What changed in COMPASS MINERALS INTERNATIONAL INC's 10-K — 2023 vs 2024

Item 1. “Business—Environmental, Health and Safety Matters and Other Regulatory Matters” . The Mineral Extraction Permit (GSL Mine M/057/0002) was granted by the Utah DOGM. The Mineral Extraction Permit enables extraction of brine from the Great Salt Lake and ultimate mineral extraction from the brine.

The Mineral Extraction Permit also enables all lake extraction, pond operations, and plant and processing operations conducted by the Company at the Ogden facility. The Mineral Extraction Permit is supported by a reclamation plan that documents all aspects of current operations and mandates certain closure and reclamation requirements in accordance with Utah Rule R647-4-104.

Financial assurance for the ultimate reclamation of facilities is documented in the reclamation plan, and security for costs that will be incurred to execute site closure is provided by a third-party insurer to the State of Utah in the form of a surety bond. The total future reclamation obligation is estimated to be $4.36 million.

Pursuant to the Royalty Agreement, the Company has rights to all salts from the Great Salt Lake, and in exchange, the Company pays a royalty to the State of Utah based on net revenues (gross revenue net of sales taxes and shipping and handling 40 2024 FORM 10-K Table of Contents COMPASS MINERALS INTERNATIONAL, INC. costs) per pound of salts produced.

Under the Royalty Agreement, the current royalty rate for SOP is 4.8% of gross revenues, the current royalty rate for magnesium chloride is 5% of gross revenues, and the current royalty rate for sodium chloride is $0.50/ton times the Producer Price Index.

The Ogden facility is the largest SOP production site in the western hemisphere, and one of only four large-scale solar brine evaporation operations for SOP in the world.

We believe the Ogden facility has the capability to produce 320,000 tons of SOP, including amounts produced with both solar-pond based feedstock and supplemental KCl feedstock when economically feasible, approximately 750,000 tons of magnesium chloride and 1.5 million tons of sodium chloride annually during normal weather and pond chemistry conditions.

These recoverable minerals exist in vast quantities in the Great Salt Lake. Solar evaporation is used in areas of the world where high-salinity brine is available and weather conditions provide for a high natural evaporation rate. Mineral-rich lake water, or brine, from the Great Salt Lake is drawn into the solar evaporation ponds.

The brine moves through a series of solar evaporation ponds over a two- to three-year production cycle. As the water evaporates and the mineral concentration increases, some of those minerals naturally precipitate out of the brine and are deposited on the pond floors. These deposits provide the minerals necessary for processing into SOP, solar salt and magnesium chloride.

The evaporation process is dependent upon sufficient lake brine levels and hot, arid summer weather conditions. The potassium-bearing salts are mechanically harvested out of the solar evaporation ponds and refined to high-purity SOP through flotation, crystallization and compaction at the Ogden plant.

After sodium chloride and potassium-rich salts precipitate from brine, a concentrated magnesium chloride brine solution remains, which becomes the raw material used to produce several magnesium chloride products. Operations have been ongoing at the Ogden facility since the late 1960s, with commercial production starting in 1970.

Lithium Corporation of America (“Lithcoa”), separately, and then in a partnership with a wholly owned subsidiary of Salzdetfurth, A.G., carried out initial exploration and development activities between 1963 and 1966. In 1967, Gulf Resources and Minerals Co., or Gulf Resources, acquired Lithcoa, and in 1973, acquired Salzdetfurth, A.G.’s (then known as Kaliund Salz A.G.) partnership interest.

Gulf Resources made significant capital expenditures in the early 1980s to protect the evaporation pond system at the Ogden facility from the rising levels of the Great Salt Lake. On May 5, 1984, a northern dike of the system breached, resulting in severe flooding and damage to about 85% of the pond complex.

The breach resulted in physical damage to dikes, pond floors, bridges, pump stations, and other structures. In addition, brine inventories were diluted, making them unusable for producing SOP.

During the next five years, Gulf Resources pumped the water from its solar ponds, reconstructed peripheral and interior dikes and roads, replaced pump stations, and laid down new salt floors in order to restart its operation at the Ogden facility. In 1993, D.G.

Harris & Associates acquired the Ogden facility, and in 1994, constructed the west ponds, which are connected to the east ponds by a 21-mile, open, underwater canal called the Behrens Trench, which was dredged in the lakebed from the west ponds’ outlet to a pump station near the east ponds.

Ownership of the Ogden facility was transferred in 1997 to IMC Global (“IMC”), following its acquisition of Harris Chemical Group (part of D.G. Harris & Associates). IMC sold a majority of its salt operations, including the Ogden facility, to Apollo Management V, L.P. through an entity called Compass Minerals Group in 2001.

Following a leveraged recapitalization, the company now known as Compass Minerals International, Inc. completed an initial public offering in 2003. The Company has operated the Ogden facility since its initial public offering in 2003.

In that time, the Company has invested funds and acquired necessary permits to increase the efficiency and expand the capacity of the Ogden facility through upgrades to the Ogden plant and solar evaporation ponds. The Company believes that the Ogden facility and its operating equipment are maintained in good working condition.

The net book value of property, plant and equipment associated with the Ogden facility as of September 30, 2024 was $220,700,000, exclusive of mineral rights and the value of assets leased under operating leases. The Ogden facility has procured and is operating in compliance with all required operating licenses, including permits pertaining to mineral extraction, effluent discharge and air permitting.

The Ogden facility operates under a Title V air permit (# 5700001003), which is administered by the Utah Department of Environmental Quality. The permit covers emissions from the pond and plant operations and expires in December 2026. Surface water discharges from the Ogden facility are regulated under Utah Pollutant Discharge Elimination System permit UT0000647.

The permit requires discharge monitoring for effluent flows from the nine outfalls that discharge into the saline waters of the Great Salt Lake and regulates inputs in pond and plant processes that may be discharged in project effluent.

Summaries of the Ogden facility’s potassium and SOP mineral resources and mineral reserves as of September 30, 2024 and 2023 are shown in Tables 3 and 4, respectively. Summaries of the Ogden facility’s magnesium and magnesium chloride mineral resources and mineral reserves as of September 30, 2024 and 2023 are shown in Tables 5 and 6, respectively.

Summaries of the Ogden facility’s sodium and sodium chloride mineral resources and mineral reserves as of September 30, 2024 and 2023 are shown in Tables 7 and 8, respectively.

Joseph Havasi, who is employed full-time as the Vice President, Natural Resources, of the Company, served as the QP and prepared the estimates of potassium and SOP, magnesium and magnesium chloride, and sodium and sodium chloride mineral resources and mineral reserves at the Ogden facility.

The material assumptions and information pertaining to the Company’s disclosure of mineral resources and mineral reserves at the Ogden facility are based on the Technical Report Summary with respect to Potassium and SOP, Magnesium and Magnesium Chloride and Salt for the Ogden facility, dated November 29, 2021, as amended on December 14, 2022, with an effective date of September 30, 2021 41 2024 FORM 10-K Table of Contents COMPASS MINERALS INTERNATIONAL, INC.

(the “Ogden Potassium/Magnesium/Sodium TRS”). This Form 10-K also reflects more recent information obtained from the QP as of September 30, 2024, which supplements and updates information from such TRS. Table 3.

Ogden Facility – Summary of Potassium and SOP Mineral Resources at September 30, 2024 and 2023 September 30, 2024 September 30, 2023 Resource Area Average Potassium Grade (mg/L) (7) Potassium Resources (tons) (1)(2)(4)(5) Cut-Off Grade (mg/L) (6) SOP Resources (tons) (1)(2)(3)(4)(5) Average Potassium Grade (mg/L) (7) Potassium Resources (tons) (1)(2)(4)(5) Cut-Off Grade (mg/L) (6) SOP Resources (tons) (1)(2)(3)(4)(5) Measured Resources Total Measured Resources — — — — — — — — Indicated Resources Great Salt Lake North Arm 7,320 14,135,094 4,000 31,461,892 7,320 14,245,372 4,000 31,707,350 Great Salt Lake South Arm 3,060 26,057,971 1,660 58,000,000 3,060 26,057,971 1,660 58,000,000 Total Indicated Resources 40,193,065 89,461,892 40,303,343 89,707,350 Measured + Indicated Resources Great Salt Lake North Arm 7,320 14,135,094 4,000 31,461,892 7,320 14,245,372 4,000 31,707,350 Great Salt Lake South Arm 3,060 26,057,971 1,660 58,000,000 3,060 26,057,971 1,660 58,000,000 Total Measured + Indicated Resources 40,193,065 89,461,892 40,303,343 89,707,350 Inferred Resources Total Inferred Resources — — — — — — — — (1) Mineral resources are not mineral reserves and do not have demonstrated economic viability.

There is no certainty that all or any part of the mineral resources will be converted into mineral reserves upon application of modifying factors. (2) Mineral resources are reported in situ for the both the north arm and the south arm of the Great Salt Lake.

(3) Conversion of potassium to SOP uses a factor of 2.2258 tons of SOP per ton of potassium. (4) Included process recovery is approximately 7.8% based on historical production results. Mining or metallurgical recovery is not applicable for this operation. (5) Based on pricing data described in Section 18.1 of the Ogden Potassium/Magnesium/Sodium TRS.

The pricing data is based on a five-year average (2020 through 2024) of historical sales data for SOP of $659.96 per ton. Sales prices are projected to increase to approximately $8,529 per ton for SOP through year 2161 (the current expected end of mine life).

(6) Estimated cut-off grade of approximately 4,000 milligrams of potassium per liter of brine extracted from the north arm of the Great Salt Lake, and a cut-off grade of 1,660 milligrams of potassium per liter of brine in the south arm of the Great Salt Lake, which ultimately flows into the north arm of the Great Salt Lake.

The QP assumes that when the north arm of the Great Salt Lake (where the Ogden facility sources its brine) reaches this concentration level, the Ogden facility will halt production of potassium and SOP.

(7) Reported potassium concentration for the Great Salt Lake assumes an indicative lake level of 4,194.4 feet in the south arm and 4,193.5 feet in the north arm. 42 2024 FORM 10-K Table of Contents COMPASS MINERALS INTERNATIONAL, INC. Table 4.

Ogden Facility – Summary of Potassium and SOP Mineral Reserves at September 30, 2024 and 2023 September 30, 2024 September 30, 2023 Reserve Area Average Potassium Grade (mg/L) (7) Potassium Reserves (tons) (1)(2)(4)(5) Cut-Off Grade (mg/L) (6) SOP Reserves (tons) (1)(2)(3)(4)(5) Average Potassium Grade (mg/L) (7) Potassium Reserves (tons) (1)(2)(4)(5) Cut-Off Grade (mg/L) (6) SOP Reserves (tons) (1)(2)(3)(4)(5) Proven Reserves Total Proven Reserves — — — — — — — — Probable Reserves Great Salt Lake North Arm 7,320 20,243,615 4,000 45,058,239 7,320 20,345,292 4,000 45,284,552 Great Salt Lake South Arm — — — — — — — — Total Probable Reserves 7,320 20,243,615 4,000 45,058,239 7,320 20,345,292 4,000 45,284,552 Total Reserves Great Salt Lake North Arm 7,320 20,243,615 4,000 45,058,239 7,320 20,345,292 4,000 45,284,552 Great Salt Lake South Arm — — — — — — — — Total Reserves 7,320 20,243,615 4,000 45,058,239 7,320 20,345,292 4,000 45,284,552 (1) Mineral reserves are as recovered, saleable product.

(2) Annual production rates for SOP are assumed to be 320,000 tons per year, relating to a depletion of 145,833 tons of potassium per year. Based on the QP’s reserve model, the life of mine is estimated to be 138 years. (3) Conversion of potassium to SOP uses a factor of 2.2258 tons of SOP per ton of potassium.

(4) Included process recovery is approximately 7.8% based on historical production results. Mining or metallurgical recovery is not applicable for this operation. (5) Based on pricing data described in Section 18.1 of the Ogden Potassium/Magnesium/Sodium TRS. The pricing data is based on a five-year average (2020 through 2024) of historical sales data for SOP of $659.96 per ton.

Sales prices are projected to increase to approximately $8,529 per ton for SOP through year 2161 (the current expected end of mine life).

(6) Estimated cut-off grade of approximately 4,000 milligrams of potassium per liter of brine extracted from the north arm of Great Salt Lake, and a cut-off grade of 1,660 milligrams of potassium per liter of brine in the south arm of the Great Salt Lake, which ultimately flows into the north arm of the Great Salt Lake.

The QP assumes that when the north arm of the Great Salt Lake (where the Ogden facility sources its brine) reaches this concentration level, the Ogden facility will halt production of potassium and SOP.