Clean Harbors, Inc.
MX ˙ BMV ˙ US1844961078
SecurityMX:CLH1 / Clean Harbors, Inc.
InstitutionMarshall Wace, Llp
Latest Disclosed Ownership44,477 shares
Latest Disclosed Value $ 12,752,892
Marshall Wace, Llp reports 31.13% decrease in ownership of CLH1 / Clean Harbors, Inc.

On May 14, 2026 - Marshall Wace, Llp filed a 13F-HR form disclosing ownership of 44,477 shares of Clean Harbors, Inc. (MX:CLH1) valued at $12,752,892 USD as of March 31, 2026. The entity filed a previous 13F-HR on February 13, 2026 disclosing 64,581 shares of Clean Harbors, Inc.. This represents a change in shares of -31.13% during the quarter.

Institutional Ownership: 13F and NPORT Filings

The Security and Class in the table below are shown exactly as filed by the investor. We do our best to track continuity of investments through acquisitions, and this will be reflected in the table as changes in names. In addition to descriptive data, performance of the investment is shown over time. To calculate quarterly performance, we first calculate cost basis of the shares purchased during the quarter, then use that to calculate gross profit. Quarterly return is Gross Profit / Starting Portfolio value.

Note that cost basis is calculated and stored in thousands, so small quarterly changes in shares frequently result in a cost basis of zero.

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Disclosed Equity Positions (from 13F/NPORT Filings)
File
Date		 Effective
Date		Form Security Class ID Avg Price
Paid (Est)		 Reported
Shares		 ΔShares ΔShares
(%)		 Reported
Value
(x1000)		 ΔValue
(%)		 Alloc
(%)		 ΔAlloc ΔAlloc (%) Cost Basis
(x1000)		 Unrealized
Gain/Loss
(x1000)
2026-05-14 2026-03-31 13F CLEAN HARBORS COMMON STOCK 184496107 44,477 -20,104 -31.13 12,753 -15.78 0.0127
2026-02-13 2025-12-31 13F CLEAN HARBORS COMMON STOCK 184496107 64,581 61,451 1,963.29 15,143 1,985.67 0.0138
2025-11-13 2025-09-30 13F CLEAN HARBORS COMMON STOCK 184496107 3,130 -190,045 -98.38 727 -98.37 0.0007
2025-08-13 2025-06-30 13F CLEAN HARBORS COMMON STOCK 184496107 193,175 7,959 4.30 44,658 22.33 0.0503
2025-05-15 2025-03-31 13F CLEAN HARBORS COMMON STOCK 184496107 185,216 -146,788 -44.21 36,506 -52.22 0.0463
2025-02-13 2024-12-31 13F CLEAN HARBORS COMMON STOCK 184496107 332,004 -6,326 -1.87 76,407 -6.57 0.0919
2024-11-14 2024-09-30 13F CLEAN HARBORS COMMON STOCK 184496107 338,330 -198,944 -37.03 81,778 -32.70 0.0996
2024-08-14 2024-06-30 13F CLEAN HARBORS COMMON STOCK 184496107 537,274 90,756 20.33 121,505 35.17 0.1622
2024-05-15 2024-03-31 13F CLEAN HARBORS COMMON STOCK 184496107 446,518 -1,464 -0.33 89,889 14.98 0.1369
2024-02-14 2023-12-31 13F CLEAN HARBORS COMMON STOCK 184496107 447,982 -114,809 -20.40 78,177 -17.00 0.1324
2023-11-14 2023-09-30 13F CLEAN HARBORS COMMON STOCK 184496107 562,791 -113,464 -16.78 94,189 -15.30 0.1908
2023-08-14 2023-06-30 13F CLEAN HARBORS COMMON STOCK 184496107 676,255 -38,877 -5.44 111,197 9.07 0.2172
2023-05-15 2023-03-31 13F CLEAN HARBORS COMMON STOCK 184496107 715,132 110,769 18.33 101,949 47.82 0.2166
2023-02-14 2022-12-31 13F CLEAN HARBORS COMMON STOCK 184496107 604,363 -119,371 -16.49 68,970 -13.35 0.1551
2022-11-14 2022-09-30 13F CLEAN HARBORS COMMON STOCK 184496107 723,734 -165,173 -18.58 79,596 2.14 0.1744
2022-08-15 2022-06-30 13F CLEAN HARBORS COMMON STOCK 184496107 888,907 -478,358 -34.99 77,931 -48.94 0.1603
2022-05-16 2022-03-31 13F CLEAN HARBORS COMMON STOCK 184496107 1,367,265 -10,395 -0.75 152,640 11.05 0.2890
2022-02-14 2021-12-31 13F CLEAN HARBORS COMMON STOCK 184496107 1,377,660 1,377,660 137,449 0.2538
2021-08-13 2021-06-30 13F CLEAN HARBORS COMMON STOCK 184496107 0 -15,866 -100.00 0 -100.00
2021-05-17 2021-03-31 13F CLEAN HARBORS COMMON STOCK 184496107 15,866 -21,648 -57.71 1,334 -53.27 0.0061
2021-02-16 2020-12-31 13F CLEAN HARBORS COMMON STOCK 184496107 37,514 -711 -1.86 2,855 33.29 0.0155
2020-11-16 2020-09-30 13F CLEAN HARBORS COMMON STOCK 184496107 38,225 -14,094 -26.94 2,142 -31.74 0.0137
2020-08-13 2020-06-30 13F CLEAN HARBORS COMMON STOCK 184496107 52,319 6,671 14.61 3,138 33.93 0.0220
2020-05-15 2020-03-31 13F CLEAN HARBORS COMMON STOCK 184496107 45,648 34,481 308.78 2,343 144.57 0.0234
2020-02-14 2019-12-31 13F CLEAN HARBORS COMMON STOCK 184496107 11,167 2,682 31.61 958 46.26 0.0066
2019-11-14 2019-09-30 13F CLEAN HARBORS COMMON STOCK 184496107 8,485 -14,431 -62.97 655 -59.79 0.0051
2019-08-14 2019-06-30 13F CLEAN HARBORS COMMON STOCK 184496107 22,916 22,916 170.08 1,629 148.70 0.0134
2019-05-14 2019-03-31 13F CLEAN HARBORS COMMON STOCK 184496107 0 -2,693 -100.00 0 -100.00
2019-02-14 2018-12-31 13F CLEAN HARBORS COMMON STOCK 184496107 2,693 2,693 133 0.0014
2018-05-15 2018-03-31 13F CLEAN HARBORS COMMON STOCK 184496107 0 -6,832 -100.00 0 -100.00
2018-03-29 2017-12-31 13F/A-1 CLEAN HARBORS COMMON STOCK 184496107 6,832 2,003 41.48 370 34.55 0.0155
2018-02-14 2017-12-31 13F CLEAN HARBORS COMMON STOCK 184496107 6,832 2,003 370
2017-11-13 2017-09-30 13F CLEAN HARBORS COMMON STOCK 184496107 4,829 4,829 -29.32 275 -25.68 0.0128
2015-08-14 2015-06-30 13F CLEAN HARBORS COMMON STOCK 184496107 0 -178,429 -100.00 0 -100.00
2015-05-11 2015-03-31 13F CLEAN HARBORS COMMON STOCK 184496107 178,429 173,445 3,480.04 10,131 4,138.91 0.1320
2015-02-17 2014-12-31 13F CLEAN HARBORS COMMON STOCK 184496107 4,984 2,561 105.70 239 82.44 0.0032
2014-11-13 2014-09-30 13F CLEAN HARBORS COMMON STOCK 184496107 2,423 2,423 131 0.0019
Legend
Shares
The total number of shares held by the institution at the end of the reporting period (the effective date). This is provided in the filing.
Value
The total value of the shares as of the effective date. This is provided in the filing.
Avg. Share Price
The weighted average share price of the shares held by the institution. We use FIFO accounting to determine this price
Class
This is the security class as indicated by the filer. There are a variety of values for this field. Common values include "EC" = equity common, "EP" - equity preferred
Allocation (%)
The percent of the institution's portfolio that this position represents. This is provided in NPORT filings. For 13F filings, we calculate it.
Change in Allocation
The change in allocation from the prior reporting period. This is calculated as current allocation - prior allocation.
Change in Allocation (%)
The percent change in allocation from the prior reporting period. This is calculated as (current allocation - prior allocation) / prior allocation.
Cost Basis
The total cost of the shares held. This is calculated as reported shares * avg. share price
Unrealized Gain/Loss
This is the market value of the position as of the effective date minus the cost basis.