches deep. Cracks and rills were shallow and did not penetrate close to the underlying soil. These erosional features appear to be concentrated in areas of unharvested salt that is adjacent to the

PAGE 7

harvested areas which enables surface water to flow across these areas. Where the salt surface is flat (i.e., Pond 3 East), rills and channels were not observed, and cracks (less than 0.5 inches wide) were filled with salt. • Moderate dissolution of salt deposits by precipitation (as evidenced by a pocked salt surface) was apparent where surficial erosional features were observed. • Evidence of dissolution of salt deposits caused by underlying groundwater was observed in a localized area in the southeastern portion of Pond 3 East. In this area, a water-filled hole (approximately 1 foot in diameter) and several other self-healed holes were observed (see photograph 44 in Attachment A). • Self-healing of erosional features (cracks, rills, and holes) was observed where surface water runoff is partially restricted to allow precipitation of salts during evapo-concentration of surface water (see photographs 27, 33, 37 through 41, and 44 in Attachment A). • The salt surface was observed to be very hard and competent across the observed areas at the Cargill facility.

Comparability to US Magnesium Materials and Conditions

Site conditions at Pond 2 East and Pond 3 East were observed to be similar to the proposed salt cap barrier remedial alternative for the US Magnesium site, as follows: • The salt deposits are halite-dominated, laterally extensive, and are deposited on a former GSL lakebed area similar to the OWP at US Magnesium. • According to Cargill, surface lithology in the pond bottoms is dominated by clay and silty clay soils associated with the GSL lakebed. These soils are comparable to soils observed within the OWP and portions of the current wastewater pond at US Magnesium.

US MAGNESIUM POND 1 SOUTH

Solar evaporation ponds operated by US Magnesium occupy approximately 65,000 acres, of which approximately 48,000 acres are

PAGE 8 covered by water (Figures 1 and 3). The US Magnesium evaporation ponds are constructed on lands leased from the State of Utah and have been in operation since the early 1970s. Brine obtained from GSL is evapo- concentrated through a series of solar evaporation ponds to a magnesium concentration of 8.5 percent by weight and then stored for use as feedstock for primary magnesium production. Some of the brine from the US Magnesium evaporation ponds is contractually supplied to Cargill Salt, where sodium chloride is precipitated and then the bitters (brine after removal of sodium chloride) are returned to the US Magnesium solar ponds complex. Approximately 5 million tons of mixed salts are precipitated within the US Magnesium evaporation ponds each year during the concentration of GSL brines. Because the solar ponding complex is active, surficial salt deposits are considered recent. Salts are periodically removed from the evaporation ponds.

Brine from GSL is pumped into Pond 1 North where it is evapo- concentrated before flowing by gravity into Pond 1 South. The brine is then pumped or flows by gravity into a second (Pond 2) and third (Pond 3) pond series, which each contain multiple evaporation ponds to control evapo-concentration of brine to optimal conditions for storage and eventual use for magnesium production. Pond 1 South is approximately 14,500 acres and is significant because its source of brine (Solar Pond 1 North) is the same as the proposed source of brine for salt cap barrier construction. Pond 1 South is also the first pond where significant salts are deposited within the US Magnesium solar evaporation pond complex.

Weathering Characteristics and Behaviors

Weathering of salt deposits at Pond 1 South was not observed during reconnaissance activities because the pond was inundated with brine.

Comparability to US Magnesium Materials and Conditions

Site conditions at Pond 1 South were observed to be similar to the proposed salt cap barrier remedial alternative for the US Magnesium site, as follows: • Surface lithology in the pond bottoms is dominated by clay and silty clay soils.

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• The source of brine within Pond 1 South is the same as the brine source proposed for the salt cap barrier (Solar Pond 1 North). • Pond 1 South is constructed within a former GSL lakebed area similar to the OWP at US Magnesium.

EVALUATION OF SHORT-TERM AND LONG-TERM SALT BEHAVIORS

The short-term and long-term behaviors were evaluated by comparing properties of salt deposits of varying ages. Approximate salt deposits ages are: • Approximately 18 to 29 years old at Ponds 0 and 1 of the Knolls solar ponds; • 8 years old at Cargill Salt ponds 2 East and 3 East; and • Active at the US Magnesium Pond 1 South.

In general, it was not meaningful to compare the active, flooded salt deposits within Pond 1 South to salt deposits at the other locations; however, conditions within Pond 1 South are likely indicative of salt deposit characteristics that would be expected during deposition-by- evaporation of a salt cap barrier.

Hardness

The hardness of salt surfaces at the Knolls and Cargill locations was comparable, with the salt deposits exhibiting very hard and competent surfaces. These observations suggest salt deposits do not soften with age or where subject to weathering, as eroded salt surfaces were also very hard.

Stratification

Stratification of salt deposits at the Cargill facility could not be observed because a vertical section of the salt deposits was not present at the areas included in the reconnaissance. Some stratification of windblown dust and salt deposits was observed at the Knolls facility. Where a vertical cross-section of salt deposits at Knolls could be observed, the hardness

PAGE 10 and appearance of salt did not vary with depth, indicating that stratification of salt had not developed over either the timeframe of salt deposition or since the salts were deposited.

Erosion

Based on the Knolls and Cargill observations, erosion of salt deposits appears to be primarily influenced by surface water runoff. As long as runoff is prevented or controlled, erosion does not appear to affect salt deposits differently in the short-term or long-term. For example, salt deposits at Knolls Pond 0 (over 25 years old) and Cargill Pond 3 East (8 years old) both had very hard, smooth, and competent surfaces.

Self-Sealing

As noted above, self-sealing of cracks and rills in salt surfaces appeared to be primarily influenced by the full (or even partial) restriction of surface water runoff. Salt self-sealing appears to flourish where precipitation is retained over a salt deposit and allowed to evaporate.

CONCLUSIONS

The conclusions below are based on the observations collected during the salt deposit reconnaissance and evaluation of the observations. • Existing salt deposits composed of the similar evaporite types are present in the vicinity of US Magnesium. • Salt deposits are compatible with substrate types found at US Magnesium. • Control of surface water runoff appears to be the most significant factor in the weathering and erosion of salt deposits. Where surface water runoff is prevented, the surfaces of the observed salt deposits retain hardness and competence over time, and salt deposition may occur over large areas (well over 1,000 acres). Where surface water runoff is not prevented, salt deposits may be moderately or significantly eroded.

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• Wind erosion does not appear to have significant effects on salt deposits, and the introduction of windblown dust appears to have little effect on the observed salt deposits. • Salt self-sealing appears to be an important process in allowing a salt deposit to retain hardness and competence over time. Self-healing of erosional features (cracks, rills, and channels) was observed where runoff of precipitation is entirely or partially retained on the salt deposit, which allows for dissolution, redistribution and precipitation of salts as the surface water accumulates in low areas and evaporates. Even where erosional features are not present, internal containment of surface water enables redistribution of salts to retain a flat, smooth, and hard salt surface. • Dissolution by groundwater may compromise salt deposit integrity in localized areas, although salt deposits dissolved by groundwater may self-heal if conditions allow for evaporation of pooled surface water. • After formation, salt deposits are competent, hard, and uniform surfaces that form effective barriers over underlying soils/sediments. The hard and cemented crystalline salt layers formed at these deposits are unsuitable for burrowing or digging.

ATTACHMENTS Figure 1 Existing Salt Deposit Locations Figure 2 Knolls Solar Ponds Figure 3 Cargill and US Magnesium Solar Ponds Table 1 Existing Salt Deposit Reconnaissance Observations Attachment A Photolog

Figures Logan o 30 '- iche ¹º NJ,oni'I F"'"" I LAKE DESERT ³

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..1. -.J US Magnesium RI/FS Study Area Boundary US Magnesium Operating Facility • Railroad Main Line

South Arm Great Salt Lake

Newfoundland Basin (West Pond)

Knolls US Magnesium Solar Solar Ponds Ponds Ä( Bonneville Ä( Salt Flats Cargill Salt Ä( Morton ¨¦§80 Salt Intrepid Potash

Figure 1 ¹º196 ¹º138 Existing Salt Deposit Locations Existing Salt Deposit Reconnaissance ¹º112 Technical Memorandum US Magnesium LLC Tooele County, Utah 0 5 10 Miles Environmental Resources Management www.erm.com

M:\Projects\0132320_USMagnesium_Confidential\maps\SaltDepositReconTechMemo\Figure1 ExistingSaltDepositLocs.mxd ERM Source: ESRI World Imagery Webservice, USDA, June 30, 2014; NAD 1983 StatePlane Utah Central FIPS 4302 Feet Logan0 \.e.:he UTAH N..tionlll GREAT SALT t"l"I I LAKE Ogden ³ DESERT 0

,, Sall Lake Wa City Nat 0 Fo / ³ %2 3 %2 2 %2 1 • I Site Location \ 0 15 30 60 Orem \ Miles i Uinta \ \ \ Legend \ Created By: Mike Appel8/23/2016 By: MikeProject: Created 0350891 %2 4 Pond 0 \ %2 Reconnaissance Observation Location \ \ Inlet Canal \ .... \ ~_, US Magnesium RI/FS Study Area Boundary \ Pond 2 Pond 3 \ US Magnesium Operating Facility \ \ • Clean \ \ Harbors \ Landfill \ \ \ \ \ \ \ \ Notes: \ 1. The inlet canal extends from the West Pond (located \ %2 5 Sand northwest of Knolls) to the Southwest corner of the Knolls \ Solar Ponds complex. The canal is connected to the Knolls \ Dunes \ Solar Ponds in the vicinity of observation locations 8 and 9. \ 2. Ponds 4 and 6 are not identified on available drawings. \ \ \ \ Pond 5 \ %2 6 \ \ \ \ \ \ \ \ \ /i \ \ \ %2\ 7 \%2 8 %2 Pond 7 9 Complex

Pond 1

%2 10 Figure 2 Knolls Solar Ponds ¨¦§80 Existing Salt Deposit Reconnaissance Technical Memorandum US Magnesium LLC Tooele County, Utah

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Pond 1 South

Notes: 1. Pond 1 North, Pond 1 South, and the Pond 2 and 3 - , complexes are part of the US Magnesium solar ponds. The I Cargill pond complex is located southwest of the US I Magnesium ponds and includes Pond 2 East and Pond 3 East. I I I I I I Pond 2 I Complex , I , , , , I Pond 3 I I Cargill Pond Complex } I Complex %2 11 %2 12 I,,, ',,..______I

Pond 3 East Pond 2 Timpie Springs East Morton Waterfowl Salt Management Area Figure 3 ¨¦§80 Cargill and US Magnesium Solar Ponds Existing Salt Deposit Reconnaissance Technical Memorandum US Magnesium LLC ¹º196 Tooele County, Utah 0 3,000 6,000 12,000 Feet Environmental Resources Management www.erm.com

M:\Projects\0132320_USMagnesium_Confidential\maps\SaltDepositReconTechMemo\Figure3 Cargill_MagSolarPondLocs.mxd ERM Source: ESRI World Imagery Webservice, USDA, June 30, 2014; NAD 1983 StatePlane Utah Central FIPS 4302 Feet

Table Table 1 Existing Salt Deposit Reconnaisance Observations

Reconnaissance Observation Northing Easting Location Description and Key Observations Location Knolls

Location 1 was in the northeast corner of Pond 0 in an area that transitions from mud flats to the west and sand dunes to the east. Salt deposits in this area are sparse and limited to depressions, such as a dredged channel that 1 4524821 306228 parallels the berm. Ground surface elevation is relatively high for Pond 0 as the location is transitional to the sand dunes. Photographs 1 and 2 in Attachment 1 were taken at this location.

Location 2 was in the north-central portion of Pond 0. Salt deposits in this area are more extensive than those at location 1, covering a majority of the mud flats. The salt deposits appear to be very thin (generally less than 1 2 4524842 303946 inch) with a smooth surface. Salt deposits in this area do not cover slightly elevated areas (mud flat "islands" surrounded by thin salt deposits). Photographs 3 and 4 in Attachment 1 were taken at this location. Location 3 was in the northwest corner of Pond 0. Salt deposits in this area are laterally extensive, completely covering mud flats in the northwest corner of Pond 0. The salt was dominated by halite, and the salt surface was very flat, smooth, and hard. No fissures, cracks, or rills were observed in the salt deposits in this area. A core sampler was driven to a depth of 8 inches below ground surface, and salt was present deeper than 8 inches. The 3 4524852 301702 core sampler was not advanced deeper based on the potential inability to remove the sampler from the hard salt. Groundwater was present at approximately 2 inches below ground surface in the borehole. Layering was not observed in the cored salt, which appeared to be relatively homogeneous halite. Photographs 5 and 6 in Attachment 1 were taken at this location. Location 4 was in the northwest corner of Pond 0. Salt deposits in this area are laterally extensive. While surface water was not present at location 3, surface water was observed to be pooled along the west berm of Pond 0. The pool appeared to be very shallow (at most a few inches deep) and stretched across an area from near location 4 4 4523143 300184 for several thousand feet south. Where surface water did not cover the salt, the salt surface was very flat and smooth. No fissures, cracks, or rills were observed in the salt deposits in this area. Photographs 7 through 9 in Attachment 1 were taken at this location. Location 5 was in the western portion of Pond 0. Salt deposits in this area are laterally extensive, completely covering mud flats in the western portion of Pond 0. Surface water was observed in a channel that parallels the west berm. Surface water in the channel was very shallow (a few inches deep), and the channel was approximately 40 feet wide. The channel extends along the west berm to the southern corner of Pond 0 at the 5 4518656 300062 location where the inlet canal enters Ponds 0 and 1. While the salt surface is generally flat and smooth in this area, rills (up to 1 feet wide) and cracks (less than 6 inches wide) in the salt surface were observed in this area. The rills in this area are generally subperpendicular to the channel along the berm. The rills and cracks appeared to have formed as a result of surface water flow into the channel. Photographs 10 through 12 in Attachment 1 were taken at this location.

1 of 4 Table 1 Existing Salt Deposit Reconnaisance Observations

Reconnaissance Observation Northing Easting Location Description and Key Observations Location

Location 6 was in the southwestern portion of Pond 0. Salt deposits in this area are laterally extensive, completely covering mud flats in the western portion of Pond 0. Surface water was observed in a channel that parallels the west berm. Surface water in the channel was very shallow (a few inches deep), and the channel was approximately 50 feet wide. Windblown dust covered portions of the salt surface, and fine layering of soil (likely 6 4516809 300015 windblown dust) and salt deposits was apparent along the channel, which has cut into the salt surface (likely through dissolution). Rills (up to 5 feet wide) and cracks (less than 6 inches wide) in the salt surface were observed in this area. The rills in this area are generally subperpendicular to the channel. The rills and cracks appeared to have formed as a result of surface water flow into the channel. Photographs 13 through 17 in Attachment 1 were taken at or near this location.

Location 7 was in the southwestern portion of Pond 0. Surface water was observed in a channel that parallels the west berm. Surface water in the channel was very shallow (a few inches deep), and the channel was approximately 60 feet wide. Salt deposits in this area are laterally extensive. Rills (up to 5 feet wide) and cracks 7 4514131 300426 (less than 6 inches wide) in the salt surface were observed in this area. In some cases, rills and cracks showed evidence of self healing where surface water may have concentrated as brine and evaporated within the rills and cracks. Berms are present within Pond 0 in the southern corner of the pond near the connection to the inlet canal. Photographs 18 through 20 and 33 in Attachment 1 were taken at or near this location.

Location 8 was in the southern corner of Pond 0 where the inlet canal is connected to Pond 0 through a concrete box culvert/gate. This location is immediately northwest of the berm that separated Ponds 0 and 1. The berm between Ponds 0 and 1 was breached after Knolls solar ponds operations ceased in 2001, and the breached berm allows surface water to flow out of Pond 1 through the southern corner of Pond 0 and into the inlet canal. Surface water was observed to be flowing from Ponds 1 and 0 through a channel into the inlet canal. Pond 1 appeared to be the source of the majority of the surface water flow, which was observed to have a relatively slow 8 4513794 300579 rate. Upon entering the inlet canal, which is approximately 150 to 200 feet wide, surface water appeared to pool and subsequently evaporate, forming salt deposits in the bottom of the inlet canal. Mr. Don Silva (US Magnesium) indicated that the inlet canal was dredged to a depth of 15 to 20 feet across a width of 25 to 30 feet for the Knolls solar ponds operations. As the inlet canal bottom elevation now appears to be within a few feet of the bottoms of Ponds 0 and 1, the inlet canal may have filled with salt deposits after pond operations ceased. Rills and cracks in the salt surface were observed in this area. Photographs 21 and 22 in Attachment 1 were taken at this location.

2 of 4 Table 1 Existing Salt Deposit Reconnaisance Observations

Reconnaissance Observation Northing Easting Location Description and Key Observations Location

Location 9 was in the northwestern corner of Pond 1 and adjacent to the breached berm between Ponds 0 and 1. Location 9 is also in the area where a historical connection of the inlet canal to Pond 1 was backfilled. As such, location 9 is in an area that had significant earthwork completed after the ponds operations were terminated in 2001. Surface water was observed to be flowing from Pond 1 through the breached berm in a channel that splits immediately upstream of the berm. One of the channels extends along the southwestern berm of Pond 1 and the other extends to the east across the Pond 1 salt deposits. Surface water in these channels has cut into the salt 9 4513709 300644 deposits at location 9, exposing a vertical cut in the salt deposits (which were measured at 4 feet thick). Salt deposits in the northwestern corner of Pond 1 have significant erosion with cracks (up to 6 inches wide), rills (up to 5 feet wide), and channels (up to 20 feet wide and 6 feet deep). The salt surface is pocked and rough, and the salt deposits are light gray to dark gray due to the concentration of sediment as the salt deposits dissolve. Thin layers (less than 1/8 inch) of soil/sediment were observed to be layered within exposed vertical sections of salt deposits. Native soil exposed in the channel was observed to be silty clay. Surface water flowing off the salt deposits is concentrated, forming halite terraces across the channel. Photographs 23 through 29 in Attachment 1 were taken at this location.

Location 10 was in the southern portion of Pond 1. Salt deposits in this area are laterally extensive, completely covering mud flats in the southern portion of Pond 1. The salt was dominated by halite, and the salt surface was flat and hard, although not as hard as the salt at Location 3. No fissures, cracks, or rills were observed in the salt 10 4511702 302398 deposits in this area. A core sampler was driven to a depth of 11 inches below ground surface, where native silty clay was encountered. Groundwater was present at approximately 1 inch below ground surface in the borehole. Layering was not observed in the cored salt, which appeared to be relatively homogeneous halite with hopper crystals up to 0.25-inch diameter. Photographs 30 through 32 in Attachment 1 were taken at this location.

Cargill Location 11 was in the northeastern portion of Pond 2 East at the Cargill pond complex. The salt surface of Pond 2 East is very flat (with a pocked texture) and very hard (vehicles drive over the salt). The salt was dominated by halite. Perimeter harvesting removed approximately 4 inches of salt, creating relief from the harvested areas to the unharvested areas. The relief causes rain water to flow toward the harvested areas, forming cracks and rills 11 4514675 361173 in the salt surface. The cracks and rills are particularly prominent in unharvested salt near the harvested areas. Rills were observed up to 1 feet wide and 4 inches deep, and cracks were typically 0.25 to 2 inches wide and 4 inches deep. The cracks and rills and do not reach underlying soil. Some rills and cracks had deposition of salts within them, indicating self healing. Photographs 34 through 41 in Attachment 1 were taken at or near this location.

3 of 4 Table 1 Existing Salt Deposit Reconnaisance Observations

Reconnaissance Observation Northing Easting Location Description and Key Observations Location Location 12 was along the southeast berm of Pond 3 East at the Cargill pond complex. The salt surface of Pond 3 East is very flat (with a pocked texture) and very hard (vehicles drive over the salt). The salt was dominated by halite. According to Cargill, Pond 3 East had not been harvested. Rills and channels were not observed in the salt deposits. Cracks (typically less than 0.5 inches wide) were observed in the salt but were filled with salt. Salt 12 4514680 361679 dissolution by underlying groundwater was apparent in a localized area at Location 12 where a water-filled hole (approximately 1 feet in diameter) was observed. According to Cargill, the hole is more than 3 feet deep. Several other self-healed holes were observed in the same area. Photographs 42 through 44 in Attachment 1 were taken at this location. Pond 1 South Location 13 was along the berm between Pond 1 South and Pond 1 North in the US Magnesium pond complex. Pond 1 South covers approximately 15,000 acres and has perimeter berms on the north, south, and west sides with Stansbury Island forming a natural shoreline on the east side. According to US Magnesium, several feet of 13 4525279 365402 halite salt deposits are present in the bottom of Pond 1 South, but the salt deposits could not be observed during the reconnaissance because the pond was full with brine. Photographs 45 and 46 in Attachment 1 were taken at this location.

Northings and eastings are UTM, Meters, Zone 12N, NAD 83 Map Projection.

4 of 4

Attachment A Photolog

Photograph: 1 Location 1 on the north berm of Pond 0 (facing west). Location: Knolls Solar Ponds US Magnesium Date: 6 June 2016 ERM Tooele County, Utah

Photograph: 2 Location 1 on the north berm of Pond 0 (facing southwest). Location: Knolls Solar Ponds US Magnesium Date: 6 June 2016 ERM Tooele County, Utah

Photograph: 3 Location 2 on the north berm of Pond 0 (facing west). Location: Knolls Solar Ponds US Magnesium Date: 6 June 2016 ERM Tooele County, Utah

Photograph: 4 Location 2 on the north berm of Pond 0 (facing southwest). Location: Knolls Solar Ponds US Magnesium Date: 6 June 2016 ERM Tooele County, Utah

Photograph: 5 Location 3 in the northwest corner of Pond 0 (facing southeast). Location: Knolls Solar Ponds US Magnesium Date: 6 June 2016 ERM Tooele County, Utah

Photograph: 6 Location 3 in the northwest corner of Pond 0 (facing southwest). Location: Knolls Solar Ponds US Magnesium Date: 6 June 2016 ERM Tooele County, Utah

Photograph: 7 Location 4 in the northwest corner of Pond 0 (facing east). Location: Knolls Solar Ponds US Magnesium Date: 6 June 2016 ERM Tooele County, Utah

Photograph: 8 Location 4 in the northwest corner of Pond 0 (facing north). Location: Knolls Solar Ponds US Magnesium Date: 6 June 2016 ERM Tooele County, Utah

Photograph: 9 Location 4 in the northwest corner of Pond 0 (facing south). Location: Knolls Solar Ponds US Magnesium Date: 6 June 2016 ERM Tooele County, Utah

Photograph: 10 Location 5 along the west berm of Pond 0 (facing east). Location: Knolls Solar Ponds US Magnesium Date: 6 June 2016 ERM Tooele County, Utah

Photograph: 11 Location 5 along the west berm of Pond 0 (facing north). Location: Knolls Solar Ponds US Magnesium Date: 6 June 2016 ERM Tooele County, Utah

Photograph: 12 Location 5 along the west berm of Pond 0 (facing south). Location: Knolls Solar Ponds US Magnesium Date: 6 June 2016 ERM Tooele County, Utah

Photograph: 13 Location 6 along the west berm of Pond 0 (facing east). Location: Knolls Solar Ponds US Magnesium Date: 6 June 2016 ERM Tooele County, Utah

Photograph: 14 Location 6 along the west berm of Pond 0 (facing northeast). Location: Knolls Solar Ponds US Magnesium Date: 6 June 2016 ERM Tooele County, Utah

Photograph: 15 Location 6 along the west berm of Pond 0 (facing north). Location: Knolls Solar Ponds US Magnesium Date: 6 June 2016 ERM Tooele County, Utah

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Photograph: 16 Location 6 along the west berm of Pond 0 (facing south). Location: Knolls Solar Ponds US Magnesium Date: 6 June 2016 ERM Tooele County, Utah

Photograph: 17 Rill near location 6 of Pond 0 (facing east). Location: Knolls Solar Ponds US Magnesium Date: 6 June 2016 ERM Tooele County, Utah

Photograph: 18 Location 7 in southern corner of Pond 0 (facing north). Location: Knolls Solar Ponds US Magnesium Date: 6 June 2016 ERM Tooele County, Utah

Photograph: 19 Location 7 in southern corner of Pond 0 (facing northeast). Location: Knolls Solar Ponds US Magnesium Date: 6 June 2016 ERM Tooele County, Utah

Photograph: 20 Location 7 in southern corner of Pond 0 (facing southeast). Location: Knolls Solar Ponds US Magnesium Date: 6 June 2016 ERM Tooele County, Utah

Photograph: 21 Location 8 at connection of inlet canal (facing southeast). Location: Knolls Solar Ponds US Magnesium Date: 6 June 2016 ERM Tooele County, Utah

Photograph: 22 Location 8 at connection of inlet canal (facing northwest). Location: Knolls Solar Ponds US Magnesium Date: 6 June 2016 ERM Tooele County, Utah

Photograph: 23 Location 9 in northwestern corner of Pond 1 (facing northeast). Location: Knolls Solar Ponds US Magnesium Date: 6 June 2016 ERM Tooele County, Utah

Photograph: 24 Location 9 in northwestern corner of Pond 1 (facing east). Location: Knolls Solar Ponds US Magnesium Date: 6 June 2016 ERM Tooele County, Utah

Photograph: 25 Location 9 in northwestern corner of Pond 1 (facing southeast). Location: Knolls Solar Ponds US Magnesium Date: 6 June 2016 ERM Tooele County, Utah

Photograph: 26 Halite terraces in channel at location 9 (facing east). Location: Knolls Solar Ponds US Magnesium Date: 6 June 2016 ERM Tooele County, Utah

Photograph: 27 Halite terraces, which indicate self-healing, in channel at location 9. Location: Knolls Solar Ponds US Magnesium Date: 6 June 2016 ERM Tooele County, Utah

Photograph: 28 Halite crystals in channel at location 9. Location: Knolls Solar Ponds US Magnesium Date: 6 June 2016 ERM Tooele County, Utah

Photograph: 29 Breached berm at location 9 (facing north). Location: Knolls Solar Ponds US Magnesium Date: 6 June 2016 ERM Tooele County, Utah

Photograph: 30 Location 10 in southern portion of Pond 1 (facing east). Location: Knolls Solar Ponds US Magnesium Date: 6 June 2016 ERM Tooele County, Utah

Photograph: 31 Location 10 in southern portion of Pond 1 (facing north). Location: Cargill Salt US Magnesium Date: 6 June 2016 ERM Tooele County, Utah

Photograph: 32 Location 10 in southern portion of Pond 1 (facing west). Location: Cargill Salt US Magnesium Date: 6 June 2016 ERM Tooele County, Utah

Photograph: 33 Rill near Location 7 showing evidence of self healing (facing east). Location: Cargill Salt US Magnesium Date: 6 June 2016 ERM Tooele County, Utah

Photograph: 34 Location 11 at Pond 2 East (facing southeast). Location: Cargill Salt US Magnesium Date: 6 June 2016 ERM Tooele County, Utah

Photograph: 35 Cut salt at Pond 2 East with harvested area on right (facing south). Location: Cargill Salt US Magnesium Date: 6 June 2016 ERM Tooele County, Utah

Photograph: 36 Crack in salt at Pond 2 East near harvested area (facing northwest). Crack is shallow (4 inches) and does not reach underlying soil. Location: Cargill Salt US Magnesium Date: 6 June 2016 ERM Tooele County, Utah

Photograph: 37 Partially self-healed rill at Pond 2 East. Location: Cargill Salt US Magnesium Date: 6 June 2016 ERM Tooele County, Utah

Photograph: 38 Partially self-healed rill at Pond 2 East. Location: Cargill Salt US Magnesium Date: 6 June 2016 ERM Tooele County, Utah

Photograph: 39 Partially self-healed rill and crack at Pond 2 East. Location: US Magnesium US Magnesium Date: 6 June 2016 ERM Tooele County, Utah

Photograph: 40 Partially self-healed crack in salt deposit at Pond 2 East. Location: US Magnesium US Magnesium Date: 6 June 2016 ERM Tooele County, Utah

Photograph: 41 Partially self-healed crack in salt deposit at Pond 2 East. Crack is shallow (4 inches) and does not reach underlying soil. Location: US Magnesium US Magnesium Date: 6 June 2016 ERM Tooele County, Utah

Photograph: 42 Location 12 at Pond 3 East (facing southeast). Location: US Magnesium US Magnesium Date: 6 June 2016 ERM Tooele County, Utah '

Photograph: 43 Location 12 at Pond 3 East (facing north). Location: US Magnesium US Magnesium Date: 6 June 2016 ERM Tooele County, Utah

Photograph: 44 Open hole and self-healed holes and cracks in salt deposit at Location 12 at Pond 3 East. Location: US Magnesium US Magnesium Date: 6 June 2016 ERM Tooele County, Utah

Photograph: 45 Location 13 at Pond 1 South (facing east). Location: US Magnesium US Magnesium Date: 6 June 2016 ERM Tooele County, Utah

Photograph: 46 Location 13 at Pond 1 South (facing west). Location: US Magnesium US Magnesium Date: 6 June 2016 ERM Tooele County, Utah