OBERWEIS ASSET MANAGEMENT INC/ CLH — Clean Harbors, Inc.

Ownership history in OBERWEIS ASSET MANAGEMENT INC/  ·  22 quarters on record

AI Ownership Summary

OBERWEIS ASSET MANAGEMENT INC/ reported Clean Harbors, Inc. (CLH) in 22 quarterly 13F filings from 2023 Q4 through 2025 Q4. Peak portfolio weight reached 1.43% in 2024 Q2. The latest visible filing shows CLH at 1.00% of the fund.

This page tracks quarterly shares, estimated market value, portfolio weight, filing dates, and disclosure-aligned stock prices directly from SEC EDGAR 13F filings. Older history is available after unlock; the visible window still shows the most recent pattern.

What this CLH ownership page tells you

This page is designed to answer the real investor question behind a 13F filing: how meaningful was OBERWEIS ASSET MANAGEMENT INC/'s position in Clean Harbors, Inc., and how did that conviction change over time? You can read the holding window, peak weight, latest reported size, disclosure timing, and quarter-by-quarter changes without piecing the story together from raw SEC rows.

Freshest filing
Latest Reported Filing
2025 Q4

CLH was reported at 1.00% of portfolio in the most recent visible filing.

High-water mark
Peak Conviction
1.43% in 2024 Q2

Peak weight helps separate a token disclosure from a real conviction holding the fund genuinely cared about.

Time in book
Holding Window
2023 Q4 to 2025 Q4

Longer holding windows often tell a very different story from short-lived tactical trades or one-quarter experiments.

Decision context
Why It Matters
Position size beats headlines

Knowing that a fund owned a stock is useful. Knowing whether it was a 0.20% placeholder or a true high-conviction position is where the signal actually starts.

CLH stock page OBERWEIS ASSET MANAGEMENT INC/ fund profile OBERWEIS ASSET MANAGEMENT INC/ full holdings
How OBERWEIS ASSET MANAGEMENT INC/ held CLH — position size vs. price
% of Fund (quarterly)    CLH price (quarter-end, indexed to 100)    SPY (indexed to 100)    QQQ (indexed to 100)
📋 Quarterly Holdings History 9 quarters  ▾
Quarter Action Sold % After 3M Timing Shares Change Chg % % of Fund Mkt Value Filed Price (Filed)
2025 Q4 ADDED — — — 116,870 +100 +0.1% 1.00% $27.4M 2026-02-14 (Est.) $273.82
2025 Q3 REDUCED — — — 116,770 -530 -0.5% 1.04% $27.1M 2025-11-17 $201.73
2025 Q2 ADDED — — — 117,300 +6,980 +6.3% 1.18% $27.1M 2025-08-14 $247.05
2025 Q1 ADDED — — — 110,320 +7,890 +7.7% 1.08% $21.7M 2025-05-15 $229.65
2024 Q4 REDUCED — — — 102,430 -2,940 -2.8% 1.11% $23.6M 2025-02-14 $229.78
2024 Q3 ADDED — — — 105,370 +2,125 +2.1% 1.30% $25.5M 2024-11-14 $250.56
2024 Q2 ADDED — — — 103,245 +21,950 +27.0% 1.43% $23.3M 2024-08-14 $236.39
2024 Q1 ADDED — — — 81,295 +24,240 +42.5% 1.18% $16.4M 2024-05-15 $212.71
2023 Q4 ADDED — — — 57,055 +11,640 +25.6% 0.93% $10.0M 2024-02-14 $182.92
13 older quarters hidden  —  Sign in free or upgrade to Premium to see full history

🏢 Other funds also holding CLH

As of 2026 Q1 — sorted by position size

SPIREPOINT PRIVATE CLIENT, LLC 2.89% Trinity Street Asset Management LLP 3Y 7Y 2.15% Leeward Investments, LLC - MA 3Y 1.99% MOUNTAIN PACIFIC INVESTMENT ADVISERS LLC 3Y 7Y 1.15% VAUGHAN NELSON INVESTMENT MANAGEMENT, L.P. 3Y 7Y 1.11% Murphy & Mullick Capital Management Corp 0.81% TECTONIC ADVISORS LLC 3Y 0.68% Congress Park Capital LLC 3Y 7Y 0.62% K.J. Harrison & Partners Inc 3Y 7Y 0.58% Putney Financial Group LLC 0.54%

FAQ About OBERWEIS ASSET MANAGEMENT INC/ and CLH

These are the practical questions this page is built to answer before you even open the full history table.

How long has OBERWEIS ASSET MANAGEMENT INC/ reported owning CLH?

OBERWEIS ASSET MANAGEMENT INC/ reported CLH across 9 quarterly 13F filings, from 2023 Q4 through 2025 Q4.

What was the largest reported CLH position in OBERWEIS ASSET MANAGEMENT INC/'s portfolio?

The largest reported portfolio weight for CLH was 1.43% in 2024 Q2.

What is the latest reported CLH position on this page?

The most recent filing on this page is 2025 Q4, when OBERWEIS ASSET MANAGEMENT INC/ reported 116,870 shares, equal to 1.00% of portfolio, with an estimated market value of $27.4M.

What does the chart on this CLH ownership page compare?

The chart compares OBERWEIS ASSET MANAGEMENT INC/'s quarterly CLH portfolio weight with the stock's indexed share price, so you can see whether the fund was building, trimming, or holding the position as price moved.

How well did OBERWEIS ASSET MANAGEMENT INC/ time their CLH position?

Based on 13F filing dates vs. subsequent CLH price moves, OBERWEIS ASSET MANAGEMENT INC/ correctly timed 14 out of 19 reported position changes (74%). The annualised alpha on CLH relative to SPY over the holding period was +11.5%.

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